A computational and experimental method for plotting multicycle fatigue curves for structural elements with concentrated stress

A theoretical method is considered for the theoretical plotting of the fatigue curves for specimens with stress concentration using the results of tests for smooth samples. The method is based on the results of a large number of experimental data for each material (from 100 to 200 specimens for each level of stress concentration). The computed and experimental data proved to be in reasonable agreement.     

鞋楦定制中非均匀有理B样条特征曲线的自适应变形

为实现无实体楦基础的数字化量足制鞋,提出了基于非均匀有理B样条(NURBS)特征曲线自适应变形的个性化鞋楦定制系统,将足部NURBS特征曲线依据一定的舒适度规则变形成相应的鞋楦特征曲线来实现鞋楦定制。该系统采用切平面法获取足部的特征点、特征曲线和特征尺寸,重建出足部NURBS特征曲线。建立了足楦舒适度匹配规则,并根据变形方式及次序不同将特征曲线分为四种类型。以特征点、特征结点和特征尺寸作为约束,结合足楦舒适度规律驱动足部特征曲线自适应变形,生成相应的鞋楦特征曲线。最后,构建出鞋楦特征框架,通过特征曲线增添操作和曲面细分造型完成定制鞋楦的设计。给出了男士皮鞋鞋楦的设计实例和定制结果,定制时间在480 s内,定制的鞋楦美观大方。该系统具有实用性,且定制鞋楦的再设计利用率显著提高。     

Flow curves and deformation of materials at different temperatures and strain rates

A basic understanding of the plastic behaviour of various metals and alloys is necessary for their successful forming. Researchers can make use of this knowledge for the better understanding and improvement of metal-forming processes, whilst the production engineer can use this knowledge for the selection and allocation of machine tools for different jobs. Flow curves facilitate understanding of the plastic behaviour of materials. In recent times, many advances have been made in numerial analysis methods — such as finite-element techniques — as a means of solving metal-forming problems: the success of such methods depends very much upon the availability of basic material-property data.The determination of flow curves at different temperatures and strain rates is therefore equally important for both the researcher and the production engineer. The different test methods used for determining the flow curves, together with their relative merits and demerits and the influencing parameters, are discussed in this paper. Some experimental results for 18-4-1 alloy steel are also presented.It is hoped that this review will be useful both for personnel engaged in industry and for researchers.     

双参考光两次曝光激光全息法测材料机械变形方向

本文利用2个平面反射镜将1束扩展激光束分成2束参考光和1束物光的光路设计，采取双参考光两次曝光的激光全息方法，记录材料在加载情况下机械变形的双参考光两次曝光全息干涉图；对全息干涉图所含有的材料机械变形的数值信息以及材料机械变形的方向信息，进行了理论分析和定量讨论；给出了一般情况下用本技术测量和计算材料机械变形方向的方法，列出了本技术测量的实验数据和结果。     

圆锥齿轮轮齿变形及测试装置研究

本文以当量齿形对圆锥齿轮轮齿变形进行了编程分析计算,而且首次提出了适于直、斜齿圆锥齿轮轮齿变形实测实验台,经仿真与理论计算吻合。     

综合误差修正方法在热变形测量装置中的应用

误差修正技术是提高测量设备精度的常用方法,但有时由于设备的误差源太多或误差不易测出,而使得误差修正不完全或无能为力.本文提出一种综合误差修正方法,其基本思想是撇开装置中每项具体误差源所引起的测量误差,而把整个测量装置看成是一个大的误差源,采用一种等价置换的方法测出这个大误差源引起的测量误差,然后在测量结果中修正.将该方法用于实验室高精度热变形测量装置中,结果表明该方法可有效提高测量装置精度和测量数据的可靠性.     

基于PLC的材料扭转试验机控制系统设计

介绍一种基于PLC控制的材料扭转试验装置,该试验装置的控制系统由机械部分、以PLC为核心的测量控制电路和PC机组成。使试验设备的测量精度和自动化水平得到较大的提高。     

Cumulative plastic deformation observed during cyclic testing in rolling ball-cylinder and static ball-flat plate experiments

The plastic deformation accompanying rolling contact and static ballflat plate fatigue tests is described for identical experimental conditions. In particular, the problem of whether or not cumulative plastic deformation accompanies repeated Brinell indentations is investigated. The occurrence of cumulative plastic deformation seems, in part, to be determined by the frequency of loading.     

Wear and deformation of ceramic-on-polyethylene total hip replacements with joint laxity and swing phase microseparation

Wear of polyethylene and the resulting wear debris-induced osteolysis remains a major cause of long-term failure in artificial hip joints. There is interest in understanding engineering and clinical conditions that influence wear rates. Fluoroscopic studies have shown separation of the head and the cup during the swing phase of walking due to joint laxity. In ceramic-on-ceramic hips, joint laxity and microseparation, which leads to contact of the head on the superior rim of the cup, has led to localized damage and increased wear in vivo and in vitro. The aim of this study was to investigate the influence of joint laxity and microseparation on the wear of ceramic on polyethylene artificial hip joints in an in vitro simulator. Microseparation during the swing phase of the walking cycle produced contact of the ceramic head on the rim of the polyethylene acetabular cup that deformed the softer polyethylene cup. No damage to the alumina ceramic femoral head was found. Under standard simulator conditions the volume change of the moderately crosslinked polyethylene cups was 25.6 +/- 5.3 mm3/million cycles and this reduced to 5.6 +/- 4.2 mm3/million cycles under microseparation conditions. Testing under microseparation conditions caused the rim of the polyethylene cup to deform locally, possibly due to creep, and the volume change of the polyethylene cup when the head relocated was substantially reduced, possibly due to improved lubrication. Joint laxity may be caused by poor soft tissue tension or migration and subsidence of components. In ceramic-on-polyethylene acetabular cups wear was decreased with a small degree of joint laxity, while in contrast in hard-on-hard alumina bearings, microseparation accelerated wear. These findings may have significant implications for the choice of fixation systems to be used for different types of bearing couples.     

Material deformation and removal due to single particle impacts on ductile materials using smoothed particle hydrodynamics

Smoothed particle hydrodynamics (SPH) was used to simulate the impact of single angular particles on Al6061-T6 targets, and the implications for solid particle erosion were discussed. The results of the simulations were verified by comparison to measurements obtained from impact experiments performed using a gas gun which was specifically designed to accelerate angular particles without disturbing their orientation with respect to the target. Both the simulations and the experiments showed that an increase in impact angle and initial orientation of the particle altered the deformation mechanism of the target material, as noted by other investigators. For impact angles close to normal, a significant amount of target material was extruded and piled up at the edge of the impact craters, due to the limited strain hardening of Al6061-T6. However, for certain combinations of incident parameters, the particle machined the surface and a chip was removed. With appropriate constitutive and failure parameters, SPH was demonstrated to be suitable for simulating all of the relevant damage phenomena, including crater formation, material pile-up and chip separation.     

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.     

Quantitative determination of deformation by sliding wear

On the basis of a model, equations have been derived to define for true shearing, the effective deformation from the deflection of the grain boundaries and from the change of grain thicknesses. A linear intercept method was developed for the direct measurement of grain thickness. The theory has been checked by sliding OFHC copper against steel SAE 1045 under conditions of true shearing. The theory may be applied to other processes besides wear where substantial deformation occurs.     

齿根过渡曲线弯曲应力的分析

使用I—DEAS软件分别计算了齿条刀具为普通圆弧形刀项、椭圆形刀顶及单圆弧刀顶加工出的齿轮的齿根弯曲应力。在有限元模型及载荷的处理上与传统方法不同，本计算所采用的载荷处理方法结合所建立的有限元模型构成了准确的有限元计算模型。     

Prediction of the occurrence of wear by friction force-displacement curves

If a contacting body is moved in the tangential direction in very small steps a rapid increase of the friction force can be observed during the early stages of motion. No transition to a constant value representing the kinetic friction was observed during the investigation of steel surfaces. The friction force increased, though at a more moderate rate. At this stage of movement wear will occur. Investigations with oil-lubricated surfaces showed similar increases. No increase was observed with MoS₂ or PTFE lubrication. It is suggested that the behaviour of the friction force after the transition displacement indicates whether deterioration of the surfaces will occur. If the movement does not exceed the transition displacement no wear occurs.     

基于Matlab语言的液压特性曲线的绘制

Matlab语言强大的运算、仿真能力，被广泛用在液压控制系统中。利用Matlab语言可以进行液压特性曲线的绘制，液压控制系统稳定性的检测，也可以进行液压控制系统的仿真。这里以两个实例，即单、双喷嘴挡板阀压力流量特性曲线的绘制，以及液压转矩放大器系统稳定性的检测，来说明它的强大的功能。     

Rolling and sliding: Separation of adhesion and deformation friction and their relative contribution to total friction

This study is concerned with determining the relative contribution of adhesion and deformation friction using rolling and sliding method. The challenges associated with in-vivo friction testing were overcome by utilising a novel substrate that mimics the viscoelastic behaviour and surface texture of human skin combined with a repeatable and reproducible test setup. The results show that in the dry state, deformation friction contributes 20% of the total friction while the remaining proportion is due to adhesion. These proportions are affected by probe material where for PTFE, deformation friction contributes 30% of the total friction. For the lubricated state, the contribution of deformation friction to total friction increases approaching 50–50% at the higher sliding speeds and normal loads investigated.     

利用AutoCAD命令过若干已知点画椭圆的研究及其应用

给出由椭圆上5点确定的椭圆方程式，进而求出该椭圆的中心和主轴，达到用AutoCAD命令快速而准确地画出椭圆（椭圆弧）的目的。该方法可用于过若干已知点画椭圆（椭圆弧）和过已知点设计椭圆形运动轨道等问题。     

First-order reversal curves acquired by a high precision ac induction magnetometer

We present a setup allowing to characterize the local irreversible behavior of soft magnetic samples. It is achieved by modifying a conventional ac induction magnetometer in order to measure first-order reversal curves (FORCs), a magnetostatic characterization technique. The required modifications were performed on a home-made setup allowing high precision measurement, with sensibility less than 0.005 Oe for the applied field and 10(-6) emu for the magnetization. The main crucial point for the FORCs accuracy is the constancy of the applied field sweep rate, because of the magnetic viscosity. Therefore, instead of the common way to work at constant frequency, each FORC is acquired at a slightly different frequency, in order to keep the field variation constant in time. The obtained results exhibit the consequences of magnetic viscosity, thus opening up the path of studying this phenomenon for soft magnetic materials.