Applied Mechanics and Materials Vol. 575

Abstract: Aiming at a 1220 strip surface, where the Cold Rolling Mill had chatter marks, on which the reasons for the formation was tracked tested for in-depth study. Based on the vibration test, the analysis was given to the dynamic characteristics of the rack ^[1-3]. It was found that had reaction to the mill that caused the forced vibration mill to further accelerate the formation of chatter marks. In the analysis of the mechanism on the chatter marks, the relationship between chatter marks spacing and vibration source was considered in successfully finding out the cause of the 1220 mill chatter marks generated, and then the chatter marks suppression measures were proposed with satisfied effects.

Abstract: Focus on the hygrothermal environment problems of CF3031/CCF300 stiffened composite panel, the stiffened composite panel absorption were studied on in the 85%RH, 70°C hygrothermal environment, the moisture equilibrium content of the composites were calculated. The compressive test were carried on after hygrothermal aging, observed the change of the strain, and draw the conclusion of the flexural load and the breaking load, contrasted with the panel of before hygrothemal aging. The results show that the rate of remained flexural load was about 85% and the rate of remained breaking load was about 75% after hygrothemal aging.

Abstract: The jet propulsion system, either for subsonic or supersonic flow, the nozzle design is a critical area of choice where its overall performance gets an adverse change. In the trending technologies, configuring any nozzle, their challenges associated with the design increases accordingly to the cruise speed of the aircraft. The latter clamshell ejector nozzle design work came up with solution for the most problems but still had its own cons of creating recirculation zone in the inner surface of the clamshells. The former world which are in next stage to design an economically conditioned nozzle system itself invents challenges in area such as jet noise suppression, exit temperature, material selection, variable throat area and exit area. The present work summarized here excelled for the most cons encountered in the latter designs. The experimental investigation and the computational studies resulted that the introduction of C-D nozzle with by-pass system had a great exposure in increasing the Mach while in cruise. The air by-pass system in the exit area supplies the atmospheric air and also acts as a cooling system for the nozzle. It was observed that the temperature curve in the exit area was found low.

Abstract: Planetary gear trains can be used as the gear reducers with high reduction ratio. This paper focused on the kinematic and meshing efficiency analysis of planetary simple gear reducer with two ring gears. First, the planetary simple gear train with two ring gears is proposed by using different shift coefficients. Then, by referring to the train value equation, the reduction-ratio equation is derived for the design the planetary gear reducer with two ring gears. According to reduction-ratio equation, the planetary gear reducers with two ring gears and having reduction ratios (20, 50, and 100) are synthesized. Then, based on the latent power theorem, the meshing efficiency equation of planetary gear train with two ring gears is derived. According to the meshing efficiency equation, the meshing efficiencies of planetary gear trains with two ring gears are analyzed. In this paper, we conclude: (1) Larger reduction ratio makes less meshing efficiency, and (2) The meshing efficiency of planetary gear reducer with two ring gears is not good.

Abstract: Tensile, Torsion, and Hardness behavior of welded and un-welded Aluminium Alloy 6061 T6 were investigated. Tests were conducted to evaluate the impact of tungsten Gas Arc welding (TIG) on some of the mechanical properties of the alloy. Different zones with different mechanical properties were created as a result of the welding process. Welding was found to have enormous impact on the tensile, torsion, and hardness properties of the alloy. Welded tensile specimens were failed at the welded area whereas not welded ones were failed at the centre. Welded torsion specimens were failed at the HAZ but not welded ones failed at the centre. The hardness of HAZ was decreased as a result of the heat generated during the welding process. Hardness values were increased as we moved away from the welded region.

Abstract: This paper aims to improve and control hydrodynamic performance of three-dimensional airfoils and investigate hydrodynamic performance of three-dimensional airfoil with tubercles on leading-edge by imitating the sinusoidal leading-edge systematically. Based on the DES method, a series of parameters, such as amplitudes and numbers of tubercles, had been studied via the FLUENT software with model constructed by ICEM software and divided by structural grid. According to the results, the amplitudes significantly affect the hydrodynamic performance of three-dimensional airfoil. With maintaining other conditions,tubercle airfoils can make stall angle delay, raise the lift and the drag ratio coefficient. Especially, if there is a bigger attack angle, it is better to reduce resistance and save energy, which will be a cornerstone for further study. It is of vital importance to find out appropriate amplitudes and numbers of tubercles to achieve further progress in hydrodynamic performance of three-dimensional airfoil.

Abstract: In the experiment, three kinds of wavy-walled tubes with different wave factor F_w were applied to study the effect of geometric parameters on mass transfer characteristics. Results show that mass transfer characteristics are influenced significantly by the oscillatory frequency and the wavelength of the wavy-walled tube. The peak value of the mass transfer enhancement is obtained at the multiple order oscillatory frequency, and the effective mass transfer enhancement is occurred when the wave factor F_w = 0.58. For the same Re number, the mass transfer enhancement factor E increases with the oscillatory fraction P, and the optimal Strouhal number St corresponding to different peak E almost does not change with P.

Abstract: The interfacial stresses of a segmented Cr coating by the hybrid technique of laser pre-quenching steel substrate plus post-deposition have been investigated. The discrete laser quenched zones (LQZs) were modeled as multiple inclusions, each of which is embedded with a prescribed uniform eigenstrain. Based on the failure criterion of the adhesion strength, the interfacial stresses are considered to be responsible for interfacial debonding. The interfacial stresses were evaluated by using the finite element (FE) method. Dimensional analysis was utilized to identify the scaling variables affecting the stresses. The dependence of a range of dimensionless variables of interest on the interfacial stresses has been assessed through a detailed parametric study.

Abstract: This work presents a method to estimate probability initiating combustion and detonation by temperature load in void in energetic material. When a void is compressed its volume decreases and the temperature in the void increases. The local thermal source due to the void deformation in energetic material forms a temperature load which may initiate combustion and detonation. The temperature-time history in the void was called temperature load in this work. Its peak value and holding time are the necessary and sufficient condition initiating combustion or detonation of energetic material surrounding the void. Comparing with the energy acted on the unit area of hot spot, the performance of transient temperature which can better serve to reflect the physical essence in ignition. The main object of this work is to study transmitting process of temperature load from void to energetic material and probability initiating combustion and detonation by temperature load in void.

Abstract: The impact of the cutting parameters; speed, feed, and depth of cut on the wear and the life of the cutting edge has long been a matter of debate among researchers. The cutting speed has long been agreed to have a prime influence in such a way that increasing speed leads to higher wear rate. Depth of cut has been concluded by majority of studies to have insignificant or negligible impact on edge wear and deformation. Despite its long established influence on the roughness of the machined surface, the effect of cutting feed on edge wear and deformation still requires more explanation. Cutting feed is a crucial parameter governing the product surface finish and dimensional accuracy and, therefore, its attitude during machining should be fully understood. This study presents experimental and modeling approach to detect the feed-wear functional interrelation considering various domains of the cutting speed. Results showed that the impact of the cutting feed is firmly associated with the level of cutting speed employed. Speed-feed interaction proved to be responsible for the performance of the cutting edge during machining.