珠擊參數對SW-C與SWP-B螺旋壓縮彈簧機械性質之影響;Effects of Shot Peening Parameters on the Mechanical Properties of SW-C and SWP-B Helical Compression Springs

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Title:	珠擊參數對SW-C與SWP-B螺旋壓縮彈簧機械性質之影響;Effects of Shot Peening Parameters on the Mechanical Properties of SW-C and SWP-B Helical Compression Springs
Authors:	陳凱翔;Chen, Kai-Hsiang
Contributors:	機械工程學系在職專班
Keywords:	螺旋壓縮彈簧;彈簧鋼;硬鋼線;琴鋼線;珠擊;疲勞測試;Helical compression spring;Spring steel;SW-C;SWP-B;Shot peening;Fatigue test
Date:	2023-07-22
Issue Date:	2024-09-19 17:21:26 (UTC+8)
Publisher:	國立中央大學
Abstract:	本研究主要是利用滾筒式珠擊機，透過噴擊時間與鋼珠大小的改變，觀察兩種材質(SW-C、SWP-B)製成的螺旋壓縮彈簧經過疲勞試驗後的幾何尺寸、荷重承載、粗糙度與硬度的變化，再將疲勞測試後的彈簧，經由掃瞄式電子顯微鏡(SEM)觀察不同珠擊參數下破斷面情況。研究結果顯示，未珠擊的螺旋壓縮彈簧呈現最差的疲勞壽命表現，經過珠擊後的實驗組以SW-C實驗組7 (Ø0.8+Ø1.2、60分)表現出最佳的疲勞壽命，達到404,202次，荷重衰退率為10.93%。SWP-B為實驗組10 (Ø0.8、60分)表現出最佳的疲勞壽命，達到254,279次，荷重衰退率為6.03%。再來由幾何尺寸觀察，珠擊處理與疲勞測試對於外徑沒有改變；自由長經珠擊處理後會縮短，隨著噴擊時間增加，自由長縮短幅度增加。粗糙度與硬度也隨著噴擊時間變長而上升。最後透過SEM的觀察得知，其斷裂模式為扁平舌狀，正常斷裂起始處為彈簧線圈內側應力較大處生成裂縫，並成長延伸至外側的最終斷裂區，而且疲勞裂縫穩定成長區的大小與疲勞壽命呈現正向關係。由於彈簧設計值使用應力達到1441.11 MPa，已超過建議的使用範圍，並且受到幾何尺寸中垂直度的影響，使得抗張強度較高的材質SWP-B 未表現出優於SW-C的疲勞壽命。 ;This study aimed to investigate the variations of geometric dimension, load capacity, roughness, and hardness of helical compression springs made of two materials (SW-C and SWP-B) after shot peening and fatigue testing. In particular, the effects of shot peening time and bead size were studied, The fracture surfaces were analyzed using scanning electron microscopy (SEM). The results showed that the helical compression spring without shot peening actually had the worst fatigue performance, while the 7th experimental group of SW-C (Ø0.8+Ø1.2、60 min) exhibited the best fatigue life, reaching up to 404,202 cycles before failure and a load decay rate of 10.93%. Group 10, SWP-B (Ø0.8、60 min), also showed the best fatigue life of 254,279 cycles and a load decay rate of 6.03%. In terms of geometric dimension, the shot peening and fatigue loading had no influence on the outer diameter. The free length was shortened after the shots and the extent of shortening was enlarged as the shot peening time increased. Roughness and hardness also increased with a longer shot peening time. Finally, it was observed by SEM that the fracture pattern was flat and tongue-like, with the fatigue fracture initiation at the point of greater stress on the inner side of the spring coils and propagation to the outer side at final fracture. There was a positive correlation between stable crack growth area and fatigue life. Due to the fact that the designed spring had a stress of 1441.11 MPa which exceeded the recommended range of use and it was also influenced by the perpendicularity in the geometry, the material SWP-B of higher strength did not have a better fatigue life than SW-C.
Appears in Collections:	[Executive Master of Mechanical Engineering] Electronic Thesis & Dissertation

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