Completed Projects

Simplified determination of the elastic-plastic accumulated distortions with the simplified yield zone theory

Brief description

The simplified yield zone theory (VFZT) is used for the simplified estimation of state variables of elastically-plastically loaded structures. In particular, it is intended to reduce the sometimes immense numerical effort for a computational fatigue analysis under cyclic loading. This includes, above all, the determination of the strain amplitude required for a fatigue analysis and the strain accumulation in the in-game state required for a ratcheting check.

An example of strain accumulation is a two-span beam under cyclic traveling load (see adjacent figure). The ratcheting mechanism can be traced back to a large number of flow joints opening and closing one after the other at different points until, due to the hardening of the material, the in-growth state is reached after approx. 40 cycles.

In the project, the focus was placed on accelerating the calculation process, expanding the range of applications and increasing the performance of the VFZT. The research results were published in seven peer-reviewed publications and conference papers.

Author
B. Vollrath, M. Sc.
Prof. Dr.-Ing. H. Hübel

Funding Institution
DFG,
project HU 1734/2-1

Funding Period
01.01.2016 - 30.06.2020

Keywords
fatigue, ratcheting, simplified elastic-plastic analysis

Peer-reviewed publications:

[1] Hübel, H.; Vollrath, B.: Ratcheting caused by moving loads. International Journal of Advanced Structural Engineering 9, Heft 2, 2017, S. 139 - 152, https://doi.org/10.1007/s40091-017-0154-0.

[2] Vollrath, B.; Hübel, H.: Determination of post-shakedown quantities of a pipe bend via the simplified theory of plastic zones compared with load history dependent incremental analysis. In: COMPUTER METHODS IN MECHANICS (CMM2017): Proceedings of the 22nd International Conference on Computer Methods in Mechanics, Lublin, Poland, 13-16 September 2017. AIP Conference Proceedings, S. 120004-1 - 120004-12, https://doi.org/10.1063/1.5019119.

[3] Hübel, H.; Vollrath, B.: Simplified Analysis of Strains Accumulated in the State of Elastic Shakedown Considering Multi-Parameter Loadings. In: Volume 3: Design and Analysis. ASME 2018 Pressure Vessels & Piping Conference, July 15-20, 2018, Prague, Czech Republic. American Society of Mechanical Engineers, S. 1 - 10, https://doi.org/10.1115/PVP2018-84070.

[4] Hübel, H.; Vollrath, B.: Simplified determination of accumulated strains to satisfy design code requirements. International Journal of Pressure Vessels and Piping 171, 2018, S. 92 - 103, https://doi.org/10.1016/j.ijpvp.2019.01.014.

[5] Hübel, H.; Vollrath, B.: Limited Versus Unlimited Strain Accumulation Due to Ratcheting Mechanisms. Journal of Pressure Vessel Technology 141, 2019, Heft 3, S. 214 - 223, https://doi.org/10.1115/1.4042853.

[6] Vollrath, B.; Hübel, H.: Direct Analysis of Post-Shakedown Quantities With the STPZ Considering Multi-Parameter Loading. In: Volume 3: Design and Analysis. ASME 2019 Pressure Vessels & Piping Conference, San Antonio, Texas, USA, July 14 - 19, 2019. American Society of Mechanical Engineers, S. 1 - 7, doi.org/10.1115/PVP2019-93268.

[7] Vollrath, B.; Hübel, H.: Efficient Fatigue and Ratcheting Computation in Case of Multi-Parameter Loading. In: Volume 2: Codes and Standards. ASME 2020 Pressure Vessels & Piping Conference, Minneapolis, Minnesota, USA, July 19 - 24, 2020, PVP2020-21089. American Society of Mechanical Engineers (paper accepted).