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The twice-interpolation finite element method (TFEM) constructs the trial function for the Galerkin weak form through two stages of sequential interpolation without additional degrees of freedom and achieves better accuracy and convergence compared to the conventional finite element method (FEM). The TFEM has been shown to be insensitive to the quality of the elemental mesh and thus has the potential to simulate fracture problems. Intense examples and issues with cracking problems are investigated in this study. It is observed that the stress intense factor (SIF) of the crack tip can be evaluated with satisfactory accuracy. Since the present TFEM can produce more continuous nodal gradients, better stress fields can be reproduced, especially around the crack, without requiring more nodes. It is also shown that crack propagation can be reproduced readily and the cracking path agrees well with the reference solution and experimental results.

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The hybrid simulation method based on Multibody Simulation (MBS) and finite element method (FEM) were proposed here and applied to study the relation between carbody structure vibration behaviors and structure fatigue strength characteristic. The detailed steps include: Firstly, rigid-flexible couple vehicle multibody system dynamic model was created and performed to obtain the load time histories corresponded to the typical load cases. Secondly, the carbody structure stresses was calculated through Finite Element (FE) quasi-static stress method. Finally, with the material fatigue property and some uncertainty factors, carbody fatigue damage distribution and life was calculated and evaluated. And the conclusions can be understood that the mechanism between the full vehicle dynamic property and structure damage distribution. The results are also shown that the hybrid simulation technology could be applied into the carbody structure fatigue design.

Three typical finite element models (FEM) of spot-welds have been created as analysis objects, and the relationship between force and displacement of the specimens were obtained under shear and tensile forces through the elastic-plastic finite element analysis. Simulation results and the shear-tensile test curves of TG301L and SUS301L stainless steel specimens which were obtained based on JIS Z 3136 shear-tensile test methods were compared. The results showed that: No matter what type of nuclear simulation, stiffness of simulation models are less than the actual stiffness of the specimen; and when the specimen was stretched and sheared, with solid element to simulate the nugget can get maximum stiffness, it is most close to the actual stiffness, umbrella model is followed, and a stiff beam model is the worst.