Safety Analysis Of Pressure Piping Containing Discontinuous Incomplete Welding Defects

While manual arc welding are always adopted by industrial pressure pipes on site, the discontinuous incomplete welding defects which was caused by the gaps that was not melt by the arc between the weld metal and base metal in the welded joints were inevitable. And the risk of these defects are obvious, it's worth to do the safety analysis research of pressure pipe with discontinuous incomplete welding defects. The calculation of plastic failure load of pipe with discontinuous incomplete welding defects, formula of flow stress, engineering simplified method for discontinuous incomplete welding defect and the interference effect, and the construction of final safety assessment curve have been studied in this paper, the finite element calculation and experimental methods are adopted, and the main research achievements are as follows:(1) The research of plastic failure load for pipe is decided to be the key-point. According to the basic theory of finite element, the software ANS YS is used to do the nonlinear analysis calculation of plastic failure load of pipe, while it can be a good foundation for the large quantities of subsequent calculation.(2) The comparative study of material flow stress formulas have been done, then the formula of flow stress which fit to the pressure pipe with discontinuous incomplete welding defects was established. And the flow stress directly affects the precision of plastic failure load.(3) The interference effect of defects has been studied. The failure loads of pipes changed under different space between the incomplete welding defects, at the same time this change has been compared to the single defect. Then the correlation formula of interference effect for different discontinuous incomplete welding defects was deduced, and the engineering simplified method of discontinuous defects was also been provided.(4) The calculation of failure load for pressure pipe with discontinuous incomplete welding defect has been studied, then the data obtained by the calculation was processed, and the safety assessment curve of pressure pipe with discontinuous incomplete welding defect was deduced, after that the safety assessment formula could be established which could be as the reference of engineering evaluation.(5) The experiment research was adopted to validate finite element calculation. The plastic failure loads for pressure pipe with defects were received through the test. Then the data was used to validate the correlation formula of interference effect.