Surface strengthening and grain refinement of AZ31B magnesium alloy by ultrasonic cavitation modification

Ultrasonic cavitation modification (UCM) employs cavitation effect to induce strong plastic deformation on the material surface and improve surface properties. To explore the surface strengthening and grain refinement of materials by UCM, the UCM orthogonal experiments of AZ31B magnesium alloy were carried out in water and kerosene, respectively. The effects of ultrasonic amplitude, distance from the sample, and processing time on Vickers hardness and grain size of the material were studied. The results showed that the Vickers hardness of samples increased to 1.5–3 times after UCM in water, which was 23.77–48.19% higher than that in kerosene. The metallographic observation indicated the grains on the surface of AZ31B were refined after UCM. The maximum fluctuation of grain size on the material surface was not more than 10 μm after UCM in water, and most of them were concentrated between 1.5 μm and 2.5 μm, while the former was more than 40 μm and the latter were concentrated between 2 μm and 10 μm in kerosene. This reflected that the grain refinement effect of UCM in water was better than that in kerosene. Ultrasonic cavitation can be used as a benign means to improve the surface properties of materials.     

TC4合金低塑性抛光过程数值模拟

为了研究低塑性抛光工艺参数对材料表面性能的影响,采用有限元分析软件ANSYS对TC4合金板材低塑性抛光表面强化过程进行了数值模拟。运用单因素试验法分别分析了液压油预压力、滚压速度、滚压道次、进给量4个工艺参数对表面残余应力的影响。结果表明:液压油预压力对残余应力分布影响最大,增加液压油预压力可使残余压应力层深度明显增加;滚压速度和滚压道次主要影响表面残余应力,表面残余压应力随滚压速度减小和滚压道次增加而增大;进给量对残余应力分布均匀性有显著影响,减小进给量可使均匀性增高。通过对比残余应力分布,建议液压油预压力设为450 N,滚压速度取为10 mm/s,进给量取为0.1 mm,滚压道次选择为3次。研究结果可为TC4合金低塑性抛光试验工艺参数选取提供理论参考。     

某压气机轮盘均压孔挤压强化数值仿真和挤压头设计

采用静力学求解算法、应用弹塑性有限元分析程序对挤压强化过程进行了仿真计算,研究了摩擦因数、挤压次数、挤压量、约束方式、倒圆半径、以及配合方式等参数对残余应力场的影响.根据某压气机轮盘均压孔的具体结构形式,设计了三种挤压头:单侧挤压头、柱形头和T形头.用两种材料(不锈钢1Cr11Ni2W2MoV和镍基高温合金ЗП742)设计加工了带孔薄板模拟件,用其中两种强化方法对孔边进行了强化试验,试验结果表明:T形头挤压工艺达到了提高疲劳强度的预期效果,且操作方便实用.将试验结果和数值仿真结果进行了对比,分析表明用静力通用程序可以解决金属材料孔板挤压过程的仿真问题,能有效指导挤压强化研究.      

小孔喷丸强化工艺试验研究

依托试验研究,对航空零件喷丸强化技术的应用范围做出了有限的扩大。试验过程中,采用了遮蔽试片的方法,解决了小于试片尺寸的小孔表面喷丸强化的测定难题,通过大量的工艺试验,获得了合理的工艺参数,为零构件小孔的喷丸强化提供了基础。该试验的成功使得零件加工过程中将小孔喷丸应用范围扩大至Ф14．2,进一步拓展了喷丸工艺应用范围,为以后产品加工中小孔喷丸强化工艺的选取打下了基础。     

航空发动机主轴轴承滚道表面光饰强化处理

表面改性处理技术是一种提高航空发动机主轴轴承疲劳寿命的有效途径。在表面改性处理理论分析基础上,提出一种新的航空发动机主轴轴承滚道表面强化处理技术(即光饰强化处理)并研制了相应的光饰强化专用设备——离心强化机,试验结果表明:该技术可以有效地提高航空发动机主轴轴承滚道表面硬度,改善滚道表面粗糙度,并在滚道接触表层产生残余压应力,显著地提高航空发动机主轴轴承疲劳寿命和降低疲劳寿命离散性。