“PHYBAL” a Short‐Time Procedure for a Reliable Fatigue Life Calculation

Abstract

The reliable calculation of the fatigue life of high‐strength steels and components requires the systematic investigation of the cyclic deformation behaviour and the comprehensive evaluation of proceeding fatigue damage. Besides mechanical stress‐strain hysteresis measurements, temperature and electrical resistance measurements were used for the detailed characterisation of the fatigue behaviour of the steel SAE 4140 in one quenched and tempered, one normalised, one bainitic and one martensitic condition. To guarantee optimal operation conditions the new fatigue life calculation method “PHYBAL” on the basis of generalised Morrow and Basquin equations was developed. It is a short‐time procedure which requires the data of only three fatigue tests for a rapid and nevertheless precise determination of S‐N (Woehler) curves. Consequently, “PHYBAL” provides the opportunity to reduce significantly experimental time and costs compared to conventional test methods.

Fatigue assessment of metallic materials beyond strain measurement

“…The investigations presented in this paper were mainly carried out at the Institute of Materials Science and Engineering at the University of Kaiserslautern/Germany [15,17,18]. In the following results from specimens of the quenched and tempered steel SAE 4140 (42CrMo4) [15] as well as of the cast irons EN-GJV-400 and EN-GJS-600 [18] are considered.…”

“…They may provide an ideal input with regard to materials' parameters and data, which have been originally generated as a database in handbooks [13,14] and consequently significantly enhanced with respect to their generation for the physically based lifetime calculation ''PHYBAL'' [15]. ''PHYBAL'' is a procedure where the complete stress-strain as well as S-N-curve of a material are generated by 3 experiments on unnotched specimens only, reducing the amount for experimentation by mainly an order of magnitude when compared to conventional approaches.…”

“…The physical quantities are linked by cross-effects associated with cyclic plastic deformation and directly related to microstructural changes in the bulk material obtained during fatigue loading. Methods commonly associated with physical parameters being used in nondestructive testing (NDT) are based on physical ''processes'' or on the interaction between different forms of external energy and the material microstructure are methods to be very much considered, specifically within the context of ''PHYBAL'' in that regard [15,17].…”

Characterisation of the mechanical and corrosive properties of newly developed glass-steel composites

“…As the fatigue strength is linked to the first increase in the material-reaction quantity within one step, 9 the estimate from this load-increase test for the endurance limit is 70 MPa. This estimation was validated with the constant-amplitude tests with N limit = 2·10 6 as the ultimate number of cycles.…”

“…During this test, the plastic-strain amplitude was measured as the parameter of the material reaction, which characterizes the proceeding fatigue damage as the basis for the estimation of the fatigue strength. 9 The estimation of the fatigue strength was validated with constant-amplitude tests, whose lifetimes (the number of cycles to failure) are shown with the S-N curve.…”