Finite Element Analysis Of Residual Stress Research Articles

Finite-element analysis of residual stresses in the TС4 titanium alloy treated by laser shock peening

Laser shock peening is an effective tool for generating deep compressive residual stresses (more than 1 mm) near the surface of metallic structures. This can improve their mechanical properties and fatigue performance. For this purpose, it is necessary to find optimal laser shock parameters. In this paper, the effect of laser intensity and peening pattern on the residual stress field in a Ti-6Al-4V titanium alloy is investigated through numerical simulations. The applied approach includes two steps. In the first stage, the modeling of elasto-plastic stress waves is performed. The second stage involves a solution of static equilibrium problem for residual stress distribution taking into account plastic deformation fields. The analysis was carried out for a square plate with a thickness of 3 mm, the central part of which is subjected to a series of square laser pulses. The pulse length was the same for all considered cases, and it was equal to 3 mm. The results of the analysis demonstrate that, when the laser pulse power density increases, the maximum value of compressive stress increases as well, and tensile stresses occur on the opposite side of the sample. The application of the two-sided laser peening (no overlap) or one-sided peening (50% overlap) can eliminate this effect. An increase in the maximum compressive stress is observed on both sides of the specimen in these cases. Due to an increase in the number of layers in the case of the one-sided peening (no overlap), the maximum compressive stress and penetration depth become greater. However, tensile stresses in the volume of the sample also increase.

Investigation on effect of thermal aging embrittlement on residual stresses of austenitic stainless steel repair welds in nuclear components subject to seismic loads

This paper presents investigation results on effect of thermal aging embrittlement on residual stresses of austenitic stainless steel repair welds in nuclear components subject to seismic loads. First, the welds on austenitic stainless steel 316L plates were manufactured consisting of the austenitic stainless steel weld metal with the δ—ferrite content sensitive to the thermal aging embrittlement. One of the welds was embrittled via conducting thermal aging acceleration test. Second, validity of finite element weld residual stress analysis was verified by performing finite element residual stress analysis and holedrilling method for the unrepaired welds. Third, effect of the thermal aging embrittlement on the residual stresses of the repair welds was evaluated by comparing the residual stresses according to whether the original welds were thermally embrittled. Last, effect of seismic loads was reviewed for the case where the repair welding was performed on the original welds being thermally embrittled. As a result, it is found that the effect of the thermal aging embrittlement on the residual stresses of the unrepaired welds is insignificant whereas tensile residual stresses of the repair welds increase in proportion to the increase in yield strength at room temperature due to the thermal aging embrittlement. In addition, the residual stresses are significantly mitigated after the seismic loads.

Effects of Substrate Preheating Temperatures on the Microstructure, Properties, and Residual Stress of 12CrNi2 Prepared by Laser Cladding Deposition Technique.

The 12CrNi2 alloy steel powder studied in the present paper is mainly used to manufacture camshafts for nuclear power emergency diesel engines. Laser cladding deposition is of great significance for the manufacture of nuclear power emergency diesel camshafts, which has the advantages of reducing material cost and shortening the manufacturing cycle. However, due to the extremely uneven heating of the components during the deposition process, a complex residual stress field occurs, resulting in crack defects and residual deformation of the components. In the present paper, 12CrNi2 bulk specimens were prepared on the Q460E high-strength structural steel substrate at different preheating temperatures by laser cladding deposition technique, and a finite element residual stress analysis model was established to investigate the effects of different preheating temperatures on the microstructure, properties, and residual stress of the specimens. The results of the experiments and finite element simulations show that with the increase of preheating temperature, the content of martensite/bainite in the deposited layer decreases, and the ferrite content increases. The proper preheating temperature (150 °C) has good mechanical properties. The residual stress on the surface of each specimen decreases with the increase of the preheating temperature. The longitudinal stress is greater at the rear-end deposition part, and the lateral residual stress is greater on both sides along the scanning direction.

Finite-Element Analysis of Residual Stresses Generated Under Nitriding Process: a Three-Dimensional Model

A numerical three-dimensional model for computing residual stresses generated in cross section of steel 42CrMo4 after nitriding is presented. The diffusion process is analyzed by the finite-element method. The internal stresses are computed using the obtained profile of the distribution of the nitrogen concentration. The special features of the intricate geometry of the treated articles including edges and angles are considered. Comparative analysis of the results of the simulation and of the experimental measurement of residual stresses is performed by the Waisman–Philips method.

Residual stress modeling and analysis for micro electroforming layer

Large residual stress in the micro electroforming layer has been considered to be the main reason for causing warpage, delamination and micro cracking of the microdevice. These undesirable phenomena dramatically influence the productivity, dimensional accuracy and service life of the microdevice. Reasonable control of the residual stress is a direct and efficient way to improve the production rate of microdevice and expand the application of microdevice. In this paper, the residual stress finite element analysis (FEA) simulation model for Ni micro electroforming layer was established by the method of “Equivalent Reference Temperature (ERT)”. The simulation result shows that the ERT for Ni micro electroforming layer is 238.15 K. The error of residual stress value is 0.37% between the simulation result and the experimental result. This error value proves the accuracy of the FEA model.

A framework for estimating residual stress profile in seam-welded pipe and vessel components part I: Weld region

A recent comprehensive investigation into residual stress distributions in pipe and vessel longitudinal seam welds is presented in this paper, covering component wall thickness from 1/4″ (6.35 mm) to 10″ (254 mm), component radius to wall thickness ratio from 2 to 20, and linear welding heat input from low (50 J/mm) to high (6000 J/mm). Through the use of a residual stress decomposition technique, two key parameters that govern through-thickness residual stress distributions in terms of their membrane and bending content have been identified. One is component radius to wall thickness ratio (r/t) and the other is a characteristic heat input density (Q^) having a unit of J/mm3. With these two parameters, a unified functional form for estimating through-thickness residual stress profile in seam welded components is proposed in this paper (Part I) for supporting fitness for service assessment for crack-like flaws in weld region. A curved beam bending theory based model is introduced in Part II as a means of analytically describing through-thickness residual stress profile as a function of circumferential position away from the weld region until residual stresses become zero. The effectiveness of this proposed framework for achieving residual stress profile estimation within weld region (Part I) for longitudinal seam welds in pressure vessel and piping components has been confirmed by finite element residual stress analysis results on a large number of component configurations and different welding conditions.

Finite Element Residual Stress Analysis of Planetary Gear Tooth

A method to simulate residual stress field of planetary gear is proposed. In this method, the finite element model of planetary gear is established and divided to tooth zone and profile zone, whose different temperature field is set. The gear's residual stress simulation is realized by the thermal compression stress generated by the temperature difference. Based on the simulation, the finite element model of planetary gear train is established, the dynamic meshing process is simulated, and influence of residual stress on equivalent stress of addendum, pitch circle, and dedendum of internal and external meshing planetary gear tooth profile is analyzed, according to non-linear contact theory, thermodynamic theory, and finite element theory. The results show that the equivalent stresses of planetary gear at both meshing and nonmeshing surface are significantly and differently reduced by residual stress. The study benefits fatigue cracking analysis and dynamic optimization design of planetary gear train.

일체형 원자로 안전주입 노즐 이종금속 용접부에 대한 레이저 피닝 적용의 수치 해석적 연구

일체형 원자로의 안전주입 노즐 이종금속 용접부의 잔류응력에 대한 레이저 피닝의 효과를 고찰하기 위해 상용 프로그램인 ABAQUS를 이용하여 implicit 동적 유한요소 해석을 통해 연구를 수행하였다. implicit 동적 유한요소 해석은 기존의 실험 결과와의 비교에 따르면 레이저 피닝을 통한 잔류응력 이완에 대해 타당하다고 확인된다. 한편 내부 보수용접이 수행된 이종금속 용접부에 대해 해석이 수행되며 그 결과는 축방향 및 원환 잔류응력 모두 내부 보수용접에 기인하여 노즐의 내표면에서 인장임을 나타낸다. 또한 용접 잔류응력 이완에 대한 최대 충격 압력, 압력 지속 시간, 스폿 직경 및 피닝 방향과 같은 여러 변수의 효과를 고찰하기 위해 변수 해석 또한 수행하였다. 결과적으로, 레이저 피닝은 내표면 근처 영역의 잔류응력을 주로 이완시키는 예방정비 효과가 있음을 확인하였다.

A study on welding residual stress analysis of a small bore nozzle with dissimilar metal welds

Recently, it is reported that axial and circumferential PWSCCs (primary water stress corrosion cracking) occurred on the dissimilar metal welds of the small bore nozzle such as a steam generator drain nozzle in PWR. In order to identify root causes of the PWSCCs and prevent the PWSCCs in the future, it is necessary to evaluate PWSCC initiation potential and growth rate of the dissimilar metal welds via residual stress assessment. In this study, the residual stress analysis has been performed in order to investigate the effect of various finite element analysis variables on PWSCC assessment result. The residual and operating stress distributions are calculated by finite element method. Based on the stress analysis results, PWSCC initiation locations are predicted by comparing the stresses with PWSCC initiation threshold values. The predicted locations are compared with the examination results using penetration, eddy current and destructive tests. It is identified that the finite element residual stress analysis methodology is valid from the fact that the PWSCC prediction has reasonable agreement with the examination results. The parametric study for various finite element analysis variables derives effect of the variables on the total stresses at steady state during normal operation including residual stress and the PWSCC initiation/growth.

FEA of Residual Stress During HVOF Thermal Spraying

Due to the recent advances in thermal spraying technology, considerable research emphasis has been placed on the development of models capable of predicting deposition mechanisms at various stages during the process. In order to gain a deeper knowledge of the mechanisms involved in thermal spraying, it is necessary to isolate the factors affecting these constitutive properties (e.g., residual stress generation) and in doing so quantify the effect of the individual factors. Finite element analysis (FEA) is used in the present research to predict the residual stress generated in a WC-Co deposit produced via the HVOF process. The model is compared to an analytical technique and validated experimentally, the result of which provides a thermo-mechanical modeling procedure with an accuracy greater than 80% of that found experimentally. Combining FEA techniques with analytical and experimental results will enhance the understanding of residual stress in thermal spray techniques.

Finite-element analysis of residual stresses in Al2O3–TiC/W18Cr4V diffusion bonded joints

Abstract The residual stress distribution in Al 2 O 3 –TiC/W18Cr4V diffusion bonded joints was calculated using finite element method (FEM). The effects of pressure and interlayer on the axial stress and shear stress were also studied. The results show that the gradients of the axial stress and shear stress are great near the joint edge and are flat near the center of the joint. The maximal tensile axial residual stress is reached on the ceramic side at the ceramic/interlayer interface. The maximal shear residual stress is at the two interfaces of ceramic/Ti interlayer. With the increase of bonding pressure, the maximal tensile axial stress decreases and the compressive axial stress increases. But there is small effect of pressure on the shear stress. With Ti–Cu–Ti interlayer instead of Ti interlayer, the maximal axial residual stress has little decrease and the maximal shear residual stress decreases greatly. Near the edge of the joint, Ti–Cu–Ti interlayer reduces the residual stresses. The site of shear fracture in Al 2 O 3 –TiC/W18Cr4V diffusion bonded joints agrees with the simulated residual stress distribution.

Numerical weld modeling — a method for calculating weld-induced residual stresses

In the past, weld-induced residual stresses caused damage to numerous (power) plant parts, components and systems (Erve, M., Wesseling, U., Kilian, R., Hardt, R., Brümmer, G., Maier, V., Ilg, U., 1994. Cracking in Stabilized Austenitic Stainless Steel Piping of German Boiling Water Reactors — Characteristic Features and Root Causes. 20. MPA-Seminar 1994, vol. 2, paper 29, pp.29.1–29.21). In the case of BWR nuclear power plants, this damage can be caused by the mechanism of intergranular stress corrosion cracking in austenitic piping or the core shroud in the reactor pressure vessel and is triggered chiefly by weld-induced residual stresses. One solution of this problem that has been used in the past involves experimental measurements of residual stresses in conjunction with weld optimization testing. However, the experimental analysis of all relevant parameters is an extremely tedious process. Numerical simulation using the finite element method (FEM) not only supplements this method but, in view of modern computer capacities, is also an equally valid alternative in its own right. This paper will demonstrate that the technique developed for numerical simulation of the welding process has not only been properly verified and validated on austenitic pipe welds, but that it also permits making selective statements on improvements to the welding process. For instance, numerical simulation can provide information on the starting point of welding for every weld bead, the effect of interpass cooling as far as a possible sensitization of the heat affected zone (HAZ) is concerned, the effect of gap width on the resultant weld residual stresses, or the effect of the ‘last pass heat sink welding’ (welding of the final passes while simultaneously cooling the inner surface with water) producing compressive stresses in the root area of a circumferential weld in an austenitic pipe. The computer program feresa (finite element residual stress analysis) was based on a commercially available abaqus code (Hibbitt, Karlsson, Sorensen, Inc, 1997. abaqus user's manual, version 5.6), and can be used as a 2-D or 3-D FEM analysis; depending on task definition it can provide a starting point for a fracture mechanics safety analysis with acceptable computing times.

Evolution of Residual Stresses Induced during Curing Processing Using a Viscoelastic Micromechanical Model

The effect of viscoelasticity of matrix material on the evolution of processing- induced residual stresses in [0/90] glass fiber/epoxy cross-ply laminate has been investigated by a finite element micromechanical model. The micromechanical model is based on a periodic array of continuous fibers embedded in an epoxy matrix. The epoxy matrix is represented by a nonlinear viscoelastic model. The finite element residual stress analysis indicates that a higher cooling rate results in higher initial residual stresses in the laminate. However, the residual stress relaxes with time and tends to an asymptotic small value independent of the cooling rate. The effect of free edge surface on the generation of residual stresses is also investigated, and it is found that they are significantly different from those in the interior region. Although the coefficients of thermal expansion (CTE) for the individual constituents (glass fiber and epoxy matrix) are constant, the CTE for composite, on the other hand, is initially time-dependent due to the mismatch constraint and approaches an asymptotic value after a long stress relaxation period.

A finite-element analysis of residual stress in stretch grinding

In this paper, effective models have been developed to simulate the mechanics states of specimens during stretch and un-stretch grinding, by the thermal elastic–plastic finite-element method. The results of calculations show that stretch grinding can, under certain conditions, very effectively reduce the residual tensile stress in the surface layer of the workpiece or even convert the residual tensile stress into residual compressive stress, Through analysis of the present results, the mechanism of the reduction of residual tensile stress by stretch grinding is revealed.

Finite-Element Analysis of Residual Stresses of Ceramic/Metal Joint. Size Effects of Interlayer on Elastic-Plastic Singularity of Residual Stresses.

In general, a very thin metal with low yield strength is inserted into a ceramic/metal joint as an interlayer to reduce the residual stresses. A two-dimensional finite-element analysis was performed to study the effect of the thickness of the interlayer on an elastic-plastic singularity of residual stresses in the ceramic/metal joint. The yielding of the interlayer caused the change of the singularity. In the case of the joint with a relatively thick interlayer, the exponent of the elastic-plastic singularity depends on only the elastic-plastic properties of the materials. When the interlayer is very thin, however, the exponent depends on not only the elastic-plastic properties but also the thickness of the interlayer. This elastic-plastic singularity can be approximately estimated by a simplified elastic-plastic analysis.

Finite-Element Analysis of Residual Stresses of Ceramic/Metal Joints. Elastic-Plastic Singularity of Residual Stresses.

A two-dimensional finite-element analysis was perfomed to study an elastic-plastic singularity of residual stresses in a ceramic/metal joint. The comparison of the elastic singularity by finite-elment analysis with the idealized theoretical results showed that the elastic singularity of residual stresses in the ceramics side was characterized by elastic properties of the ceramics and the insert material. The yielding of the insert material resulted in the change of the singularity. The exponent of the elastic-plastic singularity was larger than that of the elastic singularity. This elastic-plastic singularity can be approximately estimated by a simplified elastic-plastic analysis.