内时模型“现时近似式”与塑性增量理论的关系研究

STUDY ON RELATIONSHIP BETWEEN ‘PRESENT APPROXIMATE EQUATION’ OF ENDOCHRONIC THEORY AND THE INCREMENT PLASTIC THEORY

提出塑性时间的定义,Valanis K C提出的内蕴时间是其特例。分析了一类积分型塑性时间内时模型"现时近似式"的基本性质,揭示了此类"现时近似式"存在屈服面和塑性位势的必要条件。当"现时近似式"存在屈服面和塑性位势时证明了"现时近似式"的塑性因子等于塑性时间与其Pfaffy型积分分母之积。当Pfaffy型积分分母为正常数时塑性因子等于塑性时间。从经典塑性增量理论出发,采用塑性因子作为塑性时间,建立了一个小应变条件下干砂的内时模型,该模型能够考虑砂土的剪胀性,能够较好地拟合循环荷载作用下干砂的应力-应变响应。

The definition of a plastic time is presented and the intrinsic time suggested by Valanis K C is that of a specific case. Through analyzing the fundamental behavior of ＇present approximate equation＇ of an integral endochronic model in terms of plastic time, the author reveals the necessary condition that yield surface and plastic potential exist in the ＇present approximate equation＇. If the ＇present approximate equation＇ has yield surface and plastic potential, the plastic factor of the ＇present approximate equation＇ is equal to the product of the plastic time and Pfaffy＇s integral denominator. When pfaffy＇s integral denominator is a positive constant, the plastic factor is equal to the plastic time. The endochronic model of dry sand with small strain is derived from the classical increment plastic theory in which the plastic time is used as the plastic factor. This model can well describe the dilatancy of sand and simulate the stress-strain response of dry sand due to cyclic loadings.