Safety Analysis Of Low-carbon Steel Pressure Piping Containing Incomplete Penetration Defects Under Combined Loads

Incomplete penetration defect is one of common defects in industrial pressure piping system, few researches was reported at home and abroad. As the good toughness of pressure pipes, general failure mode of the pipes is plastic failure. By means of the non-linear FEA and experiments, the influence of the incomplete penetration defect of pressure piping under combined loads of internal pressure and bending moment was researched in this paper. The main research achievements and creative ideas are as follows:(1) The finite element models of pressure piping contain incomplete penetration defect was established. The APDL procedures suitable for the subject were made.(2) According orthogonal experimental design, worked out computational scheme. By simplifying the effect factors of plastic limit load, the plastic limit load of different defect size under simplex loads or combined loads were gained. Meanwhile, the relation between the plastic limit loads and main effect factors was studied, and the failure mode was presented.(3) Based on the results of FFA, a fitted formula for plastic limit load of pressure piping contain incomplete penetration defect was given.(4) An experimental system used for testing the limit load of pressure piping under combined loads was designed. Using the self-designed limit load test system, the experiments of pressure piping containing incomplete penetration defect ware carried out. The experimental results are consistent with those from FEA, which indicate that the modeling method and calculation of FEA are correct and it is effective to calculate the limit load by FEA.(5) On the base of results of FEA and experiments, a safety evaluation method for pressure piping containing incomplete penetration defect under combined loads is proposed.