Institute of Materials Science and Engineering

PhyBal—Physically based lifetime calculation of metallic materials

In order to calculate the lifetime of highly loaded materials and components reliably, we need to have sound knowledge of fatigue processes and a systematic understanding of fatigue behavior. Increasingly we are using methods to detect change in temperature and specific electrical resistance, in addition to stress-strain hysteresis measurements. This project used the short time procedure PhyBaLLIT to calculate the lifetime of metallic materials.

Based on the results of Basquin [1] and Morrow [2] we calculated S—N curves and reliably estimated the endurance limit using only three fatigue tests (one load increase test (LIT) and two constant amplitude tests (CAT)) (Fig. 1). We found that it was possible to detect the fatigue properties of materials ex situ in unloaded conditions by measuring specific electrical resistance. We achieved a reduction in testing time of about 90% from conventional testing methods. This has enormous potential for science and industry, particularly in terms of reducing costs and increasing efficiency.

 

Fig. 1: Schematic description of the physically based lifetime calculation method PhyBaLLIT by means of one of the described physical measurements (M)

This project is financially supported by the German Research Foundation (DFG).

[1]       O.H. Basquin: ASTM proceedings: The exponential law on endurance tests. 10: p. 625-630, (1910).

[2]       J. Morrow: ASTM Int, Cyclic plastic strain energy and fatigue of metals. STP 378: p. 45-87, (1964).

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