Project Description

High-strength steels and aluminium alloys are used in automotive components commonly and these components are subjected to cyclic loads that may consist of an initially low number of load cycles from 3 to 12 but with relatively high amplitude. Hence, it is required to evaluate the permanent deformation and the crack (breakage of the component) after repetitive high plasticization to determine the durability of the structure. Moreover, these structures may be subjected to a further higher number of load cycles with small amplitudes after a high plasticization case.

In this case, by considering the history of their plastic deformations, determining the hardening behavior plays a significant role in the further fatigue life calculations and evaluation of permanent deformation. For such cases, the hardening behavior of the materials should be estimated accurately by a reliable method and taken into account in further durability analysis, which is performed in FE simulations. The investigation of the low cycle fatigue behavior of engineering structures requires a model to determine material parameters in the elastic-plastic range, particularly also concerning hardening.

Strain-controlled cyclic tests are performed to obtain hysteresis curves for any ductile materials to determine their high amplitude cyclic loading behaviors. These test results are used to calibrate combined hardening parameters for further simulations in FE models and practical engineering applications of the material subjected to high amplitude cyclic loading.

standing narrow figure above and below blue and in the middle green, yellow and red

Figure 1: A sample FE model of the specimen after cyclic loading

Main Goals

In the present project, an optimization method is developed to estimate non-linear isotropic and kinematic hardening parameters for the ductile materials by considering minimizing the error between measurement and simulation results. It is aimed to determine the minimum number of hardening parameters that may represent reasonable hardening behavior for the materials under high amplitude cyclic loading simulations but also at different strain ranges. The estimated parameters are implemented into a realistic FE model and hysteresis behavior is simulated to compare results with the test results.

Results

The optimization methodology developed is applied for six materials (HX220-BD, AW5754, AW6082, DC04, S235, and S355) that are used in the vehicle industry frequently to obtain their nonlinear hardening parameters and very accurate simulation results for the hysteresis curves are obtained.  A sample of an FE model for the deformed specimen geometry in simulation is given in Figure 1 and a comparison of the hysteresis curves from the test and simulation results is presented in Figure 2 for aluminium alloy AW6082.

Graph with four closed curves, two red and two blue

Figure 2. Comparison of test data and FE simulation results of hysteresis curve (for aluminum alloy AW6082)

Figure 2. Comparison of test data and FE simulation results of hysteresis curve (for aluminum alloy AW6082)

Publication

Arslan, Eray, Milan Zigo, and Gerhard Kepplinger. "A Novel Approach for Determination of Hardening Parameters of an Aluminum Alloy under Cyclic Loading with High Amplitudes, opens an external URL in a new window." In IOP Conference Series: Materials Science and Engineering, vol. 947, no. 1, p. 012009. IOP Publishing, 2020.

Cooperation Partner

Duration

  • March 2018 - October 2018

Contact

Privatdoz. Dr. Eray Arslan

Send email to Eray Arslan