Advanced Materials Research Vol. 445

Abstract: Various portable applications such as a mobile phone, MP3 player, PMP player and so on, have been continuously developing with influencing on each other. In this environment, functions of IT applications have been built in the mobile phone, and consequently, the additions of them increase the size of the phone. However, the sizes of present phones have changed less than those of the past, and this trend is expected to be continued in the future because of the inherent characteristics mobility and portability of the phone. Great strides made in the industries manufacturing cellular phone components have facilitated the development of phones having similar size to the existing phone. However, in common, there are limitations on the extent to which the sizes of the parts can be reduced because of the technical reasons pertaining to mechanical or electrical properties, the forming process and assembly structure. In such a scenario, the use of a slide mechanism is the practical alternative for maintaining the mobility and portability. Reduction of the sliding space has a decisive effect on the decrease of the phone size. Therefore, a study of a novel spring to be manufactured by the etching process was performed to minimize the thickness. Meanwhile, the use of the slide mechanism is advantageous for maximizing visibility and increasing functionality with the limited space which are of utmost importance for the design of a contemporary cellular phone. In addition, various extra function keys including the main keypad buttons are required to maximize the visibility. However, the sliding stroke must increase to have them, and the existing spring units cannot be satisfied with the requirements under the limited space. Therefore, the study of a long-stroke spring unit and its manufacturing process to minimize the thickness with the stroke of 60 mm was performed.

Abstract: Metal forming processes with principally shear stresses that very high plastic strains are obtained in one pass are defined as severe plastic deformation (SPD) processes. Strain values can additionally be increased with additional passes throughout the process. Equal channel angular processing (ECAP) is the most applied method among the SPD processes due to relative ease of die manufacturing. On the other hand, die failures like corner cracking are frequently observed due to high notch effect and therefore use of the dies is limited. In the presenting study multi element die design (separated die design) approach was applied to production of ECAP dies in order to eliminate die failures and 5083 Aluminum alloy specimen were deformed with several passes. Although some additional development for die arrangement and fixation are needed, corner cracking was never observed and dies could be used safely.

Abstract: Grinding process is an energy intensive process in the sense that, it requires a larger amount of energy per unit of volume of material removal compared to other metal cutting processes. In this case, effects on the ground workpiece in terms of induced residual stresses and metallurgical changes due to heat generated play an important role on the lifetime of parts in their mechanism. In order to investigate effects on the workpiece during external cylindrical grinding process, a new analytical approach is firstly developed to model the action of the grinding wheel as a heat flux, which moves along the workpiece surface. The value and the shape of the heat flux entering the workpiece are directly identified. Based on the established model, numerical simulations are performed to predict temperature, cooling and its effects on residual stress distribution in the ground near surface.

Abstract: Nondestructive testing (NDT) methods has been increased within recent years depending on the needs of industry, parallel to new technological developments. Many studies have focused on thermal imagining, magnetic flux analysis or both, which are used in order to detect the deformation on surface and under the surface. In this study a new technique is suggested to eliminate the perturbations which are distorting effects of one point cameras in terms of perspective. A new integration is also proposed in this research such as using image recognition with magnetic flux analysis. Taking advantage of this integration and the new approach to image processing, both the surface and the inside of a mechanical product can be tested properly.

Abstract: In machining processes, great amount of the cutting energy transforms to heat energy. Tool life decreases and the quality of the machined surface changes by the effects of heat during machining. Many researches are being done on the reduction of the negative effects of the heat on the tool. In this respect, cutting fluids are used, but usages of them are limited because of their some harmfully effects to the environment. In order to reduce the tool wear and to use the tool longer, during cutting continuously variation of the contact region of the tool and the chip can been realized by using self-propelled rotary tools. The tool life is longer in rotary tools when compared with stationary cutting tools. In machining with these tools lower heat effect at the cutting edge is observed. In this study, the effects of cutting parameters on surface roughness of machined part has been investigated during the turning of mild steel using self-propelled rotary tools. In experiments, cutting tools which inclination angles were 20°, 30° and 45° and rake angles were 0° and-5° were used. Cutting speeds were taken as 60 m/min and 120m/min. RCMX insert with 32mm diameter was used. Feed were chosen as 0.1, 0.2 and 0.4 mm/rev and cutting depth was set at 0.25 mm.

Abstract: Hydro-mechanical deep drawing assisted with radial pressure (HDDRP) is used in industry to produce complex parts from sheet metals. This process is affected by parameters such as : pressure path, geometrical parameters of punch and die, friction between punch and sheet, etc. Investigating these parameters to acquire optimal parameters to produce the desired part is essential. In this study, the effects of the radius of punch tip and the radius of the transition zone from conical to cylindrical geometry, on forming and thickness distribution of parts have been studied. In performing the investigation, a specific geometry was considered for punch and different radiuses for punch tip and the transition zone were selected. The type of the sheet material examined is St14 steel. First, the process was simulated by the finite element simulation software, ABAQUS 6.9, and then some experiments were done to check the accuracy of the simulations. There is an acceptable conformity between the results. The results showed that the radius of punch tip is more effective than that of the transition zone, so with increasing the radius of punch tip, the minimum thickness increases and thickness distribution becomes more uniform.

Abstract: Conical parts have a lot of usage in industries. Therefore, it is important to form these parts with high accuracy. In sheet forming processes, producing conical parts is one of the most difficult aspects. The two major problems that occur in the production of conical parts are rupturing and wrinkling. Among the forming processes for producing conical parts, the most capable one is hydroforming deep drawing. In this study, the effects of material properties and initial sheet thickness on forming and thickness reduction of the part were examined by using hydro-mechanical deep drawing assisted by radial pressure. For investigating these two parameters, pure copper and st14 steel are used. In experimental evaluation, sheets with thicknesses of 2.5 mm were used. In the simulation study, the thicknesses of 0.5, 1, and 2 mm were also examined. There is a good agreement between experimental and simulation findings. The results showed that for thinner sheets, the thickness reduction is less, and thus, a more uniform thickness distribution curve was obtained. Also, it was illustrated that for St14 steel sheet the thickness distribution curve will be more uniform compared with that of pure copper sheet.

Abstract: In this paper, the process of bi-metallic tube backward extrusion through a conical punch, by means of upper bound method and finite element method is investigated. A cylindrical admissible velocity field is developed and by calculating the internal, shear and frictional powers, the extrusion force is estimated. The extrusion process is also simulated by using the finite element code, ABAQUS. Analysis and simulations are done for two types of bi-metallic tubes: aluminum as core, copper as sleeve (Al-Cu) and copper as core, aluminum as sleeve (Cu-Al). The extrusion force from the upper bound method is compared with the Finite Element results. This comparison shows that the upper bound predictions are in good agreement with the Finite Element results. The results also show that, the extrusion force in the case of Al-Cu tube is smaller than Cu-Al tube and in both types of bi-metallic tubes, the aluminum leaves the deformation zone sooner than the copper. Finally the effects of various extrusion parameters, such as the friction factor, reduction in area and semi-punch angle upon the extrusion force are investigated and the optimum semi-punch angle is determined.

Abstract: Broaching is a precision multipoint metal removal operation normally employed for manufacturing variety of complex parts having either internal or external features. Broaching can produce high precision and good surface finish at a high metal removal rate. The unique feature of a broach tool is that the feed/depth of cut for the teeth is built into the broach unlike other cutting tools. The tool design (e.g., rise per tooth and tooth geometry) play a vital role in the broach performance. A specially adapted machine tool modified to investigate a single broach tooth has been used. Cutting forces and material removal rate have been measured during experimental work for different combination of broaching parameters and broach tool geometry. The effect of the parameters on the surface quality produced has been established. The characteristics of chips formed have also been defined. Finally, optimum tooth geometry and rise per tooth have been recommended for tool performance, broached surface quality and efficient chip formation. The information provided in this paper will be beneficial for broach tool designers and manufacturing engineers.

Abstract: In this paper an analytical model for chemical etching in one dimensional space has been presented. Regarding to the special specifications of Ferric chloride, etching of an Aluminum work piece exposed to Ferric chloride etchant has been modeled. The proposed model shows that, in the condition of constant reaction parameters, etching rate is a linear function of time. Excellent agreement between the proposed model and the experimental results, published by Çakır (2008), validates the model. By generalization the proposed model, etching rate, or in the other word depth of etch in a specified time, for different materials with different etchants can be predicted.