Theoretical and Experimental Analysis of Surface Roughness and Adhesion Forces of MEMS Surfaces Using a Novel Method for Making a Compound Sputtering Target

Achieving a compound thin film with uniform thickness and high purity has always been a challenge in the applications concerning micro electro mechanical systems (MEMS). Controlling the adhesion force in micro/nanoscale is also critical. In the present study, a novel method for making a sputtering compound target is proposed for coating Ag–Au thin films with thicknesses of 120 and 500 nm on silicon substrates. The surface topography and adhesion forces of the samples were obtained using atomic force microscope (AFM). Rabinovich and Rumpf models were utilized to measure the adhesion force and compare the results with the obtained experimental values. It was found that the layer with a thickness of 500 nm has a lower adhesion force than the one with 120 nm thickness. The results further indicated that due to surface asperity radius, the adhesion achieved from the Rabinovich model was closer to the experimental values. This novel method for making a compound sputtering target has led to a lower adhesion force which can be useful for coating microgripper surfaces.

A Reconstruction and Contact Analysis Method of Three-Dimensional Rough Surface Based on Ellipsoidal Asperity

The 3D rough surface modeling and contact analysis is a difficult problem in the study of rough surface contact. In this paper, a new method for reconstruction and contact analysis of asperities on 3D rough surfaces is proposed based on real rough surfaces. Watershed algorithm is used to segment and determine the area of asperities on the rough surface. According to the principle of minimum mean square error, ellipsoid fitting is carried out on asperities. Based on the elastic-plastic contact model of a single ellipsoidal asperity, a stable and efficient method for 3D rough surface contact analysis and calculation is proposed. Compared with existing calculating methods, the present method has the following characteristics: (1) the constructed surface asperity is closer to the real asperity in contact, and the calculation of asperity parameters has better stability under different sampling intervals and (2) the contact pressure, contact area, and other contact parameters of the 3D rough surface are calculated with high accuracy and efficiency, and the calculation convergence is desirable. The reconstruction and contact analysis method of the 3D rough surface asperity proposed in this paper provides a more accurate reconstruction and calculation method for the study of contact fatigue life and wear failure of rough surfaces.

Calculation of constant J. Nikuradze and T. von Karman depending on water temperature and the size of bottom sediments

Основным средством повышения продуктивности заболоченных и переувлажненных лесов является лесоосушительная мелиорация, позволяющая, помимо повышения качества древесины, улучшать условия для их более полного транспортного освоения. Поскольку одним из основных параметров при проектировании мелиоративных водоотводных и инженерных водопропускных сооружений является неразмывающая скорость, то ее численная оценка крайне важна для гидравлических расчетов. Расчетное значение неразмывающей скорости зависит от принимаемого режима потока на высоте выступов шероховатости дна. Режим движения жидкости определяется эпюрой скоростей вертикального профиля канала. Характер эпюры скоростей по глубине потока до верхней границы пограничного слоя, в свою очередь, определяется параметром Т. Кармана. Толщина пограничного слоя зависит от принятого значения параметра (коэффициента) И.И. Никурадзе. В статье показано, что значения коэффициента И.И. Никурадзе не зависят от температуры воды, но являются функцией крупности донных отложений. Параметр Т. Кармана зависит от крупности донных отложений, а следовательно, от шероховатости дна и стенок канала. The main means of increasing the productivity of waterlogged and soggy forests is drainage reclamation, which, in addition to improving the quality of wood, allows improving conditions for their more complete transport development. Since one of the main parameters in the design of reclamation drainage and engineering culverts is the non-eroding water velocity, its assessment is extremely important for hydraulic calculations. The calculated value of the non-eroding water velocity depends on the accepted flow water mode at the height of surface asperity. The mode of fluid motion is determined by the water velocity curve of the vertical channel profile. The pattern of the water velocity by the depth of the flow to the height of the upper boundary layer, in turn, is determined by the T. von Karmans constant. The height of the boundary layer depends on the accepted value of the J. Nikuradzes constant. The article shows that the values of the J. Nikuradzes constant does not depend on water temperature, but it is a function of the size of bottom sediments. T. von Karmans constant depends on the size of the bottom sediments, and therefore on the roughness of the bottom and channel walls.

On the Planarization Mechanism and Pad Aging Effects of Soft Pad Polishing: A Perspective From the Micro-Mechanical Properties of Soft Pads

The local viscoelastic properties of soft polishing pads with different usage durations are measured by a micro-scale mechanical analysis testing platform. The testing reveals stimulus-adaptive local viscoelasticity of soft pads under the activation of asperity contact. This phenomenon suggests asperity-dependent local modulus. Such an increase of local modulus induced by higher asperity provides a further enhancement effect to the planarization of surface asperity. Furthermore, the measurement outcomes suggest that the reaction of local micro-scale viscoelastic properties of the soft pad surface to the workpiece asperity will decay with usage time. The current study provides a detailed understanding of the aging effects for the soft pad and explains the performance decay during soft pad polishing from a local micro-scale interfacial perspective.

Credibility of the microscopic measurement of the tool geometry and its influence on surface asperity after ball end milling

New ball end mills in various lighting conditions were examined and detailed 3D models were obtained. Differences in the geometry of the tool tip resulted in a surface with drastically different parameters. The effect of the edge break was observed. The obtained 3D models were used to create a map of the material loss on the cutting edge of cutting tool.