Cr12MoV钢电火花辅助铣削实验研究

以典型难切削金属材料Cr12MoV模具钢为研究对象，使用ABAQUS对其在电火花放电条件下温度场进行数值模拟，在不同进给率下对其进行传统铣削和电火花辅助铣削对比试验。借助高速摄像机、扫描电镜和测力计等设备，对其切削力特征、表面形貌和刀具磨损进行了对比分析研究。结果表明，电火花辅助铣削的切削力比传统铣削降低28.57%~51.47%，表面粗糙度降低2/3。与传统铣削相比，电火花辅助铣削在降低切削力、提高表面质量和减少刀具磨损方面具有显著优势。     

模具表面状态对复合材料构件固化变形的影响

为查明不同模具表面状态下的复合材料构件应变演变规律及其对固化变形的影响,采用热电偶和光纤光栅传感器对不同模具表面状态下的复合材料构件在热压罐成型工艺过程中的温度和应变进行在线监测,获得不同模具表面状态下构件应变的变化规律。结果表明:升温阶段脱模布的使用能够有效屏蔽模具-构件界面相互作用,使构件在升温阶段的应变很小。三层脱模剂模具表面条件下构件中的应变明显小于一层脱模剂;降温阶段三种实验条件下在构件中都出现了较大的压应变,其中一层脱模剂模具表面状态下模具-构件相互作用力最大,在固化工艺完成后构件发生翘曲变形,且翘曲变形以沿纤维方向为主。     

民用飞机发动机吊挂应急断离设计研究

发动机吊挂应急断离是民用飞机设计的关键核心技术之一，国外相关技术难以获取，国内以理论研究和提出主要思路为主，与工程实现存在差距。基于此，从适航标准入手，研究吊挂、保险销和机翼三者的应急断离设计载荷大小的关系，通过场景分析，研究界面结构强度计算的载荷确定方法。结果表明：吊挂应急断离设计仅需单独考虑发动机主载荷向上或主载荷向后工况，合理给定吊挂、保险销和机翼结构三者的应急断离设计载荷大小关系可有效降低结构重量；机翼/吊挂界面载荷方向则必须结合结构细节做具体的应急断离场景分析。     

应急断离剪切销的双剪切破坏过程仿真研究

民用飞机吊挂应急断离剪切销需要在紧急情况下断开并使得吊挂或者发动机脱离机翼,避免飞机在紧急着陆时,吊挂结构因受到地面反弹而损坏机翼油箱,导致油箱漏油起火引发火灾。因此应急断离剪切销对于飞机紧急着陆状态下,飞机安全着陆起到了非常重要的作用。本文以不锈钢材料的应急断离剪切销为研究对象,通过试验方法对不锈钢材料的试件进行力学性能测试,根据测试结果建立了应急断离剪切销的弹塑性本构模型,依据本构模型开展了2种不同径厚比下的应急断离剪切销双剪仿真分析。分析结果表明,在双剪工况下,随着施加在剪切销上的载荷增加,应急断离剪切销上剪切应力在两侧不断增加;剪切销的内径越大,其破坏瞬间的剪切强度越大,且破坏位移越大。     

Gaussian process regression model incorporated with tool wear mechanism

Cutting tool condition directly affects machining quality and efficiency. In order to avoid severely worn tools used during machining process and fully release the remaining useful life in the meanwhile, a reliable evaluation method of remaining useful life of cutting tools is quite necessary. Due to the variation of cutting conditions, it is a challenge to predict remaining useful life of cutting tools by a unified model. In order to address this issue, this paper proposes a method for predicting the remaining useful life of cutting tools in variable cutting conditions based on Gaussian process regression model incorporated with tool wear mechanism, where the predicted value at adjacent moments is constrained to a linear relationship by the covariance matrix of Gaussian model based on the assumption of progressive tool wear process, so the wear process under continuous changing conditions can be modelled. In addition to that, the input feature space and the output of the model are also enhanced by considering the tool wear mechanism for improving prediction accuracy. Machining experiments are performed to verify the proposed method, and the results show that the proposed could improve the prediction of tool remaining useful life significantly.     

干式铣削Al-50wt%Si高硅铝合金刀具磨损与表面粗糙度评价

本文以Al-50wt%Si高硅铝合金为研究对象，采用单因素试验方法进行无涂层硬质合金刀具干式铣削试验，分析切削参数对刀具磨损和表面粗糙度的影响。结果表明：表面粗糙度受每齿进给量的影响最显著，随每齿进给量的增加而增加，当每齿进给量从0.07 mm/z增加到0.16 mm/z时，表面粗糙度增加2倍；刀具磨损受切削速度的影响最显著，随切削速度的增加而增加，当切削速度从140 m/min增加到260 m/min时，切削总长度降低3倍，而刀具后刀面磨损量仅是260 m/min速度下的0.8倍；表面粗糙度随刀具磨损的增加呈现先增加后降低的变化趋势，切削长度从350 mm增加到1 750 mm，刀具磨损量平均增加4.5倍，而表面粗糙度却下降2倍；硬质合金刀具主要的磨损形式为磨粒磨损、崩刃。     

Improving performance of macro electrolyte jet machining of TC4 titanium alloy: Experimental and numerical studies

Electrolyte jet machining (EJM) is a promising method for shaping titanium alloys due to its lack of tool wear, thermal and residual stress, and cracks and burrs. Recently, macro-EJM has attracted increasing attention for its high efficiency in machining wide grooves or planes. However, macro-EJM generates large amounts of electrolytic products, thereby increasing the difficulty of rapid product removal with a standard tool and reducing the surface quality. Therefore, for enhanced product transport, a novel tool with a back inclined end face was proposed for macro-EJM of TC4 titanium alloy. For comparison, also proposed were ones with a standard flat end face, a front inclined end face, and both front and back inclined end faces. The flow field distributions of all proposed tools were simulated numerically, and experiments were also conducted to validate the simulation results. The results show that one with a 5° back inclined end face can decrease the low-velocity flow zone in the machining area and increase the high-velocity flow zone at the back end of tool, thereby promoting rapid product removal. A relatively smooth bright-white groove surface was obtained. The same tool also resulted in the highest machining depth and material removal rate among the tested ones. In addition, rapid product removal was beneficial to the subsequent processing. Because of its rapid product removal, the machining depth and material removal rate during deep groove machining using the tool with a 5° back inclined end face were respectively 7% and 14% higher than those produced using a standard one. Moreover, the lowest bottom height difference of 0.027 mm can be obtained when the step-over value was 8.2 mm, and a plane with a depth of 0.285 mm and a bottom height difference of 0.03 mm was fabricated using the tool with a 5° back inclined end face.