Frequency Dependent Fatigue Strength Investigations on Tempered Steel and Nodular Cast Iron

Abstract

This paper presents experimental fatigue tests on specially shaped specimens made from quenched and tempered steel 42CrMoS4 and nodular cast iron EN-GJS-600-3. The specimens are geometrically designed to resemble actual subcomponents of forming and cutting dies for sheet metal manufacturing. These subcomponents have failed in the past.Experiments are carried out using a fictive load-time function, which is a modification of an actually measured load curve and has variable mean and amplitude values. This first test series serves as a general validation of a subsequent fatigue analysis. A second test series is carried out with constant mean and amplitude values with a load ratio R % 0. Here, the load frequencies in the individual test runs are varied between f ¼ 5 Hz and f ¼ 45 Hz in order to investigate the influence of the frequency. Both series are performed on a servo-hydraulic testing machine.The experimental data is then statistically evaluated. The values for the scatter correlate with data from the literature. The data from the test series with the fictive load-time function can thus be used for subsequent validation of a fatigue calculation, which will be addressed in a future publication. Most significant are the findings from the second series of experiments with varied load frequencies, as a significant frequency influence could be detected. Furthermore, the hardening and softening behavior under cyclic loading and the fracture behavior of the materials are analyzed and compared with data from the literature.

A comparative study of Glinka and Neuber approaches for fatigue strength assessment on 42CrMoS4‐QT specimens

“…from the processes of forming and cutting. To assess the endurance capability of critical subcomponents within a complex entity like a press die, force‐controlled fatigue tests on these components were executed in Thumann et al [23] These tests are conducted on simplified specimens intentionally designed to replicate the critical part geometries found in a die, such as a slide stopper in this instance, see Figure 1 and Figure 2. The relevant root radius of the specimen is chosen to be , see Section 2.3.1.…”

“…The load functions in the present report are chosen based on measurements of such a system. For an in‐depth description of the specimen and the test setup, see Thumann et al [23] …”

“…Schematic of the clamping device for fatigue tests with an inserted 42CrMoS4 specimen, adapted from Thumann et al [23] …”

“…Figure 2 shows the FE discretised simulation model with the boundary conditions according to the component tests carried out in Thumann et al [23] Table 1 lists the individual components considered in the model. The parts columns (1) , cylinder piston (13) and all metric bolts (8) are discretised with beam elements.…”

“…In a previous investigation [23] on subcomponents of forming and cutting dies for sheet metal manufacturing, the authors carried out component tests on specimens made of steel 42CrMoS4‐QT for several load‐cases, showing a rate‐sensitivity of this material. In order to extend the findings in the field of fatigue strength evaluation of 42CrMoS4, the present work uses this experimental data for the validation of numerical fatigue strength assessment.…”