Residual Stress Analysis in Thick Uranium Films
Hodge, A M; Foreman, R J; Gallegos, G F
2004-12-06
Residual stress analysis was performed on thick, 1.0 to 25 {micro}m, depleted Uranium (DU) films deposited on an Al substrate by magnetron sputtering. Two distinct characterization techniques were used to measure substrate curvature before and after deposition. Stress evaluation was performed using the Benabdi/Roche equation, which is based on beam theory of a bi-layer material. The residual stress evolution was studied as a function of coating thickness and applied negative bias voltage (0-300V). The stresses developed were always compressive; however, increasing the coating thickness and applying a bias voltage presented a trend towards more tensile stresses and thus an overall reduction of residual stresses.
Quantifying Residual Stresses by Means of Thermoelastic Stress Analysis
NASA Technical Reports Server (NTRS)
Gyekenyesi, Andrew L.; Baaklini, George Y.
2001-01-01
This study focused on the application of the Thermoelastic Stress Analysis (TSA) technique as a tool for assessing the residual stress state of structures. TSA is based on the fact that materials experience small temperature changes when compressed or expanded. When a structure is cyclically loaded, a surface temperature profile results which correlates to the surface stresses. The cyclic surface temperature is measured with an infrared camera. Traditionally, the amplitude of a TSA signal was theoretically defined to be linearly dependent on the cyclic stress amplitude. Recent studies have established that the temperature response is also dependent on the cyclic mean stress (i.e., the static stress state of the structure). In a previous study by the authors, it was shown that mean stresses significantly influenced the TSA results for titanium- and nickel-based alloys. This study continued the effort of accurate direct measurements of the mean stress effect by implementing various experimental modifications. In addition, a more in-depth analysis was conducted which involved analyzing the second harmonic of the temperature response. By obtaining the amplitudes of the first and second harmonics, the stress amplitude and the mean stress at a given point on a structure subjected to a cyclic load can be simultaneously obtained. The experimental results showed good agreement with the theoretical predictions for both the first and second harmonics of the temperature response. As a result, confidence was achieved concerning the ability to simultaneously obtain values for the static stress state as well as the cyclic stress amplitude of structures subjected to cyclic loads using the TSA technique. With continued research, it is now feasible to establish a protocol that would enable the monitoring of residual stresses in structures utilizing TSA.
Residual Stress Analysis Based on Acoustic and Optical Methods
Yoshida, Sanichiro; Sasaki, Tomohiro; Usui, Masaru; Sakamoto, Shuichi; Gurney, David; Park, Ik-Keun
2016-01-01
Co-application of acoustoelasticity and optical interferometry to residual stress analysis is discussed. The underlying idea is to combine the advantages of both methods. Acoustoelasticity is capable of evaluating a residual stress absolutely but it is a single point measurement. Optical interferometry is able to measure deformation yielding two-dimensional, full-field data, but it is not suitable for absolute evaluation of residual stresses. By theoretically relating the deformation data to residual stresses, and calibrating it with absolute residual stress evaluated at a reference point, it is possible to measure residual stresses quantitatively, nondestructively and two-dimensionally. The feasibility of the idea has been tested with a butt-jointed dissimilar plate specimen. A steel plate 18.5 mm wide, 50 mm long and 3.37 mm thick is braze-jointed to a cemented carbide plate of the same dimension along the 18.5 mm-side. Acoustoelasticity evaluates the elastic modulus at reference points via acoustic velocity measurement. A tensile load is applied to the specimen at a constant pulling rate in a stress range substantially lower than the yield stress. Optical interferometry measures the resulting acceleration field. Based on the theory of harmonic oscillation, the acceleration field is correlated to compressive and tensile residual stresses qualitatively. The acoustic and optical results show reasonable agreement in the compressive and tensile residual stresses, indicating the feasibility of the idea. PMID:28787912
Thermal Viscoelastic Analysis of Plastic Components Considering Residual Stress
NASA Astrophysics Data System (ADS)
Choi, Chel Woo; Jeoung, Kab Sik; Moon, Hyung-Il; Kim, Heon Young
Plastics is commonly used in consumer electronics because of it is high strength per unit mass and good productivity, but plastic components may often become distorted after injection molding due to residual stress after the filling, packing, and cooling processes. In addition, plastic deteriorates depending on various temperature conditions and the operating time, which can be characterized by stress relaxation and creep. The viscoelastic behavior of plastic materials in the time domain can be expressed by the Prony series using the ABAQUS commercial software package. This paper suggests a process for predicting post-production deformation under cyclic thermal loading. The process was applied to real plastic panels, and the deformation predicted by the analysis was compared to that measured in actual testing, showing the possibility of using this process for predicting the post-production deformation of plastic products under thermal loading.
Becker, A T; Chumbley, L S; Goettee, D; Russell, A M
2014-01-01
Neutron diffraction analysis was employed to measure residual stresses near welds in used anhydrous ammonia nurse tanks. Tensile residual stresses contribute to stress corrosion cracking of nurse tanks, which can cause tanks to release toxic ammonia vapor. The analysis showed that tensile residual stresses were present in the tanks measured, and the magnitudes of these stresses approached the yield strength of the steel. Implications for agricultural safety and health are discussed.
Laser cutting of thick sheet metals: Residual stress analysis
NASA Astrophysics Data System (ADS)
Arif, A. F. M.; Yilbas, B. S.; Aleem, B. J. Abdul
2009-04-01
Laser cutting of tailored blanks from a thick mild steel sheet is considered. Temperature and stress field in the cutting sections are modeled using the finite element method. The residual stress developed in the cutting section is determined using the X-ray diffraction (XRD) technique and is compared with the predictions. The structural and morphological changes in the cut section are examined using the optical microscopy and scanning electron microscopy (SEM). It is found that temperature and von Mises stress increase sharply in the cutting section, particularly in the direction normal to the cutting direction. The residual stress remains high in the region close to the cutting section.
Neutron diffractometer RSND for residual stress analysis at CAEP
NASA Astrophysics Data System (ADS)
Li, Jian; Wang, Hong; Sun, Guangai; Chen, Bo; Chen, Yanzhou; Pang, Beibei; Zhang, Ying; Wang, Yun; Zhang, Changsheng; Gong, Jian; Liu, Yaoguang
2015-05-01
Residual Stress Neutron Diffractometer (RSND) has been built at China Academy of Engineering Physics (CAEP) in Mianyang. Due to its excellent flexibility, the residual stress measurement on different samples, as well as in-situ study for materials science, can be carried out through RSND. The basic tests on its intensity and resolution and some preliminary experimental results under mechanical load, demonstrate the high quality of RSND.
Thermoelastic Stress Analysis: An NDE Tool for the Residual Stress Assessment of Metallic Alloys
NASA Technical Reports Server (NTRS)
Gyekenyesi, Andrew L.; Baaklini, George Y.
2000-01-01
During manufacturing, certain propulsion components that will be used in a cyclic fatigue environment are fabricated to contain compressive residual stresses on their surfaces because these stresses inhibit the nucleation of cracks. Overloads and elevated temperature excursions cause the induced residual stresses to dissipate while the component is still in service, lowering its resistance to crack initiation. Research at the NASA Glenn Research Center at Lewis Field has focused on employing the Thermoelastic Stress Analysis technique (TSA, also recognized as SPATE: Stress Pattern Analysis by Thermal Emission) as a tool for monitoring the residual stress state of propulsion components. TSA is based on the fact that materials experience small temperature changes when they are compressed or expanded. When a structure is cyclically loaded (i.e., cyclically compressed and expanded), the resulting surface-temperature profile correlates to the stress state of the structure s surface. The surface-temperature variations resulting from a cyclic load are measured with an infrared camera. Traditionally, the temperature amplitude of a TSA signal has been theoretically defined to be linearly dependent on the cyclic stress amplitude. As a result, the temperature amplitude resulting from an applied cyclic stress was assumed to be independent of the cyclic mean stress.
RGB photoelasticity applied to the analysis of membrane residual stress in glass
NASA Astrophysics Data System (ADS)
Ajovalasit, A.; Petrucci, G.; Scafidi, M.
2012-02-01
The measurement of residual stresses is of great relevance in the glass industry. The analysis of residual stress in glass is usually made by photoelastic methods because glass is a photoelastic material. This paper considers the determination of membrane residual stresses in glass plates by automatic digital photoelasticity in white light (RGB photoelasticity). The proposed method is applied to the analysis of membrane residual stresses in some tempered glass. The proposed method can effectively replace manual methods based on the use of white light, which are currently provided by some technical standards.
Finite element residual stress analysis of induction heating bended ferritic steel piping
Kima, Jong Sung; Kim, Kyoung-Soo; Oh, Young-Jin; Chang, Hyung-Young; Park, Heung-Bae
2014-10-06
Recently, there is a trend to apply the piping bended by induction heating process to nuclear power plants. Residual stress can be generated due to thermo-mechanical mechanism during the induction heating bending process. It is well-known that the residual stress has important effect on crack initiation and growth. The previous studies have focused on the thickness variation. In part, some studies were performed for residual stress evaluation of the austenitic stainless steel piping bended by induction heating. It is difficult to find the residual stresses of the ferritic steel piping bended by the induction heating. The study assessed the residual stresses of induction heating bended ferriticsteel piping via finite element analysis. As a result, it was identified that high residual stresses are generated on local outersurface region of the induction heating bended ferritic piping.
Finite element residual stress analysis of induction heating bended ferritic steel piping
NASA Astrophysics Data System (ADS)
Kima, Jong Sung; Kim, Kyoung-Soo; Oh, Young-Jin; Chang, Hyung-Young; Park, Heung-Bae
2014-10-01
Recently, there is a trend to apply the piping bended by induction heating process to nuclear power plants. Residual stress can be generated due to thermo-mechanical mechanism during the induction heating bending process. It is well-known that the residual stress has important effect on crack initiation and growth. The previous studies have focused on the thickness variation. In part, some studies were performed for residual stress evaluation of the austenitic stainless steel piping bended by induction heating. It is difficult to find the residual stresses of the ferritic steel piping bended by the induction heating. The study assessed the residual stresses of induction heating bended ferriticsteel piping via finite element analysis. As a result, it was identified that high residual stresses are generated on local outersurface region of the induction heating bended ferritic piping.
Ares I-X Upper Stage Simulator Residual Stress Analysis
NASA Technical Reports Server (NTRS)
Raju, Ivatury S.; Brust, Frederick W.; Phillips, Dawn R.; Cheston, Derrick
2008-01-01
The structural analyses described in the present report were performed in support of the NASA Engineering and Safety Center (NESC) Critical Initial Flaw Size (CIFS) assessment for the Ares I-X Upper Stage Simulator (USS) common shell segment. An independent assessment was conducted to determine the critical initial flaw size (CIFS) for the flange-to-skin weld in the Ares I-X Upper Stage Simulator (USS). The Ares system of space launch vehicles is the US National Aeronautics and Space Administration s plan for replacement of the aging space shuttle. The new Ares space launch system is somewhat of a combination of the space shuttle system and the Saturn launch vehicles used prior to the shuttle. Here, a series of weld analyses are performed to determine the residual stresses in a critical region of the USS. Weld residual stresses both increase constraint and mean stress thereby having an important effect on fatigue and fracture life. The results of this effort served as one of the critical load inputs required to perform a CIFS assessment of the same segment.
Effects of weld residual stresses on crack-opening area analysis of pipes for LBB applications
Dong, P.; Rahman, S.; Wilkowski, G.
1997-04-01
This paper summarizes four different studies undertaken to evaluate the effects of weld residual stresses on the crack-opening behavior of a circumferential through-wall crack in the center of a girth weld. The effect of weld residual stress on the crack-opening-area and leak-rate analyses of a pipe is not well understood. There are no simple analyses to account for these effects, and, therefore, they are frequently neglected. The four studies involved the following efforts: (1) Full-field thermoplastic finite element residual stress analyses of a crack in the center of a girth weld, (2) A comparison of the crack-opening displacements from a full-field thermoplastic residual stress analysis with a crack-face pressure elastic stress analysis to determine the residual stress effects on the crack-opening displacement, (3) The effects of hydrostatic testing on the residual stresses and the resulting crack-opening displacement, and (4) The effect of residual stresses on crack-opening displacement with different normal operating stresses.
Effects of weld residual stresses on crack-opening area analysis of pipes for LBB applications
Dong, P.; Rahman, S.; Wilkowski, G.; Bouchard, J.; Chivers, T.; Brickstad, B.; Bergman, M.
1996-12-01
This paper summarizes four different studies undertaken to evaluate the effects of weld residual stresses on the crack-opening behavior of a circumferential through-wall crack in the center of a girth weld. The effect of weld residual stress on the crack-opening-area and leak-rate analyses of a pipe is not well understood. There are no simple analyses to account for these effects, and therefore, they are frequently neglected. The four studies involved the following efforts: (1) full-field thermoplastic finite element residual stress analyses of a crack in the center of a girth weld; (2) a comparison of the crack-opening displacements from a full-field thermoplastic residual stress analysis with a crack-face pressure elastic stress analysis to determine the residual stress effects on the crack-opening displacements; (3) the effects of hydrostatic testing on the residual stresses and the resulting crack-opening displacement; and (4) the effect of residual stresses on crack-opening displacement with different normal operating stresses.
NASA Astrophysics Data System (ADS)
Yi, Hui-Jun; Lee, Yong-Jun
2017-08-01
The primary purpose of this investigation was to study welding residual stress relaxation by repeated loading. A coupling finite element analysis model for prediction of the welding residual stress and the mechanical stress relaxation after external repeated loads was presented. The accuracy of this model was verified through experiments. Also, it is found that the residual stress of weldment is relaxed by external loads, and the greatest amount of relaxation was obtained by early repeated loads. As the repetition count increased, the amount of relaxation became smaller than the amount of relaxation in the early stage.
Residual Stress Analysis of Boronized AISI 1018 Steel
Payne,J.; Petrova, R.; White, H.; Chauhan, A.; Bai, J.
2008-01-01
AISI 1018 steel substrates were powder-pack, diffusion boronized at 850 C for 4 h, followed by air quenching. Optical microscopy in conjunction with color etching was used to obtain the average penetration depth of the iron monoboride layer (9 {mu}m) and the iron diboride layer (57 {mu}m). X-ray diffraction by synchrotron radiation, conducted at the National Synchrotron Light Source in Brookhaven National Laboratory, confirmed the presence of iron monoboride and iron diboride in the boronized plain steel substrates. The sin2 {psi} technique was employed to calculate the residual stress found in the iron monoboride layer (-237 MPa) and in the substrate layer (-150 MPa) that is intertwined with the needle-like, iron diboride penetration.
Crack Analysis in Residual Stress Field by X-FEM
NASA Astrophysics Data System (ADS)
Nagashima, Toshio; Miura, Naoki
The extended finite element method (X-FEM), which can model the domain without explicitly meshing the crack surface, can be used to perform stress analyses for solving fracture mechanics problems efficiently. In the present study, the principle of superposition is used to solve crack problems in conjunction with the X-FEM. In the proposed method, the surface load distributed on the crack surface, which is modeled implicitly by the interpolation functions with enrichment terms, is introduced to X-FEM analysis. Moreover, the energy release rate at the crack front is evaluated by the domain integral method with boundary integral terms for the surface load. The proposed method is verified through numerical analyses of two- and three-dimensional crack problems in linear fracture mechanics.
Evolution of residual stress and crack morphologies during 3D FIB tomographic analysis of alumina.
Elfallagh, F; Inkson, B J
2008-05-01
Three-dimensional focused ion beam (FIB) tomography is increasingly being used for 3D characterization of microstructures in the 50 nm-20 microm range. FIB tomography is a destructive, invasive process, and microstructural changes may potentially occur during the analysis process. Here residual stress and crack morphologies in single-crystal sapphire samples have been concurrently analyzed using Cr3+ fluorescence spectroscopy and FIB tomography. Specifically, maps of surface residual stress have been obtained from optically polished single-crystal alumina [surface orientation (1 ī 0 2)], from FIB milled surface trenches, from Vickers micro-indentation sites (loads 50 g-300 g), and from Vickers micro-indentation sites during FIB serial sectioning. The residual stress maps clearly show that FIB sputtering generates residual stress changes. For the case of the Vickers micro-indentations, FIB sputtering causes significant changes in residual stress during the FIB tomographic serial sectioning. 3D reconstruction of the crack distribution around micro-indentation sites shows that the cracks observed are influenced by the location of the FIB milled surface trenches due to localized stress changes.
Residual Stress Analysis of Overspeeded Disk with Central Hole by X-ray Diffraction
NASA Technical Reports Server (NTRS)
Good, James N
1948-01-01
An X-ray - diffraction analysis of residual surface stresses after plastic strain was introduced in a parallel-sided 3S-O aluminum disk with a central hole by two types of centrifugal overspeed is reported. Both tangential and radial stresses were generally tensile with large local variations near the hole where surface stresses may have been partly superficial. These stresses were both tensile and compressive dependent on the distance from the disk center when mass compression was effected near the hole.
NASA Astrophysics Data System (ADS)
Denks, I. A.; Genzel, Ch.
2007-08-01
The effects of the germanium detector electronics on diffraction line patterns is investigated. It is shown that not only the detector resolution and the throughput but also the energy stability depend on both the specific detector settings and the dead time. For a moderate resolution versus throughput setting a correction function is proposed and applied to the near-surface residual stress analysis of three samples with considerably different stress states. It is demonstrated that without the correction function ghost stresses up to hundreds of MPa in the near-surface region are obtained. The correction procedure is verified by conventional X-ray measurements. In conclusion, the authors strongly suggest quantifying the electronic shifts of any individual detector systems prior to the analysis of residual stresses.
Residual stress distribution analysis of heat treated APS TBC using image based modelling.
Li, Chun; Zhang, Xun; Chen, Ying; Carr, James; Jacques, Simon; Behnsen, Julia; di Michiel, Marco; Xiao, Ping; Cernik, Robert
2017-08-01
We carried out a residual stress distribution analysis in a APS TBC throughout the depth of the coatings. The samples were heat treated at 1150 °C for 190 h and the data analysis used image based modelling based on the real 3D images measured by Computed Tomography (CT). The stress distribution in several 2D slices from the 3D model is included in this paper as well as the stress distribution along several paths shown on the slices. Our analysis can explain the occurrence of the "jump" features near the interface between the top coat and the bond coat. These features in the residual stress distribution trend were measured (as a function of depth) by high-energy synchrotron XRD (as shown in our related research article entitled 'Understanding the Residual Stress Distribution through the Thickness of Atmosphere Plasma Sprayed (APS) Thermal Barrier Coatings (TBCs) by high energy Synchrotron XRD; Digital Image Correlation (DIC) and Image Based Modelling') (Li et al., 2017) [1].
NASA Astrophysics Data System (ADS)
Nadimi, S.; Khoushehmehr, R. J.; Rohani, B.; Mostafapour, A.
In the present study, Manual Metal Arc Welding (MMAW) of austenitic stainless steel to carbon steel were studied. The Schaeffler diagram were used in determining suitable filler metal for this process and then the finite element analysis of residual stresses in butt welding of two dissimilar pipes is performed with the commercial software ANSYS, which includes moving heat source, material deposit, temperature dependant material properties, metal plasticity and elasticity, transient heat transfer and mechanical analysis. The residual stresses distribution and magnitude in the hoop and axial directions in the inner and outer surfaces of two dissimilar pipes were obtained. Welding simulation considered as a sequentially coupled thermo-mechanical analysis and the element birth and death technique was employed for simulation of filler metal deposition.
Residual stresses in material processing
Kozaczek, K.J.; Watkins, T.R.; Hubbard, C.R.; Wang, Xun-Li; Spooner, S.
1994-09-01
Material manufacturing processes often introduce residual stresses into the product. The residual stresses affect the properties of the material and often are detrimental. Therefore, the distribution and magnitude of residual stresses in the final product are usually an important factor in manufacturing process optimization or component life prediction. The present paper briefly discusses the causes of residual stresses. It then adresses the direct, nondestructive methods of residual stress measurement by X-ray and neutron diffraction. Examples are presented to demonstrate the importance of residual stress measurement in machining and joining operations.
Residual stress analysis in forming process of filament wound thick-walled CFRP pipes
Kondo, Toshimi; Sekine, Hideki; Nakano, Kunio
1995-11-01
Residual stress analysis for the cracking phenomenon of filament would thick-walled CFRP pipes, which frequently occurs in the forming process of curing and thermal cycling through the course of the wet filament winding, was made from both the experimental and theoretical points of view. A simple analytical model to study the cracking in the CFRP pipes was proposed. The pipes are multilayered and reinforced in the axial and circumferential directions alternatively by carbon fibers. Taking account of the anisotropy of mechanical and thermal properties including the shrinkage strain, which depend considerably on the temperature, the residual stresses in the CFRP pipes were elucidated in the forming process, particularly, in cooling of the cure process.
NASA Astrophysics Data System (ADS)
Nakano, S.; Gao, B.; Kakimoto, K.
2017-06-01
In this study, we investigate the influence of thermal stress on the dislocation density and residual stress in GaN single crystals by numerical analysis. The results show that the dislocation density increases, but the thermal stress does not decrease, and the residual stress increases throughout the cooling process. The reason for this phenomenon is that the dislocation density is higher at the periphery of the crystal and distribution of dislocation density in the crystal is inhomogeneous. Then, the increase of dislocation does not allow the thermal stress on the entire crystal to relax.
Residual stresses in polymer matrix composite laminates
NASA Technical Reports Server (NTRS)
Hahn, H. T.
1976-01-01
Residual stresses in composites are induced during fabrication and by environmental exposure. The theory formulated can describe the shrinkage commonly observed after a thermal expansion test. Comparison between the analysis and experimental data for laminates of various material systems indicates that the residual stress-free temperature can be lower than the curing temperature, depending on the curing process. Effects of residual stresses on ply failure including the acoustic emission characteristics are discussed.
Hempel, Nico; Bunn, Jeffrey R; Nitschke-Pagel, Thomas; Payzant, E Andrew; Dilger, Klaus
2016-01-01
This paper is dedicated to the thorough experimental analysis of the residual stresses in the vicinity of tubular welds and the mechanisms involved in their formation. Pipes made of a ferritic-pearlitic structural steel and an austenitic stainless steel are investigated in this study. The pipes feature a similar geometry and are MAG welded with two passes and comparable parameters. Residual strain mappings are carried out using X-ray and neutron diffraction. The combined use of both techniques permits both near-surface and through-wall analyses of the residual stresses. The findings allow for a consistent interpretation of the mechanisms accounting for the formation of the residual stress fields due to the welding process. Since the results are similar for both materials, it can be concluded that residual stresses induced by phase transformations, which can occur in the structural steel, play a minor role in this regard.
Experimental determination of residual stress
NASA Technical Reports Server (NTRS)
Ferguson, Milton W.
1991-01-01
Residual stresses in finished parts have often been regarded as factors contributing to premature part failure and geometric distortions. Currently, residual stresses in welded structures and railroad components are being investigated. High residual stresses formed in welded structures due primarily to the differential contractions of the weld material as it cools and solidifies can have a profound effect on the surface performance of the structure. In railroad wheels, repeated use of the brakes causes high residual stresses in the rims which may lead to wheel failure and possible derailment. The goals of the study were: (1) to develop strategies for using x-ray diffraction to measure residual stress; (2) to subject samples of Inconel 718 to various mechanical and heat treatments and to measure the resulting stress using x-ray diffraction; and (3) to measure residual stresses in ferromagnetic alloys using magnetoacoustics.
Finite element analysis of residual stress field induced by laser shock peening
NASA Astrophysics Data System (ADS)
Nam, Taeksun
The finite element method is applied to analyze the laser shock peening process (LSP) for thick parts (considered as a semi-infinite half space) and thin parts (finite thickness domain). The technology of LSP is used to enhance mechanical properties such as fatigue life, fretting fatigue life, resistance to stress corrosion cracking and surface hardness. These enhanced material properties are directly related to the magnitude and distribution of the plastic strain and associated residual stresses due to shockwaves induced by LSP. To reduce the process development cost and time, the prediction of residual stress field is very useful to provide a base design guideline for selecting appropriate LSP conditions for evaluation. An axisymmetric Finite Element Analysis (FEA) code, named SHOCKWAVE, is developed in order to complement shortcomings of applying commercial FEA codes at extremely high strain rates (as high as 104 -106/sec). The rate dependent plasticity theory is applied along with the small strain assumption. The solution process consists of an explicit dynamic loading analysis for shock loading stage and a static unloading analysis (implicit) to determine the equilibrium state for the residual stress and plastic strain fields. Some of the highlights explored in this investigation entail: (i) overstress power law models for the rate dependence, (ii) various hardening models, (iii) a second-order accurate implicit algorithm for the plastic consistency condition, (iv) an adaptively expanding domain scheme to trace the stress-free boundary condition in a simple way, (v) a special uniform meshing scheme to avoid the usual assembly process and repeated calculations for the stiffness matrix, (vi) mesh sensitivity study, (vii) comparisons with measured data provided and supported by the LSP Technologies, Inc. The dynamic behavior of Ti-6Al-4V at high strain rates can be investigated by using the split torsional Hopkinson bar experiment and by a longitudinal shock
Residual Stress Analysis of Laser-Drilled Thermal Barrier Coatings Involving Various Bond Coats
NASA Astrophysics Data System (ADS)
Guinard, C.; Montay, G.; Guipont, V.; Jeandin, M.; Girardot, J.; Schneider, M.
2015-01-01
The gas turbine combustion chamber of aero-engines requires a thermal barrier coating (TBC) by thermal spraying. Further heat protection is achieved by laser drilling of cooling holes. The residual stresses play an important role in the mechanical behaviour of TBC. It could also affect the TBC response to delamination during laser drilling. In this work, studies of the cracking behaviour after laser drilling and residual stress distribution have been achieved for different bond coats by plasma spray or cold spray. From interface crack length measured pulse-by-pulse after laser percussion drilling at 20° angle, the role of the various bond coats on crack initiation and propagation are investigated. It is shown that the bond coat drastically influences the cracking behaviour. The residual stresses profiles were also determined by the incremental hole-drilling method involving speckle interferometry. An original method was also developed to measure the residual stress profiles around a pre-drilled zone with a laser beam at 90°. The results are discussed to highlight the influence of TBCs interfaces on the resulting residual stresses distribution before laser drilling, and also to investigate the modification around the hole after laser drilling. It is shown that laser drilling could affect the residual stress state.
Analysis of Residual Stresses in Laser-Shock-Peened and Shot-Peened Marine Steel Welds
NASA Astrophysics Data System (ADS)
Ahmad, Bilal; Fitzpatrick, Michael E.
2017-02-01
Laser peening is now the preferred method of surface treatment in many applications. The magnitude and depth of the compressive residual stress induced by laser peening can be influenced strongly by the number of peen layers (the number of laser hits at each point) and by processing conditions including the use of a protective ablative layer. In this study, residual stresses have been characterized in laser and shot-peened marine butt welds with a particular focus at the fatigue crack initiation location at the weld toe. X-ray diffraction, synchrotron X-ray diffraction, incremental center-hole drilling, and the contour method were used for determination of residual stress. Results showed that the use of ablative tape increased the surface compressive stress, and the depth of compressive stress increased with an increase in number of peening layers. A key result is that variation of residual stress profile across laser peen spots was seen, and the residual stress magnitude varies between the center and edges of the spots.
VAIDYA, RAJENDRA U; KAUTZ, DOUGLAS D.; GALLEGOS, DAVID E.
2007-01-30
Molybdenum disilicide (MoSi{sub 2})/stainless steel 316 L jOints were produced by high temperature brazing using a cobalt-based metallic-glass (METGLAS{trademark} 2714A). Successful joining was completed in two different ways; either by feeding excess braze into the braze gap upon heating or by constraining the MoSi{sub 2}/stainiess steel assembly with an alumina (Al{sub 2}O{sub 3}) fixture during the heating cycle. These steps were necessary to ensure the production of a high quality void free joint. Residual stress measurements were completed on these joints. Indentation results show higher tensile residual stresses in the stainless steel for the joint with the external constraint, in comparison to the unconstrained state. In contrast, the compressive residual stresses In the MoSi{sub 2} (as measured by X-ray diffraction) were lower in the constrained state relative to the unconstrained state. These results and a lack of residual stress balance indicate that the stress state in the braze is significantly different under the two joining conditions and the volume of the braze plays an important role in the development of the residual stresses. Push-out tests carried out on these joints gave higher joint strengths in the unconstrained as compared to the constrained condition. The results of this study have important implications on the selection of the appropriate joining process (use of constraint versus extra braze).
A quasi-linear analysis of the impurity effect on turbulent momentum transport and residual stress
Ko, S. H. Jhang, Hogun; Singh, R.
2015-08-15
We study the impact of impurities on turbulence driven intrinsic rotation (via residual stress) in the context of the quasi-linear theory. A two-fluid formulation for main and impurity ions is employed to study ion temperature gradient modes in sheared slab geometry modified by the presence of impurities. An effective form of the parallel Reynolds stress is derived in the center of mass frame of a coupled main ion-impurity system. Analyses show that the contents and the radial profile of impurities have a strong influence on the residual stress. In particular, an impurity profile aligned with that of main ions is shown to cause a considerable reduction of the residual stress, which may lead to the reduction of turbulence driven intrinsic rotation.
A quasi-linear analysis of the impurity effect on turbulent momentum transport and residual stress
NASA Astrophysics Data System (ADS)
Ko, S. H.; Jhang, Hogun; Singh, R.
2015-08-01
We study the impact of impurities on turbulence driven intrinsic rotation (via residual stress) in the context of the quasi-linear theory. A two-fluid formulation for main and impurity ions is employed to study ion temperature gradient modes in sheared slab geometry modified by the presence of impurities. An effective form of the parallel Reynolds stress is derived in the center of mass frame of a coupled main ion-impurity system. Analyses show that the contents and the radial profile of impurities have a strong influence on the residual stress. In particular, an impurity profile aligned with that of main ions is shown to cause a considerable reduction of the residual stress, which may lead to the reduction of turbulence driven intrinsic rotation.
NASA Astrophysics Data System (ADS)
Ganguly, S.; James, J. A.; Fitzpatrick, M. E.; Tanguy, A.
2010-06-01
Residual stress measurement using neutron diffraction is becoming an increasingly important tool in engineering stress analysis. To this effect, a new generation of dedicated engineering strain instruments are being built at neutron sources, offering considerable improvements in both counting time and spatial resolution. Alongside these improvements, measurements in complex geometry prototype components are increasingly in demand. As a result, there is a strong drive towards integrated sample positioning systems that allow for simplified setup and operating of experiments on components with complex geometries. The present study details work carried out at the ENGIN-X instrument at the UK’s ISIS pulsed neutron source, on measurements in a prototype metal matrix composite (MMC) aircraft wheel, forged from a billet produced through a powder-metallurgy route. The measurement was designed to obtain the macrostress and misfit stresses developed in the matrix and in the reinforcement phase in the wheel during fabrication. The study also demonstrates the use of the SScanSS software for experimental design and implementation, which was developed to complement the advances in the instrumentation of new strain mapping diffractometers. SScanSS simplifies the precise spatial location of the measuring gauge volume inside such complex components.
X-ray diffraction analysis of residual stress in zirconia dental composites
NASA Astrophysics Data System (ADS)
Allahkarami, Masoud
Dental restoration ceramic is a complex system to be characterized. Beside its essential biocompatibility, and pleasant appearance, it requires being mechanically strong in a catastrophic loading environment. Any design is restricted with geometry boundary and material property limits. Inspired by natural teeth, a multilayer ceramic is a smart way of achieving an enhanced restoration. Bi-layers of zirconia core covered by porcelain are known as one of the best multilayer restorations. Residual stresses may be introduced into a bi-layer dental ceramic restoration during its entire manufacturing process due to thermal expansion and elastic property mismatch. It is impossible to achieve a free of residual stresses bi-layer zirconia-porcelain restoration. The idea is to take the advantage of residual stress in design in such a way to prevent the crack initiation and progression. The hypothesis is a compressive residual stress at external contact surface would be enabling the restoration to endure a greater tensile stress. Optimizing the layers thickness, manufacturing process, and validating 3D simulations require development of new techniques of thickness, residual stresses and phase transformation measurement. In the present work, a combined mirco-tomography and finite element based method were adapted for thickness measurement. Two new 2D X-ray diffraction based techniques were adapted for phase transformation area mapping and combined phase transformation and residual stress measurement. Concerning the complex geometry of crown, an efficient method for X-ray diffraction data collection mapping on a given curved surface was developed. Finally a novel method for 3D dimensional x-ray diffraction data collection and visualization were introduced.
Elastoplastic analysis of process induced residual stresses in thermally sprayed coatings
Chen Yongxiong; Liang Xiubing; Liu Yan; Xu Binshi
2010-07-15
The residual stresses induced from thermal spraying process have been extensively investigated in previous studies. However, most of such works were focused on the elastic deformation range. In this paper, an elastoplastic model for predicting the residual stresses in thermally sprayed coatings was developed, in which two main contributions were considered, namely the deposition induced stress and that due to differential thermal contraction between the substrate and coating during cooling. The deposition induced stress was analyzed based on the assumption that the coating is formed layer-by-layer, and then a misfit strain is accommodated within the multilayer structure after the addition of each layer (plastic deformation is induced consequently). From a knowledge of specimen dimensions, processing temperatures, and material properties, residual stress distributions within the structure can be determined by implementing the model with a simple computer program. A case study for the plasma sprayed NiCoCrAlY on Inconel 718 system was performed finally. Besides some similar phenomena observed from the present study as compared with previous elastic model reported in literature, the elastoplastic model also provides some interesting features for prediction of the residual stresses.
Not Available
1993-07-01
One objective of mechanical design of welded fabrications is to compensate loads by stresses which the materials used in structural components can accommodate. Beside these load-induced stresses, residual stresses also have to be considered. These residual stresses are built up during weld pool cooling. All welded structures therefore have residual stresses, which can be relieved by heat treatment to below the yield-stress level at the annealing temperature. If not fully relieved, their presence can accelerate corrosion and corrosive cracking of welds. Quality assurance of welded structures needs tools for quantitative nondestructive analysis of stress states. The only nondestructive technique specifically developed for measurement and analysis of stress states is x-ray diffraction. Special devices for application under industrial or on-site environments have been developed and are extensively used. This type of measurement can be time-consuming, depending on the equipment, and has practical limitations. Moreover the penetration of x-rays into metals is small, in the order of 30 microns, and the measurements can be affected by other surface-related disturbance caused by machining and surface finishing. In the last ten years extensive research and development has been done to develop stress-analyzing techniques of a typical ndt-style,'' i.e., the use of a probe manipulated by hand or a manipulator, together with portable equipment. The present state of development of such an approach and the most important results obtained up to now are described in the following article.
Ultrasonics used to measure residual stress
NASA Technical Reports Server (NTRS)
1967-01-01
Ultrasonic method is used to measure residual stress in metal structures. By using this method, various forms of wave propagation in metals are possible, and more thorough analysis of complex geometric structures may be had.
Integrating Residual Stress Analysis of Critical Fastener Holes into USAF Depot Maintenance
2014-11-02
11 Figure 7. Crack growth curves for two SENT coupons tested under identical conditions. As dissimilar as the total lives are, crack...the basis of the method and resulting residual stress contours for a welded work piece are shown in Figure 32 from DeWald et. al (2009). Figure...A.T., Sebring, R.J., Dave, V.R. and Cola, M.J. (2003); “Residual Stress Mapping in Welds Using the Contour Method,” Trends in Welding Research
BOOK REVIEW: Analysis of Residual Stress by Diffraction Using Neutron and Synchrotron Radiation
NASA Astrophysics Data System (ADS)
Fitzpatrick, ed M. E.; Lodini, A.
2003-09-01
The presence of residual stresses within engineering components is often a key feature in determining their usable lifetimes and failure characteristics. Residual surface compression can, for example, restrict the propagation of surface cracks through the bulk. As a consequence, it is essential to characterize the magnitude and spatial distribution of residual stresses and, at least for non-destructive testing, this is most widely achieved using diffraction of neutron and high energy synchrotron radiations. This book aims to provide a detailed description of the methodology used to determine residual stresses. The major emphasis is placed on the neutron method, this being the more widely established approach at present. It contains 20 chapters contributed by 23 authors, divided into five major parts. The overall layout is very logical, with the first part giving a general introduction to the use of neutrons and x-rays for materials research and summarizing the methods used for their production. Part 2 considers the more specific aspects of extracting the residual stress distribution within a bulk sample and includes some valuable comments on a number of potential experimental problems, such as the determination of the stress-free lattice parameter and the effects of broadening of the Bragg peaks. The experimental facilities currently available or under development are described in part 3, with the remaining two parts devoted to general and specific applications of the residual stress measurement technique. As expected with such a large number of different authors, there is some variation in style and quality. However, the text is generally easy to follow and, more importantly, it is largely free of the problems of inconsistent notation and dupication of material that can afflict multi-authored texts. My only negative comment concerns the latter portion of the book devoted to specific applications of the technique, which is illustrative rather than comprehensive. In
Analysis and Measurement of Residual Stress in Bridge Membrane MEMS Relays
NASA Astrophysics Data System (ADS)
Ruan, Yong; Wang, Weizhong; Zhu, Yong; You, Zheng
2017-04-01
Microelectromechanical system (MEMS) relays are gradually replacing traditional relays because they are smaller and lighter and consume less power. However, performance parameters of MEMS relays, such as the pull-down voltage, response time, and resonant frequency, often deviate from those originally designed, due to residual stress generated during the fabrication process. We present herein a method to measure this residual stress, based on a metal bridge membrane MEMS relay, with the help of a nanoindenter and the finite-element method (FEM). The testing result lies in a reasonable range, indicating that this simple method is reliable and helpful for MEMS relay optimization.
Flower, E.C.; MacEwen, S.R.; Holden, T.M.
1987-05-01
Residual stresses in a body arise from nonuniform plastic deformation and continue to be an important consideration in the design and the fabrication of metal components. The finite element method offers a potentially powerful tool for predicting these stresses. However, it is important to first verify this method through careful analysis and experimentation. This paper describes experiments using neutron and x-ray diffraction to provide quantitative data to compare to finite element analysis predictions of deformation induced residual stress in a plane stress austenitic stainless steel ring. Good agreement was found between the experimental results and the numerical predictions. Effects of the formulation of the finite element model on the analysis, constitutive parameters and effects of machining damage in the experiments are addressed.
NASA Technical Reports Server (NTRS)
Bakuckas, John G., Jr.; Johnson, W. Steven
1994-01-01
In this research, thermal residual stresses were incorporated in an analysis of fiber-bridged matrix cracks in unidirectional and cross-ply titanium matrix composites (TMC) containing center holes or center notches. Two TMC were investigated, namely, SCS-6/Timelal-21S laminates. Experimentally, matrix crack initiation and growth were monitored during tension-tension fatigue tests conducted at room temperature and at an elevated temperature of 200 C. Analytically, thermal residual stresses were included in a fiber bridging (FB) model. The local R-ratio and stress-intensity factor in the matrix due to thermal and mechanical loadings were calculated and used to evaluate the matrix crack growth behavior in the two materials studied. The frictional shear stress term, tau, assumed in this model was used as a curve-fitting parameter to matrix crack growth data. The scatter band in the values of tau used to fit the matrix crack growth data was significantly reduced when thermal residual stresses were included in the fiber bridging analysis. For a given material system, lay-up and temperature, a single value of tau was sufficient to analyze the crack growth data. It was revealed in this study that thermal residual stresses are an important factor overlooked in the original FB models.
Residual stresses in welded plates
NASA Technical Reports Server (NTRS)
Bernstein, Edward L.
1994-01-01
The purpose of this project was to develop a simple model which could be used to study residual stress. The mechanism that results in residual stresses in the welding process starts with the deposition of molten weld metal which heats the immediately adjacent material. After solidification of weld material, normal thermal shrinkage is resisted by the adjacent, cooler material. When the thermal strain exceeds the elastic strain corresponding to the yield point stress, the stress level is limited by this value, which decreases with increasing temperature. Cooling then causes elastic unloading which is restrained by the adjoining material. Permanent plastic strain occurs, and tension is caused in the region immediately adjacent to the weld material. Compression arises in the metal farther from the weld in order to maintain overall static equilibrium. Subsequent repair welds may add to the level of residual stresses. The level of residual stress is related to the onset of fracture during welding. Thus, it is of great importance to be able to predict the level of residual stresses remaining after a weld procedure, and to determine the factors, such as weld speed, temperature, direction, and number of passes, which may affect the magnitude of remaining residual stress. It was hoped to use traditional analytical modeling techniques so that it would be easier to comprehend the effect of these variables on the resulting stress. This approach was chosen in place of finite element methods so as to facilitate the understanding of the physical processes. The accuracy of the results was checked with some existing experimental studies giving residual stress levels found from x-ray diffraction measurements.
Electromechanical Apparatus Measures Residual Stress
NASA Technical Reports Server (NTRS)
Chern, Engmin J.; Flom, Yury
1993-01-01
Nondestructive test exploits relationship between stress and eddy-current-probe resistance. Yields data on residual stress or strain in metal tension/compression specimen (stress or strain remaining in specimen when no stress applied from without). Apparatus is assembly of commercial equipment: tension-or-compression testing machine, eddy-current probe, impedance gain-and-phase analyzer measuring impedance of probe coil, and desktop computer, which controls other equipment and processes data received from impedance gain-and-phase analyzer.
Electromechanical Apparatus Measures Residual Stress
NASA Technical Reports Server (NTRS)
Chern, Engmin J.; Flom, Yury
1993-01-01
Nondestructive test exploits relationship between stress and eddy-current-probe resistance. Yields data on residual stress or strain in metal tension/compression specimen (stress or strain remaining in specimen when no stress applied from without). Apparatus is assembly of commercial equipment: tension-or-compression testing machine, eddy-current probe, impedance gain-and-phase analyzer measuring impedance of probe coil, and desktop computer, which controls other equipment and processes data received from impedance gain-and-phase analyzer.
Weld Residual Stress and Distortion Analysis of the ARES I-X Upper Stage Simulator (USS)
NASA Technical Reports Server (NTRS)
Raju, Ivatury; Dawicke, David; Cheston, Derrick; Phillips, Dawn
2008-01-01
An independent assessment was conducted to determine the critical initial flaw size (CIFS) for the flange-to-skin weld in the Ares I-X Upper Stage Simulator (USS). The Ares system of space launch vehicles is the US National Aeronautics and Space Administration s plan for replacement of the aging space shuttle. The new Ares space launch system is somewhat of a combination of the space shuttle system and the Saturn launch vehicles used prior to the shuttle. Here, a series of weld analyses are performed to determine the residual stresses in a critical region of the USS. Weld residual stresses both increase constraint and mean stress thereby having an important effect on fatigue and fracture life. While the main focus of this paper is a discussion of the weld modeling procedures and results for the USS, a short summary of the CIFS assessment is provided.
NASA Astrophysics Data System (ADS)
Li, H.; Liu, Y. H.
2008-11-01
The hole-drilling strain gage method is an effective semi-destructive technique for determining residual stresses in the component. As a mechanical technique, a work-hardening layer will be formed on the surface of the hole after drilling, and affect the strain relaxation. By increasing Young's modulus of the material near the hole, the work-hardening layer is simplified as a heterogeneous annulus. As an example, two finite rectangular plates submitted to different initial stresses are treated, and the relieved strains are measured by finite element simulation. The accuracy of the measurement is estimated by comparing the simulated residual stresses with the given initial ones. The results are shown for various hardness of work-hardening layer. The influence of the relative position of the gages compared with the thickness of the work-hardening layer, and the effect of the ratio of hole diameter to work-hardening layer thickness are analyzed as well.
Residual Stresses in Ground Steels.
1979-06-13
stress near the surface can be lower. The level of residual stress is also strongly affected by carbon,’3 which influences the microplastic behaviour of...1966, Vol. 14, 99-104. 14. C. 3. )4cMahon: “ Microplastic Behaviour in Iron” in Mv. in Mater . S d . Res., Vol. 2, 121-140, Interscience, New York
NASA Astrophysics Data System (ADS)
Song, Baoan; Yang, Yan; Jia, Zhitai; Chen, Feifei; Lin, Changgui; Dai, Shixun; Wang, Xunsi; Shen, Xiang; Xu, Tiefeng; Nie, Qiuhua
2013-06-01
Chalcogenide glasses (ChGs) have a relatively small temperature coefficient of refractive index, broad transmission range from almost visible to mid-infrared. It is suitable for precision molding. With the help of above mentioned merits, ChGs have a vast reservoir of value in the field of military and civilian infrared imaging. However, the internal defects of ChGs are caused by melting, cool-demoulding and annealing in a high vacuumed ampoule. The defects include the optical inhomogeneity, chemical inhomogeneity and built-in stress which trouble the homogeneity of ChGs and directly affect the imaging quality of infrared imaging devices. The detection and control of internal defects is a key technique. In this paper the platform for testing, characterization and evaluation of the inhomogeneity of ChGs will be designed and built. The appropriate testing and evaluation criteria of inhomogeneity during the preparation procedure of ChGs in the vacuumed ampoule will be studied. The transmittance of ChGs sample is measured repeatedly. The factor of internal multple reflection in ChGs sample is analysed and discussed. Analysis shows that the mean transmissivity of ChGs sample (Ge28Sb12Se60) with thick of 1 cm is approximately 66% in 8 to 11 microns. The loss is less than 2.40%/cm. The optical path difference (OPD) caused by residual stress in ChGs sample is less than 5.2 nm/cm. The results will provide a technical support to optimize the ChGs preparation process and improve the ChGs homogeneity.
The design of the radial collimator for residual stress analysis diffractometer of J-PARC
NASA Astrophysics Data System (ADS)
Torii, Shuki; Moriai, Atsushi
2006-11-01
Radial collimators are devices needed to define gauge sizes in neutron diffraction experiments. A design work of collimators needed for an engineering diffractometer that will be built at J-PARC is being progressed. Several collimators for different gauge sizes (1, 3, 5 mm, etc …) are going to be designed to define a gauge size range from 1 to 10 mm. An equation was established to express a relation between the gauge size and geometrical design parameters of the collimator, by applying a normal distribution curve to the error distribution of measured gauge size. Currently, the geometric calculations for several collimators have been finished. A prototype collimator for a gauge size of 1 mm was made and an FWHM (full width at half maximum) of the normal distribution of 1 mm was obtained from performance tests conducted at the neutron diffractometer for residual stress analysis RESA in JRR-3 (Japan Research Reactor-3) of Japan Atomic Energy Agency (JAEA). In addition, the performance test results are in a good agreement with results from a Monte Carlo simulation with the McStas using the design parameters.
Analysis of welding-induced residual stresses with the ADINA system
Wilkening, W.W,; Snow, J.L.
1993-12-01
Welding-induced residual stresses analysis procedure (WIRSAP), based on ADINA system of nonlinear finite element software, is described and results of several WIRSAP analyses are discussed. Several 2D axisymmetric WIRSAP analyses were performed for pipe girth welds and for several multi-pass girth-like welds attaching small nozzles to large, thick-walled pressure vessels. The analytical methodology follows closely Rybicki et al, enhanced by several specialized modeling techniques available in ADINA. The element birth option is used to simulate the addition of weld metal, and the mixed pressure/ displacement element formulation is used, in conjunction with temperature-dependent bi-linear plasticity material model. Some of the welds analyzed involve backing rings, which were subsequently `machined off` via use of the element death option. The auto-time-stepping algorithm and matrix update iteration scheme are used in structural solutions. WIRSAP involves, a pass-by-pass analysis of uncoupled thermal and structural problems, but some analyses have been performed with an ``enveloping`` technique for grouping several weld passes together. The analyses are all 2D, but most are large problems and pose challenge to software and hardware. Operations are performed on a network of Silicon Graphics workstations, and ADINA and ADINA-T are executed on a 64 MW, eight-processor CRAY YIMP. Nominally 50 solution steps are utilized for each weld pass and weld joints involving as many as 31 individual weld passes analyzed on a pass-by-pass basis. Results from several WIRSAP analyses are discussed, and potential use of WIRSAP in a hypothetic attachment weld design optimization study is illustrated.
An Assessment of Subsurface Residual Stress Analysis in SLM Ti-6Al-4V
Mishurova, Tatiana; Cabeza, Sandra; Artzt, Katia; Haubrich, Jan; Klaus, Manuela; Genzel, Christoph; Requena, Guillermo; Bruno, Giovanni
2017-01-01
Ti-6Al-4V bridges were additively fabricated by selective laser melting (SLM) under different scanning speed conditions, to compare the effect of process energy density on the residual stress state. Subsurface lattice strain characterization was conducted by means of synchrotron diffraction in energy dispersive mode. High tensile strain gradients were found at the frontal surface for samples in an as-built condition. The geometry of the samples promotes increasing strains towards the pillar of the bridges. We observed that the higher the laser energy density during fabrication, the lower the lattice strains. A relief of lattice strains takes place after heat treatment. PMID:28772706
Residual stresses and stress corrosion cracking in pipe fittings
NASA Astrophysics Data System (ADS)
Parrington, Ronald J.; Scott, James J.; Torres, Freddie
1994-06-01
Residual stresses can play a key role in the SCC performance of susceptible materials in PWR primary water applications. Residual stresses are stresses stored within the metal that develop during deformation and persist in the absence of external forces or temperature gradients. Sources of residual stresses in pipe fittings include fabrication processes, installation and welding. There are a number of methods to characterize the magnitude and orientation of residual stresses. These include numerical analysis, chemical cracking tests, and measurement (e.g., X-ray diffraction, neutron diffraction, strain gage/hole drilling, strain gage/trepanning, strain gage/section and layer removal, and acoustics). This paper presents 400 C steam SCC test results demonstrating that residual stresses in as-fabricated Alloy 600 pipe fittings are sufficient to induce SCC. Residual stresses present in as-fabricated pipe fittings are characterized by chemical cracking tests (stainless steel fittings tested in boiling magnesium chloride solution) and by the sectioning and layer removal (SLR) technique.
RESIDUAL STRESSES IN 3013 CONTAINERS
Mickalonis, J.; Dunn, K.
2009-11-10
The DOE Complex is packaging plutonium-bearing materials for storage and eventual disposition or disposal. The materials are handled according to the DOE-STD-3013 which outlines general requirements for stabilization, packaging and long-term storage. The storage vessels for the plutonium-bearing materials are termed 3013 containers. Stress corrosion cracking has been identified as a potential container degradation mode and this work determined that the residual stresses in the containers are sufficient to support such cracking. Sections of the 3013 outer, inner, and convenience containers, in both the as-fabricated condition and the closure welded condition, were evaluated per ASTM standard G-36. The standard requires exposure to a boiling magnesium chloride solution, which is an aggressive testing solution. Tests in a less aggressive 40% calcium chloride solution were also conducted. These tests were used to reveal the relative stress corrosion cracking susceptibility of the as fabricated 3013 containers. Significant cracking was observed in all containers in areas near welds and transitions in the container diameter. Stress corrosion cracks developed in both the lid and the body of gas tungsten arc welded and laser closure welded containers. The development of stress corrosion cracks in the as-fabricated and in the closure welded container samples demonstrates that the residual stresses in the 3013 containers are sufficient to support stress corrosion cracking if the environmental conditions inside the containers do not preclude the cracking process.
Residual stress analysis of an aircraft landing gear part using neutron diffraction
NASA Astrophysics Data System (ADS)
Shin, Eunjoo; Seong, Baek Seok; Sim, Cheul Muu
2013-07-01
The residual stress of a landing gear part of a fighter jet that has a frequent practice of takeoff and landing was evaluated for the safety. The sample was a cylindrical steel bar with a 22.2 mm diameter and 55 mm length used to fix the main landing gear to the aircraft body. For a deep measurement up to 6 mm, we used a neutron beam. From the measurements, the tensile and compressive strain in the axial direction were observed around one side of the pin hole which was across the steel bar vertically with an 8 mm diameter. The strain distribution along the length of the bar presented a similar tendency through the thickness and a larger value on the surface. The maximum value of the residual stress around the pin hole was about 100 MPa. However, there was no strain on the opposite side of the pin hole. From the results, it may be surmised that the steel bar received a steady force in one direction around the pin hole, however the force was weak and affected a small limited area and thus not influence on the steel bar on the whole.
Effects of residual stresses on fracture of welded pipes
Hou, Y.C.; Kim, M,; Pan, J.; Brust, F.W.
1996-12-01
Thermal residual stresses induced by multi-pass butt welding processes of stainless steel pipes are obtained by a thermoelastic-plastic finite element analysis with the assumption of axisymmetric conditions. After the welding processes, circumferential part-through cracks are introduced at the locations having the highest axial residual stress. Crack-tip parameters are sought for characterizing the crack-tip stress and deformation field under subsequent applied axial stresses. The computational results indicate that without residual stress mitigation processes, the residual stresses are quite large and the J integrals for several arbitrary paths are path dependent under the range of axial stresses. Therefore, J cannot be used as a characterizing parameter under the applied stresses. The results also show that, as the axial stress becomes large, the J integrals for different paths follow the same trend as those without residual stresses. This indicates that the residual stress effects become less significant when the deformation due to the applied axial stress becomes dominant. Finally, a computationally convenient parameter, the crack tip opening angle (CTOA), which can take into account the effects of residual stresses near the tip, is adopted for characterizing the crack tip deformation. The CTOA results suggest that with residual stresses the propensity for subcritical crack growth via a stress corrosion cracking or fatigue crack growth mechanism in welds may be higher than that without residual stresses.
Residual Stress Analysis of Boronized AISI 1018 Steel by Synchrotron Radiation
Payne, J A; Petrova, R S; White, H J; Chauhan, A; Bai, Jianming
2008-01-01
AISI 1018 steel substrates were powder-pack, diffusion boronized at 850 C for 4 h, followed by air quenching. Optical microscopy in conjunction with color etching was used to obtain the average penetration depth of the iron monoboride layer (9 {micro}m) and the iron diboride layer (57 {micro}m). X-ray diffraction by synchrotron radiation, conducted at the National Synchrotron Light Source in Brookhaven National Laboratory, confirmed the presence of iron monoboride and iron diboride in the boronized plain steel substrates. The sin{sup 2} {Psi} technique was employed to calculate the residual stress found in the iron monoboride layer (-237 MPa) and in the substrate layer (-150 MPa) that is intertwined with the needle-like, iron diboride penetration.
Analysis of Residual Stress for Narrow Gap Welding Using Finite Element Method
NASA Astrophysics Data System (ADS)
Lee, Choon Yeol; Hwang, Jae Keun; Bae, Joon Woo
Reactor coolant loop (RCL) pipes circulating the heat generated in a nuclear power plant consist of so large diameter pipes that the installation of these pipes is one of the major construction processes. Conventionally, a shield metal arc welding (SMAW) process has been mainly used in RCL piping installations, which sometimes caused severe deformations, dislocation of main equipments and various other complications due to excessive heat input in welding processes. Hence, automation of the work of welding is required and narrow-gap welding (NGW) process is being reviewed for new nuclear power plants as an alternative method of welding. In this study, transient heat transfer and thermo-elastic-plastic analyses have been performed for the residual stress distribution on the narrow gap weldment of RCL by finite element method under various conditions including surface heat flux and temperature dependent thermo-physical properties.
Measurements of residual stress in fracture mechanics coupons
Prime, Michael B; Hill, Michael R; Nav Dalen, John E
2010-01-01
This paper describes measurements of residual stress in coupons used for fracture mechanics testing. The primary objective of the measurements is to quantify the distribution of residual stress acting to open (and/or close) the crack across the crack plane. The slitting method and the contour method are two destructive residual stress measurement methods particularly capable of addressing that objective, and these were applied to measure residual stress in a set of identically prepared compact tension (C(T)) coupons. Comparison of the results of the two measurement methods provides some useful observations. Results from fracture mechanics tests of residual stress bearing coupons and fracture analysis, based on linear superposition of applied and residual stresses, show consistent behavior of coupons having various levels of residual stress.
NASA Astrophysics Data System (ADS)
Čuma, Matúš; Török, Jozef; Telišková, Monika
2016-12-01
Surface integrity is a broad term which includes various quality factors affecting the functional properties of parts. Residual stress is one of these factors. Machining generates residual stresses in the surface and subsurface layers of the structural elements. X-ray diffractometry is a non-destructive method applicable for the measurement of residual stresses in surface and subsurface layers of components. The article is focused on the non-destructive progressive method of triaxial measurement of residual stress after machining the surface of sample by high feed milling technology. Significance of triaxial measuring is the capability of measuring in different angles so it is possible to acquire stress tensor containing normal and shear stress components acting in the spot of measuring, using a Cartesian coordinate system.
Residual stress depth profiles of ausrolled 9310 gear steel
Paliani, C.M.; Queeney, R.A.; Kozaczek, K.J.
1995-12-31
Residual Stress analysis utilizing x-ray diffraction in conjunction with material removal by chemical polishing provides a very effective method of analyzing the near surface residual stress profile of steels. In this experiment, residual stress profiling has been used to analyze the effects of surface ausrolling during the marquenching of a 9310 gear steel which has been carburized to 1% carbon. The ausrolling process is an advanced thermomechanical processing technique used to ausform only the critical surface layer of gears and produce a hard, tough, fine-grained martensitic product. This study compares the residual stress profile of a marquenched specimen with a moderately deformed ausrolled specimen and with a heavily deformed ausrolled specimen, in order to correlate the effects of residual stress with the improved fatigue properties of the gear steel. While no significant variation was observed between the residual stress profile of the marquenched specimens (no deformation) and the line contact ausrolled specimens (moderate deformation), significant increases in the amount of compressive residual stress was noted in the residual stress profile of the point contact ausrolled (heavily deformed) samples. The maximum increase in compressive residual stress due to point contact ausrolling was approximately 500 MPa, when compared to the marquenched sample. This increased residual compressive stress will lower the effective shear stresses during rolling contact fatigue and would therefore explain some of the increase the rolling contact fatigue endurance of the point contact ausrolled specimens.
An Investigation of Residual Stresses in Machined Silicon Nitride
1992-07-01
passing the particles through a 325-mesh screen. Methodologies for the experimental determination of residual stress include Barkhausen noise analysis...AD-A254 635 ~jjMTL TR 92-46 - 154 kDl AN INVESTIGATION OF RESIDUAL STRESSES IN MACHINED SILICON NITRIDE DANIEL J. SNOHA U.S. ARMY MATERIALS...NUMBER MTL TR 92-46 4. TITLE (and Subtitle) 5. TYPE OF REPORT & PERIOD COVERED AN INVESTIGATION OF RESIDUAL STRESSES IN Final Report MACHINED SILICON
NASA Astrophysics Data System (ADS)
Memarianfard, H.; Turusov, R. A.
2016-09-01
A numerical multiscale analysis to predict the residual thermal stresses occurring during cooling in thick-walled filament-wound cylinders made of a reinforced polymer at macro-and microscales is presented. Two types of contact — bonded and unbonded — between the mandrel and the composite are considered. The fields of microstresses are calculated in three different zones across the thickness of the cylinder by using the multiscale finite-element method. Results of the microscale analysis showed that the microstresses several times exceeded the macrostresses in these areas. The value and position of the maximum microstresses were found to depend on the type of contact between the mandrel and the thick-walled cylinder.
Residual stress determination from a laser-based curvature measurement
W. D. Swank; R. A. Gavalya; J. K. Wright; R. N. Wright
2000-05-08
Thermally sprayed coating characteristics and mechanical properties are in part a result of the residual stress developed during the fabrication process. The total stress state in a coating/substrate is comprised of the quench stress and the coefficient of thermal expansion (CTE) mismatch stress. The quench stress is developed when molten particles impact the substrate and rapidly cool and solidify. The CTE mismatch stress results from a large difference in the thermal expansion coefficients of the coating and substrate material. It comes into effect when the substrate/coating combination cools from the equilibrated deposit temperature to room temperature. This paper describes a laser-based technique for measuring the curvature of a coated substrate and the analysis required to determine residual stress from curvature measurements. Quench stresses were determined by heating the specimen back to the deposit temperature thus removing the CTE mismatch stress. By subtracting the quench stress from the total residual stress at room temperature, the CTE mismatch stress was estimated. Residual stress measurements for thick (>1mm) spinel coatings with a Ni-Al bond coat on 304 stainless steel substrates were made. It was determined that a significant portion of the residual stress results from the quenching stress of the bond coat and that the spinel coating produces a larger CTE mismatch stress than quench stress.
Residual Stress Determination from a Laser-Based Curvature Measurement
Swank, William David; Gavalya, Rick Allen; Wright, Julie Knibloe; Wright, Richard Neil
2000-05-01
Thermally sprayed coating characteristics and mechanical properties are in part a result of the residual stress developed during the fabrication process. The total stress state in a coating/substrate is comprised of the quench stress and the coefficient of thermal expansion (CTE) mismatch stress. The quench stress is developed when molten particles impact the substrate and rapidly cool and solidify. The CTE mismatch stress results from a large difference in the thermal expansion coefficients of the coating and substrate material. It comes into effect when the substrate/coating combination cools from the equilibrated deposit temperature to room temperature. This paper describes a laser-based technique for measuring the curvature of a coated substrate and the analysis required to determine residual stress from curvature measurements. Quench stresses were determined by heating the specimen back to the deposit temperature thus removing the CTE mismatch stress. By subtracting the quench stress from the total residual stress at room temperature, the CTE mismatch stress was estimated. Residual stress measurements for thick (>1mm) spinel coatings with a Ni-Al bond coat on 304 stainless steel substrates were made. It was determined that a significant portion of the residual stress results from the quenching stress of the bond coat and that the spinel coating produces a larger CTE mismatch stress than quench stress.
Portnoy, S; Yarnitzky, G; Yizhar, Z; Kristal, A; Oppenheim, U; Siev-Ner, I; Gefen, A
2007-01-01
Fitting of a prosthetic socket is a critical stage in the process of rehabilitation of a trans-tibial amputation (TTA) patient, since a misfit may cause pressure ulcers or a deep tissue injury (DTI: necrosis of the muscle flap under intact skin) in the residual limb. To date, prosthetic fitting typically depends on the subjective skills of the prosthetist, and is not supported by biomedical instrumentation that allows evaluation of the quality of fitting. Specifically, no technology is presently available to provide real-time continuous information on the internal distribution of mechanical stresses in the residual limb during fitting of the prosthesis, or while using it and this severely limits patient evaluations. In this study, a simplified yet clinically oriented patient-specific finite element (FE) model of the residual limb was developed for real-time stress analysis. For this purpose we employed a custom-made FE code that continuously calculates internal stresses in the residual limb, based on boundary conditions acquired in real-time from force sensors, located at the limb-prosthesis interface. Validation of the modeling system was accomplished by means of a synthetic phantom of the residual limb, which allowed simultaneous measurements of interface pressures and internal stresses. Human studies were conducted subsequently in five TTA patients. The dimensions of bones and soft tissues were obtained from X-rays of the residual limb of each patient. An indentation test was performed in order to obtain the effective elastic modulus of the soft tissues of the residual limb. Seven force sensors were placed between the residual limb and the prosthetic liner, and subjects walked on a treadmill during analysis. Generally, stresses under the shinbones were approximately threefold higher than stresses at the soft tissues behind the bones. Usage of a thigh corset decreased the stresses in the residual limb during gait by approximately 80%. Also, the stresses
A finite element model for residual stress in repair welds
Feng, Z.; Wang, X.L.; Spooner, S.; Goodwin, G.M.; Maziasz, P.J.; Hubbard, C.R.; Zacharia, T.
1996-03-28
This paper describes a three-dimensional finite element model for calculation of the residual stress distribution caused by repair welding. Special user subroutines were developed to simulate the continuous deposition of filler metal during welding. The model was then tested by simulating the residual stress/strain field of a FeAl weld overlay clad on a 2{1/4}Cr-1 Mo steel plate, for which neutron diffraction measurement data of the residual strain field were available. It is shown that the calculated residual stress distribution was consistent with that determined with neutron diffraction. High tensile residual stresses in both the longitudinal and transverse directions were observed around the weld toe at the end of the weld. The strong spatial dependency of the residual stresses in the region around the weld demonstrates that the common two-dimensional cross-section finite element models should not be used for repair welding analysis.
RESIDUAL STRESS IN HARDENED STEEL CYLINDERS
ultimate strength of the steel and in some instances caused cracking, and (4) stress patterns of interrupted quench specimens were not consistent enough to warrant a conclusion. (Author)...A study was conducted to (1) measure residual stress in hardened steel solid cylinders, (2) correlate the stress values with heat treatments, and (3...develop a dissolution technique. Residual stress patterns for 12 solid cylinders of 4160 steel, heat treated by various methods, were determined
Grinding Induced Changes in Residual Stresses of Carburized Gears
Lemaster, Robert A; Boggs, Bryan L; Bunn, Jeffrey R; Hubbard, Camden R; Watkins, Thomas R
2009-01-01
This paper presents the results of a study performed to measure the change in residual stress that results from the finish grinding of carburized gears. Residual stresses were measured in five gears using the x-ray diffraction equipment in the Large Specimen Residual Stress Facility at Oak Ridge National Laboratory. Two of the gears were hobbed, carburized, quenched and tempered, but not finished. The remaining three gears were processed similarly, but were finish ground. The residual stresses were measured at 64 different locations on a tooth from each gear. Residual stresses were also measured at fewer points on other teeth to determine the tooth-to-tooth variation. Tooth profile measurements were made of the finished and unfinished gear samples. The results show a fairly uniform and constant compressive residual field in the nonfinished gears. There was a significant reduction in the average residual stress measured in the finished gears. Additionally, there was a significant increase in the variability of the residual stress that was introduced by the grinding process. Analysis of the data suggests a linear relationship between the change in average residual stress and the amount of material removed by the grinding process.
1978-12-01
machine and loaded to give a 10,000 psi nominal stress (applied load/reduced cross-section). A Photolastic Inc. Model 031 Reflection Polariscope , equipped...1971. 9. Photolastic Inc., Instruction Manual for 030 Series Reflection Polariscope . 10. Blakely, F. M., Design of Software Package for Incorporation...level to cause yielding at the notch tip. The largest localized strain at the notch was measured with the polariscope . The compensator reading and load
Axial residual stresses in boron fibers
NASA Technical Reports Server (NTRS)
Behrendt, D. R.
1978-01-01
The axial residual stress distribution as a function of radius was determined from the fiber surface to the core including the average residual stress in the core. Such measurements on boron on tungsten (B/W) fibers show that the residual stresses for 102, 142, 203, and 366 micron diameter fibers were similar, being compressive at the surface and changing monotonically to a region of tensile within the boron. At approximately 25 percent of the original radius, the stress reaches a maximum tensile stress of about 860 mn/sq.m and then decreases to a compressive stress near the tungsten boride core. Data were presented for 203 micron diameter B/W fibers that show annealing above 900 C reduces the residual stresses. A comparison between 102 micron diameter B/W and boron on carbon (b/C) shows that the residual stresses were similar in the outer regions of the fibers, but that large differences near and in the core were observed. The effects of these residual stresses on the fracture of boron fibers were discussed.
NASA Astrophysics Data System (ADS)
Heinze, C.; Schwenk, C.; Rethmeier, M.; Caron, J.
2011-06-01
The usage of continuous cooling transformation (CCT) diagrams in numerical welding simulations is state of the art. Nevertheless, specifications provide limits in chemical composition of materials which result in different CCT behavior and CCT diagrams, respectively. Therefore, it is necessary to analyze the influence of variations in CCT diagrams on the developing residual stresses. In the present paper, four CCT diagrams and their effect on numerical calculation of residual stresses are investigated for the widely used structural steel S355J2 + N welded by the gas metal arc welding (GMAW) process. Rather than performing an arbitrary adjustment of CCT behavior, four justifiable data sets were used as input to the numerical calculation: data available in the Sysweld database, experimental data acquired through Gleeble dilatometry tests, and TTT/CCT predictions calculated from the JMatPro and Edison Welding Institute (EWI) Virtual Joining Portal software. The performed numerical analyses resulted in noticeable deviations in residual stresses considering the different CCT diagrams. Furthermore, possibilities to improve the prediction of distortions and residual stress based on CCT behavior are discussed.
Thermal Residual Stress in Environmental Barrier Coated Silicon Nitride - Modeled
NASA Technical Reports Server (NTRS)
Ali, Abdul-Aziz; Bhatt, Ramakrishna T.
2009-01-01
When exposed to combustion environments containing moisture both un-reinforced and fiber reinforced silicon based ceramic materials tend to undergo surface recession. To avoid surface recession environmental barrier coating systems are required. However, due to differences in the elastic and thermal properties of the substrate and the environmental barrier coating, thermal residual stresses can be generated in the coated substrate. Depending on their magnitude and nature thermal residual stresses can have significant influence on the strength and fracture behavior of coated substrates. To determine the maximum residual stresses developed during deposition of the coatings, a finite element model (FEM) was developed. Using this model, the thermal residual stresses were predicted in silicon nitride substrates coated with three environmental coating systems namely barium strontium aluminum silicate (BSAS), rare earth mono silicate (REMS) and earth mono di-silicate (REDS). A parametric study was also conducted to determine the influence of coating layer thickness and material parameters on thermal residual stress. Results indicate that z-direction stresses in all three systems are small and negligible, but maximum in-plane stresses can be significant depending on the composition of the constituent layer and the distance from the substrate. The BSAS and REDS systems show much lower thermal residual stresses than REMS system. Parametric analysis indicates that in each system, the thermal residual stresses can be decreased with decreasing the modulus and thickness of the coating.
Prediction of machining induced residual stresses
NASA Astrophysics Data System (ADS)
Pramod, Monangi; Reddy, Yarkareddy Gopi; Prakash Marimuthu, K.
2017-07-01
Whenever a component is machined, residual stresses are induced in it. These residual stresses induced in the component reduce its fatigue life, corrosion resistance and wear resistance. Thus it is important to predict and control the machining-induced residual stress. A lot of research is being carried out in this area in the past decade. This paper aims at prediction of residual stresses during machining of Ti-6Al-4V. A model was developed and under various combinations of cutting conditions such as, speed, feed and depth of cut, the behavior of residual stresses were simulated using Finite Element Model. The present work deals with the development of thermo-mechanical model to predict the machining induced residual stresses in Titanium alloy. The simulation results are compared with the published results. The results are in good agreement with the published results. Future work involves optimization or the cutting parameters that effect the machining induced residual stresses. The results obtained were validated with previous work.
Cofino, B; Fogarassy, P; Millet, P; Lodini, A
2004-07-01
Plasma-sprayed hydroxyapatite (HA) coatings on titanium alloy are often used in prosthetic implants. The metallic substrate gives the implant good mechanical strength which is combined with good biocompatibility and osteointegration of the ceramic coating. However, the interface between the HA coating and titanium alloy substrate is an area of critical weakness when compared with the interlamellar cohesive strength of the HA coating structure. Knowledge of the stresses in materials near the interface seems to be an important step in understanding why failure occurs. Synchrotron radiation, using Beamline BM16 at the European Synchrotron Radiation Facility (Grenoble, France), has been used to determine local stresses near the interface, down to 10 microm in resolution, between a plasma-sprayed HA coating and a titanium alloy substrate. This experimental determination of residual stresses is compared with the results found by a finite element analysis modeling the thermal effects of the plasma-spraying process. Residual stresses have been found in deposited ceramic near the interface due to a thermal properties mismatch of the materials. If the plane stress state is assumed, meaning the perpendicular component of residual stress is ignored (sigma(z) = 0), then the synchrotron residual stress measurements should be interpreted as mainly compressive in the ceramic coating. This is in contradiction with the coefficient of thermal expansion mismatch; therefore, the simplified plane stresses assumption seems to be inappropriate for the deposited morphology characterized by pores and a network of microcracks. The detailed finite element analysis model, taking into account the real morphology of the coating and the real three-dimensional stress field distribution, allowed the estimation of sigma(z), leading to a more accurate interpretation of synchrotron measurements, which is validated by the experimental results.
Residual stress in silicon wafer using IR polariscope
NASA Astrophysics Data System (ADS)
Lu, Zhijia; Wang, Pin; Asundi, Anand
2008-09-01
The infrared phase shift polariscope (IR-PSP) is a full-field optical technique for stress analysis in Silicon wafers. Phase shift polariscope is preferred to a conventional polariscope, as it can provide quantitative information of the normal stress difference and the shear stress in the specimen. The method is based on the principles of photoelasticity, in which stresses induces temporary birefringence in materials which can be quantitatively analyzed using a phase shift polariscope. Compared to other stress analysis techniques such as x-ray diffraction or laser scanning, infrared photoelastic stress analysis provides full-field information with high resolution and in near real time. As the semiconductor fabrication is advancing, larger wafers, thinner films and more compact packages are being manufactured. This results in a growing demand of process control. Residual stress exist in silicon during semiconductor fabrication and these stresses may make cell processing difficult or even cause the failure of the silicon. Reducing these stresses would improve manufacturability and reliability. Therefore stress analysis is essential to trace the root cause of the stresses. The polariscope images are processed using MATLAB and four-step phase shifting method to provide quantitative as well as qualitative information regarding the residual stress of the sample. The system is calibrated using four-point bend specimen and then the residual stress distribution in a MEMS sample is shown.
Measurment Of Residual Stress In Ferromagnetic Materials
NASA Technical Reports Server (NTRS)
Namkung, Min; Yost, William T.; Kushnick, Peter W.; Grainger, John L.
1992-01-01
Magnetoacoustic (MAC) and magnetoacoustic emission (MAE) techniques combined to provide complete characterization of residual stresses in ferromagnetic structural materials. Combination of MAC and MAE techniques makes it possible to characterize residual tension and compression without being limited by surface conditions and unavailability of calibration standards. Significant in field of characterization of materials as well as detection of fatigue failure.
Residual stress effects in stress-corrosion cracking
NASA Astrophysics Data System (ADS)
Toribio, J.
1998-04-01
This paper describes a wide variety of residual stress effects in stress-corrosion cracking (SCC) of metallic materials on the basis of previous research of the author on high-strength steel in the form of hot-rolled bars and cold-drawn wires for prestressed concrete. It is seen that internal residual stress fields in the material play a very important—if not decisive—role in the SCC behavior of any engineering material, especially residual stresses generated near the free surface or in the vicinity of a crack tip.
Residual stress effects in stress-corrosion cracking
Toribio, J.
1998-04-01
This paper describes a wide variety of residual stress effects in stress-corrosion cracking (SCC) of metallic materials on the basis of previous research of the author on high-strength steel in the form of hot-rolled bars and cold-drawn wires for prestressed concrete. It is seen that internal residual stress fields in the material play a very important -- if not decisive -- role in the SCC behavior of any engineering material, especially residual stresses generated near the free surface or in the vicinity of a crack tip.
Residual Stress Testing of Outer 3013 Containers
Dunn, K.
2004-02-12
A Gas Tungsten Arc Welded (GTAW) outer 3013 container and a laser welded outer 3013 container have been tested for residual stresses according to the American Society for Testing Materials (ASTM) Standard G-36-94 [1]. This ASTM standard describes a procedure for conducting stress-corrosion cracking tests in boiling magnesium chloride (MgCl2) solution. Container sections in both the as-fabricated condition as well as the closure welded condition were evaluated. Significantly large residual stresses were observed in the bottom half of the as-fabricated container, a result of the base to can fabrication weld because through wall cracks were observed perpendicular to the weld. This observation indicates that regardless of the closure weld technique, sufficient residual stresses exist in the as-fabricated container to provide the stress necessary for stress corrosion cracking of the container, at the base fabrication weld. Additionally, sufficiently high residual stresses were observed in both the lid and the body of the GTAW as well as the laser closure welded containers. The stresses are oriented perpendicular to the closure weld in both the container lid and the container body. Although the boiling MgCl2 test is not a quantitative test, a comparison of the test results from the closure welds shows that there are noticeably more through wall cracks in the laser closure welded container than in the GTAW closure welded container.
Residual stress in glass: indentation crack and fractography approaches.
Anunmana, Chuchai; Anusavice, Kenneth J; Mecholsky, John J
2009-11-01
To test the hypothesis that the indentation crack technique can determine surface residual stresses that are not statistically significantly different from those determined from the analytical procedure using surface cracks, the four-point flexure test, and fracture surface analysis. Soda-lime-silica glass bar specimens (4 mm x 2.3 mm x 28 mm) were prepared and annealed at 650 degrees C for 30 min before testing. The fracture toughness values of the glass bars were determined from 12 specimens based on induced surface cracks, four-point flexure, and fractographic analysis. To determine the residual stress from the indentation technique, 18 specimens were indented under 19.6N load using a Vickers microhardness indenter. Crack lengths were measured within 1 min and 24h after indentation, and the measured crack lengths were compared with the mean crack lengths of annealed specimens. Residual stress was calculated from an equation developed for the indentation technique. All specimens were fractured in a four-point flexure fixture and the residual stress was calculated from the strength and measured crack sizes on the fracture surfaces. The results show that there was no significant difference between the residual stresses calculated from the two techniques. However, the differences in mean residual stresses calculated within 1 min compared with those calculated after 24h were statistically significant (p=0.003). This study compared the indentation technique with the fractographic analysis method for determining the residual stress in the surface of soda-lime-silica glass. The indentation method may be useful for estimating residual stress in glass.
Residual stress in glass: indentation crack and fractography approaches
Anunmana, Chuchai; Anusavice, Kenneth J.; Mecholsky, John J.
2009-01-01
Objective To test the hypothesis that the indentation crack technique can determine surface residual stresses that are not statistically significantly different from those determined from the analytical procedure using surface cracks, the four-point flexure test, and fracture surface analysis. Methods Soda-lime-silica glass bar specimens (4 mm × 2.3 mm × 28 mm) were prepared and annealed at 650 °C for 30 min before testing. The fracture toughness values of the glass bars were determined from 12 specimens based on induced surface cracks, four-point flexure, and fractographic analysis. To determine the residual stress from the indentation technique, 18 specimens were indented under 19.6 N load using a Vickers microhardness indenter. Crack lengths were measured within 1 min and 24 h after indentation, and the measured crack lengths were compared with the mean crack lengths of annealed specimens. Residual stress was calculated from an equation developed for the indentation technique. All specimens were fractured in a four-point flexure fixture and the residual stress was calculated from the strength and measured crack sizes on the fracture surfaces. Results The results show that there was no significant difference between the residual stresses calculated from the two techniques. However, the differences in mean residual stresses calculated within 1 min compared with those calculated after 24 h were statistically significant (p=0.003). Significance This study compared the indentation technique with the fractographic analysis method for determining the residual stress in the surface of soda-lime silica glass. The indentation method may be useful for estimating residual stress in glass. PMID:19671475
Measuring depth profiles of residual stress with Raman spectroscopy
Enloe, W.S.; Sparks, R.G.; Paesler, M.A.
1988-12-01
Knowledge of the variation of residual stress is a very important factor in understanding the properties of machined surfaces. The nature of the residual stress can determine a part`s susceptibility to wear deformation, and cracking. Raman spectroscopy is known to be a very useful technique for measuring residual stress in many materials. These measurements are routinely made with a lateral resolution of 1{mu}m and an accuracy of 0.1 kbar. The variation of stress with depth; however, has not received much attention in the past. A novel technique has been developed that allows quantitative measurement of the variation of the residual stress with depth with an accuracy of 10nm in the z direction. Qualitative techniques for determining whether the stress is varying with depth are presented. It is also demonstrated that when the stress is changing over the volume sampled, errors can be introduced if the variation of the stress with depth is ignored. Computer aided data analysis is used to determine the depth dependence of the residual stress.
PUFF TOO: a residual stress experiment
Smith, C.W.
1980-04-01
Following the passage of the dynamic effects in a contained explosive detonation, there remains a strong compressive stress field in the material about the cavity. In this experiment, a 454-kg (1000 lb) sphere of high explosive was detonated in saturated ashfall tuff. Instrumentation measured peak stresses over the range of 0.1 to 6.0 GPa (1 to 6 kbar) and the complete stress-time waveform, including the so-called residual stress, at the 0.1 GPa (1 kbar) peak stress range. Mineback revealed detonation-induced fractures and fractures induced by postevent work.
NASA Astrophysics Data System (ADS)
Trufanov, Aleksandr N.; Trufanov, Nikolay A.; Semenov, Nikita V.
2016-09-01
The experimental data analysis of the stress applying rod section geometry for the PANDA-type polarization maintaining optical fiber has been performed. The dependencies of the change in the radial dimensions of the preform and the doping boundary on the angular coordinate have been obtained. The original algorithm of experimental data statistic analysis, which enables determination of the specimens' characteristic form of section, has been described. The influence of actual doped zone geometry on the residual stress fields formed during the stress rod preform fabrication has been investigated. It has been established that the deviation of the boundary between pure silica and the doped zone from the circular shape results in dissymmetry and local concentrations of the residual stress fields along the section, which can cause preforms destruction at high degrees of doping. The observed geometry deviations of up to 10% lead to the increase of the maximum stress intensity value by over 20%.
Residual stress characterization for laminated composites
NASA Astrophysics Data System (ADS)
Liu, Shao-Chun
With increasing applications of advanced laminated composites, process-induced residual stress has drawn more and more attention in recent years. Efforts have been devoted to understanding residual stress both quantitatively and qualitatively. In the current study, a novel technique called the Cure Referencing Method was developed which has the capability for measuring the residual stress on the symmetric laminated composite plates. It can also differentiate residual stress into two components: one is due to the mismatch of the coefficient of thermal expansion, the other is caused by the matrix chemical curing shrinkage. The chemical curing shrinkage of the polymer matrix was investigated in further detail. A technique was developed to measure the post-gel chemical curing shrinkage which is the portion of curing shrinkage that really induces the residual stress in the polymer matrix composites. Time-dependent material property is another issue associated with polymer matrix composite materials. The data of several short-term tensile creep tests run at different temperature were used to construct a linear viscoelastic: model for describing the behavior of the composites over a long period of time. It was found that physical aging of the polymer matrix needs to be taken into account in order to have a more accurate representation of the long-term behavior. A fair agreement was obtained between the result of the long-term creep test and the master curve constructed from several momentary creep tests.
Stefenelli, Mario; Todt, Juraj; Riedl, Angelika; Ecker, Werner; Müller, Thomas; Daniel, Rostislav; Burghammer, Manfred; Keckes, Jozef
2013-10-01
Novel scanning synchrotron cross-sectional nanobeam and conventional laboratory as well as synchrotron Laplace X-ray diffraction methods are used to characterize residual stresses in exemplary 11.5 µm-thick TiN coatings. Both real and Laplace space approaches reveal a homogeneous tensile stress state and a very pronounced compressive stress gradient in as-deposited and blasted coatings, respectively. The unique capabilities of the cross-sectional approach operating with a beam size of 100 nm in diameter allow the analysis of stress variation with sub-micrometre resolution at arbitrary depths and the correlation of the stress evolution with the local coating microstructure. Finally, advantages and disadvantages of both approaches are extensively discussed.
Residual stress measurements in carbon steel
NASA Technical Reports Server (NTRS)
Heyman, J. S.; Min, N.
1986-01-01
External dc magnetic field-induced changes in natural velocity of Rayleigh surface waves were measured in steel specimens under various stress conditions. The low field slopes of curves representing the fractional changes of natural velocity were proved to provide correct stress information in steels with different metallurgical properties. The slopes of curves under uniaxial compression, exceeding about one third of the yield stress, fell below zero in all the specimens when magnetized along the stress axis. The slopes under tension varied among different steels but remained positive in any circumstances. The stress effect was observed for both applied and residual stress. A physical interpretation of these results is given based on the stress-induced domain structure changes and the delta epsilon effect. Most importantly, it is found that the influence of detailed metallurgical properties cause only secondary effects on the obtained stress information.
Mechanically induced residual stresses: Modelling and characterisation
NASA Astrophysics Data System (ADS)
Stranart, Jean-Claude E.
Accurate characterisation of residual stress represents a major challenge to the engineering community. This is because it is difficult to validate the measurement and the accuracy is doubtful. It is with this in mind that the current research program concerning the characterisation of mechanically induced residual stresses was undertaken. Specifically, the cold expansion of fastener holes and the shot peening treatment of aerospace alloys, aluminium 7075 and titanium Ti-6Al-4V, are considered. The objective of this study is to characterise residual stresses resulting from cold working using three powerful techniques. These are: (i) theoretical using three dimensional non-linear finite element modelling, (ii) semi-destructive using a modified incremental hole drilling technique and (iii) nondestructive using a newly developed guided wave method supplemented by traditional C-scan measurements. The three dimensional finite element results of both simultaneous and sequential cold expansion of two fastener holes revealed the importance of the separation distance, the expansion level and the loading history upon the development and growth of the plastic zone and unloading residual stresses. It further showed that the commonly adopted two dimensional finite element models are inaccurate and incapable of predicting these residual stresses. Similarly, the dynamic elasto-plastic finite element studies of shot peening showed that the depth of the compressed layer, surface and sub-surface residual stresses are significantly influenced by the shot characteristics. Furthermore, the results reveal that the separation distance between two simultaneously impacting shots governs the plastic zone development and its growth. In the semi-destructive incremental hole drilling technique, the accuracy of the newly developed calibration coefficients and measurement techniques were verified with a known stress field and the method was used to measure peening residual stresses. Unlike
System and method for measuring residual stress
Prime, Michael B.
2002-01-01
The present invention is a method and system for determining the residual stress within an elastic object. In the method, an elastic object is cut along a path having a known configuration. The cut creates a portion of the object having a new free surface. The free surface then deforms to a contour which is different from the path. Next, the contour is measured to determine how much deformation has occurred across the new free surface. Points defining the contour are collected in an empirical data set. The portion of the object is then modeled in a computer simulator. The points in the empirical data set are entered into the computer simulator. The computer simulator then calculates the residual stress along the path which caused the points within the object to move to the positions measured in the empirical data set. The calculated residual stress is then presented in a useful format to an analyst.
NASA Astrophysics Data System (ADS)
Nierlich, Wolfgang; Gegner, Jürgen
The conventional procedure of X-ray diffraction (XRD) residual stress measurement is improved by means of a modification of the beam path of the diffractometer and an iterative technique that includes a pre-analysis of the nearpeak line-profile. The achieved short measuring times of 5 and around 10 min per residual stress value and retained austenite content, respectively, serve as precondition for routine industrial applications over the last three decades within SKF. The line width represents a measure of material ageing within the lifetime cycle of a rolling bearing: calibration curves for the (near-) surface and the sub-surface failure mode are presented. Material response analysis permits differentiation of these failure modes and between low- and high-cycle fatigue.
Modeling Residual Stresses in Ceramic Plates
Cantavella, V.; Moreno, A.; Mezquita, A.; Reig, Y.
2008-02-15
The generation of residual stresses during cooling of layered ceramic plates has been modeled. Each plate comprises a body and two thin layers (engobe and glaze). The model takes into account two types of stresses: thermal stresses, resulting from temperature gradients inside the plate during cooling, and the stresses produced by the mismatch of the coefficient of thermal expansion (CTE) of the layers. The body has been simulated using a linear viscoelastic constitutive equation. The engobe and the glaze layer have been considered as elastic solids below a certain temperature (setting temperature: T{sub a}). Above T{sub a} these two layers have no mechanical influence on the body.
Modeling Residual Stresses in Ceramic Plates
NASA Astrophysics Data System (ADS)
Cantavella, V.; Moreno, A.; Mezquita, A.; Reig, Y.
2008-02-01
The generation of residual stresses during cooling of layered ceramic plates has been modeled. Each plate comprises a body and two thin layers (engobe and glaze). The model takes into account two types of stresses: thermal stresses, resulting from temperature gradients inside the plate during cooling, and the stresses produced by the mismatch of the coefficient of thermal expansion (CTE) of the layers. The body has been simulated using a linear viscoelastic constitutive equation. The engobe and the glaze layer have been considered as elastic solids below a certain temperature (setting temperature: Ta). Above Ta these two layers have no mechanical influence on the body.
Residual contact stresses in cryotechnical environments
NASA Astrophysics Data System (ADS)
Cretegny, J. F.; Demonicault, J. M.
Two examples were chosen to show the use of residual stress measurements in the evaluation and comprehension of possible ruptures of parts subjected to the working conditions of cryogenic turbomachines which induce wear of the surfaces in dry contact. The examples concern the ball bearings and spline of the liquid hydrogen pump of the Vulcain engine to be used on Ariane 5. The Ariane program is introduced and tribological problems of the cryogenic technique are discussed. The utility of the residual stress measurements is assessed.
A new approach for the influence of residual stress on fatigue crack propagation
NASA Astrophysics Data System (ADS)
Zhu, Lin; Jia, Min-Ping
Many manufacturing processes can induce residual stresses in produced components. These residual stresses influence the mean stress during cyclic loading. The initial residual stresses induced during manufacturing change during fatigue damage. This paper presents a research on the change of residual stress distribution during fatigue crack propagation; the research predicts crack propagation by considering residual stress. An analysis approach for the change in residual stress distribution is established according to the diffusion theory of cavity, which is also used to investigate cracks with different orientations. Experiments are conducted to verify the prediction results of residual stress. A probability density function based on Weibull distribution is established to evaluate the accuracy of predicted residual stress. The influence of residual stress on fatigue crack propagation is considered the effective stress intensity factor range, which is calculated under the combined stress field of applied stress and residual stress. An analysis model of crack propagation is established. Furthermore, the model of crack propagation is used to estimate the velocity of crack propagation for the cases, same as the cases of residual stress prediction. The case studies show that the results are basically identical with the experimental results, indicating that the proposed approach is acceptable.
Residual stresses in bilayer dental ceramics.
Taskonak, Burak; Mecholsky, John J; Anusavice, Kenneth J
2005-06-01
It is clinically observed that lithia-disilicate-based all-ceramic fixed partial dentures (FPD) can fail because of the fragmentation of the veneering material. The hypothesis of this study is that the global residual stresses within the surface of those veneered FPDs may be responsible for partial fragmentation of the veneering ceramic. Bilayer and monolithic ceramic composites were prepared using a lithia disilicate based (Li2OSiO2) glass-ceramic core and a glass veneer. A four-step fracture mechanics approach was used to analyze residual stress in bilayered all-ceramic FPDs. We found a statistically significant increase in the mean flexural strengths of bilayer specimens compared with monolithic glass specimens (p < or = 0.05). There was a statistically significant difference between the mean longitudinal and transverse indentation-induced crack sizes in bilayer specimens (p < or = 0.05), which indicates the existence of residual stress. Global residual stresses in the veneer layer, calculated using a fracture mechanics equation, were determined to be responsible for the increased strength and observed chipping, i.e., spallation in bilayer ceramic composites.
Measuring Residual Stress Using Nonlinear Ultrasound
NASA Astrophysics Data System (ADS)
Liu, M.; Kim, J.-Y.; Qu, J.; Jacobs, L. J.
2010-02-01
Near-surface compressive residual stresses, which are generated by shot peening, are known to retard crack initiation and thus extend the fatigue life of a metal component. The ability to effectively measure these near-surface residual stresses would greatly help predict the fatigue life of shot-peened components. This research uses the nonlinear surface acoustic wave technique to measure the residual stresses in a shot-peened component. Experiments are conducted on three different aluminum alloy (AA 7075) samples: as-received with no peeing, and shot-peened at the Almen intensities of 8A and 16A. Surface roughness measurements are also carried out for these three samples. The nonlinear ultrasonic results show that the measured acoustic nonlinearity parameter increases by 81% and 115% for the 8A and 16A samples. These large increases in measured acoustic nonlinearity clearly indicate the potential of the nonlinear ultrasonic technique as an NDE tool to measure the near-surface residual stresses. The effects of surface roughness on the ultrasonic measurement are briefly examined. Finally, a preliminary model prediction is presented to interpret the experimental results.
Residual Stresses and Critical Initial Flaw Size Analyses of Welds
NASA Technical Reports Server (NTRS)
Brust, Frederick W.; Raju, Ivatury, S.; Dawocke, David S.; Cheston, Derrick
2009-01-01
An independent assessment was conducted to determine the critical initial flaw size (CIFS) for the flange-to-skin weld in the Ares I-X Upper Stage Simulator (USS). A series of weld analyses are performed to determine the residual stresses in a critical region of the USS. Weld residual stresses both increase constraint and mean stress thereby having an important effect on the fatigue life. The purpose of the weld analyses was to model the weld process using a variety of sequences to determine the 'best' sequence in terms of weld residual stresses and distortions. The many factors examined in this study include weld design (single-V, double-V groove), weld sequence, boundary conditions, and material properties, among others. The results of this weld analysis are included with service loads to perform a fatigue and critical initial flaw size evaluation.
Residual stresses and plastic deformation in GTA-welded steel
Brand, P.C. ); Keijser, T.H. de; Ouden, G. den )
1993-03-01
Residual stresses and plastic deformation in single pass GTA welded low-carbon steel were studied by means of x-ray diffraction in combination with optical microscopy and hardness measurements. The residual stresses and the amount of plastic deformation (microstrain) were obtained from x-ray diffraction line positions and line broading. Since the plates were polished before welding, it was possible to observe in the optical microscope two types of Lueders bands. During heating curved Lueders bands and during cooling straight Lueders bands perpendicular to the weld are formed. The curved Lueders bands extend over a larger distance from the weld than the straight Lueders bands. The amount of plastic deformation as obtained from the x-ray diffraction analysis is in agreement with these observations. An explanation is offered for the stresses measured in combination with plastic deformations observed. It is concluded that in the present experiments plastic deformation is the main cause of the residual stresses.
Effects of cutting and specimen size on neutron measurement of residual stresses
NASA Astrophysics Data System (ADS)
Law, M.; Luzin, V.; Kirstein, O.
2010-11-01
To perform neutron residual stress measurements it is often necessary to cut samples to a manageable size. The effects of cutting a girth welded pipe were investigated with analytical methods and finite element analysis. The effect of cutting on measured stresses was calculated. A simplified method of modelling residual stresses in welds, "chill modelling", is introduced. In ring slitting a cut is made in the axial direction and the deformation is maeesured. The change in elastic stress can be calculated and added to neutron diffraction measurements made on a cut ring to calculate the original stresses. Residual stress measurements were performed to validate the ring slitting correction using ANSTO's residual stress diffractometer Kowari.
NASA Astrophysics Data System (ADS)
Shrestha, Triratna
Modified 9Cr-1 Mo (Grade 91) steel is currently considered as a candidate material for reactor pressure vessels (RPVs) and reactor internals for the Very High Temperature Reactor (VHTR), and in fossil-fuel fired power plants at higher temperatures and stresses. The tensile creep behavior of Grade 91 steel was studied in the temperature range of 600°C to 750°C and stresses between 35 MPa and 350 MPa. Heat treatment of Grade 91 steel was studied by normalizing and tempering the steel at various temperatures and times. Moreover, Thermo-Ca1c(TM) calculation was used to predict the precipitate stability and their evolution, and construct carbon isopleths of Grade 91 steel. Residual stress distribution across gas tungsten arc welds (GTAW) in Grade 91 steel was measured by the time-of-flight neutron diffraction using the Spectrometer for Materials Research at Temperature and Stress (SMARTS) diffractometer at Lujan Neutron Scattering Center, Los Alamos National Laboratory, Los Alamos, NM, USA. Analysis of creep results yielded stress exponents of ˜9-11 in the higher stress regime and ˜1 in the lower stress regime. The creep behavior of Grade 91 steel was described by the modified Bird-Mukherjee-Dorn relation. The rate-controlling creep deformation mechanism in the high stress regime was identified as the edge dislocation climb with a stress exponent of n = 5. On the other hand, the deformation mechanism in the Newtonian viscous creep regime (n = 1) was identified as the Nabarro-Herring creep. Creep rupture data were analyzed in terms of Monkman-Grant relation and Larson-Miller parameter. Creep damage tolerance factor and stress exponent were used to identify the cause of creep damage. The fracture surface morphology of the ruptured specimens was studied by scanning electron microscopy to elucidate the failure mechanisms. Fracture mechanism map for Grade 91 steel was developed based on the available material parameters and experimental observations. The microstructural
Characterization of welding residual stresses with neutron diffraction
Wang, X.L.; Spooner, S.; Hubbard, C.R.; Taljat, B.; Feng, Z.
1998-03-01
Welding residual stresses are a key concern in the fabrication and use of structural components containing welds. Residual stresses in welds are caused by non-uniform expansion and shrinkage of differently heated zones during the thermal transient of a weld pass. In some alloys, solid state phase transformations occurring during the welding transient contribute additional residual stresses. Manufacturing problems arising from welding residual stresses include cracking and dimensional distortion. During use, tensile stresses in the welded zone limit the fatigue resistance of the component under cyclic loading. In an aggressive environment, tensile welding residual stresses also create a necessary condition for stress-corrosion cracking to take place.
Finite element calculation of residual stress in dental restorative material
NASA Astrophysics Data System (ADS)
Grassia, Luigi; D'Amore, Alberto
2012-07-01
A finite element methodology for residual stresses calculation in dental restorative materials is proposed. The material under concern is a multifunctional methacrylate-based composite for dental restorations, activated by visible light. Reaction kinetics, curing shrinkage, and viscoelastic relaxation functions were required as input data on a structural finite element solver. Post cure effects were considered in order to quantify the residual stresses coming out from natural contraction with respect to those debited to the chemical shrinkage. The analysis showed for a given test case that residual stresses frozen in the dental restoration at uniform temperature of 37°C are of the same order of magnitude of the strength of the dental composite material per se.
Patterns of residual stresses due to welding
NASA Technical Reports Server (NTRS)
Botros, B. M.
1983-01-01
Residual stresses caused by welding result from the nonuniform rate of cooling and the restrained thermal contraction or non-uniform plastic deformation. From the zone of extremely high temperature at the weld, heat flows into both the adjoining cool body and the surrounding atmosphere. The weld metal solidifies under very rapid cooling. The plasticity of the hot metal allows adjustment initially, but as the structure cools the rigidity of the surrounding cold metal inhibits further contraction. The zone is compressed and the weld is put under tensile stresses of high magnitude. The danger of cracking in these structural elements is great. Change in specific volume is caused by the change in temperature.
Residual Stresses Measured In Quenched HSLA-100 Steel Plate.
Prime, M. B.
2005-01-01
Residual stresses over the cross section of a 60.75 mm thick plate of HSLA-100 steel were measured using the contour method. HSLA-100 is a low carbon, copper precipitation hardened, High-Strength Low-Alloy steel used for naval ship hulls, armor, and containment vessels. The material was prepared by hot cross-rolling, Austenitizing at 900 C for 75 minutes and water quenching, and then tempering at 660 C for 200 minutes followed by another water quench. A cross-sectional map of residual stresses was measured using the contour method: (1) the specimen was carefully cut in two using wire electric discharge machining; (2) the contour of the cut surfaces were measured by using a Coordinate Measuring Machine; and (3) the residual stresses were determined from the measured contours using a 3-D elastic finite element (FE) model. The results showed a typical quenching stress distribution with peak compressive stress of about 165 MPa a few mm below the surface and tensile stress of 200 MPa in the center of the plate thickness. The stress magnitudes, at less than 30% of yield, are somewhat low for water-quenched steels, which is discussed. An FE analysis showed that edge effects in the measured stress map were shown to be consistent with relaxation from removing the test specimen from a larger plate.
Lamination residual stresses in fiber composites
NASA Technical Reports Server (NTRS)
Daniel, I. M.; Liber, T.
1975-01-01
An experimental investigation was conducted to determine the magnitude of lamination residual stresses in angle-ply composites and to evaluate their effects on composite structural integrity. The materials investigated were boron/epoxy, boron/polyimide, graphite/low modulus epoxy, graphite/high modulus epoxy, graphite/polyimide and s-glass/epoxy. These materials were fully characterized. Static properties of laminates were also determined. Experimental techniques using embedded strain gages were developed and used to measure residual strains during curing. The extent of relaxation of lamination residual stresses was investigated. It was concluded that the degree of such relaxation is low. The behavior of angle-ply laminates subjected to thermal cycling, tensile load cycling, and combined thermal cycling with tensile load was investigated. In most cases these cycling programs did not have any measurable influence on residual strength and stiffness of the laminates. In the tensile load cycling tests, the graphite/polyimide shows the highest endurance with 10 million cycle runouts at loads up to 90 percent of the static strength.
Measurement of residual stresses using fracture mechanics weight functions
Fan, Y.
2000-10-01
A residual stress measurement method has been developed to quantify through-the-thickness residual stresses. Accurate measurement of residual stresses is crucial for many engineering structures. Fabrication processes such as welding and machining generate residual stresses that are difficult to predict. Residual stresses affect the integrity of structures through promoting failures due to brittle fracture, fatigue, stress corrosion cracking, and wear. In this work, the weight function theory of fracture mechanics is used to measure residual stresses. The weight function theory is an important development in computational fracture mechanics. Stress intensity factors for arbitrary stress distribution on the crack faces can be accurately and efficiently computed for predicting crack growth. This paper demonstrates that the weight functions are equally useful in measuring residual stresses. In this method, an artificial crack is created by a thin cut in a structure containing residual stresses. The cut relieves the residual stresses normal to the crack-face and allows the relieved residual stresses to deform the structure. Strain gages placed adjacent to the cut measure the relieved strains corresponding to incrementally increasing depths of the cut. The weight functions of the cracked body relate the measured strains to the residual stresses normal to the cut within the structure. The procedure details, such as numerical integration of the singular functions in applying the weight function method, will be discussed.
Residual stresses and vector hysteresis modeling
NASA Astrophysics Data System (ADS)
Ktena, Aphrodite
2016-04-01
Residual stresses in magnetic materials, whether the result of processing or intentional loading, leave their footprint on macroscopic data, such hysteresis loops and differential permeability measurements. A Preisach-type vector model is used to reproduce the phenomenology observed based on assumptions deduced from the data: internal stresses lead to smaller and misaligned grains, hence increased domain wall pinning and angular dispersion of local easy axes, favouring rotation as a magnetization reversal mechanism; misaligned grains contribute to magnetostatic fields opposing the direction of the applied field. The model is using a vector operator which accounts for both reversible and irreversible processes; the Preisach concept for interactions for the role of stress related demagnetizing fields; and a characteristic probability density function which is constructed as a weighed sum of constituent functions: the material is modeled as consisting of various subsystems, e.g. reversal mechanisms or areas subject to strong/weak long range interactions and each subsystem is represented by a constituent probability density function. Our assumptions are validated since the model reproduces the hysteresis loops and differential permeability curves observed experimentally and calculations involving rotating inputs at various residual stress levels are consistent and in agreement with experimental evidence.
Residual Stresses in 21-6-9 Stainless Steel Warm Forgings
Everhart, Wesley A.; Lee, Jordan D.; Broecker, Daniel J.; Bartow, John P.; McQueen, Jamie M.; Switzner, Nathan T.; Neidt, Tod M.; Sisneros, Thomas A.; Brown, Donald W.
2012-11-14
Forging residual stresses are detrimental to the production and performance of derived machined parts due to machining distortions, corrosion drivers and fatigue crack drivers. Residual strains in a 21-6-9 stainless steel warm High Energy Rate Forging (HERF) were measured via neutron diffraction. The finite element analysis (FEA) method was used to predict the residual stresses that occur during forging and water quenching. The experimentally measured residual strains were used to calibrate simulations of the three-dimensional residual stress state of the forging. ABAQUS simulation tools predicted residual strains that tend to match with experimental results when varying yield strength is considered.
Method For Characterizing Residual Stress In Metals
Jacobson, Loren A.; Michel, David J.; Wyatt, Jeffrey R.
2002-12-03
A method is provided for measuring the residual stress in metals. The method includes the steps of drilling one or more holes in a metal workpiece to a preselected depth and mounting one or more acoustic sensors on the metal workpiece and connecting the sensors to an electronic detecting and recording device. A liquid metal capable of penetrating into the metal workpiece placed at the bottom of the hole or holes. A recording is made over a period of time (typically within about two hours) of the magnitude and number of noise events which occur as the liquid metal penetrates into the metal workpiece. The magnitude and number of noise events are then correlated to the internal stress in the region of the workpiece at the bottom of the hole.
Effect of Measured Welding Residual Stresses on Crack Growth
NASA Technical Reports Server (NTRS)
Hampton, Roy W.; Nelson, Drew; Doty, Laura W. (Technical Monitor)
1998-01-01
Welding residual stresses in thin plate A516-70 steel and 2219-T87 aluminum butt weldments were measured by the strain-gage hole drilling and X-ray diffraction methods. The residual stress data were used to construct 3D strain fields which were modeled as thermally induced strains. These 3D strain fields were then analyzed with the WARP31) FEM fracture analysis code in order to predict their effect on fatigue and on fracture. For analyses of fatigue crack advance and subsequent verification testing, fatigue crack growth increments were simulated by successive saw-cuts and incremental loading to generate, as a function of crack length, effects on crack growth of the interaction between residual stresses and load induced stresses. The specimen experimental response was characterized and compared to the WARM linear elastic and elastic-plastic fracture mechanics analysis predictions. To perform the fracture analysis, the plate material's crack tearing resistance was determined by tests of thin plate M(T) specimens. Fracture analyses of these specimen were performed using WARP31D to determine the critical Crack Tip Opening Angle [CTOA] of each material. These critical CTOA values were used to predict crack tearing and fracture in the weldments. To verify the fracture predictions, weldment M(T) specimen were tested in monotonic loading to fracture while characterizing the fracture process.
Effect of Measured Welding Residual Stresses on Crack Growth
NASA Technical Reports Server (NTRS)
Hampton, Roy W.; Nelson, Drew; Doty, Laura W. (Technical Monitor)
1998-01-01
Welding residual stresses in thin plate A516-70 steel and 2219-T87 aluminum butt weldments were measured by the strain-gage hole drilling and X-ray diffraction methods. The residual stress data were used to construct 3D strain fields which were modeled as thermally induced strains. These 3D strain fields were then analyzed with the WARP31) FEM fracture analysis code in order to predict their effect on fatigue and on fracture. For analyses of fatigue crack advance and subsequent verification testing, fatigue crack growth increments were simulated by successive saw-cuts and incremental loading to generate, as a function of crack length, effects on crack growth of the interaction between residual stresses and load induced stresses. The specimen experimental response was characterized and compared to the WARM linear elastic and elastic-plastic fracture mechanics analysis predictions. To perform the fracture analysis, the plate material's crack tearing resistance was determined by tests of thin plate M(T) specimens. Fracture analyses of these specimen were performed using WARP31D to determine the critical Crack Tip Opening Angle [CTOA] of each material. These critical CTOA values were used to predict crack tearing and fracture in the weldments. To verify the fracture predictions, weldment M(T) specimen were tested in monotonic loading to fracture while characterizing the fracture process.
Araújo, Marcelo Marotta; Lauria, Andrezza; Mendes, Marcelo Breno Meneses; Claro, Ana Paula Rosifini Alves; Claro, Cristiane Aparecida de Assis; Moreira, Roger William Fernandes
2015-12-01
The aim of this study was to analyze, through Vickers hardness test and photoelasticity analysis, pre-bent areas, manually bent areas, and areas without bends of 10-mm advancement pre-bent titanium plates (Leibinger system). The work was divided into three groups: group I-region without bend, group II-region of 90° manual bend, and group III-region of 90° pre-fabricated bends. All the materials were evaluated through hardness analysis by the Vickers hardness test, stress analysis by residual images obtained in a polariscope, and photoelastic analysis by reflection during the manual bending. The data obtained from the hardness tests were statistically analyzed using ANOVA and Tukey's tests at a significance level of 5 %. The pre-bent plate (group III) showed hardness means statistically significantly higher (P < 0.05) than those of the other groups (I-region without bends, II-90° manually bent region). Through the study of photoelastic reflection, it was possible to identify that the stress gradually increased, reaching a pink color (1.81 δ / λ), as the bending was performed. A general analysis of the results showed that the bent plate region of pre-bent titanium presented the best results.
Residual stresses in continuous graphite fiber Al metal matrix composites
NASA Technical Reports Server (NTRS)
Park, Hun Sub; Zong, Gui Sheng; Marcus, Harris L.
1988-01-01
The residual stresses in graphite fiber reinforced aluminum (Gr/Al) composites with various thermal histories are measured using X-ray diffraction (XRD) methods. The XRD stress analysis is based on the determination of lattice strains by precise measurements of the interplanar spacings in different directions of the sample. The sample is a plate consisting of two-ply P 100 Gr/Al 6061 precursor wires and Al 6061 overlayers. Prior to XRD measurement, the 6061 overlayers are electrochemically removed. In order to calibrate the relationship between stress magnitude and lattice spacing shift, samples of Al 6061 are loaded at varying stress levels in a three-point bend fixture, while the stresses are simultaneously determined by XRD and surface-attached strain gages. The stresses determined by XRD closely match those determined by the strain gages. Using these calibrations, the longitudinal residual stresses of P 100 Gr/Al 6061 composites are measured for various heat treatments, and the results are presented.
Residual stresses in continuous graphite fiber Al metal matrix composites
NASA Technical Reports Server (NTRS)
Park, Hun Sub; Zong, Gui Sheng; Marcus, Harris L.
1988-01-01
The residual stresses in graphite fiber reinforced aluminum (Gr/Al) composites with various thermal histories are measured using X-ray diffraction (XRD) methods. The XRD stress analysis is based on the determination of lattice strains by precise measurements of the interplanar spacings in different directions of the sample. The sample is a plate consisting of two-ply P 100 Gr/Al 6061 precursor wires and Al 6061 overlayers. Prior to XRD measurement, the 6061 overlayers are electrochemically removed. In order to calibrate the relationship between stress magnitude and lattice spacing shift, samples of Al 6061 are loaded at varying stress levels in a three-point bend fixture, while the stresses are simultaneously determined by XRD and surface-attached strain gages. The stresses determined by XRD closely match those determined by the strain gages. Using these calibrations, the longitudinal residual stresses of P 100 Gr/Al 6061 composites are measured for various heat treatments, and the results are presented.
NASA Technical Reports Server (NTRS)
Newman, John A.; Smith, Stephen W.; Seshadri, Banavara R.; James, Mark A.; Brazill, Richard L.; Schultz, Robert W.; Donald, J. Keith; Blair, Amy
2015-01-01
An on-line compliance-based method to account for residual stress effects in stress-intensity factor and fatigue crack growth property determinations has been evaluated. Residual stress intensity factor results determined from specimens containing friction stir weld induced residual stresses are presented, and the on-line method results were found to be in excellent agreement with residual stress-intensity factor data obtained using the cut compliance method. Variable stress-intensity factor tests were designed to demonstrate that a simple superposition model, summing the applied stress-intensity factor with the residual stress-intensity factor, can be used to determine the total crack-tip stress-intensity factor. Finite element, VCCT (virtual crack closure technique), and J-integral analysis methods have been used to characterize weld-induced residual stress using thermal expansion/contraction in the form of an equivalent delta T (change in local temperature during welding) to simulate the welding process. This equivalent delta T was established and applied to analyze different specimen configurations to predict residual stress distributions and associated residual stress-intensity factor values. The predictions were found to agree well with experimental results obtained using the crack- and cut-compliance methods.
THE CONTOUR METHOD: SIMPLE 2-D MAPPING OF RESIDUAL STRESSES
M. PRIME; A. GONZALES
2000-06-01
We present an entirely new method for measuring residual stress that is extremely simple to apply yet more powerful than existing techniques. In this method, a part is carefully cut in two. The contour of the resulting new surface is measured to determine the displacements normal to the surface caused by the release of the residual stresses. Analytically, the opposite of these measured displacements are applied as boundary conditions to the surface in a finite element model. By Bueckner's superposition principle, this gives the original residual stresses normal to the plane of the cut. Unlike other relaxation methods for measuring residual stress, the measured data can be used to solve directly for the stresses without a tedious inversion technique. At the same time, an arbitrary two-dimensional variation in stresses can be determined. We demonstrate the method on a steel specimen with a known residual stress profile.
Measurement of residual stress in bent pipelines
NASA Astrophysics Data System (ADS)
Alers, G. A.; McColskey, J. D.
2002-05-01
Buried gas and oil pipelines can be subjected to unexpected bending loads caused by such earth movements as earthquakes, wash-outs, road building, or mining subsidence as well as by denting from unintentional digging. In order to make a fitness-for-service assessment, it is necessary to measure any residual stresses that are left in the pipe wall as well as the degree of plastic flow within regions of severe damage. A portable instrument that uses EMATs to rapidly measure ultrasonic shear wave birefringence in the wall of a pipe has been developed and applied to a 5 m (15 ft) long section of 0.56 m (22 in) diameter linepipe loaded in three point bending by a 22 MN (five million pound) load frame. The results showed that: (1) a large correction for shear wave anisotropy caused by texture in the steel had to be introduced and (2) the degree of plastic flow could be deduced from changes in the texture contribution alone. An attempt to separate the stress and texture effects by using SH wave modes in the pipe wall proved unreliable because of magnetostrictive effects in the periodic permanent magnet EMATs used for these experiments.
Nanohardness and Residual Stress in TiN Coatings
Hernández, Luis Carlos; Ponce, Luis; Fundora, Abel; López, Enrique; Pérez, Eduardo
2011-01-01
TiN films were prepared by the Cathodic arc evaporation deposition method under different negative substrate bias. AFM image analyses show that the growth mode of biased coatings changes from 3D island to lateral when the negative bias potential is increased. Nanohardness of the thin films was measured by nanoindentation, and residual stress was determined using Grazing incidence X ray diffraction. The maximum value of residual stress is reached at −100 V substrate bias coinciding with the biggest values of adhesion and nanohardness. Nanoindentation measurement proves that the force-depth curve shifts due to residual stress. The experimental results demonstrate that nanohardness is seriously affected by the residual stress.
Residual stress and crack propagation in laminated composites
Yttergren, R.M.F.; Zeng, K.; Rowcliffe, D.J.
1994-12-31
Residual stress distributions in several laminated ceramic composites were measured by an indentation technique. The material included alumina-zirconia laminated composites, containing strong interfaces, and alumina-porcelain laminated composites with both weak and strong interfaces. The residual stress in these material originates from the mismatch of the thermal properties, differences in elastic properties, and different shrinkage of the laminates during sintering. An experimental technique is presented which gives a direct view of the residual stress state in the materials. Values of residual tensile stress are presented as a function of position relative to the interface in each material.
Blocks and residual stresses in shaped sapphire single crystals
NASA Astrophysics Data System (ADS)
Krymov, V. M.; Nosov, Yu. G.; Bakholdin, S. I.; Maslov, V. N.; Shul‧pina, I. L.; Nikolaev, V. I.
2017-01-01
The formation of blocks and residual stresses in shaped sapphire crystals grown from the melt by the Stepanov method (EFG) has been studied. The probability of block formation is higher for the growth along the c axis compared to that grown in the a-axis direction. The distribution of residual stress in sapphire crystals of tubular, rectangular and round cross section was measured by the conoscopy method. It was found that the magnitude of the residual stress increases from the center to the periphery of the crystal and reaches up to about 20 MPa. Residual stress tensor components for solid round rod and tubular single crystals were determined by numerical integration.
Residual stresses in coronary artery stents.
Möller, D; Reimers, W; Pyzalla, A; Fischer, A
2001-01-01
In western industrial countries, coronary heart disease is the most common cause of death. The reason is a coronary sclerosis, which by the generation of plaques narrows the inner lumen of an artery and, thus, deteriorates the blood supply. This leads to symptoms like burning pain or increased pressure in the chest, and finally to an under supply and damage of the heart muscle. In order to keep those portions of arteries that are covered by a plaque open, the stent technique was developed in the 1980s and is increasingly used since about 13 years. These stents are usually made of wires or of a slotted tube and are of two kinds: self-expanding and balloon expanding. Both types are implanted after being mounted on a catheter and expanded in the desired position. Self-expanding stents make use of the elastic deformation, while the other group of stents are expanded by a balloon, which brings about a plastic deformation of certain regions of the stent structure. Thus, after implantation, parts of these stents undergo two steps of distinct plastic deformation. First during compression, which is necessary for the mounting procedure on the catheter (crimping), and second during expansion for implantation. In this article, the residual stresses generated during crimping and expansion are presented and discussed. These stresses are stored in the structure of a portion of a stent after implantation and are superimposed on those stresses generated by the more than 700 million cyclic heart beats during the patient's life. This work is a part of several interdisciplinary research projects by the authors in order to gain reliable fail-safe criteria for the static and cyclic mechanical properties of coronary stents.
Effect of Thermal Annealing on Machining-Induced Residual Stresses in Inconel 718
NASA Astrophysics Data System (ADS)
Madariaga, A.; Aperribay, J.; Arrazola, P. J.; Esnaola, J. A.; Hormaetxe, E.; Garay, A.; Ostolaza, K.
2017-08-01
Nickel-based alloys are widely employed in the manufacturing of aero-engines. These alloys are difficult to machine, and tensile residual stresses are generated during machining. These tensile residual stresses can negatively affect the performance of aero-engine components. Nevertheless, residual stresses can vary due to thermal or mechanical loading. These variations must be considered to evaluate the real influence of residual stresses on component behavior. This paper studies the effect of thermal loads on machining-induced residual stresses in the alloy Inconel 718. A ring-shaped Inconel 718 part was face-turned, and specimens were extracted from it. Specimens were exposed at 550 and 650 °C for 10 min, 1 and 10 h. Residual stresses were measured, and microstructure was observed before and after thermal exposure. Residual stress variations found after thermal exposure were the consequence of two factors: relaxation of strain bands during the early stage of exposure and diffusion-controlled creep. In addition, a modified Zener-Wert-Avrami model is proposed to predict residual stress relaxation caused by the diffusion-controlled creep. Once having fitted the modified Zener-Wert-Avrami model, the study was extended for a wider range of temperatures (400-650 °C). This analysis showed that surface residual stresses do not relax significantly at temperatures below 500 °C.
Sebastiani, M; Massimi, F; Merlati, G; Bemporad, E
2015-11-01
The production of fixed partial dentures (FPDs) induces complex residual stress profiles, due to both the thermal expansion coefficient mismatch between the veneering ceramic and the framework and to the thermal gradients occurring during the final cooling. Detailed knowledge of residual stress distributions in the veneering ceramics is important to understand the interface phenomena with the framework and the consequences of the different firing systems. The first objective of this study was to analyse the residual stress distribution in heat-pressed ceramic on zirconia core with micrometer spatial resolution, with also a focus on the stress at the interface versus porcelain-fused-to-metal samples. The second purpose was to correlate the residual stress with the fracture toughness. The micron-scale focused ion beam (FIB) ring-core method was used to map the residual stress over the cross-sections of the veneering ceramics. The methodology is based on FIB micro-milling of annular trenches, combined with high-resolution in situ scanning electron microscope (SEM) imaging, a full field strain analysis by digital image correlation (DIC) and numerical models for residual stress calculation. Fracture toughness was evaluated by using high load Vickers indentation and hardness/modulus were measured by nanoindentation testing also across the interfaces. Both prosthetic systems showed a compressive stress at the ceramic surface on a micron-scale. The stress profile for porcelain fused to metal (PFM) showed a transition to tensile stress at the half of the layer, whilst the stress in proximity of the interface was more compressive in both the cases. Residual stress on a micron scale are higher in magnitude than the corresponding macro-scale values reported in the literature, due to the stress relaxation given, at larger scales, by micro-voids and cracks. The stress field was directly correlated with the indentation fracture toughness, which was higher in those areas where the
Directionality of residual stress evaluated by instrumented indentation testing using wedge indenter
NASA Astrophysics Data System (ADS)
Ahn, Hee-Jun; Kim, Jong-hyoung; Xu, Huiwen; Lee, Junsang; Kim, Ju-Young; Kim, Young-Cheon; Kwon, Dongil
2017-05-01
In instrumented indentation testing (IIT), residual stress can be evaluated by shift in indentation load-depth curves for stress-free and stressed states. Although the average surface residual stress is able to be evaluated with Vickers indenter, in order to know stress directionality, another indentation tests with two-fold symmetric indenter, for example, Knoop indenter, are needed. As some necessities for evaluating nonequibiaxial residual stress within small indent area, we suggest a novel way to evaluate directionality of residual stress, p, using wedge indenter characterized by two parameters, edge length and inclined angle. We develop wedge-indentation-mechanics model based on predetermined conversion factors which are determined by IITs for various uniaxial stressed states combining with finite element analysis simulations. By utilizing the developed model, directionality of residual stress is evaluated through two serial wedge IITs with respect to principal directions. We find good agreements between applied residual stress and residual stress evaluated by the developed model for biaxial tensile stress states.
NASA Astrophysics Data System (ADS)
Jones, Robert
Parts machined from relatively large thickness cross sections can experience significant deformations from high residual stresses that develop in the part during the heat treatment used to form the aluminum alloy. Uphill quenching is a process that can create a part with low residual stress and stable dimensions when the process is controlled properly. The uphill quenching process involves a solution heat treat, quench, cool to liquid nitrogen, steam blast, and then age to final temper. In this thesis two parts were modeled using ANSYS. The first part underwent the uphill quench process in the rough machined state. The second part was modeled in the stock material shape and only underwent a solution heat treat, quench, and age to final temper. After the residual stress in the second part was predicted the excess material was removed by killing the associated elements and the deformation of the final machined part was predicted. For both parts analyzed measurements were made and compared against predictions with fairly good results.
Thornberg, Steven M [Peralta, NM
2012-07-31
A system is provided for testing the hermeticity of a package, such as a microelectromechanical systems package containing a sealed gas volume, with a sampling device that has the capability to isolate the package and breach the gas seal connected to a pulse valve that can controllably transmit small volumes down to 2 nanoliters to a gas chamber for analysis using gas chromatography/mass spectroscopy diagnostics.
Residual stresses and durability in cold drawn eutectoid steel wires
NASA Astrophysics Data System (ADS)
Atienza, J. M.; Elices, M.; Ruiz-Hervias, J.; Caballero, L.; Valiente, A.
2007-04-01
Prestressing steel wires have excellent mechanical properties but there is a need to improve their durability in aggressive environments. In this work, the influence of residual stresses on the environmentally assisted cracking of these wires is studied. A good correlation has been found between residual stresses at the surface of the wires and the time to rupture during stress corrosion test proposed by the International Federation of Prestressing. Wires with the same microstructure, surface quality and mechanical properties show very different behaviour in aggressive environments depending on their residual stress state. Research shows that environmentally assisted cracking can be improved significantly by acting on the surface residual stresses produced by wire drawing. In addition, in this study a post-drawing treatment to generate compressive residual stresses at the surface of the wires is proposed.
Morphology of residually stressed tubular tissues: Beyond the elastic multiplicative decomposition
NASA Astrophysics Data System (ADS)
Ciarletta, P.; Destrade, M.; Gower, A. L.; Taffetani, M.
2016-05-01
Many interesting shapes appearing in the biological world are formed by the onset of mechanical instability. In this work we consider how the build-up of residual stress can cause a solid to buckle. In all past studies a fictitious (virtual) stress-free state was required to calculate the residual stress. In contrast, we use a model which is simple and allows the prescription of any residual stress field. We specialize the analysis to an elastic tube subject to a two-dimensional residual stress, and find that incremental wrinkles can appear on its inner or its outer face, depending on the location of the highest value of the residual hoop stress. We further validate the predictions of the incremental theory with finite element simulations, which allow us to go beyond this threshold and predict the shape, number and amplitude of the resulting creases.
Thermoacoustic method for relaxation of residual stresses in welded joints
Koshovyi, V.V.; Pakhn`o, M.I.; Tsykhan, O.I.
1995-01-01
We propose a thermoacoustic method for the relaxation of residual stresses in welded joints, present a block diagram of a generator of local thermoacoustic pulses designed for implementation of this method, and describe our experiment aimed at relaxation of residual tensile stresses.
Formation of the residual stress field under local thermal actions
NASA Astrophysics Data System (ADS)
Burenin, A. A.; Dats, E. P.; Murashkin, E. V.
2014-03-01
The one-dimensional process of material deformation due to local heating and subsequent cooling is analyzed in the framework of the classical theory of elastoplastic deformations. The problem of formation of residual stresses in a thin plate made of an elastoplastic material under a given thermal action is solved. The graphs of fields of residual stresses and displacements are constructed.
NASA Astrophysics Data System (ADS)
Jiang, Wu-Gui; Feng, Xi-Qiao; Nan, Ce-Wen
2008-07-01
The stress and electric fields in multilayer ceramic capacitors (MLCCs) under an applied electric bias were investigated by using a three-dimensional finite element model of ferroelectric ceramics. A coupled thermal-mechanical analysis was first made to calculate the residual thermal stress induced by the sintering process, and then a coupled electrical-mechanical analysis was performed to predict the total stress distribution in the MLCCs under a representative applied electric bias. The effects of the number of dielectric layers, the single layer thickness as well as the residual thermal stresses on the total stresses were all examined. The numerical results show that the residual thermal stress induced by the sintering process has a significant influence on the contribution of the total stresses and, therefore, should be taken into account in the design and evaluation of MLCC devices.
Residual stress in spin-cast polyurethane thin films
Zhang, Hong; Zhang, Li
2015-01-19
Residual stress is inevitable during spin-casting. Herein, we report a straightforward method to evaluate the residual stress in as-cast polyurethane thin films using area shrinkage measurement of films in floating state, which shows that the residual stress is independent of radial location on the substrate and decreased with decreasing film thickness below a critical value. We demonstrate that the residual stress is developed due to the solvent evaporation after vitrification during spin-casting and the polymer chains in thin films may undergo vitrification at an increased concentration. The buildup of residual stress in spin-cast polymer films provides an insight into the size effects on the nature of polymer thin films.
Residual stress within nanoscale metallic multilayer systems during thermal cycling
Economy, David Ross; Cordill, Megan Jo; Payzant, E. Andrew; ...
2015-09-21
Projected applications for nanoscale metallic multilayers will include wide temperature ranges. Since film residual stress has been known to alter system reliability, stress development within new film structures with high interfacial densities should be characterized to identify potential long-term performance barriers. To understand factors contributing to thermal stress evolution within nanoscale metallic multilayers, stress in Cu/Nb systems adhered to Si substrates was calculated from curvature measurements collected during cycling between 25 °C and 400 °C. Additionally, stress within each type of component layers was calculated from shifts in the primary peak position from in-situ heated X-ray diffraction. The effects ofmore » both film architecture (layer thickness) and layer order in metallic multilayers were tracked and compared with monolithic Cu and Nb films. Analysis indicated that the thermoelastic slope of nanoscale metallic multilayer films depends on thermal expansion mismatch, elastic modulus of the components, and also interfacial density. The layer thickness (i.e. interfacial density) affected thermoelastic slope magnitude while layer order had minimal impact on stress responses after the initial thermal cycle. When comparing stress responses of monolithic Cu and Nb films to those of the Cu/Nb systems, the nanoscale metallic multilayers show a similar increase in stress above 200 °C to the Nb monolithic films, indicating that Nb components play a larger role in stress development than Cu. Local stress calculations from X-ray diffraction peak shifts collected during heating reveal that the component layers within a multilayer film respond similarly to their monolithic counterparts.« less
Residual stress within nanoscale metallic multilayer systems during thermal cycling
Economy, David Ross; Cordill, Megan Jo; Payzant, E. Andrew; Kennedy, Marian S.
2015-09-21
Projected applications for nanoscale metallic multilayers will include wide temperature ranges. Since film residual stress has been known to alter system reliability, stress development within new film structures with high interfacial densities should be characterized to identify potential long-term performance barriers. To understand factors contributing to thermal stress evolution within nanoscale metallic multilayers, stress in Cu/Nb systems adhered to Si substrates was calculated from curvature measurements collected during cycling between 25 °C and 400 °C. Additionally, stress within each type of component layers was calculated from shifts in the primary peak position from in-situ heated X-ray diffraction. The effects of both film architecture (layer thickness) and layer order in metallic multilayers were tracked and compared with monolithic Cu and Nb films. Analysis indicated that the thermoelastic slope of nanoscale metallic multilayer films depends on thermal expansion mismatch, elastic modulus of the components, and also interfacial density. The layer thickness (i.e. interfacial density) affected thermoelastic slope magnitude while layer order had minimal impact on stress responses after the initial thermal cycle. When comparing stress responses of monolithic Cu and Nb films to those of the Cu/Nb systems, the nanoscale metallic multilayers show a similar increase in stress above 200 °C to the Nb monolithic films, indicating that Nb components play a larger role in stress development than Cu. Local stress calculations from X-ray diffraction peak shifts collected during heating reveal that the component layers within a multilayer film respond similarly to their monolithic counterparts.
Nondestructive Testing Residual Stress Using Ultrasonic Critical Refracted Longitudinal Wave
NASA Astrophysics Data System (ADS)
Xu, Chunguang; Song, Wentao; Pan, Qinxue; Li, Huanxin; Liu, Shuai
Residual stress has significant impacts on the performance of the mechanical components, especially on its strength, fatigue life and corrosion resistance and dimensional stability. Based on theory of acoustoelasticity, the testing principle of ultrasonic LCR wave method is analyzed. The testing system of residual stress is build. The method of calibration of stress coefficient is proposed in order to improve the detection precision. At last, through experiments and applications on residual stress testing of oil pipeline weld joint, vehicle's torsion shaft, glass and ceramics, gear tooth root, and so on, the result show that it deserved to be studied deeply on application and popularization of ultrasonic LCR wave method.
The response of solids to elastic/plastic indentation. I. Stresses and residual stresses
Chiang, S. S.; Marshall, D. B.; Evans, A. G.
1982-01-01
We present a new approach for analyzing indentation plasticity and for determining indentation stress fields. The analysis permits relations to be established between material properties (notably hardness, yield strength, and elastic modulus) and the dimensions of the indentation and plastic zone. The predictions are demonstrated to correlate with observations performed on a wide range of materials. The indentation stress fields are computed along trajectories pertinent to three dominant indentation crack systems: radial, median, and lateral cracks. Lastly, the peak load and residual tensile stresses are shown to be consistent with observed trends in indentation fracture.
Jung, Yeon-Gil; Choi, Sung-Churl; Paik, Un-Gyu
1995-09-01
To analyze the residual stress and the fracture behavior of FGMs. disc-type TZP/Ni- and TZP/SUS304-FGM were hot passed, and compared with MM& The continuous interface and the microstructure of FGMs were characterized with EPMA, optical microscopy and SEM. The defect-like cracks in the FGMs induced by the preferential shear stress have been shown to cause fracture. This fact has well corresponded to the analysis of the residual stress distribution by FEM.
Measurement of the residual stress in hot rolled strip using strain gauge method
NASA Astrophysics Data System (ADS)
Kumar, Lokendra; Majumdar, Shrabani; Sahu, Raj Kumar
2017-07-01
Measurement of the surface residual stress in a flat hot rolled steel strip using strain gauge method is considered in this paper. Residual stresses arise in the flat strips when the shear cut and laser cut is applied. Bending, twisting, central buckled and edge waviness is the common defects occur during the cutting and uncoiling process. These defects arise due to the non-uniform elastic-plastic deformation, phase transformation occurring during cooling and coiling-uncoiling process. The residual stress analysis is very important because with early detection it is possible to prevent an object from failure. The goal of this paper is to measure the surface residual stress in flat hot rolled strip using strain gauge method. The residual stress was measured in the head and tail end of hot rolled strip considering as a critical part of the strip.
Microstructural residual stress in particle-filled dental composite.
Prejzek, Ondřej; Spaniel, Miroslav; Mareš, Tomáš
2015-01-01
The main goal of this study is to develop a micromechanical model of a particle-filled dental composite focused on the residual stress (RS) field developed during the curing process in its microstructure. A finite element model of a representative volume element of filler and resin was developed, and volumetric shrinkage was simulated during the curing process. Four material models (von Mises plasticity model, Drucker-Prager plasticity model, von Mises plasticity model with stress relaxation and Drucker-Prager plasticity with stress relaxation) of the polymer resin were built to assess the influence of the material model on the resulting internal stress. The relationship between the curing process and the magnitude of the stress components will be described, and an analysis of the post-curing state of the material in particular microstructure locations will be conducted in this study. Obtained RS is comparable to the stresses developed in the material under the external load. The substantial dependence on the choice of material model for resin is to be observed, and the suitability of particular models is discussed.
Review of Ultrasonic Velocity Methods of Determining Residual Stress.
1985-05-01
Matzkanin and D.L. Davidson, The influence of mechanical stress on ’magnetization processes and Barkhausen Jumps in ferromagnetic materials. Int. Journ...AD-A160 769 REVIEM OF ULTRASONIC VELOCITY METHODS OF DETERMINING i I RESIDUAL STRESS (U) AERONAUTICAL RESEARCH LADS MELBOURNE I (AUSTRALIA) S J RUMBLE...RESEARCH LABORATORIES MELBOURNE, VICTORIA(0Io 0 Structurs Technical I8tDzandm 416 REVIE OF ULTRASONIC VELOCITY NETHODS OF DTLR1INING RESIDUAL STRESS
Lamination residual stresses in hybrid composites, part 1
NASA Technical Reports Server (NTRS)
Daniel, I. M.; Liber, T.
1976-01-01
An experimental investigation was conducted to study lamination residual stresses for various material and loading parameters. The effects of hybridization on residual stresses and residual properties after thermal cycling under load were determined in angle-ply graphite/Kevlar/epoxy and graphite/S-glass/epoxy laminates. Residual strains in the graphite plies are not appreciably affected by the type and number of hybridizing plies. Computed residual stresses at room temperature in the S-glass plies reach values up to seventy-five percent of the transverse strength of the material. Computed residual stresses in the graphite plies exceed the static strength by approximately ten percent. In the case of Kevlar plies, computed residual stresses far exceed the static strength indicating possible early failure of these plies. Static testing of the hybrids above indicates that failure is governed by the ultimate strain of the graphite plies. In thermally cycled hybrids, in general, residual moduli were somewhat lower and residual strengths were higher than initial values.
Fukui, Yasuyoshi; Watanabe, Yoshimi
1996-12-01
A ring-cutting test and an elastic theory were applied to evaluate the macroscopic residual stress in a thick-walled ring made of Al-SiC functionally graded material (FGM). The FGM ring specimens, with outer diameter 90 mm, radial thickness approximately 8.4 to 10 mm, and width 30 mm, were fabricated by the centrifugal casting method from an ingot of Duralcan F3D.20S of Al-20 vol pct SiC master composite. Because of a difference in centrifugal forces of SiC particles and of molten aluminum alloy, the rings had a graded composition of SiC particles in the radial direction. The volume fractions of SiC particles in each ring specimen varied in the range of 0 to 43 vol pct from the inner to the outer surface of the ring, depending on the applied mold spin speed. A ring diametral compression test was performed to validate an analytical formula based on the curved beam theory that can account for the graded properties of the material. Excellent agreement between the theory that can account for the graded properties of the material. Excellent agreement between the theory and the experiment was found. The residual stress was found to be generated by a cooling of {Delta}T = 140 K, which was from half the melting point corresponding stress-free condition to the ambient temperature. The hoop residual stresses in the FGM ring varied in the range of {minus}50 to +35 MPa and from tension at the inner surface to compression at the outer space because of the graded composition. With an increase in wall thickness and/or composition gradation, the residual stresses were found to increase.
Residual stresses and their effects in composite laminates
NASA Technical Reports Server (NTRS)
Hahn, H. T.; Hwang, D. G.
1983-01-01
Residual stresses in composite laminates are caused by the anisotropy in expansional properties of constituent unidirectional plies. The effect of these residual stresses on dimensional stability is studied through the warping of unsymmetric (0 sub 4/90 sub 4)sub T graphite/epoxy laminates while their effect on ply failure is analyzed for (0/90)sub 2s Kevlar 49/epoxy laminate. The classical laminated plate theory is used to predict the warping of small and large panels. The change of warping does not indicate a noticeable stress relaxation at 75 C while it is very sensitive to moisture content and hence to environment. A prolonged gellation at the initial cure temperature reduces residual stresses while postcure does not. The matrix/interface cracking in dry (0/90)sub 2s Kevlar 49/epoxy laminate is shown to be the result of the residual stress exceeding the transverse strength.
Residual stress measurements of tension leg platform tendon welds
Kim, D.S.; Smith, J.D.
1994-12-31
Results of fatigue test of prototype welded tendons showed that fatigue life was greatly reduced for the weld repaired joint. Since tensile residual stresses near the fusion boundary were suspected to cause the fatigue life reduction, these residual stresses were measured. Residual stresses of girth welded tendon pipes for a tension leg platform (TLP) were obtained for various fabrication conditions. The stresses were measured experimentally using the blind hole drilling (BHD) technique, X-ray diffraction (XRD) technique and Barkhausen Noise (BHN) method. The results of these measurements illustrate the reliability of each measurement technique. Effects of joint configuration, weld repair, weld cap grinding, and pre-fatigue test on residual stresses were discussed.
Residual stresses in cross-ply composite tubes
NASA Technical Reports Server (NTRS)
Cohen, D.; Hyer, M. W.
1984-01-01
The residual thermal stresses in 4-layer cross-ply tubes are studied. The tubes considered has a small radius to wall-thickness ratios and so elasticity solutions were used. The residual thermal stress problem was considered to be axisymmetric and three elasticity solutions were derived and the results compared with the results using classical lamination theory. The comparison illustrates the limitations of classical lamination theory. The three elasticity solutions derived were: plane stress, plane strain, and generalized plane strain, the latter being the most realistic. Residual stresses in both the hoop and axial direction is significant. Stacking arrangement effects the residual stress to some extent, as do the material properties of the individual lamina. The benefits of hybrid construction are briefly discussed.
Evaluation Of Residual Stresses In Inner Ring Of The Bearings
NASA Astrophysics Data System (ADS)
Malotová, Šárka; Hemžský, Pavel; Pitela, David; Nicielnik, Henryk; Šoková, Dagmar; Kyncl, Ladislav; Mrázik, Jozef
2015-12-01
Residual stresses are undesirable and it should not be underestimated. They occur in many components and it is necessary to identify and try to avoid them. For detection the Residual stresses, there are many methods, but not all are suitable, because they can completely destroy of the components. The article deals with the evaluation of Residual stresses in the inner rings of Bearings, which are made from steel 100Cr6 (ČSN 14 109.4. The surfaces were turning at different cutting parameters and subsequently are evaluated Residual stresses. The stresses have been evaluated by non - destructive method X - Ray. The experiment was realized in cooperation Faculty of Mechanical Engineering VSB - TU Ostrava and Faculty of Mechanical Engineering of ZU Zilina - machining in the laboratories of ZU Žilina, Slovak Republic.
Residual stresses and their effects in composite laminates
NASA Technical Reports Server (NTRS)
Hahn, H. T.; Hwang, D. G.
1983-01-01
Residual stresses in composite laminates are caused by the anisotropy in expansional properties of constituent unidirectional plies. The effect of these residual stresses on dimensional stability is studied through the warping of unsymmetric (0 sub 4/90 sub 4)sub T graphite/epoxy laminates while their effect on ply failure is analyzed for (0/90)sub 2s Kevlar 49/epoxy laminate. The classical laminated plate theory is used to predict the warping of small and large panels. The change of warping does not indicate a noticeable stress relaxation at 75 C while it is very sensitive to moisture content and hence to environment. A prolonged gellation at the initial cure temperature reduces residual stresses while postcure does not. The matrix/interface cracking in dry (0/90)sub 2s Kevlar 49/epoxy laminate is shown to be the result of the residual stress exceeding the transverse strength.
NASA Astrophysics Data System (ADS)
Zvonarev, I. E.; Ivanov, S. L.
2016-02-01
The methodological bases for determining the energy resource of mechanical transmissions details for mining machines are considered. Based on the analysis of the accumulation of damage in metal gears, a method of estimating residual life of coarse-toothed wheels by periodically measuring the hardness of the surface layer of the teeth is justified. The regularities in change of hardness of coarse-tooth gear, conditioned by a change in metal strength properties that take into account the micro- and macromechanisms of plastic and elastic deformation, distortion of the metal crystal lattice with formation and movement of vacancies and dislocations. Experimental setup was built and the results of laboratory experiments are given related to the process of destruction of non-standard samples under different loads. Comparison of dimensions and hardness values of the sample allows concluding that a larger deformation corresponds to a greater increase in hardness, their limit value for the material being in the fracture zone. It is established that the detected changes in the local hardness occurs in areas of increased stresses above the limit of proportionality and the work of fracture forces attributed to dislocations density adjacent to the fracture plane expressed in terms of hardness increment is constant.
Water aging reverses residual stresses in hydrophilic dental composites.
Park, J W; Ferracane, J L
2014-02-01
Dental composites develop residual stresses during polymerization due to shrinkage. These stresses may change with time because of relaxation and water sorption in the oral environment. This phenomenon is likely dependent on the composition of the materials, specifically their hydrophilic characteristics, and could result in deleterious stresses on restorative materials and tooth structure. The purpose of this experiment was to use the thin ring-slitting method to compare the residual stress generated within composite materials of varying hydrophilicity when aged in wet and dry conditions after polymerization. Water sorption, solubility, elastic modulus, and residual stresses were measured in 6 commercial composites/cements aged in water and dry conditions. The self-adhesive resin cement showed the highest water sorption and solubility. All composites showed initial residual contraction stresses, which were maintained when aged dry. Residual stresses in 2 of the self-adhesive cements and the polyacid-modified composite aged in wet conditions resulted in a net expansion. This experiment verified that residual shrinkage stresses in dental composites can be reversed during aging in water, resulting in a net expansion, with the effect directly related to their hydrophilic properties.
Measured residual stresses in overlay pipe weldments removed from service
Shack, W.J.
1985-02-01
Surface and throughwall residual stresses were measured on an elbow-to-pipe weldment that had been removed from the Hatch-2 reactor about a year after the application of a weld overlay. The results were compared with experimental measurements on three mock-up weldments and with finite-element calculations. The comparison shows that there are significant differences in the form and magnitude of the residual stress distributions. However, even after more than a year of service, the residual stresses over most of the inner surface of the actual plant weldment with an overlay were strongly compressive. 3 refs., 7 figs.
Sharma, Varun; Pandey, Pulak M
2016-08-01
The residual stresses generated in the machined work piece have detrimental effect on fatigue life, corrosion resistance and tribological properties. However, the effect of cutting and vibration parameters on residual stresses in Ultrasonic Assisted Turning (UAT) has not been dealt with. The present paper highlights the effect of feed rate, depth of cut, cutting velocity and percentage intensity of ultrasonic power on residual stress generation. XRD analysis has been carried out to measure the residual stress while turning 4340 hardened steel using UAT. The experiments were performed based on response surface methodology to develop statistical model for residual stress. The outcome of ANOVA revealed that percentage intensity and feed rate significantly affect the residual stress generation. The significant interactions between process parameters have also been presented tin order to understand the thermo-mechanical mechanism responsible for residual stress generation.
Simulation on Residual Stress of Shot Peening Based on a Symmetrical Cell Model
NASA Astrophysics Data System (ADS)
WANG, Cheng; HU, Jiacheng; GU, Zhenbiao; XU, Yangjian; WANG, Xiaogui
2017-03-01
The symmetrical cell model is widely used to study the residual stress induced by shot peening. However, the correlation between the predicted residual stresses and the shot peening coverage, which is a big challenge for the researchers of the symmetrical cell model, is still not established. Based on the dynamic stresses and the residual stresses outputted from the symmetrical cell model, the residual stresses corresponding to full coverage are evaluated by normal distribution analysis. The predicted nodal dynamic stresses with respect to four corner points indicate that the equi-biaxial stress state exists only for the first shot impact. Along with the increase of shot number, the interactions of multiple shot impacts make the fluctuation of the nodal dynamic stresses about an almost identical value more and more obvious. The mean values and standard deviations of the residual stresses gradually tend to be stable with the increase of the number of shot peening series. The mean values at each corner point are almost the same after the third peening series, which means that an equi-biaxial stress state corresponding to the full coverage of shot peening is achieved. Therefore, the mean values of the nodal residual stresses with respect to a specific transverse cross-section below the peened surface can be used to correlate the measured data by X-ray. The predicted residual stress profile agrees with the experimental results very well under 200% peening coverage. An effective correlation method is proposed for the nodal residual stresses predicted by the symmetrical cell model and the shot peening coverage.
Power-law creep and residual stresses in carbopol microgels
NASA Astrophysics Data System (ADS)
Lidon, Pierre; Manneville, Sebastien
We report on the interplay between creep and residual stresses in carbopol microgels. When a constant shear stress σ is applied below the yield stress σc, the strain is shown to increase as a power law of time, γ (t) =γ0 +(t / τ) α , with and exponent α ~= 0 . 38 that is strongly reminiscent of Andrade creep in hard solids. For applied shear stresses lower than some characteristic value of about σc / 10 , the microgels experience a more complex creep behavior that we link to the existence of residual stresses and to weak aging of the system after preshear. The influence of the preshear protocol, of boundary conditions and of microgel concentration on residual stresses is investigated. We discuss our results in light of previous works on colloidal glasses and other soft glassy systems.
Effect of Residual Stresses on the Hardness of Bulk Metallic Glasses
Wang, L.; Bei, Hongbin; Gao, Y. F.; Lu, Zhao Ping; Nieh, T. G.
2011-01-01
Nanoindentation experiments were conducted on Zr-based metallic glass samples, which were elastically and plastically bent in order to investigate the effect of residual stresses on hardness. It was found that tensile residual stress reduced the hardness significantly, while compressive residual stress produced only a small effect on the hardness. These observations are consistent with three-dimensional continuum-plasticity-based finite-element simulations. The hardness was also found to vary more significantly with residual stresses, in particular in tension, than that caused by shear-banding-induced softening, suggesting hardness measurement is a practical method for the evaluation of tensile residual stresses in a metallic glass. Hardness variation in the bent sample was correlated with the residual-stress induced volume dilatation through a free-volume-based model. In this paper, we also present a detailed stress analysis based on yield asymmetry under tension and compression to describe the distribution of residual stresses in bent metallic glass specimens. The calculations agree well with the hardness variations measured experimentally.
Ultrasonic measurement of residual stress in shot peened aluminum alloy
NASA Astrophysics Data System (ADS)
Lavrentyev, Anton I.; Veronesi, William A.
2001-04-01
Shot peening is a well-known method for extending the fatigue life of metal components by introducing compressive residual stresses near their surfaces. The capability to non-destructively evaluate the near surface residual stress would greatly aid the assurance of proper fatigue life in shot-peened components. This paper addresses issues encountered in near-surface residual stress measurement by an ultrasonic surface wave method. In this method, a variation of ultrasonic surface wave speed with shot peening intensity is measured. Since the effective wave penetration depth inversely related to the excitation frequency, by making measurements at different frequencies, the method has the potential to provide the stress-depth profile. Experiments were conducted on aluminum specimens (alloy 7075-T7351) peened within the Almen peening intensity from 4A-16A. Several factors were found to contribute to the measured responses: surface roughness, near surface texture change, dislocation density increase and residual stress. In this paper, the contributions of residual stress, dislocation density and surface roughness to the overall effect are separately estimated. It is shown that the experimentally observed velocity change in shot peened samples is dominated by the effect of surface roughness while the role of residual stress is much smaller.
NASA Astrophysics Data System (ADS)
Franco, Jamal Eli
The residual stress in a high alloy ultra thin cylindrical shell is studied. The objective of this research is to quantify and develop an understanding of the residual stress produced during the fabrication process. It is shown, with the application of finite element analysis and experimental measurements, that the residual stress can be predicted and quantified. This dissertation investigates the experimental and numerical methods to determine the residual stress in high alloy ultra thin cylindrical shells. Experimental measurements of the shell profiles are used to obtain stresses during manufacturing. Finite element analysis is used to verify the experimental results. These results compare favorably with theoretical values. This dissertation shows that the thermal process applied to the shell for separation does not contribute to the residual stress. A residual stress due to the bending moment caused by the conical geometry of the shell is evident in the finite element results.
Residual thermal stresses in composites for dimensionally stable spacecraft applications
NASA Technical Reports Server (NTRS)
Bowles, David E.; Tompkins, Stephen S.; Funk, Joan G.
1992-01-01
An overview of NASA LaRC's research on thermal residual stresses and their effect on the dimensional stability of carbon fiber reinforced polymer-matrix composites is presented. The data show that thermal residual stresses can induce damage in polymer matrix composites and significantly affect the dimensional stability of these composites by causing permanent residual strains and changes in CTE. The magnitude of these stresses is primarily controlled by the laminate configuration and the applied temperature change. The damage caused by thermal residual stresses initiates at the fiber/matrix interface and micromechanics level analyses are needed to accurately predict it. An increased understanding of fiber/matrix interface interactions appears to be the best approach for improving a composite's resistance to thermally induced damage.
Residual thermal stresses in composites for dimensionally stable spacecraft applications
NASA Technical Reports Server (NTRS)
Bowles, David E.; Tompkins, Stephen S.; Funk, Joan G.
1992-01-01
An overview of NASA LaRC's research on thermal residual stresses and their effect on the dimensional stability of carbon fiber reinforced polymer-matrix composites is presented. The data show that thermal residual stresses can induce damage in polymer matrix composites and significantly affect the dimensional stability of these composites by causing permanent residual strains and changes in CTE. The magnitude of these stresses is primarily controlled by the laminate configuration and the applied temperature change. The damage caused by thermal residual stresses initiates at the fiber/matrix interface and micromechanics level analyses are needed to accurately predict it. An increased understanding of fiber/matrix interface interactions appears to be the best approach for improving a composite's resistance to thermally induced damage.
THERMAL RESIDUAL STRESSES IN BILAYERED, TRILAYERED AND GRADED DENTAL CERAMICS.
Fabris, Douglas; Souza, Júlio C M; Silva, Filipe S; Fredel, Márcio; Mesquita-Guimarães, Joana; Zhang, Yu; Henriques, Bruno
2017-03-01
Layered ceramic systems are usually hit by residual thermal stresses created during cooling from high processing temperature. The purpose of this study was to determine the thermal residual stresses at different ceramic multi-layered systems and evaluate their influence on the bending stress distribution. Finite elements method was used to evaluate the residual stresses in zirconia-porcelain and alumina-porcelain multi-layered discs and to simulate the 'piston-on-ring' test. Temperature-dependent material properties were used. Three different multi-layered designs were simulated: a conventional bilayered design; a trilayered design, with an intermediate composite layer with constant composition; and a graded design, with an intermediate layer with gradation of properties. Parameters such as the interlayer thickness and composition profiles were varied in the study. Alumina-porcelain discs present smaller residual stress than the zirconia-porcelain discs, regardless of the type of design. The homogeneous interlayer can yield a reduction of ~40% in thermal stress relative to bilayered systems. Thinner interlayers favoured the formation of lower thermal stresses. The graded discs showed the lowest thermal stresses for a gradation profile given by power law function with p=2. The bending stresses were significantly affected by the thermal stresses in the discs. The risk of failure for all-ceramic dental restorative systems can be significantly reduced by using trilayered systems (homogenous or graded interlayer) with the proper design.
THERMAL RESIDUAL STRESSES IN BILAYERED, TRILAYERED AND GRADED DENTAL CERAMICS
Fabris, Douglas; Souza, Júlio C.M.; Silva, Filipe S.; Fredel, Márcio; Mesquita-Guimarães, Joana; Zhang, Yu; Henriques, Bruno
2017-01-01
Layered ceramic systems are usually hit by residual thermal stresses created during cooling from high processing temperature. The purpose of this study was to determine the thermal residual stresses at different ceramic multi-layered systems and evaluate their influence on the bending stress distribution. Finite elements method was used to evaluate the residual stresses in zirconia-porcelain and alumina-porcelain multi-layered discs and to simulate the ‘piston-on-ring’ test. Temperature-dependent material properties were used. Three different multi-layered designs were simulated: a conventional bilayered design; a trilayered design, with an intermediate composite layer with constant composition; and a graded design, with an intermediate layer with gradation of properties. Parameters such as the interlayer thickness and composition profiles were varied in the study. Alumina-porcelain discs present smaller residual stress than the zirconia-porcelain discs, regardless of the type of design. The homogeneous interlayer can yield a reduction of ~40% in thermal stress relative to bilayered systems. Thinner interlayers favoured the formation of lower thermal stresses. The graded discs showed the lowest thermal stresses for a gradation profile given by power law function with p=2. The bending stresses were significantly affected by the thermal stresses in the discs. The risk of failure for all-ceramic dental restorative systems can be significantly reduced by using trilayered systems (homogenous or graded interlayer) with the proper design. PMID:28163345
Effect of Gradients in Multi-Axial Stress States on Residual Stress Measurements with X-Rays.
1982-03-30
previous comments on this matter. (5) 2) Analysis of even slightly curved "d" vs sin2* plots assuming a bi-axial surface stress state may cause high...AD-A13 752 NORTHWESTERN UNIV EVANSTON IL DEPT OF MATERIALS SCIENCE F/G 20/3 EFFECT OF GRADIENTS IN MULTI-AXIAL STRESS STATES ON RESIDUAL ST-ETC(U...Research March 30, 1982 Contract N00014-80-C-0116 EFFECT OF GRADIENTS IN MULTI-AXIAL STRESS STATES ON RESIDUAL STRESS MEASUREMENTS WITH X-RAYS by I. C
Experiment and numerical simulation for laser ultrasonic measurement of residual stress.
Zhan, Yu; Liu, Changsheng; Kong, Xiangwei; Lin, Zhongya
2017-01-01
Laser ultrasonic is a most promising method for non-destructive evaluation of residual stress. The residual stress of thin steel plate is measured by laser ultrasonic technique. The pre-stress loading device is designed which can easily realize the condition of the specimen being laser ultrasonic tested at the same time in the known stress state. By the method of pre-stress loading, the acoustoelastic constants are obtained and the effect of different test directions on the results of surface wave velocity measurement is discussed. On the basis of known acoustoelastic constants, the longitudinal and transverse welding residual stresses are measured by the laser ultrasonic technique. The finite element method is used to simulate the process of surface wave detection of welding residual stress. The pulsed laser is equivalent to the surface load and the relationship between the physical parameters of the laser and the load is established by the correction coefficient. The welding residual stress of the specimen is realized by the ABAQUS function module of predefined field. The results of finite element analysis are in good agreement with the experimental method. The simple and effective numerical and experimental methods for laser ultrasonic measurement of residual stress are demonstrated.
Method for residual stress relief and retained austenite destabilization
Ludtka, Gerard M.
2004-08-10
A method using of a magnetic field to affect residual stress relief or phase transformations in a metallic material is disclosed. In a first aspect of the method, residual stress relief of a material is achieved at ambient temperatures by placing the material in a magnetic field. In a second aspect of the method, retained austenite stabilization is reversed in a ferrous alloy by applying a magnetic field to the alloy at ambient temperatures.
Roller Burnishing - A Cold Working Tool to Reduce Weld Induced Residual Stress
John Martin
2002-02-19
The possibility of stress corrosion cracking (SCC) in regions of tensile residual stress introduced by weld deposited material has been a concern where environmental effects can reduce component life. Roller burnishing, a form of mechanical cold-working, has been considered as a means of providing for residual stress state improvements. This paper provides a computational evaluation of the roller burnishing process to address the permanent deformation needed to introduce a desirable residual stress state. The analysis uses a series of incrementally applied pressure loadings and finite element methodology to simulate the behavior of a roller burnishing tool. Various magnitudes of applied pressure loadings coupled with different size plates and boundary conditions are examined to assess the degree and depth of the residual compressive stress state after cold working. Both kinematic and isotropic hardening laws are evaluated.
NASA Astrophysics Data System (ADS)
Santa-aho, Suvi; Sorsa, Aki; Hakanen, Merja; Leiviskä, Kauko; Vippola, Minnamari; Lepistö, Toivo
2014-08-01
In this study, Barkhausen noise (BN) magnetizing voltage sweep (MVS) measurement is used to evaluate non-destructively the surface residual stress state of hardened components. A new computational feature, where the maximum slope of the sweep is divided by the corresponding magnetizing voltage, is introduced. The results show that this feature has a linear relationship with the residual stress state of the samples. The determination of residual stresses during online production of components is a highly recognized task because tensile stresses may be detrimental to the component. In this study, two sets of hardened samples are used in the analysis. A linear relationship is observed in each sample set indicating that the new feature is applicable in assessment of surface residual stresses of the components.
Crack prediction in EB-PVD thermal barrier coatings based on the simulation of residual stresses
NASA Astrophysics Data System (ADS)
Chen, J. W.; Zhao, Y.; Liu, S.; Zhang, Z. Z.; Ma, J.
2016-07-01
Thermal barrier coatings systems (TBCs) are widely used in the field of aerospace. The durability and insulating ability of TBCs are highly dependent on the residual stresses of top coatings, thus the investigation of the residual stresses is helpful to understand the failure mechanisms of TBCs. The simulation of residual stresses evolution in electron beam physical vapor deposition (EB-PVD) TBCs is described in this work. The interface morphology of TBCs subjected to cyclic heating and cooling is observed using scanning electron microscope (SEM). An interface model of TBCs is established based on thermal elastic-plastic finite method. Residual stress distributions in TBCs are obtained to reflect the influence of interfacial roughness. Both experimental and simulation results show that it is feasible to predict the crack location by stress analysis, which is crucial to failure prediction.
Residual stress and plastic anisotropy in indented 2024-T351 aluminum disks
Clausen, Bjorn; Prime, Michael B; Saurabh, Kabra; Brown, Donald W; Pagliaro, Pierluigi; Backlund, Peter; Shaw, Sanjiv; Criss, Everett
2009-01-01
Recent studies have proven that generating a well defined residual stress state using the indented disk approach is an excellent way to validate experimental and modeling techniques for measuring and predicting residual stresses. The previous studies dealt with indented stainless steel disks, and included experimental determination of residual stresses using the Contour Method and neutron diffraction measurements. The measured residual stress states showed good agreement between the techniques, and a Finite Element Model predicted residual stress state based upon material properties determined form standard tension and compression/tension tests was also in good agreement with the measurements. In the present work, disks of 2024-T351 Aluminum were investigated. As before, the residual stress profile was measured using neutron diffraction and the Contour Method and Finite Element Modeling was employed to predict the residual stress profile. Analysis and comparison of the three techniques were complicated by the fact that the experimental data shows evidence of plastic anisotropy and strong Bauschinger effect within the indented disks.
Mochizuki, Masahito; Hayashi, Makoto; Hattori, Toshio
2000-02-01
Residual stress in a large-diameter multi-pass butt-welded pipe joint was calculated for various welding pass sequences by thermal elastic-plastic analysis using the finite element method. The pipe joint used had an X-shaped groove, and the sequences of welding passes were changed. The distribution of residual stress depends on the welding pass sequences. The mechanism that produces residual stress in the welded pipe joint was studied in detail by using a simple prediction model. An optimum welding sequence for preventing stress-corrosion cracking was determined from the residual stress distribution.
Estimation of uncertainty for contour method residual stress measurements
Olson, Mitchell D.; DeWald, Adrian T.; Prime, Michael B.; Hill, Michael R.
2014-12-03
This paper describes a methodology for the estimation of measurement uncertainty for the contour method, where the contour method is an experimental technique for measuring a two-dimensional map of residual stress over a plane. Random error sources including the error arising from noise in displacement measurements and the smoothing of the displacement surfaces are accounted for in the uncertainty analysis. The output is a two-dimensional, spatially varying uncertainty estimate such that every point on the cross-section where residual stress is determined has a corresponding uncertainty value. Both numerical and physical experiments are reported, which are used to support the usefulness of the proposed uncertainty estimator. The uncertainty estimator shows the contour method to have larger uncertainty near the perimeter of the measurement plane. For the experiments, which were performed on a quenched aluminum bar with a cross section of 51 × 76 mm, the estimated uncertainty was approximately 5 MPa (σ/E = 7 · 10⁻⁵) over the majority of the cross-section, with localized areas of higher uncertainty, up to 10 MPa (σ/E = 14 · 10⁻⁵).
Estimation of uncertainty for contour method residual stress measurements
Olson, Mitchell D.; DeWald, Adrian T.; Prime, Michael B.; ...
2014-12-03
This paper describes a methodology for the estimation of measurement uncertainty for the contour method, where the contour method is an experimental technique for measuring a two-dimensional map of residual stress over a plane. Random error sources including the error arising from noise in displacement measurements and the smoothing of the displacement surfaces are accounted for in the uncertainty analysis. The output is a two-dimensional, spatially varying uncertainty estimate such that every point on the cross-section where residual stress is determined has a corresponding uncertainty value. Both numerical and physical experiments are reported, which are used to support the usefulnessmore » of the proposed uncertainty estimator. The uncertainty estimator shows the contour method to have larger uncertainty near the perimeter of the measurement plane. For the experiments, which were performed on a quenched aluminum bar with a cross section of 51 × 76 mm, the estimated uncertainty was approximately 5 MPa (σ/E = 7 · 10⁻⁵) over the majority of the cross-section, with localized areas of higher uncertainty, up to 10 MPa (σ/E = 14 · 10⁻⁵).« less
Watkins, Thomas R; Lance, Michael J; Kasichainula, Jagannadham
2006-01-01
Diamond films were deposited via microwave plasma chemical vapor deposition on lithium niobate (LN) substrates. Characterization of the interfacial regions formed between diamond films and LN substrates was carried out by several techniques. Secondary ion mass spectroscopy (SIMS) was used to determine the depth profiles of carbon, lithium, niobium, and oxygen in the LN substrate covered with diamond nuclei and in the substrate without nucleation. Results indicate that the diamond nuclei promoted growth of diamond, and in addition, a reduced depth of the lithium deficient zone formed in the LN substrate was observed. Grazing incidence x-ray diffraction and transmission electron microscopy observations corroborated the results obtained by SIMS. Residual stresses determined experimentally by an x-ray method or by the shift in the characteristic diamond peak in Raman spectroscopy were much smaller than the calculated thermal residual stresses. The results further emphasize that the interfacial phases are responsible for relieving the thermal stresses generated during cooling of the layered structure. The thickness of the interfacial region was found to be well below for attenuation of the surface acoustic waves in the gigahertz frequency surface acoustic wave devices.
NASA Astrophysics Data System (ADS)
Bharatish, A.; Narasimha Murthy, H. N.; Aditya, G.; Anand, B.; Satyanarayana, B. S.; Krishna, M.
2015-07-01
This paper presents evaluation of thermal residual stresses in the heat affected zone of laser drilled alumina ceramic by using Micro-Raman spectroscopy. The residual stresses were evaluated for the holes corresponding to the optimal parameters of laser power, scanning speed, frequency and hole diameter. Three such cases were considered for the study. Residual stresses were obtained as a function of the Raman shifts. The nature and magnitude of the residual stresses were indicative of the extent of damage caused in the heat affected zone. In cases where the initial tensile residual stresses exceeded the tensile strength of alumina, cracks were initiated. Laser drilling with higher laser power and lower scanning speed induced initially high compressive and cyclic thermal stresses, causing greater damage to the hole. Transient thermal analysis was performed using COMSOL Multiphysics to predict residual thermal stresses and to validate the micro-Raman results. Scanning Electron Microscopy was used to confirm the damage caused in the heat affected zone.
Nondestructive method for measuring residual stresses in metals, a concept
NASA Technical Reports Server (NTRS)
Schwebel, C. D.
1968-01-01
Nondestructive direct measurement of residual surface stresses in metals can be made because metal under stress has a different electrochemical solution potential than in the unstressed condition. The method uses two matched electrolytic cells to cancel extraneous effects on the actual solution potential of the metal specimen.
Computational modelling of bone cement polymerization: temperature and residual stresses.
Pérez, M A; Nuño, N; Madrala, A; García-Aznar, J M; Doblaré, M
2009-09-01
The two major concerns associated with the use of bone cement are the generation of residual stresses and possible thermal necrosis of surrounding bone. An accurate modelling of these two factors could be a helpful tool to improve cemented hip designs. Therefore, a computational methodology based on previous published works is presented in this paper combining a kinetic and an energy balance equation. New assumptions are that both the elasticity modulus and the thermal expansion coefficient depend on the bone cement polymerization fraction. This model allows to estimate the thermal distribution in the cement which is later used to predict the stress-locking effect, and to also estimate the cement residual stresses. In order to validate the model, computational results are compared with experiments performed on an idealized cemented femoral implant. It will be shown that the use of the standard finite element approach cannot predict the exact temporal evolution of the temperature nor the residual stresses, underestimating and overestimating their value, respectively. However, this standard approach can estimate the peak and long-term values of temperature and residual stresses within acceptable limits of measured values. Therefore, this approach is adequate to evaluate residual stresses for the mechanical design of cemented implants. In conclusion, new numerical techniques should be proposed in order to achieve accurate simulations of the problem involved in cemented hip replacements.
Determination of Residual Stress in Composite Materials Using Ultrasonic Waves
NASA Technical Reports Server (NTRS)
Rokhlin, S. I.
1997-01-01
The performance of high temperature composites can be significantly affected by the presence of residual stresses. These stresses arise during cooling processes from fabrication to room temperature due to mismatch of thermal expansion coefficients between matrix and fiber materials. This effect is especially pronounced in metal matrix and intermetallic composites. It can lead to plastic deformations, matrix cracking and fiber/matrix interface debonding. In this work the feasibility of ultrasonic techniques for residual stress assessment in composites is addressed. A novel technique for absolute stress determination in orthotropic materials from angular dependencies of ultrasonic velocities is described. The technique is applicable for determination of both applied and residual stresses and does not require calibration measurements on a reference sample. The important advantage of this method is that stress is determined simultaneously with stress-dependent elastic constants and is thus decoupled from the material texture. It is demonstrated that when the principal plane stress directions coincide with acoustical axes, the angular velocity data in the plane perpendicular to the stress plane may be used to determine both stress components. When the stress is off the acoustical axes, the shear and the difference of the normal stress components may be determined from the angular dependence of group velocities in the plane of stresses. Synthetic sets of experimental data corresponding to materials with different anisotropy and stress levels are used to check the applicability of the technique. The method is also verified experimentally. A high precision ultrasonic wave transmission technique is developed to measure angular dependence of ultrasonic velocities. Examples of stress determination from experimental velocity data are given. A method is presented for determination of velocities of ultrasonic waves propagating through the composite material with residual
Stress Free Temperature Testing and Residual Stress Calculations on Out-of-Autoclave Composites
NASA Technical Reports Server (NTRS)
Cox, Sarah; Tate, LaNetra C.; Danley, Susan; Sampson, Jeff; Taylor, Brian; Miller, Sandi
2012-01-01
Future launch vehicles will require the incorporation large composite parts that will make up primary and secondary components of the vehicle. NASA has explored the feasibility of manufacturing these large components using Out-of-Autoclave impregnated carbon fiber composite systems through many composites development projects. Most recently, the Composites for Exploration Project has been looking at the development of a 10 meter diameter fairing structure, similar in size to what will be required for a heavy launch vehicle. The development of new material systems requires the investigation of the material properties and the stress in the parts. Residual stress is an important factor to incorporate when modeling the stresses that a part is undergoing. Testing was performed to verify the stress free temperature with two-ply asymmetric panels. A comparison was done between three newly developed out of autoclave IM7 /Bismalieimide (BMI) systems. This paper presents the testing results and the analysis performed to determine the residual stress of the materials.
NASA Technical Reports Server (NTRS)
Schuessler, Philipp WH
2010-01-01
In August 2008, Schuessler Consulting was contracted by NASA GSFC in support of the NASA Electronic Parts and Packaging (NEPP) program to perform two separate studies on moisture laden air in a stainless steel cylinder that had been designed to become a consensus standard for Test Method 1018. This Test Method was originally released for hybrids under Mil. Std. 883 but was quickly utilized on other microelectronic devices under the auspice of Mil. Std. 750. The cylinder had subsequently been fabricated for the 750 community. It was back-filled with moist air and subsequently analyzed over a period of time under a previous NASA contract. It had been shown that moisture in the 4000 - 5000 ppm range could be analyzed rather precisely with a mass spectrometer, commonly referred to as a Residual Gas Analyzer (RGA). The scope of this study was to ascertain if the composition and precision varied as a function of thermal shock at sub-zero temperatures and whether there was consensus when the standard was submitted to other RGA units. It was demonstrated and published that the consensus standard would yield precise RGA data for moisture within +/- 1% when optimized for a given RGA unit. It has been subsequently shown in this study at Oneida Research Services, that sub-zero storage did not affect that precision when a well-defined protocol for the analysis was followed. The consensus standard was taken to a second facility for analysis where it was found that moisture adsorption on the transfer lines caused precision to drop to +/- 12%. The Single Sample Cylinder (SSC) is a one liter stainless steel cylinder with associated sampling valves and has considerable weight and volume. But this considerable size allows for approximately 300 gas samples of the same composition to be delivered to any RGA unit. Lastly, a smaller cylinder, approximately 75 cc, of a second consensus standard was fabricated and tested with a different mix of fixed gases where moisture was kept in the
Residual stress measurement and microstructural characterization of thick beryllium films
Detor, A; Wang, M; Hodge, A M; Chason, E; Walton, C; Hamza, A V; Xu, H; Nikroo, A
2008-02-11
Beryllium films are synthesized by a magnetron sputtering technique incorporating in-situ residual stress measurement. Monitoring the stress evolution in real time provides quantitative through-thickness information on the effects of various processing parameters, including sputtering gas pressure and substrate biasing. Specimens produced over a wide range of stress states are characterized via transmission and scanning electron microscopy, and atomic force microscopy, in order to correlate the stress data with microstructure. A columnar grain structure is observed for all specimens, and surface morphology is found to be strongly dependent on processing conditions. Analytical models of stress generation are reviewed and discussed in terms of the observed microstructure.
A New Methodology For In-Situ Residual Stress Measurement In MEMS Structures
Sebastiani, M.; Bemporad, E.; Melone, G.; Rizzi, L.; Korsunsky, A. M.
2010-11-24
In this paper, a new approach is presented for local residual stress measurement in MEMS structures. The newly proposed approach involves incremental focused ion beam (FIB) milling of annular trenches at material surface, combined with high resolution SEM imaging and Digital Image Correlation (DIC) analysis for the measurement of the strain relief over the surface of the remaining central pillar. The proposed technique allows investigating the average residual stress on suspended micro-structures, with a spatial resolution lower than 1 {mu}m. Results are presented for residual stress measurement on double clamped micro-beams, whose layers are obtained by DC-sputtering (PVD) deposition. Residual stresses were also independently measured by the conventional curvature method (Stoney's equation) on a similar homogeneous coating obtained by the same deposition parameters and a comparison and discussion of obtained results is performed.
A New Methodology For In-Situ Residual Stress Measurement In MEMS Structures
NASA Astrophysics Data System (ADS)
Sebastiani, M.; Bemporad, E.; Melone, G.; Rizzi, L.; Korsunsky, A. M.
2010-11-01
In this paper, a new approach is presented for local residual stress measurement in MEMS structures. The newly proposed approach involves incremental focused ion beam (FIB) milling of annular trenches at material surface, combined with high resolution SEM imaging and Digital Image Correlation (DIC) analysis for the measurement of the strain relief over the surface of the remaining central pillar. The proposed technique allows investigating the average residual stress on suspended micro-structures, with a spatial resolution lower than 1 μm. Results are presented for residual stress measurement on double clamped micro-beams, whose layers are obtained by DC-sputtering (PVD) deposition. Residual stresses were also independently measured by the conventional curvature method (Stoney's equation) on a similar homogeneous coating obtained by the same deposition parameters and a comparison and discussion of obtained results is performed.
Gyrokinetic Simulation of Residual Stress from Diamagnetic Velocity Shears
NASA Astrophysics Data System (ADS)
Waltz, R. E.; Staebler, G. M.; Solomon, W. M.
2010-11-01
Residual stress refers to the remaining toroidal angular momentum (TAM) flux (divided by major radius) when the shear in the parallel velocity (and parallel velocity itself) vanishes. Previously [1] we demonstrated with gyrokinetic (GYRO) simulations that TAM pinching from the diamagnetic level shear in the ExB velocity could provide the residual stress needed for spontaneous toroidal rotation. Here we show that the shear in the diamagnetic velocities themselves provide comparable residual stress (and level of stabilization). The sign of the residual stress, quantified by the ratio of TAM flow to ion power flow (M/P), depends on the signs of the various velocity shears as well as ion (ITG) versus electron (TEM) mode directed turbulence. The residual stress from these temperature and density gradient diamagnetic velocity shears is demonstrated in global gyrokinetic simulation of ``null'' rotation DIIID discharges by matching M/P profiles within experimental error. 8pt [1] R.E. Waltz, G.M. Staebler, J. Candy, and F.L. Hinton, Phys. Plasmas 14, 122507 (2007); errata 16, 079902 (2009).
Akça, K; Iplikçioğlu, H
2001-01-01
Buccolingual angulation of the mandibular posterior edentulous region may affect the prosthetic load conditions, so as to cause high stress concentrated areas that may easily lead to failure. The aim of this study was to evaluate the effect of various predetermined buccolingual angulation values on stress distribution in the mandibular posterior edentulous region restored with implant-supported fixed partial dentures, using three-dimensional finite element analysis. Stress analyses were performed applying 400N oblique force to implant-supported fixed prosthesis. Stress analyses indicated tensile stress values on the buccal surface and compressive stress values on the lingual surface of cortical bone were increased as the angulation of the edentulous bone increased (especially corresponding to the cervical region of the implants). Compressive stress values, observed where two implants were placed at the second premolar and second molar regions (5-7 design) and first and second molar regions (6-7 design), respectively, were very close to or even exceeded the ultimate compressive strength of bone. It is concluded that when a definite buccolingual angulation is added to other existing risk factors such as bruxism, placing an implant for every missing tooth might reduce the high stress concentration areas.
Measured Biaxial Residual Stress Maps in a Stainless Steel Weld
Olson, Mitchell D.; Hill, Michael R.; Patel, Vipul I.; Muransky, Ondrej; Sisneros, Thomas A.
2015-09-16
Here, this paper describes a sequence of residual stress measurements made to determine a two-dimensional map of biaxial residual stress in a stainless steel weld. A long stainless steel (316L) plate with an eight-pass groove weld (308L filler) was used. The biaxial stress measurements follow a recently developed approach, comprising a combination of contour method and slitting measurements, with a computation to determine the effects of out-of-plane stress on a thin slice. The measured longitudinal stress is highly tensile in the weld- and heat-affected zone, with a maximum around 450 MPa, and compressive stress toward the transverse edges around ₋250 MPa. The total transverse stress has a banded profile in the weld with highly tensile stress at the bottom of the plate (y = 0) of 400 MPa, rapidly changing to compressive stress (at y = 5 mm) of ₋200 MPa, then tensile stress at the weld root (y = 17 mm) and in the weld around 200 MPa, followed by compressive stress at the top of the weld at around ₋150 MPa. Finally, the results of the biaxial map compare well with the results of neutron diffraction measurements and output from a computational weld simulation.
Measured Biaxial Residual Stress Maps in a Stainless Steel Weld
Olson, Mitchell D.; Hill, Michael R.; Patel, Vipul I.; ...
2015-09-16
Here, this paper describes a sequence of residual stress measurements made to determine a two-dimensional map of biaxial residual stress in a stainless steel weld. A long stainless steel (316L) plate with an eight-pass groove weld (308L filler) was used. The biaxial stress measurements follow a recently developed approach, comprising a combination of contour method and slitting measurements, with a computation to determine the effects of out-of-plane stress on a thin slice. The measured longitudinal stress is highly tensile in the weld- and heat-affected zone, with a maximum around 450 MPa, and compressive stress toward the transverse edges around ₋250more » MPa. The total transverse stress has a banded profile in the weld with highly tensile stress at the bottom of the plate (y = 0) of 400 MPa, rapidly changing to compressive stress (at y = 5 mm) of ₋200 MPa, then tensile stress at the weld root (y = 17 mm) and in the weld around 200 MPa, followed by compressive stress at the top of the weld at around ₋150 MPa. Finally, the results of the biaxial map compare well with the results of neutron diffraction measurements and output from a computational weld simulation.« less
Residual stresses in oxide scale formed on Fe-17Cr stainless steel
NASA Astrophysics Data System (ADS)
Li, Ning; Xiao, Ji; Prud'homme, Nathalie; Chen, Zhe; Ji, Vincent
2014-10-01
The purpose of this work was to investigate residual stresses in the oxide scale formed on ferritic stainless steel, which is proposed to be used as interconnector in the planar solid oxide fuel cells (SOFCs). The oxidation of the alloy has been conducted at 700 °C, 800 °C and 900 °C for 12-96 h by thermal gravimetric analysis (TGA) system. The oxide surface morphology, cross-section microstructure and the chemical composition of the oxide scale were studied after oxidation, and the residual stresses distribution of the oxide scale were determined at room temperature. It has been found that the oxide scale composed of an inner Cr2O3 layer and an outer Mn1.5Cr1.5O4 spinel layer, the residual stresses in both oxide layers are compressive and the growth stresses plays an important role. The competition of the stresses generation and relaxation during oxidation and cooling affects the residual stresses level. The evolution of residual stresses in the two layers is different according to the oxidation temperature, and the stresses in the two layers are interactional.
Residual stresses in weld overlay tubes: A finite element study
Taljat, B.; Zacharia, T.; Wang, X.L.; Keiser, J.R.; Feng, Z.; Jirinec, M.J.
1997-01-03
Residual stresses and strains in a tube with circumferential weld overlay were analyzed by the finite element (FE) method. The objective of this work was to develop and verify a FE model, to determine the magnitude and distribution of residual stresses in the weld overlay tube, and to evaluate the significance of two contributing factors to residual stress: (1) difference in material properties between tube and weld material, and (2) thermal gradients in the weld. An axisymmetric FE model was developed to simulate the circumferential two-layer welding process of alloy 625 overlay on SA210 tube. The first layer was modeled as a gas metal arc welding process with filler metal, whereas the autogenous gas tungsten arc welding process was modeled for the second layer. Neutron diffraction technique was used to experimentally determine residual elastic strains in the weld overlay tube. Comparison with the FE results shows overall good agreement. Both the experimental and FE results show high compressive stresses at the inside tube surface and high tensile stresses in the weld overlay. This suggests that weld overlay may be used to relieve tensile or produce compressive stresses at the inside tube surface, which is significant for applications where crack initiation is found at the root pass of the joining weld.
Residual stresses in injection molded shape memory polymer parts
NASA Astrophysics Data System (ADS)
Katmer, Sukran; Esen, Huseyin; Karatas, Cetin
2016-03-01
Shape memory polymers (SMPs) are materials which have shape memory effect (SME). SME is a property which has the ability to change shape when induced by a stimulator such as temperature, moisture, pH, electric current, magnetic field, light, etc. A process, known as programming, is applied to SMP parts in order to alter them from their permanent shape to their temporary shape. In this study we investigated effects of injection molding and programming processes on residual stresses in molded thermoplastic polyurethane shape memory polymer, experimentally. The residual stresses were measured by layer removal method. The study shows that injection molding and programming process conditions have significantly influence on residual stresses in molded shape memory polyurethane parts.
Residual stress control by ion beam assisted deposition
Was, G.S.; Jones, J.W.; Parfitt, L.; Kalnas, C.E.; Goldiner, M.
1996-12-31
The origin of residual stresses were studied in both crystalline metallic films and amorphous oxide films made by ion beam assisted deposition (IBAD). Monolithic films of Al{sub 2}O{sub 3} were deposited during bombardment by Ne, Ar or Kr over a narrow range of energies, E, and a wide range of ion-to-atom arrival rate ratios, R and were characterized in terms of composition, thickness, density, crystallinity, microstructure and residual stress. The stress was a strong function of ion beam parameters and gas content and compares to the behavior of other amorphous compounds such as MoSi{sub x} and WSi{sub 2.2}. With increasing normalized energy (eV/atom), residual stress in crystalline metallic films (Mo, W) increases in the tensile direction before reversing and becoming compressive at high normalized energy. The origin of the stress is most likely due to densification or interstitial generation. Residual stress in amorphous films (Al{sub 2}O{sub 3}, MoSi{sub x} and WSi{sub 2.2}) is initially tensile and monotonically decreases into the compressive region with increasing normalized energy. The amorphous films also incorporate substantially more gas than crystalline films and in the case of Al{sub 2}O{sub 3} are characterized by a high density of voids. Stress due to gas pressure in existing voids explains neither the functional dependence on gas content nor the magnitude of the observed stress. A more likely explanation for the behavior of stress is gas incorporation into the matrix, where the amount of incorporated gas is controlled by trapping.
On Taylor-Series Approximations of Residual Stress
NASA Technical Reports Server (NTRS)
Pruett, C. David
1999-01-01
Although subgrid-scale models of similarity type are insufficiently dissipative for practical applications to large-eddy simulation, in recently published a priori analyses, they perform remarkably well in the sense of correlating highly against exact residual stresses. Here, Taylor-series expansions of residual stress are exploited to explain the observed behavior and "success" of similarity models. Until very recently, little attention has been given to issues related to the convergence of such expansions. Here, we re-express the convergence criterion of Vasilyev [J. Comput. Phys., 146 (1998)] in terms of the transfer function and the wavenumber cutoff of the grid filter.
Modeling of residual stresses by HY-100 weldments
Zacharia, T.; Taljat, B.; Radhakrishnan, B.
1997-02-01
Residual stress distribution in a HY-100 steel disk, induced by GTA spot welding, was analyzed by finite element (FE) formulations and measured by neutron diffraction (ND). Computations used temperature- dependent thermophysical and mechanical properties. FE model predictions are in good agreement with ND data in far heat affected zone (HAZ) and in base metal. Predicted residual stresses in fusion zone and near HAZ were higher than those measured by ND. This discrepancy was attributed to microstructural changes and associated material properties in the HAZ and fusion zone due to phase transformations during the weld thermal cycle.
2014-01-01
Hole drilling is the most widespread method for measuring residual stress. It is based on the principle that drilling a hole in the material causes a local stress relaxation; the initial residual stress can be calculated by measuring strain in correspondence with each drill depth. Recently optical techniques were introduced to measure strain; in this case, the accuracy of the final results depends, among other factors, on the proper choice of the area of analysis. Deformations are in fact analyzed within an annulus determined by two parameters: the internal and the external radius. In this paper, the influence of the choice of the area of analysis was analysed. A known stress field was introduced on a Ti grade 5 sample and then the stress was measured in correspondence with different values of the internal and the external radius of analysis; results were finally compared with the expected theoretical value. PMID:25276850
Hayashi, Yoshihiro; Miura, Takahiro; Shimada, Takuya; Onuki, Yoshinori; Obata, Yasuko; Takayama, Kozo
2013-10-01
Tablet characteristics of tensile strength and disintegration time were predicted using residual stress distribution, simulated by the finite element method (FEM). The Drucker-Prager Cap (DPC) model was selected as the method for modeling the mechanical behavior of pharmaceutical powders composed of lactose (LAC), cornstarch (CS), and microcrystalline cellulose (MCC). The DPC model was calibrated using a direct shear test and analysis of the hardening law of the powder. The constructed DPC model was fed into the analysis using the FEM, and the mechanical behavior of pharmaceutical powders during compaction was analyzed using the FEM. The results revealed that the residual stress distribution of the tablets was uniform when the compression force increased. In particular, the residual stress distribution of tablets composed of equal amounts of LAC, CS, and MCC was more uniform than the tablets composed of 67% LAC and 33% CS, with no MCC. The tensile strength and disintegration time were predicted accurately from the residual stress distribution of tablets using multiple linear regression analysis and partial least squares regression analysis. This suggests that the residual stress distribution of tablets is related closely to the tensile strength and disintegration time. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association.
Residual stress characterization with an ultrasonic/magnetic technique
NASA Technical Reports Server (NTRS)
Namkung, M.; Heyman, J. S.
1984-01-01
A potentially useful new technique for residual stress characterization in ferromagnetic material is described. The unique feature of this technique is the measurement of small changes in ultrasonic wave velocity by the application of external dc magnetic field in the material under various stress conditions. It was found, in steel, that the fractional change in the natural velocity Delta W/W of waves propagating along the external field direction is affected by the uniaxial stress applied in the same axis. External compression lowers the slope of the Delta W/W curve in the low field region, while external tension generally does the opposite. For most cases, the slope in this region falls below zero under external compression. The result of measurements in specimens with residual stress shows exactly the same tendency.
NASA Astrophysics Data System (ADS)
Kitamura, K.; Nagata, K.; Shibui, M.; Tachikawa, N.; Araki, M.
1998-10-01
Residual stresses in the interface region, that developed at the cool down during the brazing, were evaluated for several bonded structures to assess the mechanical strength of the bonded interface, using thermoelasto-plastic stress analysis. Normal stress components of the residual stresses around the interface edge of graphite-copper (C-Cu) bonded structures were compared for three types of bonded features such as flat-type, monoblock-type and saddle-type. The saddle-type structure was found to be favorable for its relatively low residual stress, easy fabrication accuracy on bonded interface and armor replacement. Residual stresses around the interface edge in three armor materials/copper bonded structures for a divertor plate were also examined for the C-Cu, tungsten-copper (W-Cu) and molybdenum alloy-copper (TZM-Cu), varying the interface wedge angle from 45° to 135°. An optimal bonded configuration for the least value of residual stress was found to have a wedge angle of 45° for the C-Cu, and 135° for both the W-Cu and TZM-Cu bonded ones.
NASA Astrophysics Data System (ADS)
Stegemann, Robert; Cabeza, Sandra; Lyamkin, Viktor; Bruno, Giovanni; Pittner, Andreas; Wimpory, Robert; Boin, Mirko; Kreutzbruck, Marc
2017-03-01
The residual stress distribution of tungsten inert gas welded S235JRC+C plates was determined by means of neutron diffraction (ND). Large longitudinal residual stresses with maxima around 600 MPa were found. With these results as reference, the evaluation of residual stress with high spatial resolution GMR (giant magneto resistance) sensors was discussed. The experiments performed indicate a correlation between changes in residual stresses (ND) and the normal component of local residual magnetic stray fields (GMR). Spatial variations in the magnetic field strength perpendicular to the welds are in the order of the magnetic field of the earth.
Residual Stress Measurements of Explosively Clad Cylindrical Pressure Vessels
Taylor, Douglas J; Watkins, Thomas R; Hubbard, Camden R; Hill, M. R.; Meith, W. A.
2012-01-01
Tantalum refractory liners were explosively clad into cylindrical pressure vessels, some of which had been previously autofrettaged. Using explosive cladding, the refractory liner formed a metallurgical bond with the steel of the pressure vessel at a cost of induced strain. Two techniques were employed to determine the residual stress state of the clad steel cylinders: neutron diffraction and mechanical slitting. Neutron diffraction is typically nondestructive; however, due to attenuation along the beam path, the cylinders had to be sectioned into rings that were nominally 25 mm thick. Slitting is a destructive method, requiring the sectioning of the cylindrical samples. Both techniques provided triaxial stress data and useful information on the effects of explosive cladding. The stress profiles in the hoop and radial directions were similar for an autofrettaged, nonclad vessel and a clad, nonautofrettaged vessel. The stress profiles in the axial direction appeared to be different. Further, the data suggested that residual stresses from the autofrettage and explosive cladding processes were not additive, in part due to evidence of reverse yielding. The residual stress data are presented, compared and discussed.
The impact of the residual stress on the EUV pellicle
NASA Astrophysics Data System (ADS)
Park, Eun-Sang; Choi, Jae-Keun; Kim, Min-Ha; Hwang, Sollee; Shamsi, Zahid Hussain; Kim, Dai-Gyoung; Oh, Hye-Keun
2016-05-01
High resolution patterning on the chip could be achieved by extreme ultraviolet lithography (EUVL). However, the defect on the mask becomes more important issue with very short wavelength (13.5 nm). Using the pellicle which could protect the mask from the defects can support high volume manufacturing (HVM). Most of the materials considered for pellicle have relatively high extinction coefficient in EUV region. Therefore, the thickness of the pellicle should be ~ nm thin. The stress of the pellicle is dependent not only on the temperature but also on the mechanical properties of the pellicle. The stress induced by the gravity was small compared to the thermal stress. However, the residual stress should be also considered since it is dependent on the pellicle manufacturing environment and this stress is comparable with the thermal stress. Our result shows the importance of the lowering the pellicle fabrication temperature in terms of the extending the lifetime during the scanning process.
Influence of residual stresses on ceramic-metal interfacial toughness
NASA Astrophysics Data System (ADS)
Thurston, Mark Edward
The critical property determining the extent to which ductile metal reinforcing particles can toughen a brittle ceramic matrix is the toughness of the ceramic-metal interface between particle and matrix. Unfortunately, due to the lack of understanding of the mechanics of bimaterial interfaces in the presence of residual stresses, experimental data on the fracture toughness of ceramic-metal interfaces is scarce. Consequently, the purpose of the present work is to account for the influence of residual stresses on the measured fracture toughness of a representative nickel/alumina system and, in conjunction with a maximum hoop stress criterion, to explain the observed increase in toughness with increasing mixity of loading. A finite element model incorporating the rate-dependent inelastic behavior of nickel at high temperatures was implemented in order to provide a realistic estimate of the residual stresses that develop during the bonding process. The calculated Mises equivalent stresses in the nickel averaged between 110 and 115 MPa, well above the room temperature yield strength of 82 MPa. For the sandwich specimens adopted in the current study, a simple argument yields a critical foil thickness below which residual stress effects are expected to be minimal. The influence of differing foil thicknesses below this threshold is shown to be insignificant. For sandwich specimens a general result is demonstrated: compared to the same loading applied without residual stresses present, the effect of residual stresses is to decrease the magnitude of the phase angle that will develop along the interface. Microprobe measurements verified that by controlling the bonding atmosphere the formation of a reaction product at the interface was prevented, and that the fracture mechanism was pure cleavage of the interface. The measured interfacial toughness values increased from 11 J/sq m at psi-caret approximately equals 0 deg to 22 J/sq m at psi-caret approximately equals +/-23 deg
NASA Astrophysics Data System (ADS)
Yu, H.; Tor, S. B.; Loh, N. H.; Asundi, A. K.
2013-01-01
Micro injection molding offers a promising approach to rapidly produce thermoplastic microfluidic substrates in large volumes. Many research works have been focused on the replication fidelity of microstructures by injection molding. However, there has not been any investigation on the effect of molded-in residual stress on microchannel deformation during the subsequent thermal bonding process. These effects could be important, because the residual stress developed due to anisotropic polymer flow orientation and inhomogeneous cooling may lead to abnormal microchannel distortion. In the direct thermal bonding process, asymmetric cross-sectional distortion was observed in well-formed microchannels aligned perpendicular to the polymer melt injection direction. This asymmetric distortion is attributed to the residual stress introduced into the substrates during molding, particularly in the surface region where microchannels are molded. Design of experiment on injection molding was carried out to reduce the residual stress in order to achieve the lowest microchannel deformation irregularity, which is a new term defined in this study. The direct thermal bonding was utilized as a feasible non-destructive indirectly quantitative method to evaluate the effect of residual stress around microchannel regarding deformation irregularity. The dominant molding parameters with positive effects were found to be melt temperature, mold temperature as well as cooling time after packing. The presence of the residual stress was also demonstrated through photoelastic stress analysis in terms of phase retardation. With improved molding condition, the absolute retardation difference around microchannels aligned parallel and perpendicular to the molding direction could be tuned to the same level, which indicates that the molded-in residual stresses have been moderated.
Thermoelastic Stress Analysis: The Mean Stress Effect in Metallic Alloys
NASA Technical Reports Server (NTRS)
Gyekenyesi, Andrew L.; Baaklini, George Y.
1999-01-01
The primary objective of this study involved the utilization of the thermoelastic stress analysis (TSA) method to demonstrate the mean stress dependence of the thermoelastic constant. Titanium and nickel base alloys, commonly employed in aerospace gas turbines, were the materials of interest. The repeatability of the results was studied through a statistical analysis of the data. Although the mean stress dependence was well established, the ability to confidently quantify it was diminished by the experimental variations. If calibration of the thermoelastic response to mean stress can be successfully implemented, it is feasible to use the relationship to determine a structure's residual stress state.
Study on residual stresses in ultrasonic torsional vibration assisted micro-milling
NASA Astrophysics Data System (ADS)
Lu, Zesheng; Hu, Haijun; Sun, Yazhou; Sun, Qing
2010-10-01
It is well known that machining induced residual stresses can seriously affect the dimensional accuracy, corrosion and wear resistance, etc., and further influence the longevity and reliability of Micro-Optical Components (MOC). In Ultrasonic Torsional Vibration Assisted Micro-milling (UTVAM), cutting parameters, vibration parameters, mill cutter parameters, the status of wear length of tool flank are the main factors which affect residual stresses. A 2D model of UTVAM was established with FE analysis software ABAQUS. Johnson-Cook's flow stress model and shear failure principle are used as the workpiece material model and failure principle, while friction between tool and workpiece uses modified Coulomb's law whose sliding friction area is combined with sticking friction. By means of FEA, the influence rules of cutting parameters, vibration parameters, mill cutter parameters, the status of wear length of tool flank on residual stresses are obtained, which provides a basis for choosing optimal process parameters and improving the longevity and reliability of MOC.
NASA Astrophysics Data System (ADS)
Aloraier, Abdulkareem S.; Joshi, Suraj; Price, John W. H.; Alawadhi, Khaled
2014-04-01
This paper investigates the effects of post-weld heat treatment (PWHT) and temper bead welding (TBW) on hardness, microstructure and residual stresses in multi-layer welding on low carbon steel specimens made with two different weld geometries, viz. (1) smooth-contoured and (2) U-shaped. It was found that the PWHT technique gave overall lower hardness than the TBW technique, but the hardness values in both techniques were acceptable. Microscopy analysis showed that the TBW technique was more effective in tempering the heat affected zone as the grain size decreased slightly at the fusion line in spite of the higher temperature at the fusion line. Residual stresses measured using the hole-drilling method showed that the residual stress is not reduced below yield stress near the last bead solidified in TBW. Only PWHT gives low residual stress results in this area. High tensile residual stresses may result in sensitivity to fatigue loading.
Determination of the residual stress-crack opening relationship of SFRC flexural members
NASA Astrophysics Data System (ADS)
Kaklauskas, Gintaris; Gribniak, Viktor; Meskenas, Adas; Rimkus, Arvydas; Kaklauskas, Arturas; Kupliauskas, Rimantas
2013-10-01
Steel fibre reinforced concrete (SFRC) has become widespread material in building areas such as underground shotcrete structures or industrial floors. However, due to the absence of universally accepted guidelines for SFRC, application fields of this material are still limited. This paper deals with assessment of the residual stresses of tensile SFRC. An adequate method for determination of residual stress-crack opening relation, based on test data of three-point bending beams is proposed. To verify the analysis results a numerical modelling is utilized employing a nonlinear finite element analysis program. Simulated load-crack width curves were compared with the experimental data validating adequacy of the proposed model.
Optical residual stress measurement in TFT-LCD panels
NASA Astrophysics Data System (ADS)
Wang, Wei-Chung; Sung, Po-Chi
2017-06-01
The residual stress of the glass substrate might be one of causes to produce the non-uniform light distribution defect, i.e. Mura, in thin film transistor-liquid crystal display (TFT-LCD) panels. Glass is a birefringent material with very low birefringence. Furthermore, the thinner and thinner thickness request from the market makes the traditional photoelasticity almost impossible to measure the residual stresses produced in thin glass plates. Recently, a low-level stress measurement method called transmissivity extremities theory of photoelasticity (TEToP) was successfully developed to measure the residual stress in glass plate. Besides, to measure the stress of the glass plate in the TFT-LCD panel whose rear surface may has different kinds of coatings, an advanced reflection photoelasticity was also developed. In this paper, three commercially available glass plates with 0.33mm nominal thickness and three glass circular disks with different coatings were inspected to verify the feasibility of the TEToP and the advanced reflection photoelasticity, respectively.
FEM simulation of residual stresses induced by laser Peening
NASA Astrophysics Data System (ADS)
Peyre, P.; Sollier, A.; Chaieb, I.; Berthe, L.; Bartnicki, E.; Braham, C.; Fabbro, R.
2003-08-01
Benefits from laser Peening have been demonstrated several times in fields like fatigue, wear or stress corrosion cracking. However, in spite of recent work on the calculation of residual stresses, very few authors have considered a finite element method (FEM) approach to predict laser-induced mechanical effect. This comes mainly from the high strain rates involved during LP (10^6 s^{-1}), that necessitate the precise determination of dynamic properties, and also from the possible combination of thermal and mechanical loadings in the case of LP without protective coatings. In this paper, we aim at presenting a global approach of the problem, starting from the determination of loading conditions and dynamic yield strengths, to finish with FEM calculation of residual stress fields induced on a 12% Cr martensitic stainless steel and a 7075 aluminium alloy.
Nondestructive testing and characterization of residual stress field using an ultrasonic method
NASA Astrophysics Data System (ADS)
Song, Wentao; Xu, Chunguang; Pan, Qinxue; Song, Jianfeng
2016-03-01
To address the difficulty in testing and calibrating the stress gradient in the depth direction of mechanical components, a new technology of nondestructive testing and characterization of the residual stress gradient field by ultrasonic method is proposed based on acoustoelasticity theory. By carrying out theoretical analysis, the sensitivity coefficients of different types of ultrasonic are obtained by taking the low carbon steel(12%C) as a research object. By fixing the interval distance between sending and receiving transducers, the mathematical expressions of the change of stress and the variation of time are established. To design one sending-one receiving and oblique incidence ultrasonic detection probes, according to Snell law, the critically refracted longitudinal wave (LCR wave) is excited at a certain depth of the fixed distance of the tested components. Then, the relationship between the depth of LCR wave detection and the center frequency of the probe in Q235 steel is obtained through experimental study. To detect the stress gradient in the depth direction, a stress gradient LCR wave detection model is established, through which the stress gradient formula is derived by the relationship between center frequency and detecting depth. A C-shaped stress specimen of Q235 steel is designed to conduct stress loading tests, and the stress is measured with the five group probes at different center frequencies. The accuracy of ultrasonic testing is verified by X-ray stress analyzer. The stress value of each specific depth is calculated using the stress gradient formula. Accordingly, the ultrasonic characterization of residual stress field is realized. Characterization results show that the stress gradient distribution is consistent with the simulation in ANSYS. The new technology can be widely applied in the detection of the residual stress gradient field caused by mechanical processing, such as welding and shot peening.
NASA Astrophysics Data System (ADS)
Lim, Hak-Jin; Ko, Dae-Hoon; Ko, Dae-Cheol; Kim, Byung-Min
2014-04-01
The purpose of this study is to reduce the residual stress and machining distortion of an Al6061 tube by using uphill quenching. During uphill quenching, solid-solution heat-treated aluminum parts are usually immersed in LN2 at 77 K (-196 °C), followed by the rapid heating of the parts, to produce a new residual stress that is opposite in nature to the original. The uphill quenching method used in this study employed two types of heating methods: boiling water at 373 K (100 °C) and high-velocity steam at 448 K (175 °C). First, FE-simulation coupled with a CFD analysis was performed to predict the residual stress of the backward hot-extruded Al6061 tube with the following dimensions: Ø200 mm × h200 mm × t10 mm. Experiment of uphill quenching was also conducted to measure the residual stress using the boiling water and high-velocity steam uphill quenching methods. The predicted residual stresses were compared with the experimental results obtained via micro-indentation and saw-cutting tests, and a deviation of about 10.4 pct was found. In addition, the experimental results showed that uphill quenching could relieve up to 91 pct of the residual stress induced by water quenching. Finally, the dimensional accuracy of uphill quenched tubes was evaluated by measuring the roundness after the machining process, which showed that the uphill quenching method could improve the dimensional accuracy of an Al6061 tube by reducing the residual stress.
Residual stress relaxation and fatigue behavior of an induction hardened microalloyed steel
NASA Astrophysics Data System (ADS)
Rivas, Ana Luisa Rivas De
The thermal and mechanical relaxation of compressive residual stresses during tempering and cyclic loading of an induction hardened vanadium microalloyed steel has been evaluated. A microstructural analysis was also carried out on the microalloyed steel to correlate the residual stress relaxation behavior with microstructural characteristics of the material. Vanadium carbide particle size and distribution were analyzed as well as how these characteristics are affected by the application of normalizing and induction hardening heat treatments. To determine the effect of vanadium carbide particles on the residual stress relaxation response of the microalloyed steel a parallel study was conducted on a 1530 steel which is similar in chemistry to the microalloyed steel, but without the vanadium. The thermal relaxation of compressive residual stresses due to tempering for 2 hours after induction hardening was evaluated for a range of tempering temperatures from 177sp° C\\ (350sp° F) to 579sp° C\\ (1075sp° F). Mechanical residual stress relaxation was evaluated by subjecting specimens to cyclic loading conditions. For this part of the work a special type of specimen was designed. The specimen had an overall C-shape with a T-shaped cross section. This specimen geometry generates higher levels of stresses in the induction hardened outer layer than in the soft core material along the inner layer of the C-shaped geometry. The compressive residual stresses were generated by the phase transformation that occurs during hardening heat treatments and also by mechanical means. Additional compressive stresses were put into the outer surface region of the hardened C-shaped specimens by pre-straining them plastically through the application of compressive loads. Fine vanadium carbide precipitates were observed in the microalloyed steel in the as-forged condition. The application of a normalizing and induction hardening heat treatments caused coarsening of the vanadium carbide
Forging And Milling Contribution On Residual Stresses For A Textured Biphasic Titanium Alloy
Deleuze, C.; Fabre, A.; Barrallier, L.; Molinas, O.
2011-01-17
Ti-10V-2Fe-3Al is a biphasic titanium alloy ({alpha}+{beta}) used in aeronautical applications for its mechanical properties, such as its yield strength of 1200 MPa and it weighs 40% less than steel. This alloy is particularly useful for vital parts with complex geometry, because of its high forging capability. In order to predict the capability for fatigue lifetime, the designers need to know the residual stresses. X-Ray diffraction is the main experimental technique used to determine residual stresses on the surface. In this case, stress levels are primarily influenced by the complex forging and milling process. On this alloy in particular, it may be difficult to characterize stress due to modification of the microstructure close to the surface. Results obtained by x-ray analysis depend on the correct definition of the shape of the diffraction peaks. The more precisely defined the position of the peak, the more accurately the stresses are evaluated. This paper presents a method to detect if residual stresses can be characterized by x-ray diffraction. The characterization of hardness seems to be a relevant technique to quickly analyze the capability of x-ray diffraction to determine residual stresses.
Residual Stress in Brazing of Submicron Al2O3 to WC-Co
NASA Astrophysics Data System (ADS)
Grunder, T.; Piquerez, A.; Bach, M.; Mille, P.
2016-07-01
This study evaluated the residual stresses induced by brazing and grinding submicron Al2O3, using different methods. Energy dispersive x-ray spectrometry analysis (EDX) of 72Ag-Cu filler and filler/WC-Co interface showed evidence of atomic diffusion and possible formation of titanium oxide layers between the joint and the bonding materials. An analytical model supported by the finite element method (FEM) based on strain determination due to the difference in variation of thermal expansion was used to assess the stress distribution at the coupling interface and in bulk materials. The model took into account the evolution of the Young's modulus and of the thermal expansion with temperature. The model could be used to follow strain and stress evolutions of the bonded materials during the cooling cycle. The maximum stress rose above -300 MPa at the center of the 100 × 100 × 3 mm ceramic plates. The residual stresses on the external surface of ceramic were investigated by x-ray diffraction (XRD) and indentation fracture method (IFM). After brazing and grinding the plate, the principal stresses were 128.1 and 94.9 MPa, and the shear stress was -20.1 MPa. Microscopic examination revealed grain pull-out promoted by the global residual stresses induced by the brazing and grinding processes. The surface stresses evaluated by the different methods were reasonably correlated.
Investigation of residual stresses in a multipass weld in 1 in. stainless steel plate
NASA Astrophysics Data System (ADS)
Spooner, S.; Fernandezbaca, J. A.; David, S. A.; Hubbard, C. R.; Holden, T. M.; Root, J. H.
Residual stresses and strains were measured in two welded 25-mm thick plates of type 304 stainless steel by the neutron diffraction technique. The filler metal was type 308 stainless steel and the weld zone had a two phase microstructure in which the austenitic phase lattice parameter differs from the base metal. In these circumstances strain-free samples were taken from the weld zone area for analysis of the lattice parameters and ferrite content using neutron powder diffraction. Corrections for lattice parameter variation were applied permitting the calculation of residual strains and stresses in weld zone, heat affected zone (HAZ), and base metal. One of the two welds was examined without stress relief and the other was given a stress relief treatment consisting of vibration at a frequency below the resonant condition during welding. In both plates the largest residual stress component (longitudinal) is found in the fusion zone near the boundary between the weld zone and the heat affected zone. This longitudinal component is 400 +/- 50 MPa in tension. The normal stresses are generally close to zero although large fluctuations are found in the weld zone. The transverse stresses are as high as 200 MPa in the weld zone and decrease to 50 MPa +/- 40 MPa. The lattice parameter variation was equivalent to 5 x 10(exp -4) compressive strain and the ferrite content approached 9 percent at the center of the weld zone. Variations in residual stresses with thickness through the base metal plate were small. The treated plate and untreated plate showed nearly identical patterns of stress distribution. Differences in the measured stresses between vibratory-stress-relief treated and untreated plates fall within error bars of the stress determination in these particular 25 mm thick 300-type stainless steel plates.
Hashimoto, Tadafumi; Osawa, Yusuke; Itoh, Shinsuke; Mochizuki, Masahito; Nishimoto, Kazutoshi
2013-06-01
To prevent primary water stress corrosion cracking (PWSCC), water jet peening (WJP) has been used on the welds of Ni-based alloys in pressurized water reactors (PWRs). Before WJP, the welds are machined and buffed in order to conduct a penetrant test (PT) to verify the weld qualities to access, and microstructure evolution takes place in the target area due to the severe plastic deformation. The compressive residual stresses induced by WJP might be unstable under elevated temperatures because of the high dislocation density in the compressive stress layer. Therefore, the stability of the compressive residual stresses caused by WJP was investigated during long-term operation by considering the microstructure evolution due to the working processes. The following conclusions were made: The compressive residual stresses were slightly relaxed in the surface layers of the thermally aged specimens. There were no differences in the magnitude of the relaxation based on temperature or time. The compressive residual stresses induced by WJP were confirmed to remain stable under elevated temperatures. The stress relaxation at the surface followed the Johnson-Mehl equation, which states that stress relaxation can occur due to the recovery of severe plastic strain, since the estimated activation energy agrees very well with the self-diffusion energy for Ni. By utilizing the additivity rule, it was indicated that stress relaxation due to recovery is completed during the startup process. It was proposed that the long-term stability of WJP under elevated temperatures must be assessed based on compressive stresses with respect to the yield stress. Thermal elastic-plastic creep analysis was performed to predict the effect of creep strain. After 100 yr of simulated continuous operation at 80% capacity, there was little change in the WJP compressive stresses under an actual operating temperature of 623 K. Therefore, the long-term stability of WJP during actual operation was
Measurement of Residual Stress in a Welded Branch Connection and Effects on Fracture Behaviour
NASA Astrophysics Data System (ADS)
Law, M.; Luzin, V.; Kirstein, O.
2010-11-01
The branch analysed in this paper was not post weld heat treated, resulting in significant residual stresses. Assessment codes assume these to be at, or close to, yield. An integrity assessment of a welded branch connection was carried out using these high assumed residual stresses. The weld then had residual stresses determined by neutron diffraction, performed using ANSTO's residual stress diffractometer, Kowari. The maximum measured residual stress (290 MPa or 60% of yield) was much lower than the yield value assumed by assessment codes. Reanalysing with the actual residual stresses almost doubled the critical crack size, increasing the safety of the connection.
NASA Astrophysics Data System (ADS)
Lodh, Arijit; Tak, Tawqeer Nasir; Prakash, Aditya; Guruprasad, P. J.; Hutchinson, Christopher; Samajdar, Indradev
2017-08-01
Interrupted tensile tests were coupled with ex situ measurements of residual stress and microtexture. The residual stress quantification involved measurements of six independent Laue spots and conversion of the interplanar spacings to the residual stress tensor. A clear orientation-dependent residual stress evolution emerged from the experiments and the numerical simulations. For the orientations undergoing negligible changes in ρ GND (density of geometrically necessary dislocation), the residual stress developments appeared to be governed by the elastic stiffness of the grain clusters. For the others, the evolution of the residual stress and ρ GND exhibited a clear orientation-dependent scaling.
Impurity Effects on Momentum Transport and Residual Stress
NASA Astrophysics Data System (ADS)
Ko, Sehoon; Jhang, Hogun; Singh, R.
2015-11-01
Impurities are inevitable during tokamak plasma operation because of strong interaction of plasma and plasma facing component and helium ash as a byproduct of fusion process. They cause problems such as radiation power loss and fusion fuel dilution. On the other hands, they are used to diagnosis plasma parameters (CES, XICS etc) and to suppress edge-localized mode by wall-coating. In this research, we study the impact of impurities on turbulence driven intrinsic rotation (via residual stress) in the context of the quasi-linear theory. A two-fluid formulation for main and impurity ions is employed to study ion temperature gradient modes in sheared slab geometry modified by the presence of impurities. An effective form of the parallel Reynolds stress is derived in the center of mass frame of a coupled main ion-impurity system. Analyses show that the contents and the radial profile of impurities have a strong influence on the residual stress. In particular, an impurity profile aligned with that of main ions is shown to cause a considerable reduction of the residual stress, which may lead to the reduction of turbulence driven intrinsic rotation.
Modeling of residual thermal stresses for aluminum nitride crystal growth by sublimation
NASA Astrophysics Data System (ADS)
Lee, R. G.; Idesman, A.; Nyakiti, L.; Chaudhuri, J.
2007-09-01
Residual thermal stress distribution in AlN single crystal, grown on tungsten as a crucible material, was investigated using a numerical study. It has been demonstrated that a three-dimensional, instead of a two-dimensional, formulation predicts significantly greater values of stress. Dimensionless coordinates were used to essentially simplify the stress analysis and reduce the number of calculations. In addition, thermoelasticity approach simplifies the study of stresses for a nonstationary temperature field. The stress in the AlN film along the thickness or [0001] growth direction is essentially zero but the in-plane stress is large. The stress at the corner of the film is much higher due to stress concentration and could cause formation of microcracks. The stress in the film is tensile while that in the substrate is compressive, which causes a reversal of the stress across the interface. Separation or delamination of the film from the substrate could occur due to this reversal of the stress at the interface. The stress decreases as the thickness of the film increases or the thickness of the substrate decreases. Thus, formation of microscopic cracks in the film could be avoided by using a thinner substrate. The analysis on interaction of neighboring islands in order to simulate coalescence of island growth indicates stress concentration at the boundaries of the islands, which could produce threading dislocations and hence polycrystalline growth. The analysis of the effect of misorientation of the neighboring grains on the residual thermal stress in the film has shown that a large stress can develop at the grain boundary and can lead to grain boundary cracking.
Finite Element Modeling and Validation of Residual Stresses in 304 L Girth Welds
Dike, J.J.; Ortega, A.R.; Cadden, C.H.; Rangaswamy, P. Brown, D.
1998-06-01
Three dimensional finite element simulations of thermal and mechanical response of a 304 L stainless steel pipe subjected to a circumferential autogenous gas tungsten arc weld were used to predict residual stresses in the pipe. Energy is input into the thermal model using a volumetric heat source. Temperature histories from the thermal analysis are used as loads in the mechanical analyses. In the mechanical analyses, a state variable constitutive model was used to describe the material behavior. The model accounts for strain rate, temperature, and load path histories. The predicted stresses are compared with x-ray diffraction determinations of residual stress in the hoop and circumferential directions on the outside surface of the pipe. Calculated stress profiles fell within the measured data. Reasons for observed scatter in measured stresses are discussed.
Residual Stress Measurements After Proof and Flight: ETP-0403
NASA Technical Reports Server (NTRS)
Webster, Ronald L..
1997-01-01
The intent of this testing was to evaluate the residual stresses that occur in and around the attachment details of a case stiffener segment that has been subjected to flight/recovery followed by proof loading. Not measured in this test were stresses relieved at joint disassembly due to out-of-round and interference effects, and those released by cutting the specimens out of the case segment. The test article was lightweight case stiffener segment 1U50715, S/N L023 which was flown in the forward stiffener position on flight SRM 14A and in the aft position on flight SRM24A. Both of these flights were flown with the 3 stiffener ring configuration. Stiffener L023 had a stiffener ring installed only on the aft stub in its first flight, and it had both rings installed on its second flight. No significant post flight damage was found on either flight. Finally, the segment was used on the DM-8 static test motor in the forward position. No stiffener rings were installed. It had only one proof pressurization prior to assignment to its first use, and it was cleaned and proof tested after each flight. Thus, the segment had seen 3 proof tests, two flight pressurizations, and two low intensity water impacts prior to manufacturing for use on DM-8. On DM-8 it received one static firing pressurization in the horizontal configuration. Residual stresses at the surface and in depth were evaluated by both the x-ray diffraction and neutron beam diffraction methods. The x-ray diffraction evaluations were conducted by Technology for Energy Corporation (TEC) at their facilities in Knoxville, TN. The neutron beam evaluations were done by Atomic Energy of Canada Limited (AECL) at the Chalk River Nuclear Laboratories in Ontario. The results showed general agreement with relatively high compressive residual stresses on the surface and moderate to low subsurface tensile residual stresses.
Investigation of microstructures and residual stresses in laser peened Incoloy 800H weldments
NASA Astrophysics Data System (ADS)
Chen, Xizhang; Wang, Jingjun; Fang, Yuanyuan; Madigan, Bruce; Xu, Guifang; Zhou, Jianzhong
2014-04-01
Laser Shock Peening (LSP) is an advanced surface enhancement technique to improve the mechanical properties of engineering materials. In the present study, LSP was performed on Incoloy 800H laser weldments. The microstructure and residual stress, two key factors for application of weldments, were investigated via optical and transmission electron microscopy and crystallographic and residual stress X-ray diffraction analysis. Micro-hardness tests were also used to evaluate mechanical properties. Results show that significant grain refinement occurs in the LSP-treated zone where original lath structures are refined to equiaxed grains, and dislocation density increases significantly. Because of the high strain rates produced by LSP, grain deformation by slip is limited, and therefore deformation by grain twinning occurs. The micro-hardness of weld joint increased after LSP with a hardened depth of about 1.2 mm. LSP processed welded joints exhibited high compressive residual stress, and the residual stress distribution was uniform. It is shown that LSP is an effective way to refine microstructure, increase strength and rebalance residual stress which will improve fatigue life and corrosion cracking resistance of Incoloy 800H weldments.
Evaluation of Surface Residual Stresses in Friction Stir Welds Due to Laser and Shot Peening
NASA Technical Reports Server (NTRS)
Hatamleh, Omar; Rivero, Iris V.; Lyons, Jed
2007-01-01
The effects of laser, and shot peening on the residual stresses in Friction Stir Welds (FSW) has been investigated. The surface residual stresses were measured at five different locations across the weld in order to produce an adequate residual stress profile. The residual stresses before and after sectioning the coupon from the welded plate were also measured, and the effect of coupon size on the residual stress relaxation was determined and characterized. Measurements indicate that residual stresses were not uniform along the welded plate, and large variation in stress magnitude could be exhibited at various locations along the FSW plate. Sectioning resulted in significant residual stress relaxation in the longitudinal direction attributed to the large change in dimensions in this direction. Overall, Laser and shot peening resulted in a significant reduction in tensile residual stresses at the surface of the specimens.
Tank 12H residuals sample analysis report
Oji, L. N.; Shine, E. P.; Diprete, D. P.; Coleman, C. J.; Hay, M. S.
2015-06-11
The Savannah River National Laboratory (SRNL) was requested by Savannah River Remediation (SRR) to provide sample preparation and analysis of the Tank 12H final characterization samples to determine the residual tank inventory prior to grouting. Eleven Tank 12H floor and mound residual material samples and three cooling coil scrape samples were collected and delivered to SRNL between May and August of 2014.
Estimation of residual stresses in hydraulically expanded tube-to-tubesheet joints
Allam, M.; Chaaban, A.; Bazergui, A.
1996-12-01
The knowledge of residual stresses introduced in the tubes of heat exchangers during their expansion in the tubesheet holes, is important because of their effect on the structural integrity of components. This paper presents a simplified theoretical method to calculate the maximum residual stresses introduced in the transition zone of expanded tube-to-tubesheet joint. The higher positive values of tensile residual stresses and their corresponding axial locations are determined by using a standard deviation analysis. The validation of the proposed equations was accomplished by comparing their results to those obtained by the finite element method for some arbitrary cases. An upper limit has been imposed on the expansion pressure level depending on the combination of the geometrical and material parameters that are involved in the design of the tube-to-tubesheet joints.
The Sensitivity of Residual Stresses of Cross-Ply Laminates to Manufacturing and Material Parameters
NASA Astrophysics Data System (ADS)
Lahtinen, H.
2003-01-01
By using a finite-element model elaborated, the sensitivity of residual stresses of polyester/glass cross-ply laminates to manufacturing and material parameters is investigated. The development of residual stresses in the laminates and the significance of the parameters for the problem are discussed. It is found that the main attention in calculating residual stresses should be focused on the properties of resin, which must be measured with care. The most important parameters related to the resin are, of course, its stiffness, thermal expansion, and chemical shrinkage, while the properties of fibers can be obtained from material handbooks with a sufficient accuracy. In curing a thin laminate in an autoclave, the simulation of chemical reactions and the parameters needed in thermal analysis are quite insignificant, because, in practice, the autoclave temperature and the properties of the mold determine the laminate temperature history.
A residual stress study in similar and dissimilar welds
Eisazadeh, Hamid; Goldak, John A.; Aidun, Daryush K.; ...
2016-04-01
Residual strain distributions in similar and dissimilar welds were measured using neutron diffraction (ND) method. Then, using three strain components, three-dimensional stress states were calculated. The results were used to determine the effect of the martensitic phase transformation and material properties on residual stress (RS) distribution. It was observed that smaller longitudinal RS was induced in the low carbon steel side of dissimilar weld when compared to its similar weld. Also, it was found that the transverse RS near and within the weld zone (WZ) in dissimilar weld exhibited a distinctive trend, with tensile mode reaching the yield strength ofmore » the base metal (BM). In order to characterize the WZ in dissimilar weld, we deployed optical microscopy, hardness, and energy dispersive X-ray spectroscopy (EDAX). This study not only provides further insight into the RS state in similar and dissimilar welds; it also delivers important consequences of phase transformation in the latter case.« less
A residual stress study in similar and dissimilar welds
Eisazadeh, Hamid; Goldak, John A.; Aidun, Daryush K.; Coules, Harry E.; Bunn, Jeffrey R; Achuthan, A.
2016-04-01
Residual strain distributions in similar and dissimilar welds were measured using neutron diffraction (ND) method. Then, using three strain components, three-dimensional stress states were calculated. The results were used to determine the effect of the martensitic phase transformation and material properties on residual stress (RS) distribution. It was observed that smaller longitudinal RS was induced in the low carbon steel side of dissimilar weld when compared to its similar weld. Also, it was found that the transverse RS near and within the weld zone (WZ) in dissimilar weld exhibited a distinctive trend, with tensile mode reaching the yield strength of the base metal (BM). In order to characterize the WZ in dissimilar weld, we deployed optical microscopy, hardness, and energy dispersive X-ray spectroscopy (EDAX). This study not only provides further insight into the RS state in similar and dissimilar welds; it also delivers important consequences of phase transformation in the latter case.
Measurement of residual stresses in polymer composites using moire interferometry
NASA Astrophysics Data System (ADS)
Shankar, Krishnakumar; Xie, Huimin; Asundi, Anand K.; Oh, Kim E.; Chai, Gin B.
2001-06-01
Moire interferometry is employed along with the hole drilling technique to determine residual cure stresses in symmetric cross poly graphite epoxy laminates. Traditional moire interferometry set-up using two collimated angle beams was employed to provide the virtual reference grating while a cross grating with a frequency of 1200 lines per mm was replicated on the specimen surface. Holes of different depths, each one penetrating one additional layer of the laminate, were drilled using a high speed air turbine drill to relieve the stresses in each layer sequentially. The strain distribution around each hole was computed from correlation of the undistorted carrier fringe pattern with the distorted fringe patterns around the holes. The measured strain distributions are compared to residual strain distributions predicted by classical laminate theory.
Lamination residual strains and stresses in hybrid laminates
NASA Technical Reports Server (NTRS)
Daniel, I. M.; Liber, T.
1977-01-01
An investigation is conducted of the effects of hybridization on the magnitude of lamination residual stresses. Eight-ply graphite/Kevlar 49/epoxy and graphite/S-glass/epoxy laminates were studied. The same matrix resin was selected for all basic materials to ensure compatibility and uniform curing of the various plies. The specimens, with inserted strain gages and thermocouples, were subjected to curing and postcuring cycles in an autoclave. Subsequently, the specimens were subjected to a thermal cycle from room temperature to 444 K and down to room temperature. It was found that hydridizing reduces apparently residual strains and stresses in the graphite plies. However, these strains were not affected much by the type and degree of hybridization.
Surface wave propagation in thin silver films under residual stress
NASA Astrophysics Data System (ADS)
Njeh, Anuar; Wieder, Thomas; Schneider, D.; Fuess, Hartmut; Ben Ghozlen, M. H.
Investigations using surface acoustic waves provide information on the elastic properties of thin films. Residual stresses change the phase velocity of the surface waves. We have calculated phase velocity and dispersion of surface waves in thin silver films with a strong [111]-fibre texture. A non-linear description of surface waves propagating along the [110]-direction of the substrate has been developed on the basis of an acoustoelastic theory, taking into account residual stresses. The relative change delta_v/v of the velocity v was found to be lin-ear for large excitation frequencies. The dispersion curves were measured using a photoa-coustic method. For sputtered polycrystalline thin silver films we found good agreement be-tween the experimental and calculated dispersion curves for frequencies up to 225 MHz.
On the use of the hole-drilling technique for residual stress measurements in thin plates
NASA Technical Reports Server (NTRS)
Hampton, R. W.; Nelson, D. V.
1992-01-01
The strain gage blind hole-drilling technique may be used to determine residual stresses at and below the surface of components. In this paper, the hole-drilling analysis methodology for thick plates is reviewed, and experimental data are used to evaluate the methodology and to assess its applicability to thin plates. Data on the effects of gage pattern, surface preparation, hole spacing, hole eccentricity, and stress level are also presented.
The prediction of residual stress and its influence on the mechanical properties of weld joint
NASA Astrophysics Data System (ADS)
Ni, J.; Wahab, M. A.
2017-05-01
A three-dimensional metallo-thermo-mechanical analysis of bead on plate welding is performed in this work. This coupled model enables to capture the microstructural development and temperature history at local region. As a result, the residual stress is evaluated based on the temperature-dependent mechanical properties computed by the mixture of individual phase. Isotropic hardening is assumed in the finite element (FE) analysis. At the same time, the distribution of residual stress is also predicted by treating the mechanical properties as integral values of sheet metal. The two simulated fields of stress and strain after welding are analysed and compared. Moreover, as it is known that welding changes the mechanical properties of the original material, especially in fusion zone (FZ) and heat affected zone (HAZ), the stress and strain data at interested areas (HAZ and FZ) are subtracted for comparison. The predicted stress and strain fields are imported to subsequent simulation of standard tensile test. The stress-strain curves are compared with the one of base material. It is found that residual stress has significant influence on the structural performance of weld joints.
Mechanical relaxation of localized residual stresses associatedwith foreign object damage
Boyce, B.L.; Chen, X.; Peters, J.O.; Hutchinson, J.H.; Ritchie,R.O.
2002-05-01
Foreign-object damage associated with the ingestion ofdebris into aircraft turbine engines can lead to a marked degradation inthe high-cycle fatigue life of turbine components. This degradation isgenerally considered to be associated with the premature initiation offatigue cracks at or near the damage sites; this is suspected to be dueto, at least in part, the impact-induced residual stress state, which canbe strongly tensile in these locations.
Modelling Of Residual Stresses Induced By High Speed Milling Process
Desmaison, Olivier; Mocellin, Katia; Jardin, Nicolas
2011-05-04
Maintenance processes used in heavy industries often include high speed milling operations. The reliability of the post-process material state has to be studied. Numerical simulation appears to be a very interesting way to supply an efficient residual stresses (RS) distribution prediction.Because the adiabatic shear band and the serrated chip shaping are features of the austenitic stainless steel high speed machining, a 2D high speed orthogonal cutting model is briefly presented. This finite element model, developed on Forge registered software, is based on data taken from Outeiro and al.'s paper [1]. A new behaviour law fully coupling Johnson-Cook's constitutive law and Latham and Cockcroft's damage model is detailed in this paper. It ensures results that fit those found in literature.Then, the numerical tools used on the 2D model are integrated to a 3D high speed milling model. Residual stresses distribution is analysed, on the surface and into the depth of the material. Various revolutions and passes of the two teeth hemispheric mill on the workpiece are simulated. Thus the sensitivity of the residual stresses generation to the cutting conditions can be discussed. In order to validate the 3D model, a comparison of the cutting forces measured by EDF R and D to those given by numerical simulations is achieved.
Modelling Of Residual Stresses Induced By High Speed Milling Process
NASA Astrophysics Data System (ADS)
Desmaison, Olivier; Mocellin, Katia; Jardin, Nicolas
2011-05-01
Maintenance processes used in heavy industries often include high speed milling operations. The reliability of the post-process material state has to be studied. Numerical simulation appears to be a very interesting way to supply an efficient residual stresses (RS) distribution prediction. Because the adiabatic shear band and the serrated chip shaping are features of the austenitic stainless steel high speed machining, a 2D high speed orthogonal cutting model is briefly presented. This finite element model, developed on Forge® software, is based on data taken from Outeiro & al.'s paper [1]. A new behaviour law fully coupling Johnson-Cook's constitutive law and Latham and Cockcroft's damage model is detailed in this paper. It ensures results that fit those found in literature. Then, the numerical tools used on the 2D model are integrated to a 3D high speed milling model. Residual stresses distribution is analysed, on the surface and into the depth of the material. Various revolutions and passes of the two teeth hemispheric mill on the workpiece are simulated. Thus the sensitivity of the residual stresses generation to the cutting conditions can be discussed. In order to validate the 3D model, a comparison of the cutting forces measured by EDF R&D to those given by numerical simulations is achieved.
NASA Astrophysics Data System (ADS)
Murav'ev, V. V.; Volkova, L. V.; Gromov, V. E.; Glezer, A. M.
2016-10-01
An approach to estimating the residual stresses in rails using acoustoelasticity and electromagnetic-acoustic conversion is described. The results of ultrasonic control of the residual stresses in rail segments are presented.
Pretension-Dependent Residual Stress of Alumina Fiber-Reinforced Composite Wire
NASA Astrophysics Data System (ADS)
Dai, Xiaoya; Zhang, Wenlong; Gao, Ping; Zhang, Shaozong; Gu, Mingyuan; Peng, Hua-Xin
2013-11-01
The relationship between pretension and residual stress of an aluminum wire reinforced with 45 vol pct continuous Nextel™ 610 alumina fibers is investigated. It is shown that as pretension stress increases, the matrix residual stress decreases. A transition in matrix residual stress from tension to compression occurs at a pretension stress of about 80 MPa. The initial rapidly decreased residual stress caused by pretension at relatively low pretension stresses is a result of matrix elastic compressive deformation; while the later gradually decreased residual stress at higher pretension stresses comes from matrix plastic compressive deformation. As the matrix yield stress and hardening exponent increase, the decrease in matrix residual stress with pretension stress is more rapid and the absolute value of matrix residual stress increases. An analytical model suitable for fiber-reinforced metal matrix composites (MMCs) with strong interfacial bonding is developed to describe the relationship between pretension and matrix residual stress and is shown to be in good agreement with the experimental and finite-element calculated results. The pretension-dependent matrix residual stress phenomenon suggests that the mechanical properties of fiber-reinforced MMCs associated with matrix residual stress may be effectively improved by applying tensile loads.
Woo, Wan Chuck; Feng, Zhili; Wang, Xun-Li; Hubbard, Camden R
2009-01-01
Residual stresses were generated by severe thermomechanical deformation in an aluminum alloy plate. The evolution of the residual stresses during natural aging was investigated by neutron diffraction up to 10,000h. A data reduction method was developed to eliminate microstructure influences (solute variations) on the lattice spacing changes, thereby allowing the determination of the long-range macroscopic residual stresses. The residual stress decreased ({approx}25MPa) with time due to the microstructural modification within the deformed region during natural aging.
Investigation of Residual Stresses in a Hot Cured Glass Fibre Reinforced Epoxy Resin Composite
1982-01-01
to establish confidence in its use. Little work has been reported on the magnitudes of residual curing stresses and their effect on the performance...premature failure if the residual and service stresses are additive. Fbr accurate design work it is therefore essential to take residual curing stresses...used to evaluate the residual curing stresses in a liminated plate is given in Reference 2. The computer code developed in Reference 3 was used in this
Influence of Residual Stress Field on the Fatigue Crack Propagation in Prestressing Steel Wires
Toribio, Jesús; Matos, Juan-Carlos; González, Beatriz; Escuadra, José
2015-01-01
This paper deals with the effect of several residual stress profiles on the fatigue crack propagation in prestressing steel wires subjected to tension loading or bending moment. To this end, a computer program was developed to evaluate the crack front evolution on the basis of the Walker law. Results demonstrate that the absence of residual stresses makes the crack propagate towards a preferential crack path. When surface residual stresses are tensile and, correspondingly, core residual stresses are compressive, the fatigue crack fronts rapidly converge towards a quasi-straight shape. When surface residual stresses are compressive, with their corresponding tensile stresses in the core area, a preferential crack path also appears. PMID:28793661
Residual stress alleviation of aircraft metal structures reinforced with filamentary composites
NASA Technical Reports Server (NTRS)
Kelly, J. B.; June, R. R.
1973-01-01
Methods to eliminate or reduce residual stresses in aircraft metal structures reinforced by filamentary composites are discussed. Residual stress level reductions were achieved by modifying the manufacturing procedures used during adhesive bonding. The residual stress alleviation techniques involved various forms of mechanical constraint which were applied to the components during bonding. Nine methods were evaluated, covering a wide range in complexity. All methods investigated during the program affected the residual stress level. In general, residual stresses were reduced by 70 percent or more from the stress level produced by conventional adhesive bonding procedures.
Quantification of Residual Stress from Photonic Signatures of Fused Silica
NASA Technical Reports Server (NTRS)
Cramer, K. Elliott; Hayward, Maurice; Yost, William E.
2013-01-01
A commercially available grey-field polariscope (GFP) instrument for photoelastic examination is used to assess impact damage inflicted upon the outer-most pane of Space Shuttle windows made from fused silica. A method and apparatus for calibration of the stress-optic coefficient using four-point bending is discussed. The results are validated on known material (acrylic) and are found to agree with literature values to within 6%. The calibration procedure is then applied to fused-silica specimens and the stress-optic coefficient is determined to be 2.43 +/- 0.54 x 10(exp -12)/Pa. Fused silica specimens containing impacts artificially made at NASA's Hypervelocity Impact Technology Facility (HIT-F), to simulate damage typical during space flight, are examined. The damage sites are cored from fused silica window carcasses and examined with the GFP. The calibrated GFP measurements of residual stress patterns surrounding the damage sites are presented. Keywords: Glass, fused silica, photoelasticity, residual stress
Thermoelastic Residual Stresses and Deformations at Laser Treatment
NASA Astrophysics Data System (ADS)
Gusarov, A. V.; Malakhova-Ziablova, I. S.; Pavlov, M. D.
A thermoelastic model implying relaxation of stresses at melting is applied for materials with arbitrary thermoelastic properties and the melting point. The range of Poisson's ratio 0.17 - 0.34 is numerically studied. The residual stresses are independent of the space scale. In narrow remelted zones and beads the maximum longitudinal tensile stress is approximately twice as high as the transverse one. The calculations predict cracking of alumina, even with 1600 oC preheating, plastic deformation or cracking of hard metal alloys H13 and TA6 V, and no destruction of polystyrene and thestrongest grades of quartz glass. The calculation results can be used for predicting the thermomechanical stability of materials at laser treatment.
Phase composition and residual stresses in thermal barrier coatings
NASA Astrophysics Data System (ADS)
Lozovan, A. A.; Betsofen, S. Ya; Ashmarin, A. A.; Ryabenko, B. V.; Ivanova, S. V.
2016-07-01
X-ray study of the phase composition and residual stresses distribution in two-layer APS coatings showed that the ceramic layer consists of t-ZrO2 phase with tetragonal lattice and the metal underlayer γ-solid solution based on nickel. In the transition zone thickness of ∼ 100 pm as the distance from the surface was revealed a gradual transition from t-ZrO2 to γ-solid solution. Increase in the specific volume of the metal underlayer resulting TGO growing leads to the formation of this layer high compressive stresses up to 600 MPa. In this case, the ceramic layer contains tensile stress up to 200 MPa.
Quantification of residual stress from photonic signatures of fused silica
NASA Astrophysics Data System (ADS)
Cramer, K. Elliott; Hayward, Maurice; Yost, William T.
2014-02-01
A commercially available grey-field polariscope (GFP) instrument for photoelastic examination is used to assess impact damage inflicted upon the outer-most pane of Space Shuttle windows made from fused silica. A method and apparatus for calibration of the stress-optic coefficient using four-point bending is discussed. The results are validated on known material (acrylic) and are found to agree with literature values to within 6%. The calibration procedure is then applied to fused-silica specimens and the stress-optic coefficient is determined to be 2.43 ± 0.54 × 10-12 Pa-1. Fused silica specimens containing impacts artificially made at NASA's Hypervelocity Impact Technology Facility (HIT-F), to simulate damage typical during space flight, are examined. The damage sites are cored from fused silica window carcasses and examined with the GFP. The calibrated GFP measurements of residual stress patterns surrounding the damage sites are presented.
Estimation of residual stresses in hydraulically expanded tube-to-tubesheet joints
Allam, M.; Chaaban, A.; Bazergui, A.
1998-05-01
Recent investigations show that the tube-to-tubesheet joint axial strength is a major contributor to the joint soundness, and that tensile residual stresses in the tubes cannot be ignored due to their effect on stress corrosion cracking (SCC) and subsequent leakage failures. Because of their wide industrial use the tube-to-tubesheet joints need to be designed efficiently in order to increase the joint strength and overall performance. The knowledge of residual stresses introduced in the tubes of heat exchangers during their expansion in the tubesheet holes is important because of their effect on the structural integrity of components. This paper presents a simplified theoretical method to calculate the maximum residual stresses introduced in the transition zone of expanded tube-to-tubesheet joint. The higher positive values of tensile residual stresses and their corresponding axial locations are determined by using a standard deviation analysis. The validation of the proposed equations was accomplished by comparing their results to those obtained by the finite element method for some arbitrary cases. An upper limit has been imposed on the expansion pressure level, depending on the combination of the geometrical and material parameters that are involved in the design of the tube-to-tubesheet joints.
Nonlocal continuum crystal plasticity with internal residual stresses
NASA Astrophysics Data System (ADS)
Aghababaei, Ramin; Joshi, Shailendra P.; Reddy, J. N.
2011-03-01
We derive a three-dimensional constitutive theory accounting for length-scale dependent internal residual stresses in crystalline materials that develop due to a non-homogeneous spatial distribution of the excess dislocation (edge and screw) density. The second-order internal stress tensor is derived using the Beltrami stress function tensor φ that is related to the Nye dislocation density tensor. The formulation is derived explicitly in a three-dimensional continuum setting for elastically isotropic materials. The internal stresses appear as additional resolved shear stresses in the crystallographic visco-plastic constitutive law for individual slip systems. Using this formulation, we investigate two boundary value problems involving single crystals under symmetric double slip. In the first problem, the response of a geometrically imperfect specimen subjected to monotonic and cyclic loading is investigated. The internal stresses affect the overall strengthening and hardening under monotonic loading, which is mediated by the severity of initial imperfections. Such imperfections are common in miniaturized specimens in the form of tapered surfaces, fillets, fabrication induced damage, etc., which may produce strong gradients in an otherwise nominally homogeneous loading condition. Under cyclic loading the asymmetry in the tensile and compressive strengths due to this internal stress is also strongly influenced by the degree of imperfection. In the second example, we consider simple shear of a single crystalline lamella from a layered specimen. The lamella exhibits strengthening with decreasing thickness and increasing lattice incompatibility with shearing direction. However, as the thickness to internal length-scale ratio becomes small the strengthening saturates due to the saturation of the internal stress. Finally, we present the extension of this approach for crystalline materials exhibiting elastic anisotropy, which essentially depends on the appropriate Green
Method and apparatus for determination of material residual stress
NASA Technical Reports Server (NTRS)
Chern, Engmin J. (Inventor); Flom, Yury (Inventor)
1993-01-01
A device for the determination of residual stress in a material sample consisting of a sensor coil, adjacent to the material sample, whose resistance varies according to the amount of stress within the material sample, a mechanical push-pull machine for imparting a gradually increasing compressional and tensional force on the material sample, and an impedance gain/phase analyzer and personal computer (PC) for sending an input signal to and receiving an input signal from the sensor coil is presented. The PC will measure and record the change in resistance of the sensor coil and the corresponding amount of strain of the sample. The PC will then determine, from the measurements of change of resistance and corresponding strain of the sample, the point at which the resistance of the sensor coil is at a minimum and the corresponding value and type of strain of the sample at that minimum resistance point, thereby, enabling a calculation of the residual stress in the sample.
Surface Finish and Residual Stresses Induced by Orthogonal Dry Machining of AA7075-T651
Jomaa, Walid; Songmene, Victor; Bocher, Philippe
2014-01-01
The surface finish was extensively studied in usual machining processes (turning, milling, and drilling). For these processes, the surface finish is strongly influenced by the cutting feed and the tool nose radius. However, a basic understanding of tool/surface finish interaction and residual stress generation has been lacking. This paper aims to investigate the surface finish and residual stresses under the orthogonal cutting since it can provide this information by avoiding the effect of the tool nose radius. The orthogonal machining of AA7075-T651 alloy through a series of cutting experiments was performed under dry conditions. Surface finish was studied using height and amplitude distribution roughness parameters. SEM and EDS were used to analyze surface damage and built-up edge (BUE) formation. An analysis of the surface topography showed that the surface roughness was sensitive to changes in cutting parameters. It was found that the formation of BUE and the interaction between the tool edge and the iron-rich intermetallic particles play a determinant role in controlling the surface finish during dry orthogonal machining of the AA7075-T651 alloy. Hoop stress was predominantly compressive on the surface and tended to be tensile with increased cutting speed. The reverse occurred for the surface axial stress. The smaller the cutting feed, the greater is the effect of cutting speed on both axial and hoop stresses. By controlling the cutting speed and feed, it is possible to generate a benchmark residual stress state and good surface finish using dry machining. PMID:28788534
Surface Finish and Residual Stresses Induced by Orthogonal Dry Machining of AA7075-T651.
Jomaa, Walid; Songmene, Victor; Bocher, Philippe
2014-02-28
The surface finish was extensively studied in usual machining processes (turning, milling, and drilling). For these processes, the surface finish is strongly influenced by the cutting feed and the tool nose radius. However, a basic understanding of tool/surface finish interaction and residual stress generation has been lacking. This paper aims to investigate the surface finish and residual stresses under the orthogonal cutting since it can provide this information by avoiding the effect of the tool nose radius. The orthogonal machining of AA7075-T651 alloy through a series of cutting experiments was performed under dry conditions. Surface finish was studied using height and amplitude distribution roughness parameters. SEM and EDS were used to analyze surface damage and built-up edge (BUE) formation. An analysis of the surface topography showed that the surface roughness was sensitive to changes in cutting parameters. It was found that the formation of BUE and the interaction between the tool edge and the iron-rich intermetallic particles play a determinant role in controlling the surface finish during dry orthogonal machining of the AA7075-T651 alloy. Hoop stress was predominantly compressive on the surface and tended to be tensile with increased cutting speed. The reverse occurred for the surface axial stress. The smaller the cutting feed, the greater is the effect of cutting speed on both axial and hoop stresses. By controlling the cutting speed and feed, it is possible to generate a benchmark residual stress state and good surface finish using dry machining.
NASA Astrophysics Data System (ADS)
Rong, Youmin; Zhang, Guojun; Huang, Yu
2016-10-01
Inherent strain analysis has been successfully applied to predict welding deformations of large-scale structural components, while thermal-elastic-plastic finite element method is rarely used for its disadvantages of long calculation period and large storage space. In this paper, a hybrid model considering nonlinear yield stress curves and multi-constraint equations to thermal-elastic-plastic analysis is further proposed to predict welding distortions and residual stresses of large-scale structures. For welding T-joint structural steel S355JR by metal active gas welding, the published experiment results of temperature and displacement fields are applied to illustrate the credibility of the proposed integration model. By comparing numerical results of four different cases with the experiment results, it is verified that prediction precision of welding deformations and residual stresses is apparently improved considering the power-law hardening model, and computational time is also obviously shortened about 30.14% using multi-constraint equations. On the whole, the proposed hybrid method can be further used to precisely and efficiently predict welding deformations and residual stresses of large-scale structures.
Numerical and neutron diffraction measurement of residual stress distribution in dissimilar weld
Eisazadeh, Hamid; Bunn, Jeffrey R.; Aidun, Daryush K.
2017-01-01
In this study, a model considering an asymmetric power heat distribution, temperature-dependent material properties, strain hardening and phase transformation was developed to predict temperature field and residual stress distribution in GTA dissimilar weld between austenitic stainless steel (304) and low carbon steel (1018). The effect of martensite formation on longitudinal and transverse residual stress distributions were investigated using both FE model and neutron diffraction measurement. The results indicate that martensitic phase has a significant influence on both residual stress components, i.e., transverse and longitudinal, and it not only can change the distribution shape of residual stress near the weld centermore » line but, also, can alter the peak value of the residual stresses. The calculated temperature and weld zone profile were in agreement with the experimental results. Favorable general agreement was also found between the calculated residual stress distribution and residual stress measurements by the neutron diffraction method.« less
Numerical and neutron diffraction measurement of residual stress distribution in dissimilar weld
Eisazadeh, Hamid; Bunn, Jeffrey R.; Aidun, Daryush K.
2017-01-01
In this study, a model considering an asymmetric power heat distribution, temperature-dependent material properties, strain hardening and phase transformation was developed to predict temperature field and residual stress distribution in GTA dissimilar weld between austenitic stainless steel (304) and low carbon steel (1018). The effect of martensite formation on longitudinal and transverse residual stress distributions were investigated using both FE model and neutron diffraction measurement. The results indicate that martensitic phase has a significant influence on both residual stress components, i.e., transverse and longitudinal, and it not only can change the distribution shape of residual stress near the weld center line but, also, can alter the peak value of the residual stresses. The calculated temperature and weld zone profile were in agreement with the experimental results. Favorable general agreement was also found between the calculated residual stress distribution and residual stress measurements by the neutron diffraction method.
NASA Astrophysics Data System (ADS)
Jiao, Sicheng; Zhang, Chengyan; Liu, Guancheng; Lu, Jiping; Tang, Shuiyuan
2017-08-01
A series of turning experiments have been carried out to study the effect of different cutting speed, feed rate and pre-tightening torque on residual stress distribution during turning of weak stiffness revolving parts. Surface residual stress and the peak residual compressive stress are selected from the typical residual stress distribution profile. The residual stress by turning was measured by X-ray diffraction method. In order to get the distribution of residual stress along depth direction, the specimens need to be etched layer by layer. From this investigation, it can be concluded that it is practicable to control the distribution of residual stress by changing the pre-tightening torque and cutting parameters during turning of weak stiffness revolving parts.
Uncertainty Quantification and Comparison of Weld Residual Stress Measurements and Predictions.
Lewis, John R.; Brooks, Dusty Marie
2016-10-01
In pressurized water reactors, the prevention, detection, and repair of cracks within dissimilar metal welds is essential to ensure proper plant functionality and safety. Weld residual stresses, which are difficult to model and cannot be directly measured, contribute to the formation and growth of cracks due to primary water stress corrosion cracking. Additionally, the uncertainty in weld residual stress measurements and modeling predictions is not well understood, further complicating the prediction of crack evolution. The purpose of this document is to develop methodology to quantify the uncertainty associated with weld residual stress that can be applied to modeling predictions and experimental measurements. Ultimately, the results can be used to assess the current state of uncertainty and to build confidence in both modeling and experimental procedures. The methodology consists of statistically modeling the variation in the weld residual stress profiles using functional data analysis techniques. Uncertainty is quantified using statistical bounds (e.g. confidence and tolerance bounds) constructed with a semi-parametric bootstrap procedure. Such bounds describe the range in which quantities of interest, such as means, are expected to lie as evidenced by the data. The methodology is extended to provide direct comparisons between experimental measurements and modeling predictions by constructing statistical confidence bounds for the average difference between the two quantities. The statistical bounds on the average difference can be used to assess the level of agreement between measurements and predictions. The methodology is applied to experimental measurements of residual stress obtained using two strain relief measurement methods and predictions from seven finite element models developed by different organizations during a round robin study.
Xu, Hanbing; Hubbard, Camden R; An, Ke; Wang, Xun-Li; Feng, Zhili; Qu, Jun
2009-01-01
Friction stir processing (FSP) was successfully used to stir and mix nano-sized Al2O3 particles into a Al6061-T6 aluminum plate to form a nanocomposite layer up to 3 mm thick. This nanocomposite surface has demonstrated significantly improved surface hardness, yield strength, and wear-resistance without sacrificing the substrate ductility and conductivity. Neutron diffraction analysis was conducted to determine the residual stress distribution in the nanocomposite surface layer. For comparison, the residual stress of the aluminum surface that was processed similarly but had no particle involved was also measured. Results showed that the macro-level residual stresses in the FSP zone without particles are low due to the annealing effect induced by the long heating time and large heat input. The macro-level residual stresses in the FSP-processed Al-Al2O3 nanocomposite zone are tensile up to 100 MPa in all three directions. The details of the results will be further discussed in the paper.
Residual stresses in sputter-deposited copper/330 stainless steel multilayers
Zhang, X.; Misra, A.
2004-12-15
The evolution of residual stresses as a function of bilayer period from 10 nm to 1 {mu}m in sputter-deposited Cu/330 stainless-steel (SS) multilayered films is evaluated by the substrate curvature technique. The multilayer stress evolution is compared with residual stresses in single layer Cu films and single layer 330 SS films, also measured by substrate curvature technique, with respective film thicknesses varying from 5 to 500 nm. Both single layer and multilayer films exhibit high tensile residual stresses that increase with decreasing layer thickness, but are found to be lower than the respective yield strengths. The intrinsic tensile residual stress evolution with film thickness is explained using the island coalescence model. The difference between the multilayer residual stress and the average residual stresses in single-layered Cu and 330 SS films is interpreted in terms of interface stress.
Residual Stress in Composites with the Thin-ring-slitting Approach
Park, J.W.; Ferracane, J.L.
2008-01-01
During polymerization, dental composites develop residual stresses that may compromise the marginal integrity and properties of the restorative. The objective of this study was to use the thin-walled ring-slitting method to measure and compare residual stresses. The hypotheses to be tested were that composites would generate different levels of residual stress based on their specific formulations and slitting times. Rings made from composites (Z100, Herculite, and Heliomolar) were cut at different times (10 min, 1 and 24 hrs) after being light-cured, and stress was measured. Residual stress was higher at the earlier cutting times, except for Heliomolar (α < 0.05). For the 10-minute and one-hour cutting groups, stress followed this order: Z100 > Herculite > Heliomolar. Early slitting was better to capture residual stress, and the thin-walled rings showed higher values than thick-walled rings and were better able to discriminate residual stress in composites. PMID:16998138
Modeling Residual Stress Development in Thermal Spray Coatings: Current Status and Way Forward
NASA Astrophysics Data System (ADS)
Abubakar, Abba A.; Arif, Abul Fazal M.; Al-Athel, Khaled S.; Akhtar, S. Sohail; Mostaghimi, Javad
2017-07-01
An overview of analytical and numerical methods for prediction of residual stresses in thermal spray coatings is presented. The various sources and mechanisms underlying residual stress development in thermal spray coatings are discussed, then the various difficulties associated with experimental residual stress measurement in thermal spray coatings are highlighted. The various analytical and numerical models used for prediction of residual stresses in thermal spray coatings are thoroughly discussed. While analytical models for prediction of postdeposition thermal mismatch stresses are fully developed, analytical quenching and peening stress models still require extensive development. Various schemes for prediction of residual stresses using the finite element method are identified. The results of the various numerical and analytical models are critically analyzed, and their accuracy and validity, when compared with experiments, are discussed. Issues regarding the accuracy and applicability of the models for predicting residual stresses in thermal spray coatings are highlighted, and several suggestions for future development of the models are given.
Modeling Residual Stress Development in Thermal Spray Coatings: Current Status and Way Forward
NASA Astrophysics Data System (ADS)
Abubakar, Abba A.; Arif, Abul Fazal M.; Al-Athel, Khaled S.; Akhtar, S. Sohail; Mostaghimi, Javad
2017-08-01
An overview of analytical and numerical methods for prediction of residual stresses in thermal spray coatings is presented. The various sources and mechanisms underlying residual stress development in thermal spray coatings are discussed, then the various difficulties associated with experimental residual stress measurement in thermal spray coatings are highlighted. The various analytical and numerical models used for prediction of residual stresses in thermal spray coatings are thoroughly discussed. While analytical models for prediction of postdeposition thermal mismatch stresses are fully developed, analytical quenching and peening stress models still require extensive development. Various schemes for prediction of residual stresses using the finite element method are identified. The results of the various numerical and analytical models are critically analyzed, and their accuracy and validity, when compared with experiments, are discussed. Issues regarding the accuracy and applicability of the models for predicting residual stresses in thermal spray coatings are highlighted, and several suggestions for future development of the models are given.
Thermo-Mechanical Behaviour of Turbine Disc Assembly in the Presence of Residual Stresses
NASA Astrophysics Data System (ADS)
Maricic, Luke Anthony
A comprehensive three dimensional coupled thermo-mechanical finite element study is performed on turbine blade attachments in gas turbine engines. The effects of the self-generated centrifugal forces of the disc and the associated blades, thermal loads, and shot peening residual are all considered in this thesis. Three aspects of the work were accordingly examined. The first was concerned with the coupled thermo-mechanical stress analysis and load sharing between the teeth of the fir-tree root. The second was devoted to the development of a complete model incorporating the effect of shot peening residual stresses upon the developed stress state. The effectiveness of shot peening treatment in response to cyclic thermo-mechanical loadings at the contact interface has also been studied. The third was concerned with the validation of some aspects of the developed models analytically using closed form solutions and experimentally using photoelasticity.
NASA Astrophysics Data System (ADS)
Taskonak, Burak
Bilayer dental ceramic composites used for fixed partial dentures are becoming more widely used in dental practices because of their biocompatibility, aesthetic properties, and chemical durability. However, large statistical variations in the strength of ceramics are associated with the structural flaws as a result of processing and complex stress states within the surfaces of the materials because of thermal properties of each layer. In addition, partial delaminations of the veneer layer and connector fractures of bilayer ceramic fixed partial dentures (FPDs) have been observed in a clinical study which is a part of this dissertation. Analysis of fracture surfaces of failed FPDs reveals that such fractures of the veneering ceramic are most likely caused by lateral crack growth. Global residual stresses associated with the coefficient of thermal expansion differences between core and veneering ceramics can cause lateral crack initiation. Also, rapid cooling of bilayer ceramics from the sintering temperature of the glass veneer may not allow the interfacial stresses in the viscoelastic glass to relax to equilibrium values. This can further contribute to the propagation of lateral cracks. Furthermore, local residual stresses that develop in the plastic deformation zone below sharp contact areas on the occlusal surface are another contributor to lateral crack growth. Superposition of global residual stresses and a Boussinesq stress field can incrementally increase the possibility of lateral crack growth. The long-range goals of this study are to critically analyze the lateral crack growth mechanisms associated with residual stresses, to modify residual tensile stress distributions by controlled heat treatment, and to minimize the probability of veneering ceramic fractures. Four approaches were used to accomplish these goals: (1) clinical evaluation of a bilayer ceramic fixed partial denture system; (2) fracture surface analysis of clinically failed FPDs; (3
NASA Astrophysics Data System (ADS)
Guzmán, R. E.; Hernández Arroyo, E.
2016-02-01
The properties of a metallic matrix composites materials (MMC's) reinforced with particles can be affected by different events occurring within the material in a manufacturing process. The existence of residual stresses resulting from the manufacturing process of these materials (MMC's) can markedly differentiate the curves obtained in tensile tests obtained from compression tests. One of the themes developed in this work is the influence of residual stresses on the mechanical behaviour of these materials. The objective of this research work presented is numerically estimate the thermal residual stresses using a unit cell model for the Mg ZC71 alloy reinforced with SiC particles with volume fraction of 12% (hot-forging technology). The MMC's microstructure is represented as a three dimensional prismatic cube-shaped with a cylindrical reinforcing particle located in the centre of the prism. These cell models are widely used in predicting stress/strain behaviour of MMC's materials, in this analysis the uniaxial stress/strain response of the composite can be obtained through the calculation using the commercial finite-element code.
A wafer mapping technique for residual stress in surface micromachined films
NASA Astrophysics Data System (ADS)
Schiavone, G.; Murray, J.; Smith, S.; Desmulliez, M. P. Y.; Mount, A. R.; Walton, A. J.
2016-09-01
The design of MEMS devices employing movable structures is crucially dependant on the mechanical behaviour of the deposited materials. It is therefore important to be able to fully characterize the micromachined films and predict with confidence the mechanical properties of patterned structures. This paper presents a characterization technique that enables the residual stress in MEMS films to be mapped at the wafer level by using microstructures released by surface micromachining. These dedicated MEMS test structures and the associated measurement techniques are used to extract localized information on the strain and Young’s modulus of the film under investigation. The residual stress is then determined by numerically coupling this data with a finite element analysis of the structure. This paper illustrates the measurement routine and demonstrates it with a case study using electrochemically deposited alloys of nickel and iron, particularly prone to develop high levels of residual stress. The results show that the technique enables wafer mapping of film non-uniformities and identifies wafer-to-wafer differences. A comparison between the results obtained from the mapping technique and conventional wafer bow measurements highlights the benefits of using a procedure tailored to films that are non-uniform, patterned and surface-micromachined, as opposed to simple standard stress extraction methods. The presented technique reveals detailed information that is generally unexplored when using conventional stress extraction methods such as wafer bow measurements.
Pierce, David M; Fastl, Thomas E; Rodriguez-Vila, Borja; Verbrugghe, Peter; Fourneau, Inge; Maleux, Geert; Herijgers, Paul; Gomez, Enrique J; Holzapfel, Gerhard A
2015-07-01
The existence of residual stresses in human arteries has long been shown experimentally. Researchers have also demonstrated that residual stresses have a significant effect on the distribution of physiological stresses within arterial tissues, and hence on their development, e.g., stress-modulated remodeling. Through progress in medical imaging, image analysis and finite element (FE) meshing tools it is now possible to construct in vivo patient-specific geometries and thus to study specific, clinically relevant problems in arterial mechanics via FE simulations. Classical continuum mechanics and FE methods assume that constitutive models and the corresponding simulations start from unloaded, stress-free reference configurations while the boundary-value problem of interest represents a loaded geometry and includes residual stresses. We present a pragmatic methodology to simultaneously account for both (i) the three-dimensional (3-D) residual stress distributions in the arterial tissue layers, and (ii) the equilibrium of the in vivo patient-specific geometry with the known boundary conditions. We base our methodology on analytically determined residual stress distributions (Holzapfel and Ogden, 2010, J. R. Soc. Interface 7, 787-799) and calibrate it using data on residual deformations (Holzapfel et al., 2007, Ann. Biomed. Eng. 35, 530-545). We demonstrate our methodology on three patient-specific FE simulations calibrated using experimental data. All data employed here are generated from human tissues - both the aorta and thrombus, and their respective layers - including the geometries determined from magnetic resonance images, and material properties and 3-D residual stretches determined from mechanical experiments. We study the effect of 3-D residual stresses on the distribution of physiological stresses in the aortic layers (intima, media, adventitia) and the layers of the intraluminal thrombus (luminal, medial, abluminal) by comparing three types of FE simulations
Gnaeupel-Herold, T.; Brand, P.C.; Prask, H.J.
1999-05-01
Using the Double Axis system for Residual stress, Texture, and Single crystal analysis (DARTS) at NIST, neutron diffraction residual stress measurements were carried out in the head region of five pairs of transverse and oblique cut slices of railroad track, each having a thickness of 6.35 mm. The slices were taken from a 300 HB rail of CFI 136 RE size. All slices except one unworn reference piece had the same accumulated tonnage but were ground in different intervals. The measurements confirm the results previously found which indicated the existence of high sub-surface residual tensile stresses, while the regional close to the wheel-rail contact line shows high residual compressive stresses.
NASA Astrophysics Data System (ADS)
Li, Zhichao; Freborg, Andrew M.; Hansen, Bruce D.; Srivatsan, T. S.
2013-03-01
Most steel gears are carburized and quenched prior to service to obtain the desired specific strength (σ/ρ) and hardness requirements. Use of carburization and quenching of steel gears creates a compressive residual stress on the carburized surface, which is beneficial for improving both bending and contact fatigue performance. Also, higher carbon content in the carburized surface decreases the starting temperature for formation of the martensitic phase and delaying the martensitic transformation at the part surface during the quenching hardening process. During the martensite phase formation, the material volume expands. The delayed martensitic transformation, coupled with the associated delayed volume expansion, induces residual compressive stress on the surface of the quenched part. The carburized case depth and distribution of carbon affect both the magnitude and the depth of the resulting residual compressive stress. In this article, the effect of carbon distribution on the residual stress in a spur gear is presented and discussed using finite element modeling to understand the intrinsic material mechanics contributing to the presence of internal stress. Influence of the joint on thermal gradient and the influence of phase transformation on the development of internal stresses are discussed using results obtained from modeling. The residual stress arising due to heat treatment is imported into single-tooth bending and dynamic contact stress analysis models to investigate the intrinsic interplay among carbon case depth, residual stress, bending load, and torsional load on potential fatigue life. Three carburization processes, followed by oil quenching, are examined. A method for designing minimum case depth so as to achieve beneficial residual stresses in gears subjected to bending and contact stresses is suggested.
Amplified effect of mild plastic anisotropy on residual stress and strain anisotropy
Prime, Michael B.
2017-07-01
Axisymmetric indentation of a geometrically axisymmetric disk produced residual stresses by non-uniform plastic deformation. The 2024 aluminum plate used to make the disk exhibited mild plastic anisotropy with about 10% lower strength in the transverse direction compared to the rolling and through-thickness directions. Residual stresses and strains in the disk were measured with neutron diffraction, slitting, the contour method, x-ray diffraction and hole drilling. Surprisingly, the residual-stress anisotropy measured in the disk was about 40%, the residual-strain anisotropy was an impressive 100%, and the residual stresses were higher in the weaker direction. The high residual stress anisotropy relative to themore » mild plastic anisotropy and the direction of the highest stress are explained by considering the mechanics of indentation: constraint on deformation provided by the material surrounding the indentation and preferential deformation in the most compliant direction for incremental deformation. By contrast, the much larger anisotropy in residual strain compared to that in residual stress is independent of the fabrication process and is instead explained by considering Hookean elasticity. For Poisson's ratio of 1/3, the relationship simplifies to the residual strain anisotropy equaling the square of the residual stress anisotropy, which matches the observed results (2 ≈ 1.4^2). Furthermore, a lesson from this study is that to accurately predict residual stresses and strains, one must be wary of seemingly reasonable simplifying assumptions such as neglecting mild plastic anisotropy.« less
NASA Astrophysics Data System (ADS)
Wang, Jia-Siang; Hsieh, Chih-Chun; Lin, Chi-Ming; Kuo, Che-Wei; Wu, Weite
2013-02-01
Over the last half century, vibratory stress relief (VSR) has come to be recognized as a technique with several unique benefits, and it has found applications in various industries. However, the mechanisms involved remain unclear, and the textures corresponding to residual stress relaxation were rarely reported in the existing literature. The purpose of this study is to discuss the texture evolution and residual stress relaxation in a cold-rolled Al-Mg-Si-Cu alloy using VSR technique. All the residual stress measurements were performed using a standard X-ray diffraction (XRD) technique. Measurement of texture was performed on the specimen surface using conventional pole figure (PF) as well as orientation distribution functions (ODFs) methods. Results indicate that the VSR technique can be applied to weaken the α-fiber and cause the residual stress of the rolled samples to gradually approach uniformity in XRD analysis. The best relaxation of the compressive residual stress reaches about 52.6 pct, but relaxation of the tensile residual stress is less than 10 pct. After the VSR process for 20 minutes, the texture intensities of PFs (200) and (220) as compared to those in nonvibration are nearly homogeneously distributed. Furthermore, the texture of (111) PF perpendicular to normal direction (ND), which is affected by vibratory force parallel to ND, almost disappears.
Minimization of Residual Stress in an Al-Cu Alloy Forged Plate by Different Heat Treatments
NASA Astrophysics Data System (ADS)
Dong, Ya-Bo; Shao, Wen-Zhu; Jiang, Jian-Tang; Zhang, Bao-You; Zhen, Liang
2015-06-01
In order to improve the balance of mechanical properties and residual stress, various quenching and aging treatments were applied to Al-Cu alloy forged plate. Residual stresses determined by the x-ray diffraction method and slitting method were compared. The surface residual stress measured by x-ray diffraction method was consistent with that measured by slitting method. The residual stress distribution of samples quenched in water with different temperatures (20, 60, 80, and 100 °C) was measured, and the results showed that the boiling water quenching results in a 91.4% reduction in residual stress magnitudes compared with cold water quenching (20 °C), but the tensile properties of samples quenched in boiling water were unacceptably low. Quenching in 80 °C water results in 75% reduction of residual stress, and the reduction of yield strength is 12.7%. The residual stress and yield strength level are considerable for the dimensional stability of aluminum alloy. Quenching samples into 30% polyalkylene glycol quenchants produced 52.2% reduction in the maximum compressive residual stress, and the reduction in yield strength is 19.7%. Moreover, the effects of uphill quenching and thermal-cold cycling on the residual stress were also investigated. Uphill quenching and thermal-cold cycling produced approximately 25-40% reduction in residual stress, while the effect on tensile properties is quite slight.
Residual surface stresses in laminated cross-ply fiber-epoxy composite materials
NASA Astrophysics Data System (ADS)
Gascoigne, Harold E.
Residual (curing) stresses in cross-ply laminated panels are related to the strains released when individual plies are separated. Released strains are determined using high-sensitivity moire interferometry. Elastic orthotropic stress-strain relations are used to calculate residual stresses. Residual strains and stresses are determined on the lateral surface and at the free-edge of a cross-ply panel. The circumferential and radial residual stresses near the outer surface of a thick-walled cross-ply cylinder are determined.
Kekalo, I. B.; Mogil’nikov, P. S.
2015-06-15
The reversibility of residual bending stresses is revealed in ribbon samples of cobalt- and iron-based amorphous alloys Co{sub 69}Fe{sub 3.7}Cr{sub 3.8}Si{sub 12.5}B{sub 11} and Fe{sub 57}Co{sub 31}Si{sub 2.9}B{sub 9.1}: the ribbons that are free of applied stresses and bent under the action of residual stresses become completely or incompletely straight upon annealing at the initial temperatures. The influence of annealing on the relaxation of bending stresses is studied. Preliminary annealing is found to sharply decrease the relaxation rate of bending stresses, and the initial stage of fast relaxation of these stresses is absent. Complete straightening of preliminarily annealed ribbons is shown to occur at significantly higher temperatures than that of the initial ribbons. Incomplete straightening of the ribbons is explained by the fact that bending stresses relaxation at high annealing temperatures proceeds due to both reversible anelastic deformation and viscous flow, which is a fully irreversible process. Incomplete reversibility is also caused by irreversible processes, such as the release of excess free volume and clustering (detected by small-angle X-ray scattering). The revealed differences in the relaxation processes that occur in the cobalt- and iron-based amorphous alloys are discussed in terms of different atomic diffusion mobilities in these alloys.
Permethylation Linkage Analysis Techniques for Residual Carbohydrates
USDA-ARS?s Scientific Manuscript database
Permethylation analysis is the classic approach to establishing the position of glycosidic linkages between sugar residues. Typically, the carbohydrate is derivatized to form acid-stable methyl ethers, hydrolyzed, peracetylated, and analyzed by gas chromatography-mass spectrometry (GC-MS). The pos...
Quantification of residual stress from photonic signatures of fused silica
Cramer, K. Elliott; Yost, William T.; Hayward, Maurice
2014-02-18
A commercially available grey-field polariscope (GFP) instrument for photoelastic examination is used to assess impact damage inflicted upon the outer-most pane of Space Shuttle windows made from fused silica. A method and apparatus for calibration of the stress-optic coefficient using four-point bending is discussed. The results are validated on known material (acrylic) and are found to agree with literature values to within 6%. The calibration procedure is then applied to fused-silica specimens and the stress-optic coefficient is determined to be 2.43 ± 0.54 × 10{sup −12} Pa{sup −1}. Fused silica specimens containing impacts artificially made at NASA’s Hypervelocity Impact Technology Facility (HIT-F), to simulate damage typical during space flight, are examined. The damage sites are cored from fused silica window carcasses and examined with the GFP. The calibrated GFP measurements of residual stress patterns surrounding the damage sites are presented.
Operator Manual for X-ray Residual Stress Mapping
Wright, M.C.
2003-07-30
This document is intended to serve as a operator manual for remote control of the TEC x-ray diffraction system. It is assumed that the reader is familiar with the operation of the SaraTEC{trademark} 1630 Acquisition Manager software for the TEC 1630 X-Ray Diffraction System. This manual describes the operation of the new TEC Remote Serial Control Module (RCSM) that runs on the TEC computer and Run-the-System that runs on the motion control computer. The basic goal is to add enough control of the TEC system to enable stress mapping. In stress mapping, the specimen is positioned using our X-Y-Z-Phi translation system and data is collected using the TEC system. The process is then repeated for the next position using a table of preset positions. X-Y-Z-Phi axis management is handled by ''Run-the-System'', the LabVIEW program originally developed for the Neutron Residual Stress Mapping Facility, running on a separate computer from the one that controls the TEC. Run-the-System also manages all remote start, stop, and configuration commands that are sent to the TEC system. The two computers communicate over an RS-232 serial line.
Determination of Bulk Residual Stresses in Electron Beam Additive-Manufactured Aluminum
NASA Astrophysics Data System (ADS)
Brice, Craig A.; Hofmeister, William H.
2013-11-01
Additive-manufactured aluminum alloy deposits were analyzed using neutron diffraction to characterize the effect of intermediate stress relief anneal heat treatment on bulk residual stresses in the final part. Based on measured interplanar spacing, stresses were calculated at various locations along a single bead, stacked wall deposit. A comparison between an uninterrupted deposited wall and an interrupted, stress-relieved, and annealed deposited wall showed a measureable reduction in residual stress magnitude at the interface with a corresponding shift in stress character into the deposit. This shift changes the interface stresses from purely compressive to partially tensile. The residual stress profile varied along the length of the deposit, and the heat-treatment procedure reduced the overall magnitude of the stress at the interface by 10 through 25 MPa. These results are interpreted in terms of thermal gradients inherent to the process and compared with prior residual stress-characterization studies in additive-manufactured metallic structures.
Analysis techniques for residual acceleration data
NASA Technical Reports Server (NTRS)
Rogers, Melissa J. B.; Alexander, J. Iwan D.; Snyder, Robert S.
1990-01-01
Various aspects of residual acceleration data are of interest to low-gravity experimenters. Maximum and mean values and various other statistics can be obtained from data as collected in the time domain. Additional information may be obtained through manipulation of the data. Fourier analysis is discussed as a means of obtaining information about dominant frequency components of a given data window. Transformation of data into different coordinate axes is useful in the analysis of experiments with different orientations and can be achieved by the use of a transformation matrix. Application of such analysis techniques to residual acceleration data provides additional information than what is provided in a time history and increases the effectiveness of post-flight analysis of low-gravity experiments.
Nondestructive evaluation of residual stress in short-fiber reinforced plastics by x-ray diffraction
NASA Astrophysics Data System (ADS)
Tanaka, Keisuke; Tokoro, Syouhei; Akiniwa, Yoshiaki; Egami, Noboru
2014-06-01
The X-ray diffraction method is used to measure the residual stress in injection-molded plates of short-fiber reinforced plastics (SFRP) made of crystalline thermoplastics, polyphenylene sulphide (PPS), reinforced by carbon fibers with 30 mass%. Based on the orientation of carbon fibers, injection molded plates can be modeled as three-layered lamella where the core layer is sandwiched by skin layers. The stress in the matrix in the skin layer was measured using Cr-Kα radiation with the sin2Ψ method. Since the X-ray penetration depth is shallow, the state of stresses measured by X-rays in FRP can be assumed to be plane stress. The X-ray measurement of stress in carbon fibers was not possible because of high texture. A new method was proposed to evaluate the macrostress in SFRP from the measurement of the matrix stress. According to micromechanics analysis of SFRP, the matrix stresses in the fiber direction, σ1m, and perpendicular to the fiber direction, σ2m, and shear stress τ12m can be expressed as the functions of the applied (macro-) stresses, σ1A, σ2A , τ12A as follows: σ1m = α11σ1A +α12σ2A, σ2m = α21σ1A + α22σ2A, τ12m = α66τ12A, where α11 ,α12, α21, α22, α66 are stress-partitioning coefficients. Using skin-layer strips cut parallel, perpendicular and 45° to the molding direction, the stress in the matrix was measured under the uniaxial applied stress and the stress-partitioning coefficients of the above equations were determined. Once these relations are established, the macrostress in SFRP can be determined from the measurements of the matrix stresses by X-rays.
SVD analysis of Aura TES spectral residuals
NASA Technical Reports Server (NTRS)
Beer, Reinhard; Kulawik, Susan S.; Rodgers, Clive D.; Bowman, Kevin W.
2005-01-01
Singular Value Decomposition (SVD) analysis is both a powerful diagnostic tool and an effective method of noise filtering. We present the results of an SVD analysis of an ensemble of spectral residuals acquired in September 2004 from a 16-orbit Aura Tropospheric Emission Spectrometer (TES) Global Survey and compare them to alternative methods such as zonal averages. In particular, the technique highlights issues such as the orbital variation of instrument response and incompletely modeled effects of surface emissivity and atmospheric composition.
SVD analysis of Aura TES spectral residuals
NASA Technical Reports Server (NTRS)
Beer, Reinhard; Kulawik, Susan S.; Rodgers, Clive D.; Bowman, Kevin W.
2005-01-01
Singular Value Decomposition (SVD) analysis is both a powerful diagnostic tool and an effective method of noise filtering. We present the results of an SVD analysis of an ensemble of spectral residuals acquired in September 2004 from a 16-orbit Aura Tropospheric Emission Spectrometer (TES) Global Survey and compare them to alternative methods such as zonal averages. In particular, the technique highlights issues such as the orbital variation of instrument response and incompletely modeled effects of surface emissivity and atmospheric composition.
Fluorescence of crop residue: postmortem analysis of crop conditions
NASA Astrophysics Data System (ADS)
McMurtrey, James E., III; Kim, Moon S.; Daughtry, Craig S. T.; Corp, Lawrence A.; Chappelle, Emmett W.
1997-07-01
Fluorescence of crop residues at the end of the growing season may provide an indicator of the past crop's vegetative condition. Different levels of nitrogen (N) fertilization were applied to field grown corn and wheat at Beltsville, Maryland. The N fertilizer treatments produce a range of physiological conditions, pigment concentrations, biomass levels, and grain yields that resulted in varying growth and stress conditions in the living crops. After normal harvesting procedures the crop residues remained. The fluorescence spectral characteristics of the plant residues from crops grown under different levels of N nutrition were analyzed. The blue-green fluorescence response of in-vitro residue biomass of the N treated field corn had different magnitudes. A blue-green- yellow algorithm, (460/525)*600 nm, gave the best separations between prior corn growth conditions at different N fertilization levels. Relationships between total dry biomass, the grain yield, and fluorescence properties in the 400 - 670 nm region of the spectrum were found in both corn and wheat residues. The wheat residue was analyzed to evaluate the constituents responsible for fluorescence. A ratio of the blue-green, 450/550 nm, images gave the best separation among wheat residues at different N fertilization levels. Fluorescence of extracts from wheat residues showed inverse fluorescence intensities as a function of N treatments compared to that of the intact wheat residue or ground residue samples. The extracts also had an additional fluorescence emission peak in the red, 670 nm. Single band fluorescence intensity in corn and wheat residues is due mostly to the quantity of the material on the soil surface. Ratios of fluorescence bands varied as a result of the growth conditions created by the N treatments and are thought to be indicative of the varying concentrations of the plant residues fluorescing constituents. Estimates of the amount and cost effectiveness of N fertilizers to satisfy
Modeling and validation of residual stress distribution in an HSLA-100 disk
Feng, Z.; Zhu, Y.Y.; Zacharia, T.; Fields, R.J.; Prask, H.J.; Brand, P.C.; Blackburn, J.M.
1995-12-31
The residual stress distribution in a GTA spot we 100 steel disk was analyzed using thermomechanically uncoupled and semi-coupled finite element (FE) formulations and measured with the neutron diffraction technique. The computations used temperature-dependent the and mechanical properties of the base metal. The thermal analysis was based on the heat conduction formulation with the Gaussian heat input from the arc. The semi-coupled approach is an effective alternative to the fully coupled approach in which the incompatibility in the thermal and mechanical time increments often leads to numerical convergence difficulties. Convergence was achieved in the semi-coupled approach where a larger time increment for temperature calculation was automatically divided into some sub-intervals for the thermal stress calculation. The temperature, deformation configurations, and state variables were updated at the end of the temperature increment. The predictions from the FE models are in very good agreement with the neutron measurement results in the far heat-affected zone (HAZ) and in the base metal. Both models over-predicted the residual stress field in the fusion zone and near HAZ as measured by the neutron diffraction method. The discrepancy could be attributed to the changes in microstructures and material properties in the HAZ and fusion zone due to phase transformations during the welding thermal cycle. The formation of cracks in the fusion zone is another factor that possibly contributes to the lower measured residual stress values.
NASA Technical Reports Server (NTRS)
Castelli, Michael G.
1998-01-01
In recent years, much effort has been spent examining the residual stress-strain states of advanced composites. Such examinations are motivated by a number of significant concerns that affect composite development, processing, and analysis. The room-temperature residual stress states incurred in many advanced composite systems are often quite large and can introduce damage even prior to the first external mechanical loading of the material. These stresses, which are induced during the cooldown following high-temperature consolidation, result from the coefficient of thermal expansion mismatch between the fiber and matrix. Experimental techniques commonly used to evaluate composite internal residual stress states are non-mechanical in nature and generally include forms of x-ray and neutron diffraction. Such approaches are usually complex, involving a number of assumptions and limitations associated with a wide range of issues, including the depth of penetration, the volume of material being assessed, and erroneous effects associated with oriented grains. Furthermore, and more important to the present research, these techniques can assess only "single time" stress in the composite. That is, little, if any, information is obtained that addresses the time-dependent point at which internal stresses begin to accumulate, the manner in which the accumulation occurs, and the presiding relationships between thermoelastic, thermoplastic, and thermoviscous behaviors. To address these critical issues, researchers at the NASA Lewis Research Center developed and implemented an innovative mechanical test technique to examine in real time, the time-dependent thermomechanical stress behavior of a matrix alloy as it went through a consolidation cycle.
Residual Stress Development in Explosive-Bonded Bi-Metal Composite Materials
2014-03-01
distribution of the residual stress over the welded material, especially at the interface area. Similar and dissimilar steel plate materials possessing...explosive welding for improved mechanical and corrosion properties of bimetal composite materials is the potential for a residual stress contour to exist at...residual stress over the welded material, especially at the interface area. A range of varieties of steel plate materials, possessing different
2015-08-24
residual stresses were characterized by the incremental hole drilling technique. The effect of laser peening parameters on the magnitude, depth, and the...characterised by the nanoindentation technique, and the residual stresses were characterised by the incremental hole drilling technique. The effect of laser...conditions, induced residual stresses and hardness, and material state; and also by providing validation data for various predictive models that will apply
Kartal, Mehmet E.
2013-01-01
The contour method is one of the most prevalent destructive techniques for residual stress measurement. Up to now, the method has involved the use of the finite-element (FE) method to determine the residual stresses from the experimental measurements. This paper presents analytical solutions, obtained for a semi-infinite strip and a finite rectangle, which can be used to calculate the residual stresses directly from the measured data; thereby, eliminating the need for an FE approach. The technique is then used to determine the residual stresses in a variable-polarity plasma-arc welded plate and the results show good agreement with independent neutron diffraction measurements. PMID:24204187
Neutron scattering residual stress measurements on gray cast iron brake discs
Spooner, S.; Payzant, E.A.; Hubbard, C.R.
1996-11-01
Neutron diffraction was used to investigate the effects of a heat treatment designed to remove internal residual stresses in brake discs. It is believed that residual stresses may change the rate of deformation of the discs during severe braking conditions when the disc temperature is increased significantly. Neutron diffraction was used to map out residual strain distributions in a production disc before and after a stress-relieving heat treatment. Results from these neutron diffraction experiments show that some residual strains were reduced by as much as 400 microstrain by stress relieving. 5 refs., 5 figs., 1 tab.
Internal surface residual stresses in girth butt-welded steel pipes
Mohr, W.C.
1996-12-01
Welding residual stresses are often needed as inputs in fitness for service determinations. This paper collects data on the welding residual stress at the internal surface of girth welds in steel pipes. Comparing the available measurements at the weld centerline, large variations can be noted in residual stress, both in the axial and hoop direction, even on pipes of similar thickness. The range can be somewhat reduced by including the effects of welding net heat input and material yield strength, but at best the range is {+-} 0.4 yield strength. Mechanisms of residual stress formation and estimation techniques are discussed.
Prime, M. B.; Newborn, M. A.; Balog, J. A.
2003-01-01
The cold-compression stress relief process used to reduce the quench-induced stresses in high-strength aerospace aluminum alloy forgings does not fully relieve the stresses. This study measured and predicted the residual stress in 7050-T74 (solution heat treated, quenched, and artificially overaged) and 7050-T7452 (cold compressed prior to aging) hand forgings. The manufacturing process was simulated by finite element analysis. First, a thermal analysis simulated the quench using appropriate thermal boundary conditions and temperature dependent material properties. Second, a structural analysis used the thermal history and a temperature and strain-rate dependent constitutive model to predict the stresses after quenching. Third, the structural analysis was continued to simulate the multiple cold compressions of the stress relief process. Experimentally, the residual stresses in the forgings were mapped using the contour method, which involved cutting the forgings using wire EDM and then measuring the contour of the cut surface using a CMM. Multiple cuts were used to map different stress components. The results show a spatially periodic variation of stresses that results from the periodic nature of the cold work stress relief process. The results compare favorably with the finite element prediction of the stresses.
A Mechanical Analysis of Conduit Arteries Accounting for Longitudinal Residual Strains
Wang, Ruoya; Gleason, Rudolph L.
2010-01-01
Identification of an appropriate stress-free reference configuration is critically important in providing a reasonable prediction of the intramural stress distribution when performing biomechanical analyses on arteries. The stress-free state is commonly approximated as a radially cut ring that typically opens into a nearly circular sector, relieving much of the circumferential residual strains that exist in the traction-free configuration. An opening angle is often used to characterize this sector. In this study, we first present experimental results showing significant residual deformations in the longitudinal direction of two commonly studied arteries in the pig: the common carotid artery and the left anterior descending coronary artery. We concluded that a radially cut ring cannot completely describe the stress-free state of the arteries. Instead, we propose the use of a longitudinal opening angle, in conjunction with the traditional circumferential opening angle, to experimentally quantify the stress-free state of an artery. Secondly, we propose a new kinematic model to account for the addition of longitudinal residual strains through employing the longitudinal opening angle and performed a stress analysis. We found that with the inclusion of longitudinal residual strains in the stress analysis, the predicted circumferential stress gradient was decreased by 3-fold and the predicted longitudinal stress gradient was increased by 5.7-fold. Thus, inclusion of longitudinal residual strains has a significant effect on the predicted stress distribution in arteries. PMID:20087772
Residual stress delaying phase transformation in Y-TZP bio-restorations
NASA Astrophysics Data System (ADS)
Allahkarami, Masoud; Hanan, Jay C.
2012-01-01
Engineering favorable residual stress for the complex geometry of bi-layer porcelain-zirconia crowns potentially prevents crack initiation and improves the mechanical performance and lifetime of the dental restoration. In addition to external load, the stress field depends on initial residual stress before loading. Residual stress is the result of factors such as the thermal expansion mismatch of layers and compliance anisotropy of zirconia grains in the process of sintering and cooling. Stress induced phase transformation in zirconia extensively relaxes the residual stress and changes the stress state. The objective of this study is to investigate the coupling between tetragonal to monoclinic phase transformations and residual stress. Residual stress, on the surface of the sectioned single load to failure crown, at 23 points starting from the pure tetragonal and ending at a fully monoclinic region were measured using the micro X-ray diffraction sin2 ψ method. An important observation is the significant range in measured residual stress from a compressive stress of -400 MPa up to tensile stress of 400 MPa and up to 100% tetragonal to monoclinic phase transformation.
McGregor, R.; Doherty, P.; Hornbach, D.; Abdelsalam, U.
1995-12-31
Nuclear Steam Generator (SG) service reliability and longevity have been seriously affected worldwide by corrosion at the tube-to-tubesheet joint expansion. Current SG designs for new facilities and replacement projects enhance corrosion resistance through the use of advanced tubing materials and improved joint design and fabrication techniques. Here, transition zones of hydraulic expansions have undergone detailed experimental evaluation to define residual stress and cold-work distribution on and below the secondary-side surface. Using X-ray diffraction techniques, with supporting finite element analysis, variations are compared in tubing metallurgical condition, tube/pitch geometry, expansion pressure, and tube-to-hole clearance. Initial measurements to characterize the unexpanded tube reveal compressive stresses associated with a thin work-hardened layer on the outer surface of the tube. The gradient of cold-work was measured as 3% to 0% within .001 inch of the surface. The levels and character of residual stresses following hydraulic expansion are primarily dependent on this work-hardened surface layer and initial stress state that is unique to each tube fabrication process. Tensile stresses following expansion are less than 25% of the local yield stress and are found on the transition in a narrow circumferential band at the immediate tube surface (< .0002 inch/0.005 mm depth). The measurements otherwise indicate a predominance of compressive stresses on and below the secondary-side surface of the transition zone. Excellent resistance to SWSCC initiation is offered by the low levels of tensile stress and cold-work. Propagation of any possible cracking would be deterred by the compressive stress field that surrounds this small volume of tensile material.
Residual stress near cracks of K and fused silica under 1064 nm nanosecond laser irradiation
NASA Astrophysics Data System (ADS)
Zhang, Zhen; Liu, Hongjie; Huang, Jin; Zhou, Xiaoyan; Ren, Dahua; Cheng, Xinlu; Jiang, Xiaodong; Wu, Weidong; Zheng, Wanguo
2012-11-01
Measurements of birefringence induced in K9 and fused silica specimens by cracks produced by 1064 nm Nd∶YAG laser have been presented. The Birefringence data is converted into the units of stress, thus permitting the estimation of residual stress near crack. The intensity of residual stress in K9 glass is larger than that in fused silica under the same condition. The similarity of residual stress distribution along the y-axis reveals that the nature of shock wave transmission in optical materials under 1064 nm laser irradiation is the same with each other. The value of residual stress can be influenced by laser parameters and characterization of optical material. Simulation based on a theoretical model giving the residual stress field around a crack is developed for comparison with experiment results. The probability of initial damage and the direction of the energy dissipation in cracks determine the residual stress distribution. The thermal stress coupling enlarges the asymmetry of residual stress distribution. Residual stress in optical material has a strong effect on fracture and should be taken into account in any formulation that involves the enhanced damage resistance of optical components used in laser induced damage experiments.
NASA Astrophysics Data System (ADS)
Meserve, Justin
Cold drawn AISI 4140 beams were LASER surface hardened with a 2 kW CO2 LASER. Specimens were treated in the free state and while restrained in a bending fixture inducing surface tensile stresses of 94 and 230 MPa. Knoop hardness indentation was used to evaluate the through thickness hardness distribution, and a layer removal methodology was used to evaluate the residual stress distribution. Results showed the maximum surface hardness attained was not affected by pre-stress during hardening, and ranged from 513 to 676 kg/mm2. The depth of effective hardening varied at different magnitudes of pre-stress, but did not vary proportionately to the pre-stress. The surface residual stress, coinciding with the maximum compressive residual stress, increased as pre-stress was increased, from 1040 MPa for the nominally treated specimens to 1270 MPa for specimens pre-stressed to 230 MPa. The maximum tensile residual stress observed in the specimens decreased from 1060 MPa in the nominally treated specimens to 760 MPa for specimens pre-stressed to 230 MPa. Similarly, thickness of the compressive residual stress region increased and the depth at which maximum tensile residual stress occurred increased as the pre-stress during treatment was increased Overall, application of tensile elastic pre-stress during LASER hardening is beneficial to the development of compressive residual stress in AISI 4140, with minimal impact to the hardness attained from the treatment. The newly developed approach for LASER hardening may support efforts to increase both the wear and fatigue resistance of parts made from hardenable steels.
Quantifying Volcanic Stresses from Residual Stress Preserved in Magnetite and Zircon
NASA Astrophysics Data System (ADS)
Leonhardi, T. C.; Befus, K.; Manga, M.; Stan, C. V.; Tamura, N.
2016-12-01
Stresses active in volcanic systems are intimately linked with the processes driving magma chamber evolution and volcanic eruptions. These processes are difficult to quantify directly. Instead, insights come from a combination of modeling, geophysical observations, petrology and geochemistry. To directly quantify the forces and stresses associated with volcanic systems (such as chamber over-pressure) we need to develop techniques that provide new insights into volcanic processes. Here we quantified volcanic stresses in crystals from two units erupted from Yellowstone caldera. We used the Laue x-ray microdiffraction technique to measure preserved elastic lattice strain and the equivalent stress required to produce the strain. We analyzed zircon and magnetite crystals from pumice clasts in the pyroclastic fall deposit from the Tuff of Bluff Point and a flow front sample of the effusive Summit Lake lava flow. Analyses were performed using the x-ray microdiffraction beamline (12.3.2) at the Advanced Light Source, Lawrence Berkeley National Lab. Zircon preserved residual stress values in the range of 290-430 MPa for both units. Magnetite from the Tuff of Bluff Point preserves stress values of 310-370 MPa, whereas Summit Lake magnetite preserved values of 210-280 MPa. These values are greater that the estimates for lithostatic pressure in the final shallow storage chamber. If the values do represent the minerals' formation depth, then this indicates magnetite and zircon formed early in the magmatic system at greater depth. If true, residual stress in zircon and magnetite may be used as a crystallization geobarometer. Alternatively, if these values did not result from storage depth, they could reflect other processes in the chamber and conduit (such as fragmentation and thermal quenching). The observed differences in magnetite values suggest a change in the storage depth and/or volcanic stresses active in eruptions of the two deposits. For zircon, recoil damage and trace
Thermal Stability of Residual Stresses in Ti-6Al-4V components
NASA Astrophysics Data System (ADS)
Stanojevic, A.; Angerer, P.; Oberwinkler, B.
2016-03-01
The need for light weight design while maintaining a high safety is essential for many components, especially in the aircraft industry. Therefore, it's important to consider every aspect to reduce weight, improve fatigue life and maintain safety of crucial components. Residual stresses are a major factor which can positively influence components and fulfil all three requirements. However, due to the inconstancy of the behaviour of residual stresses during the life time of a component, residual stresses are often neglected. If the behaviour of residual stresses could be described reliably over the entire life time of a component, residual stresses could be taken into account and components could be optimized even further. Mechanical and thermal loads are the main reason for relaxation of residual stresses. This work covers the thermal stability of residual stresses in Ti-6Al-4V components. Therefore, exposure tests at raised temperatures were performed on specimens with different surface conditions. Residual stresses were measured by x-ray diffraction before and after testing. Creep tests were also carried out to describe the creep behaviour and thereby the ability for residual stress relaxation. A correlation between the creep rate and amount of relaxed stress was found. The creep behaviour of the material was described by using a combination of the Norton Power law and the Arrhenius equation. The Zener-Wert-Avrami model was used to describe the residual stress relaxation. With these models a satisfying correlation between measured and calculated data was found. Hence, the relaxation of residual stresses due to thermal load was described reliably.
The influence of quench sensitivity on residual stresses in the aluminium alloys 7010 and 7075
Robinson, J.S.; Tanner, D.A.; Truman, C.E.; Paradowska, A.M.; Wimpory, R.C.
2012-03-15
The most critical stage in the heat treatment of high strength aluminium alloys is the rapid cooling necessary to form a supersaturated solid solution. A disadvantage of quenching is that the thermal gradients can be sufficient to cause inhomogeneous plastic deformation which in turn leads to the development of large residual stresses. Two 215 mm thick rectilinear forgings have been made from 7000 series alloys with widely different quench sensitivity to determine if solute loss in the form of precipitation during quenching can significantly affect residual stress magnitudes. The forgings were heat treated and immersion quenched using cold water to produce large magnitude residual stresses. The through thickness residual stresses were measured by neutron diffraction and incremental deep hole drilling. The distribution of residual stresses was found to be similar for both alloys varying from highly triaxial and tensile in the interior, to a state of biaxial compression in the surface. The 7010 forging exhibited larger tensile stresses in the interior. The microstructural variation from surface to centre for both forgings was determined using optical and transmission electron microscopy. These observations were used to confirm the origin of the hardness variation measured through the forging thickness. When the microstructural changes were accounted for in the through thickness lattice parameter, the residual stresses in the two forgings were found to be very similar. Solute loss in the 7075 forging appeared to have no significant effect on the residual stress magnitudes when compared to 7010. - Highlights: Black-Right-Pointing-Pointer Through thickness residual stress measurements made on large Al alloy forgings. Black-Right-Pointing-Pointer Residual stress characterised using neutron diffraction and deep hole drilling. Black-Right-Pointing-Pointer Biaxial compressive surface and triaxial subsurface residual stresses. Black-Right-Pointing-Pointer Quench sensitivity
Residual ozone determination by flow injection analysis
Straka, M.R.; Pacey, G.E.; Gordon, G.
1984-09-01
It has been proposed that ozone be used to replace free chlorine for the disinfection of drinking water and waste water. For the use of ozone in this capacity, it would be necessary to have a fast accurate and precise method to analyze for the presence of residuals. An automated method for ozone determination based on the indigo reagent method is presented. This method is based on the advantages of flow injection analysis (FIA) techniques. 19 references, 3 tables, 2 figures.
The effect of cutting speed on residual stresses when orthogonal cutting TC4
NASA Astrophysics Data System (ADS)
Liu, Chaofeng; Wang, Zengqiang; Zhang, Guang; Liu, Lei
2015-09-01
As one of the most important parameters in mental cutting, cutting speed has a significant influence on residual stress. Finite element method and experiment method are used to study the relationship between cutting speed and residual stress when orthogonal cutting TC4 titanium alloy. The result of simulation and experiment shows that: when the cutting speed is low, the residual stress in axial direction is compressive stress and gradually converts to tensile stress with the increase of cutting speed, but it will convert to compressive stress again if the cutting speed continues to increase; the residual stress in tangential direction is constant to compressive stress and it will decrease with the increase of cutting speed.
Residual stress effects on the impact resistance and strength of fiber composites
NASA Technical Reports Server (NTRS)
Chamis, C. C.
1973-01-01
Equations have been derived to predict degradation effects of microresidual stresses on impact resistance of unidirectional fiber composites. Equations also predict lamination residual stresses in multilayered angle ply composites.
Residual stress and dislocations density in silicon ribbons grown via optical zone melting
NASA Astrophysics Data System (ADS)
Augusto, A.; Pera, D.; Choi, H. J.; Bellanger, P.; Brito, M. C.; Maia Alves, J.; Vallêra, A. M.; Buonassisi, T.; Serra, J. M.
2013-02-01
We investigate the relationships between growth rate, time-temperature profile, residual stress, dislocation density, and electrical performance of silicon ribbons grown via optical zone melting. The time-temperature profiles of ribbons grown at different velocities were investigated using direct measurements and computational fluid dynamics (CFD) modeling. Residual stresses up to 20 MPa were measured using infrared birefringence imaging. The effect of crystallization speed on dislocation density and residual stress is discussed from the context of thermal stresses during growth. More broadly, we demonstrate the usefulness of combining spatially resolved stress and microstructure measurements with CFD simulations toward optimizing kerfless silicon wafer quality.
Hysteresis loop as the indicator of residual stress in drawn wires
NASA Astrophysics Data System (ADS)
Suliga, Maciej; Chwastek, Krzysztof; Pawlik, Piotr
2014-04-01
The paper investigates the possibility of using the magnetic method for non-destructive determination of residual stress in drawn wires. The change in residual stress for different processing speeds is reflected in the shape of hysteresis loop. A simple model for stress-dependent hysteresis, based on the concept of the effective field, is proposed. The effective field includes an additional term related to stress, in accordance with previous Jiles' and Sablik's results. The presented description may be useful for technologists seeking a simple tool for predicting residual stress.
The Effect of Creep on the Residual Stresses Generated During Silicon Sheet Growth
NASA Technical Reports Server (NTRS)
Hutchinson, J. W.; Lambropoulos, J. C.
1984-01-01
The modeling of stresses generated during the growth of thin silicon sheets at high speeds is an important part of the EFG technique since the experimental measurement of the stresses is difficult and prohibitive. The residual stresses which arise in such a growth process lead to serious problems which make thin Si ribbons unsuitable for fabrication. The constitutive behavior is unrealistic because at high temperature (close to the melting point) Si exhibits considerable creep which significantly relaxes the residual stresses. The effect of creep on the residual stresses generated during the growth of Si sheets at high speeds was addressed and the basic qualitative effect of creep are reported.
Modeling of microstructure and residual stress in cast iron calendar rolls
Jacot, A.; Maijer, D.; Cockcroft, S.
2000-04-01
A comprehensive mathematical model based on the commercial finite-element (FE) code ABAQUS has been developed to predict the evolution of temperature, microstructure, and residual stresses in cast iron castings. The thermal component of the model, applied in stage one of the analysis, is capable of simulating the formation of microstructure over a broad range of cooling conditions, including the formation of columnar white iron as well as equiaxed gray iron. To test the model, it has been evaluated against thermocouple and microstructural data collected from a reduced-scale calendar roll test casting. The model has been demonstrated to be able to predict the transition from columnar white iron to equiaxed gray iron which occurs approximately 20 mm below the outside surface of the roll test casting. In addition, the model is shown to be able to satisfactorily reproduce the evolution of temperature recorded from thermocouples embedded at various locations in the test casting. An elastic-plastic stress analysis, applied in the second stage of the analysis, was performed using the temperature history and the volume fraction of white and gray iron obtained with the thermal/microstructural model. The results were verified against residual stress measurements made at various locations along the outer-diameter (OD) surface of the roll. The elastic-plastic model accounts for the temperature-dependent plastic behavior of white and gray iron and the thermal dilatational behavior of white and gray iron, including volumetric expansion due to austenite decomposition and dilatational anisotropy in columnar white iron. The results of the mathematical analysis demonstrate that the residual stress distribution in full-scale calendar thermorolls cannot be deduced simply from knowledge of the microstructural distribution and basic dilatometric considerations, as is currently the practice in industry.
Thermomechanical modeling of residual strains and stresses in a GTAW process
Tekriwal, P.; Mazumder, J.
1995-12-31
A three-dimensional thermomechanical model was developed and the transient analysis was carried out for the autogenous Gas Tungsten Arc Welding (GTAW) process using the finite element method. Because the heat generated due to the plastic deformation in the welding process is negligible in comparison with the heat from the arc, the thermomechanical analysis is carried out in two parts. The first part performs a three-dimensional uncoupled transient heat transfer analysis and computes the thermal history of the entire weldment. The second part then uses the results of the first part and performs a three-dimensional transient thermoelasto-plastic analysis in order to compute the distortions, strains and stresses in the weld. Mild steel looses its strength almost completely in the molten state and therefore, a cut-off temperature of melting point (1,755 K) is used for the computation of transient and residual strains and stresses.
The effect of residual stress on photoluminescence in multi-crystalline silicon wafers
NASA Astrophysics Data System (ADS)
Pogue, Vanessa; Melkote, Shreyes N.; Rounsaville, Brian; Danyluk, Steven
2017-02-01
This paper presents the results of an experiment designed to understand the effect of manufacturing-induced residual stress on photoluminescence (PL) in multi-crystalline silicon (mc-Si) wafers used for photovoltaic applications. The experiment relies on the use of near-infrared birefringence polariscopy and polarized micro-Raman spectroscopy to measure casting-induced residual stress present in mc-Si wafers. High temperature annealing was used to relieve the residual stress in the mc-Si wafers, and photoluminescence was used to evaluate the electrical performance to provide a correlation of residual stress to electrical activity. High temperature annealing produced a drastic improvement in photoluminescence. A decrease in the number of points of highest maximum shear stress correlated with an increase in photoluminescence. Additionally, a direct correlation was found between higher tensile residual stress and increased PL.
Wang, Jia-Siang; Hsieh, Chih-Chun; Lai, Hsuan-Han; Kuo, Che-Wei; Wu, Paxon Ti-Yuan; Wu, Weite
2015-01-15
A systematic study of residual stress relaxation and the texture evolution of cold-rolled AZ31 Mg alloys using the vibratory stress relief technique with a simple cantilever beam vibration system was performed using a high-resolution X-ray diffractometer and a portable X-ray residual stress analyzer. The effects of vibrational stress excitation on the surface residual stress distribution and on the texture of pole figures (0002) occurring during the vibratory stress relief were examined. Compared with the effects corresponding to the same alloy under non-vibration condition, it can be observed that the uniform surface residual stress distribution and relaxation of the compressive residual stress in the stress concentration zone were observed rather than all of the residual stresses being eliminated. Furthermore, with an increase in the vibrational aging time, the compressive residual stress, texture density, and (0002) preferred orientation increased first and then decreased. It should be underlined that the vibratory stress relief process for the vibrational aging time of more than 10 min is able to weaken the strong basal textures of AZ31 Mg alloys, which is valuable for enhancement of their formability and is responsible for an almost perfect 3D-Debye–Scherrer ring. - Highlights: • 3D-Debye ring about VSR technique is not discussed in the existing literature. • A newly developed VSR method is suitable for small or thin workpieces. • The cosα method accurately and effectively determines the residual stresses. • The VSR technique is valuable for enhancement of their formability. • The texture and preferred orientation change with the vibrational aging time.
Measuring residual stress in ceramic zirconia-porcelain dental crowns by nanoindentation.
Zhang, Y; Allahkarami, M; Hanan, J C
2012-02-01
Residual stress plays a critical role in failure of ceramic dental crowns. The magnitude and distribution of residual stress in the crown system are largely unknown. Determining the residual stress quantitatively is challenging since the crown has such complex contours and shapes. This work explored the feasibility and validity of measuring residual stress of zirconia and porcelain in ceramic crowns by nanoindentation. Nanoindentation tests were performed on the cross-section of a crown for both porcelain and zirconia along four critical locations: the thickest, thinnest and medium porcelain thicknesses. Zirconia and porcelain pieces, chipped off from the crown and annealed at 400 °C, were used as reference samples. The residual stress was determined by comparing the measured hardness of the stressed sample with that of the reference sample. Nanoindentation impression images were acquired through a scanning probe microscope (SPM) equipped with a Hysitron Triboindenter. Zirconia showed large pile-up. Residual stress is determined along the thickness of crowns at the chosen locations for both porcelain and zirconia. The measured results were compared with the results from X-ray diffraction (XRD) and finite element modeling (FEM). Results show there are large amounts of residual stresses in the dental crown and their magnitude differs between locations due to the complex shape of the crown. The average residual stress readings were as high as -637 MPa and 323 MPa for zirconia and porcelain respectively.
Finite Element Modelling and Residual Stress Prediction in End Milling of Ti6Al4Valloy
NASA Astrophysics Data System (ADS)
Krishnakumar, P.; Sripathi, J.; Vijay, P.; Ramachandran, K. I.
2016-09-01
Titanium and its alloys are materials that exhibit unique combination of mechanical and physical properties that enable their usage in various fields. In spite of having a lot of advantages, their usage is limited because they are difficult to machine due to their inherent properties of high specific heat capacity, reactivity with tool and low thermal conductivity thereby causing excessive tool wear. To facilitate the process of machining, it becomes necessary to find out and relieve the residual stress caused during machining. Since experiments cannot be performed for each instance, creation of an FE model is desirable. In this paper a finite element analysis (FEA) of the machining of Ti6Al4V for different cutting speeds is presented. A 3D finite element model is developed with the Titanium alloy (Ti6Al4V) as the workpiece and a four flute carbide tip end mill cutter as the tool to predict the residual stress developed within the titanium alloy after machining. The finite element model utilises the Johnson-Cook model to depict the plasticity and the damage criteria and implements the Arbitrary Lagrangian Eulerian (ALE) formulation to increase the accuracy of the model. The FE model has been developed and the findings are presented. The results indicate that residual stresses are maximum at the surface and decrease linearly along the depth and increase as the cutting speed and depth of cut are increased.
NASA Technical Reports Server (NTRS)
Pindera, Marek-Jerzy; Salzar, Robert S.
1996-01-01
The objective of this work was the development of efficient, user-friendly computer codes for optimizing fabrication-induced residual stresses in metal matrix composites through the use of homogeneous and heterogeneous interfacial layer architectures and processing parameter variation. To satisfy this objective, three major computer codes have been developed and delivered to the NASA-Lewis Research Center, namely MCCM, OPTCOMP, and OPTCOMP2. MCCM is a general research-oriented code for investigating the effects of microstructural details, such as layered morphology of SCS-6 SiC fibers and multiple homogeneous interfacial layers, on the inelastic response of unidirectional metal matrix composites under axisymmetric thermomechanical loading. OPTCOMP and OPTCOMP2 combine the major analysis module resident in MCCM with a commercially-available optimization algorithm and are driven by user-friendly interfaces which facilitate input data construction and program execution. OPTCOMP enables the user to identify those dimensions, geometric arrangements and thermoelastoplastic properties of homogeneous interfacial layers that minimize thermal residual stresses for the specified set of constraints. OPTCOMP2 provides additional flexibility in the residual stress optimization through variation of the processing parameters (time, temperature, external pressure and axial load) as well as the microstructure of the interfacial region which is treated as a heterogeneous two-phase composite. Overviews of the capabilities of these codes are provided together with a summary of results that addresses the effects of various microstructural details of the fiber, interfacial layers and matrix region on the optimization of fabrication-induced residual stresses in metal matrix composites.
NASA Astrophysics Data System (ADS)
Salvati, Enrico; Zhang, Hongjia; Fong, Kai Soon; Song, Xu; Korsunsky, Alexander M.
2017-01-01
The introduction of an overload or underload within a constant amplitude loading fatigue test leads to a retardation or acceleration of the Fatigue Crack Growth Rate (FCGR). The understanding of the causes of these effects is essential in the context of variable amplitude fatigue loading, since in principle any loading history can be represented as a sequence of overloads and underloads. In the case of overload, along with some other minor causes, the residual stress changes at the crack tip and crack closure behind the tip can be thought of as the main factors that affect the fatigue crack growth rate. Whilst this has been recognised and accepted for many decades, controversy persists regarding the relative significance and presence of these two effects, and consensus is yet to emerge. The effect of crack closure, when the baseline loading ratio is high enough, can be inhibited so that the main cause of retardation becomes doubtless the residual stress present ahead the crack tip. In the present paper we report our attempt to deconvolve the contributions of crack closure and residual stress on crack retardation following an overload. To accomplish this task we analyse the results of fatigue tests run at two baseline load ratios, namely R=0.1 and R=0.7. At the load ratio of R=0.7 the crack closure effect is not operative, as confirmed by Digital Image Correlation analysis of the crack flanks close to the tip, and post mortem fractographic analysis of crack surfaces. Therefore, for R=0.7 the compressive residual stress region created by the overload ahead of the crack tip is the sole mechanism causing crack retardation. Therefore, for R=0.7 the focus must be placed entirely on the strain field around the crack tip. To this end, line profiles along the crack bisector of elastic strain in the crack opening direction were collected at several stages of crack propagation past the overload using in situ Synchrotron X-ray Powder Diffraction (SXRPD) technique. By
Stress Analysis of Composites.
1981-01-01
8217, Finite Elements in Nonlinear Mechanics, 1., 109-130, Tapir Publishers, Norway (1978). 9. A.J. Barnard and P.W. Sharman, ’Elastic-Plastic Analysis Using...Hybrid Stress Finite Elements,’ Finite Elements in Nonlinear Mechanics, 1, 131-148, Tapir Publishers Norway, (1978). ’.........Pian, ’Variational
Thermal residual stresses in silicon-carbide/titanium (0/90) laminate
NASA Technical Reports Server (NTRS)
Bigelow, C. A.
1992-01-01
The current work formulated a micromechanical analysis of a cross-ply laminate and calculated the thermal residual stress in a very thick (0/90)(sub 2n) silicon-carbide/titanium laminate. Results were also shown for a unidirectional laminate of the same material. Discrete fiber-matrix models assuming a rectangular array of fibers with a fiber volume fraction of 32.5 percent and a three-dimensional, finite-element analysis were used. Significant differences in the trends and magnitudes for the fiber, matrix, and interface stresses were calculated for unidirectional and (0/90) models. Larger hoop stresses calculated for the (0/90) model indicate that it may be more susceptible to radial cracking when subjected to mechanical loading than the unidirectional model. The axial stresses in the matrix were calculated to be slightly larger for the (0/90) model. The compressive axial stresses in the fiber were significantly larger in the (0/90) model. The presence of the cross-ply in the (0/90) model reduced the constraint on the fiber, producing radial interface stresses that were less compressive, which could lead to earlier failure of the fiber-matrix interface.
NASA Technical Reports Server (NTRS)
Namkung, Min (Inventor); Yost, William T. (Inventor); Kushnick, Peter W. (Inventor); Grainger, John L. (Inventor)
1992-01-01
The invention is a method and apparatus for characterizing residual uniaxial stress in a ferromagnetic test member by distinguishing between residual stresses resulting from positive (tension) forces and negative (compression) forces by using the distinct and known magnetoacoustic (MAC) and a magnetoacoustic emission (MAE) measurement circuit means. A switch permits the selective operation of the respective circuit means.
Younger, Mandy S.; Eckelmeyer, Kenneth Hall
2007-11-01
Distortion frequently occurs during machining of age hardening aluminum alloys due to residual stresses introduced during the quenching step in the heat treatment process. This report quantifies, compares, and discusses the effectiveness of several methods for minimizing residual stresses and machining distortion in aluminum alloys 7075 and 6061.
Comparison of Residual Stress Distributions of Similar and Dissimilar Thick Butt-Weld Plates
NASA Astrophysics Data System (ADS)
Suzuki, Hiroshi; Katsuyama, Jinya; Morii, Yukio
Residual stress distributions of 35 mm thick dissimilar metal butt-weld between A533B ferritic steel and Type 304 austenitic stainless steel (304SS) with Ni alloy welds and similar metal butt-weld of 304SS were measured using neutron diffraction. Effects of differences in thermal expansion coefficients (CTEs) and material strengths on the weld residual stress distributions were discussed by comparison of the residual stress distributions between the similar and dissimilar metal butt-welds. Residual stresses in the similar metal butt-weld exhibited typical distributions found in a thick butt-weld and they were distributed symmetrically on either side of the weld line. Meanwhile, asymmetric residual stress distributions were observed near the root of the dissimilar metal butt-weld, which was caused by differences in CTEs and yield strengths among both parent materials and weld metals. Transverse residual stress distribution of the dissimilar metal butt-weld was similar trend to that of the similar metal butt-weld, since effect of difference in CTEs were negligible, while magnitude of the transverse residual stress near the root depended on the yield strengths of each metal. In contrast, the normal and longitudinal residual stresses in the dissimilar metal butt-weld distributed asymmetrically on either side of weld line due to influence of differences in CTEs.
Evaluating the influence of residual stresses on the magnetic properties of electrical steel
Korzunin, G.S.; Chistyakov, V.K.
1995-04-01
The method described for evaluating the influence of residual stresses on the magnetic properties of coiled cold-rolled electrical steel consists in measuring the ratio of the magnetic characteristics that are and are not sensitive to the effect of residual stresses. The evaluation is made from the value of the ratio, using the correlations between its value and the magnetic characteristics studied.
Validation Specimen for Contour Method Extension to Multiple Residual Stress Components
Pagliaro, Pierluigi; Prime, Michael B; Zuccarello, B; Clausen, Bjorn; Watkins, Thomas R
2007-01-01
A new theoretical development of the contour method, that allow the user to measure the three normal residual stress components on cross sections of a generic mechanical part, is presented. To validate such a theoretical development, a residual stress test specimen was properly designed, fabricated and then tested with different experimental techniques.
Prediction and Optimization of Residual Stresses on Machined Surface and Sub-Surface in MQL Turning
NASA Astrophysics Data System (ADS)
Ji, Xia; Zou, Pan; Li, Beizhi; Rajora, Manik; Shao, Yamin; Liang, Steven Y.
Residual stress in the machined surface and subsurface is affected by materials, machining conditions, and tool geometry and can affect the component life and service quality significantly. Empirical or numerical experiments are commonly used for determining residual stresses but these are very expensive. There has been an increase in the utilization of minimum quantity lubrication (MQL) in recent years in order to reduce the cost and tool/part handling efforts, while its effect on machined part residual stress, although important, has not been explored. This paper presents a hybrid neural network that is trained using Simulated Annealing (SA) and Levenberg-Marquardt Algorithm (LM) in order to predict the values of residual stresses in cutting and radial direction on the surface and within the work piece after the MQL face turning process. Once the ANN has successfully been trained, an optimization procedure, using Genetic Algorithm (GA), is applied in order to find the best cutting conditions in order to minimize the surface tensile residual stresses and maximize the compressive residual stresses within the work piece. The optimization results show that the usage of MQL decreases the surface tensile residual stresses and increases the compressive residual stresses within the work piece.
Residual stress measurement in a metal microdevice by micro Raman spectroscopy
NASA Astrophysics Data System (ADS)
Song, Chang; Du, Liqun; Qi, Leijie; Li, Yu; Li, Xiaojun; Li, Yuanqi
2017-10-01
Large residual stress induced during the electroforming process cannot be ignored to fabricate reliable metal microdevices. Accurate measurement is the basis for studying the residual stress. Influenced by the topological feature size of micron scale in the metal microdevice, residual stress in it can hardly be measured by common methods. In this manuscript, a methodology is proposed to measure the residual stress in the metal microdevice using micro Raman spectroscopy (MRS). To estimate the residual stress in metal materials, micron sized β-SiC particles were mixed in the electroforming solution for codeposition. First, the calculated expression relating the Raman shifts to the induced biaxial stress for β-SiC was derived based on the theory of phonon deformation potentials and Hooke’s law. Corresponding micro electroforming experiments were performed and the residual stress in Ni–SiC composite layer was both measured by x-ray diffraction (XRD) and MRS methods. Then, the validity of the MRS measurements was verified by comparing with the residual stress measured by XRD method. The reliability of the MRS method was further validated by the statistical student’s t-test. The MRS measurements were found to have no systematic error in comparison with the XRD measurements, which confirm that the residual stresses measured by the MRS method are reliable. Besides that, the MRS method, by which the residual stress in a micro inertial switch was measured, has been confirmed to be a convincing experiment tool for estimating the residual stress in metal microdevice with micron order topological feature size.
Investigation on Residual Stress Induced by Shot Peening
NASA Astrophysics Data System (ADS)
Zhao, Chunmei; Gao, Yukui; Guo, Jing; Wang, Qiang; Fu, Lichao; Yang, Qingxiang
2015-03-01
The high strength steel widely used in the aviation industry was chosen in this paper. The shot peening (SP) tests with different technical parameters were carried out, and compressive residual stress (CRS) distribution along the depth was determined. The phase structures before and after SP were analyzed by XRD and TEM. Microhardness and fatigue life were measured, and the morphology of fatigue fracture was also observed. The effects of different technical parameters on CRS field were investigated, and the CRS features with the characteristic parameters were analyzed deeply to summarize the rules. The results show that the CRS field induced by SP can be expressed by four characteristic parameters: the surface CRS σsrs, the maximum CRS σmrs, the depth of maximum CRS ξm and the depth of CRS (strengthened depth) ξ0. Martensite matrix is not changed by SP, while its boundary changes ambiguous with the formation of dislocations. After SP, the microhardness of the specimen increase, and the fatigue crack source moves inwards. The SP saturated time is 1 min. With the increase of SP intensity, σsrs, σmrs, ξm, and ξ0 all increase. While with the increase of SP angle, ξ0 grows gradually. The strengthen effect behaves more obviously as the shot size increases, and the shot material with larger hardness cause higher level of CRS field. Dual SP mainly increases σsrs value.
Residual strain change resulting from stress corrosion in Carrara marble
NASA Astrophysics Data System (ADS)
Voigtlaender, Anne; Leith, Kerry; Krautblatter, Michael
2016-04-01
Residual stresses and strains have been shown to play a fundamental role in determining the elastic behavior of engineering materials, yet the effect of these strains on brittle and elastic behavior of rocks remains unclear. In order to evaluate the impact of stored elastic strains on fracture propagation in rock, we undertook a four-month-long three-point bending test on three large 1100 x 100 x 100 mm Carrara Marble samples. This test induced stable low stress conditions in which strains were concentrated at the tip of a saw cut and pre-cracked notch. A corrosive environment was created at the tip of the notch on two samples (M2 and M4) by dripping calcite saturated water (pH ~ 7.5-8). Sample M5 was loaded in the same way, but kept dry. Samples were unloaded prior to failure, and along with an additional non-loaded reference sample (M0), cored into cylindrical subsamples (ø = 50 mm, h = 100 mm) before being tested for changes in residual elastic strains at the SALSA neutron diffractometer at the Institute Laue-Langevin (ILL), Grenoble, France. Three diffraction peaks corresponding to crystallographic planes hkl (110), (104) and (006) were measured in all three spatial directions relative to the notch. Shifts in the diffraction peak position (d) with respect to a strain free state are indicative of intergranular strain, while changes in the width of the peak (FWHM) reflect changes in intragranular strain. We observe distinctly different patterns in residual and volumetric strains in hkℓ (104) and (006) for the dry M5 and wet tested samples (M2 and M4) indicating the presence of water changes the deformation mechanism, while (110) is strained in compression around 200 μstrain in all samples. A broadening of the diffraction peaks (006) and (110) in front of the crack tip is observed in M2 and M4, while M5 shows no changes in the peak width throughout the depth of the sample. We suggest water present at the crack tip increased the rate of corrosion, allowing a
Rangaswamy, P.; Bourke, M.A.M.; Shipley, J.C.; Goldstone, J.A.
1995-09-01
A combined experimental and numerical study of residual stress and microstructure has been performed for a carburized steel 5120 specimen. Specimens were cut from 5120 steel bar stock, in the shape of hockey pucks and were subsequently carburized and quenched. X-ray diffraction was used to record stress profiles through the case for the martensite and retained austenite on the two flat surfaces oriented up and down during the quench. Layer removal was performed by electropolishing. Rietveld analysis was used to determine the lattice parameters of the phases at each depth varying with both carbon content and stress. The experimental measurements are compared with a numerical simulation of the phase transformation and the metallurgical changes following the carburization and quench. Results am discussed in the context of the microstructure and the role played by the retained austenite in interpretation. In addition the carbon profile obtained from the lattice parameters is compared with profiles measured using burnout.
Holzapfel, Gerhard A; Ogden, Ray W
2010-05-06
This paper provides the first analysis of the three-dimensional state of residual stress and stretch in an artery wall consisting of three layers (intima, media and adventitia), modelled as a circular cylindrical tube. The analysis is based on experimental results on human aortas with non-atherosclerotic intimal thickening documented in a recent paper by Holzapfel et al. (Holzapfel et al. 2007 Ann. Biomed. Eng. 35, 530-545 (doi:10.1007/s10439-006-9252-z)). The intima is included in the analysis because it has significant thickness and load-bearing capacity, unlike in a young, healthy human aorta. The mathematical model takes account of bending and stretching in both the circumferential and axial directions in each layer of the wall. Previous analysis of residual stress was essentially based on a simple application of the opening-angle method, which cannot accommodate the three-dimensional residual stretch and stress states observed in experiments. The geometry and nonlinear kinematics of the intima, media and adventitia are derived and the associated stress components determined explicitly using the nonlinear theory of elasticity. The theoretical results are then combined with the mean numerical values of the geometrical parameters and material constants from the experiments to illustrate the three-dimensional distributions of the stretches and stresses throughout the wall. The results highlight the compressive nature of the circumferential stress in the intima, which may be associated with buckling of the intima and its delamination from the media, and show that the qualitative features of the stretch and stress distributions in the media and adventitia are unaffected by the presence or absence of the intima. The circumferential residual stress in the intima increases significantly as the associated residual deformation in the intima increases while the corresponding stress in the media (which is compressive at its inner boundary and tensile at its outer boundary
Holzapfel, Gerhard A.; Ogden, Ray W.
2010-01-01
This paper provides the first analysis of the three-dimensional state of residual stress and stretch in an artery wall consisting of three layers (intima, media and adventitia), modelled as a circular cylindrical tube. The analysis is based on experimental results on human aortas with non-atherosclerotic intimal thickening documented in a recent paper by Holzapfel et al. ( Holzapfel et al. 2007 Ann. Biomed. Eng. 35, 530–545 (doi:10.1007/s10439-006-9252-z)). The intima is included in the analysis because it has significant thickness and load-bearing capacity, unlike in a young, healthy human aorta. The mathematical model takes account of bending and stretching in both the circumferential and axial directions in each layer of the wall. Previous analysis of residual stress was essentially based on a simple application of the opening-angle method, which cannot accommodate the three-dimensional residual stretch and stress states observed in experiments. The geometry and nonlinear kinematics of the intima, media and adventitia are derived and the associated stress components determined explicitly using the nonlinear theory of elasticity. The theoretical results are then combined with the mean numerical values of the geometrical parameters and material constants from the experiments to illustrate the three-dimensional distributions of the stretches and stresses throughout the wall. The results highlight the compressive nature of the circumferential stress in the intima, which may be associated with buckling of the intima and its delamination from the media, and show that the qualitative features of the stretch and stress distributions in the media and adventitia are unaffected by the presence or absence of the intima. The circumferential residual stress in the intima increases significantly as the associated residual deformation in the intima increases while the corresponding stress in the media (which is compressive at its inner boundary and tensile at its outer
Compressive residual stress relaxation in hardened steel during cyclic and static load
NASA Astrophysics Data System (ADS)
Cseh, D.; Mertinger, V.
2017-05-01
The benefits of applied compressive residual stress on fatigue properties of materials is a well-known phenomenon, but not well described in all respects. The fatigue life and the fatigue limit could be improved by targeted created compressive residual stress in the surface layers therefore, diversified surface compressing methods are developed and used in the engineering industry. The relaxation of the compressive residual stress state during a cyclic and static load is determinative for the life time of a componenet. Compressive stress relaxation was experimentally determined during the cyclic and static load. The compressive residual stress was induced by shot penning on the surface of stainless steel, micro alloyed high strength steel and hardened steel specimens. The residual stress state was investigated nondestructively by X-ray diffraction method then these specimens were load. After a certain number of cycles the fatigue load was stopped and the residual stress state was recorded again and again until fracture. To investigate the relaxation process during static load a four-point bending bench was used. The compressive residual stress relaxation was correlated to the applied fatigue stress level, the cycle number the quality of alloys.
The Crack-contact and the Free End Problem for a Strip Under Residual Stress
NASA Technical Reports Server (NTRS)
Bakioglu, M.; Erdogan, F.
1976-01-01
The plane problem for an infinite strip with two edge cracks under a given state of residual stress is considered. The residual stress is compressive near and at the surfaces and tensile in the interior of the strip. If the crack is deep enough to penetrate into the tensile zone, then the problem is one of crack-contact problem in which the depth of the contact area is an unknown which depends on the crack depth and the residual stress profile. The problem has applications to the static fatigue of glass plates and is solved for three typical residual stress profiles. In the limiting case of the crack crossing the entire plate thickness, the problem becomes a stress-free end problem for a semi-infinite strip under a given residual stress state away from the end. This is a typical stress diffusion problem in which decay behavior of the residual stress near and the nature of the normal displacement at the end of the semi-infinite strip are of special interest. For two typical residual stress states the solution is obtained, and some numerical results are given.
Thermal evolution of residual stress in IN718 alloy subjected to laser peening
NASA Astrophysics Data System (ADS)
Xu, Suqiang; Huang, Shu; Meng, Xiankai; Sheng, Jie; Zhang, Haifeng; Zhou, Jianzhong
2017-07-01
The thermal relaxation behaviors of residual stresses induced by laser peening (LP) in IN718 alloy were investigated using an integrated numerical simulation and experimental approach. LP and heat treatments (HT) were carried out after which the X-ray diffraction (XRD) technique was employed in measuring the residual stresses. Micro-structures were observed using an optic microscope (OM) and transmission electron microscope (TEM). Dislocations induced by LP were also observed by TEM and characterized using the XRD technique. The effects of the applied temperature and the exposure time on residual stress and micro-structures were investigated. The results show that the extent of the residual stresses relaxation increased accordingly with the increase in the applied temperature. The relaxation rate was initially high and tended to stabilize for a longer exposure time. Grain size evolution during the process was subsequently discussed. Furthermore, a conceivable mechanism of residual stresses thermal relaxation behavior was obtained.
Effect of residual stress on modal patterns of MEMS vibratory gyroscope
Dutta, Shankar Panchal, Abha; Kumar, Manoj; Pal, Ramjay; Bhan, R. K.
2016-04-13
Deep boron diffusion often induces residual stress in bulk micromachined MEMS structures, which may affect the MEMS devices operation. In this study, we studied the modal patterns of MEMS vibratory gyroscope under the residual stress (100 – 1000 MPa). Modal patterns and modal frequencies of the gyro are found to be dependent on the residual stress values. Without any residual stress, the modal frequencies drive and sense modeswere found to be 20.06 kHz and 20.36 kHz respectively. In presence of 450 MPa residual stress, the modal frequencies of the drive and sense modes were changed to 42.75 kHz and 43.07 kHz respectively.
Effect of residual stress on modal patterns of MEMS vibratory gyroscope
NASA Astrophysics Data System (ADS)
Dutta, Shankar; Panchal, Abha; Kumar, Manoj; Pal, Ramjay; Bhan, R. K.
2016-04-01
Deep boron diffusion often induces residual stress in bulk micromachined MEMS structures, which may affect the MEMS devices operation. In this study, we studied the modal patterns of MEMS vibratory gyroscope under the residual stress (100 - 1000 MPa). Modal patterns and modal frequencies of the gyro are found to be dependent on the residual stress values. Without any residual stress, the modal frequencies drive and sense modeswere found to be 20.06 kHz and 20.36 kHz respectively. In presence of 450 MPa residual stress, the modal frequencies of the drive and sense modes were changed to 42.75 kHz and 43.07 kHz respectively.
NASA Astrophysics Data System (ADS)
Cucatti, S.; Droppa, R.; Figueroa, C. A.; Klaus, M.; Genzel, Ch.; Alvarez, F.
2016-10-01
The effect of low energy (<1 keV) xenon (Xe+) ion bombardment on the residual stress of polycrystalline iron alloy (AISI 316L steel) is reported. The results take into account the influence of the ion incident angle maintaining constant all other bombarding parameters (i.e., ion energy and current density, temperature, and doses). The bombarded surface topography shows that ions prompt the formation of nanometric regular patterns on the surface crystalline grains and stressing the structure. The paper focalizes on the study of the surface residual stress state stemming from the ion bombardment studied by means of the "sin2 ψ" and "Universal Plot" methods. The analysis shows the absence of shear stress in the affected material region and the presence of compressive in-plane residual biaxial stress (˜200 MPa) expanding up to ˜1 μm depth for all the studied samples. Samples under oblique bombardment present higher compressive stress values in the direction of the projected ion beam on the bombarded surface. The absolute value of the biaxial surface stress difference (σ11-σ22) increases on ion impinging angles, a phenomenon associated with the momentum transfer by the ions. The highest stress level was measured for ion impinging angles of 45° ( σ 11 = -380 ± 10 MPa and σ 22 = -320 ± 10 MPa). The different stresses obtained in the studied samples do not affect significantly the formation of characteristic surface patterns.
Hempel, Nico; Bunn, Jeffrey R.; Nitschke-Pagel, Thomas; ...
2017-02-02
This research is dedicated to the experimental investigation of the residual stress relaxation in girth-welded pipes due to quasi-static bending loads. Ferritic-pearlitic steel pipes are welded with two passes, resulting in a characteristic residual stress state with high tensile residual stresses at the weld root. Also, four-point bending is applied to generate axial load stress causing changes in the residual stress state. These are determined both on the outer and inner surfaces of the pipes, as well as in the pipe wall, using X-ray and neutron diffraction. Focusing on the effect of tensile load stress, it is revealed that notmore » only the tensile residual stresses are reduced due to exceeding the yield stress, but also the compressive residual stresses for equilibrium reasons. Furthermore, residual stress relaxation occurs both parallel and perpendicular to the applied load stress.« less
Relation Between Residual and Hoop Stresses and Rolling Bearing Fatigue Life
NASA Technical Reports Server (NTRS)
Oswald, Fred B.; Zaretsky, Erwin V.; Poplawski, Joseph V.
2015-01-01
Rolling-element bearings operated at high speed or high vibration may require a tight interference fit between the bore of the bearing and shaft to prevent rotation of the bearing bore around the shaft and fretting damage at the interfaces. Previous work showed that the hoop stresses resulting from tight interference fits can reduce bearing lives by as much as 65 percent. Where tight interference fits are required, case-carburized steel such as AISI 9310 or M50 NiL is often used because the compressive residual stresses inhibit subsurface crack formation and the ductile core inhibits inner-ring fracture. The presence of compressive residual stress and its combination with hoop stress also modifies the Hertz stress-life relation. This paper analyzes the beneficial effect of residual stresses on rolling-element bearing fatigue life in the presence of high hoop stresses for three bearing steels. These additional stresses were superimposed on Hertzian principal stresses to calculate the inner-race maximum shearing stress and the resulting fatigue life of the bearing. The load-life exponent p and Hertz stress-life exponent n increase in the presence of compressive residual stress, which yields increased life, particularly at lower stress levels. The Zaretsky life equation is described and is shown to predict longer bearing lives and greater load- and stress-life exponents, which better predicts observed life of bearings made from vacuum-processed steel.
Transient and residual stresses in dental porcelains as affected by cooling rates.
Asaoka, K; Tesk, J A
1989-06-01
The development of either transient or residual stress in a slab of dental porcelain during cooling was simulated by use of a super-computer. The temperature dependences of the elastic modulus, the thermal expansion coefficient, and the shear viscosity, and the cooling rate dependence of the glass transition temperature, Tg, were considered in this calculation. Internal stress and viscoelastic creep were computed for several cooling rates. Calculated results display stress profiles which agree reasonably well with reported measured profiles in quenched, tempered glasses. The calculated residual surface stress, sigma, could be fit by the following empirical formula, sigma = kl2(q/q0)n, q is the cooling rate, q0 is a reference cooling rate and l is the half-thickness of the porcelain. The method by which residual stress develops is also discussed. This discussion suggests a method for strengthening of the porcelain by the development of high-compressive residual stress on the surface.
Residual stress determination of rail tread using a laser ultrasonic technique
NASA Astrophysics Data System (ADS)
Wang, Jing; Feng, Qibo
2015-05-01
A non-destructive method for measuring the residual stress on rail tread that uses a laser-generated ultrasonic technique is proposed. The residual stress distribution of different parts on both the new rail and used rail were examined. The surface acoustic waves (SAWs) are excited by a scanning line laser and detected by a laser ultrasonic detection system. A digital correlation method was used for calculating the changes in velocity of SAWs, which reflects the stress distribution. A wavelet de-noising technique and a least square fit were used for signal processing to improve the measurement accuracy. The effects of ultrasonic propagation distance and surface roughness on the determination of residual stress were analyzed and simulated. Results from the study demonstrate that the stress distribution results are accordant with the practical situation, and the laser-generated SAWs technique is a promising tool for the determination of residual stress in the railway inspection and other industrial testing fields.
Effects of residual stress and texture on the high-cycle fatigue properties of light metals
NASA Astrophysics Data System (ADS)
Jiang, Xiuping
2007-12-01
High cycle fatigue tests were conducted on a commercially pure Ti, a forged Ti-6Al-4V alloy, and newly developed high strength AA2026 and AA2099 Al alloys in four-point bend. The effects of surface compressive residual stress and texture on the fatigue properties of these alloys were systematically investigated. The resistance to fatigue crack growth in an alloy was estimated using a simple model that took into account texture and grain structure. The resistance calculations were able to explain the observed behaviors of fatigue crack growth in planar slip materials. Due to strengthening in the surface by enhancement treatment, fatigue cracks were found to be initiated in the subsurface region in the short peened Ti-6Al-4V alloy and sandblasted CP Ti, in contrast to crack initiation on the surface of the untreated samples. When the shot peened Ti-6A1-4V alloy was tested between 25°C and 200°C, the surface compressive residual stress could only be slightly relaxed due to thermal exposure, which did not deteriorate the fatigue strength of the alloy. Similarly, no obvious redistribution of the residual stress was observed when the sandblasted Ti was annealed below 200°C. With increase in the annealing temperature (300°C˜700°C), the compressive residual stresses were significantly relaxed, leading to relatively a lower fatigue strength. In AA2026 & AA2099 Al alloys, crack growth was found to be in a predominantly crystallographic mode in unrecrystallized regions, and a non-crystallographic mode in recrystallized regions. Fatigue cracks were deflected at grain boundaries usually with small twist angles in the unrecrystallized regions, but with large twist angles in the recrystallized regions. The theoretical analysis verified that a large percentage of recrystallized grains could provide strong resistance to fatigue crack growth by producing larger twist angles of crack deflection at their grain boundaries than those of most of the gains in unrecrystallized
Residual Stress Effect on the Delayed Fracture of Twinning-Induced Plasticity Steels
NASA Astrophysics Data System (ADS)
Kim, Jung Gi; Yoon, Jae Ik; Baek, Seung Mi; Seo, Min Hong; Cho, Won Tae; Chin, Kwang-Geun; Lee, Sunghak; Kim, Hyoung Seop
2017-03-01
Residual stress effect of the deep drawn TWIP steel on delayed fracture was investigated. Microstructural features of the TWIP steels did not change after stress relief annealing, while the elastic lattice strain dropped to 0.0007. Delayed fracture of the drawn TWIP steel occurred after 203 hours of HCl immersion testing, but did not occur in the annealed one. It is clear that residual stress after the drawing is the primary reason for the delayed fracture of TWIP steels.
Residual Stress Effect on the Delayed Fracture of Twinning-Induced Plasticity Steels
NASA Astrophysics Data System (ADS)
Kim, Jung Gi; Yoon, Jae Ik; Baek, Seung Mi; Seo, Min Hong; Cho, Won Tae; Chin, Kwang-Geun; Lee, Sunghak; Kim, Hyoung Seop
2017-06-01
Residual stress effect of the deep drawn TWIP steel on delayed fracture was investigated. Microstructural features of the TWIP steels did not change after stress relief annealing, while the elastic lattice strain dropped to 0.0007. Delayed fracture of the drawn TWIP steel occurred after 203 hours of HCl immersion testing, but did not occur in the annealed one. It is clear that residual stress after the drawing is the primary reason for the delayed fracture of TWIP steels.
NASA Astrophysics Data System (ADS)
Havermann, Dirk; Mathew, Jinesh; MacPherson, William N.; Hand, Duncan P.; Maier, Robert R. J.
2015-09-01
Metal clad single mode optical fibres containing Fibre Bragg Gratings are embedded in stainless steel components using bespoke laser based Selective Laser Melting technology (SLM). Significant residual stresses can be created in SLM manufactured components through the strong thermal gradients during the build process. We demonstrate the ability to monitor these internal stresses through embedded optical fibres with FBGs on a layer to layer basis, confirming estimates from models for residual stresses in additive manufactured components.
NASA Technical Reports Server (NTRS)
Elber, W.
1973-01-01
The fracture strength and cyclic crack-growth properties of surface-flawed, shot-peened D6AC steel plate were investigated. For short crack lengths (up to 1.5mm) simple linear elastic fracture mechanics - based only on applied loading - did not predict the fracture strengths. Also, Paris' Law for cyclic crack growth did not correlate the crack-growth behavior. To investigate the effect of shot-peening, additional fracture and crack-growth tests were performed on material which was precompressed to remove the residual stresses left by the shot-peening. Both tests and analysis show that the shot-peening residual stresses influence the fracture and crack-growth properties of the material. The analytical method of compensating for residual stresses and the fracture and cyclic crack-growth test results and predictions are presented.
Effects of shot-peening residual stresses on the fracture and crack-growth properties of D6AC steel
NASA Technical Reports Server (NTRS)
Elber, W.
1974-01-01
The fracture strength and cyclic crack-growth properties of surface-flawed, shot-peened D6AC steel plate were investigated. For short crack lengths (up to 1.5 mm) simple linear elastic fracture mechanics - based only on applied loading - did not predict the fracture strengths. Also, Paris' Law for cyclic crack growth did not correlate the crack-growth behavior. To investigate the effect of shot-peening, additional fracture and crack-growth tests were performed on material which was precompressed to remove the residual stresses left by the shot-peening. Both tests and analysis show that shot-peening residual stresses influence the fracture and crack-growth properties of the material. This report presents the analytical method of compensating for residual stresses and the fracture and cyclic crack-growth test results and predictions.
NASA Astrophysics Data System (ADS)
Osten, W.; Pedrini, G.; Weidmann, P.; Gadow, R.
2015-08-01
A minimum invasive but high resolution method for residual stress analysis of ceramic coatings made by thermal spraycoating using a pulsed laser for flexible hole drilling is described. The residual stresses are retrieved by applying the measured surface data for a model-based reconstruction procedure. While the 3D deformations and the profile of the machined area are measured with digital holography, the residual stresses are calculated by FE analysis. To improve the sensitivity of the method, a SLM is applied to control the distribution and the shape of the holes. The paper presents the complete measurement and reconstruction procedure and discusses the advantages and challenges of the new technology.
Rideout, C. A.; Ritchie, S. J.; Denison, A.
2007-03-21
Induced Positron Analysis (IPA) has demonstrated the ability to nondestructively quantify shot peening/surface treatments and relaxation effects in single crystal superalloys, steels, titanium and aluminum with a single measurement as part of a National Science Foundation SBIR program and in projects with commercial companies. IPA measurement of surface treatment effects provides a demonstrated ability to quantitatively measure initial treatment effectiveness along with the effect of operationally induced changes over the life of the treated component. Use of IPA to nondestructively quantify surface and subsurface residual stresses in turbine engine materials and components will lead to improvements in current engineering designs and maintenance procedures.
NASA Technical Reports Server (NTRS)
Mitchell, William S.; Throckmorton, David (Technical Monitor)
2002-01-01
The purpose of this research was to further the understanding of a crack initiation problem in a highly strained pressure containment housing. Finite Element Analysis methods were used to model the behavior of shot peened materials undergoing plastic deformation. Analytical results are in agreement with laboratory tensile tests that simulated the actual housing load conditions. These results further validate the original investigation finding that the shot peened residual stress had reversed, changing from compressive to tensile, and demonstrate that analytical finite element methods can be used to predict this behavior.
1989-10-01
model was used to predict dimensionless curvatures. The model underestimates the residual stresses at high temperatures near the onset of crystallization...Crystallization (Thermal-Elastic Model ) ................... 63 Figure 46 Tensile Creep Compliance Master Curve for 33% Crystalline Neat PEEK for Testing...Curvature by Viscoelastic Analysis (VE Model ) as a Function of Cool Down Temperature .......................................... 68 V LIST OF TABLES Page
2015-11-01
induced residual stresses and distortions from weld simulations in the SYSWELD software code in structural Finite Element Analysis ( FEA ) simulations...performed in the Abaqus FEA code is presented. The translation of these results is accomplished using a newly developed Python script. Full details of...Local Weld Model in Structural FEA ....................................................15 CONCLUSIONS
Effect of preheat on residual stress distributions in arc-welded mild steel plates
Adedayo, S.M.; Adeyemi, M.B.
2000-02-01
Residual stress distribution in the longitudinal and transverse directions on a 6-mm-thick arc-welded mild steel plate was experimentally examined with and without initial preheat. Stress measurements were completed by monitoring strain changes on mounted strain gauges resulting from successive milling of the welded plate specimens. Machining stresses were also compensated for by carrying out measurements of strain changes due to milling operation of a stress-free unwelded annealed mild steel plate. High tensile residual stresses exist close to the weld line in both longitudinal and transverse stresses. Maximum longitudinal residual stress values existing close to the weld line are reduced (between 50 and 75%) due to the effect of initial metal preheat of 200 C of the welded steel plate.
The effect of residual stress on performance of high temperature coatings
NASA Technical Reports Server (NTRS)
1972-01-01
Techniques for measurement of residual stress in MoSi2 coatings and the determination of stress in coatings prepared by metalliding, pack and slurry processes are discussed. The stress level can be determined by stress induced deflections or by X-ray techniques. The deflection method is most direct. It is based on the fact that a thin substrate, coated on one side only, is usually curved at room temperature. The radius of curvature is easily measured and readily related to residual stress.
Numerical Simulation of Residual Stress in an Al-Cu Alloy Block During Quenching and Aging
NASA Astrophysics Data System (ADS)
Dong, Ya-Bo; Shao, Wen-Zhu; Lu, Liang-Xing; Jiang, Jian-Tang; Zhen, Liang
2015-12-01
In this study, residual stresses after different quenching and aging processes of Al-Cu forged blocks were investigated by numerical simulation method and experimental measurements. An iterative zone-based heat transfer calculation was coupled with the hyperbolic sine-type constitutive model to simulate the residual stress during quenching process. The simulation results were compared with experiment data using both x-ray diffraction and crack compliance methods. The simulation results were in good agreement with the experimental measurements with around 9-13% deviation at the largest. Residual stress reduction can be achieved by decreasing the cooling rate during quenching. Quenching in water with different temperatures of 60, 80, and 100 °C resulted in the maximum compressive residual stress reduction of approximately 28.2, 75.7, and 88.9%, respectively, in Al-Cu alloy samples. When quenched in 10, 20, and 30% PAG solution, the reduction of maximum compressive residual stress in Al-Cu alloy samples was approximately 35.1, 47.8, and 53.2%, respectively. In addition, in order to study the amount of residual stress relief after aging treatments, aging treatments at 140 and 170 °C for different times were also studied. Aging treatment used to obtain the peak-aged (T6) and overaged (T7) condition produces only about 22.5 to 34.7% reduction in residual stresses.
NASA Astrophysics Data System (ADS)
Skvortsov, V. F.; Arlyapov, A. Yu; Boznak, A. O.; Ogol, I. I.; Kim, A. B.
2017-02-01
Cold expansion of holes in hollow cylinders is accompanied by raise of residual stresses in the bulk of the cylinder, the largest of which are hoop residual stresses. Since hoop residual stresses affect critical performance characteristics, assessment of their nature and magnitude is one of the most significant engineering tasks. The most wide spread mechanical methods to define magnitude of hoop residual stresses are G Sachs and N N Davidenkov methods. The paper presents result of experimental studies by Sachs and Davidenkov methods of hoop residual stresses generated in hollow cylinders made of carbon steel AISI 1050 after cold expansion. It is shown that the shape of curves of hoop residual stresses calculated by the mentioned methods, depending on the hoop residual strain generated on the outer surface of the cylinder, can differ (strain is elastic) or coincide (strain is elastic-plastic). It was established that the absolute values of the stresses defined by the mentioned methods in the area adjacent to the hole differ by an average of 15%, and in the area adjacent to the outer surface differ by an average of 20%.
Residual stresses in high-velocity oxy-fuel metallic coatings
NASA Astrophysics Data System (ADS)
Totemeier, T. C.; Wright, R. N.; Swank, W. D.
2004-06-01
X-ray based residual stress measurements were made on type 316 stainless steel and Fe3Al coatings that were high-velocity oxy-fuel (HVOF) sprayed onto low-carbon and stainless steel substrates. Nominal coating thicknesses varied from 250 to 1500 µm. The effect of HVOF spray particle velocity on residual stress and deposition efficiency was assessed by preparing coatings at three different torch chamber pressures. The effect of substrate thickness on residual stress was determined by spraying coatings onto thick (6.4 mm) and thin (1.4 mm) substrates. Residual stresses were compressive for both coating materials and increased in magnitude with spray velocity. For coatings applied to thick substrates, near-surface residual stresses were essentially constant with increasing coating thickness. Differences in thermal expansion coefficient between low-carbon and stainless steels led to a 180 MPa difference in residual stress for Fe3Al coatings. Deposition efficiency for both materials is maximized at an intermediate (˜600 m/s) velocity. Considerations for X-ray measurement of residual stresses in HVOF coatings are also presented.
NASA Astrophysics Data System (ADS)
Xiao, J.; Prud'homme, N.; Li, N.; Ji, V.
2013-11-01
In order to understand the influence of humidity on high temperature oxidation of Inconel 600 alloy, in this work, water vapour (absolute humidity varying from 0% to 19%) was introduced in the thermal gravimetric analysis (TGA) system under artificial air between 600 °C and 900 °C. The oxides identification and the residual stress in the oxide layers have been studied by X-ray diffraction method in each of two oxide phases, simultaneously. The oxide surface morphology, cross-section microstructure and the chemical composition of the oxide layers were determined by FEG-SEM (Field Emission Gun Scanning Electron Microscope) observation and FEG-SEM EDS (Energy-dispersive X-ray spectroscopy) analysis. Depending on the oxidation temperature, the humidity and the oxidation duration, the oxide layer differed significantly. The residual stress levels in the different oxide layers (NiO-type layer and Cr2O3-type layer) have also been affected by the introduction of the water vapour. According to the analysis results, the residual stresses on oxide mainly came from the growth stress and thermomechanical stress; and the oxide growth stress was especially affected by humidity at high temperature.
NASA Astrophysics Data System (ADS)
Park, Jong-Sung; Kim, Sujin; Shin, Hyunho; Jung, Hyun Suk; Hong, Kug Sun
2005-05-01
The residual thermal stress in multilayer ceramic capacitors (MLCCs) with varying number of layers was analyzed using finite element analysis, in order to find the links among the dielectric constant, the number of layers, and the stress state. In the active region of the MLCC, the in-plane stresses in a ceramic layer, σ11 and σ22, were compressive while the out-of-plane stress, σ33, was mostly tensile. Changes in the dielectric constant were related to the reinforcement of the compressive in-plane stress components for small numbers of layers, while out-of-plane tensile stress was attributed to the increased dielectric constant when the number of layers was large. In the intermediate regime, in-plane stress components and out-of-plane components both affected the dielectric constant.
Toribio, Jesús; Aguado, Leticia; Lorenzo, Miguel; Kharin, Viktor
2017-01-01
Stress corrosion cracking (SCC) of metals is an issue of major concern in engineering since this phenomenon causes many catastrophic failures of structural components in aggressive environments. SCC is even more harmful under cathodic conditions promoting the phenomenon known as hydrogen assisted cracking (HAC), hydrogen assisted fracture (HAF) or hydrogen embrittlement (HE). A common way to assess the susceptibility of a given material to HAC, HAF or HE is to subject a cracked rod to a constant extension rate tension (CERT) test until it fractures in this harsh environment. This paper analyzes the influence of a residual stress field generated by fatigue precracking on the sample’s posterior susceptibility to HAC. To achieve this goal, numerical simulations were carried out of hydrogen diffusion assisted by the stress field. Firstly, a mechanical simulation of the fatigue precracking was developed for revealing the residual stress field after diverse cyclic loading scenarios and posterior stress field evolution during CERT loading. Afterwards, a simulation of hydrogen diffusion assisted by stress was carried out considering the residual stresses after fatigue and the superposed rising stresses caused by CERT loading. Results reveal the key role of the residual stress field after fatigue precracking in the HAC phenomena in cracked steel rods as well as the beneficial effect of compressive residual stress. PMID:28772845
Residual stresses of sputtering titanium thin films at various substrate temperatures.
Chang, R C; Chen, F Y; Chuang, C T; Tung, Y C
2010-07-01
This work seeks to characterize the residual stresses of titanium thin films as they are affected by various substrate temperatures during the sputtering process. The titanium thin films are deposited on silicon wafers by a RF magnetron sputter while different substrate temperatures are considered. The residual stresses are measured by both X-ray diffraction and a substrate curvature method, and consistent results are obtained by both methods. The results show that the residual stress decreases as the substrate temperature increases, in which the stress changes from tensile to compressive when the substrate temperature increases from 25 to 50 degrees C. Furthermore, the elastic modulus and hardness of the titanium thin films are tested with a nanoindenter using a standard Berkovich probe. Correlations between the residual stresses and mechanical properties measured by nanoindentation are also discussed.
The influence of alloy composition on residual stresses in heat treated aluminium alloys
Robinson, J.S.; Redington, W.
2015-07-15
The as quenched properties of eight different heat treatable aluminium alloys are related to residual stress magnitudes with the objective being to establish if there is a relationship between the residual stress and the as quenched alloy hardness and strength. Near surface residual stresses were assessed with X-ray diffraction using both the established sin{sup 2}ψ method and the more recent cos α technique. Through thickness residual stresses were also characterised using neutron diffraction. The alloys were chosen to encompass a wide range of strengths. The low to medium strength alloys were 6060 and 6082, medium to high strength 2618A, 2014A, 7075, 7010 and two variants of 7449, while the very high strength alloy was the powder metallurgy alloy N707. To assess the as quenched strength, dynamic hardness and tensile properties were determined from samples tested immediately after quenching to minimise the influence of precipitation hardening by natural aging. In addition, hot hardness measurements were made in situ on samples cooled to simulate quench paths. Within the experimental constraints of the investigation, the distribution of residual stress through the thickness was found to follow the same pattern for all the alloys investigated, varying from tensile in the interior to surface compression. The influence of alloy strength was manifested as a change in the observed residual stress magnitudes, and surface residual stresses were found to vary linearly with as quenched hardness and strength. - Highlights: • As quenched aluminium alloys contain high magnitude residual stresses. • Surface is compressive balance by a tensile core. • As quenched surface residual stress is linear function of alloy strength. • In situ hot hardness demonstrates rapid change in intrinsic hardness during rapid cooling.
Enhancement of residual stress by electromagnetic fluctuations: A quasi-linear study
NASA Astrophysics Data System (ADS)
Kaang, Helen H.; Jhang, Hogun; Singh, R.; Kim, Juhyung; Kim, S. S.
2016-05-01
A study is conducted on the impact of electromagnetic (EM) fluctuations on residual Reynolds stress in the context of the quasi-linear theory. We employ a fluid formulation describing EM ion temperature gradient turbulence. Analyses show that finite plasma β (=plasma thermal energy/magnetic energy) significantly increases the residual stress, potentially leading to the strong enhancement of flow generation in high β plasmas. We identify that this strong increase of residual stress originates from the reinforcement of radial ⟨ k ∥ ⟩ (=spectrally averaged parallel wavenumber) asymmetry due to the deformation of eigenfunctions near a rational surface.
Research on the residual stress of glass ceramic based on rotary ultrasonic drilling
NASA Astrophysics Data System (ADS)
Sun, Lipeng; Jin, Yuzhu; Chen, Jianhua
2016-10-01
In the process of machining, the glass ceramic is easy to crack and damage, etc. And the residual stress in the machined surface may cause the crack to different extent in the later stage. Some may even affect the performance of the product. The residual stress of rotary ultrasonic drilling and mechanical processing is compared in different machining parameters (spindle speed, feed rate). The effects of processing parameters and methods are researched, in order to reduce the residual stress in the mechanical processing of glass ceramic, and provide guidance for the actual processing.
NASA Astrophysics Data System (ADS)
Liljedahl, C. D. M.; Zanellato, O.; Edwards, L.; Fitzpatrick, M. E.
2008-10-01
The evolution of the residual stresses during fatigue crack growth in a welded compact tension C(T) specimen was measured using neutron diffraction. The measurements were performed by growing a fatigue crack in a sample in situ on a neutron diffractometer. The stresses were found to be unaffected by crack growth through the compressive part of the initial residual stress field. The residual stresses at the crack tip increased when the crack entered the tensile residual stress field to maintain residual stress equilibrium. Finite element (FE) modeling of the evolution of the residual stresses showed good correlation with the experimental results. The residual stress evolution was found to be governed by redistribution of the initial stress field and only slightly affected by fatigue-induced effects at the measured spatial resolution (2 mm × 2 mm × 7 mm).
Deuterium Gas Analysis by Residual Gas Analyzer
NASA Astrophysics Data System (ADS)
Das, B. K.; Shukla, R.; Das, R.; Shyam, A.; Rao, A. D. P.
2012-11-01
Hydrogen gas is generated by electrolysis method in a compact hydrogen generator. A simple procedure reduces handling and storage of hydrogen cylinders for laboratory applications. In such a system, we are producing deuterium gas from heavy water by electrolysis method. After production of the deuterium gas, we have checked the purity level of the outgoing deuterium from the electrolyser. The test was carried out in a high vacuum system in which one residual gas analyser (RGA) was mounted. The deuterium gas was inserted by one manual gas leak valve in to the vacuum system. In this study, the effect of the emission current of the RGA on the detection of the deuterium was performed. In this paper, we will discuss the detail analysis of the deuterium gas and the effect of the emission current on the partial pressure measurement.
Evaluation of Local Residual Stress Distribution of Stator Core in Rotating Machine
NASA Astrophysics Data System (ADS)
Kai, Yuichiro; Tsuchida, Yuji; Todaka, Takashi; Enokizono, Masato
It is well known that magnetic properties deteriorate in constructed cores due to conditions stressed by riveting and welding during manufacturing process, punching and sharing in cutting process of the electrical steel sheets and so on. Therefore, it is important to know the relationships between the stress and magnetic property of the electrical steel in order to design the electrical machinery. In this paper, the local residual stress distribution on the cross section of the stator core in a rotating machine is measured with a X-ray stress measurement device. As the result, the difference of the residual stress distribution of each component is obtained in the teeth and core back of the stator core. In addition, we estimated the deterioration of the magnetic property in the teeth region. It was clarified that the magnetic properties of the electrical steel sheet is deteriorated due to the residual stress.
Birefringence and residual stress induced by CO2 laser mitigation of damage growth in fused silica
NASA Astrophysics Data System (ADS)
Gallais, L.; Cormont, P.; Rullier, J. L.
2009-10-01
We investigate the residual stress field created near mitigated sites and its influence on the efficiency on the CO2 laser mitigation of damage growth process. A numerical model of CO2 laser interaction with fused silica is developed that take into account laser energy absorption, heat transfer, thermally-induced stress and birefringence. Specific photoelastic methods are developed to characterize the residual stress near mitigated sites in fused silica samples. The stress distribution and quantitative values of stress levels are obtained for sites treated with the CO2 laser in various conditions of energy deposition (beam size, pulse duration, incident power). The results obtained also show that the presence of birefringence/residual stress around the mitigated sites has a critical effect on their laser damage resistance.
Residual stress in laser welded dissimilar steel tube-to-tube joints
Sun, Zheng . Lab. of Production Engineering)
1993-09-01
Austenitic-ferritic dissimilar steel joints are widely used in power generation systems. Their utilization has proved to be efficient in terms of satisfactory properties and the economics. These types of joints have usually been produced using conventional welding processes, such as tungsten inert gas (TIG) welding. With the rapid development of high power lasers, laser welding has received considerable attention. Laser welding offers many advantages over conventional welding processes, e.g. low heat input, small heat-affected zone (HAZ), small distortion, and welding in an exact and reproducible manner. Residual stress distribution in laser welds may also differ from those made by conventional welding processes due to its special features. Residual stress, particularly tensile residual stress in the weld, can be very important factor in controlling the quality and service life of the welded structure. The formation of tensile residual stress in the weld may result in the initiation of fatigue cracking, stress corrosion cracking or other types of fractures. It is useful, therefore, to understand the distribution of residual stress in austenitic-ferritic laser welds, and thus evaluate the quality of the joints. Although residual stress distribution in the welded joints has been extensively investigated, little data are available for the residual stress distribution in laser welds. The aim of the work was to examine residual stress distribution along laser welds of dissimilar steel tube-to-tube joints, which were made by both autogeneous welding and welding with filler wire. The results were also compared with the joints made by plasma arc and TIG welding.
Modelling of Tool Wear and Residual Stress during Machining of AISI H13 Tool Steel
Outeiro, Jose C.; Pina, Jose C.; Umbrello, Domenico; Rizzuti, Stefania
2007-05-17
Residual stresses can enhance or impair the ability of a component to withstand loading conditions in service (fatigue, creep, stress corrosion cracking, etc.), depending on their nature: compressive or tensile, respectively. This poses enormous problems in structural assembly as this affects the structural integrity of the whole part. In addition, tool wear issues are of critical importance in manufacturing since these affect component quality, tool life and machining cost. Therefore, prediction and control of both tool wear and the residual stresses in machining are absolutely necessary. In this work, a two-dimensional Finite Element model using an implicit Lagrangian formulation with an automatic remeshing was applied to simulate the orthogonal cutting process of AISI H13 tool steel. To validate such model the predicted and experimentally measured chip geometry, cutting forces, temperatures, tool wear and residual stresses on the machined affected layers were compared. The proposed FE model allowed us to investigate the influence of tool geometry, cutting regime parameters and tool wear on residual stress distribution in the machined surface and subsurface of AISI H13 tool steel. The obtained results permit to conclude that in order to reduce the magnitude of surface residual stresses, the cutting speed should be increased, the uncut chip thickness (or feed) should be reduced and machining with honed tools having large cutting edge radii produce better results than chamfered tools. Moreover, increasing tool wear increases the magnitude of surface residual stresses.
NASA Astrophysics Data System (ADS)
Li, Zhichao; Ferguson, B. Lynn; Nemkov, Valentin; Goldstein, Robert; Jackowski, John; Fett, Greg
2014-12-01
Computer simulation is used to predict the residual stresses and distortion of a full-float truck axle shaft that has been induction scan hardened. Flux2D® is used to model the electromagnetic behavior and the power distributions inside the axle shaft in terms of time. The power distributions are imported and mapped into DANTE® model for thermal, phase transformation, and stress analysis. The truck axle shaft has three main geometrical regions: the flange/filet, the shaft, and the spline. Both induction heating and spray quenching processes have significant effect on the quenching results: distortion and residual stress distributions. In this study, the effects of spray quenching severity on residual stresses and distortion are investigated using modeling. The spray quenching rate can be adjusted by spray nozzle design, ratio of polymer solution, and quenchant flow rate. Different quenching rates are modeled by assigning different heat transfer coefficients as thermal boundary conditions during spray quenching. In this paper, three heat transfer coefficients, 5, 12, and 25 kW/(m2 °C), are applied while keeping all other conditions constant. With the understanding of effects of heating and quenching on residual stresses and distortion of induction hardened parts, the induction hardening process can be optimized for improved part performance.
NASA Astrophysics Data System (ADS)
Ocaña, J. L.; Porro, J. A.; Díaz, M.; Ruiz de Lara, L.; Correa, C.; Gil-Santos, A.; Peral, D.
2013-02-01
Laser shock processing (LSP) is being increasingly applied as an effective technology for the improvement of metallic materials mechanical and surface properties in different types of components as a means of enhancement of their corrosion and fatigue life behavior. As reported in previous contributions by the authors, a main effect resulting from the application of the LSP technique consists on the generation of relatively deep compression residual stresses field into metallic alloy pieces allowing an improved mechanical behaviour, explicitly the life improvement of the treated specimens against wear, crack growth and stress corrosion cracking. Additional results accomplished by the authors in the line of practical development of the LSP technique at an experimental level (aiming its integral assessment from an interrelated theoretical and experimental point of view) are presented in this paper. Concretely, follow-on experimental results on the residual stress profiles and associated surface properties modification successfully reached in typical materials (especially Al and Ti alloys characteristic of high reliability components in the aerospace, nuclear and biomedical sectors) under different LSP irradiation conditions are presented along with a practical correlated analysis on the protective character of the residual stress profiles obtained under different irradiation strategies. Additional remarks on the improved character of the LSP technique over the traditional "shot peening" technique in what concerns depth of induced compressive residual stresses fields are also made through the paper.
Ultra-fast annealing to reduce the residual stress in ultra-thin chips using flash light
NASA Astrophysics Data System (ADS)
Jeon, Eun-Beom; Park, Junhong; Kim, Hak-Sung
2014-04-01
The continuing trend of miniaturization in electronic equipment includes demands for thinner and smaller semiconductor devices with higher performance. To ensure the reliability of electronic devices and to enable high-throughput packaging processes, the mechanical properties of ultra-thin chips need to be accurately understood. One important consideration is the residual stress generated during wafer thinning due to the shear force between the grinding wheel and polish pad; this stress can degrade the fracture strength of ultra-thin devices. To reduce this residual stress, we developed a flash light irradiation annealing technique, including optimization of the irradiation conditions of flash light energy, pulse number and pulse duration. The distributions of residual stresses within ultra-thin flash memory chips before and after the annealing were measured using Raman spectroscopy, and their fracture strength was measured using a ball-on-ring test. Also, transmission electron microscopy (TEM) analysis and beam transfer function tests were performed to investigate the changes in mechanical properties and changes to the silicon lattice effected by the annealing. The ultra-fast flash light annealing was found to reduce the residual stress of ultra-thin chips by 50%, thereby improving their fracture strength by 20% compared to unannealed chips.
Residual energy applications program systems analysis report
Yngve, P.W.
1980-10-01
Current DOE plans call for building an Energy Applied Systems Test (EAST) Facility at the Savannah River Plant in close proximity to the 140 to 150/sup 0/F waste heat from one of several operating nuclear reactors. The waste water flow from each reactor, approximately 165,000 gpm, provides a unique opportunity to test the performance and operating characteristics of large-scale waste heat power generation and heat pump system concepts. This report provides a preliminary description of the potential end-use market, parametric data on heat pump and the power generation system technology, a preliminary listing of EAST Facility requirements, and an example of an integrated industrial park utilizing the technology to maximize economic pay back. The parametric heat pump analysis concluded that dual-fluid Rankine cycle heat pumps with capacities as high as 400 x 10/sup 6/ Btu/h, can utilize large sources of low temperature residual heat to provide 300/sup 0/F saturatd steam for an industrial park. The before tax return on investment for this concept is 36.2%. The analysis also concluded that smaller modular heat pumps could fulfill the same objective while sacrificing only a moderate rate of return. The parametric power generation analysis concluded that multi-pressure Rankine cycle systems not only are superior to single pressure systems, but can also be developed for large systems (approx. = 17 MW/sub e/). This same technology is applicable to smaller systems at the sacrifice of higher investment per unit output.
Otoguro, Saori; Hayashi, Yoshihiro; Miura, Takahiro; Uehara, Naoto; Utsumi, Shunichi; Onuki, Yoshinori; Obata, Yasuko; Takayama, Kozo
2015-01-01
The stress distribution of tablets after compression was simulated using a finite element method, where the powder was defined by the Drucker-Prager cap model. The effect of tablet shape, identified by the surface curvature, on the residual stress distribution was investigated. In flat-faced tablets, weak positive shear stress remained from the top and bottom die walls toward the center of the tablet. In the case of the convexly curved tablet, strong positive shear stress remained on the upper side and in the intermediate part between the die wall and the center of the tablet. In the case of x-axial stress, negative values were observed for all tablets, suggesting that the x-axial force always acts from the die wall toward the center of the tablet. In the flat tablet, negative x-axial stress remained from the upper edge to the center bottom. The x-axial stress distribution differed between the flat and convexly curved tablets. Weak stress remained in the y-axial direction of the flat tablet, whereas an upward force remained at the center of the convexly curved tablet. By employing multiple linear regression analysis, the mechanical properties of the tablets were predicted accurately as functions of their residual stress distribution. However, the multiple linear regression prediction of the dissolution parameters of acetaminophen, used here as a model drug, was limited, suggesting that the dissolution of active ingredients is not a simple process; further investigation is needed to enable accurate predictions of dissolution parameters.
NASA Astrophysics Data System (ADS)
Kapoor, K.; Lahiri, D.; Padmaprabu, C.; Sanyal, T.
2002-06-01
In the present study, the near surface residual stress in Zr-2.5%Nb pressure tubes was measured using X-ray diffraction. Both cold rolled (pilgered) and stress-relieved tubes were studied. Since the material is highly textured and the hexagonal close packed crystal lattice has anisotropic elastic constants, special care is required in collection and analysis of experimental data to minimise errors. The standard multi-exposure technique of X-ray residual-stress measurement results in inaccuracies for textured material. Diffraction intensities depend on factors like inclination of the sample, the rotation of the beam and the position of detectors. Low intensity due to texture can result in increased uncertainties in observed stress value. Anisotropy of elastic constants in textured materials can further increase the errors in measured stress. A general approach has been developed for accurate determination of the stress tensor in textured material. The measured stresses for Zr-2.5%Nb pressure tubes were highest and compressive along the rolling direction (RD) in the pilgered samples. The stress-relieved samples showed a small tensile component along the RD. Errors up to 20% are introduced if isotropic elastic constants are used in the analysis instead of the more realistic anisotropic elastic constants calculated for the observed texture.
Effect of texture and grain size on the residual stress of nanocrystalline thin films
NASA Astrophysics Data System (ADS)
Cao, Lei; Sengupta, Arkaprabha; Pantuso, Daniel; Koslowski, Marisol
2017-10-01
Residual stresses develop in thin film interconnects mainly as a result of deposition conditions and multiple thermal loading cycles during the manufacturing flow. Understanding the relation between the distribution of residual stress and the interconnect microstructure is of key importance to manage the nucleation and growth of defects that can lead to failure under reliability testing and use conditions. Dislocation dynamics simulations are performed in nanocrystalline copper subjected to cyclic loading to quantify the distribution of residual stresses as a function of grain misorientation and grain size distribution. The outcomes of this work help to evaluate the effect of microstructure in thin films failure by identifying potential voiding sites. Furthermore, the simulations show how dislocation structures are influenced by texture and grain size distribution that affect the residual stress. For example, when dislocation loops reach the opposite grain boundary during loading, these dislocations remain locked during unloading.
Dommarco, R.C.; Kozaczek, K.J.; Hahn, G.T.
1996-07-01
Residual stresses are introduced and modified during manufacturing and also by normal use. In this paper the changes in magnitude and distribution of residual stresses, attending the strain induced transformation of retained austenite are examined. Tests were conducted on SAE 52100 bearing steel with different amounts of retained austenite in a 5-ball-rod rolling contact fatigue machine. The tests were accelerated by applying well-controlled micro- indentations on the wear track and using rough balls. The magnitude and distribution of residual stresses and retained austenite were measured using x-ray diffraction techniques. The contribution of the residual stresses and amount of retained austenite to the rolling contact fatigue life is analyzed.
Residual stresses in angleplied laminates and their effects on laminate behavior
NASA Technical Reports Server (NTRS)
Chamis, C. C.
1978-01-01
Evidence of the presence of lamination residual stresses in angleplied laminates were transply cracks and warpage of unsymmetric laminates which occur prior to application of any mechanical load. Lamination residual strains were measured using the embedded strain gage technique. These strains result from the temperature differences between cure and room temperature and vary linearly within this temperature range. Lamination residual stresses were usually present in angleplied fiber composites laminates; they were also present in unidirectional hybrids and superhybrids. For specific applications, the magnitudes of lamination residual stresses were determined and evaluated relative to the anticipated applied stresses. Particular attention was given to cyclic thermal loadings in applications where the thermal cycling takes place over a wide temperature range.
On residual stresses and homeostasis: an elastic theory of functional adaptation in living matter
Ciarletta, P.; Destrade, M.; Gower, A. L.
2016-01-01
Living matter can functionally adapt to external physical factors by developing internal tensions, easily revealed by cutting experiments. Nonetheless, residual stresses intrinsically have a complex spatial distribution, and destructive techniques cannot be used to identify a natural stress-free configuration. This work proposes a novel elastic theory of pre-stressed materials. Imposing physical compatibility and symmetry arguments, we define a new class of free energies explicitly depending on the internal stresses. This theory is finally applied to the study of arterial remodelling, proving its potential for the non-destructive determination of the residual tensions within biological materials. PMID:27113413
On residual stresses and homeostasis: an elastic theory of functional adaptation in living matter
NASA Astrophysics Data System (ADS)
Ciarletta, P.; Destrade, M.; Gower, A. L.
2016-04-01
Living matter can functionally adapt to external physical factors by developing internal tensions, easily revealed by cutting experiments. Nonetheless, residual stresses intrinsically have a complex spatial distribution, and destructive techniques cannot be used to identify a natural stress-free configuration. This work proposes a novel elastic theory of pre-stressed materials. Imposing physical compatibility and symmetry arguments, we define a new class of free energies explicitly depending on the internal stresses. This theory is finally applied to the study of arterial remodelling, proving its potential for the non-destructive determination of the residual tensions within biological materials.
The effect of fibre pre-tension on residual stresses in fibre composites
NASA Astrophysics Data System (ADS)
Kim, Jang-Kyo; Mai, Yiu-Wing; Cotterell, Brian
The residual stresses resulting from fiber pretension is estimated from a simple model. The principal effect of fiber pretension is to improve the mechanical bonding at the interface which promotes frictional resistance during fiber pull-out. The fiber pull-out stresses are approximately estimated by superimposing the additional residual clamping stress at the interface due to fiber pretension. Comparison of the theory with experimental results on steel wire-epoxy matrix model composites shows a reasonable agreement, particularly for the frictional pull-out stress after complete debonding.
Factors Influencing Residual Stresses in Yttria Stabilized Zirconia Thermal Barrier Coatings
NASA Technical Reports Server (NTRS)
McGrann, Roy T. R.; Rybicki, Edmund F.; Shadley, John R.; Brindley, William J.
1997-01-01
To improve gas turbine and diesel engine performance using thermal barrier coatings (TBC's) requires an understanding of the factors that influence the in-service behavior of thermal barrier coatings. One of the many factors related to coating performance is the state of stress in the coating. The total stress state is composed of the stresses due to the in-service loading history and the residual stresses. Residual stresses have been shown to affect TBC life, the bond strength of thermal spray coatings, and the fatigue life of tungsten carbide coatings. Residual stresses are first introduced in TBC's by the spraying process due to elevated temperatures during processing and the difference in coefficients of thermal expansion of the top coat, bond coat, and substrate. Later, the residual stresses can be changed by the in-service temperature history due to a number of time and temperature dependent mechanisms, such as oxidation, creep, and sintering. Silica content has also been shown to affect sintering and the cyclic life of thermal barrier coatings. Thus, it is important to understand how the spraying process, the in-service thermal cycles, and the silica content can create and alter residual stresses in thermal barrier coatings.
Pre and post machining and release residual stresses in microelectromechanical systems (MEMS)
NASA Astrophysics Data System (ADS)
Vechery, Mary; Dick, Andrew; Balachandran, B.; Dubey, Madan
2008-03-01
A major concern in the development of microelectromechanical systems (MEMS) is the presence of residual stress. This stress, which is produced during the fabrication of multi-layer thin-film structures, can significantly affect the performance of micro-scale devices. Though experimental measurement techniques are accurate, actual stress measurements can vary dramatically from run to run and wafer to wafer. For this reason, the modeling of this stress can be a challenging task. Past work has often focused on experimental, static techniques for determining residual-stress levels in single-layer and bi-layer structures. In addition, in prior studies, the focus has primarily been on residual-stress measurements in thin films as they are being deposited and prior to the release of a particular device. In this effort, residual stresses in MEMS resonators are characterized pre- and post-micro-machining and release of the structures. This is accomplished by applying three residual-stress identification techniques. The first technique, which is based on wafer-bow measurements and Stoney's formula, is suited for determining the residual stresses in thin film layers as they are being deposited and before the occurrence of a micro-machining or release process. In the second technique, a static parametric identification technique, device deflection data is made use of to approximate individual device residual stress immediately after release of a structure. The third technique, a dynamic parametric identification technique, which can be based on linear or nonlinear frequency response data can be used to estimate device residual stress immediately after release and after the device has been polarized. The results obtained by using these techniques are used to develop an understanding of how geometry, fabrication, release and polarization of resonators affect the stress state in a piezoelectric device. The results, which show that the stress levels can be quite different after a
NASA Astrophysics Data System (ADS)
Vorontsov, G. V.; Reznichenko, A. I.
1992-04-01
A method for analyzing residual stresses in products made of composite materials by forced winding, pyrolytic precipitation, casting or extrusion is proposed. It is shown that each initial stressed state of a product may have an equivalent temperature field causing identical thermoelastic stresses in the product. This method is verified by means of analysis of the technological stresses in thick-walled conic shells made by pyrolytic carbon precipitation at temperatures above 2000 C. The method makes it possible to determine the stresses of the whole volume of the product with comparatively few data on the deformation relaxation provided by the attached strain gauges. Satisfactory agreement was found between the theoretical and experimental values of the stresses in places of the fixed strain gauges.
Influence and Modeling of Residual Stresses in Thick Walled Pressure Vessels with Through Holes
2012-02-28
Technical Report ARWSB-TR-12003 INFLUENCE AND MODELING OF RESIDUAL STRESSES IN THICK WALLED PRESSURE VESSELS WITH...DATE (DD-MM-YYYY) 28/02/2012 2. REPORT TYPE Technical Report 3. DATES COVERED (From - To) 4. TITLE AND SUBTITLE Influence and Modeling of...Residual Stresses in Thick Walled Pressure Vessels with Through Holes 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT
Assessment of Residual Stresses in 3013 Inner and Outer Containers and Teardrop Samples
Stroud, Mary Ann; Prime, Michael Bruce; Veirs, Douglas Kirk; Berg, John M.; Clausen, Bjorn; Worl, Laura Ann; DeWald, Adrian T.
2015-12-08
This report is an assessment performed by LANL that examines packaging for plutonium-bearing materials and the resilience of its design. This report discusses residual stresses in the 3013 outer, the SRS/Hanford and RFETS/LLNL inner containers, and teardrop samples used in studies to assess the potential for SCC in 3013 containers. Residual tensile stresses in the heat affected zones of the closure welds are of particular concern.
Relief of Residual Stress in Streamline Tie Rods by Heat Treatment
1941-11-01
major axis, pounds ~er square inch ~ --— modulus of elasticity (3 ‘X 107 lb/eq. in.) c1 “distance f,ron saw cut “to,neutral axis of seg- ment - 0.42...the ends of specimens with a saw cuti . The residual stress was then calculated.b~ diviaing by the ratio of partial,to mean residual stress displayed by
Choi, Bo-Hun; Kwon, Il-Bum
2015-03-09
We propose a distributed residual strain sensor that uses an Al-packaged optical fiber for the first time. The residual strain which causes Brillouin frequency shifts in the optical fiber was measured using Brillouin optical correlation domain analysis with 2 cm spatial resolution. We quantified the Brillouin frequency shifts in the Al-packaged optical fiber by the tensile stress and compared them for a varying number of Al layers in the optical fiber. The Brillouin frequency shift of an optical fiber with one Al layer had a slope of 0.038 MHz/με with respect to tensile stress, which corresponds to 78% of that for an optical fiber without Al layers. After removal of the stress, 87% of the strain remained as residual strain. When different tensile stresses were randomly applied, the strain caused by the highest stress was the only one detected as residual strain. The residual strain was repeatedly measured for a time span of nine months for the purpose of reliability testing, and there was no change in the strain except for a 4% reduction, which is within the error tolerance of the experiment. A composite material plate equipped with our proposed Al-packaged optical fiber sensor was hammered for impact experiment and the residual strain in the plate was successfully detected. We suggest that the Al-packaged optical fiber can be adapted as a distributed strain sensor for smart structures, including aerospace structures.
Verification of residual stresses in flash-butt-weld rails using neutron diffraction
NASA Astrophysics Data System (ADS)
Tawfik, David; Kirstein, Oliver; Mutton, Peter John; Chiu, Wing Kong
2006-11-01
Residual stresses developed during flash-butt welding may play a crucial role in prolonging the fatigue life of the welded tracks under service loading conditions. The finished welds typically exhibit high levels of tensile residual stresses in the web region of the weld. Moreover, the surface condition of the web may contain shear drag or other defects resulting from the shearing process which may lead to the initiation and propagation of fatigue cracks in a horizontal split web failure mode under high axle loads. However, a comprehensive understanding into the residual stress behaviour throughout the complex weld geometry remains unclear and is considered necessary to establish the correct localised post-weld heat treatment modifications intended to lower tensile residual stresses. This investigation used the neutron diffraction technique to analyse residual stresses in an AS60 flash-butt-welded rail cooled under normal operating conditions. The findings will ultimately contribute to developing modifications to the flash-butt-welding procedure to lower tensile residual stresses which may then improve rail performance under high axle load.
Residual stress characteristics in a non-circular drawing sequence of pearlitic steel wire
NASA Astrophysics Data System (ADS)
Baek, Hyun Moo; Hwang, Sun Kwang; Son, Il-Heon; Im, Yong-Taek
2016-11-01
In this paper, characteristics of residual stress in pearlitic steel wire drawn by a non-circular drawing (NCD) sequence with two processing routes, NCDA and NCDB, were experimentally and numerically investigated up to the 12th pass in comparison with conventional wire drawing (WD). For experimental investigation of the axial residual stress at the surface of the drawn wire, destructive (deflection) and non-destructive methods were employed. According to the experimental results, axial surface residual stress of the drawn wire by the NCD sequence was lower and more homogeneous compared to the conventional WD. Based on the elasto-plastic numerical simulation results from the surface to the center of the drawn wire using a commercial DEFORM-3D, an empirical relationship between residual stress and reduction of area was determined to predict the residual stress evolution in the multi-pass WD, NCDA, and NCDB, in that order. From the results of this investigation, it can be construed that the NCD sequence, especially the NCDB, might be helpful in improving the residual stress characteristics of pearlitic steel wire to improve its mechanical behavior and service life.
Extension, inflation and torsion of a residually stressed circular cylindrical tube
NASA Astrophysics Data System (ADS)
Merodio, José; Ogden, Ray W.
2016-03-01
In this paper, we provide a new example of the solution of a finite deformation boundary-value problem for a residually stressed elastic body. Specifically, we analyse the problem of the combined extension, inflation and torsion of a circular cylindrical tube subject to radial and circumferential residual stresses and governed by a residual-stress dependent nonlinear elastic constitutive law. The problem is first of all formulated for a general elastic strain-energy function, and compact expressions in the form of integrals are obtained for the pressure, axial load and torsional moment required to maintain the given deformation. For two specific simple prototype strain-energy functions that include residual stress, the integrals are evaluated to give explicit closed-form expressions for the pressure, axial load and torsional moment. The dependence of these quantities on a measure of the radial strain is illustrated graphically for different values of the parameters (in dimensionless form) involved, in particular the tube thickness, the amount of torsion and the strength of the residual stress. The results for the two strain-energy functions are compared and also compared with results when there is no residual stress.
Experimental Study of Residual Stresses in Metal Parts Obtained by Selective Laser Melting
NASA Astrophysics Data System (ADS)
Protasov, C. E.; Safronov, V. A.; Kotoban, D. V.; Gusarov, A. V.
High local temperature gradients occur at additive manufacturing by selective laser melting of powder. This gives rise to undesirable residual stresses, deformations, and cracks. To understand how to control the formation of the residual stresses, a reliable method is necessary for measuring their distribution in the fabricated part. It is proposed to cut the part into thin plates and to reconstruct the residual stresses from the measured deformation of the plates. This method is tested on beams with square cross-section built from stainless steel. The beams were cut by electrical discharge machining and chemically etched. The obtained stress profile in vertical transversal direction slightly increases from the top to the bottom of the beam. This dependency is confirmed by numerical modeling. The measured stress profile agrees with the known results by other authors.
INTERFACE RESIDUAL STRESSES IN DENTAL ZIRCONIA USING LAUE MICRO-DIFFRACTION
Bale, H. A.; Tamura, N.; Coelho, P.G.; Hanan, J. C.
2009-01-01
Due to their aesthetic value and high compressive strength, dentists have recently employed ceramics for restoration materials. Among the ceramic materials, zirconia provides high toughness and crack resistant characteristics. Residual stresses develop in processing due to factors including grain anisotropy and thermal coefficient mismatch. In the present study, polychromatic X-ray (Laue) micro-diffraction provided grain orientation and residual stresses on a clinically relevant zirconia model ceramic disk. A 0.5 mm x 0.024 mm region on zirconia was examined on a 500 nm scale for residual stresses using a focused poly-chromatic synchrotron X-ray beam. Large stresses ranging from - to + 1GPa were observed at some grains. On average, the method suggests a relatively small compressive stress at the surface between 47 and 75 MPa depending on direction.
NASA Astrophysics Data System (ADS)
Rivera, David; Wirz, Richard E.; Ghoniem, Nasr M.
2017-04-01
The thermomechanical damage and residual stresses in plasma-facing materials operating at high heat flux are experimentally investigated. Materials with micro-surfaces are found to be more resilient, when exposed to cyclic high heat flux generated by an arc-jet plasma. An experimental facility, dedicated to High Energy Flux Testing (HEFTY), is developed for testing cyclic heat flux in excess of 10 MW/m2. We show that plastic deformation and subsequent fracture of the surface can be controlled by sample cooling. We demonstrate that W surfaces with micro-pillar type surface architecture have significantly reduced residual thermal stresses after plasma exposure, as compared to those with flat surfaces. X-ray diffraction (XRD) spectra of the W-(110) peak reveal that broadening of the Full Width at Half Maximum (FWHM) for micro-engineered samples is substantially smaller than corresponding flat surfaces. Spectral shifts of XRD signals indicate that residual stresses due to plasma exposure of micro-engineered surfaces build up in the first few cycles of exposure. Subsequent cyclic plasma heat loading is shown to anneal out most of the built-up residual stresses in micro-engineered surfaces. These findings are consistent with relaxation of residual thermal stresses in surfaces with micro-engineered features. The initial residual stress state of highly polished flat W samples is compressive (≈ -1.3 GPa). After exposure to 50 plasma cycles, the surface stress relaxes to -1.0 GPa. Micro-engineered samples exposed to the same thermal cycling show that the initial residual stress state is compressive at (- 250 MPa), and remains largely unchanged after plasma exposure.
NASA Technical Reports Server (NTRS)
Dillon, O. W., Jr.
1985-01-01
An investigation of the blowing up of UK numerical results for the inplane stress calculations for silicon ribbon is presented. The inplane stress that exists in a thin plate is governed by two general equations of equilibrium and compatibility.
A survey of residual analysis and a new test of residual trend.
McDowell, J J; Calvin, Olivia L; Klapes, Bryan
2016-05-01
A survey of residual analysis in behavior-analytic research reveals that existing methods are problematic in one way or another. A new test for residual trends is proposed that avoids the problematic features of the existing methods. It entails fitting cubic polynomials to sets of residuals and comparing their effect sizes to those that would be expected if the sets of residuals were random. To this end, sampling distributions of effect sizes for fits of a cubic polynomial to random data were obtained by generating sets of random standardized residuals of various sizes, n. A cubic polynomial was then fitted to each set of residuals and its effect size was calculated. This yielded a sampling distribution of effect sizes for each n. To test for a residual trend in experimental data, the median effect size of cubic-polynomial fits to sets of experimental residuals can be compared to the median of the corresponding sampling distribution of effect sizes for random residuals using a sign test. An example from the literature, which entailed comparing mathematical and computational models of continuous choice, is used to illustrate the utility of the test.
Programmable calculator stress analysis
Van Gulick, L.A.
1983-01-01
Advanced programmable alphanumeric calculators are well suited for closed-form calculation of pressure-vessel stresses. They offer adequate computing power, portability, special programming features, and simple interactive execution procedures. Representative programs that demonstrate calculator capabilities are presented. Problems treated are stress and strength calculations in thick-walled pressure vessels and the computation of stresses near head/pressure-vessel junctures.
NASA Astrophysics Data System (ADS)
Osamura, Kozo; Kuratani, Fumiyasu; Koide, Toshio; Ogawa, Wataru; Taniguchi, Hiroyasu; Monju, Yoshiyuki; Mizuta, Taiji; Shobu, Takahisa
2016-12-01
The artistic sound of a cymbal is produced by employing a special copper alloy as well as incorporating complicated and heterogeneous residual stress/strain distributions. In order to establish a modern engineering process that achieves high-quality control for the cymbals, it is necessary to investigate the distribution of the residual stresses/strains in the cymbal and their quantitative relation with the frequency characteristics of the sound generated from the cymbal. In the present study, we have successfully used synchrotron radiation to measure the distribution of residual strain in two kinds of cymbals—after spinforming as well as after hammering. The microstructure and the mechanical properties of the cymbals were measured as well their acoustic response. Based on our experimental data, the inhomogeneous residual stress/strain distributions in the cymbals were deduced in detail and their influence on the frequency characteristics of the sound produced by the cymbals was identified.
ETP-0492, Measured Residual Stresses in CYL S/N 53 Fretted Area
NASA Technical Reports Server (NTRS)
Webster, Ronald L.
1998-01-01
This test report presents the results of a residual stress survey of the inner clevis leg of lightweight cylinder SIN 053 as described by ETP-0492. The intent of this testing was to evaluate the residual stresses that occur in and around the inner clevis leg at the capture feature contact zone during a normal flight cycle. Lightweight case cylinder segment IU50717, S/N L053 from Flight STS-27 exhibited fretting around the contact zone of the inner clevis leg and the capture feature of the field joint. Post flight inspection revealed several large fitting pits on the inside of the inner clevis leg. This cylinder was assigned for both residual stress and metallurgical evaluation. This report is concerned only with the residual so= evaluations. The effects of glass bead cleaning and fi=ing were evaluated using the x-ray diffraction method.
WELD APPLICATION OF A NEW METHOD FOR CROSS-SECTIONAL RESIDUAL STRESS MAPPING
M. PRIME; ET AL
2001-03-01
The new ''contour method'' was used to measure a cross-sectional map of residual stresses in a welded plate. Comparisons with neutron diffraction measurements confirm the capability of the contour method to measure complex, 2-D stress maps. Compared to other methods, the contour method is relatively simple and inexpensive to perform, and the equipment required is widely available.
NASA Technical Reports Server (NTRS)
Chen, P.; Malone, T.; Bond, R.; Torres, P.
2001-01-01
Investigators at Marshall Space Flight Center (MSFC) are studying the potential benefits of cryogenic treatment for aerospace Aluminum (Al) alloys. This paper reports the effects of cryogenic treatment on residual stress, tensile strength, hardness, fatigue life, and stress corrosion cracking (SCC) resistance.
NASA Technical Reports Server (NTRS)
Chen, Po; Malone, Tina; Bod, Robert; Torres, Pablo
2000-01-01
Investigators at Marshall Space Flight Center (MSFC) are studying the potential benefits of cryogenic treatment for aerospace Aluminum (Al) alloys. This paper reports the effects of cryogenic treatment on residual stress, tensile strength, hardness, fatigue life, and stress corrosion cracking (SCC) resistance.
NASA Technical Reports Server (NTRS)
Obrien, T. K.; Raju, I. S.; Garber, D. P.
1985-01-01
A laminated plate theory analysis is developed to calculate the strain energy release rate associated with edge delamination growth in a composite laminate. The analysis includes the contribution of residual thermal and moisture stresses to the strain energy released. The strain energy release rate, G, increased when residual thermal effects were combined with applied mechanical strains, but then decreased when increasing moisture content was included. A quasi-three-dimensional finite element analysis indicated identical trends and demonstrated these same trends for the individual strain energy release rate components, G sub I and G sub II, associated with interlaminar tension and shear. An experimental study indicated that for T300/5208 graphite-epoxy composites, the inclusion of residual thermal and moisture stresses did not significantly alter the calculation of interlaminar fracture toughness from strain energy release rate analysis of edge delamination data taken at room temperature, ambient conditions.
NASA Astrophysics Data System (ADS)
Larsson, Per-Lennart
2017-08-01
The determination of residual stresses in engineering materials using sharp indentation testing is studied analytically and numerically. The numerical part of the investigation is based on the finite element method. In particular, the effect from elastic deformations on global indentation properties is discussed in detail. This effect is essential when residual stresses are to be determined based on the change of the contact area due to such stresses. However, standard relations for this purpose are founded on the fact that the material hardness is invariant as regards residual (applied) stresses. Presently, this assumption is scrutinized and it is shown that it is only valid at dominating plastic deformation around the contact region. The hardness dependence of residual stresses can, however, be correlated in the same way as in the case of stress-free materials, indicating that the wealth of characterization formulas pertinent to indentation hardness is available also for the purpose of residual field determination. Only cone indentation of elastic-perfectly plastic materials is considered, but the generality of the results is discussed in some detail.
The Effect of Residual Stress on the Distortion of Gray Iron Brake Disks
NASA Astrophysics Data System (ADS)
Shin, M. W.; Jang, G. H.; Kim, J. K.; Kim, H. Y.; Jang, Ho
2013-04-01
Thermal distortion of gray iron brake disks due to residual stress and its effect on brake vibrations were studied. The residual stress of heat- and non-heat-treated gray iron disks was measured using neutron scattering. Dynamometer tests were performed to measure the friction force oscillation caused by the disk runout during brake applications. High-temperature tensile tests were carried out to find out possible plastic deformation due to residual stress during brake applications. The results showed that the average residual stress of the heat-treated disk (47.6 MPa) was lower than that of the non-heat-treated disk (99.6 MPa). Dynamometer tests at high temperatures (up to 600 °C) indicated that the residual stress pronounced the runout: the increase in disk runout after the tests for the non-heat-treated sample was more than twice that for the heat-treated sample. This difference correlated well with the neutron scattering results and the dimensional changes after a separate vacuum heat treatment. The high-temperature tensile tests showed severe reductions in yield strength at 600 °C, suggesting that disks produced with no stress relaxation could be deformed during severe braking.
Properties of the Residual Stress of the Temporally Filtered Navier-Stokes Equations
NASA Technical Reports Server (NTRS)
Pruett, C. D.; Gatski, T. B.; Grosch, C. E.; Thacker, W. D.
2002-01-01
The development of a unifying framework among direct numerical simulations, large-eddy simulations, and statistically averaged formulations of the Navier-Stokes equations, is of current interest. Toward that goal, the properties of the residual (subgrid-scale) stress of the temporally filtered Navier-Stokes equations are carefully examined. Causal time-domain filters, parameterized by a temporal filter width 0 less than Delta less than infinity, are considered. For several reasons, the differential forms of such filters are preferred to their corresponding integral forms; among these, storage requirements for differential forms are typically much less than for integral forms and, for some filters, are independent of Delta. The behavior of the residual stress in the limits of both vanishing and in infinite filter widths is examined. It is shown analytically that, in the limit Delta to 0, the residual stress vanishes, in which case the Navier-Stokes equations are recovered from the temporally filtered equations. Alternately, in the limit Delta to infinity, the residual stress is equivalent to the long-time averaged stress, and the Reynolds-averaged Navier-Stokes equations are recovered from the temporally filtered equations. The predicted behavior at the asymptotic limits of filter width is further validated by numerical simulations of the temporally filtered forced, viscous Burger's equation. Finally, finite filter widths are also considered, and a priori analyses of temporal similarity and temporal approximate deconvolution models of the residual stress are conducted.
Feng, Zhili; Bunn, Jeffrey R; Tzelepis, Demetrios A; Payzant, E Andrew; Yu, Xinghua
2016-01-01
Hydrogen induced cracking (HIC) has been a persistent issue in welding of high-strength steels. Mitigating residual stresses is one of the most efficient ways to control HIC. The current study develops a proactive in-process weld residual stress mitigation technique, which manipulates the thermal expansion and contraction sequence in the weldments during welding process. When the steel weld is cooled after welding, martensitic transformation will occur at a temperature below 400 C. Volume expansion in the weld due to the martensitic transformation will reduce tensile stresses in the weld and heat affected zone and in some cases produce compressive residual stresses in the weld. Based on this concept, a customized filler wire which undergoes a martensitic phase transformation during cooling was developed. The new filler wire shows significant improvement in terms of reducing the tendency of HIC in high strength steels. Bulk residual stress mapping using neutron diffraction revealed reduced tensile and compressive residual stresses in the welds made by the new filler wire.
Measuring the residual stress in dental composites using a ring slitting method.
Park, Jeong Won; Ferracane, Jack L
2005-09-01
The objective of this experiment was to employ the ring slitting method for the measurement of the residual stress (RS) produced in dental composite materials after polymerization. This study was designed to determine the effect of slitting and measuring time on the residual stress. Rings were made in a split brass mold from three composites (Z100/3MESPE; Herculite/Kerr; Heliomolar/Ivoclar) and cured in a Triad II (Dentsply). Two points were scribed, and the rings were slit at either 1 h (Early-group) or 24 h (Delayed-group) after curing the composite. The change in the distance between the scribed points was measured using an image analyzer system at both 1 and 24 h after slitting. From the measured change, circumferential RS was calculated and statistically analyzed with ANOVA/Tukey's (P<0.05). The degree of conversion of each composite at 1 and 24 h was measured with FTIR and analyzed using Student's t-test (P<0.05). In general, the residual stress (range=0.42-2.84 MPa) was highest for Z100 and lowest for Heliomolar, but this depended upon the test conditions. The early cut (1 h slitting), 24 h measurement groups showed the highest residual stress values. This study, describes a ring slitting method to measure residual stress generated in dental composites during and after curing. The stress of composite can be affected by the cutting and measurement time.
NASA Astrophysics Data System (ADS)
Larsson, Per-Lennart
2017-07-01
The determination of residual stresses in engineering materials using sharp indentation testing is studied analytically and numerically. The numerical part of the investigation is based on the finite element method. In particular, the effect from elastic deformations on global indentation properties is discussed in detail. This effect is essential when residual stresses are to be determined based on the change of the contact area due to such stresses. However, standard relations for this purpose are founded on the fact that the material hardness is invariant as regards residual (applied) stresses. Presently, this assumption is scrutinized and it is shown that it is only valid at dominating plastic deformation around the contact region. The hardness dependence of residual stresses can, however, be correlated in the same way as in the case of stress-free materials, indicating that the wealth of characterization formulas pertinent to indentation hardness is available also for the purpose of residual field determination. Only cone indentation of elastic-perfectly plastic materials is considered, but the generality of the results is discussed in some detail.
NASA Astrophysics Data System (ADS)
Soyama, Hitoshi; Nagasaka, Kazuya; Takakuwa, Osamu; Naito, Akima
Introducing compressive residual stress by a cavitating jet into the sub-surface of components used in nuclear power plants can mitigate stress corrosion cracking in these components. Although applying the jet is an effective method for this purpose, it should be used without causing damage to the surface from water jet droplets arising from high-pressure injection of the water jet. Thus, in introducing compressive residual stress, the injection pressure needs to be optimized. In this paper, in order to determine the optimum injection pressure, the residual stress of stainless steel treated by a jet at various injection pressures was measured using an X-ray diffraction method. The injection pressure of the jet was varied from 5 MPa to 300 MPa, and the diameter of the nozzle throat of the jet was varied from 0.35 mm to 2.0 mm. The variation of residual stress with depth was measured by alternating X-ray diffraction measurements with electropolishing. It was revealed that a cavitating jet at an injection pressure of 10 MPa with a nozzle diameter of 2.0 mm can introduce higher compressive residual stress to deeper into stainless steel compared with a jet at 300 MPa with a nozzle diameter of 0.35 mm when the downstream pressure of the nozzle was constant.
The effect of residual stresses induced by prestraining on fatigue life of notched specimens
NASA Astrophysics Data System (ADS)
Sadeler, R.; Ozel, A.; Kaymaz, I.; Totik, Y.
2005-06-01
The effect of tensile prestraining-induced residual stress on the fatigue life of notched steel parts was investigated. The study was performed on AISI 4140 steel. Rotating bending fatigue tests were carried out on semicircular notched specimens with different notch radii in the as-quenched and tempered conditions. Metallography of the specimens was performed by means of light optical microscopy. The finite-element method was used to evaluate the residual stress distribution near the notch region. Fatigue tests revealed fatigue life improvement for notched specimens, which changes depending on the notch radii and applied stress. Scanning electron microscopy was used to examine the fracture surfaces of the specimens.
Effect of Treatment Area on Residual Stress and Fatigue in Laser Peened Aluminum Sheets
NASA Astrophysics Data System (ADS)
Toparli, M. Burak; Smyth, Niall; Fitzpatrick, Michael E.
2017-01-01
Two 2.0-mm-thick aluminum sheets were laser peened and the resulting residual stresses were measured using incremental hole drilling, surface X-ray diffraction, and synchrotron X-ray diffraction techniques. Laser peening was applied to two samples using the same laser peening parameters, but one of the samples has a larger peened area. The aim of this research was to discover the effect of peen area on residual stress, for application in aerospace structures for fatigue life enhancement. It was found that a larger peened area has higher and deeper compressive stresses in the crack-opening direction, leading to greater enhancement of fatigue life.
Effect of Treatment Area on Residual Stress and Fatigue in Laser Peened Aluminum Sheets
NASA Astrophysics Data System (ADS)
Toparli, M. Burak; Smyth, Niall; Fitzpatrick, Michael E.
2017-04-01
Two 2.0-mm-thick aluminum sheets were laser peened and the resulting residual stresses were measured using incremental hole drilling, surface X-ray diffraction, and synchrotron X-ray diffraction techniques. Laser peening was applied to two samples using the same laser peening parameters, but one of the samples has a larger peened area. The aim of this research was to discover the effect of peen area on residual stress, for application in aerospace structures for fatigue life enhancement. It was found that a larger peened area has higher and deeper compressive stresses in the crack-opening direction, leading to greater enhancement of fatigue life.
Residual stresses in shape memory alloy fiber reinforced aluminium matrix composite
NASA Astrophysics Data System (ADS)
Tsz Loong, Tang; Jamian, Saifulnizan; Ismail, Al Emran; Nur, Nik Hisyammudin Muhd; Watanabe, Yoshimi
2017-01-01
Process-induced residual stress in shape memory alloy (SMA) fiber reinforced aluminum (Al) matrix composite was simulated by ANSYS APDL. The manufacturing process of the composite named as NiTi/Al is start with loading and unloading process of nickel titanium (NiTi) wire as SMA to generate a residual plastic strain. Then, this plastic deformed NiTi wire would be embedded into Al to become a composite. Lastly, the composite is heated form 289 K to 363 K and then cooled back to 300 K. Residual stress is generated in composite because of shape memory effect of NiTi and mismatch of thermal coefficient between NiTi wire and Al matrix of composite. ANSYS APDL has been used to simulate the distribution of residual stress and strain in this process. A sensitivity test has been done to determine the optimum number of nodes and elements used. Hence, the number of nodes and elements used are 15680 and 13680, respectively. Furthermore, the distribution of residual stress and strain of nickel fiber reinforced aluminium matrix composite (Ni/Al) and titanium fiber reinforced aluminium matrix composite (Ti/Al) under same simulation process also has been simulated by ANSYS APDL as comparison to NiTi/Al. The simulation results show that compressive residual stress is generated on Al matrix of Ni/Al, Ti/Al and NiTi/Al during heating and cooling process. Besides that, they also have similar trend of residual stress distribution but difference in term of value. For Ni/Al and Ti/Al, they are 0.4% difference on their maximum compressive residual stress at 363K. At same circumstance, NiTi/Al has higher residual stress value which is about 425% higher than Ni/Al and Ti/Al composite. This implies that shape memory effect of NiTi fiber reinforced in composite able to generated higher compressive residual stress in Al matrix, hence able to enhance tensile property of the composite.
Waltz, R. E.; Staebler, G. M.; Solomon, W. M.
2011-04-15
Residual stress refers to the remaining toroidal angular momentum (TAM) flux (divided by major radius) when the shear in the equilibrium fluid toroidal velocity (and the velocity itself) vanishes. Previously [Waltz et al., Phys. Plasmas 14, 122507 (2007); errata 16, 079902 (2009)], we demonstrated with GYRO [Candy and Waltz, J. Comp. Phys. 186, 545 (2003)] gyrokinetic simulations that TAM pinching from (ion pressure gradient supported or diamagnetic level) equilibrium ExB velocity shear could provide some of the residual stress needed to support spontaneous toroidal rotation against normal diffusive loss. Here we show that diamagnetic level shear in the intrinsic drift wave velocities (or ''profile shear'' in the ion and electron density and temperature gradients) provides a comparable residual stress. The individual signed contributions of these small (rho-star level) ExB and profile velocity shear rates to the turbulence level and (rho-star squared) ion energy transport stabilization are additive if the rates are of the same sign. However because of the additive stabilization effect, the contributions to the small (rho-star cubed) residual stress is not always simply additive. If the rates differ in sign, the residual stress from one can buck out that from the other (and in some cases reduce the stabilization.) The residual stress from these diamagnetic velocity shear rates is quantified by the ratio of TAM flow to ion energy (power) flow (M/P) in a global GYRO core simulation of a ''null'' toroidal rotation DIII-D [Mahdavi and Luxon, Fusion Sci. Technol. 48, 2 (2005)] discharge by matching M/P profiles within experimental uncertainty. Comparison of global GYRO (ion and electron energy as well as particle) transport flow balance simulations of TAM transport flow in a high-rotation DIII-D L-mode quantifies and isolates the ExB shear and parallel velocity (Coriolis force) pinching components from the larger ''diffusive'' parallel velocity shear driven component and
Nondestructive evaluation of near-surface residual stress in shot-peened nickel-base superalloys
NASA Astrophysics Data System (ADS)
Yu, Feng
Surface enhancement methods, which produce beneficial compressive residual stresses and increased hardness in a shallow near-surface region, are widely used in a number of industrial applications, including gas-turbine engines. Nondestructive evaluation of residual stress gradients in surface-enhanced materials has great significance for turbine engine component life extension and their reliability in service. It has been recently found that, in sharp contrast with most other materials, shot-peened nickel-base superalloys exhibit an apparent increase in electrical conductivity at increasing inspection frequencies, which can be exploited for nondestructive residual stress assessment. The primary goal of this research is to develop a quantitative eddy current method for nondestructive residual stress profiles in surface-treated nickel-base superalloys. Our work have been focused on five different aspects of this issue, namely, (i) validating the noncontacting eddy current technique for electroelastic coefficients calibration, (ii) developing inversion procedures for determining the subsurface residual stress profiles from the measured apparent eddy current conductivity (AECC), (iii) predicting the adverse effect of surface roughness on the eddy current characterization of shot-peened metals, (iv) separating excess AECC caused by the primary residual stress effect from intrinsic conductivity variations caused by material inhomogeneity, and (v) investigating different mechanisms through which cold work could influence the AECC in surface-treated nickel-base superalloys. The results of this dissertation have led to a better understanding of the underlying physical phenomenon of the measured excess AECC on nickel-base engine alloys, and solved a few critical applied issues in eddy current nondestructive residual stress assessment in surface-treated engine components and, ultimately, contributed to the better utilization and safer operation of the Air Force's aging
NASA Technical Reports Server (NTRS)
Gabb, Timothy P.; Danetti, Andrew; Draper, Susan L.; Locci, Ivan E.; Telesman, Jack
2016-01-01
The fatigue lives of disk superalloys can be increased by shot peening their surfaces, to induce compressive residual stresses near the surface that impede cracking there. As disk application temperatures increase for improved efficiency, the persistence of these beneficial stresses could be impaired, especially with continued fatigue cycling. The objective of this work was to study the retention of residual stresses introduced by shot peening, when subjected to fatigue and high temperatures. Fatigue specimens of powder metallurgy processed nickel-base disk superalloy ME3 were prepared with consistent processing and heat treatment. They were then shot peened using varied conditions. Strain-controlled fatigue cycles were run at room temperature and 704 C, to allow re-assessment of residual stresses.
Vibration of piezoelectric nanobeams with an internal residual stress and a nonlinear strain
NASA Astrophysics Data System (ADS)
Jiang, Hao; Wang, Chengyuan; Luo, Ying
2015-10-01
This Letter reports the effect of an internal residual stress and the local geometric nonlinearity on the vibration of piezoelectric nanowires (NWs). A dynamic equation is derived based on Hamilton's principle, which enables one to capture the above-mentioned effects and the influence of all lateral surfaces of a rectangular NW. Vibration frequencies are obtained for the NWs under an electrical voltage and compared with those given by the existing Young-Laplace model where zero internal stress, a linear strain and the effects of top and bottom surfaces of rectangular NWs are considered. It is found that the internal residual stress can extinguish the effect of the surface-induced residual stress and substantially down shift the frequency or qualitatively alter the size-dependence of the frequency. In addition, with a nonlinear strain the piezoelectric effect is found to be able to exert a direct impact on the bending stiffness of piezoelectric NWs.
NASA Technical Reports Server (NTRS)
Lin, Shih-Yung; Hoffman, Eric K.; Domack, Marcia S.
2007-01-01
2-D thermo-mechanical model developed to characterize distortion and residual stresses in integral structure produced by DMD. Demonstrated as a tool to guide experimental development of DMD fabrication process for aero structures. Distortion and residual stresses are local to deposit. Most distortion develops during deposition of the first few layers; Little change in distortion or residual stresses after fifth deposit layer Most of distortion is localized just beneath the build. Thicker build plates and the use of build lands results in greatest decrease in levels of distortion. Pre-straining shown to reduce distortion. Difficult to implement, particularly for complex stiffener arrays. Clamp position has complex effect on distortion and stresses. Overall distortion reduced with decreasing clamp clearance. Larger clamp clearances induce bending. Use of pre-heat and active cooling show minor influence on panel distortion. Generate changes in thermal gradients in the build plate.
Finite Element Simulation of Residual Stress Development in Thermally Sprayed Coatings
NASA Astrophysics Data System (ADS)
Elhoriny, Mohamed; Wenzelburger, Martin; Killinger, Andreas; Gadow, Rainer
2017-04-01
The coating buildup process of Al2O3/TiO2 ceramic powder deposited on stainless-steel substrate by atmospheric plasma spraying has been simulated by creating thermomechanical finite element models that utilize element death and birth techniques in ANSYS commercial software and self-developed codes. The simulation process starts with side-by-side deposition of coarse subparts of the ceramic layer until the entire coating is created. Simultaneously, the heat flow into the material, thermal deformation, and initial quenching stress are computed. The aim is to be able to predict—for the considered spray powder and substrate material—the development of residual stresses and to assess the risk of coating failure. The model allows the prediction of the heat flow, temperature profile, and residual stress development over time and position in the coating and substrate. The proposed models were successfully run and the results compared with actual residual stresses measured by the hole drilling method.
Finite Element Simulation of Residual Stress Development in Thermally Sprayed Coatings
NASA Astrophysics Data System (ADS)
Elhoriny, Mohamed; Wenzelburger, Martin; Killinger, Andreas; Gadow, Rainer
2017-03-01
The coating buildup process of Al2O3/TiO2 ceramic powder deposited on stainless-steel substrate by atmospheric plasma spraying has been simulated by creating thermomechanical finite element models that utilize element death and birth techniques in ANSYS commercial software and self-developed codes. The simulation process starts with side-by-side deposition of coarse subparts of the ceramic layer until the entire coating is created. Simultaneously, the heat flow into the material, thermal deformation, and initial quenching stress are computed. The aim is to be able to predict—for the considered spray powder and substrate material—the development of residual stresses and to assess the risk of coating failure. The model allows the prediction of the heat flow, temperature profile, and residual stress development over time and position in the coating and substrate. The proposed models were successfully run and the results compared with actual residual stresses measured by the hole drilling method.
Final Report: Characterization of Canister Mockup Weld Residual Stresses
Enos, David; Bryan, Charles R.
2016-12-01
Stress corrosion cracking (SCC) of interim storage containers has been indicated as a high priority data gap by the Department of Energy (DOE) (Hanson et al., 2012), the Electric Power Research Institute (EPRI, 2011), the Nuclear Waste Technical Review Board (NWTRB, 2010a), and the Nuclear Regulatory Commission (NRC, 2012a, 2012b). Uncertainties exist in terms of the environmental conditions that prevail on the surface of the storage containers, the stress state within the container walls associated both with weldments as well as within the base metal itself, and the electrochemical properties of the storage containers themselves. The goal of the work described in this document is to determine the stress states that exists at various locations within a typical storage canister by evaluating the properties of a full-diameter cylindrical mockup of an interim storage canister. This mockup has been produced using the same manufacturing procedures as the majority of the fielded spent nuclear fuel interim storage canisters. This document describes the design and procurement of the mockup and the characterization of the stress state associated with various portions of the container. It also describes the cutting of the mockup into sections for further analyses, and a discussion of the potential impact of the results from the stress characterization effort.
Analysis of tempering stresses in bilayered porcelain discs.
DeHoff, P H; Anusavice, K J
1992-05-01
Previous studies of opaque-porcelain/body-porcelain discs have shown that compressive stresses which develop in the porcelain surface by being tempered in air can inhibit the sizes of cracks induced within the surface. The objective of this study was to develop a theoretical model for analysis of transient and residual stresses in opaque-porcelain/body-porcelain discs which were produced under variable cooling conditions. The model incorporates the effects of stress and structural relaxation. Transient and residual stresses were calculated for bilayered porcelain discs 16 mm in diameter and 2 mm in thickness for three opaque-porcelain/body-porcelain combinations. Transient temperature distributions in the discs for simulated convective cooling were calculated by finite-element analysis. Data from microhardness indentations reported by Anusavice et al. (1989) indicate that crack lengths measured for bilayered porcelain discs subjected to slow cooling conditions, for which the model predicted residual tensile stresses, were greater than those combinations for which residual compressive stresses were calculated. Calculated values of residual compressive stress for tempered specimens were considerably higher than those for specimens that were slowly cooled and those that were cooled by free convection. In general, residual stress levels calculated by use of the analytical model were in fairly good agreement with the trends observed for crack lengths and bi-axial flexural strengths reported by Anusavice and Hojjatie (1991). The results of the present study indicate that a visco-elastic model is a viable approach for determination of transient and residual stresses in opaque-porcelain/body-porcelain discs.
X-ray diffraction measurement of residual stresses in delta plutonium
Steinmeyer, P.A.
1990-09-11
Residual stresses in delta plutonium can be measured by the x-ray diffractometer method. This was accomplished with the aid of an experimental tantalum x-ray target. Preliminary experiments are encouraging and indicate that stresses may be determined precisely and rapidly. Future work will involve determination of x-ray elastic constants, instrument calibration with stress-free standards, higher x-ray power and more sophisticated monochromatization methods. 4 refs., 4 figs., 1 tab.
Development of ultrasonic tomography for residual stress mapping. Final report
Boland, A.J.; Davis, T.J.; Doctor, S.R.; Harrington, T.P.; Hildebrand, B.P.; Lemon, D.K.; Posakony, G.J.; Skorpik, J.R.
1980-05-01
The volumetric stress distribution in nuclear reactor piping and pressure vessels is becoming an increasingly important parameter in nondestructive evaluation. This report describes research and development of instrumentation leading toward a means of measuring subsurface stress distributions in metals. Based on the principles of Computerized Tomography (CT), an ultrasonic tomographic instrument system has been developed. The microprocessor-based system uses an ultrasonic linear array to acquire time-of-flight data to an accuracy of 0.5 to 1.0 ns. The data is processed using a modified ART (Algebraic Reconstruction Technique) program. A two-dimensional map of the velocity distribution is displayed on a monitor. The velocity distribution is interpreted or calibrated in terms of stress through the acousto-elastic coefficients.
Accelerated crack growth, residual stress, and a cracked zinc coated pressure shell
NASA Technical Reports Server (NTRS)
Dittman, Daniel L.; Hampton, Roy W.; Nelson, Howard G.
1987-01-01
During a partial inspection of a 42 year old, operating, pressurized wind tunnel at NASA-Ames Research Center, a surface connected defect 114 in. long having an indicated depth of a 0.7 in. was detected. The pressure shell, constructed of a medium carbon steel, contains approximately 10 miles of welds and is cooled by flowing water over its zinc coated external surface. Metallurgical and fractographic analysis showed that the actual detect was 1.7 in. deep, and originated from an area of lack of weld penetration. Crack growth studies were performed on the shell material in the laboratory under various loading rates, hold times, and R-ratios with a simulated shell environment. The combination of zinc, water with electrolyte, and steel formed an electrolytic cell which resulted in an increase in cyclic crack growth rate by as much as 500 times over that observed in air. It was concluded that slow crack growth occurred in the pressure shell by a combination of stress corrosion cracking due to the welding residual stress and corrosion fatigue due to the cyclic operating stress.
Magnetomechanical Acoustic Emission for Residual Stress and Prior Strain Determination.
1979-10-01
cyanoacrylate glue . Resonant transducers with six different center frequencies were used in the study. These were manufactured by AET, Sacramento, CA. and...utilized a floor model Instron. MAE behavior of materials at zero stress was also tested in an all wood sample support. Results were identical to those
Local surface skimming longitudinal wave velocity and residual stress mapping.
Sathish, Shamachary; Martin, Richard W; Moran, Thomas J
2004-01-01
Local variation in surface skimming longitudinal wave (SSLW) velocity has been measured using a scanning acoustic microscope. A very narrow width electrical impulse has been used to excite the transducer of the acoustic lens. This permits the separation of the SSLW signal from the direct reflected signal in the time domain. A simple method of measuring the time delay between the directly reflected signal and the SSLW signal at two defocuses has been utilized for the local measurement of SSLW velocity. The variation in the SSLW velocity measured over an area of the sample is scaled and presented as an image. The method has been implemented to image the variation of the SSLW velocity around a crack tip in a sample of Ti-6Al-4V. Since the SSLW velocity is known to change linearly with the stress, the SSLW velocity image is considered as a representation of the image of stress around the crack tip. Local stress variation in the same region of the crack tip is directly measured using x-ray diffraction. The SSLW velocity image is compared with the x-ray diffraction stress image. The contrast in the two images, spatial resolution, and the penetration depth into the sample of acoustic waves and x rays are discussed.
A new nondestructive instrument for bulk residual stress measurement using tungsten kα1 X-ray
NASA Astrophysics Data System (ADS)
Ma, Ce; Dou, Zuo-yong; Chen, Li; Li, Yun; Tan, Xiao; Dong, Ping; Zhang, Jin; Zheng, Lin; Zhang, Peng-cheng
2016-11-01
We describe an experimental instrument used for measuring nondestructively the residual stress using short wavelength X-ray, tungsten kα1. By introducing a photon energy screening technology, the monochromatic X-ray diffraction of tungsten kα1 was realized using a CdTe detector. A high precision Huber goniometer is utilized in order to reduce the error in residual stress measurement. This paper summarizes the main performance of this instrument, measurement depth, stress error, as opposed to the neutron diffraction measurements of residual stress. Here, we demonstrate an application on the determination of residual stress in an aluminum alloy welded by the friction stir welding.
A new nondestructive instrument for bulk residual stress measurement using tungsten kα1 X-ray.
Ma, Ce; Dou, Zuo-Yong; Chen, Li; Li, Yun; Tan, Xiao; Dong, Ping; Zhang, Jin; Zheng, Lin; Zhang, Peng-Cheng
2016-11-01
We describe an experimental instrument used for measuring nondestructively the residual stress using short wavelength X-ray, tungsten kα1. By introducing a photon energy screening technology, the monochromatic X-ray diffraction of tungsten kα1 was realized using a CdTe detector. A high precision Huber goniometer is utilized in order to reduce the error in residual stress measurement. This paper summarizes the main performance of this instrument, measurement depth, stress error, as opposed to the neutron diffraction measurements of residual stress. Here, we demonstrate an application on the determination of residual stress in an aluminum alloy welded by the friction stir welding.
Measurement of residual stress in quenched 1045 steel by the nanoindentation method
Zhu Lina; Xu Binshi; Wang Haidou; Wang Chengbiao
2010-12-15
In this paper, the residual stress in quenched AISI 1045 steel was measured by a recently developed nanoindentation technique. Depth control mode was adopted to measure the residual stress. It was found that residual compressive stress was generated in the quenched steel. The material around nanoindents exhibits significant pile-up deformation. A new method was proposed to determine the real contact area for pile-up material on the basis of invariant pile-up morphology of the loaded or unloaded states. The results obtained by the new method were in good agreement with the residual stresses measured by the classical X-ray diffraction (XRD) method. - Research Highlights: {yields} A new method was proposed to measure the real contact area for pile-up materials. {yields} The real contact depth is defined as the sum of h{sub max} and the pile-up height h{sub p}. {yields} The value of residual stress measured by the nanoindentation method was in good agreement with that by the XRD method.
NASA Astrophysics Data System (ADS)
Evans, Alexander Dominic; King, Andrew; Pirling, Thilo; Peyre, Patrice; Withers, Phillip John
The fatigue behaviour of engineering alloys can be significantly improved through the application of mechanical surface treatments. These processes generate significant compressive residual stresses near surface by inhomogeneous plastic deformation. In the case of mechanical surface treatments such as laser shock peening, certain burnishing and rolling techniques and ultrasonic impact treatment (UIT), the compressive residual stress layer can extend to a depth of the order of millimeters, with balancing tensile stresses located deeper. Techniques to characterise the residual stresses generated by such mechanical surface treatments non-destructively are mainly limited to diffraction methods using penetrating neutron and synchrotron X-ray radiations. The application of these radiation sources is illustrated here by the characterisation of residual strain distributions in a two types of specimens treated with laser shock peening (LSP). Analyses of diffraction peak broadening provide qualitative information concerning the depth to which the plastic deformation of the treatments extends. Two case studies of laser shock peening of titanium and aluminium alloys is presented to demonstrate the capabilities of neutron and synchrotron diffraction techniques in the field of residual stress characterisation of surface engineered material non-destructively.
NASA Astrophysics Data System (ADS)
Wang, Chengxi; Jiang, Chuanhai; Zhao, Yuantao; Chen, Ming; Ji, Vincent
2017-10-01
As one of the most important surface strengthening method, shot peening is widely used to improve the fatigue and stress corrosion crack resistance of components by introducing the refined microstructure and compressive residual stress in the surface layer. However, the mechanical properties of this thin layer are different from the base metal and are difficult to be characterized by conventional techniques. In this work, a micro uniaxial tensile tester equipped with in-situ X-ray stress analyzer was employed to make it achievable on a nickel-aluminum bronze with shot peening treatment. According to the equivalent stress-strain relationship based on Von Mises stress criterion, the Young's modulus and yield strength of the peened layer were calculated. The results showed that the Young's modulus was the same as the bulk material, and the yield strength corresponding to the permanent plastic strain of 0.2% was increased by 21% after SP. But the fractographic analysis showed that the fracture feature of the surface layer was likely to transform from the dimple to the cleavage, indicating the improved strength might be attained at the expense of ductility. The monotonic and cyclic loading were also performed via the same combined set-up. In addition, the specific relaxation behavior of compressive residual stress was quantified by linear logarithm relationship between residual stress and cycle numbers. It was found that the compressive residual stress mainly relaxed in the first few cycles, and then reached steady state with further cycles. The relaxation rate and the stable value were chiefly depended on the stress amplitude and number of cycles. The retained residual stress kept in compressive under all given applied stress levels, suggesting that the shot peening could introduce a more stable surface layer of compressive residual stress other than the elevated strength of nickel-aluminum bronze alloy.
Hydration and radiation effects on the residual stress state of cortical bone.
Tung, Patrick K M; Mudie, Stephen; Daniels, John E
2013-12-01
The change in the biaxial residual stress state of hydroxyapatite crystals and collagen fibrillar structure in sections of bovine cortical bone has been investigated as a function of dehydration and radiation dose using combined small- and wide-angle X-ray scattering. It is shown that dehydration of the bone has a pronounced effect on the residual stress state of the crystalline phase, while the impact of radiation damage alone is less dramatic. In the initial hydrated state, a biaxial compressive stress of approximately -150 MPa along the bone axis exists in the hydroxyapatite crystals. As water evaporates from the bone material, the stress state moves to a tensile state of approximately 100 MPa. The collagen fibrillar structure is initially in a tensile residual stress state when the bone is hydrated and the state increases in magnitude slightly with dehydration. Radiation dose in continually hydrated samples also reduces the initial biaxial compressive stress magnitude in the hydroxyapatite phase; however, the stress remains compressive. Radiation exposure alone does not appear to affect the stress state of the collagen fibrillar structure.
Mapping residual stresses after foreign object damage using the contour method
Prime, M. B.; Martineau, R. L.
2002-01-01
A 51-mm thick plate of High-Strength Low-Alloy (HSLA-100) steel was impacted by a 6.4 mm diameter tungsten carbide sphere traveling at 2.2 km/sec. The projectile penetration left a 10 mm diameter and 12 mm deep crater. A residual stress map over a cross-section through the crater was measured by the contour method. The predominant feature of the stress map was a peak compressive stress of 900 MPa, or 1.3 times the yield strength, centered about 1.5 crater radii below the crater floor. The results were compared with an explicit finite element simulation of the impact event. The model has good agreement with the measured residual stresses. As part of the study, residual stresses in the as-received HSLA-100 plate were also measured and found to be a typical quenching stress distribution with peak compressive stress of about 165 MPa a few mm below the surface and tensile stress of 200 MPa in the center of the plate thickness.
Residual stresses in a shape welded steel tube by neutron diffraction
NASA Astrophysics Data System (ADS)
Taran, Yu V.; Balagurov, A. M.; Schreiber, J.; Stuhr, U.
2008-03-01
Measurements of the triaxial residual strains in a composite tube from an austenitic stainless steel as a parent material and a shape welded ferritic steel were carried out by the time-of-flight neutron diffraction method on the POLDI instrument at the PSI SINQ neutron pulsed facility. The shape weld is used to build compressive stresses and, as a result, to suppress stress corrosion. Investigations of the residual stresses in such composite tubes are important for developing optimal welding techniques. Calculation of the residual stresses was performed using measurement results with a comb-sample, machined from the tube by the electro-discharge method, as the stress free reference sample. The results of the POLDI measurements of the stress state in the composite tube are presented and compared to the results of the destructive turning out method and theoretical predictions of calculations by the finite element method. Semiquantitative agreement between all the used methods was only observed for the tangential component of the stress tensor. In this case, the ferrite cladding produced a tangential compressive stress of about 800 MPa on the austenitic tube.
Practical Application of Residual Stress Measurements on Maritime Vessels
2012-06-01
overall weight of the vessel. To get a reduction in weight without reducing functionality , the strategy has been to replace structural components...marine functions . While 5000 series aluminum has the required strength and while it is vulnerable to SCC it retains enough resistance to be useable...aluminum versus steel when aluminum is already has a much smaller resistance to fracture. These stresses can be calculated as a function of the
NASA Astrophysics Data System (ADS)
Rusakov, A. D.
2010-05-01
The results of contact resistance tests of roll steel samples with various levels of near-surface residual compressive stresses are analyzed. A relation between these stresses and the contact resistance is found. Recommendations are made for the formation of rational near-surface residual stresses in the active surfaces of rolls in order to increase their resistance.
1989-03-01
and the resulting x-ray stresses and error bands leads to several general conclusions: 1) The x-ray stresses (prior to yielding) in virtually all...cN IA __II____ I I I I .9-I LI I elIiAL O O 6p 0 .- .4 r� IS C -Wn FFTF ~F~rF1TFTFFTF~jH ~ U. N IA 35 NADC-88141-60 (Volume 1) 150 - Ti -6A - 4V...porportional counter, mounting brackets, and shaft encoder and motor drive assemblies . Alignment of the sample with respect to the center of rotation
Residual Stress Determination for A Ferritic Steel Weld Plate
Wang, D.-Q.; Hubbard, C.R.; Spooner, S.
1999-10-01
The primary objective of this experiment is to demonstrate the capability of neutron diffraction technique to reproducibly map residual strains in a ferritic steel weld. The objective includes the identification of corrections for variations in metal composition due to the welding process which produces changes in lattice parameter that are not due to mechanical effects. The second objective is to develop and demonstrate a best practice for neutron diffraction strain mapping of steel welds. The appropriate coordinate system for the measurement of a weld, which is strongly distorted from planar geometry, has to be defined. The coordinate system is important in determining the procedures for mounting and positioning of the weld so that mapping details, especially in regions of high gradients, can be conveniently inter-compared between laboratories.
The Effect of Weld Residual Stress on Life of Used Nuclear Fuel Dry Storage Canisters
Ronald G. Ballinger; Sara E. Ferry; Bradley P. Black; Sebastien P. Teysseyre
2013-08-01
With the elimination of Yucca Mountain as the long-term storage facility for spent nuclear fuel in the United States, a number of other storage options are being explored. Currently, used fuel is stored in dry-storage cask systems constructed of steel and concrete. It is likely that used fuel will continue to be stored at existing open-air storage sites for up to 100 years. This raises the possibility that the storage casks will be exposed to a salt-containing environment for the duration of their time in interim storage. Austenitic stainless steels, which are used to construct the canisters, are susceptible to stress corrosion cracking (SCC) in chloride-containing environments if a continuous aqueous film can be maintained on the surface and the material is under stress. Because steel sensitization in the canister welds is typically avoided by avoiding post-weld heat treatments, high residual stresses are present in the welds. While the environment history will play a key role in establishing the chemical conditions for cracking, weld residual stresses will have a strong influence on both crack initiation and propagation. It is often assumed for modeling purposes that weld residual stresses are tensile, high and constant through the weld. However, due to the strong dependence of crack growth rate on stress, this assumption may be overly conservative. In particular, the residual stresses become negative (compressive) at certain points in the weld. The ultimate goal of this research project is to develop a probabilistic model with quantified uncertainties for SCC failure in the dry storage casks. In this paper, the results of a study of the residual stresses, and their postulated effects on SCC behavior, in actual canister welds are presented. Progress on the development of the model is reported.
Residual stress brazing process induced in hybrid package for ISP applications
NASA Astrophysics Data System (ADS)
Monti, Riccardo; Coppola, Francesco; Gasbarri, Paolo; Lecci, Umberto
2010-03-01
One of the most used components in the RF transmission devices mounted on satellite antennas are the ISP modules. They are designed by exploiting hybrid materials technology to improve their operative characteristics. In particular they are made up of a metallic carrier, a ceramic substrate, a metallic frame and a metallic cover. Inside the ceramic substrate metallic circuits and vias they are allocated to connect microelectronic components fixed on the external surface of the substrate of RF transmission modules. Metallic cover is one of the most delicate elements of the package because it must provide for the tightness of the assembly. The cover is welded to the frame by seam-welding technique. In order to assembly ceramic substrate and metallic frame a brazing process must be carried out. This brazing process introduces residual stresses at the end of the welding process. These residual stresses induced by the thermal cycles could cause crack growth and eventually a component fracture during the operating life of the satellite. In order to foresee their criticality, qualification tests, based on MIL standard, are mandatory. This MIL procedure establishes that the package must be thermally cycled with 500 cycles in the range of 223K≤398K. On account of this, thermal loads, associated to thermal cycles, may cause fractures in ceramic substrate and the failure of electronic components. In this paper a numerical approach able to simulate all the brazing process and to evaluate numerically all the stresses inside the ISP module will be proposed. Parametric studies on thermal loadings and on geometrical characteristics of the brazing subcomponents such as the metallic carrier, the ceramic substrate, the metallic frame and the metallic cover in order to evaluate maximum and critical stresses will be also presented. To perform such numerical analysis laboratory tests such as DMA have been carried out and detailed in the paper. The aim of these tests is to characterize
NASA Astrophysics Data System (ADS)
Prabhu-Gaunkar, Gajanana; Rawat, M. S.; Prasad, C. R.
2014-02-01
Steam turbine blades in power generation equipment are made from martensitic stainless steels having high strength, good toughness and corrosion resistance. However, these steels are susceptible to pitting which can promote early failures of blades in the turbines, particularly in the low pressure dry/wet areas by stress corrosion and corrosion fatigue. Presence of tensile residual stresses is known to accelerate failures whereas compressive stresses can help in delaying failures. Shot peening has been employed as an effective tool to induce compressive residual stresses which offset a part of local surface tensile stresses in the surface layers of components. Maintaining local stresses at stress raisers, such as pits formed during service, below a threshold level can help in preventing the initiation microcracks and failures. The thickness of the layer in compression will, however, depend of the shot peening parameters and should extend below the bottom of corrosion pits. The magnitude of surface compressive drops progressively during service exposure and over time the effectiveness of shot peening is lost making the material susceptible to micro-crack initiation once again. Measurement and monitoring of surface residual stress therefore becomes important for assessing residual life of components in service. This paper shows the applicability of surface stress monitoring to life assessment of steam turbine blade material based on data generated in laboratory on residual surface stress measurements in relation to fatigue exposure. An empirical model is proposed to calculate the remaining life of shot peened steam turbine blades in service.
Validating a Model for Welding Induced Residual Stress Using High-Energy X-ray Diffraction
NASA Astrophysics Data System (ADS)
Mach, J. C.; Budrow, C. J.; Pagan, D. C.; Ruff, J. P. C.; Park, J.-S.; Okasinski, J.; Beaudoin, A. J.; Miller, M. P.
2017-03-01
Integrated computational materials engineering (ICME) provides a pathway to advance performance in structures through the use of physically-based models to better understand how manufacturing processes influence product performance. As one particular challenge, consider that residual stresses induced in fabrication are pervasive and directly impact the life of structures. For ICME to be an effective strategy, it is essential that predictive capability be developed in conjunction with critical experiments. In the present work, simulation results from a multi-physics model for gas metal arc welding are evaluated through x-ray diffraction using synchrotron radiation. A test component was designed with intent to develop significant gradients in residual stress, be representative of real-world engineering application, yet remain tractable for finely spaced strain measurements with positioning equipment available at synchrotron facilities. The experimental validation lends confidence to model predictions, facilitating the explicit consideration of residual stress distribution in prediction of fatigue life.
Validating a Model for Welding Induced Residual Stress Using High-Energy X-ray Diffraction
NASA Astrophysics Data System (ADS)
Mach, J. C.; Budrow, C. J.; Pagan, D. C.; Ruff, J. P. C.; Park, J.-S.; Okasinski, J.; Beaudoin, A. J.; Miller, M. P.
2017-05-01
Integrated computational materials engineering (ICME) provides a pathway to advance performance in structures through the use of physically-based models to better understand how manufacturing processes influence product performance. As one particular challenge, consider that residual stresses induced in fabrication are pervasive and directly impact the life of structures. For ICME to be an effective strategy, it is essential that predictive capability be developed in conjunction with critical experiments. In the present work, simulation results from a multi-physics model for gas metal arc welding are evaluated through x-ray diffraction using synchrotron radiation. A test component was designed with intent to develop significant gradients in residual stress, be representative of real-world engineering application, yet remain tractable for finely spaced strain measurements with positioning equipment available at synchrotron facilities. The experimental validation lends confidence to model predictions, facilitating the explicit consideration of residual stress distribution in prediction of fatigue life.
Study of Residual Stress and Vacancy Defects in Oxide Dispersion Strengthened Steels
NASA Astrophysics Data System (ADS)
Slugeň, V.; Veterníková, J.; Kilpeläinen, S.; Tuomisto, F.
This study was focused on commercial oxide-dispersion strengthened (ODS) steels -MA 956 (20%Cr), ODM 751 (16%Cr) and ODS Eurofer (9%Cr), developed for fuel cladding of GEN IV reactors. The ODS steels are described in order to comparison their microstructure features. Vacancy defects were observed by Doppler Broadening Spectroscopy (DBS) and Positron Annihilation Lifetime Spectroscopy (PALS). Residual stress proportional to all kinds of defects was investigated by Magnetic Barkhausen Noise (MBN) measurement. The positron techniques demonstrated the highest defect concentration for ODS Eurofer followed by MA 956. The lowest defect density belongs to ODM 751; although these defects are the largest (three or four vacancy clusters). MA 956 and ODS Eurofer have di-vacancies in predominance. MBN results are in a good accordance with positron techniques. The highest residual stress is for ODS Eurofer, followed by MA 956. Finally, the lowest residual stress proportional to hardness is found for ODM 751.
Validating a Model for Welding Induced Residual Stress Using High-Energy X-ray Diffraction
Mach, J. C.; Budrow, C. J.; Pagan, D. C.; ...
2017-03-15
Integrated computational materials engineering (ICME) provides a pathway to advance performance in structures through the use of physically-based models to better understand how manufacturing processes influence product performance. As one particular challenge, consider that residual stresses induced in fabrication are pervasive and directly impact the life of structures. For ICME to be an effective strategy, it is essential that predictive capability be developed in conjunction with critical experiments. In the present paper, simulation results from a multi-physics model for gas metal arc welding are evaluated through x-ray diffraction using synchrotron radiation. A test component was designed with intent to developmore » significant gradients in residual stress, be representative of real-world engineering application, yet remain tractable for finely spaced strain measurements with positioning equipment available at synchrotron facilities. Finally, the experimental validation lends confidence to model predictions, facilitating the explicit consideration of residual stress distribution in prediction of fatigue life.« less
Properties of low residual stress silicon oxynitrides used as a sacrificial layer
Habermehl, S.D.; Glenzinski, A.K.; Halliburton, W.M.; Sniegowski, J.J.
2000-01-04
Low residual stress silicon oxynitride thin films are investigated for use as a replacement for silicon dioxide (SiO{sub 2}) as sacrificial layer in surface micromachined microelectrical-mechanical systems (MEMS). It is observed that the level of residual stress in oxynitrides is a function of the nitrogen content in the film. MEMS film stacks are prepared using both SiO{sub 2} and oxynitride sacrificial layers. Wafer bow measurements indicate that wafers processed with oxynitride release layers are significantly flatter. Polycrystalline Si (poly-Si) cantilevers fabricated under the same conditions are observed to be flatter when processed with oxynitride rather than SiO{sub 2} sacrificial layers. These results are attributed to the lower post-processing residual stress of oxynitride compared to SiO{sub 2} and reduced thermal mismatch to poly-Si.
Bi-Metallic Composite Structures With Designed Internal Residual Stress Field
NASA Technical Reports Server (NTRS)
Brice, Craig A.
2014-01-01
Shape memory alloys (SMA) have a unique ability to recover small amounts of plastic strain through a temperature induced phase change. For these materials, mechanical displacement can be accomplished by heating the structure to induce a phase change, through which some of the plastic strain previously introduced to the structure can be reversed. This paper introduces a concept whereby an SMA phase is incorporated into a conventional alloy matrix in a co-continuous reticulated arrangement forming a bi-metallic composite structure. Through memory activation of the mechanically constrained SMA phase, a controlled residual stress field is developed in the interior of the structure. The presented experimental data show that the memory activation of the SMA composite component significantly changes the residual stress distribution in the overall structure. Designing the structural arrangement of the two phases to produce a controlled residual stress field could be used to create structures that have much improved durability and damage tolerance properties.
Calculation of residual principal stresses in CVD boron on carbon filaments
NASA Technical Reports Server (NTRS)
Behrendt, D. R.
1980-01-01
A three-dimensional finite element model of the chemical vapor deposition (CVD) of boron on a carbon substrate (B/C) is developed. The model includes an expansion of the boron after deposition due to atomic rearrangement and includes creep of the boron and carbon. Curves are presented to show how the principal residual stresses and the filament elongation vary as the parameters defining deposition strain and creep are varied. The calculated results are compared with experimental axial residual stress and elongation measurements made on B/C filaments. This comparison requires that for good agreement between calculated and experimental results, the deposited boron must continue to expand after deposition, and that the build-up of residual stresses is limited by significant boron and carbon creep rates.
Calculation of residual principal stresses in CVD boron on carbon filaments
NASA Technical Reports Server (NTRS)
Behrendt, D. R.
1980-01-01
A three-dimensional finite element model of the chemical vapor deposition of boron on a carbon substrate (B/C) is developed. The model includes an expansion of the boron after deposition due to atomic rearrangement and includes creep of the boron and carbon. Curves are presented showing the variation of the principal residual stresses and the filament elongation with the parameters defining deposition strain and creep. The calculated results are compared with experimental axial residual stress and elongation measurements made on B/C filaments. For good agreement between calculated and experimental results, the deposited boron must continue to expand after deposition, and the build up of residual stresses must be limited by significant boron and carbon creep rates.
Influence of Residual Stresses on Fretting Fatigue Life Prediction in Ti-6Al-4V (POSTPRINT)
2008-01-01
DATE (DD-MM-YY) 2. REPORT TYPE 3. DATES COVERED (From - To) January 2008 Journal Article Postprint 4 . TITLE AND SUBTITLE INFLUENCE OF RESIDUAL...62102F 6 . AUTHOR(S) Patrick J. Golden (AFRL/RXLMN) Dennis Buchanan (University of Dayton Research Institute) Sam Naboulsi (The University of...induced compressive residual stresses by methods such as shot-peening could also be disrupted by this plasticity. Manuscript received December 4 , 2007
Programmable calculator stress analysis
Van Gulick, L.A.
1983-01-01
This paper assesses the suitability of advanced programmable alphanumeric calculators for closed form calculation of pressure vessel stresses and offers, as their advantages, adequate computing power, portability, special programming features, and simple interactive execution procedures. Representative programs which demonstrate their capacities are presented. Problems dealing with stress and strength calculations in thick-walled pressure vessels and with the computation of stresses near head/pressure vessel junctures are treated. Assessed favorably in this paper as useful contributors to computeraided design of pressure vessels, programmable alphanumeric calculators have areas of implementation in checking finite element results, aiding in the development of an intuitive understanding of stresses and their parameter dependencies, and evaluating rapidly a variety of preliminary designs.
NASA Technical Reports Server (NTRS)
Brenner, Malcolm; Shipp, Thomas
1988-01-01
In a study of the validity of eight candidate voice measures (fundamental frequency, amplitude, speech rate, frequency jitter, amplitude shimmer, Psychological Stress Evaluator scores, energy distribution, and the derived measure of the above measures) for determining psychological stress, 17 males age 21 to 35 were subjected to a tracking task on a microcomputer CRT while parameters of vocal production as well as heart rate were measured. Findings confirm those of earlier studies that increases in fundamental frequency, amplitude, and speech rate are found in speakers involved in extreme levels of stress. In addition, it was found that the same changes appear to occur in a regular fashion within a more subtle level of stress that may be characteristic, for example, of routine flying situations. None of the individual speech measures performed as robustly as did heart rate.
NASA Astrophysics Data System (ADS)
Kohandehghan, A. R.; Serajzadeh, S.
2012-06-01
This study concentrates on the effects of weld sequence and welding fixtures on distribution and magnitude of induced arc welding residual stresses built up in butt-joint of Gas Tungsten Arc Welding (GTAW) AA5251 plates. Aluminum plates have been welded under different welding conditions and then, longitudinal and transverse residual stresses were measured in different points of the welded plates employing hole-drilling technique. The results indicate that welding sequence significantly alters the distributions of both longitudinal and transverse residual stresses while the changing in the weld sequence leads to 44% decrease in longitudinal residual stress. Besides, both the geometry of weld pool and distribution of residual stresses are affected by the welding fixtures while implementation of fixture causes about 21 and 76% reductions in the depth of weld pool and transverse residual stress, respectively, for the material and welding conditions used in this research.
Fluorine Implantation and Residual Stresses in Polysilicon Films
NASA Technical Reports Server (NTRS)
Lowery, Lynn; Zschack, Paul; Angelis, Robert De
1994-01-01
As microelectronic device dimensions are reduced below one micron, the hot carrier effect is a major barrier to continued scaling and VLSI reliability. Several reports have shown that fluorine diffusion into the device gate greatly enhances the resistance to hot carriers. There has been some disagreement as to the mechanism of influence; however, several reports have suggested that the polysilicon is physically modified by the fluorine implant and that the beneficial effects are at least in part due to stress relaxation in the polysilicon.
Residual stress, strain, and faults in nanocrystalline palladium and copper
Sanders, P.G.; Witney, A.B.; Weertman, J.R.; Valiev, R.Z.; Siegel, R.W.
1995-02-01
Nanocrystalline Pd and Cu, prepared by inert gas condensation and warm compaction, were studied using x-ray diffraction techniques. A sample of Cu with sub-micrometer grain size produced by severe plastic deformation was also examined. The Warren-Averbach technique was used to separate the line broadening due to grain size, root-mean-squared strain, and faults. Peak shifts and asymmetry were used to determine the long range surface stresses, stacking fault probability, and twin probability. The Young`s modulus of a Pd sample was determined by an ultrasonic technique, and compared with the coarse-grained, fully-dense value.
Fluorine Implantation and Residual Stresses in Polysilicon Films
NASA Technical Reports Server (NTRS)
Lowery, Lynn; Zschack, Paul; Angelis, Robert De
1994-01-01
As microelectronic device dimensions are reduced below one micron, the hot carrier effect is a major barrier to continued scaling and VLSI reliability. Several reports have shown that fluorine diffusion into the device gate greatly enhances the resistance to hot carriers. There has been some disagreement as to the mechanism of influence; however, several reports have suggested that the polysilicon is physically modified by the fluorine implant and that the beneficial effects are at least in part due to stress relaxation in the polysilicon.
Structural transformations in Mn{sub 2}NiGa due to residual stress
Singh, Sanjay; Maniraj, M.; D'Souza, S. W.; Barman, S. R.; Ranjan, R.
2010-02-22
Powder x-ray diffraction study of Mn{sub 2}NiGa ferromagnetic shape memory alloy shows the existence of a 7M monoclinic modulated structure at room temperature (RT). The structure of Mn{sub 2}NiGa is found to be highly dependent on residual stress. For higher stress, the structure is tetragonal at RT, and for intermediate stress it is 7M monoclinic. However, only when the stress is considerably relaxed, the structure is cubic, as is expected at RT since the martensitic transition temperature is 230 K.
Ultrasonic evaluation of residual stresses in rolled aluminum plate
Bray, Don E.; Kim, Seon-Jin; Fernandes, Micky
1999-12-02
The L{sub CR} ultrasonic technique has shown an ability to distinguish between three aluminum plates furnished by Kaiser Aluminum. The 1.22x1.19 m(48x47 in) plates are 19 mm (0.75 inch) thick, but differ in heat treatment and rolling conditions. One is fully annealed (O temper), the second was heat-treated to T651 temper, and the third is a stress relieved plate. Travel-times were obtained at twenty-five locations on each side of all plates. The O temper plate showed large travel-time differences between the sides, but the variation for a side was small. The heat-treated plate showed large differences both between the sides and on each side. The stress relieved plate, on the other hand, showed very uniform L{sub CR} travel-times both for the two sides and on each side. These preliminary results indicate that the L{sub CR} method may be further developed for use in quality control in the manufacture of rolled aluminum plates.
A mathematical model for the estimation of the effects of residual stresses in aluminum plates
NASA Astrophysics Data System (ADS)
Nervi, Sebastian
2005-07-01
A mathematical model for the prediction of distortion of parts machined from aluminum plates (in particular 7050-T7451 aluminum plates), caused by the bulk (or material) stresses, together with its resultant residual stress state is given. The proposed model is studied as the simplest model of a hierarchical model structure, its predictive capabilities are evaluated by following the verification and validation processes, consisting in assessment of numerical accuracy and experimental correlation. The good correlation between the numerical simulation and the experimental results imply that the proposed model provides an efficient tool to estimate the distortion and residual stress field of a part machined from aluminum plates, when the machining induced stress can be considered negligible. It is proven that, under this condition, the distortion of a part depends exclusively on the stress distribution within the plate and the shape and the through thickness location of the part. Therefore, the final distortion of a part can be predicted considering the initial state (i.e., the residual stress in the plate) and the final state (i.e., the shape and location of the machined part). Furthermore, a procedure to reduce the distortion caused by machining-induces stress is proposed.
Residual stresses and phase transformations in Ytterbium silicate environmental barrier coatings
NASA Astrophysics Data System (ADS)
Stolzenburg, Fabian
Due to their high melting temperature, low density, and good thermomechanical stability, silicon-based ceramics (SiC, Si3N4) are some of the most promising materials systems for high temperature structural applications in gas turbine engines. However, their silica surface layer reacts with water vapor contained in combustion environments. The resulting hydroxide layer volatilizes, leading to component recession. Environmental barrier coatings (EBCs) have been developed to shield the substrate from degradation. Next generation coatings for silicon-based ceramics based on ytterbium silicates have shown a promising combination of very low and good thermomechanical properties. The focus of this thesis is threefold: In the first part, phase transformations in plasma sprayed ytterbium silicates were investigated. Plasma sprayed materials are known to contain large amounts of amorphous material. Phase changes during the conversion from amorphous to crystalline materials were investigated as they have been known to lead to failure in many coatings. The second part of this work focused on measuring residual stresses in multilayer EBCs using synchrotron X-ray diffraction (XRD). Strains were resolved spatially, with probe sizes as small as 20 um. Stresses were calculated using mechanical properties of ytterbium silicates, determined with in-situ loading and heating experiments. In-situ and ex-situ heating experiments allowed for the study of changes in stress states that occur in these EBC materials during heating and cooling cycles. Lastly, the interaction of ytterbium silicates with low-melting environmental calcium-magnesium-aluminosilicate (CMAS) glasses was studied. Synchrotron XRD was used to study the influence of CMAS on the stress state in the coating, X-ray computed tomography was used to provide 3D images of coatings, and EDS and TEM analysis were used to study the interactions at the CMAS/ytterbium silicate interface in detail.
The measurement of X-ray residual stress in textured cubic materials
NASA Astrophysics Data System (ADS)
Gazzara, C. P.
1983-01-01
An X-ray diffraction procedure for measuring residual stress assumes a linear relationship between the d spacing and sin 2psi in isotropic materials. This study attempts to deal with the use of such a relationship in textured steel and aluminum using parallel beam optics. It was found that a phase difference occurs in the d spacing and the X-ray intensity of the CrK alpha diffraction peak with psi resulting in errors in computing the residual stress. Possible contributing factors are considered, such as systematic errors, specimen preparation, absorption, grain size, and the optical system employed.
NASA Technical Reports Server (NTRS)
Saravanos, D. A.; Chamis, C. C.; Morel, M.
1991-01-01
A methodology is presented to reduce the residual matrix stresses in continuous fiber metal matrix composites (MMC) by optimizing the fabrication process and interphase layer characteristics. The response of the fabricated MMC was simulated based on nonlinear micromechanics. Application cases include fabrication tailoring, interphase tailoring, and concurrent fabrication-interphase optimization. Two composite systems, silicon carbide/titanium and graphite/copper, are considered. Results illustrate the merits of each approach, indicate that concurrent fabrication/interphase optimization produces significant reductions in the matrix residual stresses and demonstrate the strong coupling between fabrication and interphase tailoring.
Myhr, O.R.; Kluken, A.O.; Klokkehaug, S.; Fjaer, H.G.; Grong, O.
1998-07-01
This article illustrates the applications of process modeling for prediction of microstructure evolution, residual stresses and distortions in welding of hollow AA6082-T6 extrusions. The model consists of three components, i.e., a numerical heat flow model, a microstructure model and a mechanical model that are sequentially coupled. It is shown that the model adequately predicts the temperature and local strength distribution. The calculated distortions were found to depend strongly on the welding sequence. Moreover, the local softening of the heat-affected zone was shown to have a significant effect on the simulated residual stress distribution.
Influence of physical parameters on residual stresses of polymer composites during the cure process
NASA Astrophysics Data System (ADS)
Wang, Hui; Feng, Jiemin; Guo, Zhansheng; Hu, Hongjiu; Zhang, Junqian
2011-11-01
A developed process model including the effects of chemical and thermal strains and the cure related elastic material behavior is established in order to simulate the cure process before cooling stage more realistically. A three-dimensional finite element method is used to analyze the effect of the curing related parameters on residual stresses in the cure progress of polymer composites. The obtained results show that the density, the specific heat, the thermal conductivity and the anisotropic chemical shrinkage have different influences on the final residual stresses before cooling stage.
Influence of physical parameters on residual stresses of polymer composites during the cure process
NASA Astrophysics Data System (ADS)
Wang, Hui; Feng, Jiemin; Guo, Zhansheng; Hu, Hongjiu; Zhang, Junqian
2012-04-01
A developed process model including the effects of chemical and thermal strains and the cure related elastic material behavior is established in order to simulate the cure process before cooling stage more realistically. A three-dimensional finite element method is used to analyze the effect of the curing related parameters on residual stresses in the cure progress of polymer composites. The obtained results show that the density, the specific heat, the thermal conductivity and the anisotropic chemical shrinkage have different influences on the final residual stresses before cooling stage.
Longitudinal residual strain and stress-strain relationship in rat small intestine.
Dou, Yanling; Fan, Yanhua; Zhao, Jingbo; Gregersen, Hans
2006-06-07
To obtain a more detailed description of the stress-free state of the intestinal wall, longitudinal residual strain measurements are needed. Furthermore, data on longitudinal stress-strain relations in visceral organs are scarce. The present study aims to investigate the longitudinal residual strain and the longitudinal stress-strain relationship in the rat small intestine. The longitudinal zero-stress state was obtained by cutting tissue strips parallel to the longitudinal axis of the intestine. The longitudinal residual stress was characterized by a bending angle (unit: degrees per unit length and positive when bending outwards). Residual strain was computed from the change in dimensions between the zero-stress state and the no-load state. Longitudinal stresses and strains were computed from stretch experiments in the distal ileum at luminal pressures ranging from 0-4 cmH2O. Large morphometric variations were found between the duodenum and ileum with the largest wall thickness and wall area in the duodenum and the largest inner circumference and luminal area in the distal ileum (p < 0.001). The bending angle did not differ between the duodenum and ileum (p > 0.5). The longitudinal residual strain was tensile at the serosal surface and compressive at the mucosal surface. Hence, the neutral axis was approximately in the mid-wall. The longitudinal residual strain and the bending angle was not uniform around the intestinal circumference and had the highest values on the mesenteric sides (p < 0.001). The stress-strain curves fitted well to the mono-exponential function with determination coefficients above 0.96. The alpha constant increased with the pressure, indicating the intestinal wall became stiffer in longitudinal direction when pressurized. Large longitudinal residual strains reside in the small intestine and showed circumferential variation. This indicates that the tissue is not uniform and cannot be treated as a homogenous material. The longitudinal stiffness
Longitudinal residual strain and stress-strain relationship in rat small intestine
Dou, Yanling; Fan, Yanhua; Zhao, Jingbo; Gregersen, Hans
2006-01-01
Background To obtain a more detailed description of the stress-free state of the intestinal wall, longitudinal residual strain measurements are needed. Furthermore, data on longitudinal stress-strain relations in visceral organs are scarce. The present study aims to investigate the longitudinal residual strain and the longitudinal stress-strain relationship in the rat small intestine. Methods The longitudinal zero-stress state was obtained by cutting tissue strips parallel to the longitudinal axis of the intestine. The longitudinal residual stress was characterized by a bending angle (unit: degrees per unit length and positive when bending outwards). Residual strain was computed from the change in dimensions between the zero-stress state and the no-load state. Longitudinal stresses and strains were computed from stretch experiments in the distal ileum at luminal pressures ranging from 0–4 cmH2O. Results Large morphometric variations were found between the duodenum and ileum with the largest wall thickness and wall area in the duodenum and the largest inner circumference and luminal area in the distal ileum (p < 0.001). The bending angle did not differ between the duodenum and ileum (p > 0.5). The longitudinal residual strain was tensile at the serosal surface and compressive at the mucosal surface. Hence, the neutral axis was approximately in the mid-wall. The longitudinal residual strain and the bending angle was not uniform around the intestinal circumference and had the highest values on the mesenteric sides (p < 0.001). The stress-strain curves fitted well to the mono-exponential function with determination coefficients above 0.96. The α constant increased with the pressure, indicating the intestinal wall became stiffer in longitudinal direction when pressurized. Conclusion Large longitudinal residual strains reside in the small intestine and showed circumferential variation. This indicates that the tissue is not uniform and cannot be treated as a homogenous
An Overview of Some Current Research on Welding Residual Stresses and Distortion in the U.S. Navy
1997-10-01
RESEARCH ON WELDING RESIDUAL STRESSES AND DISTORTION IN THE U.S. NAVY System Number: Patron Number: • Requester: Notes: Paper #39 contained in...Overview of Some Current Research on Welding Residual Stresses and Distortion in the U.S. Navy 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM...managing residual stresses and distortion during weld fabrication. These efforts include model development, model verification, thermo-mechanical and
A survey of gunshot residue analysis methods.
Singer, R L; Davis, D; Houck, M M
1996-03-01
A survey was sent to 80 forensic laboratories in 44 States and two Canadian Provinces concerning methodology in analyzing gunshot residue (GSR) and interpreting the results. Of the 80 surveys, 50 (63%) were returned completed. Questions included standard procedures, collection methods, thresholding problems and specificity of data. These results are compared to a previous survey reported in 1990. Implications for the interpretation and future study of these methods are discussed.
Acoustic Measurements of Residual Stresses and Grain Sizes in Aluminum Alloys
NASA Astrophysics Data System (ADS)
Fisher, Martin John
The theory of acoustoelasticity relates the velocity of an acoustic wave in a solid to the elastic stress state in that solid. This thesis presents new theories, measurement techniques, and methodologies related to the use of longitudinal wave acoustoelasticity in aluminum alloys. A one-dimensional model has been developed to provide a simple understanding of the acoustoelastic effect. A new acoustic device for accurately measuring relative thickness variations has been designed and built. This device is used--in conjunction with a pulse-echo phase measurement device and a computer controlled scanning system--to measure acoustic velocity variations in plastically deformed and non-flat-and-parallel samples. Acoustic velocity variations from point to point in an unstressed sample can sometimes be on the same order as velocity changes due to applied or residual stresses, and this can make stress measurements difficult. A statistical theory has been developed to relate these unstressed velocity variations to the average grain size in the sample and to the active area of the acoustic transducer used. Large transducers and small grain sizes will minimize these variations. This relationship has been verified by tests on a number of aluminum alloys and a new method for non-destructive grain size determination has been suggested. A systematic methodology has been developed and tested for studying the influence of uniaxial plastic deformation on the acoustoelastic response. Samples have been plastically deformed in four-point bending to produce elastic-plastic and residual stress states. Acoustic measurements of these stresses have then been compared directly to theoretical predictions based on the materials' stress-strain curves and simple beam theory. In the aluminum alloys tested (2024-T351 and 7075-T651), the acoustoelastic constants are shown to be virtually unchanged by uniaxial plastic strains of less than 2.5%. Thus, the acoustoelastic technique can be reliably
NASA Astrophysics Data System (ADS)
Bauer, A.; Mehner, T.; Binotsch, C.; Sieber, M.; Awiszus, B.; Lampke, T.
2016-03-01
The process of cold flat rolling is a widespread industrial technique to manufacture semi-finished products, e.g., for the automotive or homewares industry. Basic knowledge of the process regarding dimensioning and adjustment of defined characteristics is already state of the art. However, a detailed consideration and analysis with respect to local inhomogeneous residual stresses in several process steps mostly remains disregarded. A broad understanding of the process due to the distribution of residual stresses in the workpiece and the direction of the stress tensors allows for a definition of the characteristics of the workpiece even before the actual manufacturing process. For that purpose, it is necessary to perform numerical investigations by means of the finite element analysis (FEA) of cold flat rolling processes. Within this contribution, several approaches for the calibration of the FEA with the real flat rolling process will be addressed and discussed. To ensure that the numerical consideration provides realistic results, this calibration is indispensable. General parameters such as geometry, height reduction, rolling temperature, process time, and the rolling speed are considered as well as a photogrammetric survey, and calculated residual stresses with results of X-ray diffraction (XRD) will be compared. In the course of the experiments, a good agreement between the stress results of the FEA and the XRD was found in the center of the specimen. In combination with the allocation of the stress orientations, the agreement close to the edges is also fine. Some issues that cause differences between the FEA and the experiment are dis-cussed.
Residual Stresses in a NiCrY-Coated Powder Metallurgy Disk Superalloy
NASA Technical Reports Server (NTRS)
Gabb, Timothy P.; Rogers, Richard B.; Nesbitt, James A.; Puleo, Bernadette J.; Miller, Robert A.; Telesman, Ignacy; Draper, Susan L.; Locci, Ivan E.
2017-01-01
Protective ductile coatings will be necessary to mitigate oxidation and corrosion attack on superalloy disks exposed to increasing operating temperatures in some turbine engine environments. However, such coatings must be resistant to harmful surface cracking during service. The objective of this study was to investigate how residual stresses evolve in such coatings. Cylindrical gage fatigue specimens of powder metallurgy-processed disk superalloy LSHR were coated with a NiCrY coating, shot peened, and then subjected to fatigue in air at room and high temperatures. The effects of shot peening and fatigue cycling on average residual stresses and other aspects of the coating were assessed. Shot peening did induce beneficial compressive residual stresses in the coating and substrate. However, these stresses became more tensile in the coating with subsequent heating and contributed to cracking of the coating in long intervals of cycling at 760 C. Substantial compressive residual stresses remained in the substrate adjacent to the coating, sufficient to suppress fatigue cracking. The coating continued to protect the substrate from hot corrosion pitting, even after fatigue cracks initiated in the coating.
NASA Astrophysics Data System (ADS)
Gopinath, Abhay; Lim, Andre; Nagarajan, Balasubramanian; Cher Wong, Chow; Maiti, Rajarshi; Castagne, Sylvie
2016-11-01
Mechanical surface treatments such as Shot Peening (SP) and Deep Cold Rolling (DCR) are being used to introduce Compressive Residual Stress (CRS) at the surface and subsurface layers of aerospace components, respectively. This paper investigates the feasibility of a combined introduction of both the surface and sub-surface compressive residual stress on Ti6Al4V material through a successive application of the two aforementioned processes, one after the other. CRS profiles between individual processes were compared to that of combination of processes to validate the feasibility. It was found out that shot peening introduces surface compressive residual stress into the already deep cold rolled sample, resulting in both surface and sub-surface compressive residual stresses in the material. However the drawback of such a combination would be the increased surface roughness after shot peening a deep cold rolled sample which can be critical especially in compressor components. Hence, a new technology, Vibro-Peening (VP) may be used as an alternative to SP to introduce surface stress at reduced roughness.
A study of evolution of residual stress in single crystal silicon electrode using Raman spectroscopy
NASA Astrophysics Data System (ADS)
Jana, M.; Singh, Raj N.
2017-08-01
Silicon is a promising anode material for lithium ion batteries. However, lithiation of silicon generates stress that is known to be the primary reason for the failure of the anode. This study explored the existence of residual stress in single crystalline silicon electrodes after full de-lithiation, i.e., under no mechanical or electrical load. The magnitude of residual stress and its evolution with the number of lithiation-delithiation cycles is measured by Raman spectroscopy and a simple mechanics based approach. It is shown that the residual stress is tensile in nature and increased from 69 ± 11 MPa after the 1st cycle to ˜291 ± 56 MPa after 50 cycles of lithiation and de-lithiation. Concurrently, microstructural studies were performed to demonstrate the consequence of the evolution of residual stress on failure by the fracture of the silicon anode. These results provide understanding on the progressive failure mechanism of single crystalline-based silicon electrodes upon lithiation-delithiation.
NASA Astrophysics Data System (ADS)
Liu, Hai-Yun; Li, Wei-Hua; Zhou, Zai-Fa; Huang, Qing-An
2013-07-01
In this research, micromachined devices consisting of four micro-rotating structures for the in situ determination of the thermal expansion coefficient (TEC), tensile and compressive residual stress of polysilicon thin films are studied. The structures are heated electrically and deflect due to the thermal expansion. The lateral displacements of the devices are related to the thermal stress and residual stress of the test beams. The micro-rotating structures are arranged, so that the lateral displacements are designed to be either a constant value which is used to determine the TEC of the thin film or a variable value that changes with the residual stress of the thin film. An analytical model of the test structure is presented. The finite element software ANSYS is used to verify the analytical model and provide guidelines for the structure design. Experimental results with a surface micromachined polysilicon thin film are used to demonstrate the proposed method. In the experiments, a current-voltage measurement system only is required. The TEC for the polysilicon thin film is obtained to be (2.61 ± 0.04) × 10-6 K-1 from 400 to 420 K and the residual stress is measured as -(10.15 ± 0.70) MPa.
Hayashi, Yoshihiro; Otoguro, Saori; Miura, Takahiro; Onuki, Yoshinori; Obata, Yasuko; Takayama, Kozo
2014-01-01
A multivariate statistical technique was applied to clarify the causal correlation between variables in the manufacturing process and the residual stress distribution of tablets. Theophylline tablets were prepared according to a Box-Behnken design using the wet granulation method. Water amounts (X1), kneading time (X2), lubricant-mixing time (X3), and compression force (X4) were selected as design variables. The Drucker-Prager cap (DPC) model was selected as the method for modeling the mechanical behavior of pharmaceutical powders. Simulation parameters, such as Young's modulus, Poisson rate, internal friction angle, plastic deformation parameters, and initial density of the powder, were measured. Multiple regression analysis demonstrated that the simulation parameters were significantly affected by process variables. The constructed DPC models were fed into the analysis using the finite element method (FEM), and the mechanical behavior of pharmaceutical powders during the tableting process was analyzed using the FEM. The results of this analysis revealed that the residual stress distribution of tablets increased with increasing X4. Moreover, an interaction between X2 and X3 also had an effect on shear and the x-axial residual stress of tablets. Bayesian network analysis revealed causal relationships between the process variables, simulation parameters, residual stress distribution, and pharmaceutical responses of tablets. These results demonstrated the potential of the FEM as a tool to help improve our understanding of the residual stress of tablets and to optimize process variables, which not only affect tablet characteristics, but also are risks of causing tableting problems.
NASA Astrophysics Data System (ADS)
Wang, Ruzhuan; Li, Weiguo
2017-08-01
The strength of SiC-depleted layer of ultra-high-temperature ceramics on high temperature oxidation degrades seriously. The research for residual stresses developed within the SiC-depleted layer is important and necessary. In this work, the residual stress evolutions in the SiC-depleted layer and the unoxidized substrate in various stages of oxidation are studied by using the characterization models. The temperature and oxidation time dependent mechanical/thermal properties of each phase in SiC-depleted layer are considered in the models. The study shows that the SiC-depleted layer would suffer from large tensile stresses due to the great temperature changes and the formation of pores on high temperature oxidation. The stresses may lead to the cracking and even the delamination of the oxidation layer.
NASA Astrophysics Data System (ADS)
Wang, Ruzhuan; Li, Weiguo
2016-11-01
The strength of SiC-depleted layer of ultra-high-temperature ceramics on high temperature oxidation degrades seriously. The research for residual stresses developed within the SiC-depleted layer is important and necessary. In this work, the residual stress evolutions in the SiC-depleted layer and the unoxidized substrate in various stages of oxidation are studied by using the characterization models. The temperature and oxidation time dependent mechanical/thermal properties of each phase in SiC-depleted layer are considered in the models. The study shows that the SiC-depleted layer would suffer from large tensile stresses due to the great temperature changes and the formation of pores on high temperature oxidation. The stresses may lead to the cracking and even the delamination of the oxidation layer.
NASA Astrophysics Data System (ADS)
Zhao, Yu; Ma, Chunli; Huang, Fengxian; Wang, Chunjie; Zhao, Sumei; Cui, Qiliang; Cao, Xueqiang; Li, Fangfei
2013-08-01
A non-destructive inspection technique was developed to measure the residual stresses in thermal barrier coatings (TBCs) by using Eu3+ photoluminescence piezo-spectroscopy. The new approach is based on the relationship between stress and the position of the main peak of 5D0→7F2 transition, which is built by the high-pressure techniques. The Eu3+ luminescent sublayer was applied in the current method to ensure that the detected position in TBCs can be well controlled. The laser used to detect Eu3+ luminescence gives a proper penetration depth and spatial resolution, which make this method suitable to detect the stresses concentrated near the interfaces between different layers. This method was successfully applied in detecting residual stress in plasma sprayed TBCs with a 8YSZ:Eu (1 mol. %) sublayer.
NASA Astrophysics Data System (ADS)
Rohr, Garth D.; Rasberry, Roger D.; Kaczmarowski, Amy K.; Stavig, Mark E.; Gibson, Cory S.; Udd, Eric; Roach, Allen R.; Nation, Brendan
2015-05-01
Internal residual stresses and overall mechanical properties of thermoset resins are largely dictated by the curing process. It is well understood that fiber Bragg grating (FBG) sensors can be used to evaluate temperature and cure induced strain while embedded during curing. Herein, is an extension of this work whereby we use FBGs as a probe for minimizing the internal residual stress of an unfilled and filled Epon 828/DEA resin. Variables affecting stress including cure cycle, mold (release), and adhesion promoting additives will be discussed and stress measurements from a strain gauge pop-off test will be used as comparison. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.
Microscopic imaging of residual stress using a scanning phase-measuring acoustic microscope
NASA Astrophysics Data System (ADS)
Meeks, Steven W.; Peter, D.; Horne, D.; Young, K.; Novotny, V.
1989-10-01
A high-resolution scanning phase-measuring acoustic microscope (SPAM) has been developed and used to image the near-surface residual stress field around features etched in sputtered alumina via the acoustoelastic effect. This microscope operates at 670 MHz and has a resolution of 5-10 microns, depending upon the amount of defocus. Relative velocity changes of sample surface waves as small as 50 ppm are resolved. Images of the stress field at the tip of a 400-micron-wide slot etched in alumina are presented and compared with a finite element simulation. The SPAM uses an unconventional acoustic lens with an anisotropic illumination pattern which can measure anisotropic effects and map residual stress fields with several-micron resolution and a stress sensitivity of 1/3 MPa in an alumina film.
Hasanuzzaman, Md; Davies, Noel W; Shabala, Lana; Zhou, Meixue; Brodribb, Tim J; Shabala, Sergey
2017-06-19
While most water loss from leaf surfaces occurs via stomata, part of this loss also occurs through the leaf cuticle, even when the stomata are fully closed. This component, termed residual transpiration, dominates during the night and also becomes critical under stress conditions such as drought or salinity. Reducing residual transpiration might therefore be a potentially useful mechanism for improving plant performance when water availability is reduced (e.g. under saline or drought stress conditions). One way of reducing residual transpiration may be via increased accumulation of waxes on the surface of leaf. Residual transpiration and wax constituents may vary with leaf age and position as well as between genotypes. This study used barley genotypes contrasting in salinity stress tolerance to evaluate the contribution of residual transpiration to the overall salt tolerance, and also investigated what role cuticular waxes play in this process. Leaves of three different positions (old, intermediate and young) were used. Our results show that residual transpiration was higher in old leaves than the young flag leaves, correlated negatively with the osmolality, and was positively associated with the osmotic and leaf water potentials. Salt tolerant varieties transpired more water than the sensitive variety under normal growth conditions. Cuticular waxes on barley leaves were dominated by primary alcohols (84.7-86.9%) and also included aldehydes (8.90-10.1%), n-alkanes (1.31-1.77%), benzoate esters (0.44-0.52%), phytol related compounds (0.22-0.53%), fatty acid methyl esters (0.14-0.33%), β-diketones (0.07-0.23%) and alkylresorcinols (1.65-3.58%). A significant negative correlation was found between residual transpiration and total wax content, and residual transpiration correlated significantly with the amount of primary alcohols. Both leaf osmolality and the amount of total cuticular wax are involved in controlling cuticular water loss from barley leaves under well
NASA Astrophysics Data System (ADS)
Regener, B.; Krempaszky, C.; Werner, E.
2010-06-01
shot peening and chemical treatment in a mixture of nitric and hydroflouric acid finishes the processing. The residual stress state in the parts is quantified through correlation of results obtained by finite element simulations and high precision deflection experiments. Experimental measuring errors are minimized by using the capability of the wire cutting machine to measure locations on the specimens with respect to the fixed machine coordinate system. A sophisticated design of cutting operations allows an analysis of the part without removing the fixture and hence makes it possible to achieve a very high accuracy of the displacement measurements of about 4 µm. The quality of the obtained results also depends on the finite element models describing the mechanics of the experimental investigations as precise as possible. Since numerical modeling of shot peening and chemical milling is rather complicated, the whole processing route of the shapes is simplified assuming that the individual contribution of all process steps to the residual stress state can be described by virtual heat transfer coefficients. The overall virtual heat transfer coefficient for the whole processing route is calculated from the linear superposition of the individual heat transfer coeffcients for each processing step. Detailed analysis of the obtained overall virtual heat transfer coefficients in comparison with experimentally obtained ones shows, that other processing steps besides the heat treatment considerably influence the residual stress state. In order to make the conducted simulation scheme applicable in practise, advanced finite element modeling techniques are developed. The experimentally derived deflection curves are correlated to the finite element results via a least square fit.
Residual stress dependant anisotropic band gap of various (hkl) oriented BaI2 films
NASA Astrophysics Data System (ADS)
Kumar, Pradeep; Gulia, Vikash; Vedeshwar, Agnikumar G.
2013-11-01
The thermally evaporated layer structured BaI2 grows in various completely preferred (hkl) film orientations with different growth parameters like film thickness, deposition rate, substrate temperature, etc. which were characterized by structural, morphological, and optical absorption measurements. Structural analysis reveals the strain in the films and the optical absorption shows a direct type band gap. The varying band gaps of these films were found to scale linearly with their strain. The elastic moduli and other constants were also calculated using Density Functional Theory (DFT) formalism implemented in WIEN2K code for converting the strain into residual stress. Films of different six (hkl) orientations show stress free anisotropic band gaps (2.48-3.43 eV) and both positive and negative pressure coefficients. The negative and positive pressure coefficients of band gap are attributed to the strain in I-I (or Ba-Ba or both) and Ba-I distances along [hkl], respectively. The calculated band gaps are also compared with those experimentally determined. The average pressure coefficient of band gap of all six orientations (-0.071 eV/GPa) found to be significantly higher than that calculated (-0.047 eV/GPa) by volumetric pressure dependence. Various these issues have been discussed with consistent arguments. The electron effective mass me*=0.66m0 and the hole effective mass mh*=0.53m0 have been determined from the calculated band structure.
Residual stresses in a stainless steel - titanium alloy joint made with the explosive technique
NASA Astrophysics Data System (ADS)
Taran, Yu V.; Balagurov, A. M.; Sabirov, B. M.; Evans, A.; Davydov, V.; Venter, A. M.
2012-02-01
Joining of pipes from stainless steel (SS) and titanium (Ti) alloy still experience serious technical problems. Recently, reliable and hermetic joining of SS and Ti pipes has been achieved with the explosive bonding technique in the Russian Federal Nuclear Center. Such adapters are earmarked for use at the future International Linear Collider. The manufactured SS-Ti adapters have excellent mechanical behavior at room and liquid nitrogen temperatures, during high-pressure tests and thermal cycling. We here report the first neutron diffraction investigation of the residual stresses in a SS-Ti adapter on the POLDI instrument at the SINQ spallation source. The strain scanning across the adapter walls into the SS-SS and SS-Ti pipes sections encompassed measurement of the axial, radial and hoop strain components, which were transformed into residual stresses. The full stress information was successfully determined for the three steel pipes involved in the joint. The residual stresses do not exceed 300 MPa in magnitude. All stress components have tensile values close to the adapter internal surface, whilst they are compressive close to the outer surface. The strong incoherent and weak coherent neutron scattering cross-sections of Ti did not allow for the reliable determination of stresses inside the titanic pipe.
Residual Strength Analysis Methodology: Laboratory Coupons to Structural Components
NASA Technical Reports Server (NTRS)
Dawicke, D. S.; Newman, J. C., Jr.; Starnes, J. H., Jr.; Rose, C. A.; Young, R. D.; Seshadri, B. R.
2000-01-01
The NASA Aircraft Structural Integrity (NASIP) and Airframe Airworthiness Assurance/Aging Aircraft (AAA/AA) Programs have developed a residual strength prediction methodology for aircraft fuselage structures. This methodology has been experimentally verified for structures ranging from laboratory coupons up to full-scale structural components. The methodology uses the critical crack tip opening angle (CTOA) fracture criterion to characterize the fracture behavior and a material and a geometric nonlinear finite element shell analysis code to perform the structural analyses. The present paper presents the results of a study to evaluate the fracture behavior of 2024-T3 aluminum alloys with thickness of 0.04 inches to 0.09 inches. The critical CTOA and the corresponding plane strain core height necessary to simulate through-the-thickness effects at the crack tip in an otherwise plane stress analysis, were determined from small laboratory specimens. Using these parameters, the CTOA fracture criterion was used to predict the behavior of middle crack tension specimens that were up to 40 inches wide, flat panels with riveted stiffeners and multiple-site damage cracks, 18-inch diameter pressurized cylinders, and full scale curved stiffened panels subjected to internal pressure and mechanical loads.
Henriques, Bruno; Fabris, Douglas; Souza, Júlio C. M.; Silva, Filipe S.; Mesquita-Guimarães, Joana; Zhang, Yu; Fredel, Márcio
2017-01-01
Residual thermal stresses are formed in dental restorations during cooling from high temperature processing. The aim of this study was to evaluate the influence of constructive design variables (composition and interlayer thickness) on residual stresses in alumina- and zirconia-graded restorations. Restorations' real-like cooling conditions were simulated using finite elements method and temperature-dependent material properties were used. Three different designs were evaluated: a bilayered restoration (sharp transition between materials); a trilayered restoration with a homogenous interlayer between core and veneer; and a trilayered restoration with a graded interlayer. The interlayer thickness and composition were varied. Zirconia restorations presented overall higher thermal stress values than alumina ones. Thermal stresses were significantly reduced by the presence of a homogeneous interlayer. The composition of the interlayer showed great influence on the thermal stresses, with the best results for homogeneous interlayers being observed for porcelain contents in the composite ranging between 30%-50% (vol.%), for both alumina and zirconia restorations. The interlayer's thickness showed a minor contribution in the thermal stress reduction. The graded interlayer showed an optimized reduction in restorations' thermal stresses. The use of graded interlayer, favoring enhanced thermal stress distributions and lower magnitude is expected to reduce the risk of catastrophic failure. PMID:27987657
Strengthening, Crack Arrest And Multiple Cracking In Brittle Materials Using Residual Stresses.
Green, David J.; Sglavo, Vincenzo M.; Tandon, Rajan
2003-02-11
Embodiments include a method for forming a glass which displays visible cracking prior to failure when subjected to predetermined stress level that is greater than a predetermined minimum stress level and less than a failure stress level. The method includes determining a critical flaw size in the glass and introducing a residual stress profile to the glass so that a plurality of visible cracks are formed prior to failure when the glass is subjected to a stress that is greater than the minimum stress level and lower than the critical stress. One method for forming the residual stress profile includes performing a first ion exchange so that a first plurality of ions of a first element in the glass are exchanged with a second plurality of ions of a second element that have a larger volume than the first ions. A second ion exchange is also performed so that a plurality of the second ions in the glass are exchanged back to ions of the first element.
Henriques, Bruno; Fabris, Douglas; Souza, Júlio C M; Silva, Filipe S; Mesquita-Guimarães, Joana; Zhang, Yu; Fredel, Márcio
2017-02-01
Residual thermal stresses are formed in dental restorations during cooling from high temperature processing. The aim of this study was to evaluate the influence of constructive design variables (composition and interlayer thickness) on residual stresses in alumina- and zirconia-graded restorations. Restorations' real-like cooling conditions were simulated using finite elements method and temperature-dependent material properties were used. Three different designs were evaluated: a bilayered restoration (sharp transition between materials); a trilayered restoration with a homogenous interlayer between core and veneer; and a trilayered restoration with a graded interlayer. The interlayer thickness and composition were varied. Zirconia restorations presented overall higher thermal stress values than alumina ones. Thermal stresses were significantly reduced by the presence of a homogeneous interlayer. The composition of the interlayer showed great influence on the thermal stresses, with the best results for homogeneous interlayers being observed for porcelain contents in the composite ranging between 30%-50% (vol.%), for both alumina and zirconia restorations. The interlayer's thickness showed a minor contribution in the thermal stress reduction. The graded interlayer showed an optimized reduction in restorations' thermal stresses. The use of graded interlayer, favoring enhanced thermal stress distributions and lower magnitude is expected to reduce the risk of catastrophic failure. Copyright © 2016 Elsevier B.V. All rights reserved.
Infrared birefringence imaging of residual stress and bulk defects in multicrystalline silicon
Ganapati, Vidya; Schoenfelder, Stephan; Castellanos, Sergio; Oener, Sebastian; Koepge, Ringo; Sampson, Aaron; Marcus, Matthew A.; Lai, Barry; Morhenn, Humphrey; Hahn, Giso; Bagdahn, Joerg; Buonassisi1, Tonio
2010-05-05
This manuscript concerns the application of infrared birefringence imaging (IBI) to quantify macroscopic and microscopic internal stresses in multicrystalline silicon (mc-Si) solar cell materials. We review progress to date, and advance four closely related topics. (1) We present a method to decouple macroscopic thermally-induced residual stresses and microscopic bulk defect related stresses. In contrast to previous reports, thermally-induced residual stresses in wafer-sized samples are generally found to be less than 5 MPa, while defect-related stresses can be several times larger. (2) We describe the unique IR birefringence signatures, including stress magnitudes and directions, of common microdefects in mc-Si solar cell materials including: {beta}-SiC and {beta}-Si{sub 3}N{sub 4} microdefects, twin bands, nontwin grain boundaries, and dislocation bands. In certain defects, local stresses up to 40 MPa can be present. (3) We relate observed stresses to other topics of interest in solar cell manufacturing, including transition metal precipitation, wafer mechanical strength, and minority carrier lifetime. (4) We discuss the potential of IBI as a quality-control technique in industrial solar cell manufacturing.
Infrared birefringence imaging of residual stress and bulk defects in multicrystalline silicon
NASA Astrophysics Data System (ADS)
Ganapati, Vidya; Schoenfelder, Stephan; Castellanos, Sergio; Oener, Sebastian; Koepge, Ringo; Sampson, Aaron; Marcus, Matthew A.; Lai, Barry; Morhenn, Humphrey; Hahn, Giso; Bagdahn, Joerg; Buonassisi, Tonio
2010-09-01
This manuscript concerns the application of infrared birefringence imaging (IBI) to quantify macroscopic and microscopic internal stresses in multicrystalline silicon (mc-Si) solar cell materials. We review progress to date, and advance four closely related topics. (1) We present a method to decouple macroscopic thermally-induced residual stresses and microscopic bulk defect related stresses. In contrast to previous reports, thermally-induced residual stresses in wafer-sized samples are generally found to be less than 5 MPa, while defect-related stresses can be several times larger. (2) We describe the unique IR birefringence signatures, including stress magnitudes and directions, of common microdefects in mc-Si solar cell materials including: β-SiC and β-Si3N4 microdefects, twin bands, nontwin grain boundaries, and dislocation bands. In certain defects, local stresses up to 40 MPa can be present. (3) We relate observed stresses to other topics of interest in solar cell manufacturing, including transition metal precipitation, wafer mechanical strength, and minority carrier lifetime. (4) We discuss the potential of IBI as a quality-control technique in industrial solar cell manufacturing.
Voice stress analysis and evaluation
NASA Astrophysics Data System (ADS)
Haddad, Darren M.; Ratley, Roy J.
2001-02-01
Voice Stress Analysis (VSA) systems are marketed as computer-based systems capable of measuring stress in a person's voice as an indicator of deception. They are advertised as being less expensive, easier to use, less invasive in use, and less constrained in their operation then polygraph technology. The National Institute of Justice have asked the Air Force Research Laboratory for assistance in evaluating voice stress analysis technology. Law enforcement officials have also been asking questions about this technology. If VSA technology proves to be effective, its value for military and law enforcement application is tremendous.
Forensic Determination of Residual Stresses from Fracture Surfaces
Prime, Michael B.; DeWald, Adrian T.; Hill, Michael R.
2012-07-19
Forensic engineering - the scientific examination and analysis of failed structures and parts relating to their failure or cause of damage. Real advances in experimental mechanics require innovative theoretical and analytical thinking to go with innovative capabilities. For example, taking full field data (e.g., DIC) and treating it like discrete data (strain gauge) misses a wonderful opportunity.
Modeling of residual stresses in core shroud structures
Zhang, J.; Dong, P.; Brust, F.W.; Mayfield, M.; McNeil, M.; Shack, W.J.
1997-10-01
A BWR core shroud is a cylindrical shell that surrounds the reactor core. Feedwater for the reactor is introduced into the annulus between the reactor vessel wall and the shroud. The shroud separates the feedwater from the cooling water flowing up through the reactor core. The shroud also supports the top guide which provides lateral support to the fuel assemblies and maintains core geometry during operational transients and postulated accidents to permit control rod insertion and provides the refloodable volume needed to ensure safe shutdown and cooling of the core during postulated accident conditions. Core shrouds were fabricated from welded Type 304 or 304L stainless steel plates and are supported at the top and bottom by forged ring support structures. In 1990, cracking was reported in the core shroud of a non-U.S. BWR. The cracks were located in the heat-affected zone (HAZ) of a circumferential core shroud weld. Subsequent inspections in U.S. BWRs have revealed the presence of numerous flaw indications in some BWR core shrouds, primarily in weld HAZs. In several instances, this cracking was quite extensive, with the cracks extending 75% or more around the circumference of some welds. However, because the applied stresses on the shroud are low during operation and postulated accidents and because of the high fracture toughness of stainless steel, adequate structural margins can be preserved even in the presence of extensive cracking. Although assessments by the USNRC staff of the potential significance of this cracking have shown that core shroud cracking does not pose a high degree of risk in the short term, the staff concluded that the cracking was a safety concern for the long term because of the uncertainties associated with the behavior of core shrouds with complete 360{degrees} through-wall cracks under accident conditions and because it could eliminate a layer of defense-in-depth.
1989-03-01
Report No. NADC-88141-60 (Volume II) DTIC S F-!. r-CT E MAY 2 6 1~98D RESIDUAL STRESS CHANGES IN FATIGUE VOLUME II - A SIMULATION MODEL FOR STRESS ...Residual Stress Changes in Fatigue: Vol. II. A Simulation Model for Stress Measurements in Notched Test Specimens by X-Ray Diffraction 12 PERSONAL...Simulation; Residual Stress ; X-Ray Difraction ’/ -, . .. 20 11 1 19 ABSTRACT (Continue on reverse if necessary and identif by block number) The state of
Residual stress evaluation and fatigue life prediction in the welded joint by x-ray diffraction
NASA Astrophysics Data System (ADS)
Yoo, Keun Bong; Hwang, Kwon Tae; Chang, Jung Chel; Kim, Jae Hoon
2009-07-01
In the fossil power plant, the reliability of the components which consist of the many welded parts depends on the quality of welding. The residual stress is occurred by the heat flux of high temperature during weld process. This decreases the mechanical properties as the strength of fatigue and fracture. The residual stress of the welded part in the recently constructed power plants has been the cause of a variety of accidents. The objective of this study is measurement of the residual stress and the full width at half maximum intensity (FWHM) by X-ray diffraction method and to estimate the feasibility of this application for fatigue life assessment of the high-temperature pipeline. The materials used for the study is P92 steel for the use of high temperature pipe on super critical condition. The test results were analyzed by the distributed characteristics of residual stresses and FWHM in x-ray diffraction intensity curve. Also, X-ray diffraction tests using specimens simulated low cycle fatigue damage were performed in order to analyze fatigue properties when fatigue damage conditions become various stages. As a result of X-ray diffraction tests for specimens simulated fatigue damages, we conformed that the ratio of the FWHM due to fatigue damage has linear relationship with fatigue life ratio algebraically. From this relationship, it was suggested that direct expectation of the life consumption rate was feasible.
Uran, S.; Veal, B.; Grimsditch, M.; Pearson, J.; Berger, A.; Materials Science Division
2000-08-01
The effect of surface roughness on the properties of the oxide scale formed on Fe-Cr-Al alloys during oxidation in air at high temperatures has been investigated. Large and systematic differences in scale thickness, in the composition of the oxides forming the scale, and in the residual stress levels are found.
Phelippeau,A.; Pommier, S.; Zakharchenko, I.; Levy-Tubiana, R.; Tsakalakos, T.; Clavel, M.; Croft, M.; Zhong, Z.; Prioul, C.
2006-01-01
Cold drawing of steel wires leads to an increase of their mechanical strength and to a drop in their ductility. The increase of their mechanical strength has long been related to the reduction of the various material scales by an intense plastic deformation. Besides, it was discussed in the companion paper that large plastic deformation leads to the loss of the material hardening capabilities and that, in such a case, residual stresses preserve the elongation to failure of wires. Experimental measurements of residual stresses inside the wire have therefore been undertaken. In this paper, lattice parameters as measured using synchrotron diffraction are compared with those calculated using the residual stress fields as determined by the finite-element method. There is a major disagreement between experimental and numerical results that is too large to be attributed to the errors of the finite-element analyses. Therefore, neutron diffraction experiments have also been performed. These measurements show that there is a significant variation of the lattice parameter with the drawing level, which is not inherited from residual stresses, and that variation is very sensitive to the cooling rate after processing. It is therefore proposed that cold drawing would induce a phase transformation of the steel, possibly a martensitic transformation.
Cold pulse and rotation reversals with turbulence spreading and residual stress
Hariri, F.; Naulin, V.; Juul Rasmussen, J.; Xu, G. S.; Yan, N.
2016-05-15
Transport modeling based on inclusion of turbulence spreading and residual stresses shows internal rotation reversals and polarity reversal of cold pulses, with a clear indication of nonlocal transport effects due to fast spreading in the turbulence intensity field. The effects of turbulence spreading and residual stress are calculated from the gradient of the turbulence intensity. In the model presented in this paper, the flux is carried by the turbulence intensity field, which in itself is subject to radial transport effects. The pulse polarity inversion and the rotation profile reversal positions are close to the radial location of the stable/unstable transition. Both effects have no direct explanation within the framework of classical transport modeling, where the fluxes are related directly to the linear growth rates, the turbulence intensity profile is not considered and the corresponding residual stress is absent. Our simulations are in qualitative agreement with measurements from ohmically heated plasmas. Rotation reversal at a finite radius is found in situations not displaying saturated confinement, which we identify as situations where the plasma is nearly everywhere unstable. As an additional and new effect, the model predicts a perturbation of the velocity profile following a cold pulse from the edge. This allows direct experimental confirmation of both the existence of residual stress caused by turbulence intensity profiles and fundamental ideas of transport modeling presented here.
Study of residual stress distribution in the machined stainless steel components
NASA Astrophysics Data System (ADS)
Jang, Dong Y.; Liou, J.; Cho, U.
1994-07-01
The demand for high quality and fully automated production, coupled with advances in alloy development, focuses attention on the surface condition of products, especially the residual stresses on the machined surface because of its effect on component performance, longevity, and reliability. Although stainless steel is an important material with wide application, it is not easy to obtain a favorable surface condition due to its sensitivity to thermal and mechanical operations. In order to obtain favorable surface conditions in a stainless steel component, it is necessary to have practical data which include information concerning tool wear, surface roughness and surface residual stress. In the research toward developing a machinability chart which can provide suitable cutting parameters for the high production rate and good quality surface, and can be used in computer controlled machining tools, surface residual stress distributions in the turning process for stainless steel were studied. Austenitic 304 stainless steel bars were selected as the workpieces and uncoated carbide tools were used in the tests. The obtained results will show residual stress conditions on the machined stainless steel components varying according to cutting conditions.
The Numerical Simulation of Crack Growth in Weld-Induced Residual Stress Fields
1981-07-01
Regulatory Commission, NUREG -0376 (November, 1977). 5. F. W. Brust and R. B. Stonesifer, "Effect of Weld Parameters on Residual Stresses in BWR Piping...Plastic Fracture Mechanics to Nuclear Pressure Vessels and Piping", Battelle’s Columbus Laboratories Report to the U.S. Nuclear Regulatory Commission, NUREG CR-2110 (May, 1981). S. . . 7 : ," . . .. . . . . . . .. . • -. .
NASA Astrophysics Data System (ADS)
Waltz, R. E.; Staebler, G. M.; Solomon, W. M.
2011-04-01
Residual stress refers to the remaining toroidal angular momentum (TAM) flux (divided by major radius) when the shear in the equilibrium fluid toroidal velocity (and the velocity itself) vanishes. Previously [Waltz et al., Phys. Plasmas 14, 122507 (2007); errata 16, 079902 (2009)], we demonstrated with GYRO [Candy and Waltz, J. Comp. Phys. 186, 545 (2003)] gyrokinetic simulations that TAM pinching from (ion pressure gradient supported or diamagnetic level) equilibrium E ×B velocity shear could provide some of the residual stress needed to support spontaneous toroidal rotation against normal diffusive loss. Here we show that diamagnetic level shear in the intrinsic drift wave velocities (or "profile shear" in the ion and electron density and temperature gradients) provides a comparable residual stress. The individual signed contributions of these small (rho-star level) E ×B and profile velocity shear rates to the turbulence level and (rho-star squared) ion energy transport stabilization are additive if the rates are of the same sign. However because of the additive stabilization effect, the contributions to the small (rho-star cubed) residual stress is not always simply additive. If the rates differ in sign, the residual stress from one can buck out that from the other (and in some cases reduce the stabilization.) The residual stress from these diamagnetic velocity shear rates is quantified by the ratio of TAM flow to ion energy (power) flow (M/P) in a global GYRO core simulation of a "null" toroidal rotation DIII-D [Mahdavi and Luxon, Fusion Sci. Technol. 48, 2 (2005)] discharge by matching M/P profiles within experimental uncertainty. Comparison of global GYRO (ion and electron energy as well as particle) transport flow balance simulations of TAM transport flow in a high-rotation DIII-D L-mode quantifies and isolates the E ×B shear and parallel velocity (Coriolis force) pinching components from the larger "diffusive" parallel velocity shear driven component and