Simulation of industrial elbow response under strong cyclic loading

Elbow components are widely used in industrial facilities as parts of piping/tubing systems. Their performance under severe loading conditions may be critical for the structural integrity of an industrial facility In the case of an earthquake event in addition to other ser-vice loads, such as internal pressure, they are subjected to strong repeated cyclic structural loading. When these elements are subjected to strong repeated loading, they present failure modes associated with cyclic plasticity phenomena (material degradation or cyclic creep). Furthermore, due to their flexibility, significant non-linearities occur and the elbow cross-section shape distorts as cyclic loading takes place resulting at an oval or flatten shape at the end of the loading sequence. Accumulation of plastic strains (cyclic creep or ratcheting) also takes place at the most stressed parts of the element, associated with extensive bulging of the cross-section which is more pronounced in the presence of internal pressure. The present study is numerical, based on a finite element simulation of the elbow, and investigates the el-bow component behavior subjected to strong cyclic bending of various amplitudes in the presence of different levels of internal pressure. The material constitutive model has a domi-nant effect on the elbow response, and this is shown trough the use of 3 different plasticity models. The capabilities and drawbacks of each plasticity model regarding the simulation of cyclic plasticity phenomena are discussed in detail

Finite element analysis of industrial steel elbows under strong cyclic loading

Steel elbows are used in petrochemical facilities and power plants. In the case of an earthquake event, in addition to other service loads, they are subjected to strong repeated cyclic structural loading that may lead to failure due to cyclic accumulation of plastic strain or collapse. Furthermore, due to their flexibility, significant non-linearities occur and the elbow cross-section shape distorts as cyclic loading takes place resulting at an oval or flatten shape at the end of the loading sequence. Accumulation of plastic strains takes place at the most stressed parts of the elbow, associated with extensive bulging of the cross-section which is more pronounced in the presence of internal pressure. The present study is numerical, based on a finite element simulation of the elbow, and examines elbow behavior subjected to strong cyclic bending in the presence of internal pressure. The material constitutive model has a dominant effect on describing the elbow response, and this is shown through the employment of three different classical plasticity models. [26]. Copyright © 2011 by ASME