内外因素作用下隔振橡胶材料本构模型的修正方法

橡胶材料是一种性能优良的非金属黏弹性材料,广泛应用于机械和汽车产品的振动噪声控制领域。为了对橡胶产品的力学性能进行分析,有必要在材料试验的基础上,采用合适的本构模型,建立橡胶材料的应力-应变模型并辨析模型参数,从而为进一步的橡胶件有限元仿真和动力学分析提供材料参数。普遍应用的Mooney-Rivlin模型和Yeoh模型等唯象模型无法描述内外部复杂因素,如胶料硬度和环境温度对胶料力学特性的影响。在分析实测胶料应力-应变数据的基础上,分别对传统唯象模型进行修正,引入硬度强化因子和温度软化因子,使得本构关系模型更加完善。在所建立的修正模型基础上,采用非线性最小二乘法对修正模型进行参数辨识,并通过与实测结果对比,验证了所建模型的有效性。

Catastrophe analysis on pillar instability considered mining effect

The instability of the pillar was discussed based on the potential energy principle and the cusp catastrophe theory, and a simplified mechanical model of the pillar was established considering the mining effect. The necessary-sufficient conditions, the jump value of displacement of pillar and the released energy expressions were deduced. The results show that the instability of the pillar is related to the properties of the rock, the external force and the relative stiffness of the elastic area to the plastic area. The instability of system is like to occur with the enlarging of the softening area or the decreasing of E/λ. The calculation done shows that the estimated results correspond to practical experience.

Relationship between Dysglycemia and Carotid Atherosclerosis in Tibetan Population

People with dysglycemia are at high risk for atherosclerotic diseases. This study aims at investigating the atherosclerotic vascular damage in dysglycemia and its metabolic origin in Tibetan population.