Comparative study of shakedown load calculation methods of pressure vessels and vessel-piping system
For the shakedown load calculation for pressure vessels and vessel-piping system,three methods,i.e.the cyclic elastoplastic analysis method,the lower-bound shakedown theorem method and the double limit load method were introduced for determining shakedown loads.Based on these three methods,the shakedown load of three structures,namely,thick wall cylinder,standard elliptical head with central nozzle under mechanical load and standard elliptical head with central piping system under thermal loads were calculated.A comparative analysis of the advantages and disadvantages of the three methods were presented.The results show that the cyclic elastoplastic analysis method could provide a more accurate reflection of the structure's load carrying capacity,but the solution is complex and requires a significant workload.Compared to the cyclic elastoplastic analysis method,both the double limit load method and the lower-bound shakedown theorem method have a maximum error of less than 5%and are conservative,and the double limit load method has the smallest computational effort.Considering the calculation accuracy and workload comprehensively,the double limit load method can be used in engineering design.For cases requiring higher calculation accuracy and weaker restraining ability of the surrounding elastic material to the maximum stress point,the cyclic elastoplastic analysis method was recommended.
pressure vessels and piping systemshakedown analysiselastic-plastic analysislimit load
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