bluuebunny/crossref_metadata_2025 huggingface dataset:
Flexible quasi-solid-state 2.4 V aqueous asymmetric microsupercapacitors with ultrahigh energy density
Authors: Zhang Qichong , Zhang Jun , Zhou Zhenyu , Wei Lei , Yao Yagang
Published: September 2018

A simple and cost-effective cut-and-transfer method is demonstrated to fabricate flexible 2.4 V asymmetric microsupercapacitors by adopting hierarchical Na-MnOx nanosheets on 3D nitrogen-doped carbon fibers as the cathode and VN nanosheet arrays as the anode.
Promising ITO-free perovskite solar cells with WO3–Ag–SnO2as transparent conductive oxide
Authors: Liang Fengxia , Lin Yi , He Zhenfei , Chen Wei , Zhu Yudong , Chen Tian , Liang Lin , Ma Suman , Wu Yinghui , Tu Bao , Wang Dong , Zhang Zhixiang , Luo Linbao , He Zhubing
Published: September 2018

Substituting indium-tin-oxide, one-pot deposition of WO3/Ag/SnO2films with high transmittance and low sheet resistance enables the formulation of high-performance perovskite solar cells.
An ultrathin cobalt-based zeolitic imidazolate framework nanosheet array with a strong synergistic effect towards the efficient oxygen evolution reaction
Authors: Cao Junhui , Lei Chaojun , Yang Jian , Cheng Xiaodi , Li Zhongjian , Yang Bin , Zhang Xingwang , Lei Lecheng , Hou Yang , Ostrikov Kostya (Ken)
Published: September 2018

A novel ultrathin cobalt-based zeolitic imidazolate framework hybrid nanosheet array exhibits enhanced electrocatalytic activity for the oxygen evolution reaction.
Photostable and biocompatible AIE-active conjugated polyelectrolytes for efficient heparin detection and specific lysosome labelling
Authors: Wang Yinan , Yao Hongming , Zhuang Zeyan , Yao Jinya , Zhou Jian , Zhao Zujin
Published: September 2018

A series of new conjugated polyelectrolytes (CPEs) with emissive tetraphenylethene-containing backbones and specific targeting pendants are synthesized and characterized.
Enhanced efficiency of polymer solar cells through synergistic optimization of mobility and tuning donor alloys by adding high-mobility conjugated polymers
Authors: Li Jianfeng , Liang Zezhou , Wang Yufei , Li Hongdong , Tong Junfeng , Bao Xichang , Xia Yangjun
Published: September 2018

A diketopyrrolopyrrole-based small bandgap polymer (DPPT-TT) with high mobility is introduced as an additive to D–A1–D–A2 type thieno[3,4-b]thiophene-based random copolymer (P3):(6,6)-phenyl-C70-butyric acid methyl ester (PC71BM) polymer solar cells (PSCs).
Coumarin-based emissive hexacatenars: synthesis, 2D and 3D self-assembly and photodimerization
Authors: Xiao Yulong , Tan Xiaoping , Xing Wei , Zhao Kai , Zhang Bei , Cheng Xiaohong
Published: September 2018

Various 2D columnar LC phases and gels with abnormal morphologies as well as reversible LC–LC and gel–gel phase transitions caused by photodimerization were observed in novel unsymmetric coumarin polycatenars.
Learning‐based natural geometric matching with homography prior
Authors: Xu Yifang , Liao Tianli , Chen Jing
Published: September 2018

Geometric matching is a key step in computer vision tasks. Previous learning‐based methods for geometric matching concentrate more on improving alignment quality, while the importance of naturalness issue is argued simultaneously. To this end, a novel homography geometric matching architecture with homography prior is proposed. Specifically, two choices for different purposes in geometric matching are provided. When compositing homography prior with affine transformation, the alignment accuracy improves and all lines are preserved, which results in a more natural transformed image. When compositing homography prior with thin‐plate‐spline transformation, the alignment accuracy further improves. Experimental results on Proposal Flow dataset show that the proposed method outperforms state‐of‐the‐art methods, both in terms of alignment accuracy and naturalness.
Research on an online diagnosis for rotating diode faults in three‐phase brushless exciter with two coils
Authors: Yucai Wu , Bochong Cai , Qianqian Ma
Published: September 2018

The rotating rectifier is prone to be damaged in the exciter of the brushless excitation system, wherein a diode open‐circuit fault which is common can affect the normal and safe operations of a generator. On the basis of the structure of the brushless exciter, this study, analysed the effect that an open‐circuit in one and two diodes had on armature current and armature field, and put forward a new online detection method for diode open‐circuit fault. In this method, two magnetic field detection coils are installed on the stator iron yoke of the brushless exciter, and the open‐circuit fault of the diodes can be reflected by the induced voltage difference of the two detection coils. Using a 16‐pole, three‐phase brushless exciter as an example, the performance of this new diagnosis method was verified by using a finite element simulation.
Method for division of urban load power supply district based on cluster analysis
Authors: Li Yan , Du Mingqiu , Xie Wei , Yang Bingzhen , Fang Chen , Zhang Yong , Wang Shaorong
Published: September 2018

The division of urban power supply district is an essential issue in the medium voltage distribution network plan. This study develops a method for division of an urban load power supply district, integrating the open source data into the distribution network planning, at first, raw georeferenced point of information data is crawled by crawler program based on location retrieval service interface (Place API), the buildings’ data of the planned urban district is extracted and power load estimation are introduced in detail, the dataset of the low‐voltage load spatial distribution is set‐up; secondly, the clustering algorithm selects both the local density of samples and the distance between samples as criteria to form the clusters, cluster centres are recognised from the binary pair in ‘decision map’, as load density peaks. Thirdly, the spatial distribution dataset of the low‐voltage users is taken as the data points in the clustering algorithm; the result of clusters corresponds to division in the power distribution with certain capability. Consequently, the methodologies proposed are verified on one example district of ∼71.7587 hectares, the division scheme can provide theoretical guidance for the location and sizing of power distributors in the urban distribution network.
Fast and accurate compressed sensing model in magnetic resonance imaging with median filter and split Bregman method
Authors: Yang Yunyun , Qin Xuxu , Wu Boying
Published: September 2018

Magnetic resonance (MR) images have great importance to assist doctors in diagnosing diseases, however, the long MR images scan duration remains the primary obstacle in clinical medicine. Compressed sensing reconstructed technique in MR imaging (CS‐MRI) makes it possible to reconstruct a faithful MR image from very few measurements data, which helps to reduce the scan time. The purpose of this study is to improve the accuracy and efficiency of the CS‐MRI. The authors propose a fast compressed sensing reconstruction model for MR images that can alleviate the aliasing artefacts that come from the reconstruction process by jointly minimising a total variation term, a fitting data term and a median filter term. Moreover, they accelerate the proposed algorithm by applying the split Bregman method to solve the proposed model. Then, the proposed model is applied to reconstruct a large number of MR images. They also compare the performance of the proposed model with another model. It can be observed from the experimental results that the proposed model has shown higher precision in reconstructing image quality and much more efficiency than the other one. Additionally, they also give a discussion on how to choose proper parameters in the proposed model to obtain more satisfactory results.
Multiple‐detection multi‐target tracking with labelled random finite sets and efficient implementations
Authors: Wang Jun , Yang Bin , Wang Wenguang , Bi Yanxian
Published: September 2018

Traditional multi‐target tracking algorithms assume that each target can generate at most one detection per scan. However, a target may produce multiple detections (MDs) in many practical applications, e.g. over‐the‐horizon radar (OTHR), tracking for extended target and tracking with multiple sensors. In this study, the authors propose a new algorithm for tracking multiple targets with MD observation. The proposed technique is based on the labelled random finite set (RFS), which estimates the number of targets and the trajectories of their states. Furthermore, they propose two methods, pre‐partition and joint partition, to implement the labelled RFS density recursion. The joint partition method derives a joint prediction, partition and update formulation of the MD filtering and extends the Gibbs sampler to provide global optimal results with low computational cost. The authors’ algorithm is demonstrated on an OTHR simulation compared with the previous approach, such as the MD probability hypothesis density filter and the multipath cardinality‐balance multi‐target multi‐Bernoulli filter.
Theory of data‐driven SAR autofocus to compensate for refraction effects
Authors: Alan Garren David
Published: September 2018

There are challenges in attempting to acquire sufficient atmospheric measurements that are required in order to model the physical atmospheric refraction effects for all transmission pulses within a typical synthetic aperture radar (SAR) collection interval. In particular, atmospheric turbulence can induce spatial variations of the air density, temperature, and other physical variables along the synthetic aperture, which can have differing effects on the local refraction‐induced bending and delay of each of the transmission pulses. The primary goal of the current investigation is to develop an alternate approach based on data‐driven techniques in order to develop methods for automatically correcting such refraction‐induced defocus effects on SAR image data. This alternate methodology applies two‐dimensional maximum likelihood signal‐theoretic techniques in order to estimate and compensate for the refraction‐induced phase errors of the input defocused SAR imagery, thus yielding improved scene refocus wherein the majority of the refraction‐induced defocusing effects have been corrected. The efficacy of this data‐driven approach is demonstrated through the injection of known bending and delay effects applied to measured Ku‐band SAR data.
Eccentric correction of piston based on bionic micro‐texture technology for the gap seal hydraulic cylinder
Authors: Chen Xiaolan , Zeng Liangcai , Chen Xiaobo
Published: September 2018

The eccentricity of the piston in the continuous casting machine cannot be ignored, which not only increases the internal leakage of the hydraulic cylinder, but also increases the friction on the surface of the friction pair, and even has serious consequences such as deformation failure. In this work, the biomimetic micro‐texture technology is used to construct the microtextures on the surface of the cylinder so that it produces a continuous centring force during operation, and the problem of piston eccentricity is corrected. Moreover, the influence of hydraulic cylinder operating parameters and biomimetic microtexture parameters on the dynamic pressure support force is also analysed. This has a very positive effect on improving the response frequency of the hydraulic cylinder and the working efficiency of the hydraulic system.
Synthesis of nanoV3.6Mo2.4O16 and their catalytic activity in the selective oxidation of toluene
Authors: Liu Ying Ying , Xia Huan , Liu Zhao Qing , Liu Zi Li , Zuo Jian Liang
Published: September 2018

Molybdenum vanadate is a novel vanadate. It is a functional material with good magnetic, electrical and catalytic properties. However, it is rarely used in the selective catalytic oxidation field, while the transition metal molybdenum and vanadium are usually used as a catalytic oxidation catalyst, the complex oxide and salt are naturally concerned. The structure of high‐quality single crystalline Molybdenum vanadate (V3 .6Mo2.4O16) nanorods was synthesised by sol–gel method and high‐temperature solid‐state reaction. The effects of vanadium and molybdenum molar ratio and calcination temperature on the preparation of V3.6Mo2.4O16 were studied. The structure of the catalyst was characterised by X‐ray diffraction, thermogravimetry, X‐ray photoelectron spectroscopy, scanning electron microscope and transmission electron microscope. The experimental results show that the molar ratio of vanadium–molybdenum is 10:7 when the precursor calcination temperature is 540°C, the single crystalline V3.6Mo2.4O16 nanorods with regular shape has been obtained, the diameter of about 200 nm and the length up to tens of micrometres and the surface is smooth. Catalytic oxidation of toluene to benzaldehyde is used as a probe reaction for nanoV3.6Mo2.4O16. The catalytic activity of the catalyst is good, the conversion of toluene is 39.8% and the selectivity of benzaldehyde is 70.1%.
CORDIC-like method for solving Kepler’s equation
Authors: Zechmeister M.
Published: September 2018

Context. Many algorithms to solve Kepler’s equations require the evaluation of trigonometric or root functions.

Aims. We present an algorithm to compute the eccentric anomaly and even its cosine and sine terms without usage of other transcendental functions at run-time. With slight modifications it is also applicable for the hyperbolic case.

Methods. Based on the idea of CORDIC, our method requires only additions and multiplications and a short table. The table is independent of eccentricity and can be hardcoded. Its length depends on the desired precision.

Results. The code is short. The convergence is linear for all mean anomalies and eccentricities e (including e = 1). As a stand-alone algorithm, single and double precision is obtained with 29 and 55 iterations, respectively. Half or two-thirds of the iterations can be saved in combination with Newton’s or Halley’s method at the cost of one division.
Resonant damping of kink oscillations of thin cooling and expanding coronal magnetic loops
Authors: Shukhobodskiy A. A. , Ruderman M. S. , Erdélyi R.
Published: September 2018

We have considered resonant damping of kink oscillations of cooling and expanding coronal magnetic loops. We derived an evolutionary equation describing the dependence of the oscillation amplitude on time. When there is no resonant damping, this equation reduces to the condition of conservation of a previously derived adiabatic invariant. We used the evolutionary equation describing the amplitude to study the competition between damping due to resonant absorption and amplification due to cooling. Our main aim is to investigate the effect of loop expansion on this process. We show that the loop expansion acts in favour of amplification. We found that, when there is no resonant damping, the larger the loop expansion the faster the amplitude growths. When the oscillation amplitude decays due to resonant damping, the loop expansion reduces the damping rate. For some values of parameters the loop expansion can fully counterbalance the amplitude decay and turn the amplitude evolution into amplification.
AEg̅IS latest results
Authors: Guatieri F. , Aghion S. , Amsler C. , Angela G. , Bonomi G. , Brusa R.S. , Caccia M. , Caravita R. , Castelli F. , Cerchiari G. , Comparat D. , Consolati G. , Demetrio A. , Di Noto L. , Doser M. , Evans C. , Fanì M. , Ferragut R. , Fesel J. , Fontana A. , Gerber S. , Giammarchi M. , Gligorova A. , Haider S. , Hinterberger A. , Holmestad H. , Kellerbauer A. , Krasnický D. , Lagomarsino V. , Lansonneur P. , Lebrun P. , Malbrunot C. , Mariazzi S. , Matveev V. , Mazzotta Z. , Müller S.R. , Nebbia G. , Nedelec P. , Oberthaler M. , Pacifico N. , Pagano D. , Penasa L. , Petracek V. , Prelz F. , Prevedelli M. , Rienaecker B. , Robert J. , Rhne. O.M. , Rotondi A. , Sacerdoti M. , Sandaker H. , Santoro R. , Simon M. , Smestad L. , Sorrentino F. , Testera G. , Tietje I.C. , Widmann E. , Yzombard P. , Zimmer C. , Zmeskal J. , Zurlo N.
Published: September 2018

The validity of the Weak Equivalence Principle (WEP) as predicted by General Relativity has been tested up to astounding precision using ordinary matter. The lack hitherto of a stable source of a probe being at the same time electrically neutral, cold and stable enough to be measured has prevented highaccuracy testing of the WEP on anti-matter. The AEg̅IS (Antimatter Experiment: Gravity, Interferometry, Spectroscopy) experiment located at CERN's AD (Antiproton Decelerator) facility aims at producing such a probe in the form of a pulsed beam of cold anti-hydrogen, and at measuring by means of a moiré deflectometer the gravitational force that Earth's mass exerts on it. Low temperature and abundance of the H̅ are paramount to attain a high precision measurement. A technique employing a charge-exchange reaction between antiprotons coming from the AD and excited positronium atoms is being developed at AEg̅IS and will be presented hereafter, alongside an overview of the experimental apparatus and the current status of the experiment
Applications of the Gurson’s model in sheet metal forming
Authors: Banabic Dorel , Kami Abdolvahed
Published: September 2018

Recent advances in the modelling of metals encompass modelling of metals structural inhomogeneity, damage, porosity, twinning/untwining and non-local and second order effects. This presentation is focused on modelling the void growth in ductile fractures. The growth and coalescence of microscopic voids are the main mechanisms in ductile fracture of bulk metallic parts. In sheet metals, ductile fracture is preceded by necking during which existing voids do not have significant growth. However, necking is highly sensitive to plastic flow direction which in turn is sensitive to the presence of voids. Also, under biaxial strain loading, the final fracture in the necking region is still controlled by void growth; hence an accurate fracture prediction is crucial for crash simulations. Finally, in super-plastic sheet forming, void growth and coalescence may precede or accompany necking. Therefore, there is as increasing interest in modelling of voids in the sheet metals. As an application, we show how the predictions of some forming limit curves (FLCs) can be affected by accurate simulation of voids growth.
Deburring and rounding of sheet metals and functionally relevant edges of parts using laser radiation
Authors: Kumstel Judith , Lüken Sven
Published: September 2018

The manufacturing of sheet metal parts or component edges often leads to burrs. Due to different requirements regarding the appearance, haptics, tribology et cetera the edges have to be deburred or rounded in a subsequent process. Especially for complex geometries, automated post-processing has been difficult up to now. Laser remelting is one possible solution. It is fully automated and suitable for most 3D geometries. During laser remelting the laser beam is focused on the surface, thus a thin surface layer up to 100 μm is melted. The surface tension in the liquid state is smoothing out the surface and the edge resolidifies rounded. The radius of the rounding is adjustable by the chosen process parameters, especially laser power PL and feed speed vfeed. Furthermore the resulting roughness and the gloss level are controllable via the process parameters. Typical processing speeds are 100 mm edge length per second. First studies with industry partners showed promising results. Laser remelting of push belts for the torque transmission in CVTs lead to an increase of fatigue strength by up to 200% which enables a higher torque.
Effect on the mechanical properties of sheet metals after the use of drawbeads in deep drawing
Authors: Schmid Harald , Merklein Marion
Published: September 2018

The use of modern and more complex materials leads to a need for detailed knowledge and controlling of the material flow. Next to the blank holder force or the lubrication system, drawbeads are nowadays one common way to bring serial forming processes under control. Although drawbeads are already well investigated regarding their retention forces, the effect on the resulting mechanical properties after a drawbead passage is not analysed in detail yet. This work will show the influence of a common drawbead geometry used in forming processes on typical mechanical properties of sheet metal. Therefore, two different sheet metal materials are preloaded in a modified strip drawing test with industrial used drawbead geometry. In testing, three different pressure levels between 2.5 MPa and 7.5 MPa and three levels of drawing speed between 10 mm/s and 50 mm/s are combined to nine variations which will be examined. Afterwards, specimens are cut out by a laser cutting machine of the drawn strips. Those already preloaded and deformed specimens are then tested under standard conditions with the use of an optical measurement system. The results like tensile strength or elongation at fracture are compared to the initial state and each other and discussed with consideration of pressure and speed levels to work out the main effects. Those results are a contribution for the optimization of deep drawing simulations of parts including drawbeads or to evaluate the influence of drawbeads on forming processes to specify or even expand process limitations.
Influence of heat treatment on the microstructure and mechanical properties of TC17 Titanium Alloy
Authors: Min Wang , Darong Huang , Ya Fan , YongQuan Nin , Hongzhen Guo , Zekun Yao
Published: September 2018

The influence of heat treatment on the microstructure and mechanical properties of TC17 titanium alloy was investigated by changing holding time before forging and aging temperature after β-forging. A better heat treatment mechanism was chosen according to its working requirements. The results showed that the holding time and aging temperature had a significant influence on microstructures and mechanical properties of TC17 alloy. With the increase of holding time before forging in the single β phase region, the original β grain size enlarge, the strength and fracture toughness decrease, and the plasticity increases. The size of lamellar α-phase bundles enlarge with the rise of aging temperature after β-forging, the orientated relationship becomes simple, and the content of β-transformation increases. And the plasticity and fracture toughness of the alloy increase, the strength and hardness decreases. The fracture toughness is better under the heat treatment mechanism at 873°C/2h +918°C/64min before forging, 800°C/4h,WC+660°C /8h AC after forging, with the high and low cycle fatigue properties meet the technical requirements.
Investigation of a Modified Hydrodynamic Deep Drawing Assisted by Radial Pressure with Inward Flowing Liquid Process
Authors: Khademi Maziar , Sadegh yazdi Milad , Bakhshi-Jooybari Mohammad , Gorji Hamid
Published: September 2018

Hydrodynamic Deep Drawing (HDDRP), the combination of hydroforming and conventional deep drawing, accommodates the advantages of the two processes. A technique, called HDDRP with inward flowing liquid, has been introduced based on the idea of insertion of radial pressure around the blank rim. The radial pressure created on the blank edge, can increase the drawing ratio. Thus, increasing the radial pressure to an amount greater than the cavity pressure, and independent control of these pressures is the basic idea of this research for forming cylindrical parts. To perform the experiments, two independent pumps were used to provide the two pressures independently. The pressure supply system and the die set were designed in a way that provides simultaneous control of the pressures throughout the process. Then, the effects of radial pressure paths on thickness distribution of cylindrical St13 cups were investigated. In addition, a comparison between HDDRP and HDDRP with inward flowing liquid processes has been performed experimentally. Results indicated that using a higher radial pressure than the cavity pressure and controlling their values at any moment of the process enhances the thickness distribution of the formed part in all regions.
Hot embossing of polypropylene micro-tubes into functional tubular components with controlled inner-pore sizes
Authors: Zhao Jie , Qin Yi
Published: September 2018

To meet ever-increasing demands on the micro-components for medical and non-medical applications, a new micro-shaping technology - “hot embossing of micro-tubes”, had been developed for the forming of polymeric tubular micro-components. The paper presents the results from the forming of Polypropylene(PP) micro-tubes with outer diameters of 1.3mm and inner diameters 0.6mm, to achieve various reduced inner-features. The study was effected by combining experiment, numerical simulation and SEM analysis. FE simulation was implemented by using the material data obtained from the material characterisation tests. The forming experiment was conducted with a high-precision hot-embossing machine, developed in-house, with automated handling and good reliability and repeatability. The Polypropylene (PP) micro-tubes were successfully formed into the desired features at the temperatures of 60°C and 100°C respectively. The influences of the parameters/factors, such as tool design, temperature, forming pressure and holding time, on the quality of the shaped parts, are discussed in details. Based on this study, it is concluded that PP is an ideal candidate material among the polymeric materials for hot embossing of tubular micro-components, due to its good ductility, low transition temperature and low viscosity. Keywords: Micro forming, Manufacturing process, Tool geometry
Fabrication of Miniature Components from ZrO2 Powder by Combining Electrical-field Activated Sintering Technique and Micro-forming
Authors: Hijji Hasan , Qin Yi , Haung Kunlan , Bin Zulkipli Muhammad , Zhao Jie
Published: September 2018

There is an increased demand for miniature/micro products (such as MEMS) and nanotechnology-based products (such as nano-materials). Micro-manufacturing is a link between Macro-and Nano Manufacturing and an effective means for transferring nanotechnology-product designs into volume production. The micro forming has the potential for low-cost, high volume manufacturing applications. In order to meet the high demands on miniaturised products, a rapid production technique and the system, high flexibility, cost-effectiveness and processing a wide range of materials are needed. Recently, a series of studies have been undertaken to investigate forming miniature/micro-components by using a combination of micro-forming and Electrical-field activated sintering (Micro-FAST). The process uses low voltage and high current density, pressure-assisted densification and synthesis technique, which renders several significant merits. The work to be reported in this paper will be focused on the forming of miniature components from Zirconia (ZrO2) powder, without using binders. Several processing parameters have been investigated, such as pressure, heating rate, heating temperature and holding time, which helped to obtain high-quality parts. Using graphite dies and punches, sample parts (solid cylinders of Ø4.00mm × 4.00 mm) were formed. These were subjected to detailed examinations and analysis, such as analysis of the relative density, hardness at the necks formed among the particles and in the particle bodies, as well as the microstructures. The results showed that directly forming the parts from loose powder is feasible, and by properly designing and control the processing parameters, high-quality parts could be achieved, among which heating temperature and holding time are extremely important. At the same time, due to low conductivity of the powder material, carefully designing the tooling is essentials for ensuring properly heating, pressurisation and cooling.
Internal Flow-Turning – extended manufacturing possibilities in tailored tube production
Authors: Wiens Eugen , Homberg Werner
Published: September 2018

The motivation behind the development of a new approach to the manufacture of tailored tubes is the need for greater flexibility in the wall thickness variation of semi-finished parts compared with present manufacturing processes. In the so-called Internal Flow-Turning (IFT) process, the wall thickness contour of regular tubes with a uniform wall thickness is adjusted by means of a rolling process employing an innovative roller tool on the inside of the tube and a die on the outside of the tube. The gap between the roller element and the die can be adjusted through the axial infeed of the roller tool. The gap defines the current wall thickness of the tube during the manufacturing process. In this way, the wall thickness contour can be set in a precise manner by varying the gap distance as the tube is being pulled through the die. Besides the possibility of locally adjusting the wall thickness, IFT can also be used to form geometrical rib elements in the radial tube direction by using a radially shaped die. As the material flow in the IFT-process is mainly caused by compressive stress, the grooves of the die can be “filled up” by radial material displacement.
Adaption of tribological behavior of a-C:H coatings for application in dry deep drawing
Authors: Häfner Tom , Rothammer Benedict , Tenner Jennifer , Krachenfels Kim , Merklein Marion , Tremmel Stephan , Schmidt Michael
Published: September 2018

Nowadays the sheet metal forming industry faces challenges regarding efficient usage of resources and sustainability. One strategy to increase the environmental friendliness is to abandon the application of lubricants. The direct contact between tool and workpiece leads to an intensive interaction which increases friction. Especially for deep drawing processes with long sliding distances, this causes distinctive wear. The tool sided application of carbon based coatings is a well-known approach to reduce friction and wear. Former studies have shown a beneficial behavior of hydrogenated amorphous carbon based coatings (a-C:H) to improve the tribological conditions in contact with steel sheets and aluminium alloys under dry conditions. Within this study the coating process and the resulting coating properties will be analyzed. Afterwards mechanical and laser based surface treatment processes prior and after the deposition process will be investigated to reduce the coating roughness. Different roughness values were achieved by varying the surface treatment processes. The laser based finishing enables a reduction of the Spk values by removing single roughness asperities. In order to identify the necessary process parameters for the laser treatment, an analytical model of the material removal was applied. The laser surface treatment achieved similar roughness characteristics compared to mechanical treatment. In this study the tribological behavior of a-C:H coated tools was analyzed under dry conditions within strip drawing tests. The tribological investigations revealed that for dry deep drawing of zinc coated DC04 a broader range of Spk values leads to acceptable tribological conditions whereas for AA5182 a smoother tool surface has to be ensured to prevent adhesion and utilize the full potential of a-C:H coatings.
Influence of alternating bending on springback behavior of parts in deep drawing process with macro-structured tools
Authors: Mousavi Ali , Ridolfi Kevin Sven , Brosius Alexander
Published: September 2018

In today’s industry, waste prevention and an efficient use of resources are becoming more important due to economic and environmental requirements. Especially in forming processes such as deep drawing, a reduced use of lubricants is highly promising for saving resources and reducing production costs. Deep drawing with macro-structured tools is a novel approach to reduce the amount of friction forces and realize a lubricant free process. The induced alternating bending in sheet metal during the deep drawing process with macro-structured tools leads to an increase of its geometrical moment of inertia and consequently stabilizes the sheet against wrinkling. The induced alternating bending increases the back force in the sheet metal during the process and as a result affects the springback behaviour of the formed part. Furthermore, the resulted cyclic loading in flange area can leads to a kinematic hardening of some material. Within the scope of this paper, the influence of alternating bending on springback behaviour of parts in deep drawing process with macro-structured tools is studied. For this purpose, numerical simulations as well as experimental tests to form a U-channel with macro-structured tools are carried out.
Tool surface with a supporting plateau of hard particles for deep drawing of high alloy steel
Authors: Freiße Hannes , Seefeld Thomas
Published: September 2018

Sheet metal forming normally requires the application of lubricants to protect the tool and the sheet against wear. The parts must be cleaned to remove the lubricants before joining and coating. This process step wastes energy and water resources. In the case of non-lubricated sheet metal forming, cleaning processes would not be necessary anymore and the process chain could be optimized regarding ecological and economical aspects. However, forming without lubrication leads to an intensive contact between the tool and the sheet. Thus, higher wear occurs and process reliability cannot be ensured for industrial mass production. High alloy steels are applied for mass-market products e.g. for appliances. Because of the higher strength, strain hardening and galling effects the austenitic steels are comparatively difficult to form. For dry metal forming of high alloy steels new tool concept must be developed to withstand the higher loads. In this work, a laser generated tool surface with a supporting plateau of hard particles (metal matrix composite (MMC-surface)) is presented. Spherical fused tungsten carbides were injected into the surface by laser melt injection. The metallic matrix of the composite was rejected by applying laser ablation. In consequence, the hard particles stood out of the matrix and were in direct contact with the sheet material. The surface of hard particles had a high hardness about 3000 HV and less metallic character. Cold working steel and aluminium bronze were tested as reference tool materials. Dry and lubricated forming experiments were carried out by strip drawing with bending and deep drawing of cups. Dry deep drawing of cups was not possible by using cold work tool steel. This can be traced back to the occurrence of wrinkles and cup base fracture at the same time. Applying aluminium bronze as tool material for dry metal forming resulted in high adhesive wear. Within this work the feasibility of dry metal forming of high alloy steel could be demonstrated by applying the MMC-surface whereby adhesive wear could be reduced.
High productivity micro rotary swaging
Authors: Moumi Eric , Herrmann Marius , Schenck Christian , Kuhfuss Bernd
Published: September 2018

Rotary swaging is an incremental forming process with two main process variations plunge and infeed rotary swaging. With plunge rotary swaging, the diameter is reduced within a limited section whereas the infeed rotary swaging enables a diameter reduction over the entire workpiece length. The process is now subject to intensive investigation for manufacturing of micro parts. By increasing the process speed, failures occur particularly due to inappropriate material flow. In plunge rotary swaging, the workpiece material can flow radially into the gap between the dies and thus the workpiece quality suffers. In infeed rotary swaging the workpiece material flows against the feeding direction and can provoke bending or braking of the workpiece. Therefore, additional measures to control both the radial and the axial material flow to enable high productivity micro rotary swaging are investigated. The radial material flow during plunge rotary swaging can be controlled by elastic intermediate elements that enable an increase of productivity by factor three. A spring-loaded clamping device that enables an increase of the productivity by factor four can temporarily buffer the axial material flow in infeed rotary swaging against the feeding direction.
Interactions between feed system and process in production of preforms as linked micro parts
Authors: Wilhelmi Philipp , Schattmann Christine , Schenck Christian , Kuhfuss Bernd
Published: September 2018

This contribution deals with interactions between feed system and process in the production of preforms as linked parts, which is the first step of a multi-stage process chain for cold forming of micro parts. Due to the interconnection of the parts, the feed system is not only used for part transport, but also for the positioning during the generation of the preforms by laser rod melting. Thereby, the influence of the feed system on the production is more significant. Absorbed laser energy melts a wire, so that a melt pool is formed. While the wire is fixed on one side, the other side is fed into the melt pool whose volume increases. The production can be divided in the steps of preheating, active melting, solidification and transportation. The positioning takes place in parallel to the melting. Until now, the increase of the output rate was based especially on the consideration of the melting process and higher feed velocities. In this contribution, the interactions between feed and process are analyzed with the goal of further increasing the output rate. For that reason, the positioning behavior and its influence on the geometry of the produced preforms are analyzed. Finally, a method is presented, which unites the steps of transportation, preheating and melting. It is shown, that by a favorable coordination of the individual process steps, a further increase of the output rate is achievable without significantly worsening part quality.
Methodology for Reliable Tribological Investigations Applying a Micro Tribometer in Ball-on-Plate Configuration
Authors: Böhmermann Florian , Riemer Oltmann
Published: September 2018

Aim of this work is the development of a methodology for reliable tribological investigations when applying a micro tribometer. Experiments were conducted in ball-on-plate configuration with linear reciprocating motion. Two different sphere materials were applied: Al99.9 aluminum alloy and 1.4301 austenitic stainless steel. A textured surface from 1.2379 hardened tool steel machined by micro milling exhibiting an areal arithmetic mean height of Sa = 295 nm was used as counterpart. The experiments comprised of the investigation of the coefficient of friction and the evolution of the facet area on the spheres in contact with the textured surface depending on the normal load applied and the number of reciprocating cycles. For the early stage of the experiments an ongoing increase of the area of the facet on the spheres was found; occurring friction was manly governed by abrasion of the sphere’s material and three-body deformation. This was considered as unstable state of the tribological investigation process, not producing meaningful results. For the later stage equilibrium facet areas on the spheres were found and an ongoing conduction of the tribological experiments did not provoke any increase of their sizes. Here, occurring friction was mainly governed by adhesion. The final facet area on a sphere was directly dependent on the sphere’s materials and the applied normal loads. For all subsequent investigations applying a micro tribometer, only spheres exhibiting an equilibrium facet area should be used to gain robust results of tribological investigations, required for the development of e.g. dry deep drawing processes.
Development and application of methods to characterize micro semi-finished products and micro components
Authors: Köhler Bernd , Clausen Brigitte , Zoch Hans-Werner
Published: September 2018

In the production of semi-finished products for the production of microcomponents and the components themselves, the characterization of their physical properties is of particular importance. Due to the often oligocrystalline character of these semi-finished products and components, it is necessary to use a suitable testing technique for static and dynamic investigations, as the mechanical properties are not transferable from the macroscopic point of view. In addition, the micro semi-finished products and components often show inhomogeneities induced by the manufacturing process. On the one hand, these are directly reflected in the microstructure and on the other hand they have an effect on quantities such as hardness or residual stresses, which play a decisive role in the application. Mechanical testing, conventional metallography, scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), ultra-microhardness testing and X-ray residual stress analysis were used as measuring and analysis techniques suitable for the sub-millimeter range. In the following, the possibilities and limitations of two these methods are illustrated using the example of mechanical testing and EBSD. In this paper several examples for possible characterization techniques are given.
Analysis of masonry arches reinforced with FRP sheets: experimental results and numerical evaluations
Authors: Galassi Stefano
Published: September 2018

In recent years fiber-reinforced polymers (FRP) have been widely used for strengthening masonry structures. In particular, in the case of masonry arches, the use of FRP sheets increases load-bearing capacity by limiting or preventing the occurrence of tensile cracks that could activate collapse mechanisms. The effectiveness of the strengthening intervention depends on the bond between FRP and substrate, due to the shear and normal stresses that occur in the bond interface, so much so that the typical failure mode of an arch reinforced with narrow FRP sheets at the intrados is exactly delamination. In this paper a predictive numerical procedure of the combined mode I and mode II failure is proposed. Numerical results provided by this procedure are compared to the experimental results on in-scale arch models taken from a recent work of the author.
Correction and accuracy improvement of non-parallel shear zone model
Authors: Wang Yaoke , Kou Meng , Ding Wei , Ma Huan , Xiong Liangshan
Published: September 2018

When applying the non-parallel shear zone model to predict the cutting process parameters of carbon steel workpiece, it is found that there is a big error between the prediction results and the experimental values. And also, the former approach to obtain the relevant cutting parameters of the non-parallel shear zone model by applying coordinate transformation to the parallel shear zone model has a theoretical error – it erroneously regards the determinant (|J|) of the Jacobian matrix (J) in the coordinate transformation as a constant. The shape of the shear zone obtained when |J| is not constant is drew and it is found that the two boundaries of the shear zone are two slightly curved surfaces rather than two inclined planes. Also, the error between predicted values and experimental values of cutting force and cutting thrust is slightly smaller than that of constant |J|. A corrected model where |J| is a variable is proposed. Since the specific values of inclination of the shear zone (α, β), the thickness coefficient of the shear zone (as) and the constants related to the material (f0, p) are not given in the former work, a method to obtain the above-mentioned five constants by solving multivariable constrained optimization problem based on experimental data was also proposed; based on the obtained experimental data of AISI 1045 steel workpiece cutting force, cutting thrust, chip thickness, the results of five above-mentioned model constants are obtained. It is found that, compared with prediction from uncorrected model, the cutting force and cutting thrust of AISI 1045 steel predicted by the corrected model with the obtained constants has a better agreement with the experimental values obtained by Ivester.
Structural Failure Trends of the Assembly Welding Fixture for the Front Sidewall on the basis of Finite Element Analysis
Authors: Sun Duo , Guan Tianmin , Lei Lei
Published: September 2018

The operating conditions of the assembly welding fixture for the front sidewall have been analyzed in this paper, and all the typical conditions have been applied with the nonlinear finite element analysis of the contact, aiming to ensure the safe utilization of the assembly welding fixture for the front sidewall of tooling equipment for the production of rail vehicles. The potentially risky component locations are predicted and the weak spots are discovered on the basis of the analysis results of the static strength. The anticipation of the component failure trends shows a guiding role in the failure prediction in actual production and facilitates accident prevention.
Research on Several Tool Chuck Technology in High Speed Milling
Authors: Zhao Zhenyu , Xu Xiaomei , Zhou Yongquan , Xiao Haibin
Published: September 2018

In order to meet the requirements of high-speed precision machining technology, the paper elaborates the tool clamping technology commonly used in high-precision machining, such as the static pressure expansion chuck, CoroGrip chuck, and stress locking chuck and so on. How to correctly select the tool clamping system, the characteristics of the tool clamping system and the existing problems are analyzed.
T-phase formation and its effect on mechanical properties of Al-Cu-Mn alloys
Authors: Dar SobanMuddassir , Liao HengCheng , Li GuangJing
Published: September 2018

Al-Cu-Mn alloys are used in components in automotive and aircraft industry which work at high temperature. Recent research is focused on Al-Cu-Mn alloys to enhance their performance by promoting the formation of thermally stable phase particles. In this study, the effect of Cu/Mn content on microstructure and mechanical properties of two Al-Cu-Mn alloys (Cu/Mn wt.% ratio = 5.56, 2.75) is investigated by optical microscopy, scanning electron microscopy, energy dispersive spectroscopy and tensile testing. Results reveal that as-cast microstructure of both the alloys consists of trunks of α-Al dendrites surrounded by Cu-rich interdendritic region. After solution treatment, a great amount of Al-Cu-Mn intermetallic compound particles are found to precipitate adjacent to this region. Alloy with low Cu/Mn content ratio exhibits high strength due to relatively high amount of Al-Cu-Mn (T-phase) particles.
Study of feature extraction method of multi-information source for continuous casting process parameters
Authors: Liang Xianqi , Lei Zhufeng , Su Wenbin , Fali Zhong , Zhao Hang , Zheng Yanni , Ding Mingjie
Published: September 2018

The control of the roll gap of the segment is one of the key links to ensure the quality of cast billet. In this paper, the big data in traditional continuous casting production operations is studied through in-depth experimental comparative analysis of linear and nonlinear dimension reduction method. The method is suitable for continuous casting to obtain the data of the dimension reduction. The method of principal component analysis is improved by using standardized data increment method. A faster and more efficient method of dimension reduction is obtained when the unrelated data, training time and reconstruction error are removed. Actual data simulation results show that this method is more efficient and suitable for continuous casting than any other dimension reduction method.
Research on Capability Evaluation System for Elevator Inspector
Authors: Fei Kexi , Zhou Qinqiao , Huang Kai
Published: September 2018

This paper analyzes the current situation of elevator inspectors’ training based on the QFD method. Then, an elevator inspector’s capability evaluation system for elevator inspector is established. The evaluation index and the weight determination are presented in detail. The research can favor to assess the comprehensive capabilities of elevator inspectors, and provide a theoretical reference of appropriate training activities for elevator inspectors.