Simplified estimation of accumulated strain at ratcheting

Background

Methods for the computational analysis of ratcheting (progressive accumulation of one-sided plastic strain) are complex and labor-intensive. Leading to the malfunction of structures ratcheting is a deformation caused by the behavioral characteristics of both the material and the structure. Combining these two causes in calculations complicates the further analysis.

Aim

To simplify the calculation assessment of a possible one-sided strain accumulation, as well as safety limits.

Materials and methods

The study uses non-standard applying of the finite element method and calculations without analytical solution of shakedown theory problems and labor-intensive numerical analysis of deformation kinetics. Only the upper limit of the exact solution interval is determined. The two-stage assessment includes conditionally elastic calculation of one cycle to determine the stress ranges and inelastic calculation with yield strengths reduced by the value of ranges. The software and calculation model are the same as in classical calculations. The procedure can be easily automated.

Results

The performed study demonstrates that the obtained estimate of accumulated strain is upper or exact in the case of a single possible deformation mechanism. The error or overestimation of accumulated strain is guaranteed to be included in the safety margin. The feature of the proposed method is the ability to account for material hardening.

Conclusion

The present method may prove sufficient in practice for justifying the strength according to the criterion of progressive strain without the laborious calculation of inelastic deformation kinetics.