For mixed mode fracture problems, you must include the Mode III stress intensity factor- SIFS (K3), to calculate the Equivalent SIF Factor (SIF) and Kink Angle. Using beta options, Mechanical supports certain Equivalent SIF calculation methods. Specify the Equivalent SIF calculation method and related property definitions/options using the Equivalent SIF Method property of the SMART Crack Growth object. As illustrated below, the Equivalent SIF Method (Beta) property includes the following options:
Program Controlled (default): The application uses the Maximum Tangential Stress calculation method.
Maximum Tangential Stress: This method does not include Stress Intensity Factor K3 from Mode III fracture in the Equivalent SIFS calculation.
Richard Function/Pook Criterion/Empirical Function: These methods consider the Stress Intensity Factor K3 from Mode III fracture in the Equivalent SIFS calculation.
Based on the method you select, define the following additional properties:
Factor Alpha 1: Displayed when the Equivalent SIF Method (Beta) is set to Richard Function, or Empirical Function. Specify the positive multiplicative factor for K2 term in the Equivalent Stress Intensity Factor calculation function. The default value is 1.155. This property can be parameterized.
Factor Alpha 2: Displayed when the Equivalent SIF Method (Beta) property is set to Richard Function or Empirical Function. Specify the positive multiplicative factor for K3 term in the Equivalent Stress Intensity Factor calculation function. The default value is 1. This property can be parameterized.
Kink Angle Method (Beta): Displayed when the Equivalent SIF Method (Beta) property is set to any option other than Program Controlled. Use this property to specify the method to be used for kink angle calculation. Options include Maximum Tangential Stress (default) and Richard Function. This Richard Function option is only supported for when the Equivalent SIF Method (Beta) property is set to Richard Function or Empirical Function.
Coefficient A: Displayed when the Kink Angle Method (Beta) property is set to Richard Function. Specify the coefficient of the first order term in the Richard Function for the kink angle calculation. The default value is 140°. The valid entry range for this property is -180° to 180°. This property can be parameterized.
Coefficient B: Displayed when the Kink Angle Method (Beta) property is set to Richard Function. Specify the coefficient of the second order term in the Richard Function for the kink angle calculation. The default value is -70°. The valid range for this property is -180° to 180°. This property can be parameterized.