Nano-scale coating wear measurement by introducing Raman-sensing underlayer

For gaining fundamental insight into coating wear mechanisms and increasing operational efficiency and automation degree of equipment in important application fields of coating techniques,it is of great importance to developing novel wear measurement techniques enabling nanoscale studies of coating wear in the running process,but this remains a significant challenge.Here,a facile strategy is reported to achieve accurate coating thickness quantification at nanoscale level,which is based on a bilayer structure:a top target layer of a-C:H(hydrogenated amorphous carbon)film is considered as a light attenuating and anti-wear layer while underlayer of silicon serves as Raman-sensing layer.Through constructing the relationship between the thickness of a-C:H and Raman intensity of attenuated silicon signal,the coating thickness quantification method is established and successfully applied to quantify coating wear in the friction process.This approach can effectively avoid remarkable errors caused by tribo-induced effects in the interface regions,demonstrating its advantage in error tolerance.Details about these tribo-induced effects are also elucidated by a combination of Raman spectroscopy,optical profilometer,EELS,and TEM.In particular,the proposed approach enables the possibility of measuring coating wear with oil film on top,which breaks an important limitation of existed wear measurement methods,i.e.,incapable of applying in oil-lubricated conditions.This approach can be used to quantify the wear condition of diverse target coatings and has the potential of online wear monitoring when combining a compact laser excitation and detection system.

ONLINE GRINDING WHEEL WEAR COMPENSATION BY IMAGE BASED MEASURING TECHNIQUES

Automatic compensation of grinding wheel wear in dry grinding is accomplished by an image based online measurement method. A kind of PC-based charge-coupled device image recognition system is schemed out, which detects the topography changes of the grinding wheel surface. Profile data, which corresponds to the wear and the topography, is measured by using a digital image processing method. The grinding wheel wear is evalualed by analyzing the position deviation of the grinding wheel edge. The online wear compensation is achieved according to the measure results. The precise detection and automatic compensation system is integrated into an open structure CNC curve grinding machine. A practical application is carried out to fulfil the precision curve grinding. The experimental results confirm the benefits of the proposed techniques, and the online detection accuracy is less than 5 um. The grinding machine provides higher precision according to the in-process grinding wheel error compensation.

On-machine measurement of tool nose radius and wear during precision/ultra-precision machining

The tool state exerts a strong influence on surface quality and profile accuracy during precision/ultraprecision machining.However,current on-machine measurement methods cannot precisely obtain the tool nose radius and wear.This study therefore investigated the onmachine measurement of tool nose radius on the order of hundreds of microns and wear on the order of a few microns to tens of microns during precision/ultra-precision machining using the edge reversal method.To provide the necessary replication,pure aluminum and pure copper soft metal substrates were evaluated,with pure copper exhibiting superior performance.The feasibility of the measurement method was then demonstrated by evaluating the replication accuracy using a 3D surface topography instrument;the measurement error was only 0.1%.The wear of the cutting tool was measured using the proposed method to obtain the maximum values for tool arc wear,flank wear,and wear depth of 3.4 lm,73.5 lm and 3.7 lm,respectively.