Table of Content

25 June 2016, Volume 4 Issue 2

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Articles

Metallurgical concepts for optimized processing and properties of carburizing steel

Hardy Mohrbacher

2016, 4(2):  105-114.  doi:10.1007/s40436-016-0142-9

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Carburized steel grades are widely used in applications where high surface near hardness is required in combination with good core toughness as well as high strength and fatigue resistance. The process of carburizing lower to medium carbon containing steel can generally provide this combination of properties and has been practiced for several decades. Such steel is essential in the vehicle power-train, machines and power generation equipment. However, the increasing performance demands by such applications as well as economical considerations forced steel producers to develop better alloys and fabricators to design more efficient manufacturing processes. The present paper describes recent concepts for alloy design optimization of carburizing steel and demonstrates the forthcoming beneficial consequences with regard to manufacturing processes and final properties.

High speed steel produced by spray forming

Shun-Li Zhao, Jun-Fei Fan, Jie-Yu Zhang, Kuo-Chih Chou, Hai-Rong Le

2016, 4(2):  115-122.  doi:10.1007/s40436-016-0137-6

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In this paper, ASP2030 (A30) high speed steel (HSS) was produced by spray forming and the microstructure was studied by optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron probe microanalysis (EPMA) and X-ray diffraction (XRD). The spray formed A30 (SF A30) steel exhibited a very uniform and fine microstructure consisting of martensite, retained austenite and uniformly distributed network carbides. Microstructure refining can be explained in terms of the rapid solidification of spray forming. M₂C, MC and M₆C type carbides were found in the as-sprayed A30 HSS by XRD and TEM. A uniform distribution of carbides was obtained after forging and annealing. The microstructure properties of SF A30 steel indicate that spray forming can be considered as a cost-effective route for the production of A30 steels and other highly alloyed steels.

Gate design and filling process analysis of the cavity in injection molding process

Mehdi Moayyedian, Kazem Abhary, Romeo Marian

2016, 4(2):  123-133.  doi:10.1007/s40436-016-0138-5

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This paper presents a new geometry of an edge gate in the injection molding process called modified edge gate. The corners of current edge gate result in the turbulence of molten plastic into the cavity which leads to internal and external defects. The aim of the new geometry is to reduce the internal and external defects of injected part such as sink marks and short shot. The easier de-gating analysis for the new geometry to decrease the visible blemish of the injected part was proposed in this study. A modified edge gate was proposed for two circular flat plates with thickness 1 mm. Finite element method (FEM) was used along with SolidWorks plastic. Internal and external defects of the injected part were analyzed via SolidWorks plastic. To validate the new geometry, an experimental study was implemented for two polypropylene (PP) circular flat plates with modified edge gate to confirm the simulation results. The contribution of this research is to modify the geometry of current edge gate by removing the corners of rectangular edge gate which leads to the reduction of scrap. The new geometry presents easier degating of gate and less visible blemish of the injected part. A smooth flow of molten plastic into the cavities reduces the internal and external defects. The outcome of this study demonstrates filling of the cavities with no short shot. In addition, no sink marks were detected with modified edge gate. Finally, the modified edge gate has less visible blemish on the injected part in comparison with current edge gate.

Fabrication and functional characterization of engineered features on pyrolytic carbon

Vivek Bajpai, Bablu Prasad, Ramesh Singh

2016, 4(2):  134-141.  doi:10.1007/s40436-016-0139-4

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Engineered features on pyrolytic carbon (PyC) have been reported to improve the functional performance of the bio-implants. This paper is focused on the functional characterization of micro-features created on the surface of PyC. Two different types of micro-features (wide channels and arrayed holes) have been created by micro-electrical discharge machining (micro-EDM). Two other micro-features (fine channels and micro-pillars) have been created by micromilling process. Coliform bacterial strain was isolated from a sample of water and grown on all four textured. Cell growth was carried out on an unmachined surface to see the behavior of the isolated bacterial strain on the textured/non-textured surfaces. The samples were examined under SEM before and after wash to see cell growth and cell adhesion capability of the textures. The wide channels by micro-EDM show the maximum cell growth but poor cell adhesion. 184% higher cell growth has been observed on the wide channels in comparison with unmachined surface. The fine channels by micro-milling show comparatively lower growth but the cell adhesion on this surface was found excellent. 71% cells remain unwashed after washing of the surface having fine channel textures. It means that the channels structure shows the maximum cell growth and adhesion independent of machining process.

An adaptive multi-population genetic algorithm for job-shop scheduling problem

Lei Wang, Jing-Cao Cai, Ming Li

2016, 4(2):  142-149.  doi:10.1007/s40436-016-0140-y

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Job-shop scheduling problem (JSP) is a typical NP-hard combinatorial optimization problem and has a broad background for engineering application. Nowadays, the effective approach for JSP is a hot topic in related research area of manufacturing system. However, some JSPs, even for moderate size instances, are very difficult to find an optimal solution within a reasonable time because of the process constraints and the complex large solution space. In this paper, an adaptive multi-population genetic algorithm (AMGA) has been proposed to solve this problem. Firstly, using multi-populations and adaptive crossover probability can enlarge search scope and improve search performance. Secondly, using adaptive mutation probability and elite replacing mechanism can accelerate convergence speed. The approach is tested for some classical benchmark JSPs taken from the literature and compared with some other approaches. The computational results show that the proposed AMGA can produce optimal or near-optimal values on almost all tested benchmark instances. Therefore, we can believe that AMGA can be considered as an effective method for solving JSP.

Numerical study of heat transfer and solidification behavior of gas-atomized Fe-6.5%Si (mass fraction) droplets

Ke-Feng Li, Yun-Hu Zhang, Chang-Jiang Song, Qi-Jie Zhai

2016, 4(2):  150-156.  doi:10.1007/s40436-016-0141-x

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During spray atomization process, the heat transfer and solidification of droplets play very important roles for the deposition quality. Due to the difficulties of experimental approach, a numerical model is developed, which integrates liquid undercooling, nucleation recalescence and post-recalescence growth to present the full solidification process of Fe-6.5%Si (mass fraction) droplet. The droplet velocity, temperature, cooling rate as well as solid fraction profiles are simulated for droplets with different sizes to demonstrate the critical role of the size effect during the solidification process of droplets. The relationship between the simulated cooling rate and the experimentally obtained secondary dendrite arm spacing is in excellent agreement with the well-established formula. The pre-constant and exponent values lie in the range of various rapid solidified Fe-based alloys reported, which indicates the validity of the numerical model.

Bionic tracking method by hand & eye-vergence visual servoing

Wei Song, Mamoru Minami, Lin-Yong Shen, Ya-Nan Zhang

2016, 4(2):  157-166.  doi:10.1007/s40436-016-0143-8

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Animals rotate their eyes to gaze at the target prey, enhancing the ability of measuring the distance to the target precisely for catching it. These animals, visual tracking includes the triangular eye-vergence control and their body's motion control by visual servoing. The research aims to realize a bionic robot tracking performance, in which the body links moves together with eyes' view orientation. This paper proposed a hand & eye-vergence dual control system which included two feedback loops: an outer loop for conventional visual servoing to direct a manipulator toward a target object and an inner loop for active motion control of binocular cameras to change the viewpoint along with the moving object to give an accurate and broad observation. This research also foused on how to compensate a fictional motion of the target seen by camera images in an eye-in-hand system, where the camera was fixed on the end-effector and moved together with the hand motion. A robust motion-feedforward (MFF) recognition method is proposed to compensate the fictional motion of the target based on the manipulator's joint velocity, then the real motion of the target seen by camera images is extracted, which can improve the feedback image sensing unit to make the whole servoing system dynamically stable. The effectiveness of the proposed hand & eye-vergence visual servoing method is shown by tracking experiments using a 6-DoF robot manipulator and a 3-DoF binocular vision system.

Experimental investigation into fabrication of microfeatures on titanium by electrochemical micromachining

Sandip S. Anasane, B. Bhattacharyya

2016, 4(2):  167-177.  doi:10.1007/s40436-016-0145-6

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Titanium machining is one of the challenging tasks to modern machining processes. Especially fabricating microfeatures on titanium appear as a potential research interest. Electrochemical micromachining (EMM) is an effective process to generate microfeatures by anodic dissolution. Machining of titanium by anodic dissolution is different than other metals because of its tendency to form passive oxide layer. The phenomenon of progression of microfeature by conversion of passive oxide layer into transpassive has been investigated with the help of maskless EMM technique. Suitable range of machining voltage has been established to attain the controlled anodic dissolution of titanium by converting passive oxide film of titanium into transpassive with nonaqueous electrolyte. The experimental outcomes revealed that the micromachining of titanium with controlled anodic dissolution could be possible even at lower machining voltage in the range of 6-8 V. This work successfully explored the possibility of generation of microfeatures on commercially pure titanium by anodic dissolution process in microscopic domain by demonstrating successful fabrication of various microfeatures, such as microholes and microcantilevers.

Balancing multiple criteria in formulation of weighted, single-objective genetic algorithm optimization for CNC machining problems

Agathocles A. Krimpenis, Nikolaos A. Fountas

2016, 4(2):  178-188.  doi:10.1007/s40436-016-0144-7

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This paper presents results obtained from the implementation of a genetic algorithm (GA) to a simplified multi-objective machining optimization problem. The major goal is to examine the effect of crucial machining parameters imparted to computer numerical control machining operations when properly balanced conflicting criteria referring to part quality and process productivity are treated as a single optimization objective. Thus the different combinations of weight coefficient values were examined in terms of their significance to the problem's response. Under this concept, a genetic algorithm was applied to optimize the process parameters exist in typical; commercially available CAM systems with significantly low computation cost. The algorithm handles the simplified linear weighted criteria expression as its objective function. It was found that optimization results vary noticeably under the influence of different weighing coefficients. Thus, the obtained optima differentiate, since balancing values strongly affect optimization objective functions.