The Study On The Yield Procedure Of A Ship-building Steel Under Torsional Load

The yield procedure and mechanics of steel 35 under torsional load were studied by standard cylinder specimen in this paper.The results indicated that the yield strength of steel 35 under torsional load derived according to GB10128-88 was not accordance with either Mises or Tresca yield criterions, and the relative error was separately 20% and 27.7%. The error stuck out a mile. In this paper, the yield procedure of the material under torsional load was researched. The formulas of the yield strength of solid cylinder specimen and hollow cylinder specimen were made out. The formula was separately . The formula was derived too. The yield strength derived according to the formula of solid cylinder specimen was accordance with Mises and Tresca yield criterions much better, and the relative error was separately 1.7% and 6.0%. The results of hollow cylinder specimen experiments indicated that the yield strength formula of hollow cylinder specimen was exactly. So, an outlook that the assurancecoefficient n_s needed to larger than 1.25 during verified the strength of thematerials was made out in this paper.In the shear stress-shear strain coordinate system, when the material was in wholly yield stage, the stress of hollow cylinder specimens which were in the same external diameter but in different inner diameter was computed. It was verified that the maximum stress of the materials under torsional load was at the outmost zone fibers. When the torque increased to the certain value, the plastic deformation was happened to the outmost zone fibers firstly, but the inner fibers were in elastic stage. When the torque further increased, the inner fibers entered the plastic stage too. It was shown in the stress-strain curve that the stress of the material in wholly yield stage increased gradually. When the wall thickness of the specimen increased to the solid, the yield strength of the thick-wall hollow cylinder specimen was approach to the same external diameter solid cylinder's. When the wall thickness of the hollow cylinder specimen was 0.4~lmm, the stress of the material in original yield stage was equal to the stress of the material in wholly yield stage. And the stress value was approximately equal to the stress of solid cylinder specimen in original yield stage. When the torque increased sequentially, the material entered deformation hardening stage.