Chih-Fu Wu

A residual-stress model for the milling of aluminum alloy (2014-T6)

Abstract One of the important problems encountered in the milling processes is the elastic deformation of the workpiece; thus, how to select the cutting parameters to reduce the residual stress is especially crucial. A mathematical model is presented for predicting the residual stresses of alloy 2014-T6 caused by end-milling. Factors such as the cutting conditions (cutting speed, feed, and cutting depth) and the tool geometries (tool nose radius and flank wear) are considered in this paper. To reduce the number of experiments required and to build the mathematical model for these variables, Response Surface Methodology (RSM) with the Takushi method are used. In addition, variance analysis and an experimental check are conducted to determine the prominent parameters and the adequacy of the model. According to the above processes, it is shown that the cutting speed, feed, tool nose radius and flank wear have the most significant effect on the residual stresses and there is an interaction between the cutting speed and flank wear. The affect on the residual stress of the cutting conditions and tool geometries can be explained in terms of the cutting force, the rise in temperature and the microstructure variation. Therefore, this model, offering good correlation between the experimental and predicted results, is useful in selecting suitable cutting parameters for the machining of alloy 2014-T6.

Design optimization of a split-point drill by force analysis

Abstract A modified force model incorporating the splitting parameters for predicting the thrust forces and torque of a split-point drill has been developed. The effect of the notch angle on the thrust forces and torque has been deduced, also from the proposed force model. Experiments were conducted to evaluate the thrust forces and torque, the calculated thrust forces and torque being shown to compare favorably with those obtained from drilling tests on a JIS S45C steel. The optimization of the drill-point geometry was obtained by minimizing the thrust forces and torque, as well as by using the finite-element method to compute the displacement and stress distributions of the drill point. According to the experimental results for both thrust forces and torque, and the calculated values of the maximum displacement and maximum stress at the drill point, the optimal value of the notch angle was about 57.7°.

Performance Optimization and Selection of Operating Parameters for a Solid Oxide Fuel Cell Stack

In this study, a model of current densities for a ten-cell solid oxide fuel cell (SOFC) stack is learned and developed due to the utilization of an improved backpropagation neural network (BPNN). To build the learning data of the BPNN, the operating parameters are suitably arranged by the Taguchi orthogonal array, which totals seven factors with five levels, respectively, that act as the inputs of BPNN. Also, the average current densities for the ten-cell SOFC stack achieved by the numerical method act as the outputs of the BPNN. The effectiveness of the developed BPNN mathematical algorithm to predict performance of the SOFC stack is proved by the learning errors smaller than 0.11% and the predicting errors less than 0.52%. Then, the calculating algorithms of the BPNN are adopted to proceed with the optimization based on the electrical performance of the sum of the average current densities for the ten-cell SOFC stack. Thus, the best and the worst performances are found to be Fmax ¼57795.622 Am � 2 and Fmin ¼33939.362 Am � 2 , respectively. It is also the operating window of the performance for the SOFC stack developed by the improved BPNN. Furthermore, an inverse predicting model of the SOFC stack is developed by the calculating algorithms of the BPNN. This model is proved to effectively predict the operating parameters to achieve a desired performance output of the SOFC stack. Combination of these calculating algorithms developed by the improved BPNN gives the possibility to complete dynamic control of the operating parameters, such as the mole fraction of species and mole flow rate in the inlet, which are considered to be changeable. [DOI: 10.1115/1.4024966]

Display and device size effects on the usability of mini-notebooks (netbooks)/ultraportables as small form-factor Mobile PCs

A balance between portability and usability made the 10.1″ diagonal screens popular in the Mobile PC market (e.g., 10.1″ mini-notebooks/netbooks, convertible/hybrid ultraportables); yet no academic research rationalizes this phenomenon. This study investigated the size effects of display and input devices of 4 mini-notebooks (netbooks) ranged in size on their performances in 2 simple and 3 complex applied tasks. It seemed that the closer the display and/or input devices (touchpad/touchscreen/keyboard) sizes to those sizes of a generic notebook, the shorter the operation times (there was no certain phenomenon for the error rates). With non-significant differences, the 10.1″ and 8.9″ mini-notebooks (netbooks) were as fast as the 11.6″ one in almost all the tasks, except for the 8.9″ one in the typing tasks. The 11.6″ mini-notebook (netbook) was most preferred; while the difference in the satisfactions was not significant between the 10.1″ and 11.6″ ones but between the 7″ and 11.6″ ones.

Size effects on the touchpad, touchscreen, and keyboard tasks of netbooks.

The size of a netbook plays an important role in its success. Somehow, the viewing area on screen and ability to type fast were traded off for portability. To further investigate, this study compared the performances of different-sized touchpads, touchscreens, and keyboards of four-sized netbooks for five application tasks. Consequently, the 7″ netbook was significantly slower than larger netbooks in all the tasks except the 8.9” netbook touchpad (successive selecting and clicking) or keyboard tasks. Differences were non-significant for the operating times among the 8.9″, 10.1”, and 11.6″ netbooks in all the tasks except between the 8.9” and 11.6″ netbooks in keyboards tasks. For error rates, device-type effects rather than size effects were significant. Gender effects were not significant for operating times in all the tasks but for error rates in touchscreen (multi-direction touching) and keyboard tasks. Considering size effects, the 10.1” netbooks seemed to optimally balance between portability and productivity.

Investigation of the performance of trackpoint and touchpads with varied right and left buttons function locations.

This study investigates the relationships of the following 5 factors with commonly-used task patterns: 4 (2 existing and 2 newly-designed) built-in cursor input devices of notebook PCs, usage experiences, genders, sensitivity of cursor movements, and 5 tasks of input applications (including click, drag-drop, click-select, select-drag-drop, and type-select-click). This experiment reveals that there are significant differences among these factors in the operating times and/or error rates of particular tasks. Although somewhat influenced by the task patterns, the results show that the touchpad with the cursor-tracking pad located on the bottom-center and the right and left buttons on the bottom-left beneath the keyboard, which avoids ulnar and radial deviation and hindrance of text-entry-pointer-manipulation switching, leads to higher performance and preference, while the trackpoint leads to lower performance and preference. In addition, the touchpads with sensitivity values of 10 and 12 for cursor movement are preferred over those with the value of 8.

PC-Based Rehabilitation System with Biofeedback

The purpose of this research is to emphasize on the concept of integrating computer and interactive technologies to the rehabilitation robotic with biofeedback. First, the robot is actuated with pneumatic muscle actuator which have interesting characteristics that can be exploited for upper limbed machines. The rehabilitation robotic system is using measurement which has two channels to detect and collect the rehabilitation robotic system from electromyography and the rotary encoder. Through PCI interface transferring the rehabilitation robotic system to personal computer, we can use our algorithms to attain real-time the force and/or contraction velocity of the muscle detection and other common information like the frequency of under muscle curve of user. Finally, the human-computer interface for rehabilitation system is designed. In this human computer interface consists of three main parts: detect the signal; a control scheme of robotic system combined with multimodal environment based biofeedback system; clinical database.

A study on the straight-line drawing tasks for the non-sighted people

A new ruler employs the finger touch to be the main pointing sensor with two locators at the two ends, and a unique pen in a smooth track to draw a line. The tasks of making straight line with two difference rulers (Ruler S: ruler used at school; Ruler C: new touch ruler) between non-sighted people (blindfolds and blinds) were observed: (1) free-line; (2) constrained-line; (3) extension-line; (4) closing-line; and (5) conjoining-line. Stages of those tasks were measured: searching, positioning, plotting, and checking, with reacting time and the deviation. The Paired t-test shown Ruler S had a larger reacting time for blinds at task (4), (5). MANOVA shown the blinds had larger reacting time at task (3), while (5) on deviation; Ruler C had a larger error at start- point of task (3) and a larger length error of task (3); while Ruler S had a larger error at end-point of task (4). Conclude that some revised design of the ruler really affected the performance of the straight-line tasks, while some did not.

Effects of light, rotation, and texture on errors in the estimated length of a three-dimensional object in a two-dimensional display.

This study investigated the effects of light type (spot, directional, and point), forward-rotated stimulus angle (20°, 45°, and 70°), and surface texture (wood, metal, transparent glass, dark brown leather, and translucent plastic) on errors in the estimated vertical diameter of a three-dimensional object. Twenty female and 12 male Taiwanese college students, ages 18–22 years, participated in the current study. Participants were asked to judge the vertical diameter of an elliptical hole within a square plate that was displayed on an LCD monitor. Analysis indicated that the errors in estimated vertical diameter for rotated angles of 20° and 45° were greater than were those for 70°. Additionally, the error of estimated vertical diameter for a rotated angle of 45° was less than was that for 20°. The surface texture also affected errors in estimated vertical diameter: transparent glass was associated with more errors than were wood and metal textures. However, light type had no effect on errors in estimated vertical diameter. These results have implications for the graphics-based design of interfaces.