Safety Analysis Of Stainless Steel Piping Containing Incomplete Welding Defects Under Proportional Loads

It is known to all that pressure piping has always been an important component in modern process industry. However, there still exist quite a few incomplete welding defects (IWD) in the industrial pressure piping, which researchers at home and abroad have not paid full attention to. Even fewer researches have been done in the anynasis of the pressure piping under bending momnet and internal pressure.Based on a theoretical analysis, we have found out the relationship between bending moment and internal pressure for the risk-point of pressure pipe under combined load, which is the design load line of pressure piping. From a finite element analysis (FEA), the limit load of pressure piping under internal pressure, bending moment and combined load is studied, and the influence of IWD on the plastic limit load of pressure pipingwas is also discussed. The main contents and conclusions are summarized as follows:(1) The three-dimensional finite element models of pressur piping containing IWD have been built and preprocess and calculation programs have been found.(2) After simplifying the influencing factors of pressur piping containing IWD plastic limit load, the plastic limit load calculation of different size IWD under simplex lodas or combined loads has been finished and relevant FEA databases have been established. We have studied the relationship between the plastic limit loads and main influencing factors and put forward the failure mode of IWD pressure piping.Finally, a formula for plastic limit load of IWD pressure piping was given.(3) Based on the above anynasis,we then make a comparison between design load line of pressure piping and FEA, from which the margin depth of piping containing IWD. In most cases, we need not make a stress analysis of pipe system the application of which is easy.(4) We have acquired an envelope line of a bunch of curves which can also be used as limit load formula under internal pressure and bending moment based on our studies of a bunch of limit load curves gained from FEA calculation. Finally, a safety assessment method aims at IWD pressure piping which is validated by experiments has been put forward.