Effects of hardness and thickness of polyurethane foam midsoles on bending properties of the footwear

In sports shoe design to achieve better athletics performance, the bending stiffness of a footwear is an important parameter. Its bending stiffness is mostly dependent on its midsole material. Specifically, hardness and thickness of the midsole material are the major factors on its bending stiffness. Hence, this study focuses on studying the effect of hardness and thickness on bending stiffness of sports shoes by using polyurethane(PU) foam midsole. The results from the experiments show that the bending moment increases as the bending angle increases. Increased hardness and increased thickness of midsole also cause a greater bending moment of the sports shoe, respectively. Moreover, the effect of hardness and thickness of midsole on bending moment measured with assembled shoes is much greater than the one measured with midsoles alone. Therefore, low bending stiffness of the midsole material can not be ignored in shoe design because it could result in high bending stiffness of an assembled shoe.     

Failure Mechanism and Mechanical Properties of CFRP Strengthened Super-servicing Reinforced Concrete Poles

Super-servicing reinforced concrete poles (RCP) which come from a road section in a power grid, including six pole shafts and six specimens with a mid-span steel joint, were selected as samples to conduct a flexural strength test, in which three shafts and three poles with steel joint in the middle span were strengthened by CFRP in the longitudinal direction. The mechanical behavior and failure mechanism under different CFRP layers pasted were comparatively studied. Based on the measured test data, the calculation methods of strength and stiffness were investigated, and the mathematical expression of stiffness degradation mechanism was proposed. The result shows that the final failure mode of CFRP strengthened poles is the local bond failure between CFRP material and the external concrete, and the longitudinal CFRP is snapped. The process of damage is rapid and brittleness. The mean strain of cross-section is in accord with the assumption of plane cross-section. The strength degradation of shaft specimens without strengthened is throughly serious. As for the strengthened poles, the bearing capacity and stiffness under each forcing stage are improved with different levels. The damage of strengthened specimens develops faster and more intensive than that of none-strengthened ones. When multi-aspects are synthetically considered, there is a suggestion that double layers of CFRP should be pasted along the longitudinal in the joint of the site within a certain distance, and the single layer of CFRP should be adopted in the shaft.     

基于ANSYS的汽车车门下沉刚度有限元分析

用有限元分析方法分析了某轿车车门简化模型的下沉刚度。直接运用APDL命令流在ANSYS中建立车门装配体模型,通过实验得出结果数据并对其进行分析,得出优化方案,为车门结构设计和优化提供思路和参考依据。     

Effect of pressure phase plane derived τ and K on evaluation of left ventricular diastolic function in isolated rat heart during ischemia/reperfusion

AIM: To analyze and compare the changes of pressure phase plane (PPP) derived τ and K on isolated rat heart during ischemia/reperfusion, and to explore the value of PPP derived τ and K for evaluation of left ventricular diastolic dysfunction. METHODS: LVEDP, -(dp/dt)_max, τ and K were measured and calculated during ischemia/reperfusion in Sprague-Dawley rat hearts. Meanwhile, the level of lactate dehydrogenase (LDH) in the coronary effluent was measured, and the ultrastructure changes in myocardium were observed under electron microscope. RESULTS: Compared with control group, τ increased and K reduced significantly in each ischemic group in a time dependent manner (P<0.05). With prolonged ischemia, τ was even higher and K was even lower (P<0.05). Compared with control group, except ischemia 15 min, LDH in other groups increased significantly at 10 min and 20 min after reperfusion (P<0.05). Compared with ischemia 30 min, LDH of ischemia 45 min and ischemia 60 min were even higher at 10 min and 20 min after reperfusion (P<0.05). With prolonged ischemia, the abnormal changes of the myocardial ultrastructure were observed. CONCLUSION: PPP derived τ and K may be promising indexes for quantitative assessment of left ventricular diastolic function on isolated rat heart during ischemia/reperfusion, and indication of the severity of ischemia/reperfusion injury.     

金属材料结合部法切向刚度修正与实验验证

推导了分形维数、分形粗糙度的近似解析解,修正了结合部法向接触刚度相关公式。编写了求解域扩展系数的通用Matlab程序,推导出结合部切向接触刚度的解析解。以XHK5140型自动换刀计算机数控立式镗铣床上的结合部为研究对象,以测试试件的实验结果为基准,按照相似振型相关性、固有频率定量比较的原则,对结合部法向与切向接触刚度的理论解进行了验证。验证表明理论模型的振型与实验的振型都一致,理论与实验固有频率的相对误差在-16.8%～16.8%之间。     

基于初参数法的丝杠轴向支撑刚度辨识方法

针对丝杠轴向支撑刚度辨识问题,基于初参数解析方法建立丝杠的初参数矩阵方程,使用边界条件和内力平衡条件,求出矩阵方程中的初参数值.利用初参数值,建立丝杠两端支撑处和螺母处的轴向刚度辨识模型.测量丝杠振幅、简谐力幅值与频率、左轴承组右端面与螺母中间位置点的间距以及螺母中间位置点与右轴承组左端面的间距等参数,识别丝杠支撑点轴向刚度.实验研究表明:基于初参数解析方法建立的丝杠支撑点轴向刚度辨识模型简单,具有可行性.     

Effects of Spherical Joint Stiffness on Seismic Response of Single-Layer Cylindrical Reticulated Shell Changing with Peak Ground Acceleration

The previous studies find that the hollow spherical joint stiffness has a certain influence on seismic response of single-layer cylindrical reticulated shell. In order to analyze the rule of this influence with PGA (peak ground acceleration) changing, two types of finite element models are built. The two types of models have the same size except the spherical joint. The first type is a fine model built by shell element and its spherical joints and tubes are built by considering the real size; the other type is the common model which is built by beam element, and the spherical joints are neglected. Comparing with the seismic response of the two types of models when PGA changes, the results show the difference between the two types of model in node displacement-time curves is increased as PGA increases; when the PGA is larger than the collapse acceleration of structure, the influence of increasing joint wall thickness on improving the structural capacity of anti-stability is decreased as PGA increases.     

A calculation method of the stiffness of face gear tooth and analysis of its influence factors

Tooth stiffness of face gear is one of the components of meshing stiffness of face gear drives. Its resolve can build excellent base for calculation method of meshing stiffness and analysis of dynamic for face gear drives. Based on Buckingham’s standpoint, along the length direction of the tooth of face gear, any one of its sections can be considered as a section of rack with varying pressure angle. According to above theory, the tooth form of face gear is simulated successfully. The method of calculation of the tooth’s stiffness of face gear is obtained. Compared with conclusion of tooth’s stiffness by FEM in the same parameters, it is proofed to be correct. Through analysis of influence of tooth’s stiffness by main design parameters of face gear, the benefit conclusions are drawn. That is, the changing ratio of tooth’s stiffness decreases with the increase of module, and the tooth’s stiffness increases with the increase of pressure angle but the changing ratio almost remains constant. The tooth’s stiffness increases with the increase of tooth width and the influence of changing ratio from tooth root to tooth crest is bigger than that of pressure angle.     

Correlations of seed traits with tofu texture in 48 soybean cultivars and breeding lines

Food‐grade soybeans [Glycine max (L.) Merr] used to produce tofu have specific seed composition, shape, size and colour requirements. Seed qualities, such as protein content, have been correlated with tofu texture. The objective of this study was to determine the relationships between textural qualities of tofu and seed characters, including shape, size, density, weight, protein content and oil content. Tofu was produced from the seed of 48 high‐protein or food‐grade soybean lines grown at two locations in 2010. Four tofu textural traits were assessed including work to failure, deformability, stiffness and hardness. Seed protein and oil content were significantly correlated with stiffness and hardness, and protein was additionally correlated with work to failure. Pearson's correlation coefficients ranged from 0.45 to 0.60 (adjusted P‐values < 0.002) for protein and ?0.49 to ?0.35 for oil (adjusted P‐values < 0.016). No significant correlations between tofu texture and seed volume or shape were detected. Seed protein content can be assessed for indirect selection for tofu firmness, whereas this study reveals no evidence that seed size affects tofu texture.     

类Exechon并联模块的结构设计与刚度建模

针对Exechon并联机构工作空间内动平台转动能力较差这一问题,采用机构变异方法,提出了机构构型为2RPU1RPS的类Exechon并联模块,并对其进行了结构设计。围绕所设计的类Exechon并联模块,借鉴子结构综合思想,建立了该并联模块的刚度模型,并推导出动平台刚度矩阵的解析表达。分析了类Exechon并联模块在典型位姿下的刚度性能,并将其与有限元仿真结果进行了对比。结果表明,所建解析模型具有较高计算精度,可用于机构工作全域内刚度特性的快速预估。