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Sample records for mapping residual stresses

  1. Operator Manual for X-ray Residual Stress Mapping

    SciTech Connect

    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.

  2. THE CONTOUR METHOD: SIMPLE 2-D MAPPING OF RESIDUAL STRESSES

    SciTech Connect

    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.

  3. Development of ultrasonic tomography for residual stress mapping. Final report

    SciTech Connect

    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.

  4. Mapping Residual Stress Distributions at the Micron Scale in Amorphous Materials

    NASA Astrophysics Data System (ADS)

    Winiarski, Bartlomiej; Langford, Richard M.; Tian, Jiawan; Yokoyama, Yoshihiko; Liaw, Peter K.; Withers, Philip J.

    2010-07-01

    Residual stresses in crystalline or glassy materials often play a key role in the performance of advanced devices and components. However, stresses in amorphous materials cannot easily be determined at the micron scale by diffraction, or by other conventional laboratory methods. In this article, a technique for mapping residual stress profiles in amorphous materials with high spatial definition is presented. By applying a focused ion beam (FIB)-based semidestructive mechanical relaxation method, the stresses are mapped in a peened and fatigued bulk metallic glass (BMG) (Zr50Cu40Al10 at. pct). The residual stresses are inferred using finite element analysis (FEA) of the surface relaxations, as measured by digital image correlation (DIC), that occur when a microslot is micromachined by FIB. Further, we have shown that acceptable accuracy can in most cases be achieved using a simple analytical model of the slot. It was found that the fatigue cycling significantly changes the distribution of compressive residual stresses with depth in the plastically deformed surface layer. Our observations point to the scalability of this method to map residual stresses in volumes as small as 1 × 1 × 0.2 μm3 or less.

  5. Mapping residual stresses after foreign object damage using the contour method

    SciTech Connect

    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.

  6. 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.

  7. Mapping residual stress fields from Vickers hardness indents using Raman microprobe spectroscopy

    SciTech Connect

    Sparks, R.G.; Enloe, W.S.; Paesler, M.A.

    1988-12-01

    Micro-Raman spectroscopy is used to map the residual stress fields in the vicinity of Vickers hardness indents. Both 514.5 and 488.0 nm, light is used to excite the effect and the resulting shifted and broadened Raman peaks are analyzed using computer deconvolution. Half-wave plates are used to vary the orientation of the incident later light`s polarization state with respect to crystal orientation. The Raman scattered light is then analyzed for polarization dependences which are indicative of the various components of the Raman scattering tensor. Such studies can yield valuable information about the orientation of stress components in a well known stress field. The results can then be applied to the determination of stress components in machined semiconductor materials.

  8. Residual stress mapping by micro X-ray diffraction: Application to the study of thin film buckling

    SciTech Connect

    Goudeau, P.; Villain, P.; Tamura, N.; Celestre, R.S.; Padmore, H.A.

    2002-11-06

    Thin films deposited by Physical Vapour Deposition techniques on substrates generally exhibit large residual stresses which may be responsible of spontaneous detachment of the film from its substrate and in the case of compressive stresses, thin film buckling. Although these effects are undesirable for future applications, one may take benefit of it for thin film mechanical properties investigation. Since the 80's, a lot of theoretical works have been done to develop mechanical models with the aim to get a better understanding of driven mechanisms giving rise to this phenomenon and thus to propose solutions to avoid such problems. Nevertheless, only a few experimental works have been done on this subject to support these theoretical results and nothing concerning local stress/strain measurement mainly because of the small dimension of the buckling (few tenth mm). This paper deals with the application of micro beam x-ray diffraction available on synchrotron radiation sources for stress/ strain mapping analysis of gold thin film buckling.

  9. Residual stresses in material processing

    SciTech Connect

    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.

  10. Residual stress patterns in steel welds

    SciTech Connect

    Spooner, S.; Hubbard, C.R.; Wang, X.L.; David, S.A.; Holden, T.M.; Root, J.H.; Swainson, I.

    1994-12-31

    Neutron strain scanning of residual stress is a valuable nondestructive tool for evaluation of residual stress in welds. The penetrating characteristic of neutrons permits mapping of strain patterns with a spatial resolution approaching 1mm at depths of 20mm in steels. While the overall patterns of the residual stress tensor in a weld are understood, the detailed patterns depend on welding process parameters and the effects of solid state transformation. The residual strain profiles in two multi-pass austenitic welds and a ferritic steel weld are presented. The stress-free lattice parameters within the fusion zone and the adjacent heat affected zone in the two austenitic welds show that the interpretation of residual stress from strains are affected by welding parameters. An interpretation of the residual strain pattern in the ferritic steel plate can be made using the strain measurements of a Gleeble test bar which has undergone the solid state austenite decomposition.

  11. 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.

  12. enceladus_stress_map

    NASA Video Gallery

    This is a map of the changing stress on the surface of Enceladus' icy crust from the wobble and gravitational tides. Blue lines show the direction of forces pulling the crust apart, and red lines s...

  13. RESIDUAL STRESSES IN 3013 CONTAINERS

    SciTech Connect

    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.

  14. Digital image correlation utilization in pipeline oriented residual stress estimation

    NASA Astrophysics Data System (ADS)

    Brynk, Tomasz; Mezyk, Dariusz; Kukla, Dominik

    2014-10-01

    The aim of the paper is to present an idea of the utilization of Digital Image Correlation (DIC) method for industrial pipelines residual stress oriented investigation. For this purpose results of tests performed in laboratory and industrial conditions are presented. Obtained results showed that DIC method gives reliable near drilled hole strain/displacement distribution maps which may be used for accurate residual stress calculations.

  15. A Benchmark Study on Casting Residual Stress

    SciTech Connect

    Johnson, Eric M.; Watkins, Thomas R; Schmidlin, Joshua E; Dutler, S. A.

    2012-01-01

    Stringent regulatory requirements, such as Tier IV norms, have pushed the cast iron for automotive applications to its limit. The castings need to be designed with closer tolerances by incorporating hitherto unknowns, such as residual stresses arising due to thermal gradients, phase and microstructural changes during solidification phenomenon. Residual stresses were earlier neglected in the casting designs by incorporating large factors of safety. Experimental measurement of residual stress in a casting through neutron or X-ray diffraction, sectioning or hole drilling, magnetic, electric or photoelastic measurements is very difficult and time consuming exercise. A detailed multi-physics model, incorporating thermo-mechanical and phase transformation phenomenon, provides an attractive alternative to assess the residual stresses generated during casting. However, before relying on the simulation methodology, it is important to rigorously validate the prediction capability by comparing it to experimental measurements. In the present work, a benchmark study was undertaken for casting residual stress measurements through neutron diffraction, which was subsequently used to validate the accuracy of simulation prediction. The stress lattice specimen geometry was designed such that subsequent castings would generate adequate residual stresses during solidification and cooling, without any cracks. The residual stresses in the cast specimen were measured using neutron diffraction. Considering the difficulty in accessing the neutron diffraction facility, these measurements can be considered as benchmark for casting simulation validations. Simulations were performed using the identical specimen geometry and casting conditions for predictions of residual stresses. The simulation predictions were found to agree well with the experimentally measured residual stresses. The experimentally validated model can be subsequently used to predict residual stresses in different cast

  16. Macro stress mapping on thin film buckling

    SciTech Connect

    Goudeau, P.; Villain, P.; Renault, P.-O.; Tamura, N.; Celestre, R.S.; Padmore, H.A.

    2002-11-06

    Thin films deposited by Physical Vapour Deposition techniques on substrates generally exhibit large residual stresses which may be responsible of thin film buckling in the case of compressive stresses. Since the 80's, a lot of theoretical work has been done to develop mechanical models but only a few experimental work has been done on this subject to support these theoretical approaches and nothing concerning local stress measurement mainly because of the small dimension of the buckling (few 10th mm). This paper deals with the application of micro beam X-ray diffraction available on synchrotron radiation sources for stress mapping analysis of gold thin film buckling.

  17. Residual stress measurement in YBCO thin films.

    SciTech Connect

    Cheon, J. H.; Singh, J. P.

    2002-05-13

    Residual stress in YBCO films on Ag and Hastelloy C substrates was determined by using 3-D optical interferometry and laser scanning to measure the change in curvature radius before and after film deposition. The residual stress was obtained by appropriate analysis of curvature measurements. Consistent with residual thermal stress calculations based on the thermal expansion coefficient mismatch between the substrates and YBCO film, the measured residual stress in the YBCO film on Hastelloy C substrate was tensile, while it was compressive on the Ag substrate. The stress values measured by the two techniques were generally in good agreement, suggesting that optical interferometry and laser scanning have promise for measuring residual stresses in thin films.

  18. 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.

  19. Longitudinal residual stresses in boron fibers

    NASA Technical Reports Server (NTRS)

    Behrendt, D. R.

    1976-01-01

    A method of measuring the longitudinal residual stress distribution in boron fibers is presented. The residual stresses in commercial CVD boron on tungsten fibers of 102, 142, and 203 microns (4, 5.6, and 8 mil) diameters were determined. Results for the three sizes show a compressive stress at the surface 800 to -1400 MN/sq m 120 to -200 ksi), changing monotonically to a region of tensile stress within the boron. At approximately 25 percent of the original radius, the stress reaches a maximum tensile 600 to 1000 MN/sq m(90 to 150 ksi) and then decreases to compressive near the tungsten boride core. The core itself is under a compressive stress of approximately -1300 MN/sq m (-190 ksi). The effects of surface removal on core residual stress and core-initiated fracture are discussed.

  20. A stress-free model for residual stress assessment using thermoelastic stress analysis

    NASA Astrophysics Data System (ADS)

    Howell, Geoffrey; Dulieu-Barton, Janice M.; Achintha, Mithila; Robinson, Andrew F.

    2015-03-01

    Thermoelastic Stress Analysis (TSA) has been proposed as a method of obtaining residual stresses. The results of a preliminary study demonstrated that when Al-2024 plate containing holes that were plastically deformed by cold expansion process to 2% and 4% strain the thermoelastic response in the material around the hole was different to that obtained from a plate that had not experienced any plastic cold expansion (i.e. a reference specimen). This observation provides an opportunity for obtaining residual stresses based on TSA data. In many applications a reference specimen (i.e. residual stress free specimen) may not be available for comparison, so a synthetic, digital bitmap has been proposed as an alternative. An elastic finite element model is created using commercially available software Abaqus/Standard and the resultant stress field is extracted. The simulated stress field from the model is mapped onto a grid that matches the TSA pixel data from a physical reference specimen. This stress field is then converted to a ΔT/T field that can be compared to the full-field TSA data. When the reference experimental data is subtracted from the, bitmap dataset the resultant ΔT/T field is approximately zero. Further work proposes replacing the experimental reference data with that from specimens that have undergone cold expansion with the aim of revealing the regions affected by residual stress through a departure from zero in the resultant stress field. The paper demonstrates the first steps necessary for deriving the residual stresses from a general specimen using TSA.

  1. Residual stresses in injection molded products

    NASA Astrophysics Data System (ADS)

    Jansen, K. M. B.

    2015-12-01

    During the molding process residual stresses are formed due to thermal contraction during cooling as well as the local pressure history during solidification. In this paper a simple analytical model is reviewed which relates residual stresses, product shrinkage as well as warpage to the temperature and pressure histories during molding. Precise excimer laser layer removal measurements were performed to verify the predicted residual stress distributions. In addition, detailed shrinkage and warpage measurements on a large series of polymers and for different molding conditions were performed and are shown to compare well with the model predictions.

  2. An Integrated Modeling Approach for Predicting Process Maps of Residual Stress and Distortion in a Laser Weld: A Combined CFD-FE Methodology

    NASA Astrophysics Data System (ADS)

    Turner, Richard P.; Panwisawas, Chinnapat; Sovani, Yogesh; Perumal, Bama; Ward, R. Mark; Brooks, Jeffery W.; Basoalto, Hector C.

    2016-07-01

    Laser welding has become an important joining methodology within a number of industries for the structural joining of metallic parts. It offers a high power density welding capability which is desirable for deep weld sections, but is equally suited to performing thinner welded joints with sensible amendments to key process variables. However, as with any welding process, the introduction of severe thermal gradients at the weld line will inevitably lead to process-induced residual stress formation and distortions. Finite element (FE) predictions for weld simulation have been made within academia and industrial research for a number of years, although given the fluid nature of the molten weld pool, FE methodologies have limited capabilities. An improvement upon this established method would be to incorporate a computational fluid dynamics (CFD) model formulation prior to the FE model, to predict the weld pool shape and fluid flow, such that details can be fed into FE from CFD as a starting condition. The key outputs of residual stress and distortions predicted by the FE model can then be monitored against the process variables input to the model. Further, a link between the thermal results and the microstructural properties is of interest. Therefore, an empirical relationship between lamellar spacing and the cooling rate was developed and used to make predictions about the lamellar spacing for welds of different process parameters. Processing parameter combinations that lead to regions of high residual stress formation and high distortion have been determined, and the impact of processing parameters upon the predicted lamellar spacing has been presented.

  3. Residual Stress Analysis in Thick Uranium Films

    SciTech Connect

    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.

  4. Residual stress effects in stress-corrosion cracking

    SciTech Connect

    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.

  5. 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.

  6. 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.

  7. Residual Stress Predictions in Polycrystalline Alumina

    SciTech Connect

    VEDULA,VENKATA R.; GLASS,S. JILL; SAYLOR,DAVID M.; ROHRER,GREGORY S.; CARTER,W. CRAIG; LANGER,STEPHEN A.

    1999-12-13

    Microstructure-level residual stresses arise in polycrystalline ceramics during processing as a result of thermal expansion anisotropy and crystallographic disorientation across the grain boundaries. Depending upon the grain size, the magnitude of these stresses can be sufficiently high to cause spontaneous microcracking during the processing of these materials. They are also likely to affect where cracks initiate and propagate under macroscopic loading. The magnitudes of residual stresses in untextured and textured alumina samples were predicted using object oriented finite (OOF) element analysis and experimentally determined grain orientations. The crystallographic orientations were obtained by electron-backscattered diffraction (EBSD). The residual stresses were lower and the stress distributions were narrower in the textured samples compared to those in the untextured samples. Crack initiation and propagation were also simulated using the Griffith fracture criterion. The grain boundary to surface energy ratios required for computations were estimated using AFM groove measurements.

  8. Dependence of diffuse ultrasonic backscatter on residual stress in 1080 steel.

    PubMed

    Du, Hualong; Turner, Joseph A

    2016-04-01

    In this article, the effects of residual stress on the ultrasonic scattering in a quenched steel sample are investigated by calculating the change of spatial variance amplitudes of ultrasonic signals after removing residual stress via annealing. The experimental results show that the average spatial variance amplitude decreases by about 11.89% for a scan area on the quenched surface after removing residual stress. This quantity was used to estimate the residual stress based on the developed stress-dependent backscatter model. In addition, the residual stress on the whole scan area was mapped by calculating the change of the spatial variance amplitude for each subarea after annealing, respectively. Diffuse ultrasonic backscatter signals show a high sensitivity to residual stress such that this technique has potential as a non-destructive method for measuring residual stress. PMID:26784273

  9. Residual Stress Testing of Outer 3013 Containers

    SciTech Connect

    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.

  10. PUFF TOO: a residual stress experiment

    SciTech Connect

    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.

  11. Residual stresses and stress corrosion cracking in pipe fittings

    SciTech Connect

    Parrington, R.J.; Scott, J.J.; Torres, F.

    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.

  12. Accuracy evaluation of residual stress measurements

    SciTech Connect

    Yerman, J.A.; Kroenke, W.C.; Long, W.H.

    1996-05-01

    The accuracy of residual stress measurement techniques is difficult to assess due to the lack of available reference standards. To satisfy the need for reference standards, two specimens were designed and developed to provide known stress magnitudes and distributions: one with a uniform stress distribution and one with a nonuniform linear stress distribution. A reusable, portable load fixture was developed for use with each of the two specimens. Extensive bench testing was performed to determine if the specimens provide desired known stress magnitudes and distributions and stability of the known stress with time. The testing indicated that the nonuniform linear specimen and load fixture provided the desired known stress magnitude and distribution but that modifications were required for the uniform stress specimen. A trial use of the specimens and load fixtures using hole drilling was successful.

  13. 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.

  14. System and method for measuring residual stress

    DOEpatents

    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.

  15. 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.

  16. Modeling Residual Stresses in Ceramic Plates

    SciTech Connect

    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.

  17. Neutron scattering residual stress measurements on gray cast iron brake discs

    SciTech Connect

    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.

  18. Mapping residual transmission for malaria elimination.

    PubMed

    Reiner, Robert C; Le Menach, Arnaud; Kunene, Simon; Ntshalintshali, Nyasatu; Hsiang, Michelle S; Perkins, T Alex; Greenhouse, Bryan; Tatem, Andrew J; Cohen, Justin M; Smith, David L

    2015-01-01

    Eliminating malaria from a defined region involves draining the endemic parasite reservoir and minimizing local malaria transmission around imported malaria infections . In the last phases of malaria elimination, as universal interventions reap diminishing marginal returns, national resources must become increasingly devoted to identifying where residual transmission is occurring. The needs for accurate measures of progress and practical advice about how to allocate scarce resources require new analytical methods to quantify fine-grained heterogeneity in malaria risk. Using routine national surveillance data from Swaziland (a sub-Saharan country on the verge of elimination), we estimated individual reproductive numbers. Fine-grained maps of reproductive numbers and local malaria importation rates were combined to show 'malariogenic potential', a first for malaria elimination. As countries approach elimination, these individual-based measures of transmission risk provide meaningful metrics for planning programmatic responses and prioritizing areas where interventions will contribute most to malaria elimination. PMID:26714110

  19. X-ray diffraction measurement of residual stresses in thick, multi-pass steel weldments

    SciTech Connect

    Ruud, C.O.; Di Mascio, P.S.; Pangborn, R.N.; Snoha, D.J.

    1985-05-01

    A unique X-ray diffraction instrument for residual stress measurement has been developed that provides for speed, ease of measurement, accuracy, and economy of surface stress measurement. Application of this instrument with a material removal technique, e.g., electropolishing, has facilitated detailed, high resolution studies of three-dimensional stress fields. This paper describes the instrumentation and techniques applied to conduct the residual stress measurement and presents maps of the residual stress data obtained for the surfaces of a heavy 21/4 Cr 1 Mo steel plate weldment.

  20. 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.

  1. 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.

  2. 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.

  3. Measurement of residual stresses using fracture mechanics weight functions

    SciTech Connect

    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.

  4. 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.

  5. Effects of residual stresses on fracture of welded pipes

    SciTech Connect

    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.

  6. Mapping residual transmission for malaria elimination

    PubMed Central

    Reiner, Robert C; Le Menach, Arnaud; Kunene, Simon; Ntshalintshali, Nyasatu; Hsiang, Michelle S; Perkins, T Alex; Greenhouse, Bryan; Tatem, Andrew J; Cohen, Justin M; Smith, David L

    2015-01-01

    Eliminating malaria from a defined region involves draining the endemic parasite reservoir and minimizing local malaria transmission around imported malaria infections . In the last phases of malaria elimination, as universal interventions reap diminishing marginal returns, national resources must become increasingly devoted to identifying where residual transmission is occurring. The needs for accurate measures of progress and practical advice about how to allocate scarce resources require new analytical methods to quantify fine-grained heterogeneity in malaria risk. Using routine national surveillance data from Swaziland (a sub-Saharan country on the verge of elimination), we estimated individual reproductive numbers. Fine-grained maps of reproductive numbers and local malaria importation rates were combined to show ‘malariogenic potential’, a first for malaria elimination. As countries approach elimination, these individual-based measures of transmission risk provide meaningful metrics for planning programmatic responses and prioritizing areas where interventions will contribute most to malaria elimination. DOI: http://dx.doi.org/10.7554/eLife.09520.001 PMID:26714110

  7. Residual Stress Measurement Using Rectangular Spiral Coils

    NASA Astrophysics Data System (ADS)

    Sun, Haiyan; Plotnikov, Yuri

    2008-02-01

    Shot peening process provides compressive residual stress within a depth of about 150˜200 um from the surface. It has been demonstrated that multi-frequency eddy current measurement can be effectively used for the residual stress estimation on Ni-based superalloys. In order to measure the stress profile over the entire compressive zone, the probe needs to work in a wide frequency range from 0.1 MHz to above 50 MHz. Due to its wide bandwidth and high precision fabrication process, spiral coils fabricated on flexible substrate using photolithographic technology are good candidate for this task It is useful to develop a coil model in order to optimize coil design, minimize liftoff effect and maximize coil gauge factor. In this work, a 3D analytical model was used to simulate rectangular spiral coil response on a half-space conductor. The results were compared with commercial available 3D finite element software and experimental results. The analytical model was also used to simulate 4-point calibration process that was used to calculate apparent eddy current conductivity (AECC). The experimental setup was described and AECC profile was obtained for shot-peening samples with different peening intensity and different heat treatment.

  8. Measurements of residual stress in fracture mechanics coupons

    SciTech Connect

    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.

  9. Method For Characterizing Residual Stress In Metals

    DOEpatents

    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.

  10. Residual Stresses Modeled in Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Freborg, A. M.; Ferguson, B. L.; Petrus, G. J.; Brindley, W. J.

    1998-01-01

    Thermal barrier coating (TBC) applications continue to increase as the need for greater engine efficiency in aircraft and land-based gas turbines increases. However, durability and reliability issues limit the benefits that can be derived from TBC's. A thorough understanding of the mechanisms that cause TBC failure is a key to increasing, as well as predicting, TBC durability. Oxidation of the bond coat has been repeatedly identified as one of the major factors affecting the durability of the ceramic top coat during service. However, the mechanisms by which oxidation facilitates TBC failure are poorly understood and require further characterization. In addition, researchers have suspected that other bond coat and top coat factors might influence TBC thermal fatigue life, both separately and through interactions with the mechanism of oxidation. These other factors include the bond coat coefficient of thermal expansion, the bond coat roughness, and the creep behavior of both the ceramic and bond coat layers. Although it is difficult to design an experiment to examine these factors unambiguously, it is possible to design a computer modeling "experiment" to examine the action and interaction of these factors, as well as to determine failure drivers for TBC's. Previous computer models have examined some of these factors separately to determine their effect on coating residual stresses, but none have examined all the factors concurrently. The purpose of this research, which was performed at DCT, Inc., in contract with the NASA Lewis Research Center, was to develop an inclusive finite element model to characterize the effects of oxidation on the residual stresses within the TBC system during thermal cycling as well as to examine the interaction of oxidation with the other factors affecting TBC life. The plasma sprayed, two-layer thermal barrier coating that was modeled incorporated a superalloy substrate, a NiCrAlY bond coat, and a ZrO2-8 wt % Y2O3 ceramic top coat. We

  11. Neutron diffraction measurements of residual stresses in friction stir welding: a review

    SciTech Connect

    Woo, Wan Chuck; Feng, Zhili; Wang, Xun-Li; David, Stan A

    2011-01-01

    Significant amounts of residual stresses are often generated during welding and result in critical degradation of the structural integrity and performance of components. Neutron diffraction has become a well established technique for the determination of residual stresses in welds because of the unique deep penetration, three-dimensional mapping capability, and volume averaged bulk measurements characteristic of the scattering neutron beam. Friction stir welding has gained prominence in recent years. The authors reviewed a number of neutron diffraction measurements of residual stresses in friction stir welds and highlighted examples addressing how the microstructures and residual stresses are correlated with each other. An example of in situ neutron diffraction measurement result shows the evolution of the residual stresses during welding.

  12. Residual stress depth profiles of ausrolled 9310 gear steel

    SciTech Connect

    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.

  13. Residual Stresses in LENS-Deposited AISI 410 Stainless Steel Plates

    SciTech Connect

    Wang, L; Felicellli, S D; Pratt, Phillip R

    2008-01-01

    The residual stress in thin plate components deposited by the laser engineered net shaping (LENS{reg_sign}) process was investigated experimentally and numerically. Neutron diffraction mapping was used to characterize the residual stress in LENS-deposited AISI 410 stainless steel thin wall plates. Using the commercial welding software SYSWELD, a thermo-mechanical three-dimensional finite element model was developed, which considers also the effect of metallurgical phase transformations. The model was employed to predict the temperature history and the residual stress field during the LENS process. Several simulations were performed with the geometry and process parameters that were used to build the experimental samples. The origin of the residual stress distribution is discussed based on the thermal histories of the samples, and the modeling results are compared with measurements obtained by neutron diffraction mapping.

  14. Experimental determination of residual stress by neutron diffraction in a boiling water reactor core shroud

    SciTech Connect

    Payzant, A.; Spooner, S.; Zhu, Xiaojing; Hubbard, C.R.

    1996-06-01

    Residual strains in a 51 mm (2-inch) thick 304L stainless steel plate have been measured by neutron diffraction and interpreted in terms of residual stress. The plate, measuring (300 mm) in area, was removed from a 6m (20-ft.) diameter unirradiated boiling water reactor core shroud, and included a multiple-pass horizontal weld which joined two of the cylindrical shells which comprise the core shroud. Residual stress mapping was undertaken in the heat affected zone, concentrating on the outside half of the plate thickness. Variations in residual stresses with location appeared consistent with trends expected from finite element calculations, considering that a large fraction of the residual hoop stress was released upon removal of the plate from the core shroud cylinder.

  15. Residual stress determination from a laser-based curvature measurement

    SciTech Connect

    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.

  16. Residual Stress Determination from a Laser-Based Curvature Measurement

    SciTech Connect

    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.

  17. Measurement of residual stress in a multi-layer semiconductor heterostructure by micro-Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Qiu, Wei; Cheng, Cui-Li; Liang, Ren-Rong; Zhao, Chun-Wang; Lei, Zhen-Kun; Zhao, Yu-Cheng; Ma, Lu-Lu; Xu, Jun; Fang, Hua-Jun; Kang, Yi-Lan

    2016-07-01

    Si-based multilayer structures are widely used in current microelectronics. During their preparation, some inhomogeneous residual stress is induced, resulting in competition between interface mismatching and surface energy and even leading to structure failure. This work presents a methodological study on the measurement of residual stress in a multi-layer semiconductor heterostructure. Scanning electron microscopy (SEM), micro-Raman spectroscopy (MRS), and transmission electron microscopy (TEM) were applied to measure the geometric parameters of the multilayer structure. The relationship between the Raman spectrum and the stress/strain on the [100] and [110] crystal orientations was determined to enable surface and cross-section residual stress analyses, respectively. Based on the Raman mapping results, the distribution of residual stress along the depth of the multi-layer heterostructure was successfully obtained.

  18. Residual stress and crack propagation in laminated composites

    SciTech Connect

    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.

  19. Measuring of residual stresses in thermal sprayed coatings

    SciTech Connect

    Brandt, O.C.

    1995-12-31

    The Modified Almen Method (MAM) uses the deformation of test samples for measuring the residual stress and with small mathematical expenditure it yields the distribution in the coating. This paper presents the basic theory of MAM and the boundary conditions for using this method for the classification of thermal sprayed coatings with respect to the residual stress. The residual stress distribution of different HVOF coatings are shown in this work. Typical spray parameters are compared. The results are also compared with the ones calculated with other methods for the determination of the residual stress in thermal sprayed coatings.

  20. Residual stress characterization of welds and post-weld processes using x-ray diffraction techniques

    NASA Astrophysics Data System (ADS)

    Brauss, Michael E.; Pineault, James A.; Eckersley, John S.

    1998-03-01

    This paper illustrates the importance of residual stress characterization in welds and post weld processes. The failure to characterize residual stresses created during welding and/or post weld processes can lead to unexpected occurrences of stress corrosion cracking, distortion, fatigue cracking as well as instances of over design or over processing. The development of automated residual stress mapping and the availability of portable and fast equipment have now made the characterization of residual stresses using x-ray diffraction practical for process control and optimization. The paper presents examples where x-ray diffraction residual stress characterization techniques were applied on various kinds of welds including arc welds, TIG welds, resistance welds, laser welds and electron beam welds. The nondestructive nature of the x-ray diffraction technique has made the residual stress characterization of welds a useful tool for process optimization and failure analysis, particularly since components can be measured before and after welding and post welding processes. Some examples presented show the residual stresses before and after the application of post weld processes such as shot peening, grinding and heat treatment.

  1. 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.

  2. A finite element model for residual stress in repair welds

    SciTech Connect

    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.

  3. Grinding Induced Changes in Residual Stresses of Carburized Gears

    SciTech Connect

    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.

  4. Prediction of residual stress and distortion from residual stress in heat treated and machined aluminum parts

    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.

  5. Residual stresses in darrieus vertical axis wind turbine blades

    SciTech Connect

    Veers, P.

    1981-04-01

    A numerical package called RESID has been assembled to calculate the residual stresses in VAWT blades induced during cold forming. Using a strength of materials - elementary beam theory approach, RESID models the material response with a bilinear stress-strain curve, and the cross-sectional geometry with an array of area increments. Through an iterative solution procedure residual stresses are predicted for a specified final radius of curvature or applied bending moment. RESID results are compared to theoretical solutions for simple geometries and with MARC Finite element results for VAWT blade geometries. Calculating residual stress levels, determining acceptable residual stress levels, and a method of reducing residual stresses are discussed. A complete listing and sample run are included in the appendicies.

  6. Residual stress of physical vapor-deposited polycrystalline multilayers

    NASA Astrophysics Data System (ADS)

    Zhang, Song; Zhang, Hui; Zheng, LiLi

    2015-02-01

    An extended one-dimensional stress model for the deposition of multilayer films is built based on the existing stress model by considering the influence of deposition conditions. Both thermal stress and intrinsic stress are considered to constitute the final residual stress in the model. The deposition process conditions such as deposition temperature, oxygen pressure, and film growth rate are correlated to the full stress model to analyze the final residual stress distribution, and thus the deformation of the deposited multilayer system under different process conditions. Also, the model is numerically realized with in-house built code. A deposition of Ag-Cu multilayer system is simulated with the as-built extended stress model, and the final residual stresses under different deposition conditions are discussed with part of the results compared with experiment from other literature.

  7. Residual stresses in sapphire rods grown by the Stepanov method

    NASA Astrophysics Data System (ADS)

    Krymov, V. M.; Nosov, Yu. G.; Bakholdin, S. I.; Galaktionov, E. V.; Maslov, V. N.; Tropp, E. A.

    2015-04-01

    The residual stresses in cylindrical [0001] sapphire crystals have been studied using the polarization-optical method. The angle between the optical axes 2 V and the difference in the normal components of the tensor of elastic residual stresses (σφ - σ r ) have been determined from the isogyre divergence. It has been found that a tangential tensile stress of no more than 20 MPa acts on the ingot surface. The residual stresses have been compared with the calculated thermoelastic stresses generated during the crystal growth in a given heating zone. It has been shown that the determined pattern of residual stresses can be caused by thermoelastic stresses developing in the immediate vicinity of the crystallization front.

  8. Estimation of uncertainty for contour method residual stress measurements

    DOE PAGESBeta

    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 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

  9. Estimation of uncertainty for contour method residual stress measurements

    SciTech Connect

    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).

  10. Improved analytical model for residual stress prediction in orthogonal cutting

    NASA Astrophysics Data System (ADS)

    Qi, Zhaoxu; Li, Bin; Xiong, Liangshan

    2014-09-01

    The analytical model of residual stress in orthogonal cutting proposed by Jiann is an important tool for residual stress prediction in orthogonal cutting. In application of the model, a problem of low precision of the surface residual stress prediction is found. By theoretical analysis, several shortages of Jiann's model are picked out, including: inappropriate boundary conditions, unreasonable calculation method of thermal stress, ignorance of stress constraint and cyclic loading algorithm. These shortages may directly lead to the low precision of the surface residual stress prediction. To eliminate these shortages and make the prediction more accurate, an improved model is proposed. In this model, a new contact boundary condition between tool and workpiece is used to make it in accord with the real cutting process; an improved calculation method of thermal stress is adopted; a stress constraint is added according to the volumeconstancy of plastic deformation; and the accumulative effect of the stresses during cyclic loading is considered. At last, an experiment for measuring residual stress in cutting AISI 1045 steel is conducted. Also, Jiann's model and the improved model are simulated under the same conditions with cutting experiment. The comparisons show that the surface residual stresses predicted by the improved model is closer to the experimental results than the results predicted by Jiann's model.

  11. Improved analytical model for residual stress prediction in orthogonal cutting

    NASA Astrophysics Data System (ADS)

    Qi, Zhaoxu; Li, Bin; Xiong, Liangshan

    2014-09-01

    The analytical model of residual stress in orthogonal cutting proposed by Jiann is an important tool for residual stress prediction in orthogonal cutting. In application of the model, a problem of low precision of the surface residual stress prediction is found. By theoretical analysis, several shortages of Jiann's model are picked out, including: inappropriate boundary conditions, unreasonable calculation method of thermal stress, ignorance of stress constraint and cyclic loading algorithm. These shortages may directly lead to the low precision of the surface residual stress prediction. To eliminate these shortages and make the prediction more accurate, an improved model is proposed. In this model, a new contact boundary condition between tool and workpiece is used to make it in accord with the real cutting process; an improved calculation method of thermal stress is adopted; a stress constraint is added according to the volume-constancy of plastic deformation; and the accumulative effect of the stresses during cyclic loading is considered. At last, an experiment for measuring residual stress in cutting AISI 1045 steel is conducted. Also, Jiann's model and the improved model are simulated under the same conditions with cutting experiment. The comparisons show that the surface residual stresses predicted by the improved model is closer to the experimental results than the results predicted by Jiann's model.

  12. Residual stresses in a multi-pass weld in an austenitic stainless steel plate before and after thermal stress relief

    SciTech Connect

    Spooner, S.; Wang, X.L.; Hubbard, C.R.; David, S.A.

    1994-06-01

    Changes in residual stresses due to thermal stress relief were determined in a welded 1/2 in. thick 304 stainless steel plate from two residual stress maps determined with the neutron diffraction technique. The 304 stainless plate was made from two 6 {times} 12 {times} 1/2 in. pieces joined along the length by a gas tungsten arc welding process. Multi-pass welds were made with a semiautomatic welding machine employing cold-wire feed of type 308 stainless steel filler alloy. The thermal stress relief treatment consisted of heating to 1150 F, holding for one hour at temperature and then air cooling. Strain components were measured along the weld direction (longitudinal), perpendicular to the weld line in the plate (transverse), and normal to the plate. Measurements were confined to the plane bisecting the weld at the center of the plate. The strain components were converted to stresses assuming that the measured strains were along the principal axes of the strain tensor. Parameters used in the calculation were E=224 GPa and v=0.25. As-welded longitudinal stresses are compressive in the base metal and become strongly tensile through the heat affected zone and into the fusion zone. The transverse stresses follow the longitudinal trend but with a lower magnitude while the normal stresses are small throughout. The stress relief treatment reduced the magnitudes of all the stresses. In the weld zone the longitudinal stress was lowered by 30% and the spatial range of residual stresses was reduced as well.

  13. 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.

  14. Residual stress in spin-cast polyurethane thin films

    NASA Astrophysics Data System (ADS)

    Zhang, Hong; Zhang, Li

    2015-01-01

    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.

  15. Residual stress in spin-cast polyurethane thin films

    SciTech Connect

    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.

  16. Consideratons Regarding the Alignment of Diffractometers for Residual stress Analysis

    SciTech Connect

    Watkins, Thomas R; Cavin, Odis Burl; Matlock, Beth

    2006-01-01

    Proper alignment of an X-ray diffractometer is critical to performing credible measurements, particularly for residual stress determinations. This article will emphasize practical aspects of diffractometer alignment and standards usage with regards to residual strain measurement. Essentially, what to do when one is confronted with a residual stress problem and an unfamiliar goniometer. Various alignment techniques, use of standards, and related issues will be discussed.

  17. Phase unwrapping by accumulation of residual maps

    NASA Astrophysics Data System (ADS)

    Rivera, Mariano; Hernandez-Lopez, Francisco J.; Gonzalez, Adonai

    2015-01-01

    We present a path independent (global) algorithm for phase unwrapping based on the minimisation of a robust cost function. The algorithm incorporates an outlier rejection mechanism making it robust to large inconsistencies and discontinuities. The proposal consists on an iterative incremental scheme that unwraps a sub-estimation of the residual phase at each iteration. The sub-estimation degree is controlled by an algorithm's parameter. We present an efficiently computational multigrid implementation based on a nested strategy: the process is iterated by using multiple resolutions. The proposal's performance is demonstrated by experiments with synthetic and real data, and successfully compared with algorithms of the state of the art.

  18. 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.

  19. Residual stress measurements on thick plate low-alloy steel narrow gap weldments by x-ray diffraction

    SciTech Connect

    Rund, C.O.; DiMascio, P.S.; Pangborn, R.N.; Snoha, D.J.

    1984-06-01

    A unique x-ray diffraction instrument for residual stress measurement has been developed that provides for speed, ease of measurement, accuracy, and economy of surface stress measurement. Application of this instrument with a material removal technique, e.g., electropolishing, has facilitated detailed, high resolution studies of three-dimensional stress fields. This paper describes the instrumentation and techniques applied to conduct the residual stress measurement and presents maps of the residual stress data obtained for the surfaces of a heavy 2 1/4 Cr 1 Mo steel plate weldment.

  20. Low-field magnetoacoustic residual stress measurement in steel

    NASA Technical Reports Server (NTRS)

    Namkung, M.; Utrata, D.; Heyman, J. S.; Allison, S. G.

    1987-01-01

    Much of the recent development of the magnetoacoustic technique has been devoted to refine this technique as a reliable and practical tool for measuring bulk residual stress in steel components. For this, the effects of structural and metallurgical properties on the magnetoacoustic interaction have been studied for various types of steel samples. Also, progress is being made to obtain quantitative residual stress measurements in railroad wheels. This paper reviews the physical basis and the experimental results of the magnetoacoustic stress measurements in steels.

  1. Effects of residual stress on irradiation hardening in stainless steels

    NASA Astrophysics Data System (ADS)

    Okubo, N.; Miwa, Y.; Kondo, K.; Kaji, Y.

    2009-04-01

    Effects of residual stress on irradiation hardening were studied in advance for predicting irradiation assisted stress corrosion cracking. The specimens of SUS316 and SUS316L with several % plastic strains, which correspond to weld residual stress, were prepared by bending and keeping deformation under irradiation. Ion irradiations of 12 MeV Ni 3+ were performed at 330, 400 and 550 oC to 45 dpa. No bended specimen was simultaneously irradiated with the bended specimen. The residual stress was estimated by X-ray residual stress measurements before and after the irradiation. The micro-hardness was measured by using nanoindenter. The residual stress did not relax even for the case of the higher temperature aging at 500 oC for the same time of irradiation. The residual stress after ion irradiation up to high dpa, however, relaxed at these experimental temperatures. The irradiation hardening of stressed specimen was obviously lower than that of un-stressed one in case of SUS316L irradiated at 300 oC to 12 dpa.

  2. 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.

  3. 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.

  4. 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.

  5. Residue stress analysis of molding aspherical plastic lens

    NASA Astrophysics Data System (ADS)

    Hsu, Ming-Ying; Cheng, Yuan-Chieh; Chang, Shenq-Tsong; Huang, Ting-Ming

    2015-09-01

    The aspherical plastic lens is widely used in commercial optical products. Warpage and residue stress are two important factors that influence wavefront error. Several investigators have discussed warpage. We propose a methodology to study the effect of residue stress on wavefront error. Mold flow software was adopted to calculate the residue stress in injection processes. Optical software was used to find optical ray paths through the lens. Corresponding Optical Path Different (OPD) in each ray path was simulated by self-developed software. A 50-mm diameter plastic lens was used in this study. The mild- and high-frequency wavefront errors and the stress OPD effect at the injection area were found to be a result of the molding process. The proposed methodology was found to be very suitable for finding the effect of residue stress on wavefront error in plastic lenses.

  6. Residual stress measurements of tension leg platform tendon welds

    SciTech Connect

    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.

  7. Methodologies for measuring residual stress distributions in epitaxial thin films

    NASA Astrophysics Data System (ADS)

    Liu, M.; Ruan, H. H.; Zhang, L. C.

    2013-01-01

    Residual stresses in a thin film deposited on a dissimilar substrate can bring about various interface or subsurface damages, such as delamination, dislocation, twinning and cracking. In high performance integrated circuits and MEMS, a too high residual stress can significantly alter their electronic properties. A proper residual stress characterization needs the description of full stress tensors and their variations with thickness. The problem is that film thickness measurement requires different means, and that direct measurement techniques to fulfill the tasks are not straightforward. This paper provides a simple method using X-ray diffraction (XRD) and Raman scattering for the measurement of residual stresses and their thickness dependence. Using the epitaxial silicon film on a sapphire substrate as an example, this paper demonstrates that the improved XRD technique can make use of multiple diffraction peaks to give rise to a highly accurate stress tensor. The co-existence of silicon and sapphire peaks in a Raman spectrum then allows a simultaneous measurement of film thickness from the peak intensity ratio and the residual stress from the peak shift. The paper also concludes the relation between film thickness and residual stresses.

  8. Water aging reverses residual stresses in hydrophilic dental composites.

    PubMed

    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. PMID:24272790

  9. Photoelastic measurements of residual stresses for NDE

    NASA Technical Reports Server (NTRS)

    Redner, Alex S.

    1988-01-01

    Photoelastic measurements of residual strains are used extensively in the QC and inspection of transparent materials. A new method of measurements, based on Spectral Contents Analysis, is described in this paper. The method uses a personal computer for photoelastic data acquisition, eliminating personal skill and subjectivity. the new tool should make the measurements of residual strains for QC simpler and more reliable.

  10. Measured residual stresses in overlay pipe weldments removed from service

    SciTech Connect

    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.

  11. Noninvasive in vivo determination of residual strains and stresses.

    PubMed

    Donmazov, Samir; Piskin, Senol; Pekkan, Kerem

    2015-06-01

    Vascular growth and remodeling during embryonic development are associated with blood flow and pressure induced stress distribution, in which residual strains and stresses play a central role. Residual strains are typically measured by performing in vitro tests on the excised vascular tissue. In this paper, we investigated the possibility of estimating residual strains and stresses using physiological pressure-radius data obtained through in vivo noninvasive measurement techniques, such as optical coherence tomography or ultrasound modalities. This analytical approach first tested with in vitro results using experimental data sets for three different arteries such as rabbit carotid artery, rabbit thoracic artery, and human carotid artery based on Fung's pseudostrain energy function and Delfino's exponential strain energy function (SEF). We also examined residual strains and stresses in the human swine iliac artery using the in vivo experimental ultrasound data sets corresponding to the systolic-to-diastolic region only. This allowed computation of the in vivo residual stress information for loading and unloading states separately. Residual strain parameters as well as the material parameters were successfully computed with high accuracy, where the relative errors are introduced in the range of 0-7.5%. Corresponding residual stress distributions demonstrated global errors all in acceptable ranges. A slight discrepancy was observed in the computed reduced axial force. Results of computations performed based on in vivo experimental data obtained from loading and unloading states of the artery exhibited alterations in material properties and residual strain parameters as well. Emerging noninvasive measurement techniques combined with the present analytical approach can be used to estimate residual strains and stresses in vascular tissues as a precursor for growth estimates. This approach is also validated with a finite element model of a general two-layered artery

  12. Measuring depth profiles of residual stress with Raman spectroscopy

    SciTech Connect

    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.

  13. 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.

  14. Residual stresses in weld deposited clad pressure vessels and nozzles

    SciTech Connect

    Jones, D.P.; Mabe, W.R.; Shadley, J.R.; Rybicki, E.F.

    1998-04-01

    Results of through-thickness residual stress measurements are provided for a variety of samples of weld deposited 308/309L stainless steel and Alloy 600 cladding on low-alloy pressure vessel ferritic steels. Clad thicknesses between 5 and 9mm on samples that vary in thickness from 45 to 200mm were studied. The samples were taken from flat plates, from a spherical head of a pressure vessel, from a ring-segment of a nozzle bore, and from the transition radius between a nozzle and a pressure vessel shell. A layer removal method was used to measure the residual stresses. The effects of uncertainties in elastic constants (Young`s modulus and Poisson`s ratio) as well as experimental error are assessed. All measurements were done at room temperature. The results of this work indicate that curvature plays a significant role in cladding residual stress and that tensile residual stresses as high as the yield stress can be measured in the cladding material. Since the vessel from which the spherical and nozzle corner samples were taken was hydrotested, and the flat plate specimens were taken from specimens used in mechanical fatigue testing, these results suggest that rather high tensile residual stresses can be retained in the cladding material even after some mechanical loading associated with hydrotesting and that higher levels of hydrotest loading would be required to alter the cladding residual stresses.

  15. Sonographic measurement versus mapping for determination of residual ridge width.

    PubMed

    Traxler, M; Ulm, C; Solar, P; Lill, W

    1992-03-01

    To achieve long-term success of dental implants, evaluation of the dimensions of the resorbing alveolar process must be accurate because an implant should be surrounded by at least 1 mm of bone. Estimating the thickness of bone is more difficult because the mucosal contour can mask the actual dimension of the residual ridge. With ultrasound, it is possible to analyze and visualize the diameter of maxillary or mandibular residual ridges. Data obtained from ultrasound measurement of residual ridges were compared with the data from ridge mapping with the Wilson bone caliper and the Spoerlein caliper. The ultrasound measurement produced nearly the same data at all measurement points as ridge mapping. Ultrasound also provides exact information about the location of the mental foramen and the maxillary sinus. By using all three methods the initial stage of implant treatment can be planned. PMID:1507101

  16. Mode-coupling analysis of residual stresses in colloidal glasses.

    PubMed

    Fritschi, S; Fuchs, M; Voigtmann, Th

    2014-07-21

    We present results from computer simulation and mode-coupling theory of the glass transition for the nonequilibrium relaxation of stresses in a colloidal glass former after the cessation of shear flow. In the ideal glass, persistent residual stresses are found that depend on the flow history. The partial decay of stresses from the steady state to this residual stress is governed by the previous shear rate. We rationalize this observation in a schematic model of mode-coupling theory. The results from Brownian-dynamics simulations of a glassy two-dimensional hard-disk system are in qualitative agreement with the predictions of the theory. PMID:24841537

  17. Evaluation of residual stress in sputtered tantalum thin-film

    NASA Astrophysics Data System (ADS)

    Al-masha'al, Asa'ad; Bunting, Andrew; Cheung, Rebecca

    2016-05-01

    The influence of deposition conditions on the residual stress of sputtered tantalum thin-film has been evaluated in the present study. Films have been deposited by DC magnetron sputtering and curvature measurement method has been employed to calculate the residual stress of the films. Transitions of tantalum film stress from compressive to tensile state have been observed as the sputtering pressure increases. Also, the effect of annealing process at temperature range of 90-300 °C in oxygen ambient on the residual stress of the films has been studied. The results demonstrate that the residual stress of the films that have been deposited at lower sputtering pressure has become more compressive when annealed at 300 °C. Furthermore, the impact of exposure to atmospheric ambient on the tantalum film stress has been investigated by monitoring the variation of the residual stress of both annealed and unannealed films over time. The as-deposited films have been exposed to pure Argon energy bombardment and as result, a high compressive stress has been developed in the films.

  18. Residual stresses and damage in unidirectional model composites

    SciTech Connect

    Chatterjee, A.; Moschler, J.W.; Mall, S.; Kerans, R.J.; Pagano, N.J.

    1989-10-01

    Unidirectional model composites were fabricated with SiC fibers and different borosilicate glasses to study the effect of residual stress states on the damage progression in these composites. A specially designed straining stage was employed to study the failure modes in these materials under stepwise loading. Although both fiber and matrix cracks were observed in all specimens, the mechanisms of failure were found to be different and strongly dependent on the residual stress state in these materials. 15 refs.

  19. 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.

  20. Method for residual stress relief and retained austenite destabilization

    DOEpatents

    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.

  1. 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.

  2. Residual stresses in a cast iron automotive brake disc rotor

    NASA Astrophysics Data System (ADS)

    Ripley, Maurice I.; Kirstein, Oliver

    2006-11-01

    Runout, and consequent juddering and pulsation through the brake pedal, is a multi-million dollar per year warranty problem for car manufacturers. There is some suspicion that the runout can be caused by relaxation of residual casting stresses when the disc is overheated during severe-braking episodes. We report here neutron-diffraction measurements of the levels and distribution of residual strains in a used cast iron brake disc rotor. The difficulties of measuring stresses in grey cast iron are outlined and three-dimensional residual-strain distributions are presented and their possible effects discussed.

  3. 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.

  4. 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

  5. Modelling of residually stressed materials with application to AAA.

    PubMed

    Ahamed, T; Dorfmann, L; Ogden, R W

    2016-08-01

    Residual stresses are generated in living tissues by processes of growth and adaptation and they significantly influence the mechanical behaviour of the tissues. Thus, to effectively model the elastic response of the tissues relative to a residually stressed configuration the residual stresses need to be incorporated into the constitutive equations. The purposes of this paper are (a) to summarise a general elastic constitutive formulation that includes residual stress, (b) to specify the tensors needed for the three-dimensional implementation of the theory in a nonlinear finite element code, and (c) to use the theory and its implementation to evaluate the wall stress distribution in an abdominal aortic aneurysm (AAA) using patient specific geometry and material model parameters. The considered material is anisotropic with two preferred directions indicating the orientation of the collagen fibres in the aortic tissue. The method described in this paper is general and can be used, by specifying appropriate energy functions, to investigate other residually stressed biological systems. PMID:26874252

  6. Residual stresses and plastic deformation in GTA-welded steel

    SciTech Connect

    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.

  7. 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.

  8. Residual stress measurement and microstructural characterization of thick beryllium films

    SciTech Connect

    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.

  9. Residual strain mapping of Roman styli from Iulia Concordia, Italy

    SciTech Connect

    Salvemini, Filomena; Grazzi, Francesco; Angelini, Ivana; Davydov, Vadim; Vontobel, Peter; Vigoni, Alberto; Artioli, Gilberto; Zoppi, Marco

    2014-05-01

    Iulia Concordia is an important Roman settlement known for the production of iron objects and weapons during the Roman Empire. A huge number of well-preserved styli were found in the past century in the bed of an old channel. In order to shed light about the production processes used by Roman for stylus manufacturing, a neutron diffraction residual strain analysis was performed on the POLDI materials science diffractometer at the Paul Scherrer Institut in Switzerland. Here, we present results from our investigation conducted on 11 samples, allowing to define, in a non-invasive way, the residual strain map related to the ancient Roman working techniques. - Highlights: • We examined 11 Roman styli from the settlement of Iulia Concordia, Italy. • We performed a neutron diffraction residual strain analysis on POLDI at PSI (CH). • We identified the production processes used by Roman for stylus manufacturing. • We clarified the way and direction of working applied for different classes of styli.

  10. Quantitative assessments of residual stress fields at the surface of alumina hip joints.

    PubMed

    Pezzotti, Giuseppe; Munisso, Maria Chiara; Lessnau, Kristina; Zhu, Wenliang

    2010-11-01

    In-depth and in-plane response functions of photo- and electro-stimulated probes have been modeled and quantitatively evaluated in order to assess their suitability to detect the highly graded residual stress fields generated at the surface of alumina hip joints. Optical calibrations revealed large differences in probe size, which strongly affected the detected magnitude of residual stress. A comparison between the responses of Raman and fluorescence probes in polycrystalline alumina showed that the depth of those probes spread to an extent in the order of the tens of microns even with using a confocal probe configuration. On the other hand, the electro-stimulated luminescence emitted by oxygen vacancy sites (F(+) center) in the alumina lattice represented the most suitable choice for confining to a shallow volume the stress probe. This latter probe enabled us to reduce the measurement depth to the order of the tens of nanometers. We show maps of surface residual stress as collected on both main-wear and nonwear zones of an alumina femoral head. A comparison among stress maps taken at exactly the same location, but employing different probes, revealed averaging effects on the stress magnitude detected with photo-stimulated probes, while proving the superior spatial resolution of the electron probe. PMID:20848660

  11. Effect of kinetics on residue curve maps for reactive distillation

    SciTech Connect

    Venimadhavan, G.; Buzad, G.; Doherty, M.F.; Malone, M.F. . Dept. of Chemical Engineering)

    1994-11-01

    A class of models is derived for studying the effects of chemical kinetics on residue curve maps for reactive distillation. Activity-based rate and phase equilibrium expressions provide an accurate and thermodynamically consistent description of composition changes in nonideal, reacting vapor-liquid mixtures. For certain strategies of operation, which dictate the rate of product removal, the model equations are nonautonomous, leading to unusual dynamic behavior. However, for a certain special product removal policy, the effects of kinetics can be described by a single parameter, the Damkoehler number, which measures the rate of reaction relative to product removal. For small values of the Damkoehler number, the nonreactive simple distillation residue curve map is recovered and the singular points are the pure components and azeotropes in the nonreactive mixture. A bifurcation analysis shows the deformation and, in some cases, the disappearance of these singular points as the Damkoehler number is increased until the equilibrium reactive residue curve map is recovered at large values. A model problem for the reactive distillation of methyl tert-butyl ether from isobutene and methanol is solved.

  12. 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).

  13. Residual stress measurement and analysis using ultrasonic techniques.

    NASA Technical Reports Server (NTRS)

    Noronha, P. J.; Chapman, J. R.; Wert, J. J.

    1973-01-01

    A technique which utilizes ultrasonic radiation has been developed to measure residual stresses in metals. This technique makes it possible to detect and measure the magnitude of the principle stresses and also to obtain their direction. The velocities of ultrasonic waves in materials are measured as the time to travel a fixed path length, and the change in transit time is related to the applied stress. The linear relationship obtained allows a procedure based on this principle to be used for the measurement of residual stress using surface waves and shear waves. A method for plotting stress profiles through a material using surface waves uses varying frequencies for the ultrasonic wave. A limitation of the shear wave method is considered. The system used for this technique is called the Modified Time of Flight System.

  14. Residual stresses in weld overlay tubes: A finite element study

    SciTech Connect

    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.

  15. 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.

  16. 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.

  17. Phase composition and residual stresses in thermal barrier coatings

    NASA Astrophysics Data System (ADS)

    Betsofen, S. Ya.; Ryabenko, B. V.; Ashmarin, A. A.; Molostov, D. E.

    2015-10-01

    The phase composition and the residual stresses in multilayer thermal barrier coatings, which consist of an external ZrO2-8Y2O3 ceramic layer, an intermediate gradient (metal ceramic) layer, and a transient metallic NiCrAlY sublayer, are studied. It is shown that an increase in the specific volume of the metallic sublayer as a result of the formation of thermal growing oxide Al2O3 generates high compressive stresses in this sublayer. The ceramic layer undergoes tensile stresses in this case. A method is proposed to estimate the stresses in gradient coatings from X-ray diffraction results.

  18. Mapping wave breaking and residual foam using infrared remote sensing

    NASA Astrophysics Data System (ADS)

    Carini, R. J.; Jessup, A. T.; Chickadel, C.

    2012-12-01

    Quantifying wave breaking in the surfzone is important for the advancement of models that seek to accurately predict energy dissipation, near-shore circulation, wave-current interactions, and air-sea gas transfer. Electro-optical remote sensing has been used to try to identify breaking waves. However, the residual foam, left over after the wave has broken, is indistinguishable from active foam in the visible band, which makes identification of active breaking difficult. Here, we explore infrared remote sensing of breaking waves at near-grazing incidence angles to differentiate between active and residual foam in the surfzone. Measurements were made at two field sites: Duck, NC, in September 2010 (Surf Zone Optics) and New River Inlet, NC, in May 2012 (RIVET). At both sites, multiple IR cameras were mounted to a tower onshore, viewing the surfzone at near-grazing incidence angles. For near-grazing incidence angles, small changes in viewing angle, such as those produced by the slope of a wave face, cause large modulations of the infrared signal. Therefore, the passage of waves can be seen in IR imagery. Wave breaking, however, is identified by the resulting foam. Foam has a higher emissivity than undisturbed water and thus appears warmer in an IR image. Residual foam cools quickly [Marmorino and Smith, 2005], thereby making its signal distinct from that of foam produced during active wave breaking. We will use these properties to develop a technique to produce spatial and temporal maps of active breaking and residual foam. These products can then be used to validate current models of surfzone bubbles and foam coverage. From the maps, we can also estimate energy dissipation due to wave breaking in the surfzone and compare this to estimates made with in situ data.; Infrared image of the surfzone at Duck, NC. Examples of actively breaking foam and cool residual foam are labeled.

  19. Modeling of residual stresses by HY-100 weldments

    SciTech Connect

    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.

  20. 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.

  1. Residual Stress Measurements of Explosively Clad Cylindrical Pressure Vessels

    SciTech Connect

    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.

  2. Residual Stress Assessment in Thin Angle Ply Tubes

    NASA Astrophysics Data System (ADS)

    Kaddour, A. S.; Al-Hassani, S. T. S.; Hinton, M. J.

    2003-05-01

    This preliminary study aims to investigate the residual stresses developed in hot cured thin-walled angle-ply filament wound tubes made of E-glass/epoxy, Kevlar/epoxy and carbon/epoxy materials. The residual stresses were estimated from change in geometry of these tubes when axially slitted at ambient temperature. Three basic deformation modes; namely opening up, closing-in and twisting, were observed and these depended on the winding angle, material and wall thickness. The residual stresses were also determined from hoop and axial strain gauges mounted on both the inner and outer surfaces at various locations around the tube. The stresses were compared with theoretical prediction based upon a linear thermo-elastic analysis. Both the predicted and measured values were found to increase with increasing hoop stiffness but there was a large discrepancy between the predicted and measured data, reaching a factor of 5 for the thinnest case. When compared with predicted failure stresses, the experimentally determined stresses were some 15% of the computed compressive strength.

  3. Surface Residual Stresses in Ti-6Al-4V Friction Stir Welds: Pre- and Post-Thermal Stress Relief

    NASA Astrophysics Data System (ADS)

    Edwards, P.; Ramulu, M.

    2015-09-01

    The purpose of this study was to determine the residual stresses present in titanium friction stir welds and if a post-weld thermal stress relief cycle would be effective in minimizing those weld-induced residual stresses. Surface residual stresses in titanium 6Al-4V alloy friction stir welds were measured in butt joint thicknesses ranging from 3 to 12 mm. The residual stress states were also evaluated after the welds were subjected to a post-weld thermal stress relief cycle of 760 °C for 45 min. High (300-400 MPa) tensile residual stresses were observed in the longitudinal direction prior to stress relief and compressive residual stresses were measured in the transverse direction. After stress relief, the residual stresses were decreased by an order of magnitude to negligible levels.

  4. Residual stress distribution in oxide films formed on Zircaloy-2

    NASA Astrophysics Data System (ADS)

    Sawabe, T.; Sonoda, T.; Furuya, M.; Kitajima, S.; Takano, H.

    2015-11-01

    In order to evaluate residual the stress distribution in oxides formed on zirconium alloys, synchrotron X-ray diffraction (XRD) was performed on the oxides formed on Zircaloy-2 after autoclave treatment at a temperature of 360° C in pure water. The use of a micro-beam XRD and a micro-sized cross-sectional sample achieved the detailed local characterization of the oxides. The oxide microstructure was observed by TEM following the micro-beam XRD measurements. The residual compressive stress increased in the vicinity of the oxide/metal interface of the pre-transition oxide. Highly oriented columnar grains of a monoclinic phase were observed in that region. Furthermore, at the interface of the post-first transition oxide, there was only a small increase in the residual compressive stress and the columnar grains had a more random orientation. The volume fraction of the tetragonal phase increased with the residual compressive stress. The results are discussed in terms of the formation and transition of the protective oxide.

  5. The effect of focused ion beam machining on residual stress and crack morphologies in alumina

    NASA Astrophysics Data System (ADS)

    Inkson, B. J.; Leclere, D.; Elfallagh, F.; Derby, B.

    2006-02-01

    Focused ion beams (FIB) are widely used to locally sputter away material from surfaces at the nanoscale, but the effect of localised geometry changes and surface damage generated by FIB processing on material stress states are poorly understood. Evolution of stress states has been investigated in alumina samples with high local residual stress concentrations around nanoindents and scratches. Crack morphologies under the nanoindents and scratches have been investigated with respect to the location and geometry of the 'cross-sectional' surface trenches machined by FIB. It is found that the density of cracks observed around the nanoindentation sites depends on the location and milling sequence of the cross-sectional FIB trenches which alter local stress states. Cr3+ fluorescence spectroscopy has additionally been used to map stresses around alumina scratch and FIB-machined surface trenches.

  6. Measurements of residual stresses and surface topography using optical techniques

    NASA Astrophysics Data System (ADS)

    Wang, Baishi

    The dissertation presents two breakthrough optical interferometric techniques for the measurements of both whole-field residual stresses and surface topography. First, the whole-field residual stress measurement technique is developed for the first time using moire interferometry and Twyman/Green interferometry coupled high temperature resistant grating technique and thermal annealing. In the measurement, a special high temperature resistant cross grating is firstly made on the sample surface, and the whole-field residual stress relief is achieved by thermal annealing. Moire interferometry and Twyman/Green interferometry are then utilized to measure both in-plane and out-of-plane deformations generated by the residual stress relaxation, and then to obtain the whole-field strain redistribution due to the residual stress relief. The technique has been successfully applied to the measurement of the whole-field generalized 2-D residual stresses (i.e. both in-plane stresses and the out-of-plane normal stresses) in the rail using a transverse rail slice based on plausible assumptions. Its comparison to hole-drilling method with moire interferometry shows good quantitative agreement. Some key issues for further development are identified and discussed. Second, a novel polarization phase-stepping shearing interferometry (PPSSI) is presented for the calibration-free measurement of surface topography regardless of any surface reflectivity variation. The PPSSI incorporates the polarization phase modulation and Nomarski shearing interferometry to measure wavefront phase difference, or surface slope, irrespective of any wavefront amplitude change. The principle and theory of the PPSSI are described using Jones matrix method. Experimental results and its applications to the topographic measurements and flat wafers and speckle samples are shown. In addition, the modulation transfer function (MTF) and impulse response of a PPSSI system are studied both analytically and

  7. 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.

  8. 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.

  9. Residual Stresses in Porcelain-veneered Zirconia Prostheses

    PubMed Central

    Baldassarri, Marta; Stappert, Christian F. J.; Wolff, Mark S.; Thompson, Van P.; Zhang, Yu

    2012-01-01

    Objectives Compressive stress has been intentionally introduced into the overlay porcelain of zirconia-ceramic prostheses to prevent veneer fracture. However, recent theoretical analysis has predicted that the residual stresses in the porcelain may be also tensile in nature. This study aims to determine the type and magnitude of the residual stresses in the porcelain veneers of full-contour fixed-dental prostheses (FDPs) with an anatomic zirconia coping design and in control porcelain with the zirconia removed using a well-established Vickers indentation method. Methods Six 3-unit zirconia FDPs were manufactured (NobelBiocare, Gothenburg, Sweden). Porcelain was hand-veneered using a slow cooling rate. Each FDP was sectioned parallel to the occlusal plane for Vickers indentations (n = 143; load = 9.8 N; dwell time = 5 s). Tests were performed in the veneer of porcelain-zirconia specimens (bilayers, n = 4) and porcelain specimens without zirconia cores (monolayers, n = 2). Results The average crack lengths and standard deviation, in the transverse and radial directions (i.e. parallel and perpendicular to the veneer/core interface, respectively), were 67 ± 12 μm and 52 ± 8 μm for the bilayers and 64 ± 8 μm and 64 ± 7 μm for the monolayers. These results indicated a major hoop compressive stress (~40 to 50 MPa) and a moderate radial tensile stress (~10 MPa) in the bulk of the porcelain veneer. Significance Vickers indentation is a powerful method to determine the residual stresses in veneered zirconia systems. Our findings revealed the presence of a radial tensile stress in the overlay porcelain, which may contributed to the large clinical chip fractures observed in these prostheses. PMID:22578663

  10. Bioinjection Treatment: Effects of Post-Injection Residual Stress on Left Ventricular Wall Stress

    PubMed Central

    Lee, Lik Chuan; Wall, Samuel T.; Genet, Martin; Hinson, Andy; Guccione, Julius M.

    2014-01-01

    Injection of biomaterials into diseased myocardium has been associated with decreased myofiber stress, restored left ventricular (LV) geometry and improved LV function. However, its exact mechanism(s) of action remained unclear. In this work, we present the first patient-specific computational model of biomaterial injection that accounts for the possibility of residual strain and stress introduced by this treatment. We show that the presence of residual stress can create more heterogeneous regional myofiber stress and strain fields. Our simulation results show that the treatment generates low stress and stretch areas between injection sites, and high stress and stretch areas between the injections and both the endocardium and epicardium. Globally, these local changes are translated into an increase in average myofiber stress and its standard deviation (from 6.9 ± 4.6 to 11.2 ± 48.8 kPa and 30 ± 15 to 35.1 ± 50.9 kPa at end-diastole and end-systole, respectively). We also show that the myofiber stress field is sensitive to the void-to-injection size ratio – for a constant void size, the myofiber stress field became less heterogeneous with decreasing injection volume. These results suggest that the residual stress and strain possibly generated by biomaterial injection treatment can have large effects on the regional myocardial stress and strain fields, which may be important in the remodeling process. PMID:25065728

  11. A micromechanical study of residual stresses in functionally graded materials

    SciTech Connect

    Dao, M.; Gu, P.; Maewal, A.; Asaro, R.J.

    1997-08-01

    A physically based computational micromechanics model is developed to study random and discrete microstructures in functionally graded materials (FGMs). The influences of discrete microstructure on residual stress distributions at grain size level are examined with respect to material gradient and FGM volume percentage (within a ceramic-FGM-metal three-layer structure). Both thermoelastic and thermoplastic deformation are considered, and the plastic behavior of metal grains is modeled at the single crystal level using crystal plasticity theory. The results are compared with those obtained using a continuous model which does not consider the microstructural randomness and discreteness. In an averaged sense both the micromechanics model and the continuous model give practically the same macroscopic stresses; whereas the discrete micromechanics model predicts fairly high residual stress concentrations at the grain size level (i.e., higher than 700 MPa in 5--6 vol% FGM grains) with only a 300 C temperature drop in a Ni-Al{sub 2}O{sub 3} FGM system. Statistical analysis shows that the residual stress concentrations are insensitive to material gradient and FGM volume percentage. The need to consider microstructural details in FGM microstructures is evident. The results obtained provide some insights for improving the reliability of FGMs against fracture and delamination.

  12. 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.

  13. 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.

  14. Comparison of Residual Stresses in Inconel 718 Simple Parts Made by Electron Beam Melting and Direct Laser Metal Sintering

    NASA Astrophysics Data System (ADS)

    Sochalski-Kolbus, L. M.; Payzant, E. A.; Cornwell, P. A.; Watkins, T. R.; Babu, S. S.; Dehoff, R. R.; Lorenz, M.; Ovchinnikova, O.; Duty, C.

    2015-03-01

    Residual stress profiles were mapped using neutron diffraction in two simple prism builds of Inconel 718: one fabricated with electron beam melting (EBM) and the other with direct laser metal sintering. Spatially indexed stress-free cubes were obtained by electrical discharge machining (EDM) equivalent prisms of similar shape. The (311) interplanar spacings from the EDM sectioned sample were compared to the interplanar spacings calculated to fulfill stress and moment balance. We have shown that applying stress and moment balance is a necessary supplement to the measurements for the stress-free cubes with respect to accurate stress calculations in additively manufactured components. In addition, our work has shown that residual stresses in electron beam melted parts are much smaller than that of direct laser metal sintered parts most likely due to the powder preheating step in the EBM process.

  15. 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.

  16. 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.

  17. An approximate method for residual stress calculation infunctionally graded materials

    SciTech Connect

    Becker, T.L.

    1999-06-02

    Thermal residual stresses in functionally graded materials(FGMs) arise primarily from nonlinear spatial variations in the thermalexpansion coefficient, but can be significantly adjusted by variations inmodulus. Thermoelastic analysis of FGMs is complicated by such modulusgradients. A class of problems for which thermal stress solutions formaterials with constant modulus can be used as a basis for approximationsfor FGMs is discussed. The size of the error in this approximation due togradients in elastic modulus is investigated. Analytical and finiteelement solutions for the thermal stresses in various FGM geometries arecompared to results from this approximate method. In a geometry ofpractical interest, a right cylinder graded along the z-axis, the errorfor a Ni-Al2O3 FGM was found to be within 15 percent for all gradientsconsidered. The form of the approximation makes it easier to identifydesirable types of spatial nonlinearity in expansion coefficient andvariations in modulus: this would allow the manipulation of the locationof compressive stresses.

  18. 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.

  19. Dual-axis hole-drilling ESPI residual stress measurements

    SciTech Connect

    Steinzig, Michael; Schajer, Gary

    2008-01-01

    A novel dual-axis ESPI hole-drilling residual stress measurement method is presented. The method enables the evaluation of all the in-plane normal stress components with similar response to measurement errors, significantly lower than with single-axis measurements. A numerical method is described that takes advantage of, and compactly handles, the additional optical data that are available from the second measurement axis. Experimental tests were conducted on a calibrated specimen to demonstrate the proposed method, and the results supported theoretical expectations.

  20. Magnetic Barkhausen noise analysis of residual stress and carburization

    NASA Astrophysics Data System (ADS)

    Stewart, D. M.; Stevens, K. J.; Kaiser, A. B.

    2001-04-01

    Magnetic Barkhausen noise analysis is an effective non-destructive testing technique for determining both residual stress and carburization, with potential for improving the accuracy of remaining-life estimates of critical components in operational plant such as that used in thermal power stations and the petrochemical industry. We have measured Barkhausen noise in magnetic Durehete 1055 samples under stress and in carburized ethylene pyrolysis tubes. The Barkhausen power as a function of applied field is modeled using Sablik's function for Barkhausen power as a function of irreversible differential permeability (μirr); the Jiles-Atherton model of hysteresis is used to determine μirr as a function of applied field.

  1. Residual stresses calculation in autofrettage using variable material properties method

    SciTech Connect

    Jahed, H.; Dubey, R.N.

    1996-12-01

    Autofrettaged cylinders are used for variety of applications in chemical and nuclear industries where large internal pressures have to be withstood. Autofrettage is in the process by which beneficial residual stresses are introduced into thick-walled tubes by initially subjected the tube to high internal pressure which causes inelastic deformation. Here, the variable material properties method is employed to obtain elastic-plastic analysis of an autofrettaged tube. This method develops inelastic solution from the elastic solution by treating the material properties as field variables. The distribution of these parameters are obtained in an iterative manner as a part of the solution. An energy based scheme is used to update these variables. The residual stress field of autofrettaged tubes based on the actual material curve and isotropic and kinematic hardening models are obtained. The results are shown to be in good agreement with the published experimental and finite element results.

  2. A residual stress study in similar and dissimilar welds

    DOE PAGESBeta

    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 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

  3. Mechanical relaxation of localized residual stresses associatedwith foreign object damage

    SciTech Connect

    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.

  4. Research opportunities and facilities at ORNL`s residual stress user center

    SciTech Connect

    Hubbard, C.R.; Watkins, T.R.; Kozaczek, K.; Wang, X.-L.; Spooner, S.

    1994-09-01

    The High Temperature Materials Laboratory (HTML) User Program at ORNL was established to help solve high-temperature materials problems that limit the efficiency and reliability of advanced energy-conversion systems. Both proprietary and nonproprietary research can be conducted within the user program. The facilities are open to researchers in US industry, universities, and federal laboratories. The Residual Stress User Center (RSUC), one of the six HTML user centers, was recently established and consists of two high precision x-ray diffraction systems for measurement of residual strain and texture. Both biaxial and triaxial residual strain data can be collected. Attachments to the diffraction system include a position sensitive detector and a laser specimen positioning system. The RSUC has capabilities for electropolishing and strain measurement with strain gauges. A complementary neutron diffraction facility has recently been developed and demonstrated at the High Flux Isotope Reactor at ORNL. The neutron diffraction facility enables mapping of macro residual stresses throughout the volume of a component, complementing the near surface stress measurements available by x-ray diffraction. The neutron facility has been proposed as an addition to the RSUC.

  5. 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.

  6. Modelling Of Residual Stresses Induced By High Speed Milling Process

    SciTech Connect

    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.

  7. Residual stress within nanoscale metallic multilayer systems during thermal cycling

    SciTech Connect

    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.

  8. Residual stress within nanoscale metallic multilayer systems during thermal cycling

    DOE PAGESBeta

    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 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

  9. Residual Stresses in Inertia-Friction-Welded Dissimilar High-Strength Steels

    NASA Astrophysics Data System (ADS)

    Moat, R. J.; Hughes, D. J.; Steuwer, A.; Iqbal, N.; Preuss, M.; Bray, S. E.; Rawson, M.

    2009-09-01

    The welding of dissimilar alloys is seen increasingly as a way forward to improve efficiencies in modern aeroengines, because it allows one to tailor varying material property demands across a component. Dissimilar inertia friction welding (IFW) of two high-strength steels, Aermet 100 and S/CMV, has been identified as a possible joint for rotating gas turbine components and the resulting welds are investigated in this article. In order to understand the impact of the welding process and predict the life expectancy of such structures, a detailed understanding of the residual stress fields present in the welded component is needed. By combining energy-dispersive synchrotron X-ray diffraction (EDSXRD) and neutron diffraction, it has been possible to map the variations in lattice spacing of the ferritic phase on both sides of two tubular Aermet 100-S/CMV inertia friction welds (as-welded and postweld heat-treated condition) with a wall thickness of 37 mm. Laboratory-based XRD measurements were required to take into account the variation in the strain-free d-spacing across the weld region. It was found that, in the heat-affected zone (HAZ) slightly away from the weld line, residual stress fields showed tensile stresses increasing most dramatically in the hoop direction toward the weld line. Closer to the weld line, in the plastically affected zone, a sharp drop in the residual stresses was observed on both sides, although more dramatically in the S/CMV. In addition to residual stress mapping, synchrotron XRD measurements were carried out to map microstructural changes in thin slices cut from the welds. By studying the diffraction peak asymmetry of the 200- α diffraction peak, it was possible to demonstrate that a martensitic phase transformation in the S/CMV is responsible for the significant stress reduction close to the weld line. The postweld heat treatment (PWHT) chosen to avoid any overaging of the Aermet 100 and to temper the S/CMV martensite resulted in little

  10. 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.

  11. 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

  12. 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.

  13. 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.

  14. 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.

  15. Consequences of Residual Stresses in Thin Polymer Films

    NASA Astrophysics Data System (ADS)

    Reiter, Guenter

    2010-03-01

    In our quest for making functional devices smaller, the thickness of polymer films has reached values even smaller than the diameter of the unperturbed molecule. However, despite enormous efforts over the last decade, our understanding of the origin of some puzzling properties of such thin films is still not satisfactory and several peculiar observations remain rather mysterious. In this context, we explore the consequences of the transition from a dilute polymer solution to the glassy state with respect to the properties of polymers in thin films. This transition is likely to result in residual stresses, arising from out-of-equilibrium chain conformations due to rapid solvent loss. Consequently, depending on thermal history and ageing time, such films exhibit significant changes even in the glassy state ^ which we quantify by performing detailed studies of viscoelastic dewetting of thin polystyrene films on solid substrates. We explored relaxation times, residual stresses, and temporal changes of the stability of non-equilibrated thin films as they progress toward stable equilibrium behaviors. To do so, we have focused primarily on times shorter than the reptation time of the polymer. The number of spontaneously nucleated holes per unit area is seen to decrease as the films were aged below the glass transition, showing the meta-stability of the system. The ratio of stress over elastic modulus was found to increase strongly with decreasing film thickness and increasing chain length. Full equilibration of chain conformations required long times comparable to bulk reptation times. However, for chains longer than about 3000 monomers, the residual stress relaxed faster, at a rate independent of chain length. We present some tentative ideas on the relation between these observed atypical mechanical and relaxational behaviors and meta-stable states introduced by sample preparation.

  16. 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.

  17. 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.

  18. 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.

  19. Neutron diffraction residual stress studies for aero-engine component applications

    NASA Astrophysics Data System (ADS)

    Clay, K.; Small, C.

    1991-12-01

    Computer graphics for a presentation describing how Rolls-Royce is refining the method of residual stress measurement by neutron diffraction to suit the characteristic stress fields of components are presented. Results to date are given. An outline of how this residual stress data is to be used in developing stress models for critical rotating components is given.

  20. Comparison of residual stresses in Inconel 718 simple parts made by electron beam melting and direct laser metal sintering

    DOE PAGESBeta

    Kolbus, Lindsay M.; Payzant, E. Andrew; Cornwell, Paris A.; Watkins, Thomas R.; Babu, Sudarsanam Suresh; Dehoff, Ryan R.; Duty, Chad E.; Lorenz, M.; Ovchinnikova, O. S.

    2015-01-10

    Residual stress profiles were mapped using neutron diffraction in two simple prism builds of Inconel 718: one fabricated with electron beam melting and the other with direct laser sintering. Spatially indexed stress-free cubes were obtained by EDM sectioning equivalent prisms of similar shape. The (311) interplanar spacing examined for the EDM sectioned sample was compared to the interplanar spacings calculated to fulfill force and moment balance. We have shown that Applying force and moment balance is a necessary supplement to the measurements for the stress-free cubes with respect to accurate stress calculations in additively manufactured components. Furthermore, our work hasmore » shown that residual stresses in electron beam melting parts are much smaller than that of direct laser metal sintering parts.« less

  1. Comparison of residual stresses in Inconel 718 simple parts made by electron beam melting and direct laser metal sintering

    SciTech Connect

    Kolbus, Lindsay M.; Payzant, E. Andrew; Cornwell, Paris A.; Watkins, Thomas R.; Babu, Sudarsanam Suresh; Dehoff, Ryan R.; Duty, Chad E.; Lorenz, M.; Ovchinnikova, O. S.

    2015-01-10

    Residual stress profiles were mapped using neutron diffraction in two simple prism builds of Inconel 718: one fabricated with electron beam melting and the other with direct laser sintering. Spatially indexed stress-free cubes were obtained by EDM sectioning equivalent prisms of similar shape. The (311) interplanar spacing examined for the EDM sectioned sample was compared to the interplanar spacings calculated to fulfill force and moment balance. We have shown that Applying force and moment balance is a necessary supplement to the measurements for the stress-free cubes with respect to accurate stress calculations in additively manufactured components. Furthermore, our work has shown that residual stresses in electron beam melting parts are much smaller than that of direct laser metal sintering parts.

  2. The formation mechanism and the influence factor of residual stress in machining

    NASA Astrophysics Data System (ADS)

    Qi, Zhaoxu; Li, Bin; Xiong, Liangshan

    2014-09-01

    Residual stresses generated in cutting process have important influences on workpiece performance. The paper presents a method of theoretical analysis in order to explicate the formation mechanism of residual stresses in cutting. An important conclusion is drawn that the accumulated plastic strain is the main factor which determines the nature and the magnitude of surface residual stresses in the workpiece. On the basis of the analytical model for residual stress, a series of simulations for residual stress prediction during cutting AISI 1045 steel are implemented in order to obtain the influences of cutting speed, depth of cut and tool edge radius on surface residual stress in the workpiece. And these influences are explained from the perspective of formation mechanism of residual stress in cutting. The conclusions have good applicability and can be used to guide the parameters selection in actual production.

  3. Experimental study of cumulative effect of residual stress on machined surface on HSM

    NASA Astrophysics Data System (ADS)

    Li, Yueen; Zhao, Jun; Wang, Wei

    2010-03-01

    The high speed milling experiments are performed for hardened H13 die steel by using coated ball end milling cutter, the experiment was design for testing distribution properties of the residual stress in HSM. And the residual stress of the work-piece surface on the feed and cross feed direction are measured by the X-ray stress analyzer (X-stress 3000), and the distribution characteristics of residual stress is analyzed. The result shows that the residual stress presents gradient distribution on feed direction, and furthermore, the three-dimensional surface micro topography has been observed by the WykoNT9300, it shows that the micro topography has no close relation with the residual stress. In addition, the cumulative effect is discussed for explaining the phenomena. It could be one explanation for the residual stress gradient on the machined surface on mechanism.

  4. Experimental study of cumulative effect of residual stress on machined surface on HSM

    NASA Astrophysics Data System (ADS)

    Li, Yueen; Zhao, Jun; Wang, Wei

    2009-12-01

    The high speed milling experiments are performed for hardened H13 die steel by using coated ball end milling cutter, the experiment was design for testing distribution properties of the residual stress in HSM. And the residual stress of the work-piece surface on the feed and cross feed direction are measured by the X-ray stress analyzer (X-stress 3000), and the distribution characteristics of residual stress is analyzed. The result shows that the residual stress presents gradient distribution on feed direction, and furthermore, the three-dimensional surface micro topography has been observed by the WykoNT9300, it shows that the micro topography has no close relation with the residual stress. In addition, the cumulative effect is discussed for explaining the phenomena. It could be one explanation for the residual stress gradient on the machined surface on mechanism.

  5. Residual stresses in sputter-deposited copper/330 stainless steel multilayers

    SciTech Connect

    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.

  6. Residual stresses in sputter-deposited copper/330 stainless steel multilayers

    NASA Astrophysics Data System (ADS)

    Zhang, X.; Misra, A.

    2004-12-01

    The evolution of residual stresses as a function of bilayer period from 10nmto1μm 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 5to500nm. 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.

  7. Quantifying residual stress in nanoscale thin polymer films via surface wrinkling.

    PubMed

    Chung, Jun Young; Chastek, Thomas Q; Fasolka, Michael J; Ro, Hyun Wook; Stafford, Christopher M

    2009-04-28

    Residual stress, a pervasive consequence of solid materials processing, is stress that remains in a material after external forces have been removed. In polymeric materials, residual stress results from processes, such as film formation, that force and then trap polymer chains into nonequilibrium stressed conformations. In solvent-cast films, which are central to a wide range of technologies, residual stress can cause detrimental effects, including microscopic defect formation and macroscopic dimensional changes. Since residual stress is difficult to measure accurately, particularly in nanoscale thin polymer films, it remains a challenge to understand and control. We present here a quantitative method of assessing residual stress in polymer thin films by monitoring the onset of strain-induced wrinkling instabilities. Using this approach, we show that thin (>100 nm) polystyrene films prepared via spin-coating possess residual stresses of approximately 30 MPa, close to the crazing and yield stress. In contrast to conventional stress measurement techniques such as wafer curvature, our technique has the resolution to measure residual stress in films as thin as 25 nm. Furthermore, we measure the dissipation of residual stress through two relaxation mechanisms: thermal annealing and plasticizer addition. In quantifying the amount of residual stress in these films, we find that the residual stress gradually decreases with increasing annealing time and plasticizer amounts. Our robust and simple route to measure residual stress adds a key component to the understanding of polymer thin film behavior and will enable identification of more effective processing routes that mitigate the detrimental effects of residual stress. PMID:19298053

  8. Compressional residual stress in Bastogne boudins revealed by synchrotron X-ray microdiffraction

    NASA Astrophysics Data System (ADS)

    Chen, Kai; Kunz, Martin; Li, Yao; Zepeda-Alarcon, Eloisa; Sintubin, Manuel; Wenk, Hans-Rudolf

    2016-06-01

    Lattice distortions in crystals can be mapped at the micron scale using synchrotron X-ray Laue microdiffraction (μXRD). From lattice distortions the shape and orientation of the elastic strain tensor can be derived and interpreted in terms of residual stress. Here we apply the new method to vein quartz from the original boudinage locality at Bastogne, Belgium. A long-standing debate surrounds the kinematics of the Bastogne boudins. The μXRD measurements reveal a shortening residual elastic strain, perpendicular to the vein wall, corroborating the model that the Bastogne boudins formed by layer-parallel shortening and not by layer-parallel extension, as is in the geological community generally inferred by the process of boudinage.

  9. Residual Stresses in 21-6-9 Stainless Steel Warm Forgings

    SciTech Connect

    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.

  10. Relaxation of bending stresses and the reversibility of residual stresses in amorphous soft magnetic alloys

    SciTech Connect

    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.

  11. The effect of microstructure on residual-stress development in short-fiber composites

    SciTech Connect

    Eduljee, R.F.

    1991-01-01

    The aim of this study was the identification of the key processing and microstructural parameters that affect thermal residual stresses through a series of parametric analyses on an infinite-plate geometry. In these analyses polycarbonate was chosen as a representative amorphous resin while polyetheretherketone (PEEK) was used as an example of a semicrystalline resin. The residual stress model of Indenbom was used to investigate residual stresses in amorphous polymers. Due to the inapplicability of this model to semicrystalline polymers and composites where the material properties varied through the thickness of the specimen, a residual stress model based on incremental stress analysis was developed. The parametric analyses on the neat polymers showed that the thermal history and the thermoelastic properties played major roles in the residual stress development in both amorphous and semicrystalline polymers. Crystallization increased the level of residual stresses. The mechanisms for this increase are discussed.

  12. Nondestructive characterization of residual stress within CMOS-based composite microcantilevers

    NASA Astrophysics Data System (ADS)

    Rendon-Hernandez, Adrian A.; Camacho-Leon, Sergio; Martinez-Chapa, Sergio O.

    2013-04-01

    Residual stress can affect the performance of thin-film micromachined structures and lead to curling in cantilevers as well as distortion in the frequency of resonant devices. As the origin of residual stress is dependent on the fabrication processes, a nondestructive method for characterization of residual stress independent of processes conditions is desirable for supporting the design of microcantilever-based microsystems. In this paper we present a nondestructive characterization of the residual stress within composite microcantilever beams providing valuable insights toward predicting their deflection profile after mechanical releasing from the substrate. The approach relies on the assumption of a linear gradient stress and a quadratic deflection profile across a composite microcantilever.

  13. Quantification of residual stress from photonic signatures of fused silica

    SciTech Connect

    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.

  14. Characterization of Residual Stress Effects on Fatigue Crack Growth of a Friction Stir Welded Aluminum Alloy

    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.

  15. A Comparison of Residual Stress Development in Inertia Friction Welded Fine Grain and Coarse Grain Nickel-Base Superalloy

    NASA Astrophysics Data System (ADS)

    Iqbal, N.; Rolph, J.; Moat, R.; Hughes, D.; Hofmann, M.; Kelleher, J.; Baxter, G.; Withers, P. J.; Preuss, M.

    2011-12-01

    The effect of the base material microstructure on the development of residual stresses across the weld line in inertia friction welds (IFWs) of high-strength nickel-base superalloy RR1000 was studied using neutron diffraction. A comparison was carried out between tubular IFW specimens generated from RR1000 heat treated below (fine grain (FG) structure) and above (coarse grain (CG) structure) the γ'-solvus. Residual stresses were mapped in the as-welded (AW) condition and, after a postweld heat treatment (PWHT), optimized for maximum alloy strength. The highest tensile stresses were generally found in the hoop direction at the weld line near the inner diameter of the tubular-shaped specimens. A comparison between the residual stresses generated in FG and CG RR1000 suggests that the starting microstructure has little influence on the maximum residual stresses generated in the weld even though different levels of energy must be input to achieve a successful weld in each case. The residual stresses in the postweld heat treated samples were about 35 pct less than for the AW condition. Despite the fact that the high-temperature properties of the two parent microstructures are different, no significant differences in terms of stress relief were found between the FG and CG RR1000 IFWs. Since the actual weld microstructures of FG and CG RR1000 inertia welds are very similar, the results suggest that it is the weld microstructure and its associated high-temperature properties rather than the parent material that affects the overall weld stress distribution and its subsequent stress relief.

  16. Mapping of residual strains of a ceramic-to-metal joint using X-ray diffraction

    SciTech Connect

    Watkins, T.R.; Wang, X.L.; Spooner, S.; Hubbard, C.R.; Vance, S.J.; Rabin, B.H.; Williamson, R.L.

    1994-03-01

    In this study, the residual strains in the iron layer of a zirconia-iron joint, brazed with a metal alloy, were measured with X-ray diffraction as a function of distance from the joint. The residual strains were measured at various key locations indicated by a finite element model (FEM). The X-ray residual strain mapping results were compared to neutron diffraction mapping results. These data were combined to provide a complete residual strain profile of these samples and were compared with results of FEM.

  17. Microstructure and residual stress of laser rapid formed Inconel 718 nickel-base superalloy

    NASA Astrophysics Data System (ADS)

    Liu, Fencheng; Lin, Xin; Yang, Gaolin; Song, Menghua; Chen, Jing; Huang, Weidong

    2011-02-01

    The microstructure and residual stress of laser rapid formed (LRFed) nickel-base superalloy Inconel 718 was investigated. The as-deposited microstructure of an LRFed Inconel 718 alloy is composed of columnar dendrites growing epitaxially along the deposition direction, and the columnar dendrites transformed to unevenly distributed equiaxed grains after annealing treatment at high temperature. Residual stress evaluation in microstructure scale by Vickers micro-indentation method indicates that the residual thermal stress is unevenly distributed in the LRFed sample, and it has a significant effect on the recrystallization during solution annealing treatment. The residual stress is introduced by rapid heating and cooling during laser rapid forming. There is an alternative distribution between high residual stress regions and low residual stress regions, within a single deposited layer, resulting in a similar distribution of recrystallized grain size.

  18. Finite element residual stress analysis of induction heating bended ferritic steel piping

    SciTech Connect

    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.

  19. Residual stress variation due to piping processes of austenitic stainless steel

    NASA Astrophysics Data System (ADS)

    Ihara, R.; Hashimoto, T.; Mochizuki, M.

    2012-08-01

    In nuclear power plants, stress corrosion cracking (SCC) has been observed near the heat affected zone (HAZ) of the primary loop recirculation pipes made of austenitic stainless steel type 316L. Residual stress is a major cause of SCC. In the joining process of pipes, butt-welding is conducted after machining. Machining is performed to match the inside pipe diameter. Residual stress is generated by both machining and welding. In the case of welding after machining in manufacturing processes of pipes, it appears that residual stress due to machining is varied by the welding thermal cycle. In this study, residual stress variation caused by manufacturing processes was investigated. Residual stress variation was examined by the X-ray diffraction method. The residual stress distribution generated by welding after machining has a local maximum point in the HAZ. The Vickers hardness distribution also has a local maximum point. By the EBSD method, it is clarified that recovery and recrystallization due to welding heat do not occurred in the local maximum point. Residual stress distribution results from the superposition effect of hardening due to machining and welding. The location and value of the local maximum stress are varied by welding conditions. The region of the local maximum stress corresponds to the region where SCC has been observed. Therefore, in addition to a part of the manufacturing processes such as welding or machining, evaluation of all parts of the processes is important to investigate the effect of residual stress distribution on SCC.

  20. Residual Stress Analysis of Cold-Sprayed Copper Coatings by Numerical Simulation

    NASA Astrophysics Data System (ADS)

    Li, Wenya; Yang, Kang; Zhang, Dongdong; Zhou, Xianglin

    2016-01-01

    In this paper, an analysis on the residual stress evolution of cold-sprayed copper coatings on Cu and Al substrates was performed. To investigate the influences of particle velocity, temperature and material combination on the final residual stresses, an integrated frame of calculation was proposed based on the simulation results obtained from the developed thermo-mechanically coupled Eulerian model. In a single Cu splat, generally speaking, the maximum residual stress and plastic deformation are concentrated at the outside contact zone rather than at the center point of initial impact. The action of friction shear between the particle and substrate during impacting should be considered as one of the essential factors on the final residual stress. And the states of residual stresses can vary significantly depending on the material combination, particle velocity, and temperature. In a single pass Cu coating, the residual stress fluctuates across the coating and there exists both compressive stress and tensile stress within the coating. At a certain range of impacting velocities, the resultant residual stresses increase with the increase of particle velocity. The present simulated results are related to the reported experiments by others, showing that the residual stress states and stress change trend are different from some of the reported results.

  1. 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.

  2. 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.

  3. Analytical solutions for determining residual stresses in two-dimensional domains using the contour method

    PubMed Central

    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

  4. Monitoring of residual stresses in injection-molded plastics with holographic interferometry

    NASA Astrophysics Data System (ADS)

    Sanchez, Lilia A.; Hornberger, Lee E.

    2002-01-01

    Residual stresses are often trapped in injection-molded plastic parts due to the rapid cooling of the material in this manufacturing process. These stresses are a common source of failure in plastic components in automobiles, appliances and computers and are difficult to measure with conventional residual-stress experimental methods. Real-time holographic interferometry appears to be a viable technique to identify and monitor these stresses in plastic parts. In this investigation, holographic interferometry was used to monitor the relaxation of residual stresses in the plastic-molded actuator arm of a computer hard drive. In the first phase of this study, the relaxation of these residual stresses as a function of temperature was observed. In the second phase, the time to completely relax the residual stresses in the plastic part at an elevated temperature, the annealing temperature, was determined. In the third phase of this investigation, the rate of relaxation of these residual stresses as a function of time at various operating temperatures, was studied. Based on the results of this study, holographic interferometry appears to be a powerful research tool in the study of residual stresses in plastic parts. It also has the potential to be a practical tool for the inspection of manufactured plastic parts for the presence of residual stress.

  5. An analytical method on the surface residual stress for the cutting tool orientation

    NASA Astrophysics Data System (ADS)

    Li, Yueen; Zhao, Jun; Wang, Wei

    2009-12-01

    The residual stress is measured by choosing 8 kinds orientations on cutting the H13 dies steel on the HSM in the experiment of this paper. The measured data shows on that the residual stress exists periodicity for the different rake angle (β) and side rake angle (θ) parameters, further study find that the cutting tool orientations have closed relationship with the residual stresses, and for the original of the machined residual stress on the surface from the cutting force and the axial force, it can be gained the simply model of tool-workpiece force, using the model it can be deduced the residual stress model, which is feasible to calculate the size of residual stress. And for almost all the measured residual stresses are compressed stress, the compressed stress size and the direction could be confirmed by the input data for the H13 on HSM. As the result, the residual stress model is the key for optimization of rake angle (β) and side rake angle (θ) in theory, using the theory the more cutting mechanism can be expressed.

  6. An analytical method on the surface residual stress for the cutting tool orientation

    NASA Astrophysics Data System (ADS)

    Li, Yueen; Zhao, Jun; Wang, Wei

    2010-03-01

    The residual stress is measured by choosing 8 kinds orientations on cutting the H13 dies steel on the HSM in the experiment of this paper. The measured data shows on that the residual stress exists periodicity for the different rake angle (β) and side rake angle (θ) parameters, further study find that the cutting tool orientations have closed relationship with the residual stresses, and for the original of the machined residual stress on the surface from the cutting force and the axial force, it can be gained the simply model of tool-workpiece force, using the model it can be deduced the residual stress model, which is feasible to calculate the size of residual stress. And for almost all the measured residual stresses are compressed stress, the compressed stress size and the direction could be confirmed by the input data for the H13 on HSM. As the result, the residual stress model is the key for optimization of rake angle (β) and side rake angle (θ) in theory, using the theory the more cutting mechanism can be expressed.

  7. Study on residual stress of AISI304 TIG welding line with laser shock processing by x-ray stress analyzer

    NASA Astrophysics Data System (ADS)

    Zhang, Y. K.; Kong, D. J.; Yin, S. M.; Feng, A. X.; Lu, J. Z.; Ge, T.

    2006-02-01

    The surface of AISI304 TIG welding line was processed by LSP (laser shock processing). The effects on the microstructure, hardness and residual stress of AISI304 welding line by LSP were observed, and its mechanical properties were researched by SEM (scanning electron microscope) and test device of mechanical property. Residual stresses of AISI304 TIG welding line by LSP were measured with Model X-350A X ray analyzer. The test results show that compressive residual stress values of AISI304 TIG welding line by LSP are about 110MPa. Strengthening effects of AISI304 TIG welding line by LSP is very obvious, and fatigue properties of welding line is improved, and tensile residual stresses of welding line are obviously reduced, the distribution of residual stress tends to equality, and service life of AISI304 TIG welding line is improved.

  8. Mapping Evaporative Stress at Continental Scales Using GOES Thermal Imagery

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Robust, operational methodologies for mapping daily evapotranspiration (ET), soil moisture, and moisture stress over large areas using satellite remote sensing will have widespread utility in applications such as drought detection, crop yield forecasting, irrigation scheduling, water resource manage...

  9. Effect of Quenching Rate on Distortion and Residual Stresses During Induction Hardening of a Full-Float Truck Axle Shaft

    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.

  10. The influence of quench sensitivity on residual stresses in the aluminium alloys 7010 and 7075

    SciTech Connect

    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

  11. 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.

  12. 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.

  13. 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.

  14. The relationships between residual stress relaxation and texture development in AZ31 Mg alloys via the vibratory stress relief technique

    SciTech Connect

    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.

  15. 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.

  16. 3D Dynamic Finite Element Analysis of the Nonuniform Residual Stress in Ultrasonic Impact Treatment Process

    NASA Astrophysics Data System (ADS)

    Hu, Shengsun; Guo, Chaobo; Wang, Dongpo; Wang, Zhijiang

    2016-07-01

    The nonuniform distributions of the residual stress were simulated by a 3D finite element model to analyze the elastic-plastic dynamic ultrasonic impact treatment (UIT) process of multiple impacts on the 2024 aluminum alloy. The evolution of the stress during the impact process was discussed. The successive impacts during the UIT process improve the uniformity of the plastic deformation and decrease the maximum compressive residual stress beneath the former impact indentations. The influences of different controlled parameters, including the initial impact velocity, pin diameter, pin tip, device moving, and offset distances, on the residual stress distributions were analyzed. The influences of the controlled parameters on the residual stress distributions are apparent in the offset direction due to the different surface coverage in different directions. The influences can be used to understand the UIT process and to obtain the desired residual stress by optimizing the controlled parameters.

  17. 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.

  18. Determination of the residual stress tensor in textured zirconium alloy by neutron diffraction

    NASA Astrophysics Data System (ADS)

    Sumin, V. V.; Papushkin, I. V.; Vasin, R. N.; Venter, А. M.; Balagurov, А. М.

    2012-02-01

    Results of neutron diffraction studies of crystallographic texture and residual stress tensor components in cold-worked and annealed cylindrical components made from E-110 zirconium alloy are presented. Those components are used as plugs in the fuel elements of the VVER-type reactors; the resident residual stresses influence the durability and safety of the fuel elements. The experiments were carried out on the neutron diffractometers at Dubna (the IBR-2 pulsed reactor) and Berlin Helmholtz-Zentrum (the BER II research reactor). It is shown that the samples have fiber texture that is changed considerably with annealing. The type I residual stress tensors for both samples were calculated by the BulkPathGEO model. The cold worked component has 136-166 MPa tensile residual stress in the radial direction and zero stress along the axial direction. Residual stress values in the annealed component are close to zero.

  19. The Italian present-day stress map

    NASA Astrophysics Data System (ADS)

    Montone, Paola; Mariucci, Maria Teresa; Pierdominici, Simona

    2012-05-01

    In this paper, we present a significant update of the Italian present-day stress data compilation not only to improve the knowledge on the tectonic setting of the region or to constrain future geodynamic models, but also to understand the mechanics of processes linked to faulting and earthquakes. In this paper, we have analysed, revised and collected new contemporary stress data from borehole breakouts and we have assembled earthquake and fault data. In total, 206 new quality-ranked entries complete the definition of the horizontal stress orientation and tectonic regime in some areas, and bring new information mainly in Sicily and along the Apenninic belt. Now the global Italian data set consists of 715 data points, including 499 of A-C quality, representing an increase of 37 per cent compared to the previous compilation. The alignment of horizontal stresses measured in some regions, closely matches the ˜N-S first-order stress field orientation of ongoing relative crustal motions between Eurasia and Africa plates. The Apenninic belt shows a diffuse extensional stress regime indicating a ˜NE-SW direction of extension, that we interpret as related to a second-order stress field. The horizontal stress rotations observed in peculiar areas reflect a complex interaction between first-order stress field and local effects revealing the importance of the tectonic structure orientations. In particular, in Sicily the new data delineate a more complete tectonic picture evidencing adjacent areas characterized by distinct stress regime: northern offshore of Sicily and in the Hyblean plateau the alignment of horizontal stresses is consistent with the crustal motions, whereas different directions have been observed along the belt and foredeep.

  20. Overcoming residual stresses and machining distortion in the production of aluminum alloy satellite boxes.

    SciTech Connect

    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.

  1. 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.

  2. Method of characterizing residual stress in ferromagnetic materials using a pulse histogram of acoustic emission signals

    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.

  3. The new release of the Italian contemporary stress map

    NASA Astrophysics Data System (ADS)

    Montone, Paola; Mariucci, Maria Teresa

    2016-03-01

    We provide an updated present-day stress map for the Italian territory. Following the World Stress Map (WSM) Project guidelines, we list the different stress indicators, explaining the criteria used to select data. We discuss the data, which will also be included in the 2016 release of the WSM, highlighting the areas for which we have added stress information. Our map displays the minimum horizontal stress orientations inferred from crustal stress indicators down to 40 km depth using data of A to C quality, updated for earthquakes until December 2015. We have completely reviewed all data, and the dataset now contains 855 entries, in contrast to the previous 715. The number of data with A to C quality of 630 corresponds to an increase of 26% relative to the previous dataset. In particular, the new dataset contains the results of the analysis of borehole breakouts, critically reviewed data from earthquake focal mechanisms, data concerning active faults, formal inversions of focal mechanisms of seismic sequences or of restricted areas, and one stress determination from overcoring. In Italy, the complex plate motion and the presence of more than one subduction zone cause different stress regimes in geographic proximity. The new dataset defines the stress field in areas not well covered by the previous data: the region north to the Po Plain and the central Adriatic sea, both characterized by a thrust- and strike-faulting regime, the northern Sicilian belt with a prevailing normal-faulting regime, and the Ionian sea with a strike-slip regime.

  4. Iterative Inversion Method for Eddy Current Evaluation of Near-Surface Residual Stress Profile in Surface-Treated Metals

    SciTech Connect

    Abu-Nabah, Bassam A.; Nagy, Peter B.

    2007-03-21

    Because of their frequency-dependent penetration depth, eddy current measurements are capable of mapping the near-surface depth profile of the electric conductivity. This technique can be used to nondestructively characterize the subsurface residual stress distribution in certain types of shot-peened metals, e.g., in nickel-base superalloys. To predict the depth-dependent, but frequency-independent, intrinsic electric conductivity from the frequency-dependent apparent eddy current conductivity (AECC), a highly convergent iterative inversion procedure is presented. The proposed technique exploits three specific features of the subsurface electric conductivity variation caused by near-surface residual stresses in shot-peened metals. First, compressive residual stresses are limited to a shallow surface region of depth much less than typical probe coil diameters. Second, the change in electric conductivity due to residual stresses is always very small, typically less than 1%. Third, the electric conductivity profile is fairly smooth and continuous. The accuracy of the proposed iterative inversion procedure is one order of magnitude better than that of the previously developed simpler method (J. Appl. Phys. 96, 1257 2004)

  5. Inversion Procedure for Eddy Current Profiling of the Near-Surface Residual Stress in Shot-Peened Metals

    SciTech Connect

    Yu, F.; Nagy, P.B.

    2005-04-09

    Because of their frequency-dependent penetration depth, eddy current measurements are capable of mapping the near-surface depth profile of the electrical conductivity. This technique can be used to nondestructively characterize the subsurface residual stress distribution in certain types of shot-peened metals, e.g., in nickel-base superalloys. For quantitative evaluation of the experimental results, analytical and computational techniques are needed to solve the direct and inverse problems, i.e., to predict the frequency-dependent apparent eddy current conductivity from the depth profile of the frequency-independent intrinsic electrical conductivity of the specimen and vice versa. Simple analytical approximations are presented for both the direct and inverse eddy current problems by exploiting two specific features of the electrical conductivity variation caused by near-surface residual stresses in shot-peened metals. First, compressive residual stresses are limited to a shallow surface region of depth much less than typical probe coil diameters. Second, the change in electrical conductivity due to residual stresses is always very small, typically less than 1%. The proposed approximations are verified by numerical comparison to much more complicated numerical solutions.

  6. 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.

  7. 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

  8. Predicting residual and flow stresses from surface topography created by laser cutting technology

    NASA Astrophysics Data System (ADS)

    Harničárová, Marta; Valíček, Jan; Öchsner, Andreas; Grznárik, Radovan; Kušnerová, Milena; Neugebauer, Josef; Kozak, Dražan

    2013-11-01

    The paper deals with the engineering method for laser cutting technology that utilizes stress equations derived from surface topography for determining residual stresses. It presents an original method for residual stress assessment in a non-contact and non-destructive manner. The high temperature around cut edges results in the development of residual stresses during the cutting process, which decreases the quality of the end product. Surface topographical parameters themselves carry information on a concrete state of technological process in the concrete moment of its usage. This method for the assessment of residual stress in materials being cut by a laser beam provides sufficient information on the residual stress state evaluation with sufficient accuracy by applying an analytical and experimental approach. Experiments were conducted on three different materials, namely steel, aluminium alloy and titanium. It was necessary to check calculation by measuring the residual stress distribution in the vicinity of cut edge using the ultrasonic method. The novelty of the method for the determination of residual stresses in a workpiece lies in the physics-based approach focusing on the mechanical and stress-deformation parameters of the material being cut and on the mechanical equilibrium of the system: material properties-tool properties-deformation properties.

  9. In-situ measurement of residual stresses during the nitriding process

    SciTech Connect

    Hoffman, F.T.; Kreft, U.; Hirsch, T.; Mayr, P.

    1995-12-31

    Residual stresses have a strong influence on the properties of nitrided parts. Therefore knowledge of their origin and magnitude is of great interest and a prerequisite if changes in the stresses are intended. From the relevant theories of residual stresses in gas nitrided materials it can be concluded that stresses which are generated during nitriding can be reduced by plastic deformation during the nitriding process and increased during cooling from nitriding temperature to room temperature. The increase of residual stresses in the compound layer should be a result of the volume misfit generated by different thermal expansion coefficients of compound layer and diffusion zone. These theories mentioned have not been confirmed by experimental work up to now. Therefore, one aim of the investigations was to clarify the origin of residual stresses as well as the different influences on the formation of residual stresses. Previously, residual stresses of nitrided parts could only be measured after nitriding. In the present work it will be shown, for the first time, that residual stresses can successfully be determined in situ during the gas nitriding process by a special nitriding device installed in an X-ray diffractometer. By this way the influences of the parameters nitriding potential, nitriding temperature, cooling process, and carbon content of the investigated material can be shown.

  10. Effects of weld residual stresses on crack-opening area analysis of pipes for LBB applications

    SciTech Connect

    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.

  11. Issues related to prediction of residual stresses in titanium alloy matrix composites

    SciTech Connect

    Rangaswamy, P.; Jayaraman, N.

    1995-01-01

    Recently, a detailed study of residual stresses on the as-processed SCS-6/Ti-24Al-11Nb [0]{sub 8} composite, and SCS-6/Beta-21S composites in unidirectional [0]{sub 4}, cross-ply [0/90]s, and quasi-isotropic [0/{+-}45/90]s lay-ups has been completed. In this study, residual stresses have been measured using x-ray diffraction (Sin{sup 2}{Psi}) technique. We have shown that the use of conventional unit cell models consisting of a quarter fiber surrounded by the matrix material to predict residual stresses for verification of experimental results is inadequate. Such models have successfully predicted the stresses at the fiber-matrix interface. However, experimental work to measure residual stresses have always been on surfaces far away from the interface region. In this paper, the approach taken in extending the conventional unit cell model to the concept of multi-fiber models to predict average stresses are presented. In this process, several modeling issues have been identified. These issues are (i) use of conventional unit models for prediction of average surface residual stresses, (ii) effect of orientation of the sub-surface plies on the residual stresses in the surface ply, (iii) residual stresses in the interior plies, and (iv) constituent material properties.

  12. Investigation of purification process stresses on erythropoietin peptide mapping profile

    PubMed Central

    Sepahi, Mina; Kaghazian, Hooman; Hadadian, Shahin; Norouzian, Dariush

    2015-01-01

    Background: Full compliance of recombinant protein peptide mapping chromatogram with the standard reference material, is one of the most basic quality control tests of biopharmaceuticals. Changing a single amino acid substitution or side chain diversity for a given peptide changes protein hydrophobicity and causes peak shape or retention time alteration in a peptide mapping assay. In this work, the effect of different stresses during the recombinant erythropoietin (EPO) purification process, including pH 4, pH 5, and room temperature were checked on product peptide mapping results. Materials and Methods: Cell culture harvest was purified under stress by different chromatographic techniques consisting of gel filtration, anionic ion exchange, concentration by ultrafiltration, and high resolution size exclusion chromatography. To induce more pH stresses, the purified EPO was exposed to pH stress 4 and 5 by exchanging buffer by a 10 KDa dialysis sac overnight. The effects of temperature and partial deglycosylation (acid hydrolysis) on purified EPO were also studied by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and peptide mapping analysis. Removal of sialic acid by mild hydrolysis was performed by exposure to two molar acetic acid at 80°C for 3 h. Results: No significant effect was observed between intact and stressed erythropoietin peptide mapping profiles and SDS-PAGE results. To validate the sensibility of the technique, erythropoietin was partially acid hydrolyzed and significant changes in the chromatographic peptide map of the intact form and a reduction on its molecular weight were detected, which indicates some partial deglycosylation. Conclusions: Purification process does not alter the peptide mapping profile and purification process stresses are not the cause of peptide mapping noncompliance. PMID:26261816

  13. Stress field modelling from digital geological map data

    NASA Astrophysics Data System (ADS)

    Albert, Gáspár; Barancsuk, Ádám; Szentpéteri, Krisztián

    2016-04-01

    To create a model for the lithospheric stress a functional geodatabase is required which contains spatial and geodynamic parameters. A digital structural-geological map is a geodatabase, which usually contains enough attributes to create a stress field model. Such a model is not accurate enough for engineering-geological purposes because simplifications are always present in a map, but in many cases maps are the only sources for a tectonic analysis. The here presented method is designed for field geologist, who are interested to see the possible realization of the stress field over the area, on which they are working. This study presents an application which can produce a map of 3D stress vectors from a kml-file. The core application logic is implemented on top of a spatially aware relational database management system. This allows rapid and geographically accurate analysis of the imported geological features, taking advantage of standardized spatial algorithms and indexing. After pre-processing the map features in a GIS, according to the Type-Property-Orientation naming system, which was described in a previous study (Albert et al. 2014), the first stage of the algorithm generates an irregularly spaced point cloud by emitting a pattern of points within a user-defined buffer zone around each feature. For each point generated, a component-wise approximation of the tensor field at the point's position is computed, derived from the original feature's geodynamic properties. In a second stage a weighted moving average method calculates the stress vectors in a regular grid. Results can be exported as geospatial data for further analysis or cartographic visualization. Computation of the tensor field's components is based on the implementation of the Mohr diagram of a compressional model, which uses a Coulomb fracture criterion. Using a general assumption that the main principal stress must be greater than the stress from the overburden, the differential stress is

  14. 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.

  15. Measurement and theory of the dependence of hardness on residual stress

    NASA Astrophysics Data System (ADS)

    Abbate, A.; Frankel, J.; Scholz, W.

    1993-05-01

    The Rockwell C hardness (Rc) was measured as a function of position on the three steel rings cut from tubes with different amounts of autofrettage. These rings had different residual stress profiles through the wall that were measured using an ultrasonic technique. An experimental correlation between residual stress and Rc was obtained. In order to model the effects of residual stress on the measured hardness, the Tresca (linear) and the von Mises-Hencky (power) yield criteria were utilized within a model given by Shaw, Hoshi, and Henry that depicts the stress state within a spherical indenter. The von Mises-Hencky method was more successful in matching the data.

  16. High energy X-ray diffraction measurement of residual stresses in a monolithic aluminum clad uranium–10 wt% molybdenum fuel plate assembly

    SciTech Connect

    D. W. Brown; M. A. Okuniewski; J. D. Almer; L. Balogh; B. Clausen; J. S. Okasinski; B. H. Rabin

    2013-10-01

    Residual stresses are expected in monolithic, aluminum clad uranium 10 wt% molybdenum (U–10Mo) nuclear fuel plates because of the large mismatch in thermal expansion between the two bonded materials. The full residual stress tensor of the U–10Mo foil in a fuel plate assembly was mapped with 0.1 mm resolution using high-energy (86 keV) X-ray diffraction. The in-plane stresses in the U–10Mo foil are strongly compressive, roughly -250 MPa in the longitudinal direction and -140 MPa in the transverse direction near the center of the fuel foil. The normal component of the stress is weakly compressive near the center of the foil and tensile near the corner. The disparity in the residual stress between the two in-plane directions far from the edges and the tensile normal stress suggest that plastic deformation in the aluminum cladding during fabrication by hot isostatic pressing also contributes to the residual stress field. A tensile in-plane residual stress is presumed to be present in the aluminum cladding to balance the large in-plane compressive stresses in the U–10Mo fuel foil, but cannot be directly measured with the current technique due to large grain size.

  17. 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.

  18. Assessment of Bending Fatigue Strength of Crankshaft Sections with Consideration of Quenching Residual Stress

    NASA Astrophysics Data System (ADS)

    Qin, W. J.; Dong, C.; Li, X.

    2016-03-01

    High-cycle bending fatigue is the primary failure mode of crankshafts in engines. Compressive residual stresses are often introduced by induction quenching to improve the fatigue strength of crankshafts. The residual stresses, which are commonly obtained by numerical methods, such as the finite element method (FEM), should be included in fatigue failure analysis to predict the fatigue strength of crankshafts accurately. In this study, the simulation method and theory of quenching process are presented and applied to investigate the residual stresses of a diesel engine crankshaft. The coupling calculation of temperature, microstructure, and stress fields of the crankshaft section is conducted by FEM. Then, the fatigue strength of the crankshaft section is analytically assessed by Susmel and Lazzarin's criterion based on the critical plane approach that superimposes the residual stresses onto the bending stresses. The resonant bending fatigue tests of the crankshaft sections are conducted, and the tests and analytical assessments yield consistent results.

  19. Transient and residual stresses in dental porcelains as affected by cooling rates.

    PubMed

    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. PMID:2638963

  20. The new release of the Italian contemporary stress map

    NASA Astrophysics Data System (ADS)

    Montone, Paola; Mariucci, Maria Teresa

    2016-06-01

    We provide an updated present-day stress map for the Italian territory. Following the World Stress Map (WSM) Project guidelines, we list the different stress indicators, explaining the criteria used to select data. We discuss the data, which will also be included in the 2016 release of the WSM, highlighting the areas for which we have added stress information. Our map displays the minimum horizontal stress orientations inferred from crustal stress indicators down to 40 km depth using data of A-C quality, updated for earthquakes until December 2015. We have completely reviewed all data, and the data set now contains 855 entries, in contrast to the previous 715. The number of data with A-C quality of 630 corresponds to an increase of 26 per cent relative to the previous data set. In particular, the new data set contains the results of the analysis of borehole breakouts, critically reviewed data from earthquake focal mechanisms, data concerning active faults, formal inversions of focal mechanisms of seismic sequences or of restricted areas and one stress determination from overcoring. The new data set defines the stress field in areas not well covered by the previous data: the region north to the Po Plain and the central Adriatic sea, both characterized by a thrust- and strike-faulting regime, the northern Sicilian belt with a prevailing normal-faulting regime, and the Ionian sea with a strike-slip regime.

  1. Effect of Residual Stresses on the Hardness of Bulk Metallic Glasses

    SciTech Connect

    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.

  2. Effect of Ultrasonic Peening and Accelerated Corrosion Exposure on the Residual Stress Distribution in Welded Marine Steel

    NASA Astrophysics Data System (ADS)

    Ahmad, Bilal; Fitzpatrick, Michael E.

    2015-03-01

    Specimens of DH36 marine steel were prepared with welded attachments. Residual stress measurements were made on the samples as-welded, following an ultrasonic peening treatment, and following accelerated corrosion exposure after ultrasonic peening. Neutron diffraction and the contour method were used for determining the residual stress profiles. The welding introduces tensile near-surface residual stress, approaching the material yield strength, and the ultrasonic peening overlays this with a compressive residual stress. Material removal by corrosion decreases the peak surface compressive stress slightly, by removal of a layer of stressed material, but does not cause significant redistribution of the residual stress profile.

  3. Measuring residual stresses in metallic components manufactured with fibre Bragg gratings embedded by selective laser melting

    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.

  4. Automation of a neutron diffractometer for analysis of residual stress inside complex engineering components

    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.

  5. Effect of preheat on residual stress distributions in arc-welded mild steel plates

    SciTech Connect

    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.

  6. Residual Stress of Multilayer Ceramic Capacitors with Ni-Electrodes (Ni-MLCCs)

    NASA Astrophysics Data System (ADS)

    Nakano, Yukie; Nomura, Takeshi; Takenaka, Tadashi

    2003-09-01

    The residual stress of multilayer ceramic capacitors (MLCCs) has been studied. The capacitance decreased significantly under external compressive stress applied to MLCCs in the thickness direction, on the other hand, the capacitance increased under external stress in the width direction. These capacitance changes depended on the number of dielectric layers in MLCCs. The compressive residual stress at the surface of MLCCs has been shown by X-ray diffraction (XRD) analysis. The stress increased with the number of dielectric layers in MLCCs. Moreover the tensile stress was confirmed in the thickness direction of MLCCs by XRD analysis also. Therefore the dependence of electrical characteristics dependence on the number of dielectric layers, i.e., apparent dielectric constant, temperature dependence of capacitance, and aging deterioration can be explained by the residual stress.

  7. 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.

  8. Residual Stresses in High-Velocity Oxy-Fuel Metallic Coatings

    SciTech Connect

    Terry C. Totemeier; Richard N. Wright; W. David Swank

    2004-06-01

    X-ray based residual stress measurements were made on type 316 stainless steel and Fe3A1 coatings that were high-velocity oxy-fuel (HVOF) sprayed onto low-carbon and stainless steel substrates. Nominal coating thicknesses varied from 250 to 1500 mm. 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. Difference in thermal expansion coefficient between low-carbon and stainless steels led to a 180 MPa difference in residual stress for Fe3A1 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.

  9. 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.

  10. Residual stress and plastic anisotropy in indented 2024-T351 aluminum disks

    SciTech Connect

    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.

  11. Roller Burnishing - A Cold Working Tool to Reduce Weld Induced Residual Stress

    SciTech Connect

    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.

  12. Numerical and Experimental Study on the Residual Stresses in the Nitrided Steel

    NASA Astrophysics Data System (ADS)

    Song, X.; Zhang, Zhi-Qian; Narayanaswamy, S.; Huang, Y. Z.; Zarinejad, M.

    2016-07-01

    In the present work, residual stresses distribution in the gas nitrided AISI 4140 sample has been studied using finite element (FE) simulation. The nitrogen concentration profile is obtained from the diffusion-controlled compound layer growth model, and nitrogen concentration controls the material volume change through phase transformation and lattice interstitials which results in residual stresses. Such model is validated through residual stress measurement technique—micro-ring-core method, which is applied to the nitriding process to obtain the residual stresses profiles in both the compound and diffusion layer. The numerical and experimental results are in good agreement with each other; they both indicate significant stress variation in the compound layer, which was not captured in previous research works due to the resolution limit of the traditional methods.

  13. The influence of alloy composition on residual stresses in heat treated aluminium alloys

    SciTech Connect

    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.

  14. Effects of surface preparation on pitting resistance, residual stress, and stress corrosion cracking in austenitic stainless steels

    NASA Astrophysics Data System (ADS)

    Rhouma, A. Ben; Sidhom, H.; Braham, C.; Lédion, J.; Fitzpatrick, M. E.

    2001-10-01

    Surface finishing treatments such as shot blasting and wire brushing can be beneficial in improving the integrity of machined surfaces of austenitic stainless steels. These operations optimize in-service properties such as resistance to pitting corrosion and stress corrosion cracking (SCC). In this study, ground steel surfaces were subjected to a series of sand blasting and wire brushing treatments. The surfaces were then characterized by their hardness, surface residual stress state, and resistance to stress corrosion and pitting corrosion. Some samples were selected for depth profiling of residual stress. It is found that surface hardening and the generation of near-surface compressive residual stress are the benefits that can be introduced by sand blasting and brushing operations.

  15. Simplified micromechanical equations for thermal residual stress analysis of coated fiber composites

    NASA Technical Reports Server (NTRS)

    Naik, R. A.

    1991-01-01

    The fabrication of metal matrix composites poses unique problems to the materials engineer. The large thermal expansion coefficient (CTE) mismatch between the fiber and matrix leads to high tensile residual stresses at the fiber/matrix (F/M) interface which could lead to premature matrix cracking during cooldown. Fiber coatings could be used to reduce thermal residual stresses. A simple closed form analysis, based on a three phase composite cylinder model, was developed to calculate thermal residual stresses in a fiber/interphase/matrix system. Parametric studies showed that the tensile thermal residual stresses at the F/M interface were very sensitive to the CTE and thickness of the interphase layer. The modulus of the layer had only a moderate effect on tensile residual stresses. For a silicon carbide titanium aluminide composite, the tangential stresses were 20 to 30 pct. larger than the axial stresses, over a wide range of interphase layer properties, indicating a tendency to form radial matrix cracks during cooldown. Guidelines for the selection of appropriate material properties of the fiber coating were also derived in order to minimize thermal residual stresses in the matrix during fabrication.

  16. 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.

  17. Residual stress distribution in FeAl weld overlay on steel

    SciTech Connect

    Wang, X.L.; Spooner, S.; Hubbard, C.R.; Maziasz, P.J.; Goodwin, G.M.; Feng, Z.; Zacharia, T.

    1994-12-31

    Neutron diffraction was used to measure the residual stress distribution in an FeAl weld overlay on steel. It was found that the residual stresses accumulated during welding were essentially removed by the post-weld heat treatment that was applied to the specimen; most residual stresses in the specimen developed during cooling following the post-weld heat treatment. The experimental data were compared with a plasto-elastic finite element analysis. While some disagreement exists in absolute strain values, there is satisfactory agreement in strain spatial distribution between the experimental data and the finite element analysis.

  18. Threading Dislocation Characterization and Stress Mapping Depth Profiling via Ray Tracing Technique

    NASA Astrophysics Data System (ADS)

    Zhou, Tianyi

    Zinc oxide (ZnO) has been well known as a transparent, dielectric, piezoelectric and wide band gap material. The potential capabilities have been demonstrated for a wide range of applications such as piezoelectric transducer, gas sensor, optical waveguides and transparent electrode. It could also be applied as a substrate material for GaN-based devices. However, while some applications have already been realized, issues relating to crystalline defects remain a barrier to the successful realization of several others. In this thesis, the central focus of Chapter II is to characterize threading dislocations in hydrothermal grown ZnO substrates through simulation work as well as other techniques. The goal of this study is to find the origin of threading dislocations and design strategies to mitigate their negative effects by either reducing their densities or completely eliminating them. In Chapter III, the technique of SMART (stress mapping analysis via ray tracing) is discussed in detail to measure residue stress in packaged silicon circuits. Residual stress plays an important role in the performance and lifetime of single crystal device material. There are mainly two advantages of SMART compared with other techniques: (a) all six components of the stress tensor could be evaluated; (b) it is non-destructive and no damaging trace will be left on the sample. In this study, our goal is to build a relationship between stress distribution and depth. The concept of penetration depth is critically important in this study and its value may cause great changes for real space stress distribution. A new function is applied to get better fitting curves. Data in this study is obtained from various penetration depth, which represents exponentially decaying weighted average of actual stress value or in other words this stress profile is Laplace transform of real stress profile. Mathematical procedure is described to determine real stress profile from Laplace profile. Experiment

  19. Neutron diffraction analysis of residual strain/stress distribution in the vicinity of high strength welds

    NASA Astrophysics Data System (ADS)

    Mráz, L.; Karlsson, L.; Hamák, I.; Vrána, M.; Mikula, P.

    2010-06-01

    Residual stresses resulting from non homogeneous heat distribution during welding process belong to most significant factor influencing behavior of welded structures. These stresses are responsible for defect occurrence during welding and they are also responsible for crack initiation and propagation at the either static or dynamic load. The significant effect of weld metal chemical composition as well as the effect of fatigue load and local plastic deformation on residual stress distribution and fatigue life have been recognized for high strength steels welds. The changes in residual stress distribution have then positive effect on cold cracking behavior and also on fatigue properties of the welds [1-3]. Several experimental methods, both destructive and non-destructive, such as hole drilling method, X-ray diffraction, neutron diffraction and others, have been used to examine residual stress distribution in all three significant orientations in the vicinity of the welds. The present contribution summarizes the results of neutron diffraction measurements of residual stress distribution in the vicinity of single-pass high-strength-steel welds having different chemical composition as well as the influence of fatigue load and local plastic deformation. It has been observed that the chemical composition of the weld metal has a significant influence on the stress distribution around the weld. Similarly, by aplying both cyclic load or pre-stress load on the specimens, stress relaxation was observed even in the region of approximately 40 mm far from the weld toe.

  20. Residual stress in zinc oxide thin films deposited by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Elam, David; Kotha, Ramakrishna; Ayon, Arturo; Chabanov, Andrey

    2010-10-01

    The residual stress in a thin film can have an impact on the electrical and optical properties of the film. In addition, stress is an important consideration when incorporating the material into a microelectromechanical (MEMS) device as large unexpected stresses can cause such a device to fail. The residual stress in ZnO thin films prepared by atomic layer deposition was measured using a radius of curvature technique. The results show relatively low residual stresses on the order of ˜0.1 GPa. The stress is observed to change from tensile to compressive as a function of increasing deposition temperature. The polycrystalline structures of the films are also investigated using XRD techniques.

  1. Accurate measurement of residual stress in glass rod by photoelastic experiment

    SciTech Connect

    Baek, Tae Hyun; Lee, Jae Choon; Kim, Dong Hyun

    1996-12-31

    Photoelastic law is used to measure residual stresses in glass rods which have been heat-treated at different temperatures ranging from 560{degrees}C to 665 {degrees}C. This research is performed to analyze the variation of residual stresses with respect to heat-treatment temperatures of glass rods. In order to measure the stresses accurately, both fringe sharpening and fringe multiplication techniques are applied to the determination of photoelastic fringe orders. The experimental results show that all the hoop stress components are changed from tensile stresses to compressive ones at approximate R/R{sub o}=0.6, where R is any measured radius and R{sub o} outer radius. For the borosilicate glass rods which are used in this experiment, residual stresses increase as heat-treatment temperatures are raised from 560{degrees}C to 665{degrees}C. These experimental results are compared with ones calculated by Instant Freezing Numerical Model.

  2. Initial Results from the New Stress Map of Texas Project

    NASA Astrophysics Data System (ADS)

    Lund Snee, J. E.; Zoback, M. D.

    2015-12-01

    Modern techniques for characterizing tectonic stress orientation and relative magnitude have been successfully used for more than 35 years. Nevertheless, large areas of North America lack high spatial resolution maps of stress orientation, magnitude, and faulting regime. In Texas, for example, <30 A-C-quality stress orientations are currently registered on the World Stress Map and only 7 of these points also describe the stress regime. Stress data are foundational elements of attempts to characterize tectonic driving forces, understand hazards associated with induced seismicity, and optimize production of oil, gas, and geothermal resources. This year, we launched the Texas Stress Map project to characterize tectonic stress patterns at higher spatial resolution across Texas and nearby areas. Following a successful effort just completed in Oklahoma, we will evaluate borehole breakouts, drilling-induced tensile fractures, shear wave anisotropy, and earthquake data. The principal data source will be FMI (fullbore formation microimager), UBI (ultrasonic borehole imager), cross-dipole sonic, density, and caliper logs provided by private industry. Earthquake moment tensor solutions from the U.S. Geological Survey, Saint Louis University and other sources will also be used. Our initial focus is on the Permian Basin and Barnett Shale petroleum plays due to the availability of data, but we will expand our analysis across the state as the project progresses. In addition, we hope to eventually apply the higher spatial resolution data coverage to understanding tectonic and geodynamic characteristics of the southwestern United States and northeastern Mexico. Here we present early results from our work to constrain stress orientations and faulting regime in and near Texas, and we also provide a roadmap for the ongoing research.

  3. Residual stress in laser welded dissimilar steel tube-to-tube joints

    SciTech Connect

    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.

  4. New Crustal Stress Map of the Mediterranean and Central Europe

    NASA Astrophysics Data System (ADS)

    Heidbach, Oliver; Custodio, Susana; Kingdon, Andrew; Mariucci, Maria Teresa; Montone, Paola; Müller, Birgit; Pierdominicini, Simona; Rajabi, Mojtaba; Reinecker, John; Reiter, Karsten; Tingay, Mark; Williams, John; Ziegler, Moritz

    2016-04-01

    The World Stress Map (WSM) Project was initiated in 1986 under the auspices of the International Lithosphere Program in order to compile globally the information on the contemporary crustal stress state. For the 30th anniversary the WSM database has been updated and increased the number of data records from 21,750 to 42,410 worldwide. For the Mediterranean and Central European stress map the number of data records has increased from 3877 to 8192. The data come from a wide range of stress indicators such as borehole data (e.g. hydraulic fracturing, drilling induced tensile fractures, borehole breakouts), earthquake focal mechanism solutions and stress inversions from these, engineering methods (overcoring, borehole slotter) and geological data (e.g. volcanic alignment, inversion of fault slip data). To guarantee the comparability of the different stress indicator the resulting data are quality-ranked using the WSM quality ranking scheme. The new data set has a better coverage and enables us to identifying the regional and local variability of the stress pattern. For the Mediterranean and Central Europe we analysed the wave-length of the stress pattern by determining the mean orientation of the maximum horizontal stress SHmax on a regular grid using an updated version of the hybrid approach of Heidbach et al. [2010]. The preliminary results show that the Africa-Eurasia plate convergence is a key control of the overall stress pattern. However, given the complex tectonic setting in particular due to the indentation/collision of the Adriatic micro block, the Alpine topography as well as forces that control the movement of the Anatolian and Aegean block, the stress pattern shows in these regions significant changes in the mean SHmax orientation as well as in the tectonic regime.

  5. Optimizing amorphous indium zinc oxide film growth for low residual stress and high electrical conductivity

    NASA Astrophysics Data System (ADS)

    Kumar, Mukesh; Sigdel, A. K.; Gennett, T.; Berry, J. J.; Perkins, J. D.; Ginley, D. S.; Packard, C. E.

    2013-10-01

    With recent advances in flexible electronics, there is a growing need for transparent conductors with optimum conductivity tailored to the application and nearly zero residual stress to ensure mechanical reliability. Within amorphous transparent conducting oxide (TCO) systems, a variety of sputter growth parameters have been shown to separately impact film stress and optoelectronic properties due to the complex nature of the deposition process. We apply a statistical design of experiments (DOE) approach to identify growth parameter-material property relationships in amorphous indium zinc oxide (a-IZO) thin films and observed large, compressive residual stresses in films grown under conditions typically used for the deposition of highly conductive samples. Power, growth pressure, oxygen partial pressure, and RF power ratio (RF/(RF + DC)) were varied according to a full-factorial test matrix and each film was characterized. The resulting regression model and analysis of variance (ANOVA) revealed significant contributions to the residual stress from individual growth parameters as well as interactions of different growth parameters, but no conditions were found within the initial growth space that simultaneously produced low residual stress and high electrical conductivity. Extrapolation of the model results to lower oxygen partial pressures, combined with prior knowledge of conductivity-growth parameter relationships in the IZO system, allowed the selection of two promising growth conditions that were both empirically verified to achieve nearly zero residual stress and electrical conductivities >1480 S/cm. This work shows that a-IZO can be simultaneously optimized for high conductivity and low residual stress.

  6. Modelling of Tool Wear and Residual Stress during Machining of AISI H13 Tool Steel

    NASA Astrophysics Data System (ADS)

    Outeiro, José C.; Umbrello, Domenico; Pina, José C.; Rizzuti, Stefania

    2007-05-01

    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.

  7. Numerical analysis of residual stress distribution in tubes with spiral weld cladding

    SciTech Connect

    Taljat, B.; Zacharia, T.; Wang, X.L.; Keiser, J.R.; Swindeman, R.W.; Feng, Z.; Jirinec, M.J.

    1998-08-01

    Residual stresses and strains in a tube with spiral weld cladding were analyzed by the finite element (FE) method. The objective of this work was to determine the residual stress-strain state in the weld clad tube and verify the developed FE model, which might serve for future parametric sensitivity studies of various welding parameters on residual stresses in such tubes. An axisymmetric FE model was developed to simulate the circumferential weld cladding process of Alloy 625 on SA210 carbon steel tube and to analyze the residual stress-strain state. The analysis was uncoupled in that the thermal and mechanical analyses were conducted in two separate runs. The results show high tensile residual stresses in the weld cladding and at the interface with a gradual transition to compressive stresses at the inner tube surface. A neutron diffraction technique was used to experimentally determine residual elastic strains in the clad tube. Comparison with the FE results shows good overall agreement. The agreement is excellent in radial and axial elastic strain components, whereas the calculated tangential elastic strain overpredicted the measured value. The difference is discussed, and certain conclusions are given. Finally, some attempts on how to prevent or relieve high tensile stresses in the weld cladding are presented and discussed in this paper.

  8. Modelling of Tool Wear and Residual Stress during Machining of AISI H13 Tool Steel

    SciTech Connect

    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.

  9. Prediction of Residual Stresses and Distortion in Quenched Extruded Shapes Using Generalized Plane Strain Theory

    NASA Astrophysics Data System (ADS)

    Cherukuri, Harish P.; Ulysse, Patrick; Smelser, Ronald E.; Subramanian, Kannan; Kotaru, Deepti

    2010-06-01

    Rapid quenching of aluminum extrusions often results in residual stresses and distortion. The out-of-plane normal component of the residual stress is typically very large and results in undesirable bending (bowing) of the extruded shape. Three-dimensional models to predict the residual stresses and bending of extruded thin-walled shapes are difficult to implement since the wall-thicknesses are often very small compared with the axial dimensions. In this paper, a generalized plane-strain model is presented to predict the residual stresses and distortion. For illusrative purposes of the model, a Z-shaped extrusion is chosen. The model predicts the bowing of the extruded shape along with the in-plane and out-of-plane stress components. An internal state-variable model is used for the constitutive description. The residual stresses and distortion are studied for cold and warm water quenching and three different cases of spray quenching. The numerical results indicate that cold water quenching and the two spray quenching cases with the higher discharge rates lead to significantly larger residual stresses compared to the remaining two cases. For each case, the out-of-plane bows of the extruded shapes are also shown to be significant.

  10. A model for residual stress evolution in air-plasma-sprayed zirconia thermal barrier coatings

    SciTech Connect

    Nair, B. G.; Singh, J. P.; Grimsditch, M.

    2000-02-28

    Ruby fluorescence spectroscopy indicates that residual stress in air-plasma-sprayed zirconia thermal barrier coatings is a function of the local interface geometry. The stress profile of a simulated rough interface characterized by ``peaks'' and ``valleys'' was modeled with a finite-element approach that accounted for thermal mismatch, oxide scale growth, and top coat sintering. Dependence of the stress profile on interface geometry and microstructure was investigated, and the results were compared with measured stresses.