The objective of this work is to investigate the use of metallurgical gradients (MG) in the design of structural components made of ductile cast iron (DCI). MG have been realized in this study by locally varying the pearlite fraction of the matrix. Exemplarily, the allowable cyclic load for a drive shaft as well as the allowable static displacement are calculated. The performed calculations are based on static and cyclic strength data of four different DCI with amounts of pearlite ranging from 0% to 96.8%. To show the advantage of the purposeful usage of local MG, ten different configurations are examined by numerical simulation studies of a generic drive shaft comprising a circumferential notch. Four configurations are calculated assuming homogenous material throughout the entire component. In the other six configurations the surface region of the notch root has an increased amount of pearlite. For each configuration the allowable multiaxial cyclic load by combinations of torsion and bending was calculated and subsequently the allowable static bending displacement. The results show that the targeted realization of MG results in a significant increase in the multiaxial fatigue strength of the shaft as well as in a slight improvement of the allowable static bending displacement.

The stiffness of adhesively bonded single-lap joints is of fundamental importance in the static and dynamic sizings of engineering structures. Nevertheless, existing analytical stiffness determination models show a large discrepancy when compared to experimental results or finite element analyses. Within the present paper, a novel analytical approach for stiffness determination of single-lap joints under tensile loading is derived, which takes the out-of-plane deformation of the adherends into account. In order to provide a comprehensive model validation, single-lap joint experiments with two different adherend materials, two different adhesives and two different bondline thicknesses are conducted. Furthermore, analytical results are compared to two-dimensional finite element analyses. The presented model shows a good agreement with stiffness determination when compared to experimental and numerical results while offering a higher degree of accuracy when compared to existing stiffness determination models.

The crushing of crash boxes is a complex phenomenon characterized by a strong interaction of structural and material properties. Many attempts to improve their energy absorption by adopting one aspect resulted in unacceptable unprogressive bucking. Thus, special considerations are required for crash box optimization including both material and structural effects. In this study, the structural behavior of the crash box is analyzed and a new design approach is introduced to fulfill these requirements. Currently, components, processes, and materials are mainly developed independently. However, to exploit the full potential of modern materials in component design, integrative development work is necessary. Component performance-based requirements and corresponding local material properties must be taken into account concurrently. In this work, a component-driven material design approach is presented, in which local-material-property requirements are derived from component simulations. This new approach is demonstrated by the use case of a quasistatically deformed crash box produced out of steel DP600 for the optimization target “energy absorption”. The finite element simulations were carried out on the crash box, and required material properties for improving the crash box performance were derived based on the simulations. Heat treatment strategies were developed afterwards and experimentally validated to fulfill these requirements. The finite element (FE) simulations based on the experimentally extracted material properties reveal the potential of the component-driven material design approach to improve the crash box performance. The introduced approach enables exploiting the full energy-absorption capacity of the material while ensuring the desired service behavior of the component.

Considering the aerospace sector, the use of adhesively bonded joints is constantly increasing over the last decades. Due to its lightweight and capability of joining various materials with different coefficient of thermal expansion, this joining technique offers many benefits over conventional methods like rivets, screws and welding. On the other hand, structural adhesives consists of polymer chains that can be severely affected by the environment. An example of such an environmental effect is the interaction of the polymer chains of the adhesive with ionizing radiation in space. Nevertheless in the literature, the influence of ionizing radiation on the mechanical properties of epoxides is covered but not well understood. The present work describes a method of determining the stiffness of an adhesively bonded single lap joint (SLJ) using closed form solution equations. This analytical approach is compared with a numerical model. The mechanical properties of the adhesive in both models is degraded due to irradiation, based on experiments conducted by the European Organization for Nuclear Research (CERN). The results show that the degradation of the mechanical properties of the adhesive layer has a significant influence on the joint stiffness. This effect increases with growing adhesive layer thickness. Comparing the results with a finite element model, it is shown that the developed calculation scheme overestimates the stiffness of the SLJ. This is caused by the neglection of bending stresses within the adherends.

Currently, components, processes and materials are mainly developed independently. However, to exploit the full potential of modern materials in component design, integrative development work is necessary. Component performance-based requirements and corresponding local material properties must be taken into account. In this work, a component-driven approach and therefore an inverted process chain is presented and demonstrated on the performance of a crash box, produced from DP600 steel. This is aimed to increase the energy absorption of the crash box without losing progressive buckling behavior. The finite element simulations were carried out on the crash box. It was shown that the crash box corners play an important role in the crash box performance, and required material properties for improving the crash box performance were derived based on the simulations. Heat treatment strategies were afterward developed and experimentally validated to fulfill these requirements. Then different local heat-treatment processes were applied to the corners of the crash boxes and tested experimentally. The experiments results validate the potential of the inverted process chain to improve the components performance. Furthermore, in this paper, optimal material properties were extracted for crash box strengthening, which lead to high energy absorption and a low peak force of it.