When a workpiece contains complex burr edges from a combination of drilling and milling, conventional deburring tools such as wire brushes may not be effective in their removal. In this study, abrasive flow machining was used to gain access to complex burr edges. Experiments on two types of flow guides suggest that an abrupt change in direction of flow around the area with targeted burr edges is essential. The effects of several process parameters are investigated based on the experiments set up.

In this paper, we describe high-stable RF-frequency generation using a low-cost 8-bit microcontroller for amplitudemodulation based distance measurement, which is one of the indispensable technologies for cost-effective Lidar application. The RF frequency generator using the microcontroller was implemented by externally referencing to an atomic clock and 8- bit timer/pulse width modulation (PWM) functions, which are embedded in a microcontroller. The microcontroller we used was ATmega128 of Microchip with 16 MHz clock and 8-bit timer, which generates the maximum frequency of up to 62.5 kHz, enabling 2.4-kilometer ranging without phase ambiguity. The stability of RF-frequency generated from the implemented system was evaluated in terms of Allan deviation using a commercial frequency counter. The stability indicated 10^-11 at 1-s averaging time and 10^-12 at 100 s averaging time, which represents a 1/10 degradation compared to the stability of the commercial function generator. Along with the stability evaluation, we interrogated frequency tunability, which extends a measurable range without phase ambiguity.

Printed electronics is a technology which is used for manufacturing flexible electronic devices dubbed as next-generation electronics such as wearable applications. To commercialize them, it is important to guarantee their electrical performance under various environmental conditions such as temperature and humidity. Moreover, flexible electronic devices usually undergo mechanical deformations such as bending and twisting, hence, it is necessary to observe the electrical performance of flexible devices under mechanical deformation considering both temperature and humidity. The effects of temperature and humidity on flexible printed electrodes, as an example of the simplest flexible electronics, under static deformation of bending and twisting are studied. Electrodes that do not deform are also strongly affected by temperature and humidity, and the increase in resistances of the electrodes with deformation is highest when twisting. The magnitude of static deformation does not affect the conductivity. The effect of line width is important for the twisting deformation. To commercialize printed electronics devices, the effects of temperature and humidity should be considered, with further consideration of the effects of mechanical deformation on the design of the devices.

As the exoskeleton robot for the assistance of walking is on the rise, HRI (Human-Robot Interaction) come to be an important issue. So in this research the angle following Variable Stiffness Actuator by using cam for overcoming the limitation of volume and weight in existing mechanisms. For this mechanism determinant of stiffness is not an absolute value but it can be change from zero to rigid by the location of the pivot in the gage between the application point of the input force and output force. So it can be miniaturized and have the volumetric advantage by kinematic design. This variable stiffness system make the HRI effective and the safety from injury resulted from the malfunction and the wrong control can be guaranteed.

Majority of deformation and ruptures as a result of severe deformation of mechanical structures are due to the existence of cracks or cracks generated through specific situations. These cracks causes stress concentration and eventually ruptures under lower load conditions than they are designed to withstand. In this study, simulation tensile analysis was done by designing compact tension specimen models with the number of holes that existed inside and the materials of the test specimens by focusing on the effects of the cracks. The study results from all the analysis (deformations, equivalent stress and strain energy) confirmed that the specimen models having two holes had better strength characteristics than those with only one hole. Additionally, the durability and strength characteristics of specific mechanical structures against the load improved through appropriate arrangement of holes thereby reducing stress generation. As such the results of this study could be utilized as the basic data for future researches on composite materials and sandwich type homogenous materials. Furthermore, the study results can assist in designing more durable products.

Crash analyses was carried out to characterize crash behavior and injury of a wheelchair user in a train during collision based on SAFETRAIN PROJECT and AV/ST 9001, train safety regulations. There is no restraint system such as seat belt or air-bag in train, a wheelchair user is normally injured by bumping against wall. Crash behavior and injury of a wheelchair user was evaluated with respect to the distance (Dw) of the wheelchair from the wall and the wall foam thickness (tF). Additional crash analysis for a wheelchair user with seat belt was also performed in order to check the significance of the seat belt effect during crash.

This paper describes the development of a power assistive device controller with user intention detection for fire fighters. In order to detect the intention of users, an F/T sensor frame was designed for the power assistive device controller. Using the numerical approach, each directional strain value of the F/T sensor frame was evaluated singly to determine the optimum point to mount the strain gauge under varying load conditions. The numerical analysis was conducted using the commercial program Ansys v11.0. The finite element model for the F/T sensor frame consisted of 37,547 elements and 157,154 nodes. A sensor bonding device and calibration jig were designed for the F/T sensor frame. In an effort to obtain the decoupling matrix for the F/T sensor frame of the proposed power assist device, calibration tests were conducted in the x-direction, y-direction, z-direction, My-direction and Mz-direction. In addition, the operating system was tested using the power assistive device controller that comprised of the F/T sensor frame.

Major aerospace developers continue to push for new structural composite applications to reduce the environmental impact of greenhouse gas emissions, improve both aircraft performance and costs. In this study, the parts that carry the load in the regions where mechanical joints are applied, require whole processing to tighten and identify stress concentration points. In addition, failure modes caused by bearing and by-pass loads were set as the main design factors. Optimum sizing was performed through the application of factors taken into account in the buckling failure mode and production using the preliminary design analysis model of the composite wing structure. In the area where the fuselage is joined with the fuselage, bearing and bypass load were considered important design factors.

As environmental and energy issues increase, energy efficiency is of great significance in the automobile industries. Drag torque of a wet clutch in an automatic transmission system is one of the causes of energy loss. In this work, the drag torque characteristics of a wet clutch as a function of rotational speed was experimentally investigated with respect to the test parameters such as automatic transmission fluid (ATF) temperature and flow rate, clearance between friction disk and separator, and the number of disks in the test system, using two different friction materials. Drag torque was found to decrease with increasing ATF temperature as a result of the decrease in viscosity. Also, drag torque decreased as the clearance between friction disk and separator increased. In addition, the drag torque increased along with the delay in the generation of maximum drag torque as the ATF flow rate increased. Furthermore, it was observed that drag torque increased with the increase in the number of disks in the test system. The drag torque characteristics as a function of rotational speed may be dependent on the friction materials. The results obtained from this work may aid in the design of wet clutch system to enhance performance.

With regard to 3D orientation estimation based on IMMU (Inertial Magnetic Measurement Unit) signals, the yaw estimation accuracy may be significantly degraded as a result of magnetic distortions. Consequently, several yaw estimation Kalman filters (KFs) possessing distortion compensation mechanisms have been proposed. However, majority of the conventional methods fail to effectively curb inaccuracies due to distortion when magnetic fields are extremely distorted. In this paper, we propose a new KF projecting a kinematic constraint to minimize yaw estimation errors induced by magnetic distortions. After the measurement update using magnetometer signals, the proposed method additionally corrects the yaw estimation through projection of a kinematic constraint on a conventional unconstrained KF. Experimental results show that the proposed KF outperformed the conventional KF by approximately 52-67%.

We propose a novel fin-tube expanding process using a spiral-grooved-expanding ball, prepared by the metal additive manufacturing process, to improve heat exchange performance in a fin-tube type heat exchanger. In this study, deformation of inner grooves in a tube, was minimized during the expanding process. For this, we developed lab-scale expanding equipment, and a spiral-grooved-expanding ball, was newly designed and fabricated. Comparing to a conventional tube expanding process, it was deduced that a deformation rate of groove height was reduced to approximately 8.3%, when the proposed process was used. Through this fundamental study, we validate that the developed process can be used to fabricate large-surface grooved tubes, for application to a high efficiency heat exchanger.

The solid state dissimilar joining of mild steel and aluminum 5052-O alloy is successfully achieved by friction stir welding (FSW). The 2 mm thick sheets are butt welded using a convex scrolled tool made of tungsten carbide. With a constant weld speed of 75 mm/min, two different tool at rotation speeds of, 800 and 1000 rpm, were employed to determine the feasibility of the joint formation. Macroscopic observation of the cross section confirmed the formation of a sound FSW joint. However, the formation of an intermetallic in the Stir Zone (SZ) is also observed for the both sets of process parameters. Comparatively, better material mixing is observed when the parameters are set at, 1000 rpm and 75 mm/min respectively. The hardness test revealed the presence of three distinct hardness zones in the SZ for the two parameter sets.