In rotational incremental sheet forming( RISF) process,the friction heating of rotational tool could lead to local temperature rise of the sheet and cause the improvement of sheet's formability.Lightweight metal,s...In rotational incremental sheet forming( RISF) process,the friction heating of rotational tool could lead to local temperature rise of the sheet and cause the improvement of sheet's formability.Lightweight metal,such as magnesium alloy,could be deformed by RISF without additional heating. The objective of this study is to investigate the effects of forming parameters,namely,tool rotational speed,feed-rate,step size and wall angle,on the local temperature rise. Using response surface methodology and central composite design( CCD) experimental design,the significance,sequence of parameters and regression models would be analyzed with AZ31 B as the experimental material,and 3D response surface plots would be shown. Combined with actual processing conditions,the measures to improve the local temperature rise by modifying each parameter would be discussed in the end. The results showed that hierarchy of the parameters with respect to the significance of their effects on the local temperature at the side wall was: feed-rate,step size,and rotational speed,while at the bottom it was: feed-rate,step size,wall angle, and rotational speed, and no significant interaction appeared. It was found that the most significant parameter was not rotational speed,but feed-rate,followed by step size,for both test positions. In addition, the local temperature would increase by elevating step size,wall angle,rotating rate,and bringing down of feed-rate.展开更多
采用微弧氧化法在纯钛材及大变形纯钛材表面制备了含钙、磷的多孔氧化膜层,研究膜层的微观形貌、硬度、膜基结合力、滚动摩擦磨损性能等性能,探讨钛基材组织细化对其膜层结构及力学性能的影响。结果表明:与纯钛材微弧氧化膜层相比,大变...采用微弧氧化法在纯钛材及大变形纯钛材表面制备了含钙、磷的多孔氧化膜层,研究膜层的微观形貌、硬度、膜基结合力、滚动摩擦磨损性能等性能,探讨钛基材组织细化对其膜层结构及力学性能的影响。结果表明:与纯钛材微弧氧化膜层相比,大变形纯钛材微弧氧化膜层表面微纳米尺度的孔洞更多,孔隙率更高(10.84%vs.9.68%),孔洞孔径更小(8.67μm vs.9.68μm),表面更平坦,锐钦矿相含量更高(43.13%vs.37.74%),膜-基结合能力更强(17 N vs.8N),摩擦系数较低(0.338 vs.0.358),耐磨性能更优,以上的膜层结构及力学性能的改善归因于其钛基材大变形化提高了晶体缺陷。展开更多
基金National Natural Science Foundation of China(No.51205217)the Project of Shandong Province Higher Educational Science and Technology Program,China(No.J10LD13)+1 种基金the Taishan Scholar Project of Shandong Province,China(No.ts 201511038)the Key Research Project of Shandong Province,China(No.2016ZDJS02A15)
文摘In rotational incremental sheet forming( RISF) process,the friction heating of rotational tool could lead to local temperature rise of the sheet and cause the improvement of sheet's formability.Lightweight metal,such as magnesium alloy,could be deformed by RISF without additional heating. The objective of this study is to investigate the effects of forming parameters,namely,tool rotational speed,feed-rate,step size and wall angle,on the local temperature rise. Using response surface methodology and central composite design( CCD) experimental design,the significance,sequence of parameters and regression models would be analyzed with AZ31 B as the experimental material,and 3D response surface plots would be shown. Combined with actual processing conditions,the measures to improve the local temperature rise by modifying each parameter would be discussed in the end. The results showed that hierarchy of the parameters with respect to the significance of their effects on the local temperature at the side wall was: feed-rate,step size,and rotational speed,while at the bottom it was: feed-rate,step size,wall angle, and rotational speed, and no significant interaction appeared. It was found that the most significant parameter was not rotational speed,but feed-rate,followed by step size,for both test positions. In addition, the local temperature would increase by elevating step size,wall angle,rotating rate,and bringing down of feed-rate.
文摘采用微弧氧化法在纯钛材及大变形纯钛材表面制备了含钙、磷的多孔氧化膜层,研究膜层的微观形貌、硬度、膜基结合力、滚动摩擦磨损性能等性能,探讨钛基材组织细化对其膜层结构及力学性能的影响。结果表明:与纯钛材微弧氧化膜层相比,大变形纯钛材微弧氧化膜层表面微纳米尺度的孔洞更多,孔隙率更高(10.84%vs.9.68%),孔洞孔径更小(8.67μm vs.9.68μm),表面更平坦,锐钦矿相含量更高(43.13%vs.37.74%),膜-基结合能力更强(17 N vs.8N),摩擦系数较低(0.338 vs.0.358),耐磨性能更优,以上的膜层结构及力学性能的改善归因于其钛基材大变形化提高了晶体缺陷。
