Potential of Metallurgical Gradients in the Design of Structural Components Made of Nodular Cast Iron

Abstract

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.

Potential of inverted process-chain development to improve crash box performance

“…Similar approaches of fully integrated design workflows can be found in the field of aminated continuous fiber-reinforced composites [39]. In this context, local property grading for nodular cast iron has been studied by Gebhardt et al [40] and Ripplinger et al [41]. Both works showed a benefit in terms of increased fatigue strength in the case of high silicone-alloyed nodular cast iron and ferrite graded nodular cast iron.…”

Data analysis of striation spacing, lifetime, and crack length in crankshaft ductile cast iron under cyclic bending loading through high-cycle fatigue regime

“…As an important note, Ripplinger et al. [8] found that by increasing the pearlite concentration and thereby the static and fatigue strength in the near-surface region at a notch, a significant increase of the fatigue strength was achieved. Therefore, it could be suggested that the effect of graphite nodules and the amount of pearlite on the experimental results are considered for future research.…”

Key Determinants for High-Alloyed Cast Irons for Mechanical Engineering

“…Ductile iron components are often metallurgically optimised to obtain the most homogeneous microstructure possible. This results from the established guidelines for strength confirmation, which are based on the strength parameters published in standards such as [23] including three categories of microstructures and properties depending on the wall thickness [24].…”

“…These include locally applied additives and the influence of flow and cooling conditions on the solidification kinetics of the surface layer. As reported [24], in addition to strengthening and tempering in solid solution, the main approach to controlling the mechanical properties of ductile iron is to use the amount of perlite and ferrite in the metallic matrix Looking at typical ductile iron grades, the effect of strengthening the strength of the perlite for static loads is obvious [66]. Fig.…”

“…According to Ripplinger et al [24], in the case of ductile iron it is known that the failure occurs due to local plastic deformations in the areas surrounding the graphite nodules Once a critical level is reached, these deformations result in the formation of interfacial cracks. Increasing loads lead to a circumferential growth of these interfacial cracks until the entire nodule is detached from the matrix.…”