Sensitivity of structural materials to stress concentration in multicyclic fatigue

A method of plotting fatigue curves is proposed on the basis of the material’s sensitivity to stress concentration.     

Sensitivity of structural materials to stress concentration in multicyclic fatigue

The fatigue curves of samples with stress concentration are considered on the basis of fatigue curves for smooth samples. The calculation results are in satisfactory agreement with experimental data.     

Evaluating the reliability of the cylinder liner of a low-speed marine engine subjected to high-cycle fatigue with high mean stress

Reliability evaluation was performed on the cylinder liner of a low-speed marine engine experiencing high-cycle fatigue with high mean stress. The stress distribution in the cylinder liner under operating condition was estimated through structural analysis, which included thermal boundary conditions and material nonlinearity. Results indicated that the highest stress concentration developed at the round part below the liner collar. Material tests revealed that the Goodman relation can predict the effect of mean stress on fatigue limit. As indicated by the combined results of the structural analysis and experiment, the cylinder liner is reliable under operating condition.     

Stereological method for estimating relative membrane surface area in freeze-fracture preparations of subcellular fractions*

Microsomal fractions from liver cells are a mixture of vesicles derived from a number of different cellular membranes. These can be differentiated on freeze-fracture preparations by their characteristic density of intramembranous particles. A stereological method is developed which allows the estimation of the relative membrane surface of the various membrane types by using freeze-fracture preparations. The sample is restricted to concave profiles without cast shadow. The numerical frequency distribution of vesicles with respect to particle density is determined. The estimation of relative surface area must consider the effects on sampling of (a) variable size distributions of vesicles and (b) loss of small profiles. Correction coefficients are derived which allow a differential vesicle count to be transformed into an estimate of relative membrane surface.     

渐开线少齿数齿轮弯曲疲劳应力计算系数的研究

通过设计实验方案、实验、数据处理、实验误差分析和修正,对Z＝4～11的少齿数齿轮,得到弯曲疲劳应力计算中的齿形系数和应力修正系数变化曲线、齿顶变尖极限曲线和齿根根切极限曲线.应用其完成了某设计,通过动力学仿真以及样机运行试验,证明了设计的合理性.完善了齿轮设计资料.     

冲击作用下的载荷波形对动态应力集中系数的影响

本文从理论上证明了在一定条件下阶越波入射产生的最大应力集中系数是冲击作用下种瞬态波形入射时的极限值。有限元法计算结果不仅证实了这一结论，而且展示了在一般无理论解的情况下获得极值应力集中系数的可行性。     

The effect of different contact materials on the fretting fatigue strength of an aluminium alloy

The fretting fatigue strength of Al-4Mg-0.7Mn in contact with pads of aluminium, copper, $\text{70}\text{30}$ brass, and 0.7 C steel has been determined. Copper and brass produced little reduction in fatigue strength because of the severe wear of the pads, The steel and aluminium pads produced reductions of 34% and 28% respectively. The effect of fretting on fatigue strength is explained in terms of the added shear stress arising from the frictional force between the pad and the specimen. Although the coefficient of friction is initially low it rises after 500–1000 cycles to approximately 1.0 and remains constant at this figure.     

The effect of amplitude of vibration on the coefficient of friction for different materials

This work examines how friction coefficients are affected by amplitude of normal vibration at different frequencies. Variation of friction coefficient with the amplitude of normal vibration is investigated experimentally when mild steel pin slides on different types of material such as glass fiber reinforced plastic, cloth reinforced ebonite, polytetrafluoroethylene (PTFE), rubber and mild steel. For this, a pin-on-disc apparatus having facility of vibrating the test samples at different amplitudes and frequencies of vibration was designed and fabricated. During the experiments, the effects of sliding velocity, roughness, normal load and duration of rubbing were also investigated. Studies have shown that the friction coefficient decreases with the increase of amplitude of vibration within the observed range. The observed ranges of amplitude of vibration were 10–200 μm. In this study, it is also observed that the rate of reduction of friction coefficient has a particular relationship on the amplitude and frequency of vibration. The experimental results are compared with those available in the literature and simple physical explanations are provided.     

Apparatus for the high temperature measurement of the Seebeck coefficient in thermoelectric materials

The Seebeck coefficient is a physical parameter routinely measured to identify the potential thermoelectric performance of a material. However, researchers employ a variety of techniques, conditions, and probe arrangements to measure the Seebeck coefficient, resulting in conflicting materials data. To compare and evaluate these methodologies, and to identify optimal Seebeck coefficient measurement protocols, we have developed an improved experimental apparatus to measure the Seebeck coefficient under multiple conditions and probe arrangements (300 K-1200 K). This paper will describe in detail the apparatus design and instrumentation, including a discussion of its capabilities and accuracy as measured through representative diagnostics. In addition, this paper will emphasize the techniques required to effectively manage uncertainty in high temperature Seebeck coefficient measurements.     

Determination of the damage mechanisms in armor structural materials via self-organizing map analysis

Dynamic compression fracture behaviors together with damage mechanisms of materials subjected to a compressive load at a high strain rate were studied by using a Self-organizing map (SOM). The materials used for the analysis were Al5083, Rolled homogeneous armor (RHA) and tungsten heavy alloy (WHA). The deformation behavior and Acoustic emission (AE) signal were acquired through a Split Hopkinson pressure bar (SHPB)-AE coupled test. The self-organization map which is one of the artificial neural network technique was employed to classify the AE energy, amplitude, and peak frequency according to the characteristics of the signal. In addition, distributions of AE signals were represented in stress-strain curves. The correlation between AE characteristics and material damage mechanisms was investigated. Based on the results, it was found that cluster 1 with high AE energy, high amplitude and low frequency was the cluster of the AE signal generated near the yield point of the material. Cluster 3, which has the opposite tendency, was confirmed as a cluster of AE signals that occurred just before a fracture of the material. The change in the measured value can be seen depending on the strain rate and the material, but the overall tendency was similar.     

一种鞋面材料的成分分析

用有机溶剂萃取方法分离和提纯样品,通过傅立叶变换红外光谱仪器对一种鞋面材料中的各种组分进行测试,并对测试结果进行综合分析,给出分析结果。     

风力发电机齿轮箱扭力轴的疲劳分析

应用有限单元法,对风力发电机齿轮箱中的扭力轴的进行了疲劳寿命分析.利用Solid-works和ANSYS-Workbench软件建立了扭力轴的三维有限元模型,并在ANSYS-Workbench中对轴进行了结构疲劳分析,证明其疲劳寿命符合设计要求.     

基于力学性能的钢货架立柱截面结构参数的敏感性研究

钢货架立柱是货架承受荷载的基础构件之一,其截面形状对立柱的力学性能有着极其重要的影响。基于理想轴心受压构件稳定理论,建立了受压立柱力学模型,推导了常见立柱截面的截面特性计算公式。以M120型号立柱为例,采用倍率化分析方法计算了立柱宽度,厚度等参数对立柱的稳定临界压力的敏感程度,为立柱的优化设计提供理论指导。     

塑性分析在产品结构强度设计中的应用

通过分析有限元计算中结构模型简化与计算结果精度相互矛盾的现象,从考虑材料的塑性特性入手,介绍了如何在模型合理简化的条件下来提高计算结果的准确性。     

On the stress concentration around a hole in an infinite plate subject to a uniform load at infinity

In this paper stress concentration around a hole in an infinite plate that is subjected to a uniform load at infinity is considered. The stress is calculated by using a modified Muskhelishvili complex variable method. The method is illustrated by several examples of stress distribution around polygonal holes of a complex geometry utilizing the Schwartz-Chistoffel mapping function.     

Cryotechnology for the structural analysis of lubricants in relation to their friction properties

A phenomenological model is developed to explain the friction and wear characteristics of high speed sliding contact between blade tips and shrouds in high performance turbomachinery. Equal emphasis is placed on thermal and mechanical mechanisms, and a synergistic relation between the two is derived which yields quantitative predictions of rubbing forces, friction coefficient, total heat input, heat split and relative wear rates between the blade and the shroud. The focal point of the model is a convecting plastic “shear mix” layer on each rubbing surface which is deduced to form regardless of the rub mechanisms initially assumed to prevail.     

电动轿车副车架的疲劳试验及仿真分析

通过原设计的副车架进行的疲劳试验,研究了副车架工作环境和特性;在优化软件的协助下,对原副车架进行了疲劳仿真分析;同时对采用新材料的副车架也进行了疲劳仿真分析.经过对比分析得出,新副车架在轻量化的同时各项性能都较原件有很大的改善.     

圆盘阀壳体应力分析

通过建立圆盘阀阀体的三维有限元模型,研究了预紧工况和承压工况下螺柱和垫片等元件的受载与变形情况。分析了在预紧力和压力作用下壳体的应力分布。