Prediction Of Residual Stresses Research Articles

Measurement and prediction of residual strains and stresses during the cooling of a glass fibre reinforced PA66 matrix composite

The forming process of thermoplastic composites inevitably leads to the development of residual stresses. This study proposes a model to predict the residual stresses at the ply scale of a thermoplastic composite laminate. It accounts for the heat transfer, crystallization kinetics and mechanical behaviour of the laminate. The model is applied to the cooling of a polyamide 66 (PA66) matrix reinforced with continuous glass fibres. The Stress Free Temperature is considered as the starting point of stresses accumulation within each ply and its identification is discussed. The curvatures of [904/04] laminates and their evolution with temperature are recorded with a digital image correlation technique. They are compared to the curvatures predicted by the model, which permits to validate it. The predicted stresses distribution is then discussed. Finally, the model is compared to the Classical Lamination Theory, demonstrating the interest of the developed model.

A novel analytical modeling for prediction of residual stress induced by thermal-mechanical load during orthogonal machining

Residual stress on the surface and subsurface has a great influence on the distortion and fatigue life. Rapid and accurate prediction of residual stress is important for the optimization of the machining process in intelligent manufacturing. A novel analytical model is proposed based on the equivalent stress method in this paper. The nonlinear flow characteristics of the work-piece material in the tool-work-piece contact surface and thermal-mechanical coupling effect are fully considered. A new cutting force prediction model was established and the relative errors are within 12%, which verifies the accuracy and the effectiveness of the model for further application to residual stress prediction. The thermal-mechanical conditions of the primary shear plane and machined surface are revealed based on the equivalent stress method. Then, internal stress of work-piece is caused by mechanical load and thermal load obtained on account of linear elasticity theory and heat-elastic-plastic mechanics theory. The predicted residual stress profiles have a high degree of consistency with measurement results of orthogonal turning of 20Cr2Ni4A alloy steel. Prediction accuracy of surface residual stresses was 11.3%, 12.2%, and 12.7% for the condition of v = 24 m/min, ap = 0.1 mm; v = 36 m/min, ap = 0.2 mm; v = 48 m/min, ap = 0.3 mm respectively. The predicted results of the maximum compressive stresses and DMCS are also acceptable. Ultimately, the residual stress profiles obtained from proposed model were reliable. The proposed model has high computational efficiency and provides a new idea for the analytical prediction of residual stress. And the proposed model can be used for further residual stress analysis and prediction of 3D cutting process.

Numerical Simulation Development and Computational Optimization for Directed Energy Deposition Additive Manufacturing Process.

The rapid growth of Additive Manufacturing (AM) in the past decade has demonstrated a significant potential in cost-effective production with a superior quality product. A numerical simulation is a steep way to learn and improve the product quality, life cycle, and production cost. To cope with the growing AM field, researchers are exploring different techniques, methods, models to simulate the AM process efficiently. The goal is to develop a thermo-mechanical weld model for the Directed Energy Deposition (DED) process for 316L stainless steel at an efficient computational cost targeting to model large AM parts in residual stress calculation. To adapt the weld model to the DED simulation, single and multi-track thermal simulations were carried out. Numerical results were validated by the DED experiment. A good agreement was found between predicted temperature trends for numerical simulation and experimental results. A large number of weld tracks in the 3D solid AM parts make the finite element process simulation challenging in terms of computational time and large amounts of data management. The method of activating elements layer by layer and introducing heat in a cyclic manner called a thermal cycle heat input was applied. Thermal cycle heat input reduces the computational time considerably. The numerical results were compared to the experimental data for thermal and residual stress analyses. A lumping of layers strategy was implemented to reduce further computational time. The different number of lumping layers was analyzed to define the limit of lumping to retain accuracy in the residual stress calculation. The lumped layers residual stress calculation was validated by the contour cut method in the deposited sample. Thermal behavior and residual stress prediction for the different numbers of a lumped layer were examined and reported computational time reduction.

Theoretical investigation of machining-induced residual stresses in longitudinal torsional ultrasonic–assisted milling

In order to realize the compressive stress and antifatigue manufacturing of titanium alloy TI-6Al-4V, a compound processing of longitudinal-torsional ultrasonic vibration and milling (LTUM) is proposed, a theoretical prediction model of machining-induced residual stress (RS) is established, and it is validated by experiments. The trajectory model of cutting edge in LTUM is constructed; furthermore, the undeformed chip thickness (UCT) model of LTUM is structured; The mechanical stress model of LTUM is established from the shear stress and plow stress; the thermal stress model of LTUM is established from shear thermal stress and plow thermal stress; Considering mechanical and thermal stress, the residual stress of longitudinal-torsional ultrasonic milling is established by loading and releasing stress. From numerical simulation of mechanical stress and thermal stress model, it shows that in LTUM, stress fluctuates with ultrasonic vibration, and mechanical stress absolute value is larger than that of traditional machining (TM); thermal stress absolute value is less than that of TM. A series of experiments are carried out to verify the RS model of LTUM. From present work, through theoretical prediction and experimental verification of machining-induced residual stress, it is concluded that established theoretical model predicts properties, and distribution of residual stress with high accuracy and the LTUM significantly increases surface compressive stress and compressive stress layer depth. It lays a foundation for the compressive stress and fatigue resistance of titanium alloys.

Predictive Manufacturing: Subtractive and Additive

Manufacturing is the key to today’s industrial competitiveness, and it is broadly classified into two categories, subtractive and additive. In current study, the ability to predictively model manufacturing performance attributes in both categories is introduced. In subtractive manufacturing, modeling of laser-assisted and ultrasonic vibration-assisted milling are presented. In laser-assisted milling, the laser preheating temperature field is predicted, and the dynamic recrystallization as well as grain growth triggered under high temperature is considered, which enhances the accuracy of force and residual stress prediction. In ultrasonic vibration-assisted milling, the intermittent effect is considered through tool-workpiece separation criteria. And the force reduction in ultrasonic vibration-assisted milling is accurately predicted. In additive manufacturing, laser-assisted metal additive manufacturing is introduced. And the predictive modeling of temperature field in powder bed metal additive manufacturing is presented. The model considers heat transfer boundary including heat loss from convection and radiation at the part boundary. Through the comparison between measured and calculated molten pool dimensions, the model is proven to have high computational efficiency and high prediction accuracy.

Analytical Modeling of Residual Stress in Laser Powder Bed Fusion Considering Part’s Boundary Condition

Rapid and accurate prediction of residual stress in metal additive manufacturing processes is of great importance to guarantee the quality of the fabricated part to be used in a mission-critical application in the aerospace, automotive, and medical industries. Experimentations and numerical modeling of residual stress however are valuable but expensive and time-consuming. Thus, a fully coupled thermomechanical analytical model is proposed to predict residual stress of the additively manufactured parts rapidly and accurately. A moving point heat source approach is used to predict the temperature field by considering the effects of scan strategies, heat loss at part’s boundaries, and energy needed for solid-state phase transformation. Due to the high-temperature gradient in this process, the part experiences a high amount of thermal stress which may exceed the yield strength of the material. The thermal stress is obtained using Green’s function of stresses due to the point body load. The Johnson–Cook flow stress model is used to predict the yield surface of the part under repeated heating and cooling. As a result of the cyclic heating and cooling and the fact that the material is yielded, the residual stress build-up is precited using incremental plasticity and kinematic hardening behavior of the metal according to the property of volume invariance in plastic deformation in coupling with the equilibrium and compatibility conditions. Experimental measurement of residual stress was conducted using X-ray diffraction on the fabricated IN718 built via laser powder bed fusion to validate the proposed model.

An improved case based reasoning method and its application in estimation of surface quality toward intelligent machining

In the high speed milling process, the accurate predictions of surface roughness and residual stress can avoid the deterioration of machined surface quality. But it’s hard to estimate the surface roughness and residual stress under different tool wear status and cutting parameters. In this work, a novel intelligent reasoning method-improved case based reasoning (ICBR) was proposed to predict the surface roughness and residual stress. The inputs of ICBR are cutting parameters and tool wear status. The corresponding outputs of ICBR are surface roughness and residual stress. In the ICBR, K-nearest neighbor method and artificial neural network (ANN) as case retrieval was introduced to retrieve the K similar cases to the inputs. Through retrieving K similar cases, the Gaussian process regression (GPR) model as case reuse was established to output the surface roughness and residual stress. The vibration particle swarm optimization algorithm is proposed to optimize the ANN and GPR models. The high speed milling experiments of Compacted Graphite Iron was performed to validate the performance of ICBR. The experimental results showed that the cutting speed is the most important factor affecting the surface roughness. The feed rate is the most important factor affecting the residual stress. The ICBR gives the accurate estimation of surface roughness with the Mean Absolute Percentage Error of 11.6%. As for residual stress, the prediction accuracy using ICBR is 87.5%. Compared with Back-Propagation neural network, standard CBR and GPR models, the ICBR has better predictive performance and can be used for estimations of surface roughness and residual stress in the actual machining process.

Analytical Prediction of Residual Stress in the Machined Surface during Milling

An analytical prediction model for residual stress during milling is established, which considers the thermal-mechanical coupling effect. Considering the effects of thermal-mechanical coupling, the residual stress distribution in the workpiece is determined by the stress loading history according to McDowell′s hybrid algorithm. Based on the analysis of the geometric relationship of orthogonal cutting, the prediction model for milling force and residual stress in the machined surface is established. The research results can provide theoretical basis for stress control during milling.

Development of unified framework for microstr ucture, residual stress, and crack propensity prediction using phase-field simulations

Development of unified framework for microstr ucture, residual stress, and crack propensity prediction using phase-field simulations

Efficient LPBF process simulation using finite element modeling with adaptive remeshing for distortions and residual stresses prediction

As-built metallic parts manufactured by the laser powder bed fusion (LPBF) process are usually associated with high residual stresses and distortions due to the thermal cycles during the process. Finite Element Modeling (FEM) is widely used to simulate the build process with the assumption of the lumped layer thickness. This paper proposes an adaptive remeshing framework by which the assumed layer thickness value can be reduced while minimizing model size and the number of nodes. Preliminary results show that model results find good agreement with experimental results and previous FEM predictions, along with significant computational reduction.

Numerically simulated prediction of residual stresses in welding considering phase transformation effects

This work deals with investigating the effects of solid-state phase transformation on residual stresses during the welding of low carbon and high carbon steels. In this study, depending on MSC Marc code, the simulation considers the local microstructure properties changes due to the thermal welding cycles. A sequentially coupled thermal and mechanical 2-D finite element model (FEM) was used. In FEM, phase transformation temperature diagrams are used to anticipate the amount of martensite in the fusion zone (FZ), and heat affects zone (HAZ). The simulation results demonstrated that the residual stress in low carbon steel is not affected by the volume change caused bythe austenite-martensite transformation. In contrarily,the residual stressesin the high carbon steel are considerably influenced by the martensitic transformation.

Prediction of the residual state of stress in a superduplex stainless steel produced by sand casting (using a coupled thermo-mechanical approach)

The present work aims at investigating the effect, in terms of residual stress prediction, determined by the adoption of different material constitutive models in the Finite Element simulation of the casting process of a superduplex stainless steel benchmark, from the cooling after the pouring phase to the subsequent heat treatment (heating and water quenching). A 3D thermo-mechanical Finite Element (FE) model was created with the commercial code Abaqus: the preliminary thermal problem, i.e. the determination of the heat transfer coefficients during both the mould cooling and the quenching, was solved by means of an inverse analysis approach by minimizing the difference between the numerical evolution of temperature and the experimental acquisition coming from real casting test. Two separate routes were followed according to the adopted constitutive equations: modelling the material as (i) elasto-plastic or (ii) elasto-viscoplastic. The numerical prediction of the residual state of stress in terms of casting relaxation was compared with the experimental data after the cut of the casting using an electro-discharge machine. The analysis revealed that when the elasto-viscoplastic modelling was adopted, the simulations underestimated the relaxation with an error larger than 50%; on the other hand, the elasto-plastic model leads to an overestimation with an error of about 30%.

Measurement and prediction of residual stresses in welded girders

Residual stresses can have a significant impact on the stability of structural members. In the case of I-section beam elements, such stresses can impact lateral–torsional buckling (LTB) capacity, particularly in the inelastic range. I-sections are typically fabricated by either rolling as a single shape or welding three plates together; residual stress distributions can differ considerably between the two section types. It is therefore possible for a built-up welded girder to have a different LTB capacity than that of a rolled one of identical cross-section. Concerns have been raised that such a difference may render North American steel design standards unconservative for welded girders. Because of the lack of recent physical LTB tests on welded girders, finite element modelling was used as a tool in making this assessment, and the assumed residual stress distributions were based on data from 1970 to 1980 that may not account for advancements in welding technologies and processes since the publication of these data. The paucity of recent residual stress data, however, prevents a direct assessment of these assumed distributions. In this study, residual stress measurements were carried out on a series of four welded steel test girders using the sectioning method. A comparison of the measured distributions with four existing models finds these models to be inaccurate in important ways; an updated model is therefore required for use in numerical simulations of LTB behaviour of welded girders used in industry today.

Multi-physics continuum modelling approaches for metal powder additive manufacturing: a review

PurposeThis paper aims to present a systematic approach in the literature survey related to metal additive manufacturing (AM) processes and its multi-physics continuum modelling approach for its better understanding.Design/methodology/approachA systematic review of the literature available in the area of continuum modelling practices adopted for the powder bed fusion (PBF) AM processes for the deposition of powder layer over the substrate along with quantification of residual stress and distortion. Discrete element method (DEM) and finite element method (FEM) approaches have been reviewed for the deposition of powder layer and thermo-mechanical modelling, respectively. Further, thermo-mechanical modelling adopted for the PBF AM process have been discussed in detail with its constituents. Finally, on the basis of prediction through thermo-mechanical models and experimental validation, distortion mitigation/minimisation techniques applied in PBF AM processes have been reviewed to provide a future direction in the field.FindingsThe findings of this paper are the future directions for the implementation and modification of the continuum modelling approaches applied to PBF AM processes. On the basis of the extensive review in the domain, gaps are recommended for future work for the betterment of modelling approach.Research limitations/implicationsThis paper is limited to review only the modelling approach adopted by the PBF AM processes, i.e. modelling techniques (DEM approach) used for the deposition of powder layer and macro-models at process scale for the prediction of residual stress and distortion in the component. Modelling of microstructure and grain growth has not been included in this paper.Originality/valueThis paper presents an extensive review of the FEM approach adopted for the prediction of residual stress and distortion in the PBF AM processes which sets the platform for the development of distortion mitigation techniques. An extensive review of distortion mitigation techniques has been presented in the last section of the paper, which has not been reviewed yet.

A fast matrix-free elasto-plastic solver for predicting residual stresses in additive manufacturing

Process planning for additive manufacturing (AM) today relies heavily on multi-physics, multi-scale simulation. The focus of this paper is on one aspect of AM simulation, namely, part-level elasto-plastic simulation for residual stress and distortion predictions. This is one of the crucial steps in AM process optimization, but is computationally expensive, often requiring the use of large computer clusters.The primary bottleneck in elasto-plastic simulation is the repeated solution of large linear systems of equations. While there is a wide range of linear solvers, most cannot exploit the unique structured nature of the mesh underlying AM simulation. Here, we revisit a specific matrix-free solver, namely rigid-body deflated solver that has been successfully deployed for solving large linear elastic problems in such scenarios. The salient feature of this solver is that the stiffness matrix is never assembled, thereby reducing the memory requirements significantly, leading to large computational gains.The objective of this paper is to extend the above solver to elasto-plasticity by efficiently updating the element tangent stiffness matrices, and the corresponding deflation matrix. The performance of the proposed method is evaluated on a benchmark problem using multi-core CPU and GPU architectures, and compared against ANSYS. Then, part-level residual stresses and distortion are predicted using the proposed solver. The present work is restricted to associative plasticity with von-Mises yield criteria, but can be extended to other plasticity models.

Prediction of machining-induced residual stress in orthogonal cutting of Ti6Al4V

In addition to having significant effects on the service life of machined parts, residual stress can cause large deformations during machining of thin-walled parts in aerospace field. The residual stress in machined part surface layer is induced by mechanical and thermal stress in the machining process of parts. Therefore, it is essential to accurately predict the generated residual stress due to the machining process. To address this issue, an improved prediction model of the residual stress for orthogonal cutting process based on analytical method is presented by taking the mechanical and thermal stress into consideration. Oxley’s cutting force model and Waldorf’s plowing force model are used to calculate the chip formation force and plowing force based on the contact mechanics, Johnson-Cook constitutive model, and slip line theory. The cutting temperature is predicted according to our previous work based on the Huang-Liang model and the Komanduri-Hou model. The final residual stress is predicted by calculating the loading and relaxation of mechanical and thermal stress. The presented prediction method of residual stress is validated by orthogonal cutting of a Ti6Al4V pipe. It is found that the prediction values of the presented model show a good agreement with the experimental results, which indicates that the presented model can be adopted to predict the residual stress of Ti6Al4V during orthogonal cutting.

Numerical simulation of martensitic transformation plasticity of 42CrMo steel based on spot continual induction hardening model

Spot continual induction hardening (SCIH), as a new selective surface hardening technology proposed in recent years, has unique advantages in strengthening metallic component with complex geometric shapes. However, the prediction of residual stress distribution after SCIH is very complicated due to the existence of different kinds of strains during the process, especially the influence of transformation-induced plasticity (TRIP) strain on residual stress field. In this paper, a SCIH model considering the influence of transformation plasticity was proposed via the secondary development of commercial finite element software ABAQUS. The results show that the existence of transformation plasticity can coordinate the internal stress between parent phase and product phase effectively in martensitic transformation. The main contribution of this paper is to clarify the influence of the transformation plasticity coefficient (K) on the accuracy of residual stress prediction. The amplification effect of the equivalent stress on the value of K needs to be considered in martensitic transformation of SCIH process. However, the increment of K will reduce the equivalent stress during martensitic transformation and residual stress after SCIH treatment. Due to the feedback mechanism of transformation plasticity coefficient on the equivalent stress, the value of the TRIP strain doesn't increase linearly with the value of K increasing during SCIH process.

Integrated Numerical-Experimental Assessment of the Effect of the AZ31B Anisotropic Behaviour in Extended-Surface Treatments by Laser Shock Processing

In recent years, an increasing interest in designing magnesium biomedical implants has been presented due to its biocompatibility, and great effort has been employed in characterizing it experimentally. However, its complex anisotropic behaviour, which is observed in rolled alloys, leads to a lack of reliable numerical simulation results concerning residual stress predictions. In this paper, a new model is proposed to focus on anisotropic material hardening behaviour in Mg base (in particular AZ31B as a representative alloy) materials, in which the particular stress cycle involved in Laser Shock Processing (LSP) treatments is considered. Numerical predictions in high extended coverage areas obtained by means of the implemented model are presented, showing that the realistic material’s complex anisotropic behaviour can be appropriately computed and—much more importantly—it shows a particular non-conventional behaviour regarding extended areas processing strategies.

Prediction of residual stress in the process of turning high strength alloy steel by innovative coated carbide microgroove tools

Residual stress (RS) of machined surface is one of essential factors affecting the service performance of mechanical structures and parts. By a combination of cutting experiment, theoretical analysis, and finite element analysis, this paper focuses on the radial distribution of RS of machined surfaces of a coated carbide microgroove turning tool (CCMTT), firstly, in the turning of the high strength alloy steel. The effect of cutting parameters on the radial distribution of RS of machined surfaces produced by the CCMTT is further researched. Finally, the prediction model of RS produced by the CCMTT is established and verified. Research results show that the cutting experiments and FE simulation both have the same variation tendency of RS and are validated well each other. The microgroove on the rake face of the CCMT is beneficial to increase the thickness and the maximum value of residual compressive stress of surface material. The coefficient of multiple correlation of the forecasting model of surface residual stress (SRS) machined by the CCMTT reaches 97.4%, which illustrates that the model has relatively high reliability.

Measurement and Prediction of Residual Stresses in Low Carbon Steel Pipes Welded Shielded Metal Arc Welding

Welding is carried out with a very complex thermal cycle, which results in irreversible elastic-plastic deformation, and residual stresses in and around fusion zone and heat-affected zone (HAZ). A residual stress due to welding arises from the differential heating of the pipes due to the weld heat source. However, due to the presence of residual stresses in and around the weld zone the strength and life of the component is also reduced. The objective of this work is to measure the welding residual stress in ASTM (A-106 Gr. b) steel pipes with 4" diameter and 6 mm thickness welded manually (SMAW) in three-pass butt joint where shielded metal arc welding process consists of heating, melting and solidification of parent metals and a filler material in localized fusion zone by a transient heat source to form a joint between the parent metals. The welding process will have accrued without preheating and heat treatment. This measuring of residual stress occurs by using hole-drilling strain gauge method according to (ASTM E-873) then the experimental results for residual stresses obtained from welded carbon steel pipes used to provide validation for finite element simulations. The welding process and welding residual stress distribution is calculated by Ansys Finite Element techniques. Theoretical considerations can be assessed by a mechanical model. The overall, there is good agreement between the predicated and measured distributions of residual stress, but the magnitude of predicted stress tend to greater in welding region.