Axial Residual Stress Research Articles

Nonlinear three-dimensional stability characteristics of geometrically imperfect nanoshells under axial compression and surface residual stress

Abstract Through reduction of thickness value in nanostructures, the features of surface elasticity become more prominent due to having a high surface-to-volume ratio. The main aim of this research work was to examine the surface residual stress effect on the three-dimensional nonlinear stability characteristics of geometrically perfect and imperfect cylindrical shells at nanoscale under axial compression. To do so, an unconventional three-dimensional shell model was established via combination of the three-dimensional shell formulations and the Gurtin–Murdoch theory of elasticity. The silicon material is selected as a case study, which is the most utilized material in the design of micro-electromechanically systems. Then, the moving Kriging meshfree approach was applied to take numerically into account the surface free energy effects and the initial geometrical imperfection in the three-dimensional nonlinear stability curves. Accordingly, the considered cylindrical shell domain was discretized via a set of nodes together using the quadratic polynomial type of basis shape functions and an appropriate correlation function. It was found that the surface stress effects lead to an increase the critical axial buckling load of a perfect silicon nanoshell about 82.4 % 82.4 \% for the shell thickness of 2 nm 2{\rm{nm}} , about 32.4 % 32.4 \% for the shell thickness of 5 nm 5{\rm{nm}} , about 15.8 % 15.8 \% for the shell thickness of 10 nm 10{\rm{nm}} , and about 7.5 % 7.5 \% for the shell thickness of 20 nm 20{\rm{nm}} . These enhancements in the value of the critical axial buckling load for a geometrically imperfect silicon nanoshell become about 92.9 % 92.9 \% for the shell thickness of 2 nm 2{\rm{nm}} , about 36.5 % 36.5 \% for the shell thickness of 5 nm 5{\rm{nm}} , about 17.7 % 17.7 \% for the shell thickness of 10 nm 10{\rm{nm}} , and about 8.8 % 8.8 \% for the shell thickness of 20 nm 20{\rm{nm}} .

DETERMINATION OF RESIDUAL STRESSES IN PIPES

During production, operation, transportation, and aging of finished products, stresses occur in the pipe metal. As a rule, these residual stresses affect the quality of pipes. The presence of residual stresses in products can cause brittle fracture, cracking due to corrosion, reduced elasticity, warping, etc. The development of methods for managing residual stresses in metals and products is the realization of a powerful reserve for improving the quality of metal products, which means increasing the reliability of machinery. The question arises as to which method, convenient in production conditions, should be used to assess residual stresses. A simple and affordable method for estimating residual stresses is needed in production conditions. This paper presents a simplified method for estimating residual stresses in pipes. The purpose of the work is to improve and present a methodology for estimating tangential and axial residual stresses in cold-formed pipes and tubes after heat treatment according to the method of M.M. Davydenko. Research methods: M.M. Davydenko's method for cutting rings and cutting strips from pipes. Calculation of residual stresses. Results. The method for estimation of tangential and axial residual stresses in pipes after cold deformation and after heat treatment is improved and presented. The formulas for calculating residual stresses are given. Practical value. Pipe plants need to estimate residual stresses to develop technological processes for the manufacture of new types of pipes and to meet pipe standards. The improved and presented methodology will help manufacturers in assessing residual stresses. Conclusions. Modern methods for assessing residual stresses have been considered. A methodology for calculating tangential and axial residual stresses according to M.M. Davydenko by cutting rings and cutting strips from the metal of the studied pipes is presented. The methodology is officially registered, which allows it to be used for official assessment of pipe quality.

Bearing Inner Ring Raceway Low-Temperature Aerosol Cooling Lubrication Grinding

A low-temperature aerosol cooling and lubrication grinding test bench was built to evaluate the cooling and lubrication performance of the low-temperature aerosol. The mechanism of grinding residual stresses in the inner ring raceway under the coupling effect of grinding force and grinding heat was studied, and the effects of the grinding process parameters and cooling and lubrication conditions on the distribution state of the grinding residual stresses in the surface layer of the inner ring raceway were revealed. The results showed that reducing the initial temperature of the grinding fluid could reduce the residual tensile stresses on the raceway surface. The results also showed that the low-temperature aerosol cooling lubrication method is conducive to the generation of the axial residual compressive stress of −500 MPa and tangential residual compressive stress of −300 MPa in the inner ring raceway surface layer of the bearing. Compared with the convective heat transfer coefficient, the effect of the initial temperature of the grinding fluid is smaller.

Dry Hard Turning versus Grinding—The Influence of Machining-Induced Surface Integrity on Fatigue Performance

Dry hard turning (DHT) provides an effective process for finishing high-hardness materials. Machining-induced surface integrity has a direct impact on functional performance. This study compares the effects of the DHT and grinding processes on machining-induced surface integrity and fatigue performance of 18CrNiMo7-6 steel. The DHT and grinding experiment were carried out by using a polycrystalline cubic boron nitride tool and corundum wheel, respectively. The 3D surface morphology, surface roughness, surface residual stress, and machining accuracy of the hourglass-shaped specimen were measured. The fatigue fracture was characterized by scanning electron microscopy. The experimental results show that compared to grinding, DHT has obtained a larger surface compressive residual stress (the maximum axial and tangent residual stresses are −762.6 MPa and −442.8 MPa, respectively) and a lower surface roughness (the minimum Ra and Rq are 0.172 μm and 0.230 μm, respectively). This study is an attempt to use DHT instead of a grinding process to finish 18CrNiMo7-6 steel, providing a reference for high-quality and sustainable manufacturing of hardened steel.

Effect of cryogenic machining-strengthening process on enhanced surface integrity and fatigue properties of ZK61M magnesium alloy

Excessive heat and fatigue are important factors affecting the machinability and service performance of magnesium alloy. Cryogenic processing is an effective method to reduce the temperature of the tool and the component, thus improving the machinability of magnesium alloys. The fatigue of workpieces is affected by machining and strengthening processes. However, the current studies on cryogenic processing hardly comprehensively consider the effect of cutting and rolling. To investigate the effect of cryogenic air and pre-cutting processes on rolling, the sequential cutting and rolling experiments were conducted on ZK61M magnesium alloy under dry and two cryogenic cooling conditions. Effects of coolant during sequential machining and rolling processes on forces, surface roughness, microstructure, hardness and residual stresses were investigated. The fatigue properties of ZK61M in the cryogenic processes were also studied. The results show that the rolling force is affected by the coolant lubrication and the surface hardening generated by the previous process. Cryogenic rolling can effectively reduce the surface roughness, increase the circumferential residual compressive stress and reduce the axial residual compressive stress. The feed force of the dry turning followed by rolling with liquid nitrogen (ST + NR) process is the smallest, which is 136.4 N. And the surface roughness (Ra) is also the smallest, which is 0.42 μm, 46.8 % lower than the traditional process. Meanwhile, the ST + NR process can prolong the fatigue life of ZK61M magnesium alloy by 62.9 % compared with conventional process. Moreover, the surface roughness and residual stress have significant influences on fatigue life of ZK61M magnesium alloy, followed by the depth of work hardening layer, and finally the surface hardness. Cryogenic cutting and strengthening process can effectively suppress the initiation and propagation of fatigue cracks.

Impact of process parameters on temperature and residual stress distribution of X80 pipe girth welds

This paper studies the impact of process parameters on the temperature field and residual stress distribution of X80 pipe girth welds. The process parameters investigated were welding power, pre-heating temperature, inter-pass temperature, welding speed, diameter-to-thickness ratio (D/t) and restraint. 2D axisymmetric finite element models with a 8-pass girth weld in the middle were established. The thermal analysis was carried out by using the double ellipsoid heat source model. This was followed by mechanical analysis to study the residual stress distributions. The results revealed that the distribution of axial and hoop residual stresses along the center of the weld was generally symmetrical. The welding power had the greatest impact on the maximum temperature of the molten pool. The other parameters had the following sequence in terms of their influence on the maximum temperature of the molten pool: D/t, welding speed, inter-pass temperature and pre-heat temperature. The sequence from large to small that the process parameters affecting the maximum axial residual stress is: restraint > power > inter-pass temperature > pre-heat temperature > D/t > welding speed. However, the sequence changed for the maximum hoop residual stress as: welding speed > inter-pass temperature > power > pre-heat temperature > D/t > Restraint. In general, all process parameters had a greater influence on the axial residual stress than the hoop residual stress.

Study on Surface Integrity and Fatigue Properties of TC4 Titanium Alloy by Surface Ultrasonic Rolling.

In this paper, the influence of a surface ultrasonic rolling process on the surface integrity of TC4 titanium alloy and its influence on the fatigue properties were studied. By comparing and analyzing the surface roughness, microhardness, residual stress, microstructure, and fatigue fracture, the surface strengthening and modification mechanism of TC4 titanium alloy is discussed. The results show that the surface roughness of titanium alloy is observably decreased after the suitable surface ultrasonic rolling process, and the maximum Ra value can be reduced to 0.052 μm. The axial residual stress on the specimen surface can be increased to -685 MPa. The hardening rate of the surface hardness of the sample was 35%. The residual compressive stress and hardness of the sample surface increased with the increase of static pressure. However, the increase of feed rate and rational speed was less. After surface ultrasonic rolling, the sample surface exhibited obvious grain refinement, the number of high-angle boundaries increased to include the formation of nano-equiaxed grains. The fatigue strength increased by 52% from 280 MPa to 425 MPa. Under 450 MPa, the fatigue life of samples with SUR 2 was the highest, at about 7.7 times that of the original samples. The surface integrity of titanium alloy samples after surface ultrasonic rolling treatment is greatly improved, which is the reason for the significant increase in fatigue life of the samples.

Residual stresses study in butt welded joint of Inconel 617 alloy and effect of post weld heat treatment on residual stresses

Distribution of weld-induced residual stress plays a significant effect on the service life of a welded component. The accumulation of high residual stress accelerates the crack propagation even if the crack is of microscopic level, reducing the service life of the welded component. Prior understanding of residual stress distribution can aid in the design of a component with an adequate factor of safety and reduce the probability of failure. In the present study, two separate circumferential butt welded pipes were fabricated using Alloy 617 and then subjected to post weld heat treatment) at 720°C and 980°C. The deep hole drilling method was used to measure the distribution of residual stress. The fabrication of the welded joint was done using the hot-wire TIG welding process. High welding speeds are possible with hot-wire tungsten inert gas (TIG) welding because it uses less heat than conventional TIG welding. Using hot-wire TIG welding, the welded joint's mechanical properties, such as hardness, are improved in addition to its metallurgical properties. The computational approach is provided to analyze temperature and residual stress fields in multi-pass TIG welds with different passes. Based on ABAQUS FEA software, a coupled thermomechanical computational approach was developed to analyze the residual stress distribution on the welded joint. A 3D finite element model for Alloy 617 tube was created to estimate the welding stress field in two separate multi-pass welded joints. Mixed hardening model (kinematic and isotropic) was used during the numerical analysis. The effectiveness of the computational approach was verified with experimental measurements. The magnitude of hoop and axial residual stresses were observed to be maximum at a depth of 6 mm from the upper surface. The stress gradient in the welded zone and heat-affected zone is dramatically reduced by 70–80% of the as-welded condition during the post weld heat treatment at 980°C.

ИССЛЕДОВАНИЕ ОСТАТОЧНЫХ НАПРЯЖЕНИЙ ПРИ ПЛОСКОМ ШЛИФОВАНИИ ПРЕРЫВИСТЫМ АБРАЗИВНЫМ КРУГОМ

A technique for investigating residual stresses during flat grinding with an intermittent abrasive wheel is given. As a result of the study, it was found that tangential residual tensile stresses are formed in the direction of the cutting speed. Axial residual compression stresses are formed in the direction perpendicular to the cutting speed. It is shown that during grinding, residual stresses in the parts are formed from the action of force and thermal fields.

ИССЛЕДОВАНИЕ ОСТАТОЧНЫХ НАПРЯЖЕНИЙ, ВОЗНИКАЮЩИХ ПРИ ИНКРЕМЕНТАЛЬНОМ ФОРМООБРАЗОВАНИИ

In this article, studies have been carried out to determine the magnitude of residual stresses arising during incremental shaping of a truncated cone, depending on the angle of inclination of its formative. To assess the residual stresses the method of cutting rings was used, according to the results of which it was found that the rings, cut out along the height, manufactured conical parts, when cutting are closed. This indicates the formation of compressive circumferential stresses during incremental shaping. There is also an insignificant axial displacement of the ring ends after cutting rings, which indicates the presence of axial residual stresses, the value of which is negligibly small compared to the value of circumferential stresses. As the degree of deformation increases during incremental shaping (increasing the taper angle), the magnitude of residual stresses decreases.

Numerical Prediction of Axial Residual Stress Relaxation caused by Bending-Straightening in Quenching-Induction-Hardened Axle Shafts

Numerical Prediction of Axial Residual Stress Relaxation caused by Bending-Straightening in Quenching-Induction-Hardened Axle Shafts

Interfacial reaction and interface mechanical behaviors of the 2.5D aluminosilicate fiber reinforced ZrO2 composites

The interfacial reaction and interface mechanical behaviors were carefully studied in the 2.5D aluminosilicate fiber reinforced ZrO2 (ASf/ZrO2) composites which had been prepared by polymer impregnation and pyrolysis. The study confirmed that the interfacial reactions can be attributed to the contact of Si-OH with Zr-OH groups and the diffusion of Si4+ in ZrO2 matrix. A chemical bonding significantly formed between the fiber and the matrix. The investigation showed that the interfacial bonding strength enhanced slowly from 113.13 ± 4.83 MPa to 153.01 ± 11.35 MPa with the temperature increasing from 800 °C to 1000 °C, which could be attributed to the interfacial reaction and the great radial compressive stress. At 1100 °C, the interfacial bonding strength declined to 142.11 ± 6.66 MPa. The reason of the decrease could be the shear damage of the interfacial bonding induced by the axial residual stress which were − 476.52 ± 12.47 MPa and 492.57 ± 12.90 MPa in the fiber and in the matrix, respectively.

Investigating the influence of the superfinishing process on the residual stress of the raceway

The residual stress of bearing inner race after superfinishing machining along the axial direction is usually measured by using an X-ray analyzer. The experimental results show that the residual stress on the surface of the bearing raceway is compressive stress with an average value of −266 to −438 MPa, and the circumferential residual stress on the bottom surface of the bearing raceway is greater than the axial residual stress. The obtained results reveal that the oilstone pressure has a significant effect on the residual compressive stress. It is found that increasing the oilstone pressure can significantly improve the residual compressive stress on the surface of the bearing raceway.

Effect of simulated axial residual stress and transverse residual stress in welded P92 pipe and plates including plasticity error

The paper deals with the measurement of the residual stresses in P92 welded pipe using the blind hole drilling technique.The post weld heat treatment (PWHT) of P92 welded pipe was also conducted to study their effect on residual stresses .The P92 pipe weld joints were prepared using gas tungsten arc welding process. The residual stress measurement was carried out using the strain gauge rosette that was associated with the plastic deformation of material and stress concentration effect of multi-point cutting tool. The corrective formulation was developed for calculating the corrected value of residual stresses from the experimentally obtained strain value. The Strain gauge response was estimated experimentally using the tensile testing for the uniaxial loading while finite element analysis was performed for biaxial loading. Gas tungsten arc welds joint was prepared for conventional V-groove and narrow groove design.

Metal Forming-Induced Residual Stresses and Rule of Mixtures’ Prediction of Tensile Behavior of Bimetallic Wires

The present study investigates the tensile behavior of the two bimetallic composite wires Cu-Al and Fe-Al. The purpose is to understand the deviation their tensile strengths show from the Rule of Mixtures’ prediction. To that end, an experimental-numerical approach was adopted. Following tensile testing of the above cold-drawn composite wires, the manufacturing process (wire drawing) was simulated via finite element analysis. The prominent role of processing-induced residual stresses on the yield strength of cold-drawn products is known. Therefore, a discussion based on the axial tensile residual stress profile was developed. It was concluded that the higher-magnitude-near-surface tensile residual stresses in the Fe-Al wire causes its tensile curve to show a negative deviation from the Rule of Mixtures (RoM). The Cu-Al wire, on the contrary, exhibits a slight positive deviation.

AN INFLUENCE OF ROLLER STRENGTHENING ON MULTCYCLIC FATIGUE OF SPECIMENS WITH CUTS OF VARIOUS DEPTH AND A PRESSURIZED HUB

The influence of roller strengthening on a residual stresses distribution and multicyclic fatigue of solid cylindrical specimens of 50 mm diameter made of steel 20 with cuts of various depths and a pressurized hub has been examined. As a result, an endurance limit of roller strengthened specimens diminishes. In order to preserve the effect of hardening with a cuts depth increase, its necessary to increase the thickness of a layer with compressive residual stresses. Surface hardening influence on an endurance limit of specimens has been estimated by two criteria: axial residual stresses on a concentrators surface and average integral residual stresses, calculated through the dangerous sections surface layer thickness that equal a critical depth of a non-propagating fatigue crack. Its been stated that its more reasonable to use the average integral residual stresses criterion for an evaluation of roller strengthening influence on an endurance limit of specimens with cuts of various depth and a pressurized hub.

A comparative analysis of chip shape, residual stresses, and surface roughness in minimum-quantity-lubrication turning with various flow rates

In this research, an experimental investigation was carried out to investigate the interaction between various turning parameters and different minimum quantity lubrication (MQL) flow rates and compare their effects on chip shape and surface integrity characteristics in low speed turning and high speed turning of AA6061-T6. The turning parameters included cutting speed, feed rate, and depth of cut. The flow rates comprised 3.5 $$\mathrm{ml}/\mathrm{min}$$ , 10 $$\mathrm{ml}/\mathrm{min}$$ , and 15 $$\mathrm{ml}/\mathrm{min}$$ , and the surface integrity characteristics consisted of average arithmetic surface roughness, height peak from the valley, and axial and hoop surface residual stresses. The results showed that cutting conditions including cutting speed, feed rate, and depth of cut affected chip shape, while MQL flow rate had no impact on chip shape. The lowest values of cutting speed, feed rate, and depth of cut, equal to 145 $$\mathrm{m}/\mathrm{min}$$ , 0.07 $$\mathrm{mm}/\mathrm{rev}$$ , and 0.66 $$\mathrm{mm}$$ , respectively, resulted in the smallest residual stresses for all the flow rates. Moreover, the smallest surface roughness parameters were obtained at the lowest feed rate (0.07 $$\mathrm{mm}/\mathrm{rev}$$ ) for all the flow rates, whereas there were high interaction effects between cutting speed and flow rate and depth of cut and flow rate. Finally, turning with the minimum quantity lubrications of 3.5 $$\mathrm{ml}/\mathrm{min}$$ and 10 $$\mathrm{ml}/\mathrm{min}$$ , respectively, is suggested to obtain the best overall surface integrity characteristics. These lower values of flow rate are suitable to reduce machining costs, protect the environment, and preserve the machinist’s health. Since most of the previous research studies focused on the comparison of the turning environments including dry, MQL, wet, and cryogenic and only a few research works on the comparative analysis of MQL turning with different flow rates were carried out, the results of the present research can be utilized as a reference for future works in this field.

Experimental investigation of residual stress distribution on girth welds fabricated at proximity using neutron diffraction technique

Maintaining minimum distance between repair and existing welds often becomes impractical due to the presence of compact layouts, original welds of branches, nozzles, etc. on offshore structural elements, pipelines, and piping. Although some international codes and standards provide criteria for maintaining a minimum distance between proximity welds, most of them lack technical justification in relation to their effect on the structural integrity of welded components. The development of residual stresses has a significant effect (i.e., a negative effect on tensile stresses and a positive effect on compressive stresses) on the integrity of the welds fabricated at proximity. Hence, it is important to investigate the residual stress distribution on welds fabricated at proximity, especially at a distance away from the weld toe. This study presents findings on the characterization of residual stresses by neutron diffraction at the proximity region between two girth welds. The two welds were fabricated at proximity, using two different welding procedure specifications and at three different distances, on a structural steel pipe, grade S355. The three different welding distances between weld toes were maintained at 5, 10, and 15 mm respectively. The neutron diffraction-based residual stress distributions were investigated at the POLDI neutron instrument at the Swiss spallation source SINQ in Switzerland. The axial, hoop, and radial components of the residual stresses were experimentally investigated between proximity welds. The findings revealed that residual axial stresses at a 5-mm proximity distance were increased beyond the yield strength of the structural steel, grade S355. The findings of this study enable practitioners to take remedial actions to minimize the residual stresses developed in girth welds fabricated at proximity. Also, the findings enable us to derive technical justification for maintaining a minimum distance and developing welding procedure for welds fabricated at proximity.

Stress assessment and fracture surface analysis in a foreign object damaged 7075-T6 specimen under rotating bending

The damage caused by impact of hard particles on aircraft components is called Foreign object damage (FOD) and it may cause premature failure. 7075-T6 is one of the alloys frequently used for manufacturing aircraft parts and components. In this paper, the failure mechanism of a damaged 7075-T6 specimen subject to rotating bending was explained from a phenomenological point of view using the Finite Element (FE) method and the fracture surface observation. The results showed that the crack initiation occurred in the locations of the highest residual tensile axial stresses after the impact, where also the tensile axial stresses in the simulated fatigue cycle are the highest, and at the surface of the FOD dent. A discontinuity was observed under the dent, in the area subject to compression after the impact and in the fatigue cycle. The damage induces a 30 ± 10% reduction in fatigue strength compared to undamaged specimens.

Effect of thermo-mechanical loading on machining induced residual stresses in ultrasonic vibration assisted turning of Ti6Al4V alloy

The study of residual stresses induced during machining is of considerable importance due to their effect on fatigue life of machined components. The metallurgical changes occurred due to thermo-mechanical phenomenon in cutting process affects the distribution of residual stress in machined components. Ultrasonic vibration assisted turning (UVAT) is effective machining process for low thermal conductivity materials like Ti6Al4V alloy and improves the surface characteristics by reducing cutting force and cutting temperature. In this paper, experimental and finite element (FE) studies are conducted to study the circumferential and axial residual stress distribution in UVAT of Ti6Al4V alloy. FE model is developed to study the effect of vibrating parameter (ultrasonic power intensity) and cutting parameters (cutting speed, feed rate, and depth of cut) on the residual stress profiles of machined surface. The FE simulation results of cutting force and cutting temperature are validated with experimental results. The circumferential and axial surface residual stresses obtained from FE simulation are also compared with experimental results using X-ray diffraction method. The effect of thermo-mechanical loading on residual stress distribution is analyzed with respect to force components (cutting force and feed force) and cutting temperature. Finally, the effect of each cutting parameter on subsurface layer of machined component is analyzed.