Abstract
Ultrasonic resonance fatigue test method at 20 kHz related to the very high cycle fatigue (VHCF) aims to accelerate a time-consuming experiment. In this paper, an ultrasonic fatigue device with a data acquisition system was improved for monitoring and recording the data from fatigue tests in which self-heating phenomenon exists. Symmetric tension-compression sinusoidal vibrating mode (R = −1) was observed in this study. VHCF behavior and mechanism of Inconel 718 were carried out using this device. It was concluded that more than 99% of fatigue life is consumed in initiation duration. Specimen temperature increase was not a decisive factor in VHCF strength for Inconel 718, as long as it was far less than the design temperature limitation. A single initiation site existed at the subsurface facet or grain cluster, observed from scanning electron microscope (SEM) micrographs. Quasi-cleavage fracture in transgranular ductile mode emerged and then tended to trace grain boundaries in an intergranular manner by cleavage-dominated mixed mode.
Highlights
With the development of modern industry, the total life cycle of mechanical components, such as aircraft engines, exceeds already up to 109 ~1010 during the whole lifetime
The self-heating of Inconel 718 specimen caused by internal friction and microscopic plasticity under a high frequency was significant during the test
The number of cycles corresponds to the total fatigue lifetime, which was counted from when the test device started until when it stopped due to the frequency loss when fracturing
Summary
With the development of modern industry, the total life cycle of mechanical components, such as aircraft engines, exceeds already up to 109 ~1010 during the whole lifetime. Relative to the standardized low-frequency tests methods, high-frequency fatigue results are influenced by some factors, such as loading mode and frequency, specimen geometry and size, material type and heat treatment, etc. Behavior of Inconel 718 in as-built and double-aging conditions at 10 Hz. Zhong et al [18] compared the HCF performance of solution and aged material using a high-frequency machine at 130 Hz. few results have been presented on the VHCF behavior and crack mechanism of Inconel. The present paper aimed at (1) the development of data acquisition system for monitoring and recording the parameters during fatigue test with self-heating phenomenon and at (2) the VHCF behavior and crack mechanism of high-temperature superalloy Inconel 718
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