Residual Stress Relief Research Articles

Creep relaxation to relieve residual stress in girth-butt welded X80 pipelines: Simulation and experiment

The residual stress in girth-butt weld presents safety risks for large-diameter oil-gas pipelines, necessitating an in-depth investigation into the welding residual stress and the development of effective methods to mitigate these stresses, thereby enhancing structural integrity. In this work, a finite element girth-butt welding model was developed to predict the residual stress of X80 pipelines. The residual stress relief resulting from local post-weld heat treatment (PWHT) was simulated based on the Norton creep model applicable to X80 steel. The simulation results, encompassing the residual stress both before and after PWHT, were validated through blind-hole drilling measurements. The results demonstrate that the welding residual stresses across all orientations were significantly reduced following PWHT, with a maximum stress reduction of approximately 360 MPa. The primary mechanical mechanism for residual stress relief was identified as high-temperature creep, and it was concluded that the PWHT alleviated welding residual stress effectively when the heating temperature exceeded the creep activation temperature. The consistency between the finite element analysis results and the experimentally measured residual stresses affirms the validity and feasibility of the finite-element-based approach for predicting welding residual stresses.

The influence of tensile stress on the strength and residual stress of C19400 alloy under ultrasonic vibration treatment

The C19400 alloy strip used for etching lead frames was studied, and the evolution law of its mechanical properties, residual stress, and microstructure under the ultrasonic vibration and tensile stress treatment was studied. The influence mechanism of ultrasonic vibration and tensile stress on the strength and residual stress of C19400 alloy was determined. The results show that high strength, high conductivity and low residual stress of C19400 alloy can be obtained under the coupling effect of ultrasonic vibration and tensile stress. The tensile strength is 430.57 MPa, the electrical conductivity is 57.73 % IACS, the transverse direction residual stress is −1 MPa, and the rolling direction residual stress is −21 MPa, and the residual stress relief rates are 97 % and 68 %, respectively. Under the coupling effect of alternating load and tensile stress, dislocations are annihilated and reorganized, the dislocation configuration tends to be uniformly arranged, and the dislocation density decreases. Compared with the original cold rolled state, the proportion of high angle grain boundaries of the alloy is slightly increased, and the texture strength is significantly reduced. These results have guiding significance for producing high strength, high conductivity and low residual stress of C19400 alloy.

Failure analysis of fatigue crack propagation in specimens of AlSi10Mg aluminum alloy produced by L-PBF: Effect of different heat treatments

Fatigue crack growth behavior of AlSi10Mg aluminum alloy processed by laser powder bed fusion (L-PBF) was studied for three material conditions: as-built, stress relieved and hot isostatic pressed. An improvement in the fatigue crack growth resistance was found for the heat-treated conditions which was attributed to the residual stress relief induced by the heat treatments. The stress ratio did not affect the fatigue crack growth in regime II which was explained by the absence of crack closure. Fatigue crack growth rates were predicted using a model based on the cyclic plasticity of the tested aluminum alloy. The proposed model agreed well with the experimental results.

Residual stress relief strategy in thick steel weldments via local induction heat treatment: Simulation and neutron diffraction experiment

This study investigated the effect of local induction post-weld heat treatment (PWHT) on residual stress relief in thick submerged arc welded steel plates. A combination of numerical and neutron diffraction methods was used to examine the effect of various PWHT parameters, such as annealing temperature and holding time, on the relief of residual stress in welded plates with various thicknesses. A sequentially coupled thermal–mechanical finite element model was used to calculate the residual stress distribution in welded AH36 steel plates before and after PWHT. The model was validated by comparing its predictions with the experimental measurements, and the results showed good agreement. The residual stress of the thick welded plates was effectively reduced via PWHT with local induction. The primary mechanism for this stress release was identified as stress relaxation caused by creep strain. Furthermore, a process map was established considering the PWHT conditions and plate geometry. This map provides a means of determining the optimal PWHT conditions to achieve desired stress reduction levels.

Relief of Residual Stress in Bulk Thermosets in the Glassy State by Local Bond Exchange

Relief of Residual Stress in Bulk Thermosets in the Glassy State by Local Bond Exchange

REDUCING RESIDUAL STRESSES USING CRYOGENIC THERMAL TREATMENT

This work deals with the reduction of residual stresses using cryogenic thermal treatment as all alternative to normal thennal treatment .The work was performed on a solid z-shaped model component. Ihe models were fabricated from two difl'erent types of materials (alloy steel & alumin:tm). If any residual stresses exist in a manufactured cornponent, then these residual stresses will have an effect on the natural frequency of that component. A new type of measurement method was used to measure the level of residual stresses present. The nahral frequency of the models at a stress fiee state was used as a reference. This method was also used to find the extent of the residual stress relief and percentage of reduction. Residual stresses were incluced by flame heating with different boundary conditions and at different rates of cooling. They were stress relieved by the use of liquid nitrogen (-198uC) and at different various treatment times. This rvas done to find the effect of time on the treatment. Reduction in residual stress level reached 92.38yo.'firis reduction was compared with a normal thermal stress relief. Also a comparison was macie between the two types of material that were stress relieved. It was found that over treatment tends to re-stress the models.

The prediction of residual stress of welding process based on deep neural network

The welding process has been an efficient method for producing essential and complex manufacturing parts in various industrial design fields. The post-weld residual stress can have detrimental effects on welded components. Therefore, systematic studies of residual stress are essential for evaluating welding behaviors and mechanisms in welded structures. They can provide a valuable reference and optimization for addressing residual stress relief. Numerical finite element analyses based on thermal-mechanical models offer a comprehensive approach to simulate real welding, providing a reliable means to determine and quantify the distribution of residual stress based on welding parameters and material properties. Furthermore, the finite element analysis is capable of generating adequate and dependable datasets in relation to the classical experiment. However, the finite element simulation is not considered an efficient method for predicting the magnitude and distortion of residual stress due to its high computational cost. A deep learning framework with powerful automatic learning abilities could potentially be used as an alternative method to efficiently predict residual stress. The purpose of the current study is to propose an innovative modeling approach for accurately and effectively predicting residual stress. A deep network model with Convolutional Neural Network using Adam optimization is integrated with numerical finite element analyses of a single-pass beam weld in SUS304 stainless steel. Finite element analysis is used to generate extensive residual stress datasets, which are partly used to train the deep network model and partly used for model validation. The deep network model aligns closely with the finite element analysis results, with a root-mean-square error (RMSE) of less than 12, an absolute fraction of variation (R2) of greater than 0.95, a mean absolute error (MAE) of less than 6.8 and a mean absolute percentage error (MAPE) of less than 1.1. Furthermore, this study highlights the potential advantage of using a deep network model with strong memory capabilities to directly predict residual stress for identical structural components and welding processes.

Direct artificial aging of the PBF-LB AlSi10Mg alloy designed to enhance the trade-off between strength and residual stress relief

The AlSi10Mg alloy is one of the most studied alloys processed by the Powder Bed Fusion-Laser Beam (PBF-LB). Many already published works focus on post-process heat treatments to reduce residual stress or improve mechanical strength. Instead, the present study aims to identify direct artificial aging (AA) heat treatment able to optimize both aspects, thus enhancing the trade-off between strengthening and residual stress relief for the PBF-LB AlSi10Mg alloy produced using a no-heated platform. Higher temperatures (190–240 °C) than those typically used in AA heat treatment were selected based on thermal analysis to benefit both residual stress relief and precipitation of reinforcing phases from the supersaturated solid solution of the metastable as-built alloy. The effects of AA heat treatment on mechanical properties (i.e. hardness) and residual stress were evaluated by plotting aging curves and by XRD and Raman analyses and demonstrated that different trade-offs between strengthening and stress relief can be achieved by tuning heat treatment parameters (temperature and time). In particular, the exposure at the lowest temperature (190 °C) induced a partial decrease in residual stress and a slight increase in hardness. By increasing heat treatment temperature and soaking time, the relief was more significant, whilst the decrease in hardness was rather limited. The results are supported by the microstructural changes observed on the samples due to the different heat treatment conditions applied and show the feasibility of designing an AA heat treatment for the PBF-LB AlSi10Mg alloy capable of satisfying the mechanical response required by the final application.

Relief of Residual Stress in Bulk Thermosets in the Glassy State by Local Bond Exchange.

The covalently cross-linked network gives thermosets superior thermal, mechanical, and electrical properties, which, however, squarely makes the large residual stress that is inevitably induced during preparation hardly relieved in the glassy state. In this work, an incredible reduction in residual stress is successfully achieved in bulk thermosets in the glassy state through introducing highly dynamic thiocarbamate bonds by "click" reactions of thiols and isocyanates. Due to the excellent dynamic behaviors of thiocarbamate bonds, local network rearrangement is achieved through thermal stimulation, while the strong 3D cross-linked network is well maintained. Ultimately, a decrease by 44% in residual stress is detected by simply annealing samples at 30°C below glass transition temperature (Tg), during which they could well maintain more than 98.4% of the storage modulus. After the annealing, more uniform residual stress distribution is also observed, showing a 32% decline in sample standard deviation. However, the residual stress of epoxy resin, a typical thermoset as a reference, changes little even after annealing at Tg. The results prove it a feasible strategy to reduce residual stress in bulk thermosets in the glassy state by introducing proper dynamic covalent bonds.

Efficient residual stress mitigation in additively manufactured 18Ni300 maraging steel

This study explored an effective post-heat treatment (PHT) strategy for achieving optimal residual stress relief in 18Ni300 maraging steel. The primary focus was to investigate and enhance the mechanisms underlying residual stress relief in distinct PHT processes, including aging and annealing-aging. The investigation considered various parameters, including PHT conditions, component size, and initial residual stress field. Components with cubic geometry were fabricated through laser powder bed fusion (LPBF) and subjected to both aging and annealing-aging processes. The residual stresses were extracted from these specimen variants using the contour method. The simulation involved generating the initial residual stress in the LPBF using the flash heating method and simulating the PHT process using the Arrhenius equation-based creep model. Simulations complemented and elucidated the experimental results. The validated model was employed to comprehensively investigate the intricate interrelationships among the various PHT parameters. The results indicate that the annealing-aging process leads to a substantial reduction in the residual stress compared to the aging process. Furthermore, a process map was established by considering the PHT conditions and component size. This map aids in determining the optimal PHT conditions for achieving the desired levels of stress reduction. Therefore, the present study comprehensively explored the PHT effect and its interrelated parameters, suggesting an effective PHT strategy for residual stress mitigation in LPBF, and particularly a process map that is beneficial for practical applications.

Effect of stress relief and solubilization heat treatments on laser additive manufactured Inconel 625: microstructure and properties

This work assesses the effect of the energy input and the stress relief and solubilization heat treatment on the microstructure and mechanical properties of an Inconel 625 alloy processed by laser additive manufacturing using directed energy deposition. Two processing conditions were used to deliver high productivity with a high energy input (HEI) and another with better geometrical precision using a lower energy input (LEI). The mechanical test samples were built vertically and horizontally aligned with the tensile test direction. The samples were submitted to residual stress relief (SR) and SR + solubilization (S) heat treatments (SR + S). Results showed increased elongation with solubilization heat treatment, while UTS and YS decreased with heat treatment combination, which was linked to the stronger texture developed in HEI condition. Samples built in the vertical direction presented lower YS. The fracture toughness of solubilization heat-treated samples showed higher values, while LEI gave just slightly higher values. Although the microstructural and mechanical features are similar between the HEI and LEI conditions, the first stands out because parts can be fabricated quickly without losing mechanical performance under quasi-static conditions, impact fracture tests, or the production of unwanted phases.

Fatigue behavior of SMA490BW welded components considering AHT with traction structural stress

Quantitative characterization on fatigue properties of SMA490BW welded components with annealing heat treatment is very significant for steel structure service. In this work, the relief of residual stress during welding and the subsequent annealing heat treatment process of plate and tube-to-plate components is simulated using the finite element method with the Norton-Bailey creep model. Traction structural stress is used to evaluate the fatigue life of SMA490BW plates and tube-to-plate components under two annealing heat treatment processes by considering residual stress. It is found that the residual stress distribution state of welded components keeps the same tendency by annealing heat treatment, while the peak value of longitudinal and transverse residual stress is decreased significantly due to the increase of equivalent creep strain with the width of the welded plate exceeding 6 times the thickness. The fatigue data for two annealing heat treatment processes and welding of plate and tube-to-plate components are within a 95% confidence interval of the ASME Master SN curve. The influence of load range on fatigue life is more significant than that of welding residual stress. By quantifying the residual stress in the load ratio correction, the standard deviation of fatigue data for different full-scale components more convergent.

Effect of cold drawing reduction rate on edge-to-center-characterized microstructure and orientation alongside residual stresses in conjunction with magnetic properties of low-carbon high-alloy ferromagnetic steel

In the current research, the effect of cold drawing reduction rate (CDRR) of 15% and 45% and the required subsequent isothermal static recrystallization annealing heat treatment (ISRAHT) on the microstructures, textures, residual stresses, and magnetic properties of ferritic/ferromagnetic stainless steel (FSS), EN 1.4106, are investigated by a series of experimental analyses. The study is carried out by the theoretical well-known model of Johnson-Mehl-Avrami-Kolmogorov (JMAK) in conjunction with aforesaid properties. According to the results, by increasing the CDRR, the recrystallization fractions (RF) become faster in accordance with the JMAK theory. Such an increment also affects more fragmented and elongated grains, which leads to provide smaller grains in size. However, by the effect of slow cooling process (SCP), the grain growth is another noticeable part of study. Likewise, the effects of CDRR and the subsequent ISRAHT find to be beneficial for the evolution of microstructures, textures, and relief of residual stresses, and better performance of magnetic behavior. For instance, higher relative magnetic permeabilities approximately above 1000 causes to reach residual stresses closer to zero. The cold-drawn FSSs are consisted of the α-fibre texture, which is close to {223} 〈110〉 and {111} 〈110〉, with higher intensity while by gradual higher recrystallization, the orientation tendency to {111} 〈011〉 of γ-fibre are formed following to the more distributed texture with lesser intensity. The findings display that while the recrystallization process addresses the formation of new grains, resulting in the more equiaxed grains, more well-aligned textures are also achieved in respect to the lower misorientation uniformity density and even with more distributed clusters.

Effective Platform Heating for Laser Powder Bed Fusion of an Al-Mn-Sc-Based Alloy.

Platform heating is one of the effective strategies used in laser powder bed fusion (LPBF) to avoid cracking during manufacturing, especially when building relatively large-size components, as it removes significant process-induced residual strains. In this work, we propose a novel and simple method to spare the elaborate post-processing heat treatment typically needed for LPBF Al-Sc alloys without compromising the mechanical properties. We systematically investigated the effects of LPBF platform heating at 200 °C on the residual stress relief, microstructure, and mechanical performance of a high-strength Al-Mn-Sc alloy. The results reveal that LPBF platform heating at 200 °C is sufficient to largely relieve the process-induced residual stresses compared to parts built on an unheated 35 °C platform. Meanwhile, the platform heating triggered the dynamic precipitation of uniformly dispersed (1.5-2 nm) Sc-rich nano-clusters. Their formation in a high number density (1.75 × 1024 m-3) resulted in a ~20% improvement in tensile yield strength (522 MPa) compared to the build on the unheated platform, without sacrificing the ductility (up to 18%). The improved mechanical properties imply that platform heating at 200 °C can strengthen the LPBF-synthesised Sc-containing Al alloys via in situ aging, which is further justified by an in situ measurement study revealing that the developing temperatures in the LPBF part are within the aging temperature range of Al-Sc alloys. Without any post-LPBF treatments, these mechanical properties have proven better than those of most Al-Sc alloys through long-time post-LPBF heat treatment.

Effect of high-density pulsed electric current on residual stress relief and microstructural modification of cold-bent commercially pure titanium

The effect of high-density pulsed electric current (HDPEC) on removing residual stress of the cold-bent commercially pure titanium TP270 was investigated. After HDPEC treatment, the tensile residual stress on the external surface decreased from 287.75 MPa to 77.33 MPa, and the internal compressive residual stress recovered from −166.56–1.28 MPa. In addition, the hardness on the external and internal surfaces showed the same tendency and almost recovered to the initial state. The microstructural characterization showed that the cold-bending process introduced plenty of dislocations and twins into samples, which were evidently removed by HDPEC due to the coupling effects of electron wind force and Joule heating, thereby resulting in the recovery of residual stress and hardness. Furthermore, through comparison with rapid heat treatment experiments, we have found that both electron wind force and Joule heating effects play equally significant roles in eliminating dislocations and deformed twins. More importantly, the HDPEC treatment maintains the original microstructure, such as grain size, grain boundary characteristics, crystalline orientation, etc. Hence, this method provides a promising way to relieve the residual stress of processed components without affecting the microstructure.

Experiment and mechanism investigation on the effect of heat treatment on residual stress and mechanical properties of SiCp/Al–Cu–Mg composites

Low-volume fraction particle-reinforced aluminum matrix composites (PRAMCs) are commonly prepared using powder metallurgy (PM) technology, followed by heat treatment processes to improve the performance of PRAMCs. PRAMCs are prone to produce significant uneven residual stresses during the quenching process. It is difficult to eliminate the quenching residual stress of PRAMCs via the heat treatment process of the matrix aluminum alloy. Therefore, this study systematically investigates the effects of solid solution and artificial aging treatment processes on residual stress, mechanical properties, and microstructure of SiCp/Al–Cu–Mg composites through orthogonal and single-factor experimental methods. After optimizing the heat treatment process, minor residual stress with a 71.6% von Mises residual stress relief rate and good comprehensive mechanical properties are achieved. Based on the experimental results, macro and micro mechanisms of residual stress evolution and strengthening of SiCp/Al–Cu–Mg composites during heat treatment are revealed, providing valuable insights into the process of heat treatment of PRAMCs.

Effect of electromagnetic coupling treatment on the residual stress relief and mechanical properties of 7050 aluminum alloy

Effect of electromagnetic coupling treatment on the residual stress relief and mechanical properties of 7050 aluminum alloy

Unusual interface phase transformation during continuous additive manufacturing of maraging steel and Co–30Cr–7Mo alloy

The high strength and hardness of maraging steel (MS1) can be functionally integrated with the thermal stability and toughness of Co–30Cr–7Mo alloy (MP1) through multi-material additive manufacturing via laser powder bed fusion. However, appropriate heat treatment is necessary to stabilize the multi-phase interface post-printing and achieve desired material properties. In the present study, we investigate the effects of solution and aging heat treatment on the interface characteristics and mechanical properties of MS1-MP1 multi-material components. The results reveal that a discontinuous martensitic transformation occurs in the interface after printing due to the combined effects of solute segregation, local stress distribution, and intermixed cellular growth. In contrast, consistent parallel martensite laths were observed after heat treatment due to the homogenized alloying element distribution, extensive residual stress relief and stable interface structure. Furthermore, the mechanical testing results revealed that the tensile strength of the MP1-MS1 alloy was maintained at about 1185 ± 18 MPa before and after heat treatment, complemented by an increase in elongation from 14.7 ± 1.3% to 27.1 ± 2.1%. The microstructure and mechanical properties obtained are then correlated based on phase boundary orientation relationships and simulated martensite start temperatures in different regions along the interface. Based on overall results, it can be concluded that MP1 forms a compatible interface with MS1. Heat treatment can still be performed to improve the strength of MS1 by precipitation strengthening without compromising the strength of MP1 and the MS1-MP1 interface.

A Uniformed Calculation Criterion on Heat Band Width of Local PWHT on Welded Joint with Dissimilar Thickness

Local post-weld heat treatment is used to reduce welding residual stresses. The existing standards have great differences in the selection of the width of the heated band, and the heating width, as an important control parameter of the local heat treatment, will directly affect the quality of the heat treatment. In this paper, the numerical simulation method is used to simulate the welding and heat treatment process of unequal-thickness joints. The stress and deformation of the joint with different thickness ratios under different heating widths are studied by finite element simulation, focusing on the influence of the width of the heated band on the residual stress relief of the joint. Based on these studies, the criteria for determining the optimal width of the heating zone are consistent. Finally, the formula HB=HB1+HB2=3RT+1+k2RT for calculating local heat treatment heating width based on the thickness of welded joint for SA738Gr.B steel is established. Among them, HB1 is the width of the main heating zone, HB2 is the width of the auxiliary heating zone, k is the thickness ratio of the thick plate to the thin plate, and t is the wall thickness of the thin plate.

Welding Residual Stress Elimination Technique in the Top Chord of Main Truss of Steel Truss Bridge

The large-amplitude fluctuations of ultrasound in high-energy ultrasonic stress relieving cause the crystal grains or lattices in the high residual stress zone to vibrate or creep alternately. This triggers secondary effects such as ultrasonic softening and dislocation movement. The sound field also produces periodic shock waves or intermittent shock waves, which form local pressure gradients at the wave front. These pressure gradients cause local heating of the grain boundary, accelerating material softening and promoting slip between grains, ultimately resulting in residual stress elimination. This technique was applied to detect the welding residual stress of the upper chord of the main truss of Sanguantang Bridge by using an ultrasonic stress meter. After the measurement, it was found that the welding residual stress in some areas was too large, and the welding residual stress needed to be eliminated. The welding seam was re-inspected after the residual stress relief operation was completed. The test results showed a maximum reduction rate of 63.91% and an average overall reduction rate ranging from 24.52% to 37.23%. The reduction effect is more significant in areas with higher welding residual stress.