Mechanical behavior of an asymmetrically rolled and annealed 1050-O sheet

In this work, 1050-O aluminum alloy sheets are asymmetrically rolled and annealed. The asymmetric rolling process imposes intense shear deformations across the sheet thickness, leading to the development of shear texture and also grain refinement. The shear texture obtained is found to be retained after annealing. The improvements of the mechanical response and the texture evolution after heat treatment processing are inferred based on experimental shear tests and numerical simulations. It is proven that it is difficult to spread shear texture through the entire sheet thickness from a general asymmetric rolling process. Based on the fact, future research is discussed at closure.     

Texture control and grain refinement of AA1050 Al alloy sheets by asymmetric rolling

Asymmetric rolling, in which the circumferential velocities of the upper and lower rolls are different, can give rise to intense plastic shear strains and in turn shear deformation textures through the sheet thickness. The ideal shear deformation texture of fcc metals can be approximated by the {0 0 1}1 1 0 plus 1 1 1ND orientations, among which the latter improves the Lankford values or the deep drawability. The intense shear strains can result in the grain refinement and hence improve mechanical properties. In this paper, a study has been made of effects of asymmetric rolling variables such as reductions per pass, changes in shear direction each pass, reductions in the last pass, roll rotation rate ratios, changes in shear direction in the last pass, and different frictions on the upper and lower surfaces of AA1050 Al alloy sheets on the evolution of their deformation and annealing textures and grain refinement.     

Analysis of ribbed-strip rolling by rigid-viscoplastic FEM

The rolling of ribbed-strips is analysed in the paper using the slightly compressible rigid-viscoplastic finite element method. The energy functional and the rigid-plastic finite element equations for the ribbed-strip rolling process are derived. The simulation results are compared with those obtained by experiments and found to be in good agreement with the latter.     

Lateral-torsional buckling analysis of thin-walled beams including shear and pre-buckling deformation effects

In this paper, lateral-torsional buckling behavior of open-section thin-walled beams is investigated based on a geometrically nonlinear formulation, which considers the effects of shear deformations. A finite element numerical solution along with an incremental-iterative solution procedure is adopted to trace the pre-buckling as well as the post-buckling equilibrium paths. Formulation is applicable to a general type of open-section and load position effects are also included. Numerical results are validated through comparisons with experimental results and those based on other formulations presented in the literature. Comparisons have also been made between the results based on fully nonlinear analysis and linearized buckling analysis in order to illustrate the effects of pre-buckling deformations as well as the shear deformations on the buckling load predictions. Examples illustrate the influence of beam slenderness and moment gradient on the effects of pre-buckling deformations in predicting bucking loads.     

Effects of initial condition of steel plate on welding deformation and residual stress due to welding

The effects of initial deflection and initial residual stress in steel plate on the out-of-plane deformation and residual stress due to welding are investigated from analysis results of thermal elastic-plastic FEM modeling with large deflection theory. Initial residual stress due to plate forming has very little effects on welding deformation and welding residual stress. For initial deflection, with concave profile (Type I), welding induced deformation has the same type as initial deflection and its magnitudes are small. When initial deflection is in the direction parallel to weld Une (Type II), welding induced deformation has minor variations. When initial deflection is bended in the direction normal to weld line (Type III), welding deformation was largely generated along the width direction of the steel plate. On the other hand, the variation in type of initial deflection does not affect the residual stress and plastic strain.     

冷轧钢压印接头拉伸-剪切和疲劳性能研究

对冷轧钢圆形连接点和矩形连接点的压印接头进行拉伸-剪切试验,研究连接点形状对接头拉伸-剪切性能的影响.并对圆形连接点压印接头进行疲劳试验.试验结果表明,两种接头拉伸-剪切强度和刚度相当.圆形连接点拉伸-剪切过程中的能量吸收值大于矩形连接点,矩形连接点的失效形式为上板拉脱失效.应力比R=0.5,当最大疲劳载荷为接头强度的95％时,接头循环寿命可以达到137万次,为80％时,可以达到疲劳极限500万次.疲劳失效形式为上板接头处产生裂纹,裂纹方向与加载方向大致呈90°.提出了圆形点压印接头的拉伸-剪切强度预测公式和疲劳寿命计算公式,拉伸-剪切强度公式的误差为6.9％.     

Analysis and modeling of flexural deformation of laminated steel

Steel/polymer/steel laminate sheets, commonly known as laminated steels, received attention for their superior noise damping properties in automotive applications. Published work indicates that the tensile properties of the laminated steel follow the prediction of the rule of mixtures. The flexural response of the laminated steel, however, depends on the type of the sandwich configuration. The flexural rigidity of the vibration-damping type of laminated steel is lower than the value calculated using beam theory. In industrial scale numerical simulations, automotive body panels are usually represented by using a single layer of shell element. Limited research work on finite element (FE) modeling of laminated steel has indicated that the vibration-damping type of laminated steel is better represented by using two layers of shells. It is logical to relate the simplest FE representation to the way the flexural rigidity of the laminated steel that conforms to the prediction using the beam theory. This paper examines the flexural response of the vibration-damping type of laminated steel through the comparison of beam theory predictions with the experimental results for cantilever beam and three-point bending configurations. It was found that the analytical solution for the split beam is in good agreement with the experimental results. This finding confirms the FE model that represents the vibration-damping type of laminated steel using two layers of shell with tied interface. The simulations using this method yielded good correlations with the experimental results for the two flexural loading cases studied in this paper.     

CO2 laser welding of zinc-coated steel sheets

Welding of zinc-coated steel sheets for the automotive industry has been investigated experimentally and theoretically, using a continuous wave 2 kW CO₂ laser. The specimens of 0.8, 1.0 and 1.2 mm thickness were welded as butt joint and lap joint. Argon gas was shielded co-axially to reduce the plasma and to protect the molten, pool from atmosphere. The mechanical tests of specimens were carried out to investigate the ductility of welds in butt joint and lap joint, using the Erichsen test, ball punch test and tensile shear test. The value of transverse weld pattern is higher than others. The fatigue life of longitudinal weld is superior, but that of circular weld pattern is inferior due to the high tensile residual stresses in the weld. The maximum Erichsen value was obtained as 96% and the deformability of zinc coated steel butt-welded was found to be 80% in the ball punch test. The high pressure formed by vaporization of zinc with the low boiling temperature during laser lap-joint welding splattered the molten pool and created porosities in the weld. The optimum gap was calculated to be 0.1 mm in the lap joint welding of zinc-coated steel sheet which was a good agreement with the experimental result.     

Modeling subsurface deformation induced by machining of Inconel 718

Traditionally, the development and optimization of the machining process with regards to the subsurface deformation are done through experimental method which is often expensive and time consuming. This article presents the development of a finite element model based on an updated Lagrangian formulation. The numerical model is able to predict the depth of subsurface deformation induced in the high- speed machining of Inconel 718 by use of a whisker-reinforced ceramic tool. The effect that the different cutting parameters and tool microgeometries has on subsurface deformation will be investigated both numerically and experimentally. This research article also addresses the temperature distribution in the workpiece and the connection it could have on the wear of the cutting tool. The correlation of the numerical and experimental investigations for the subsurface deformation has been measured by the use of the coefficient of determination, R². This confirms that the finite element model developed here is able to simulate this type of machining process with sufficient accuracy.     

不同变形温度和变形速率对SUS316L不锈钢流变应力及金相组织的影响

通过使用Gleeble-1500热模拟试验机，就不同变形温度和变形速率对SUS316L不锈钢流变应力及金相组织的影响进行了分析，并得到了相关规律。     

Secondary torsional moment deformation effect by BEM

In this paper, a boundary element method is developed for the nonuniform torsion of simply or multiply connected bars of doubly symmetrical arbitrary constant cross section, taking into account secondary torsional moment deformation effect. The bar is subjected to arbitrarily distributed or concentrated twisting and warping moments, while its edges are restrained by the most general torsional boundary conditions. To account for secondary shear deformations, the concept of shear deformation coefficient is used leading to a secondary torsion constant. Four boundary value problems with respect to the variable along the bar primary and secondary angles of twist and to the primary and secondary warping functions are formulated and solved employing a pure BEM approach, that is only boundary discretization is used. The warping and the primary torsion constants are evaluated employing the aforementioned primary and secondary warping functions using only boundary integration, while the secondary torsion constant is computed employing an effective automatic domain integration. Numerical examples with great practical interest are worked out to illustrate the efficiency and the range of applications of the developed method. The influence of the secondary torsional moment deformation effect of closed shaped cross sections is verified, while the accuracy of the proposed numerical procedure for the calculation of the secondary torsion constant compared with a FEM one is noteworthy.     

Influence of deformation path change on static strain aging of cold rolled steel strip

Effect of deformation path change on the static strain aging of low carbon steel was studied in this work. In the first stage, strip samples were subjected to cold rolling processes under different paths with the same total reduction in thickness while the deformation behaviors of the rolled samples were also evaluated using a mathematical analysis. Then, cold-rolled strips were aged in room temperature up to 45?days while hardness and tensile evaluations were performed to assess the mechanical properties of the as-rolled and the aged samples. Finally, the influence of rolling pass schedule on the subsequent strain aging phenomenon was investigated by means of the experimental results and the predictions. The results indicate that rolling path schedule significantly changes plastic strain and residual stress distributions. Furthermore, the kinetics of aging phenomenon also varies after different rolling paths where a schedule containing two-pass reverse layout may result in the fastest aging kinetics.     

底支承对小口径反射镜镜面变形的影响

论述了运用有限元技术研究镜面变形的方法及分析底支承在不同口径，焦比、厚径比和相对支承半径时镜面变形的技术；在取得的相互关联的最大镜面变形数据基础上，研究了影响小口径反射镜底支承镜面变形的因素。     

钢管压力矫直模型有限元分析计算

采用MARC有限元分析方法建立了钢管压力矫直计算模型,应用该模型进行矫直力的计算,解决有限元计算方法在自动矫直机中的应用问题.实例计算表明:该方法与理论计算吻合良好,证实了方法的实用性,为矫直设备向数控化和柔性化发展提供了参考.     

Effects of groove textures on fully lubricated sliding with cavitation

A two-dimensional computational fluid dynamics (CFD) model was developed to investigate the effects of groove textures on fully lubricated sliding with cavitation. The effects of cavitation pressure, sliding speed, sliding pitch angle and texture scale were discussed. It was found that the hydrodynamic pressure effect becomes more pronounced with higher cavitation pressure, and the hydrodynamic pressure decreases with the reduction of the sliding speed. Also with a sliding pitch angle, the hydrodynamic pressure is dependent on both pocket and wedge effects. Increasing groove number and reducing the groove size enhances the overall load capacity, but has a little effect on friction coefficient.     

Inclusion of elastic deformation in rigid-plastic finite element analysis

A rigid-plastic finite element method combined with the effect of elastic deformation is proposed. In the present method, elastically and elastic-plastically deforming elements are mixed with rigid-plastically deforming elements in the deforming material. In this formulation based on an implicit scheme, the nodal forces for the rigid-plastic elements are equilibrated with those for the elastic and elastic-plastic elements at the end of each deformation step. The nodal forces for the elastic and elastic-plastic elements are derived by considering the effect of rigid-body rotation during deformation increment. The elastic-plastic element is transformed into the rigid-plastic one during the loading when the elastic strain increment is small. The reverse transformation is carried out in the unloading. This leads to a comparatively small computing time and the improvement of the calculated results. Plane-strain bending of a plate with a round punch is simulated by the present method under a mixed condition of elastic, elastic-plastic and rigid-plastic elements in the plate. Deformation behaviour in early stages of bending is successfully calculated. The calculated amounts of springback are in reasonable agreement with the experimental ones for aluminium plates because the stress distribution in the elastic regions without achieving yielding around the edges of the plate is taken into consideration.     

An exact solution for buckling of functionally graded circular plates based on higher order shear deformation plate theory under uniform radial compression

In this research, mechanical buckling of circular plates composed of functionally graded materials (FGMs) is considered. Equilibrium and stability equations of a FGM circular plate under uniform radial compression are derived, based on the higher order shear deformation plate theory (HSDT). Assuming that the material properties vary as a power form of the thickness coordinate variable z and using the variational method, the system of fundamental partial differential equations are established. A buckling analysis of a functionally graded circular plate (FGCP) under uniform radial compression is carried out and the results are given in closed-form solutions. The results are compared with the buckling loads of plates obtained for FGCP based on the first order shear deformation plate theory (FSDT) and classical plate theory (CPT) given in the literature. The study concludes that HSDT accurately predicts the behavior of FGCP, whereas the FSDT and CPT overestimates buckling loads.     

光电经纬仪主镜系统自重变形的有限元分析

为了了解主镜整体支撑系统的重力变形情况,采用有限元分析软件,对某光电经纬仪主镜系统进行有限元力学分析,分析在各个倾角状态下主镜镜面自重变形情况,以掌握支撑条件下镜面变形变化规律,供系统光学修正或采用自适应系统的调整机构作用力参考。     

箱型钢结构件焊接变形的控制

箱型钢结构件,焊接施工中既要保证焊接质量,又要控制焊接变形,保证箱型钢结构件的几何尺寸及形位公差。通过工艺分析、反复试验确定合理的施工方案,达到符合GB/T19804几何尺寸A级和形位公差E级、美国石油协会API-4F规范的设计要求,取得满意的效果。     

D2钢轧坯纵裂的分析

分析D2钢轧坯产生纵向开裂的原因。