Formation Mechanism Of Residual Stress Research Articles

Tuning residual stress in electrodeposited nickel films via pulse current

The pulse current electrodeposition has proved to be effective in the preparation of metal films with a low residual stress, while the formation mechanism of residual stress under the pulse current remains unclear. In this study, in situ measurements of residual stress in electrodeposited nickel films was performed. Nickel films with the lowest average stress were obtained under the frequency of 800 Hz, average current density of 1 A/dm2 and duty cycle of 50%. Based on X-ray diffraction and TEM analysis, the relationship between dislocation density and residual stress was studied, revealing that a high dislocation density contributed to the formation of cross slip, as well as the release of residual stress. Furthermore, charge time of the electric double layer was measured by multi-current step tests, and the possible mechanism for residual stress formation under pulse currents was proposed. The results indicated the stress was modulated by two competing factors: overpotential and fraction of the charge time. The overpotential played a leading role on average stress at low frequency and high current density, while fraction of the charge time played a dominant role at high frequency and low current density (less than 1 A/dm2). Our study provides a valuable insight to understand how pulse current parameters influence the residual stress in electrodeposited nickel films.

Analytical model of hot-rolled strip residual stress and flatness in run-out table cooling

The residual stress formed in the run-out table cooling stage of hot-rolled strip has a great influence on flatness and subsequent cutting. Based on the fiber rods model, the formation mechanism of residual stress induced by incompatible deformation caused by temperature and phase transformation is studied in this paper. Meanwhile, the present study makes a first attempt to establishing the analytical model for calculating residual stresses at different run-out table cooling stages. Moreover, in order to further investigate the relationship between residual stress and flatness defects, a strip buckling model is introduced. The traditional buckling equilibrium equation of Lagrange system is introduced into the Hamiltonian system of symplectic space, and the mathematical relationship between residual stress and strip flatness is obtained directly without assuming stress and deflection function. Then the strip flatness is calculated by using this mathematical relationship and residual stress analytical model. Furthermore, to verify the accuracy of the analytical model, a multi-field coupled finite element model based on the validation of the measured data is established. Finally, the distribution of residual stress calculated by the analytical model and the finite element model is basically consistent. The analytical model calculated that the strip would have edge wave defects during run-out table cooling, which is highly consistent with the results of finite element model.

Experimental study on residual stress in high-speed grinding of noncircular equidistant profile

To explore the formation mechanism of residual stress in the high-speed grinding of noncircular equidistant profiles, orthogonal experiments of three grinding parameters—the grinding wheel speed, workpiece speed, and grinding depth—were designed. A ceramic bond CBN grinding wheel was used for the high-speed grinding of noncircular equidistant profile by the X-C axis linkage. The effects of the grinding parameters on the grinding temperature, surface roughness, and residual stress were analyzed. The results show that with the increase of grinding wheel speed, the grinding temperature and residual stress increase, and the surface roughness decreases. With the increase of workpiece speed, the grinding temperature and residual stress decrease, and the surface roughness increases. With the increase of grinding depth, the grinding temperature, residual stress, and surface roughness increase. Besides, the grinding depth has the greatest influence on the residual stress, followed by the grinding wheel speed and workpiece speed.

Distribution characteristics of residual stresses in typical wall and pipe components built by wire arc additive manufacturing

It is of great importance to thoroughly understand residual stress distribution in wire arc additive manufacturing (WAAM) and its relationship with the deposition variables. In this study, stainless steels 308LSi and 304 were used as WAAM feedstock and substrate, respectively, for additive manufacturing of two typical structures, namely wall and pipe structures. A thermomechanical coupling analysis model for WAAM was developed to investigate the formation mechanism of residual stresses in both structures, and their relationship with the deposition height and shape. The validity of the analysis was evaluated by comparing the simulated residual stresses with those measured by the contour method. Regardless of the wall or pipe structure, the tensile longitudinal (or circumferential) residual stress exists on the WAAM top surface and has the largest value (~300 MPa) at the position of several layers below the top surface. The distribution pattern of the longitudinal (or circumferential) residual stress is tensile in the layers near the top surface, compressive in the layers near the substrate surface, and tensile near the bottom surface of the substrate. This distribution pattern reaches a quasi-stable state when the total deposition height is greater than a certain size (~10 mm and 15 mm for wall and pipe structures, respectively). For the pipe structure, however, the residual stress distribution is not symmetric along the height direction. This analysis model can provide guidance for effective tailoring of residual stresses in WAAM components.

A review on manufacturing defects and their detection of fiber reinforced resin matrix composites

Fiber reinforced resin matrix composites are more and more widely used in aerospace and automobile manufacturing industries. However, the probability of manufacturing defects in composites is very high due to the complex physical and chemical properties of component materials and molding processes. Therefore, the research on the manufacturing defects and their detection of composites becomes important in evaluating the quality of composites. First, the formation mechanism of residual stresses, void defects and resin-rich defects in the matrix of composites are summarized. Especially, the curing of thermosetting resin and thermoplastic resin, the resin infiltration process in hot pressing, resin transfer molding and 3D printing, and resin-rich defects in molding process are described in this article. Second, the forming mechanism of fiber reinforcement defects such as fiber wrinkle and waviness in composites is introduced, and the influence of such defects on the bending and compression properties of composites is analyzed, which shows that fiber misalignment defects will seriously reduce the modulus, strength and stability of the supporting structures. Third, formation mechanism, damage causes and optimization methods of interfacial defects such as delamination and debonding in the interface between reinforcements and matrix are elaborated. Fourth, machining defects such as drilling and cutting defects are revealed. The main manifestations are delamination, tearing, and burrs, which will seriously affect the strength and reliability of the connection between components. Finally, the non-contact detection of defects in composites are shown in the article. Different detection methods can be used to measure defects of different scales to predict composite damage and life in advance. This review analyzes manufacturing defects in laminated, woven, braided, and additive manufactured composites, and summarizes common defect detection methods, also presents an outlook for composite manufacturing.

A prediction model of residual stress for belt‐grinding blade based on geometrical characteristic and progressive wear of abrasive grains

AbstractThe formation mechanism of residual stress on the machined surface of belt grinding is sophisticated, and residual stress is an important factor affecting the fatigue life of aero‐engine blades. In this study, a prediction model of residual stress in a belt grinding blade is proposed with the geometrical characteristics and progressive wear of the grains as the research topic. By extracting the morphological features of abrasive belt, the residual stress based on different geometrical characteristics of grains (pyramidal, hexahedral, spherical, and conical belts) were investigated, and the optimal grain geometry was determined to be a uniformly arranged positive quadrilateral cone. Accordingly, a grinding experiment with a pyramidal belt was conducted to obtain an experienced model of the grain wear height. A numerical simulation model of the grain wear evolution under four wear states (no abrasion, early abrasion, middle abrasion, and late abrasion) was developed. Additionally, more detailed progressive wear of the abrasive grains was also applied to grind the entire profile of the complex curved blade. The residual stress on the blade surface was mainly compressive, and the surface stress values were distributed between −385 and −117 MPa with the service life of the pyramidal abrasive belt.

Study on Residual Stress of Blasting Erosion Arc Machined Ti6Al4V and TiAl Alloys

In this paper, Blasting Erosion Arc Machining (BEAM) was applied to perform high efficiency rough machining of difficult-to-cut materials such as Ti6Al4V and TiAl alloys. In order to investigate the influence of BEAM on workpiece surface quality and material properties, the formation mechanism of residual stress was studied based on simulations and experiments. First of all, a thermo-elastoplastic simulation model was established to predict the residual stress after discharging. Then, a single arc discharge experiment was carried out under different discharge parameters. The results showed that after discharging, a high tensile residual stress existed on the surface, and the peak value increases with the increasing of discharge energy. The highest tensile residual stress of Ti6Al4V could reach up to 679 MPa when the peak current was 500 A and the pulse duration was 8 ms. The residual stress of Ti6Al4V decreases rapidly beneath the machined surface and is close to the material matrix at the depth of 700 μm. But for TiAl, the residual stress increased first and then decreased with increasing depth. A probable reason for the difference is that longer and wider cracks existed on the surface of TiAl and they can release residual stress partially. The simulation predicted the large tensile residual stress and the trend of residual stress distribution, which agrees well with the experiment results.

Study on formation mechanism and regularity of residual stress in ultrasonic vibration grinding of high strength alloy steel

The surface residual stress of the part has a crucial influence on its service performance. This paper studies the formation mechanism of residual stress in Ultrasonic Vibration Grinding (UVG) of high strength alloy steel, and obtains the correlation law between processing parameters and residual stress. First, based on the kinematics analysis of UVG, the formulas of ultrasonic grinding force and ultrasonic grinding transient moving heat source temperature field are analyzed. A thermal-mechanical coupled ultrasonic vibration grinding residual stress prediction model was established by FEM and verified by experiments. Second, the thermal behavior of the workpiece surface during UVG is analyzed, and the formation mechanism of the residual stress on the workpiece surface is explained. Finally, combining simulation and experimental results, a comprehensive correlation law between multiple grinding process parameters and residual stress is obtained. The research results show that compared with common grinding (CG), UVG can reduce the grinding temperature by about 8%. Both UVG and CG will reduce the original compressive stress on the surface, but UVG can make the surface of the workpiece retain greater compressive residual stress and prevent the emergence of tensile residual stress. This work of the thesis provides a basis for the research of residual stress in UVG.

Numerical and experimental investigation of tool geometry effect on residual stresses in orthogonal machining of Inconel 718

Residual stress has become more important than ever with the increasing performance requirement of components especially for those applied in safety-critical areas. As the machining process is fundamentally correlated with the acquired component properties, it is essential to fully understand the formation mechanism of residual stresses in the cutting process and its influence on the performance of the component. This paper presents results based on numerical and experimental analysis on the effect of tool geometry on thermal-mechanical load and residual stresses in orthogonal machining Inconel718 alloy. The Coupled Eulerian-Lagrangian (CEL) method is used to simulate the effect of tool geometry on temperatures, forces, equivalent plastic strains, and residual stresses. The local normal/tangential stress is introduced to determine the degree of the tensile plastic deformation induced by the tool. It is observed that a negative rake angle and a sharp edge radius tool tend to generate more compressive stress on the machined surface than the ones generated with positive rake angle tools and/or lager edge radius. Besides, an increase in flank wear produces less magnitude of compressive stress in subsurface due to a decreased local normal stress caused by increased flank contact length.

Formation Mechanism of Residual Stresses in Micro-Injection Molding of PMMA: A Molecular Dynamics Simulation.

Injection molding is an economical and effective method for manufacturing polymer parts with nanostructures and residual stress in the parts is an important factor affecting the quality of molding. In this paper, taking the injection molding of polymethyl methacrylate (PMMA) polymer in a nano-cavity with an aspect ratio of 2.0 as an example, the formation mechanism of residual stresses in the injection molding process was studied, using a molecular dynamics simulation. The changes in dynamic stress in the process were compared and analyzed, and the morphological and structural evolution of molecular chains in the process of flow were observed and explained. The effects of different aspect ratios of nano-cavities on the stress distribution and deformation in the nanostructures were studied. The potential energy, radius of gyration and elastic recovery percentage of the polymer was calculated. The results showed that the essence of stress formation was that the molecular chains compressed and entangled under the flow pressure and the restriction of the cavity wall. In addition, the orientation of molecular chains changed from isotropic to anisotropic, resulting in the stress concentration. At the same time, with the increase in aspect ratio, the overall stress and deformation of the nanostructures after demolding also increased.

Distribution and formation mechanism of residual stress in duplex stainless steel weld joint by neutron diffraction and electron backscatter diffraction

The residual stress distribution of duplex stainless steel multi-pass weld joint and its formation mechanism still lacks systematic research. In this study, neutron diffraction and electron backscatter diffraction were used to systematically investigate the through-thickness residual stresses. The results show that both the macroscopic and macroscopic plus elastic mismatch residual stresses decrease along the through-thickness direction and the maximum area is located near the weld top surface. The elastic residual stresses in austenitic phase are larger in comparison to those in ferritic phase. In addition, tensile and compressive stress components are generally found in austenite and ferrite, respectively. Furthermore, it shows that higher level of high angle boundaries, Σ3 coincidence-site-lattice and local misorientation, which can generate larger thermal misfit plus plastic misfit residual stresses, are found in austenite. The formation mechanism of the residual stresses in both ferrite and austenite are also discussed.

Research on flexible adaptive CNC polishing process and residual stress of blisk blade

Flexible adaptive polishing process can be used to polish blisk. In order to verify the feasibility of polishing blisk and improve the surface integrity of blisk, this paper analyzes residual stress and its effect on deformation. Firstly, the formation mechanism of residual stress and deformation was analyzed. Secondly, the influence of polishing process on surface profile was analyzed and qualitatively analyzed the non-interference polishing of blisk polishing. Thirdly, the effects of polishing process on surface residual stress, residual stress of depth layer, and residual stress uniformity were analyzed. Fourthly, the empirical model of surface residual stress to polishing process parameters was established, and the sensitivity and stable range of the process parameters were analyzed. Finally, the influence of polishing process on deformation was quantitatively analyzed by FEA and experimental testing though contrasting polishing and milling process. The results show that the surface residual stress is reduced by 60 Mpa by flexible polishing process and can be reduced by more than 80 Mpa if appropriate polishing process parameters are used, and the surface residual stress is mostly sensitive to spindle speed, followed by compression depth, granularity, and feed rate. Flexible polishing process can make the surface residual stress become more uniform. Flexible polishing process has no effect on the change rule in the depth direction of residual stress. The second deformation of polished blisk blade is less than the milled blisk blade’s. Flexible polishing process can effectively improve surface integrity and be widely used for polishing blisk.

Understanding processing parameters affecting residual stress in selective laser melting of Inconel 718 through numerical modeling

Abstract

Effects of low-temperature transformation and transformation-induced plasticity on weld residual stresses: Numerical study and neutron diffraction measurement

In this study, the weld residual stresses (RS) in a 25mm thick ferrite steel plate with newly developed low-temperature transformation (LTT) welding wire were investigated by finite element method and neutron diffraction (ND) measurement. A thermo-elastic–plastic finite element model coupled with solid-state phase transformation (SSPT) was developed to investigate the distribution and formation mechanism of RS, which has been verified by ND measurement. The results demonstrate that the developed LTT alloy can significantly reduce the RS and even generate compressive RS in the weld zone, due to the interrupted cooling shrinkage caused by the LTT. The higher inter-pass temperatures related to the microstructure evolution result in an increased region of compressive stress within the weldment. Moreover, the longitudinal RS in the weld zone gradually changes to tension as the initial temperature of martensitic transformation increases. Notably, the relaxation effect of transformation-induced plasticity on RS and its influence on model accuracy were discussed.

Research on Formation Mechanism of Dynamic Response and Residual Stress of Sheet Metal Induced by Laser Shock Wave

In order to reveal the quantitative control of the residual stress on the surface of metal materials, the relevant theoretical and experimental studies were carried out to investigate the dynamic response of metal thin plates and the formation mechanism of residual stress induced by laser shock wave. In this paper, the latest research trends on the surface residual stress of laser shock processing technology were elaborated. The main progress of laser shock wave propagation mechanism and dynamic response, laser shock, and surface residual stress were discussed. It is pointed out that the multi-scale characterization of laser and material, surface residual stress and microstructure change is a new hotspot in laser shock strengthening technology.

Using X-Ray Diffraction and Finite Element Method to Analyze Residual Stress of Tube-to-Tubesheet Welded Joints in a Shell and Tube Heat Exchanger

A lot of failures have been generated in the tube-to-tubesheet joints of a shell and tube heat exchanger, which are greatly affected by the weld residual stresses. In order to ensure the structure integrity, it is very important to predict and decrease the residual stress in the joint between tube and tubesheet. In this paper, a combination of X-ray diffraction and finite element method (FEM) was used to analysis the residual stress distribution in the tube-to-tubesheet joints. The formation mechanism of residual stress before and after cosmetic welding was explicated. The effects of heat input and welding sequence on residual stresses were studied. The results show that the large tensile residual stresses which are in excess of yield strength, are generated in the tube-to-tubesheet joints. The residual stresses at the bottom surface and the edge of the tubesheet are relatively small even become compressive. The formation of the weld residual stress is mainly induced by the cosmetic welding rather than the back welding. The residual stresses increase as the heat input increases. The duplex welding method is recommended to decrease the residual stress.

Effect of Cutting Parameters on Residual Stress for Ti1023 Using FEM and RSM

Machining induced residual stress has a major influence on the life time of machined parts, especially in their corrosion resistance and fatigue life. In this paper, finite element model (FEM) and response surface methodology (RSM) are applied to investigate the residual stress for machining titanium alloy Ti1023. The process of orthogonal cutting Ti1023 is successfully simulated by FEM using Power-Law constitutive model. The formation mechanism of residual stress is briefly described utilizing elastoplastic theory. Based on the analysis and simulations, the residual stresses profile in cutting and feed direction are successfully explained. Then, RSM is introduced to study the effects of the cutting speed and feed on surface residual stress. The results show that their interactions have no significant influence on surface residual stress. And the cutting speed and feed has strong nonlinear effect on surface residual stress.

Effect of Cutting Parameters on Residual Stress for Ti1023 Using FEM and RSM

Machining induced residual stress has a major influence on the life time of machined parts, especially in their corrosion resistance and fatigue life. In this paper, finite element model (FEM) and response surface methodology (RSM) are applied to investigate the residual stress for machining titanium alloy Ti1023. The process of orthogonal cutting Ti1023 is successfully simulated by FEM using Power-Law constitutive model. The formation mechanism of residual stress is briefly described utilizing elastoplastic theory. Based on the analysis and simulations, the residual stresses profile in cutting and feed direction are successfully explained. Then, RSM is introduced to study the effects of the cutting speed and feed on surface residual stress. The results show that their interactions have no significant influence on surface residual stress. And the cutting speed and feed has strong nonlinear effect on surface residual stress.

Research on the Mechanism of Residual Stress and Its Influence on Fatigue Life in Grinding Superalloy

This research is focused on the formation mechanism of residual stress and effect of various process parameters, thermal coupling levels and grinding ways on residual stress during grinding superalloy, as well as analyzed the relationship between residual stress and fatigue life. The results show that the residual stress for grinding process is caused by the interaction between grinding temperature and grinding force, and in general the thermoplastic deformation and the plastic pressure coarse effect generated tensile residual stress because of grinding temperature and abrasive mechanical action, respectively, while the burnishing effect generated the compressive residual stress. From the experimental results, it is observed that using plunge-cut grinding process resulted in tensile residual stress on machined surface and the tensile residual stress increases with increasing grinding depth and wheel speed, while the maximum tensile residual stress occurred near the grinding surface, and then declined sharply. The residual stress layer is approximately 100μm while the depth of residual stress layer and the maximum tensile residual stress are increased with increases the grinding parameters. Meanwhile, the studies also indicate that the fatigue life improves with increase in compressive residual stress, whereas the tensile residual stress has the opposite effect on fatigue life. Thus, this paper provides the related experimental data for the study of anti-fatigue manufacturing in grinding superalloy.

The formation mechanism and the influence factor of residual stress in machining

Residual stresses generated in cutting process have important influences on workpiece performance. The paper presents a method of theoretical analysis in order to explicate the formation mechanism of residual stresses in cutting. An important conclusion is drawn that the accumulated plastic strain is the main factor which determines the nature and the magnitude of surface residual stresses in the workpiece. On the basis of the analytical model for residual stress, a series of simulations for residual stress prediction during cutting AISI 1045 steel are implemented in order to obtain the influences of cutting speed, depth of cut and tool edge radius on surface residual stress in the workpiece. And these influences are explained from the perspective of formation mechanism of residual stress in cutting. The conclusions have good applicability and can be used to guide the parameters selection in actual production.