Improvement of the Inverse Finite Element Analysis Approach for Tensile and Toughness Predictions by Means of Small Punch Technique

This paper focuses on the inverse FEA to calculate the SPT tests and the prediction of the tensile and fracture toughness behavior. For the description of the SPT tests via FEA the hardening rule of Ramberg-Osgood and the damage model of Gursson-Tvergaard-Needleman (GTN) were used. The inverse FEA optimization process cannot provide a unique solution for the 12 parameters included in the material model. This results from a dependency between some parameters, which leads to the same solution in the optimization. Hence a novel description of the dependent parameters was developed and implemented within the optimization process. Therefore, an enhanced inverse FEA approach was proposed which provides a fast converging solu- tion for determination of the material model parameters. Within this study the forged turbine shaft material EN: 27NiCrMoV15-6 was investigated. For comparison purposes SPT tests as well as tensile tests and fracture toughness tests were carried out. In the case of the tensile properties the test and simulation show coincidence in the curve as well as the characteristic values. For the toughness behavior the characteristic value of the test was met by the simulation.

Using Full Field Data to Produce a Single Indentation Test for Fully Characterising the Mooney-Rivlin Material Model

A theoretical testing method for fully characterising the Mooney-Rivlin hyper-elastic material model is proposed by capturing full-field data, namely displacement field and indentation force data. A finite element model with known parameters will act as the experimental model against which all data will be referenced. This paper proposes a method of inverse finite element analysis operating under the assumption of equally objective function optimal planes or “hyper-planes”. The paper concludes that the Mooney-Rivlin material model can theoretically be fully characterised in a single indentation test by applying methods discussed in the paper when using full-field data operating under the assumption of hyper-planes.

Improvement of the Inverse Finite Element Analysis Approach for Tensile and Toughness Predictions by Means of Small Punch Technique

This paper focuses on the inverse FEA to calculate the SPT tests and the prediction of the tensile and fracture toughness behavior. For the description of the SPT tests via FEA the hardening rule of Ramberg-Osgood and the damage model of Gursson-Tvergaard-Needleman (GTN) were used. The inverse FEA optimization process cannot provide a unique solution for the 12 parameters included in the material model. This results from a dependency between some parameters, which leads to the same solution in the optimization. Hence a novel description of the dependent parameters was developed and implemented within the optimization process. Therefore, an enhanced inverse FEA approach was proposed which provides a fast converging solution for determination of the material model parameters. Within this study the forged turbine shaft material EN: 27NiCrMoV15-6 was investigated. For comparison purposes SPT tests as well as tensile tests and fracture toughness tests were carried out. In the case of the tensile properties the test and simulation show coincidence in the curve as well as the characteristic values. For the toughness behavior the characteristic value of the test was met by the simulation.