盘式刹车片的固有频率分析

对盘式刹车片的固有频率进行理论分析,并通过半金属刹车片和新型刹车片的计算实例对理论分析结果进行验证。从分析结果可以看出,摩擦材料的比模量对刹车片固有频率有重要影响,摩擦材料的比模量越高,盘式刹车片的各阶固有频率就越高。     

根据不同模量弹性理论设计铸铁液压缸壁厚

根据不同模量弹性理论,推导出不同弹性模量材料圆筒承受均匀分布内压的应力解答,并应用莫尔强度理论对铸铁液压缸的壁厚进行了计算.     

不同模量结构温差应力的解析法及数值模型

随着科学技术的不断发展,工程中许多材料具有拉压不同模量性质,特别是近年发展起来的复合材料,其拉压模量之比高达4倍以上,经典力学中的相同模量本构关系已不能完全反映材料的力学行为。文中用流动的坐标体系及分段积分方法推导出不同模量结构的中性层计算表达式,编制温差内力的非线性迭代程序。为工程应用中计算不同模量结构提供一种简捷有效的解析一迭代法,并同时建立有限元数值计算模型。通过对同一实例的计算及分析,得出不同模量与经典力学相同模量两种方法计算结构内力的差异较大,最后提出对该类结构计算的合理建议以及利用不同模量优化结构的思想。     

基于均匀化理论粘弹性复合材料松弛规律的研究

基于均匀化理论研究了粘弹性复合材料的松驰规律,推导出了均匀化方法计算等效松驰模量的一般形式。在Laplace域中计算等效松弛模量,并用最小二乘法拟合Prony级数表示的松弛函数,然后在时间域中进行数值的Laplace逆转换,得到时间域内等效复合模量。给出了算例来验证这个计算方法的可行性并讨论了松弛模量随夹杂体积分数变化的规律。     

三维编织C/SiC复合材料弹性常数预报

基于纤维倾角模型 ,根据层合板理论推导出其弹性常数计算公式。三维编织C/SiC复合材料不同于树脂基复合材料 ,一是纤维模量低于基体模量 ,二是碳纤维在高温沉积热解碳和碳化硅后模量有较大幅度的下降 ,还有较多的空洞存在。考虑到这些因素对三维编织C/SiC复合材料弹性性能的影响 ,编制了相应的C语言计算程序 ,预报了三维编织C/SiC复合材料的纵向弹性性能 ,对程序计算结果进行了分析讨论。另外 ,通过力学实验来验证了理论分析的可靠性。     

超弹性蒙皮蜂窝芯的设计及等效模量研究

可变形机翼的蒙皮需要有很高的各向异性,在特定方向具有较低的弹性模量而在其他方向具有较高的气动承载能力,为此设计了一种柔韧性较好、特定方向模量低且承载能力较强的新型超弹性蒙皮结构,对其蜂窝芯单元的力学性能进行了理论计算和有限元分析,并对不同几何参数单个蜂窝芯单元体和多个蜂窝芯单元体进行了轴向刚度测定试验,最后通过理论仿真和试验的对比分析,得到了该超弹性蒙皮蜂窝芯结构轴向刚度的等效模量近似工程计算公式。
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短玻璃纤维增强PA66的偏轴拉伸模量和强度研究

对含30%质量分数短玻璃纤维注塑增强PA66材料,按照与注塑方向成0°、30°、45°、60°和90°裁取试验件,进行偏轴拉伸试验,得到了5组试验件的载荷-位移曲线、拉伸模量和拉伸强度。应用45°偏轴拉伸测定了材料的剪切弹性模量。通过对偏轴拉伸模量和强度对比,以及应用复合材料计算剪切模量的结果对比应用各向同性计算的结果,证明了短纤维复合材料并不能当做传统各向同性材料来处理分析,是具有各向异性的材料。分析表明,连续纤维偏轴拉伸模量计算方法对于短纤维复合材料仍然适用,蔡-希尔失效判据也能较好的适用于这种材料。从试验结果和偏轴模量以及强度计算发现,60°是最差承载角。     

三维编织C/SiC复合材料剪切和弯曲性能的实验研究

对三维编织C/SiC复合材料进行剪切试验和两种弯曲试验,得到材料的剪切性能和弯曲性能以及相应的失效规律.在剪切试验中发现两种剪切试验的剪切模量相差较大,但由于两种剪切的破坏面相同,所以剪切强度相差不大.通过分析得到由两种弯曲试验获得的弯曲模量不同的原因.通过分析还得到拉压模量不同的材料的四点弯曲模量计算公式,发现计算值在试件上下表面应变相差不大时与均质材料的计算结果相差不大.     

有限元求解精度研究

首先对一实例进行理论计算,然后对其进行有限元分析,并对不同网格划分状态下的模型计算结果与理论结果进行比较。最后对有限元分析误差进行评估及原因分析,并得出有限元分析计算时网格划分并不是越细小越好,关键是＂适度＂的结论。     

提高国产DM-1型动态模量仪测量精度的分析研究

本文对国产 DM-1型动态模量仪测量精度较低的原因进行了较详细的理论分析和试验研究。对其理论计算式中形状因子的取值问题进行了分析与修正;对有关仪器参数的标定,指出应该从动态观点出发,进行动态标定。测量结果说明了理论分析和实测结果吻合较好,从而证明理论分析是正确的,表明改进后的 DM-1型模量仪的测量精度水平与国外先进仪器的水平相当接近,从而把 DM-1型动态模量仪由一台测量精度较差的仪器改进成为精度较高而实用的仪器,为该仪器正式投产和批量生产提供了理论和试验依据。     

Elastic–plastic response of unpressurised pipes subjected to axially-long radial indentation

Elastic–plastic force-deflection analysis of unpressurised pipes with long axial indentations are carried out. Solutions from an analytical method are compared to the corresponding finite element solutions and experimental test results. The analytical method is based on a simple energy-based approach developed to predict the initial gradients of the force-deflection curves and the limit loads of the indented rings using linear beam bending theory and upper bound theories. A comprehensive finite element study of indented unpressurised pipes is performed to study their sensitivities to the elastic–plastic responses. The finite element analysis covers six different materials, four different geometries and two different boundary conditions, and is compared with the corresponding analytical solutions. The results presented in this paper indicate that by using the analytical solutions for limit loads incorporating a representative flow stress as the average value of the yield stress and ultimate tensile stress, it is possible to obtain reasonably accurate predictions for the peak loads.     

负泊松比可变弧角曲边内凹蜂窝结构的力学性能

在环形蜂窝结构的基础上,提出了一种具有负泊松比效应的可变弧角曲边内凹蜂窝结构。分析了刚架结构的弯曲内力,利用能量法给出了曲边内凹蜂窝结构的横/纵向等效弹性模量和等效泊松比的解析公式。当弧角为180°时,所提出的曲边内凹蜂窝结构可退化为已有的环形蜂窝结构。所得解析解、已有理论解和有限元结果三者有较好的吻合度,表明了所提出方法的有效性。基于所得解析解讨论了微结构几何参数对等效弹性模量和等效泊松比的影响,研究结果表明：等效弹性模量受弧角的影响显著;等效泊松比受弧角、竖直壁板长度和两竖直壁板间宽度的影响较为明显,而受连接部分长度的影响不明显。     

双层缩套厚壁筒自增强残余应力分析

基于ANSYS平台,使用APDL语言开发了双层缩套厚壁筒自增强残余应力求解参数化有限元接触模型。考虑缩套预应力的影响,基于理想弹塑性材料模型和Mises屈服准则,推导出了双层缩套厚壁筒自增强残余应力解析解,并将其有限元分析值和解析解进行了比较,有限元分析值与解析解在屈服区结果一致,而在弹性区略有差别,与已有的解析解相比,由于考虑了缩套初始预应力对自增强处理过程应力状态的影响,其残余应力有限元模型的仿真结果和解析解都具有更高的精度。     

Elastic lateral-torsional buckling of circular arches subjected to a central concentrated load

An arch under an in-plane central concentrated radial load is subjected to combined axial compressive and bending actions. When these combined axial compressive and bending actions reach a certain value, the arch may suddenly deflect laterally and twist out of its plane of loading and fail in a lateral-torsional buckling mode. This paper derives analytical solutions for the elastic lateral-torsional buckling load of pin-ended circular arches that are subjected to a central concentrated load, using the principle of stationary potential energy in conjunction with the Rayleigh-Ritz method. Analytical solutions of the buckling load for in-plane fixed and out-of-plane pin-ended arches and for the case of the load acting above or below the shear centre are also derived. The analytical solutions are compared with results of a commercial finite element package ANSYS and a finite element code developed by authors elsewhere for arches with different slendernesses, included angles, and cross-sections. The agreement between the analytical solutions and the finite element results is very good.     

MANUFACTURING PROCESSES AND EQUIPMENT

ABSTRACT

For the past fifty years researchers have developed various machining models to improve cutting performance. Several approaches have been taken including analytical techniques, slipline field solutions, empirical approaches and finite element techniques. Of these, the finite element approach provides the most detailed information on chip formation and chip interaction with the cutting tool. Finite element models have been developed for calculating the stress, strain, strain-rate, and temperature distributions in both the chip and the workpiece. In addition, tool temperatures, machining forces and cutting power requirements can be determined. This information is extremely, useful for developing more fundamental understanding of complex machining problems. This paper presents a critique of finite element approaches used for simulating machining processes. Several applications of the finite element technique for simulating various machining problems are also reviewed. A new application for determining diffusion wear rates in cutting tools is described, and future directions for finite element modeling of machining processes are discussed.     

积分方程法对含复杂孔形复合材料板孔边应力分布的研究

根据非均质各向异性弹性理论对含复杂孔形复合材料板进行孔边应力分析,解决复杂孔形的边界条件问题.建立基于准确的边界条件的边界积分方程,最终得到开口结构的应力分布,给出含六边形、矩形和机翼检修孔复合材料板的精确解析解,并用有限元方法进行对比计算.平面应力场借助保角映射的方法通过复变应力函数得到.     

Buckling analysis of laminated composite rectangular plates reinforced by SWCNTs using analytical and finite element methods

In this paper, the buckling analysis of laminated composite plates reinforced by single-walled carbon nanotubes (SWCNTs) is carried out using an analytical approach as well as the finite element method. The developed model is based on the classical laminated plate theory (CLPT) and the third-order shear deformation theory for moderately thick laminated plates. The critical buckling loads for the symmetrical layup are determined for different support edges. The Mori-Tanaka method is employed to calculate the effective elastic modulus of composites having aligned oriented straight nanotubes. The effect of the agglomeration of the randomly oriented straight nanotubes on the critical buckling load is also analyzed. The results of analytical solution are compared and verified with the FEM calculations The critical buckling loads obtained by the finite element and the analytical methods for different layup and boundary conditions are in good agreement with each other. In this article, the effects of the carbon nanotubes (CNTs) orientation angle, the edge conditions, and the aspect ratio on the critical buckling load are also demonstrated using both the analytical and finite element methods.     

复合材料细观几何结构对有效模量的影响

基于平均值坐标插值的多边形有限元方法--重心有限元,以代表性单胞为计算模型,讨论增强相的细观几何特征对纤维增强复合材料有效模量的影响.通过改变增强相的尺寸、形状和方位等几何特征后得到的计算结果表明,增强相尺寸是影响有效模量的最基本的因素.除此之外,方位的影响较之形状的影响要更加显著.     

惯性平台橡胶减振器弹性特性的有限元分析

以某型号惯性平台减振器为研究对象，探讨了橡胶减振器弹性特性的有限元分析方法。利用有限元ANSYS分析软件，进行了橡胶减振器有限元建模的数值试验分析。为了精确描述橡胶的特性，采用了弹性应变能函数方法，选取本构方程拟合试验数据，对橡胶材料特性曲线进行评估。预测的计算结果与试验吻合较好，表明所建的数学模型和有限元计算方法能较理想地获得橡胶减振器静态、动态解。该方法对同类减振器度其复杂结构系统的静态、动态计算奠定了基础，同时为以后同类减振器的设计提供一定的参考。