PSI - Issue 42

D. Weiß et al. / Procedia Structural Integrity 42 (2022) 879–885 Author name / Structural Integrity Procedia 00 (2019) 000–000

881

3

the investigation of a possible influence of different crack locations in relation to the clinched joint, the CC-specimen is also taken from three different positions according to Fig. 2. The clinched joint is moved at intervals of 3 mm from the radius to the center of the C-shape, leading to the three different crack positions A, B and C.

Fig. 2. Schematic illustration of the extraction of the CC-specimen and the different positions of the crack in relation to the clinched joint.

3. Numerical preliminary investigations For the determination of the fracture mechanical parameters of the CC-specimen, some preliminary investigations are essential. In the ASTM E 647 standard, specimens for the determination of the fracture mechanical parameters are illustrated. The most common specimen is the Compact Tension (CT) specimen. For these standard specimens, all necessary functions such as the geometry factor function as well as the calibration function for the crack length measurement are known for the experimental investigations. Since the sheets in the clinching process are only 1.5 mm thick and the geometry is dependent on the clinched joint, a special specimen is developed and investigated whose geometry is shown in Section 2. For this CC-specimen, the geometry factor function and the calibration function have to be determined numerically. 3.1. Geometry factor function In order to determine the crack growth rate with the CC-specimen, knowledge of the stress intensity factor K is required. The stress intensity factor is a measure of the magnitude of the stresses and the displacements in the vicinity of the crack and is influenced by the crack location, the specimen geometry as well as the type and location of loading. All of these influencing factors are considered in the geometry factor function, Richard and Sander (2016). This function is numerically determined for the CC-specimen using the crack growth simulation program F RANC 3 D TM . In Fig. 3 a comparison of the geometry factor function of the extended Mini-CT specimen and of the CC-specimen is presented. It can be stated that only at the beginning of the geometry factor function an influence of the different geometries can be observed. This results from the C-shape of the CC-specimen. Since the geometry function of the CC-specimen is stored in the program during the tests, this influence is also taken into account.