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Showing 2 results for Strain Accumulation
Mahmoud Shariati, Hamid Zabihi Ferezqi, Saeid Hadidi Moud,
Volume 16, Issue 8 (10-2016)
Abstract
The Assessment of strain accumulation due to nonlinear events like creep, plasticity or ratcheting phenomenon has gained importance, since it causes an increase in creep and fatigue damage of materials. Some factors like the magnitude of loading, constitutive equations or the elastic regions around the nonlinear events have effect on the rate of strain accumulation. The elastic follow-up can explain the mechanism of strain accumulation. This phenomenon may occur when a mechanical structure with elastic manner is connected to non-linear events and they are subjected to a displacement load. In these cases, the high rigidity portion of elastic region of mechanical structure may enhance the force to the regions with low rigidity. So in the local non-linear portion, the strain is accumulated. This phenomenon is proposed as an important instruction in mechanical assessment codes. In this study, the effects of Elastic Follow-up phenomenon on strain accumulation due to elastic-plastic and local creep are investigated. So the Elastic Follow-up parameter is defined by the methods which are described in high temperature assessment procedures (R5). The results revealed that the strain accumulation depends on the elastic region in structures which is described by the Elastic Follow-up phenomenon.
Seyed Javid Zakavi, Esmaeil Bakhshipour,
Volume 22, Issue 7 (7-2022)
Abstract
In this paper, by using the Chaboche kinematic hardening model with the isotropic hardening law, the effect of temperature and bending moments is investigated on the strain accumulation behavior of carbon steel piping branch. Carbon steel branch junctions under internal pressure and temperature with dynamic bending moment are tested at five temperatures of 20, 50, 100, 150 and 200 ° C. The results obtained by numerical analysis show that the highest amount of ratcheting occurred near the branch junctions in the circumferential direction. The strain ratcheting occurred mainly because of dynamic moments and high temperatures. The results show that in all three samples, the amount of strain ratcheting increases with increasing of dynamic moment level and temperature. With increasing of the ratio of diameter to thickness in branch junctions, the onset of strain accumulation occurs at low moment levels. It can be concluded that initially, the rate of strain ratcheting is high and with the increase of loading cycles, this rate decreased due to the strain hardening phenomenon. The increase of strain ratcheting at high temperatures is due creep strain because of high temperature and mainly accumulated plastic strain under dynamic bending moments because of cyclic plasticity.
