Table of Content

25 September 2014, Volume 2 Issue 3

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Laser-based manufacturing concepts for efficient production of tailor welded sheet metals

Marius Spo¨ttl,Hardy Mohrbacher

2014, 2(3):  193-202.  doi:10.1007/s40436-014-0088-8

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Laser welding is an established manufacturing technology for a large variety of automotive applications due to its attractive properties such as low heat input, high precision and fast welding speed. Especially when welding high strength steels, which are dominantly used in today’s car body construction, the low heat input by laser welding bears significant advantages with regard to the properties of the weld seam. The exploitation of the full application potential of laser welding in mass production requires an appropriate manufacturing concept and corresponding auxiliary technologies. The present paper demonstrates the integration of laser welding into the surrounding manufacturing concepts by a modular setup with different levels of automation. This approach offers flexible solutions for individual needs thereby optimizing investment cost, labor cost and productivity. Recently available laser sources enable exceptionally high welding speed on thin gauged sheet metals but require efficient material handling concepts to utilize the full speed potential. Industrial concepts are presented offering efficient material handling and high process robustness for mass production welding.

Tackling the storage problem through genetic algorithms

Lapo Chirici,Ke-Sheng Wang

2014, 2(3):  203-211.  doi:10.1007/s40436-014-0074-1

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The capability of a company to implement an automated warehouse in an optimized way might be nowadays a crucial leverage in order to gain competitive advantage to satisfy the demand. The order picking is a warehouse function that needs to deal with the retrieval of articles from their storage locations. Merging several single customer orders into one, a picking order can increase efficiency of warehouse operations. The aim of this paper is to define throughout the use of ad-hoc genetic algorithm (GA) how better a warehouse can be set up. The paper deals with order batching, which has a major effect on
efficiency of warehouse operations to avoid wastes of
resources in terms of processes and to control possibility of
unexpected costs in advance.

A review on high power SOFC electrolyte layer manufacturing using thermal spray and physical vapour deposition technologies

Pierre Coddet,Han-lin Liao,Christian Coddet

2014, 2(3):  212-221.  doi:10.1007/s40436-013-0049-7

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Manufacturing of solid oxide fuel cell (SOFC) components remains nowadays a key point for the industrial development of this technology. Especially, the
deposition of the dense electrolyte layer which is sandwiched between the porous anode and the porous cathode is of paramount importance and thus focuses a lot of attention. Therefore, this paper considers and reviews recent developments concerning solid electrolyte layers manufacturing using thermal spray (TS) and physical vapour deposition (PVD) technologies.

Optimum calibration of a parallel kinematic manipulator using digital indicators

V. B. Saputra,S. K. Ong,A. Y. C. Nee

2014, 2(3):  222-230.  doi:10.1007/s40436-013-0052-z

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This paper presents a calibration method for parallel manipulators using a measurement system specially installed on an external fixed frame. The external fixed frame is important as an error reference for calibration in certain operations, such as in the configuration of a parallel manipulator functioning as a machine tool where the workpiece is fixed to a worktable. The pose of the end-effector is measured using three digital indicators installed on the external
fixed frame. To enable measurement, the end-effector is assumed to be a plane large enough that all digital indicators could touch. The error is defined as the difference between the theoretical and actual readings of the digital indicators. The geometric parameters of the parallel manipulator are optimized to minimize this error. This calibration method is low cost and feasible for compensating geometric parameter errors for a parallel manipulator. Optimal pose selection for the calibration is achieved using a swarm intelligence search algorithm. The method is implemented on a prototype of a six degrees-of-freedom (DOFs) Gough-Stewart platform constructed to function as a machine tool.

Fabrication of hierarchical polycaprolactone/gel scaffolds via combined 3D bioprinting and electrospinning for tissue engineering

Yong-Ze Yu,Lu-Lu Zheng,Hai-Ping Chen,Wei-Hua Chen,Qing-Xi Hu

2014, 2(3):  231-238.  doi:10.1007/s40436-014-0081-2

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It is a severe challenge to construct 3D scaffolds which hold controllable pore structure and similar morphology of the natural extracellular matrix (ECM). In
this study, a compound technology is proposed by combining the 3D bioprinting and electrospinning process to fabricate 3D scaffolds, which are composed by orthogonal array gel microfibers in a grid-like arrangement and intercalated by a nonwoven structure with randomly distributed polycaprolactone (PCL) nanofibers. Human adiposederived stem cells (hASCs) are seeded on the hierarchical scaffold and cultured 21 d for in vitro study. The results of cells culturing show that the microfibers structure with controlled pores can allow the easy entrance of cells and the efficient diffusion of nutrients, and the nanofiber webs layered in the scaffold can significantly improve initial cell attachment and proliferation. The present work demonstrates that the hierarchical PCL/gel scaffolds consisting of controllable 3D architecture with interconnected pores and biomimetic nanofiber structures resembling the ECM can be designed and fabricated by the combination of 3D bioprinting and electrospinning to improve biological performance in tissue engineering applications.

Application of nonlinear fatigue damage models in power electronic module wirebond structure under various amplitude loadings

Pushparajah Rajaguru,Hua Lu,Chris Bailey

2014, 2(3):  239-250.  doi:10.1007/s40436-014-0054-5

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This paper presents mean fatigue lifetime prediction of a wire-bond structure model in power electronic module using a failure physics approach that integrates high fidelity modelling and reduced order modelling. Loading current with variable amplitudes is applied to a finite element model of simplified wirebond structures. The resulting accumulated fatigue damage due to random loads is predicted by using reduced order modelling based on failure physics, a cycle counting algorithm, and various nonlinear fatigue damage models widely used in the literature. The reduced order modelling approach based on failure physics uses prediction data for the electro-thermo-mechanical behaviour of the wire-bond design of a powermodule obtained through non-linear transient finite element simulations, in particular for the fatigue life-time of the aluminium wire attached to the silicon chip of thewire in the module. The reduced order models that capture the black box function of the accumulated plastic strain are used in predicting the mean fatigue life time of the wire bond structure under random loads. One of the widely used cycle counting algorithms, rainflow counting algorithm, is used to count cycles of the temperature profile at the specific point of the wire bond structure in a power electronicmodule. The cycle data fromthe rainflow algorithmmean life time of the wire bond structure are predicted with various cumulative fatigue models. Non-linear cumulative fatigue models such as damage curve approach (DCA), double linear damage rule (DLDR), and double damage curve approach (DDCA), and linear cumulative fatigue damage model such as Palmgren–Miner rule are used to predict the mean fatigue life of the wire bond structure, and the resultsare compared.

Application of multi-criteria decision making methods for selection of micro-EDM process parameters

A. P. Tiwary,B. B. Pradhan,B. Bhattacharyya

2014, 2(3):  251-258.  doi:10.1007/s40436-013-0050-1

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Ti-6Al-4V super alloy is an important engineering material with good strength to weight ratio and a wide range of applications in a number of engineering
fields because of its excellent physical and mechanical properties. This work determines optimum process parameters such as pulse on time, peak current, gap voltage and flushing pressure, which influence the micro-electro discharge machining (EDM) process during machining of Ti-6Al-4V using combined methods of response surface methodology (RSM) and fuzzy-technique for order preference by similarity to ideal solution (TOPSIS). Central composite design (CCD) is used in the experimental investigation, and a decision making model is developed to identify the optimum process parameters in the micro-EDM  process, which influence several machining criterions such as material removal rate (MRR), tool wear rate (TWR), overcut (OC) and taper. Triangular fuzzy numbers are used to determine the weighting factor for each process criterion. Further a fuzzy-TOPSIS method is used to select the most desirable factor level combinations. The proposed technique can be used to select optimal process parameters from various sets of combinations of process parameters in
a micro-EDM process.

CFD simulation of micro-particle trapping under water tweezers

Xin-Hua Yi,Xiao-Min Cheng,Feng-Lian Niu,Hong-Chao Fan

2014, 2(3):  259-264.  doi:10.1007/s40436-014-0055-4

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In early research, capture and manipulation of particles were mainly achieved by means of light, electricity and plasma in micro-fabrication and micro-assembly. A new method is proposed using micro-water jet to form water tweezers to capture solid particles and implement position control of micro-particles. This paper analyzes the basic principle of water tweezers, and the discrete element method and smoothed particle hydrodynamics method are employed to establish a solid-liquid coupling model used in analyzing the trapping mechanism. A flow field model is set up to simulate dynamic characteristic of water tweezers based on computational fluid dynamics (CFD). Selection of boundary conditions, initial guess, solver control and convergence strategies of the model are discussed. Velocity and pressure of streamline are predicted and discussed under certain input conditions. Simulation results demonstrate that it is an efficiently theoretical method to eventually trap solid particles by water tweezers.

Effect of controlled rolling/controlled cooling parameters on microstructure and mechanical properties of the novel pipeline steel

Min Jiang,Li-Na Chen,Jin He,Guang-Yao Chen,Chong-He Li,Xiong-Gang Lu

2014, 2(3):  265-274.  doi:10.1007/s40436-014-0084-z

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The study of controlled rolling/controlled cooling process parameters which affect the microstructure and mechanical properties of a novel pipeline steel have
been optimized by the orthogonal experiment with four factors and three levels in this paper. However, the parameters of thermo-mechanical control process (TMCP) optimized by the Gleeble-3500 hot simulator could not satisfy performance requirements of the X100 pipeline steel. In order to improve the performance of this steel, the influence of finish cooling temperature (FCT) on the microstructure and property is studied in detail. It is found that, as this steel is thermo-mechanically treated by this set of parameters (the start heating temperature, finish rolling temperature (FRT), FCT and cooling rate of 1,180 C,
810 C, 350 C and 35 C/s, respectively), the microstructures are mainly composed of granular bainite (GB) and acicular ferrite (AF). The effective grain sizes are below 20 lm; the steel reached the optimal balance between the strength and the toughness; the yield strength is 695 MPa; the tensile strength is 768 MPa; the elongation is 16.6 %; the impact energy is 262 J at room temperature. All indexes could meet the requirements of X100 pipeline steel.