Applied Mechanics and Materials Vols. 284-287

Abstract: By virtual prototype technology, the kinematic and dynamic characteristic analysis of the sieving box was carried out. The motion path, natural frequencies and mode shapes of the sieving box were calculated, the stress and deformation distribution in every part of the sieving box under rate load were obtained, and the dynamic strength analysis of the sieving box was carried out. The results show that, the structure design of the shaker is reasonable, and its dynamic strength is satisfied.

Abstract: Bicycle helmets aim to reduce the risk of injury due to impacts on the head. Generally, a bike helmet consists of the outer shell, liner, vents and straps. The liner helps absorb the effects of the impact to keep that force away from your head. To satisfy the functions of helmet liner, several criteria should be considered. The ideal liner would be stiffer in hard impacts, softer in lighter impacts, light, cheap, reliable to manufacture and easy to ventilate. Currently, there are many different design trends and concepts in the design of helmet liner. Researchers have tended to focus on the liner material. The Expended Polystyrene (EPS) foam is the most popular choice for liner material of helmet. The EPS foam is commonly used in helmets as an energy absorbing liner. However, EPS has some disadvantages, such as the difficulty to optimize energy absorbing in different areas of head and inferior effect of heat dissipation. Moreover, EPS is generally too brittle. In order to overcome its drawback, to search a better alternative is necessary. In this study, a dual layer liner is proposed to yield enhanced impact absorption, that is to say, the liner is constructed by two layers of polycarbonate with deformable semi-spherical convex. The energy absorbed by deformation of convexes which is described by a combination of folding and collapsing. The main advantages of this liner design not only show the energy absorbing capabilities like EPS foam but also gain a better optimization of energy absorbing for different sites. This study focuses on assessment of a helmet with dual layer liner based on the shock absorbing test of CPSC’s standard. Finite element method (FEM) is available contribution greatly to helmet test modeling. This study performs finite element analyses of helmet impact tests using LS-DYNA software. The simulation of helmeted headform drop test is implemented for the four kinds of liner thickness. To confirm the energy absorbing capabilities of dual layer liner, the resultant CG linear acceleration of the headform is measured from the helmet test simulation. According to the CPSC’s standard specification, the acceleration of headform should be less than 300 g's during the impact.

Abstract: The propeller shaft of rear-wheel drive vehicle transfers power from the engine to rear wheels through the differential gear box. Generally the propeller shaft has a two-piece steel structure of more than 10kg of weight. In this paper, we designed the one-piece hybrid propeller shaft using the aluminum, carbon fiber composite material and glass fiber composite material. Research on the adhesive strength of the hybrid propeller shaft with respect to roughness of aluminum surface was conducted. The one piece hybrid propeller shaft satisfying the performance standards of propeller shaft such as statistic torsion torque strength and first bending natural frequency was manufactured. The manufactured hybrid shaft was assembled with the suitable connecting parts and analyzed for performance verification. This hybrid propeller shaft satisfies all performance standards of propeller shaft for automobile application. The hybrid shaft has vibration characteristics of 237Hz significantly higher than the standard characteristic of 150Hz of the existing two-piece steel structure propeller shaft.

Abstract: Skewing is one of the most common methods to reduce the cogging torque of permanent magnet synchronous motors. This technique may cause manufacturing troubles such as impossible automatic slot filling due to skewing stator slot. One method to overcome this problem is to use the step twisted stator structure with shifted slot opening. Compared to other methods of skewing, in the presented method, the stator slots are still straight slots and the skewing effect is implemented by shifting slot openings coupled with a step twisted stator design. This paper discusses the use of the step twisted stator structure with shifted slot opening and the associated effects on machine performance. We address the cogging torque, average torque, torque ripple, and back-EMF and its total harmonic distortion (THD). We examine the results using finite element analysis (FEA).

Abstract: The device made of fan and pin-fin heat sink should be a powerful heat sink for LED lamp. This study used transient liquid crystal experimentation to measure the end-wall heat transfer coefficient of linearly arrayed square pin array in the rectangular channel, and discussed the influence of axial spacing on heat transfer. The air was used as operating fluid, and the square pin size was 8 mm (d) × 8 mm (d) × 64 mm (Hf), arrayed in a 240 mm (L) × 120 mm (W) × 64 mm (H) rectangular channel. The relative lateral spacing (XT=ST/d) was set as 3, and the relative axial spacing (XL=SL/d=1.88~5) and the Reynolds number (Re=11047~17937) were changed. Considering the end-wall area, the average Nusselt number with square pin was 1.46~2.58 times of that without square pin, and the square pin array of XL= 3.75 had the maximum end-wall heat transfer gain.

Abstract: The objective of this study is to determine the optimal geometrical features of a microdrill with the diameter of 0.11 mm. The optimal geometrical dominant features of a micro-drill have been determined by carrying out the optimization stress/displacement analysis of the Pro/Mechanica software so that the maximum stress von Mises of the micro-drill was minimal. Based on the verification of the drilling test, the mean total hits to breakage of the micro-drills, fabricated with the determined optimal geometrical features, was 16% more than that of the micro-drills fabricated with the original geometric parameters.

Abstract: This paper proposes a novel nano-scale micro-machining machine based on the pantograph mechanism. It is designed to satisfy the need for achieving high accuracy and process efficiency in the manufacture of increasingly small industrial products. The target platform is mounted on a pantograph and small x-y sliders, and is driven by a traditional X-Y platform with common precision. The theoretical and simulation results indicate that the proposed method is feasible for development of a micro-machining machine capable of achieving nano-level precision. In addition, test results indicate that the micro-machining machine can position the target platform with a resolution of 500nm

Abstract: In the viewpoint of energy reutilization, this study combined high efficiency heat transfer with thermoelectric conversion technology to construct an efficiency testing platform for the waste heat recovering thermoelectric conversion system for real vehicles. A Toyota 2200c.c. vehicle with four-cylinder four-cycle engine was used for vehicle test to discuss the influence of the vehicle's engine speed and external cooling air flow on the energy output of the waste heat recovering thermoelectric conversion system. This study found that the energy output increases with the engine speed. However, if the engine speed is too high (exceeding 2500rpm), the thermoelectric generator can be overheated and damaged, which should be avoided. In addition, there is an optimal external cooling air flow generating the maximum energy output. The optimal external cooling air flow is 0.04 m3/sec in this study. At present, the 6 thermoelectric generator modules connected in series have the maximum electric power (P) output about 16W when the blowing air flow is 0.04 m3/sec and the engine speed is 2500 rpm.

Abstract: Hydrogen energy fuel cell is one of the clean/green energy solutions for the environmental pollution, global warming, and petroleum energy shortage. This study investigates the dynamic characteristic of the green hydrogen energy fuel cell: Proton Exchange Membrane Fuel Cell (PEMFC). PEMFC has been adopted to be the power supplier of the vehicle, small train, etc. A lot of researchers aim on pure electrical property analysis. However, to put PEMFC power system on the road, some mechanical properties of the system should also been examined. In this paper, the dynamic characteristic of a single PEMFC is studied. A single PEMFC (L112×W82×D6 mm) is set up and measured for the time and frequency response. Several fundamental modes are found experimentally which should be avoid during operation period of PEMFC especially in a moving vehicle.

Abstract: This paper proposes a method of the geometric design for a new conjugate tooth profiles based on the envelope theory and coordinate transformation method, the mathematical and geometric models for the conforming gears design are proposed. A comparison study on the dynamic contact stress with the involute gear drive is carried out in this work.