Element Analysis Of Residual Stresses Research Articles

Mathematical Modeling and Finite Element Analysis of Residual Stress (RS) Field after Multipass Ultrasonic Surface Rolling

In order to achieve the change rule of the induced residual stress (RS) field after multipass ultrasonic surface rolling (USR), a mathematical model of the induced residual stress (RS) field after multipass ultrasonic surface rolling is first established. Then, the coupling mechanisms of the RS field after dual-pass USR and multipass USR are analyzed, respectively. Subsequently, a finite element (FE) model is established, and the influence of the interval between two adjacent rolling paths LS is investigated. Finally, both the mathematical model and the FE model are experimentally verified. The results show that both the mathematical model and the FE model can predict the RS field after multipass USR. Two adjacent RS fields will couple with each other in their overlapping regions. For a relatively small interval LS, the RS field after multipass USR can be fully coupled, so as to form a uniform compressive RS layer. In this study, when LS = 0.05 mm, the values of the surface compressive RS, the maximum compressive RS, the depth of the maximum compressive RS, and the depth of the compressive RS layer reach 426.71 MPa, 676.54 MPa, 0.05 mm, and 0.54 mm, respectively.

Finite Element Analysis of Residual Stress Induced by Single-Pass Ultrasonic Surface Rolling Process

Finite Element Analysis of Residual Stress Induced by Single-Pass Ultrasonic Surface Rolling Process

Finite element analysis of residual stress and warpage in a 3D printed semi-crystalline polymer: Effect of ambient temperature and nozzle speed

The printing conditions in Fused Deposition Modelling (FDM) affect the amount of induced residual stresses within the printed part and its dimensional accuracy. Among the thermoplastic feedstock for FDM, semi-crystalline polymers are more prone to part distortion due to crystallisation. Therefore, this study aims to numerically investigate the behaviour of semi-crystalline polymer under various FDM printing conditions (namely print speed and ambient temperature) and the resultant residual stress and warpage in the printed parts. For this, the coefficient of thermal expansion (CTE) and the thermo-mechanical properties of the polymer under study (polypropylene), and the crystallisation kinetics are coupled with the evolving temperature and time during printing. The values of residual stress and warpage are calculated and compared for the bottom and top layers of the samples. From the results, it was observed that increasing the nozzle speed from 30 mm/s to 60 mm/s resulted in the bottom and top layers exhibiting a 15% and 13% decrease in residual stress, respectively. Similarly, a drop in warpage (~30%) was observed for both layers. The reduction in residual stress and warpage with increased printing speed is attributed to the improved heat transfer between the deposited roads and the reduced cooling rate. Increasing the ambient temperature from 25 °C to 75 °C resulted in a 2% and 3% decrease in residual stress in the bottom and top layers, respectively. In terms of warpage, an insignificant increase (~1%) was observed in both top and bottom layers. This is explained by the counter effects of reduced thermal gradients (i.e., lower cooling rate) and increased crystallisation on the overall amount of residual stress and warpage. 3D scanning of experimentally printed samples was used for verification of the simulation results, and good agreement between these is reported.

Finite Element Analysis of Residual Stress in TC4/TC11 Titanium Alloy Gradient Material Produced by Laser Additive Manufacturing

Finite Element Analysis of Residual Stress in TC4/TC11 Titanium Alloy Gradient Material Produced by Laser Additive Manufacturing

Finite element analysis of residual stress in 2.25Cr-1Mo steel pipe during welding and heat treatment process

The circumferential butt-welded pipe was fabricated using 2.25Cr-1Mo steel and then subjected to local post-weld heat treatment (LPWHT) for releasing residual stress after multi-pass welding. The sectioning method was employed to measure residual stress. Based on SYSWELD software, a thermo-metallurgical-mechanical coupled computational approach was developed to analyses the residual stress distribution on 2.25Cr-1Mo welded pipe. A three-dimensional finite element model and moving heat source model were employed in simulation. The effects of solid-state phase transformation (SSPT), tempering as well as creep were considered simultaneously. The effectivity of computational approach was verified by experimental measurement. The simulation results showed that SSPT could induce an undulating stress profile and large stress gradient in welded zone. The stress gradient could be reduced during LPWHT while there were stress peaks at the edges of heated region. Tempering effect could decrease the residual stress at high-stress region by material softening and yielding. Creep caused a global transformation from elastic strain to plastic strain, which led to a macro-scale stress relaxation. It is necessary to consider SSTP, tempering as well as creep in material model for more accurate simulation results.

Finite Element Analysis of Residual Stress in Welded Joints of T91 Steel

The pressure equipment is the key equipment in the petrochemical industry, natural gas chemical industry and coal chemical industry. Without safe and reliable pressure equipment, advanced process industry cannot be realized. It is important of the quality assurance of pressure vessel in order to prevent the failure of pressure vessel, especially some rupture accidents. One of the key reasons for quality assurance of pressure vessel is the treatment of residual stress in welded joint. In this paper, the working stress and welding residual stress of the thick plate of pressure equipment material and the welding joint of pressure equipment have been measured and analyzed successively by means of actual stress measurement and finite element simulation analysis. The influencing factors of welding stress are introduced, and the control of residual stress is analyzed and some suggestions are put forward in this paper.

Viscoelastic finite element analysis of residual stresses in porcelain-veneered zirconia dental crowns.

The main problem of porcelain-veneered zirconia (PVZ) dental restorations is chipping and delamination of veneering porcelain owing to the development of deleterious residual stresses during the cooling phase of veneer firing. The aim of this study is to elucidate the effects of cooling rate, thermal contraction coefficient and elastic modulus on residual stresses developed in PVZ dental crowns using viscoelastic finite element methods (VFEM). A three-dimensional VFEM model has been developed to predict residual stresses in PVZ structures using ABAQUS finite element software and user subroutines. First, the newly established model was validated with experimentally measured residual stress profiles using Vickers indentation on flat PVZ specimens. An excellent agreement between the model prediction and experimental data was found. Then, the model was used to predict residual stresses in more complex anatomically-correct crown systems. Two PVZ crown systems with different thermal contraction coefficients and porcelain moduli were studied: VM9/Y-TZP and LAVA/Y-TZP. A sequential dual-step finite element analysis was performed: heat transfer analysis and viscoelastic stress analysis. Controlled and bench convection cooling rates were simulated by applying different convective heat transfer coefficients 1.7E-5 W/mm2 °C (controlled cooling) and 0.6E-4 W/mm2 °C (bench cooling) on the crown surfaces exposed to the air. Rigorous viscoelastic finite element analysis revealed that controlled cooling results in lower maximum stresses in both veneer and core layers for the two PVZ systems relative to bench cooling. Better compatibility of thermal contraction coefficients between porcelain and zirconia and a lower porcelain modulus reduce residual stresses in both layers.

Three-dimensional finite element analysis of residual stresses in circumferential welds of 2205/X65 bimetallic pipe

Corrosion has a great negative influence on the pipe service life, and high welding residual stress will accelerate corrosion and reduce the strength of the pipe. Traditional carbon pipe is highly susceptible to corrosion, especially in the oil transport industry, and the stainless steel pipe is expensive. So bimetallic steel is a good choice for high-pressure and corrosion-resistant pipe. Multi-pass butt-welded 2205/X65 bimetallic pipe in this article is simulated numerically in non-linear thermo-mechanical finite element method (FEM), a three-dimensional (3D) finite element model is developed, the temperature history and the residual stress distribution are plotted, and the results are compared with the available measured data to evaluate the accuracy of the finite element model. In addition, the stresses changing with weld pass and the effect of the welding speed on stress distribution are also studied. The results show that the tensile stresses after cooling are larger than the tensile stresses after pass four on the inside surface, and the compressive stresses after cooling are larger than the compressive stresses after pass four on the outside surface, and the position of the maximum stress is farther away from the weld center when the welding speed decreases.

Finite element analysis of residual stress in hybrid laser-arc welding for butt joint of 12 mm-thick steel plate

As a high-efficiency and high-quality welding process, hybrid laser-arc welding (HLAW) has significant potential of application in welding thick plate. Understanding the features of welding residual stress benefits the optimization of HLAW process. In the present study, based on thermal elastic–plastic theory, a three-dimensional finite element model is developed to predict the residual stress and distortion in HLAW for butt joint of 12-mm-thick steel plate. GMAW heat input and laser energy are modeled as one double-ellipsoid body heat source and one cone body heat source with enhanced peak density along the central axis, respectively. Residual stresses and distortions are calculated for single-pass and multi-pass hybrid welding processes. The results show that the distribution features of longitudinal and von Mises equivalent residual stresses in single-pass hybrid welding are similar to that in multi-pass hybrid welding. A large tensile stress is generated at the weld zone and its vicinity. Compared with GMAW, the zone with high residual stress in hybrid welding is decreased largely, but there is no improvement in peak residual stress. Among three cases, the distortion in single-pass hybrid welding has the lowest value.

Finite Element Analysis of Residual Stress in the Diffusion Zone of Mg/Al Alloys

In this study, the finite element method was applied for analyzing the effect of annealing temperatures on residual stress in the diffusion zone of AZ31 Mg and 6061 Al alloys. The microstructure and mechanical behavior of the diffusion zone were also investigated. Simulations on the annealing of the welded specimens at 200°C, 250°C, and 300°C were conducted. Moreover, experiments such as diffusion bonding and annealing, analysis of residual stress by X‐ray diffraction, elemental analysis using an electron probe microanalyzer, and microstructure investigation via scanning electron microscopy were performed for further investigation of the diffusion layers. According to the results of the simulations and experiments, the diffusion layers widen with increasing annealing temperatures, and the results of the simulations are in good agreement with those of the experiments. The microstructure and elemental distribution were the most uniform and the residual stress was the least for samples annealed at 250°C. Thus, 250°C was found to be the most appropriate annealing temperature.

Finite element analysis of residual stress in cold expanded plate with different thickness and expansion ratio

Cold expansion of fastener/rivet holes is a common way to generate beneficial compressive residual stress around the fastener hole. In this study, cold expansion process was simulated by finite-element method in order to determine the residual stress field around two cold expanded holes by varying the plate thickness and expansion ratio of the hole. The model was developed in ANSYS and assigned to aluminium alloy 7475-T61 material model. The results showed that the residual stress become more compressive as the plate thickness is increased up to t/d = 2.6 and decreased for further level of thickness. In addition, the residual stress at the edge of the hole become more compressive as the expansion ratio is increased up to 4.5% and decreased for further level of expansion. This study also found that the residual stresses near the entrance and the exit face of the plate are less compressive than the residual stresses on the mid-thickness of the plate.

Experimental and finite element analysis of residual stresses in cold tube drawing process with a fixed mandrel for AISI 1010 steel tube

Cold tube drawing with a fixed straight mandrel (fixed plug) is one of the major drawing process in tube drawing operations. Although the process has high dimensional accuracy and good surface finish in general, the process parameters have significant effects on part quality. Therefore, an accurate finite element model is extremely important to improve part quality and reduce the cost of the part. In this article, a cold tube drawing with a fixed straight mandrel is studied experimentally and numerically for AISI 1010 steel tube. Two different reduction of areas of 16 and 23% are considered. X-ray diffraction (XRD) method is used to determine hoop residual stresses inside the tube wall at five different orientations. The experimental models are validated successfully with finite element analysis (FEA) by correlations of the compression force vs. the displacement and the residual stress vs. the position. Effect of the drawing parameters on the hoop residual stress is studied by an axisymmetric finite element model. Although the reduction of area strongly affects the residual stress compared to other process parameters, the friction coefficient has minimum effect on residual stresses. This study concludes that the residual stress states inside the tube wall produced by cylindrical and conical plugs are completely different.

Novel approach towards finite element analysis of residual stresses in electrical discharge machining process

The high temperature gradients generated in electrical discharge machining process by electric discharges result in residual stresses on the surface layers of electrodes. These residual stresses can lead to deficiencies in machined workpiece such as micro-cracks, reduction in strength and fatigue life, and possibly catastrophic failure. In the present research, a finite element model (FEM) has been developed to estimate the distribution of residual stress in the machined surface of workpiece through considering temperature-dependency of the physical properties of AISI H13 tool steel as workpiece and solid-state phase transformation. The data achieved by FE simulation have been validated using experiments handled by nano-indentation measurement on the side of cubic ED-machined workpiece. The results showed that the profile form of residual stress is independent from discharge energy; though with increase in pulse energy, the maximum of tensile residual stress and the depth where the maximum is observed slightly increase. Furthermore, the maximum calculated value for residual stress exceeds ultimate strength of AISI H13 tool steel, 1990 MPa, and reaches the amount of 2150 MPa for lowest pulse energy. The maximum residual stress measured by nano-indentation is 2040 which represents the slight deviation of 50 MPa or 2.5 % with the predicted values.

Finite Element Analysis of Residual Stress in Ti-6Al-4V Alloy Plate Induced by Deep Rolling Process under Complex Roller Path

The kinematics of the deep rolling tool, contact stress, and induced residual stress in the near-surface material of a flat Ti-6Al-4V alloy plate are numerically investigated. The deep rolling tool is under multiaxis nonlinear motion in the process. Unlike available deep rolling simulations in the open literature, the roller motion investigated in this study includes penetrative and slightly translational motions. A three-dimensional finite element model with dynamic explicit technique is developed to simulate the instantaneous complex roller motions during the deep rolling process. The initial motion of the rollers followed by the penetration motion to apply the load and perform the deep rolling process, the load releasing, and material recovery steps is sequentially simulated. This model is able to capture the transient characteristics of the kinematics on the roller and contacts between the roller and the plate due to variations of roller motion. The predictions show that the magnitude of roller reaction force in the penetration direction starts to decrease with time when the roller motion changes to the deep rolling step and the residual stress distributions in the near-surface material after the material recovery step varies considerably along the roller path.

Experimental and finite element analysis of residual stress and distortion in GTA welding of modified 9Cr-1Mo steel

In this paper, investigation of residual stress and distortion induced in 3 mm thick Modified 9Cr-1Mo steel plates during GTA welding is carried out. SYSWELD software is used for the thermo-mechanical analysis. A 3D meshed model is created for the simulation and double ellipsoidal heat source distribution is used for the thermal analysis. Thermal cycles predicted near the fusion zone are compared with experimentally measured thermal cycles using thermocouples. Predicted residual stress profile across the fusion zone is compared with the measured profile using X-ray diffraction method. There is a good agreement between measured and predicted thermal cycles and residual stress profile. Distortion of the weld joint is measured using vertical electronic height gauge. Finite element analysis of distortion of the weld joint is carried out by applying both large and small distortion theories. Comparison of experimental and numerical results showed better accuracy if large distortion theory is applied.

Finite Element Analysis of Residual Stresses in Metallic Coatings through a Compound Casting

Al and Mg alloys are widely used in industry as main lightweight alloys. They have excellent properties, such as low density, high ductility, and high specific strength, and so on. Generally speaking, Mg alloys are better than Al alloys. However the corrosion of Mg alloys is much more difficult to control compared Al alloys. Therefore to combine these two lightweight alloys, a composite-like structure is an ideal solution since Al alloys can be used as protective coatings for Mg alloys. Compound casting is a realistic technique to get this coating system. In the current study, we numerically study the compound casting using finite element method (FEM) to make these two alloys, a composite-like structure, satisfy requirements to resist corrosion required from industry, in which the aluminum layer is acting as a protective coating for the magnesium substrate. Several finite element models have been developed by using the birth and death element technique and we focus on compound casting-induced residual stresses in the compounded structure. The numerical results obtained from the proposed finite element models show the distribution profiles of thermal residual stresses. We found the major factors influencing the residual stresses are the temperature to pre-heating the Al substrate and the thickness of Mg deposits.

Three-dimensional finite element analysis of residual stresses in dissimilar steel pipe welds

Dissimilar steel pipe welds are commonly found in various industrial applications due to both technical and economic reasons. The safety assessment practice for such welds requires residual stresses to be taken into consideration. Therefore, it is of critical importance to estimate the magnitude and distribution of residual stresses in dissimilar steel girth-welded pipe joints. This study describes the three-dimensional thermal elastic–plastic analysis using finite element (FE) techniques to accurately capture the residual stress states in dissimilar steel pipe welds between carbon and stainless steel pipes. The thermo-mechanical FE model used as well as the analysis methodology is detailed. Analysis of the results has revealed that residual stresses in the dissimilar steel girth-welded pipe are by no means of the same magnitude or distribution as those in the corresponding similar steel counterparts.

Thermo Mechanical Analysis of SS304 Circular Grid Plate Hard Faced with Colmonoy

In this paper, plasma transfer arc welding using hard faced material Colmonoy which is deposited on a annular groove of a circular grid plate made up of SS 304 was studied. Hard face deposition made by Plasma Transferred Arc Welding (PTAW) on a annular groove of a grid plate at relatively high temperature, generates residual stresses due to differential shrinkage of the molten deposit, process-induced thermal gradients and difference in coefficients of thermal expansion between the colmonoy deposit and base material SS 304. However, the magnitude and distribution of the residual stresses vary depending on the heat input, deposition process, and the geometry of the component. Finite element analysis of residual stress is performed with commercial FEA package of ANSYS 12.0 which includes moving heat source, material deposit, temperature dependent material properties, metal plasticity and elasticity. Coupled thermo-mechanical analysis is done for welding simulation and the element birth and death technique is employed for simulation of filler metal deposition. Finally residual stress is evaluated so that annealing is performed accordingly to relieve residual stresses in order to carry out fracture analyses thereafter.

A study of the residual stress and deformation in the welding between half-pipe jacket and shell

Half-pipe jacketed vessels are widely used as the heating or cooling structure in the chemical industries. But the leakage of the welding joint between the jacket and cylinder is a big problem, which is greatly affected by the residual stress and deformation. This paper presents a finite element analysis of residual stress and deformation induced by welding half-pipe jacket to shell, and the effects of heat input, cooling inside the shell and welding sequence on residual stress have been discussed. It is found that large longitudinal stress is generated in the weld metal. Due to the local weld heating, the jacket and shell become un-circle. A wave shape of stress along the circumferential of shell is generated. With the heat input increase, the residual stress and ellipticity increase linearly. On the premise of entire penetration welding, smaller heat input should be used to avoid too big deformation. Filling the shell with cooling water can decrease the residual stress and ellipticity during the welding, and welding the two joints of one jacket simultaneously is also available, which provides a reference for the welding of half-pipe jacket.

Thermo Mechanical Analysis of Hard Faced Circular Grid Plate

In this paper, plasma transfer arc welding of hard faced circular grid plate was studied. Hard face deposition made by Plasma Transferred Arc Welding (PTAW) on grid plate at relatively high temperature, generates residual stresses due to differential shrinkage of the molten deposit, process-induced thermal gradients and difference in coefficients of thermal expansion between the deposit and base material. However, the magnitude and distribution of the residual stresses vary depending on the preheat temperature, heat input, deposition process, and the geometry of the component. Finite element analysis of residual stress is performed with commercial FEA package ANSYS 12.0 which includes moving heat source, material deposit, temperature dependent material properties, metal plasticity and elasticity. Coupled thermo-mechanical analysis is done for welding simulation and the element birth and death technique is employed for simulation of filler metal deposition.