# Failure Prediction for the Tearing of a Pin-Loaded Dual Phase Steel (DP980) Adjusting Guide
## 4 Validation by Tearing of Adjusting Guide  
For the validation of the material properties obtained in Section 3, a segment of an adjusting guide (thickness \(T\) = 1.0 mm) used in a vehicle was torn by a circular pin, sticking through the upper hole (Figure 11). The whole segment contained four holes, the centers of which were slightly off the vertical center line. The lower end was clamped, as depicted in Figure 11), where the lower two holes were hidden inside the lower clamp; during the test, the pin in the upper hole was displaced at a constant speed of 20 mm/min until failure. Again, DIC was employed to obtain the displacement and strain fields.  
The numerical model consisted of 1400 second order shell elements, that is, the same type as that previously used in Section 3 (note that the damage parameters are only valid for this element type, and they cannot be used for others such as solid elements). The characteristic element length was \(e\) = 1.0 mm.  
The validation of the material parameters was performed by comparing the (i) external force-displacement curves and (ii) the strain distributions at selected points obtained by experiment and FE analyses. An additional FE analysis was performed with the damage model deactivated to show the point where damage sets in. The externally applied force is plotted over the displacement (i.e., pin travel) in Figure 12. We can state that although the numerical analysis somewhat underestimated the maximum forces, the deviation was small (\(-5\%\)), and the curves were of a similar shape. The first sharp decrease in load was due to the bulging of the hole rim, for which the pin was in contact with, in an out-of-plane direction, and was apparently not accompanied by damage. The subsequent \"load arrest\" between an approximately 8-10 mm displacement was very well reflected by the numerical analysis. The departure of the \"no damage\" curve from the \"GISSMO\" curve indicates the beginning of material weakening (i.e., \(D\) surpassed \(D_{c}\)). Furthermore, fracture occurred at approximately equal displacements (10.8 vs. 11.5 mm), although the exact failure displacement depends on numerous factors (for both experiment and FE analysis), and is therefore hard to predict.  
Figure 10: Experimental average FD curves and numerical FD curves obtained with the final damage parameters.  
The equivalent strain distributions at fracture are shown in Figure 13. Crack formation was preceded by severe deformation. It was found that the maximum compressive strains in the \(y\)-direction (\(\varepsilon_{y}\)) in the part of the guide that was in contact with the pin were of a similar magnitude (\(-0.34\) (test) vs. \(-0.38\) (FE analysis)), and the values in the other regions were also in good agreement. Furthermore, for the experiment and simulation, the crack formed in the same region, namely on the left side of the ligament between two holes, which is subject to high strains, and grows in the \(y\)-direction.  
The results show that the introduction of GISSMO facilitates quite a good reproduction of the experimental results. The presented FE model is proven to be applicable to complex cases, such as the one shown here. The discrepancies between the experiment and FE analysis may be explained by the neglect of the material anisotropy, which, despite the mild anisotropy of the sheets used here, may gain some significance under certain loading conditions. Furthermore, the rise of \(\eta\) with a plastic strain cannot be considered. However, the error in the externally applied maximum force is considered to be too small to justify an extensive investigation into the error's possible origins, such as the compliance of a jig or frame, thickness variations in the strip, possible burrs around the holes, or friction.  
Figure 11: Test setup for adjusting the guide tearing: as in GOM Aramis (left) and the model (right).  
Figure 12: External FD curves from experiment and numerical analysis with and without consideration of damage.