Research On Plastic Limit Load Of Local Thinning Elbow For Engineering Calculation Method

Based on research of nondefective pipe elbows under either plastic internalpressure or in-plane bending moment, the effect of local thinning area (LTA) on plasticlimit load of elbows subject to internal pressure, bending moment and combined loadwas investigated in this thesis with finite element analysis (FEA). The main contentsand achievements were summarized as follows:1. The three-dimension finite element models of both nondefective and defeative elbows were built and preprocess and calculation programs were written down.2. Considered the reinforcement effect of straight pipe connected, same FEA plastic limit solutions of different size nondefective elbow under either plastic internal pressure or in-plane bending moment were calculated. Based on calculation results, estimation formulas with high accuracy of plastic limit internal pressure and plastic limit bending moment were given respectively.3. By simplifying the effect factors of local thing elbow's plastic limit load, mainly on common size elbows, the plastic limit load calculation of different size LTA under simplex lodas or combined loads was finished. Meanwhile, the relation between the plastic limit loads and main effect factors was studied, and the failure mode of LTA elbow was presented. Finally, a fitted formula for plastic limit load of local wall thinning elbow was given.4. Through changing the constraint, the effects of constraint conditions on plastic limit load of nondefective elbow were studied. The results showed that the FEA solutions in this thesis to actual pressure piping assessment were applicable.