4032铝合金销轴热挤压成形过程的有限元分析

基于DEFORM-3D有限元分析软件,采用刚黏塑性热力耦合有限元模拟技术,对4032铝合金销轴热挤压成形过程进行了模拟与分析,获得了金属流动、挤压载荷、等效应变以及坯料内部温度等相关场量的变化规律。结果表明：4032铝合金销轴热挤压变形时,坯料心部金属的流动速度大于表层金属;内部变形可分为4个区域,即未变形区、变形区、已变形区和死区;坯料在凹模模口附近变形最为剧烈,挤压载荷急剧增加,等效应变梯度最大,局部温升明显。     

理想弹塑性悬臂梁双重非线性问题的优化算法

研究了理想弹塑性悬臂梁双重非线性变形问题。着重分析了悬臂梁受力变形前后的状态为研究对象,建立结构变形的力学模型,构建端点未知的目标函数,进而确定结构变形的优化问题,通过编制优化程序求解,结合典型案例并同有限元方法的计算结果相比较,验证优化算法的正确性和有效性,从而为理想弹塑性悬臂梁双重非线性分析增加了一种新的处理方法。     

压弯构件的弹塑性分析

在很多弹塑性问题分析中需要随应力状态的变化,不断调整单元刚度矩阵中的有关元素。对于压弯构件,当截面出现塑性时,弹性时期的单元刚度矩阵已经不再适用,即轴力弯距出现耦合现象,需要重新计算本阶段的单元刚度矩阵。可基于截面刚度矩阵以及现有的位移模式推导出弹塑性阶段的单元刚度矩阵。     

采用粘弹塑性模型计算地基的变形

本文认为,当外加荷载小于土的连结强度时,土体表现为弹性,当外加荷载大于土的连结强度时,土体表现为粘弹塑性,故土的力学性质可以采用文献提出的粘弹塑性力学模型来分析。土的连结强度与土体本身的c、φ、σ_3′有关。在此基础上,编制了计算程序,分析了两个例子,结果表明,土体的变形仅限于某一个区域内,采用粘弹塑性力学模型分析地基的变形与实际是比较吻合的。     

铝合金框架结构二阶效应的有限元分析

基于几何非线性和材料非线性,对弱硬化合金和强硬化合金两种典型合金类型的铝合金框架结构进行了一阶弹性分析、二阶弹性分析和二阶弹塑性分析,并与现行《铝合金结构设计规范》(GB50429-2007)中框架设计方法的计算结果进行比较。结果表明,只考虑几何非线性不能真实地反映铝合金框架结构的实际受力情况,材料非线性引起的塑性效应不能忽视,铝合金框架结构设计应进行二阶弹塑性分析。     

弹塑性力学中的体积不可压缩假设及其应用

在弹塑性力学中,“Bridgeman 和其他研究者的试验指出,固体的体积压缩是一种弹性变形,而且体积的相对改变与压力的关系非常接近干线性关系”“物体的密度变化是一种弹     

低脉动液压马达凸轮环变形预补偿优化设计（英文）

目的：内曲线液压马达在重载工况下凸轮环与滚子接触产生的弹性变形,改变了预设的运行轨迹,使得马达产生较大的转速转矩脉动。本文提出一种凸轮环变形预补偿的优化设计方法,在设计阶段耦合弹性变形的影响,以降低马达在实际工作时的脉动,从而提高马达的稳定性。创新点：1.通过赫兹接触理论和马达结构的受力分析,建立凸轮环弹性变形非均匀分布的计算方法;2.建立凸轮环弹性变形预补偿的设计方法,并通过实验进行验证。方法：1.通过理论推导建立凸轮环非均匀弹性变形与工作压力之间的直接关系,基于此提出凸轮环弹性变形预补偿的设计方法,并给出完整的流程与计算方法。2.通过仿真模拟,对凸轮环变形计算进行验证,初步证明所提方法的正确性。3.通过实验验证,对在不同工况下,马达的脉动率进行分析,验证所提方法的有效性。结论：1.提出凸轮环变形预补偿优化设计方法,包括初始的整体补偿和二次局部补偿。2.在对马达进行详细运动学和受力分析的基础上,推导出凸轮环变形的计算过程,并用有限元仿真方法进行实例验证。3.脉动降低率随着工作压力的增加而增加,并且在45 MPa工作压力下可以实现40%的高脉动降低率。     

基于弹塑性理论带肋填砂管桩承载力的研究与应用

带肋填砂管桩是对普通预应力混凝土管桩改进后形成的一种新的管桩应用类型。基于弹塑性理论的带肋填砂管桩沉降计算方法,既考虑桩身在荷载传递作用下的弹性压缩沉降,也考虑桩端以下土层的弹性和弹塑性变形沉降,并给出端阻力和桩侧阻力的分配系数确定方法。根据该模型计算结果,可进一步分析有关数据的特点及其产生的原理。结果表明,该模型的计算结果与实测结果较吻合,具有一定的应用价值。     

一种新型自动润滑装置在液压破碎锤销轴上的应用

当前,液压破碎锤销轴的润滑方式大多为在销轴内部钻打润滑油路,通过压注油杯注入润滑油来达到润滑销轴的目的。润滑油脂棒是一种新型的自动润滑装置,其在液压破碎锤销轴上应用具有环保意义,并且提高了销轴的生产效率。     

圆轴的扭转

根据材料力学对线弹性材料圆轴扭转时应力计算的基本方法，计算一弹／粘塑性材料，塑性强化材料的扭转圆轴的应力与变形，分析了扭转时圆轴的蠕变。     

Stress field near an interface edge of linear hardening materials

The elastic-plastic singular stress field near an interface edge of bounded linear hardening material is substantially as same as that of bonded elastic materials whose Young's modulus and Poisson ratio are substituted by equivalent values, respectively. Further investigation by the elasto-plastic boundary element method (BEM) on the stress field near the interface edge showed that the stress field there can be divided into three regions: the domain region of the elastic-plastic singular stress field, the transitional region and the elastic region. The domain region of the elastic-plastic singular stress becomes larger with the increasing of the linear hardening coefficient. When the linear hardening coefficient decreases to a certain value, the effective stress in most of the yield zone equals approximately the yield stress. The stress distribution in the elastic region under small-scale yielding condition was also investigated. Project (No. 19972060) supported by the National Natural Science Foundation of China.     

Growth of a Void in a Rubber Rectangular Plate under uniaxial Extension

The finite deformation and stress analyses for a rectangular plate with a center void and center void and made of rubber with the Yeoh elastic strain energy function under uniaxial extension were studied in this paper.An approximation solution was botained from the minimum potential energy principle.The num,erical results for the growth of the cavitation and stresses along the edge of the cavitation were discussed.In addition,the stress concentration phenomenon was considered.     

Heat treatment process optimization for face gears based on deformation and residual stress control

In this paper, based on the principle of heat transfer and thermal elastic-plastic theory, the heat treatment process optimization scheme for face gears is proposed according to the structural characteristics of the face gear and material properties of 12Cr2Ni4 steel. To simulate the effect of carburizing and quenching process on tooth deformation and residual stress distribution, a heat treatment analysis model of face gears is established, and the microstructure, stress and deformation of face gear teeth changing with time are analyzed. The simulation results show that face gear tooth hardness increases, tooth surface residual compressive stress increases and tooth deformation decreases after heat treatment process optimization. It is beneficial to improving the fatigue strength and performance of face gears.     

Pure bending of simply supported circular plate of transversely isotropic functionally graded material

INTRODUCTION In recent years, functionally graded materials (FGMs) have attracted more and more attention. Due to their continuously varying material properties in space on the macroscopic scale, FGMs, therefore, are usually superior to conventional fiber-matrix materi-als in mechanical behavior, especially for perform-ance under thermal loading. Now FGMs have been widely used in various fields including electronics, chemistry, optics, biomedicine, etc. Heretofore, volumes of literatu…     

巷道围岩松动圈弹塑性分布探讨

巷道掘进工作破坏了周围原岩应力分布产生了松动圈,对松动圈弹塑性应力分布和范围进行理论分析,得到松动圈弹塑性应力分布半径并进行了讨论。     

随机荷载作用下梁的弹塑性极限分析

讨论了随机荷载特性与结构弹塑性极限分析的基本假设，基于机动法和静力法，对矩形截面梁的随机弹塑性极限分析进行了研究，其结果对结构随机优化设计具有重要意义。     

板材激光弯曲成形规律的研究

本文用大变形弹塑性有限元法对金属板材柔性成形新工艺——激光弯曲进行了动态数值模拟。从热力学的观点出发，阐明了该工艺的变形机理；论证了板材厚度和光束移动速度对温度梯度和弯曲角度的影响，为该工艺进一步深入研究奠定了基础。模拟结果与试验吻合较好。     

H_2S Stress Corrosion Tests of Welded Joint for X65 Pipeline Steel and Finite Element Numerical Analysis of Crack Tip

Theresistanceofapipelinesteeltohydrogensulfidestresscorrosioncracking (SCC)andhydrogen inducedcrack ing (HIC)isveryimportantforsteeltobeusedinsouroil/gasapplications.ElongatedMnSinclusionsarethemostsus ceptiblesitesforHICinitiation[1] ashydrogenatomscaneasi lyaccumulateattheinterfacebetweenthesteelmatrixandnon metallicinclusions.ThesegregationofsuchelementsasP ,Mn ,Cinthesteelenhancestheformationofhardbandsoncooling[2 ] .Theexistenceofthebandingstructurenotonlydecreasestheresistanceofthe…     

Finite element modeling of superplastic co-doped yttria-stabilized tetragonal-zirconia polycrystals

Yttria-stabilized tetragonal-zirconia polycrystals (Y-TZP) have been shown to have superplastic properties at high temperatures, opening a way for the manufacture of complex pieces for industrial applications by a variety of techniques. However, before that is possible, it is important to analyze the deformation and fracture mechanisms at a macroscopic level based on continuum theory. In this paper, an elastic-plastic material model with a theoretical large deformation is constructed to simulate the true stress-true strain relationships of superplastic ceramics. The simplified constitutive law used for the numerical simulations is based on piecewise linear connections at the turning points of different deformation stages on the experimental stress-strain curves. The finite element model (FEM) is applied to selected tensile tests on 3-mol%-Y-TZP (3Y-TZP) co-doped with germanium oxide and other oxides (titanium, magnesium, and calcium) to verify its applicability. The results show that the stress-strain characteristics and the final deformed shapes in the finite element analysis (FEA) agree well with the tensile test experiments. It can be seen that the FEM presented can simulate the mechanical behavior of superplastic co-doped 3Y-TZP ceramics and that it offers a selective numerical simulation method for advanced development of superplastic ceramics.     

Use of Plastic Correction Formula to Improve Accuracy of Welding Residual Stress Test with Blind-Hole Method

The blind-hole method is the most widely used approach to experimentally determine the distribution of residual stress. This paper aims to improve test accuracy of welding residual stress and conducts an experimental study on the strain release factors involved when using the blind-hole method for Q235 and Q345, two steels commonly used in building structures. The ranges of strain release factors A and B in the elastic stage, the effects of strain release factors on residual stress calculated values, and the plastic corrected strain release factors are analyzed considering of the effect of plastic deformation around the blind hole on measurement accuracy. Finally, a simplified calculation formula to determine strain release factors is proposed for use with the blind-hole method. Results show that in the elastic stage, strain release factor A for Q235 and Q345 ranges from-0.399 to-0.525 and strain release factor B from-0.791 to-0.960. Changing the strain release factors A and B shows that calculated residual tensile stress varies in relation to a decrease in both factor values. However, there is a increase in calculated residual compressive stress with a decrease in the strain release factor A value, but there is an decrease with a decrease in strain release factor B value. Calculated residual stress applied to elastic strain release factors is compared with that applied to amended plastic strain release factors for Q235 steel. The maximum deviation between calculated residual stress and test stress is reduced from 21.1 to 1.0%,and for Q345 steel from 26.5 to 1.2%. It is thus evident that the plastic correction formula proposed in this paper can be used in calculations when conducting a residual stress test.