Abstract
The effects of shot peening treatment (SPT) were studied at (10,20, and 30) minutes on the rotating bending fatigue behavior and the behavior of the alloy steel DIN 41Cr4 vibrations. The hardness test, tensile test, constant amplitude fatigue tests, and the vibration measurements were performed on samples with and without cracks at room temperature (RT), also, the fracture surface was examined and analyzed by a Scanning Electron Microscope (SEM). The results of the investigations, for example, Stress to Number of cycles to failure (S-N) curves, fatigue strength improvement factor of 5% to 10%, the decreasing percentage of maximum Fast Fourier Transform (FFT) acceleration of the shot-peened condition were compared to untreated conditions ranging between 25% and 40%. All these improvements occurred for up to 20 minutes of shot peening time (20 SPT), exceeding that time the fatigue behavior tended to decrease due to high roughness and the generation of tensile residual stress.
Highlights
It was well known that most of the structural components are subject to periodic loading during service and are subject to the failure to start the cracks of fatigue from the surface and propagate to the critical length
Group A: Fatigue test of alloy steel (DIN 41Cr4) before and after shot peening at room temperature. 48 samples were prepared for fatigue test at room temperature
Where the decreasing in the vibration occurred after peening treatments. (FFT) or Fast Fourier transform, the aim is the response or a vibration of a system can be represented by the amplitudes of acceleration, velocity, and displacement in both frequency and time domains
Summary
It was well known that most of the structural components are subject to periodic loading during service and are subject to the failure to start the cracks of fatigue from the surface and propagate to the critical length. Through the application of proper surface treatments, of which shot peening, it is potential to improve the fatigue strength of engineering parts (Al-khazraji, 2016). SP is creating a compressive residual-stress layer in the near-surface region to improve the fatigue strength of mechanical parts. (Wang et al, 1998) proved that SP presents compressive residual stress into the surface layer, pushes the crack source into the tensile residual stress region beneath the hardened surface layer, and leads to the best of strengthening influences. (1) Surface fracture type: a large amount of compressive residual stress reduces at the surface layer through the initial stage of fatigue life when the stress amplitude is high. (2) Internal fracture type: the initial residual stress remains stable and a crack cannot be started at the surface where compressive residual stress exists if the stress amplitude is low. Measure the natural frequency and mode shape numerically by using ANSYS before and after SP
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