Residual Stress In Machined Surface Research Articles

Simulation Study on Residual Stress Distribution of Machined Surface Layer in Two-Step Cutting of Titanium Alloy.

Ti-6Al-4V titanium alloy is known as one of the most difficult metallic materials to machine, and the machined surface residual stress distribution significantly affects properties such as static strength, fatigue strength, corrosion resistance, etc. This study utilized finite element software Abaqus 2020 to simulate the two-step cutting process of titanium alloy, incorporating stages of cooling, unloading, and de-constraining of the workpiece. The chip morphology and cutting force obtained from orthogonal cutting tests were used to validate the finite element model. Results from the orthogonal cutting simulations revealed that with increasing cutting speed and the tool rake angle, the residual stress undergoes a transition from compressive to tensile stress. To achieve greater residual compressive stress during machining, it is advisable to opt for a negative rake angle coupled with a lower cutting speed. Additionally, in two-step machining of titanium alloy, the initial cutting step exerts a profound influence on the subsequent cutting step, thereby shortening the evolution time of the Mises stress, equivalent plastic strain, and stiffness damage equivalent in the subsequent cutting step. These results contribute to optimizing titanium alloy machining processes by providing insights into controlling residual stress, ultimately enhancing product quality and performance of structural part of titanium alloy.

Effects of multi-pass turning on surface properties of AISI 52100 bearing steel

Hard turning is extensively used in the machining of bearings. The turning process has a significant influence on the properties of machined surface. In this paper, multi-pass turning experiments were machined on AISI 52100 bearing steel, and corresponding simulation model was established. The effects of multiple pass turning on microhardness and residual stress were investigated. The results demonstrate that the machined surface hardness of single, double, and triple pass turning is 30.0%, 25.2%, and 24.5% higher than the initial surface, respectively, at a turning depth of 0.1mm and a speed of 100m/min. Double pass turning significantly reduces the residual stress of machined surface. With the change of turning speed, the residual stress after double pass turning is 88 MPa lower than single pass on average, while the difference of residual stress is relatively minor after double pass and triple pass turning. At a cutting depth of 0.05 mm, the residual stresses after double pass turning and triple pass turning are 152 MPa lower than those after one-pass turning. As the turning depth increases, the influence of the previous pass turning gradually decreases in terms of residual stress.

Research on the Residual Stress of the Machined Surface of Cutting Superalloy under High Pressure Cooling

High pressure cooling assisted cutting has certain advantages in cutting difficult materials such as superalloy. Therefore, the residual stress on the machined surface of superalloy is studied with the application background of high pressure cooling cutting. Firstly, the formation mechanism of the machined surface residual stress was analyzed. Then, the influence mechanism of high pressure coolant on the residual stress of machined surface was studied. Finally, it is concluded that the maximum residual compressive stress in cutting depth direction of cutting superalloy under high pressure cooling should be less than that of dry cutting by theoretical analysis and experimental research.

Nano-lubricant influence on surface residual stresses in hard milling

Residual stress could be induced by machining processes like milling which can greatly affect the fatigue life of fabricated parts, especially in dynamic loading conditions. In metal cutting operations, machining induced residual stresses can be explained in the terms of machining forces and temperatures of the cutting zones. This thermo mechanical loading along with the resulted metallurgical changes are the main sources of residual stresses generation at the surface of machined workpiece. Researchers have proved the superior properties of nanofluids over the conventional coolants to reduce the intensity of thermo mechanical loading in machining process which will affect the residual stresses caused by machining. Therefore, in this paper, silver nanoparticles in the water-soluble oil have been used for reducing the mechanical and thermal loads in the milling process. The cutting forces, temperature of the cutting zone, surface roughness and the residual stress of machined surface have been measured experimentally in milling of hardened steel AISI 4140 for various nanoparticle’s concentration, feeds and cutting speeds. Results show that increasing the concentration of Nano-particles in base fluid from 0.5 to 3.0% wt., will make machining surface residual stresses more compressive averagely by about 66.67% compared to conventional cutting fluid.

Comparative Analysis of Residual Stress and Dislocation Density of Machined Surface during Turning of High Strength Steel

Dislocation density and residual stress of machined surface are essential factors affecting the service performance of mechanical structures. Through cutting experiments and theoretical analysis, this paper focused on the residual stress and dislocation density of machined surfaces in the turning of high strength steel by a self-developed coated carbide micro-structure turning tool and an original turning tool under the same cutting conditions using X-ray diffraction. Research results show that the micro-structure on the rake face of the coated carbide turning tool is beneficial to reduce the dislocation density and the residual tensile stress and improve the microstructural uniformity of the machined surface, which is more beneficial to the service performance of the mechanical parts.

Semi-Empirical Prediction of Residual Stress Distributions Introduced by Turning Inconel 718 Alloy Based on Lorentz Function.

The residual stress of machined surface has a crucial influence on the performance of parts. It results in large deviations in terms of the position accuracy, dimension accuracy and service life. The purpose of the present study is to provide a novel semi-empirical residual stress prediction approach for turning Inconel 718. In the method, the bimodal Lorentz function was originally applied to express the residual stress distribution. A statistical model between the coefficients of the bimodal Lorentz function and cutting parameters was established by the random forest regression, in order to predict the residual stress distribution along the depth direction. Finally, the turning experiments, electrolytic corrosion peeling, residual stress measurement and correlation analysis were carried out to verify the accuracy of predicted residual stress. The results show that the bimodal Lorentz function has a great fitting accuracy. The adjusted R2 (Ad-R2) are ranging from 95.4% to 99.4% and 94.7% to 99.6% in circumferential and axial directions, respectively. The maximum and minimum errors of the surface residual tensile stress (SRTS) are 124.564 MPa and 18.082 MPa, those of the peak residual compressive stress (PRCS) are 84.649 MPa and 3.009 MPa and those of the depth of the peak residual compressive stress (DPRCS) are 0.00875 mm and 0.00155 mm, comparing three key feature indicators of predicted and simulated residual stress. The predicted residual stress is highly correlated with the measured residual stress, with correlation coefficients greater than 0.8. In the range of experimental measurement error, the research in the present work provides a quite accurate method for predicting the residual stress in turning Inconel 718, and plays a vital role in controlling the machining deformation of parts.

Impacts of Machining and Heat Treating Practices on Residual Stresses in Alpha-Beta Titanium Alloys

Machining and thermal processing can introduce undesirable residual stresses and distortion in titanium alloy components, and although the distribution and magnitude of these residual stresses is highly relevant for component and process design in the aerospace industry, the relationships between processing variables, processing steps, residual stress signature, and subsurface microstructures are not well understood. The current study reports on the preliminary results of experiments designed to mimic typical machining and thermal processing practices for aerospace alpha-beta Ti alloys. Traditional climb cutting and high-speed peel cutting operations are included in CNC machining experiments, and both solution treating and aging heat treatments are considered for thermal processing experiments. Characterization of samples includes strain measurement using the sin2ψ and cosine α methods with x-ray diffraction as well as microstructural characterization using traditional metallographic techniques. The results of this study show a large tool-path dependence for residual stresses in machined surfaces as well as a significant difference in the residual stress behavior for solution treated and quenched compared to solution treated and aged samples of Ti 6Al-4V alloy.

THE INFLUENCE OF CUTTING CONDITIONS ON THE SELECTED PARAMETERS OF THE SURFACE INTEGRITY

The article deals with an investigation of residual stress in machined surface under conditions of high-feed milling and determination of the influence of machining conditions on the size and types of stress resulting from cutting into the machined surface. As a testing material, the hardened tool steel W. Nr. 1.2343 (CSN 19552) was used. For the realization of the experimental activity, a high-feed milling head was used with exchangeable cutting inserts marked H600 WXCU 070515T. All surfaces were machined under different cutting conditions (200, 300, 350, 400 and 500mmin−1 cutting speed) in regard to the recommended parameters and machine tool options. The evaluated residual stress was measured in the depth of 8 μm under the surface with the device PROTO iXRD working on the principle of the X-Ray diffraction. Monitoring was carried out using an analysis of occurrence of tensile or compressive residual stress, and from these results, a possible dependence of the residual stress on the cutting conditions during milling process was determined.

Effects of Cutting Edge Microgeometry on Residual Stress in Orthogonal Cutting of Inconel 718 by FEM.

Service performance of components such as fatigue life are dramatically influenced by the machined surface and subsurface residual stresses. This paper aims at achieving a better understanding of the influence of cutting edge microgeometry on machined surface residual stresses during orthogonal dry cutting of Inconel 718. Numerical and experimental investigations have been conducted in this research. The cutting edge microgeometry factors of average cutting edge radius , form-factor K, and chamfer were investigated. An increasing trend for the magnitudes of both tensile and compressive residual stresses was observed by using larger or introducing a chamfer on the cutting edges. The ploughing depth has been predicted based on the stagnation zone. The increase of ploughing depth means that more material was ironed on the workpiece subsurface, which resulted in an increase in the compressive residual stress. The thermal loads were leading factors that affected the surface tensile residual stress. For the unsymmetrical honed cutting edge with K = 2, the friction between tool and workpiece and tensile residual stress tended to be high, while for the unsymmetrical honed cutting edge with K = 0.5, the high ploughing depth led to a higher compressive residual stress. This paper provides guidance for regulating machine-induced residual stress by edge preparation.

Residual Stress in Disc Milling Grooving of Titanium Alloy

In the present study, the formation mechanism and distribution rule of residual stress in disc milling grooving of titanium alloy were studied. The residual stress was measured by x ray diffraction method. First, a polybasic linear regression model about residual stress was established by linear regression technology, which was tested by “F” method. Then, the effect of milling parameters (spindle speed, depth of cut and feed speed) on residual stress was investigated. The results showed that Ax and Ay (Ax and Ay represented the residual stress of machined surface made by the tool main cutting edge in x and y directions, respectively) increased with the increase of depth of cut and feed speed, but decreased with the increased spindle speed. For Bx (Bx represented the residual stress of machined surface made by the tool minor cutting edge in x direction), the residual stress decreased with the increase of spindle speed and depth of cut, but increased with the increase of feed speed. The effect of feed speed on Ax and Ay was most obvious, then was spindle speed. Bx was most sensitive to depth of cut, then was feed speed, the last was spindle speed. Residual compressive stress was observed on all machined surface and subsurface. In addition, the residual stress on A surface and subsurface was bigger than B surface and subsurface, it was due to the combination effect of milling force and milling heat.

Grey-RBF-FA method to optimize surface integrity for inclined end milling Inconel 718

Performance and service life of aerospace component are significantly influenced by surface integrity, especially for cyclically loaded thin-walled structure component. This work focuses on the surface roughness and residual stress of machined surface, which are considered the most important indications of surface integrity, for inclined end milling Ni-based superalloy Inconel 718. The purpose is to minimize surface roughness and maximize compressive residual stress by optimizing the cutter geometry. Based on the grey relational analysis (GRA), an integrated multi-objective optimization approach with the radial basis function (RBF) neural network and the firefly algorithm (FA) is developed. The end-tooth rake angle, end-tooth relief angle, and helix angle are selected as design factors, while the residual stress and the 3D surface roughness are taken as performance characteristics. The orthogonal array L16 (43) is employed to generate sample data set. Then, the GRA is introduced to search the most influential factor by the grey relational grade (GRG). Subsequently, the proposed grey-RBF-FA method is applied to the multi-objective optimization problem. After calculating the GRG, the RBF network is used to relate the GRG with cutter geometric parameters. The test data show the RBF model has a low prediction error of 11.11%. Finally, the FA is utilized to search the optimal parameter-level combination. Validation experiments show that, compared with the original GRA, the proposed method further greatly improves the surface roughness and residual stresses in both directions by 1.20 μm, 249.1 MPa, and 176.5 MPa, respectively. The developed approach is proved to be feasible and can be generalized for other multi-objective optimization in manufacturing industry.

Residual Stresses during Hard Turning of AISI 52100 Steel: Numerical Modelling with Experimental Validation

Residual stresses induced by machining processes are a consequence of thermo-mechanical and microstructural phenomena generated during the machining operation. In this study, a numerical approach has been developed to predict the near surface residual stresses resulting from turning of AISI 52100 alloys steel and validated by experimental results. Effect of cutting parameters, namely cutting speed and depth of cut on induced residual stresses in machined surface was investigated by modelling using ABAQUS/CAE 14.0 software. Explicit Dynamics time integration with adaptive meshing finite element method is employed to simulate the 2D model. The Johnson-Cook material model is used to describe the work material behaviour to simulate high speed machining with an orthogonal cutting. And also for experimental analysis X-Ray diffraction method is considered. While study residual stresses at different cutting speed, feed rate, and depth of cut is studied. As a conclusion we can say that cutting speed and feed rate plays major role as compared to depth of cut. And as cutting speed or feed rate increases tensile residual stresses increases.

Simulation of the cutting sequence of AISI 316L steel based on the smoothed particle hydrodynamics method

Smoothed particle hydrodynamics (SPH) method, one of the latest and developing methods, is used for modeling metal cutting process in this paper. SPH is a powerful technique that can be efficient in handling problems of large deformation that are difficult to be tackled using traditional finite element methods. SPH method is used to investigate the effect of sequential cuts on the residual stresses in machined surface for AISI 316L steel. The simulation results show that residual stresses increase with of the following parameters increasing, including cutting speed and cutting depth. With sequential cuts, a slight drop was noticed in cutting force, while the thrust force in the first cutting was smaller than that in the second cutting, but the residual stresses will increase as the result of the accumulative effect.

Experimental investigation on variation of machined residual stresses by turning and grinding of hardened AISI 1053 steel

Residual stresses in machined surfaces are of great importance to the service life of a component under various loading conditions. In many cases, the material damage initiates from the weakest spot with the least compressive stress in the component surfaces. This situation leads to the consideration of residual stress moving beyond the traditional thinking of single or average values to the inclusion of variation of stress values on different measurement points. In this paper, we experimentally investigated the surface and in-depth residual stresses in hardened AISI 1053 steels machined using hard turning and surface grinding processes. Cubic boron nitride (CBN) cutting tools were used in both processes. The effects of depth of cut and number of passes were also studied. It was found that both processes produce a significant amount of compressive stress on the machined surfaces, as well as steep stress gradients underneath the surfaces. Compared with hard turning, surface grinding produces higher magnitudes of average compressive residual stresses, but it also generates up to 14 times higher scattering of residual stresses, indicated by the standard deviation of the residual stress measurements. As a result, the benefits of a highly compressive average residual stress will be offset by highly scattered individual measurements. The stochastic nature of abrasive grit distribution and orientations in grinding wheels is believed to be the contributing factor for the significant scattering. Meanwhile, for hard turning, the variation of surface and in-depth residual stresses greatly increases, up to 3.8 times, with a larger depth of cut and the use of multiple passes; however, this trend is less significant for surface grinding.

The Cutting Residual Stress Included in the Surface Integrity

This article is for the integrity of the cutting surface, explaining the reason for the cutting residual stress generated from the mechanism, proposed several typical methods to reduce the residual stress. According to some experimental researches on cutting parameters which have been done by previous scholars, this article gives some analysis of the effects of cutting parameters of residual stress. And preliminary summary of the influence of residual stress on cutting parameters, it also provides a way for further discussion of cutting parameters and material effect on the machined surface residual stress distribution law.

Improving surface integrity in finish machining of Inconel 718 alloy using intelligent systems

In machining of hard materials, surface integrity is one of the major customer requirements which comprise the study of the changes induced to the workpiece. Surface roughness and residual stress are often considered as the most significant indications of surface integrity. Inducing tensile residual stress during the machining processes is a critical problem which should be avoided or minimized to obtain better service quality and component life. This problem becomes more evident in the presence of rough machined surface because fatigue life of manufactured components might be decreased significantly. Inconel 718 superalloy is one of the hard materials used extensively in the aerospace industries. It is prone to tensile residual stress in machined surface. Thus, controlling and optimizing residual stress and surface roughness in machining of Inconel 718 are so needed. Intelligent techniques based on the predictive and optimization models can be used efficiently for this purpose. In this study, the optimal machining parameters including cutting speed, depth of cut, and feed rate were accessed by intelligent systems to evaluate the state of residual stress and surface roughness in finish turning of Inconel 718. The results of experiments and analyses indicated that implemented techniques in this work provided a robust framework for improving surface integrity in machining of Inconel 718 alloy. It was shown that cutting speed has more effect on surface integrity than other investigated parameters. Also, depth of cut and feed rate were found in the moderate range to obtain satisfactory state of tensile residual stress and surface roughness.

A numerical study of residual stress induced in machined silicon surfaces by molecular dynamics simulation

Residual stresses in machined surface are regarded as a critical factor affecting the quality and service life of components. However, little research has been conducted to reveal the formation of residual stresses as well as the relation between machining conditions and residual stresses at the nanometric scale. In this study, residual stresses in machined surfaces of monocrystalline silicon are computed based on molecular dynamics simulation. An orthogonal machining configuration is adopted, and diamond cutting tools are used. The numerical approach developed is able to reveal stress evolution during and after machining, as well as in-depth residual stress distributions. The results indicate that the material stresses are stabilized within a manageable amount of computation time, and the in-depth normal stress along the tool moving direction has a more dynamical and significant pattern compared with other stress components. Meanwhile, the effects of depth of cut and tool rake angle are investigated. It is found that the increase of depth of cut results in the decrease of maximum tensile residual stress on the machined surfaces and the increase of maximum compressive residual stress underneath the surface. Similar observations are observed when the tool rake angle changes from positive to negative. It is believed that the more negative tool rake angles or the larger depths of cut induce a more drastic phase transformation to the machined surfaces, and this makes the in-depth residual stress distributions more compressive.

The Simulation and Experimental Study of Residual Stress Based on Thermo-Mechanical Model of GCr15

The metal machining 3D finite element model was established on the basis of the thermal-elastic-plastic finite element theory. And the machined surface residual stress simulation in different cutting parameters was obtained through the finite element analysis. It is concluded that the residual stress distribution variation is spoon-shaped curve. When the feed increased, the slope of the curves is smaller, however the speed increased, the slope of the curves is higher and the stress tends to negative values quicker. Finally, the experiments are carried out. The result was basically consistent with the simulation.

Research on the machined surface integrity under combination of various inclination angles in multi-axis ball end milling

It is well known that the multi-axis machining technology has been developed into a key technique applied in the manufacturing field. The machined surface integrity is one of the most important factors influencing the performance of the produced components. Hence, this research concentrated on the machined surface integrity induced by the multi-axis milling operation with different inclination angle combinations. In this research work, the cutting conditions of the conventional or up-milling process with tool orientations were divided into eight different types, and the machining characteristics corresponding to different cutting strategies were discussed. The varying conditions of surface topography, texture and other machining features induced in machining process which corresponds to different inclination angle combinations were analyzed by geometrical analysis, and the surface roughness and linear profile along specific directions on the machined surface were also investigated. There is a special corresponding relationship between the rotation angle and tool tilt and lead angles. Better surface roughness could be achieved when rotation angles are 0° (positive lead), 60° (combination of positive tilt and positive lead), 90° (positive tilt) and 330° (combination of negative tilt and positive lead). Then, the samples used for study of the metamorphic layer were produced by lapping and polishing process, and the macro hardness (HL) and micro-hardness (HV) of the top machined surface were investigated. According to the measured results of both Leeb hardness and micro-hardness, higher surface hardness could be obtained under rotation angles of 60° (combination of positive tilt and positive lead), 120° (combination of positive tilt and negative lead) and 210° (negative tilt and negative lead). Moreover, the variations of the micro-hardness along the depth direction of the samples were studied. Finally, discussions on the machined surface residual stresses in both feed and cross-feed direction were carried out. Compressive surface residual stress in both feed and cross-feed direction could be generated when rotation angles are 210° (combination of negative tilt angle with smaller value and negative lead angle with larger value) and 330° (combination of negative tilt angle with smaller value and positive lead angle with larger value). Generally, the evaluation indicators of surface integrity are not all very satisfying under one special cutting condition with a certain inclination angle combination, and the optimal cutting parameters should be selected based on the specific application requirements. Finally, the optimal tool orientations and related cutting parameters were recommended, and further studies of the related topics were also presented.

Influences of sequential cuts on micro-cutting process studied by smooth particle hydrodynamic (SPH)

Machined surface properties have a great influence on the service life of component. The residual stress in machined surface layer is affected by the micro-cutting process. Sequential cuts influence the machined surface layer. In this paper, a mesh-less method called SPH (smooth particle hydrodynamic) is used to investigate the effect of sequential cuts and residual stress on chip formation, cutting force and the residual stress in machined surface for oxygen-free high-conductivity copper (OFHC). In micro-cutting process the cutting edge radius plays a crucial role. The effect of the cutting edge radius on residual stress is also investigated in this paper. The simulation results showed that the chip curled severely and the minimum chip thickness decreased in the second cut because of residual stress in the machined surface after the first cut. Meanwhile, the cutting force in the second cut was smaller than the first cut, while the thrust force was nearly the same during two cuts. In addition, the tensile residual stress beneath the machined surface layer would change to compressive stress after the second cut. Therefore, the residual stress in machined surface can be changed through sequential cuts with proper machining parameters to get high quality machined surface.