Applied Mechanics and Materials Vol. 575

Abstract: With high optical transparency and electrical conductivity, ITO thin films were fabricated by DC magnetron sputtering. Series of research and exploration are presented on DC magnetron sputtering method for preparing ITO thin film. With substrate temperature of 60 °C, sputtering power of 200W,sputtering pressure of 1 mTorr, water pressure of 2×10-5Torr, the sheet resistance of the ITO conductive substrate is 53 Ω/□ and the transmittance is 83%.

Abstract: This study examines the feasibility of using high-porosity and conductive bamboo charcoal in electrophoretic deposition (EPD)-assisted polishing of silicon wafers and explored the influence of various parameters on surface roughness. EPD-assisted polishing with bamboo charcoal offers an alternative to the lapping process prior to CMP. According to the results, the best parameter combination obtained under the current experimental setting is machining time, 12 min; rotational speed of platen, 75 rpm; and voltage, 6V. EPD indeed contributes to more effective and efficient polishing, with better surface quality attained within a shorter machining time.

Abstract: In this study, new thin corrugated metal gasket will be developed by using simulation experiment. The optimal design and dies design for gasket manufacturing is determined by using computer simulation based on finite element analysis (FEA). In the design stage, the Taguchi method is used to predict optimal design of new thin corrugated metal gasket. The L9 orthogonal array was concerned to design experimental matrix for four factors with three levels. In the manufacturing stage, gasket product is simulated by using ANSYS 14.5 and experimental press forming process by using press hydraulic machine. From the result, the optimal design is the model with R = 3 mm, p = 6 mm, OH = 3 mm and h = 0.2 mm. Based on simulation results and experimental press forming product, it can be concluded that the virtual design from computer simulation results can be used for predicting the real product.

Abstract: Relationships among the forming conditions (such as shapes of dies, lubrication conditions, and slide motion of the press machine) and the thickening ratio (thickness after forming / thickness before forming) has been clarified in uniaxial press forming by experiments and a three dimensional finite element simulation. Steel pipes with 39.0mm and 7.6mm thickness were used in the experiment. The relationship between thickening ratio and the forming load that depends on the die shape, lubrication, and slide motion of the press machine was investigated. It has also been found that an eight percent increase of the wall thickness of the pipes could be possible without buckling. It has been clarified that thickening ratio during die forming could be predictable by using a finite element simulation.

Abstract: The correlation of an effective thermal conductivity (k_eff) on spherical packed bed porous media with stagnant fluid was proposed. Alumina-Cordierite ceramic ball (Al-Co) having average diameter (d) of 2.1 cm and porosity (Φ) of 0.468 was examined. The experimental procedure was operated based on ASTM E1225. The tested porous sample was sandwiched by references materials (Solid Brass, 70%Cu, 30%Zn). A higher temperature (T_H) on the top of test set was obtained from wire heater with a constant electrical power of 350 W. The water cooling set was installed at the bottom of to generate a lower temperature (T_L). Four previous models established from geometrical structure were compared to validate the present correlation. From experiment, it was found that k_eff decreased with increasing T_H. Thus, the relation between k_eff and T_H was appropriately proposed by a correlating linear-equation (k_eff/k_f = 329.2(1-0.1028(T_H/100)). Agreement between the present correlation and literature models was satisfied particular.

Abstract: Shaving cutter is the most important tool for the refinement manufacture of gears with high precision and manufacturing efficiency. In this study, design parameters of shaving cutter are studied considering the strength of shaving cutter and the tooth profile of shaved gears. The finite element analysis and Taguchi method are adopted to analyze the shaving process for the optimum shaving cutter design parameters. The main objectives are due to increase the strength of shaving cutter and reduce the concavity phenomenon of the generated tooth profile.

Abstract: Diamond-like carbon (DLC) thin films are prepared using plasma enhanced chemical vapour deposition (PECVD) process at different bias voltage. We have studied their microstructural and electrical properties using Raman spectroscopy and current (I) – voltage (V) relationships. Electrical conductivity is gradually decreases with bias voltage as the films are becoming more and more diamond like carbon as observed from Raman spectroscopy results. Raman spectroscopy result shows that the ID/I_G ratio gradually decreases indicating formation of more diamond like carbon films that responsible for the decrease of conductivity of the films. The full width half maximum of G peak increase with increase the bias voltage indicating the ring-like sp² transforms to sp² chains and raises the amount of sp³-chains. The structural disorder arises from the bond angle and bond length distortions in amorphous carbon films. Thus the structural disorder and mechanical properties such as hardness and elastic modulus increase with bias voltage.

Abstract: The aim of this study was to create stress relieving features to reduce the root fillet stress in spur gear. A pilot model was established to predict von Mises stress at the root fillet of the gear without holes and was used as a reference model. Finite element modeling was adopted using Abaqus^® package. The predicted stresses were compared with stresses obtained by AGMA analytical solution. A good agreement was found in the comparison between the calculated and predicted stresses. Then, another model, namely hole model, was built to investigate the effect of various hole parameters (number, diameter, location, angle). The hole model was performed by creating hole/holes in the gear body. The results obtained showed that increasing the diameter size of hole/holes resulted in higher percentage of stress reductions compared to the pilot case. Furthermore, increasing the number of holes resulted in higher percentage of stress reductions compared to the pilot case, but gear rigidity in this case was highly affected.

Abstract: Aerodynamic drag plays an important role in fuel economy of the vehicle especially for electric cars directly affecting the range. The objective of Aerodynamics subsystem of IIT Bombay racing team is to predict and minimize drag force on the Formula student electric race car thereby improving the performance. A standard generic car body known as Ahmed body is taken to set up simulation parameters in FLUENT by validating a test case against the experimental data available in literature. Variation and dependence of drag force on parameters such as frontal area, distribution of pressure coefficient and pressure loss in wake region is studied numerically. Comparison is made between Formula Student 2013 car Evo2 and newly designed car Evo3 for coming season of Formula Student 2014. A substantial reduction in drag force of 18.8% is achieved which can be attributed to lower frontal area and streamlined bodyworks design. Energy consumption of the vehicle for endurance race is reduced by 11.5 % improving the fuel economy.

Abstract: Two sets of new and in-service helmets were impact tested using a drop test machine, in accordance to established helmet test protocols. The first test for full helmets was executed in compliance with standard speed requirements of 5.9 m/s in which three of five new helmets performed poorly. The second set utilized lower impact speed of 4 m/s for individual helmet components test. New helmet liners absorbed 5 times more impact energy than the in-service liners while the new shell was 19.3% better in dispersing impact energy than the in-service shell. The undesirable changes in liner thickness have explicit effect on the liner density which is translated into reduction in energy absorbing potential. In brief, exposure to weathering stresses and use intensities has affected helmet impact performance, regardless of service duration.