contact have the effect of compressing the eigenvalue spectrum, which the element by element estimates do not take into account. ABAQUS/Explicit contains a global estimation algorithm, which determines the maximum frequency of the entire model. This algorithm continuously updates the estimate for the maximum frequency. ABAQUS/Explicit initially uses the element by element estimates. As the step proceeds, the stability limit will be determined from the global estimator once the algorithm determines that the accuracy of the global estimation is acceptable. The global estimation algorithm is not used when any of the following capabilities are included in the model: fluid elements, JWL equation of state, infinite elements, material damping, dashpots, thick shells (thickness to 99 characteristic length ratio larger than 0.92) or thick beams (thickness to length ratio larger than 1.0), and nonisotropic elastic materials with temperature and field variable dependency. 5.1.3 Material model Considering the high strain rate (10 6 ) in shot peening process, rate dependant material law is considered for modeling the elasto-plastic behavior of the workpiece material. Two types of steels are used as targets in simulating the shot peening process – AISI 52100 bearing steel and AISI 4340 steel. Detailed material model for AISI 52100 is described in Chapter 4.1.3. Material model for AISI 4340 is detailed in the following paragraphs. Johnson-Cook model is widely used to describe the strain rate and temperature effect on the flow stress. In this research, the famous JC model is adopted to describe the constitutive law of AISI 4340 steel. The Johnson-Cook (JC) model [Johnson and Cook 1999] is purely empirical and has the form m n p p y T C B T * * 0 0 1 ln 1 1 , , (5.9) Where p is the equivalent plastic strain, is the plastic strain rate, ( 0 , B, C, n, m) are material constants, 0 * ; r m r T T T T T * (5.10) 0 is a reference strain rate, T r is a reference temperature, and T m is the melt temperature.
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- Spring '16
- Fundamental physics concepts, Wadge hierarchy, AISI, Shot peening