Ceramic Shot-Peening of a Landing Gear Component

喷丸是一种冷加工工艺，在此过程中，结构零件的表面被称为喷丸的小球状介质轰击。喷丸会导致金属表面的塑性变形，从而在凹痕正下方的区域产生高压缩残余应力。由于疲劳裂纹通常起源于零件表面，喷丸产生的压应力可显著提高零件寿命。起落架法兰销传统上用钢丸进行喷丸处理。然而，钢丸会留下颗粒嵌入等残留物，这可能会损害销钉的使用寿命。此外，使用钢丸的整个过程也很漫长。最重要的是，在高冲击轰击过程中，球形钢丸塑性变形(改变形状)，不能重复使用。因此，该行业正在尝试采用陶瓷弹丸，这种弹丸不仅可以重复使用，而且表面光滑，颗粒嵌入/污染水平非常低。拟议的研究目的是探索用更硬的陶瓷弹丸取代钢丸的可能性。通过测量喷丸后的表面粗糙度来确定喷丸后的表面质量，研究喷丸界面的微观结构，并用X射线衍射仪测量从表面到试件中心的残余应力，生成应力分布。通过显微压痕硬度和拉伸试验研究喷丸处理后表面的力学性能，并与未喷丸处理后的数据进行比较。

Shot peening is a cold working process in which the surface of a structural part is bombarded with small spherical medium called shot. The shots cause plastic deformation of the metal surface, which results in high compressive residual stresses in the area right beneath the dents. Since fatigue cracks generally originate at the surface of a part, compressive stresses induced by shot peening provide considerable increase in the part life.Landing gear flange pins are traditionally shot-peened by steel shots. However, the steel shots leave residue such as particle embedment, which could be detrimental to the service life of the pins. Also, the overall process using steel shots is lengthy. The most important is that during the high impact bombardment, the spherical shaped steel shots are plastically deformed (change the shape) and are not reusable. Therefore, the industry is trying to adopt ceramic shots that are not only reusable, but also give smoother surface finish and very low level of particle embedment/contamination.The objective of the proposed research is to investigate the possibility of replacing steel shots with harder ceramic shots. The surface quality after ceramic shot peening will be determined by measuring the roughness profile, the microstructure at the peened interface will be studied, and the residual stress will be measured from surface to the center of the specimen by XRD and stress profiles will be generated. The mechanical properties of the peened surface will be investigated via micro-indentation hardness and tensile testing, which will be compared with the unpeened specimen data.