磨料喷射喷嘴的应力分析及FGM模型设计

分析表明磨料喷射加工中喷嘴承受的应力在喷嘴入口最大、出口次之、中间区域相对较小。试验显示喷嘴的冲蚀磨损在喷嘴入口最严重、出口次之、中间区域相对较小。试验结果与应力分析结果一致,得出磨料喷射加工中喷嘴入口、出口处承受的高拉应力是造成其冲蚀磨损严重的主要原因的结论。针对提高均质陶瓷材料喷嘴抗冲蚀磨损能力的力度有限,提出运用梯度功能材料(Function gradient material,FGM)理论于喷嘴材料的设计和制造中,研发新型非均质的陶瓷喷嘴材料,将梯度功能陶瓷喷嘴制备中产生的残余压应力引入喷嘴入口、出口,使其减缓磨料喷射加工中喷嘴承受的拉应力,以提高喷嘴抗冲蚀磨损能力。结合喷嘴的冲蚀磨损特点、结构特点及陶瓷喷嘴材料制备工艺性等,建立了梯度陶瓷喷嘴物理模型和成分分布模型。根据本模型设计结果,研制出梯度 SiC／(W,Ti)C陶瓷喷嘴。结果表明,相同条件下制各的梯度SiC／(W,Ti)C陶瓷喷嘴的抗冲蚀磨损能力高于非梯度 SiC／(W,Ti)C陶瓷喷嘴。

STRESS ANALYSIS AND FGM MODELS DESIGN OF ABRASIVE JET MACHINING NOZZLE

The stress states of the nozzle in abrasive jet machining (AJM) process are analyzed. Results show that the maximum stress appears in entrance area of the nozzle and minimum stress in middle area, while the stress of exit area is lower than entrance area and higher than middle area. Blasting results reveal that the nozzle entry region always suffers form severe abrasive impact, and generates large tensile stress, which leads to an increased erosion wear at the nozzle entry area. The idea of functionally gradient material (FGM) theory is used to design ceramic nozzle. The design of composition distribution of the gradient ceramic nozzle is carried out with the aim of partial relaxation of the stress resulting from external loadings by residual thermal stress. Based on the design results, a SiC/(W,Ti)C gradient ceramic nozzle is produced. The erosion behavior of the SiC/(W,Ti)C gradient ceramic nozzle is investigated in comparison with the common ceramic nozzles. Results show that the SiC/(W,Ti)C gradient ceramic nozzles exhibit an apparent increase in erosion wear resistance over the common ceramic nozzles under the same test conditions.