Thermography in high cycle fatigue short‐term evaluation procedures applied to a medium carbon steel

Abstract

This paper focuses on the fatigue life calculation for an unalloyed medium carbon steel SAE1045 (German DIN-standard: C45E), by applying an energy dissipation-based approach quantified through thermographic measurements. The purpose of this approach is to establish an intrinsic dissipation model and to predict characteristics derived from the cyclic deformation behavior of stress-controlled fatigue tests, eg, the fatigue limit and the S-N data by using simplified (zero-dimensional, 0D) thermodynamic equations. In order to investigate the possibilities for a rapid evaluation while simultaneously reducing the experimental effort, one load increase test (LIT) and two constant amplitude tests (CATs) were carried out. The S-N data evaluated on such a basis is competitive to conventionally determined S-N data as will be shown. K E Y W O R D Sfatigue life evaluation, intrinsic dissipation, medium carbon steel, thermography

Thermodynamic entropy as a marker of high‐cycle fatigue damage accumulation: Example for normalized SAE 1045 steel

“…In order to evaluate the processes of fatigue damage evolution, two types of fatigue tests were performed: the one being a constant amplitude and the other a load increase test, respectively. The details of the respective load types for the tests performed are summarized as follows: Constant amplitude tests: five tests at stress amplitudes between 320 and 400 MPa, with each test differing in 20 MPa of stress amplitude. Load increase tests: all tests starting from a stress amplitude level of σ a,start = 100 MPa, being below the fatigue strength, σ f = 300 MPa, 31 of the normalized SAE 1045 steel investigated at R = − 1 and being loaded for a defined number of cycles ∆N before increasing the stress amplitude by an increment ∆σ a to a next stress amplitude level while cycling again the specimen with a number ∆N of cycles and this to be continued so forth until the specimen failed. A distinction has been made between tests in which (a) ∆N was retained constant at 9,000 cycles and ∆σ a increased in steps of 5 MPa from 20 to 40 MPa as well as in tests where (b) ∆σ a was kept at 25 MPa and ∆N was varied to step lengths of 1000, 2000, 3000, 4500 and 6000 cycles, respectively. …”

Rapid characterization of the fatigue limit of additive-manufactured maraging steels using infrared measurements

“…In particular, Munier et al [25] worked on the differences between the two thermal regimes in the self-heating response, namely below and above the fatigue limit of the material. Teng et al [27] proposed a procedure to determine the Wöhler curve by IR thermography. Akai et al [28] used high spatial resolution thermography for the observation of slip bands in 316L austenitic stainless steel (SS) under fatigue loading.…”

Quantitative thermographic method for fatigue life prediction under variable amplitude loading

“…A flow diagram of the fatigue testing procedure based on QTM is shown in Figure 1. A stepwise amplitudeincreasing fatigue loading procedure is applied to the specimen block by block, 65,66 and the temperature of the specimen surface is measured simultaneously using an infrared camera. In each loading block, fatigue loading is not suspended until the stabilized Stage II is reached, which usually requires thousands of cycles for steels.…”