Axial Residual Stress Research Articles

Numerical analysis of surface integrity in parallel turning Part A: Influence of cutting tool nose radius

Nose radius of a cutting tool is an important factor in finding the surface integrity of turned parts. The current research work deals with numerical analysis of surface residual stress generated during parallel turning using finite element method based software. Appropriate material model was used for parting the chip from work material. Nose radius is a vital process variable especially in parallel turning. The main motive of the current research work is to estimate the influence of nose radius on axial and circumferential residual stresses retained by machined work surfaces. The results revealed that with the increment in cutting tool nose radius, the residual stress of compressive nature along cutting and feed direction increases for the machined surface of front and rear tool. For all the nose radii, residual stresses raised with the rise in cutting speed. For nose radius of 0.5 mm and 250 m/min cutting speed with feed 0.2 mm/rev, the highest compressive circumferential and axial stress of the surface turned by second tool is 1696 MPa and 1838 MPa respectively. Higher nose radius causes larger dead metal and stagnation zone which in turn causes higher surface residual stresses.

Novel residual stress measurement technique to evaluate through thickness residual stress fields

In this present study, a novel approach of measuring through-thickness residual stresses based on the general strain relaxation methodologies has been described. This new method is an amalgam of the conventional deep hole drilling technique and the contour method with a reduced degree of damage to the component made during measurements. The annular deformation of a reference hole made at the measurement location has been interpreted as the displacement boundary conditions in a two-dimensional finite element model. In this regard, a thick, partially plastic four-point bent bar specimen was used to validate the proposed method. Through-thickness axial residual stresses induced in the bar were measured using the proposed technique and were observed to be in a reasonably close match with the theoretical and DHD results.

Numerical analysis of surface integrity in parallel turning process Part I: Influence of cutting tool parting distance

Surface integrity is one among the prime quality features of turned parts. In the present research work, surface residual stress generated during parallel turning is analysed numerically using finite element method based software. Parting of cut-chip from uncut-work material is dealt by Johnson-Cook criteria. Tool-chip friction was modelled by penalty contact method. Cutting tool parting distance is an important process parameter in parallel turning. The main objective of the current research work is to evaluate the significance of parting distance on axial and circumferential surface residual stresses induced on machined work surfaces. The analysis revealed that with the increment in parting distance, the surface integrity raised. When the distances was raised from 0.4 to 0.8 mm, for a cutting velocity of150 m/min and feed 0.2 mm/rev the axial and circumferential residual stresses elevated by 34% and 33% for surface machined by second tool. For all chosen parting distances, the stresses raised with the increase in cutting velocity. Parallel turning was advantageous in increasing the machined surface integrity.

Effect of shot peening coverage on residual stress and surface roughness of 18CrNiMo7-6 steel

Shot peening is becoming a widely used surface strengthening technique for various key mechanical components for its enhanced influence on the fatigue performance. This technique allows to strengthen the mechanical properties of material via introduce a certain depth of compressive stress layer and change the surface topography. The relation of the shot peening processing parameters, the surface integrity including residual stress and the surface roughness remains a large unmet practical need. In this paper, the residual stress and surface topography obtained by various shot peening treatments were experimentally and theoretically examined. A random multi-shots peening model of a carburized roller, accounting for the initial hardness gradient and residual stress was developed. The measured residual stress and surface roughness present good agreements with the predicted results. Both the experimental and simulated results reveal that the axial and tangential residual stress components tend to be consistent after shot peening. In addition, the influence of peening coverage on detailed evolution of surface topography and residual stress is investigated. It is found that the ratio between the layer thickness of compressive stress and the critical depth of maximum stress generally lies in the regime of 3.6–4.3 after shot peening. As the coverage increases from 100% to 400%, surface roughness parameters Sa, Sq, S5z, Sku decrease, while the maximum magnitude of compressive stress fluctuates in the range of 1105∼1230 MPa. This work could act as an advisory reference for shot peening engineering practices.

Effect of diamond burnishing parameters on the state of the processed surface layer of billets made of high-strength "30ХГСН2А-ВД" steel

The influence of the burnishing force, tool radius, processing speed and feed on the distribution of circumferential and axial residual strses, microhardness and the depth of strain hardening in the surface layer when pr ssing of "30ХГСН2А-ВД" steel with synthetic diamond "ACB-1" is considered. Empirical dependencies determining these parameters are given. Keywords diamond burnishing, strain hardening depth, circumferential residual stresses, axial residual stresses, microhardness. shvecovalexey@yandex.ru, skuratov.sdl56@yandex.ru

A new contour method for rapid evaluation of the cross-sectional residual stress distribution in complex geometries using a 3D scanner

This paper presents a new method for contour measurements using a 3D scanner to determine cross-sectional residual stresses in structural components with complex configurations. The proposed method was applied to evaluate the axial residual stress distribution in a dissimilar pipe weld and the obtained results were compared with those obtained using a benchmarked contour measurement machine (CMM) equipped with a confocal laser probe for verification. It reveals a quantitative agreement between the two methods in terms of both the measured contours and the calculated residual stresses. Most importantly, this method allows a significantly reduced measurement time by ≈99 % (≈20 min, with an effective measurement speed of ≈0.2 sec/mm2), compared to the benchmarked method (≈48 hr, with an effective measurement speed of ≈28.7 sec/mm2). Based on stress uncertainty analysis, this method guarantees a longer range of stable fits due to fewer noisy data points than the benchmarked method.

An Investigation on Wear Behavior of ER8 and SSW-Q3R Wheel Steel under Pure Rolling Condition

In this paper, the wear property of ER8 and SSW-Q3R wheel steel under pure rolling condition was studied by GMP-30 wear tester. The results showed that the wear loss of the ER8 wheel steel was higher than that of the SSW-Q3R wheel steel at the same cycles. The high carbon content of the SSW-Q3R improved the surface hardness during rolling wear. The high hardness increased the wear resistance of the SSW-Q3R wheel steel. During rolling wear, the fatigue wear resistance of ER8 wheel was worse than that of the SSW-Q3R wheel steel due to more proeutectoid ferrite content in ER8 wheel steel. The surface residual stress of ER8 and SSW-Q3R wheel steel increased with the increase in cycles. The axial residual compressive stress on the surface of the sample was greater than the circumferential residual compressive stress. The residual stress at the trough was higher than that at the crest.

Simulation of the residual stress in a multi-pass oil and gas pipe weld joint

In this paper, a welding simulation procedure is developed using the FE software MSC Marc to predict the residual stresses.Numerical simulation was used to predict the thermal, mechanical and residual stresses behaviour in dissimilar material welded pipes which were found to be in good concurrence with experiments. Both two-dimensional FE model (2D) and three-dimensional FE model (3D) models are used to simulate the residual stressesin different directions in several regions of the weld zone under the same welding conditions. The 2D modelwas used toreduce the time and cost of numerical simulation.The aimof the present work is to understand the evolution of residual stresses (axial, radial and hoop stresses) in weldments. The results of thesimulationreveal that the hoop and the axial residual stresses around the weld region arenoticeablyvarying from those in the steady range.

Effect of preheating temperature of the substrate on residual stress of Mo/8YSZ functionally gradient thermal barrier coatings prepared by plasma spraying

Based on the thermal elastic-plastic finite element theory and ANSYS finite element analysis software, a numerical model of Mo/8YSZ functionally gradient thermal barrier coatings prepared by the plasma spraying technology on the surface of aluminum alloy was established. The model considered the change of the thermophysical properties of the material with temperature and analyzed the influence of different preheating temperatures of the substrate on the value and distribution of the residual stress of the functionally gradient thermal barrier coating. The results showed that as the preheating temperature of the substrate increased, the distribution range of the radial residual tensile stress of the coating gradually decreased, and the distribution range of the radial residual compressive stress gradually increased. However, as the preheating temperature of the substrate increased, the distribution range of the axial residual tensile stress of the coating gradually increased and the distribution range of the axial residual compressive stress gradually decreased. With the increase of the preheating temperature of the substrate, the maximum value of the radial residual tensile stress, the maximum value of the radial residual compressive stress and the maximum value of the axial residual compressive stress of the component increased, but the maximum value of the axial residual tensile stress of the component showed a tendency of decreasing first and then increasing. Compared with the axial residual tensile stress of the component, the change of the preheating temperature of the substrate had a greater impact on the axial residual compressive stress, the radial residual compressive stress and the radial residual tensile stress of the component. Compared with other locations of the interface between the substrate and the coating, there was a larger abrupt change in the residual stress at a position about 0.5 mm from the edge of the interface. Considering the distribution of residual stress and sudden changes in stress, the preheating temperature of the substrate should be controlled at 150 °C.

Effects of material type, preheating and weld pass number on residual stress of welded steel pipes by multi-pass TIG welding (C-Mn, SUS304, SUS316)

A numerical procedure is provided to analyze temperature and residual stress fields in multi-pass TIG welds with different pipe and electrode material. Based on the ABAQUS software and FORTRAN codes, to appraise the temperature fields and the residual stresses over the TIG process, an uncoupled thermo-mechanical, finite element model (FEM) is developed. For considering volumetric thermal flux on the workpiece, the “GOLDACK” method is used. The silent element method is utilized to model the weld deposit. To validate the presented simulation model, the TIG process is performed in two passes on SUS304 stainless steel pipe. Then, the process is modeled for three and four passes to consider the effect of pass number on axial and hoop residual stresses in the outer and inner surfaces of the welded pipes. Additionally, the effects of base material and preheating temperature on the internal and external surface stresses of pipe are investigated. Results show that, the base material type has a greater effect on the tensile axial residual stress of the outer surface rather than that of the inner surface. However, the welding pass number shows no significant influence on the peak of the tensile axial residual stress on the inner surface of the pipe. In terms of preheating, the stress magnitude is reduced by raising the preheating temperature but with more intense in the inner surface of the pipe. Additionally, to keep the tensile axial residual stress below the base metal yield strength, the preheating at least up to 325 °C is essential.

Influences of welding parameters on axial force and deformations of micro pinless friction stir welding

0.5-mm-thick 7075-T6 aluminum alloy sheets were butt joined successfully by high-speed micro friction stir welding (μFSW) as well as conventional μFSW using a pinless tool. The influences of welding parameters on the axial force, residual stresses, and deformations were studied through experiments. Good surface morphology and defect-free joints were obtained by high-speed μFSW as well as conventional μFSW in a fixed rotational speed/welding speed of 6.67 rad/mm. The axial force during μFSW increased with the increment in welding speed and decreased with the increment in rotational speed. When the ratio of rotational speed/welding speed was 6.67 rad/mm, compared with conventional μFSW (2000/300), the lower axial force of 1460 N was obtained by using high-speed μFSW (10,000/1500). Longitudinal tensile residual stress and transverse compressive residual stress occurred around the weld zone for all μFSW joints. The residual stresses of joint fabricated by a parameter of 10,000/1500 were slightly less than that fabricated by 2000/300. Both longitudinal maximum bending deformation Zmax and transverse angular deformation α increased with the increment in rotational speed and decreased with the increment in welding speed. As a comparison to 2000/300, the welded sheet with a parameter of 10,000/1500 exhibited slightly lower Zmax and α.

Effect of the welding parameters on residual stresses in pipe weld using numerical simulation

The objective of this article is to predict the residual welding stress in a dissimilar pipe weld. The 2D model, instead of 3D was used to reduce the time and cost of the numerical calculation. The 2D numerical simulation MSC MARC code is used to predict the residual stress developed during pipe welding. The present model was validated using hardness measurement. Good agreement was found between the measurement and numerical simulation results. The effects of welding parameters on residual stress field on the outer and inner surface were assessed. The effect of welding parameter (welding current) is examined. The axial and hoop residual stresses in dissimilar pipe joints of different thickness for pipe weld were simulated in outer and inner surfaces. When the other parameters remain fixed, and the current has great effect on the weld shape and size, and then affects the residual stress level significantly.

Optimization of cutting parameters of residual stresses in simultaneous turning technique

The simultaneous turning technique is used to increase the rotary component’s fatigue life by increasing the surface compressive residual stresses. Cutting velocity, cutting tool rake angle, nose radius, feed and tool separation distances are the major cutting parameters in simultaneous turning. Computer simulation was performed by finite element analysis software ABAQUS 6.14. It was used to predict the surface residual stresses and optimization of the cutting parameters was carried out using Taguchi method. MINITAB software was employed for this purpose. The study revealed that the optimal combination of cutting parameters are 150 m/min cutting speed, 0.1 mm/rev feed, 4° negative rake angle, 0.1 mm tool nose radius and 0.4 mm tool separation distance. These optimal values yielded a highest circumferential and axial surface residual stresses of −817.59 and −928.04 MPa for the surface turned by first tool whereas for surface machined by other tool it was −875.89 and −1010.44 MPa.

Low-pressure turbine disc fi rtree slots’ life and reliability enhancement by ultrasonic surface hardening

The possibility of life and reliability enhancing of AL-31F low pressure turbine disc’s fir-tree slots by ultrasonic hardening is considered. Having disc’s material properties studied, working stress derivation is executed which was further used for following comparative fatigue tests. Also, Davidenkov method residual stress analysis is carried out which showed 95.3 % change to compression stress for circumferential residual stress and 80.9 % change to compression stress for axial residual stress which proves possibility of fir-tree slots’ life and reliability enhancement by ultrasonic hardening. Comparative fatigue tests with N = 4•10 5 cycles basis showed that the hardened samples standing out the cycle basis during higher oscillatory amplitudes (and, thus, affecting loads) than the non-hardened basic ones.

Influence of different cooling strategies during hard turning of AISI 52100 – part II: characterization of the surface and near surface microstructure morphology

Abstract This two-part paper addresses the impact of seven different cooling conditions on the finishing process as well as the resulting surface and near-surface microstructure morphology of the rolling bearing steel AISI 52100 in martensitic heat treatment state. The applied cooling strategies are liquid nitrogen (LN2-) cooling, CO2-snow cooling at varied mass flows, sub-zero metalworking fluids (MWF) at varied supply temperatures, and dry machining. Part II of the paper concerns the changes in surface roughness, examined by an angle resolved scatter light sensor, micro hardness measurement, microstructure observations, residual stress and phase composition analyses in the near-surface area, caused by the turning process, that is characterized in Part I. The lowest cooling performance, i.e. dry machining, results in low compressive axial residual stresses and a high proportion of retained austenite at the near-surface area. High cooling performance strategies like CO2 cooling or sub-zero MWF show an opposite distribution of the mentioned parameters, wherein the coolants’ lubrication effect is an important aspect. Microstructural differences resulting from the process parameters used in these investigations tend to be less significant. Thus, they do not allow reliable assignment of the microstructure to the cooling strategies used. However, different cooling conditions show an impact on residual stresses, phase distribution and surface topography of the workpieces to varying extents.

Effect of Initial Residual Stress on Machining Deformation of a Casing Part

Initial residual stress of blank is the main cause for the workpiece machining deformation. Based on the simplified equivalent model and the finite element analysis method, the effects of initial residual stress in bidirectional, axial direction and tangential direction on the deformation of an aluminum alloy conical case were studied respectively. The deformations of case were judged by flatness and roundness error of the end face of the case. From the results, it can be seen that the influence of the initial axial residual stress on the roundness error of the end face is greater than that of the radial residual stress; among all the errors, the roundness error of the large end face is much larger than that of other errors. It is shown that the roundness error of the large end face and the initial axial residual stress of the workpiece are the most important issues to be controlled in actual machining process. This conclusion has certain guiding significance for practical application.

Residual Stress Relief in 2219 Aluminium Alloy Ring Using Roll-Bending.

Relieving the residual stress in components is essential to improve their service performance. In this study, a roll-bending process was proposed to reduce the quenching residual stress in a large-size 2219 Al alloy ring. The roll-bending effect on quenching residual stress was evaluated via the finite element method (FEM) combined with experiment. The effect of radial feed quantity, friction coefficient, and roller rotational speed during the roll-bending process on quenching residual stress was analyzed. A set of optimized roll-bending parameters with radial feed quantity, friction coefficient, and roller rotational speed was obtained. The results reveal that the best reduction rates of circumferential and axial residual stress reached 61.72% and 86.24%, respectively. Furthermore, the difference of the residual stress reduction effect between the roll-bended ring and the three-roller bended beam was analyzed.

Numerical study of residual stresses in duplex turning process

In this paper numerical study was performed to evaluate the surface residual stresses in duplex turning process. A computational model was created using commercially available software ABAQUS 6.14. The chip separation was based on Johnson-Cook damage criteria. Penalty contact approach was used to model the friction between the chip and the cutting tools. The effect of process parameters such as cutting speed and feed on circumferential and axial residual stresses was investigated. The surface residual stresses increased with the increase in cutting speed and feed. The numerical results indicated that higher circumferential and axial compressive residual stresses are induced on the surface machined by second cutting tool when simultaneously machined along with the first cutting tool. The duplex turning process proved advantageous in increasing the compressive surface residual stress.

Modeling birefringence in SiO2 glass fiber using surface stress relaxation

AbstractThe retardance of silica glass fibers was evaluated using photoelastic techniques. Here, surface birefringence in glass fibers is shown to be a consequence of surface stress relaxation for as‐received fibers drawn from Suprasil II. The surface features of the birefringent fibers were compared to a model of the residual axial stress profile resulting from a diffusion‐controlled surface stress relaxation. Additionally, a uniform birefringence in the fiber equivalent to a constant tensile stress was recognized and attributed to structural anisotropy produced during fiber drawing. The contribution of structural anisotropy to the observed birefringence remained constant as the surface features were successively etched away. Surface compressive stress generation was also observed, as retardance corresponding to a surface compressive stress was found to increase with applied tensile stress during short heat treatments. Significant features of the retardance profile in as‐received silica glass fibers, with a thin surface compressive stress layer and compensating interior tensile stress, agreed with the residual stress profiles predicted by the surface stress relaxation model after correcting for this observed structural anisotropy.

Residual Normal and Shear Stresses on Different Machining-Finished Surfaces of Martensitic Ultrahigh Strength Steel

Machining induced residual stresses are known to have influenced mechanical properties of high strength metallic alloys. In this paper, we have compared the surface residual stresses of an ultrahigh strength martensitic/bainitic steel grade 56NiCrMoV7 induced by two different machining processes, namely turning and milling. Using the established d~sin2ψ method, x-ray diffraction technique was employed to measure the residual stresses on both the axial and hoop directions of cylindrical samples. The results reveal that, turning finish led to tensile residual stress in the axial direction and compressive residual stress in the hoop direction. On the other hand, milling finish led to compressive residual stresses in both the axial and hoop directions. In addition, large splitting in the d~sin2ψ linear regressions has been interpreted by the presence of residual shear stresses.