Residual Stress In Joint Research Articles

Role of Nb elements in SiCf/SiC/(CoFeNiCrMn)100-xNbx/GH536 brazed joints: Joint residual stress transfer and pinning of dislocations

Brazing is a critical method to address the challenge of connecting composite materials to metals. This study joined SiCf/SiC composites and GH536 superalloy using (CoFeNiCrMn)100-xNbx high-entropy alloy filler with varying Nb element contents successfully. The microstructural evolution and mechanical property changes of brazed joints were systematically investigated. Notably, when the Nb element content in the filler reached 12 %, a diffuse distribution of Nb(s, s) emerged in the joint, playing a vital role in effectively transferring residual stress on the SiCf/SiC side. This effect is attributed to the disparity in thermal expansion coefficients between the Nb(s, s) and face-centered cubic (FCC) phases. The resulting joint exhibited remarkable room temperature and high temperature shear strengths of 89.7 MPa and 49.7 MPa, respectively. Furthermore, the presence of Nb(s, s) in the brazing seam proved to impede the movement of dislocations during joint fracture. This work introduces a new technical paradigm for aero-engine manufacturing.

Methods to reduce residual welding stresses in mining excavator metal structures

Residual stresses in metal structures of mining machinery caused by welding occur due to simultaneous uneven heating and cooling of local sections of structures, variable cooling rates in the different areas of the weld and deformations caused by metallurgical phase transformations. Residual stress in the welded joint can significantly increase the external load that can lead to structural failure. Research on the calculation, measurement and relief of residual stresses under welding is an important issue when predicting the service life of metal structure units of mining machinery and equipment. An accurate quantitative estimation of residual stresses in welded products, repair welds included, as well as the search for the fundamental principles of the elimination methods of residual deformations are of considerable practical interest, which is relevant for the authors of this paper. The study involved a general review of the latest researches in the field of estimation and measurement of residual stresses caused by electrogas welding. It has been proposed to use various techniques and analytical methods for quantitative estimation of welded joint residual stresses on the basis of fracture mechanics, which enabled to take preventative measures at early stages to reduce the cost of repair and maintenance of welded metal structures of mining excavators. The conducted study resulted in formulating the proposals on relief of residual welding stresses in the metal structures of mining excavators.

Predicting residual stress in a 316L electron beam weld joint incorporating plastic properties derived from a crystal plasticity finite element model

Electron beam welding is an advanced joining technique which induces narrow weld region with minimal heat affected zone and weld-induced distortion. This reduces residual stresses in the joints which can be detrimental to structural performance of components in safety critical industries. Being an autogenous process, electron- beam welding generates a highly textured, columnar microstructure in the weld zone which have distinct properties when compared to the parent material region. Determining mechanical properties of the weld material assists in accurate assessment of the joint. However, extracting weld material specimens to determine plastic properties becomes increasingly cumbersome in thinner weld joints. An alternate approach has been demonstrated in this work wherein mechanical properties were derived using the weld microstructure in a crystal plasticity finite element (CPFE) framework. The initial calibration of the CPFE parameters was done using experimental data from thick weldment. These calibrated values were used to obtain the elastic and elastic-plastic properties of thinner weld materials by deforming corresponding synthetic microstructures whose attributes were determined by Electron Backscatter Diffraction analysis. The resultant properties were incorporated in a finite element (FE) based weld simulation to determine the residual strain. These results were compared with the residual strain data obtained using X-ray diffraction and good agreement was observed.

Releasing the residual stress of Cf/SiC-GH3536 joint by designing an Ag-Cu-Ti + Sc2(WO4)3 composite filler metal

• The work is the first one to introduce Sc 2 (WO 4 ) 3 into brazing process. • The Sc 2 (WO 4 ) 3 maintains its negative thermal expansion effect in Ag-Cu-Ti system. • The residual stress releasing mechanism is revealed by finite element analysis method. • The shear strength improves 2.6 times by introducing Sc 2 (WO 4 ) 3 reinforcing phase. Due to native character of thermal expansion coefficient (CTE) mismatch between C f /SiC and GH3536, achieving high strength joint was a huge challenge for C f /SiC-GH3536 joints. Herein, a composite filler metal of Ag-Cu-Ti + Sc 2 (WO 4 ) 3 was developed to join C f /SiC and GH3536. This work introduced Sc 2 (WO 4 ) 3 to Ag-Cu-Ti system as a negative thermal expansion (NTE) reinforcing phase to release joint residual stress. Sc 2 (WO 4 ) 3 was evenly distributed in the brazing seam and reacted with Ti to form Ti 3 O 5 reaction layer. The results of finite element analysis showed that the residual stress of the joints was effectively released by introducing Sc 2 (WO 4 ) 3 reinforcing phase, and the mises stress was decreased from 447 to 401 MPa. The maximum shear strength of the C f /SiC-GH3536 joint brazed with Ag-Cu-Ti + 6 vol% Sc 2 (WO 4 ) 3 filler alloys was 64 MPa, which was about 2.6 times higher than that of Ag-Cu-Ti alloys. The results of this study provide a promising strategy for the introduction of new Sc 2 (WO 4 ) 3 reinforcing phase in Ag-Cu-Ti system, and improve the reliability and feasibility of composite brazing alloy in brazing filed.

Joining of Al2O3 ceramic to Cu using refractory metal foil

Joining of Al 2 O 3 ceramic to Cu has been conducted with Ag-26.7Cu-4.5Ti braze and refractory metal (W or Ta) foil. The interfacial microstructure in the joint with W foil is similar to that with Ta foil. The joining region in the joint consists of a reaction zone, braze zone I, refractory metal layer and braze zone II. The reaction zone of Cu 3 Ti 3 O with a thickness of about 5 μm develops close to Al 2 O 3 side due to the reactions of Ti and Cu in the braze with Al 2 O 3 substrate. The braze zones I and II are mainly composed of Ag- and Cu-based solid solutions. For the joint with W foil, the adsorption of Ti at the braze/W interfaces followed by the Ti diffusion into W foil occurs, whilst slight dissolution and diffusion of Ta into the brazes take place in the joint with Ta foil. The average shear strengths of joints with W and Ta foils are much higher than those without refractory metal foil, indicating the contribution of the refractory metal foil to the improvement of joint mechanical strength. Introduction of refractory metal foil in Al 2 O 3 /Cu joining is beneficial for the shift of joint residual stress distribution and the decrease of stress concentration in the joint since the coefficient of thermal expansion (CTE) of refractory metal layer approximately approaches that of Al 2 O 3 . Furthermore, a slight thickness increase of the Cu 3 Ti 3 O reaction zone in the joint with refractory metal foil may also give rise to the joint strength promotion.

Влияние формы заготовок на остаточные напряжения при линейной сварке трением

Linear friction welding is an advanced technology for manufacturing titanium blisks for gas-turbine engine compressors, which are subjected to stringent requirements for cyclic strength and dimensional accuracy. Substitution of conventional butt joints with more technological T-shape joints is a promising area, which provides reducing of the pre-welding machining costs. The introduction of T-form joints requires additional research of thermal distribution specifics and strain-stress state formation in the welding process and after its end. Therefore, the study of residual stresses in titanium alloy T-shape joints produced by linear friction welding is topical. The paper investigates the residual stresses in imitating welded blisk joints. The authors consider the results of welding where the blade imitator has a reamed relief of a smaller section. The finite element model covering forging, cooling, and disassembly of welded specimens is offered. The authors developed the model in ANSYS Workbench to describe the strain-stress state of welded specimens, which allows for estimating the residual stress levels and spreading. The main distinctive feature of the model is an accounting of asymmetric temperature distribution obtained by finite-difference solving of a T-shape joint thermal problem and weld shape simulation obtained as a result of welded joints metallographic research. The presented model allows the evaluation of the residual stresses in joints. The distribution of residual stresses in T-shaped welded joints is specific – compressive stresses existing in a weld are balanced by tensile stresses acting at a distance of 1 mm from the joint. The formation of compressive stresses in a weld is caused by plastic deformation due to the forging force action.

Post-Treatment of Welding Joints of High Strength Steels II.:Improving Residual Stress Condition – Overview

High strength steel welding joints fatigue strength could be improved by changing the as weld condition with post-weld treatment. These post-weld treatments are classified to two categories which are the weld geometry and residual stress condition improvement methods. Post-weld treatment methods of high strength steel welding joints by improving weld geometry were overviewed in the first part of our article. The post-weld treatment methods for improving the welding joint residual stress condition are also applicable in high strength steels, but some consideration have to take in place when applying these techniques. The aim of this paper to review the welding joint residual stress condition improvement techniques considers application of these techniques in high strength steels.

The use of a carbonized phenolic formaldehyde resin coated Ni foam as an interlayer to increase the high-temperature strength of C/C composite-Nb brazed joints

A novel carbonized phenolic formaldehyde resin (PF) resin-coated Ni foam was used as an interlayer for brazing carbon fiber reinforced carbon composites (C/C) and Nb using a Ti–Ni filler. At first, uniformly distributed carbonaceous laminae with different mass fractions on the Ni foam surface were acquired after the carbonization process by controlling the concentration of the PF solution. Afterwards, the obtained carbonaceous laminae covered Ni foam composite (C-Nif) was applied as an interlayer for brazing C/C and Nb via an assembly of C/C/Ti foil/Ni foil/C-Nif interlayer/Ti foil/Nb. The morphologies and microstructures of the carbonization product and the interfacial microstructures of the joints were investigated. The brazing mechanism has been elaborated in detail. With the help of the interconnected porous structure of the Ni foam, the distribution of the in-situ formed (Ti,Nb)2Ni particles, (Ti,Nb)C ring reinforcements as well as the Nb solid solution were uniformly obtained throughout the brazing seam. As a result, the joint residual stress was effectively released and consequently, the joint shear strength at elevated temperature (1000 °C) reached up to 33 MPa, which is 4.5 times higher than the directly brazed joint without an interlayer.

Recent Advances in Brazing Fillers for Joining of Dissimilar Materials

Brazing fillers for joining applications are essential for manufacturing and designing advanced materials. Several types of brazing fillers have been developed in recent decades to join similar or different engineering materials. Important parts of automotive and aircraft components, including steel, are often joined by brazing. In addition, ceramic components in microwave devices and circuits have been joined with a high level of integration in microelectronic devices. Similarly, in the medical field, metallic implants have been brazed to ceramic dental crowns. These advances have made human life more convenient. However, in brazing, there are certain issues with intermetallic compound (IMC) formation and residual stresses in joints at high temperatures. Nanoparticle-reinforced fillers have been proposed to control IMCs, but there are other dispersion and particle segregation issues at the joints. In this study, various types of brazing fillers, joint fabrication processes, and brazing technologies developed in recent decades are reviewed. Furthermore, new developments in brazing materials and their specific applications are presented. Finally, the emerging areas in brazing, including the recent entropy-modified brazing fillers for various structural and technological fields, are discussed.

Design of multi-layered architecture in dissimilar ceramic/metal joints with reinforcements clustering away from both substrates

To combine the advantages of ductile fillers and composite fillers and alleviate residual stress in joints between ZrB2-SiC ceramics (ZS) and TC4-TiBw composites, a novel multi-layered joint architecture composed of a layer of clustering SiC at the center of the joint (L-C-SiC) and two ductile layers without SiC particles bordering both substrates (L-DS) was designed. To achieve this, SiC particle skeletons with continuous micro-channels (SSCC) were integrated with AgCu filler as an interlayer. The effects of SSCC porosity and brazing temperature on joint microstructure and mechanical properties were investigated. In particular, the braze/ZS and braze/SSCC interfaces were analyzed through X-ray diffractometry (XRD), transmission electron microscopy (TEM), and wavelength-dispersive spectroscopy (WDS). The residual stress was also evaluated. The results indicate that increasing the brazing temperate improved the infiltration into the SSCC and promoted the SSCC/braze interface reaction (was detrimental to the SiC particle skeleton). Reducing the SSCC porosity changed the thicknesses of the two L-DSs and enhanced the inhomogeneity of the SSCC/braze interface reaction (induced a shear stress in L-C-SiC). For brazing with an interlayer of 30% porosity at 820 °C, the joint shear strength reached a maximum of ~41.2 MPa, mainly due to the construction of the multi-layered joint architecture.

Investigation of tungsten/MA956 steel diffusion bonding with an Nb/Ni composite interlayer

Diffusion bonding is an effective method for joining dissimilar materials. In this study, dissimilar metals of MA956 steel and tungsten (W) were diffusion bonded with Ni/Nb composite interlayer. The experiments were carried out at [Formula: see text], 20 MPa for 20 min in vacuum by spark plasma sintering (SPS) technique. The microstructure and mechanical properties of the bonded joints were evaluated. SEM images and the results of elementary composition indicate that no intermetallics formed at Ni/MA956 steel and Nb/W interfaces, but [Formula: see text] and [Formula: see text] formed at the Nb/Ni interface. Compared with the directly bonded joint between W and MA956 steel, the average shear strength of the joint with Nb/Ni composite interlayer significantly increased to 270 MPa. Although the result of joint residual stresses simulation shows that the maximum residual stress was near the W substrate, the joints with composite interlayer in shear experiments fractured at Nb/Ni interface. The hardness changes along joint interfaces indicate the formation of intermetallic compounds and solid solution phases in the diffusion layers.

Fatigue crack growth rates in high pressure hydrogen gas for multiple X100 pipeline welds accounting for crack location and residual stress

Fatigue crack growth rates (FCGR) of multiple X100 pipeline steel welds and heat affected zones were measured in high-pressure hydrogen gas to investigate their behavior compared to lower strength pipeline welds. A total of five high strength welds and two heat affected zones (HAZ) were examined all of which were fabricated using the same X100 base material. Different welding wires and techniques were used to fabricate the welds to provide a variety of end products to evaluate susceptibility to fatigue in high pressure hydrogen gas. Residual stresses were measured for each weld and HAZ using the slitting method and the effect of residual stress on the stress intensity factor, Kres, was determined. Using Kres, the fatigue crack growth rate curves were corrected to remove the effects of residual stress by examining the influence of Kres on stress ratio, R. Comparisons were then made between the high strength welds, which were corrected for residual stress, and lower strength welds from the literature. It was found that the higher strength welds and heat affected zones exhibited comparable fatigue crack growth rates to lower strength welds, as the FCGR data of the high strength welds overlaid the lower strength welds. This suggests that despite distinct differences in strength and microstructure between the different welds, hydrogen-assisted fatigue crack growth susceptibility is similar. A comparison was made between the Kres measured in extracted coupons and residual stress estimates provided in relevant welded pipe assessment standards such as API 579-1/ASME FFS-1. It was found the residual stress values in the test coupons extracted from welded pipe were significantly lower than those expected in the intact welded pipes and highlights the importance in quantifying and removing coupon residual stresses when fatigue crack growth rates are measured and including expected weld joint residual stress when making structural assessments.

Probing residual stresses in stationary shoulder friction stir welding process

Stationary shoulder friction stir welding (SSFSW) is a new variant of the conventional FSW with rotation of only the tool probe to reduce the rate of heat generation along the tool–workpiece interface and hence, weld joint residual stresses. Studies on the evolution of residual stresses in SSFSW are rare as the process is new. A detailed investigation on the evolution of welding-induced residual stress is reported here for SSFSW and the conventional FSW of four different aluminum alloys. A finite element method–based numerical model, JWRIAN-Hybrid, is used for the three-dimensional heat transfer and thermo-mechanical stress analyses. The computed results are validated extensively with the corresponding experimentally measured results. The results show approximately 10% to 20% reduction in the peak residual stresses in SSFSW under identical welding conditions.

Acoustic Emission Study of Fatigue Crack Propagation of Weld Joint for X52 Pipeline Steel

The crack propagation of different weld joint samples were detected by acoustic emission (AE) technique. The samples were from the basic metal, weld seam and heat affected zone (HAZ), The results showed that the crack growth rate of basic metal was higher than weld seam and HAZ because of the transverse compressive residual stress in joint. But the coarse of grains was the reason for higher rate of weld seam than that of HAZ. And AE waveforms of crack propagation from three microstructures were different. The most compositions of AE signals were higher frequency of 300KHz for weld seam and lower one of 100KHz for basic metal and HAZ.

Microstructure and shear strength of ZrB2[sbnd]SiC/Ti[sbnd]6Al[sbnd]4V joint by TiCuZrNi with Cu foam

In this paper, brazing behaviors between ZrB2SiC and Ti6Al4V by Cu foam interlayer were studied. The microstructure, formation mechanism, mechanical property and fracture surface of the joints were systematically studied. The results showed that the phases in the joints were α+β-Ti, TiCu, Ti2Cu, Cu(s, s), TiC, TiB2 and Ti3SiC2. An optimum shear strength reached up to 435 MPa at a brazing temperature of 910 °C and holding time of 20 min. Such a shear strength was 90 MPa higher than the one without the Cu foam. The obtained high shear strength of joint was discussed from microstructure and residual stress. With the increase of brazing time, Cu(s,s) gradually disappeared and the content of Ti2Cu intermetallic compound increased, which was harmful for the joint. Furthermore, the residual stress of joint with Cu foam was calculated to be 324 MPa, lower than the one without Cu foam interlayer.

Microstructural mechanism and mechanical properties of Cf/SiC composite/TC4 alloy joints composite-diffusion brazed with TiZrCuNi + TiCp composite filler

in this paper, Cf/SiC composites and TC4 alloys were joined by the novel composite-diffusion brazing process using (Ti-Zr-Cu-Ni) + TiCp composite filler. The microstructural behavior and mechanism of the joints was deeply investigated by SEM, TEM and XRD. Mechanical properties versus different process parameters of the joints were thoroughly discussed. It was discovered that a reaction-breaking phenomenon occurred for TiC particles. During the bonding process, Zr atoms concentrated around TiC particles and reacted with them to form Ti(Zr)C compound layer on the surface of TiCp. As the reactions progressed, the Ti(Zr)C layer split into fine particles from TiC and then distributed uniformly in the joining layer together with the residual TiC particles. The smaller the TiC particle was, the less time it took to complete the breaking and dispersion process. These low coefficient thermal expansion (CTE) particles were beneficial for releasing the joint residual stress and significantly improved the mechanical properties of the joints. The shear strength of the joints at room temperature (RT) showed a peak value as the bonding temperature was raised or the holding time was prolonged when the TiCp content kept constant. With the increase of TiCp content, the bonding temperature corresponding to the peak shear strength of the joints became higher, the holding time corresponding to peak shear strength of the joints became longer. The shear strength of the joints at 800 °C had similar variation trend with the changing of bonding temperature, holding time and the content of TiCp. But, compared with the RT shear strength, the shear strength of joints at 800 °C was much smaller and the peak shear strength corresponded to longer holding time. The maximum shear strength of the joints at room temperature and 800 °C were 224 MPa and 157 MPa respectively.

The relation between residual stress, interfacial structure and the joint property in the SiO2f/SiO2-Nb joints

In order to achieve a high-quality joint between SiO2f/SiO2 and metals, it is necessary to address the poor wettability of SiO2f/SiO2 and the high residual stress in SiO2f/SiO2-Nb joint. Here, we simultaneously realize good wettability and low residual stress in SiO2f/SiO2-Nb joint by combined method of HF etching treatment and Finite Element Analysis (FEA). After etching treatment, the wettability of E-SiO2f/SiO2 was improved, and the residual stress in the joint was decreased. In order to better control the quality of joints, efforts were made to understand the relationship between surface structure of E-SiO2f/SiO2 and residual stress in joint using FEA. Based on the direction of FEA results, a relationship between residual stress, surface structure and joint property in the brazed joints were investigated by experiments. As well the FEA and the brazing test results both realized the high-quality joint of E-SiO2f/SiO2-Nb and the shear strength of the joint reached 61.9 MPa.

Numerical Evaluation of Temperature Field and Residual Stresses in an API 5L X80 Steel Welded Joint Using the Finite Element Method

Metallic materials undergo many metallurgical changes when subjected to welding thermal cycles, and these changes have a considerable influence on the thermo-mechanical properties of welded structures. One method for evaluating the welding thermal cycle variables, while still in the project phase, would be simulation using computational methods. This paper presents an evaluation of the temperature field and residual stresses in a multipass weld of API 5L X80 steel, which is extensively used in oil and gas industry, using the Finite Element Method (FEM). In the simulation, the following complex phenomena were considered: the variation in physical and mechanical properties of the material as a function of the temperature, welding speed and convection and radiation mechanisms. Additionally, in order to characterize a multipass weld using the Gas Tungsten Arc Welding process for the root pass and the Shielded Metal Arc Welding process for the filling passes, the analytical heat source proposed by Goldak and Chakravarti was used. In addition, we were able to analyze the influence of the mesh refinement in the simulation results. The findings indicated a significant variation of about 50% in the peak temperature values. Furthermore, changes were observed in terms of the level and profile of the welded joint residual stresses when more than one welding pass was considered.

Effect of tool material on microstructure and mechanical properties in friction stir welding

Abstract Although the number of experimental studies investigating the effect of friction stir welding (FSW) parameters on joining properties have increased recently, there are not sufficient numbers of studies on the effect of the stirring tool material in friction stir welding. This study investigated the effect of stirring tool materials on microstructure, mechanical properties and residual stress of joints. Samples of 7075-T651 Al alloys were joined by FSW using uncoated and TiN-coated X210Cr12 alloy steel stirring tools. The welding processes were performed at rotational speeds of 900, 1250 and 1600 rpm and at a welding speed of 60 mm × min−1. Mechanical and metallographic tests were applied to the welded joints and residual stress analysis was performed using the hole drilling method. The best mechanical properties were determined in the welded samples joined by the uncoated tool at a rotational speed of 900 rpm. It was also determined that the TiN-coated tool negatively affected the mechanical and metallurgical properties of the weldements. Moreover, the highest longitudinal residual stresses were specified in the joining performed by the uncoated tool.

Design and Application of MMM System for Welding Residual Stress Test

In order to apply metal magnetic memory (MMM) technology to welding residual stress testing, the MMM hardware and software system is designed. The software subsystem is based on object-oriented programming and the hardware subsystem is portable. The MMM system can test the welded joint residual stress distribution, residual stress concentration zones and defects at workshop. Moreover, the MMM testing system can output data to a computer not only for automatic evaluation but also for further analysis and evaluation with expert intervention. According to the trend of the MMM characteristic, the welding residual stress concentration and defects can be detected and evaluated. The field X-ray examination result is consistent with the result of the MMM testing system, which has proved the accuracy and engineering practicality of the MMM testing system.