不同超弹性本构模型和多维应力下开裂能密度的计算方法

橡胶隔振器的疲劳失效多属于大变形(有限变形)下的多轴疲劳问题。在多轴疲劳载荷下,有效用来驱动裂纹扩展的那部分应变能密度称为开裂能密度。基于开裂能密度和橡胶材料的裂纹扩展特性预测橡胶部件的疲劳寿命时,须计算在外载荷下橡胶部件的开裂能密度。为了由有限元软件ABAQUS默认输出的应变计算在有限变形下的开裂能密度,该文推导了不同超弹性本构模型下开裂能密度在主坐标系下的计算式和所需的积分方法。基于该文开裂能密度的计算方法,采用3次Ogden本构来描述大变形下橡胶材料的本构行为,计算分析了不同应变状态下开裂能密度的分布特点。通过分析计算得到的开裂能密度与应变能密度的关系,说明该文开裂能密度计算方法的准确性。最后将上述计算方法应用到橡胶隔振器的多轴疲劳寿命预测中。

A METHOD FOR CALCULATING CRACKING ENERGY DENSITY OF RUBBER COMPONENTS UNDER DIFFERENT HYPERELASTIC MODELS AND MULTIAXIAL STRESS STATES

Multiaxial fatigue is a common issue encountered in fatigue failure of rubber isolators. The portion of Strain Energy Density (SED) to initiate crack growth under multiaxial fatigue loads is defined as the Cracking Energy Density (CED). Using the measured fatigue crack growth characteristics of rubber material and the calculated CED of rubbers under external loads, one can predict fatigue life of rubber components. The key issue using this estimation method is to calculate the CED of rubber components under external loads. To calculate CED using the output strain from the finite element software (ABAQUS) as input data, the formula for CED under the principal coordinate system and the integral technology are proposed. Six hyperelastic constitutive models for rubber materials are included into this method for calculating CED. Taking some typical strain states (uniaxial tension, planar tension and simple shear) as examples, the CED calculated from the proposed formula is compared with the corresponding SED. The comparisons validate the proposed method for calculating CED. Finally, the CED developed using the method proposed is used to predict multiaxial fatigue life of rubber isolators.