Circumferential Residual Stress Research Articles

Optimization of machining parameters applied in hard turning of large components for cooling lubrication methods

The increasing demands concerning renewable energy have required ever-bigger projects, as seen with wind turbine cases; in these large projects, the surface contact presents high load and wear resistance requirements. The cooling and lubrication methods in machining are highlighted due to the reduction of costs and environmental impacts. In functional hardened surfaces, it is critical to understand the integrity aspects once they significantly affect the durability of the component. This work clarifies, how the machining parameters of feed, depth of cut, velocity of cut, minimum quantity of lubrication, and abundant cooling affected the machined surface in a large component, with a discussion about microstructural altered layer, residual stresses, and Sa, Sq, and Sz statistical parameters. The results indicated that the minimum quantity lubrication and abundant cooling produced highly compressive circumferential residual stresses. Both methods produced surfaces free of significant microstructure altered layers. The altered surface layer was very thin when detected, with a thickness of up to 2.35 µm. On optimal conditions, the minimum quantity lubrication, in relation to abundant cooling, presented residual stresses 37% higher, a thickness of altered layer 74% lower, and Sa and Sz roughness, respectively, 47% and 11% lower and Sz 12% higher.

Orientation and Residual Stress Distributions in Thick Melt Spun Polystyrene and Polycarbonate Filaments

Abstract A study of orientation development and residual stresses in thick melt spun polystyrene filaments and polycarbonate filaments described. Linear relationships between spinline stress and mean birefringence under different melt spinning conditions were obtained. These results were used together with models of the dynamics of melt spinning to predict the characteristics of thick melt spun filaments. Birefringence distrbutions and residual stresses were computed. High orientations and compressive circumferential residual stresses were predicted at the larger radii and low orientation and tensile circumferential and radial residual stress in the fiber core are obtained. The distribution of birefringence across the thickness of thick melt spun filaments was measured by determining changes of retardation across a wedge. The birefringence distributions were correlated with severity of quench and model prediction. Thick melt spun fibers were peeled and found to have fibrillar cores.

A biodegradable magnesium alloy vascular stent structure: Design, optimisation and evaluation

The existing biodegradable magnesium alloy stent (BMgS) structure is prone to problems, such as insufficient support capacity and early fracture at areas of concentrated stress. Herein, a stent structural design, which reduced the cross section of the traditional sin-wave stent by nearly 30% and introduces a regular arc structure in the middle of the support ring. The influence of the dual-parameter design of bending radius (r) and ring length (L) on plastic deformation, expansion and compression resistance performances are discussed. The non-dominated sorting genetic algorithm II (NSGA-II) was used to search for the optimal solution. It was found that the introduction of parameter r effectively improved the plastic deformation and expansion performance, and the reduction of L improved stent compression resistance. Finally, an optimized stent configuration was obtained. In vitro mechanical tests, including balloon inflation, radial strength and flexibility, verified the simulation results. The radial strength for the optimised stent increases by approximately 40% compared with that for the sinusoidal stent. Microarea X-ray diffraction result shows that the circumferential residual stress for the optimised stent decreases by half compared with that for the sinusoidal stent, thus effectively reducing the stress concentration phenomenon. Statement of significanceDespite current progress in BMgS research, the optimal design of the structure is limited. We present a new type of structurally designed stent. The performance of this stent was analysed by a finite element method and experimentally verified. The structural design positively influenced stent performance.

Intramural Distributions of GAGs and Collagen vs. Opening Angle of the Intact Porcine Aortic Wall.

The heterogeneity and contribution of collagen and elastin to residual stresses have been thoroughly studied, but more recently, glycosaminoglycans (GAGs) also emerged as potential regulators. In this study, the opening angle of aortic rings (an indicator of circumferential residual stresses) and the mural distributions of sulfated GAGs (sGAG), collagen, and elastin were quantified in the ascending, aortic arch and descending thoracic regions of 5- to 6-month-old pigs. The opening angle correlated positively with the aortic ring's mean radius and thickness, with good and moderate correlations respectively. The correlations between the sGAG, collagen, elastin, and collagen:sGAG ratio and the opening angle were evaluated to identify aortic compositional factors that could play roles in regulating circumferential residual stresses. The total collagen:sGAG ratio displayed the strongest correlation with the opening angle (r = -0.715, p < 0.001), followed by the total sGAG content which demonstrated a good correlation (r = 0.623, p < 0.001). Additionally, the intramural gradients of collagen, sGAG and collagen:sGAG correlated moderately with the opening angle. We propose that, in addition to the individual role sGAG play through their content and intramural gradient, the interaction between collagen and sGAG should be considered when evaluating circumferential residual stresses in the aorta.

РАСЧЕТНОЕ ПРОГНОЗИРОВАНИЕ ТЕХНОЛОГИЧЕСКИХ ОСТАТОЧНЫХ ДЕФОРМАЦИЙ ЛОПАТОК ГТД НА ЭТАПЕ КОНЦЕВОГО ФРЕЗЕРОВАНИЯ

The article presents a technique that makes it possible to predict the technological residual deformations of GTE blades obtained at the stages of end milling as a result of the effect of residual stresses. The first part of the technique makes it possible to determine the magnitude, bijugat and character of the residual stresses distribution formed in the surface layer of the workpieces in the operations of end milling. The adequacy of the technique was verified by investigating the convergence of the numerical computation results with the results of field experiments. As a result of the research, a power-law dependence was obtained, which makes it possible to determine the value of the maximum circumferential residual stresses depending on the parameters of the end milling processing mode. The second part of the technique makes it possible to determine the residual deformations of the GTE blade based on the residual stress distribution diagrams obtained when using of the first part of the technique or obtained on the basis of field experimental investigations. Also, power-law dependences are obtained in this work, which make it possible to determine the value of the maximum deviations of the control sections of the investigated GTE blade, depending on the parameters of the end milling mode.

Nature of metal drop displacement during deposit welding elements of railway transport

The transformation of the microstructure of the heat-strengthened steel 65G section deposited with an electrode with a low-carbon rod is complex. Increased hardness values of individual areas contribute to an increase in the abrasive wear resistance of the part. The presence of a fusion zone ensures the resistance of the deposited area of an element on railway transport to cracking. The use of electrodes with a low-carbon rod is advisable when carrying out surfacing reinforcement of heat-hardened steels. The authors obtained mathematical expressions for the speed of displacement of a metal drop falling from the electrode material and the path it traverses when deposit welding elements on railway transport. They show that the displacement of this drop is accompanied by acceleration followed by deceleration. In electromagnetic deposit welding, the experimental assessment of the level of circumferential and radial residual thermal stresses during deposit welding of a coating on a hollow cylinder is of considerable practical interest. As an example, the calculation and experimental analysis of the stress state during deposit welding of the cylinder on the inner surface is made. He showed that residual compressive stresses, significant in magnitude, are formed on the outer surface. The method, which is limited to cutting the cylinder along the generatrix, without subsequent layer-by-layer removal of metal from its inner surface, is a simple and effective method for determining the circumferential residual stresses that provides the required accuracy.

A study on strengthening and machining integrated ultrasonic peening drilling of Ti-6Al-4V

In aircraft assembly filed, introducing compressive residual stress by cold expansion around the fastening hole is considered as a common method to enhance hole fatigue resistance. However, the conventional cold expansion technology inevitably extends the processing cycle of fastening hole. Therefore, this study proposes a strengthening and machining integrated ultrasonic peening drilling (UPD) to solve this problem by introducing ultrasonic vibration perpendicular to the hole surface during drilling. Both the strengthening principle and dimension accuracy improvement mechanism in UPD were analyzed to better understand the cutting mechanism. The feasibility experiments of UPD of Ti-6Al-4V were conducted to evaluate surface integrity and machining accuracy. The results show that compared to conventional drilling (CD), smoother machined surface and narrower dimensional tolerance were obtained with UPD. Moreover, the subsurface plastic deformation was increased by as high as 4 times with severer deformation degree. Accordingly, the surface residual stress and the depth of circumferential residual stress in the subsurface was increased by 115.7% and 125% respectively. In addition, surface micro-hardness and subsurface hardening layer depth were also significantly increased. The results demonstrated that UPD achieved the integration of strengthening and precision-machining and could be a promising method for finish drilling of aircraft fastening holes.

Residual stress analysis and measurement in multi-layer bellows

Because large plastic deformation occurs in hydroforming bellows there is a residual stress distributing in the metal after forming, which is complex and not easy to be measured. The existence of residual stress might have an effect on the corrosive property and bulking performance of bellows. A finite element model was established to simulate the forming residual stress of the nickel alloy multi-layer bellow. The distribution of residual stress was calculated out and validated by cosα X-ray diffraction measurement. Thus the forming mechanics and the effects of layer number and forming pressure on the residual stress in the hydroforming bellow were both discussed in detail based on the established model. It was shown that the calculated residual stress had the same trend with the experimental results. The axial and circumferential residual stresses at the outer surface of the peak were both compressive. There existed the maximal Von Mises stress at the inner surface of the peak of the bellow. At this position the radial and axial residual stresses were both tensile. When applying multi-layer bellows and less forming pressure a lower forming residual stress could be obtained because of the narrow plastic strain region during forming.

Analysis and Control of Cracking and Wrinkling at the End of Seamless Steel Tube with Multi-Pass Large Deformation Diameter-Reducing

Axial cracking and circumferential wrinkling are found at the end of seamless steel tubes during multi-pass large deformations pushing diameter-reducing (PDR), which seriously affects product quality. However, the cracking and wrinkling mechanism of PDR has not been elucidated yet. In this paper, the Equation of circumferential residual stress at the end was deduced from the warping deformation and shear stress. It is revealed that the circumferential residual stress in the end warping area from the inner to outer surface is tensile, and the generation mechanism of circumferential wrinkling on the inner wall at the end was revealed through the deformation analysis of PDR. The geometric model of the tube with periodic alternating variation of wall thickness was established to reveal the generation and development of circumferential wrinkling. In addition, the four-pass PDR experiments and simulations were developed to reveal the influence of reducing pass and wall thickness deviation on the end warpage, unevenness and circumferential residual tensile stress. The pushing-pulling diameter-reducing (PPDR) method was proposed to control the wrinkling and cracking. The simulation and experimental results showed that the end warpage, unevenness and circumferential residual tensile stress are all greatly decreased, and the risk of axial cracking and circumferential wrinkling is eliminated.

In-Situ Measurement of Residual Stress in Solid Oxide Fuel Cells

Introduction Solid oxide fuel cells (SOFCs) are attracting attention as highly efficient energy conversion devices. However, durability and mechanical reliability are issues. To improve durability and mechanical reliability, it is essential to evaluate the residual stress generated in the constituent materials, especially the residual stress generated in the electrolyte. While residual stress is measured by various methods, the optimum measurement method has not been established yet. The purpose of this study is to evaluate the residual stress of the cell using in-situ cosα method, which has an advantage in measurement speed and easy handling. Experiment method High-temperature x-ray stress measurement was performed as a quantitative evaluation method for mechanical behaviors. A portable X-ray residual stress measuring device μ-X360s manufactured by Pulstec Industries was used. The cos α method, which is faster and easier than the sin2ψ method, was used for high-temperature X-ray stress measurement. In the cosα method, the Debye ring is acquired by a two-dimensional detector, and the stress is calculated from the difference between the stress-free Debye ring and the Debye ring of the measurement sample. High temperature chamber was designed and prepared for high temperature x-ray stress measurement. A capton film is used to separate outside and measurement atmosphere. In addition, the measurement position can be adjusted by moving stage.Commercial sofc cells (Ningbo SOFCman cell and Elcogen) were used to compare the residual stress during the various operation procedures. Results and discussion Fig. 1 shows the difference in change in residual stress of YSZ electrolyte depending on the structure of the anode. Anode of Ningbo SOFCman cell has small porosity, while anode of Elcogen cell has large porosity. We measured changes in residual stress during heating, anode reduction, and reoxidation processes.The Elcogen cell was reduced much faster than Ningbo cell, because hydrogen gas can diffuse more easily in anode due to higher porosity. Therefore, residual stress of Elcogen cell steeply changed after hydrogen introduction. Then, the residual stresses after anode reduction were completely different in these two cells at room temperature. Compressive stress of 800 MPa remained in the electrolyte of Ningbo cell. On the other hand, less compressive stress of 400 MPa remained in the electrolyte of Elcogen cell. The temperature dependence of residual stress is also different in the two cells. The deformation of the cell after reoxidation was also completely different. Ningbo cell was deformed convexly toward the anode side, although Elcogen cell was hardly deformed. The difference may come from the difference in porosity of anode.Fig. 1 Circumferential residual stress of YSZ during reoxidation heating in 20％O2-N2 and SEM images of anode structures. Figure 1

Analysis of Residual Stress Distribution in Rods after Drawing Process with Regard to Process Variables

Currently, many researchers pay attention to studying the influence of process variables on the quality of metal products after manufacture. The most common methods of metalworking are forming processes, in which a high degree of deformation, uneven plastic deformation, and elevated temperatures are utilized. In most cases of manufacturing using these methods, a self-balanced system of residual stresses is formed that significantly affects the accuracy, strength, durability, reliability, corrosion resistance, and fatigue strength of machine parts after manufacture and processing. At the same time, the level of technological residual stresses depends on the main process variables. And in this regard, the analysis of the residual stress calculation for the deformation of rods will identify the effect of process variables, mechanical properties of the material, the geometry of the workpiece on the level and distribution of formed residual stresses. The object of the study is distributions of residual stresses formed after plastic deformation in rods and wire. In the work, experimental data on the distribution of residual stresses in rods after drawing were investigated. The residual stress calculation method takes into account parameters of technology, geometry and mechanical constants of material. Dependencies of axial and circumferential residual stresses in steel rods and wires after drawing were found.

Influence of boss-backing welding to ERW pipe

Station and valve chamber design often encounter the situation of drilling hole at the main pipeline and welding boss-backing to connect the branch pipe. Boss hole location should generally be at least 100 mm away from the longitudinal weld or spiral weld. However, because the electric resistance weld (ERW) is difficult to distinguish in practice, some bosses mounting position coincide with ERW or close to. In this paper, the influence of boss-backing welding directly on the longitudinal weld to the original residual stresses of ERW pipe was studied. The microstructure of pipe body and longitudinal weld after welding was also analysis. The testing results showed that the overall residual stresses of ERW pipe were relatively small. Residual stress at the longitudinal weld region were smaller than those at the pipe body region. After the boss-backing welding, the axial residual stress at the longitudinal weld and the circumferential residual stress at the pipe body region near the intersection increased sharply to 2.5 (444 MPa) and 3.8 (433 MPa) times, respectively. The invaded width and depth to the ERW pipe after welding were about 15.167 mm and 3.376 mm. Granular bainite with necklace type M-A constituents could be observed at the invaded zone. It is suggested that small welding heat input should be adopted for boss-backing welding.

Bifurcation analysis of elastic residually-stressed circular cylindrical tubes

The theory of superimposed incremental elastic deformations is applied to a deformed configuration of a residually-stressed circular cylindrical tube. The tube is subject to internal or external pressure and an axial load that maintain its circular cylindrical shape, and then bifurcations from this shape are analysed. Detailed governing equations and boundary conditions are provided for axisymmetric, prismatic and asymmetric bifurcations for a general form of strain–energy function that incorporates radial and circumferential residual stress components. The theory is applied to a simple model strain–energy function with two material parameters and a parameter that reflects the magnitude of the residual stress. Numerical computations are used to illustrate the dependence of the results of the bifurcation analysis on these parameters and the axial and radial underlying deformation. It is shown that in general the presence of residual stress has a significant effect compared with the corresponding results without residual stress.

The effect of residual stress on the stability of a circular cylindrical tube

Residual stresses in an unloaded configuration of an elastic material have a significant influence on the response of the material from that configuration, but the effect of residual stress on the stability of the material, whether loaded or unloaded, has only been addressed to a limited extent. In this paper we consider the level of residual stress that can be supported in a thick-walled circular cylindrical tube of non-linearly elastic material without loss of stability when subjected to fixed axial stretch and either internal or external pressure. In particular, we consider the tube to have radial and circumferential residual stresses, with a simple form of elastic constitutive law that accommodates the residual stress, and incremental deformations restricted to the cross section of the tube. Results are described for a tube subject to a level of (internal or external) pressure characterized by the internal azimuthal stretch. Subject to restrictions imposed by the strong ellipticity condition, the emergence of bifurcated solutions is detailed for their dependence on the level of residual stress and mode number.

Prediction of residual stresses in turning of pure iron using artificial intelligence-based methods

Residual stresses (RS) induced in machined components have substantial impact on the quality and lifetime of the final products. There are several cutting parameters and conditions that affect the generation of RS, so understanding the relationship between the RS generation and those parameters to minimize the induced tensile RS is a crucial issue. This paper presents a study on the utilization of artificial intelligence-based methods to model the RS generation during dry turning of DT4E pure iron. The experiments were designed based on central composite design method. The effects of the cutting parameters such as cutting speed, feed and cutting depth on the generated RSes in both circumferential and radial directions are investigated. Two hybrid artificial neural network (ANN) models are used to predict the process responses after training them using the experimental results. The prediction accuracy of the two models are enhanced via integration with two different metaheuristic optimization algorithms, namely particle swarm optimization (PSO) and flower pollination algorithm (FPA). These optimization algorithms are used as subroutine algorithms to determine the optimal parameters of the ANN model. The predicted results by the proposed models were compared with the experimental results as well as those obtained by standalone ANN. The accuracy of all models was evaluated using different statistical measures. The ANN-FPA had the best prediction accuracy followed by ANN-PSO. The coefficient of determination of ANN-FPA has high values of 0.996 and 0.997 for radial RS and circumferential RS, while they were 0.971 and 0.992 for ANN-PSO and 0.649 and 0.815 for standalone ANN.

Numerical Determination of the Circumferential Residual Stress of Porcine Aorta by Pulling-Back Method

Residual stress is very important for the study of cardiovascular-relevant issues, such as assessing the vulnerability of atherosclerosis and aneurysm. In this paper, the circumferential residual stress of porcine aorta was characterized by combining ex vivo experiments with numerical studies. In the experiments, porcine aortic rings were prepared and cut open, and the cross sections of the opened aortic rings were extracted to construct finite element models. The 5-parameter Mooney–Rivlin model was chosen to describe the tensile mechanical behavior of the aorta. In numerical studies, based on the finite element models and hyperelastic material model, a pulling-back displacement was applied to reclose the models of the opened aortic rings, and the equivalent circumferential residual stress to the pre-opened aorta was analyzed. The results showed that the circumferential residual stress of the aorta generally decreased from the proximal to the distal ends, and the residual stresses of the aortic rings close to the distal end did not show a great difference. This work provides an improved understanding of the residual stress distribution in aorta and may be used as a more realistic initial condition for future stress analysis of the arterial tissue.

Influence of expansion rate on circumferential residual stress distribution of expandable casing

To study the distribution law of circumferential residual stress after casing expansion, using the finite element explicit dynamic analysis method analyzed the expansion process of expandable casings under different expansion rates. The analysis obtained key technical parameters of circumferential residual stress, average circumferential residual stress and elastic recovery along the wall thickness direction after casing expansion. It is recognized that the maximum residual tensile stress after casing expansion locates in the middle part of the casing thickness direction. The maximum residual compressive stress locates in the outer wall of the casing. When the expansion rate exceeds 18%, the increase in expansion rate will not lead to an increase in circumferential residual stress after casing expansion. The elastic recovery after casing expansion will reduce the circumferential stress during the expansion process. Considering collapse strength and the influence of elastic recovery on casing patch sealing performance after casing expansion, 23% is the most suitable expansion rate, which can effectively reduce the circumferential residual stress and improve the casing collapse strength. The analysis in this paper can provide bases for the calculation of casing collapse strength after expansion.

ИССЛЕДОВАНИЕ ФОРМИРОВАНИЯ ОСТАТОЧНЫХ НАПРЯЖЕНИЙ ПОСЛЕ УПРУГОПЛАСТИЧЕСКОЙ ДЕФОРМАЦИИ СТЕНОК ТРУБЫ ИЗ ДИСПЕРСНО-УПРОЧНЕННОГО АЛЮМИНИЕВОГО СПЛАВА В РЕЗУЛЬТАТЕ ВОЗДЕЙСТВИЯ ВНЕШНЕГО ДАВЛЕНИЯ

The formation of residual stresses after elastic-plastic deformation of pipe walls as a result of external pressure is studied using the approach based on a combination of methods of the physical theory of plasticity and mechanics of a deformable solid. As a result of the research, it is found that at the same value of the applied pressure, the thickness of the area subjected to plastic deformation is less for the alloys reinforced with large particles than for those reinforced with small particles. The values of the circumferential and axial residual stresses exceed the value of the radial residual stresses by more than an order of magnitude. Therefore, in the first approximation, the radial residual stresses can be neglected.

Effect of laser scanning speed on the thermal-mechanical coupling field of laser remelting of valve seat

A numerical simulation model for the thermal-mechanical coupling of laser remelting of valve seat was established. The changes of thermophysical properties of the material with temperature, latent heat of phase transformation, and the absorption rate of laser energy on the surface of the material were considered in the model. The results showed that as the laser scanning speed increased, the maximum temperature and the area of the molten pool decreased, and the cooling rate of the molten pool increased. In the laser irradiation area, the temperature gradient in the molten pool decreased and the temperature gradient in the phase transformation region near the molten pool increased. When the laser scanning speed was increased from 1 mm/s to 4 mm/s, the circumferential residual stress was increased from 132 MPa to 183 MPa, and the radial residual stress was increased from 20 MPa to 51 MPa. In the laser remelting process, there was a competitive relationship between the increase in the deformation trend caused by the increase in the temperature amplitude and the decrease in the deformation constraint due to the decrease in the temperature gradient, resulting in a reduction in the residual stress accompanying the decrease in the laser scanning speed. The change trend of the simulation results was basically consistent with the experimental results, which showed the effectiveness of the simulation model.

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.