Residual Stress Values Research Articles

Experimental and numerical analyses of residual stress redistributions in large steel dies: Influence of tempering cycles and rough milling

The aim of the present research was to study the residual stress variations induced by heat treatment and rough milling operations of large forged steel blocks. The heat treatment process includes quenching and tempering operations. An efficient strategy based on a size sensitivity analysis (SSA) was proposed to reach the actual values of residual stresses in large-size steel blocks by using small-size workpieces in laboratory scale without damaging the blocks. The residual stresses were measured and compared after the first and second tempering and the rough milling. A 3D finite element (FE) model was developed to predict superficial residual stresses and was then calibrated experimentally. The results showed that the residual stresses after the first and second tempering were highly compressive on and near the surface. In addition, the resultants of the residual stresses after double tempering processes were almost equal. Therefore, the second tempering could be omitted from the manufacturing process. It was also found that both surface and sub-surface hoop and radial residual stresses were highly tensile after the rough milling. Finally, the 3D FE model can be used as a predictive tool to predict residual stresses for rough milling to avoid conducting expensive, time-consuming experimentations and measurements.

РЕЛАКСАЦИЯ ОСТАТОЧНЫХ НАПРЯЖЕНИЙ ПРИ ОХЛАЖДЕНИИ ЗАГОТОВКИ С ПОКРЫТИЕМ, НАНЕСЕННЫМ МЕТОДОМ ЦЕНТРОБЕЖНОЙ ИНДУКЦИОННОЙ НАПЛАВКИ

As a result of a theoretical analysis of the cooling process of parts with deposited coatings applied by the method of centrifugal induction surfacing, the patterns of formation of residual stresses are established, taking into account relaxation. It is shown that a decrease in the cooling rate after surfacing makes it possible to reduce the level of residual stresses due to the relaxation phenomenon. Calculation relations are derived that allow predicting the permissible value of residual stresses depending on the required adhesive strength. As the analysis of the ratios obtained shows, the reduction of residual stresses in the resulting coatings due to their relaxation can be achieved by reducing the cooling rate or, accordingly, increasing its time. In the technological process of induction surfacing, a two-stage cooling mode of the workpiece was used; at the first stage, cooling is carried out at the maximum possible rate. If the temperature stresses reach the maximum allowable value τmax, the pairing condition for the transition from the previous cooling stage to the next one is the equality τmax = τi, where τi is determined from the equations derived in the work. In this case, one should be guided by the observance of the condition τi < τc, where τc is the theoretical adhesive strength of coatings in the absence of residual stresses. An example of the practical use of the twostage cooling after the process of applying coatings by centrifugal induction surfacing on the bushings of tamping blocks of a STS track machine is given.

Effect of Co/P micro-alloying on stress relaxation behaviour of Cu-15Ni-8Sn alloy

To improve the stress relaxation resistance of the Cu-5Ni-S8n alloy, the effects of Co or P addition on its stress relaxation resistance were investigated by scanning electron microscopy, transmission electron microscopy, electron backscatter diffraction), X-ray diffraction, and high-temperature creep durability tester. The results revealed that the relaxation rate increased dramatically as the temperature rose. The thermal stress relaxation resistance of Cu-15Ni-8Sn alloy was significantly improved with Co addition; After 100 h of stress relaxation tests at 200°C or 250°C, the residual stress value of the Cu-15Ni-8Sn alloy increased by 23 MPa or 22 MPa with Co addition, which was associated with the consumption of vacancies by Co atoms and the pinning effect of Co atoms on dislocation. However, at 250°C, the stress relaxation resistance of the Cu-15Ni-8Sn-0.2P alloy was lower than that of the Cu-15Ni-8Sn alloy. This difference was due to the inclusion of P, which promoted the recrystallization reaction. Article highlights Recrystallization and the decrease of dislocation density are the major reasons for the stress relaxation of the samples. The stress relaxation resistance of Cu-15Ni-8Sn alloy was significantly improved with Co addition. The addition of the P element is not conducive to the improvement of thermal stress relaxation resistance.

Investigation on the mechanism of micro-milling CoCrFeNiAlX high entropy alloys with end milling cutters

This paper aims to explore the influence mechanism of different Al contents on the mechanism of CoCrFeNiAlX high entropy alloy micro-milling by studying CoCrFeNi (Al0), CoCrFeNiAl0.6 (Al0.6) and CoCrFeNiAl (Al1). The law of changes in the temperature field, cutting force, residual stress, and surface roughness of Al0, Al0.6 and Al1 is investigated by the simulation method. The research results showed that the chips produced during the milling of three workpieces with different Al contents are different in the milling process. In particular, those produced by Al0 are shaped like long flakes and easy to adhere to the milling part, thus leading to short-duration chip accumulation. This is also the reason why the milling temperature of Al0 is obviously higher than that of Al0.6. The milling temperature of each workpiece gradually increases with the increase in milling speed, reaching the maximum when the milling speed reaches 450 mm/s. At the same milling speed, the milling temperature of each workpiece is sequenced as follows: Al1>Al0>Al0.6. Also, the milling temperature of the three types of workpieces shows an upward trend within a complete milling cycle, with the maximum milling temperature being far lower than that of traditional milling. With the increase in milling speed, the changes in the cutting forces of Y and Z directions are virtually the same for the three types of workpieces with different Al contents. However, the influence of milling speed on X-direction cutting force is relatively complex. The X-direction cutting force of Al1 and Al0 changes little, almost forming a horizontal line, while that of Al0.6 tends to increase first and then decrease. With the increase in milling speed, all the three-way cutting forces of three types of workpieces increase. With the increase in the feed rate, for each workpiece with three different Al contents, the X-direction cutting force first rises and then falls; the Z-direction cutting force tends to decrease gradually and the Y-direction cutting force almost forms a horizontal line. Also, the cutting force of Al0.6 is the smallest among the three under the same parameter and its peak value in the X direction is 68% of that of Al1 and 93% of that of Al0. With the increase in milling speed and milling depth, the changes of the residual stress for the workpieces with three different Al contents tend to be “spoon” shaped and the peak value of the residual stress for each workpiece is sequenced as follows: Al1>Al0.6>Al0. Among them, the peak value of residual stress for Al0.6 is 57% of that of Al0. The machined surface roughness of Al0.6 is the smallest after the whole micro-milling process is completed for the three types of workpieces with different Al contents.

Effect of ultrasonic nanocrystal treatment combined with nitriding process on fretting wear behavior of textured 20CrMoH steel

Individual and synergy effects of laser surface texturing (LST) followed by plasma nitriding (PN) and surface ultrasonic nanocrystal technology (SUNT) on fretting wear behaviors of 20CrMoH steel were systematically investigated at various loads and lubrication conditions. Results indicated that the combined treated (LST + PN + SUNT) 20CrMoH steel got the lowest surface roughness Ra value of 0.46 μm, the highest surface microhardness of 940 HV0.2, and the maximum residual compressive stress (RCS) value of −750 MPa. Consequently, the best fretting wear resistance was obtained by the combined treated 20CrMoH steel. Wear loss of untreated specimen reduced by 131 % after the combined treatment. The predominant wear mechanisms of the untreated, PN treated and LST + PN treated 20CrMoH steel under dry friction were oxidation wear and delamination. Besides, Oxidation and adhesion occurred for the combined treated specimen in dry friction. Especially, texture, residual stress and microhardness are key factors enhancing the anti-wear resistance.

Optimization of modes of pendular surface plastic deformation for intensification of the stress-strain state of carbon steel parts

The results of modeling on the influence of the main parameters and modes of the pendulum SPD process on the stress-strain state (SSS) of the surface layer are presented. It has been established that the obtained dependences of the SSS indicators on the technological parameters of the pendulum RPM process are not linear, for the solution of which polynomial equations are used as input data in the Statictiska 10.1 software package. Using the software package Statictiska 10.1, the optimal modes of the pendulum RPM process were determined. It has been established that the optimal modes of the pendulum SPD, which allow simultaneously obtaining the maximum intensity values of temporary (560–580 MPa) and residual compressive stresses (340–350 MPa) of the surface layer of hardened parts, are quite close. To optimize the value of work hardening (h), a significant increase in the value of the radial interference and a decrease in the value of the longitudinal feed are required, which lead to the approach of the intensity of temporary stresses to the u l timate strength of the material (600 MPa), and the intensity of residual stresses to the yield strength of the material (360 MPa). Such regimes lead to a decrease, and perhaps even to a complete removal of the residual stresses of the hardened layer, as well as to a decrease in the degree of work hardening. Thus, the rational maximum value of the hardened layer with pendulum RPM is 2.45 mm.

Mechanical and electrical properties of sodium potassium niobate ceramic coating by plasma spraying

Potassium sodium niobate ceramics are environmentally friendly piezoelectric ceramics with excellent electrical properties. It is the most promising green piezoelectric ceramic for current applications. Currently, ceramics are needed in the form of thin films or coatings for brakes, sensors, etc. Most of the current ceramic films are prepared by physical vapor deposition and chemical vapor deposition. However, the ceramic layers prepared by the above methods are thin. The thickness of the ceramic layer has a large influence on its mechanical and electrical properties. The coatings prepared by thermal spraying are thicker, but there is no in-depth study about the relationship between the coating thickness and the mechanical and electrical properties of the coating. In this article, four different thicknesses of coatings were prepared by plasma spraying technology, and the relationship between the mechanical and electrical properties of the coatings and the thickness was studied and discussed. The results show that the coating microhardness and residual compressive stress values reach the maximum and the dielectric and ferroelectric properties are optimal when the coating thickness reaches 300 μm. The study of the connection between coating thickness and coating mechanical and electrical properties provides a theoretical study for the application of the coating in practice.

Multi-Objective Optimization of Liquid Silica Array Lenses Based on Latin Hypercube Sampling and Constrained Generative Inverse Design Networks.

Injection molding process parameters have a great impact on plastic production quality, manufacturing cost, and molding efficiency. This study proposes to apply the method of Latin hypercube sampling, and to combine the response surface model and "Constraint Generation Inverse Design Network (CGIDN)" to achieve multi-objective optimization of the injection process, shorten the time to find the optimal process parameters, and improve the production efficiency of plastic parts. Taking the LSR lens array of automotive LED lights as the research object, the residual stress and volume shrinkage were taken as the optimization objectives, and the filling time, melt temperature, maturation time, and maturation pressure were taken as the influencing factors to obtain the optimization target values, and the response surface models between the volume shrinkage rate and the influencing factors were established. Based on the "Constraint-Generated Inverse Design Network", the optimization was independently sought within the set parameters to obtain the optimal combination of process parameters to meet the injection molding quality of plastic parts. The results showed that the optimal residual stress value and volume shrinkage rate were 11.96 MPa and 4.88%, respectively, in the data set of 20 Latin test samples obtained based on Latin hypercube sampling, and the optimal residual stress value and volume shrinkage rate were 8.47 MPa and 2.83%, respectively, after optimization by the CGIDN method. The optimal process parameters obtained by CGIDN optimization were a melt temperature of 30 °C, filling time of 2.5 s, maturation pressure of 40 MPa, and maturation time of 15 s. The optimization results were obvious and showed the feasibility of the data-driven injection molding process optimization method based on the combination of Latin hypercube sampling and CGIDN.

A study on residual stress generation versus recrystallisation in FSW joint of dissimilar alloy pair of the AA5083 and HSLA steel

The distribution of residual stresses across the joint interface of dissimilar joining between AA5083 and HSLA steel by friction stir welding technique was investigated through 2D XRD method and a numerical simulation model. The measured and simulated residual stress distributions are compared and discussed in the context of active recrystallisation mechanism and the possible presence of intermetallic compound (IMC) layers across the joint interface. The active dynamic recrystallisation (DRX) and multiple Fe/Al series IMCs as evident from the EBSD and 2D XRD, respectively critically demonstrated the variation in residual stresses between the experimental and theoretical values. The highest residual stress values of 375 and 281 MPa were recorded for the HSLA steel side and AA5083 side, respectively.

Residual stress and deformation in UHS quenched steel butt-welded joint

For the low-alloy ultra-high strength (UHS) quenched steels with a yield strength of 1500 MPa, the welded joints have two obvious characteristics, namely solid-state phase transformation (SSPT) in the heat-affected zone (HAZ) and softening effect in the subcritical heat-affected zone (SCHAZ). In the current study, a UHS single-pass butt-welded joint with filler wire of ER307Si was fabricated, and thermal cycles at specific points were measured by thermocouples. After welding, relevant measurements of residual stress, deformation, microstructure and hardness were carried out. In this paper, based on the experimental hardness on the cross-section of the joint, a novel softening model was proposed. Meanwhile, based on coding subroutines of ABAQUS software, an advanced computational approach considering the thermal-metallurgical-mechanical coupling behaviour including the strain hardening as well as the annealing effect in fusion zone, SSPT in HAZ, and softening in SCHAZ was developed to implement thermal, metallurgical and mechanical analyses of the UHS quenched steel butt-welded joint. Comparing numerical and experimental results of temperature field, residual stress distribution and welding deformation of the joint, the calculated results of welding residual stress, angular distortion and transverse shrinkage are in good agreement with the measured data when both SSPT and softening effect were considered in the finite element model. The computed results indicate that SSPT has a significant influence on both the magnitude and the distribution of longitudinal residual stress, but it has a small effect on transverse residual stress. Moreover, the softening effect dramatically decreases the peak value of longitudinal residual stress in the SCHAZ, while it has an insignificant influence on transverse residual stress. The simulation results suggest that SSPT has a small effect on both transverse shrinkage and angular distortion, while the softening effect has very limited influence on welding deformation.

ВДОСКОНАЛЕННЯ ПРОЦЕСУ АДИТИВНОГО ВИРОБНИЦТВА АЛЮМІНІЄВОЇ ДЕТАЛІ З ВИКОРИСТАННЯМ ТЕХНОЛОГІЇ ЕЛЕКТРОДУГОВОГО ЗВАРЮВАННЯ

The article provides original findings of the improvement of the production of the wire arc additive manufacturing of aluminum. The simulation of the process of wire arc additive manufacturing of a three-level hierarchical model was carried out, while taking into account the requirements for manufacturability and quality of the obtained part, such as its geometric dimensions, residual stresses and maintaining of the optimal production speed. During the occurrence of problems with heat distribution, various trajectories of movement and topologies were used to solve them. The optimal trajectory and print pa-rameters are created in the form of temperature control for the specified part. Implemented the ability to use a telecommuni-cation feedback system using telecommunication devices such as pyro camera andinfrared temperature laser sensors to mon-itor temperature during problems detected by print simulation. The obtained data were used for the further possibility of generating an automated program for controlling the robot during the additive manufacturing process. Residual stresses and the possibility of defects in the manufactured part are determined. Based on the obtained data, the values of residual stresses and defects in the manufactured parts were determined.Improved print topology using a three-level hierarchical system. Introducing the use of laser sensors and thermal cameras to the telecommunications system of additive manufacturing using wire arc welding with the improvement of the direct printingprocess by means of controlling the spread of heat.

Effect of Welding Speed on Residual Stress and Distortion of AISI 1045 Plate Using the Finite Element Method (FEM)

Welding is one of the metals joining methods to assembly parts which are used in manufacturing, automotive, and aerospace industries. The welding process merely simulated in modelling using finite element method (FEM). Simulation is used to determine how the effect of welding speed on the distribution of temperature, residual stress, and deformation in the V-Butt Joint welding model. The material used in this welding simulation is AISI 1045 plate with a thickness of 8 mm. Variable speed of welding performed in 30 cm/minute, 40 cm/minute and 50 cm/minute. As the result, the residual stress and distortion will be compared in order to find the best welding speed which produces the smallest residual stress and distortion value. Welding simulation based on SMAW with 6.3 mm of E7016 electrode, current of 150 A, voltage of 26 V, and single-pass welding. The finite element method using the ANSYS 2020 R2 software for simulation. Welding simulation uses transient thermal and moving heat flux features, while residual stresses and distortion use static structural features. From this research, the maximum temperature distribution after welding at welding speeds of 30 cm/minute, 40 cm/minute and 50 cm/minute were 295.22 ℃, 240.59 ℃ and 205.94 ℃, respectively. In this study, the welding speed of 30cm/minute has the highest values of residual stress and distortion, which is about 0.00000036965 MPa and 0.090894 mm. Besides, for welding speed of 40 cm/minute and 50 cm/minute, the total residual stress and total distortion value are 0.00000027744 MPa; 0.067248 mm and 0.00000022218 MPa; 0.053419 mm, respectively.

Rapid prediction and optimization of the impact of printing parameters on the residual stress of FDM-ABS parts using L27 orthogonal array design and FEA

Fused Deposition Modelling (FDM) is now one of the most widely used techniques for building complicated 3D prototypes straightforwardly from an STL model. In this process, the part is fabricated as a layer-upon-layer deposition of a filamentwire. This deposition technique has numerous benefits; however, it causes rapid heating and cooling cycles of the filamentmaterial, which introduces residual stresses in the component during the building-up process. As a result of residual stresses, warping and distortions of the componentsduring the print process are common concerns in FDM parts. In the FDM process, there are many printing parameters that affect the mechanical properties of printed parts, such as printing speed, layer thickness, printing temperature, printing orientation, and infill density. Experimentally investigating these parameters is costly and time-consuming. This work employs a numerical solution to find the correlation between the residual stress and three printing parameters: printing orientation, raster angle, and infill pattern. The results showed that the printing orientation has the most significant influence on the residual stress value. The raster angle was the second important parameter, while the infill pattern did not influence the residual stress.

Methodology and technological equipment development for treatment processes metal plastic flow research. Part 2. Special equipment and methodology development for experiment research by digital image correlation method

The metal plastic flow regularities experimental estimation, as well as the residual stresses (RS) values in the treatment processes is an important task to correctness justification of obtained finite element modeling solutions. However, the currently known and used plastic flow regularities and RS experimental determination methods in most cases have a significant disadvantages: labor intensity, low accuracy, sample preparation necessity and difficult to apply on real parts. This work purpose is to develop special equipment and methods for researches by the digital image correlation method for conducting experimental metal plastic flow and RS researches during free orthogonal cutting and surface plastic deformation (SPD) under the technological treatment factors variation. The paper substantiates orthogonal loading schemes in the metal plastic flow research in the cutting and SPD processes, research accessories and equipment is developed. The machine movement errors were determined, the sample sizes and loading routines were determined and justified. Using the digital image correlation method, the metal plastic flow experimental researches in the deformation zone during free orthogonal cutting and surface plastic deformation processes were performed. For experimental samples RS determinination after free orthogonal cutting and surface plastic deformation, the digital image correlation and probing hole drilling methods combination was used for the first time, which idea is to determine the material particles movements on the sample top from two images: the sample surface having residual stresses and the same surface after high-speed probing hole.

Optimizing Parameters with FEM Model for 20CrMnTi Laser Shocking

As a new surface treatment technology, laser shock peening (LSP) is a multi-point overlay process of single-point laser shock. In this study, the finite element method (FEM) was used to build a model of single-point laser shock, and the model was verified by experiments. The difference in residual stresses between the experimental and simulated results was less than 20%. Then, the effects of the stress field and deformation of 20CrMnTi with different laser shock parameters were simulated and analyzed. According to the mechanical response of 20CrMnTi to different laser shock parameters, the optimal shocking process parameters for single-point shocking via LSP were determined to be a shock energy of 5 J, a laser pulse width of 20 ns, and an impact number of 5. Lastly, a simulation of multi-point laser shock was performed with the optimal parameters, and the residual compressive stress values of multi-point impacts are close to those of single-point impacts under the same process conditions.

Methods for characterizing the interfacial adhesion in thermal barrier coating systems

Thermal barrier coatings (TBC) are widely used to protect the hot section structural components, such as aircraft gas turbine, against hot corrosion and large thermal gradients during the service life. The resistance to interfacial debonding (adhesion) is one of the key factors for predicting the TBC durability during operation. The goal of the study is analysis of the existing approaches to quantification of the interfacial adhesion for multi-layered thermal barrier coating systems and thermally-grown oxide on Ni-based superalloys and discussion of the problem regarding the reasons for a large spread of the adhesion characteristics. Theoretical prerequisites for determining the adhesion characteristics are considered to provide a theoretical background for quantification of the interfacial adhesion. The absence of national standard tests applicable to TBC is marked along with a significant scatter of the values obtained using international test-regulating documents and proprietary technologies. The values of the intensity of the strain energy release are found to vary from 0.3 to 230 J/m2 depending on the method for measuring adhesion, experimental details and type of the system considered. The factors that determine a large spread of the interfacial adhesion values were divided into two groups: 1 — intrinsic, attributed to the features of TBC layer formation and temperature affecting the value and distribution of residual strains and stresses and direction of the failure initiation; 2 — extrinsic, which are related to test conditions and technique of experimental data processing. A complex approach involving both intrinsic and extrinsic parameters is required to address the problem of interfacial adhesion quantification.

Influence of auxiliary mold stretch-bend forming on the forming quality for L-section aluminum alloy profile

To improve the stretch-bend forming precision of aluminum alloy profiles with complex open sections, the relationship stress–strain distribution and the spring-back radius variation were analyzed under different stretch-bend stages. Numerical simulation was performed on the auxiliary mold stretch-bend and spring-back process for the L-section aluminum alloy profile with variable curvature. The effects of cover plate pressure and baffle gap on residual stress, section deformation and spring-back value after forming were investigated. The results show that the stretch-bend warpage can be avoided by setting the cover plate on the straight section of the profile web plate. With the increase of the cover plate pressure, the section distortion of the vertical plate increases by 82%, and the maximum spring-back increases by 71%. A baffle plate was added to the outside of the vertical plate, and the baffle gap is proportional to the amount of section distortion and inversely proportional to the spring-back value. The critical cover force (1 kN) and the critical baffle gap (1 mm) obtained by numerical analysis are used in the stretch-bend forming experiment, and the maximum error between the two results is 2.39%. The numerical simulation has a certain reference value for the rational design of the auxiliary mold stretch-bend process parameters.

Welding Residual Stress Distributions in the Thickness Direction under Constraints Using Neutron Diffraction and Contour Methods

Using high-strength steel for offshore structures with a yield stress of 500 MPa, this study evaluated the distribution characteristics of welding residual stress in the thickness direction under the influence of constrained conditions during welding using cutting, neutron diffraction, and contour methods. Welding residual stress inevitably occurs during welding and impacts fracture stability in structures. As high-strength steel better reflects the effects of phase transformation, the behavior of welding residual stress is known to differ from that of general steel. This study fabricated fully constrained and unconstrained specimens and evaluated them under identical conditions to evaluate welding residual stress according to the influence of constraints on high-strength steel welds. The results indicated that the maximum tensile residual stress of the fully constrained specimen occurred in the first layer of the weld joint, while the maximum tensile residual stress of the fully unconstrained specimen occurred in the last layer of the weld joint. Additionally, the welding residual stress of the fully constrained specimen was larger. Although some errors occurred in the residual stress values in the thickness direction depending on the measurement method, both methods applied in this study exhibited nearly identical distributions. Meanwhile, a maximum angular deformation of about 6° occurred in the fully unconstrained specimen, and we considered that the residual stress decreased owing to the occurrence of angular deformation. The maximum welding residual stress is generally the degree of yield stress. When residual stress greater than the yield stress occurs, it changes to the plastic range and appears in the form of angular, longitudinal, and lateral deformation. Under the fully unconstrained condition, reduced residual stress is considered to appear in the form of angular deformation. The welding tensile residual stress decreased to around 42% in the unconstrained specimen compared to the constrained specimen, and at that time, angular deformation of approximately 6° occurred. Therefore, it is estimated that an angular distortion of about 2.4° occurs as the stress of 100 MPa decreases.

Correlation between residual stress and geometric tolerances in ultrasonic assisted turning

High accuracy in production parts and manufacturing quality are the requirements of production. Residual stress affects the surface quality and dimensional accuracy of manufactured parts. Production of parts with geometric tolerance, optimal residual stress, and suitable surface quality is always required by manufacturing industries. When machining parts, tensile residual stresses are created in them, which is one of the main reasons for the loss of geometric tolerances and distortion in the workpiece. This study investigated the effect of the ultrasonic-assisted vibration compared with conventional machining in various conditions of a 2024 aluminum workpiece on the surface quality, runout, straightness, and tensile residual stresses. In this article, the effects of geometric tolerance parameters, tensile residual stress, and surface roughness have been investigated simultaneously. A total of 18 experiments in different cutting speeds and feed rates in two machining states of conventional and ultrasonic vibration states were performed. The results showed that ultrasonic vibrations could be used to achieve 31% lower run out and 36% lower straightness in the parts. Also, the values of tensile residual stress in the ultrasonic vibration machining were 11% lower compared to conventional machining. Ultrasonic vibrations can also be used in most cases to achieve better surface quality, tolerance, and tensile residual stress according to machining parameters compared to conventional machining. The experimental results show that ultrasonic-assisted turning is a reliable method for machining, which can obtain lower tensile residual stress and improve the machined surface integrity and better tolerances.

Experimental investigation and estimation of compressive residual stress of ball burnished rare earth based magnesium alloy

The present study focuses on the experimental investigation and optimization of compressive residual stress on ball burnished Mg Ze41A alloy. The optimum compressive residual stress value of −182 MPa is obtained at burnishing force of 50 N, speed of 1200 r/min, feed of 150 mm/min and 4 number of passes. Burnishing force and speed are found to be the most sensitive parameters in affecting the compressive residual stress, followed by number of passes and burnishing feed. The demarcation lines in residual stress-burnishing maps of Mg Ze41A alloy are non-parallel and non-uniform, indicating significant interactions among burnishing parameters. Ball burnishing process imparted desired amount of work hardening, which resulted in homogenized ( σx1 = σx2) and isotropic stress ( σ1 = σ2) state. Additionally, the fuzzy logic model has been deployed to estimate the compressive residual stress values at different burnishing conditions. Fuzzy logic model estimated the results with an error of 6.11%. The results demonstrate that ball burnishing process is an effective method in inducing compressive residual stresses on Mg alloy. The outcome of this study can be of great help in enhancing the fatigue performance of small size products.