Fatigue Behavior of Metastable Austenitic Stainless Steels in LCF, HCF and VHCF Regimes at Ambient and Elevated Temperatures

Abstract

Corrosion resistance has been the main scope of the development in high-alloyed low carbon austenitic stainless steels. However, the chemical composition influences not only the passivity but also significantly affects their metastability and, consequently, the transformation as well as the cyclic deformation behavior. In technical applications, the austenitic stainless steels undergo fatigue in low cycle fatigue (LCF), high cycle fatigue (HCF), and very high cycle fatigue (VHCF) regime at room and elevated temperatures. In this context, the paper focuses on fatigue and transformation behavior at ambient temperature and 300 °C of two batches of metastable austenitic stainless steel AISI 347 in the whole fatigue regime from LCF to VHCF. Fatigue tests were performed on two types of testing machines: (i) servohydraulic and (ii) ultrasonic with frequencies: at (i) 0.01 Hz (LCF), 5 and 20 Hz (HCF) and 980 Hz (VHCF); and at (ii) with 20 kHz (VHCF). The results show the significant influence of chemical composition and temperature of deformation induced ´-martensite formation and cyclic deformation behavior. Furthermore, a “true” fatigue limit of investigated metastable austenitic stainless steel AISI 347 was identified including the VHCF regime at ambient temperature and elevated temperatures.

Modeling short crack propagation under variable structural and thermal loadings

“…19 Many austenitic steels show a plasticity-induced phase transformation when mechanically loaded at room temperature. 20,21 The material investigated here does not make an exception. However, the maximum operating temperature of the components of interest is about $370 C. While a phase transformation from austenite to martensite is observed at room temperature, this phenomenon does not occur under higher temperatures.…”

Sonotrodes for Ultrasonic Welding of Titanium/CFRP-Joints—Materials Selection and Design

“…Besides Young's modulus, mass density and Poisson's ratio, the fatigue strength was considered. Therefore, the fatigue strength of the selected materials was characterised by ultrasonic fatigue testing system (20 kHz) close to ambient temperature up to an ultimate number of cycles of 2.5 × 10 9 to estimate the very high cycle fatigue (VHCF) behaviour (see [36,37]). The samples were tested in pulse/pause-sequences of 2500 ms/500 ms, leading to an effective testing frequency of 16.6 kHz.…”

Fatigue Life Evaluation Considering Fatigue Reliability and Fatigue Crack for FV520B-I in VHCF Regime Based on Fracture Mechanics

“…Quantitatively expressing the fatigue reliability of FV520B-I is a key research topic, especially for those who can use the information to improve the manufacturing of mechanical equipment and avoid fatigue failure. Fatigue reliability [3][4][5][6][7][8] refers to the probability that theoretical fatigue life will meet the actual required life time of the material, which can be quantitatively expressed by a probability of the fatigue life without the fatigue failure in solving real engineering fatigue problems, especially for the core components of large mechanical equipment. With FV520B-I being more and more widely used, there is increasing interest in detailed study modelling its fatigue reliability in the VHCF regime, and developing a new precise fatigue life evaluation model (which is beneficial to clarify fatigue failure characteristics, and also very essential to avoid fatigue failure efficiently in real engineering practice).…”

“…and the data in Tab 6,. a nonlinear fitting algorithm should be adopted to identify the unknown parameters in Equation(13).…”