Fatigue Life Analysis of Solid Elastomer-Like Polyurethanes
The material behaviour of polymeric materials under cyclic fatigue loads is complex and forms a vast field of research activities. Elastomer-like polyurethane materials form an excellent fit for cyclically loaded system components in many cases. The prese
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Fatigue Life Analysis of Solid Elastomer-Like Polyurethanes Robert Eberlein, Yuta Fukada, and Lucian Pasieka
Contents 1 Introduction 2 Test Equipment and Material 3 FCG Analysis 3.1 Determination of the Tearing Energy 3.2 Room Temperature Experiments 3.3 60 C Experiments 4 Fatigue Life Concept 4.1 Material Model Calibration 4.2 TNM Validation 4.3 ESEDEN for Lifetime Prediction 5 Cross-Validation of Lifetime Prediction Concept 6 Conclusion and Discussion References
Abstract The material behaviour of polymeric materials under cyclic fatigue loads is complex and forms a vast field of research activities. Elastomer-like polyurethane materials form an excellent fit for cyclically loaded system components in many cases. The present work aims to quantify fatigue crack growth (FCG) in a highperformance, commercially available hydrolysis-resistant thermoplastic polyurethane (TPU). This TPU material is often used in water or oil hydraulics and applications in mining, tunneling, etc. due to its high resistance to abrasion and tear strength. For those heavy-duty applications, the critical lifetime is reached as R. Eberlein (*) Zurich University of Applied Sciences, Winterthur, Switzerland e-mail: [email protected] Y. Fukada Sophia University, Tokyo, Japan L. Pasieka Eugen Seitz AG, Wetzikon, Switzerland
R. Eberlein et al.
soon as cracks reach a critical threshold in the TPU material. The first part of the current work illustrates the FCG analysis of the TPU material, i.e. crack propagation measurements on a Tear and Fatigue Analyzer (TFA, Coesfeld GmbH & Co. KG, Germany). Based on the TFA measurements, it is shown how the tearing energy and the FCG rate have a certain regularity at different strain levels and quite a different behaviour compared to standard rubber material. Secondly, a lifetime prediction of the TPU material is derived by means of advanced finite element analysis (FEA). By using Abaqus simulation software (Dassault Systèmes) with advanced material modeling concepts, simulations are performed under the identical conditions as the TFA experiments. The results are plotted in terms of total elastic strain energy density per element (ESEDEN) over FCG rate in the vicinity of the crack tip. In a third step, the lifetime prediction concept ESEDEN is cross-validated by comparing experimental results from a test bench that applies cyclic high strain rate loading to the TPU material with corresponding FEA. As demonstrated the ESEDEN data proves being a promising criterion for lifetime prediction of critical TPU components under cyclic loading conditions. Keywords Crack growth · Fatigue · FEM · Lifetime prediction · Polyurethane
1 Introduction Polymeric materials such as rubber and polyurethanes are used for a broad range of applications, e.g. tires, seals, bushings, boots and so on. The characteristics of rubber and TPU materials are similar; both are elastic and flexible. However, TPUs are typically chosen instead of rubber due to their rubber-like characteristics combined with their high resistance to fatigue un
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