Applied Mechanics and Materials Vols. 284-287

Abstract: Ultrasonic Tomography has a dominant role in industry to generate cross sectional images of any object. In this paper, method of designing an Ultrasonic Tomography System due to the propagation manner of ultrasonic wave inside the various materials is investigated. The correct method of mounting of Ultrasonic sensors and behavior of the ultrasonic wave propagation in different layers has been simulated by the use of finite element software (COMSOL Multiphysics 3.5). To increase in practical nondestructive evaluation and inspection, we should increase our understanding of the basic physics and wave mechanics associated with guided wave inspection. A suitable ultrasonic sensor base on its efficiency and satisfying the simulation criteria is found and practically implemented on the surface of metal pipe. it is done by estimating the resonance frequency of sensor due to manner of ultrasonic wave propagation in different frequencies shown in simulation results. The proposed optimum frequency for the applied sensors is 40 kHz in which is tested practically and experimental results prove the high efficiency of this system.

Abstract: A dynamic finite element (FE) approach to contact and fillet bending stresses of helical gear pairs (HGPs) is presented. Using derived tooth profiles, high quality elements of HGPs can be efficiently constructed. The resulted maximum stresses of elements on teeth are 3D illustrated. Design of relief and profile modifications is also condisered. The effect of tooth modifications on HGP dynamic responses including misalignment errors is discussed. It shows adequate modification of tip relief and crowning can reduce dynamic stress peaks of HGPs.

Abstract: This study presents a device, which can be used to detect density of various liquid. The device is composed of at least three buoys and a mechanism that is balanced by rotary moment. The design of the device presented in this study is based on the moment balanced position of the buoy on liquid. Designing parameters such as mass and volume of the buoys, relative angles of installation, and distance between the mass center and rotation center are adjustable. The device can be designed not only as a detector of liquid density but also a logic sensor of liquid density. The device will turn over and rotate 180^o when density of the liquid reached some value, which can be preset in designing by adjusting relative parameters. The device has been practically tested that when the density of liquid changes from 1 g/cm³ to 0.933 g/cm³, the position of balanced angle changes about 90^o. Turn over rotation occurs at the density of 0.933 g/cm³, which is about 2.8% of error from the designed value, 0.96 g/cm³. This device is proved to be feasible.

Abstract: Conventionally, a motorcycle has headlight and mirrors to provide front illumination and rear views for drivers, respectively. Rearview mirrors on conventional motorcycles are fixed, which is easy to cause instant rear blind area for drivers on turns or hubbly roads. Therefore, the drivers cannot get traffic information behind motorcycles, and easily lead to traffic accidents. In this paper, actuation for an adaptive rearview mirror system for motorcycles was proposed. According to sensor inputs, this system adaptively adjusts the rearview mirrors to compensate the changes of vehicle dynamics in pitching, steering and rolling under different road conditions. A grey predictor was also developed in this paper to estimate the change of vehicle dynamics in advance. With the properly designed actuation, this system can provide wide and appropriate rear views to motorcycle riders. It significantly enhances riders’ safety and reduces the occurrence of traffic accidence.

Abstract: In this paper, the methods of the safety evaluation for thin-walled shells containing defects based on “Fitness for Service” principle were reviewed. The latest authoritative standards and codes for assessment in both domestic and international fields are introduced. The paper also proposes the existing problems in this field and discusses the main solutions of them. The innovation of the method and technical route mentioned in the resolvent are introduced at the same time. As a result, the trend of safety assessment method for thin-walled shell’s structure containing defects is prospected.

Abstract: Flexure hinges have been widely used as mechanisms for high precision positioning stages that have a micrometer or nanometer resolution. This paper describes the analysis of a 3-DOF rotationally symmetric hinge for the vertical mask aligner stage. The vertical mask aligner stage was designed to overcome the bending of masks by gravity. In order to align the mask and the wafer, the vertical mask aligner stage has one linear motion and yaw rotating motions (Z, Θx, Θy). The new vertical mask aligner stage will try to use rotationally symmetric hinges. These rotationally symmetric hinges would act as guide mechanisms. However, the exact 6-DOF stiffness analysis of the rotationally symmetric hinge did not use these hinges as guide mechanisms. Therefore, this paper focuses on the stiffness analysis of the rotationally symmetric hinges.

Abstract: Though hydrogen fuel reduces the carbon dioxide emission, it still produces NOx. However, gaps exist in the fundamental understanding of hydrogen-air combustion and the NO emission; most previous research has focused on the flames burning with mixture such as H2 mixed with CH4, rather than pure H2 flame. Here, a computational study is presented to investigate the effects of stretch rate on NO formation in counter-flow premixed hydrogen-air flame. The simulations of premixed hydrogen flames were performed with OPPDIF code with UCSD chemical mechanism. Results indicate that the NO formation is affected by three factors: radical concentration, flame temperature, and residence time of reactants. The flame temperature, the reaction rate of NO, and the NO emission index all decrease when the stretch rate increases. Moreover, the formation of NO through thermal mechanism, NNH mechanism, and N2O mechanism are discussed, as well as the percentages of their contribution.

Abstract: Light weight design is critical to a sports car. In the study, a prototype of the newly developed modern classical concept sports car was presented. The design process followed the common vehicle design procedure starting from blue print, clay model and then vehicle build. The structure was designed and analyzed using Computer Aided Design (CAD) and Computer Aided Engineering (CAE) tools. A space frame design concept was proposed based on the topology optimization results. Carbon composite material was used for light weight structure design. Three-step design optimization process was proposed to use for the detailed composite vehicle structure design with the consideration of manufacturing constraints. The thickness, fiber orientation and stack sequence were obtained through the optimization process. Manufacturing constraints could be imposed to the optimization process in order to obtain a practical design that could be manufactured. A design with total structure weight of 296.7 kg was obtained. It was a much lighter design compared to the earlier metal structure design.

Abstract: This paper talks about the application of TRIZ principles (the Russian acronym for the "Theory of Inventive Problem Solving”) in manufacturing coconut cutting machine with a semi-automatic feeder. This machine is used to cut coconuts for getting water and endosperm inside. By using TRIZ, a prototype of coconut cutting machine which is more efficient and profitable than manual cutting is designed and manufactured. The capacity of the machine is 720 coconuts/hour compared to 500 coconuts/hour by manual cutting. This prototype can also be used for further research into the manufacturing of coconut cutting machine.

Abstract: Much work has already been done with this end in mind; however, given the high degree of complexity associated with a large system such as this, there is opportunity for improvements in modeling capability. The FAA system for assessing Aviation’s Global Emissions (SAGE) is a well-established model for the creation of global inventories of aviation fuel use and emissions. The first is the way in which the specific fuel consumption (SFC) is calculated. Previous to this study, SFC was calculated through the methods put forward in EUROCONTROL’s Base of Aircraft Data (BADA). The results of this analysis provide insight into not only the benefits of RVSM, but also the effects of these model improvements and the efficacy of the different efficiency metrics used.