• Journal of Applied Reliability
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• v.17 no.4
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• pp.325-331
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• 2017

Purpose: There is active research that improves both reliability and fatigue life of structures which widely used in the aerospace fields of defense industry. The effects of three parameters (pressure, peening time, nozzle distance) on Almen intensity and coverage will be investigated by using the experimental and analyzed data. Methods: we employed a Box-Behnken design. Additionally, to verify the validity of the optimal condition obtained from experimental results, metallurgical analyses of the shot-peened aerospace part were conducted with respect to surface morphology, residual stress. Results: Optimal shot peening condition is determined as (distance, pressure, time) by optimizing simultaneously the two responses of intensity and coverage. At the optimal peening condition the prediction interval for Almen intensity is well within the required range. And, the validity of the condition was checked by using the real aerospace aluminum alloy plate. Conclusion: Shot peening introduces significant levels of compressive residual stress and induces improves both reliability and fatigue life of structures.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.4
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• pp.63-68
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• 2008

The fatigue characteristics of bevel gear used for differential gear of automobile was investigated in this paper. From the A-N(Almen intensity-Number of fracture)curve of bevel gear it was shown that there was a specific time that have a maximum fatigue life. Optimal peening condition was 65m/s of project velocity and 8min of project time. Fatigue life was also investigated from the S-N curve between optimal peened specimen and unpeened specimen. Another very significant point is that the crack initiation of bevel gear by shot peening was generated in the subsurface from fractography. This paper shows that shot peening process tremendously improve fatigue characteristics of bevel gear.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.7
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• pp.63-68
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• 2003

Shot peening process is most often used to improve the fatigue properties of metal parts, In order to achieve an optimum, repeatable, and reliable fatigue enhancement from the shot peening process, the important shot peening parameters must be optimized, In this paper, the optimum peening intensity(Almen intensity) condition is investigated by experiment. Rotary bending fatigue test has been adopted to investigate the effects of optimum peening on the fatigue characteristics, Experimental results show that the fatigue strength and fatigue life has been tremendously increased by optimum-peening treatment. However, the fatigue strength and fatigue life has been decreased by under or over peening.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2005.05a
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• pp.185-190
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• 2005

The shot peening process is often used to improve fatigue properties of metal parts. Among them, It is the most use in an auto-component. In order to achieve optimum, repeatable and reliable fatigue enhancement from the shot peening process, the important shot peening parameters must be controlled. In this paper, the optimum peening intensity (Almen intensity) condition is investigated by experiment. The Spur Gear steel was used to investigate shot peening effects. The fatigue life at $\sigma_a=1,050$ and $\sigma_a=1,250MPa$ first gently increases, then drops gently as peening intensity increases compared with unpeened specimen. Experimental results show that the optimum peening intensity range is $0.391\~0.434mmA$..So the fatigue strength and fatigue life have been tremendously increased by optimum-peening treatment. However, the fatigue strength and fatigue life have been decreased by over peeing.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2005.05a
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• pp.191-196
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• 2005

The effects of shot peening on the fatigue strength of SK-5M steel is investigated by experiment. The shot peening process is investigated optimum peening condition by changing impeller speed and exposure time. Bending fatigue test is accomplished to investigate the effect of optimum peening condition on the fatigue characteristics. As exposure time is increased, fatigue life in high stress is increased in early stage, become the maximum from 60 to 100 seconds, and then is decreased. Observing fracture surface through SEM after fatigue test, we can see clear configuration of cracks and peening layer.