Improved TIG weld joint strength in aluminum alloy 2219-T87 by filler metal substitution

NASA Technical Reports Server (NTRS)

Poorman, R. M.; Lovoy, C. V.

1972-01-01

The results of an investigation on weld joint characteristics of aluminum alloy 2219-T87 are given. Five different alloys were utilized as filler material. The mechanical properties of the joints were determined at ambient and cryogenic temperatures for weldments in the as-welded condition and also, for weldments after elevated temperature exposures. Other evaluations included hardness surveys, stress corrosion susceptibility, and to a limited extent, the internal metallurgical weld structures. The overall results indicate that M-943 filler weldments are superior in strength to weldments containing either the standard 2319 filler or fillers 2014, 2020, and a dual wire feed consisting of three parts 2319 and one part 5652. In addition, no deficiencies were evident in M-934 filler weldments with regard to ductility, joint strength after elevated temperature exposure, weld hardness, metallographic structures, or stress corrosion susceptibility.

Fabricating niobium test loops for the SP-100 space reactor

NASA Technical Reports Server (NTRS)

Bryhan, Anthony J.; Chan, Ricky C.

1993-01-01

This article describes the successful fabrication, operation, and evaluation of a series of niobium-alloy (Nb-1 Zr and PWC-11) thermal convection loops designed to contain and circulate molten lithium at 1,350 K. These loops were used to establish the fabrication variables of significance for a nuclear power supply for space. Approximately 200 weldments were evaluated for their tendency to be attacked by lithium as a function of varying atmospheric contamination. No attack occurred for any weldment free of contamination, with or without heat treatment, and no welds accidentally deviated from purity. The threshold oxygen content for weldment attack was determined to be 170-200 ppm. Attack varied directly with weldment oxygen and nitrogen contents.

Investigations on Microstructure and Corrosion behavior of Superalloy 686 weldments by Electrochemical Corrosion Technique

NASA Astrophysics Data System (ADS)

Arulmurugan, B.; Manikandan, M.

2018-02-01

In the present study, microstructure and the corrosion behavior of Nickel based superalloy 686 and its weld joints has been investigated by synthetic sea water environment. The weldments were fabricated by Gas Tungsten Arc Welding (GTAW) and Pulsed Current Gas Tungsten Arc Welding (PCGTAW) techniques with autogenous mode and three different filler wires (ERNiCrMo-4, ERNiCrMo-10 and ERNiCrMo-14). Microstructure and Scanning electron microscope examination was carried out to evaluate the structural changes in the fusion zones of different weldments. Energy Dispersive X-ray Spectroscopy (EDS) analysis was carried out to evaluate the microsegregation of alloying elements in the different weld joints. Potentiodynamic polarization study was experimented on the base metal and weld joints in the synthetic sea water environment to evaluate the corrosion rate. Tafel’s interpolation technique was used to obtain the corrosion rate. The microstructure examination revealed that the fine equiaxed dendrites were observed in the pulsed current mode. EDS analysis shows the absence of microsegregation in the current pulsing technique. The corrosion rates of weldments are compared with the base metal. The results show that the fine microstructure with the absence of microsegregation in the PCGTA weldments shows improved corrosion resistance compared to the GTAW. Autogenous PCGTAW shows higher corrosion resistance irrespective of all weldments employed in the present study.

Atmosphere

NASA Astrophysics Data System (ADS)

Ghosh, D.; Mitra, S. K.

2014-05-01

This paper investigates the high-temperature corrosion behavior of microstructurally different regions of the weldment of 9 Cr-1 Mo steel used in thermal power plant boiler in SO2 + O2 environment. The weldment is produced by tungsten inert gas welding method, and the different regions of the weldment (weld metal, heat-affected zone, and base metal) are exposed in SO2 + O2 (ratio 2:1) environment at 973 K for 120 h. The reaction kinetics and corrosion growth rate of different regions of weldment in isothermal condition are evaluated. The post corroded scales of the different specimens are studied in SEM, EDS, and XRD. The results indicate that the weld metal shows higher corrosion rate followed by HAZ and base metal. The higher rate of corrosion of weldmetal is mainly attributed to the least protective inner scale of Cr2O3 with minimum Cr Content. This is due to the formation of delta ferrite, which leads to the precipitation of the Cr-based secondary phases and depletes the free Cr from the matrix. The thermal cycles during welding at high temperature are favorable for the formation of delta ferrite. On the other hand, in absence of delta ferrite, the base metal and HAZ regions of the weldment show lower corrosion rate than weld metal. The difference in corrosion rate in the three regions of the weldment is supplemented by post-corroded scale characterizations.

Saturn S-2 quality assurance techniques: Nondestructive testing processes. Volume 1: Requirements and procedures

NASA Technical Reports Server (NTRS)

Eller, H. H.; Sugg, F. E.

1970-01-01

The methods and procedures used to perform nondestructive testing inspections of the Saturn S-2 liquid hydrogen and liquid oxygen tank weldments during fabrication and after proof testing are described to document special skills developed during the program. All post-test inspection requirements are outlined including radiographic inspections procedures.

Radiation Tolerance of Controlled Fusion Welds in High Temperature Oxidation Resistant FeCrAl Alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gussev, Maxim N.; Field, Kevin G.

High temperature oxidation resistant iron-chromium-aluminum (FeCrAl) alloys are candidate alloys for nuclear applications due to their exceptional performance during off-normal conditions such as a loss-of-coolant accident (LOCA) compared to currently deployed zirconium-based claddings [1]. A series of studies have been completed to determine the weldability of the FeCrAl alloy class and investigate the weldment performance in the as-received (non-irradiated) state [2,3]. These initial studies have shown the general effects of composition and microstructure on the weldability of FeCrAl alloys. Given this, limited details on the radiation tolerance of FeCrAl alloys and their weldments exist. Here, the highest priority candidate FeCrAlmore » alloys and their weldments have been investigated after irradiation to enable a better understanding of FeCrAl alloy weldment performance within a high-intensity neutron field. The alloys examined include C35M (Fe-13%Cr-5% Al) and variants with aluminum (+2%) or titanium carbide (+1%) additions. Two different sub-sized tensile geometries, SS-J type and SS-2E (or SS-mini), were neutron irradiated in the High Flux Isotope Reactor to 1.8-1.9 displacements per atom (dpa) in the temperature range of 195°C to 559°C. Post irradiation examination of the candidate alloys was completed and included uniaxial tensile tests coupled with digital image correlation (DIC), scanning electron microscopy-electron back scattered diffraction analysis (SEM-EBSD), and SEM-based fractography. In addition to weldment testing, non-welded parent material was examined as a direct comparison between welded and non-welded specimen performance. Both welded and non-welded specimens showed a high degree of radiation-induced hardening near irradiation temperatures of 200°C, moderate radiation-induced hardening near temperatures of 360°C, and almost no radiation-induced hardening at elevated temperatures near 550°C. Additionally, low-temperature irradiations showed the non-welded specimens to exhibit strain-induced softening (decrease in the true stress level) with increasing plastic strain during tensile testing. Fracture for the weldments was found to occur exclusively within the fusion zone. The mechanical performance of the weldment was speculated to be directly linked to variances in the radiation-induced microstructure including the formation of dislocation loops and precipitation of the Cr-rich α' phase. The localized microstructural variation within the weldments, including grain size, was determined to play a significant role in the radiation-induced microstructure. The results summarized within highlight the need for additional data on the radiation tolerance of weldments as the mechanical performance of the fusion zone was shown to be the limiting factor in the overall performance of the weldments.« less

The use of supercomputer modelling of high-temperature failure in pipe weldments to optimize weld and heat affected zone materials property selection

NASA Astrophysics Data System (ADS)

Wang, Z. P.; Hayhurst, D. R.

1994-07-01

The creep deformation and damage evolution in a pipe weldment has been modeled by using the finite-element continuum damage mechanics (CDM) method. The finite-element CDM computer program DAMAGE XX has been adapted to run with increased speed on a Cray XMP/416 supercomputer. Run times are sufficiently short (20 min) to permit many parametric studies to be carried out on vessel lifetimes for different weld and heat affected zone (HAZ) materials. Finite-element mesh sensitivity was studied first in order to select a mesh capable of correctly predicting experimentally observed results using at least possible computer time. A study was then made of the effect on the lifetime of a butt welded vessel of each of the commomly measured material parameters for the weld and HAZ materials. Forty different ferritic steel welded vessels were analyzed for a constant internal pressure of 45.5 MPa at a temperature of 565 C; each vessel having the same parent pipe material but different weld and HAZ materials. A lifetime improvement has been demonstrated of 30% over that obtained for the initial materials property data. A methodology for weldment design has been established which uses supercomputer-based CDM analysis techniques; it is quick to use, provides accurate results, and is a viable design tool.

Electron beam weld development on a Filter Pack Assembly

NASA Astrophysics Data System (ADS)

Dereskiewicz, J. P.

1994-06-01

A continuous electron beam welding procedure was developed to replace the manual gas tungsten arc welding procedure on the Filter Pack Assembly. A statistical study was used to evaluate the feasibility of electron beam welding 6061-T6 aluminum covers to A356 cast weldments throughout the joint tolerance range specified on product drawings. Peak temperature exposures were not high enough to degrade the heat sensitive electrical components inside the cast weldment. Actual weldments with alodine coating on the weld joint area were successfully cleaned using a nonmetallic fiberglass brush cleaning method.

Corrosion of 2205 Duplex Stainless Steel Weldment in Chloride Medium Containing Sulfate-Reducing Bacteria

NASA Astrophysics Data System (ADS)

Antony, P. J.; Singh Raman, R. K.; Kumar, Pradeep; Raman, R.

2008-11-01

Influence of changes in microstructure caused due to welding on microbiologically influenced corrosion of a duplex stainless steel was studied by exposing the weldment and parent metal to chloride medium containing sulfate-reducing bacteria (SRB). Identically prepared coupons (same area and surface finish) exposed to sterile medium were used as the control. Etching-type attack was observed in the presence of SRB, which was predominant in the heat-affected zone (HAZ) of the weldment. The anodic polarization studies indicated an increase in current density for coupon exposed to SRB-containing medium as compared to that obtained for coupon exposed to sterile medium. The scanning electron microscopy (SEM) observations after anodic polarization revealed that the attack was preferentially in the ferrite phase of HAZ of the weldment, whereas it was restricted to the austenite phase of the parent metal.

Significance of reheat cracks to the integrity of pressure vessels for light-water reactors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Canonico, D.A.

1979-05-01

Reheat cracks manifest themselves as macroscopic defects detectable by nondestructive testing (NDT) procedures or as microscopic grain boundary decohesions (GBD) that are beyond the limit of detection by NDT. The significance of the microscopic cracks that may go undetected are discussed. The probability that GBD exist in the heat-affected zones (HAZ) of weldments of pressure vessel steels is high; particularly in SA508 Class 2 weldments. GBD reside in the coarse-grained region of the HAZ. The microstructure of this region tends to be a tempered martensite or lower bainite, a structure whose fracture toughness is superior to that of a highermore » temperature transformation product. This region should be less sensitive to irradiation embrittlement. Toughness data for this region in either the unirradiated or irradiated condition are sparse; however, those data that are available indicate that this area is superior in toughness to the base metal. A sample of the HAZ from the prolongation-weldment from the Heavy Section Steel Technology program Intermediate Test Vessel (ITV) No. 4 was examined by the Staatliche Materialpruefungsanstalt (MPA). They reported GBD 5 mm (0.2 in.) long. This prompted an examination of the HAZ from the ITV vessel that had been tested to failure at 24 C (75 F). During testing, the region of the weld which contained the flaw that initiated the failure was strained up to 0.5%. A metallographic examination of this region of the weldment revealed GBD, but none of the size reported by the MPA. Further, there was no evidence that the GBD had extended as a consequence of the tests. Fracture toughness tests were made of the HAZ of welds from ITV-4. The electron-beam welding procedure, which permits more accurate siting of the crack, was used. Fracture toughness values in excess of 220 MPa/m (200 ksi/in.) were obtained at -18 C (O F).« less

On dissimilar metal welding of AISI4140 and AISI410 by GTAW

NASA Astrophysics Data System (ADS)

Velu, M.; Dixit, Shantanu; Choure, Shubham

2017-11-01

This paper presents the results of metallurgical and mechanical examinations of Gas Tungsten Arc Welding of dissimilar steels AISI4140 and AISI410. Two different filler materials viz., ERNiCr3 and SS410 were used. The various properties of the weldments made using the fillers were compared to select the most appropriate one to get the sound joint. The ultimate tensile and yield strengths of the weldments of SS410 were greater than those of ERNiCr3. The fracture occurred at the weld in weldments made with ERNiCr3, whereas, in the base metal of AISI410 for weldments made with SS410. Microstructure of fusion zone of ERNiCr3 was fully austenitic. Microhardness values in the weld of SS410 were higher and fluctuating compared to those in the weld of ERNiCr3. From this research work, it shall be concluded that SS410 is the best filler material to weld these base materials.

Fatigue crack growth behavior of pressure vessel steels and submerged arc weldments in a high-temperature pressurized water environment

NASA Astrophysics Data System (ADS)

Liaw, P. K.; Logsdon, W. A.; Begley, J. A.

1989-10-01

The fatigue crack growth rate (FCGR) properties of SA508 C1 2a and SA533 Gr A C1 2 pressure vessel steels and the corresponding automatic submerged are weldments were developed in a high-temperature pressurized water (HPW) environment at 288 °C (550°F) and 7.2 MPa (1044 psi) at load ratios of 0.02 and 0.50. The HPW enviromment FCGR properties of these pressure vessel steels and submerged arc weldments were generally conservative, compared with the approrpriate American Society of Mechanical Engineers (ASME) Section XI water environmental reference curve. The growth rate of fatigue cracks in the base materials, however, was considerably faster in the HPW environment than in a corresponding 288°C (550°F) base line air environment. The growth rate of fatigue cracks in the two submerged are weldments was also accelerated in the HPW environment but to a significantly lesser degree than that demonstrated by the corresponding base materials. In the air environment, fatigue striations were observed, independent of material and load ratio, while in the HPW environment, some intergranular facets were present. The greater environmental effect on crack growth rates displayed by the base materials, as compared with the weldments, was attributed to a different sulfide composition and morphology.

Mechanical properties of weldments in experimental Fe-12Mn-0.2Ti and Fe-12Mn-1Mo-0.2Ti alloys for cryogenic service

NASA Technical Reports Server (NTRS)

Stephens, J. R.; Witzke, W. R.; Devletian, J. H.

1981-01-01

Mechanical properties of weldments in two Fe-12Mn experimental alloys designed for cryogenic service were evaluated. Weldments were made using the GTA welding process. Tests to evaluate the weldments were conducted at -196 C and included: equivalent energy fracture toughness tests; autogenous transverse weld, notched transverse weld, and longitudinal weld tensile tests; and all-weld-metal tensile tests. The Fe-12Mn-0.2Ti and Fe-12Mn-1Mo-0.2Ti alloys proved weldable for cryogenic service, with weld metal and heat-affected zone properties comparable with those of the base metal. Optimum properties were achieved in the base alloys, weld metals, and heat-affected zones after a two-step heat treatment consisting of austenitizing at 900 C followed by tempering at 500 C. The Mo-containing alloy offered a marked improvement in cryogenic properties over those of the Mo-free alloy. Molybdenum increased the amount of retained austenite and reduced the amount of epsilon martensite observed in the microstructure of the two alloys.

Fatigue crack growth behavior of pressure vessel steels and submerged arc weldments in a high-temperature pressurized water environment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liaw, P.K.; Logsdon, W.A.; Begley, J.A.

1989-10-01

The fatigue crack growth rate (FCGR) properties of SA508 Cl 2a and SA533 Gr A Cl 2 pressure vessel steels and the corresponding automatic submerged arc weldments were developed in a high-temperature pressurized water (HPW) environment at 288{degrees} C (550{degrees} F) and 7.2 MPa (1044 psi) at load ratios of 0.20 and 0.50. The properties were generally conservative compared to American Society of Mechanical Engineers Section XI water environment reference curve. The growth rate of fatigue cracks in the base materials, however, was faster in the HPW environment than in a 288{degrees} C (550{degrees} F) base line air environment. Themore » growth rate of fatigue cracks in the two submerged arc weldments was also accelerated in the HPW environment but to a lesser degree than that demonstrated by the base materials. In the air environment, fatigue striations were observed, independent of material and load ratio, while in the HPW environment, some intergranular facets were present. The greater environmental effect on crack growth rates displayed by the base materials compared the weldments attributed to a different sulfide composition and morphology.« less

Use of photostress and strain gages to analyze behavior of weldments and use of photostress and strain gages to analyze behavior of an aft skirt test specimen

NASA Technical Reports Server (NTRS)

Gambrell, S. C.; Karr, Gerald R.

1993-01-01

Previous work using Photostress on TIG welded, heat treated specimens of 2219-T87 parent material and 2319 weld material indicated that behavior of the joint can be highly irregular and non-uniform. Welded joints 1.40 inches thick exhibited a totally non-uniform behavior through the weld thickness with the 'wide' side of the weld being much more ductile than the 'narrow' side. It is believed that this difference in behavior through the weld is, in part, caused by procedures used when laying the weld bead. Joints similar to weldments in references 1 and 2 are an integral part of the aft skirt of the SRB of the shuttle. Since the ultimate safety factor for the lower portion of the weld is below the minimum required safety factor, a photostress analysis of this lower portion will be conducted in the vicinity of the weld. A test program using photostress will be conducted in accordance with the project planning document entitled 'Photostress Evaluation Requirements for AFT Skirt Test Article No. 4'.

An experimental and computational investigation of dynamic ductile fracture in stainless steel welds

NASA Astrophysics Data System (ADS)

Kothnur, Vasanth Srinivasa

The high strain rate viscoplastic flow and fracture behavior of NITRONIC-50 and AL6XN stainless steel weldments are studied under dynamic loading conditions. The study is primarily motivated by interest in modeling the micromechanics of dynamic ductile failure in heterogeneous weldments. The high strain rate response of specimens machined from the parent, weld and heat-affected zones of NITRONIC-50 and AL6XN weldments is reported here on the basis of experiments conducted in a compression Kolsky bar configuration. The failure response of specimens prepared from the various material zones is investigated under high rate loading conditions in a tension Kolsky bar set-up. The microstructure of voided fracture process zones in these weldments is studied using X-ray Computed Microtomography. To model the preferential evolution of damage near the heat-affected zone, a finite deformation elastic-viscoplastic constitutive model for porous materials is developed. The evolution of the macroscopic flow response and the porous microstructure have been analysed in two distinctive regimes: pre-coalescence and post-coalescence. The onset of void coalescence is analyzed on the basis of upper-bound models to obtain the limit-loads needed to sustain a localized mode of plastic flow in the inter-void ligament. A finite element framework for the integration of the porous material response under high rate loading conditions is implemented as a user-subroutine in ABAQUS/Explicit. To address the effect of mesh sensitivity of numerical simulations of ductile fracture, a microstructural length scale is used to discretize finite element models of test specimens. Results from a detailed finite element study of the deformation and damage evolution in AL6XN weldments are compared with experimental observations.

Study of Residual Stresses and Distortion in Structural Weldments in High-Strength Steels.

DTIC Science & Technology

1981-11-30

diagram of the material under consideration which is either known experimentally or can be derived from the TTT diagram. Using the CCT diagram and the...strains are incorporated into the finite element program ADINA replacing the conventional thermal strains, T TH e i" I Computed CCT Diagram . Experimentally...derived CCT diagrams exist today for several steel alloys, enabling one to predict the microstructure [history during the cooling stage of the

Investigation of the Fracture Behavior of Scaled HY-130 Weldments

DTIC Science & Technology

1990-06-01

RESULTS OF EPFM ANALYSIS OF TFREE-POINT BEND SPECIMENS OF DIFFERENT SIZES ........... D-48 xi NAVSWC TR 90-360 TABLES 1 RESULTS OF DYNAMIC FRACTURE...characterize the critical loading needed to cause fracture of the welded joint. An example of such a measure of severity applicable to structures with...weldments. Application of the approach to two titanium alloys and the results of that hwvestigation will be presented in another report. The next four

Reactor Materials Program - Baseline Material Property Handbook - Mechanical Properties of 1950's Vintage Stainless Steel Weldment Components, Task Number 89-23-A-1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stoner, K.J.

1999-11-05

The Process Water System (primary coolant) piping of the nuclear production reactors constructed in the 1950''s at Savannah River Site is comprised primarily of Type 304 stainless steel with Type 308 stainless steel weld filler. A program to measure the mechanical properties of archival PWS piping and weld materials (having approximately six years of service at temperatures between 25 and 100 degrees C) has been completed. The results from the mechanical testing has been synthesized to provide a mechanical properties database for structural analyses of the SRS piping.

The Quantitative Microstructural Characterization of Multipass TIG Ultra Low Carbon Bainitic Steel Weldments and Correlation with Mechanical Properties

DTIC Science & Technology

1993-09-01

in TIG weldments. The alloying elements used in ULCB steels are; Carbon (C), Manganese (Mn), Molybdenum (Mo), Nickel (Ni), Niobium (Nb), Chromium (Cr...process. 7 C. WELDING PROCESSES 1. Tungsten Inert Gas (TIG) Welding Tungsten Inert Gas (TIG) Welding (or Gas Tungsten Arc Welding ( GTAW )), produces... chromium (Cr), molybdenum (Mo), and sometimes vanadium (V). Reheat cracking occurs in the HAZ during postweld stress relieving, especially in thick

First Annual Progress Report on Radiation Tolerance of Controlled Fusion Welds in High Temperature Oxidation Resistant FeCrAl Alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Field, Kevin G.; Gussev, Maxim N.; Hu, Xunxiang

2015-12-01

The present report summarizes and discusses the first year efforts towards developing a modern, nuclear grade FeCrAl alloy designed to have enhanced radiation tolerance and weldability under the Department of Energy (DOE) Nuclear Energy Enabling Technologies (NEET) program. Significant efforts have been made within the first year of this project including the fabrication of seven candidate FeCrAl alloys with well controlled chemistry and microstructure, the microstructural characterization of these alloys using standardized and advanced techniques, mechanical properties testing and evaluation of base alloys, the completion of welding trials and production of weldments for subsequent testing, the design of novel tensilemore » specimen geometry to increase the number of samples that can be irradiated in a single capsule and also shorten the time of their assessment after irradiation, the development of testing procedures for controlled hydrogen ingress studies, and a detailed mechanical and microstructural assessment of weldments prior to irradiation or hydrogen charging. These efforts and research results have shown promise for the FeCrAl alloy class as a new nuclear grade alloy class.« less

Performance of repair welds on aged Cr-Mo piping girth welds

NASA Astrophysics Data System (ADS)

Viswanathan, R.; Gandy, D. W.

1999-10-01

This article documents the results of an industry survey of weld repair practices and describes the results of experimental evaluations performed on service-aged 21/4 Cr-1Mo steel piping using SMAW with both conventional postweld heat treatments and temper bead repair techniques. The overall results of this program provide substantial evidence that service-aged piping systems can be successfully weld repaired with and without postweld heat treatments and that life extension by several decades is achievable under the right design and repair conditions. Weld repairs performed on degraded exservice welds resulted in restoration or improvement of tensile and creep properties. Microhardness test results within the heat-affected zone of each weldment indicated that the temper bead weld repairs produced only slightly higher peak hardness values than those measured for the fully postweld heat treated repairs. Finally, in terms of toughness, temper bead weld repairs consistently produced higher impact properties than those measured for the postweld heat treated weldments. Gas tungsten arc weld repairs with postweld heat treatment resulted in the best combination of tensile strength, uniform microhardness distribution across the weld, Charpy toughness, and creep rupture life.

Galvanic Corrosion Behavior of Microwave Welded and Post-weld Heat-Treated Inconel-718 Joints

NASA Astrophysics Data System (ADS)

Bansal, Amit; Sharma, Apurbba Kumar; Kumar, Pradeep

2017-05-01

In the present study, corrosion behavior of microwave welded Inconel-718 at various conditions was investigated. Welding of Inconel-718 in 980 °C solution-treated condition was performed using microwave hybrid heating technique. The microwave welds were subjected to post-heat treatment for improving its microstructure and mechanical properties by solubilizing the Nb-enriched Laves phase. The microstructural features of the fabricated welds at various conditions were investigated through scanning electron microscopy. The electrochemical testing results revealed that Inconel-718 welds were galvanic corroded when they were anodically polarized in 3.5 wt.% NaCl solution at 28 °C. The difference in the corrosion potentials between the base metal (BM) and fusion zone (FZ) in an Inconel-718 weld was the main factor for galvanic corrosion. The highest corrosion was occurred in the as-welded/aged weldments, followed by 980 °C solution-treated and aged weldments, as-welded specimen, and 1080 °C solution-treated and aged (1080STA) weldments. The least galvanic corrosion was occurred in the 1080STA specimens due to almost uniform microstructure developed in the weldment after the treatment. Thus, it was possible to minimize the galvanic corrosion in the microwave welded Inconel-718 by 1080STA treatment which resulted in reducing the difference in corrosion potentials between the BM and the FZ.

Influence of Alloy Content and Prior Microstructure on Evolution of Secondary Phases in Weldments of 9Cr-Reduced Activation Ferritic-Martensitic Steel

NASA Astrophysics Data System (ADS)

Thomas Paul, V.; Sudha, C.; Saroja, S.

2015-08-01

9Cr-Reduced Activation Ferritic-Martensitic steels with 1 and 1.4 wt pct tungsten are materials of choice for the test blanket module in fusion reactors. The steels possess a tempered martensite microstructure with a decoration of inter- and intra-lath carbides, which undergoes extensive modification on application of heat. The change in substructure and precipitation behavior on welding and subsequent thermal exposure has been studied using both experimental and computational techniques. Changes i.e., formation of various phases, their volume fraction, size, and morphology in different regions of the weldment due to prolonged thermal exposure was influenced not only by the time and temperature of exposure but also the prior microstructure. Laves phase of type Fe2W was formed in the high tungsten steel, on aging the weldment at 823 K (550 °C). It formed in the fine-grained heat-affected zone (HAZ) at much shorter durations than in the base metal. The accelerated kinetics has been understood in terms of enhanced precipitation of carbides at lath/grain boundaries during aging and the concomitant depletion of carbon and chromium and enrichment of tungsten in the vicinity of the carbides. Therefore, the fine-grained HAZ in the weldment was identified as a region susceptible for failure during service.

Fatigue and Fracture-Toughness Characterization of SAW and SMA A537 Class I Ship-Steel Weldments.

DTIC Science & Technology

1981-12-01

Charpy criterion and proposed NDT-DT criterion of Rolfe . Recommendations are made and further research is suggested to help clarify the assessment of...acceptable performance at -60aF. Likewise, at -60OF the NDT and DT data for these weldments marginally exceed the criteria proposed by Rolfe when the...exceed the CVN values equivalent to the 5/8 DT values required by Rolfe . The 5/8-inch dynamic-tear specimen is not recommended as a quality-control test

The Effect of Heat Input and Composition on Weld Metal Microstructures in Thin Section HY-130 GMAW(Gas Metal Are Welding) Weldments

DTIC Science & Technology

1988-12-01

weldments, Glover et al. [Ref. Ej show, via a schematic CCT diagram , that austenite should transform to coarse polygonal ferrite with regions of pearlite...are essentially subjected to continuous cooling during solidification, so the resultant microstructures should be predictable from CCT diagrams . Unfortunately...cooling rate variaticn just within a single weld pass. Although individual CCT diagrams for weld metals are generally not available, the influence of

Method and device for controlling plume during laser welding

DOEpatents

Fuerschbach, Phillip W.; Jellison, James L.; Keicher, David M.; Oberkampf, William L.

1991-01-01

A method and apparatus for enhancing the weldment of a laser welding system is provided. The laser weld plume control device includes a cylindrical body defining an upside-down cone cavity; the upper surface of the body circumscribes the base of the cone cavity, and the vertex of the cone cavity forms an orifice concentrically located with respect to the laser beam and the plume which forms as a result of the welding operation. According to the method of the invention, gas is directed radially inward through inlets in the upper surface of the body into and through channels in the wall of the body and finally through the orifice of the body, and downward onto the surface of the weldment. The gas flow is then converted by the orifice of the device from radial flow to an axisymmetric gas jet flowing away from the weldment surface in a direction perpendicular to the surface and opposite to that of the laser.

Detection of lack of fusion using opaque additives, phase 1

NASA Technical Reports Server (NTRS)

Cook, J. L.

1972-01-01

Two major problems in welded aluminum spacecraft structure, reliable nondestructive inspection for incomplete weldment penetration and the rapid oxidation of aluminum surfaces left exposed to the atmosphere are investigated. The approach employed to solve both problems was to employ copper as a coating to prevent oxidation of the aluminum and as an opaque additive in the weldment to enhance X-ray detection in the event of incomplete penetration. Both plasma spray and vacuum vapor deposition techniques were evaluated for depositing the copper. A series of welded panels was made using three thicknesses of vacuum-vapor-deposited copper. All weldments were nondestructively inspected by X-ray, then excised into tensile and bend specimens. Mechanical tests were conducted and all data evaluated. It was determined that the vacuum-vapor-deposited coating was superior to a plasma sprayed coating of the same thickness. The vacuum-vapor-deposited coating was more uniform in thickness, provided complete coverage of the aluminum, and was free of cracks and porosity.

Pulsed Magnetic Welding for Advanced Core and Cladding Steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cao, Guoping; Yang, Yong

2013-12-19

To investigate a solid-state joining method, pulsed magnetic welding (PMW), for welding the advanced core and cladding steels to be used in Generation IV systems, with a specific application for fuel pin end-plug welding. As another alternative solid state welding technique, pulsed magnetic welding (PMW) has not been extensively explored on the advanced steels. The resultant weld can be free from microstructure defects (pores, non-metallic inclusions, segregation of alloying elements). More specifically, the following objectives are to be achieved: 1. To design a suitable welding apparatus fixture, and optimize welding parameters for repeatable and acceptable joining of the fuel pinmore » end-plug. The welding will be evaluated using tensile tests for lap joint weldments and helium leak tests for the fuel pin end-plug; 2 Investigate the microstructural and mechanical properties changes in PMW weldments of proposed advanced core and cladding alloys; 3. Simulate the irradiation effects on the PWM weldments using ion irradiation.« less

Mechanical Characteristics of Submerged Arc Weldment in API Gas Pipeline Steel of Grade X65

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hashemi, S. H.; Mohammadyani, D.

The mechanical properties of submerged arc weldment (SAW) in gas transportation pipeline steel of grade API X65 (65 ksi yield strength) were investigated. This steel is produced by thermo mechanical control rolled (TMC), and is largely used in Iran gas piping systems and networks. The results from laboratory study on three different regions; i.e. base metal (BM), fusion zone (FZ) and heat affected zone (HAZ) were used to compare weldment mechanical characteristics with those specified by API 5L (revision 2004) standard code. Different laboratory experiments were conducted on test specimens taken from 48 inch outside diameter and 14.3 mm wallmore » thickness gas pipeline. The test results showed a gradient of microstructure and Vickers hardness data from the centerline of FZ towards the unaffected MB. Similarly, lower Charpy absorbed energy (compared to BM) was observed in the FZ impact specimens. Despite this, the API specifications were fulfilled in three tested zones, ensuring pipeline structural integrity under working conditions.« less

High-Temperature Tensile Behaviors of Base Metal and Electron Beam-Welded Joints of Ni-20Cr-9Mo-4Nb Superalloy

NASA Astrophysics Data System (ADS)

Gupta, R. K.; Anil Kumar, V.; Sukumaran, Arjun; Kumar, Vinod

2018-05-01

Electron beam welding of Ni-20Cr-9Mo-4Nb alloy sheets was carried out, and high-temperature tensile behaviors of base metal and weldments were studied. Tensile properties were evaluated at ambient temperature, at elevated temperatures of 625 °C to 1025 °C, and at strain rates of 0.1 to 0.001 s-1. Microstructure of the weld consisted of columnar dendritic structure and revealed epitaxial mode of solidification. Weld efficiency of 90 pct in terms of strength (UTS) was observed at ambient temperature and up to an elevated temperature of 850 °C. Reduction in strength continued with further increase of test temperature (up to 1025 °C); however, a significant improvement in pct elongation is found up to 775 °C, which was sustained even at higher test temperatures. The tensile behaviors of base metal and weldments were similar at the elevated temperatures at the respective strain rates. Strain hardening exponent `n' of the base metal and weldment was 0.519. Activation energy `Q' of base metal and EB weldments were 420 to 535 kJ mol-1 determined through isothermal tensile tests and 625 to 662 kJ mol-1 through jump-temperature tensile tests. Strain rate sensitivity `m' was low (< 0.119) for the base metal and (< 0.164) for the weldment. The δ phase was revealed in specimens annealed at 700 °C, whereas, twins and fully recrystallized grains were observed in specimens annealed at 1025 °C. Low-angle misorientation and strain localization in the welds and the HAZ during tensile testing at higher temperature and strain rates indicates subgrain formation and recrystallization. Higher elongation in the weldment (at Test temperature > 775 °C) is attributed to the presence of recrystallized grains. Up to 700 °C, the deformation is through slip, where strain hardening is predominant and effect of strain rate is minimal. Between 775 °C to 850 °C, strain hardening is counterbalanced by flow softening, where cavitation limits the deformation (predominantly at lower strain rate). Above 925 °C, flow softening is predominant resulting in a significant reduction in strength. Presence of precipitates/accumulated strain at high strain rate results in high strength, but when the precipitates were coarsened at lower strain rates or precipitates were dissolved at a higher temperature, the result was a reduction in strength. Further, the accumulated strain assisted in recrystallization, which also resulted in a reduction in strength.

Fiber laser welding of austenitic steel and commercially pure copper butt joint

NASA Astrophysics Data System (ADS)

Kuryntsev, S. V.; Morushkin, A. E.; Gilmutdinov, A. Kh.

2017-03-01

The fiber laser welding of austenitic stainless steel and commercially pure copper in butt joint configuration without filler or intermediate material is presented. In order to melt stainless steel directly and melt copper via heat conduction a defocused laser beam was used with an offset to stainless steel. During mechanical tests the weld seam was more durable than heat affected zone of copper so samples without defects could be obtained. Three process variants of offset of the laser beam were applied. The following tests were conducted: tensile test of weldment, intermediate layer microhardness, optical metallography, study of the chemical composition of the intermediate layer, fractography. Measurements of electrical resistivity coefficients of stainless steel, copper and copper-stainless steel weldment were made, which can be interpreted or recalculated as the thermal conductivity coefficient. It shows that electrical resistivity coefficient of cooper-stainless steel weldment higher than that of stainless steel. The width of intermediate layer between stainless steel and commercially pure copper was 41-53 μm, microhardness was 128-170 HV0.01.

Effect of filler metals on the mechanical properties of Inconel 625 and AISI 904L dissimilar weldments using gas tungsten arc welding

NASA Astrophysics Data System (ADS)

Senthur Prabu, S.; Devendranath Ramkumar, K.; Arivazhagan, N.

2017-11-01

In the present research work, dissimilar welding between Inconel 625 super alloy and AISI 904L super austenitic stainless steel using manual multi-pass continuous current gas tungsten arc (CCGTA) welding process employed with ERNiCrMo-4 and ERNiCrCoMo-1 fillers were performed to determine the mechanical properties and weldability. Tensile test results corroborated that the fracture had occurred at the parent metal of AISI 904L irrespective of filler used for all the trials. The presence of the macro and micro void coalescence in the fibrous matrix characterised for ductile mode of fracture. The hardness values at the weld interface of Inconel 625 side were observed to be higher for ERNiCrMo-4 filler due to the presence of strengthening elements such as W, Mo, Ni and Cr. The impact test accentuated that the weldments using ERNiCrMo-4 filler offered better impact toughness (41J) at room temperature. Bend test results showed that the weldments using these fillers exhibited good ductility without cracks.

Determination of a temperature sensor location for monitoring weld pool size in GMAW

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boo, K.S.; Cho, H.S.

1994-11-01

This paper describes a method of determining the optimal sensor location to measure weldment surface temperature, which has a close correlation with weld pool size in the gas metal arc (GMA) welding process. Due to the inherent complexity and nonlinearity in the GMA welding process, the relationship between the weldment surface temperature and the weld pool size varies with the point of measurement. This necessitates an optimal selection of the measurement point to minimize the process nonlinearity effect in estimating the weld pool size from the measured temperature. To determine the optimal sensor location on the top surface of themore » weldment, the correlation between the measured temperature and the weld pool size is analyzed. The analysis is done by calculating the correlation function, which is based upon an analytical temperature distribution model. To validate the optimal sensor location, a series of GMA bead-on-plate welds are performed on a medium-carbon steel under various welding conditions. A comparison study is given in detail based upon the simulation and experimental results.« less

Deformation behavior of a 16-8-2 GTA weld as influenced by its solidification substructure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Foulds, J.R.; Moteff, J.; Sikka, V.K.

1983-07-01

Weldment sections from formed and welded type 316 stainless steel pipe are characterized with respect to some time-independent (tensile) and time-dependent (creep) mechanical properties at temperatures between 25/sup 0/C and 649/sup 0/C. The GTA weldment, welded with 16-8-2 filler metal, is sectioned from pipe in the formed + welded + solution annealed + straightened condition, as well as in the same condition with an additional re-solution treatment. Detailed room temperature microhardness measurements on these sections before and after reannealing enable a determination of the different recovery characteristics of weld and base metal. The observed stable weld metal solidification dislocation substructuremore » in comparison with the base metal random dislocation structure, in fact, adequately explains weld/base metal elevated temperature mechanical behavior differences from this recovery characteristic standpoint. The weld metal substructure is the only parameter common to the variety of austenitic stainless steel welds exhibiting the consistent parent/weld metal deformation behavior differences described. As such, it must be considered the key to understanding weldment mechanical behavior.« less

Microstructure-dependent fracture toughness (JIC) variations in dissimilar pipe welds for pressure vessel system of nuclear plants

NASA Astrophysics Data System (ADS)

Rathod, Dinesh W.; Pandey, Sunil; Singh, P. K.; Kumar, Suranjit

2017-09-01

In present study, dissimilar metal weld (DMW) joints between SA508Gr.3cl.1 ferritic steel and SS304LN pipes were prepared using Inconel 82/182, and Inconel 52/152 consumables. Metallurgical properties and their influence on fracture toughness of weldment regions and interfacial regions could play a significant role in integrity assessment of these joints. Ni-based consumables exhibit complex metallurgical properties at interfacial regions. The metallurgical characterization and fracture toughness studies of Inconel 82/182 and Inconel 52/152 joints have been carried out for determining the optimum consumable for DMW joint requirements and the effect of microstructure on fracture toughness in weldment regions. The present codes and procedures for integrity assessment of DMW joints have not given due considerations of metallurgical properties. The requirements for metallurgical properties by considering their effect on fracture toughness properties in integrity assessment have been discussed for reliable analysis. Inconel 82/182 is preferred over Inconel 52/152 joints owing to favorable metallurgical and fracture toughness properties across the interfacial and weldment regions.

Deep flaws in weldments of aluminum and titanium

NASA Technical Reports Server (NTRS)

Masters, J. N.; Engstrom, W. L.; Bixler, W. D.

1974-01-01

Surface flawed specimens of 2219-T87 and 6Al-4V STA titanium weldments were tested to determine static failure modes, failure strength, and fatigue flaw growth characteristics. Thicknesses selected for this study were purposely set at values where, for most test conditions, abrupt instability of the flaw at fracture would not be expected. Static tests for the aluminum weldments were performed at room, LN2 and LH2 temperatures. Titanium static tests for tests were performed at room and LH2 temperatures. Results of the static tests were used to plot curves relating initial flaw size to leakage- or failure-stresses (i.e. "failure" locus curves). Cyclic tests, for both materials, were then performed at room temperature, using initial flaws only slightly below the previously established failure locus for typical proof stress levels. Cyclic testing was performed on pairs of specimens, one with and one without a simulated proof test cycle. Comparisons were made then to determine the value and effect of proof testing as affected by the various variables of proof and operating stress, flaw shape, material thickness, and alloy.

Optimization of process parameters in welding of dissimilar steels using robot TIG welding

NASA Astrophysics Data System (ADS)

Navaneeswar Reddy, G.; VenkataRamana, M.

2018-03-01

Robot TIG welding is a modern technique used for joining two work pieces with high precision. Design of Experiments is used to conduct experiments by varying weld parameters like current, wire feed and travelling speed. The welding parameters play important role in joining of dissimilar stainless steel SS 304L and SS430. In this work, influences of welding parameter on Robot TIG Welded specimens are investigated using Response Surface Methodology. The Micro Vickers hardness tests of the weldments are measured. The process parameters are optimized to maximize the hardness of the weldments.

X-ray online detection for laser welding T-joint of Al-Li alloy

NASA Astrophysics Data System (ADS)

Zhan, Xiaohong; Bu, Xing; Qin, Tao; Yu, Haisong; Chen, Jie; Wei, Yanhong

2017-05-01

In order to detect weld defects in laser welding T-joint of Al-Li alloy, a real-time X-ray image system is set up for quality inspection. Experiments on real-time radiography procedure of the weldment are conducted by using this system. Twin fillet welding seam radiographic arrangement is designed according to the structural characteristics of the weldment. The critical parameters including magnification times, focal length, tube current and tube voltage are studied to acquire high quality weld images. Through the theoretical and data analysis, optimum parameters are settled and expected digital images are captured, which is conductive to automatic defect detection.

Design, properties, and weldability of advanced oxidation-resistant FeCrAl alloys

DOE PAGES

Gussev, M. N.; Field, K. G.; Yamamoto, Y.

2017-05-05

FeCrAl alloys are promising as corrosion- and oxidation-resistance materials for extreme high-temperature applications. However, further alloy design and improvement requires a delicate balance between workability, weldability, propensity for '-phase formation, among other factors. Here, a series of advanced oxidant resistant FeCrAl alloys were produced and investigated. Variants with Al (+2%), Nb (+1%), and TiC (0.1, 0.3, and 1%) additions over the reference alloy (Fe-13%Cr-5%Al) were characterized in detail before and after controlled laser beam welding using tensile tests with digital image correlation, SEM-EBSD analysis, and fractography. All investigated alloys demonstrated yield stress in the weldment over 500 MPa; no welding-inducedmore » cracking was observed. However, it was shown that the increase in the Al-content over 5% was detrimental leading to a brittle fracture mechanism and decreased ductility in the weldment. At the same time, Nb and TiC additions were beneficial for preventing grain growth and reducing local softening (yield stress reduction) in the heat-affected zone. The 1% TiC addition also effectively refined grain size in the weldment.« less

Design, properties, and weldability of advanced oxidation-resistant FeCrAl alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gussev, M. N.; Field, K. G.; Yamamoto, Y.

FeCrAl alloys are promising as corrosion- and oxidation-resistance materials for extreme high-temperature applications. However, further alloy design and improvement requires a delicate balance between workability, weldability, propensity for '-phase formation, among other factors. Here, a series of advanced oxidant resistant FeCrAl alloys were produced and investigated. Variants with Al (+2%), Nb (+1%), and TiC (0.1, 0.3, and 1%) additions over the reference alloy (Fe-13%Cr-5%Al) were characterized in detail before and after controlled laser beam welding using tensile tests with digital image correlation, SEM-EBSD analysis, and fractography. All investigated alloys demonstrated yield stress in the weldment over 500 MPa; no welding-inducedmore » cracking was observed. However, it was shown that the increase in the Al-content over 5% was detrimental leading to a brittle fracture mechanism and decreased ductility in the weldment. At the same time, Nb and TiC additions were beneficial for preventing grain growth and reducing local softening (yield stress reduction) in the heat-affected zone. The 1% TiC addition also effectively refined grain size in the weldment.« less

Tensile Property of ANSI 304 Stainless Steel Weldments Subjected to Cavitation Erosion Based on Treatment of Laser Shock Processing.

PubMed

Zhang, Lei; Liu, Yue-Hua; Luo, Kai-Yu; Zhang, Yong-Kang; Zhao, Yong; Huang, Jian-Yun; Wu, Xu-Dong; Zhou, Chuang

2018-05-16

Tensile property was one important index of mechanical properties of ANSI 304 stainless steel laser weldments subjected to cavitation erosion (CE). Laser shock processing (LSP) was utilized to strengthen the CE resistance, and the tensile property and fracture morphology were analyzed through three replicated experiment times. Results showed tensile process of treated weldments was composed of elastic deformation, plastic deformation, and fracture. The elastic limit, elastic modulus, elongation, area reduction, and ultimate tensile strength of tensile sample after CE were higher in view of LSP. In the fracture surface, the fiber zone, radiation zone and shear lip zone were generated, and those were more obvious through LSP. The number and size of pores in the fracture surface were smaller, and the fracture surface was smoother and more uniform. The dimples were elongated along the unified direction due to effects of LSP, and the elongated direction was in agreement with the crack propagation direction. Their distribution and shape were uniform with deeper depth. It could be reflected that the tensile property was improved by LSP and the CE resistance was also enhanced.

Acoustic emission investigation of cold cracking in gas metal-arc welding of AISI 4340 steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fang, C.K.; Kannatey-Asibu, E. Jr.; Barber, J.R.

1995-06-01

Acoustic emission (AE) has been used to investigate the propagation of a finite crack in a weldment subjected to nonuniform longitudinal residual stresses during gas metal arc welding (GMAW). Cold cracking in selected weldments was accelerated using the electrochemical method to cathodically charge the weldments with hydrogen in order to induce hydrogen embrittlement. Cold cracking was observed about 40 min after charging in the specimen subjected to hydrogen embrittlement, while it was observed two days after welding for the one that was left in the atmosphere. The AE signals were generated as the specimen cracked and were recorded, and themore » effects from structure and instrumentation were removed from the measured signals by deconvolution in the frequency domain. Most of the high-amplitude signal components were found to be clustered in the frequency range below 200 kHz. The experimentally obtained spectrum was compared with theoretical results derived in earlier work, and reasonable agreement with theoretical surface displacement in both time and frequency domains was obtained. The envelopes for both spectra were found to decrease with increasing frequency, while the fluctuations in each curve diminished at high frequencies.« less

Tensile Property of ANSI 304 Stainless Steel Weldments Subjected to Cavitation Erosion Based on Treatment of Laser Shock Processing

PubMed Central

Zhang, Lei; Liu, Yue-Hua; Luo, Kai-Yu; Zhang, Yong-Kang; Zhao, Yong; Huang, Jian-Yun; Wu, Xu-Dong; Zhou, Chuang

2018-01-01

Tensile property was one important index of mechanical properties of ANSI 304 stainless steel laser weldments subjected to cavitation erosion (CE). Laser shock processing (LSP) was utilized to strengthen the CE resistance, and the tensile property and fracture morphology were analyzed through three replicated experiment times. Results showed tensile process of treated weldments was composed of elastic deformation, plastic deformation, and fracture. The elastic limit, elastic modulus, elongation, area reduction, and ultimate tensile strength of tensile sample after CE were higher in view of LSP. In the fracture surface, the fiber zone, radiation zone and shear lip zone were generated, and those were more obvious through LSP. The number and size of pores in the fracture surface were smaller, and the fracture surface was smoother and more uniform. The dimples were elongated along the unified direction due to effects of LSP, and the elongated direction was in agreement with the crack propagation direction. Their distribution and shape were uniform with deeper depth. It could be reflected that the tensile property was improved by LSP and the CE resistance was also enhanced. PMID:29772661

Microstructural characterization of dissimilar welds between Incoloy 800H and 321 Austenitic Stainless Steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sayiram, G., E-mail: sayiram.g@vit.ac.in; Arivazhagan, N.

2015-04-15

In this work, the microstructural character of dissimilar welds between Incoloy 800H and 321 Stainless Steel has been discussed. The microscopic examination of the base metals, fusion zones and interfaces was characterized using an optical microscope and scanning electron microscopy. The results revealed precipitates of Ti (C, N) in the austenitic matrix along the grain boundaries of the base metals. Migration of grain boundaries in the Inconel 82 weld metal was very extensive when compared to Inconel 617 weldment. Epitaxial growth was observed in the 617 weldment which increases the strength and ductility of the weld metal. Unmixed zone nearmore » the fusion line between 321 Stainless Steel and Inconel 82 weld metal was identified. From the results, it has been concluded that Inconel 617 filler metal is a preferable choice for the joint between Incoloy 800H and 321 Stainless Steel. - Highlights: • Failure mechanisms produced by dissimilar welding of Incoloy 800H to AISI 321SS • Influence of filler wire on microstructure properties • Contemplative comparisons of metallurgical aspects of these weldments • Microstructure and chemical studies including metallography, SEM–EDS • EDS-line scan study at interface.« less

Study of gas tungsten arc welding procedures for tantalum alloy T-111 (Ta-8 W-2Hf) plate

NASA Technical Reports Server (NTRS)

Gold, R. E.; Kesterson, R. L.

1973-01-01

Methods of eliminating or reducing underbread cracking in multipass GTA welds in thick T-111 plate were studied. Single V butt welds prepared using experimental filler metal compositions and standard weld procedures resulted in only moderate success in reducing underbread cracking. Subsequent procedural changes incorporating manual welding, slower weld speeds, and three or fewer fill passes resulted in crack-free single V welds only when the filler metal was free of hafnium. The double V joint design with successive fill passes on opposite sides of the joint produced excellent welds. The quality of each weld was determined metallographically since the cracking, when present, was very slight and undetectable using standard NDT techniques. Tensile and bend tests were performed on selected weldments. The inherent filler metal strength and the joint geometry determined the strength of the weldment. Hardness and electron beam microprobe traverses were made on selected specimens with the result that significant filler metal-base metal dilution as well as hafnium segregation was detected. A tentative explanation of T-111 plate underbread cracking is presented based on the intrinsic effects of hafnium in the weldment.

Characterization of GTA weldments in 10Ni-8CO-2Cr-1MO steel

NASA Technical Reports Server (NTRS)

Stonesifer, F. R.; Smith, H. L.

1972-01-01

This study of 10Ni-8Co-2Cr-1Mo steel includes evaluations of tensile, impact, hardness, fracture toughness properties, and metallographic features. Base plate and three weldments in one-inch thicknesses were examined to compare as-welded properties with those obtained after reaging, and results of welding the 10%Ni alloy with 9-4-20 wire as opposed to a matching weld wire composition. Critical crack sizes are calculated for the material. The most desirable weld properties are obtained using the matching weld wire and a reaging cycle. However, the improvement gained through reaging is probably not sufficient to justify the additional cost for most practical applications.

View southeast of weldment assembly floor in structures shop, building ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

View southeast of weldment assembly floor in structures shop, building 57; the floor is fabricated of cast iron and features a grillwork of 1 1/2 square holes which are used as sockets for gripping positioning or lock down pins; a lock down pin is shown left and below the center of the photograph; the vertical section of the pin is placed into a hole in the cast steel floor while the angles section of the pin rests on the piece under construction; the pin is hammered into the hole and spring tension in the pin holds the work piece in position. - Naval Base Philadelphia-Philadelphia Naval Shipyard, Structure Shop, League Island, Philadelphia, Philadelphia County, PA

Corrosion Development of Carbon Steel Grids and Shear Connectors in Cracked Composite Beams Exposed to Wet–Dry Cycles in Chloride Environment

PubMed Central

Xue, Wen; Chen, Ju; Jiang, Ao-yu

2018-01-01

The corrosion development of the reinforcement and shear stud connectors in the cracked steel–concrete composite beams under the salt-fog wet–dry cycles is presented in this investigation. Seven identical composite beams with load-induced concrete cracks were exposed to an aggressive chloride environment. The reinforcement and shear connectors were retrieved after specimens underwent a specified number of wet–dry cycles to obtain the corrosion pattern and the cross-section loss at different exposure times and their evolutions. The crack map, the corrosion pattern and the cross-section loss were measured and presented. Based on the experimental results, the influence of crack characteristics, including crack widths, orientations and positions on the corrosion rate and distribution, were accessed. Moreover, the effects of the connecting weldments on the corrosion initiations and patterns were analyzed. It was shown that the corrosion rate would increase with the number of wet–dry cycles. The characteristics of load-induced cracks could have different influences on the steel grids and shear stud connectors. The corrosion tended to initiate from the connecting weldments, due to the potential difference with the parent steel and the aggressive exposure environment, leading to a preferential weldment attack. PMID:29565836

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.

Metallurgy and deformation of electron beam welded similar titanium alloys

NASA Astrophysics Data System (ADS)

Pasang, T.; Sabol, J. C.; Misiolek, W. Z.; Mitchell, R.; Short, A. B.; Littlefair, G.

2012-04-01

Butt welded joins were produced between commercially pure titanium and various titanium alloys using an electron beam welding technique. The materials used represent commercially pure grade, α-β alloy and β alloy. They were CP Ti, Ti-6Al-4V (Ti64) and Ti-5Al-5V-5Mo-3Cr (Ti5553), respectively. Grains were largest in the FZs of the different weldments, decreasing in size towards the heat affected zones (HAZs) and base metals. Hardness measurements taken across the traverse cross-sections of the weldments were constant from base metal-to-weld-to-base metal for CP Ti/CP Ti and Ti64/Ti64 welds, while the FZ of Ti5553/Ti5553 had a lower hardness compared with the base metal. During tensile testing the CP Ti/CP Ti weldments fractured at the base metal, whereas both the Ti64/Ti64 and Ti5553/Ti5553 broke at the weld zones. Fracture surface analysis suggested microvoid coalescence as the failure mechanism. The compositional analysis showed a relatively uniform distribution of solute elements from base metal-to-weld-to-base metal. CP Ti has always been known for its excellent weldability, Ti64 has good weldability and, preliminary results indicated that Ti5553 alloy is also weldable.

Influence of low nickel (0.09 wt%) content on microstructure and toughness of P91 steel welds

NASA Astrophysics Data System (ADS)

Arivazhagan, B.; Vasudevan, M.; Kamaraj, M.

2015-05-01

Modified 9Cr-1Mo (P91) steel is widely used as a high temperature structural material in the fabrication of power plant components. Alloying elements significantly influences the microstructure and mechanical properties of P91 steel weldments. The alloying elements manganese and nickel significantly influence the lower critical phase transformation temperature (AC1) as well as tempering response of welds. In the existing published information there was wide spread use of high Mn+Ni filler wire. In the present study, weldment preparation was completed using GTA filler wire having low Nickel content (Mn+Ni of 0.58 wt% including nickel content of 0.09 wt%). Microstructure and mechanical properties characterization was done. There is a requirement on minimum toughness of 47 Joules for P91 steel tempered welds at room temperature. Microstructural observation revealed that the GTA welds have low δ-ferrite content (<0.5%) in the martensite matrix. In the as-weld condition, the toughness was 28 Joules whereas after PWHT at 760 °C-2 h it was 115 Joules. In the present study, toughness of low nickel weld was higher due to low δ-ferrite content (<0.5%), multipass grain refinement and weld metal deposition of single pass per layer of weldment.

Impact of neutron irradiation on mechanical performance of FeCrAl alloy laser-beam weldments

NASA Astrophysics Data System (ADS)

Gussev, M. N.; Cakmak, E.; Field, K. G.

2018-06-01

Oxidation-resistant iron-chromium-aluminum (FeCrAl) alloys demonstrate better performance in Loss-of-Coolant Accidents, compared with austenitic- and zirconium-based alloys. However, further deployment of FeCrAl-based materials requires detailed characterization of their performance under irradiation; moreover, since welding is one of the key operations in fabrication of light water reactor fuel cladding, FeCrAl alloy weldment performance and properties also should be determined prior to and after irradiation. Here, advanced C35M alloy (Fe-13%Cr-5%Al) and variants with aluminum (+2%) or titanium carbide (+1%) additions were characterized after neutron irradiation in Oak Ridge National Laboratory's High Flux Isotope Reactor at 1.8-1.9 dpa in a temperature range of 195-559 °C. Specimen sets included as-received (AR) materials and specimens after controlled laser-beam welding. Tensile tests with digital image correlation (DIC), scanning electron microscopy-electron back scatter diffraction analysis, fractography, and x-ray tomography analysis were performed. DIC allowed for investigating local yield stress in the weldments, deformation hardening behavior, and plastic anisotropy. Both AR and welded material revealed a high degree of radiation-induced hardening for low-temperature irradiation; however, irradiation at high-temperatures (i.e., 559 °C) had little overall effect on the mechanical performance.

Non Destructive Analysis of Fsw Welds using Ultrasonic Signal Analysis

NASA Astrophysics Data System (ADS)

Pavan Kumar, T.; Prabhakar Reddy, P.

2017-08-01

Friction Stir Welding is an evolving metal joining technique and is mostly used in joining materials which cannot be easily joined by other available welding techniques. It is a technique which can be used for welding dissimilar materials also. The strength of the weld joint is determined by the way in which these material are mixing with each other, since we are not using any filler material for the welding process the intermixing has a significant importance. The complication with the friction stir welding process is that there are many process parameters which effect this intermixing process such as tool geometry, rotating speed of the tool, transverse speed etc., In this study an attempt is made to compare the material flow and weld quality of various weldments by changing the parameters. Ultrasonic signal Analysis is used to characterize the microstructure of the weldments. use of ultrasonic waves is a non destructive, accurate and fast way of characterization of microstructure. In this method the relationship between the ultrasonic measured parameters and microstructures are evaluated using background echo and backscattered signal process techniques. The ultrasonic velocity and attenuation measurements are dependent on the elastic modulus and any change in the microstructure is reflected in the ultrasonic velocity. An insight into material flow is essential to determine the quality of the weld. Hence an attempt is made in this study to know the relationship between tool geometry and the pattern of material flow and resulting weld quality the experiments are conducted to weld dissimilar aluminum alloys and the weldments are characterized using and ultra Sonic signal processing. Characterization is also done using Scanning Electron Microscopy. It is observed that there is a good correlation between the ultrasonic signal processing results and Scanning Electron Microscopy on the observed precipitates. Tensile tests and hardness tests are conducted on the weldments and compared for determining the weld quality.

Fundamental studies of hydrogen attack in carbon-0.5molybdenum steel and weldments applied in petroelum and petrochemical industries

NASA Astrophysics Data System (ADS)

Liu, Peng

High temperature hydrogen attack (HTHA) is a form of surface decarburization, internal decarburization, and/or intergranular cracking in steels exposed to high temperature (>400°F) and high hydrogen pressure. Hydrogen attack is an irreversible process which can cause permanent damage resulting in degradation of mechanical properties and failures such as leakage, bursting, fire, and/or explosion. The continuous progression of hydrogen attack in C-0.5Mo steel and weldments below the C-0.5Mo Nelson Curve has caused a significant concern for the integrity and serviceability of C-0.5Mo steel utilized for pressure vessels and piping in the petroleum refinery and petrochemical industries. A state-of-the-art literature review was implemented to provide a comprehensive overview of the published research efforts on hydrogen attack studies. The evolution of "Nelson Curves" for carbon steel, C-0.5Mo, and Cr-Mo steels was historically reviewed in regard to design applications and limitations. Testing techniques for hydrogen attack assessment were summarized under the categories of hydrogen exposure testing, mechanical evaluation, and dilatometric swelling testing. In accord with the demands of these industries, fundamental studies of hydrogen attack in C-0.5Mo steel and weldments were accomplished in terms of quantitative methodologies for hydrogen damage evaluation; hydrogen damage assessment of service exposed weldments and autoclave exposed materials; effects of carbon and alloying elements, heat treatments, hot and cold working, welding processes and postweld heat treatment (PWHT) on hydrogen attack susceptibility; development of continuous cooling transformation (CCT) diagrams for C-0.5Mo base metals and the coarse grained heat-affected zone (CGHAZ); carbide evaluation for the C-0.5Mo steel after service exposure and heat treatment; methane evolution by the reaction of hydrogen and carbides; hydrogen diffusion and methane pressure through the wall thickness of one-sided hydrogen exposure assembly; hydrogen attack mechanism and hydrogen attack limit modeling.

Fatigue behavior of 5Ni-Cr-Mo-V steel weldments containing fabrication discontinuities

NASA Technical Reports Server (NTRS)

Gill, Steven J.; Hauser, Joseph A., II; Crooker, Thomas W.; Kruse, Brian J.; Menon, Ravi

1988-01-01

The applicability of linear elastic fracture mechanics to characterize the fatigue behavior of high-strength steel weldments containing lack-of-penetration (LOP) and slag/lack-of-fusion (S/LOF) discontinuities is explored. Full penetration, double-V butt welds with reinforcements removed were tested under zero-to-tension axial loading. Various filler metals and welding techniques were used. Both sound welds and welds containing discontinuities were cycled to failure. Where possible, cycles to crack initiation were estimated by strain gage measurements. The fracture mechanics approach was successful in correlating the fatigue lifetimes of specimens containing single LOP discontinuities of varying size. However, the fatigue behavior of specimens containing multiple S/LOF discontinuities proved to be much more complex and difficult to analyze.

Microstructural evolution in ultra-low-carbon steel weldments—Part I: Controlled thermal cycling and continuous cooling transformation diagram of the weld metal

NASA Astrophysics Data System (ADS)

Fonda, R. W.; Spanos, G.

2000-09-01

The transformation behavior and microstructural evolution of the as-deposited weld metal from an ultra-low-carbon (ULC) weldment were characterized by dilatometry, optical microscopy, transmission electron microscopy, and microhardness measurements. These results were used to construct a continuous cooling transformation (CCT) diagram for this weld metal. The major microconstituents observed in this ULC weldment were (in order of decreasing cooling rate) coarse autotempered martensite, fine lath martensite, lath ferrite, and degenerate lath ferrite. No polygonal ferrite was observed. These results were also used to develop criteria to differentiate between the two predominant microstructures in these ULC steels, lath martensite, and lath ferrite, which can look quite similar but have very different properties.

Effects of Laser Shock Processing on Morphologies and Mechanical Properties of ANSI 304 Stainless Steel Weldments Subjected to Cavitation Erosion

PubMed Central

Zhang, Lei; Lu, Jin-Zhong; Zhang, Yong-Kang; Ma, Hai-Le; Luo, Kai-Yu; Dai, Feng-Ze

2017-01-01

Effects of laser shock processing (LSP) on the cavitation erosion resistance of laser weldments were investigated by optical microscope (OM), scanning electron microscope (SEM) observations, roughness tester, micro hardness tester, and X-ray diffraction (XRD) technology. The morphological microstructures were characterized. Cumulative mass loss, incubation period, erosion rate, and damaged surface areas were monitored during cavitation erosion. Surface roughness, micro-hardness, and residual stress were measured in different zones. Results showed that LSP could improve the damage of morphological microstructures and mechanical properties after cavitation erosion. The compressive residual stresses were generated during the process of LSP, which was an effective guarantee for the improvement of the above mentioned properties. PMID:28772652

SCC Initiation Behavior of Alloy 182 in PWR Primary Water

DOE Office of Scientific and Technical Information (OSTI.GOV)

Toloczko, Mychailo B.; Zhai, Ziqing; Bruemmer, Stephen M.

SCC initiation behavior of 15% cold forged specimens cut from four different alloy 182 weldments was investigated in 360°C simulated PWR primary water under constant load at the yield stress using direct current potential drop to perform in-situ monitoring of SCC initiation time. Within each weldment, one or more specimens underwent SCC initiation within 24 hours of reaching full load while some specimens had much longer initiation times, in a few cases exceeding 2500 hours. Detailed examinations were conducted on these specimens with a focus on different microstructural features such as preexisting defects, grain orientation and second phases, highlighting anmore » important role of microstructure in crack initiation of alloy 182.« less

Quality Enhancement of Ultrasonic TOFD Signals from Carbon Steel Weld Pad with Notches.

PubMed

Manjula, K; Vijayarekha, K; Venkatraman, B

2018-03-01

Welding is an integral part of component fabrication in industry. Even though the science and art of welding are more than 100 years old, defects continue to occur during welding. Codes of practice require that the welds be tested and evaluated. Conventionally ultrasonic testing has been widely applied in industry for the detection and evaluation of the flaws/defects in the weldments. With advances in sensor and signal analysis technologies, the last two decades have seen extensive developments in the field of ultrasonic testing. We have advanced techniques such as Time of Flight Diffraction (TOFD) which has better probability of detection for linear defects. A major irritant during the application of TOFD, especially for the testing of carbon steel weldments, is the presence of noise. A variety of approaches has been used internationally for the suppression of such noise and each has its own merits and demerits. This paper focuses on a method of enhancing the TOFD A-scan signals in carbon steel weldments by suppressing the noise from them using the discrete wavelet transform (DWT). The analysis clearly indicates that the DWT gives better signal-to-noise ratio improvement using higher-order wavelet filters with 4-level DWT decomposition. However the computational cost of this signal enhancement depends on the wavelet filter chosen along with the chosen level of DWT decomposition. Copyright © 2017 Elsevier B.V. All rights reserved.

Investigation of galvanic corrosion in laser-welded stainless steel sheets

NASA Astrophysics Data System (ADS)

Kwok, Chi-Tat; Fong, Siu Lung; Cheng, Fai Tsun; Man, Hau-Chung

2004-10-01

In the present study, bead-on-plate specimens of 1-mm sheets of austenitic and duplex stainless steels were fabricated by laser penetration welding with a 2.5-kW CW Nd:YAG laser. The galvanic corrosion behavior of laser-weldment (LW) against as-received (AR) specimens with an area rato of 1:1 in 3.5% NaCL solution was studied by means of a zero-resistance ammeter. The free corrosion potentials of as-received specimens were found to be considerably higher than those of laser weldments, indicating that the weldments are more active and always act as anodes. The ranking of galvanic current densities (IG) of the couples in ascending order is: AR S31603-LW S31603 < AR S31803-LW S31803 < AR S32760-LW S32760 < AR S30400-LW S30400. For the galvanic couple between AR S30400 and LW S30400, the IG is the highest (78.6 nA/cm2) because large amount of δ-ferrite in the weld zone acts as active sites. On the other hand, the IG of the galvanic couple between AR S31603 and LW S31603 is the lowest (-26 nA/cm2) because no δ-ferrite is present after laser welding. The recorded IG of all couples revealed constantly low values (in the rnage of nA/cm2) and sometimes stayed negative, which indicated polarity reversal.

Biaxial Creep Specimen Fabrication

DOE Office of Scientific and Technical Information (OSTI.GOV)

JL Bump; RF Luther

This report documents the results of the weld development and abbreviated weld qualification efforts performed by Pacific Northwest National Laboratory (PNNL) for refractory metal and superalloy biaxial creep specimens. Biaxial creep specimens were to be assembled, electron beam welded, laser-seal welded, and pressurized at PNNL for both in-pile (JOYO reactor, O-arai, Japan) and out-of-pile creep testing. The objective of this test campaign was to evaluate the creep behavior of primary cladding and structural alloys under consideration for the Prometheus space reactor. PNNL successfully developed electron beam weld parameters for six of these materials prior to the termination of the Navalmore » Reactors program effort to deliver a space reactor for Project Prometheus. These materials were FS-85, ASTAR-811C, T-111, Alloy 617, Haynes 230, and Nirnonic PE16. Early termination of the NR space program precluded the development of laser welding parameters for post-pressurization seal weldments.« less

Heat sink effects on weld bead: VPPA process

NASA Technical Reports Server (NTRS)

Steranka, Paul O., Jr.

1990-01-01

An investigation into the heat sink effects due to weldment irregularities and fixtures used in the variable polarity plasma arc (VPPA) process was conducted. A basic two-dimensional model was created to represent the net heat sink effect of surplus material using Duhamel's theorem to superpose the effects of an infinite number of line heat sinks of variable strength. Parameters were identified that influence the importance of heat sink effects. A characteristic length, proportional to the thermal diffusivity of the weldment material divided by the weld torch travel rate, correlated with heat sinking observations. Four tests were performed on 2219-T87 aluminum plates to which blocks of excess material were mounted in order to demonstrate heat sink effects. Although the basic model overpredicted these effects, it correctly indicated the trends shown in the experimental study and is judged worth further refinement.

Heat sink effects on weld bead: VPPA process

NASA Technical Reports Server (NTRS)

Steranka, Paul O., Jr.

1989-01-01

An investigation into the heat sink effects due to weldment irregularities and fixtures used in the variable polarity plasma arc (VPPA) process was conducted. A basic two-dimensional model was created to represent the net heat sink effect of surplus material using Duhamel's theorem to superpose the effects of an infinite number of line heat sinks of variable strength. Parameters were identified that influence the importance of heat sink effects. A characteristic length, proportional to the thermal diffusivity of the weldment material divided by the weld torch travel rate, correlated with heat sinking observations. Four tests were performed on 2219-T87 aluminum plates to which blocks of excess material were mounted in order to demonstrate heat sink effects. Although the basic model overpredicted these effects, it correctly indicated the trends shown in the experimental study and is judged worth further refinement.

Mechanical Behavior of Commercially Pure Titanium Weldments at Lower Temperatures

NASA Astrophysics Data System (ADS)

Gupta, R. K.; Anil Kumar, V.; Xavier, X. Roshan

2018-05-01

Commercially pure titanium is used for low-temperature applications due to good toughness attributed to single-phase microstructure (α). Electron beam welding (EBW) and gas tungsten arc welding (GTAW) processes have been used for welding two grades of commercially pure titanium (Grade 2 and Grade 4). Martensitic microstructure is found to be finer in the case of EBW joint as compared to GTAW joint due to faster rate of cooling in the former process. Weldments have been characterized to study the mechanical behavior at ambient (298 K) and cryogenic temperatures (20 and 77 K). Strength of weldments increases with the decrease in temperature, which is found to be more prominent in case of Grade 4 titanium as compared to Grade 2. Weld efficiency of Grade 4 is found to be higher at all the temperatures (ambient, 77 and 20 K). However, ultimate tensile strength/yield strength ratio is higher for Grade 2 as compared to Grade 4. % Elongation is found to increase/retained at cryogenic temperatures for Grade 2, and it is found to decrease for Grade 4. Electron backscattered diffraction analysis and transmission electron microscopy of deformed samples confirmed the presence of extensive twinning in Grade 2 and the presence of finer martensitic structure in Grade 4. Fractography analysis of tested specimens revealed the presence of cleavage facets in Grade 4 and dimples in specimens of Grade 2. Higher strength in Grade 4 is attributed to higher oxygen restricting the twin-assisted slip, which is otherwise prominent in Grade 2 titanium.

Fracture and crack growth resistance studies of 304 stainless steel weldments relating to retesting of cryogenic vessels

NASA Technical Reports Server (NTRS)

Hall, L. R.; Finger, R. W.

1972-01-01

Fracture and crack growth resistance characteristics of 304 stainless steel alloy weldments as relating to retesting of cryogenic vessels were examined. Welding procedures were typical of those used in full scale vessel fabrication. Fracture resistance survey tests were conducted in room temperature air, liquid nitrogen and liquid hydrogen. In air, both surface-flawed and center-cracked panels containing cracks in weld metal, fusion line, heat-affected zone, or parent metal were tested. In liquid nitrogen and liquid hydrogen, tests were conducted using center-cracked panels containing weld centerline cracks. Load-unload, sustained load, and cyclic load tests were performed in air or hydrogen gas, liquid nitrogen, and liquid hydrogen using surface-flawed specimens containing weld centerline cracks. Results were used to evaluate the effectiveness of periodic proof overloads in assuring safe and reliable operation of over-the-road cryogenic dewars.

Grain Refinement of AZ31 Magnesium Alloy Weldments by AC Pulsing Technique

NASA Astrophysics Data System (ADS)

Kishore Babu, N.; Cross, C. E.

2012-11-01

The current study has investigated the influence of alternating current pulsing on the structure and mechanical properties of AZ31 magnesium alloy gas tungsten arc (GTA) weldments. Autogenous full penetration bead-on-plate GTA welds were made under a variety of conditions including variable polarity (VP), variable polarity mixed (VPM), alternating current (AC), and alternating current pulsing (ACPC). AC pulsing resulted in significant refinement of weld metal when compared with the unpulsed conditions. AC pulsing leads to relatively finer and more equiaxed grain structure in GTA welds. In contrast, VP, VPM, and AC welding resulted in predominantly columnar grain structures. The reason for this grain refinement may be attributed to the periodic variations in temperature gradient and solidification rate associated with pulsing as well as weld pool oscillation observed in the ACPC welds. The observed grain refinement was shown to result in an appreciable increase in fusion zone hardness, tensile strength, and ductility.

Optimization and Prediction of Angular Distortion and Weldment Characteristics of TIG Square Butt Joints

NASA Astrophysics Data System (ADS)

Narang, H. K.; Mahapatra, M. M.; Jha, P. K.; Biswas, P.

2014-05-01

Autogenous arc welds with minimum upper weld bead depression and lower weld bead bulging are desired as such welds do not require a second welding pass for filling up the upper bead depressions (UBDs) and characterized with minimum angular distortion. The present paper describes optimization and prediction of angular distortion and weldment characteristics such as upper weld bead depression and lower weld bead bulging of TIG-welded structural steel square butt joints. Full factorial design of experiment was utilized for selecting the combinations of welding process parameter to produce the square butts. A mathematical model was developed to establish the relationship between TIG welding process parameters and responses such as upper bead width, lower bead width, UBD, lower bead height (bulging), weld cross-sectional area, and angular distortions. The optimal welding condition to minimize UBD and lower bead bulging of the TIG butt joints was identified.

Tensile Behavior of Electron Beam-Welded and Post-Weld Vacuum-Annealed Nb-10% Hf-1% Ti Refractory Alloy Weldments

NASA Astrophysics Data System (ADS)

Anil Kumar, V.; Gupta, R. K.; Venkateswaran, T.; Ram Kumar, P.

2018-02-01

Nb-10% Hf-1% Ti refractory alloy is a high performance material extensively used for high temperature applications. Electron beam welding is one of the most widely used techniques to join refractory and reactive alloys. Bigger sizes of nozzles for rocket propulsion applications can be either made through deep drawing and flow turning route or by roll bending and welding route both using sheets/plates as input material for fabrication. The latter is a more economical option for mass production of the hardware using such exotic and expensive alloys. In view of this, both as-welded (AW) coupon and weld plus post-weld vacuum-annealed (AW + VA) coupon have been prepared to study their mechanical behavior. It has been observed that tensile strength and ductility have not been reduced in both these conditions vis-à-vis the base metal, confirming weld efficiency of the alloy to be 100%. Microhardness is found to be 150-160 VHN in the base metal and 200-225 VHN in the weld fusion zone in AW condition, which became uniform (145-155 VHN) throughout the weldment in AW + VA condition. Microstructure of the weldment in AW condition is found to be consisting of grains solidified by epitaxial mode from base metal toward the weld centre. In AW + VA condition, improvement in tensile elongation is observed, which is found to be due to the presence of homogenized grains/more uniform microstructure near the heat-affected zone as compared to the steep gradient in grain size in different zones in the weld in AW condition.

Finite element modeling of residual stresses in electroslag butt welds

DOT National Transportation Integrated Search

2000-03-01

Shop fabricated electroslag (ES) welds used in bridge construction have had a history of low toughness in the fusion and heat affected zones. In addition, conventional inspection of ES weldments under shop fabrication conditions fail to consistently ...

Brittle-ductile transition of steel bridges, volume I : final report.

DOT National Transportation Integrated Search

1990-05-01

The transition behavior of bridge steels and weldments largely determines the ir toughness under : service loading rates and temperatures. Two aspects of the transition were investigated in this : project: The first was to develop a better understand...

Milder Etchant For Penetrant Inspection

NASA Technical Reports Server (NTRS)

O'Tousa, Joseph E.; Thomas, Clark S.

1990-01-01

New etching solution for chemical penetrant inspection of Inconel(R) 718 castings and weldments. Etchant does not introduce artifacts mistaken for defects. Applied by swabbing or by immersion. Used to detect unwanted residues of Nioro(R) (or equivalent) gold brazing alloy on type 347 stainless steel.

An air-bearing weight offload system for ground test of heavy LSS structures

NASA Technical Reports Server (NTRS)

Rice, R. B.

1989-01-01

The capability and use of the Gravity Offload Facility (GOF) are discussed. Briefly explained are the: truss and base casting; carriage assembly; carriage weldment; vertical lift axis control; lifting cylinder; payload gimbal; motion base layout; and control processor.

The microstructure and fracture behavior of the dissimilar alloy 690-SUS 304L joint with various Nb addition

NASA Astrophysics Data System (ADS)

Lee, H. T.; Jeng, S. L.; Kuo, T. Y.

2003-05-01

This study investigates the microstructure and fracture behavior of dissimilar weldments of alloy 690 and SUS 304L for various additions of niobium (0.1, 1.03, 2.49, and 3.35 wt pct) in the flux. With identical parameters and procedures, weldments were butt welded by the shielding metal arc welding (SMAW) process using three layers, with each layer being deposited in a single pass. The results indicate that the microstructure of the fusion zone was primarily dendritic and that the contents of Ni, Cr, and Fe within this zone remain relatively constant and resemble alloy 690. With Nb addition, it is noted that the microstructure changes from a cellular to columnar dendrite and equiaxed dendrite. Meanwhile, the dendrite arm spacing reduces and the secondary arms grow longer. Moreover, the composition of the interdendritic phase, whose precipitate volume percentage increases from 5 to 25 pct, changes from Al-Ti-O to Nb rich. The spread of the interdendritic phase is less in the root bead than in the cap bead due to the greater influence of base metal dilution in this region. Mechanical tests indicate that Nb addition increases the average hardness of the weldment and reduces its elongation prior to rupture. However, the tensile strength is essentially unchanged by Nb addition. It is found that the average hardness of the root bead is generally lower than the cap bead, and that the tensile specimens all rupture in the fusion zone, with the fracture surfaces exhibiting ductile features. It is noted that the cap bead tends to rupture interdendritically with increasing Nb addition. Finally, fractography shows that the dimples in the root become larger and shallower with Nb addition and are rich with an interdendritic phase.

Effects of surface preparation on quality of aluminum alloy weldments

NASA Technical Reports Server (NTRS)

Kizer, D.; Saperstein, Z.

1968-01-01

Study of surface preparations and surface contamination effects on the welding of 2014 aluminum involves several methods of surface analysis to identify surface properties conducive to weld defects. These methods are radioactive evaporation, spectral reflectance mass spectroscopy, gas chromatography and spark emission spectroscopy.

Effects of high frequency current in welding aluminum alloy 6061

NASA Technical Reports Server (NTRS)

Fish, R. E.

1968-01-01

Uncontrolled high frequency current causes cracking in the heat-affected zone of aluminum alloy 6061 weldments during tungsten inert gas ac welding. Cracking developed when an improperly adjusted superimposed high frequency current was agitating the semimolten metal in the areas of grain boundary.

The effects of alloying elements on microstructures and mechanical properties of tungsten inert gas welded AZ80 magnesium alloys joint

NASA Astrophysics Data System (ADS)

Li, Hui; Zhang, Jiansheng; Ding, Rongrong

2017-11-01

The effects of alloying elements on the macrostructures, microstructures and tensile strength of AZ80 Mg alloy weldments were studied in the present study. The results indicate that with the decrease of Al element content of filler wire, the welding defects of seam are gradually eliminated and the β-Mg17Al12 phases at α-Mg boundaries are refined and become discontinuous, which are beneficial to the improvement of tensile strength. With AZ31 Mg alloy filler wire, the maximum tensile strength of AZ80 weldment is 220 MPa and fracture occurs at the welding seam of joint. It is experimentally proved that robust AZ80 Mg alloy joints can be obtained by tungsten inert gas (TIG) welding process with AZ31 Mg alloy filler wire. However, further study is required to improve the microstructures and reduce welding defects of joint in order to further improve the joining strength of AZ80 Mg alloy joint.

Fatigue Behavior of HY-130 Steel Weldments Containing Fabrication Discontinuities.

DTIC Science & Technology

1985-04-18

discontinuities to solutions for elliptical discontinuities. One such approach has been formalized in the ASME Section XI Boiler and Pressure Vessel Code [1... Boiler and Pressure Vessel Code , Section XI, "Rules for Inservice Inspection of Nuclear Reactor Coolant Systems," American Society of Mechanical

46 CFR 56.50-105 - Low-temperature piping.

Code of Federal Regulations, 2010 CFR

2010-10-01

... ASTM E 23 (incorporated by reference, see § 56.01-2), “Notched Bar Impact Testing of Metallic Materials”, Type A, Figure 4. The toughness testing requirements of subpart 54.05 of this subchapter shall be... testing of production weldments for low temperature piping systems and assemblies is not required. (3...

46 CFR 54.05-15 - Weldment toughness tests-procedure qualifications.

Code of Federal Regulations, 2010 CFR

2010-10-01

...) Plate for which Charpy V-notch impact testing is required in the parent material and for which V-notch minima are specified shall similarly have welding procedures qualified for toughness by Charpy V-notch testing. For these tests, the test plates shall be oriented with their final rolling direction parallel to...

The Effect of Weld Metal Strength Mismatch on the Deformation and Fracture Behavior of Steel Butt Weldments

DTIC Science & Technology

1991-01-01

Society 6 of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code [ 1980]. Their results are similar to those of Satoh and Toyoda, and are...E813-89. American Society of Mechanical Engineers, Boiler and Pressure Vessel Code , Section III, Nuclear Power Plant Components, 1980. American

A Review of Weldment Failure Modes and Weldability Testing Methods.

DTIC Science & Technology

1994-01-01

tearing ...................................... 9 4a. Macrostructure of reheat cracking in a chromium -molybdenum.vanadium steel ................ 10 4b...Figure 5. Schematic of the subscale varesatrai teSL 12 all1൒ 2.5cm rl SPOT WELD TOP VIEW SPECIMEN • GTAW TORCH F 4 -DIE BLOCK SIDE VIEW FORCE Figure

Stress-Intensity Factors for Three-Point Bend Specimens by Boundary Collocation

DTIC Science & Technology

1965-12-01

ref. 5) and by Kies, Smith, Romine, and Bernstein (ref. 6). Limited results of an analytical study by H. F. Bueckner have been published by Wundt (ref...Weldments. Fracture Toughness Testing and Its Applications, STP No. 381, ASTM, 1965, pp. 328-356. 7. Wundt , B. M.: A Unified Interpretation of Room

Life Assessment for Cr-Mo Steel Dissimilar Joints by Various Filler Metals Using Accelerated Creep Testing

NASA Astrophysics Data System (ADS)

Petchsang, S.; Phung-on, I.; Poopat, B.

2016-12-01

Accelerated creep rupture tests were performed on T22/T91 dissimilar metal joints to determine the fracture location and rupture time of different weldments. Four configurations of deposited filler metal were tested using gas tungsten arc welding to estimate the service life for Cr-Mo steel dissimilar joints at elevated temperatures in power plants. Results indicated that failure in all configurations occurred in the tempered original microstructure and tempered austenite transformation products (martensite or bainite structure) as type IV cracking at the intercritical area of the heat-affected zone (ICHAZ) for both T22 and T91 sides rather than as a consequence of the different filler metals. Creep damage occurred with the formation of precipitations and microvoids. The correlation between applied stress and the Larson-Miller parameter (PLM) was determined to predict the service life of each material configuration. Calculated time-to-failure based on the PLM and test results for both temperature and applied stress parameters gave a reasonable fit. The dissimilar joints exhibited lower creep rupture compared to the base material indicating creep degradation of the weldment.

Modeling Long-term Creep Performance for Welded Nickel-base Superalloy Structures for Power Generation Systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shen, Chen; Gupta, Vipul; Huang, Shenyan

The goal of this project is to model long-term creep performance for nickel-base superalloy weldments in high temperature power generation systems. The project uses physics-based modeling methodologies and algorithms for predicting alloy properties in heterogeneous material structures. The modeling methodology will be demonstrated on a gas turbine combustor liner weldment of Haynes 282 precipitate-strengthened nickel-base superalloy. The major developments are: (1) microstructure-property relationships under creep conditions and microstructure characterization (2) modeling inhomogeneous microstructure in superalloy weld (3) modeling mesoscale plastic deformation in superalloy weld and (4) a constitutive creep model that accounts for weld and base metal microstructure and theirmore » long term evolution. The developed modeling technology is aimed to provide a more efficient and accurate assessment of a material’s long-term performance compared with current testing and extrapolation methods. This modeling technology will also accelerate development and qualification of new materials in advanced power generation systems. This document is a final technical report for the project, covering efforts conducted from October 2014 to December 2016.« less

Microstructure, Composition, and Impact Toughness Across the Fusion Line of High-Strength Bainitic Steel Weldments

NASA Astrophysics Data System (ADS)

Lan, Liangyun; Kong, Xiangwei; Chang, Zhiyuan; Qiu, Chunlin; Zhao, Dewen

2017-09-01

This paper analyzed the evolution of microstructure, composition, and impact toughness across the fusion line of high-strength bainitic steel weldments with different heat inputs. The main purpose was to develop a convenient method to evaluate the HAZ toughness quickly. The compositions of HAZ were insensitive to higher contents of alloy elements ( e.g., Ni, Mo) in the weld metal because their diffusion distance is very short into the HAZ. The weld metal contained predominantly acicular ferrite at any a heat input, whereas the main microstructures in the HAZ changed from lath martensite/bainite to upper bainite with the increasing heat input. The evolution of HAZ toughness in relation to microstructural changes can be revealed clearly combined with the impact load curve and fracture morphology, although the results of impact tests do not show an obvious change with heat input because the position of Charpy V notch contains the weld metal, HAZ as well as a part of base metal. As a result, based on the bead-on-plate welding tests, the welding parameter affecting the HAZ toughness can be evaluated rapidly.

Study on underclad cracking in nuclear reactor vessel steels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Horiya, T.; Takeda, T.; Yamato, K.

1985-02-01

Susceptibility to underclad cracking in nuclear reactor vessel steels, such as SA533 Grade B Class 1 and SA508 Class 2, was studied in detail. A convenient simulation test method using simulated HAZ specimens of small size has been developed for quantitative evaluation of susceptibility to underclad cracks. The method can predict precisely the cracking behavior in weldments of steels with relative low crack susceptibility. The effect of chemical compositions on susceptibility to the cracking was examined systematically using the developed simulation test method and the following index was obtained from the test results: U = 20(V) + 7(C) + 4(Mo)more » + (Cr) + (Cu) - 0.5(Mn) + 1.5 log(X) X = Al . . . Al/2N less than or equal to 1 X = 2N . . . Al/2N > 1 It was confirmed that the new index (U) is useful for the prediction of crack susceptibility of the nuclear vessel steels; i.e., no crack initiation is detected in weldments in the roller bend test for steels having U value below 0.90.« less

Effect of zirconium addition on welding of aluminum grain refined by titanium plus boron

NASA Astrophysics Data System (ADS)

Zaid, A. I. O.

2014-06-01

Aluminum oxidizes freely in ordinary atmosphere which makes its welding difficult and weak, particularly it solidifies in columnar structure with large grains. Therefore, it is anticipated that the effect of addition of some grain refiners to its melt before solidification is worth while investigating as it may enhance its weldabilty and improve its mechanical strength. In this paper, the effect of addition of zirconium at a weight of 0.1% (which corresponds to the peretictic limit on the aluminum-zirconium base phase diagram) to commercially pure aluminum, grain refined by Ti+B on its weldability, using gas tungsten arc welding, GTAW, method which was formerly known as TIG. A constant current level of 30 AC Ampere was used because it removes the oxides during the welding process. Metallographic examination of the weldments of the different combinations of Al with Al and Al with its microalloys: in the heat affected zone, HAZ, and away from it was carried out and examined for HAZ width, porosity, cracks and microhardness. It was found that grain refining by Ti+B or Zr resulted in enhancement of the weldment.

Method for welding an article and terminating the weldment within the perimeter of the article

NASA Technical Reports Server (NTRS)

Snyder, John H. (Inventor); Smashey, Russell W. (Inventor); Boerger, Eric J. (Inventor); Borne, Bruce L. (Inventor)

2000-01-01

An article is welded, as in weld repair of a defect, by positioning a weld lift-off block at a location on the surface of the article adjacent to the intended location of the end of the weldment on the surface of the article. The weld lift-off block has a wedge shape including a base contacting the surface of the article, and an upper face angled upwardly from the base from a base leading edge. A weld pool is formed on the surface of the article by directly heating the surface of the article using a heat source. The heat source is moved relative to the surface of the article and onto the upper surface of the weld lift-off block by crossing the leading edge of the wedge, without discontinuing the direct heating of the article by the heat source. The heating of the article with the heat source is discontinued only after the heat source is directly heating the upper face of the weld lift-off block, and not the article.

UAH mathematical model of the variable polarity plasma ARC welding system calculation

NASA Technical Reports Server (NTRS)

Hung, R. J.

1994-01-01

Significant advantages of Variable Polarity Plasma Arc (VPPA) welding process include faster welding, fewer repairs, less joint preparation, reduced weldment distortion, and absence of porosity. A mathematical model is presented to analyze the VPPA welding process. Results of the mathematical model were compared with the experimental observation accomplished by the GDI team.

Cutting Tool For Shaving Weld Beads

NASA Technical Reports Server (NTRS)

Hoffman, David S.; Mcferrin, David C.; Daniel, Ronald L., Jr.; Coby, John B., Jr.; Dawson, Sidney G.

1995-01-01

Cutting tool proposed for use in shaving weld beads flush with adjacent surfaces of weldments. Modified version of commercial pneumatically driven rotary cutting tool, cutting wheel of which turns at speeds sufficient for machining nickel alloys, titanium, and stainless steels. Equipped with forward-mounted handle and rear-mounted skid plate to maximize control and reduce dependence on skill of technician.

Effects of Cluster Porosity on the Tensile Properties of Butt-Weldments in T-1 Steel

DTIC Science & Technology

1974-11-01

i 12 Boiler and Pressure Vessel Code .19 In this code, the algebraic difference between the largest and smallest principal stresses is defined...Report U1LU- HN(J 7l-2()24 (University ot Illinois. 1971). "Nuclear Power Components.’* ASME Boiler and Pressure Vessel Code . Section HI. Subsections

46 CFR 54.05-15 - Weldment toughness tests-procedure qualifications.

Code of Federal Regulations, 2012 CFR

2012-10-01

... the weld metal. (2) Three specimens with the notch centered on the fusion line between parent plate and weld. (The fusion line may be identified by etching the specimen with a mild reagent.) (3) Three specimens with the notch centered in the heat affected zone, 1 mm from the fusion line. (4) Same as...

46 CFR 54.05-15 - Weldment toughness tests-procedure qualifications.

Code of Federal Regulations, 2011 CFR

2011-10-01

... the weld metal. (2) Three specimens with the notch centered on the fusion line between parent plate and weld. (The fusion line may be identified by etching the specimen with a mild reagent.) (3) Three specimens with the notch centered in the heat affected zone, 1 mm from the fusion line. (4) Same as...

46 CFR 54.05-15 - Weldment toughness tests-procedure qualifications.

Code of Federal Regulations, 2013 CFR

2013-10-01

... the weld metal. (2) Three specimens with the notch centered on the fusion line between parent plate and weld. (The fusion line may be identified by etching the specimen with a mild reagent.) (3) Three specimens with the notch centered in the heat affected zone, 1 mm from the fusion line. (4) Same as...

46 CFR 54.05-15 - Weldment toughness tests-procedure qualifications.

Code of Federal Regulations, 2014 CFR

2014-10-01

... the weld metal. (2) Three specimens with the notch centered on the fusion line between parent plate and weld. (The fusion line may be identified by etching the specimen with a mild reagent.) (3) Three specimens with the notch centered in the heat affected zone, 1 mm from the fusion line. (4) Same as...

Prediction and Control of Residual Stresses and Distortion in HY-130 Thick Pipe Weldments

DTIC Science & Technology

1979-05-01

quality. The most common type of shielding gas used in GMAW of low carbon steel is Argon with 25% CO2 . However, in the case of HY-130, experience has...supporting struc- ture for the cylinder which would permit cylinder rotation at a controlled speed with respect to the fixed position of the GMAW torch

Factors Influencing the Microstructural and Mechanical Properties of ULCB Steel Weldments

DTIC Science & Technology

1991-12-01

18 3. Molybdenum.................................... 19 4. Chromium ...................................... 19 5...WELDING METHODS UTILIZED IN ANALYSIS 1. Tungsten Inert Gas (TIG) Tungsten inert gas welding, also known as gas tungsten arc welding ( GTAW ), produces a weld...Abson, Pargeter, 1986, p.166). The role of molybdenum and chromium is not fully understood but the formation of molybdenum or chromium carbides may

Microstructure and Hydrogen-Induced Failure Mechanisms in Fe and Ni Alloy Weldments

NASA Astrophysics Data System (ADS)

Fenske, J. A.; Robertson, I. M.; Ayer, Raghavan; Hukle, Martin; Lillig, Dan; Newbury, Brian

2012-09-01

The microstructure and fracture morphology of AISI 8630-IN625 and ASTM A182-F22-IN625 dissimilar metal weld interfaces were compared and contrasted as a function of postweld heat treatment (PWHT) duration. For both systems, the microstructure along the weld interface consisted of a coarse grain heat-affected zone in the Fe-base metal followed by discontinuous martensitic partially mixed zones and a continuous partially mixed zone on the Ni side of the fusion line. Within the partially mixed zone on the Ni side, there exists a 200-nm-wide transition zone within a 20- μm-wide planar solidification region followed by a cellular dendritic region with Nb-Mo-rich carbides decorating the dendrite boundaries. Although there were differences in the volume of the partially mixed zones, the major difference in the metal weld interfaces was the presence of M7C3 precipitates in the planar solidification region, which had formed in AISI 8630-IN625 but not in ASTM A182-F22-IN625. These precipitates make the weldment more susceptible to hydrogen embrittlement and provide a low energy fracture path between the discontinuous partially mixed zones.

In vitro mesenchymal stem cell responses on laser-welded NiTi alloy.

PubMed

Chan, C W; Hussain, I; Waugh, D G; Lawrence, J; Man, H C

2013-04-01

The biocompatibility of NiTi after laser welding was studied by examining the in vitro (mesenchymal stem cell) MSC responses at different sets of time varying from early (4 to 12h) to intermediate phases (1 and 4 days) of cell culture. The effects of physical (surface roughness and topography) and chemical (surface Ti/Ni ratio) changes as a consequence of laser welding in different regions (WZ, HAZ, and BM) on the cell morphology and cell coverage were studied. The results in this research indicated that the morphology of MSCs was affected primarily by the topographical factors in the WZ: the well-defined and directional dendritic pattern and the presence of deeper grooves. The morphology of MSCs was not significantly modulated by surface roughness. Despite the possible initial Ni release in the medium during the cell culture, no toxic effect seemed to cause to MSCs as evidenced by the success of adhesion and spreading of the cells onto different regions in the laser weldment. The good biocompatibility of the NiTi laser weldment has been firstly reported in this study. Copyright © 2012 Elsevier B.V. All rights reserved.

Recent Aspects on the Effect of Inclusion Characteristics on the Intragranular Ferrite Formation in Low Alloy Steels: A Review

NASA Astrophysics Data System (ADS)

Mu, Wangzhong; Jönsson, Pär Göran; Nakajima, Keiji

2017-04-01

Intragranular ferrite (IGF), which nucleates from specific inclusion surfaces in low alloy steels, is the desired microstructure to improve mechanical properties of steel such as the toughness. This microstructure is especially important in the coarse grain heat affected zone (CGHAZ) of weldments. The latest review paper focusing on the role of non-metallic inclusions in the IGF formation in steels has been reported by Sarma et al. in 2009 (ISIJ int., 49(2009), 1063-1074). In recent years, large amount of papers have been presented to investigate different issues of this topic. This paper mainly highlights the frontiers of experimental and theoretical investigations on the effects of inclusion characteristics, such as the composition, size distribution and number density, on the IGF formation in low carbon low-alloyed steels, undertaken by the group of Applied Process Metallurgy, KTH Royal Institute of Technology. Related results reported in previous studies are also introduced. Also, plausible future work regarding various items of IGF formation is mentioned in each section. This work aims to give a better control of improving the steel quality during casting and in the heat affected zone (HAZ) of weldment, according to the concept of oxide metallurgy.

Effects of porosity on weld-joint tensile strength of aluminum alloys

NASA Technical Reports Server (NTRS)

Lovoy, C. V.

1974-01-01

Tensile properties in defect-free weldments of aluminum alloys 2014-T6 and 2219-T87 (sheet and plate) are shown to be related to the level or concentration of induced simulated porosity. The scatter diagram shows that the ultimate tensile strength of the weldments displays the most pronounced linear relationship with the level of porosity. The relationships between yield strength or elongation and porosity are either trivial or inconsequential in the lower and intermediate levels of porosity content. In highly concentrated levels of porosity, both yield strength and elongation values decrease markedly. Correlation coefficients were obtained by simple straight line regression analysis between the variables of ultimate tensile strength and pore level. The coefficients were greater, indicating a better correlation, using a pore area accumulation concept or pore volume accumulation than the accumulation of the pore diameters. These relationships provide a useful tool for assessing the existing aerospace radiographic acceptance standards with respect to permissible porosity. In addition, these relationships, in combination with known design load requirements, will serve as an engineering guideline in determining when a weld repair is necessary based on accumulative pore level as detected by radiographic techniques.

A three-dimensional thermal finite element analysis of AISI 304 stainless steel and copper dissimilar weldment

NASA Astrophysics Data System (ADS)

Singh, Gurdeep; Saxena, Ravindra K.; Pandey, Sunil

2018-04-01

The aim of this study to developed a 3-D thermal finite element model for dissimilar material welding of AISI-304 stainless steel and copper. Welding of similar material is widely studied using experimental and numerical methods but the problem becomes trivial for the welding of dissimilar materials especially in ferrous and nonferrous materials. Finite element analysis of dissimilar material welding is a cost-effective method for the understanding and analysis of the process. The finite element analysis has been performed to predict the heat affected zone and temperature distribution in AISI-304 stainless steel and copper dissimilar weldment using MSC Marc 2017®. Due to the difference in physical properties of these materials the behavior of heat affected zone and temperature distribution are perceived to be different. To verify the accuracy of the thermal finite element model, the welding process was simulated with butt-welded joints having same dimensions and parameters from Attarha and Far [1]. It is found from the study that the heat affected zone is larger in copper weld pads than in AISI 304 stainless steel due to large difference in thermal conductivity of these two weld pads.

PERFORMANCE IMPROVEMENT OF CREEP-RESISTANT FERRITIC STEEL WELDMENTS THROUGH THERMO-MECHANICAL TREATMENT AND ALLOY DESIGN

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yamamoto, Yukinori; Babu, Prof. Sudarsanam Suresh; Shassere, Benjamin

Two different approaches have been proposed for improvement of cross-weld creep properties of the high temperature ferrous structural materials for fossil-fired energy applications. The traditional creep strength-enhanced ferritic (CSEF) steel weldments suffer from Type IV failures which occur at the fine-grained heat affected zone (FGHAZ). In order to minimize the premature failure at FGHAZ in the existing CSEF steels, such as modified 9Cr-1Mo ferritic-martensitic steels (Grade 91), a thermo-mechanical treatment consisting of aus-forging/rolling and subsequent aus-aging is proposed which promotes the formation of stable MX carbonitrides prior to martensitic transformation. Such MX remains undissolved during welding process, even in FGHAZ,more » which successfully improves the cross-weld creep properties. Another approach is to develop a new fully ferrtic, creep-resistant FeCrAl alloy which is essentially free from Type IV failure issues. Fe-30Cr-3Al base alloys with minor alloying additions were developed which achieved a combination of good oxidation/corrosion resistance and improved tensile and creep performance comparable or superior to Grade 92 steel.« less

Gas Metal Arc Welding Parameters Effect on Properties of Tailored Orbital Weld of SS304 and BS1387

NASA Astrophysics Data System (ADS)

Ayof, M. N.; Hussein, N. I. S.; Noh, M. Z. Mohd

2017-09-01

Dissimilar material pipes in a power plant boiler water piping system are used to transmit water at various temperatures, either in extremely high temperature water or room temperature water. In this study, tailored orbital welding of dissimilar material of Stainless Steel (SS) 304 and British Steel (BS) 1387 were performed by Gas Metal Arc Welding (GMAW) with automated fixed nozzle-rotational jig. This study focused on GMAW parameters variation effects on mechanical properties of SS304 and BS1387 dissimilar material tailored orbital welding. The weldment quality was tested by performing non-destructive dye penetrant test. The tensile strength and microhardness were studied to verify the influence of welding parameters variations. Design of Experiment (DOE) was employed to generate process parameter using Response Surface Methodology (RSM) method. Welding parameters that were arc current, arc voltage and travel speed as input response, whilst, tensile strength and microhardness as output response. Results from non-destructive test showed no major defect occurred. The tensile strength and microhardness increased when arc current and voltage increased and travel speed decreased. Microhardness at weldment was higher than base material.

Fracture toughness determination using spiral-grooved cylindrical specimen and pure torsional loading

DOEpatents

Wang, Jy-An; Liu, Kenneth C.

2003-07-08

A method for determining fracture toughness K.sub.IC of materials ranging from metallic alloys, brittle ceramics and their composites, and weldments. A cylindrical specimen having a helical V-groove with a 45.degree. pitch is subjected to pure torsion. This loading configuration creates a uniform tensile-stress crack-opening mode, and a transverse plane-strain state along the helical groove. The full length of the spiral groove is equivalent to the thickness of a conventional compact-type specimen. K.sub.IC values are determined from the fracture torque and crack length measured from the test specimen using a 3-D finite element program (TOR3D-KIC) developed for the purpose. In addition, a mixed mode (combined tensile and shear stress mode) fracture toughness value can be determined by varying the pitch of the helical groove. Since the key information needed for determining the K.sub.IC value is condensed in the vicinity of the crack tip, the specimen can be significantly miniaturized without the loss of generality.

Mechanical Property Analysis in the Retracted Pin-Tool (RPT) Region of Friction Stir Welded (FSW) Aluminum Lithium 2195

NASA Technical Reports Server (NTRS)

Ding, R. Jeffrey; Oelgoetz, Peter A.

1999-01-01

The "Auto-Adjustable Pin Tool for Friction Stir Welding", was developed at The Marshall Space Flight Center to address process deficiencies unique to the FSW process. The auto-adjustable pin tool, also called the retractable pin-tool (R.PT) automatically withdraws the welding probe of the pin-tool into the pin-tool's shoulder. The primary function of the auto-adjustable pin-tool is to allow for keyhole closeout, necessary for circumferential welding and localized weld repair, and, automated pin-length adjustment for the welding of tapered material thickness. An overview of the RPT hardware is presented. The paper follows with studies conducted using the RPT. The RPT was used to simulate two capabilities; welding tapered material thickness and closing out the keyhole in a circumferential weld. The retracted pin-tool regions in aluminum- lithium 2195 friction stir weldments were studied through mechanical property testing and metallurgical sectioning. Correlation's can be =de between retractable pin-tool programmed parameters, process parameters, microstructure, and resulting weld quality.

Real time computer controlled weld skate

NASA Technical Reports Server (NTRS)

Wall, W. A., Jr.

1977-01-01

A real time, adaptive control, automatic welding system was developed. This system utilizes the general case geometrical relationships between a weldment and a weld skate to precisely maintain constant weld speed and torch angle along a contoured workplace. The system is compatible with the gas tungsten arc weld process or can be adapted to other weld processes. Heli-arc cutting and machine tool routing operations are possible applications.

Preliminary Analysis of the General Performance and Mechanical Behavior of Irradiated FeCrAl Base Alloys and Weldments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gussev, Maxim N.; Field, Kevin G.; Briggs, Samuel A.

The iron-based, iron-chromium-aluminum (FeCrAl) alloys are promising, robust materials for deployment in current and future nuclear power plants. This class of alloys demonstrates excellent performance in a range of environments and conditions, including high-temperature steam (>1000°C). Furthermore, these alloys have the potential to have prolonged survival under loss-of-coolant accident (LOCA) conditions compared to the more traditional cladding materials that are either Zr-based alloys or austenitic steels. However, one of the issues associated with FeCrAl alloys is cracking during welding. The present project investigates the possibility of mitigating welding-induced cracking via alloying and precise structure control of the weldments; in themore » frame work of the project, several advanced alloys were developed and are being investigated prior to and after neutron irradiation to provide insight into the radiation tolerance and mechanical performance of the weldments. The present report provides preliminary results on the post-irradiation characterization and mechanical tests performed during United States Fiscal Year (FY) 2016. Chapter 1 provides a general introduction, and Chapter 2 describes the alloy compositions, welding procedure, specimen geometry and manufacturing parameters. Also, a brief discussion of the irradiation at the High Flux Isotope Reactor (HFIR) is provided. Chapter 3 is devoted to the analysis of mechanical tests performed at the hot cell facility; tensile curves and mechanical properties are discussed in detail focusing on the irradiation temperature. Limited fractography results are also presented and analyzed. The discussion highlights the limitations of the testing within a hot cell. Chapter 4 underlines the advantages of in-situ testing and discusses the preliminary results obtained with newly developed miniature specimens. Specimens were moved to the Low Activation Materials Development and Analysis (LAMDA) laboratory and prepared for mechanical tests. Tensile tests were conducted at LAMDA using a modern digital image correlation approach allowing for strain distribution analysis. Plastic strain initiation and necking are discussed in detail; a concept of strain rate maps is also introduced and discussed. Follow-on SEM-EBSD and FIBTEM analysis is planned.« less

Crack Initiation and Propagation Properties of HY 130 Steel Weldments Following Temper Embrittlement.

DTIC Science & Technology

1982-09-01

mechanics ( EPFM ) may be applied to engineering problems to determine material properties related to crack initiation and propagation. Specifically, these...Introduction The application of linear elastic fracture mechanics (LEFM) to engineering fracture analyses has become increasingly widespread and the use...structures to which the particular material was to be applied. The advent of elastic-plastic fracture mechanics ( EPFM ) has proven valuable because a

Current issues and problems in welding science

NASA Astrophysics Data System (ADS)

David, S. A.; Debroy, T.

1992-07-01

Recent advances in welding science are examined with consideration given to the progress made in understanding physical processes of welding and in understanding weldment microstructure and properties and the correlation between microstructure and properties of the welds. Particular attention is given to the methods used for intelligent control and automation of welding. Also discussed are issues and problems that were brought to the surface by technological advances and interdisciplinary research on welding.

Dye penetrant indications caused by superficial surface defects in 2014 aluminum alloy welds.

NASA Technical Reports Server (NTRS)

Hocker, R. G.; Wilson, K. R.

1971-01-01

Demonstration that dye penetrant indications on the heat-affected zone of 2014-T6 aluminum GMA weldments are frequently caused by superficial surface conditions and are less than 0.007 in. deep. The following methods are suggested for minimization of these surface defects: stabilization of the arc, application of dc ?GTA' welding procedures, reduction of the caustic etch time, and use of fine grain materials.

High Strength Steel Weldment Reliability: Weld Metal Hydrogen Trapping.

DTIC Science & Technology

1998-02-01

Reliability : Weld Metal Hydrogen Trapping submitted to : United States Army Research Office Materials Science Division P.O. Box 12211 Research Triangle...Conf. Proc. of Welding and Related Technologies for the XXIth Century, November 1998, Kiev, Ukraine : "Hydrogen Assisted Cracking in...appendices (see appendix IV). Next TTCP workshop will be held from 6th to 8th October 1998, at CANMET , Ottawa, Ontario, Canada. 20 III. Figures 18

Creep properties of PWC-11 base metal and weldments as affected by heat treatment

NASA Technical Reports Server (NTRS)

Titran, R. H.; Moore, T. J.; Grobstein, T. L.

1986-01-01

In a preliminary study using single specimens for each condition, PWC-11 (a niobium-base alloy with a nominal composition of Nb-1%Zr-0.1%C) was creep tested at 1350 K and 40 MPa. Base metal specimens and specimens with transverse electron beam welds were tested with and without a 1000 hr, 1350 K aging treatment prior to testing. In the annealed condition (1 hr at 1755 K + 2 hr at 1475 K), the base metal exhibited superior creep strength compared to the nonaged condition, reaching 1 percent strain in 3480 hr. A 1000 hr, 1350 K aging treatment prior to creep testing had a severe detrimental effect on creep strength of the base metal and transverse electron beam weldments, reducing the time to attain 1 percent strain by an order of magnitude. Extrapolated temperature compensated creep rates indicate that the present heat of PWC-11 may be four times as creep resistant as similarly tested Nb-1%Zr. The extrapolated stress to achieve 1 percent creep strain in 7 yr at 1350 K is 2.7 MPa for annealed Nb-1%Zr and 12 MPa for annealed and aged PWC-11 base metal with and without a transverse electron beam weld.

A study of mechanical properties for aluminum GMA weldments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kluken, A.O.; Bjoerneklett, B.

1997-02-01

Medium- to high-strength aluminum alloys represent an attractive alternative to steel as a material for critical structural members. One area of great interest for their use is the transportation industry due to the increasing demands for less environmental impact through improved fuel efficiency, weight reductions, and increased load capacity. Fabrication of structural bodies involves, in most instances, the application of a joining process. Load-carrying members must be joined together or nonload-carrying parts attached to the primary structure. Although adhesive bonding, laser beam welding and friction stir welding are attractive processes for joining of aluminum, gas metal arc welding (GMAW) ismore » by far the most widely used process at present. Fusion welding of a heat-treatable aluminum alloy represents an additional local heat treatment of material that previously has been processed through tight temperature control to obtain the desired mechanical properties. Hence, great attention must be given to selection of alloy and temper condition, welding parameters, and postweld aging procedures for a given application. The objective of this investigation was to establish mechanical property data, i.e., tensile strength and impact toughness, for Al-Mg-Si and Al-Zn-Mg gas metal arc weldments applicable to the automotive and shipbuilding industries.« less

Microstructural characterization of weld joints of 9Cr reduced activation ferritic martensitic steel fabricated by different joining methods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thomas Paul, V.; Saroja, S.; Albert, S.K.

This paper presents a detailed electron microscopy study on the microstructure of various regions of weldment fabricated by three welding methods namely tungsten inert gas welding, electron beam welding and laser beam welding in an indigenously developed 9Cr reduced activation ferritic/martensitic steel. Electron back scatter diffraction studies showed a random micro-texture in all the three welds. Microstructural changes during thermal exposures were studied and corroborated with hardness and optimized conditions for the post weld heat treatment have been identified for this steel. Hollomon–Jaffe parameter has been used to estimate the extent of tempering. The activation energy for the tempering processmore » has been evaluated and found to be corresponding to interstitial diffusion of carbon in ferrite matrix. The type and microchemistry of secondary phases in different regions of the weldment have been identified by analytical transmission electron microscopy. - Highlights: • Comparison of microstructural parameters in TIG, electron beam and laser welds of RAFM steel • EBSD studies to illustrate the absence of preferred orientation and identification of prior austenite grain size using phase identification map • Optimization of PWHT conditions for indigenous RAFM steel • Study of kinetics of tempering and estimation of apparent activation energy of the process.« less

Recent Developments and Research Progress on Friction Stir Welding of Titanium Alloys: An Overview

NASA Astrophysics Data System (ADS)

Karna, Sivaji; Cheepu, Muralimohan; Venkateswarulu, D.; Srikanth, V.

2018-03-01

Titanium and its alloys are joined by various welding processes. However, Fusion welding of titanium alloys resulted solidification problems like porosity, segregation and columnar grains. The problems occurred in conventional welding processes can be resolved using a solid state welding i.e. friction stir welding. Aluminium and Magnesium alloys were welded by friction stir welding. However alloys used for high temperature applications such as titanium alloys and steels are arduous to weld using friction stir welding process because of tool limitations. Present paper summarises the studies on joining of Titanium alloys using friction stir welding with different tool materials. Selection of tool material and effect of welding conditions on mechanical and microstructure properties of weldments were also reported. Major advantage with friction stir welding is, we can control the welding temperature above or below β-transus temperature by optimizing the process parameters. Stir zone in below beta transus condition consists of bi-modal microstructure and microstructure in above β-transus condition has large prior β- grains and α/β laths present in the grain. Welding experiments conducted below β- transus condition has better mechanical properties than welding at above β-transus condition. Hardness and tensile properties of weldments are correlated with the stir zone microstructure.

Investigation of fatigue assessments accuracy for beam weldments considering material data input and FE-mode type

NASA Astrophysics Data System (ADS)

Gorash, Yevgen; Comlekci, Tugrul; MacKenzie, Donald

2017-05-01

This study investigates the effects of fatigue material data and finite element types on accuracy of residual life assessments under high cycle fatigue. The bending of cross-beam connections is simulated in ANSYS Workbench for different combinations of structural member shapes made of a typical structural steel. The stress analysis of weldments with specific dimensions and loading applied is implemented using solid and shell elements. The stress results are transferred to the fatigue code nCode DesignLife for the residual life prediction. Considering the effects of mean stress using FKM approach, bending and thickness according to BS 7608:2014, fatigue life is predicted using the Volvo method and stress integration rules from ASME Boiler & Pressure Vessel Code. Three different pairs of S-N curves are considered in this work including generic seam weld curves and curves for the equivalent Japanese steel JIS G3106-SM490B. The S-N curve parameters for the steel are identified using the experimental data available from NIMS fatigue data sheets employing least square method and considering thickness and mean stress corrections. The numerical predictions are compared to the available experimental results indicating the most preferable fatigue data input, range of applicability and FE-model formulation to achieve the best accuracy.

Development of Advanced 9Cr Ferritic-Martensitic Steels and Austenitic Stainless Steels for Sodium-Cooled Fast Reactor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sham, Sam; Tan, Lizhen; Yamamoto, Yukinori

2013-01-01

Ferritic-martensitic (FM) steel Grade 92, with or without thermomechanical treatment (TMT), and austenitic stainless steels HT-UPS (high-temperature ultrafine precipitate strengthening) and NF709 were selected as potential candidate structural materials in the U.S. Sodium-cooled Fast Reactor (SFR) program. The objective is to develop advanced steels with improved properties as compared with reference materials such as Grade 91 and Type 316H steels that are currently in nuclear design codes. Composition modification and/or processing optimization (e.g., TMT and cold-work) were performed to improve properties such as resistance to thermal aging, creep, creep-fatigue, fracture, and sodium corrosion. Testings to characterize these properties for themore » advanced steels were conducted by the Idaho National Laboratory, the Argonne National Laboratory and the Oak Ridge National Laboratory under the U.S. SFR program. This paper focuses on the resistance to thermal aging and creep of the advanced steels. The advanced steels exhibited up to two orders of magnitude increase in creep life compared to the reference materials. Preliminary results on the weldment performance of the advanced steels are also presented. The superior performance of the advanced steels would improve reactor design flexibility, safety margins and economics.« less

Performance of Underwater Weldments

DTIC Science & Technology

1990-09-05

gas or cathodic overprotection remains to be investigation. Subcritical crack propagation from corrosion fatigue must be considered. Crack propagation...toughness = .83 c. There is no redundancy so 1.8 times maximum stress or 1.0 times yield stress. Since the yield stress of the parent plate is being used...on the stress is required even though the stress will now be below yield strength in the parent plate. Since K is directly proportional to the stress

Study of Residual Stresses and Distortion in Structural Weldments in High-Strength Steels.

DTIC Science & Technology

1982-11-30

02139 II. CONTROLLING OFFICE NAME AND ADDRESS 12. REPORT DATE Department of the Navy November 30, 1982 Office of Naval Research 13. NUMBER OF PAGES...Arlington, Virginia 22217 14. MONITORING AGENCY NAME & ADDRESS(if different from Controlling Office) 15. SECURITY CLASS. (of this report) Unclassified 15a...a residual stress field were calculated. Finally, results from all of the afLrementioned analyses were compared with data obtained from experimental

Lamb wave scattering by a surface-breaking crack in a plate

NASA Technical Reports Server (NTRS)

Datta, S. K.; Al-Nassar, Y.; Shah, A. H.

1991-01-01

An NDE method based on finite-element representation and modal expansion has been developed for solving the scattering of Lamb waves in an elastic plate waveguide. This method is very powerful for handling discontinuities of arbitrary shape, weldments of different orientations, canted cracks, etc. The advantage of the method is that it can be used to study the scattering of Lamb waves in anisotropic elastic plates and in multilayered plates as well.

Corrosion-Fatigue of a Composite Laser Weldment

DTIC Science & Technology

1989-07-01

interaction of the bolt metal with the salt water solution. 43 Two specimen grips and two pins were machined from type 431 stainless steel and then heat...presented as follows. Body- centered cubic or tetragonal steels , namely ferrite and martensite , allow rapid movement of 5 hydrogen and solubility of...hydrogen is low. High strength martensitic steels are very susceptible to becoming embrittled by the diffusion of hydrogen down a stress gradient to a

Effects of Preheat on Weldments of NICOP Steel.

DTIC Science & Technology

1983-09-01

copper in this low alloy steel . Taken into solid solution in the austenite phase , the copper can precipitate as fine... low alloy steel was intro- duced which contains 1.0-1.3% copper with a maximum of 0.07% carbon. This steel is designated as AST4 A710 grade A for... ferrite has formed, some copper may precipitate as a fine epsilon copper phase in the ferrite as the solubility of

Tensile strength of simulated and welded butt joints in W-Cu composite sheet

NASA Technical Reports Server (NTRS)

Moore, Thomas J.; Watson, Gordon K.

1994-01-01

The weldability of W-Cu composite sheet was investigated using simulated and welded joints. The welded joints were produced in a vacuum hot press. Tensile test results showed that simulated joints can provide strength and failure mode data which can be used in joint design for actual weldments. Although all of the welded joints had flaws, a number of these joints were as strong as the W-Cu composite base material.

Computer automation of ultrasonic testing. [inspection of ultrasonic welding

NASA Technical Reports Server (NTRS)

Yee, B. G. W.; Kerlin, E. E.; Gardner, A. H.; Dunmyer, D.; Wells, T. G.; Robinson, A. R.; Kunselman, J. S.; Walker, T. C.

1974-01-01

Report describes a prototype computer-automated ultrasonic system developed for the inspection of weldments. This system can be operated in three modes: manual, automatic, and computer-controlled. In the computer-controlled mode, the system will automatically acquire, process, analyze, store, and display ultrasonic inspection data in real-time. Flaw size (in cross-section), location (depth), and type (porosity-like or crack-like) can be automatically discerned and displayed. The results and pertinent parameters are recorded.

Investigation of Weld Pool Structure and Property Control in Pulsed Arc Welding.

DTIC Science & Technology

1981-03-04

noted, elsewhere, freezing rate in the trailing and transverse directions show similarly contrasting behavior (6 𔄁 ). The movement of the solidus and...rise to low freezing eutectics and, hence, should be kept to the lowest possible level.1 3 󈧒 Solidification Cracking in Stainless Steel Welds It has...been observed 1 5 that hot cracking in austenitic stainless steel weldments is reduced or prevented when a small amount of delta ferrite is present

Prevention of Hydrogen-Induced Cracking in HY-130 Weldments.

DTIC Science & Technology

1977-09-30

cubic delta ferrite at the melting point (1538 C). The solu- bility increases from about k.9 to 8.3 ppm when delta ferrite transforms to * 3 The H... ferrite at 912 C. The solubility in ferrite then de- creases to less than 0.5 ppm at ambient temperature. This theory postulates that atomic...content than the dark- etching bands, and thus correspond to the regions last to freeze between the dendritic arms in the original ingot. During

Ship Structure Committee Publications: A Special Bibliography.

DTIC Science & Technology

1983-01-01

structural surfaces, even more so when the surfaces were machined after straining. damage; heavy weather damage to the forefoot and forward weather deck...One of the striking ORDER FROM: NTIS inadequacies of the impact test was the failure to show a difference between AD-72963 steels A and C, a...weldment in the range of 40 deg to 0 deg F. The effects of various types of defects, including arc strikes , Contract NObs-50238 porosity, and partial

Microstructural Characterization of HSLA-100 GMA-Weldments

DTIC Science & Technology

1987-09-01

Intermeiate Oxygen Regime ----------- 66 D.) Schematic CCT Diagram - --------------- 66 9 ACKNOWLEDGEMENTS I wish to express my appreciation to my thesis...have been observed in this research [review Figures 31 (a), (b) and 35 (a)]. Figure 38 (d) shows a schematic CCT diagram reported by Glover (Ref. 5) and...Regime B.) High Ox. gen Regime C. )Interme late Oxygen Regime D.1 Schematic CCT Diagram 66 LIST OF REFERENCES 1. Anderson, T.L., Hyatt J A West, J.C

Mechanical Properties and Seawater Behavior of Nitronic 50 (22Cr-13Ni- 5Mn) Plate

DTIC Science & Technology

1976-01-01

Bal - balance misc - miscellaneous cfh - cubic feet per hour mpy - mils per year c/m - cycles per minute my - millivolts CVN - Charpy V-notch No...High-Cycle Fatigue Specimens F_gure 6 - Drawings; Low-Cycle Fatigue Specimens Figure 7 - Curve; Charpy V-Notch Impact Toughness Versus Temperature...for Nitronic 50 Base Plate FiGure 8 - Curve; Charpy V-Notch Toughness Versus Tempera- ture for Nitrcnic 50 Weldments Figure 9 - Photographs; Fracture

The Effect of Welding Process on the Microstructure of HY-130 Steel Weldments

DTIC Science & Technology

1988-12-01

low -carbon, high-strength, low - alloy (HSLA) steels (C below 0.07 per- cent), the weld metal changed from coarse polygonal ferrite to...17. Ricks. R. A., Barritte, G. S., and Howell, P. R., "The Influence of Second Phase Particles on Diffusional Phase Transformations in Steels ... phase , austenite, may transform to mar- tensite on rapid cooling. The martensite has the exact same composi- tion as the austenite (up to two

Fatigue Characterization of Fabricated Ship Details for Design.

DTIC Science & Technology

1982-08-01

than the ques- tion of brittle fracture. Such cracking has been found in the forepeak region, bottom amidships, at the bulwark at both ends of the...results of the laboratory studies are presented in the Appendices. 1.3 References 1.1 Vedeler, G. "To What Extent Do Brittle Fracture and Fatigue...Civil Engineering. Appre- ciation is extended to Mr. John R. Williams who prepared the weldments, to Mr. Glen Lafenhagen who assisted in the fatigue

The application of statistically designed experiments to resistance spot welding

NASA Technical Reports Server (NTRS)

Hafley, Robert A.; Hales, Stephen J.

1991-01-01

State-of-the-art Resistance Spot Welding (RSW) equipment has the potential to permit realtime monitoring of operations through advances in computerized process control. In order to realize adaptive feedback capabilities, it is necessary to establish correlations among process variables, welder outputs, and weldment properties. The initial step toward achieving this goal must involve assessment of the effect of specific process inputs and the interactions among these variables on spot weld characteristics. This investigation evaluated these effects through the application of a statistically designed experiment to the RSW process. A half-factorial, Taguchi L sub 16 design was used to understand and refine a RSW schedule developed for welding dissimilar aluminum-lithium alloys of different thickness. The baseline schedule had been established previously by traditional trial and error methods based on engineering judgment and one-factor-at-a-time studies. A hierarchy of inputs with respect to each other was established, and the significance of these inputs with respect to experimental noise was determined. Useful insight was gained into the effect of interactions among process variables, particularly with respect to weldment defects. The effects of equipment related changes associated with disassembly and recalibration were also identified. In spite of an apparent decrease in equipment performance, a significant improvement in the maximum strength for defect-free welds compared to the baseline schedule was achieved.

Dissimilar welding of nickel-based Alloy 690 to SUS 304L with Ti addition

NASA Astrophysics Data System (ADS)

Lee, H. T.; Jeng, S. L.; Yen, C. H.; Kuo, T. Y.

2004-10-01

This study investigates the effects of Ti addition on the weldability, microstructure and mechanical properties of a dissimilar weldment of Alloy 690 and SUS 304L. Shielding metal arc welding (SMAW) is employed to butt-weld two plates with three welding layers, where each layer is deposited in a single pass. To investigate the effects of Ti addition, the flux coatings of the electrodes used in the welding process are modified by varying additions of either a Ti-Fe compound or a Ti powder. The results indicate that the microstructure of the fusion zone (FZ) is primarily dendritic. With increasing Ti content, it is noted that the microstructure changes from a columnar dendritic to an equiaxed dendritic, in which the primary dendrite arm spacing (PDAS) becomes shorter. Furthermore, it is observed that the amount of Al-Ti oxide phase increases in the inter-dendritic region, while the amount of Nb-rich phase decreases. Moreover, the average hardness of the FZ increases slightly. The results indicate that Ti addition prompts a significant increase in the elongation of the weldment (i.e. 36.5%, Ti: 0.41 wt%), although the tensile strength remains relatively unchanged. However, at an increased Ti content of 0.91 wt%, an obvious reduction in the tensile strength is noted, which can be attributed to a general reduction in the weldability of the joint.

Correlation Between Intercritical Heat-Affected Zone and Type IV Creep Damage Zone in Grade 91 Steel

NASA Astrophysics Data System (ADS)

Wang, Yiyu; Kannan, Rangasayee; Li, Leijun

2018-04-01

A soft zone in Cr-Mo steel weldments has been reported to accompany the infamous Type IV cracking, the highly localized creep damage in the heat-affected zone of creep-resistant steels. However, the microstructural features and formation mechanism of this soft zone are not well understood. In this study, using microhardness profiling and microstructural verification, the initial soft zone in the as-welded condition was identified to be located in the intercritical heat-affected zone of P91 steel weldments. It has a mixed structure, consisting of Cr-rich re-austenitized prior austenite grains and fine Cr-depleted, tempered martensite grains retained from the base metal. The presence of these further-tempered retained grains, originating from the base metal, is directly responsible for the hardness reduction of the identified soft zone in the as-welded condition. The identified soft zone exhibits a high location consistency at three thermal stages. Local chemistry analysis and thermodynamic calculation show that the lower chromium concentrations inside these retained grains thermodynamically decrease their potentials for austenitic transformation during welding. Heterogeneous grain growth is observed in the soft zone during postweld heat treatment. The mismatch of strengths between the weak Cr-depleted grains and strong Cr-rich grains enhances the creep damage. Local deformation of the weaker Cr-depleted grains accelerates the formation of creep cavities.

Beam Splitter For Welding-Torch Vision System

NASA Technical Reports Server (NTRS)

Gilbert, Jeffrey L.

1991-01-01

Compact welding torch equipped with along-the-torch vision system includes cubic beam splitter to direct preview light on weldment and to reflect light coming from welding scene for imaging. Beam splitter integral with torch; requires no external mounting brackets. Rugged and withstands vibrations and wide range of temperatures. Commercially available, reasonably priced, comes in variety of sizes and optical qualities with antireflection and interference-filter coatings on desired faces. Can provide 50 percent transmission and 50 percent reflection of incident light to exhibit minimal ghosting of image.

Detection of lack of fusion using opaque additives, phase 2

NASA Technical Reports Server (NTRS)

Cook, J. L.

1973-01-01

Plasma-sprayed copper coatings were developed to protect the aluminum surfaces of spacecraft structures from oxidation, as well as to provide a means of reliable nondestructive X-ray inspection of possible incomplete weldment penetration. Sixty day storage tests of coated aluminum samples indicated the promise of long-term oxidation protection, but revealed no advantage in detecting penetration defects. Delta-scan techniques were used, and peen plating as a means of applying copper to the aluminum surface was investigated.

Mechanical, Corrosion, and Fatigue Properties of 15-5 PH, Inconel 718, and Rene 41 Weldments

DTIC Science & Technology

1975-05-01

TUCUMvARI (PGH 2) It was originally developed for high - temperature use by Armco Steel Corporation. 2 High strength is obtained by the precipitation...Rene 41 was developed by General Electric Company as a high - temperature turbine alloy. It is a nickel-base alloy, high in chromium, cobalt, and... molybdenum . Its high strength comes from the precipitation of a gamma-prime phase consisting of Ni3AI and Ni5Ti, and from the solid solution effects of

Ballistic-Failure Mechanisms in Gas Metal Arc Welds of MIL A46100 Armor-Grade Steel: A Computational Investigation

DTIC Science & Technology

2014-06-12

distribution is unlimited. Ballistic-Failure Mechanisms in Gas Metal Arc Welds of Mil A46100 Armor-Grade Steel : A Computational Investigation The views...Welds of Mil A46100 Armor-Grade Steel : A Computational Investigation Report Title In our recent work, a multi-physics computational model for the...introduction of the sixth module in the present work in recognition of the fact that in thick steel GMAW weldments, the overall ballistic performance

Oxygen-Free Welding Contact Tips

NASA Technical Reports Server (NTRS)

Pike, James F.

1993-01-01

Contact tips for gas/metal arc welding (GMAW) fabricated from oxygen-free copper. Prototype tips tested in robotic welding, for which application intended. Reduces electrical erosion, increases electrical conductivity, and reduces mechanical wear. Productivity of robotic welding increases while time during welding interrupted for removal and replacement of contact tips minimal. Improves alignment of joints and filler metal, reducing rate of rejection and repair of unacceptable weldments. Utility extends beyond aerospace industry to mass production of various types of hardware, including heavy off-highway construction equipment.

Flaw Growth of 6Al-4V Titanium in a Freon TF Environment

NASA Technical Reports Server (NTRS)

Tiffany, C. F.; Masters, J. N.; Bixler, W. D.

1969-01-01

The plane strain threshold stress intensity and sustained stress flaw growth rates were experimentally determined for 6AI-4V S.T.A. titanium forging and weldments in environments of Freon TF at room temperature. Sustained load tests of surface flawed specimens were conducted with the experimental approach based on linear elastic fracture mechanics. It was concluded that sustained stress flaw growth rates, in conjunction with threshold stress intensities, can be used in assessing the service life of pressure vessels.

Determination of design allowable properties. Fracture of 2219-T87 aluminum alloy

NASA Technical Reports Server (NTRS)

Engstrom, W. L.

1972-01-01

A literature survey was conducted to provide a comprehensive report of available valid data on tensile properties, fracture toughness, fatigue crack propagation, and sustained load behavior of 2219-T87 aluminum alloy base metal and weldments, as applicable to manned spacecraft tankage. Most of the data found were from tests conducted at room temperature, -320 F and -423 F. Data are presented in graphical and tabular form, and areas in which data are lacking are established.

Factors Influencing the Microstructure and Mechanical Properties of Ultra Low Carbon Bainitic 100 Tungsten Inert Gas Multipass Weldments

DTIC Science & Technology

1992-09-01

Optical macrograph of flat-etched sample 75B3-8 ........................ 30 Figure 4.15 Constitutional supercooling in alloy solidification ... alloying elements such as Mn, Mo, Ni and Cr are added to increase the strength and hardenability of the steel. However, substantial limitations on...0.9 Carbon Equivalent CE = C + Mn + Si + Ni + Cu + Cr + Mo + V 6 15 5 Figure 2.1 Graville Diagram (Blicharski et al, 1989, p.318) 3 B. ULTRA LOW

Identification and Characterization of Intercritical Heat-Affected Zone in As-Welded Grade 91 Weldment

NASA Astrophysics Data System (ADS)

Wang, Yiyu; Kannan, Rangasayee; Li, Leijun

2016-12-01

A metallurgical method is proposed for locating the intercritical heat-affected zone in the as-welded Grade 91 steel. New austenitic grains, preferentially formed along the original prior austenite grain boundaries, are characterized to contain finer M23C6 carbides and higher strain levels than the original prior austenite grains. Kurdjumov-Sachs Group 1 variant pairs, with a low misorientation of 7 deg within a martensitic block, are identified as the dominant variants in the new PAGs.

Proceedings of the Joint Seminar; Hydrogen Management in Steel Weldments, Melbourne, Australia, 23rd October 1996.

DTIC Science & Technology

1997-01-01

Cr-Mo quenched and tempered (Q&T) steel . Both A723 Grade 1 and Grade 2 compositions were evaluated to determine the effects of strength, composition ...15] Craig, B., "Limitations of Alloying to Improve the Threshold for Hydrogen Stress Cracking of Steels ", Hydrogen Effects on Material Behavior ...considered are as follows: 1. Hydrogen mass transfer in steels and welded joints: analytical equipment; effect of element composition of weld metal and

Closure development for high-level nuclear waste containers for the tuff repository; Phase 1, Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Robitz, E.S. Jr.; McAninch, M.D. Jr.; Edmonds, D.P.

1990-09-01

This report summarizes Phase 1 activities for closure development of the high-level nuclear waste package task for the tuff repository. Work was conducted under U.S. Department of Energy (DOE) Contract 9172105, administered through the Lawrence Livermore National Laboratory (LLNL), as part of the Yucca Mountain Project (YMP), funded through the DOE Office of Civilian Radioactive Waste Management (OCRWM). The goal of this phase was to select five closure processes for further evaluation in later phases of the program. A decision tree methodology was utilized to perform an objective evaluation of 15 potential closure processes. Information was gathered via a literaturemore » survey, industrial contacts, and discussions with project team members, other experts in the field, and the LLNL waste package task staff. The five processes selected were friction welding, electron beam welding, laser beam welding, gas tungsten arc welding, and plasma arc welding. These are felt to represent the best combination of weldment material properties and process performance in a remote, radioactive environment. Conceptual designs have been generated for these processes to illustrate how they would be implemented in practice. Homopolar resistance welding was included in the Phase 1 analysis, and developments in this process will be monitored via literature in Phases 2 and 3. Work was conducted in accordance with the YMP Quality Assurance Program. 223 refs., 20 figs., 9 tabs.« less

A Review on Inertia and Linear Friction Welding of Ni-Based Superalloys

NASA Astrophysics Data System (ADS)

Chamanfar, Ahmad; Jahazi, Mohammad; Cormier, Jonathan

2015-04-01

Inertia and linear friction welding are being increasingly used for near-net-shape manufacturing of high-value materials in aerospace and power generation gas turbines because of providing a better quality joint and offering many advantages over conventional fusion welding and mechanical joining techniques. In this paper, the published works up-to-date on inertia and linear friction welding of Ni-based superalloys are reviewed with the objective to make clarifications on discrepancies and uncertainties reported in literature regarding issues related to these two friction welding processes as well as microstructure, texture, and mechanical properties of the Ni-based superalloy weldments. Initially, the chemical composition and microstructure of Ni-based superalloys that contribute to the quality of the joint are reviewed briefly. Then, problems related to fusion welding of these alloys are addressed with due consideration of inertia and linear friction welding as alternative techniques. The fundamentals of inertia and linear friction welding processes are analyzed next with emphasis on the bonding mechanisms and evolution of temperature and strain rate across the weld interface. Microstructural features, texture development, residual stresses, and mechanical properties of similar and dissimilar polycrystalline and single crystal Ni-based superalloy weldments are discussed next. Then, application of inertia and linear friction welding for joining Ni-based superalloys and related advantages over fusion welding, mechanical joining, and machining are explained briefly. Finally, present scientific and technological challenges facing inertia and linear friction welding of Ni-based superalloys including those related to modeling of these processes are addressed.

Microstructural characterization of an SA508–309L/308L–316L domestic dissimilar metal welded safe-end joint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ming, Hongliang; Zhang, Zhiming; Wang, Jianqiu, E-mail: wangjianqiu@imr.ac.cn

2014-11-15

The microstructure of an SA508–309L/308L–316L domestic dissimilar metal welded safe-end joint was characterized in this work by optical microscopy, scanning electron microscopy (with electron back scattering diffraction) and micro-hardness testing. Epitaxial growth and competitive growth are evident in the 308L–316L fusion boundary regions. A martensite layer, carbon-depleted zones, and type-II and type-I boundaries are found in the SA508–309L fusion boundary regions, while only martensite and austenite mixed zones are observed in the SA508–308L fusion boundary regions. The microstructure near the fusion boundary and the microstructure transition in the SA508 heat affected zone are quite complex. Both for SA508–309L/308L and 308L–316L,more » the highest residual strain is located on the outside of the weldment. The residual strain and the grain boundary character distribution change with increasing distance from the fusion boundary in the heat affected zone of 316L. Micro-hardness measurements also reveal non-uniform mechanical properties across the weldment. - Highlights: • The microstructure of SA508 HAZ, especially near the FB, is very complex. • The outside of the dissimilar metal welded joint has the highest residual. • The micro-hardness distributions along the DMWJ are non-uniform.« less

Electron Beam Welding of Gear Wheels by Splitted Beam

NASA Astrophysics Data System (ADS)

Dřímal, Daniel

2014-06-01

This contribution deals with the issue of electron beam welding of high-accurate gear wheels composed of a spur gearing and fluted shaft joined with a face weld for automotive industry. Both parts made of the high-strength low-alloy steel are welded in the condition after final machining and heat treatment, performed by case hardening, whereas it is required that the run-out in the critical point of weldment after welding, i. e. after the final operation, would be 0.04 mm max.. In case of common welding procedure, cracks were formed in the weld, initiated by spiking in the weld root. Crack formation was prevented by the use of an interlocking joint with a rounded recess and suitable welding parameters, eliminating crack initiation by spiking in the weld root. Minimisation of the welding distortions was achieved by the application of tack welding with simultaneous splitting of one beam into two parts in the opposite sections of circumferential face weld attained on the principle of a new system of controlled deflection with digital scanning of the beam. This welding procedure assured that the weldment temperature after welding would not be higher than 400 °C. Thus, this procedure allowed achieving the final run-outs in the critical point of gearwheels within the maximum range up to 0.04 mm, which is acceptable for the given application. Accurate optical measurements did not reveal any changes in the teeth dimensions.

Low-Cycle Fatigue Behavior of 10CrNi3MoV High Strength Steel and Its Undermatched Welds

PubMed Central

Liu, Xuesong; Berto, Filippo

2018-01-01

The use of high strength steel allows the design of lighter, more slender and simpler structures due to high strength and favorable ductility. Nevertheless, the increase of yield strength does not guarantee the corresponding improvement of fatigue resistance, which becomes a major concern for engineering structure design, especially for the welded joints. The paper presents a comparison of the low cycle fatigue behaviors between 10CrNi3MoV high strength steel and its undermatched weldments. Uniaxial tension tests, Push-pull, strain-controlled fatigue tests were conducted on base metal and weldments in the strain range of 0.2–1.2%. The monotonic and cyclic stress-strain curves, stress-life, strain-life and energy-life in terms of these materials were analyzed for fatigue assessment of materials discrepancy. The stress-life results of base metal and undermatched weld metal exhibit cyclic softening behaviors. Furthermore, the shapes of 10CrNi3MoV steel hysteresis loops show a satisfactory Masing-type behavior, while the weld metal shows a non-Masing type behavior. Strain, plastic and total strain energy density amplitudes against the number of reversals to failure results demonstrate that the undermatched weld metal presents a higher resistance to fatigue crack initiation than 10CrNi3MoV high strength steel. Finally, fatigue fracture surfaces of specimens were compared by scanning electron microscopy to identify the differences of crack initiation and the propagation between them. PMID:29695140

Low-Cycle Fatigue Behavior of 10CrNi3MoV High Strength Steel and Its Undermatched Welds.

PubMed

Song, Wei; Liu, Xuesong; Berto, Filippo; Razavi, S M J

2018-04-24

The use of high strength steel allows the design of lighter, more slender and simpler structures due to high strength and favorable ductility. Nevertheless, the increase of yield strength does not guarantee the corresponding improvement of fatigue resistance, which becomes a major concern for engineering structure design, especially for the welded joints. The paper presents a comparison of the low cycle fatigue behaviors between 10CrNi3MoV high strength steel and its undermatched weldments. Uniaxial tension tests, Push-pull, strain-controlled fatigue tests were conducted on base metal and weldments in the strain range of 0.2⁻1.2%. The monotonic and cyclic stress-strain curves, stress-life, strain-life and energy-life in terms of these materials were analyzed for fatigue assessment of materials discrepancy. The stress-life results of base metal and undermatched weld metal exhibit cyclic softening behaviors. Furthermore, the shapes of 10CrNi3MoV steel hysteresis loops show a satisfactory Masing-type behavior, while the weld metal shows a non-Masing type behavior. Strain, plastic and total strain energy density amplitudes against the number of reversals to failure results demonstrate that the undermatched weld metal presents a higher resistance to fatigue crack initiation than 10CrNi3MoV high strength steel. Finally, fatigue fracture surfaces of specimens were compared by scanning electron microscopy to identify the differences of crack initiation and the propagation between them.

Comparison between instrumented precracked Charpy and compact specimen tests of carbon steels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nanstad, R.K.

1980-01-01

The General Atomic Company High Temperature Gas-Cooled Reactor (HTGR) is housed within a prestressed concrete reactor vessel (PCRV). Various carbon steel structural members serve as closures at penetrations in the vessel. A program of testing and evaluation is underway to determine the need for reference fracture toughness (K/sub IR/) and indexing procedures for these materials as described in Appendix G to Section III, ASME Code for light water reactor steels. The materials of interest are carbon steel forgings (SA508, Class 1) and plates (SA537, Classes 1 and 2) as well as weldments of these steels. The fracture toughness behavior ismore » characterized with instrumented precracked Charpy V-votch specimens (PCVN) - slow-bend and dynamic - and compact specimens (10-mm and 25-mm thicknesses) using both linear elastic (ASTM E399) and elastic-plastic (equivalent Energy and J-Integral) analytical procedures. For the dynamic PCVN tests, force-time traces are analyzed according to the procedures of the Pressure Vessel Research Council (PVRC)/Metal Properties Council (MPC). Testing and analytical procedures are discussed and PCVN results are compared to those obtained with compact specimens.« less

Fracture Characteristics of Structural Steels and Weldments

DTIC Science & Technology

1975-11-01

CARACTERISTICS 0F.$ýTRUCTURAL TEL/ - "AD E NTSA .INAL 1 A7 sk S. CONTRACT OR GRANT NUMBER(&) Y.2G. im 9. PERFORMING ORGANIZATION NAME AND ADDRESS -017...36, T- 1,and HY-Y130 Steel and AX. Il 30 15 I Tensile F~racture Surface of A-36 Steel, 12x 31 16 Dimple Rupture in A-6Sel 0X 31 17 Plastic ...sites and the relative plasticity of thle The objective of this study was to use a scanning metal. If many fracture icleation sites initiate mticro

Transverse-Weld Tensile Properties of a New Al-4Cu-2Si Alloy as Filler Metal

NASA Astrophysics Data System (ADS)

Sampath, K.

2009-12-01

AA2195, an Al-Cu-Li alloy in the T8P4 age-hardened condition, is a candidate aluminum armor for future combat vehicles, as this material offers higher static strength and ballistic protection than current aluminum armor alloys. However, certification of AA2195 alloy for armor applications requires initial qualification based on the ballistic performance of welded panels in the as-welded condition. Currently, combat vehicle manufacturers primarily use gas metal arc welding (GMAW) process to meet their fabrication needs. Unfortunately, a matching GMAW consumable electrode is currently not commercially available to allow effective joining of AA2195 alloy. This initial effort focused on an innovative, low-cost, low-risk approach to identify an alloy composition suitable for effective joining of AA2195 alloy, and evaluated transverse-weld tensile properties of groove butt joints produced using the identified alloy. Selected commercial off-the-shelf (COTS) aluminum alloy filler wires were twisted to form candidate twisted filler rods. Representative test weldments were produced using AA2195 alloy, candidate twisted filler rods and gas tungsten arc welding (GTAW) process. Selected GTA weldments produced using Al-4wt.%Cu-2wt.%Si alloy as filler metal consistently provided transverse-weld tensile properties in excess of 275 MPa (40 ksi) UTS and 8% El (over 25 mm gage length), thereby showing potential for acceptable ballistic performance of as-welded panels. Further developmental work is required to evaluate in detail GMAW consumable wire electrodes based on the Al-Cu-Si system containing 4.2-5.0 wt.% Cu and 1.6-2.0 wt.% Si.

An improved diffusion welding technique for TD-NiCr

NASA Technical Reports Server (NTRS)

Holko, K. H.

1973-01-01

An improved diffusion welding technique has been developed for TD-NiCr sheet. In the most preferred form, the improved technique consists of diffusion welding 320-grit sanded plus chemically polished surfaces of unrecrystallized TD-NiCr at 760 C under 140 MN/m2 pressure for 1hr followed by postheating at 1180 C for 2hr. Compared to previous work, this improved technique has the advantages of shorter welding time, lower welding temperature, lower welding pressure, and a simpler and more reproducible surface preparation procedure. Weldments were made that had parent-metal creep-rupture shear strength at 1100 C.

Extended electrode technique. [gas metal arc welding of metal plates

NASA Technical Reports Server (NTRS)

Schaper, V. D.; Pollack, A.

1972-01-01

The extended electrode technique is a unique welding process which utilizes manual gas-metal-arc (GMAW) semi-automatic equipment and close, square butt joints to effectively produce a weld. The technique takes advantage of the resistance heating of the electode extension to effect the root pass. Weldments as large as 72-X30-X2-inch have been fabricated with this technique under normal shipyard welding conditions. Mechanical properties and explosion bulge tests indicate that satisfactory results are obtained with this process. Potential savings of approximately 50 percent can be achieved in flat welding and repair of heavy structural steel members.

Inertial Weldment of Rhenium and Inconel 718

NASA Technical Reports Server (NTRS)

Cavender, D. P.; Courtright, Z. S.; Hostetter, G.; Laiman, M.

2018-01-01

Inertia welding has been found to be a successful method for joining pure rhenium to Inconel 718, and with additional experimentation, this process may have great potential for rocket nozzle applications. Refractory metals are ideally suited to this application, where high temperatures and oxidizing environment survivability is required, but not all of the thruster must be made of these materials, only the areas that require them. A bolted joint between the two metals is not ideal, especially for small thrusters where the mess of a bolted join will come at a steep price. A welded joint would be preferred for flight thrusters.

Fractography of modern engineering materials: composites and metals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Masters, J.E.; Au, J.J.

1987-01-01

The fractographic analysis of fracture surfaces in composites and metals is discussed in reviews and reports of recent theoretical and experimental investigations. Topics addressed include fracture-surface micromorphology in engineering solids, SEM fractography of pure and mixed-mode interlaminar fractures in graphite/epoxy composites, determination of crack propagation directions in graphite/epoxy structures, and the fracture surfaces of irradiated composites. Consideration is given to fractographic feature identification and characterization by digital imaging analysis, fractography of pressure-vessel steel weldments, the micromechanisms of major/minor cycle fatigue crack growth in Inconel 718, and fractographic analysis of hydrogen-assisted cracking in alpha-beta Ti alloys.

Investigation on microstructure and mechanical properties on pulsed current gas tungsten arc welded super alloy 617

NASA Astrophysics Data System (ADS)

Mageshkumar, K.; Kuppan, P.; Arivazhagan, N.

2017-11-01

The present research work investigates the metallurgical and mechanical properties of weld joint fabricated by alloy 617 by pulsed current gas tungsten arc welding (PCGTAW) technique. Welding was done by ERNiCrCoMo-1 filler wire. Optical and Scanning Electron Microscope (SEM) revealed the fine equiaxed dendritic in the fusion zone. Electron Dispersive Spectroscopy (EDS) demonstrates the presence of Mo-rich secondary phases in the grain boundary regions. Tensile test shows improved mechanical properties compared to the continuous current mode. Bend test didn’t indicate the presence of defects in the weldments.

Optimized postweld heat treatment procedures for 17-4 PH stainless steels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhaduri, A.K.; Sujith, S.; Srinivasan, G.

1995-05-01

The postweld heat treatment (PWHT) procedures for 17-4 PH stainless steel weldments of matching chemistry was optimized vis-a-vis its microstructure prior to welding based on microstructural studies and room-temperature mechanical properties. The 17-4 PH stainless steel was welded in two different prior microstructural conditions (condition A and condition H 1150) and then postweld heat treated to condition H900 or condition H1150, using different heat treatment procedures. Microstructural investigations and room-temperature tensile properties were determined to study the combined effects of prior microstructural and PWHT procedures.

Analysis of WC/Ni-Based Coatings Deposited by Controlled Short-Circuit MIG Welding

NASA Astrophysics Data System (ADS)

Vespa, P.; Pinard, P. T.; Gauvin, R.; Brochu, M.

2012-06-01

This study investigates the recently developed controlled short-circuit metal inert gas (CSC-MIG) welding system for depositing WC/Ni-based claddings on carbon steel substrates. WC/Ni-based coatings deposited by CSC-MIG were analyzed by optical light microscopy and scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS) and electron backscatter diffraction (EBSD) capabilities. X-ray diffraction (XRD) and hardness measurements of depositions are also reported. The CSC-MIG welding system provides a significant amount of user control over the current waveform during welding and has lower heat input when compared with traditional MIG welding. Heat input for the analyzed coatings ranged from 10.1 to 108.7 J/mm. Metallurgically bonded coatings free from spatter and with 0.75% average porosity were produced. It was found that the detrimental decarburization of the WC particles seen in thermal spray systems does not occur when welding with the CSC-MIG. Precipitation of a reaction layer around the reinforcing phase was identified as WC; the average thickness of which increases from 3.8 to 7.2 μm for the low and high heat input condition, respectively. Precipitation of newly formed WC particles was observed; their size distribution increased from D 50 of 2.4 μm in the low heat input weldment to 6.75 μm in the high heat input weldment. The level of dilution of the reinforcing phase increases significantly with heat input. The hardness of the deposited coatings decreases from 587 HV10 to 410 HV10 when the energy input was increased from 10.1 to 108.7 J/mm.

Microstructural and mechanical characterization of CO{sub 2} laser and gas tungsten arc welds of an Al-Li-Cu alloy 2195

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hou, K.H.; Baeslack, W.A. III; Szabo, A.

1994-12-31

Lithium-containing aluminum alloys offer an attractive combination of low density and high strength and stiffness and have been the focus of vigorous research for their promising aerospace applications. To achieve the full potential advantages in using these alloys, the integrity of welded joints, both n the fusion zone and the heat-affected zone, must be ensured. In the present study, Weldalite{sup TM} 049 (designated as alloy 2195) with nominal composition of Al-1.0Li-4.0Cu-0.4Mg0.4Ag-0.14Zr (wt%) was welded autogenously using the gas tungsten-arc (GTA) and CO{sub 2} laser beam (LB) welding processes. The average ultimate tensile strengths for as-welded, 160{degrees}C/16 h-aged, and 190{degrees}C/16 h-agedmore » GTA welds were 296.4 MPa, 304.6 MPa, and 336.8 MPa, and corresponded to joint efficiencies of 61.4%, 48.1% and 56.0%, respectively. Porosity was found occasionally in the laser welds and slightly affected the performance of the aluminum weldments. For laser welds, average ultimate tensile strengths and corresponding joint efficiencies for a-welded, 160{degrees}C/16 h-aged, and 190{degrees}C/16 h-aged weldments were 293.2 MPa (60.8%) 305.9 MPa (48.3%), and 331.0 MPa (55.0%), respectively. Scanning electron fractography revealed that failure of the GTA and LB tensile specimens occurred either within the weld metal or along the fusion boundary. The latter was related to the existence of an equiaxed band along the fusion boundary.« less

Creep Strength of Nb-1Zr for SP-100 Applications

NASA Astrophysics Data System (ADS)

Horak, James A.; Egner, Larry K.

1994-07-01

Power systems that are used to provide electrical power in space are designed to optimize conversion of thermal energy to electrical energy and to minimize the mass and volume that must be launched. Only refractory metals and their alloys have sufficient long-term strength for several years of uninterrupted operation at the required temperatures of 1200 K and above. The high power densities and temperatures at which these reactors must operate require the use of liquid-metal coolants. The alloy Nb-1 wt % Zr (Nb-lZr), which exhibits excellent corrosion resistance to alkali liquid-metals at high temperatures, is being considered for the fuel cladding, reactor structural, and heat-transport systems for the SP-100 reactor system. Useful lifetime of this system is limited by creep deformation in the reactor core. Nb-lZr sheet procured to American Society for Testing and Materials (ASTM) specifications for reactor grade and commercial grade has been processed by several different cold work and annealing treatments to attempt to produce the grain structure (size, shape, and distribution of sizes) that provides the maximum creep strength of this alloy at temperatures from 1250 to 1450 K. The effects of grain size, differences in oxygen concentrations, tungsten concentrations, and electron beam and gas tungsten arc weldments on creep strength were studied. Grain size has a large effect on creep strength at 1450 K but only material with a very large grain size (150 μm) exhibits significantly higher creep strength at 1350 K. Differences in oxygen or tungsten concentrations did not affect creep strength, and the creep strengths of weldments were equal to, or greater than, those for base metal.

Effect of long-term aging on microstructure and local behavior in the heat-affected zone of a Ni–Cr–Mo–V steel welded joint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu, Ming-Liang, E-mail: mlzhu@ecust.edu.cn; Wang, De-Qiang; Xuan, Fu-Zhen

2014-01-15

Evolution of microstructure, micro-hardness and micro-tensile strength behavior was investigated in the heat-affected zone of a Ni–Cr–Mo–V steel welded joint after the artificial aging at 350 °C for 3000 h. After detailed characterization of microstructures in optical microscopy, scanning electron microscopy and transmission electron microscopy, it is revealed that the change of martensite–bainite constituent promotes more homogeneous microstructure distribution. The aging treatment facilitates redistribution of carbon and chromium elements along the welded joint, and the micro-hardness is increased slightly through the welds due to enrichment of carbon. The types of precipitates in the weldment mainly include M{sub 3}C, MC, M{submore » 2}C and M{sub 23}C{sub 6}. The carbides in base metal, weld metal and coarse-grained heat-affected zone are prone to change from ellipsoidal to platelet form whereas more uniform spherical carbides are observed in the fine-grained zone. Precipitation and coarsening of M{sub 23}C{sub 6} near the fusion line, and formation of MC and M{sub 2}C, are responsible for the tensile strength decrease and its smooth distribution in the aged heat-affected zone. This implies that the thermal aging can relieve strength mismatch in the weldments. - Highlights: • Microstructure homogeneity improved in HAZ after long-term aging. • Tensile strength decreased in HAZ due to precipitation and coarsening of M{sub 23}C{sub 6}. • Strength mismatch in NiCrMoV steel welds was relieved after aging at 350 °C × 3000 h.« less

Limit load solution for electron beam welded joints with single edge weld center crack in tension

NASA Astrophysics Data System (ADS)

Lu, Wei; Shi, Yaowu; Li, Xiaoyan; Lei, Yongping

2012-05-01

Limit loads are widely studied and several limit load solutions are proposed to some typical geometry of weldments. However, there are no limit load solutions exist for the single edge crack weldments in tension (SEC(T)), which is also a typical geometry in fracture analysis. The mis-matching limit load for thick plate with SEC(T) are investigated and the special limit load solutions are proposed based on the available mis-matching limit load solutions and systematic finite element analyses. The real weld configurations are simplified as a strip, and different weld strength mis-matching ratio M, crack depth/width ratio a/ W and weld width 2H are in consideration. As a result, it is found that there exists excellent agreement between the limit load solutions and the FE results for almost all the mis-matching ration M, a/ W and ligament-to-weld width ratio ( W-a)/ H. Moreover, useful recommendations are given for evaluating the limit loads of the EBW structure with SEC(T). For the EBW joints with SEC(T), the mis-matching limit loads can be obtained assuming that the components are wholly made of base metal, when M changing from 1.6 to 0.6. When M decreasing to 0.4, the mis-matching limit loads can be obtained assuming that the components are wholly made of base metal only for large value of ( W-a)/ H. The recommendations may be useful for evaluating the limit loads of the EBW structures with SEC(T). The engineering simplifications are given for assessing the limit loads of electron beam welded structure with SEC(T).

Method and apparatus for determining weldability of thin sheet metal

DOEpatents

Goodwin, Gene M.; Hudson, Joseph D.

1988-01-01

A fixture is provided for testing thin sheet metal specimens to evaluate hot-cracking sensitivity for determining metal weldability on a heat-to-heat basis or through varying welding parameters. A test specimen is stressed in a first direction with a load selectively adjustable over a wide range and then a weldment is passed along over the specimen in a direction transverse to the direction of strain to evaluate the hot-cracking characteristics of the sheet metal which are indicative of the weldability of the metal. The fixture provides evaluations of hot-cracking sensitivity for determining metal weldability in a highly reproducible manner with minimum human error.

Use of photostress and strain gages to analyze behavior of weldments

NASA Astrophysics Data System (ADS)

Gambrell, S. C., Jr.

1993-09-01

Tensile and pure bending tests were conducted on specimens having welded joints made from 2219-T87 aluminum alloy and 2319 filler. Data were collected using photoelastic coatings and strain gages. Stress-strain relationships and contraction ratios were determined at several points in a grid covering the weld material and heat affected zone. Material behavior was nonlinear and nonuniform at all points in the grid and contraction ratios did not conform to those predicted by Chakrabarty's plasticity theory. Yielding in joints made using four new welding procedures was examined. None of the new procedures produced more uniform yielding in the joint.

Atomic-scale bonding of bulk metallic glass to crystalline aluminum

NASA Astrophysics Data System (ADS)

Liu, K. X.; Liu, W. D.; Wang, J. T.; Yan, H. H.; Li, X. J.; Huang, Y. J.; Wei, X. S.; Shen, J.

2008-08-01

A Ti40Zr25Cu12Ni3Be20 bulk metallic glass (BMG) was welded to a crystalline aluminum by the parallel plate explosive welding method. Experimental evidence and numerical simulation show that atomic-scale bonding between the BMG and the crystalline aluminum can be achieved, and the weldment on the BMG side can retain its amorphous state without any indication of crystallization in the welding process. Nanoindentation tests reveal that the interface of the explosive joints exhibits a significant increase in hardness compared to the matrix on its two sides. The joining of BMG and crystalline materials opens a window to the applications of BMGs in engineering.

Friction plug welding

NASA Technical Reports Server (NTRS)

Takeshita, Riki (Inventor); Hibbard, Terry L. (Inventor)

2001-01-01

Friction plug welding (FPW) usage is advantageous for friction stir welding (FSW) hole close-outs and weld repairs in 2195 Al--Cu--Li fusion or friction stir welds. Current fusion welding methods of Al--Cu--Li have produced welds containing varied defects. These areas are found by non-destructive examination both after welding and after proof testing. Current techniques for repairing typically small (<0.25) defects weaken the weldment, rely heavily on welders' skill, and are costly. Friction plug welding repairs increase strength, ductility and resistance to cracking over initial weld quality, without requiring much time or operator skill. Friction plug welding while pulling the plug is advantageous because all hardware for performing the weld can be placed on one side of the workpiece.

Assesment of influncing factors on mechanical and electrical properties of Al/Cu joints

NASA Astrophysics Data System (ADS)

Selvaraj, R. Meby; Hynes, N. Rajesh Jesudoss

2018-05-01

Joining of dissimilar materials opens up challenging opportunities in todays technology. Al/Cu weldments are used in applications that demands corrosion resistance, thermal and electrical conducting properties. In dissimilar joining mechanical and thermal properties result in large stress gradients during heating. The Al-Cu joints are lighter, cheaper and have conductivity equal to copper alloy. The main scope of this study is to assess the influencing factors of Al/Cu joints in mechanical and electrical properties. It includes the influence of the dilution between the base metals, influence of physical properties, influence of welding parameters, influence of filler metal, influence of heat treatment, and influence of electrical properties

Friction Stir Welding of Steel Alloys

NASA Technical Reports Server (NTRS)

Ding, R. Jeffrey; Munafo, Paul M. (Technical Monitor)

2001-01-01

The friction stir welding process has been developed primarily for the welding of aluminum alloys. Other higher melting allows such, as steels are much more difficult to join. Special attention must be given to pin tool material selection and welding techniques. This paper addresses the joining of steels and other high melting point materials using the friction stir welding process. Pin tool material and welding parameters will be presented. Mechanical properties of weldments will also be presented. Significance: There are many applications for the friction stir welding process other than low melting aluminum alloys. The FSW process can be expanded for use with high melting alloys in the pressure vessel, railroad and ship building industries.

The effects of multiple repairs on Inconel 718 weld mechanical properties

NASA Technical Reports Server (NTRS)

Russell, C. K.; Nunes, A. C., Jr.; Moore, D.

1991-01-01

Inconel 718 weldments were repaired 3, 6, 9, and 13 times using the gas tungsten arc welding process. The welded panels were machined into mechanical test specimens, postweld heat treated, and nondestructively tested. Tensile properties and high cycle fatigue life were evaluated and the results compared to unrepaired weld properties. Mechanical property data were analyzed using the statistical methods of difference in means for tensile properties and difference in log means and Weibull analysis for high cycle fatigue properties. Statistical analysis performed on the data did not show a significant decrease in tensile or high cycle fatigue properties due to the repeated repairs. Some degradation was observed in all properties, however, it was minimal.

Weldability of a high entropy CrMnFeCoNi alloy

DOE PAGES

Wu, Zhenggang; David, Stan A.; Feng, Zhili; ...

2016-07-19

We present the high-entropy alloys are unique alloys in which five or more elements are all in high concentrations. In order to determine its potential as a structural alloy, a model face-centered-cubic CrMnFeCoNi alloy was selected to investigate its weldability. Welds produced by electron beam welding show no cracking. The grain structures within the fusion zone (FZ) are controlled by the solidification behavior of the weld pool. The weldment possesses mechanical properties comparable to those of the base metal (BM) at both room and cryogenic temperatures. Finally, compared with the BM, deformation twinning was more pronounced in the FZ ofmore » the tested alloy.« less

A Lifting Ball Valve for cryogenic fluid applications

NASA Astrophysics Data System (ADS)

Cardin, Joseph M.; Reinicke, Robert H.; Bruneau, Stephen D.

1993-11-01

Marotta Scientific Controls, Inc. has designed a Lifting Ball Valve (LBV) capable of both flow modulation and tight shutoff for cryogenic and other applications. The LBV features a thin-walled visor valving element that lifts off the seal with near axial motion before rotating completely out of the flow path. This is accomplished with a simple, robust mechanism that minimizes cost and weight. Conventional spherical rotating seats ar plagued by leakage due to 'scuffing' as the seal and seat slide against one another while opening. Cryogenic valves, which typically utilize plastic seals, are particularly susceptible to this type of damage. The seat in the LBV lifts off the seal without 'scuffing' making it immune to this failure mode. In addition, the LBV lifting mechanism is capable of applying the very high seating loads required to seal at cryogenic temperatures. These features make the LBV ideally suited for cryogenic valve applications. Another major feature of the LBV is the fact that the visor rotates completely out of the flow path. This allows for a smaller, lighter valve for a given flow capacity, especially for line sizes above one inch. The LBV is operated by a highly integrated 'wetted' DC brushless motor. The motor rotor is 'wetted' ion that it is immersed in the fluid. To ensure compatibility, the motor rotor is encased in a thin-walled CRES weldment. The motor stator is outside the fluid containment weldment and therefore is not in direct contact with the fluid. To preclude the potential for external leakage there are no static or dynamic seals or bellows across the pressure boundary. The power required to do the work of operating the valving mechanism is transmitted across the pressure boundary by electromagnetic interaction between the motor rotor and the stator. Commutation of the motor is accomplished using the output of a special 'wetted' resolver. This paper describes the design, operation, and element testing of the LBV.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Yiyu; Kannan, Rangasayee; Li, Leijun, E-mail

Non-equilibrium microstructure of the heat-affected zone (HAZ) in the as-welded modified 9Cr–1Mo–V–Nb pipe steel (P91) weldment deposited by gas tungsten arc welding (GTAW) and flux core arc welding (FCAW) has been characterized by field-emission scanning electron microscope (FESEM) and electron backscatter diffraction (EBSD). The heterogeneous structures in the sub-layers of the as-welded HAZ are attributable to phase transformations caused by the welding thermal cycles and the local structure variations in the as-received base metal. Coarse-grained heat-affected zone (CGHAZ) has a prior austenite grain (PAG) size of 20 μm. Fine uniformly-distributed precipitates and a higher fraction of MX carbonitrides are observedmore » in the CGHAZ. Fine-grained heat-affected zone (FGHAZ) consists of the finest grains (1.22 μm measured by EBSD, 5 μm PAG size), coarse undissolved M{sub 23}C{sub 6} carbides within the PAG boundaries and fine nucleated M{sub 23}C{sub 6} particles within the martensite laths. Inter-critical heat-affected zone (ICHAZ) consists of partially austenitized grains and over-tempered martensite laths. EBSD kernel average misorientation (KAM) map in the FGHAZ close to the ICHAZ illustrates the greatest local strain variations with a moderate normalized KAM value of 0.92°. The majority (88.1%) of the matrix grains in the CGHAZ are classified as deformed grains by EBSD grain average misorientation (GAM) evaluation. The FGHAZ close to the ICHAZ has the most recrystallized grains with an area fraction of 14.4%. The highest density variation of precipitates within grains in the FGHAZ originates from the inhomogeneous chemistry in the base metal. - Highlights: •A comprehensive characterization of the as-welded HAZ of P91 weldment is conducted. •Structural features in the each layer of the HAZ are quantified by EBSD. •Structural heterogenities in HAZ are due to welding cycle and base metal structure. •FGHAZ contains the finest grain structure and largest precipitate density variation.« less

The structural significance of HAZ sigma phase formation in welded 25%Cr super duplex pipework

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wiesner, C.S.; Garwood, S.J.; Bowden, P.L.

1993-12-31

The welding of 25%Cr duplex stainless steel can lead to the formation of sigma phase in both weld metal and heat affected zone (HAZ) regions. It has generally been accepted that this can be avoided by the adoption of appropriate welding procedure controls, generally aimed at reducing heat input and promoting rapid cooling rates. However, experience during pipe spool fabrication for the Marathon East Brae Project has shown that it is extremely difficult to satisfy a welding specification requiring sigma free HAZs. This has proved a particular problem with thin wall pipe welds made in the 2G/5G or 6G fixedmore » positions, where the joint geometry reduces heat flow away from the weld and welding conditions tend to result in the use of higher heat inputs. This paper examines the effect of sigma phase on the fracture toughness of 25%Cr super duplex steel (UNS S32760). It is shown that the CTOD toughness at {minus}20 C decreases as soon as any sigma phase is present and continues to decrease with increasing sigma levels. The toughness of the sigmatized specimens produced by heat treatment was shown to be conservative compared to the toughness measured in the HAZ of 14.2mm and 7.1mm thick pipe weldments, made with welding parameters chosen to enhance HAZ sigma phase formation. Based on the CTOD versus percent sigma level relationship derived from the laboratory specimens, fracture assessment calculations of tolerable flaw sizes were performed. These demonstrated that under the severest design conditions, assuming the maximum flaw sizes which could remain undetected in the pipework, sigma levels up to 2.5% can be tolerated safely. The conservatism of the fracture assessments for predicting the performance of weldments was demonstrated by full scale tensile testing of 2 inch nominal bore x 2.77 mm wall thickness pipe butt welds containing through-thickness circumferential fatigue cracks located in the sigmatized HAZ.« less

Experimental Investigation of Material Flows Within FSWs Using 3D Tomography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Charles R. Tolle; Timothy A. White; Karen S. Miller

2008-06-01

There exists significant prior work using tracers or pre-placed hardened markers within friction stir welding (FSWing) to experimentally explore material flow within the FSW process. Our experiments replaced markers with a thin sheet of copper foil placed between the 6061 aluminum lap and butt joints that were then welded. The absorption characteristics of x-rays for copper and aluminum are significantly different allowing for non-destructive evaluation (NDE) methods such as x-ray computed tomography (CT) to be used to demonstrate the material movement within the weldment on a much larger scale than previously shown. 3D CT reconstruction of the copper components ofmore » the weldment allows for a unique view into the final turbulent state of the welding process as process parameters are varied. The x-ray CT data of a section of the weld region was collected using a cone-beam x-ray imaging system developed at the INL. Six-hundred projections were collected over 360-degrees using a 160-kVp Bremsstrahlung x-ray generator (25-micrometer focal spot) and amorphoussilicon x-ray detector. The region of the object that was imaged was about 3cm tall and 1.5cm x 1cm in cross section, and was imaged at a magnification of about 3.6x. The data were reconstructed on a 0.5x0.5x0.5 mm3 voxel grid. After reconstruction, the aluminum and copper could be easily discriminated using a gray level threshold allowing visualization of the copper components. Fractal analysis of the tomographic reconstructed material topology is investigated as a means to quantify macro level material flow based on process parameters. The results of multi-pass FSWs show increased refinement of the copper trace material. Implications of these techniques for quantifying process flow are discussed.« less

Characterisation of metallic glass incorporated Zircaloy-2 weldments

NASA Astrophysics Data System (ADS)

Mishra, S.; Savalia, R. T.; Bhanumurthy, K.; Dey, G. K.; Banerjee, S.

1995-12-01

In this study the effect of incorporation of Zr based Fe and Ni bearing metallic glass in spot welds in Zircaloy components has been examined. A comparison of strength and microstructure of the welded joint with and without glass has been carried out. The welded joint with metallic glass has been found to be stronger than the one without metallic glass. The microstructure of the welded region with metallic glass has been found to comprise a large region having martensite. This large martensitic region has also been found to have considerable amount of excess solute (Fe, Ni). The higher strength of the weld with metallic glass seems to originate due to solid solution strengthening, small grain size and the presence of martensitic structure over a large region.

Study of austenitic stainless steel welded with low alloy steel filler metal. [tensile and impact strength tests

NASA Technical Reports Server (NTRS)

Burns, F. A.; Dyke, R. A., Jr.

1979-01-01

The tensile and impact strength properties of 316L stainless steel plate welded with low alloy steel filler metal were determined. Tests were conducted at room temperature and -100 F on standard test specimens machined from as-welded panels of various chemical compositions. No significant differences were found as the result of variations in percentage chemical composition on the impact and tensile test results. The weldments containing lower chromium and nickel as the result of dilution of parent metal from the use of the low alloy steel filler metal corroded more severely in a marine environment. The use of a protective finish, i.e., a nitrile-based paint containing aluminum powder, prevented the corrosive attack.

Hot cracking susceptibility of fillers 52 and 82 in alloy 690 welding

NASA Astrophysics Data System (ADS)

Wu, Weite; Tsai, C. H.

1999-02-01

The hot cracking susceptibility of fillers 52 and 82 in a alloy 690 weldment is analyzed by the Varestraint test. Weld characteristics, microstructure, hardness distribution, and thermal analysis of the two filler metals are also examined. The weld metal of both fillers develops an extremely dense oxide layer. A stainless steel brush cannot remove the oxide layer, and a grinder may be needed between weld passes to assure a sound weld. Differential temperature analysis (DTA) shows that filler 82 has a lower melting point and a wider melting/solidification temperature differential (Δ T). These characteristics correlate with greater hot cracking susceptibility of filler 82 than 52 in Varestraint tests. The hot cracks are intergranular and are caused by elements segregating in grain boundies.

Features of residual stresses in duplex stainless steel butt welds

NASA Astrophysics Data System (ADS)

Um, Tae-Hwan; Lee, Chin-Hyung; Chang, Kyong-Ho; Nguyen Van Do, Vuong

2018-04-01

Duplex stainless steel finds increasing use as an alternative to austenitic stainless steel, particularly where chloride or sulphide stress corrosion cracking is of primary concern, due to the excellent combination of strength and corrosion resistance. During welding, duplex stainless steel does not create the same magnitude or distribution of weld-induced residual stresses as those in welded austenitic stainless steel due to the different physical and mechanical properties between them. In this work, an experimental study on the residual stresses in butt-welded duplex stainless steel is performed utilizing the layering technique to investigate the characteristics of residual stresses in the weldment. Three-dimensional thermos-mechanical-metallurgical finite element analysis is also performed to confirm the residual stress measurements.

Microstructure, Properties and Weldability of Duplex Stainless Steel 2101

NASA Astrophysics Data System (ADS)

Ma, Li; Hu, Shengsun; Shen, Junqi

2017-01-01

The continuous development of duplex stainless steels (DSSs) is due to their excellent corrosion resistance in aggressive environments and their mechanical strength, which is usually twice of conventional austenitic stainless steels (ASSs). In this paper, a designed lean duplex stainless steel 2101, with the alloy design of reduced nickel content and increased additions of manganese and nitrogen, is studied by being partly compared with typical ASS 304L steels. The microstructure, mechanical properties, impact toughness, corrosion resistance and weldability of the designed DSS 2101 were conducted. The results demonstrated that both 2101 steel and its weldment show excellent mechanical properties, impact toughness and corrosion resistance, so DSS 2101 exhibits good comprehensive properties and can be used to replace 304L in numerous applications.

Optimization of Performance of Arc Welding Using Fluxes in Welded Ship Structures from HY-100 and HY-130 KPSI.

DTIC Science & Technology

1981-09-01

production and formulation for several decades. NMgO + NCaO + NMnO + NFeO + NAI 20 3Basicity = NSiO 2 + NTi0 2 + NZr0 2 + NA1 203 This differs from the widely...20 3 100 (CaO-SiO, )(40) slag CaO/SiO 2 0.15 none 2600 NCaO /NSiO2 0.17 8% FeSi 1900 16% FeSi 1700 32% FeSi 1400 52 I Table 8 (continued). Islag Ca0...SiO~e .79 none 1200 NCaO /NSiOz .84 2% FeSi 1000 4% FeSi 900 16% FeSi 500 32% FeSi 500 Mechanical Property Tests Mechanical property weldments were

Glass Coats For Hot Isostatic Pressing

NASA Technical Reports Server (NTRS)

Ecer, Gunes M.

1989-01-01

Surface voids sealed from pressurizing gas. Coating technique enables healing of surface defects by hot isostatic pressing (HIP). Internal pores readily closed by HIP, but surface voids like cracks and pores in contact with pressurizing gas not healed. Applied to casting or weldment as thick slurry of two glass powders: one melts at temperature slightly lower than used for HIP, and another melts at higher temperature. For example, powder is glass of 75 percent SiO2 and 25 percent Na2O, while other powder SiO2. Liquid component of slurry fugitive organic binder; for example, mixture of cellulose acetate and acetone. Easy to apply, separates voids from surrounding gas, would not react with metal part under treatment, and easy to remove after pressing.

Corrosion behavior of stainless steel weldments in physiological solutions

NASA Astrophysics Data System (ADS)

Farooq, A.; Azam, M.; Deen, K. M.

2018-01-01

In this study corrosion behavior of TIG welded 316L stainless steel plates in simulated biological solutions is investigated. The mechanical testing results showed slight decrease in ductility after welding and the fracture surface represented mixed cleavage and inclusions containing dimple structure. The heat affected and weld zone (WZ) demonstrated higher corrosion potential and relatively large pitting tendency than base metal (BM) in both Hank’s and Ringer’s solution. The formation of delta (δ) ferrite in the heat affected and WZ decreased the corrosion resistance as confirmed from potentiodynamic Tafel scans. The decrease in pitting resistance and lower protection tendency of the WZ compared to BM and heat affected zone was also quantified from the cyclic polarization trends.

Effect of proof testing on the flaw growth characteristics of 304 stainless steel. [crack propagation in welded joints

NASA Technical Reports Server (NTRS)

Finger, R. W.

1974-01-01

The effects of proof overload frequency and magnitude on the cyclic crack growth rates of 304 stainless steel weldments were investigated. The welding procedure employed was typical of those used on over-the-road cryogenic vessels. Tests were conducted at room temperature with an overload ratio of 1.50 to determine the effect of overload frequency. Effect of overload magnitude was determined from tests where a room temperature overload was applied between blocks of 1000 cycles applied at 78 K (-320 F). The cyclic stress level used in all tests was typical of the nominal membrane stress generally encountered in full scale vessels. Test results indicate that judicious selection of proof overload frequency and magnitude can reduce crack growth rates for cyclic stress levels.

Surface-crack growth: Models, experiments, and structures; Proceedings of the Symposium, Sparks, NV, Apr. 25, 1988

NASA Technical Reports Server (NTRS)

Reuter, Walter G. (Editor); Underwood, John H. (Editor); Newman, James C., Jr. (Editor)

1990-01-01

The present volume on surface-crack growth modeling, experimental methods, and structures, discusses elastoplastic behavior, the fracture analysis of three-dimensional bodies with surface cracks, optical measurements of free-surface effects on natural surfaces and through cracks, an optical and finite-element investigation of a plastically deformed surface flaw under tension, fracture behavior prediction for rapidly loaded surface-cracked specimens, and surface cracks in thick laminated fiber composite plates. Also discussed are a novel study procedure for crack initiation and growth in thermal fatigue testing, the growth of surface cracks under fatigue and monotonically increasing load, the subcritical growth of a surface flaw, surface crack propagation in notched and unnotched rods, and theoretical and experimental analyses of surface cracks in weldments.

Thick section aluminum weldments for SRB structures

NASA Technical Reports Server (NTRS)

Bayless, E.; Sexton, J.

1978-01-01

The Space Shuttle Solid Rocket Booster (SRB) forward and aft skirts were designed with fracture control considerations used in the design data. Fracture control is based on reliance upon nondestructive evaluation (NDE) techniques to detect potentially critical flaws. In the aerospace industry, welds on aluminum in the thicknesses (0.500 to 1.375 in.) such as those encountered on the SRB skirts are normally welded from both sides to minimize distortion. This presents a problem with the potential presence of undefined areas of incomplete fusion and the inability to detect these potential flaws by NDE techniques. To eliminate the possibility of an undetectable defect, weld joint design was revised to eliminate blind root penetrations. Weld parameters and mechanical property data were developed to verify the adequacy of the new joint design.

Hot cracking susceptibility of fillers 52 and 82 in alloy 690 welding

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, W.; Tsai, C.H.

1999-02-01

The hot cracking susceptibility of fillers 52 and 82 in a alloy 690 weldment is analyzed by the Varestraint test. Weld characteristics, microstructure, hardness distribution, and thermal analysis of the two filler metals are also examined. The weld metal of both fillers develops an extremely dense oxide layer. A stainless steel brush cannot remove the oxide layer, and a grinder may be needed between weld passes to assure a sound weld. Differential temperature analysis (DTA) shows that filler 82 has a lower melting point and a wider melting/solidification temperature differential ({Delta} T). These characteristics correlate with greater hot cracking susceptibilitymore » of filler 82 than 52 in Varestraint tests. The hot cracks are intergranular and are caused by elements segregating in grain boundaries.« less

Status Report on Irradiation Capsules Containing Welded FeCrAl Specimens for Radiation Tolerance Evaluation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Field, Kevin G.; Howard, Richard H.

2016-02-26

This status report provides the background and current status of a series of irradiation capsules, or “rabbits”, that were designed and built to test the contributions of microstructure, composition, damage dose, and irradiation temperature on the radiation tolerance of candidate FeCrAl alloys being developed to have enhanced weldability and radiation tolerance. These rabbits will also test the validity of using an ultra-miniature tensile specimen to assess the mechanical properties of irradiated FeCrAl base metal and weldments. All rabbits are to be irradiated in the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory (ORNL) to damage doses up tomore » ≥15 dpa at temperatures between 200-550°C.« less

The effect of inhibitor sodium nitrate on pitting corrosion of dissimilar material weldment joint of stainless steel AISI 304 and mild steel SS 400

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hilca, B. R., E-mail: bangkithilca@yahoo.com; Triyono, E-mail: triyonomesin@uns.ac.id

This study experimentally evaluated the effect of Sodium Nitrate inhibitor (NaNO{sub 3}) of 0.1%, 0.3%, and 0.5% on NaCl 3.5% toward pitting corrosion of dissimilar metal welding joint between stainless steel AISI 304 and mild steel SS 400. Electrochemical corrosion was tested using potentiodynamic polarization. Further the Scanning Electron Microscope (SEM) conducted to analyze the specimen. Chemical composition analysis used Energy Dispersive X-ray Spectrometry (EDS). The highest efficiency of sodium nitrate for ER 308 attained 63.8% and 64.89%for ER 309L. The specimen surface which observed through SEM showed decrease of pitting corrosion respectively with the addition of sodium nitrate contentmore » as inhibitor.« less

Quantitative methods in fractography; Proceedings of the Symposium on Evaluation and Techniques in Fractography, Atlanta, GA, Nov. 10, 1988

DOE Office of Scientific and Technical Information (OSTI.GOV)

Strauss, B.M.; Putatunda, S.K.

1990-01-01

Papers are presented on the application of quantitative fractography and computed tomography to fracture processes in materials, the relationships between fractographic features and material toughness, the quantitative analysis of fracture surfaces using fractals, and the analysis and interpretation of aircraft component defects by means of quantitative fractography. Also discussed are the characteristics of hydrogen-assisted cracking measured by the holding-load and fractographic method, a fractographic study of isolated cleavage regions in nuclear pressure vessel steels and their weld metals, a fractographic and metallographic study of the initiation of brittle fracture in weldments, cracking mechanisms for mean stress/strain low-cycle multiaxial fatigue loadings,more » and corrosion fatigue crack arrest in Al alloys.« less

Thermo-mechanical process for treatment of welds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Malik, R K

1980-03-01

Benefits from thermo-mechanical processing (TMP) of austenitic stainless steel weldments, analogous to hot isostatic pressing (HIP) of castings, most likely result from compressive plastic deformation, enhanced diffusion, and/or increased dislocation density. TMP improves ultrasonic inspectability of austenitic stainless steel welds owing to: conversion of cast dendrites into equiaxed austenitic grains, reduction in size and number of stringers and inclusions, and reduction of delta ferrite content. TMP induces structural homogenization and healing of void-type defects and thus contributes to an increase in elongation, impact strength, and fracture toughness as well as a significant reduction in data scatter for these properties. Anmore » optimum temperature for TMP or HIP of welds is one which causes negligible grain growth and an acceptable reduction in yield strength, and permits healing of porosity.« less

Microstructure and hydrogen induced failure mechanisms in iron-nickel weldments

NASA Astrophysics Data System (ADS)

Fenske, Jamey Alan

A recent series of inexplicable catastrophic failures of specific subsea dissimilar metal Fe-Ni butter welds has illuminated a fundamental lack of understanding of both the microstructure created along the fusion line as well as its impact on the hydrogen susceptibility of these interfaces. In order to remedy this, the present work compares and contrasts the microstructure and hydrogen-induced fracture morphology of AISI 8630-IN 625 and F22-IN 625 dissimilar metal weld interfaces as a function of post-weld heat treatment duration. A variety of techniques were used to study details of both the microstructure and fracture morphology including optical microscopy, scanning electron microscopy, secondary ion mass spectrometry, transmission electron microscopy, electron backscatter diffraction, and energy dispersive x-ray spectroscopy. For both systems, the microstructure along the weld interface consisted of a coarse grain heat-affected zone in the Fe-base metal followed by discontinuous martensitic partially-mixed zones and a continuous partially-mixed zone on the Ni-side of the fusion line. Within the partially mixed zone on the Ni-side there exists a 200 nm-wide transition zone within a 20 mum-wide planar solidification region followed by a cellular dendritic region with Nb-Mo rich carbides decorating the dendrite boundaries. The size, area fraction and composition of the discontinuous PMZ were determined to be controlled by uneven mixing in the liquid weld pool influenced by convection currents produced from the welding procedure. The virgin martensitic microstructure produced in these regions is formed as consequence of a both the local composition and the post-weld heat treatment. The local higher Ni content results in these regions being retransformed into austenite during the post-weld heat treatment and then virgin martensite while cooling to room temperature. Although there were differences in the volume of the discontinuous partially mixed-zones, the major difference in the weld metal interfaces was the presence of M 7C3 precipitates in the planar solidification region. The formation of these precipitates, which were found in what was previously referred to as the "featureless-zone," were determined to be dependent on the carbon content of the Fe-base metal and the duration of the post-weld heat treatment. A high density of these ordered 100 nm-long by 10 nm-wide needle-like precipitates were found in the AISI 8630-IN 625 weldment in the 10 hour post-weld heat treatment condition while only the initial stages of their nucleation were evident in the F22-IN 625 15 hour post-weld heat treatment specimen. The study of the fractured specimens revealed that the M7C 3 carbides play a key role in the susceptibility to hydrogen embrittlement of the Fe-Ni butter weldments. The fractures initially nucleate along the isolated Fe-base metal -- discontinuous partially mixed zone interfaces. The M7C3 carbides accumulate hydrogen and then provide a low energy fracture path between the discontinuous partially mixed zones leading to catastrophic failure. The result is a fracture morphology that alternates between flat regions produced by fracture along the discontinuous partially mixed zones and cleavage-like fracture regions produced by fracture along the ordered carbide matrix interfaces.

Probing heat transfer, fluid flow and microstructural evolution during fusion welding of alloys

NASA Astrophysics Data System (ADS)

Zhang, Wei

The composition, geometry, structure and properties of the welded joints are affected by the various physical processes that take place during fusion welding. Understanding these processes has been an important goal in the contemporary welding research to achieve structurally sound and reliable welds. In the present thesis research, several important physical processes including the heat transfer, fluid flow and microstructural evolution in fusion welding were modeled based on the fundamentals of transport phenomena and phase transformation theory. The heat transfer and fluid flow calculation is focused on the predictions of the liquid metal convection in the weld pool, the temperature distribution in the entire weldment, and the shape and size of the fusion zone (FZ) and heat affected zone (HAZ). The modeling of microstructural evolution is focused on the quantitative understanding of phase transformation kinetics during welding of several important alloys under both low and high heating and cooling conditions. Three numerical models were developed in the present thesis work: (1) a three-dimensional heat transfer and free surface flow model for the gas metal arc (GMA) fillet welding considering the complex weld joint geometry, (2) a phase transformation model based on the Johnson-Mehl-Avrami (JMA) theory, and (3) a one-dimensional numerical diffusion model considering multiple moving interfaces. To check the capabilities of the developed models, several cases were investigated, in which the predictions from the models were compared with the experimental results. The cases studied are the follows. For the modeling of heat transfer and fluid flow, the welding processes studied included gas tungsten arc (GTA) linear welding, GTA transient spot welding, and GMA fillet welding. The calculated weldment geometry and thermal cycles was validated against the experimental data under various welding conditions. For the modeling of microstructural evolution, the welded materials investigated included AISI 1005 low-carbon steel, 1045 medium-carbon steel, 2205 duplex stainless steel (DSS) and Ti-6Al-4V alloy. The calculated phase transformation kinetics were compared with the experimental results obtained using an x-ray diffraction technique by Dr. John W. Elmer of Lawrence Livermore National Laboratory. (Abstract shortened by UMI.)

Welding of gamma titanium aluminide alloys

NASA Technical Reports Server (NTRS)

Smashey, Russell W. (Inventor); Snyder, John H. (Inventor); Kelly, Thomas J. (Inventor); Sheranko, Ronald L. (Inventor)

1998-01-01

An article made of a gamma titanium aluminide alloy is welded, as for example in the weld repair of surface cracks, by removing foreign matter from the area to be welded, first stress relieving the article, cooling the entire article to a welding temperature of from about 1000.degree. F. to about 1400.degree. F., welding a preselected region in an inert atmosphere at the welding temperature, and second stress relieving the article. Welding is preferably accomplished by striking an arc in the preselected region so as to locally melt the alloy in the preselected region, providing a filler metal having the same composition as the gamma titanium aluminide alloy of the article, and feeding the filler metal into the arc so that the filler metal is melted and fused with the article to form a weldment upon solidification.

Exploratory study of friction welds in Udimet 700 and TD-Nickel bar

NASA Technical Reports Server (NTRS)

Moore, T. J.

1971-01-01

Friction welded butt joints were made in both Udimet 700 and TD-Nickel bar. Also, dissimilar metal friction welds were made between these materials. Friction welding of Udimet 700 shows great promise because the welds were found to be as strong as the parent metal in stress rupture and tensile tests at 760 and 980 C. The weld line was not detectable metallographically in the heat treated condition. Friction welding for TD-Nickel, however, holds little if any promise. TD-Nickel friction weldments could support only 9 percent as much stress as the base metal for a 10-hour stress-rupture life at 1090 C. Dissimilar Udimet 700/TD-Nickel friction welds could sustain only 15 percent as much stress as the TD-Nickel parent metal for a 10-hour rupture life at 930 C.

Microstructural dependence of Barkhausen noise and magnetic relaxation in the weld HAZ of an RPV steel

NASA Astrophysics Data System (ADS)

Park, Duck-Gun; Kim, Cheol Gi; Hong, Jun-Hwa

2000-06-01

Magnetic Barkhausen noise and permeability spectra have been measured to characterize different microstructure regions such as coarse-grain region, fine-grain region, intercritical structure (composed of tempered martensite and bainite) within the heat-affected zone (HAZ) of SA508-3 steel weldments using simulated HAZ microstructure sample. The intercritical region and coarse-grained region can be distinguished from the BNE and relaxation frequency. The BNE was decreased in the martensite regions and increased in the bainite regions by the post-weld heat treatment (PWHT). The change of relaxation frequency also showed similar trends, but the rate of change was less than that of BNE. The behavior of BNE and permeability spectra on the corresponding microstructure can be explained in terms of carbide morphology and residual stress related with domain wall motion.

Investigating the Effects of Pin Tool Design on Friction Stir Welded Ti-6Al-4V

NASA Technical Reports Server (NTRS)

Rubisoff, H. A.; Querin, J. A.; Schneider, Judy A.; Magee, D.

2009-01-01

Friction stir welding (FSWing), a solid state joining technique, uses a non-consumable rotating pin tool to thermomechanically join materials. Heating of the weldment caused by friction and deformation is a function of the interaction between the pin tool and the work piece. Therefore, the geometry of the pin tool is in part responsible for the resulting microstructure and mechanical properties. In this study microwave sintered tungsten carbide (WC) pin tools with tapers and flats were used to FSW Ti-6Al-4V. Transverse sections of welds were mechanically tested, and the microstructure was characterized using optical microscopy (OM) and scanning election microscopy (SEM). X-ray diffraction (XRD) and electron back-scatter diffraction (EBSD) were used to characterize the texture within the welds produced from the different pin tool designs.

Improving the corrosion properties of magnesium AZ31 alloy GTA weld metal using microarc oxidation process

NASA Astrophysics Data System (ADS)

Siva Prasad, M.; Ashfaq, M.; Kishore Babu, N.; Sreekanth, A.; Sivaprasad, K.; Muthupandi, V.

2017-05-01

In this work, the morphology, phase composition, and corrosion properties of microarc oxidized (MAO) gas tungsten arc (GTA) weldments of AZ31 alloy were investigated. Autogenous gas tungsten arc welds were made as full penetration bead-on-plate welding under the alternating-current mode. A uniform oxide layer was developed on the surface of the specimens with MAO treatment in silicate-based alkaline electrolytes for different oxidation times. The corrosion behavior of the samples was evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy. The oxide film improved the corrosion resistance substantially compared to the uncoated specimens. The sample coated for 10 min exhibited better corrosion properties. The corrosion resistance of the coatings was concluded to strongly depend on the morphology, whereas the phase composition and thickness were concluded to only slightly affect the corrosion resistance.

Effect of Cr Contents and Heat Treating on Reverted Austenite in Maraging Steel Weldments

NASA Astrophysics Data System (ADS)

Kim, S. W.; Lee, H. W.

2018-05-01

By conducting flux cored arc welding (FCAW) on maraging steels with Cr contents of 1.4 and 5.2 wt%, this study observed the effects of Cr content and heat treating on reverted austenite formation in welded maraging steel. Aging treatment was carried out at the temperatures of 450, 480 and 530 °C for 3 h in each condition. As the aging temperature increased, reverted austenite was formed along the interdendritic and intercellular grain boundaries, and the proportion of reverted austenite increased with increasing Cr addition. The aging process led to the segregation of Ti and Mo along the interdendritic and intercellular grain boundaries. Some of the welded specimens were subjected to solution heat treatment at 820 and 1250 °C for 1 h after welding, resulting in a decrease in reverted austenite fraction.

Microstructural evolution and precipitation behavior in heat affected zone of Inconel 625 and AISI 904L dissimilar welds

NASA Astrophysics Data System (ADS)

Senthur Prabu, S.; Devendranath Ramkumar, K.; Arivazhagan, N.

2017-11-01

In the present investigation an attempt has been made to join the dissimilar combination of Inconel 625 super alloy and super austenitic stainless steel (AISI 904L) using manual multi-pass continuous current gas tungsten arc (CCGTA) welding processes. Two different filler wires such as ERNiCrMo-4 and ERNiCrCoMo-1 have been used to compare the metallurgical properties of these welded joints. Both optical microscopy and scanning electron microscopy techniques were adopted to disseminate the microstructure traits of these weldments. Formation of secondary phases at the HAZ and weld interface of AISI 904L was witnessed while using the ERNiCrCoMo-1 filler, along with Solidification Grain Boundary (SGB) and Migrated Grain Boundary (MGB) were also observed at the weld zone.

The variable polarity plasma arc welding process: Characteristics and performance

NASA Technical Reports Server (NTRS)

Hung, R. J.; Zhu, G. J.

1991-01-01

Significant advantages of the Variable Polarity Plasma Arc (VPPA) Welding Process include faster welding, fewer repairs, less joint preparation, reduced weldment distortion, and absence of porosity. The power distribution was analyzed for an argon plasma gas flow constituting the fluid in the VPPA Welding Process. The major heat loss at the torch nozzle is convective heat transfer; in the space between the outlet of the nozzle and the workpiece; radiative heat transfer; and in the keyhole in the workpiece, convective heat transfer. The power absorbed at the workpiece produces the molten puddle that solidifies into the weld bead. Crown and root widths, and crown and root heights of the weld bead are predicted. The basis is provided for an algorithm for automatic control of VPPA welding machine parameters to obtain desired weld bead dimensions.

Effect of Cr Contents and Heat Treating on Reverted Austenite in Maraging Steel Weldments

NASA Astrophysics Data System (ADS)

Kim, S. W.; Lee, H. W.

2018-03-01

By conducting flux cored arc welding (FCAW) on maraging steels with Cr contents of 1.4 and 5.2 wt%, this study observed the effects of Cr content and heat treating on reverted austenite formation in welded maraging steel. Aging treatment was carried out at the temperatures of 450, 480 and 530 °C for 3 h in each condition. As the aging temperature increased, reverted austenite was formed along the interdendritic and intercellular grain boundaries, and the proportion of reverted austenite increased with increasing Cr addition. The aging process led to the segregation of Ti and Mo along the interdendritic and intercellular grain boundaries. Some of the welded specimens were subjected to solution heat treatment at 820 and 1250 °C for 1 h after welding, resulting in a decrease in reverted austenite fraction.

DEVELOPMENT AND APPLICATION OF MATERIALS PROPERTIES FOR FLAW STABILITY ANALYSIS IN EXTREME ENVIRONMENT SERVICE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sindelar, R; Ps Lam, P; Andrew Duncan, A

Discovery of aging phenomena in the materials of a structure may arise after its design and construction that impact its structural integrity. This condition can be addressed through a demonstration of integrity with the material-specific degraded conditions. Two case studies of development of fracture and crack growth property data, and their application in development of in-service inspection programs for nuclear structures in the defense complex are presented. The first case study covers the development of fracture toughness properties in the form of J-R curves for rolled plate Type 304 stainless steel with Type 308 stainless steel filler in the applicationmore » to demonstrate the integrity of the reactor tanks of the heavy water production reactors at the Savannah River Site. The fracture properties for the base, weld, and heat-affected zone of the weldments irradiated at low temperatures (110-150 C) up to 6.4 dpa{sub NRT} and 275 appm helium were developed. An expert group provided consensus for application of the irradiated properties for material input to acceptance criteria for ultrasonic examination of the reactor tanks. Dr. Spencer H. Bush played a lead advisory role in this work. The second case study covers the development of fracture toughness for A285 carbon steel in high level radioactive waste tanks. The approach in this case study incorporated a statistical experimental design for material testing to address metallurgical factors important to fracture toughness. Tolerance intervals were constructed to identify the lower bound fracture toughness for material input to flaw disposition through acceptance by analysis.« less

HAZARDS OF THERMAL EXPANSION FOR RADIOLOGICAL CONTAINER ENGULFED IN FIRE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Donna Post Guillen

2013-05-01

Fire accidents pose a serious threat to nuclear facilities. It is imperative that transport casks or shielded containers designed to transport/contain radiological materials have the ability to withstand a hypothetical fire. A numerical simulation was performed for a shielded container constructed of stainless steel and lead engulfed in a hypothetical fire as outlined by 10 CFR §71.73. The purpose of this analysis was to determine the thermal response of the container during and after the fire. The thermal model shows that after 30 minutes of fire, the stainless steel will maintain its integrity and not melt. However, the lead shieldingmore » will melt since its temperature exceeds the melting point. Due to the method of construction of the container under consideration, ample void space must be provided to allow for thermal expansion of the lead upon heating and melting, so as to not overstress the weldment.« less

Automatic weld torch guidance control system

NASA Technical Reports Server (NTRS)

Smaith, H. E.; Wall, W. A.; Burns, M. R., Jr.

1982-01-01

A highly reliable, fully digital, closed circuit television optical, type automatic weld seam tracking control system was developed. This automatic tracking equipment is used to reduce weld tooling costs and increase overall automatic welding reliability. The system utilizes a charge injection device digital camera which as 60,512 inidividual pixels as the light sensing elements. Through conventional scanning means, each pixel in the focal plane is sequentially scanned, the light level signal digitized, and an 8-bit word transmitted to scratch pad memory. From memory, the microprocessor performs an analysis of the digital signal and computes the tracking error. Lastly, the corrective signal is transmitted to a cross seam actuator digital drive motor controller to complete the closed loop, feedback, tracking system. This weld seam tracking control system is capable of a tracking accuracy of + or - 0.2 mm, or better. As configured, the system is applicable to square butt, V-groove, and lap joint weldments.

Keyhole and weld shapes for plasma arc welding under normal and zero gravity

NASA Technical Reports Server (NTRS)

Keanini, R. G.; Rubinsky, B.

1990-01-01

A first order study of the interfacial (keyhole) shape between a penetrating argon plasma arc jet and a stationary liquid metal weld pool is presented. The interface is determined using the Young-Laplace equation by assuming that the plasma jet behaves as a one-dimensional ideal gas flow and by neglecting flow within the weld pool. The solution for the keyhole shape allows an approximate determination of the liquid-solid metal phase boundary location based on the assumption that the liquid melt is a stagnant thermal boundary layer. Parametric studies examine the effect of plasma mass flow rate, initial plasma enthalpy, liquid metal surface tension, and jet shear on weldment shape under both normal and zero gravity. Among the more important findings of this study is that keyhole and weld geometries are minimally affected by gravity, suggesting that data gathered under gravity can be used in planning in-space welding.

Microstructural and mechanical properties on friction welding of dissimilar metals used in motor vehicles

NASA Astrophysics Data System (ADS)

Jesudoss Hynes, N. Rajesh; Shenbaga Velu, P.

2018-02-01

In the last two decades, major car manufacturing companies are exploring the possibilities of joining magnesium with aluminium, via friction welding technique for many crucial automotive applications. Our primary objective, is to carry out an experimental investigation in order to study the behaviour of dissimilar joints. The microscopic structure at the welded joint interface was analysed using an optical microscopy and scanning electron microscope. It was found that, by increasing the value of friction time, the value of the tensile strength increases and the result of tensile strength is found to be 120 MPa at a friction time of 10 s. Micro hardness was found to be higher at the interface of the weldment due to the development of a brittle intermetallic compound. Micro structural studies using SEM reveals, distinct zones such as an unaffected parent metal zone, the heat affected zone, a thermo-mechanically affected zone and a fully deformed plasticised zone.

Development of advanced high strength tantalum base alloys. Phase 3: Influence of metallurgical condition on the mechanical properties of ASTAR-811C sheet

NASA Technical Reports Server (NTRS)

Ammon, R. L.; Buckman, R. W., Jr.; Harrod, D. L.

1972-01-01

Metallurgical condition was shown to have a significant effect on the creep properties of ASTAR-811C (Ta-8W-1Re-0.7Hf-0.025C) sheet. Cold worked material exhibited creep rates 30 times higher than solution annealed material and 10 times greater than for recrystallized material. Both grain size and the carbide morphology changes as the final annealing temperature was raised from 3000 F to 3600 F. However, the lowest creep rates were achieved for material which retained the high temperature form of the Ta2C precipitate. Samples with GTA weldments had essentially identical properties as recrystallized base metal. Cooling rates from 3600 F of 5, 50, and 800 F deg/min. had little effect on the 2000 and 2400 F creep behavior of ASTAR-811C.

Evaluation of ultrasonics and optimized radiography for 2219-T87 aluminum weldments

NASA Technical Reports Server (NTRS)

Clotfelter, W. N.; Hoop, J. M.; Duren, P. C.

1975-01-01

Ultrasonic studies are described which are specifically directed toward the quantitative measurement of randomly located defects previously found in aluminum welds with radiography or with dye penetrants. Experimental radiographic studies were also made to optimize techniques for welds of the thickness range to be used in fabricating the External Tank of the Space Shuttle. Conventional and innovative ultrasonic techniques were applied to the flaw size measurement problem. Advantages and disadvantages of each method are discussed. Flaw size data obtained ultrasonically were compared to radiographic data and to real flaw sizes determined by destructive measurements. Considerable success was achieved with pulse echo techniques and with 'pitch and catch' techniques. The radiographic work described demonstrates that careful selection of film exposure parameters for a particular application must be made to obtain optimized flaw detectability. Thus, film exposure techniques can be improved even though radiography is an old weld inspection method.

Effect of post weld heat treatment on the microstructure and mechanical properties of ITER-grade 316LN austenitic stainless steel weldments

NASA Astrophysics Data System (ADS)

Xin, Jijun; Fang, Chao; Song, Yuntao; Wei, Jing; Xu, Shen; Wu, Jiefeng

2017-04-01

The effect of postweld heat treatment (PWHT) on the microstructure and mechanical properties of ITER-grade 316LN austenitic stainless steel joints with ER316LMn filler material was investigated. PWHT aging was performed for 1 h at four different temperatures of 600 °C, 760 °C, 870 °C and 920 °C, respectively. The microstructure revealed the sigma phase precipitation occurred in the weld metals heat-treated at the temperature of 870 °C and 920 °C. The PWHT temperatures have the less effect on the tensile strength, and the maximum tensile strength of the joints is about 630 MPa, reaching the 95% of the base metal, whereas the elongation is enhanced with the rise of PWHT temperatures. Meanwhile, the sigma phase precipitation in the weld metals reduces the impact toughness.

Development of references of anomalies detection on P91 material using Self-Magnetic Leakage Field (SMLF) technique

NASA Astrophysics Data System (ADS)

Husin, Shuib; Afiq Pauzi, Ahmad; Yunus, Salmi Mohd; Ghafar, Mohd Hafiz Abdul; Adilin Sekari, Saiful

2017-10-01

This technical paper demonstrates the successful of the application of self-magnetic leakage field (SMLF) technique in detecting anomalies in weldment of a thick P91 materials joint (1 inch thickness). Boiler components such as boiler tubes, stub boiler at penthouse and energy piping such as hot reheat pipe (HRP) and H-balance energy piping to turbine are made of P91 material. P91 is ferromagnetic material, therefore the technique of self-magnetic leakage field (SMLF) is applicable for P91 in detecting anomalies within material (internal defects). The technique is categorized under non-destructive technique (NDT). It is the second passive method after acoustic emission (AE), at which the information on structures radiation (magnetic field and energy waves) is used. The measured magnetic leakage field of a product or component is a magnetic leakage field occurring on the component’s surface in the zone of dislocation stable slipbands under the influence of operational (in-service) or residual stresses or in zones of maximum inhomogeneity of metal structure in new products or components. Inter-granular and trans-granular cracks, inclusion, void, cavity and corrosion are considered types of inhomogeneity and discontinuity in material where obviously the output of magnetic leakage field will be shown when using this technique. The technique does not required surface preparation for the component to be inspected. This technique is contact-type inspection, which means the sensor has to touch or in-contact to the component’s surface during inspection. The results of application of SMLF technique on the developed P91 reference blocks have demonstrated that the technique is practical to be used for anomaly inspection and detection as well as identification of anomalies’ location. The evaluation of this passive self-magnetic leakage field (SMLF) technique has been verified by other conventional non-destructive tests (NDTs) on the reference blocks where simulated defects/anomalies have been developed inside at the weldment. The results from the inspection test showed that the signatures of magnetic leakage field gradient distribution prove that the peak is found on the location of defect/anomaly in the reference block. It is in agreement with the evidence of anomaly that seen in the radiography test film (RT).

Detection of Cracks at Welds in Steel Tubing Using Flux Focusing Electromagnetic Probe

NASA Technical Reports Server (NTRS)

Wincheski, Buzz; Fulton, Jim; Nath, Shridhar; Simpson, John; Namkung, Min

1994-01-01

The inspection of weldments in critical pressure vessel joints is a major concern in the nuclear power industry. Corrosive environments can speed the fatigue process and access to the critical area is often limited. Eddy current techniques have begun to be used to help overcome these obstacles [1]. As direct contact and couplants are not required, remote areas can be inspected by simply snaking an eddy current coil into the intake tube of the vessel. The drawback of the eddy current method has been the high sensitivity to small changes in the conductivity and permeability of the test piece which are known to vary at weldments [1]. The flaw detection mechanism of the flux focusing electromagnetic probe can help alleviate these difficulties and provide a unique capability for detecting longitudinal fatigue cracks in critical tube structures. The Flux Focusing Electromagnetic Flaw Detector, originally invented for the detection of fatigue and corrosion damage in aluminum plates [2-3], has been adapted for use in testing steel tubing for longitudinal fatigue cracks. The modified design allows for the probe to be placed axisymmetrically into the tubing, inducing eddy currents in the tube wall. The pickup coil of the probe is fixed slightly below the primary windings and is rotated 90 so that its axis is normal to the tube wall. The magnetic flux of the primary coil is focused through the use of ferromagnetic material so that in the absence of fatigue damage there will be no flux linkage with the pickup coil. The presence of a longitudinal fatigue crack will cause the eddy currents induced in the tube wall to flow around the flaw and directly under the pickup coil. The magnetic field associated with these currents will then link the pickup coil and an unambiguous increase in the output voltage of the probe will be measured. The use of the flux focusing electromagnetic probe is especially suited for the detection of flaws originating at or near tube welds. The probe is shown to discriminate against signals due solely to the weld joint so that flaw signals are not hidden in the background in these locations. Experimental and finite element modeling results are presented for the flaw detection capabilities of the probe in stainless steel tubes.

CHARACTERIZATION OF DEFECTS IN ALLOY 152, 52 AND 52M WELDS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bruemmer, Stephen M.; Toloczko, Mychailo B.; Olszta, Matthew J.

2009-08-27

Defect distributions have been documented by optical metallography, scanning electron microscopy and electron backscatter diffraction in alloy 152 and 52 mockups welds, alloy 52 and 52M overlay mockups and an alloy 52M inlay. Primary defects were small cracks at grain boundaries except for more extensive cracking in the dilution zone of an alloy 52 overlay on 304SS. Detailed characterizations of the dilution zone cracks were performed by analytical transmission electron microscopy identifying grain boundary titanium-nitride precipitation associated with the intergranular separations. I. INTRODUCTION Weldments continue to be a primary location of stress-corrosion cracking (SCC) in light-water reactor systems. While problemsmore » related to heat-affected-zone (HAZ) sensitization and intergranular (IG) SCC of austenitic stainless alloys in boiling-water reactors (BWRs) have been significantly reduced, SCC has now been observed in HAZs of non-sensitized materials and in dissimilar metal welds where Ni-base alloy weld metals are used. IGSCC in weld metals has been observed in both BWRs and pressurized water reactors (PWRs) with recent examples for PWR pressure vessel penetrations producing the most concern. This has led to the replacement of alloy 600/182/82 welds with higher Cr, more corrosion-resistant replacement materials (alloy 690/152/52/52M). Complicating this issue has been a known susceptibility to cracking during welding [1-7] of these weld metals. There is a critical need for an improved understanding of the weld metal metallurgy and defect formation in Ni-base alloy welds to effectively assess long-term performance. A series of macroscopic to microscopic examinations were performed on available mockup welds made with alloy 52 or alloy 152 plus selected overlay and inlay mockups. The intent was to expand our understanding of weld metal structures in simulated LWR service components with a focus on as-welded defects. Microstructural features, defect distributions, defect characteristics and weld residual strains were examined by optical metallography, scanning electron microscopy, electron backscatter diffraction and transmission electron microscopy. Industry-supplied mock-up welds were characterized including alloy 52 and 152 weldments, alloy 52M overlay and inlay welds, and an alloy 52 overlay. II. WELDMENTS II.A. Alloy 52 and 152 Weld Mockups The alloy 52 and 152 weld mockups were fabricated by MHI for the Kewaunee reactor and were obtained from the EPRI NDE Center. The mockups were U-groove welds joining two plates of 304SS as shown in Figure 1. Alloy 152 butter (heat 307380) was placed on the U-groove surface for both mockups by shielded metal arc welding (SMAW). For the alloy 152 weld mockup, the alloy 152 fill (heat 307380) was also applied using SMAW while for the alloy 52 weld mockup, the alloy 52 fill (heat NX2686JK) was applied using gas tungsten arc welding (GTAW). Welding parameters for the fill materials were substantially different with the alloy 152 SMAW having a deposition speed of 4-25 cm/min with a current of 95-145 A and the alloy 52 GTAW having a deposition speed of 4-10 cm/min with a current of 150-300 A. One prominent feature in these mockup welds is the presence of a crack starting at the 304SS butt joint at the bottom of the U-groove and extending up into the weld. It appears that the 304SS plate on either side of the butt joint acted as an anchor for the weld resulting in a stress rise across the slit that drove crack formation and extension up into the fill weld. As will be shown in the next section, the extent of the cracking around this stress riser was much greater in the MHI 52 weld mockup.« less

Welding and Weldability of AZ31B by Gas Tungsten Arc and Laser Beam Welding Processes

NASA Astrophysics Data System (ADS)

Lathabai, S.; Barton, K. J.; Harris, D.; Lloyd, P. G.; Viano, D. M.; McLean, A.

Welding will play an important role in the fabrication of modular lightweight structures based on magnesium alloy die castings, extrusion profiles and wrought products. Minimisation of rejection rates during fabrication requires that satisfactory weldability be established for a particular combination of materials and welding procedures. In this paper, we present the results of a study to quantify the weldability of wrought alloy AZ31B by gas tungsten arc (GTA) and laser beam (LB) welding processes. The susceptibility to weld metal solidification cracking was evaluated using the Circular Patch weldability test. Operating windows of welding parameters for crack-free and porosity-free GTA and LB welding were identified, based on which welding procedures were developed for sheet and plate AZ31B. The microstructure and mechanical properties of welded test plates were assessed, leading to a better understanding of microstructurat development and structure-property relationships in GTA and LB weldments in AZ31B.

A process model for the heat-affected zone microstructure evolution in duplex stainless steel weldments: Part II. Application to electron beam welding

NASA Astrophysics Data System (ADS)

Hemmer, H.; Grong, Ø.; Klokkehaug, S.

2000-03-01

In the present investigation, a process model for electron beam (EB) welding of different grades of duplex stainless steels (i.e. SAF 2205 and 2507) has been developed. A number of attractive features are built into the original finite element code, including (1) a separate module for prediction of the penetration depth and distribution of the heat source into the plate, (2) adaptive refinement of the three-dimensional (3-D) element mesh for quick and reliable solution of the differential heat flow equation, and (3) special subroutines for calculation of the heat-affected zone (HAZ) microstructure evolution. The process model has been validated by comparison with experimental data obtained from in situ thermocouple measurements and optical microscope examinations. Subsequently, its aptness to alloy design and optimization of welding conditions for duplex stainless steels is illustrated in different numerical examples and case studies pertaining to EB welding of tubular joints.

Stress Corrosion Cracking of Ferritic Materials for Fossil Power Generation Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pawel, Steven J; Siefert, John A.

2014-01-01

Creep strength enhanced ferritic (CSEF) steels Grades 23, 24, 91, and 92 have been widely implemented in the fossil fired industry for over two decades. The stress corrosion cracking (SCC) behavior of these materials with respect to mainstay Cr-Mo steels (such as Grades 11, 12 and 22) has not been properly assessed, particularly in consideration of recent reported issues of SCC in CSEF steels. This report details the results of Jones test exposures of a wide range of materials (Grades 11, 22, 23, 24, and 92), material conditions (as-received, improper heat treatments, normalized, weldments) and environments (salt fog; tube cleaningmore » environments including decreasing, scale removal, and passivation; and high temperature water) to compare the susceptibility to cracking of these steels. In the as-received (normalized and tempered) condition, none of these materials are susceptible to SCC in the environments examined. However, in the hardened condition, certain combinations of environment and alloy reveal substantial SCC susceptibility.« less

Experimental Investigation and Optimization of TIG Welding Parameters on Aluminum 6061 Alloy Using Firefly Algorithm

NASA Astrophysics Data System (ADS)

Kumar, Rishi; Mevada, N. Ramesh; Rathore, Santosh; Agarwal, Nitin; Rajput, Vinod; Sinh Barad, AjayPal

2017-08-01

To improve Welding quality of aluminum (Al) plate, the TIG Welding system has been prepared, by which Welding current, Shielding gas flow rate and Current polarity can be controlled during Welding process. In the present work, an attempt has been made to study the effect of Welding current, current polarity, and shielding gas flow rate on the tensile strength of the weld joint. Based on the number of parameters and their levels, the Response Surface Methodology technique has been selected as the Design of Experiment. For understanding the influence of input parameters on Ultimate tensile strength of weldment, ANOVA analysis has been carried out. Also to describe and optimize TIG Welding using a new metaheuristic Nature - inspired algorithm which is called as Firefly algorithm which was developed by Dr. Xin-She Yang at Cambridge University in 2007. A general formulation of firefly algorithm is presented together with an analytical, mathematical modeling to optimize the TIG Welding process by a single equivalent objective function.

Titanium Alloys Thin Sheet Welding with the Use of Concentrated Solar Energy

NASA Astrophysics Data System (ADS)

Pantelis, D. I.; Kazasidis, M.; Karakizis, P. N.

2017-12-01

The present study deals with the welding of titanium alloys thin sheets 1.3 mm thick, with the use of concentrated solar energy. The experimental part of the work took place at a medium size solar furnace at the installation of the Centre National de la Recherche Scientifique, at Odeillo, in Southern France, where similar and dissimilar defect-free welds of titanium Grades 4 and 6 were achieved, in the butt joint configuration. After the determination of the appropriate welding conditions, the optimum welded structures were examined and characterized microstructurally, by means of light optical microscopy, scanning electron microscopy, and microhardness testing. In addition, test pieces extracted from the weldments were tested under uniaxial tensile loading aiming to the estimation of the strength and the ductility of the joint. The analysis of the experimental results and the recorded data led to the basic concluding remarks which demonstrate increased hardness distribution inside the fusion area and severe loss of ductility, but adequate yield and tensile strength of the welds.

Investigation of a Modified 9Cr-1Mo (P91) Pipe Failure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Klueh, Ronald L; Shingledecker, John P

2006-04-01

A modified 9Cr-1Mo feedwater (condensate) line at an Eastman Chemical Company plant failed in January 2005. The line was in continuous service since start-up December 2001 until failure. The Plant Superintendent estimated there were three thermal cycles since start-up, although there may have been as many as 25 thermal cycles during commissioning. Normal operating temperature was 325 F (163 C) and pressure was 1762 psig. The line was steam traced with the tracing activated only when ambient outdoor temperature dropped to 40 F (5 C). A modified 9Cr-1Mo steel (P91) pipe failure in a feedwater line in a chemical plantmore » was investigated. The failure occurred in the vicinity of an elbow produced with socket welds of the pipe to the elbow. Based on metallography and hardness measurements, it was concluded that failure occurred because of an improper post-weld heat treatment of the socket weldment.« less

Influence of Temperature and Chloride Concentration on Passivation Mechanism and Corrosion of a DSS2209 Welded Joint

NASA Astrophysics Data System (ADS)

Hachemi, Hania; Azzaz, Mohamed; Djeghlal, Mohamed Elamine

2016-10-01

The passivity behavior of a 2209 duplex stainless steel welded joint was investigated using potentiodynamic polarization, Mott-Schottky analysis and EIS measurements. In order to evaluate the contribution of temperature, chloride concentration and microstructure, a sequence of polarization tests were carried out in aerated NaCl solutions selected according to robust design of a three level-three factors Taguchi L9 orthogonal array. Analysis of signal-to-noise ratio and ANOVA were achieved on all measured data, and the contribution of every control factor was estimated. The results showed that the corrosion resistance of 2209 duplex stainless steel welded joint is related to the evolution of the passive film formed on the surface. It was found that the passive film on the welded zone possessed n- and p-type semiconductor characteristics. With the increase of solution temperature and chlorides concentration, the corrosion resistance of the passive film is more affected in the weldment than in the base metal.

Continuous AE crack monitoring of a dissimilar metal weldment at Limerick Unit 1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hutton, P.H.; Friesel, M.A.; Dawson, J.F.

1993-12-01

Acoustic emission (AE) technology for continuous surveillance of a reactor component(s) to detect crack initiation and/or crack growth has been developed at Pacific Northwest Laboratory (PNL). The technology was validated off-reactor in several major tests, but it had not been validated by monitoring crack growth on an operating reactor system. A flaw indication was identified during normal inservice inspection of piping at Philadelphia Electric Company (PECO) Limerick Unit 1 reactor during the 1989 refueling outage. Evaluation of the flaw indication showed that it could remain in place during the subsequent fuel cycle without compromising safety. The existence of this flawmore » indication offered a long sought opportunity to validate AE surveillance to detect and evaluate crack growth during reactor operation. AE instrumentation was installed by PNL and PECO to monitor the flaw indication during two complete fuel cycles. This report discusses the results obtained from the AE monitoring over the period May 1989 to March 1992 (two fuel cycles).« less

Modifications of Hinge Mechanisms for the Mobile Launcher

NASA Technical Reports Server (NTRS)

Ganzak, Jacob D.

2018-01-01

The further development and modifications made towards the integration of the upper and lower hinge assemblies for the Exploration Upper Stage umbilical are presented. Investigative work is included to show the process of applying updated NASA Standards within component and assembly drawings for selected manufacturers. Component modifications with the addition of drawings are created to precisely display part geometries and geometric tolerances, along with proper methods of fabrication. Comparison of newly updated components with original Apollo era components is essential to correctly model the part characteristics and parameters, i.e. mass properties, material selection, weldments, and tolerances. 3-Dimensional modeling software is used to demonstrate the necessary improvements. In order to share and corroborate these changes, a document management system is used to store the various components and associated drawings. These efforts will contribute towards the Mobile Launcher for Exploration Mission 2 to provide proper rotation of the Exploration Upper Stage umbilical, necessary for providing cryogenic fill and drain capabilities.

The influence of process parameters on porosity formation in hybrid LASER-GMA welding of AA6082 aluminum alloy

NASA Astrophysics Data System (ADS)

Ascari, Alessandro; Fortunato, Alessandro; Orazi, Leonardo; Campana, Giampaolo

2012-07-01

This paper deals with an experimental campaign carried out on AA6082 8 mm thick plates in order to investigate the role of process parameters on porosity formation in hybrid LASER-GMA welding. Bead on plate weldments were obtained on the above mentioned aluminum alloy considering the variation of the following process parameters: GMAW current (120 and 180 A for short-arc mode, 90 and 130 A for pulsed-arc mode), arc transfer mode (short-arc and pulsed-arc) and mutual distance between arc and LASER sources (0, 3 and 6 mm). Porosities occurring in the fused zone were observed by means of X-ray inspection and measured exploiting an image analysis software. In order to understand the possible correlation between process parameters and porosity formation an analysis of variance statistical approach was exploited. The obtained results pointed out that GMAW current is significant on porosity formation, while the distance between the sources do not affect this aspect.

Theoretical prediction of welding distortion in large and complex structures

NASA Astrophysics Data System (ADS)

Deng, De-An

2010-06-01

Welding technology is widely used to assemble large thin plate structures such as ships, automobiles, and passenger trains because of its high productivity. However, it is impossible to avoid welding-induced distortion during the assembly process. Welding distortion not only reduces the fabrication accuracy of a weldment, but also decreases the productivity due to correction work. If welding distortion can be predicted using a practical method beforehand, the prediction will be useful for taking appropriate measures to control the dimensional accuracy to an acceptable limit. In this study, a two-step computational approach, which is a combination of a thermoelastic-plastic finite element method (FEM) and an elastic finite element with consideration for large deformation, is developed to estimate welding distortion for large and complex welded structures. Welding distortions in several representative large complex structures, which are often used in shipbuilding, are simulated using the proposed method. By comparing the predictions and the measurements, the effectiveness of the two-step computational approach is verified.

Experimental Investigations on Formability of Aluminum Tailor Friction Stir Welded Blanks in Deep Drawing Process

NASA Astrophysics Data System (ADS)

Kesharwani, R. K.; Panda, S. K.; Pal, S. K.

2015-02-01

In the present work, tailor friction stir welded blanks (TFSWBs) were fabricated successfully using 2.0-mm-thick AA5754-H22 and AA5052-H32 sheet metals with optimized tool design and process parameters. Taguchi L9 orthogonal array has been used to design the friction stir welding experiments, and the Grey relational analysis has been applied for the multi objective optimization in order to maximize the weld strength and total elongation reducing the surface roughness and energy consumption. The formability of the TFSWBs and parent materials was evaluated and compared in terms of limiting drawing ratio (LDR) using a conventional circular die. It was found that the formability of the TFSWBs was comparable with that of both the parent materials without failure in the weldment. A modified conical tractrix die (MCTD) was proposed to enhance the LDR of the TFSWBs. It was found that the formability was improved by 27% using the MCTD.

Abnormal macropore formation during double-sided gas tungsten arc welding of magnesium AZ91D alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shen Jun; You Guoqiang; Long Siyuan

2008-08-15

One of the major concerns during gas tungsten arc (GTA) welding of cast magnesium alloys is the presence of large macroporosity in weldments, normally thought to occur from the presence of gas in the castings. In this study, a double-sided GTA welding process was adopted to join wrought magnesium AZ91D alloy plates. Micropores were formed in the weld zone of the first side that was welded, due to precipitation of H{sub 2} as the mushy zone freezes. When the reverse side was welded, the heat generated caused the mushy zone in the initial weld to reform. The micropores in themore » initial weld then coalesced and expanded to form macropores by means of gas expansion through small holes that are present at the grain boundaries in the partially melted zone. Macropores in the partially melted zone increase with increased heat input, so that when a filler metal is used the macropores are smaller in number and in size.« less

Welding of nickel-base superalloys having a nil-ductility range

NASA Technical Reports Server (NTRS)

Smashey, Russell W. (Inventor); Kelly, Thomas J. (Inventor); Snyder, John H. (Inventor); Sheranko, Ronald L. (Inventor)

1999-01-01

An article made of a nickel-base superalloy having a nil-ductility range from the solidus temperature of the alloy to about 600.degree. F. below the solidus temperature is welded, as for example in the weld repair of surface cracks, by removing foreign matter from the area to be welded, first stress relieving the article, adjusting the temperature of the article to a welding temperature of from about 1800.degree. F. to about 2100.degree. F., welding a preselected area in an inert atmosphere at the welding temperature, and second stress relieving the article. Welding is preferably accomplished by striking an arc in the preselected area so as to locally melt the alloy in the preselected area, providing a filler metal having the same composition as the nickel-based superalloy of the article, and feeding the filler metal into the arc so that the filler metal is melted and fused with the article to form a weldment upon solidification.

Weldment for austenitic stainless steel and method

DOEpatents

Bagnall, Christopher; McBride, Marvin A.

1985-01-01

For making defect-free welds for joining two austenitic stainless steel mers, using gas tungsten-arc welding, a thin foil-like iron member is placed between the two steel members to be joined, prior to making the weld, with the foil-like iron member having a higher melting point than the stainless steel members. When the weld is formed, there results a weld nugget comprising melted and then solidified portions of the joined members with small portions of the foil-like iron member projecting into the solidified weld nugget. The portions of the weld nugget proximate the small portions of the foil-like iron member which project into the weld nugget are relatively rich in iron. This causes these iron-rich nugget portions to display substantial delta ferrite during solidification of the weld nugget which eliminates weld defects which could otherwise occur. This is especially useful for joining austenitic steel members which, when just below the solidus temperature, include at most only a very minor proportion of delta ferrite.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feng, Zhili; Bunn, Jeffrey R; Tzelepis, Demetrios A

Hydrogen induced cracking (HIC) has been a persistent issue in welding of high-strength steels. Mitigating residual stresses is one of the most efficient ways to control HIC. The current study develops a proactive in-process weld residual stress mitigation technique, which manipulates the thermal expansion and contraction sequence in the weldments during welding process. When the steel weld is cooled after welding, martensitic transformation will occur at a temperature below 400 C. Volume expansion in the weld due to the martensitic transformation will reduce tensile stresses in the weld and heat affected zone and in some cases produce compressive residual stressesmore » in the weld. Based on this concept, a customized filler wire which undergoes a martensitic phase transformation during cooling was developed. The new filler wire shows significant improvement in terms of reducing the tendency of HIC in high strength steels. Bulk residual stress mapping using neutron diffraction revealed reduced tensile and compressive residual stresses in the welds made by the new filler wire.« less

Process Model for Friction Stir Welding

NASA Technical Reports Server (NTRS)

Adams, Glynn

1996-01-01

Friction stir welding (FSW) is a relatively new process being applied for joining of metal alloys. The process was initially developed by The Welding Institute (TWI) in Cambridge, UK. The FSW process is being investigated at NASA/MSEC as a repair/initial weld procedure for fabrication of the super-light-weight aluminum-lithium shuttle external tank. The FSW investigations at MSFC were conducted on a horizontal mill to produce butt welds of flat plate material. The weldment plates are butted together and fixed to a backing plate on the mill bed. A pin tool is placed into the tool holder of the mill spindle and rotated at approximately 400 rpm. The pin tool is then plunged into the plates such that the center of the probe lies at, one end of the line of contact, between the plates and the shoulder of the pin tool penetrates the top surface of the weldment. The weld is produced by traversing the tool along the line of contact between the plates. A lead angle allows the leading edge of the shoulder to remain above the top surface of the plate. The work presented here is the first attempt at modeling a complex phenomenon. The mechanical aspects of conducting the weld process are easily defined and the process itself is controlled by relatively few input parameters. However, in the region of the weld, plasticizing and forging of the parent material occurs. These are difficult processes to model. The model presented here addresses only variations in the radial dimension outward from the pin tool axis. Examinations of the grain structure of the weld reveal that a considerable amount of material deformation also occurs in the direction parallel to the pin tool axis of rotation, through the material thickness. In addition, measurements of the axial load on the pin tool demonstrate that the forging affect of the pin tool shoulder is an important process phenomenon. Therefore, the model needs to be expanded to account for the deformations through the material thickness and the forging affect of the shoulder. The energy balance at the boundary of the plastic region with the environment required that energy flow away from the boundary in both radial directions. One resolution to this problem may be to introduce a time dependency into the process model, allowing the energy flow to oscillate across this boundary. Finally, experimental measurements are needed to verify the concepts used here and to aid in improving the model.

Advanced Ultrasupercritical (AUSC) Tube Membrane Panel Development

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pschirer, James; Burgess, Joshua; Schrecengost, Robert

Alstom Power Inc., a wholly owned subsidiary of the General Electric Company (GE), has completed the project “Advanced Ultrasupercritical (AUSC) Tube Membrane Panel Development” under U.S. Department of Energy (DOE) Award Number DE-FE0024076. This project was part of DOE’s Novel Crosscutting Research and Development to Support Advanced Energy Systems program. AUSC Tube Membrane Panel Development was a two and one half year project to develop and verify the manufacturability and serviceability of welded tube membrane panels made from high performance materials suitable for the AUSC steam cycles, defined as high pressure steam turbine inlet conditions of 700-760°C (1292-1400°F) and 24.5-35MPamore » (3500-5000psi). The difficulty of this challenge lies in the fact that the membrane-welded construction imposes demands on the materials that are unlike any that exist in other parts of the boiler. Tube membrane panels have been designed, fabricated, and installed in boilers for over 50 years with relatively favorable experience when fabricated from carbon and Cr-Mo low alloy steels. The AUSC steam cycle requires membrane tube panels fabricated from materials that have not been used in a weldment with metal temperatures in the range of 582-610°C (1080-1130°F). Fabrication materials chosen for the tubing were Grade 92 and HR6W. Grade 92 is a creep strength enhanced ferritic Cr-Mo alloy and HR6W is a high nickel alloy. Once the materials were chosen, GE performed the engineering design of the panels, prepared shop manufacturing drawings, and developed manufacturing and inspection plans. After the materials were purchased, GE manufactured and inspected the tube membrane panels, determined if post fabrication heat treatment of the tube membrane panels was needed, performed pre- and post-weld heat treatment on the Grade 92 panels, conducted final nondestructive inspection of any heat treated tube membrane panels, conducted destructive inspection of the completed tube membrane panels,and performed simulated shop repairs on the panel fabricated using Grade 92. GE executed the program as the prime contractor under the direction of Principal Investigator Mr. James Pschirer. Other participants in this project included GE Boiler Engineering, GE Chattanooga Manufacturing, GE Materials Technology Center, GE Rocky Mountain Service Center, and a Technical Consultant from Electric Power Research Institute (EPRI).« less

Report on the completion of the procurement of the first heat of Alloy 709

DOE Office of Scientific and Technical Information (OSTI.GOV)

Natesan, K.; Zhang, X.; Sham, T. -L.

2017-01-01

This report provides details on the completion of the procurement of the first commercial-sized heat of Alloy 709. The report is a Level 3 deliverable in FY17 (M3AT- 17OR1602053), under the Work Package AT-17OR160205, “Advanced Alloy Development” performed by Oak Ridge National Laboratory, as part of Advanced Structural Materials Program for the Advanced Reactor Technologies (ART). This work project supports the fabrication scale up effort for Alloy 709 that was started in FY16. The effort culminated in the placement of a Purchase Order in August 2016 with a commercial vendor to melt an Alloy 709 heat using industrial melt practice.more » Four ingots, totaling about 45,000 lb, had been bottom-poured from the melt in September 2016. Two of the ingots were hot rolled into 1.2”x60”x155” and 1.1”x60”x100” plates using standard hot rolling process in FY17. Some small test pieces were cut from the asrolled plates and sent to Argonne National Laboratory (ANL) for archival. The plates were then heat treated and surface pickled by the vendor. The plates were subsequently delivered to ANL and Oak Ridge National Laboratory (ORNL). Properties and microstructure screening were performed on these plates upon delivery in February 2017 at ANL. Several samples were cut from the as-rolled and heattreated plates and were analyzed for their microstructures, hardness values, grain sizes, and room temperature tensile properties. The results indicate that the scaled-up heat of Alloy 709 fabricated using commercial practice exhibit tensile properties that exceed the minimum values specified in the ASME Code Case for commercial heat of NF709. These plates will be used to support base metal testing for the 650°C, 100,000-h Alloy 709 Code Case development, for fabrication of weldments, and for the NEUP projects.« less

On Improving the Quality of Gas Tungsten Arc Welded 18Ni 250 Maraging Steel Rocket Motor Casings

NASA Astrophysics Data System (ADS)

Gupta, Renu N.; Raja, V. S.; Mukherjee, M. K.; Narayana Murty, S. V. S.

2017-10-01

In view of their excellent combination of strength and toughness, maraging steels (18Ni 250 grade) are widely used for the fabrication of large sized solid rocket motor casings. Gas tungsten arc welding is commonly employed to fabricate these thin walled metallic casings, as the technique is not only simple but also provides the desired mechanical properties. However, sometimes, radiographic examination of welds reveals typical unacceptable indications requiring weld repair. As a consequence, there is a significant drop in weld efficiency and productivity. In this work, the nature and the cause of the occurrence of these defects have been investigated and an attempt is made to overcome the problem. It has been found that weld has a tendency to form typical Ca and Al oxide inclusions leading to the observed defects. The use of calcium fluoride flux has been found to produce a defect free weld with visible effect on weld bead finish. The flux promotes the separation of inclusions, refines the grain size and leads to significant improvement in mechanical properties of the weldment.

Microstructural and Electrochemical Evaluation of Fusion Welded Low-Nickel and 304 SS at Different Heat Input

NASA Astrophysics Data System (ADS)

Bansod, Ankur V.; Patil, Awanikumar P.; Moon, Abhijeet P.; Shukla, Sourabh

2017-12-01

The present research study investigates the effect of heat input using E 308 electrode (controlled by welding current, i.e., 70, 85 and 100 A) on microstructure, mechanical properties and corrosion behavior of low-nickel and 304 stainless steel (SS) weldments produced by shielded metal arc welding technique. SEM investigation shows that with the higher heat input, δ-ferrite content was reduced. Dendrite and inter-dendritic length is also reduced by lowering the heat input. For all the heat inputs, it is observed that δ-ferrite content was higher in 304 stainless steel (SS) as compared to that of low-nickel austenitic stainless steel (Cr-Mn SS). Considering the heat input for Cr-Mn SS, coarse grains were observed in the heat-affected zone region. For low heat input (LHI), tensile fracture surface has exhibited river-like pattern with dimple appearance. Corrosion studies show better pitting resistance for low heat input (LHI) samples due to higher δ-ferrite present in the weld region. Similarly, higher interphase corrosion resistance is observed in both the SS grades causing more dissolution in the LHI samples.

How to control hydrogen level in (super) duplex stainless steel weldments using the GTAW or GMAW process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mee, V.V.D.; Meelker, H.; Schelde, R.V.D.

1999-01-01

In this investigation, an attempt is made to further the understanding of factors influencing the hydrogen content in duplex stainless steel gas tungsten arc (GTA) and gas metal arc (GMA) welds as well as to what extent it affects hydrogen-induced cracking susceptibility. The results indicated that susceptibility to hydrogen cracking using the GTA or GMA process appears to be limited. In practice, maintaining a moisture level below 10 ppm in the shielding gas is of less importance than the choice of welding parameters. Even a moisture level of 1000 ppm in the shielding gas, in combination with the correct weldingmore » parameters, will result in a sufficient low hydrogen content in the weld. Similarly, a moisture level in the shielding gas below 10 ppm does not necessarily result in low hydrogen content in the weld metal. Although very high ferrite levels were combined with high restrain and high hydrogen content, none of the GMA and GTA welds cracked. Susceptibility to hydrogen cracking is concluded to be limited.« less

Materials studies for magnetic fusion energy applications at low temperatures, 7

NASA Astrophysics Data System (ADS)

Reed, R. P.; Simon, N. J.

1984-05-01

Work leading toward development of strong, tough structural alloys for use in superconducting magnets of magnetic fusion power plants is reported. Low temperature studies were conducted to assess the quantitative dependence of the yield strength, density, and elastic constants of AISI 304 stainless steels upon carbon and nitrogen concentration. Tensile property measurements of developmental austenitic steels confirmed the dependence of yield strength upon temperature. Evidence is presented to show that the flow strength and austenite stability of stainless steels are not significantly affected by 8-T fields at 4 K. Instrumentation developed for low temperature testing included a computer assisted apparatus used to measure threshold fatigue. Low temperature welding research involved an investigation of the weld reinforcement effect on the weld joint strength and measurements of the 4 K fracture toughness of magnesium-chromium steel weldments and electroodes. In the area of non-metallics, a standardized test specimen was devised to aid in screening radiation-resistant composites for magnet insulation. Mechanical properties of concrete mortar and polyurethane foam at 4 K are reported.

More About Arc-Welding Process for Making Carbon Nanotubes

NASA Technical Reports Server (NTRS)

Benavides, Jeanette M.; Leidecker, Henning

2005-01-01

High-quality batches of carbon nanotubes are produced at relatively low cost in a modified atmospheric-pressure electric-arc welding process that does not include the use of metal catalysts. What would normally be a welding rod and a weldment are replaced by an amorphous carbon anode rod and a wider, hollow graphite cathode rod. Both electrodes are water-cooled. The cathode is immersed in ice water to about 0.5 cm from the surface. The system is shielded from air by flowing helium during arcing. As the anode is consumed during arcing at 20 to 25 A, it is lowered to maintain it at an approximately constant distance above the cathode. The process causes carbon nanotubes to form on the lowest 5 cm of the anode. The arcing process is continued until the anode has been lowered to a specified height. The nanotube-containing material is then harvested. The additional information contained in the instant report consists mostly of illustrations of carbon nanotubes and a schematic diagram of the arc-welding setup, as modified for the production of carbon nanotubes.

Correlation of Fracture Behavior With Microstructure in Friction Stir Welded, and Spin Formed AI-Li 2195 Domes

NASA Technical Reports Server (NTRS)

Tayon, Wesley A.; Domack, Marcia S.; Hales, Stephen J.

2012-01-01

Single-piece, spin-formed domes manufactured from friction stir welded (FSW) plates of Al-Li alloy 2195 have the potential to reduce the cost of fabricating cryogenic propellant tanks. Mechanical properties in the completed domes can be related directly to the final material condition and the microstructures developed. However, these new fabrication techniques have resulted in unexpected material challenges, such as abnormal grain growth in the weld nugget and the propensity for fracture in the adjacent thermo-mechanically affected zone (TMAZ). In this study, the microstructure and texture transformations within the TMAZ are related to fracture location in the vicinity of the weldment. The texture variations in the TMAZ are caused primarily by the varying amounts of shear deformation introduced during the FSW process. Grain morphology and microtexture characteristics are examined as a function of location in the TMAZ via electron backscatter diffraction (EBSD). A strong correlation between fracture location and the presence of texture banding in the TMAZ is observed. The fracture path tends to follow a distinct region of low Taylor Factor (TF) grains.

UPT scenarios: Implications for system reliability

NASA Technical Reports Server (NTRS)

Walsh, Daniel W.

1992-01-01

The objective of this project was to examine the corrosion resistance of 316L stainless steel in several urine pre-treat solutions. Four solutions were examined: untreated urine (control); urine pretreated with oxone (potassium peroxymonosulfate sulfate); urine pretreated with sodium hypochlorite (NaOCl); and urine pretreated with ozone (O3). In accordance with current procedures, all solutions but the control were acidified to a pH of 2.5 using sulfuric acid--this suppresses the generation of ammonia in the solutions and is intended to limit microbial growth. Welded and unwelded coupons were exposed to each solution. In addition, Titanium coupons (welded and unwelded) were exposed to biologically active environmental control and life support system (ECLSS) water. Microbial attachment and biofilm growth were monitored. Ozone was examined as a biocide/oxidizer/corrosion preventative (simultaneous addition) and as a remediation method (added one week after exposure). In an unrelated effort, HP 9-4-30 coupons were exposed to biologically active solutions. Corrosion rates for welded and unwelded samples were determined--results were correlated to the ongoing HP 9-4-30 weldment stress corrosion study.

Diffusion welding of MA 6000 and a conventional nickel-base superalloy

NASA Technical Reports Server (NTRS)

Moore, T. J.; Glasgow, T. K.

1985-01-01

A feasibility study of diffusion welding the oxide dispersion strengthened (ODS) alloy MA 6000 to itself and to conventional Ni-base superalloy Udimet 700 was conducted. Butt joints between MA 6000 pieces and lap joints between Udimet 700 and the ODS alloy were produced by hot pressing for 1.25 hr at temperatures ranging from 1000 to 1200 C (1832-2192 F) in vacuum. Following pressing, all weldments were heat treated and machined into mechanical property test specimens. While three different combinations of recrystallized and unrecrystallized MA 6000 butt joints were produced, the unrecrystallized to unrecrystallized joint was most successful as determined by mechanical properties and microstructural examination. Failure to weld the recrystallized material probably related to a lack of adequate deformation at the weld interface. While recrystallized MA 6000 could be diffusion welded to Udimet 700 in places, complete welding over the entire lap joint was not achieved, again due to the lack of sufficient deformation at the faying surfaces. Several methods are proposed to promote the intimate contact necessary for diffusion welding MA 6000 to itself and to superalloys.

Microstructure Characterization and Stress Corrosion Evaluation of Autogenous and Hybrid Friction Stir Welded Al-Cu-Li 2195 Alloy

NASA Technical Reports Server (NTRS)

Li, Zhixian; Arbegast, William J.; Meletis, Efstathios I.

1997-01-01

Friction stir welding process is being evaluated for application on the Al-Cu-Li 2195 Super-Light Weight External Tank of the Space Transportation System. In the present investigation Al-Cu-Li 2195 plates were joined by autogenous friction stir welding (FSW) and hybrid FSW (friction stir welding over existing variable polarity plasma arc weld). Optical microscopy and transmission electron microscopy (TEM) were utilized to characterize microstructures of the weldments processed by both welding methods. TEM observations of autogenous FSW coupons in the center section of the dynamically-recrystallized zone showed an equiaxed recrystallized microstructure with an average grain size of approx. 3.8 microns. No T(sub 1), precipitates were present in the above-mentioned zone. Instead, T(sub B) and alpha precipitates were found in this zone with a lower population. Alternate immersion, anodic polarization, constant load, and slow strain tests were carried out to evaluate the general corrosion and stress-corrosion properties of autogenous and hybrid FSW prepared coupons. The experimental results will be discussed.

Subtask 12B1: Welding development for V-Cr-Ti alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

King, J.F.; Goodwin, G.M.; Grossbeck, M.L.

1995-03-01

Development of the metallurgical and technological basis for the welding of thick sections of V-Cr-Ti alloys. The weldability and weldment properties of the V-5Cr-5Ti alloy have been evaluated. Results for the Sigmajig test of the vanadium alloy were similar to the cracking resistance of stainless steels, and indicates hot-cracking is unlikely to be a problem. Subsize Charpy test results for GTA weld metal in the as-welded condition have shown a significant reduction in toughness compared to the base metal. The weld metal toughness properties were restored to approximately that of the base metal after exposure to a PWHT 950{degrees}C. Themore » subsize Charpy toughness results for the EB weld metal from this same heat of vanadium alloy has shown significant improvement in properties compared to the GTA weld metal and the base metal. Further testing and analysis will be conducted to more fully characterize the properties of weld metal for each welding process and develop a basic understanding of the cause of the toughness decrease in the GTA welds. 5 figs., 1 tab.« less

Characteristics and performance of the variable polarity plasma arc welding process used in the Space Shuttle external tank

NASA Technical Reports Server (NTRS)

Hung, R. J.; Lee, C. C.; Liu, J. W.

1990-01-01

Significant advantages of the Variable Polarity Plasma Arc (VPPA) Welding Process include faster welding, fewer repairs, less joint preparation, reduced weldment distortion, and absence of porosity. Flow profiles and power distribution of argon plasma gas as a working fluid to produce plasma arc jet in the VPPA welding process was analyzed. Major loss of heat transfer for flow through the nozzle is convective heat transfer; for the plasma jet flow between the outlet of the nozzle and workpiece is radiative heat transfer; and for the flow through the keyhole of the workpiece is convective heat transfer. The majority of the power absorbed by the keyhole of the workpiece is used for melting the solid metal workpiece into a molten metallic puddle. The crown and root widths and the crown and root heights can be predicted. An algorithm for promoting automatic control of flow parameters and the dimensions of the final product of the welding specification to be used for the VPPA Welding System operated at MSFC are provided.

Submerged Arc Stainless Steel Strip Cladding—Effect of Post-Weld Heat Treatment on Thermal Fatigue Resistance

NASA Astrophysics Data System (ADS)

Kuo, I. C.; Chou, C. P.; Tseng, C. F.; Lee, I. K.

2009-03-01

Two types of martensitic stainless steel strips, PFB-132 and PFB-131S, were deposited on SS41 carbon steel substrate by a three-pass submerged arc cladding process. The effects of post-weld heat treatment (PWHT) on thermal fatigue resistance and hardness were evaluated by thermal fatigue and hardness testing, respectively. The weld metal microstructure was investigated by utilizing optical microscopy, scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS) and transmission electron microscopy (TEM). Results showed that, by increasing the PWHT temperature, hardness decreased but there was a simultaneous improvement in weldment thermal fatigue resistance. During tempering, carbide, such as (Fe, Cr)23C6, precipitated in the weld metals and molybdenum appeared to promote (Fe, Cr, Mo)23C6 formation. The precipitates of (Fe, Cr, Mo)23C6 revealed a face-centered cubic (FCC) structure with fine grains distributed in the microstructure, thereby effectively increasing thermal fatigue resistance. However, by adding nickel, the AC1 temperature decreased, causing a negative effect on thermal fatigue resistance.

Deformation During Friction Stir Welding

NASA Technical Reports Server (NTRS)

White, Henry J.

2002-01-01

Friction Stir Welding (FSW) is a solid state welding process that exhibits characteristics similar to traditional metal cutting processes. The plastic deformation that occurs during friction stir welding is due to the superposition of three flow fields: a primary rotation of a radially symmetric solid plug of metal surrounding the pin tool, a secondary uniform translation, and a tertiary ring vortex flow (smoke rings) surrounding the tool. If the metal sticks to the tool, the plug surface extends down into the metal from the outer edge of the tool shoulder, decreases in diameter like a funnel, and closes up beneath the pin. Since its invention, ten years have gone by and still very little is known about the physics of the friction stir welding process. In this experiment, an H13 steel weld tool (shoulder diameter, 0.797 in; pin diameter, 0.312 in; and pin length, 0.2506 in) was used to weld three 0.255 in thick plates. The deformation behavior during friction stir welding was investigated by metallographically preparing a plan view sections of the weldment and taking Vickers hardness test in the key-hole region.

Correlation of Fracture Behavior with Microstructure in Friction Stir Welded, and Spin-Formed Al-Li 2195 Domes

NASA Astrophysics Data System (ADS)

Tayon, Wesley A.; Domack, Marcia S.; Hales, Stephen J.

Single-piece, spin-formed domes manufactured from friction stir welded (FSW) plates of Al-Li alloy 2195 have the potential to reduce the cost of fabricating cryogenic propellant tanks. Mechanical properties in the completed domes can be related directly to the final material condition and the microstructures developed. However, these new fabrication techniques have resulted in unexpected material challenges, such as abnormal grain growth in the weld nugget and the propensity for fracture in the adjacent thermo-mechanically affected zone (TMAZ). In this study, the microstructure and texture transformations within the TMAZ are related to fracture location in the vicinity of the weldment. The texture variations in the TMAZ are caused primarily by the varying amounts of shear deformation introduced during the FSW process. Grain morphology and microtexture characteristics are examined as a function of location in the TMAZ via electron backscatter diffraction (EBSD). A strong correlation between fracture location and the presence of texture banding in the TMAZ is observed. The fracture path tends to follow a distinct region of low Taylor Factor (TF) grains.

Considerations on repeated repairing of weldments in Inconel 718 alloy

NASA Technical Reports Server (NTRS)

Bayless, E. O.; Lovoy, C. V.; Mcilwain, M. C.; Munafo, P.

1981-01-01

The effects of repeated weld repairs on the metallurgical characteristics, high cycle fatigue (HCF), and tensile properties of Inconel 718 butt weld joints were determined. A 1/4 in thick plate and a 1/2 in thick plate were used as well as tungsten inert gas welding, and Inconel 718 filler wire. Weld panels were subjected to 2, 6, and 12 repeated repairs and were made in a highly restrained condition. Post weld heat treatments were also conducted with the welded panel in the highly restrained condition. Results indicate that no significant metallurgical anomaly is evident as a result of up to twelve repeated weld repairs. No degradation in fatigue life is noted for up to twelve repeated repairs. Tensile results from specimens which contained up to twelve repeated weld repairs revealed no significant degradation in UTS and YS. However, a significant decrease in elongation is evident with specimens (solution treated and age hardened after welding) which contained twelve repeated repairs. The elongation loss is attributed to the presence of a severe notch on each side (fusion line) of the repair weld bead reinforcement.

Measurement of groove features and dimensions of the vertical test cathode and the choke joint of the superconducting electron gun cavity of the Energy Recovery LINAC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hammons, L.; Ke, M.

2011-10-13

A testing program for the superconducting electron gun cavity that has been designed for the Energy Recovery LINAC is being planned. The goal of the testing program is to characterize the RF properties of the gun cavity at superconducting temperatures and, in particular, to study multipacting that is suspected to be occurring in the choke joint of the cavity where the vertical test cathode is inserted. The testing program will seek to understand the nature and cause of this multipacting and attempt to eliminate it, if possible, by supplying sufficient voltage to the cavity. These efforts are motivated by themore » multipacting issues that have been observed in the processing of the fine-grain niobium gun cavity. This cavity, which is being processed at Thomas Jefferson National Laboratory for Brookhaven, has encountered multipacting at a gradient of approximately 3 MV/m and, to date, has resisted efforts at elimination. Because of this problem, a testing program is being established here in C-AD that will use the large-grain niobium gun cavity that currently resides at Brookhaven and has been used for room-temperature measurements. The large-grain and fine-cavities are identical in every aspect of construction and only differ in niobium grain size. Thus, it is believed that testing and conditioning of the large-grain cavity should yield important insights about the fine-grain cavity. One element of this testing program involves characterizing the physical features of the choke joint of the cavity where the multipacting is believed to be occurring and, in particular the grooves of the joint. The configuration of the cavity and the vertical test cathode is shown in Figure 1. In addition, it is important to characterize the groove of the vertical test cathode. The grooved nature of these two components was specifically designed to prevent multipacting. However, it is suspected that, because of the chemical processing that the fine-grain gun cavity underwent along with the vertical test cathode, the geometry of these grooves was altered, presenting the possibility that multipacting may, in fact, be occurring in this area and contributing to the low gradients that have been observed in the fine-grain cavity. Therefore, the Survey and Alignment group in C-AD engaged in measurements of the cavity joint, shown in Figure 2 and the cathode weldment, shown in Figure 3 for the purpose of characterizing the grooves in both the cavity and the vertical test cathode and comparing the dimensions of the cathode with those of the prints supplied by Advanced Energy Systems (AES), the original designer and manufacturer of both the test cathode and the electron gun cavity, in preparation to have a new one manufactured. The goal was to ensure that the articles as built matched the design prints in preparation for manufacturing a new vertical test cathode. This report describes the data collected by the Survey group in these efforts. The endeavor was challenging for the group given the millimeter-scale dimensions of the grooves and the requirement for high precision.« less

Microstructural Characteristics and Mechanical Properties of an Electron Beam-Welded Ti/Cu/Ni Joint

NASA Astrophysics Data System (ADS)

Zhang, Feng; Wang, Ting; Jiang, Siyuan; Zhang, Binggang; Feng, Jicai

2018-04-01

Electron beam welding experiments of TA15 titanium alloy to GH600 nickel superalloy with and without a copper sheet interlayer were carried out. Surface appearance, microstructure and phase constitution of the joint were examined by optical microscopy, scanning electron microscopy and x-ray diffraction analysis. Mechanical properties of Ti/Ni and Ti/Cu/Ni joint were evaluated based on tensile strength and microhardness tests. The results showed that cracking occurred in Ti/Ni electron beam weldment for the formation of brittle Ni-Ti intermetallics, while a crack-free electron beam-welded Ti/Ni joint can be obtained by using a copper sheet as filler metal. The addition of copper into the weld affected the welding metallurgical process of the electron beam-welded Ti/Ni joint significantly and was helpful for restraining the formation of Ti-Ni intermetallics in Ti/Ni joint. The microstructure of the weld was mainly characterized by a copper-based solid solution and Ti-Cu interfacial intermetallic compounds. Ti-Ni intermetallic compounds were almost entirely suppressed. The hardness of the weld zone was significantly lower than that of Ti/Ni joint, and the tensile strength of the joint can be up to 282 MPa.

Resistance Spot Welding of AA5052 Sheet Metal of Dissimilar Thickness

NASA Astrophysics Data System (ADS)

Mat Din, N. A.; Zuhailawati, H.; Anasyida, A. S.

2016-02-01

Resistance spot welding of dissimilar thickness of AA5052 aluminum alloy was performed in order to investigate the effect of metal thickness on the weldment strength. Resistance spot welding was done using a spot welder machine available in Coraza Systems Sdn Bhd using a hemispherical of chromium copper electrode tip with radius of 6.00 mm under 14 kA of current and 0.02 bar of pressure for all thickness combinations. Lap joint configuration was produced between 2.0 mm thick sheet and 1.2 - 3.2 mm thick sheet, respectively. Microstructure of joint showed asymmetrical nugget shape that was larger on the thicker side indicating larger molten metal volume. Joint 2.0 mm x 3.2 mm sheets has the lowest hardness in both transverse direction and through thickness direction because less heat left in the weld nugget. The microstructure shows that this joint has coarse grains of HAZ. As thickness of sheet metal increased, the failure load of the joints increased. However, there was no linear correlation established between joint strength and metal thickness due to different shape of fusion zone in dissimilar thickness sheet metal.

Friction welding.

NASA Technical Reports Server (NTRS)

Moore, T. J.

1972-01-01

Results of an exploratory study of the structure and properties of friction welds in Udimet 700 (U-700) and TD-nickel (TD-Ni) bar materials, as well as dissimilar U-700/TD-Ni friction welds. Butt welds were prepared by friction welding 12.7-mm-diam U-700 bars and TD-Ni bars. Specimens for elevated temperature tensile and stress rupture testing were machined after a postweld heat treatment. Friction welding of U-700 shows great potential because the welds were found to be as strong as the parent metal in stress rupture and tensile tests at 760 and 980 C. In addition, the weld line was not detectable by metallographic examination after postheating. Friction welds in TD-Ni or between U-700 and TD-Ni were extremely weak at elevated temperatures. The TD-Ni friction welds could support only 9% as much stress as the base metal for 10-hour stress rupture life at 1090 C. The U-700/TD-Ni weld could sustain only 15% as much stress as the TD-Ni parent metal for a 10-hour stress rupture life at 930 C. Thus friction welding is not a suitable joining method for obtaining high-strength TD-Ni or U-700/TD-Ni weldments.

Microstructural Influence on Mechanical Properties in Plasma Microwelding of Ti6Al4V Alloy

NASA Astrophysics Data System (ADS)

Baruah, M.; Bag, S.

2016-11-01

The complexity of joining Ti6Al4V alloy enhances with reduction in sheet thickness. The present work puts emphasis on microplasma arc welding (MPAW) of 500-μm-thick Ti6Al4V alloy in butt joint configuration. Using controlled and regulated arc current, the MPAW process is specifically designed to use in joining of thin sheet components over a wide range of process parameters. The weld quality is assessed by carefully controlling the process parameters and by reducing the formation of oxides. The combined effect of welding speed and current on the weld joint properties is evaluated for joining of Ti6Al4V alloy. The macro- and microstructural characterizations of the weldment by optical microscopy as well as the analysis of mechanical properties by microtensile and microhardness test have been performed. The weld joint quality is affected by specifically designed fixture that controls the oxidation of the joint and introduces high cooling rate. Hence, the solidified microstructure of welded specimen influences the mechanical properties of the joint. The butt joint of titanium alloy by MPAW at optimal process parameters is of very high quality, without any internal defects and with minimum residual distortion.

Microstructural Evolution in Friction Stir Welding of Ti-6Al-4V

NASA Technical Reports Server (NTRS)

Rubisoff, H.; Querin, J.; Magee, D.; Schneider, J.

2008-01-01

Friction stir welding (FSW) is a thermo-mechanical process that utilizes a nonconsumable rotating pin tool to consolidate a weld joint. In the conventional FSW process, the pin tool is responsible for generating both the heat required to soften the material and the forces necessary to deform and combine the weld seam. As such, the geometry of the pin tool is important to the quality of the weld and the process parameters required to produce the weld. Because the geometry of the pin tool is limitless, a reduced set of pin tools was formed to systematically study their effect on the weldment with respect to mechanical properties and resultant microstructure. In this study 0deg, 15deg, 30deg, 45deg, and 60deg tapered, microwave sintered, tungsten carbide (WC) pin tools were used to FSW Ti-6Al-4V. Transverse sections of the weld were used to test for mechanical properties and to document the microstructure using optical microscopy. X-ray diffraction (XRD) was also used to characterize the microstructure in the welds. FSW results for the 45deg and 60deg pin tools are reported in this paper.

Effect of pin tool design on the material flow of dissimilar AA7075-AA6061 friction stir welds

NASA Astrophysics Data System (ADS)

Hasan, Mohammed M.; Ishak, M.; Rejab, M. R. M.

2017-10-01

Tool design is the most influential aspect in the friction stir welding (FSW) technology. Influence of pin tool geometry on material flow pattern are studied in this work during the FSW of dissimilar AA7075 and AA6061 aluminium alloys. Three truncated pin tool profiles (threaded, threaded with single flat, and unthreaded with single flat) were used to prepare the weldments. The workpieces were joined using a custom-made clamping system under 1100 rpm of spindle speed, 300 mm/min of traverse rate and 3° of tilt angle. The metallographic analysis showed that defect-free welds can be produced using the three pin tools with significant changes in the mixing stir zone structure. The results declared that the introducing of the flat on the cone of the probe deviates the pattern of the onion rings without changing the chemical composition of the created layers. This in turn improves the hardness distribution and tensile strength of the welded joint. It was also noted that both heat affected zone (HAZ) and thermal-mechanical affected zone (TMAZ) are similar in composition to their corresponding base materials (BM).

SEM stereo-section fractography (SSF) observations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, X.J.; Tregoning, R.L.; Armstrong, R.W.

1997-12-31

Cleavage initiation in engineering materials is governed by local microstructural inhomogeneities. These features are often the principal reason for the large scatter evident in fracture toughness measurements which, in extreme cases, can mask the fundamental relationship between cracking resistance and global material properties. The SEM stereo-section fractography (SSF) technique can be used to carefully evaluate these local inhomogeneities through simultaneous observation of both the fracture surface and the underlying microstructure. By sectioning the fracture surface close to the cleavage initiation site (within 10 {micro}m), and perpendicular to both the fracture surface and the precrack front, a direct correspondence between initiationmore » and the local microstructure can be established. Information obtained from this technique can provide quantitative input about important, local microstructural features which can then be used to calibrate or create realistic micromechanical models. A compendium of SSF results is presented herein for cleavage cracking in disparate materials (A533B steel plates, MIL-70S multi-pass weldments, and Ti6A14V forgings), under various testing conditions. In each case, the SSF technique was able to unambiguously identify the dominant, local features which triggered cleavage initiation.« less

SEM stereo-section fractography observations. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, X.J.; Tregoning, R.L.; Armstrong, R.W.

1998-05-01

Cleavage initiation in engineering materials is governed by local microstructural inhomogeneities. These features are often the principal reason for the large scatter evident in fracture toughness measurements which, in extreme cases, can mask the fundamental relationship between cracking resistance and global material properties. The SEM stereo-section fractography (SSF) technique can be used to carefully evaluate these local inhomogeneities through simultaneous observation of both the fracture surface and the underlying microstructure. By sectioning the fracture surface close to the cleavage initiation site (within 10 microns), and perpendicular to both the fracture surface and the pre crack front, a direct correspondence betweenmore » initiation and the local microstructure can be established. Information obtained from this technique can provide quantitative input about important, local microstructural features which can then be used to calibrate or create realistic micromechanical models. A compendium of SSF results is presented herein for cleavage cracking in disparate materials (A533B steel plates, MIL-70S multi-pass weldments, and Ti6A14V forgings), under various testing conditions. In each case, the SSF technique was able to unambiguously identify the dominant, local features which triggered cleavage initiation.« less

Friction Stir Welding for Aluminum Metal Matrix Composites (MMC's) (Center Director's Discretionary Fund, Project No. 98-09)

NASA Technical Reports Server (NTRS)

Lee, J. A.; Carter, R. W.; Ding, J.

1999-01-01

This technical memorandum describes an investigation of using friction stir welding (FSW) process for joining a variety of aluminum metal matrix composites (MMC's) reinforced with discontinuous silicon-carbide (SiC) particulate and functional gradient materials. Preliminary results show that FSW is feasible to weld aluminum MMC to MMC or to aluminum-lithium 2195 if the SiC reinforcement is <25 percent by volume fraction. However, a softening in the heat-affected zone was observed and is known to be one of the major limiting factors for joint strength. The pin tool's material is made from a low-cost steel tool H-13 material, and the pin tool's wear was excessive such that the pin tool length has to be manually adjusted for every 5 ft of weldment. Initially, boron-carbide coating was developed for pin tools, but it did not show a significant improvement in wear resistance. Basically, FSW is applicable mainly for butt joining of flat plates. Therefore, FSW of cylindrical articles such as a flange to a duct with practical diameters ranging from 2-5 in. must be fully demonstrated and compared with other proven MMC joining techniques for cylindrical articles.

Microstructural Characteristics and Mechanical Properties of an Electron Beam-Welded Ti/Cu/Ni Joint

NASA Astrophysics Data System (ADS)

Zhang, Feng; Wang, Ting; Jiang, Siyuan; Zhang, Binggang; Feng, Jicai

2018-05-01

Electron beam welding experiments of TA15 titanium alloy to GH600 nickel superalloy with and without a copper sheet interlayer were carried out. Surface appearance, microstructure and phase constitution of the joint were examined by optical microscopy, scanning electron microscopy and x-ray diffraction analysis. Mechanical properties of Ti/Ni and Ti/Cu/Ni joint were evaluated based on tensile strength and microhardness tests. The results showed that cracking occurred in Ti/Ni electron beam weldment for the formation of brittle Ni-Ti intermetallics, while a crack-free electron beam-welded Ti/Ni joint can be obtained by using a copper sheet as filler metal. The addition of copper into the weld affected the welding metallurgical process of the electron beam-welded Ti/Ni joint significantly and was helpful for restraining the formation of Ti-Ni intermetallics in Ti/Ni joint. The microstructure of the weld was mainly characterized by a copper-based solid solution and Ti-Cu interfacial intermetallic compounds. Ti-Ni intermetallic compounds were almost entirely suppressed. The hardness of the weld zone was significantly lower than that of Ti/Ni joint, and the tensile strength of the joint can be up to 282 MPa.

Weldability Characteristics of Sintered Hot-Forged AISI 4135 Steel Produced through P/M Route by Using Pulsed Current Gas Tungsten Arc Welding

NASA Astrophysics Data System (ADS)

Joseph, Joby; Muthukumaran, S.; Pandey, K. S.

2016-01-01

Present investigation is an attempt to study the weldability characteristics of sintered hot-forged plates of AISI 4135 steel produced through powder metallurgy (P/M) route using matching filler materials of ER80S B2. Compacts of homogeneously blended elemental powders corresponding to the above steel were prepared on a universal testing machine (UTM) by taking pre-weighed powder blend with a suitable die, punch and bottom insert assembly. Indigenously developed ceramic coating was applied on the entire surface of the compacts in order to protect them from oxidation during sintering. Sintered preforms were hot forged to flat, approximately rectangular plates, welded by pulsed current gas tungsten arc welding (PCGTAW) processes with aforementioned filler materials. Microstructural, tensile and hardness evaluations revealed that PCGTAW process with low heat input could produce weldments of good quality with almost nil defects. It was established that PCGTAW joints possess improved tensile properties compared to the base metal and it was mainly attributed to lower heat input, resulting in finer fusion zone grains and higher fusion zone hardness. Thus, the present investigation opens a new and demanding field in research.

Development of electromagnetic welding facility of flat plates for nuclear industry

NASA Astrophysics Data System (ADS)

Kumar, Rajesh; Sahoo, Subhanarayan; Sarkar, Biswanath; Shyam, Anurag

2017-04-01

Electromagnetic pulse welding (EMPW) process, one of high speed welding process uses electromagnetic force from discharged current through working coil, which develops a repulsive force between the induced current flowing parallel and in opposite direction. For achieving the successful weldment using this process the design of working coil is the most important factor due to high magnetic field on surface of work piece. In case of high quality flat plate welding factors such as impact velocity, angle of impact standoff distance, thickness of flyer and overlap length have to be chosen carefully. EMPW has wide applications in nuclear industry, automotive industry, aerospace, electrical industries. However formability and weldability still remain major issues. Due to ease in controlling the magnetic field enveloped inside tubes, the EMPW has been widely used for tube welding. In case of flat components control of magnetic field is difficult. Hence the application of EMPW gets restricted. The present work attempts to make a novel contribution by investigating the effect of process parameters on welding quality of flat plates. The work emphasizes the approaches and engineering calculations required to effectively use of actuator in EMPW of flat components.

Use of photostress to characterize the mechanical behavior of weldments

NASA Technical Reports Server (NTRS)

Gambrell, S. C., Jr.

1992-01-01

Welded aluminum is an important part of many space structures. Knowledge of the properties and behavior of weld material and the material surrounding the weld is important for modeling and design of the structures. Photoelastic coatings (Photostress) and strain gages were used to determine behavior of heat treated and as welded joints made from 2219T87 parent material and 2319 weld material subjected to tensile loads. TIG welds of 1/8, 1/2, and 1.4 inches thickness were investigated. Discontinuous yielding was observed in all tests and highly non-uniform behavior through the weld thickness was observed in joints having welds 1.4 inches thick. Joints having welds 1/8 and 1/2 inches thick had only small differences in behavior through the thickness of the weld. Joints in the 1/2 inch thick material contained distinct zones of constant strain within the normal strain gradient extending outward from the weld centerline. These zones had different thickness and locations. Points at the weld centerline, and for a distance of nearly one inch from the centerline, exhibited very nonlinear behavior during the first loading but exhibited near perfect strain hardening during the second loading.

Study of the Performance of Stainless Steel A-TIG Welds

NASA Astrophysics Data System (ADS)

Shyu, S. W.; Huang, H. Y.; Tseng, K. H.; Chou, C. P.

2008-04-01

The purpose of the present work was to investigate the effect of oxide fluxes on weld morphology, arc voltage, mechanical properties, angular distortion and hot cracking susceptibility obtained with TIG welding, which applied to the welding of 5 mm thick austenitic stainless steel plates. A novel variant of the autogenous TIG welding process, oxide powders (Al2O3, Cr2O3, TiO2, SiO2 and CaO) was applied on a type 304 stainless steel through a thin layer of the flux to produce a bead on plate welds. The experimental results indicated that the increase in the penetration is significant with the use of Cr2O3, TiO2, and SiO2. A-TIG welding can increase the weld depth to bead-width ratio, and tends to reduce the angular distortion of the weldment. It was also found that A-TIG welding can increase the retained delta-ferrite content of stainless steel 304 welds and, in consequence, the hot-cracking susceptibility of as-welded is reduced. Physically constricting the plasma column and reducing the anode spot are the possible mechanism for the effect of certain flux on A-TIG penetration.

A New Test Method for Determining the Strength and Fracture Toughness of Cement Mortar and Concrete

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Jy-An John; Liu, Ken C; Naus, Dan J

2010-01-01

The Spiral Notch Torsion Fracture Toughness Test (SNTT) was developed recently to determine the intrinsic fracture toughness (KIC) of structural materials. The SNTT system operates by applying pure torsion to uniform cylindrical specimens with a notch line that spirals around the specimen at a 45 a pitch. KIC values are obtained with the aid of a three-dimensional finite-element computer code, TOR3D-KIC. The SNTT method is uniquely suitable for testing a wide variety of materials used extensively in pressure vessel and piping structural components and weldments. Application of the method to metallic, ceramic, and graphite materials has been demonstrated. One importantmore » characteristic of SNTT is that neither a fatigue precrack or a deep notch are required for the evaluation of brittle materials, which significantly reduces the sample size requirement. In this paper we report results for a Portland cement-based mortar to demonstrate applicability of the SNTT method to cementitious materials. The estimated KIC of the tested mortar samples with compressive strength of 34.45 MPa was found to be 0.19 MPa m^(1/2).« less

Development of a Novel Method for Determination of Residual Stresses in a Friction Stir Weld

NASA Technical Reports Server (NTRS)

Reynolds, Anthony P.

2001-01-01

Material constitutive properties, which describe the mechanical behavior of a material under loading, are vital to the design and implementation of engineering materials. For homogeneous materials, the standard process for determining these properties is the tensile test, which is used to measure the material stress-strain response. However, a majority of the applications for engineering materials involve the use of heterogeneous materials and structures (i.e. alloys, welded components) that exhibit heterogeneity on a global or local level. Regardless of the scale of heterogeneity, the overall response of the material or structure is dependent on the response of each of the constituents. Therefore, in order to produce materials and structures that perform in the best possible manner, the properties of the constituents that make up the heterogeneous material must be thoroughly examined. When materials exhibit heterogeneity on a local level, such as in alloys or particle/matrix composites, they are often treated as statistically homogenous and the resulting 'effective' properties may be determined through homogenization techniques. In the case of globally heterogeneous materials, such as weldments, the standard tensile test provides the global response but no information on what is Occurring locally within the different constituents. This information is necessary to improve the material processing as well as the end product.

Influence of nitrogen in the shielding gas on corrosion resistance of duplex stainless steel welds

NASA Astrophysics Data System (ADS)

Bhatt, R. B.; Kamat, H. S.; Ghosal, S. K.; de, P. K.

1999-10-01

The influence of nitrogen in shielding gas on the corrosion resistance of welds of a duplex stainless steel (grade U-50), obtained by gas tungsten arc (GTA) with filler wire, autogenous GTA (bead-on-plate), electron beam welding (EBW), and microplasma techniques, has been evaluated in chloride solutions at 30 °C. Pitting attack has been observed in GTA, electron beam welding, and microplasma welds when welding has been carried out using pure argon as the shielding gas. Gas tungsten arc welding with 5 to 10% nitrogen and 90 to 95% argon, as the shielding gas, has been found to result in an improved pitting corrosion resistance of the weldments of this steel. However, the resistance to pitting of autogenous welds (bead-on-plate) obtained in pure argon as the shielding gas has been observed to remain unaffected. Microscopic examination, electron probe microanalysis (EPMA), and x-ray diffraction studies have revealed that the presence of nitrogen in the shielding gas in the GTA welds not only modifies the microstructure and the austenite to ferrite ratio but also results in a nearly uniform distribution of the various alloying elements, for example, chromium, nickel, and molybdenum among the constitutent phases, which are responsible for improved resistance to pitting corrosion.

Competing Grain Boundary and Interior Deformation Mechanisms with Varying Sizes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Wei; Gao, Yanfei; Nieh, T. G.

In typical coarse-grained alloys, the dominant plastic deformations are dislocation gliding or climbing, and material strengths can be tuned by dislocation interactions with grain boundaries, precipitates, solid solutions, and other defects. With the reduction of grain size, the increase of material strengths follows the classic Hall-Petch relationship up to nano-grained materials. Even at room temperatures, nano-grained materials exhibit strength softening, or called the inverse Hall-Petch effect, as grain boundary processes take over as the dominant deformation mechanisms. On the other hand, at elevated temperatures, grain boundary processes compete with grain interior deformation mechanisms over a wide range of the appliedmore » stress and grain sizes. This book chapter reviews and compares the rate equation model and the microstructure-based finite element simulations. The latter explicitly accounts for the grain boundary sliding, grain boundary diffusion and migration, as well as the grain interior dislocation creep. Therefore the explicit finite element method has clear advantages in problems where microstructural heterogeneities play a critical role, such as in the gradient microstructure in shot peening or weldment. Furthermore, combined with the Hall-Petch effect and its breakdown, the above competing processes help construct deformation mechanism maps by extending from the classic Frost-Ashby type to the ones with the dependence of grain size.« less

Final Report: Characterization of Canister Mockup Weld Residual Stresses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Enos, David; Bryan, Charles R.

2016-12-01

Stress corrosion cracking (SCC) of interim storage containers has been indicated as a high priority data gap by the Department of Energy (DOE) (Hanson et al., 2012), the Electric Power Research Institute (EPRI, 2011), the Nuclear Waste Technical Review Board (NWTRB, 2010a), and the Nuclear Regulatory Commission (NRC, 2012a, 2012b). Uncertainties exist in terms of the environmental conditions that prevail on the surface of the storage containers, the stress state within the container walls associated both with weldments as well as within the base metal itself, and the electrochemical properties of the storage containers themselves. The goal of the workmore » described in this document is to determine the stress states that exists at various locations within a typical storage canister by evaluating the properties of a full-diameter cylindrical mockup of an interim storage canister. This mockup has been produced using the same manufacturing procedures as the majority of the fielded spent nuclear fuel interim storage canisters. This document describes the design and procurement of the mockup and the characterization of the stress state associated with various portions of the container. It also describes the cutting of the mockup into sections for further analyses, and a discussion of the potential impact of the results from the stress characterization effort.« less

Microstructure and fatigue resistance of high strength dual phase steel welded with gas metal arc welding and plasma arc welding processes

NASA Astrophysics Data System (ADS)

Ahiale, Godwin Kwame; Oh, Yong-Jun; Choi, Won-Doo; Lee, Kwang-Bok; Jung, Jae-Gyu; Nam, Soo Woo

2013-09-01

This study presents the microstructure and high cycle fatigue performance of lap shear joints of dual phase steel (DP590) welded using gas metal arc welding (GMAW) and plasma arc welding (PAW) processes. High cycle fatigue tests were conducted on single and double lap joints under a load ratio of 0.1 and a frequency of 20 Hz. In order to establish a basis for comparison, both weldments were fabricated to have the same weld depth in the plate thickness. The PAW specimens exhibited a higher fatigue life, a gentle S-N slope, and a higher fatigue limit than the GMAW specimens. The improvement in the fatigue life of the PAW specimens was primarily attributed to the geometry effect that exhibited lower and wider beads resulting in a lower stress concentration at the weld toe where cracks initiate and propagate. Furthermore, the microstructural constituents in the heat-affected zone (HAZ) of the PAW specimens contributed to the improvement. The higher volume fraction of acicular ferrite in the HAZ beneath the weld toe enhanced the PAW specimen's resistance to fatigue crack growth. The double lap joints displayed a higher fatigue life than the single lap joints without changing the S-N slope.

A model for heat and mass input control in GMAW

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smartt, H.B.; Einerson, C.J.

1993-05-01

This work describes derivation of a control model for electrode melting and heat and mass transfer from the electrode to the work piece in gas metal arc welding (GMAW). Specifically, a model is developed which allows electrode speed and welding speed to be calculated for given values of voltage and torch-to-base metal distance, as a function of the desired heat and mass input to the weldment. Heat input is given on a per unit weld length basis, and mass input is given in terms of transverse cross-sectional area added to the weld bead (termed reinforcement). The relationship to prior workmore » is discussed. The model was demonstrated using a computer-controlled welding machine and a proportional-integral (PI) controller receiving input from a digital filter. The difference between model-calculated welding current and measured current is used as controller feedback. The model is calibrated for use with carbon steel welding wire and base plate with Ar-CO[sub 2] shielding gas. Although the system is intended for application during spray transfer of molten metal from the electrode to the weld pool, satisfactory performance is also achieved during globular and streaming transfer. Data are presented showing steady-state and transient performance, as well as resistance to external disturbances.« less

Hot Corrosion of Inconel 625 Overlay Weld Cladding in Smelting Off-Gas Environment

NASA Astrophysics Data System (ADS)

Mohammadi Zahrani, E.; Alfantazi, A. M.

2013-10-01

Degradation mechanisms and hot corrosion behavior of weld overlay alloy 625 were studied. Phase structure, morphology, thermal behavior, and chemical composition of deposited salt mixture on the weld overlay were characterized utilizing XRD, SEM/EDX, DTA, and ICP/OES, respectively. Dilution level of Fe in the weldment, dendritic structure, and degradation mechanisms of the weld were investigated. A molten phase formed on the weld layer at the operating temperature range of the boiler, which led to the hot corrosion attack in the water wall and the ultimate failure. Open circuit potential and weight-loss measurements and potentiodynamic polarization were carried out to study the hot corrosion behavior of the weld in the simulated molten salt medium at 873 K, 973 K, and 1073 K (600 °C, 700 °C, and 800 °C). Internal oxidation and sulfidation plus pitting corrosion were identified as the main hot corrosion mechanisms in the weld and boiler tubes. The presence of a significant amount of Fe made the dendritic structure of the weld susceptible to preferential corrosion. Preferentially corroded (Mo, Nb)-depleted dendrite cores acted as potential sites for crack initiation from the surface layer. The penetration of the molten phase into the cracks accelerated the cracks' propagation mainly through the dendrite cores and further crack branching/widening.

Fast and low-dose computed laminography using compressive sensing based technique

NASA Astrophysics Data System (ADS)

Abbas, Sajid; Park, Miran; Cho, Seungryong

2015-03-01

Computed laminography (CL) is well known for inspecting microstructures in the materials, weldments and soldering defects in high density packed components or multilayer printed circuit boards. The overload problem on x-ray tube and gross failure of the radio-sensitive electronics devices during a scan are among important issues in CL which needs to be addressed. The sparse-view CL can be one of the viable option to overcome such issues. In this work a numerical aluminum welding phantom was simulated to collect sparsely sampled projection data at only 40 views using a conventional CL scanning scheme i.e. oblique scan. A compressive-sensing inspired total-variation (TV) minimization algorithm was utilized to reconstruct the images. It is found that the images reconstructed using sparse view data are visually comparable with the images reconstructed using full scan data set i.e. at 360 views on regular interval. We have quantitatively confirmed that tiny structures such as copper and tungsten slags, and copper flakes in the reconstructed images from sparsely sampled data are comparable with the corresponding structure present in the fully sampled data case. A blurring effect can be seen near the edges of few pores at the bottom of the reconstructed images from sparsely sampled data, despite the overall image quality is reasonable for fast and low-dose NDT.

Influence of nitrogen in the shielding gas on corrosion resistance of duplex stainless steel welds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhatt, R.B.; Kamat, H.S.; Ghosal, S.K.

1999-10-01

The influence of nitrogen in shielding gas on the corrosion resistance of welds of a duplex stainless steel (grade U-50), obtained by gas tungsten arc (GTA) with filler wire, autogenous GTA (bead-on-plate), electron beam welding (EBW), and microplasma techniques, has been evaluated in chloride solutions at 30 C. Pitting attack has been observed in GTA, electron beam welding, and microplasma welds when welding has been carried out using pure argon as the shielding gas. Gas tungsten arc welding with 5 to 10% nitrogen and 90 to 95% argon, as the shielding gas, has been found to result in an improvedmore » pitting corrosion resistance of the weldments of this steel. However, the resistance of pitting of autogenous welds (bead-on-plate) obtained in pure argon as the shielding gas has been observed to remain unaffected. Microscopic examination, electron probe microanalysis (EPMA), and x-ray diffraction studies have revealed that the presence of nitrogen in the shielding gas in the GTA welds not only modifies the microstructure and the austenite to ferrite ratio but also results in a nearly uniform distribution of the various alloying elements, for example, chromium, nickel, and molybdenum among the constituent phases, which are responsible for improved resistance to pitting corrosion.« less

Evaluation of flow properties in the weldments of vanadium alloys using a novel indentation technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gubbi, A.N.; Rowcliffe, A.F.; Lee, E.H.

1996-10-01

Automated Ball Indentation (ABI) testing, was successfully employed to determine the flow properties of the fusion zone, heat affected zone (HAZ), and base metal of the gas tungsten arc (GTA) and electron beam (EB) welds of the V-4Cr-4Ti (large heat no. 832665) and the V-5Cr-5Ti (heat 832394) alloys. ABI test results showed a clear distinction among the properties of the fusion zone, HAZ, and base metal in both GTA and EB welds of the two alloys. GTA and EB welds of both V-4Cr-4Ti and V-5Cr-5Ti alloys show strengthening of both the fusion zone and the HAZ (compared to base metal)more » with the fusion zone having higher strength than the HAZ. These data correlate well with the Brinell hardness. On the other hand, GTA welds of both alloys, after a post-weld heat treatment of 950{degrees}C for 2 h, show a recovery of the properties to base metal values with V-5Cr-5Ti showing a higher degree of recovery compared to V-4Cr-4Ti. These measurements correlate with the reported recovery of the Charpy impact properties.« less

Influence of M-TIG and A-TIG Welding Process on Microstructure and Mechanical Behavior of 409 Ferritic Stainless Steel

NASA Astrophysics Data System (ADS)

Vidyarthy, R. S.; Dwivedi, D. K.; Vasudevan, M.

2017-03-01

The current study investigates the effects of activating flux tungsten inert gas welding (A-TIG) and multipass tungsten inert gas welding (M-TIG) on the weld morphology, angular distortion, microstructures and mechanical properties when welding 8-mm-thick 409 ferritic stainless steel (FSS). SiO2 was used as activating flux for A-TIG welding, while SUPERTIG ER309L was used as filler for M-TIG welding. Bead-on-plate weld trials were carried out to obtain the full penetration by using different combinations of flux coating density, welding speed and welding current. An optical microscope, field emission scanning microscope (FESEM), and x-ray diffractometer were used for the metallurgical characterizations. Vickers hardness, tensile test, Charpy toughness test, and creep behavior test were carried out to evaluate the mechanical properties of the base and weld metals. Experimental results indicate that the A-TIG process can increase the joint penetration and tends to reduce the angular distortion of the 409 FSS weldment. The A-TIG welded joint also exhibited greater mechanical strength. However, a critically low Charpy toughness was measured for the A-TIG weld fusion zone, which was later sufficiently improved after post weld heat treatment (PWHT). It was concluded that PWHT is mandatory for A-TIG welded 409 FSS.

Characterization of Al-Cu-Li Alloy 2090 Near Net Shape Extrusion

NASA Technical Reports Server (NTRS)

Birt, M. J.; Domack, M. S.; Hafley, R. A.; Pollock, W. D.

1998-01-01

Aluminum-lithium (Al-Li) alloys near net shape extrusions are being evaluated for potential application in launch vehicle structures. The objective of this study was to determine tensile and fracture properties, corrosion resistance, and weldability of integrally stiffened panels of Al-Cu-Li alloy 2090 in the T8 temper. The microstructure was pre-dominantly unrecrystallized. Texture analyses revealed the presence of fiber components in the stiffeners and a combination of fiber and rolling components in the skin. Variations in grain morphology and texture through the extruded cross section were correlated with the tensile, fracture, and corrosion behavior. Tensile strengths at room and cryogenic temperatures of the 2090 extrusions were similar to other 2090 product forms and were higher than 2219-T87, the primary structural material in the Space Shuttle external tank; however, ductilities were lower. The fracture resistance of the 2090 extrusion was lower than 2219-T87 plate at room temperature. At cryogenic temperatures, tensile ductility and fracture behavior of the 2090 extrusion were similar to other 2090 product forms but were lower than 2219-T87 plate. The exfoliation and stress corrosion resistance of the 2090 extrusion compared favorably with the characteristics of other 2090 product forms. The weldability and weldment properties of the extrusions were similar to 2090 and 2219 plates.

Evolution of Microstructure and Stress Corrosion Cracking Behavior of AA2219 Plate to Ring Weld Joints in 3.5 Wt Pct NaCl Solution

NASA Astrophysics Data System (ADS)

Venugopal, A.; Narayanan, P. Ramesh; Sharma, S. C.

2016-04-01

AA2219 aluminum alloy plate (T87) and ring (T851) were joined by tungsten inert gas (TIG) welding using multi-pass welding. The mechanical properties and stress corrosion cracking (SCC) resistance of the above base metals (BMs) in different directions (L, LT, and ST) were examined. Similarly, the weld metal joined by plate to plate and plate to ring (PR) joints was evaluated. The results revealed that the mechanical properties of the ring were comparatively lower than the plate. This was found to be due to the extremely coarse grain size of the ring along with severe Cu-rich segregation along the grain boundaries when compared to the plate material. The SCC resistance of the base and weldments were found to be good and not susceptible to SCC. This was shown to be due to high values of SCC index (>0.9) and the typical ductile cracking morphology of the BM and the weld joints after SCC test in the environment (3.5 wt pct NaCl) when compared to test performed in the control environment (air). However, the corrosion resistance of the weld interface between the FZ and ring was inferior to the FZ-plate interface.

Nondestructive and Destructive Examination Studies on Removed-from-Service Control Rod Drive Mechanism Penetrations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cumblidge, Stephen E.; Crawford, Susan L.; Doctor, Steven R.

2007-06-07

Studies conducted at the Pacific Northwest National Laboratory (PNNL) in Richland, Washington, focused on assessing the effectiveness of nondestructive examination (NDE) techniques for inspecting control rod drive mechanism (CRDM) nozzles and J-groove weldments. The primary objectives of this work are to provide information to the U.S. Nuclear Regulatory Commission (NRC) on the effectiveness of NDE methods as related to the in-service inspection of CRDM nozzles and J-groove weldments and to enhance the knowledge base of primary water stress corrosion cracking (PWSCC) through destructive characterization of the CRDM assemblies. Two CRDM assemblies were removed from service, decontaminated, and then used inmore » a series of NDE and destructive examination (DE) measurements; this report addresses the following questions: 1) What did each NDE technique detect? 2) What did each NDE technique miss? 3) How accurately did each NDE technique characterize the detected flaws? 4) Why did the NDE techniques perform or not perform? Two CRDM assemblies including the CRDM nozzle, the J-groove weld, buttering, and a portion of the ferritic head material were selected for this study. This report focuses on a CRDM assembly that contained suspected PWSCC, based on in-service inspection data and through-wall leakage. The NDE measurements used to examine the CRDM assembly followed standard industry techniques for conducting in-service inspections of CRDM nozzles and the crown of the J-groove welds and buttering. These techniques included eddy current testing (ET), time-of-flight diffraction ultrasound, and penetrant testing. In addition, laboratory-based NDE methods were employed to conduct inspections of the CRDM assembly with particular emphasis on inspecting the J-groove weld and buttering. These techniques included volumetric ultrasonic inspection of the J-groove weld metal and visual testing via replicant material of the J-groove weld. The results from these NDE studies were used to guide the development of the destructive characterization plan. The NDE studies found several crack-like indications. The NDE and DE studies determined that one of these was a through-weld, radially oriented PWSCC crack in the wetted surface of the J-groove weld, located at the transition point between the weld and the buttering. The crack was 6 mm long on the surface and quickly grew to 25 mm long at a depth of 8 mm, covering the length of the weld between the penetration tube and the carbon steel. The NDE studies found that only ET was able to detect the through-weld crack. The crack was oriented poorly for the ultrasonic testing and was too tight for accurate dye penetrant testing or visual testing. The ET voltage response of the through-wall crack was 30% of the response from a deep electrical discharge machined notch. Destructive examination showed the crack is PWSCC and that it initiated on the wetted surface, grew and expanded through the weld metal, and exited into the annulus. The crack was branched and discontinuous along its length.« less

Study on Microstructure and Mechanical Properties of 304 Stainless Steel Joints by Tig-Mig Hybrid Welding

NASA Astrophysics Data System (ADS)

Ogundimu, Emmanuel O.; Akinlabi, Esther T.; Erinosho, Mutiu F.

Stainless steel is a family of Fe-based alloys having excellent resistance to corrosion and as such has been used imperatively for kitchen utensils, transportation, building constructions and much more. This paper presents the work conducted on the material characterizations of a tungsten inert gas (TIG)-metal inert gas (MIG) hybrid welded joint of type 304 austenitic stainless steel. The welding processes were conducted in three phases. The phases of welding employed are MIG welding using a current of 170A, TIG welding using a current of 190A, and a hybrid TIG-MIG welding with currents of 190/170A, respectively. The MIG, TIG, and hybrid TIG-MIG weldments were characterized with incomplete penetration, full penetration and excess penetration of weld. Intergranular austenite was created toward transition and heat affected zones. The thickness of the delta ferrite (δ-Fe) formed in the microstructures of the TIG weld is more than the thickness emerged in the microstructures of MIG and hybrid TIG-MIG welds. A TIG-MIG hybrid weld of specimen welded at the currents of 190/170A has the highest ultimate tensile strength value and percentage elongation of 397.72MPa and 35.7%. The TIG-MIG hybrid welding can be recommended for high-tech industrial applications such as nuclear, aircraft, food processing, and automobile industry.

A process model for the heat-affected zone microstructure evolution in duplex stainless steel weldments: Part I. the model

NASA Astrophysics Data System (ADS)

Hemmer, H.; Grong, Ø.

1999-11-01

The present investigation is concerned with modeling of the microstructure evolution in duplex stainless steels under thermal conditions applicable to welding. The important reactions that have been modeled are the dissolution of austenite during heating, subsequent grain growth in the delta ferrite regime, and finally, the decomposition of the delta ferrite to austenite during cooling. As a starting point, a differential formulation of the underlying diffusion problem is presented, based on the internal-state variable approach. These solutions are later manipulated and expressed in terms of the Scheil integral in the cases where the evolution equation is separable or can be made separable by a simple change of variables. The models have then been applied to describe the heat-affected zone microstructure evolution during both thick-plate and thin-plate welding of three commercial duplex stainless steel grades: 2205, 2304, and 2507. The results may conveniently be presented in the form of novel process diagrams, which display contours of constant delta ferrite grain size along with information about dissolution and reprecipitation of austenite for different combinations of weld input energy and peak temperature. These diagrams are well suited for quantitative readings and illustrate, in a condensed manner, the competition between the different variables that lead to structural changes during welding of duplex stainless steels.

Hybrid Laser-Arc Welding of 10-mm-Thick Cast Martensitic Stainless Steel CA6NM: As-Welded Microstructure and Mechanical Properties

NASA Astrophysics Data System (ADS)

Mirakhorli, Fatemeh; Cao, Xinjin; Pham, Xuan-Tan; Wanjara, Priti; Fihey, Jean-Luc

2016-07-01

Cast CA6NM martensitic stainless steel plates, 10 mm in thickness, were welded using hybrid laser-arc welding. The effect of different welding speeds on the as-welded joint integrity was characterized in terms of the weld bead geometry, defects, microstructure, hardness, ultimate tensile strength, and impact energy. Significant defects such as porosity, root humping, underfill, and excessive penetration were observed at a low welding speed (0.5 m/min). However, the underfill depth and excessive penetration in the joints manufactured at welding speeds above 0.75 m/min met the specifications of ISO 12932. Characterization of the as-welded microstructure revealed untempered martensite and residual delta ferrite dispersed at prior-austenite grain boundaries in the fusion zone. In addition, four different heat-affected zones in the weldments were differentiated through hardness mapping and inference from the Fe-Cr-Ni ternary phase diagram. The tensile fracture occurred in the base metal for all the samples and fractographic analysis showed that the crack path is within the martensite matrix, along primary delta ferrite-martensite interfaces and within the primary delta ferrite. Additionally, Charpy impact testing demonstrated slightly higher fracture energy values and deeper dimples on the fracture surface of the welds manufactured at higher welding speeds due to grain refinement and/or lower porosity.

Post-weld Tempered Microstructure and Mechanical Properties of Hybrid Laser-Arc Welded Cast Martensitic Stainless Steel CA6NM

NASA Astrophysics Data System (ADS)

Mirakhorli, Fatemeh; Cao, Xinjin; Pham, Xuan-Tan; Wanjara, Priti; Fihey, Jean-Luc

2016-12-01

Manufacturing of hydroelectric turbine components involves the assembly of thick-walled stainless steels using conventional multi-pass arc welding processes. By contrast, hybrid laser-arc welding may be an attractive process for assembly of such materials to realize deeper penetration depths, higher production rates, narrower fusion, and heat-affected zones, and lower distortion. In the present work, single-pass hybrid laser-arc welding of 10-mm thick CA6NM, a low carbon martensitic stainless steel, was carried out in the butt joint configuration using a continuous wave fiber laser at its maximum power of 5.2 kW over welding speeds ranging from 0.75 to 1.2 m/minute. The microstructures across the weldment were characterized after post-weld tempering at 873 K (600 °C) for 1 hour. From microscopic examinations, the fusion zone was observed to mainly consist of tempered lath martensite and some residual delta-ferrite. The mechanical properties were evaluated in the post-weld tempered condition and correlated to the microstructures and defects. The ultimate tensile strength and Charpy impact energy values of the fully penetrated welds in the tempered condition were acceptable according to ASTM, ASME, and industrial specifications, which bodes well for the introduction of hybrid laser-arc welding technology for the manufacturing of next generation hydroelectric turbine components.

Microstructure of Friction Stir Welded AlSi9Mg Cast with 5083 and 2017A Wrought Aluminum Alloys

NASA Astrophysics Data System (ADS)

Hamilton, C.; Kopyściański, M.; Dymek, S.; Węglowska, A.; Pietras, A.

2018-03-01

Wrought aluminum alloys 5083 and 2017A were each joined with cast aluminum alloy AlSi9Mg through friction stir welding in butt weld configurations. For each material system, the wrought and cast alloy positions, i.e., the advancing side or the retreating side, were exchanged between welding trials. The produced weldments were free from cracks and discontinuities. For each alloy configuration, a well-defined nugget comprised of alternating bands of the welded alloys characterized the microstructure. The degree of mixing, however, strongly depended on which wrought alloy was present and on its position during processing. In all cases, the cast AlSi9Mg alloy dominated the weld center regardless of its position during welding. Electron backscattered diffraction analysis showed that the grain size in both alloys (bands) constituting the nugget was similar and that the majority of grain boundaries exhibited a high angle character (20°-60°). Regardless of the alloy, however, all grains were elongated along the direction of the material plastic flow during welding. A numerical simulation of the joining process visualized the material flow patterns and temperature distribution and helped to rationalize the microstructural observations. The hardness profiles across the weld reflected the microstructure formed during welding and correlated well with the temperature changes predicted by the numerical model. Tensile specimens consistently fractured in the cast alloy near the weld nugget.

Microstructural Characterization of the Heat-Affected Zones in Grade 92 Steel Welds: Double-Pass and Multipass Welds

NASA Astrophysics Data System (ADS)

Xu, X.; West, G. D.; Siefert, J. A.; Parker, J. D.; Thomson, R. C.

2018-04-01

The microstructure in the heat-affected zone (HAZ) of multipass welds typical of those used in power plants and made from 9 wt pct chromium martensitic Grade 92 steel is complex. Therefore, there is a need for systematic microstructural investigations to define the different regions of the microstructure across the HAZ of Grade 92 steel welds manufactured using the traditional arc welding processes in order to understand possible failure mechanisms after long-term service. In this study, the microstructure in the HAZ of an as-fabricated two-pass bead-on-plate weld on a parent metal of Grade 92 steel has been systematically investigated and compared to a complex, multipass thick section weldment using an extensive range of electron and ion-microscopy-based techniques. A dilatometer has been used to apply controlled thermal cycles to simulate the microstructures in distinctly different regions in a multipass HAZ using sequential thermal cycles. A wide range of microstructural properties in the simulated materials were characterized and compared with the experimental observations from the weld HAZ. It has been found that the microstructure in the HAZ can be categorized by a combination of sequential thermal cycles experienced by the different zones within the complex weld metal, using the terminology developed for these regions based on a simpler, single-pass bead-on-plate weld, categorized as complete transformation, partial transformation, and overtempered.

Effect of Continuous and Pulsed Current Gas Tungsten Arc Welding on Dissimilar Weldments Between Hastelloy C-276/AISI 321 Austenitic Stainless Steel

NASA Astrophysics Data System (ADS)

Sharma, Sumitra; Taiwade, Ravindra V.; Vashishtha, Himanshu

2017-03-01

In the present investigation, an attempt has been made to join Hastelloy C-276 nickel-based superalloy and AISI 321 austenitic stainless steel using ERNiCrMo-4 filler. The joints were fabricated by continuous and pulsed current gas tungsten arc welding processes. Experimental studies to ascertain the structure-property co-relationship with or without pulsed current mode were carried out using an optical microscope and scanning electron microscope. Further, the energy-dispersive spectroscope was used to evaluate the extent of microsegregation. The microstructure of fusion zone was obtained as finer cellular dendritic structure for pulsed current mode, whereas columnar structure was formed with small amount of cellular structure for continuous current mode. The scanning electron microscope examination witnessed the existence of migrated grain boundaries at the weld interfaces. Moreover, the presence of secondary phases such as P and μ was observed in continuous current weld joints, whereas they were absent in pulsed current weld joints, which needs to be further characterized. Moreover, pulsed current joints resulted in narrower weld bead, refined morphology, reduced elemental segregation and improved strength of the welded joints. The outcomes of the present investigation would help in obtaining good quality dissimilar joints for industrial applications and AISI 321 ASS being cheaper consequently led to cost-effective design also.

Local mechanical properties of Alloy 82/182 dissimilar weld joint between SA508 Gr.1a and F316 SS at RT and 320 °C

NASA Astrophysics Data System (ADS)

Kim, Jin Weon; Lee, Kyoungsoo; Kim, Jong Sung; Byun, Thak Sang

2009-02-01

The distributions of mechanical and microstructural properties were investigated for the dissimilar metal weld joints between SA508 Gr.1a ferritic steel and F316 austenitic stainless steel with Alloy 82/182 filler metal using small-size tensile specimens. The material properties varied significantly in different zones while those were relatively uniform within each material. In particular, significant gradient of the mechanical properties were observed near the both heat-affected zones (HAZs) of F316 SS and SA508 Gr.1a. Thus, the yield stress (YS) was under-matched with respect to the both HAZs, although, the YS of the weld metal was over-matched with respect to both base metals. The minimum ductility occurred in the HAZ of SA508 Gr.1a at both test temperatures. The plastic instability stress also varied considerably across the weld joints, with minimum values occurring in the SA508 Gr.1a base metal at RT and in the HAZ of F316 SS at 320 °C. The transmission electron micrographs showed that the strengthening in the HAZ of F316 SS was attributed to the strain hardening, induced by a strain mismatch between the weldment and the base metal, which was evidenced by high dislocation density in the HAZ of F316 SS.

Metallurgical and mechanical properties of laser welded high strength low alloy steel

PubMed Central

Oyyaravelu, Ramachandran; Kuppan, Palaniyandi; Arivazhagan, Natarajan

2016-01-01

The study aimed at investigating the microstructure and mechanical properties of Neodymium-Doped Yttrium Aluminum Garnet (Nd:YAG) laser welded high strength low alloy (HSLA) SA516 grade 70 boiler steel. The weld joint for a 4 mm thick plate was successfully produced using minimum laser power of 2 kW by employing a single pass without any weld preheat treatment. The micrographs revealed the presence of martensite phase in the weld fusion zone which could be due to faster cooling rate of the laser weldment. A good correlation was found between the microstructural features of the weld joints and their mechanical properties. The highest hardness was found to be in the fusion zone of cap region due to formation of martensite and also enrichment of carbon. The hardness results also showed a narrow soft zone at the heat affected zone (HAZ) adjacent to the weld interface, which has no effect on the weld tensile strength. The yield strength and ultimate tensile strength of the welded joints were 338 MPa and 549 MPa, respectively, which were higher than the candidate metal. These tensile results suggested that the laser welding process had improved the weld strength even without any weld preheat treatment and also the fractography of the tensile fractured samples showed the ductile mode of failure. PMID:27222751

Metallurgical and Corrosion Characterization of POST Weld Heat Treated Duplex Stainless Steel (uns S31803) Joints by Friction Welding Process

NASA Astrophysics Data System (ADS)

Asif M., Mohammed; Shrikrishna, Kulkarni Anup; Sathiya, P.

2016-02-01

The present study focuses on the metallurgical and corrosion characterization of post weld heat treated duplex stainless steel joints. After friction welding, it was confirmed that there is an increase in ferrite content at weld interface due to dynamic recrystallization. This caused the weldments prone to pitting corrosion attack. Hence the post weld heat treatments were performed at three temperatures 1080∘C, 1150∘C and 1200∘C with 15min of aging time. This was followed by water and oil quenching. The volume fraction of ferrite to austenite ratio was balanced and highest pit nucleation resistance were achieved after PWHT at 1080∘C followed by water quench and at 1150∘C followed by oil quench. This had happened exactly at parameter set containing heating pressure (HP):40 heating time (HT):4 upsetting pressure (UP):80 upsetting time (UP):2 (experiment no. 5). Dual phase presence and absence of precipitates were conformed through TEM which follow Kurdjumov-Sachs relationship. PREN of ferrite was decreasing with increase in temperature and that of austenite increased. The equilibrium temperature for water quenching was around 1100∘C and that for oil quenching was around 1140∘C. The pit depths were found to be in the range of 100nm and width of 1.5-2μm.

Fast and low-dose computed laminography using compressive sensing based technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abbas, Sajid, E-mail: scho@kaist.ac.kr; Park, Miran, E-mail: scho@kaist.ac.kr; Cho, Seungryong, E-mail: scho@kaist.ac.kr

2015-03-31

Computed laminography (CL) is well known for inspecting microstructures in the materials, weldments and soldering defects in high density packed components or multilayer printed circuit boards. The overload problem on x-ray tube and gross failure of the radio-sensitive electronics devices during a scan are among important issues in CL which needs to be addressed. The sparse-view CL can be one of the viable option to overcome such issues. In this work a numerical aluminum welding phantom was simulated to collect sparsely sampled projection data at only 40 views using a conventional CL scanning scheme i.e. oblique scan. A compressive-sensing inspiredmore » total-variation (TV) minimization algorithm was utilized to reconstruct the images. It is found that the images reconstructed using sparse view data are visually comparable with the images reconstructed using full scan data set i.e. at 360 views on regular interval. We have quantitatively confirmed that tiny structures such as copper and tungsten slags, and copper flakes in the reconstructed images from sparsely sampled data are comparable with the corresponding structure present in the fully sampled data case. A blurring effect can be seen near the edges of few pores at the bottom of the reconstructed images from sparsely sampled data, despite the overall image quality is reasonable for fast and low-dose NDT.« less

NDE and DE of PWSCC Found in the J-Groove Weld of a Removed-From-Service Control Rod Drive Mechanism

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cumblidge, Stephen E.; Doctor, Steven R.; Schuster, George J.

2008-01-01

Studies conducted at the Pacific Northwest National Laboratory (PNNL) in Richland, Washington focused on assessing the effectiveness of nondestructive examination (NDE) techniques for inspecting control rod drive mechanism (CRDM) nozzles and J-groove weldments. The primary objective of this work is to provide information to the United States Nuclear Regulatory Commission (US NRC) on the effectiveness of NDE methods as related to the in-service inspection of CRDM nozzles and J-groove weldments, and to enhance the knowledge base of primary water stress corrosion cracking (PWSCC) through destructive characterization of the CRDM assemblies. Two CRDM assemblies were removed from service, decontaminated, and thenmore » used in a series of laboratory NDE and DE measurements; this report addresses the following questions: 1) What did each NDE technique detect?, 2) What did each NDE technique miss?, 3) How accurately did each NDE technique characterize the detected flaws?, and finally 4) What were the basis for the NDE techniques performance? Two CRDM assemblies including the CRDM nozzle, the J-groove weld, buttering, and a portion of the ferritic head material were selected for this study. This paper focuses on a CRDM assembly that contained suspected PWSCC, based on in-service inspection data and through-wall leakage. The laboratory NDE measurements used to examine the CRDM assembly followed standard industry techniques for conducting in-service inspections of CRDM nozzles and the crown of the J-groove welds and buttering. These techniques included eddy current testing, time of flight diffraction ultrasound, and penetrant testing. In addition, other laboratory-based NDE methods were employed to conduct inspections of the CRDM assembly with particular emphasis on inspecting the J-groove weld and buttering. These techniques included volumetric ultrasonic inspection of the J-groove weld metal, visual testing via replicant material of the J-groove weld and high resolution photography of the J-groove weld crown and buttering. The results from these NDE studies were used to guide the development of the destructive characterization plan. The NDE studies found several crack-like indications. The NDE and DE studies determined that one of these was a through-weld radially-oriented PWSCC crack in the wetted surface of the J-groove weld, located at the transition point between the weld and the buttering. The crack was 6 mm long on the surface and quickly grew to 25 mm long at a depth of 8 mm, covering the length of the weld between the penetration tube and the carbon steel. The NDE studies found that only ET was able to detect the through-weld crack. The crack was oriented poorly for the ultrasonic testing, and was too tight for accurate PT or VT. The ET voltage response of the flaw was 30% that of a deep EDM notch. The DE performed on the crack consisted of slicing the crack into thin sections, polishing the sections, and then using optical and scanning electron microscopy (SEM) to characterize the crack. DE shows the crack was PWSCC and that it initiated on the wetted surface, grew and expanded through the weld metal, and exited into the annulus. The SEM examinations showed the crack followed the weld grain boundaries as it progressed through the weld. The crack was branched and discontinuous along its length.« less

Effect of PWHT on Microstructure, Mechanical and Corrosion Behaviour of Gas Tungsten Arc Welds of IN718 Superalloys

NASA Astrophysics Data System (ADS)

Dilkush; Mohammed, Raffi; Madhusudhan Reddy, G.; Srinivasa Rao, K.

2018-03-01

The present work aims to improve corrosion resistance and mechanical behavior of the welds with suitable post weld heat treatment i.e. direct aging and solutionizing treatments (980STA, 1080STA). Gas tungsten arc welding (GTAW) has been performed on Inconel 718 (IN718) nickel based super alloy plates with 3mm thickness. The structural –property relationship of the post weld heat treated samples is judged by correlating the microstructural changes with observed mechanical behavior and pitting corrosion resistance of the welds As-recevied, direct aging (DA), 980STA,1080STA were studied. Welds were characterized for microstructure changes with scanning electron microscopy (SEM) and optical microscopy (OM).Vickers micro- hardness tester was used to measure the hardness of the weldments. Potential-dynamic polarization testing was carried out to study the pitting corrosion resistance in 3.5%NaCl (Sodium chloride) solution at 30°C.Results of the present study established that post weld heat treatments resulted in promoting the element segregation diffusion and resolve them from brittle laves particles in the matrix. Increased precipitation of strengthening phases lead to a significant increase in fusion zone hardness of 1080STA post weld heat treated condition compared to as welded, direct aged, 980STA conditions. Due to significant changes in the microstructural behavior of 1080STA condition resulted in superior pitting corrosion resistance than 980STA, direct aged and as- recevied conditions of IN718 GTA welds

Comparative Studies on Microstructure, Mechanical and Pitting Corrosion of Post Weld Heat Treated IN718 Superalloy GTA and EB Welds

NASA Astrophysics Data System (ADS)

Dilkush; Mohammed, Raffi; Madhusudhan Reddy, G.; Srinivasa Rao, K.

2018-03-01

In the present study, an attempt has been made to weld Inconel 718 nickel-base superalloy (IN718 alloy) using gas tungsten arc welding (GTAW) and electron beam welding (EBW) processes. Both the weldments were subjected to post-weld heat treatment condition as follows -980°C / 20 min followed by direct aging condition (DA) as 720°C/8 h/FC followed by 620°C/8 h/AC. The GTA and EB welds of IN718 alloy were compared in two conditions as-received and 980STA conditions. Welds were characterized to observe mechanical properties, pitting corrosion resistance by correlating with observed microstructures. The rate of higher cooling ranges, the fusion zone of EBW exhibited discrete and relative finer lave phases whereas the higher niobium existed laves with coarser structure were observed in GTAW. The significant dissolution of laves were observed at 980STA of EBW. Due to these effects, the EBW of IN718 alloy showed the higher mechanical properties than GTAW. The electrochemical potentiostatic etch test was carried out in 3.5wt% sodium chloride (NaCl) solution to study the pitting corrosion behaviour of the welds. Results of the present investigation established that mechanical properties and pitting corrosion behaviour are significantly better in post weld heat treated condition. The comparative studies showed that the better combination of mechanical properties and pitting corrosion resistance were obtained in 980STA condition of EBW than GTAW.

High Temperature Corrosion and Characterization Studies in Flux Cored Arc Welded 2.25Cr-1Mo Power Plant Steel

NASA Astrophysics Data System (ADS)

Kumaresh Babu, S. P.; Natarajan, S.

2010-07-01

Higher productivity is registered with Flux cored arc welding (FCAW) process in many applications. Further, it combines the characteristics of shielded metal arc welding (SMAW), gas metal arc welding (GMAW), and submerged arc welding (SAW) processes. This article describes the experimental work carried out to evaluate and compare corrosion and its inhibition in SA 387 Gr.22 (2.25Cr-1Mo) steel weldments prepared by FCAW process with four different heat inputs exposed to hydrochloric acid medium at 0.1, 0.5, and 1.0 M concentrations. The parent metal, weld metal, and heat-affected zone are chosen as regions of exposure for the study carried out at 100 °C. Electrochemical polarization techniques such as Tafel line extrapolation (Tafel) and linear polarization resistance (LPR) have been used to measure the corrosion current. The role of hexamine and mixed inhibitor (thiourea + hexamine in 0.5 M HCl), each at 100 ppm concentration is studied in these experiments. Microstructural observation, hardness survey, surface characterization, and morphology using scanning electron microscope (SEM) and x-ray diffraction (XRD) have been made on samples to highlight the nature and extent of film formation. The film is found to contain Fe2Si, FeSi2, FeMn3, Fe7Mo3, Fe3O4, FeO, FeCr, AlO7Fe3SiO3, and KFe4Mn77Si19.

Alloy 33: A new material for the handling of HNO{sub 3}/HF media in reprocessing of nuclear fuel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koehler, M.; Heubner, U.; Eichenhofer, K.W.

Alloy 33, an austenitic 33Cr-32Fe-31Ni-1.6Mo-0.6Cu-0.4N material shows excellent resistance to corrosion when exposed to highly oxidizing media as e.g. HNO{sub 3} and HNO{sub 3}/HF mixtures which are encountered in reprocessing of nuclear fuel. According to the test results available so far, resistance to corrosion in boiling azeotropic (67%) HNO{sub 3} is about 6 and 2 times superior to AISI 304 L and 310 L. In higher concentrated nitric acid it can be considered corrosion resistant up to 95% HNO{sub 3} at 25 C, up to 90% HNO{sub 3} at 50 C and up to somewhat less than 85% HNO{sub 3}more » at 75 C. In 20% HNO{sub 3}/7% HF at 50 C its resistance to corrosion is superior to AISI 316 Ti and Alloy 28 by factors of about 200 and 2.4. Other media tested with different results include 12% HNO{sub 3} with up to 3.5% HF and 0.4% HF with 32 to 67.5% HNO{sub 3} at 90 C. Alloy 33 is easily fabricated into all product forms required for chemical plants (e.g. plate, sheet, strip, wire, tube and flanges). Components such as dished ends and tube to tube sheet weldments have been successfully fabricated facilitating the use of Alloy 33 for reprocessing of nuclear fuel.« less

Friction-Stir-Welded and Spin-Formed End Domes for Cryogenic Tanks

NASA Technical Reports Server (NTRS)

Hales, S. J.; Tayon, W. A.; Domack, M. S.

2012-01-01

Manufacturing of single-piece end domes for cryogenic tanks employing spin forming of tailored, friction-stir-welded blanks of Al-Li alloy 2195 plate offers cost and reliability benefits. The introduction of plastic deformation into a friction stir weld is a unique feature of the proposed manufacturing route. This investigation addressed abnormal grain growth [AGG] within the friction stir weldments during postfabrication processing of a prototype dome. The phenomenon of AGG was observed during the solution heat treatment [SHT] phase of T8 tempering and is a major concern for meeting specifications. Such abrupt microstructural transitions can be detrimental to notch-sensitive mechanical properties, such as ductility and/or fracture toughness. If the issue of AGG cannot be resolved, then the acceptance of this approach as a viable manufacturing route may be in jeopardy. The innovative approach adopted in this investigation was the insertion of a stand-alone, Intermediate Annealing Treatment [IAT] between the spin forming and T8 processing operations. A simple, recovery annealing step was deemed to be the most readily-scalable solution when fabricating thin-walled, ellipsoidal domes. The research effort culminated in the development of an effective IAT, which resulted in a significant decrease in AGG following SHT. The processing philosophy adopted in designing the IAT is outlined and the microstructural reasons for success are discussed. The analytical results presented are consistent with promoting continuous grain growth during the IAT, thereby suppressing AGG during the SHT.

PWHT effect on the mechanical properties of borated stainless steel GTA weldments for nuclear shield

NASA Astrophysics Data System (ADS)

Park, T.-D.; Baek, K.-K.; Kim, D.-S.

1997-02-01

To improve ductility of the welded joint of B-added austenitic stainless steels, postweld annealing effect has been studied. Gas Tungsten Arc (GTA) welds of AlSI 304-B3 stainless steel plates were annealed either at 700 1100°C for 1 hour or at 1100°C and 1200°C, for 1 7 hours. Bending test of the welds in as-welded and annealed conditions resulted in cracks propagated along the welds' fusion line except the one annealed at 1200°C, which revealed no cracks. Tensile elongations of the as-welded and annealed welds at the temperature up to 1000°C were only a half value of the base metal, whereas the welds annealed at 1200°C had fully recovered the original elongation of the base metal. Charpy impact test result exhibited the same tendency with annealing temperature. Elongated and accicular morphology of Y-(Cr, Fe)2B eutectic phase at the Partially Melted Heat Affected Zone (P.M.HAZ) of welds seemed to be responsible for the poor ductility of the welds. The welds annealed at 1200°C for various durations, on the other hand, showed fully spheroidized eutectic phases at the P.M.HAZ with its size increased with annealing durations, suggesting that postweld annealing at the temperature as high as 1200°C is required for the welds to have ductility matching that of base metal.

Creep Strength of Dissimilar Welded Joints Using High B-9Cr Steel for Advanced USC Boiler

NASA Astrophysics Data System (ADS)

Tabuchi, Masaaki; Hongo, Hiromichi; Abe, Fujio

2014-10-01

The commercialization of a 973 K (700 °C) class pulverized coal power system, advanced ultra-supercritical (A-USC) pressure power generation, is the target of an ongoing research project initiated in Japan in 2008. In the A-USC boiler, Ni or Ni-Fe base alloys are used for high-temperature parts at 923 K to 973 K (650 °C to 700 °C), and advanced high-Cr ferritic steels are planned to be used at temperatures lower than 923 K (650 °C). In the dissimilar welds between Ni base alloys and high-Cr ferritic steels, Type IV failure in the heat-affected zone (HAZ) is a concern. Thus, the high B-9Cr steel developed at the National Institute for Materials Science, which has improved creep strength in weldments, is a candidate material for the Japanese A-USC boiler. In the present study, creep tests were conducted on the dissimilar welded joints between Ni base alloys and high B-9Cr steels. Microstructures and creep damage in the dissimilar welded joints were investigated. In the HAZ of the high B-9Cr steels, fine-grained microstructures were not formed and the grain size of the base metal was retained. Consequently, the creep rupture life of the dissimilar welded joints using high B-9Cr steel was 5 to 10 times longer than that of the conventional 9Cr steel welded joints at 923 K (650 °C).

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Wei, E-mail: wang_wei_310@163.com; Lu, Yonghao, E-mail: lu_yonghao@mater.ustb.edu.cn; Ding, Xianfei, E-mail: xfding@ustb.edu.cn

Microstructures and microhardness at fusion boundary of a weld joint were investigated in a 316 stainless steel/Inconel 182 dissimilar weldment. The results showed that there were two alternately distributed typical fusion boundaries, a narrow random boundary (possessed 15% in length) with a clear sharp interface and an epitaxial fusion one with (100){sub BM}//(100){sub WM} at the joint interface. The composition transition, microstructure and hardness across the fusion boundary strongly depended on the type of the fusion boundary. For the random boundary, there was a clear sharp interface and the composition transition with a width of 100 μm took place symmetricallymore » across the grain boundary. For the epitaxial fusion one, however, there were Type-I and Type-II grain boundaries perpendicular and parallel to the epitaxial fusion boundary, respectively. The composition transition took place in the Inconel 182 weld side. Σ3 boundaries in the HAZ of 316SS side and Σ5 grain boundaries in weld metal were usually observed, despite the type of fusion boundary, however the former was much more in epitaxial fusion boundary. Microhardness was continuously decreased across the random fusion boundary from the side of Inconel 182 to 316SS, but a hardening phenomenon appeared in the epitaxial fusion boundary zone because of its fine cellular microstructure. - Highlights: • Two typical fusion boundaries alternately distributed in the fusion interface • The microstructure, composition and hardness across fusion boundary depended on its type. • Different regions in welded joint have different special CSL value boundaries. • Hardening phenomenon only appeared in the epitaxial fusion boundary.« less

Evaluation of advanced austenitic alloys relative to alloy design criteria for steam service

DOE Office of Scientific and Technical Information (OSTI.GOV)

Swindeman, R.W.; Maziasz, P.J.; Bolling, E.

1990-05-01

The results are summarized for a 6-year activity on advanced austenitic stainless steels for heat recovery systems. Commercial, near-commercial, and developmental alloys were evaluated relative to criteria for metallurgical stability, fabricability, weldability, and mechanical strength. Fireside and steamside corrosion were also considered, but no test data were collected. Lean stainless steel alloys that were given special attention in the study were type 316 stainless steel, fine-grained type 347 stainless steel, 17-14CuMo stainless steel, Esshete 1250, Sumitomo ST3Cu{reg sign} stainless steel, and a group of alloys identified as HT-UPS (high-temperature, ultrafine-precipitation strengthened) steels that were basically 14Cr--16Ni--Mo steels modified by variousmore » additions of MC-forming elements. It was found that, by solution treating the MC-forming alloys to temperatures above 1150{degree}C and subsequently cold or warm working, excellent metallurgical stability and creep strength could be achieved. Test data to beyond 35,000 h were collected. The ability to clad the steels for improved fireside corrosion resistance was demonstrated. Weldability of the alloys was of concern, and hot cracking was found to be a problem in the HT-UPS alloys. By reducing the phosphorous content and selecting either CRE 16-8-2 stainless steel or alloy 556 filler metal, weldments were produced that had excellent strength and ductility. The major issues related to the development of the advanced alloys were identified and ways to resolve the issues suggested. 89 refs., 45 figs., 8 tabs.« less

Tensile properties and impact toughness of S30408 stainless steel and its welded joints at cryogenic temperatures

NASA Astrophysics Data System (ADS)

Ding, Huiming; Wu, Yingzhe; Lu, Qunjie; Xu, Ping; Zheng, Jinyang; Wei, Lijun

2018-06-01

Designing a cryogenic pressure vessel based on the mechanical properties of the austenitic stainless steel (ASS) at its cryogenic operating temperature fully utilizes the potential of the material at low temperatures, resulting in lightweight and compact products. A series of tensile tests and impact tests were carried out in a wide range of 77-293 K, to investigate the mechanical properties of S30408 base metal (BM) and welded joints (WJ) at cryogenic temperatures. As the temperature decreases, yield stress (Rp0.2) and ultimate tensile stress (Rm) increase significantly thanks to the low-temperature strengthening effects. To estimate strengths at cryogenic temperatures, quadratic polynomial model was used to accurately predict the variations of Rp0.2 and Rm from 77 K to 293 K. As an important phase in the WJ, ferrite presents a radial pattern and an inhomogeneity in the WJ's cross-section. Due to the formation of ferrite in the WJ, the WJ has higher Rp0.2 and lower Rm , Charpy absorbed energy and lateral expansion compared with the BM. Strain-induced martensite transformation is an important role influencing the deformation of ASS at low temperatures. In this study, less martensite amount was measured in the weldment zone with higher Nickel equivalents which stabilize the austenite phase at cryogenic temperatures. Additionally, due to higher ferrite content and more precipitates forming, the SAW joints has lower Rm and impact toughness than PAW + GTAW joints. To ensure the structural integrity and safety, the PAW + GTAW method should be chosen and ferrite content be controlled.

Friction stir welding of T joints of dissimilar aluminum alloy: A review

NASA Astrophysics Data System (ADS)

Thakare, Shrikant B.; Kalyankar, Vivek D.

2018-04-01

Aluminum alloys are preferred in the mechanical design due to their advantages like high strength, good corrosion resistance, low density and good weldability. In various industrial applications T joints configuration of aluminum alloys are used. In different fields, T joints having skin (horizontal sheet) strengthen by stringers (vertical sheets) were used to increase the strength of structure without increasing the weight. T joints are usually carried out by fusion welding which has limitations in joining of aluminum alloy due to significant distortion and metallurgical defects. Some aluminum alloys are even non weldable by fusion welding. The friction stir welding (FSW) has an excellent replacement of conventional fusion welding for T joints. In this article, FSW of T joints is reviewed by considering aluminum alloy and various joint geometries for defect analysis. The previous experiments carried out on T joints shows the factors such as tool geometry, fixturing device and joint configurations plays significant role in defect free joints. It is essential to investigate the material flow during FSW to know joining mechanism and the formation of joint. In this study the defect occurred in the FSW are studied for various joint configurations and parameters. Also the effect of the parameters and defects occurs on the tensile strength are studied. It is concluded that the T-joints of different joint configurations can be pretended successfully. Comparing to base metal some loss in tensile strength was observed in the weldments as well as overall reduction of the hardness in the thermos mechanically affected zone also observed.

Laser beam welding of Waspaloy: Characterization and corrosion behavior evaluation

NASA Astrophysics Data System (ADS)

Shoja Razavi, Reza

2016-08-01

In this work, a study on Nd:YAG laser welding of Waspaloy sheets has been made. Microstructures, phase changes and hardness of the laser joint were investigated using optical microscopy, scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), X-ray diffraction analysis (XRD) and vickers microhardness (HV0.3). Corrosion behavior of the weldment at low temperature in 3.5%wt NaCl solution at room temperature was also investigated using open circuit potential and cyclic potentiodynamic polarization tests. Hot corrosion studies were conducted on samples in the molten salt environment (Na2SO4-60%V2O5) at 900 °C for 50 h. Results indicated that the microstructure of weld zone was mainly dendritic grown epitaxially in the direction perpendicular to the weld boundary and heat transfer. Moreover, the Ti-Mo carbide particles were observed in the structure of the weld zone and base metal. The average size of carbides formed in the base metal (2.97±0.5 μm) was larger than that of the weld zone (0.95±0.2 μm). XRD patterns of the weld zone and base metal showed that the laser welding did not alter the phase structure of the weld zone, being in γ-Ni(Cr) single phase. Microhardness profile showed that the hardness values of the weld zone (210-261 HV) were lower than that of the base metal (323-330 HV). Electrochemical and hot corrosion tests indicated that the corrosion resistance of the weld metal was greater than the base metal in both room and high temperatures.

Effect of different stages of tensile deformation on micromagnetic parameters in high-strength, low-alloy steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vaidyanathan, S.; Moorthy, V.; Kalyanasundaram, P.

The influence of tensile deformation on the magnetic Barkhausen emissions (MBE) and hysteresis loop has been studied in a high-strength, low-alloy steel (HSLA) and its weldment. The magnetic measurements were made both in loaded and unloaded conditions for different stress levels. The root-mean-square (RMS) voltage of the MBE has been used for analysis. This study shows that the preyield and postyield deformation can be identified from the change in the MBE profile. The initial elastic deformation showed a linear increase in the MBE level in the loaded condition, and the MBE level remained constant in the unloaded condition. The microplasticmore » yielding, well below the macroyield stress, significantly reduces the MBE, indicating the operation of grain-boundary dislocation sources below the macroyield stress. This is indicated by the slow increase in the MBE level in the loaded condition and the decrease in the MBE level in the unloaded condition. The macroyielding resulted in a significant increase in the MBE level in the loaded condition and, more clearly, in the unloaded condition. The increase in the MBE level during macroyielding has been attributed to the grain rotation phenomenon, in order to maintain the boundary integrity between adjacent grains, which would preferentially align the magnetic domains along the stress direction. This study shows that MBE during tensile deformation can be classified into four stages: (1) perfectly elastic, (2) microplastic yielding, (3) macroyielding, and (4) progressive plastic deformation. A multimagnetic parameter approach, combining the hysteresis loop and MBE, has been suggested to evaluate the residual stresses.« less

Modern fiber laser beam welding of the newly-designed precipitation-strengthened nickel-base superalloys

NASA Astrophysics Data System (ADS)

Naffakh Moosavy, Homam; Aboutalebi, Mohammad-Reza; Seyedein, Seyed Hossein; Goodarzi, Massoud; Khodabakhshi, Meisam; Mapelli, Carlo; Barella, Silvia

2014-04-01

In the present research, the modern fiber laser beam welding of newly-designed precipitation-strengthened nickel-base superalloys using various welding parameters in constant heat input has been investigated. Five nickel-base superalloys with various Ti and Nb contents were designed and produced by Vacuum Induction Melting furnace. The fiber laser beam welding operations were performed in constant heat input (100 J mm-2) and different welding powers (400 and 1000 W) and velocities (40 and 100 mm s-1) using 6-axis anthropomorphic robot. The macro- and micro-structural features, weld defects, chemical composition and mechanical property of 3.2 mm weldments were assessed utilizing optical and scanning electron microscopes equipped with EDS analysis and microhardness tester. The results showed that welding with higher powers can create higher penetration-to-width ratios. The porosity formation was increased when the welding powers and velocities were increased. None of the welds displayed hot solidification and liquation cracks in 400 and 1000 W welding powers, but liquation phenomenon was observed in all the heat-affected zones. With increasing the Nb content of the superalloys the liquation length was increased. The changing of the welding power and velocity did not alter the hardness property of the welds. The hardness of welds decreased when the Ti content declined in the composition of superalloys. Finally, the 400 and 1000 W fiber laser powers with velocity of 40 and 100 m ms-1 have been offered for hot crack-free welding of the thin sheet of newly-designed precipitation-strengthened nickel-base superalloys.

Influence of laser beam incidence angle on laser lap welding quality of galvanized steels

NASA Astrophysics Data System (ADS)

Mei, Lifang; Yan, Dongbing; Chen, Genyu; Wang, Zhenhui; Chen, Shuixuan

2017-11-01

Based on the characteristics of laser welded structural parts of auto bodies, the influence of variation in laser beam incidence angle on the lap welding performance of galvanized auto-body sheets was studied. Lap welding tests were carried out on the galvanized sheets for auto-body application at different laser beam incidence angles by using the optimal welding parameters obtained through orthogonal experiment. The effects of incidence angle variation on seam appearance, cross-sectional shape, joint mechanical properties and microstructure of weldments were analyzed. In addition, the main factors influencing the value of incidence angle were investigated. According to the results, the weld seams had a good appearance as well as a fine, and uniform microstructure when the laser beam incidence angle was smaller than the critical incidence angle, and thus they could withstand great tensile and shear loads. Moreover, all tensile-shear specimens were fractured in the base material zone. When the laser beam incidence angle was larger than the critical incidence angle, defects like shrinkage and collapse tended to emerge, thereby resulting in the deteriorated weldability of specimens. Meanwhile, factors like the type and thickness of sheet, weld width as well as inter-sheet gap all had a certain effect on the value of laser beam incidence angle. When the sheet thickness was small and the weld width was narrow, the laser beam incidence angle could be increased appropriately. At the same time, small changes in the inter-sheet gap could greatly impact the value of incidence angle. When the inter-sheet gap was small, the laser beam incidence angle should not be too large.

Study of in-situ formation of Fe-Mn-Si shape memory alloy welding seam by laser welding with filler powder

NASA Astrophysics Data System (ADS)

Ju, Heng; Lin, Chengxin; Liu, Zhijie; Zhang, Jiaqi

2018-08-01

To reduce the residual stresses and improve the mechanical properties of laser weldments, produced with the restrained mixing uniform design method, a Fe-Mn-Si shape memory alloy (SMA) welding seam was formed inside the 304 stainless steel by laser welding with powder filling. The mass fraction, shape memory effect, and phase composition of the welding seam was measured by SEM-EDS (photometric analyser), bending recovery method, and XRD, respectively. An optical microscope was used to observe the microstructure of the Fe-Mn-Si SMA welding seam by solid solution and pre-deformation treatment. Meanwhile, the mechanical properties (residual stress distribution, tensile strength, microhardness and fatigue strength) of the laser welded specimen with an Fe-Mn-Si SMA welding seam (experimental material) and a 304 stainless steel welding seam (contrast material) were measured by a tensile testing machine hole drilling method and full cycle bending fatigue test. The results show that Fe15Mn5Si12Cr6Ni SMA welding seam was formed in situ with shape memory effect and stress-induced γ → ε martensite phase transformation characteristic. The residual stress of the experimental material is lower than that of the contrast material. The former has larger tensile strength, longer elongation and higher microhardness than the latter has. The experimental material and contrast material possess 249 and 136 bending fatigue cycles at the strain of 6%, respectively. The mechanisms by which mechanical properties of the experimental material are strengthened includes (1) release of the residual stress inside the Fe-Mn-Si SMA welding seam due to the stress-induced γ → ε martensite phase transformation and (2) energy absorption and plastic slip restraint due to the deformations in martensite and reverse phase transformation.

Ballistic-Failure Mechanisms in Gas Metal Arc Welds of Mil A46100 Armor-Grade Steel: A Computational Investigation

NASA Astrophysics Data System (ADS)

Grujicic, M.; Snipes, J. S.; Galgalikar, R.; Ramaswami, S.; Yavari, R.; Yen, C.-F.; Cheeseman, B. A.

2014-09-01

In our recent work, a multi-physics computational model for the conventional gas metal arc welding (GMAW) joining process was introduced. The model is of a modular type and comprises five modules, each designed to handle a specific aspect of the GMAW process, i.e.: (i) electro-dynamics of the welding-gun; (ii) radiation-/convection-controlled heat transfer from the electric-arc to the workpiece and mass transfer from the filler-metal consumable electrode to the weld; (iii) prediction of the temporal evolution and the spatial distribution of thermal and mechanical fields within the weld region during the GMAW joining process; (iv) the resulting temporal evolution and spatial distribution of the material microstructure throughout the weld region; and (v) spatial distribution of the as-welded material mechanical properties. In the present work, the GMAW process model has been upgraded with respect to its predictive capabilities regarding the spatial distribution of the mechanical properties controlling the ballistic-limit (i.e., penetration-resistance) of the weld. The model is upgraded through the introduction of the sixth module in the present work in recognition of the fact that in thick steel GMAW weldments, the overall ballistic performance of the armor may become controlled by the (often inferior) ballistic limits of its weld (fusion and heat-affected) zones. To demonstrate the utility of the upgraded GMAW process model, it is next applied to the case of butt-welding of a prototypical high-hardness armor-grade martensitic steel, MIL A46100. The model predictions concerning the spatial distribution of the material microstructure and ballistic-limit-controlling mechanical properties within the MIL A46100 butt-weld are found to be consistent with prior observations and general expectations.

Prediction and Verification of Ductile Crack Growth from Simulated Defects in Strength Overmatched Butt Welds

NASA Technical Reports Server (NTRS)

Nishioka, Owen S.

1997-01-01

Defects that develop in welds during the fabrication process are frequently manifested as embedded flaws from lack of fusion or lack of penetration. Fracture analyses of welded structures must be able to assess the effect of such defects on the structural integrity of weldments; however, the transferability of R-curves measured in laboratory specimens to defective structural welds has not been fully examined. In the current study, the fracture behavior of an overmatched butt weld containing a simulated buried, lack-of-penetration defect is studied. A specimen designed to simulate pressure vessel butt welds is considered; namely, a center crack panel specimen, of 1.25 inch by 1.25 inch cross section, loaded in tension. The stress-relieved double-V weld has a yield strength 50% higher than that of the plate material, and displays upper shelf fracture behavior at room temperature. Specimens are precracked, loaded monotonically while load-CMOD measurements are made, then stopped and heat tinted to mark the extent of ductile crack growth. These measurements are compared to predictions made using finite element analysis of the specimens using the fracture mechanics code Warp3D, which models void growth using the Gurson-Tvergaard dilitant plasticity formulation within fixed sized computational cells ahead of the crack front. Calibrating data for the finite element analyses, namely cell size and initial material porosities are obtained by matching computational predictions to experimental results from tests of welded compact tension specimens. The R-curves measured in compact tension specimens are compared to those obtained from multi-specimen weld tests, and conclusions as to the transferability of R-curves is discussed.

Characterization of microstructure and texture across dissimilar super duplex/austenitic stainless steel weldment joint by super duplex filler metal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eghlimi, Abbas, E-mail: a.eghlimi@ma.iut.ac.ir; Shamanian, Morteza; Eskandarian, Masoomeh

In the present paper, microstructural changes across an as-welded dissimilar austenitic/duplex stainless steel couple welded by a super duplex stainless steel filler metal using gas tungsten arc welding process is characterized with optical microscopy and electron back-scattered diffraction techniques. Accordingly, variations of microstructure, texture, and grain boundary character distribution of base metals, heat affected zones, and weld metal were investigated. The results showed that the weld metal, which was composed of Widmanstätten austenite side-plates and allotriomorphic grain boundary austenite morphologies, had the weakest texture and was dominated by low angle boundaries. The welding process increased the ferrite content but decreasedmore » the texture intensity at the heat affected zone of the super duplex stainless steel base metal. In addition, through partial ferritization, it changed the morphology of elongated grains of the rolled microstructure to twinned partially transformed austenite plateaus scattered between ferrite textured colonies. However, the texture of the austenitic stainless steel heat affected zone was strengthened via encouraging recrystallization and formation of annealing twins. At both interfaces, an increase in the special character coincident site lattice boundaries of the primary phase as well as a strong texture with <100> orientation, mainly of Goss component, was observed. - Graphical abstract: Display Omitted - Highlights: • Weld metal showed local orientation at microscale but random texture at macroscale. • Intensification of <100> orientated grains was observed adjacent to the fusion lines. • The austenite texture was weaker than that of the ferrite in all duplex regions. • Welding caused twinned partially transformed austenites to form at SDSS HAZ. • At both interfaces, the ratio of special CSL boundaries of the primary phase increased.« less

Effect of Repair Welding on Electrochemical Corrosion and Stress Corrosion Cracking Behavior of TIG Welded AA2219 Aluminum Alloy in 3.5 Wt Pct NaCl Solution

NASA Astrophysics Data System (ADS)

Venugopal, A.; Sreekumar, K.; Raja, V. S.

2010-12-01

The stress corrosion cracking (SCC) behavior of AA2219 aluminum alloy in the as-welded (AW) and repair-welded (RW) conditions was examined and compared with that of the base metal (BM) in 3.5 wt pct NaCl solution using the slow strain rate technique (SSRT). The reduction in ductility was used as a parameter to evaluate the SCC susceptibility of both BM and welded joints. The results show that the ductility ratio ( ɛ NaCl/( ɛ air)) of the BM was close to one (0.97) and reduced to 0.9 for the AW joint. This value further reduced to 0.77 after carrying out one repair welding operation. However, the RW specimen exhibited higher ductility than the single-weld specimens even in 3.5 wt pct NaCl solution. SSRT results obtained using pre-exposed samples followed by post-test metallographic observations clearly showed localized pitting corrosion along the partially melted zone (PMZ), signifying that the reduction in ductility ratio of both the AW and RW joints was more due to mechanical overload failure, caused by the localized corrosion and a consequent reduction in specimen thickness, than due to SCC. Also, the RW joint exhibited higher ductility than the AW joint both in air and the environment, although SCC index (SI) for the former is lower than that of the latter. Fractographic examination of the failed samples, in general, revealed a typical ductile cracking morphology for all the base and welded joints, indicating the good environmental cracking resistance of this alloy. Microstructural examination and polarization tests further demonstrate grain boundary melting along the PMZ, and that provided the necessary electrochemical condition for the preferential cracking on that zone of the weldment.

UNS S31603 Stainless Steel Tungsten Inert Gas Welds Made with Microparticle and Nanoparticle Oxides

PubMed Central

Tseng, Kuang-Hung; Lin, Po-Yu

2014-01-01

The purpose of this study was to investigate the difference between tungsten inert gas (TIG) welding of austenitic stainless steel assisted by microparticle oxides and that assisted by nanoparticle oxides. SiO2 and Al2O3 were used to investigate the effects of the thermal stability and the particle size of the activated compounds on the surface appearance, geometric shape, angular distortion, delta ferrite content and Vickers hardness of the UNS S31603 stainless steel TIG weld. The results show that the use of SiO2 leads to a satisfactory surface appearance compared to that of the TIG weld made with Al2O3. The surface appearance of the TIG weld made with nanoparticle oxide has less flux slag compared with the one made with microparticle oxide of the same type. Compared with microparticle SiO2, the TIG welding with nanoparticle SiO2 has the potential benefits of high joint penetration and less angular distortion in the resulting weldment. The TIG welding with nanoparticle Al2O3 does not result in a significant increase in the penetration or reduction of distortion. The TIG welding with microparticle or nanoparticle SiO2 uses a heat source with higher power density, resulting in a higher ferrite content and hardness of the stainless steel weld metal. In contrast, microparticle or nanoparticle Al2O3 results in no significant difference in metallurgical properties compared to that of the C-TIG weld metal. Compared with oxide particle size, the thermal stability of the oxide plays a significant role in enhancing the joint penetration capability of the weld, for the UNS S31603 stainless steel TIG welds made with activated oxides. PMID:28788704

A novel weld seam detection method for space weld seam of narrow butt joint in laser welding

NASA Astrophysics Data System (ADS)

Shao, Wen Jun; Huang, Yu; Zhang, Yong

2018-02-01

Structured light measurement is widely used for weld seam detection owing to its high measurement precision and robust. However, there is nearly no geometrical deformation of the stripe projected onto weld face, whose seam width is less than 0.1 mm and without misalignment. So, it's very difficult to ensure an exact retrieval of the seam feature. This issue is raised as laser welding for butt joint of thin metal plate is widely applied. Moreover, measurement for the seam width, seam center and the normal vector of the weld face at the same time during welding process is of great importance to the welding quality but rarely reported. Consequently, a seam measurement method based on vision sensor for space weld seam of narrow butt joint is proposed in this article. Three laser stripes with different wave length are project on the weldment, in which two red laser stripes are designed and used to measure the three dimensional profile of the weld face by the principle of optical triangulation, and the third green laser stripe is used as light source to measure the edge and the centerline of the seam by the principle of passive vision sensor. The corresponding image process algorithm is proposed to extract the centerline of the red laser stripes as well as the seam feature. All these three laser stripes are captured and processed in a single image so that the three dimensional position of the space weld seam can be obtained simultaneously. Finally, the result of experiment reveals that the proposed method can meet the precision demand of space narrow butt joint.

Evaluation of pitting corrosion resistance of high-alloyed stainless steels welds for FGD plants in Korea

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baek, K.K.; Sung, H.J.; Im, C.S.

1998-12-31

For successful application of high-alloyed stainless steels for Flue Gas Desulfurization (FGD) plants, pitting corrosion resistance of arc welds of N-added 6%Mo austenitic stainless steels (UNS N 08367) and super duplex stainless steels (UNS S 32550) made with various filler metals were evaluated using the Green Death solution. For Gas Tungsten Arc (GTA) and Gas Metal Arc (GMA) welds of N 08367, Critical Pitting Temperature (CPT) of base metal was 65--70 C, whereas weld made by ERNiCrMo-3 filler metal yielded CPT of 50 C. Welds made by ERNiCrMo-10 or ERNiCrMo-4 filler metals showed CPT of 60--65 C and 65--70C, respectively.more » For GTA and GMA welds of S 32550, CPT of welds made by ERNiCrMo-3 was 45--50 C, indicating that the filler metal can provide pitting corrosion resistance matching the S 32550 alloy. Thus, a proper pitting corrosion resistance of weldments of high-alloy stainless steels can be achieved by selecting filler metals having at least +10 higher Pitting Resistance Equivalent Number (PRE{sub N}) value than the base metal regardless of the type of arc welding process. The over-alloyed filler metals would compensate preferential segregation of Cr, MO along the dendrite boundary, which made the dendrite core more susceptible to pitting. Nitrogen addition to the GTA welds of N 08367 made with ERNiCrMo-3 failed to improve pitting corrosion resistance, which was attributed to the precipitation of nitrogen in the weld metal in the form of Nb-nitride.« less

Effect of Heat Input on Geometry of Austenitic Stainless Steel Weld Bead on Low Carbon Steel

NASA Astrophysics Data System (ADS)

Saha, Manas Kumar; Hazra, Ritesh; Mondal, Ajit; Das, Santanu

2018-05-01

Among different weld cladding processes, gas metal arc welding (GMAW) cladding becomes a cost effective, user friendly, versatile method for protecting the surface of relatively lower grade structural steels from corrosion and/or erosion wear by depositing high grade stainless steels onto them. The quality of cladding largely depends upon the bead geometry of the weldment deposited. Weld bead geometry parameters, like bead width, reinforcement height, depth of penetration, and ratios like reinforcement form factor (RFF) and penetration shape factor (PSF) determine the quality of the weld bead geometry. Various process parameters of gas metal arc welding like heat input, current, voltage, arc travel speed, mode of metal transfer, etc. influence formation of bead geometry. In the current experimental investigation, austenite stainless steel (316) weld beads are formed on low alloy structural steel (E350) by GMAW using 100% CO2 as the shielding gas. Different combinations of current, voltage and arc travel speed are chosen so that heat input increases from 0.35 to 0.75 kJ/mm. Nine number of weld beads are deposited and replicated twice. The observations show that weld bead width increases linearly with increase in heat input, whereas reinforcement height and depth of penetration do not increase with increase in heat input. Regression analysis is done to establish the relationship between heat input and different geometrical parameters of weld bead. The regression models developed agrees well with the experimental data. Within the domain of the present experiment, it is observed that at higher heat input, the weld bead gets wider having little change in penetration and reinforcement; therefore, higher heat input may be recommended for austenitic stainless steel cladding on low alloy steel.

UNS S31603 Stainless Steel Tungsten Inert Gas Welds Made with Microparticle and Nanoparticle Oxides.

PubMed

Tseng, Kuang-Hung; Lin, Po-Yu

2014-06-20

The purpose of this study was to investigate the difference between tungsten inert gas (TIG) welding of austenitic stainless steel assisted by microparticle oxides and that assisted by nanoparticle oxides. SiO₂ and Al₂O₃ were used to investigate the effects of the thermal stability and the particle size of the activated compounds on the surface appearance, geometric shape, angular distortion, delta ferrite content and Vickers hardness of the UNS S31603 stainless steel TIG weld. The results show that the use of SiO₂ leads to a satisfactory surface appearance compared to that of the TIG weld made with Al₂O₃. The surface appearance of the TIG weld made with nanoparticle oxide has less flux slag compared with the one made with microparticle oxide of the same type. Compared with microparticle SiO₂, the TIG welding with nanoparticle SiO₂ has the potential benefits of high joint penetration and less angular distortion in the resulting weldment. The TIG welding with nanoparticle Al₂O₃ does not result in a significant increase in the penetration or reduction of distortion. The TIG welding with microparticle or nanoparticle SiO₂ uses a heat source with higher power density, resulting in a higher ferrite content and hardness of the stainless steel weld metal. In contrast, microparticle or nanoparticle Al₂O₃ results in no significant difference in metallurgical properties compared to that of the C-TIG weld metal. Compared with oxide particle size, the thermal stability of the oxide plays a significant role in enhancing the joint penetration capability of the weld, for the UNS S31603 stainless steel TIG welds made with activated oxides.

Effect of Different Chromium Additions on the Microstructure and Mechanical Properties of Multipass Weld Joint of Duplex Stainless Steel

NASA Astrophysics Data System (ADS)

Kang, Dong Hoon; Lee, Hae Woo

2012-12-01

The correlation between the mechanical properties and ferrite volume fraction (approximately 40, 50, and 60 Ferrite Number [FN]) in duplex stainless steel weld metals were investigated by changing the Cr content in filler wires with a flux-cored arc-welding (FCAW) process. The interpass temperature was thoroughly maintained under a maximum of 423 K (150 °C), and the heat input was also sustained at a level under 15 KJ/cm in order to minimize defects. The microstructure examination demonstrated that the δ-ferrite volume fraction in the deposited metals increased as the Cr/Ni equivalent ratio increased, and consequently, chromium nitride (Cr2N) precipitation was prone to occur in the ferrite domains due to low solubility of nitrogen in this phase. Thus, more dislocations are pinned by the precipitates, thereby lowering the mobility of the dislocations. Not only can this lead to the strength improvement, but also it can accentuate embrittlement of the weld metal at subzero temperature. Additionally, the solid-solution strengthening by an increase of Cr and Mo content in austenite phase depending on the reduction of austenite proportion also made an impact on the increase of the tensile and yield strength. On the other hand, the impact test (at 293 K, 223 K, and 173 K [20 °C, -50 °C, and -100 °C]) showed that the specimen containing about 40 to 50 FN had the best result. The absorbed energy of about 40 to 50 J sufficiently satisfied the requirements for industrial applications at 223 K (-50 °C), while the ductile-to-brittle transition behavior exhibited in weldment containing 60 FN. As the test temperature decreased under 223 K (-50 °C), a narrow and deep dimple was transformed into a wide and shallow dimple, and a significant portion of the fracture surface was occupied by a flat cleavage facet with river patterns.

Thermal Recovery of Plastic Deformation in Dissimilar Metal Weld

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qiao, Dongxiao; Yu, Xinghua; Zhang, Wei

Stainless steel has been widely used in challenging environments typical to nuclear power plant structures, due its excellent corrosion resistance. Nickel filler metals containing high chromium concentration, including Alloy 82/182, are used for joining stainless steel to carbon steel components to achieve similar high resistance to stress corrosion cracking. However, the joint usually experience weld metal stress corrosion cracking (SCC), which affects the safety and structural integrity of light water nuclear reactor systems. A primary driving force for SCC is the high tensile residual stress in these welds. Due to large dimension of pressure vessel and limitations in the field,more » non-destructive residual stress measurement is difficult. As a result, finite element modeling has been the de facto method to evaluate the weld residual stresses. Recent studies on this subject from researchers worldwide report different residual stress value in the weldments [5]. The discrepancy is due to the fact that most of investigations ignore or underestimate the thermal recovery in the heat-affect zone or reheated region in the weld. In this paper, the effect of heat treatment on thermal recovery and microhardness is investigated for materials used in dissimilar metal joint. It is found that high equivalent plastic strains are predominately accumulated in the buttering layer, the root pass, and the heat affected zone, which experience multiple welding thermal cycles. The final cap passes, experiencing only one or two welding thermal cycles, exhibit less plastic strain accumulation. Moreover, the experimental residual plastic strains are compared with those predicted using an existing weld thermo-mechanical model with two different strain hardening rules. The importance of considering the dynamic strain hardening recovery due to high temperature exposure in welding is discussed for the accurate simulation of weld residual stresses and plastic strains. In conclsuion, the experimental result reveals that the typical post-buttering heat treatment for residual stress relief may not be adequate to completely eliminate the residual plastic strains in the buttering layer.« less

Development and trial manufacturing of 1/2-scale partial mock-up of blanket box structure for fusion experimental reactor

NASA Astrophysics Data System (ADS)

Hashimoto, Toshiyuki; Takatsu, Hideyuki; Sato, Satoshi

1994-07-01

Conceptual design of breeding blanket has been discussed during the CDA (Conceptual Design Activities) of ITER (International Thermonuclear Experimental Reactor). Structural concept of breeding blanket is based on box structure integrated with first wall and shield, which consists of three coolant manifolds for first wall, breeding and shield regions. The first wall must have cooling channels to remove surface heat flux and nuclear heating. The box structure includes plates to form the manifolds and stiffening ribs to withstand enormous electromagnetic load, coolant pressure and blanket internal (purge gas) pressure. A 1/2-scale partial model of the blanket box structure for the outboard side module near midplane is manufactured to estimate the fabrication technology, i.e. diffusion bonding by HIP (Hot Isostatic Pressing) and EBW (Electron Beam Welding) procedure. Fabrication accuracy is a key issue to manufacture first wall panel because bending deformation during HIP may not be small for a large size structure. Data on bending deformation during HIP was obtained by preliminary manufacturing of HIP elements. For the shield structure, it is necessary to reduce the welding strain and residual stress of the weldment to establish the fabrication procedure. Optimal shape of the parts forming the manifolds, welding locations and welding sequence have been investigated. In addition, preliminary EBW tests have been performed in order to select the EBW conditions, and fundamental data on built-up shield have been obtained. Especially, welding deformation by joining the first wall panel to the shield has been measured, and total deformation to build-up shield by EBW has been found to be smaller than 2 mm. Consequently, the feasibility of fabrication technologies has been successfully demonstrated for a 1m-scaled box structure including the first wall with cooling channels by means of HIP, EBW and TIG (Tungsten Inert Gas arc)-welding.

Origins of Line Defects in Self-Reacting Friction Stir Welds and Their Impact on Weld Quality

NASA Technical Reports Server (NTRS)

Schneider, Judy; Nunes, Arthur C., Jr.

2016-01-01

Friction stir welding (FSWing) is a solid state joining technique which reduces the occurrence of typical defects formed in fusion welds, especially of highly alloyed metals. Although the process is robust for aluminum alloys, occasional reductions in the strength of FSWs have been observed. Shortly after the NASA-MSFC implemented a variation of FSW called self-reacting (SR), low strength properties were observed. At that time, this reduction in strength was attributed to a line defect. At that time, the limited data suggested that the line defect was related to the accumulation of native oxides that form on the weld lands and faying surfaces. Through a series of improved cleaning methods, tool redesign, and process parameter modifications, the reduction in the strength of the SR-FSWs was eliminated. As more data has been collected, the occasional reduction in the strength of SR-FSW still occurs. These occasional reductions indicate a need to reexamine the underlying causes. This study builds off a series of self reacting (SR)-FSWs that were made in 3 different thickness panels of AA2219 (0.95, 1.27 and 1.56 cm) at 2 different weld pitches. A bead on plate SR-FSW was also made in the 1.56 cm thick panel to understand the contribution of the former faying surfaces. Copper tracer studies were used to understand the flow lines associated with the weld tool used. The quality of the SR-FSWs was evaluated from tensile testing at room temperature. Reductions in the tensile strength were observed in some weldments, primarily at higher weld pitch or tool rotations. This study explores possible correlations between line defects and the reduction of strength in SR-FSWs. Results from this study will assist in a better understand of the mechanisms responsible for reduced tensile strength and provide methodology for minimizing their occurrence.

Global and Local Mechanical Properties of Autogenously Laser Welded Ti-6Al-4V

NASA Astrophysics Data System (ADS)

Cao, Xinjin; Kabir, Abu Syed H.; Wanjara, Priti; Gholipour, Javad; Birur, Anand; Cuddy, Jonathan; Medraj, Mamoun

2014-03-01

Ti-6Al-4V sheets, 3.2-mm in thickness, were butt welded using a continuous wave 4 kW Nd:YAG laser welding system. The effect of two main process parameters, laser power and welding speed, on the joint integrity was characterized in terms of the joint geometry, defects, microstructure, hardness, and tensile properties. In particular, a digital image correlation technique was used to determine the local tensile properties of the welds. It was determined that a wide range of heat inputs can be used to fully penetrate the Ti-6Al-4V butt joints during laser welding. At high laser power levels, however, significant defects such as underfill and porosity, can occur and cause marked degradation in the joint integrity and performance. At low welding speeds, however, significant porosity occurs due to its growth and the potential collapse of instable keyholes. Intermediate to relatively high levels of heat input allow maximization of the joint integrity and performance by limiting the underfill and porosity defects. In considering the effect of the two main defects on the joint integrity, the underfill defect was found to be more damaging to the mechanical performance of the weldment than the porosity. Specifically, it was determined that the maximum tolerable underfill depth for Ti-6Al-4V is approximately 6 pct of the workpiece thickness, which is slightly stricter than the value of 7 pct specified in AWS D17.1 for fusion welding in aerospace applications. Hence, employing optimized laser process parameters allows the underfill depth to be maintained within the tolerable limit (6 pct), which in turn prevents degradation in both the weld strength and ductility. To this end, the ability to maintain weld ductility in Ti-6Al-4V by means of applying a high energy density laser welding process presents a significant advantage over conventional arc welding for the assembly of aerospace components.

Characterization of microstructure and texture across dissimilar super duplex/austenitic stainless steel weldment joint by austenitic filler metal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eghlimi, Abbas, E-mail: a.eghlimi@ma.iut.ac.ir; Shamanian, Morteza; Eskandarian, Masoomeh

The evolution of microstructure and texture across an as-welded dissimilar UNS S32750 super duplex/UNS S30403 austenitic stainless steel joint welded by UNS S30986 (AWS A5.9 ER309LMo) austenitic stainless steel filler metal using gas tungsten arc welding process was evaluated by optical micrography and EBSD techniques. Due to their fabrication through rolling process, both parent metals had texture components resulted from deformation and recrystallization. The weld metal showed the highest amount of residual strain and had large austenite grain colonies of similar orientations with little amounts of skeletal ferrite, both oriented preferentially in the < 001 > direction with cub-on-cube orientationmore » relationship. While the super duplex stainless steel's heat affected zone contained higher ferrite than its parent metal, an excessive grain growth was observed at the austenitic stainless steel's counterpart. At both heat affected zones, austenite underwent some recrystallization and formed twin boundaries which led to an increase in the fraction of high angle boundaries as compared with the respective base metals. These regions showed the least amount of residual strain and highest amount of recrystallized austenite grains. Due to the static recrystallization, the fraction of low degree of fit (Σ) coincident site lattice boundaries, especially Σ3 boundaries, was increased in the austenitic stainless steel heat affected zone, while the formation of subgrains in the ferrite phase increased the content of < 5° low angle boundaries at that of the super duplex stainless steel. - Graphical abstract: Display Omitted - Highlights: • Extensive grain growth in the HAZ of austenitic stainless steel was observed. • Intensification of < 100 > orientated grains was observed adjacent to both fusion lines. • Annealing twins with Σ3 CSL boundaries were formed in the austenite of both HAZ. • Cub-on-cube OR was observed between austenite and ferrite in the weld metal. • Weld metal had the lowest texture intensity and ratio of low angle and CSL boundaries.« less

Local mechanical properties of Alloy 82/182 dissimilar weld joint between SA508 Gr.1a and F316 SS at RT and 320C

DOE Office of Scientific and Technical Information (OSTI.GOV)

Byun, Thak Sang; Kim, Jin Weon

2009-01-01

This paper presents the variations of local mechanical and microstructural properties in dissimilar metal weld joints consisting of the SA508 Gr.1a ferritic steel, Alloy 82/182 filler metal, and F316 austenitic stainless steel. Flat or round tensile specimens and transmission electron microscopy disks were taken from the base metals, welds, and heat-affected zones (HAZ) of the joints and tested at room temperature (RT) and/or at 320 C. The tensile test results indicated that the mechanical property was relatively uniform within each material zone, but varied considerably between different zones. Further, significant variations were observed both in the austenitic HAZ of F316more » SS and in the ferritic HAZ of SA508 Gr.1a. The yield stress (YS) of the weld metal was under-matched with respect to the HAZs of SA508 Gr.1a and F316 SS by 0.78 to 0.92, although the YS was over-matched with respect to both base metals. The minimum ductility occurred in the HAZ of SA508 Gr.1 at both test temperatures. The plastic instability stress also varied considerably in the weld joints, with minimum values occurring in the SA508 Gr.1a base metal at RT and in the HAZ of F316 SS at 320 C, suggesting that the probability of ductile failure caused by a unstable deformation at the Alloy 82/182 buttering layer is low. Within the HAZ of SA508 Gr.1a, the gradient of the YS and ultimate tensile strength (UTS) was significant, primarily because of the different microstructures produced by the phase transformation during the welding process. The increment of YS was unexpectedly high in the HAZ of F316 SS, which was explained by the strain hardening induced by a strain mismatch between the weldment and the base metal. This was confirmed by the transmission electron micrographs showing high dislocation density in the HAZ.« less

Magnetic Particle Recovery of Serial Numbers

DOE Office of Scientific and Technical Information (OSTI.GOV)

D. Utrata; M.J. Johnson

One method used by crime labs to recover obliterated serial numbers in steel firearms (ferrous samples) is the magnetic particle technique. The use of this method is predicated on the detection of metal deformation present under stamped serial numbers after the visible stamp has been removed. Equipment specialized for this detection is not used in these attempts; a portable magnetic yoke used typically for flaw detection on large weldments or structures, along with dry visible magnetic powders, have been the tools of criminologists working in this area. Crime labs have reported low success rates using these tools [1, 2]. Thismore » is not surprising when one considers that little formal development has apparently evolved for use in such investigations since the publication of seminal work in this area some time ago [3]. The aim of this project is to investigate specific aspects of magnetic particle inspection for serial number recovery. This includes attempts to understand the magnetic characteristics of different steels that affect their performance in the test, such as varying results for carbon steels and alloy steels after different thermal and forming treatments. Also investigated are the effects of the nature of the sample magnetization (AC, rectified DC, and true DC) and the use of various detection media, such as visible powders and fluorescent sprays, on test outcome. Additionally, some aspects of surface preparation of firearm samples prior to number recovery were included in this work. The scope of this report includes a brief overview of the magnetic particle inspection method in general and its applications to forensic serial number recovery. This is followed by a description of how such investigations were simulated on lab samples, including a look at how the microstructure of a given steel will affect its performance in the test. Investigations into the serial number recovery in a series of ferromagnetic firearms (both steel and certain stainless steels) will then be presented. Recommendations for modifications to current approaches used in crime labs for serial number recovery, as well as suggestions for future work, conclude this document.« less

Heat transfer, fluid flow and mass transfer in laser welding of stainless steel with small length scale

NASA Astrophysics Data System (ADS)

He, Xiuli

Nd: YAG Laser welding with hundreds of micrometers in laser beam diameter is widely used for assembly and closure of high reliability electrical and electronic packages for the telecommunications, aerospace and medical industries. However, certain concerns have to be addressed to obtain defect-free and structurally sound welds. During laser welding, Because of the high power density used, the pressures at the weld pool surface can be greater than the ambient pressure. This excess pressure provides a driving force for the vaporization to take place. As a result of vaporization for different elements, the composition in the weld pool may differ from that of base metal, which can result in changes in the microstructure and degradation of mechanical properties of weldments. When the weld pool temperatures are very high, the escaping vapor exerts a large recoil force on the weld pool surface, and as a consequence, tiny liquid metal particles may be expelled from the weld pool. Vaporization of alloying elements and liquid metal expulsion are the two main mechanisms of material loss. Besides, for laser welds with small length scale, heat transfer and fluid flow are different from those for arc welds with much larger length scale. Because of small weld pool size, rapid changes of temperature and very short duration of the laser welding process, physical measurements of important parameters such as temperature and velocity fields, weld thermal cycles, solidification and cooling rates are very difficult. The objective of the research is to quantitatively understand the influences of various factors on the heat transfer, fluid flow, vaporization of alloying elements and liquid metal expulsion in Nd:YAG laser welding with small length scale of 304 stainless steel. In this study, a comprehensive three dimensional heat transfer and fluid flow model based on the mass, momentum and energy conservation equations is relied upon to calculate temperature and velocity fields in the weld pool, weld thermal cycle, weld pool geometry and solidification parameters. Surface tension and buoyancy forces were considered for the calculation of transient weld pool convection. Very fine grids and small time steps were used to achieve accuracy in the calculations. The calculated weld pool dimensions were compared with the corresponding measured values to validate the model. (Abstract shortened by UMI.)

Gas tungsten arc welding and friction stir welding of ultrafine grained AISI 304L stainless steel: Microstructural and mechanical behavior characterization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sabooni, S., E-mail: s.sabooni@ma.iut.ac.ir; Karimzadeh, F.; Enayati, M.H.

In the present study, an ultrafine grained (UFG) AISI 304L stainless steel with the average grain size of 650 nm was successfully welded by both gas tungsten arc welding (GTAW) and friction stir welding (FSW). GTAW was applied without any filler metal. FSW was also performed at a constant rotational speed of 630 rpm and different welding speeds from 20 to 80 mm/min. Microstructural characterization was carried out by High Resolution Scanning Electron Microscopy (HRSEM) with Electron Backscattered Diffraction (EBSD) and Transmission Electron Microscopy (TEM). Nanoindentation, microhardness measurements and tensile tests were also performed to study the mechanical properties ofmore » the base metal and weldments. The results showed that the solidification mode in the GTAW welded sample is FA (ferrite–austenite) type with the microstructure consisting of an austenite matrix embedded with lath type and skeletal type ferrite. The nugget zone microstructure in the FSW welded samples consisted of equiaxed dynamically recrystallized austenite grains with some amount of elongated delta ferrite. Sigma phase precipitates were formed in the region ahead the rotating tool during the heating cycle of FSW, which were finally fragmented into nanometric particles and distributed in the weld nugget. Also there is a high possibility that the existing delta ferrite in the microstructure rapidly transforms into sigma phase particles during the short thermal cycle of FSW. These suggest that high strain and deformation during FSW can promote sigma phase formation. The final austenite grain size in the nugget zone was found to decrease with increasing Zener–Hollomon parameter, which was obtained quantitatively by measuring the peak temperature, calculating the strain rate during FSW and exact examination of hot deformation activation energy by considering the actual grain size before the occurrence of dynamic recrystallization. Mechanical properties observations showed that the welding efficiency of the FSW welded sample is around 70%, which is more than 20% higher than the GTAW welded sample. - Highlights: • Microstructure and mechanical properties of UFG 304L stainless steel were studied during GTAW and FSW. • Sigma phase formation mechanism was studied during FSW of 304L stainless steel. • THERMOCALC analysis was performed to obtain possible formation temperatures for sigma phase. • Nano-mechanical twins were found in the TMAZ region.« less

Effect of heat input on the microstructure, residual stresses and corrosion resistance of 304L austenitic stainless steel weldments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Unnikrishnan, Rahul, E-mail: rahulunnikrishnannair@gmail.com; Idury, K.S.N. Satish, E-mail: satishidury@gmail.com; Ismail, T.P., E-mail: tpisma@gmail.com

Austenitic stainless steels are widely used in high performance pressure vessels, nuclear, chemical, process and medical industry due to their very good corrosion resistance and superior mechanical properties. However, austenitic stainless steels are prone to sensitization when subjected to higher temperatures (673 K to 1173 K) during the manufacturing process (e.g. welding) and/or certain applications (e.g. pressure vessels). During sensitization, chromium in the matrix precipitates out as carbides and intermetallic compounds (sigma, chi and Laves phases) decreasing the corrosion resistance and mechanical properties. In the present investigation, 304L austenitic stainless steel was subjected to different heat inputs by shielded metalmore » arc welding process using a standard 308L electrode. The microstructural developments were characterized by using optical microscopy and electron backscattered diffraction, while the residual stresses were measured by X-ray diffraction using the sin{sup 2}ψ method. It was observed that even at the highest heat input, shielded metal arc welding process does not result in significant precipitation of carbides or intermetallic phases. The ferrite content and grain size increased with increase in heat input. The grain size variation in the fusion zone/heat affected zone was not effectively captured by optical microscopy. This study shows that electron backscattered diffraction is necessary to bring out changes in the grain size quantitatively in the fusion zone/heat affected zone as it can consider twin boundaries as a part of grain in the calculation of grain size. The residual stresses were compressive in nature for the lowest heat input, while they were tensile at the highest heat input near the weld bead. The significant feature of the welded region and the base metal was the presence of a very strong texture. The texture in the heat affected zone was almost random. - Highlights: • Effect of heat input on microstructure, residual stresses and corrosion is studied. • HAZ and width of dendrite in the welded region increase with heat input. • Residual stresses are tensile near the welded region after the highest heat input. • Welded region has the highest pit density after highest heat input. • Dendrites and δ-ferrite were highly oriented in the welded region.« less

Modeling growth and dissolution of inclusions during fusion welding of steels

NASA Astrophysics Data System (ADS)

Hong, Tao

The characteristics of inclusions in the weld metals are critical factors to determine the structure, properties and performance of weldments. The research in the present thesis applied computational modeling to study inclusion behavior considering thermodynamics and kinetics of nucleation, growth and dissolution of inclusion along its trajectory calculated from the heat transfer and fluid flow model in the weld pool. The objective of this research is to predict the characteristics of inclusions, such as composition, size distribution, and number density in the weld metal from different welding parameters and steel compositions. To synthesize the knowledge of thermodynamics and kinetics of nucleation, growth and dissolution of inclusion in the liquid metal, a set of time-temperature-transformation (TTT) diagrams are constructed to represent the effects of time and temperature on the isothermal growth and dissolution behavior of fourteen types of individual inclusions. The non-isothermal behavior of growth and dissolution of inclusions is predicted from their isothermal behavior by constructing continuous-cooling-transformation (CCT) diagrams using Scheil additive rule. A well verified fluid flow and heat transfer model developed at Penn State is used to calculate the temperature and velocity fields in the weld pool for different welding processes. A turbulent model considering enhanced viscosity and thermal conductivity (k-ε model) is applied. The calculations show that there is vigorous circulation of metal in the weld pool. The heat transfer and fluid flow model helps to understand not only the fundamentals of the physical phenomena (luring welding, but also the basis to study the growth and dissolution of inclusions. The calculations of particle tracking of thousands of inclusions show that most inclusions undergo complex gyrations and thermal cycles in the weld pool. The inclusions experience both growth and dissolution during their lifetime. Thermal cycles of thousand of inclusions nucleated in the liquid region are tracked and their growth and dissolution are calculated to estimate the final size distribution and number density of inclusions statistically. The calculations show that welding conditions and weld metal compositions affect the inclusion characteristics significantly. Good agreement between the computed and the experimentally observed inclusion size distribution indicates that the inclusion behavior in the weld pool can be understood from the fundamentals of transport phenomena and transformation kinetics.

2016 Accomplishments. Tritium aging studies on stainless steel. Forging process effects on the fracture toughness properties of tritium-precharged stainless steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morgan, Michael J.

Forged austenitic stainless steels are used as the materials of construction for pressure vessels designed to contain tritium at high pressure. These steels are highly resistant to tritium-assisted fracture but their resistance can depend on the details of the forging microstructure. During FY16, the effects of forging strain rate and deformation temperature on the fracture toughness properties of tritium-exposed-and-aged Type 304L stainless steel were studied. Forgings were produced from a single heat of steel using four types of production forging equipment – hydraulic press, mechanical press, screw press, and high-energy-rate forging (HERF). Each machine imparted a different nominal strain ratemore » during the deformation. The objective of the study was to characterize the J-Integral fracture toughness properties as a function of the industrial strain rate and temperature. The second objective was to measure the effects of tritium and decay helium on toughness. Tritium and decay helium effects were measured by thermally precharging the as-forged specimens with tritium gas at 34.5 MPa and 350°C and aging for up to five years at -80°C to build-in decay helium prior to testing. The results of this study show that the fracture toughness properties of the as-forged steels vary with forging strain rate and forging temperature. The effect is largely due to yield strength as the higher-strength forgings had the lower toughness values. For non-charged specimens, fracture toughness properties were improved by forging at 871°C versus 816°C and Screw-Press forgings tended to have lower fracture toughness values than the other forgings. Tritium exposures reduced the fracture toughness values remarkably to fracture toughness values averaging 10-20% of as-forged values. However, forging strain rate and temperature had little or no effect on the fracture toughness after tritium precharging and aging. The result was confirmed by fractography which indicated that fracture modes in the tritium-exposed specimens were similar for all forgings. Another FY16 objective was to prepare fracture toughness specimens from Types 304L and 21-6-9 stainless steel weldments and heat-affected zones (HAZ) for tritium charging.« less

Characterization of nitrogen effects in high energy density weldments of Nitronic 40 stainless steel

NASA Astrophysics Data System (ADS)

Pfeif, Erik Andrew

Variation in the welding environment for laser beam welding and electron beam welding can alter the resulting weld chemical composition, microstructure and therefore the mechanical properties. The room temperature mechanical properties of Nitronic 40 stainless steel weld metal from three different heats containing 0.24, 0.28, and 0.31 wt. pct. nitrogen were evaluated for continuous mode Ytterbium doped Fiber laser welds conducted with argon and nitrogen shielding gases, and for electron beam welds. The bulk nitrogen contents were monitored and the resulting properties were then related to microstructural features measured using Electron BackScatter Diffraction (EBSD). Traditional tensile testing of weld metal is conducted on composite tensile bars consisting of base metal and weld metal often leading to failure in the region adjacent to the weld due to strength mismatch at the weld interface. These tests provide composite strength but do not specifically determine the mechanical properties of the heterogeneous weld metal. In this research, microtensile testing was conducted to characterize the properties of the different regions of the weld. The microtensile testing procedures were developed using two geometries of tensile bars measuring the properties through the thickness of 3 mm full penetration welds. In all cases an increase in the strength of the weld metal was found to occur, though the electron beam welds exhibited a higher strength than the laser welds. Standard predictive equations were found to under-predict the strength of the laser welds, even when average grain size or intercept distances were measured. The contribution of nitrogen solid solution strengthening was consistent at approximately 513 MPa per wt. pct. nitrogen. Similar cooling rates and heat inputs allow for a comparison across high energy density welding techniques. Though microstructural differences through the depth of the weld metal were observed as nitrogen vaporization decreased and cooling rates increased. Vermicular ferrite, lacy ferrite and intercellular ferrite were identified as predicted in prior research done on high nitrogen austenitic stainless steels. The resulting laser weld metal microstructures were analyzed with EBSD for grain size and ferrite content measurements, while grain boundary character was determined for a Hansen model used for multi-scale mechanical property measurements. It was found that the low angle grain boundaries were the predominant microstructural feature responsible for strengthening within the weld metal and that this contribution must be accounted for when predicting yield strength of the weld metal.

Advanced characterization techniques in understanding the roles of nickel in enhancing strength and toughness of submerged arc welding high strength low alloy steel multiple pass welds in the as-welded condition

NASA Astrophysics Data System (ADS)

Sham, Kin-Ling

Striving for higher strength along with higher toughness is a constant goal in material properties. Even though nickel is known as an effective alloying element in improving the resistance of a steel to impact fracture, it is not fully understood how nickel enhances toughness. It was the goal of this work to assist and further the understanding of how nickel enhanced toughness and maintained strength in particular for high strength low alloy (HSLA) steel submerged arc welding multiple pass welds in the as-welded condition. Using advanced analytical techniques such as electron backscatter diffraction, x-ray diffraction, electron microprobe, differential scanning calorimetry, and thermodynamic modeling software, the effect of nickel was studied with nickel varying from one to five wt. pct. in increments of one wt. pct. in a specific HSLA steel submerged arc welding multiple pass weldment. The test matrix of five different nickel compositions in the as-welded and stress-relieved condition was to meet the targeted mechanical properties with a yield strength greater than or equal to 85 ksi, a ultimate tensile strength greater than or equal to 105 ksi, and a nil ductility temperature less than or equal to -140 degrees F. Mechanical testing demonstrated that nickel content of three wt. pct and greater in the as-welded condition fulfilled the targeted mechanical properties. Therefore, one, three, and five wt. pct. nickel in the as-welded condition was further studied to determine the effect of nickel on primary solidification mode, nickel solute segregation, dendrite thickness, phase transformation temperatures, effective ferrite grain size, dislocation density and strain, grain misorientation distribution, and precipitates. From one to five wt. pct nickel content in the as-welded condition, the primary solidification was shown to change from primary delta-ferrite to primary austenite. The nickel partitioning coefficient increased and dendrite/cellular thickness was refined. Austenite decomposition temperatures into different ferrite products were also suppressed to refine the effective ferrite grain size with increasing nickel. Finally, dislocation density and strain increased and a more preferred orientation behavior was observed. At five wt. pct nickel, a precipitate in the form of MnNi3 or FeNi3 was observed. Its presence in both inter and intragranular regions enhanced strength and toughness by limiting the ferrite grain size and precipitation strengthening.

Boiler materials for ultra supercritical coal power plants

DOE Office of Scientific and Technical Information (OSTI.GOV)

Purgert, Robert; Shingledecker, John; Pschirer, James

2015-12-29

The U.S. Department of Energy (DOE) and the Ohio Coal Development Office (OCDO) have undertaken a project aimed at identifying, evaluating, and qualifying the materials needed for the construction of the critical components of coal-fired boilers capable of operating at much higher efficiencies than current generation of supercritical plants. This increased efficiency is expected to be achieved principally through the use of advanced ultrasupercritical (A-USC) steam conditions up to 760°C (1400°F) and 35 MPa (5000 psi). A limiting factor to achieving these higher temperatures and pressures for future A-USC plants are the materials of construction. The goal of this projectmore » is to assess/develop materials technology to build and operate an A-USC boiler capable of delivering steam with conditions up to 760°C (1400°F)/35 MPa (5000 psi). The project has successfully met this goal through a focused long-term public-private consortium partnership. The project was based on an R&D plan developed by the Electric Power Research Institute (EPRI) and an industry consortium that supplemented the recommendations of several DOE workshops on the subject of advanced materials. In view of the variety of skills and expertise required for the successful completion of the proposed work, a consortium led by the Energy Industries of Ohio (EIO) with cost-sharing participation of all the major domestic boiler manufacturers, ALSTOM Power (Alstom), Babcock and Wilcox Power Generation Group, Inc. (B&W), Foster Wheeler (FW), and Riley Power, Inc. (Riley), technical management by EPRI and research conducted by Oak Ridge National Laboratory (ORNL) has been developed. The project has clearly identified and tested materials that can withstand 760°C (1400°F) steam conditions and can also make a 700°C (1300°F) plant more economically attractive. In this project, the maximum temperature capabilities of these and other available high-temperature alloys have been assessed to provide a basis for materials selection and application under a range of conditions prevailing in the boiler. A major effort involving eight tasks was completed in Phase 1. In a subsequent Phase 2 extension, the earlier defined tasks were extended to finish and enhance the Phase 1 activities. This extension included efforts in improved weld/weldment performance, development of longer-term material property databases, additional field (in-plant) corrosion testing, improved understanding of long-term oxidation kinetics and exfoliation, cyclic operation, and fabrication methods for waterwalls. In addition, preliminary work was undertaken to model an oxyfuel boiler to define local environments expected to occur and to study corrosion behavior of alloys under these conditions. This final technical report provides a comprehensive summary of all the work undertaken by the consortium and the research findings from all eight (8) technical tasks including A-USC boiler design and economics (Task 1), long-term materials properties (Task 2), steam- side oxidation (Task 3), Fireside Corrosion (Task 4), Welding (Task 5), Fabricability (Task 6), Coatings (Task 7), and Design Data and Rules (Task 8).« less

5 CFR 792.216 - Are Federal employees with children who are enrolled in summer programs and part-time programs...

Code of Federal Regulations, 2012 CFR

2012-01-01

... are enrolled in summer programs and part-time programs eligible for the child care subsidy program... summer programs and part-time programs eligible for the child care subsidy program? Federal employees... enrolled in daytime summer programs and part-time programs such as before and after school programs are...

5 CFR 792.216 - Are Federal employees with children who are enrolled in summer programs and part-time programs...

Code of Federal Regulations, 2011 CFR

2011-01-01

... are enrolled in summer programs and part-time programs eligible for the child care subsidy program... summer programs and part-time programs eligible for the child care subsidy program? Federal employees... enrolled in daytime summer programs and part-time programs such as before and after school programs are...

5 CFR 792.216 - Are Federal employees with children who are enrolled in summer programs and part-time programs...

Code of Federal Regulations, 2010 CFR

2010-01-01

... are enrolled in summer programs and part-time programs eligible for the child care subsidy program... summer programs and part-time programs eligible for the child care subsidy program? Federal employees... enrolled in daytime summer programs and part-time programs such as before and after school programs are...

Positive youth development programs for adolescents with greater psychosocial needs: evaluation based on program implementers.

PubMed

Shek, Daniel T L; Ng, Catalina S M; Law, Moon Y M

2017-02-01

As program implementers' views are seldom included in program evaluation and there are few related studies in different Chinese communities, this study examined the perceptions of the program implementers who implemented the Tier 2 Program of the P.A.T.H.S. Program in Hong Kong. The Tier 2 Program was designed to promote the development of adolescents with greater psychosocial needs. In the community-based P.A.T.H.S. Project, 400 program implementers completed a subjective outcome evaluation form (Form D) for program implementers. Consistent with the previous findings, program implementers generally held positive views towards the program, implementers, and program effectiveness and their views towards these three domains did not differ across grades. In line with the hypotheses, perceived program quality and perceived implementer quality predicted program effectiveness. The present findings provided an alternative perspective showing that the Tier 2 Program was well received by the program implementers and they regarded the program to be beneficial to the program participants.

Leisure Today. Leisure Programming: The State of the Art.

ERIC Educational Resources Information Center

Busser, James A.; And Others

1993-01-01

Nine articles examine current topics in leisure programing, including program design and evaluation, program design through imagery, keys to quality leisure programing, programing with style, total quality program planning, evaluation of leisure programs, programing for older adults, and the intergenerational entrepreneurship demonstration…

14 CFR 91.1411 - Continuous airworthiness maintenance program use by fractional ownership program manager.

Code of Federal Regulations, 2010 CFR

2010-01-01

... program use by fractional ownership program manager. 91.1411 Section 91.1411 Aeronautics and Space FEDERAL... airworthiness maintenance program use by fractional ownership program manager. Fractional ownership program... through 91.1443. Any program manager who elects to maintain the program aircraft using a continuous...

DEVELOPMENT OF EMERGING TECHNOLOGIES WITHIN THE SITE PROGRAM

EPA Science Inventory

The Site Program is formed by five research programs: the Demonstration Program, the Emerging Technology Program, the Measurement and Monitoring Technology Development Program, the Innovative Technology Program, and the Technology Transfer Program. The Emerging Technology (ET) P...

Enablers and barriers in delivery of a cancer exercise program: the Canadian experience

PubMed Central

Mina, D. Santa; Petrella, A.; Currie, K.L.; Bietola, K.; Alibhai, S.M.H.; Trachtenberg, J.; Ritvo, P.; Matthew, A.G.

2015-01-01

Background Exercise is an important therapy to improve well-being after a cancer diagnosis. Accordingly, cancer-exercise programs have been developed to enhance clinical care; however, few programs exist in Canada. Expansion of cancer-exercise programming depends on an understanding of the process of program implementation, as well as enablers and barriers to program success. Gaining knowledge from current professionals in cancer-exercise programs could serve to facilitate the necessary understanding. Methods Key personnel from Canadian cancer-exercise programs (n = 14) participated in semistructured interviews about program development and delivery. Results Content analysis revealed 13 categories and 15 subcategories, which were grouped by three organizing domains: Program Implementation, Program Enablers, and Program Barriers. ■ Program Implementation (5 categories, 8 subcategories) included Program Initiation (clinical care extension, research project expansion, program champion), Funding, Participant Intake (avenues of awareness, health and safety assessment), Active Programming (monitoring patient exercise progress, health care practitioner involvement, program composition), and Discharge and Follow-up Plan.■ Program Enablers (4 categories, 4 subcategories) included Patient Participation (personalized care, supportive network, personal control, awareness of benefits), Partnerships, Advocacy and Support, and Program Characteristics.■ Program Barriers (4 categories, 3 subcategories) included Lack of Funding, Lack of Physician Support, Deterrents to Participation (fear and shame, program location, competing interests), and Disease Progression and Treatment. Conclusions Interview results provided insight into the development and delivery of cancer-exercise programs in Canada and could be used to guide future program development and expansion in Canada. PMID:26715869

--No Title--

Science.gov Websites

-- OAS Intranet -- Sunday 27 May 2018 Approved Program-Budget 2018 Proposed Program-Budget 2018 Approved Program-Budget 2017 Proposed Program-Budget 2017 Approved Program-Budget 2016 Proposed Program -Budget 2016 Approved Program-Budget 2015 Proposed Program-Budget 2015 Approved Program-Budget 2014

Influence of composition on precipitation behavior and stress rupture properties in INCONEL RTM740 series superalloys

NASA Astrophysics Data System (ADS)

Casias, Andrea M.

Increasing demands for energy efficiency and reduction in CO2 emissions have led to the development of advanced ultra-supercritical (AUSC) boilers. These boilers operate at temperatures of 760 °C and pressures of 35 MPa, providing efficiencies close to 50 pct. However, austenitic stainless steels typically used in boiler applications do not have sufficient creep or oxidation resistance. For this reason, nickel (Ni)-based superalloys, such as IN740, have been identified as potential materials for AUSC boiler tube components. However, IN740 is susceptible to heat-affected-zone liquation cracking in the base metal of heavy section weldments. To improve weldability, IN740H was developed. However, IN740H has lower stress rupture ductility compared to IN740. For this reason, two IN740H modifications have been produced by lowering carbon content and increasing boron content. In this study, IN740, IN740H, and the two modified IN740H alloys (modified 1 and 2) were produced with equiaxed grain sizes of 90 ìm (alloys IN740, IN740H, and IN740H modified 1 alloys) and 112 µm (IN740H modified 2 alloy). An aging study was performed at 800 °C on all alloys for 1, 3, 10, and 30 hours to assess precipitation behavior. Stress rupture tests were performed at 760 °C with the goal of attaining stress levels that would yield rupture at 1000 hours. The percent reduction in area was measured after failure as a measure of creep ductility. Light optical, scanning electron, and transmission electron microscopy were used in conjunction with X-ray diffraction to examine precipitation behavior of annealed, aged, and stress rupture tested samples. The amount and type of precipitation that occurred during aging prior to stress rupture testing or in-situ during stress rupture testing influenced damage development, stress rupture life, and ductility. In terms of stress rupture life, IN740H modified 2 performed the best followed by IN740H modified 1 and IN740, which performed similarly, and IN740H. In terms of stress rupture ductility, IN740H modified 1 performed the best, followed by IN740H modified 2, IN740, and IN740H. G-phase, η, M23C 6, and MX precipitated in IN740 during stress rupture testing. IN740H and the two modified alloys displayed M23C6 precipitates that were often in lamellar form and blocky MX precipitates. However, IN740H displayed more extensive formation of lamellar precipitates along grain boundaries after both aging and during stress rupture testing, which negatively influenced stress rupture life and ductility. Grain size was also shown to influence stress rupture life and ductility; a larger grain size increased stress rupture life, but decreased ductility as shown by the IN740H modified 1 and 2 alloy results. Transmission electron microscopy analysis was performed to assess the lamellar precipitation in IN740H. These precipitates were identified to be Cr-rich M23C6 that form by discontinuous cellular precipitation (DCP). The M23C6 precipitates were found to adopt different {111} habit planes based on the conditions of DCP boundary migration. Discontinuous precipitation of lamellar M23C6 is harmful to stress rupture life and ductility.

Creep of A508/533 Pressure Vessel Steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Richard Wright

2014-08-01

ABSTRACT Evaluation of potential Reactor Pressure Vessel (RPV) steels has been carried out as part of the pre-conceptual Very High Temperature Reactor (VHTR) design studies. These design studies have generally focused on American Society of Mechanical Engineers (ASME) Code status of the steels, temperature limits, and allowable stresses. Initially, three candidate materials were identified by this process: conventional light water reactor (LWR) RPV steels A508 and A533, 2¼Cr-1Mo in the annealed condition, and Grade 91 steel. The low strength of 2¼Cr-1Mo at elevated temperature has eliminated this steel from serious consideration as the VHTR RPV candidate material. Discussions with themore » very few vendors that can potentially produce large forgings for nuclear pressure vessels indicate a strong preference for conventional LWR steels. This preference is based in part on extensive experience with forging these steels for nuclear components. It is also based on the inability to cast large ingots of the Grade 91 steel due to segregation during ingot solidification, thus restricting the possible mass of forging components and increasing the amount of welding required for completion of the RPV. Grade 91 steel is also prone to weld cracking and must be post-weld heat treated to ensure adequate high-temperature strength. There are also questions about the ability to produce, and very importantly, verify the through thickness properties of thick sections of Grade 91 material. The availability of large components, ease of fabrication, and nuclear service experience with the A508 and A533 steels strongly favor their use in the RPV for the VHTR. Lowering the gas outlet temperature for the VHTR to 750°C from 950 to 1000°C, proposed in early concept studies, further strengthens the justification for this material selection. This steel is allowed in the ASME Boiler and Pressure Vessel Code for nuclear service up to 371°C (700°F); certain excursions above that temperature are allowed by Code Case N-499-2 (now incorporated as an appendix to Section III Division 5 of the Code). This Code Case was developed with a rather sparse data set and focused primarily on rolled plate material (A533 specification). Confirmatory tests of creep behavior of both A508 and A533 are described here that are designed to extend the database in order to build higher confidence in ensuring the structural integrity of the VHTR RPV during off-normal conditions. A number of creep-rupture tests were carried out at temperatures above the 371°C (700°F) Code limit; longer term tests designed to evaluate minimum creep behavior are ongoing. A limited amount of rupture testing was also carried out on welded material. All of the rupture data from the current experiments is compared to historical values from the testing carried out to develop Code Case N-499-2. It is shown that the A508/533 basemetal tested here fits well with the rupture behavior reported from the historical testing. The presence of weldments significantly reduces the time to rupture. The primary purpose of this report is to summarize and record the experimental results in a single document.« less

Menu-Driven Solver Of Linear-Programming Problems

NASA Technical Reports Server (NTRS)

Viterna, L. A.; Ferencz, D.

1992-01-01

Program assists inexperienced user in formulating linear-programming problems. A Linear Program Solver (ALPS) computer program is full-featured LP analysis program. Solves plain linear-programming problems as well as more-complicated mixed-integer and pure-integer programs. Also contains efficient technique for solution of purely binary linear-programming problems. Written entirely in IBM's APL2/PC software, Version 1.01. Packed program contains licensed material, property of IBM (copyright 1988, all rights reserved).

Bystander programs addressing sexual violence on college campuses: A systematic review and meta-analysis of program outcomes and delivery methods.

PubMed

Jouriles, Ernest N; Krauss, Alison; Vu, Nicole L; Banyard, Victoria L; McDonald, Renee

2018-02-06

This systematic review and meta-analysis evaluates the effectiveness of bystander programs that address sexual violence on college campuses. Program effects on student attitudes/beliefs and bystander behavior were examined. Durability of program outcomes and the influence of program-delivery methods (e.g., facilitator-led programs vs. video, online or poster campaign programs) and program-parameters (e.g., program length) were also evaluated. Twenty-four studies met criteria for inclusion in the meta-analysis, and 207 separate results from these studies were coded. Students who participated in a bystander program, compared to those who had not, had more pro-social attitudes/beliefs about sexual violence and intervening to prevent it, and engaged in more bystander behavior. Program effects diminished over time, but meaningful changes persisted for at least three months following program delivery. Longer programs had greater effects than shorter programs on attitudes/beliefs. Bystander programs can be a valuable addition to colleges' violence prevention efforts.

75 FR 19185 - Direct and Counter-Cyclical Program and Average Crop Revenue Election Program, Disaster...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-04-14

... Program, Disaster Assistance Programs, Marketing Assistance Loans and Loan Deficiency Payments Program... Disaster Program (LFP), the Supplemental Revenue Assistance Payments Program (SURE) and the Marketing... losses, unless the loss has already been reported for the Noninsured Crop Disaster Assistance Program...

Educational Programs and Services.

ERIC Educational Resources Information Center

American Annals of the Deaf, 1989

1989-01-01

Listed are over 1,000 programs for the deaf including preschool through secondary schools and classes in the U.S. and Canada, postsecondary programs, teacher training programs, programs for professional specialists, programs for training interpreters for the deaf, programs for the deaf-blind, the Helen Keller National Center, and programs for…

The MSFC Program Control Development Program

NASA Technical Reports Server (NTRS)

1994-01-01

It is the policy of the Marshall Space Flight Center (MSFC) that employees be given the opportunity to develop their individual skills and realize their full potential consistent with their selected career path and with the overall Center's needs and objectives. The MSFC Program Control Development Program has been designed to assist individuals who have selected Program Control or Program Analyst Program Control as a career path to achieve their ultimate career goals. Individuals selected to participate in the MSFC Program Control Development Program will be provided with development training in the various Program Control functional areas identified in the NASA Program Control Model. The purpose of the MSFC Program Control Development Program is to develop individual skills in the various Program Control functions by on-the-job and classroom instructional training on the various systems, tools, techniques, and processes utilized in these areas.

Environmental Sciences Division annual progress report for period ending September 30, 1981

DOE Office of Scientific and Technical Information (OSTI.GOV)

Auerbach, S.I.; Reichle, D.E.

1982-04-01

Research programs from the following sections and programs are summarized: aquatic ecology, environmental resources, earth sciences, terrestrial ecology, advanced fossil energy program, toxic substances program, environmental impacts program, biomass, low-level waste research and development program, US DOE low-level waste management program, and waste isolation program.

38 CFR 41.520 - Major program determination.

Code of Federal Regulations, 2011 CFR

2011-07-01

... auditor shall identify the larger Federal programs, which shall be labeled Type A programs. Type A... programs not labeled Type A under paragraph (b)(1) of this section shall be labeled Type B programs. (3... programs as Type A programs. When a Federal program providing loans significantly affects the number or...

A simulation model for wind energy storage systems. Volume 3: Program descriptions

NASA Technical Reports Server (NTRS)

Warren, A. W.; Edsinger, R. W.; Burroughs, J. D.

1977-01-01

Program descriptions, flow charts, and program listings for the SIMWEST model generation program, the simulation program, the file maintenance program, and the printer plotter program are given. For Vol 2, see .

The contributions and future direction of Program Science in HIV/STI prevention.

PubMed

Becker, Marissa; Mishra, Sharmistha; Aral, Sevgi; Bhattacharjee, Parinita; Lorway, Rob; Green, Kalada; Anthony, John; Isac, Shajy; Emmanuel, Faran; Musyoki, Helgar; Lazarus, Lisa; Thompson, Laura H; Cheuk, Eve; Blanchard, James F

2018-01-01

Program Science is an iterative, multi-phase research and program framework where programs drive the scientific inquiry, and both program and science are aligned towards a collective goal of improving population health. To achieve this, Program Science involves the systematic application of theoretical and empirical knowledge to optimize the scale, quality and impact of public health programs. Program Science tools and approaches developed for strategic planning, program implementation, and program management and evaluation have been incorporated into HIV and sexually transmitted infection prevention programs in Kenya, Nigeria, India, and the United States. In this paper, we highlight key scientific contributions that emerged from the growing application of Program Science in the field of HIV and STI prevention, and conclude by proposing future directions for Program Science.

34 CFR 477.1 - What is the State Program Analysis Assistance and Policy Studies Program?

Code of Federal Regulations, 2011 CFR

2011-07-01

... ANALYSIS ASSISTANCE AND POLICY STUDIES PROGRAM General § 477.1 What is the State Program Analysis Assistance and Policy Studies Program? The State Program Analysis Assistance and Policy Studies Program... 34 Education 3 2011-07-01 2011-07-01 false What is the State Program Analysis Assistance and...

34 CFR 477.1 - What is the State Program Analysis Assistance and Policy Studies Program?

Code of Federal Regulations, 2010 CFR

2010-07-01

... ANALYSIS ASSISTANCE AND POLICY STUDIES PROGRAM General § 477.1 What is the State Program Analysis Assistance and Policy Studies Program? The State Program Analysis Assistance and Policy Studies Program... 34 Education 3 2010-07-01 2010-07-01 false What is the State Program Analysis Assistance and...

Implementing reduced-risk integrated pest management in fresh-market cabbage: improved net returns via scouting and timing of effective control.

PubMed

Burkness, Eric C; Hutchison, W D

2008-04-01

During 1998-2001, field studies were done to assess the efficacy of an integrated pest management (IPM) program using an action threshold and "reduced-risk" insecticides. The IPM program was compared with a conventional grower-based program. Program performance was evaluated based on management of Trichoplusia ni (Hiibner), Pieris (=Artogeia) rapae (L.), and Plutella xylostella (L.), as well as the economic impact of each program on net returns. The action threshold used in the IPM program consisted of 10% plants infested with T. ni larvae, based on previous small-plot experiment station trials. In all years of the study, the IPM program resulted in significantly lower percentages of plants infested than the conventional program or untreated check. The mean reduction in insecticide applications for the IPM program compared with the conventional program was 23.5%, whereas, on average, the costs of the IPM program were 46.0% higher than the conventional program. Pest reduction in the IPM program resulted in an average of 10.5% higher marketable yields than the conventional program. Percentages of marketable heads in the IPM program ranged from 82 to 99% and from 63 to 96% in the conventional program. Mean net returns for the IPM program exceeded the conventional program by $984.20/ha. These results indicated that the IPM program reduced insecticide use overall, even though costs of the IPM program, with either spinosad or indoxacarb, were sometimes higher. Overall, net returns of the IPM program were higher due to active pest scouting, improved application timing, and increases in marketable yield. Given the potential decrease in insecticide applications and increases in net profit resulting from this IPM program, additional analyses should be conducted to quantify the economic risk, or consistency of the results, to fully evaluate the benefits of the IPM program compared with a conventional program.

Ideas for Secondary School Physical Education.

ERIC Educational Resources Information Center

Barry, Patricia E., Ed.

This book contains descriptions of secondary school physical education programs. The programs described fall into the following categories: (1) career/leadership programs, (2) contract/individualized instruction programs, (3) elective physical education programs, (4) motivational programs, (5) outdoor/environmental programs, (6)…

Afghanistan: U.S. Rule of Law and Justice Sector Assistance

DTIC Science & Technology

2010-11-09

Sector Support Program ( JSSP ) and Corrections System Support Program (CSSP); • U.S. Agency for International Development’s (USAID’s) formal and informal...Sector Support Program ( JSSP )........................................................................ 28 Corrections System Support Program (CSSP...programs are the Judicial Sector Support Program ( JSSP ), the Corrections System Support Program (CSSP), the ROL Stabilization (RLS) Program, and the

76 FR 22603 - Geographic Preference Option for the Procurement of Unprocessed Agricultural Products in Child...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-04-22

... Program, Special Milk Program for Children, Child and Adult Care Food Program and Summer Food Service... Program, Fresh Fruit and Vegetable Program, Special Milk Program, Child and Adult Care Food Program and... and 10.553, respectively. The Special Milk Program is listed under No. 10.556. The Child and Adult...

A strategy for automatically generating programs in the lucid programming language

NASA Technical Reports Server (NTRS)

Johnson, Sally C.

1987-01-01

A strategy for automatically generating and verifying simple computer programs is described. The programs are specified by a precondition and a postcondition in predicate calculus. The programs generated are in the Lucid programming language, a high-level, data-flow language known for its attractive mathematical properties and ease of program verification. The Lucid programming is described, and the automatic program generation strategy is described and applied to several example problems.

Human operator identification model and related computer programs

NASA Technical Reports Server (NTRS)

Kessler, K. M.; Mohr, J. N.

1978-01-01

Four computer programs which provide computational assistance in the analysis of man/machine systems are reported. The programs are: (1) Modified Transfer Function Program (TF); (2) Time Varying Response Program (TVSR); (3) Optimal Simulation Program (TVOPT); and (4) Linear Identification Program (SCIDNT). The TV program converts the time domain state variable system representative to frequency domain transfer function system representation. The TVSR program computes time histories of the input/output responses of the human operator model. The TVOPT program is an optimal simulation program and is similar to TVSR in that it produces time histories of system states associated with an operator in the loop system. The differences between the two programs are presented. The SCIDNT program is an open loop identification code which operates on the simulated data from TVOPT (or TVSR) or real operator data from motion simulators.

Effective Practices for Evaluating Education and Public Outreach Programs

NASA Astrophysics Data System (ADS)

Wilkerson, S.

2013-12-01

Stephanie Baird Wilkerson, PhD Carol Haden EdD Magnolia Consulting,LLC Education and public outreach (EPO) program developers and providers seeking insights regarding effective practices for evaluating EPO activities programs benefit from understanding why evaluation is critical to the success of EPO activities and programs, what data collection methods are appropriate, and how to effectively communicate and report findings. Based on our extensive experience evaluating EPO programs, we will share lessons learned and examples of how these practices play out in actual evaluation studies. EPO program developers, providers, and evaluators must consider several factors that influence which evaluation designs and data collection methods will be most appropriate, given the nature of EPO programs. Effective evaluation practices of EPO programs take into account a program's phase of development, duration, and budget as well as a program's intended outcomes. EPO programs that are just beginning development will have different evaluation needs and priorities than will well-established programs. Effective evaluation practices consider the 'life' of a program with an evaluation design that supports a program's growth through various phases including development, revision and refinement, and completion. It would be premature and inappropriate to expect the attainment of longer-term outcomes of activities during program development phases or early stages of implementation. During program development, EPO providers should clearly define program outcomes that are feasible and appropriate given a program's scope and expected reach. In many respects, this directly relates to the amount of time, or duration, intended audiences participate in EPO programs. As program duration increases so does the likelihood that the program can achieve longer-term outcomes. When choosing which outcomes are reasonable to impact and measure, program duration should be considered. Effective evaluation practices include selecting appropriate data collection methods given a program's duration and corresponding intended outcomes. Data collection methods for programs of short duration might involve simple evaluation activities, whereas programs of longer duration might involve ongoing data collection measures including longitudinal student surveys, implementation logs, student journals, and student achievement measures. During our presentation, we will share examples from our own experience to illustrate how effective evaluation practices can be applied to various EPO programs based on program duration. Irrespective of duration, we find that EPO program developers and providers want both formative feedback to guide improvements and summative feedback on outcomes. More often than not, evaluation budgets for EPO programs are meager at best, yet come with the same information needs and priorities as programs with larger evaluation budgets. So how do program providers get the information they need given their limited funds for evaluation? We will offer several recommendations for helping EPO program providers work with evaluators to become better-informed consumers of evaluation by maximizing evaluation offerings and minimizing costs. During our presentation we also will share examples of communicating and reporting results for EPO program developers, EPO facilitators and practitioners, and funders.

Guidelines for the Evaluation of Bilingual Education Programs.

ERIC Educational Resources Information Center

Cardoza, Desdemona

Principles of program evaluation research are outlined so that bilingual education program coordinators can conduct methodologically acceptable program evaluations. The three basic principles of evaluation research are: identification of the program participants, definition of the program intervention, and assessment of program effectiveness.…

7 CFR 610.24 - Responsibilities of State Technical Committees.

Code of Federal Regulations, 2011 CFR

2011-01-01

... programs under Title XII of the Food Security Act of 1985 including, but not limited to, the Conservation Reserve Program, Wetlands Reserve Program, Conservation Security Program, Conservation Stewardship Program, Farm and Ranch Lands Protection Program, Grassland Reserve Program, Environmental Quality Incentives...

7 CFR 610.24 - Responsibilities of State Technical Committees.

Code of Federal Regulations, 2010 CFR

2010-01-01

... programs under Title XII of the Food Security Act of 1985 including, but not limited to, the Conservation Reserve Program, Wetlands Reserve Program, Conservation Security Program, Conservation Stewardship Program, Farm and Ranch Lands Protection Program, Grassland Reserve Program, Environmental Quality Incentives...

7 CFR 610.24 - Responsibilities of State Technical Committees.

Code of Federal Regulations, 2012 CFR

2012-01-01

... programs under Title XII of the Food Security Act of 1985 including, but not limited to, the Conservation Reserve Program, Wetlands Reserve Program, Conservation Security Program, Conservation Stewardship Program, Farm and Ranch Lands Protection Program, Grassland Reserve Program, Environmental Quality Incentives...

7 CFR 610.24 - Responsibilities of State Technical Committees.

Code of Federal Regulations, 2013 CFR

2013-01-01

... programs under Title XII of the Food Security Act of 1985 including, but not limited to, the Conservation Reserve Program, Wetlands Reserve Program, Conservation Security Program, Conservation Stewardship Program, Farm and Ranch Lands Protection Program, Grassland Reserve Program, Environmental Quality Incentives...

45 CFR 1304.51 - Management systems and procedures.

Code of Federal Regulations, 2013 CFR

2013-10-01

... control program quality, maintain program accountability, and advise governing bodies, policy groups, and... DELEGATE AGENCIES Program Design and Management § 1304.51 Management systems and procedures. (a) Program... program planning that includes consultation with the program's governing body, policy groups, and program...

Program closure and change among VA substance abuse treatment programs.

PubMed

Floyd, A S

1999-10-01

The population of Veterans Affairs (VA) substance abuse treatment programs in 1990 and 1994 was examined to determine which factors-program legitimacy or cost-accounted for program closure and change. Legitimacy is a concept in institutional theory that organizations tend to take on a form appropriate to the environment. The study had two competing hypotheses. The first was that if external pressures push programs to produce high-quality and efficient treatment, then those that are initially closer to the legitimate form should be less likely to close later, and among surviving programs they should be less likely to experience change. The second hypothesis was that cost is the primary factor in program closure and change. The study used data from administrative surveys of all VA programs (273 in 1990 and 389 in 1994). Program legitimacy variables measured whether programs offered the prevalent type of treatment, such as 12-step groups or behavioral treatment, and had the prevalent type of staff. Program costs did not explain closure or change. For inpatient programs, the risk of closure increased in facilities with more than one substance abuse treatment program. The risk of closure increased for outpatient programs offering the prevalent type of treatment, contrary to what was predicted by the legitimacy hypothesis. Inpatient programs that offered the prevalent treatment were less likely to change the type of treatment offered. Patterns of change differed over time for inpatient and outpatient programs. Legitimacy factors, rather than cost, seem to play a role in program closure and change, although the picture is clearer for inpatient programs than for outpatient programs.

The impact of including incentives and competition in a workplace smoking cessation program on quit rates.

PubMed

Koffman, D M; Lee, J W; Hopp, J W; Emont, S L

1998-01-01

To determine the effectiveness of a multicomponent smoking cessation program supplemented by incentives and team competition. A quasi-experimental design was employed to compare the effectiveness of three different smoking cessation programs, each assigned to separate worksite. The study was conducted from 1990 to 1991 at three aerospace industry worksites in California. All employees who were current, regular tobacco users were eligible to participate in the program offered at their site. The multicomponent program included a self-help package, telephone counseling, and other elements. The incentive-competition program included the multicomponent program plus cash incentives and team competition for the first 5 months of the program. The traditional program offered a standard smoking cessation program. Self-reported questionnaires and carbon monoxide tests of tobacco use or abstinence were used over a 12-month period. The incentive-competition program had an abstinence rate of 41% at 6 months (n = 68), which was significantly better than the multicomponent program (23%, n = 81) or the traditional program (8%, n = 36). At 12 months, the quit rates for the incentive and multicomponent-programs were statistically indistinguishable (37% vs. 30%), but remained higher than the traditional program (11%). Chi-square tests, t-tests, and logistic regression were used to compare smoking abstinence across the three programs. Offering a multicomponent program with telephone counseling may be just as effective for long-term smoking cessation as such a program plus incentives and competition, and more effective than a traditional program.

Program Director Participation in a Leadership and Management Skills Fellowship and Characteristics of Program Quality.

PubMed

Carek, Peter J; Mims, Lisa D; Conry, Colleen M; Maxwell, Lisa; Greenwood, Vicki; Pugno, Perry A

2015-01-01

The association between a residency program director completing a leadership and management skills fellowship and characteristics of quality and innovation of his/her residency program has not been studied. Therefore, the aim of this study is to examine the association between a residency program director's completion of a specific fellowship addressing these skills (National Institute for Program Director Development or NIPDD) and characteristics of quality and innovation of the program they direct. Using information from the American Academy of Family Physicians (AAFP), National Resident Matching Program (NRMP) and FREIDA® program characteristics were obtained. Descriptive statistics were used to summarize the data. The relationship between programs with a NIPDD graduate as director and program quality measures and indicators of innovation was analyzed using both chi square and logistic regression. Initial analyses showed significant associations between the NIPDD graduate status of a program director and regional location, mean years of program director tenure, and the program's 5-year aggregate ABFM board pass rate from 2007--2011. After grouping the programs into tertiles, the regression model showed significant positive associations with programs offering international experiences and being a NIPDD graduate. Program director participation in a fellowship addressing leadership and management skills (ie, NIPDD) was found to be associated with higher pass rates of new graduates on a Board certification examination and predictive of programs being in the upper tertile of programs in terms of Board pass rates.

ACHP GUIDANCE ON PROGRAM COMMENTS AS A PROGRAM ALTERNATIVE

Science.gov Websites

the benefits of the program comment process? Are program comments appropriate for all classes of undertakings or agency programs? Who can make requests for program comments? Does my agency need to justify the agency's responsibility in the program comment process? What is the ACHP's responsibility in the program

Compendium of Programs to Assist the Transition

DTIC Science & Technology

1993-02-01

Program Description The Interagency Placement Assistance Program (IPAP) offices maintain computerized listings of data on employees faced with...possible reduction in force (RIF) separations. Program Objective To provide placement assistance to employees faced with possible RIF separations by making... employees . 23 2/93 TRANSITION ASSISTANCE PROGRAM Short Name of Program TAP Program Description Begun in 1991, TAP is a joint program of

INSTRUCTIONAL PROGRAMMING PROCEDURES, A PROGRAMED COURSE IN THE BASIC METHODS AND TECHNIQUES OF PREPARING PROGRAMED INSTRUCTIONAL MATERIALS.

ERIC Educational Resources Information Center

DETERLINE, WILLIAM A.

A PROGRAMED COURSE IN METHODS AND TECHNIQUES OF PREPARING PROGRAMED INSTRUCTIONAL MATERIALS WAS PRESENTED IN THIS DOCUMENT. AN ATTEMPT WAS MADE TO TEACH BASIC PROCEDURES WELL ENOUGH TO PRODUCE AN EMBRYO PROGRAMER AND TO PROVIDE HIM WITH REFERENCES HE WOULD NEED IN ORDER TO PRODUCE PROGRAMS. INCLUDED WERE PROGRAMED INSTRUCTIONS ON PREPARATORY…

Rocket exhaust plume computer program improvement. Volume 1: Summary: Method of characteristics nozzle and plume programs

NASA Technical Reports Server (NTRS)

Ratliff, A. W.; Smith, S. D.; Penny, N. M.

1972-01-01

A summary is presented of the various documents that discuss and describe the computer programs and analysis techniques which are available for rocket nozzle and exhaust plume calculations. The basic method of characteristics program is discussed, along with such auxiliary programs as the plume impingement program, the plot program and the thermochemical properties program.

An Evaluation Program for the Eckerd Foundation Therapeutic Wilderness Camping Program: An Evaluation of an Atypical Alternative Education Program.

ERIC Educational Resources Information Center

Griffin, William H.; Carter, James D.

The strategy used in evaluating an out-of-doors resident camping program for emotionally disturbed children is outlined. This strategy calls for examining the following elements in the program: (1) program goals and objectives; (2) collection and processing program data; (3) camper progress assessment; (4) program audit; (5) assessment of past…

A National Survey of Tobacco Cessation Programs for Youths

PubMed Central

Curry, Susan J.; Emery, Sherry; Sporer, Amy K.; Mermelstein, Robin; Flay, Brian R.; Berbaum, Michael; Warnecke, Richard B.; Johnson, Timothy; Mowery, Paul; Parsons, Jennifer; Harmon, Lori; Hund, Lisa; Wells, Henry

2007-01-01

Objectives. We collected data on a national sample of existing community-based tobacco cessation programs for youths to understand their prevalence and overall characteristics. Methods. We employed a 2-stage sampling design with US counties as the first-stage probability sampling units. We then used snowball sampling in selected counties to identify administrators of tobacco cessation programs for youths. We collected data on cessation programs when programs were identified. Results. We profiled 591 programs in 408 counties. Programs were more numerous in urban counties; fewer programs were found in low-income counties. State-level measures of smoking prevalence and tobacco control expenditures were not associated with program availability. Most programs were multisession, school-based group programs serving 50 or fewer youths per year. Program content included cognitive-behavioral components found in adult programs along with content specific to adolescence. The median annual budget was $2000. Few programs (9%) reported only mandatory enrollment, 35% reported mixed mandatory and voluntary enrollment, and 56% reported only voluntary enrollment. Conclusions. There is considerable homogeneity among community-based tobacco cessation programs for youths. Programs are least prevalent in the types of communities for which national data show increases in youths’ smoking prevalence. PMID:17138932

Using a visual programming language to bridge the cognitive gap between a novice's mental model and program code

NASA Astrophysics Data System (ADS)

Smith, Bryan J.

Current research suggests that many students do not know how to program very well at the conclusion of their introductory programming course. We believe that a reason novices have such difficulties learning programming is because engineering novices often learn through a lecture format where someone with programming knowledge lectures to novices, the novices attempt to absorb the content, and then reproduce it during exams. By primarily appealing to programming novices who prefer to understand visually, we research whether programming novices understand programming better if computer science concepts are presented using a visual programming language than if these programs are presented using a text-based programming language. This method builds upon previous research that suggests that most engineering students are visual learners, and we propose that using a flow-based visual programming language will address some of the most important and difficult topics to novices of programming. We use an existing flow-model tool, RAPTOR, to test this method, and share the program understanding results using this theory.

45 CFR 1306.34 - Combination program option.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 45 Public Welfare 4 2010-10-01 2010-10-01 false Combination program option. 1306.34 Section 1306... START PROGRAM HEAD START STAFFING REQUIREMENTS AND PROGRAM OPTIONS Head Start Program Options § 1306.34 Combination program option. (a) Combination program option requirements: (1) Grantees implementing a...

Hospitality Management. Florida Vocational Program Guide.

ERIC Educational Resources Information Center

Florida State Univ., Tallahassee. Center for Instructional Development and Services.

This program guide is intended for the implementation of a hospitality management program in Florida secondary and postsecondary schools. The program guide describes the program content and structure, provides a program description, describes jobs under the program, and includes a curriculum framework and student performance standards for…

40 CFR 68.170 - Prevention program/Program 2.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 15 2011-07-01 2011-07-01 false Prevention program/Program 2. 68.170 Section 68.170 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) CHEMICAL ACCIDENT PREVENTION PROVISIONS Risk Management Plan § 68.170 Prevention program/Program...

24 CFR 4001.01 - Purpose of program.

Code of Federal Regulations, 2010 CFR

2010-04-01

...) BOARD OF DIRECTORS OF THE HOPE FOR HOMEOWNERS PROGRAM HOPE FOR HOMEOWNERS PROGRAM HOPE for Homeowners Program-General Requirements § 4001.01 Purpose of program. The HOPE for Homeowners Program is a temporary... avoid foreclosure. The HOPE for Homeowners Program is administered by HUD through FHA. ...

40 CFR 68.170 - Prevention program/Program 2.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 15 2010-07-01 2010-07-01 false Prevention program/Program 2. 68.170 Section 68.170 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) CHEMICAL ACCIDENT PREVENTION PROVISIONS Risk Management Plan § 68.170 Prevention program/Program...

Minority Engineering Program Pipeline: A Proposal to Increase Minority Student Enrollment and Retention in Engineering

NASA Technical Reports Server (NTRS)

Charity, Pamela C.; Klein, Paul B.; Wadhwa, Bhushan

1995-01-01

The Cleveland State University Minority Engineering Program Pipeline consist of programs which foster engineering career awareness, academic enrichment, and professional development for historically underrepresented minority studies. The programs involved are the Access to Careers in Engineering (ACE) Program for high school pre-engineering students: the LINK Program for undergraduate students pursuing degree which include engineering; and the PEP (Pre-calculus Enrichment Program) and EPIC (Enrichment Program in Calculus) mathematics programs for undergraduate academic enrichment. The pipeline is such that high school graduates from the ACE Program who enroll at Cleveland State University in pursuit of engineering degrees are admitted to the LINK Program for undergraduate level support. LINK Program students are among the minority participants who receive mathematics enrichment through the PEP and EPIC Programs for successful completion of their engineering required math courses. THese programs are interdependent and share the goal of preparing minority students for engineering careers by enabling them to achieve academically and obtain college degree and career related experience.

Collectively loading programs in a multiple program multiple data environment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aho, Michael E.; Attinella, John E.; Gooding, Thomas M.

Techniques are disclosed for loading programs efficiently in a parallel computing system. In one embodiment, nodes of the parallel computing system receive a load description file which indicates, for each program of a multiple program multiple data (MPMD) job, nodes which are to load the program. The nodes determine, using collective operations, a total number of programs to load and a number of programs to load in parallel. The nodes further generate a class route for each program to be loaded in parallel, where the class route generated for a particular program includes only those nodes on which the programmore » needs to be loaded. For each class route, a node is selected using a collective operation to be a load leader which accesses a file system to load the program associated with a class route and broadcasts the program via the class route to other nodes which require the program.« less

An Examination of New Counselor Mentor Programs

ERIC Educational Resources Information Center

Bass, Erin; Gardner, Lauren; Onwukaeme, Chika; Revere, Dawn; Shepherd, Denise; Parrish, Mark S.

2013-01-01

An analysis of current new counselor mentor programs reveals the need for such programs, but information regarding established programs is limited. A review of the literature addresses program characteristics and data obtained from existing mentor program participants. An overview of four programs explaining the framework outlined for mentoring…

COMPENSATORY EDUCATION PROGRAM. NEWSLETTER.

ERIC Educational Resources Information Center

Fresno City Unified School District, CA.

TWO NEWSLETTERS FROM THE COMPENSATORY EDUCATION PROGRAM IN FRESNO INCLUDED PLANS FOR THE PLANNING GRANT PROGRAM, THE BASIC PROGRAM, AND THE INTENSIVE PROGRAM. THE BASIC PROGRAM SHOULD REDUCE PUPIL-TEACHER RATIO, PROVIDE PRESCHOOL PROJECTS THROUGH THE USE OF EITHER SCHOOL FACILITIES OR PRIVATE FACILITIES, PROVIDE REMEDIAL AND CORRECTIVE PROGRAMS IN…

47 CFR 79.3 - Video description of video programming.

Code of Federal Regulations, 2014 CFR

2014-10-01

... transmission by a video programming distributor. (8) Children's Programming. Television programming directed at children 16 years of age and under. (b) The following video programming distributors must provide... or on children's programming, on each programming stream on which they carry one of the top four...

Numerical analysis of stiffened shells of revolution. Volume 7: Satellite programs for the STARS system

NASA Technical Reports Server (NTRS)

Svalbonas, V.; Ogilvie, P.

1973-01-01

The user and programming information necessary for the application of the SATELLITE programs for the STARS system are presented. The individual program functions are: (1) data debugging for the STARS-2S program, (2) Fourier series conversion program, (3) data debugging for the STARS-2B program, and (4) data debugging for the STARS-2V program.

Military and academic programs outperform community programs on the American Board of Surgery Examinations.

PubMed

Falcone, John L; Charles, Anthony G

2013-01-01

There is a paucity of American Board of Surgery (ABS) Qualifying Examination (QE) and Certifying Examination (CE) outcomes comparing residency programs by academic, community, or military affiliation. We hypothesize that the larger academic programs will outperform the smaller community programs. In this retrospective study from 2002 to 2012, examination performance on the ABS QE and CE were obtained from the ABS for all of the general surgery residency programs. Programs were categorized by academic, community, and military affiliation. Both nonparametric and parametric statistics were used for comparison, using an α = 0.05. There were 137/235 (58.3%) academic programs, 90/235 (38.3%) community programs, and 8/235 (3.4%) military programs that satisfied inclusion criteria for this study. The Mann-Whitney U tests showed that the military programs outperformed academic and community programs on the ABS QE and the ABS CE, and had a higher proportion of examinees passing both examinations on the first attempt (all p≤0.02). One-tailed Student t-tests showed that academic programs had higher pass rates than community programs on the ABS QE (85.4%±9.5% vs. 81.9%±11.5%), higher pass rates on the ABS CE (83.6%±8.3% vs. 80.6%±11.0%), and a higher proportion of examinees passing both examinations on the first attempt (0.73±0.12 vs. 0.68±0.15) (all p≤0.01). The chi-square and Fisher exact tests showed that examinees performed highest in military programs, followed by academic programs, and lowest in community programs on the ABS QE and ABS CE (all p≤ 0.01). Military programs have the highest degrees of success on all of the ABS examinations. Academic programs outperform community programs. These results have the potential to affect application patterns to established general surgery residency programs. Copyright © 2013 Association of Program Directors in Surgery. Published by Elsevier Inc. All rights reserved.

Federal Programs in PUHSS: An Evaluation Report.

ERIC Educational Resources Information Center

Phoenix Union High School District, AZ.

The programs described in this report, including the South Mountain High School Reading Program, the Carl Hayden High School Reading Program, the Phoenix Union High School Reading Program, the South Mountain High School Saturation Guidance and Counseling Program (SGCP), the Work Incentive Program (WIN), the Phoenix Union High School Star Reach…

Interactions among Social Welfare Programs.

ERIC Educational Resources Information Center

Lewis, Gordon H.; Morrison, Richard J.

1990-01-01

This paper explores interactions between social welfare programs and associated supportive taxation programs. Focus was on the effect of one program on another, effects of one program on a set of other programs, effects of tax and benefit reduction rates, and effects of interacting programs on the governments that create/maintain them. (TJH)

Basic Gasoline Engine Mechanics. Florida Vocational Program Guide.

ERIC Educational Resources Information Center

University of South Florida, Tampa. Dept. of Adult and Vocational Education.

This packet contains a program guide and Career Merit Achievement Plan (Career MAP) for the implementation of a basic gasoline engine mechanics program in Florida secondary and postsecondary schools. The program guide describes the program content and structure, provides a program description, lists job titles under the program, and includes a…

Individuals with Disabilities Education Act: Reauthorization Overview. CRS Report for Congress.

ERIC Educational Resources Information Center

Aleman, Steven R.

This report provides an overview of programs authorized under the Individuals with Disabilities Education Act (IDEA) and discusses potential reauthorization issues. Programs include the Grants to States program, preschool program, infants and toddlers program, and discretionary grant programs. For each program, information includes fiscal year…

The Status of Child Nutrition Programs in Colorado.

ERIC Educational Resources Information Center

McMillan, Daniel C.; Vigil, Herminia J.

This report describes federal and state child nutrition programs in effect in Colorado elementary and secondary schools. Programs discussed include the National School Lunch Program (NSLP), the School Breakfast Program (SBP), school breakfast start-up grants, the Special Milk Program, the Summer Food Service Program, and the Nutrition Education…

The Status of Child Nutrition Programs in Colorado.

ERIC Educational Resources Information Center

McMillan, Daniel C.; Vigil, Herminia J.

This report provides descriptive and statistical data on the status of child nutrition programs in Colorado. The report contains descriptions of the National School Lunch Program, school breakfast programs, the Special Milk Program, the Summer Food Service Program, the Nutrition Education and Training Program, state dietary guidelines, Colorado…

20 CFR 632.255 - Program planning.

Code of Federal Regulations, 2011 CFR

2011-04-01

... EMPLOYMENT AND TRAINING PROGRAMS Summer Youth Employment and Training Programs § 632.255 Program planning. (a)(1) In developing the summer program, the Native American grantee shall coordinate the summer plan..., except that 45 days prior to the beginning of the summer program and 45 days after the summer program...

20 CFR 632.255 - Program planning.

Code of Federal Regulations, 2012 CFR

2012-04-01

... EMPLOYMENT AND TRAINING PROGRAMS Summer Youth Employment and Training Programs § 632.255 Program planning. (a)(1) In developing the summer program, the Native American grantee shall coordinate the summer plan..., except that 45 days prior to the beginning of the summer program and 45 days after the summer program...

Consumer Electronic Product Servicing. Florida Vocational Program Guide.

ERIC Educational Resources Information Center

University of South Florida, Tampa. Dept. of Adult and Vocational Education.

This packet contains a program guide and Career Merit Achievement Plan (Career MAP) for the implementation of a consumer electronic product servicing program in Florida secondary and postsecondary schools. The program guide describes the program content and structure, provides a program description, lists job titles under the program, and includes…

Computer Integrated Manufacturing. Florida Vocational Program Guide.

ERIC Educational Resources Information Center

University of South Florida, Tampa. Dept. of Adult and Vocational Education.

This packet contains a program guide and Career Merit Achievement Plan (Career MAP) for the implementation of a computer-integrated manufacturing program in Florida secondary and postsecondary schools. The program guide describes the program content and structure, provides a program description, lists job titles under the program, and includes a…

Computer Engineering Technology. Florida Vocational Program Guide.

ERIC Educational Resources Information Center

University of South Florida, Tampa. Dept. of Adult and Vocational Education.

This packet contains a program guide and Career Merit Achievement Plan (Career MAP) for the implementation of a computer engineering technology program in Florida secondary and postsecondary schools. The program guide describes the program content and structure, provides a program description, lists job titles under the program, and includes a…

Q Methodology as a Tool for Program Assessment

ERIC Educational Resources Information Center

Ramlo, Susan E.

2015-01-01

Program assessment is now commonplace at most colleges and universities and is required for accreditation of specific degree programs. Key aspects of program assessment include program improvement, improved student learning, and adequate student preparation for the workforce. Thus, program assessment is a key ingredient to program health. Although…

7 CFR 662.2 - Definitions.

Code of Federal Regulations, 2011 CFR

2011-01-01

.... These programs include: Conservation Stewardship Program, Farm and Ranch Lands Protection Program, Grassland Reserve Program, Environmental Quality Incentives Program, Conservation Innovation Grants, Agricultural Water Enhancement Program, Conservation of Private Grazing Land, Wildlife Habitat Incentive...

45 CFR 1388.2 - Program criteria-purpose.

Code of Federal Regulations, 2012 CFR

2012-10-01

... DISABILITIES PROGRAM THE UNIVERSITY AFFILIATED PROGRAMS § 1388.2 Program criteria—purpose. The program criteria will be used to assess the quality of the University Affiliated Programs (UAP). The overall purpose of...

45 CFR 1388.2 - Program criteria-purpose.

Code of Federal Regulations, 2013 CFR

2013-10-01

... DISABILITIES PROGRAM THE UNIVERSITY AFFILIATED PROGRAMS § 1388.2 Program criteria—purpose. The program criteria will be used to assess the quality of the University Affiliated Programs (UAP). The overall purpose of...

45 CFR 1388.2 - Program criteria-purpose.

Code of Federal Regulations, 2014 CFR

2014-10-01

... DISABILITIES PROGRAM THE UNIVERSITY AFFILIATED PROGRAMS § 1388.2 Program criteria—purpose. The program criteria will be used to assess the quality of the University Affiliated Programs (UAP). The overall purpose of...

45 CFR 1388.2 - Program criteria-purpose.

Code of Federal Regulations, 2011 CFR

2011-10-01

... DISABILITIES PROGRAM THE UNIVERSITY AFFILIATED PROGRAMS § 1388.2 Program criteria—purpose. The program criteria will be used to assess the quality of the University Affiliated Programs (UAP). The overall purpose of...

Lessons learned from employee fitness programs at the Marshfield Clinic.

PubMed

McCarty, Catherine A; Scheuer, Dave

2005-07-01

To describe and evaluate employee fitness programs at the Marshfield Clinic. A 16-week program was offered to employees from April-July 2004, and a 12-week program was offered from August-November, 2004. Weekly e-mails included suggestions to increase physical activity and eat a healthy diet. Incentives were offered for meeting program goals. A total of 1129 employees signed up for the first program (approximately 18% of all employees) and 610 for the second program. More than 95% of the participants in both programs were female. The activity program goal was met by 231 (20.5%) participants in the first program and 31% (n = 190) of participants in the second program. There was a significant increase in the percent of people with good or excellent fitness levels from baseline (46.4%, 95% CL = 40.5, 52.3) to follow-up (70.7%, 95% CL = 65.3, 76.0) in the first program. In the second program, there was a significant association between the number of program goals met and self-report of having increased energy, better weight control, and feeling better overall and about body image. Emphasis in future programs should be placed on increasing employee participation. Program evaluation could be expanded to include health care costs and employee absenteeism.

Formulation of advanced consumables management models: Environmental control and electrical power system performance models requirements

NASA Technical Reports Server (NTRS)

Daly, J. K.; Torian, J. G.

1979-01-01

Software design specifications for developing environmental control and life support system (ECLSS) and electrical power system (EPS) programs into interactive computer programs are presented. Specifications for the ECLSS program are at the detail design level with respect to modification of an existing batch mode program. The FORTRAN environmental analysis routines (FEAR) are the subject batch mode program. The characteristics of the FEAR program are included for use in modifying batch mode programs to form interactive programs. The EPS program specifications are at the preliminary design level. Emphasis is on top-down structuring in the development of an interactive program.

Measurement and Analysis of P2P IPTV Program Resource

PubMed Central

Chen, Xingshu; Wang, Haizhou; Zhang, Qi

2014-01-01

With the rapid development of P2P technology, P2P IPTV applications have received more and more attention. And program resource distribution is very important to P2P IPTV applications. In order to collect IPTV program resources, a distributed multi-protocol crawler is proposed. And the crawler has collected more than 13 million pieces of information of IPTV programs from 2009 to 2012. In addition, the distribution of IPTV programs is independent and incompact, resulting in chaos of program names, which obstructs searching and organizing programs. Thus, we focus on characteristic analysis of program resources, including the distributions of length of program names, the entropy of the character types, and hierarchy depth of programs. These analyses reveal the disorderly naming conventions of P2P IPTV programs. The analysis results can help to purify and extract useful information from chaotic names for better retrieval and accelerate automatic sorting of program and establishment of IPTV repository. In order to represent popularity of programs and to predict user behavior and popularity of hot programs over a period, we also put forward an analytical model of hot programs. PMID:24772008

Results of the Association of Directors of Radiation Oncology Programs (ADROP) Survey of Radiation Oncology Residency Program Directors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harris, Eleanor; Abdel-Wahab, May; Spangler, Ann E.

2009-06-01

Purpose: To survey the radiation oncology residency program directors on the topics of departmental and institutional support systems, residency program structure, Accreditation Council for Graduate Medical Education (ACGME) requirements, and challenges as program director. Methods: A survey was developed and distributed by the leadership of the Association of Directors of Radiation Oncology Programs to all radiation oncology program directors. Summary statistics, medians, and ranges were collated from responses. Results: Radiation oncology program directors had implemented all current required aspects of the ACGME Outcome Project into their training curriculum. Didactic curricula were similar across programs nationally, but research requirements and resourcesmore » varied widely. Program directors responded that implementation of the ACGME Outcome Project and the external review process were among their greatest challenges. Protected time was the top priority for program directors. Conclusions: The Association of Directors of Radiation Oncology Programs recommends that all radiation oncology program directors have protected time and an administrative stipend to support their important administrative and educational role. Departments and institutions should provide adequate and equitable resources to the program directors and residents to meet increasingly demanding training program requirements.« less

Overview of Mars Technology Program

NASA Technical Reports Server (NTRS)

Hayati, Samad A.

2006-01-01

This viewgraph presentation reviews the development of a technology program leading to Mars missions. The presentation includes: the goals of technology program, elements of technology program, program metrics, major accomplishments, examples and Information about the Mars Technology Program.

30 CFR 900.13 - Federal programs and Federal coal exploration programs.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 3 2010-07-01 2010-07-01 false Federal programs and Federal coal exploration... INTRODUCTION § 900.13 Federal programs and Federal coal exploration programs. The rules for each Federal program and Federal coal exploration program are codified below under the assigned part for the particular...

30 CFR 900.13 - Federal programs and Federal coal exploration programs.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 30 Mineral Resources 3 2012-07-01 2012-07-01 false Federal programs and Federal coal exploration... INTRODUCTION § 900.13 Federal programs and Federal coal exploration programs. The rules for each Federal program and Federal coal exploration program are codified below under the assigned part for the particular...

30 CFR 900.13 - Federal programs and Federal coal exploration programs.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 30 Mineral Resources 3 2013-07-01 2013-07-01 false Federal programs and Federal coal exploration... INTRODUCTION § 900.13 Federal programs and Federal coal exploration programs. The rules for each Federal program and Federal coal exploration program are codified below under the assigned part for the particular...

30 CFR 900.13 - Federal programs and Federal coal exploration programs.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 30 Mineral Resources 3 2011-07-01 2011-07-01 false Federal programs and Federal coal exploration... INTRODUCTION § 900.13 Federal programs and Federal coal exploration programs. The rules for each Federal program and Federal coal exploration program are codified below under the assigned part for the particular...

30 CFR 900.13 - Federal programs and Federal coal exploration programs.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 30 Mineral Resources 3 2014-07-01 2014-07-01 false Federal programs and Federal coal exploration... INTRODUCTION § 900.13 Federal programs and Federal coal exploration programs. The rules for each Federal program and Federal coal exploration program are codified below under the assigned part for the particular...

Undergraduate Programs of Cooperative Education in the United States & Canada.

ERIC Educational Resources Information Center

Northeastern Univ., Boston, MA. Cooperative Education Research Center.

Information on cooperative education programs gathered by survey is presented. Listed are 992 programs operational with 459 junior-college programs and 533 four-year-college programs. In addition to listing the colleges and universities with such programs, six categories of information about the institution and the program are provided if known.…

45 CFR 1306.33 - Home-based program option.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 45 Public Welfare 4 2013-10-01 2013-10-01 false Home-based program option. 1306.33 Section 1306.33... PROGRAM HEAD START STAFFING REQUIREMENTS AND PROGRAM OPTIONS Head Start Program Options § 1306.33 Home-based program option. (a) Grantees implementing a home-based program option must: (1) Provide one home...

45 CFR 1306.33 - Home-based program option.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 45 Public Welfare 4 2014-10-01 2014-10-01 false Home-based program option. 1306.33 Section 1306.33... PROGRAM HEAD START STAFFING REQUIREMENTS AND PROGRAM OPTIONS Head Start Program Options § 1306.33 Home-based program option. (a) Grantees implementing a home-based program option must: (1) Provide one home...

45 CFR 1306.33 - Home-based program option.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 45 Public Welfare 4 2012-10-01 2012-10-01 false Home-based program option. 1306.33 Section 1306.33... PROGRAM HEAD START STAFFING REQUIREMENTS AND PROGRAM OPTIONS Head Start Program Options § 1306.33 Home-based program option. (a) Grantees implementing a home-based program option must: (1) Provide one home...

31 CFR 103.125 - Anti-money laundering programs for money services businesses.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 31 Money and Finance: Treasury 1 2010-07-01 2010-07-01 false Anti-money laundering programs for... Laundering Programs Anti-Money Laundering Programs § 103.125 Anti-money laundering programs for money..., and maintain an effective anti-money laundering program. An effective anti-money laundering program is...

Commitments: A Guide to Community Involvement Programs at The George Washington University.

ERIC Educational Resources Information Center

George Washington Univ., Washington, DC.

This guide to community involvement programs sponsored by the George Washington University provides a synopsis and a contact person for 33 general university programs, 38 medical school and hospital programs, eight National Law Center programs, eight School of Engineering and Applied Science programs, and two programs of the Division of…

An Investigation of Teaching and Learning Programs in Pharmacy Education

PubMed Central

Baia, Patricia

2016-01-01

Objective. To investigate published, peer-reviewed literature on pharmacy teaching and learning development programs and to synthesize existing data, examine reported efficacy and identify future areas for research. Methods. Medline and ERIC databases were searched for studies on teaching development programs published between 2001 and 2015. Results. Nineteen publications were included, representing 21 programs. Twenty programs were resident teaching programs, one program described faculty development. The majority of programs spanned one year and delivered instruction on teaching methodologies and assessment measures. All except one program included experiential components. Thirteen publications presented outcomes data; most measured satisfaction and self-perceived improvement. Conclusion. Published literature on teacher development in pharmacy is focused more on training residents than on developing faculty members. Although programs are considered important and highly valued by program directors and participants, little data substantiates that these programs improve teaching. Future research could focus on measurement of program outcomes and documentation of teaching development for existing faculty members. PMID:27293226

An Investigation of Teaching and Learning Programs in Pharmacy Education.

PubMed

Strang, Aimee F; Baia, Patricia

2016-05-25

Objective. To investigate published, peer-reviewed literature on pharmacy teaching and learning development programs and to synthesize existing data, examine reported efficacy and identify future areas for research. Methods. Medline and ERIC databases were searched for studies on teaching development programs published between 2001 and 2015. Results. Nineteen publications were included, representing 21 programs. Twenty programs were resident teaching programs, one program described faculty development. The majority of programs spanned one year and delivered instruction on teaching methodologies and assessment measures. All except one program included experiential components. Thirteen publications presented outcomes data; most measured satisfaction and self-perceived improvement. Conclusion. Published literature on teacher development in pharmacy is focused more on training residents than on developing faculty members. Although programs are considered important and highly valued by program directors and participants, little data substantiates that these programs improve teaching. Future research could focus on measurement of program outcomes and documentation of teaching development for existing faculty members.

Ranking Surgical Residency Programs: Reputation Survey or Outcomes Measures?

PubMed

Wilson, Adam B; Torbeck, Laura J; Dunnington, Gary L

2015-01-01

The release of general surgery residency program rankings by Doximity and U.S. News & World Report accentuates the need to define and establish measurable standards of program quality. This study evaluated the extent to which program rankings based solely on peer nominations correlated with familiar program outcomes measures. Publicly available data were collected for all 254 general surgery residency programs. To generate a rudimentary outcomes-based program ranking, surgery programs were rank-ordered according to an average percentile rank that was calculated using board pass rates and the prevalence of alumni publications. A Kendall τ-b rank correlation computed the linear association between program rankings based on reputation alone and those derived from outcomes measures to validate whether reputation was a reasonable surrogate for globally judging program quality. For the 218 programs with complete data eligible for analysis, the mean board pass rate was 72% with a standard deviation of 14%. A total of 60 programs were placed in the 75th percentile or above for the number of publications authored by program alumni. The correlational analysis reported a significant correlation of 0.428, indicating only a moderate association between programs ranked by outcomes measures and those ranked according to reputation. Seventeen programs that were ranked in the top 30 according to reputation were also ranked in the top 30 based on outcomes measures. This study suggests that reputation alone does not fully capture a representative snapshot of a program's quality. Rather, the use of multiple quantifiable indicators and attributes unique to programs ought to be given more consideration when assigning ranks to denote program quality. It is advised that the interpretation and subsequent use of program rankings be met with caution until further studies can rigorously demonstrate best practices for awarding program standings. Copyright © 2015 Association of Program Directors in Surgery. Published by Elsevier Inc. All rights reserved.

Service-linked scholarships, loans, and loan repayment programs for nurses in the southeast.

PubMed

Thaker, Samir I; Pathman, Donald E; Mark, Barbara A; Ricketts, Thomas C

2008-01-01

A variety of public and private programs provide financial support for the costs of nurses' training in exchange for service commitments to work in rural, underserved, and other needy areas. Little is known about the number, size, and operations of these support-for-service programs for nurses. We identified and in this article describe such programs in eight southeastern states. Eligible programs were those that in 2004 paid for all or a portion of nurses' education costs in exchange for a period of clinical nursing service within one or more of the eight targeted states. Programs obligating nurses to a specific hospital, practice, or community or to teaching roles were excluded. Programs were identified through available compendia, online searches, and telephone contacts with program directors, nursing school administrators, and state officials. Additional data on eligible programs were gathered through telephone interviews and questionnaires mailed to program staff and from publicly available documents. Data were double coded, and qualitative and quantitative analyses were conducted. Twenty-four nursing support-for-service programs met our eligibility criteria in the eight-state region: nine scholarship programs; six loan repayment programs; five service-cancelable loan programs; two loan interest rate reduction programs; and two direct incentive programs. These programs had fiscal year 2004 budgets totaling approximately $28.8-31.8 million; collectively, they received approximately 11,700 applications from nurses, signed approximately 8,300 contracts, and had a combined field strength of approximately 4,900 nurses working to fulfill their program obligations. Individual states offered between zero and five eligible programs each. Support-for-service programs are a substantial component of federal and state nursing workforce distribution efforts in the Southeast. Future research should identify and describe these programs for other regions, measure outcomes, and offer recommendations to maximize their effectiveness in alleviating nursing shortages.

40 CFR 52.1131 - Control strategy: Particulate matter.

Code of Federal Regulations, 2014 CFR

2014-07-01

...) (PSD program only), (D)(i)(II) (PSD program only), (D)(ii), and (J) (PSD program only). (e) Approval...) (PSD program only), (D)(i)(II) (PSD program only), (D)(ii), and (J) (PSD program only). [45 FR 2044...

40 CFR 52.1131 - Control strategy: Particulate matter.

Code of Federal Regulations, 2013 CFR

2013-07-01

...) (PSD program only), (D)(i)(II) (PSD program only), (D)(ii), and (J) (PSD program only). (e) Approval...) (PSD program only), (D)(i)(II) (PSD program only), (D)(ii), and (J) (PSD program only). [45 FR 2044...

LTRC Annual Research Program : Fiscal Year July 1, 2017 - June 30, 2018.

DOT National Transportation Integrated Search

2017-06-01

FHWA Part II SPR Research Program FAP Number SPR-0010(34) & FHWA Funded Research Program & FHWA LTAP Funded Program & FHWA STP Funded Program & Federal & Self-Generated Funded Research Program & Other DOTD Funded Projects

Reducing Gridlock on the Grid: Utility Trends in Managing Peak Electric Load through Residential Demand Response

NASA Astrophysics Data System (ADS)

McDonald, Betsy

Utilities across the United States are piloting residential demand response programs to help manage peak electric demand. Using publicly available program evaluations, this thesis analyzes nine such programs to uncover and synthesize the range of program offerings, goals, enrollment strategies, and customer experiences. This review reveals that program participation, components, and results differ based on a variety of factors, including geographic characteristics, program goals, and implementation strategies. The diversity of program designs and evaluation findings suggests an underlying tension between the need to generate cost-effective program impacts and the desire to increase accessibility so that program benefits are not exclusive to certain segments of the population. For more significant and impactful engagement, program goals may need to shift. State level policy support could help shift program goals toward increasing program accessibility. Future research should explore creative strategies that target existing barriers and allow for more inclusive deployment.

Carnegie Mellon University's MMM program: management education for 21st-century physicians.

PubMed

Korevaar, W C; Pearson, R W

2001-01-01

The number and types of executive and graduate-level management programs for physicians have exploded in recent years. These programs take on a variety of formats, ranging from executive seminars to master's-level degree programs. Options for physicians obtaining the master's degree tend to be either regionally based programs in traditional evening classes or nationally based programs that combine executive education formats with distance education. This paper examines a nationally based program - the Master of Medical Management (MMM) - from the perspectives of an administrator and a graduate of the program. It offers reasons for the growth of similar programs and data from students enrolled in the Carnegie Mellon University MMM program. The paper also examines educational outcomes in the form of behavioral competencies that the physicians acquired in the program. It concludes with reflections on the future of the MMM and related programs for physician executives in the 21st century.

The Education and Public Outreach Program at the University of Virginia

NASA Astrophysics Data System (ADS)

Murphy, E. M.; Rood, R. T.; Patterson, R. J.

2003-12-01

The Department of Astronomy at the University of Virginia has embarked on an ambitious program to expand their education and public outreach (E/PO) program. The comprehensive program addresses undergraduate education for non-science majors, teacher professional development, outreach programs for local schools, informal science education through collaborations with museums, and outreach through the public night program at McCormick Observatory. This poster presents example programs and their outcomes, including funding and staffing strategies. We believe that this E/PO program could serve as a model for other departments wishing to begin, or expand, an E/PO program. The E/PO program has been supported by funding from the Celerity Foundation, the University of Virginia, and NASA E/PO supplements to Chandra, HST, SIM, and FUSE science programs.

External quality-assurance programs managed by the U.S. Geological Survey in support of the National Atmospheric Deposition Program/National Trends Network

USGS Publications Warehouse

Latysh, Natalie E.; Wetherbee, Gregory A.

2005-01-01

The U.S. Geological Survey, Branch of Quality Systems, operates the external quality-assurance programs for the National Atmospheric Deposition Program/National Trends Network (NADP/NTN). Beginning in 1978, six different programs have been implemented?the intersite-comparison program, the blind-audit program, the sample-handling evaluation program, the field-audit program, the interlaboratory-comparison program, and the collocated-sampler program. Each program was designed to measure error contributed by specific components in the data-collection process. The intersite-comparison program, which was discontinued in 2004, was designed to assess the accuracy and reliability of field pH and specific-conductance measurements made by site operators. The blind-audit and sample-handling evaluation programs, which also were discontinued in 2002 and 2004, respectively, assessed contamination that may result from sampling equipment and routine handling and processing of the wet-deposition samples. The field-audit program assesses the effects of sample handling, processing, and field exposure. The interlaboratory-comparison program evaluates bias and precision of analytical results produced by the contract laboratory for NADP, the Illinois State Water Survey, Central Analytical Laboratory, and compares its performance with the performance of international laboratories. The collocated-sampler program assesses the overall precision of wet-deposition data collected by NADP/NTN. This report documents historical operations and the operating procedures for each of these external quality-assurance programs. USGS quality-assurance information allows NADP/NTN data users to discern between actual environmental trends and inherent measurement variability.

Repository-Based Software Engineering Program: Working Program Management Plan

NASA Technical Reports Server (NTRS)

1993-01-01

Repository-Based Software Engineering Program (RBSE) is a National Aeronautics and Space Administration (NASA) sponsored program dedicated to introducing and supporting common, effective approaches to software engineering practices. The process of conceiving, designing, building, and maintaining software systems by using existing software assets that are stored in a specialized operational reuse library or repository, accessible to system designers, is the foundation of the program. In addition to operating a software repository, RBSE promotes (1) software engineering technology transfer, (2) academic and instructional support of reuse programs, (3) the use of common software engineering standards and practices, (4) software reuse technology research, and (5) interoperability between reuse libraries. This Program Management Plan (PMP) is intended to communicate program goals and objectives, describe major work areas, and define a management report and control process. This process will assist the Program Manager, University of Houston at Clear Lake (UHCL) in tracking work progress and describing major program activities to NASA management. The goal of this PMP is to make managing the RBSE program a relatively easy process that improves the work of all team members. The PMP describes work areas addressed and work efforts being accomplished by the program; however, it is not intended as a complete description of the program. Its focus is on providing management tools and management processes for monitoring, evaluating, and administering the program; and it includes schedules for charting milestones and deliveries of program products. The PMP was developed by soliciting and obtaining guidance from appropriate program participants, analyzing program management guidance, and reviewing related program management documents.

25 CFR 39.132 - Can a school integrate Language Development programs into its regular instructional program?

Code of Federal Regulations, 2010 CFR

2010-04-01

... 25 Indians 1 2010-04-01 2010-04-01 false Can a school integrate Language Development programs into... Language Development Programs § 39.132 Can a school integrate Language Development programs into its regular instructional program? A school may offer Language Development programs to students as part of its...

25 CFR 170.804 - How is BIA's Road Maintenance Program related to the IRR Program?

Code of Federal Regulations, 2010 CFR

2010-04-01

... 25 Indians 1 2010-04-01 2010-04-01 false How is BIA's Road Maintenance Program related to the IRR... WATER INDIAN RESERVATION ROADS PROGRAM BIA Road Maintenance § 170.804 How is BIA's Road Maintenance Program related to the IRR Program? The following chart illustrates how BIA's Road Maintenance Program is...

48 CFR 819.7114 - Measurement of program success.

Code of Federal Regulations, 2010 CFR

2010-10-01

... SOCIOECONOMIC PROGRAMS SMALL BUSINESS PROGRAMS VA Mentor-Protégé Program 819.7114 Measurement of program success. The overall success of the VA Mentor-Protégé Program encompassing all participating mentors and... subcontract awards to protégé firms since the time of their entry into the program attributable to the mentor...

Impact of Alternative Programs on an Urban School District.

ERIC Educational Resources Information Center

Vincenzi, Harry; Fishman, Roger J.

The number of secondary alternative programs in the school district of Philadelphia has grown to 75 giving it one of the largest networks of alternative programs in the country. The object of this paper is to report on the impact of those programs. The programs are divided into four categories: (1) disruptive/ truant programs, (2) career programs,…

Evaluating Continuing Education Needs and Program Effectiveness Using a Survey of Virginia's SHARP Logger Program Participants

ERIC Educational Resources Information Center

Barrett, Scott M.; Bolding, M. Chad; Munsell, John F.

2012-01-01

Virginia's SHARP logger program is a Cooperative Extension program currently providing training to over 1,500 loggers, foresters, and others. We conducted a mail survey of SHARP loggers to characterize program participants, assess programming needs, and evaluate program effectiveness. Results indicate a diverse group of participants in terms of…

Houston Operations Predictor/Estimator (HOPE) programming manual, volume 1. [Apollo orbit determination

NASA Technical Reports Server (NTRS)

Daly, J. K.

1974-01-01

The programming techniques used to implement the equations and mathematical techniques of the Houston Operations Predictor/Estimator (HOPE) orbit determination program on the UNIVAC 1108 computer are described. Detailed descriptions are given of the program structure, the internal program structure, the internal program tables and program COMMON, modification and maintainence techniques, and individual subroutine documentation.

Near-term hybrid vehicle program, phase 1. Appendix B: Design trade-off studies report. Volume 3: Computer program listings

NASA Technical Reports Server (NTRS)

1979-01-01

A description and listing is presented of two computer programs: Hybrid Vehicle Design Program (HYVELD) and Hybrid Vehicle Simulation Program (HYVEC). Both of the programs are modifications and extensions of similar programs developed as part of the Electric and Hybrid Vehicle System Research and Development Project.

Developing Childhood Injury Prevention Programs: An Administrative Guide for State Maternal and Child Health (Title V) Programs.

ERIC Educational Resources Information Center

Birch & Davis Associates, Inc., Silver Spring, MD.

Based primarily on the experience of three childhood injury prevention demonstration projects, this manual provides state Title V program directors with an action guide for developing targeted childhood injury prevention programs. The manual is divided into four sections: background; program planning; program design; and program implementation and…

NASA's educational programs

NASA Technical Reports Server (NTRS)

Brown, Robert W.

1990-01-01

The educational programs of NASA's Educational Affairs Division are examined. The problem of declining numbers of science and engineering students is reviewed. The various NASA educational programs are described, including programs at the elementary and secondary school levels, teacher education programs, and undergraduate, graduate, and university faculty programs. The coordination of aerospace education activities and future plans for increasing NASA educational programs are considered.

25 CFR 39.132 - Can a school integrate Language Development programs into its regular instructional program?

Code of Federal Regulations, 2011 CFR

2011-04-01

... 25 Indians 1 2011-04-01 2011-04-01 false Can a school integrate Language Development programs into... Language Development Programs § 39.132 Can a school integrate Language Development programs into its regular instructional program? A school may offer Language Development programs to students as part of its...

Multicultural Training in Doctoral School Psychology Programs: In Search of the Model Program?

ERIC Educational Resources Information Center

Kearns, Tori; Ford, Laurie; Brown, Kimberly

The multicultural training (MCT) of APA-accredited School Psychology programs was studied. The sample included faculty and students from five programs nominated for strong MCT and five comparison programs randomly selected from the list of remaining APA-accredited programs. Program training was evaluated using a survey based on APA guidelines for…

Community College Programs for Older Adults: A Resource Directory of Guidelines, Comprehensive Programming Models, and Selected Programs.

ERIC Educational Resources Information Center

Beckman, Brenda Marshall; Ventura-Merkel, Catherine

In an effort to more effectively disseminate information about community college programs for older adults, this directory was developed for three purposes: to make guidelines available for establishing, expanding, or revising programs; to offer a selection of successful programming models; and to provide a compendium of existing programs. Part I…

Documentation of structures branch programs and program updates. Project 3200

NASA Technical Reports Server (NTRS)

Probe, D. G.

1975-01-01

Update programming of applications programs for the integrated structural analysis system is reported. An attempt is made to layout a standard document format for the preparation of program documents. Documentation which involves changes, additions, and I/O capability revisions to existing programs includes a checklist which should be reviewed each time a programming effort is documented.

Program Fair Evaluation--Summative Appraisal of Instructional Sequences with Dissimilar Objectives.

ERIC Educational Resources Information Center

Popham, W. James

A comparative evaluation involving two instructional programs is given, although the approach can easily serve to compare more than two programs. The steps involved in conducting a program fair evaluation of two instructional programs are: (1) Identify objectives (a) common to both programs, (b) unique to one program, and (c) unique to the other…

Results of Descriptive Study of Crisis Nursery and Respite Care Programs.

ERIC Educational Resources Information Center

Huntington, Gail S.; And Others

This report describes results of an evaluation of respite care programs and crisis nursery programs for children with disabilities, based on survey forms received from 81 programs and site visits to selected programs across the United States. The survey of crisis nursery programs and the survey of respite care programs gathered data on amount of…

49 CFR 381.400 - What is a pilot program?

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 5 2011-10-01 2011-10-01 false What is a pilot program? 381.400 Section 381.400... PILOT PROGRAMS Initiation of Pilot Programs § 381.400 What is a pilot program? (a) A pilot program is a... that would be subject to the regulations. (b) During a pilot program, the participants would be given...

49 CFR 381.400 - What is a pilot program?

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 5 2010-10-01 2010-10-01 false What is a pilot program? 381.400 Section 381.400... PILOT PROGRAMS Initiation of Pilot Programs § 381.400 What is a pilot program? (a) A pilot program is a... that would be subject to the regulations. (b) During a pilot program, the participants would be given...

LTRC Annual Research Program : Fiscal Year July 1, 2012-June 30, 2013

DOT National Transportation Integrated Search

2012-06-01

Contents: Budget Recap Sheets; Project Summary Sheets; FHWA Part II SPR Funded Research Program; FHWA IBRD Funded Research Program; FHWA LTAP Funded Program; FHWA STP Funded Technology Transfer & Education Program; State Funded Research Program; Fede...

LTRC annual research program : fiscal year July 1, 2011-June 30, 2012.

DOT National Transportation Integrated Search

2011-06-01

Contents: Budget Recaps Sheets; Project Summary Sheets; FHWA Part II SPR Funded Research Program; FHWA IBRD Funded Research Program; FHWA LTAP Funded Program; FHWA STP Funded Technology Transfer & Education Program; State Funded Research Program; Sel...

75 FR 34093 - Information Collection; General Program Administration

Federal Register 2010, 2011, 2012, 2013, 2014

2010-06-16

... DEPARTMENT OF AGRICULTURE Farm Service Agency Information Collection; General Program... supports Farm Loan Programs (FLP) for the General Program Administration. DATES: We will consider comments.... SUPPLEMENTARY INFORMATION: Title: Farm Loan Programs--General Program Administration (7 CFR part 761). OMB...

45 CFR 1388.2 - Program criteria-purpose.

Code of Federal Regulations, 2010 CFR

2010-10-01

... inclusion of individuals with developmental disabilities. Compliance with the program criteria is a..., DEPARTMENT OF HEALTH AND HUMAN SERVICES THE ADMINISTRATION ON DEVELOPMENTAL DISABILITIES, DEVELOPMENTAL DISABILITIES PROGRAM THE UNIVERSITY AFFILIATED PROGRAMS § 1388.2 Program criteria—purpose. The program criteria...

Incorporating Reporting Efforts to Manage and Improve Health and Wellness Programs.

PubMed

Wells, Timothy S; Ozminkowski, Ronald J; McGinn, Michael P; Hawkins, Kevin; Bhattarai, Gandhi R; Serxner, Seth A; Greame, Chris

2017-06-01

Wellness programs are designed to help individuals maintain or improve their health. This article describes how a reporting process can be used to help manage and improve a wellness program. Beginning in 2014, a wellness pilot program became available in New Jersey for individuals with an AARP Medicare Supplement Insurance plan insured by UnitedHealthcare Insurance Company. The program has since expanded to include Missouri, Texas, Alabama, and Washington. This wellness program includes an online health portal, one-on-one telephonic coaching, gym membership discounts, and local health events. To assure smooth program operations and alignment with program objectives, weekly and monthly reports are produced. The weekly report includes metrics on member engagement and utilization for the aforementioned 4 program offerings and reports on the last 4 weeks, as well as for the current month and the current year to date. The monthly report includes separate worksheets for each state and a summary worksheet that includes all states combined, and provides metrics on overall engagement as well as utilization of the 4 program components. Although the monthly reports were used to better manage the 4 program offerings, the weekly reports help management to gauge response to program marketing. Reporting can be a data-driven management tool to help manage wellness programs. Reports provide rapid feedback regarding program performance. In contrast, in-depth program evaluations serve a different purpose, such as to report program-related savings, return on investment, or to report other longer term program-related outcomes.

A distributed program composition system

NASA Technical Reports Server (NTRS)

Brown, Robert L.

1989-01-01

A graphical technique for creating distributed computer programs is investigated and a prototype implementation is described which serves as a testbed for the concepts. The type of programs under examination is restricted to those comprising relatively heavyweight parts that intercommunicate by passing messages of typed objects. Such programs are often presented visually as a directed graph with computer program parts as the nodes and communication channels as the edges. This class of programs, called parts-based programs, is not well supported by existing computer systems; much manual work is required to describe the program to the system, establish the communication paths, accommodate the heterogeneity of data types, and to locate the parts of the program on the various systems involved. The work described solves most of these problems by providing an interface for describing parts-based programs in this class in a way that closely models the way programmers think about them: using sketches of diagraphs. Program parts, the computational modes of the larger program system are categorized in libraries and are accessed with browsers. The process of programming has the programmer draw the program graph interactively. Heterogeneity is automatically accommodated by the insertion of type translators where necessary between the parts. Many decisions are necessary in the creation of a comprehensive tool for interactive creation of programs in this class. Possibilities are explored and the issues behind such decisions are presented. An approach to program composition is described, not a carefully implemented programming environment. However, a prototype implementation is described that can demonstrate the ideas presented.

Incorporating Reporting Efforts to Manage and Improve Health and Wellness Programs

PubMed Central

Ozminkowski, Ronald J.; McGinn, Michael P.; Hawkins, Kevin; Bhattarai, Gandhi R.; Serxner, Seth A.; Greame, Chris

2017-01-01

Abstract Wellness programs are designed to help individuals maintain or improve their health. This article describes how a reporting process can be used to help manage and improve a wellness program. Beginning in 2014, a wellness pilot program became available in New Jersey for individuals with an AARP Medicare Supplement Insurance plan insured by UnitedHealthcare Insurance Company. The program has since expanded to include Missouri, Texas, Alabama, and Washington. This wellness program includes an online health portal, one-on-one telephonic coaching, gym membership discounts, and local health events. To assure smooth program operations and alignment with program objectives, weekly and monthly reports are produced. The weekly report includes metrics on member engagement and utilization for the aforementioned 4 program offerings and reports on the last 4 weeks, as well as for the current month and the current year to date. The monthly report includes separate worksheets for each state and a summary worksheet that includes all states combined, and provides metrics on overall engagement as well as utilization of the 4 program components. Although the monthly reports were used to better manage the 4 program offerings, the weekly reports help management to gauge response to program marketing. Reporting can be a data-driven management tool to help manage wellness programs. Reports provide rapid feedback regarding program performance. In contrast, in-depth program evaluations serve a different purpose, such as to report program-related savings, return on investment, or to report other longer term program-related outcomes. PMID:27575977

Mississippi Curriculum Framework for Computer Information Systems Technology. Computer Information Systems Technology (Program CIP: 52.1201--Management Information Systems & Business Data). Computer Programming (Program CIP: 52.1201). Network Support (Program CIP: 52.1290--Computer Network Support Technology). Postsecondary Programs.

ERIC Educational Resources Information Center

Mississippi Research and Curriculum Unit for Vocational and Technical Education, State College.

This document, which is intended for use by community and junior colleges throughout Mississippi, contains curriculum frameworks for two programs in the state's postsecondary-level computer information systems technology cluster: computer programming and network support. Presented in the introduction are program descriptions and suggested course…

Remote programming of cochlear implants: a telecommunications model.

PubMed

McElveen, John T; Blackburn, Erin L; Green, J Douglas; McLear, Patrick W; Thimsen, Donald J; Wilson, Blake S

2010-09-01

Evaluate the effectiveness of remote programming for cochlear implants. Retrospective review of the cochlear implant performance for patients who had undergone mapping and programming of their cochlear implant via remote connection through the Internet. Postoperative Hearing in Noise Test and Consonant/Nucleus/Consonant word scores for 7 patients who had undergone remote mapping and programming of their cochlear implant were compared with the mean scores of 7 patients who had been programmed by the same audiologist over a 12-month period. Times required for remote and direct programming were also compared. The quality of the Internet connection was assessed using standardized measures. Remote programming was performed via a virtual private network with a separate software program used for video and audio linkage. All 7 patients were programmed successfully via remote connectivity. No untoward patient experiences were encountered. No statistically significant differences could be found in comparing postoperative Hearing in Noise Test and Consonant/Nucleus/Consonant word scores for patients who had undergone remote programming versus a similar group of patients who had their cochlear implant programmed directly. Remote programming did not require a significantly longer programming time for the audiologist with these 7 patients. Remote programming of a cochlear implant can be performed safely without any deterioration in the quality of the programming. This ability to remotely program cochlear implant patients gives the potential to extend cochlear implantation to underserved areas in the United States and elsewhere.

The effectiveness of environmental education programs from the perspectives of three stakeholders: Participants, sponsors, and professionals

NASA Astrophysics Data System (ADS)

Luera, Gail Rose

As the field of environmental education has matured since its inception in 1970, so have the number and variety of environmental programs. Along with the increased number of programs has come a need for in-depth program evaluations. This is especially critical because of reductions in educational funding and competition for a place in an already crowded curriculum. Evaluation is essential to convince the educational community that environmental education can improve the curriculum, ensure cost effectiveness, and become more relevant to students. Drawing on program evaluation research, action research, and interpretive (qualitative) research to strengthen the research design and methodology, this dissertation explores how different stakeholders of two environmental education programs determine program effectiveness. Effectiveness was investigated primarily through the use of in-depth interviews of participants, program sponsors, and professionals. Program success at the professional field level was determined by criteria set by the North American Association for Environmental Education. Characteristics considered in the selection of programs for this study included: method of dissemination, sponsor, subject focus, the method of action which they encourage, and their vision for the future. Using the qualitative case study approach, the Orange County Outdoor Science School in California and Project WILD in Michigan were evaluated. The results show that all levels of stakeholders perceived the two programs to be effective. Areas of effectiveness varied with each program and by stakeholder level. Issues facing each program also differed. At the Orange County Outdoor Science School, program cost was named as the major issue. The most often cited issues for Project WILD was public awareness of the program and stabilizing long term financial support for the Michigan program. Interview data were analyzed at the question level in addition to the thematic level. Themes which emerged from the interview responses included cost of the program, respondent and program receptivity to change, reconciling program philosophy with personal philosophy (Orange County program), perception of environmental education, definition of the program's boundaries and barriers to implementation (Project WILD). The dissertation concludes with a presentation of a preliminary model for environmental education program evaluation and recommendations for future related research.

76 FR 19683 - Conservation Program Recipient Reporting

Federal Register 2010, 2011, 2012, 2013, 2014

2011-04-08

... regulation that has application or plan due dates after October 1, 2010. The Watershed Operations and Flood Prevention Program, Emergency Watersheds Protection Program, Healthy Forests Reserve Program, Agricultural Management Assistance Program, and the Conservation Stewardship Program have application or plan due dates...

Evaluating the effectiveness of the Safety Investment Program (SIP) policies for Oregon.

DOT National Transportation Integrated Search

2009-10-01

The Safety Investment Program (SIP) was originally called the Statewide Transportation Improvement Program - : Safety Investment Program (STIP-SIP). The concept of the program was first discussed in October 1997 and the : program was adopted by the O...

40 CFR 195.1 - Purpose and applicability.

Code of Federal Regulations, 2010 CFR

2010-07-01

... PROGRAMS RADON PROFICIENCY PROGRAMS General Provisions § 195.1 Purpose and applicability. (a) Purpose. The... following programs: The National Radon Measurement Proficiency (RMP) Program, the individual proficiency component of the RMP Program, and the National Radon Contractor Proficiency (RCP) Program. (b) Applicability...

5 CFR 362.301 - Program administration.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 5 Administrative Personnel 1 2014-01-01 2014-01-01 false Program administration. 362.301 Section 362.301 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT CIVIL SERVICE REGULATIONS PATHWAYS PROGRAMS Recent Graduates Program § 362.301 Program administration. The Recent Graduates Program provides...

5 CFR 362.301 - Program administration.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 5 Administrative Personnel 1 2013-01-01 2013-01-01 false Program administration. 362.301 Section 362.301 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT CIVIL SERVICE REGULATIONS PATHWAYS PROGRAMS Recent Graduates Program § 362.301 Program administration. The Recent Graduates Program provides...

General Aviation Propulsion

NASA Technical Reports Server (NTRS)

1980-01-01

Programs exploring and demonstrating new technologies in general aviation propulsion are considered. These programs are the quiet, clean, general aviation turbofan (QCGAT) program; the general aviation turbine engine (GATE) study program; the general aviation propeller technology program; and the advanced rotary, diesel, and reciprocating engine programs.

40 CFR 195.1 - Purpose and applicability.

Code of Federal Regulations, 2011 CFR

2011-07-01

... PROGRAMS RADON PROFICIENCY PROGRAMS General Provisions § 195.1 Purpose and applicability. (a) Purpose. The... following programs: The National Radon Measurement Proficiency (RMP) Program, the individual proficiency component of the RMP Program, and the National Radon Contractor Proficiency (RCP) Program. (b) Applicability...

An Examination of the Indiana State University Aerospace Administration Program

NASA Technical Reports Server (NTRS)

Schwab, Gregory L.

2005-01-01

Declining enrollments in the Indiana State University (ISU) aerospace administration program prompted this case study. which evaluates the program in comparison with parallel programs at other universities, industry standards, and an independent audit. Survey instruments were administered to graduates, faculty, and employers for their views on competencies of an excellent aerospace administration program Results show the deficiency of the ISU program. Graduates, faculty, and employers rated all competencies-from moderate to considerable importance-similarly for an excellent program. Recommendations for program improvement were made, and suggestions for further research include studies to evaluate the effectiveness of a revised aerospace administration program.

NEMAR plotting computer program

NASA Technical Reports Server (NTRS)

Myler, T. R.

1981-01-01

A FORTRAN coded computer program which generates CalComp plots of trajectory parameters is examined. The trajectory parameters are calculated and placed on a data file by the Near Earth Mission Analysis Routine computer program. The plot program accesses the data file and generates the plots as defined by inputs to the plot program. Program theory, user instructions, output definitions, subroutine descriptions and detailed FORTRAN coding information are included. Although this plot program utilizes a random access data file, a data file of the same type and formatted in 102 numbers per record could be generated by any computer program and used by this plot program.

Global health training in ophthalmology residency programs.

PubMed

Coombs, Peter G; Feldman, Brad H; Lauer, Andreas K; Paul Chan, Robison V; Sun, Grace

2015-01-01

To assess current global health education and international electives in ophthalmology residency programs and barriers to global health implementation in ophthalmology resident education. A web-based survey regarding participation in global health and international electives was emailed to residency program directors at 116 accredited ophthalmology residency programs via an Association of University Professors in Ophthalmology (AUPO) residency program director listserv. Fifty-nine (51%) ophthalmology residency program directors responded. Thirty-seven program directors (63%) said global health was important to medical students when evaluating residency programs. Thirty-two program directors (55%) reported developing international electives. Reported barriers to resident participation in international electives were: 1) insufficient financial support, 2) inadequate resident coverage at home, and 3) lack of ACGME approval for international electives. Program directors requested more information about resident international electives, funding, and global ophthalmology educational resources. They requested ACGME recognition of international electives to facilitate resident participation. More than half (54%) of program directors supported international electives for residents. This survey demonstrates that program directors believe global health is an important consideration when medical students evaluate training programs. Despite perceived barriers to incorporating global health opportunities into residency training, program directors are interested in development of global health resources and plan to further develop global health opportunities. Copyright © 2015 Association of Program Directors in Surgery. Published by Elsevier Inc. All rights reserved.

Factors contributing to intervention fidelity in a multi-site chronic disease self-management program.

PubMed

Perrin, Karen M; Burke, Somer Goad; O'Connor, Danielle; Walby, Gary; Shippey, Claire; Pitt, Seraphine; McDermott, Robert J; Forthofer, Melinda S

2006-10-26

Disease self-management programs have been a popular approach to reducing morbidity and mortality from chronic disease. Replicating an evidence-based disease management program successfully requires practitioners to ensure fidelity to the original program design. The Florida Health Literacy Study (FHLS) was conducted to investigate the implementation impact of the Pfizer, Inc. Diabetes Mellitus and Hypertension Disease Self-Management Program based on health literacy principles in 14 community health centers in Florida. The intervention components discussed include health educator recruitment and training, patient recruitment, class sessions, utilization of program materials, translation of program manuals, patient retention and follow-up, and technical assistance. This report describes challenges associated with achieving a balance between adaptation for cultural relevance and fidelity when implementing the health education program across clinic sites. This balance was necessary to achieve effectiveness of the disease self-management program. The FHLS program was implemented with a high degree of fidelity to the original design and used original program materials. Adaptations identified as advantageous to program participation are discussed, such as implementing alternate methods for recruiting patients and developing staff incentives for participation. Effective program implementation depends on the talent, skill and willing participation of clinic staff. Program adaptations that conserve staff time and resources and recognize their contribution can increase program effectiveness without jeopardizing its fidelity.

General surgery vs fellowship: the role of the Independent Academic Medical Center.

PubMed

Adra, Souheil W; Trickey, Amber W; Crosby, Moira E; Kurtzman, Scott H; Friedell, Mark L; Reines, H David

2012-01-01

To compare career choices of residency graduates from Independent Academic Medical Center (IAMC) and University Academic Medical Center (UAMC) programs and evaluate program directors' perceptions of residents' motivations for pursuing general surgery or fellowships. From May to August 2011, an electronic survey collected information on program characteristics, graduates' career pursuits, and career motivations. Fisher's exact tests were calculated to compare responses by program type. Multivariate logistic regression was used to identify independent program characteristics associated with graduates pursuing general surgery. Data were collected on graduates over 3 years (2009-2011). Surgery residency program directors. Seventy-four program directors completed the survey; 42% represented IAMCs. IAMCs reported more graduates choosing general surgery. Over one-quarter of graduates pursued general surgery from 52% of IAMC vs 37% of UAMC programs (p = 0.243). Career choices varied significantly by region: over one-quarter of graduates pursue general surgery from 78% of Western, 60% of Midwestern, 40% of Southern, and 24% of Northeastern programs (p = 0.018). On multivariate analysis, IAMC programs were independently associated with more graduates choosing general surgery (p = 0.017), after adjustment for other program characteristics. Seventy-five percent of UAMC programs reported over three-fourths of graduates receive first choice fellowship, compared with only 52% of IAMC programs (p = 0.067). Fellowships were comparable among IAMC and UAMC programs, most commonly MIS/Bariatric (16%), Critical Care/Trauma (16%), and Vascular (14%). IAMC and UAMC program directors cite similar reasons for graduate career choices. Most general surgery residents undergo fellowship training. Graduates from IAMC and UAMC programs pursue similar specialties, but UAMC programs report more first choice acceptance. IAMC programs may graduate proportionately more general surgeons. Further studies directly evaluating surgical residents' career choices are warranted to understand the influence of independent and university programs in shaping these choices and to develop strategies for reducing the general surgeon shortage. Copyright © 2012 Association of Program Directors in Surgery. Published by Elsevier Inc. All rights reserved.

Program manual for the Shuttle Electric Power System analysis computer program (SEPS), volume 1 of program documentation

NASA Technical Reports Server (NTRS)

Bains, R. W.; Herwig, H. A.; Luedeman, J. K.; Torina, E. M.

1974-01-01

The Shuttle Electric Power System (SEPS) computer program is considered in terms of the program manual, programmer guide, and program utilization. The main objective is to provide the information necessary to interpret and use the routines comprising the SEPS program. Subroutine descriptions including the name, purpose, method, variable definitions, and logic flow are presented.

25 CFR 170.2 - What is the IRR Program and BIA Road Maintenance Program policy?

Code of Federal Regulations, 2014 CFR

2014-04-01

... 25 Indians 1 2014-04-01 2014-04-01 false What is the IRR Program and BIA Road Maintenance Program... INDIAN RESERVATION ROADS PROGRAM Policies, Applicability, and Definitions § 170.2 What is the IRR Program and BIA Road Maintenance Program policy? (a) It is the policy of the Secretary of the Interior and the...

25 CFR 170.2 - What is the IRR Program and BIA Road Maintenance Program policy?

Code of Federal Regulations, 2012 CFR

2012-04-01

... 25 Indians 1 2012-04-01 2011-04-01 true What is the IRR Program and BIA Road Maintenance Program... INDIAN RESERVATION ROADS PROGRAM Policies, Applicability, and Definitions § 170.2 What is the IRR Program and BIA Road Maintenance Program policy? (a) It is the policy of the Secretary of the Interior and the...

25 CFR 170.2 - What is the IRR Program and BIA Road Maintenance Program policy?

Code of Federal Regulations, 2013 CFR

2013-04-01

... 25 Indians 1 2013-04-01 2013-04-01 false What is the IRR Program and BIA Road Maintenance Program... INDIAN RESERVATION ROADS PROGRAM Policies, Applicability, and Definitions § 170.2 What is the IRR Program and BIA Road Maintenance Program policy? (a) It is the policy of the Secretary of the Interior and the...

A Handbook for the Father's Program: How to Organize a Program for Fathers and Their Handicapped Children. [Appendix B].

ERIC Educational Resources Information Center

Meyer, Donald J.; And Others

Based on the SEFAM (Supporting Extended Family Members) program, the manual is intended to help organize a program for fathers of handicapped young children. A program for fathers and infants focuses on unique father concerns and resources. The first chapter further explores reasons for father programs while the second describes program components…

A Qualitative Program Evaluation of a Structured Leadership Mentoring Program at a Large Aerospace Corporation

ERIC Educational Resources Information Center

Teller, Romney P.

2011-01-01

The researcher utilized a qualitative approach to conduct a program evaluation of the organization where he is employed. The study intended to serve as a program evaluation for the structured in-house mentoring program at a large aerospace corporation (A-Corp). This program evaluation clarified areas in which the current mentoring program is…