Research on the underlying mechanism behind abrasive flow machining on micro-slit structures and simulation of viscoelastic media

In this study, the machining mechanism of abrasive flow machining (AFM) microstructures was analyzed in depth according to the transmission morphology and rheological behaviors of the abrasive media. The transmission morphology demonstrated the excellent combination of the polymer melt with abrasive grains at the interface, indicating that the polymer melt, combined with the uniform distribution of the polymer chains, could exert a harmonious axial force on the abrasive grains. Based on the rheological behavior analysis of the abrasive media, for example, the stress relaxation and moduli of storage and loss, a machining mechanism model was established incorporating the effect of microplastic deformation and continuous viscous flow, which was further verified by the grooves along the flow direction. In addition, the PhanThien-Tanner (PTT) model combined with a wall slipping model was employed to simulate the machining process for the first time here. The value of the simulated pressure (1.3 MPa) was similar to the measured pressure (1.45 MPa), as well as the simulated volumetric rate (0.011 4 mL/s) to the measured volumetric rate (0.067 mL/s), which further proved the validity of the simulation results. The flow duration (21 s) derived from a velocity of 1.2 mm/s further confirmed the residual stretched state of the polymer chains, which favored the elasticity of the abrasive media on the grains. Meanwhile, the roughly uniform distribution of the shear rate at the main machining region exhibited the advantages of evenly spread storage and loss moduli, contributing to the even extension of indentation caused by the grains on the target surface, which agreed with the mechanism model and machined surface morphology.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-022-00395-0     

基于涡轮叶片修复的电解修型非加工面保护工艺

为提高民用客机涡轮叶片修复效率,对叶片修复工艺链中电解修型非加工面保护工艺进行了研究。通过建立电场的数学模型,对叶片表面电流密度分布进行数值计算,研究修型规律,并以此分析传统电解修型工艺的缺陷形成机理。提出了牺牲层工艺保护非加工面,并建立实验系统,对堆焊修复后的TC4叶片进行电解修型。结果表明:直接修型、绝缘层保护两种传统工艺将分别形成杂散腐蚀和"台阶"缺陷;采用牺牲层工艺,单组叶片修型时间60s,修型后的叶片精度较高,表面粗糙度Ra≤0.6μm,具有较好重复性,满足设计要求。     

Experimental investigation into fabrication of microfeatures on titanium by electrochemical micromachining

Titanium machining is one of the challenging tasks to modern machining processes. Especially fabricating microfeatures on titanium appear as a potential research interest. Electrochemical micromachining (EMM) is an effective process to generate microfeatures by anodic dissolution. Machining of titanium by anodic dissolution is different than other metals because of its tendency to form passive oxide layer. The phenomenon of progression of microfeature by conversion of passive oxide layer into transpassive has been investigated with the help of maskless EMM technique. Suitable range of machining voltage has been established to attain the controlled anodic dissolution of titanium by converting passive oxide film of titanium into transpassive with nonaqueous electrolyte. The experimental outcomes revealed that the micromachining of titanium with controlled anodic dissolution could be possible even at lower machining voltage in the range of 6-8 V. This work successfully explored the possibility of generation of microfeatures on commercially pure titanium by anodic dissolution process in microscopic domain by demonstrating successful fabrication of various microfeatures, such as microholes and microcantilevers.     

Are quality management practices enough to improve process innovation?

The popularity of quality management as a system for continuous improvement has not been accompanied by deep theoretical understanding of its effects on process innovation. In this work, the resource-based view serves as the basis for the construction of a model designed to explain the effects of quality management practices (QMP) on process innovation performance and the mediating role of dynamic capabilities in this relationship. The empirical data were analysed using the structural equation modelling technique by examining 6 competing models that represent full, partial mediation and non-mediation relationships on a sample of 550 Spanish industrial companies. The findings indicate that the implementation level of QMP is not directly related to process innovation performance, but learning and technological capabilities fully mediate this relationship. Therefore, QMP needs to enhance and develop dynamic capabilities to effectively achieve the improvement and transformation of a firm’s processes.