The effect of oscillation of internal pressure on the formability and shape accuracy of the products in a pulsating hydroforming process of T-shaped parts was examined by finite element simulation. The local thinning was prevented by oscillating the internal pressure. The filling ratio of the die cavity and the symmetrical degree of the filling was increased by the oscillation of pressure. The calculated deforming shape and the wall thickness are in good agreement with the experimental ones. It was found that pulsating hydroforming is useful in improving the formability and shape accuracy in the T-shape hydroforming operation.

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The filling of the die corner in hydroforming of a tube with a box die was improved by controlling wrinkling under oscillation of internal pressure. In this process, a small wrinkle occurs near the die corner in the former stage, and then the wrinkle is eliminated in the latter stage because the flat bulge appears in the former stage due to the oscillation of internal pressure. A hydroforming process of steel tubes with a box die was performed in both three dimensional finite element simulation and experiment. The filling of the die corner for the mean linear pressure was not sufficient due to large wrinkles appearing in the former stage, whereas bursting occurs for the peak linear pressure due to round bulging. On the other hand, the uniformity of wall thickness of the formed tube was improved by the pulsating pressure.

In this research, axial crushing of grooved thin-walled steel tubes with different geometric dimensions has been investigated by carrying out experiments and finite element simulation. The crushing manner, load-displacement curves and initial crushing load have been studied. The simulations have been performed by ABAQUS 6.7 software in 3-D model and explicit method. Grooves were modeled circumferentially and alternately inside and outside the tubes. Quasi-static axial load was applied. The results obtained from experiments and simulations are in a good agreement. Results demonstrate that crushing manner and initial crushing load in axial crushing of grooved thin-walled tubes could be controlled by introducing different groove distances.