Abstract: Bulging and pressing is a new process for manufacture complex hollow parts,such as axle housing.For the forming of square straight arm filled in liquid and pressed of a 5t axle housing with flat die,the simulation is done by ABAQUS software,and the square arm area appears a significant concave.To eliminate this phenomenon,the pressing die is designed to concave curve on indent defect area of the straight arm.Using twelve groups of different concave curve mold,the simulation of pressing process is done,and the relationship between straight arm indent and mold curve chord length and concavity is given,and the structural parameters of the mold concave curve is given without indent on the square tube surface.Finally,the pressing forming test is done,and the test results agree with the simulation results.

Key words: automobile axle housing, bulging-pressing, square tube, surface concave, finite element simulation