bluuebunny/crossref_metadata_2025 huggingface dataset:
Esterification of glycerol and solketal by oxidative NHC-catalysis under heterogeneous batch and flow conditions
Authors: Ragno Daniele , Brandolese Arianna , Urbani Daniele , Di Carmine Graziano , De Risi Carmela , Bortolini Olga , Giovannini Pier Paolo , Massi Alessandro
Published: September 2018

Heterogeneous NHC-catalysis in batch and flow modes is an effective synthetic platform for the production of monoacylglycerols.
Kinetic analysis of the steam reforming of ethanol over Ni/SiO2for the elucidation of metal-dominated reaction pathways
Authors: Zhurka Marinela D. , Lemonidou Angeliki A. , Anderson James A. , Kechagiopoulos Panagiotis N.
Published: September 2018

Reaction mechanism strongly affected by temperature with two steam-independent pathways being active, involving acetaldehyde and an ethanol decomposition-derived surface intermediate.
Asking more from metabolic oligosaccharide engineering
Authors: Gilormini Pierre-André , Batt Anna R. , Pratt Matthew R. , Biot Christophe
Published: September 2018

Metabolic Oligosaccharide Engineering (MOE) is a groundbreaking strategy which has been largely used in the last decades, as a powerful strategy for glycans understanding. The present review aims to highlight recent studies that are pushing the boundaries of MOE applications.
Branched BBB-shuttle peptides: chemoselective modification of proteins to enhance blood–brain barrier transport
Authors: Díaz-Perlas Cristina , Oller-Salvia Benjamí , Sánchez-Navarro Macarena , Teixidó Meritxell , Giralt Ernest
Published: September 2018

THRre is a protease resistant BBB-shuttle. A branched version of THRre displaying two copies of the peptide increases the transport of a model protein in BBB cell-based models.
Precise supramolecular control of surface coverage densities on polymer micro- and nanoparticles
Authors: Zhang Shuai , Domínguez Zoe , Assaf Khaleel I. , Nilam Mohamed , Thiele Thomas , Pischel Uwe , Schedler Uwe , Nau Werner M. , Hennig Andreas
Published: September 2018

Competitive occupation of surface-bound supramolecular hosts allows precise control of surface coverage densities on particles.
Ultrathin Fe-NiO nanosheets as catalytic charge reservoirs for a planar Mo-doped BiVO4 photoanode
Authors: Li Lei , Yang Xiaogang , Lei Yan , Yu Haili , Yang Zhongzheng , Zheng Zhi , Wang Dunwei
Published: September 2018

Charge accumulation at the interface reflects the charge separation and recombination kinetics, and will strongly contribute to the photoelectrochemical reactions.
Facile fabrication of Cu-based alloy nanoparticles encapsulated within hollow octahedral N-doped porous carbon for selective oxidation of hydrocarbons
Authors: Zhong Hong , Wang Yangxin , Cui Caiyan , Zhou Feng , Hu Shuangqi , Wang Ruihu
Published: September 2018

HKUST-1 serves as a template for an imidazolium-based ionic polymer; anion exchange and subsequent topotactic transformation generate hollow nitrogen-doped porous carbon incorporated with Cu-based alloy nanoparticles.
Morphology of depletant-induced erythrocyte aggregates
Authors: Nehring Austin , Shendruk Tyler N. , de Haan Hendrick W.
Published: September 2018

Red blood cells suspended in quiescent plasma tend to aggregate into multicellular assemblages, including linearly stacked columnar rouleaux, which can reversibly form more complex clusters or branching networks.
CdS/NH2-UiO-66 hybrid membrane reactors for the efficient photocatalytic conversion of CO2
Authors: Zhao Hui , Yang Xue , Xu Rui , Li Jingjun , Gao Shuiying , Cao Rong
Published: September 2018

CdS/NH2-UiO-66 membrane reactors are explored for artificial CO2 photo-transformation under mild conditions.
Copper manganese oxide enhanced nanoarray-based monolithic catalysts for hydrocarbon oxidation
Authors: Chen Sheng-Yu , Tang Wenxiang , He Junkai , Miao Ran , Lin Hui-Jan , Song Wenqiao , Wang Sibo , Gao Pu-Xian , Suib Steven L.
Published: September 2018

Copper manganese oxide (CuMn2O4) was introduced into the nanoarray-based monolithic catalysts system for advanced exhaust after-treatment.
Enhanced storage ability by using a porous pyrrhotite@N-doped carbon yolk–shell structure as an advanced anode material for sodium-ion batteries
Authors: Veerasubramani Ganesh Kumar , Subramanian Yuvaraj , Park Myung-Soo , Nagaraju Goli , Senthilkumar Baskar , Lee Yun-Sung , Kim Dong-Won
Published: September 2018

The yolk–shell structured Fe1−xS encapsulated by N-doped carbon exhibited high discharge capacity, good cycling stability and excellent rate capability.
Dramatically improving thermoelectric performance of topological half-Heusler compound LuPtSb via hydrostatic pressure
Authors: Huang Shan , Liu Xiaowei , Zheng Wenwen , Guo Jingjing , Xiong Rui , Wang Ziyu , Shi Jing
Published: September 2018

The thermoelectric figure of merit (ZT) of topological half-Heusler compound LuPtSb dramatically increases from 0.3 to 1.5 via hydrostatic pressure.
Reliable seawater battery anode: controlled sodium nucleationviadeactivation of the current collector surface
Authors: Kim Do Hyeong , Choi Hongkyw , Hwang Dae Yeon , Park Jaehyun , Kim Keun Soo , Ahn Seokhoon , Kim Youngsik , Kwak Sang Kyu , Yu Young-Jun , Kang Seok Ju
Published: September 2018

Deactivated current collector surface for reliable seawater battery.
Controllable fabrication of redox-active conjugated microporous polymers on reduced graphene oxide for high performance faradaic energy storage
Authors: Khattak Abdul Muqsit , Sin Haksong , Ghazi Zahid Ali , He Xiao , Liang Bin , Khan Niaz Ali , Alanagh Hamideh Rezvani , Iqbal Azhar , Li Lianshan , Tang Zhiyong
Published: September 2018

Two-dimensional (2D) composites composed of redox active conjugated microporous polymer (CMP) and reduced graphene oxide (rGO) enable efficient faradaic energy storage.
High-performance n-type thermoelectric composites of acridones with tethered tertiary amines and carbon nanotubes
Authors: Gao Chunmei , Liu Yijia , Gao Yuan , Zhou Yan , Zhou Xiaoyan , Yin Xiaojun , Pan Chengjun , Yang Chuluo , Wang Hanfu , Chen Guangming , Wang Lei
Published: September 2018

Acridone derivatives with different terminal tertiary amine groups were first developed as good n-type thermoelectric composites, and a high power factor of 289.4 μW m−1 K−2 at 430 K was achieved.
Ultrathin stimuli-responsive polymer film-based optical sensor for fast and visual detection of hazardous organic solvents
Authors: Wang Zhaoyi , Liu Xueyao , Wu Yuxin , Liu Bingbing , Wang Zhanhua , Zhang Junhu , Liu Kun , Yang Bai
Published: September 2018

UV cross-linkable stimuli-responsive terpolymer (PMMA-co-HEMA-co-GMA)-based “sandwich-structure” ultrathin film sensor for the visual and rapid detection of hazardous organic solvents.
Ultra-stable 2D layered methylammonium cadmium trihalide perovskite photoelectrodes
Authors: Hsu Hsien-Yi , Ji Li , Zhang Chengxi , Mak Chun Hong , Liu Rugeng , Wang Tie , Zou Xingli , Leu Shao-Yuan , Yu Edward T.
Published: September 2018

For the first time, we demonstrate that 2D layered (MA)2CdCl4-based perovskite photoelectrodes show photoelectrochemical response with enhanced long-term stability.
Pyran-annulated perylene diimide derivatives as non-fullerene acceptors for high performance organic solar cells
Authors: Li Gang , Zhang Yu , Liu Tao , Wang Shuaihua , Li Dandan , Li Jiewei , Li Fengting , Yang Lian-Ming , Luo Zhenghui , Yang Chuluo , Yan He , Hao Pin , Shang Qiaoyan , Tang Bo
Published: September 2018

Through the coupling of acetylene substituted triphenylamine and pyran-annulated perylene diimides, two novel non-fullerene electron acceptors, coded as TPA-PDI2 and TPA-PDI3, were designed, synthesized and applied in BHJ organic solar cells.
Localized optical-quality doping of graphene on silicon waveguides through a TFSA-containing polymer matrix
Authors: Misseeuw Lara , Ciuk Tymoteusz , Krajewska Aleksandra , Pasternak Iwona , Strupinski Wlodek , Feigel Benjamin , Khoder Mulham , Vandriessche Isabelle , Van Erps Jürgen , Van Vlierberghe Sandra , Thienpont Hugo , Dubruel Peter , Vermeulen Nathalie
Published: September 2018

The use of graphene in optical and photonic applications has gained much attention in recent years.
Enhanced dielectric performance of PDMS-based three-phase percolative nanocomposite films incorporating a high dielectric constant ceramic and conductive multi-walled carbon nanotubes
Authors: Liu Guifang , Chen Yi , Gong Minjie , Liu Xiaoyun , Cui Zhong-Kai , Pei Qibing , Gu Jinlou , Huang Chen , Zhuang Qixin
Published: September 2018

Enhanced dielectric constant of PDMS incorporating chain-ball structured CCTO@MWCNT nanoparticles.
Effectiveness of Audiologist-Delivered Cognitive Behavioral Therapy for Tinnitus and Hyperacusis Rehabilitation: Outcomes for Patients Treated in Routine Practice
Authors: Aazh Hashir , Moore Brian C. J.
Published: September 2018

Objective

The aim was to assess the effectiveness of cognitive behavioral therapy (CBT) for tinnitus and/or hyperacusis delivered by audiologists working in the National Health Service in the United Kingdom.

Design

This was a retrospective study, based on questionnaires assessing tinnitus and hyperacusis and insomnia before and after CBT.

Study Sample

Data were gathered for 68 consecutive patients (average age = 52.5 years) who enrolled for CBT.

Results

All measures showed significant improvements after CBT. Effect sizes for patients who completed CBT were 1.13 for Tinnitus Handicap Inventory scores; 0.76 for Hyperacusis Questionnaire scores; 0.71, 0.95, and 0.93 for tinnitus loudness, annoyance, and effect on life, respectively, measured using the Visual Analog Scale; and 0.94 for the Insomnia Severity Index score. An analysis including those who dropped out also showed significant improvements for all measures.

Conclusion

Audiologist-delivered CBT led to significant improvements in self-report measures of tinnitus and hyperacusis handicap and insomnia. The methods described here may be used when designing future randomized controlled trials of efficacy.
Stealing Cookies in the Twenty-First Century: Measures of Spoken Narrative in Healthy Versus Speakers With Aphasia
Authors: Berube Shauna , Nonnemacher Jodi , Demsky Cornelia , Glenn Shenly , Saxena Sadhvi , Wright Amy , Tippett Donna C. , Hillis Argye E.
Published: September 2018

Purpose

Our goal was to evaluate an updated version of the “Cookie Theft” picture by obtaining norms based on picture descriptions by healthy controls for total content units (CUs), syllables per CU, and the ratio of left–right CUs. In addition, we aimed to compare these measures from healthy controls to picture descriptions obtained from individuals with poststroke aphasia and primary progressive aphasia (PPA) to assess whether these measures can capture impairments in content and efficiency of communication.

Method

Using an updated version of this picture, we analyzed descriptions from 50 healthy controls to develop norms for numbers of syllables, total CUs, syllables per CU, and left–right CU. We provide preliminary data from 44 individuals with aphasia (19 with poststroke aphasia and 25 with PPA).

Results

A total of 96 CUs were established based on the written transcriptions of spoken picture descriptions of the 50 control participants. There was a significant effect of group on total CUs, syllables, syllables per CU, and left–right CUs. The poststroke participants produced significantly fewer total CU and syllables than those with PPA. Each aphasic group produced significantly fewer total CUs, fewer syllables, more syllables per CU, and lower left–right CUs (indicating a right-sided bias) compared to controls.

Conclusions

Results show that the measures of numbers of syllables, total CUs, syllables per CU, and left–right CUs can distinguish language output of individuals with aphasia from controls and capture impairments in content and efficiency of communication. A limitation of this study is that we evaluated only 44 individuals with aphasia. In the future, we will evaluate other measures, such as CUs per minute, lexical variability, grammaticality, and ratio of nouns to verbs.

Supplemental Material

https://doi.org/10.23641/asha.7015223
The Mandarin Version of the Consensus Auditory-Perceptual Evaluation of Voice (CAPE-V) and Its Reliability
Authors: Chen Zhen , Fang Rui , Zhang Yi , Ge Pingjiang , Zhuang Peiyun , Chou Adriana , Jiang Jack
Published: September 2018

Purpose

The purpose of this study is to develop the Mandarin version of the Consensus Auditory-Perceptual Evaluation of Voice (CAPE-V) and evaluate its reliability compared with the Grade, Roughness, Breathiness, Asthenia, Strain (GRBAS).

Method

The Mandarin version of the CAPE-V tool was translated from the validated English version with phonemic adaptations, content adjustment, and scale modification. Sixty dysphonic, 20 normal, and 20 repeated voice samples were included in this study. Ten of these were used for preassessment training; the remaining 90 were evaluated using the Mandarin CAPE-V and GRBAS for comparison of their interrater and intrarater reliabilities.

Results

Intrarater reliability was measured by Pearson
r
for the CAPE-V and Spearman rho for the GRBAS. Average CAPE-V Pearson
r
ranged from 0.80 for strain to 0.91 for overall severity, compared with average GRBAS Spearman rho of 0.83 for strain to 0.89 for asthenia. Interrater reliability was measured by an intraclass coefficient (ICC). Average CAPE-V ICCs ranged from .57 for pitch to .81 for overall severity, compared with average GRBAS ICCs of .60 for asthenia to .83 for grade.

Conclusions

The Mandarin CAPE-V addresses some limits of the English version. It also demonstrates good intrarater and interrater reliability, comparable to those of GRBAS.
Approach for minimising network effect of VNF migration
Authors: Zhou Xinhao , Yi Bo , Wang Xingwei , Huang Min
Published: September 2018

In the software defined network (SDN) environment, network function virtualisation enables the virtual machine migration. Owing to the fact that transferring large amount of data will impede competing workflows, virtual network function (VNF) migration has brought a new perspective. Many optimised algorithms focusing on limiting migration time and migration cost have been proposed. In this study, the authors address the problem from a different perspective. They view the network topology from a global perspective and focus on the network effect of the whole network caused by VNF migration in the context of SDN. They introduce a parameter delay to formulate the network effect and an effect model is proposed to evaluate the migration effect of the network. In addition, a heuristic algorithm is proposed to minimise network effect while balancing network load and improving the service considering the migration cost and resources limit at the same time. The practicability and efficiency of the proposed model and algorithm are validated by simulation evaluation. By comparing their proposed algorithm with traditional benchmarks and closely related benchmarks, the experimental results show that their proposed algorithm largely reduces the network effect, while at the same time limiting the run time.
Deep clipping noise mitigation using ISTA with the specified observations for LED‐based DCO‐OFDM system
Authors: Miao Pu , Qi Chenhao , Fang Lanting , Song Kang , Bu Qingkai
Published: September 2018

Deep clipping is beneficial for the optical orthogonal frequency division multiplexing (O‐OFDM) system, since it can lower the peak‐to‐average power ratio, reduce the direct current requirement in light emitting diodes (LEDs), and relax the bit‐resolution requirement in digital‐to‐analogue converters (DACs). However, it is accompanied by more signal distortions. In this study, a deep clipping noise mitigation scheme using iterative shrinkage/thresholding algorithm (ISTA) with three steps is proposed to improve bit error rate (BER) performance of the LED‐based DCO‐OFDM systems. In the first step, the estimated observation interference is eliminated from the received symbols to minimise the negative effect of channel noise. In the second step, two strategies are presented to generate the specified observations thus reduce the component of measurement noise in the whole observation vector. In the last step, combining the generalised cross validation and the estimation of observation interference, the appropriate regularisation parameter are calculated for ISTA to improve the robustness of the sparse recovery performance. They use simulations to show that the proposed scheme can correct the deep clipping noise with favourable reconstruction quality, which significantly improves the BER performance and therefore assist the LED non‐linearity mitigation.
Mitigation of communication failures in distributed model predictive control strategies
Authors: Ananduta Wicak , Barreiro‐Gomez Julian , Ocampo‐Martinez Carlos , Quijano Nicanor
Published: September 2018

Information sharing among local controllers is the key feature of any distributed model predictive control (DMPC) strategy. This study addresses the problem of communication failures in DMPC strategies and proposes a distributed solution to cope with them. The proposal consists in an information‐exchange protocol that is based on distributed projection dynamics. By applying this protocol as a complementary plug‐in to a DMPC strategy, the controllers improve the resilience against communication failures and relax the requirements of the communication network. Furthermore, a reconfiguration algorithm, which is a contingency procedure to maintain the connectivity of the network, and a discussion on the selection criteria of the information‐sharing network are also presented. In order to demonstrate the performance and advantages of the proposed approach when it is applied to a DMPC strategy, a case study of a power‐network control problem is provided.
Meta‐heuristic technique for network reconfiguration in distribution system with photovoltaic and D‐STATCOM
Authors: Ganesh Selvaraj , Kanimozhi Rajangam
Published: September 2018

This study presents a reconfiguration methodology based on a multi‐objective modified flower pollination algorithm (MO‐MFPA) that aims to achieve the power loss reduction, minimum load balancing index, and maximum voltage profile in radial distribution networks with photovoltaic (PV) arrays and distribution static compensator (D‐STATCOM). Here, PV array is considered as distributed generation and D‐STATCOM acts as a distribution flexible AC transmission system. The MO‐MFPA is a meta‐heuristic technique based on the combination of flower pollination algorithm and cloning selection algorithm. A reconfiguration is done through changing the tie and sectional line positions in the distribution system. At the time of reconfiguration, movement of load node to a set of power nodes secures the radial structure of the network. Voltage stability index is used to pre‐identify the most candidate buses for placing PV arrays and D‐STATCOM. Then the proposed MO‐MFPA is employed to deduce the size and locations of PV arrays and D‐STATCOM from the elected buses. For more practical applications, different cases of reconfiguration, PV, and D‐STATCOM installation are considered to evaluate the performance approach at different load factors. The proposed method has been effectively tested on IEEE 33, 69, and 118‐bus distribution systems and encouraging results have been obtained.
Metasurface‐based wideband, low‐profile, and high‐gain antenna
Authors: Yang Zhen‐Zhong , Liang Feng , Yi Yu , Zhao Deshuang , Wang Bing‐Zhong
Published: September 2018

A wideband, low‐profile, and high‐gain antenna loaded with a dual‐layer metasurface is proposed in this study. The metasurface consists of two metallic layers printed on two dielectric layers, in which each metallic layer contains an array of square patch cells. The proposed antenna is fed by an aperture coupled layer under the metasurface. This design makes the antenna work at two different modes with different resonant frequencies close to each other, to enhance the bandwidth. To achieve the best bandwidth performance, a genetic algorithm is adopted to optimise the geometrical parameters of this antenna. This metasurface‐based antenna maintains a low profile of at 5 GHz, meanwhile yields wideband characteristics for both the impedance and gain bandwidth. The −10 dB impedance bandwidth of the proposed antenna is about 44% (4.08–6.38 GHz) and the 3 dB gain bandwidth reaches 45% (4.16–6.56 GHz) with a peak realised gain of 11.6 dBi. A prototype of the antenna is fabricated and the measured results demonstrate the authors’ design.
Tunable channelised bandstop passive filter using reconfigurable phase shifter
Authors: Lababidi Raafat , Al Shami Maryam , Le Roy Marc , Le Jeune Denis , Khoder Khaled , Pérennec André
Published: September 2018

A novel tunable channelised two‐branches passive bandstop filter using a reconfigurable parallel‐coupled‐line‐based phase shifter (PS) is presented. The filter topology uses the signal destructive principle and aims to protect the receiver against an unwanted interference signal received by the antenna. The global filter topology contains two branches, each of which has a different function. The bandpass tunable branch selects the frequency to be rejected while the reconfigurable PS plays the signal inverter role. The simultaneous tunabilities of both bandpass and PS branches are ensured by using identical varactor diodes and features 550–700 MHz tuning range. In addition to having a constant and relatively high rejection level over all the tuning range and low insertion loss in the passband area, the filter guaranties ultra‐low power consumption. Moreover, synthesis equations are proposed and used to illustrate the operating principle, and finally validated by comparing simulations results to measurements.
Biologically‐inspired wideband target localisation
Authors: Reich Galen M. , Antoniou Michail , Baker Christopher J.
Published: September 2018

In this study, the authors present two biologically‐inspired angular localisation techniques for radar which separately use the magnitudes and phases of the wideband received signals as the cues for angular target localisation. By comparison with predetermined map functions, the angle to a target may be estimated with good accuracy and over a wide angular range of operation. These techniques are implemented in a radar system with a single transmitter and two offset receiving antennas, allowing us to draw upon cues derived from biological systems that are often only explored in psychology, biology, and psychoacoustics.
An integrated precise engineering for micro forming
Authors: YANG Ming , Shimizu Tetsuhide , Hu Jun , Shiratori Tomomi
Published: September 2018

An integrated precise engineering was proposed and developed to push the micro metal forming technology to higher level for manufacturing micro metallic devices in this study. A textured Diamond Liked Carbon (DLC) coating was applied to micro die for improving tribological performance. High-energy assisted processes, such as die-embedded localize heating and ultrasonic vibration systems were developed to improve formability of micro materials and accuracy of processes. The results show that .the integrated precise engineering solved the issues due to the size effects, and improved very much the tribological properties, formability of work materials and accuracy of product. Furthermore, the integrated precise engineering was applied in micro forming to manufacturing a micro metallic pump which realized commercialization.
Simulation of thermal behaviours and powder flow for direct laser metal deposition process
Authors: Zeng Quanren , Tian Yankang , Xu Zhenhai , Qin Yi
Published: September 2018

Laser engineering net-shaping (LENS), based on directed energy deposition (DED), is one of the popular AM technologies for producing fully dense complex metal structural components directly from laser metal deposition without using dies or tooling and hence greatly reduces the lead-time and production cost. However, many factors, such as powder-related and laser-related manufacturing parameters, will affect the final quality of components produced by LENS process, especially the powder flow distribution and thermal history at the substrate. The powder concentration normally determines the density and strength of deposited components; while the thermal behaviours of melt pool mainly determines the cooling rate, residual stress and consequent cracks in deposited components. Trial and errors method is obviously too expensive to afford for diverse applications of different metal materials and various manufacturing input parameters. Numerical simulation of the LENS process will be an effective means to identify reasonable manufacturing parameter sets for producing high quality crack-free components. In this paper, the laser metal powder deposition process of LENS is reported. The gas-powder flow distribution below the deposition nozzle is obtained via CFD simulation. The thermal behaviours of substrate and as-deposited layer/track during the LENS process are investigated by using FEM analysis. Temperature field distributions caused by the moving laser beam and the resultant melt pool on the substrate, are simulated and compared. The research offers a more accurate and practical thermal behaviour model for LENS process, which could be applied to further investigation of the interactions between laser, melt pool and powder particles; it will be particularly useful for manufacturing key components which has more demanding requirement on the components’ functional performance.
Laser edge forming to increase the bending radius in hemming
Authors: Woizeschke Peer , Heinrich Lukas , Eichner Philip
Published: September 2018

Hemming can be used, for example, to join dissimilar materials which cannot be welded by conventional laser or arc based processes. A critical value in hemming is the ratio of outer sheet bending radius and outer sheet thickness because cracks can occur in outer sheets with low ductility due to a small bending radius. In this study, a novel approach is introduced for increasing the bending radius by laser based edge forming. The laser beam melts the edge of the inner sheet prior to the hemming process. In laser edge forming, the edge thickness increases due to the surface tension of the melt. The edge cross-section has typically a nearly circular shape after solidification. Two laser beam irradiation strategies were investigated. In case of the first strategy, a defocused laser beam was applied. The second strategy combined a focused laser beam resulting in the formation of a vapor capillary (keyhole) with sinusoidal beam oscillation transversal to the sheet edge. The results show that the position of the cylindrical edge cross-section according to the sheet plane could be affected by the applied irradiation strategy. The needed laser power was significantly lower when using a focused laser beam due to the deep penetration effect. The potential of the laser edge forming technique for crack-free hemming processes was demonstrated with 1 mm thick aluminum alloy sheets by carrying out stripe tests.
Energy of Laser Induced Shockwaves
Authors: Czotscher Tobias , Wünderlich Tim
Published: September 2018

High throughput experimentation is a possibility to develop new materials in a short time in order to meet the demands of efficient characterisation of compositions. Thus, fundamentals of a new hardness measurement method are investigated based on laser-induced shockwaves. In this study, plasma is created with a nanosecond pulsed TEA CO2 laser on top of an indenter. Further interactions of the plasma with the high intensity laser beam result in a shockwave. The pressure of the shockwave is used to push an indenter inside a material surface. So far, the energy transfer of the shockwave on indenters is not fully understood. Therefore, pendulum experiments are conducted to calculate how much energy can be transferred from the shockwave into the indenter. For these experiments, a bob, which geometry is equal to the indenter geometry, is connected to a thread pendulum and maximum deflection angles are recorded with a high-speed camera. Under standard conditions and the assumption of a spherical expansion of the shockwave, the experiments show that with a 6 J pulse energy a shockwave energy of up to 9 μJ can be used for indentation tests.
Generation of residual stresses in rotary swaging process
Authors: Charni Dhia , Ishkina Svetlana , Epp Jérémy , Herrrmann Marius , Schenck Christian , Zoch Hans-Werner , Kuhfuss Bernd
Published: September 2018

Infeed rotary swaging is an established incremental cold forming production technique for axisymmetric workpieces. Among others, work hardening as well as near net shape forming are advantages of this production technique. Due to the incremental open die forging process, the rotary swaging induces a complex material flow history which is dependent on the process control. This material flow history influences the material modifications such as work hardening as well as residual stresses. In this study, the properties of steel tubes were investigated after rotary swaging using varying parameters by experimental and simulation analysis. In particular, the influence of lubrication with different feeding velocities was analysed. The workpiece quality, the hardness and the residual stresses were characterized in detail. After rotary swaging, an influence of the process parameters on the geometrical and surface quality could be observed. The workpieces showed significant work hardening which was higher at the surface and process dependent, while below 100 μm, this increased hardness was observed over the complete wall thickness independently of the process parameters. The residual stress state was highly fluctuating at the surface and was in tensile for all conditions. The results showed that the process parameters influenced the properties near the surface, while a few hundred micrometers below the surface, the workpiece properties seemed to be driven only by the total deformation.
Axial and Radial Material Flow Analysis in Infeed Rotary Swaging of Tubes
Authors: Liu Yang , Herrmann Marius , Schenck Christian , Kuhfuss Bernd
Published: September 2018

In rotary swaging – an incremental cold forming production technique to reduce the diameter of axisymmetric parts – the material flow can be assumed to be predominantly axial and radial. The actual ratio of this axial and radial flow influences the mechanical properties and especially in tube forming the final geometry. It is known that during mandrel free infeed rotary swaging of tubes the wall thickness changes. The change is depending on the process parameters like incremental and cumulated strain. Hence, the ratio of axial and radial material flow changes. Consequently, the analysis of the wall thickness of rotary swaged tubes enables fundamental insight how to control the material flow direction. In this study, the infeed rotary swaging process of steel tubes with different wall thicknesses from 3 mm to 7 mm and rods were investigated with FEM under two feeding velocities. The axial and radial material flow and the resulting geometry were studied by the relative wall thickness. It could be seen that the relative wall thickness was affected by the feeding velocity as well as the initial wall thickness. The findings of the simulation were validated by rotary swaging experiments.
Development of a novel high straining backward extrusion process
Authors: Wang Qiang , Zhang Zhimin , Li Xubin , Zhang Huifang
Published: September 2018

In this study, a new method of backward extrusion is proposed. In this new process, a punch with a movable mandrel was designed. A hollow billet was firstly backward extruded and subsequently upset with the use of the punch after the mandrel returned. The extrusion and upsetting processes were successively executed in order for a higher effective strain to be imposed and a fibrous tissue flow direction to be controlled. In order for the capability of this process to be investigated, experimental and finite element (FE) methods were used. The effective strain of the final part prepared by both the conventional and the new process were compared along the bottom radial and wall axial direction respectively. In the results, it is shown that the plastic strain applied through the processed sample was approximately higher in twice the value of the sample processed via conventional backward extrusion. Consequently, this may improve the mechanical properties and anisotropy of the final products. The difference of the UTS and the TYS between radial and tangential at the bottom was less than 3%.This new process has proven to be promising for parts with a central hole at the bottom production in order for the parts low performance to be improved.
In-situ measurement technologies for flow behaviour and contact status of fibre-reinforced thermoplastics during forming with a six degree of freedom press
Authors: Wonnenberg Birk , Dietrich Franz , Dröder Klaus
Published: September 2018

The paper presents investigations on a forming process, which is implemented in a forming press based on a Stewart platform. In contrast to common forming techniques, this buildup offers not only one but six degrees of freedom. This is of particular interest when it comes to the forming of materials that show significant anisotropic behaviour such as fibre-reinforced plastics. Therefore, an experimental setup is presented to record characteristic variables during the forming process of fibre-reinforced thermoplastics. The contact state is of particular interest for this kind of forming process because it changes continuously in shape and position as the forming process progresses. For this purpose, temperatures at different places in the tool are recorded to provide information about the flow velocity of the material and the contact state between tool and workpiece. This allows the determination of the exact time and position of the contact between material and forming tool as well as the duration of this contact. The results are compared with optical measurements analysed by image processing algorithm and process forces measured by load cells.
Characterisation of the contact pressure dependent interfacial heat transfer coefficient for a hot stamping process following a data driven approach
Authors: Liu Xiaochuan , Zheng Yang , El Fakir Omer , Said Rajab , Wang LiLiang
Published: September 2018

In the present research, the contact pressure characteristics of a hot stamping process was revealed by data mining an existing data base of verified FE simulation results, collected by a cloud-based finite element (FE) simulation platform. Following a data driven approach, a dedicated, novel testing scheme for a hot stamping process was developed and applied to determine the effect of contact pressure on the interfacial heat transfer coefficient (IHTC) between an AA7075 aluminium alloy and cast-iron tools. In this novel testing scheme, only one single IHTC test was required which has improved testing efficiency significantly.
Effect of annealing on microstructure and hardness of thin aluminium strips fabricated by micro flexible rolling
Authors: Huo Mingshuai , Zhao Jingwei , Xie Haibo , Jiang Zhengyi
Published: September 2018

Thin strips with varying thicknesses (TSVTs) produced by micro flexible rolling have wide applications in diverse micro manufacturing areas such as micro electromechanical systems (MEMS) and micro system technologies (MST). TSVTs consist of three regions based on different thicknesses, i.e. the thicker, the transition and the thinner zones. Among them, the transition zone plays a key role in evaluating the quality of TSVTs. In the current work, thin 1060 aluminium alloy strips were flexibly rolled under various thickness ratios followed by annealing treatment. The influences of annealing temperature on the microstructural evolution and hardness variation of the transition zone of TSVTs were investigated. The results reveal that the recrystallisation has happened after annealing at 400 °C for 30 min, which induces fine and homogeneously-distributed grains in both of the thinner and transition zones. Only moderate increase in hardness is found from the thicker to the thinner zones after annealing treatment.
The effect of radial-shear rolling on microstructure and mechanical properties of stainless austenitic steel AISI-321
Authors: Naizabekov Abdrakhman , Lezhnev Sergey , Arbuz Alexandr , Panin Evgeniy
Published: September 2018

Improving the quality of metal products by crushing of the microstructure of material is one of the promising areas of modern metallurgy. The basic idea consists in refinement the grain structure of the material to sizes less than a micron, i.e. the obtaining of ultrafine-grained (UFG) materials, offering higher strength properties of the material under preservation or a small loss of ductility. Stainless austenitic steel AISI 321 is widely used in all the above areas as well as in chemical, vacuum and nuclear technology. For the obtaining of UFG structure in this material the method of radial-shear rolling is used. For the purpose of identifying the influence of radial-shear rolling on microstructure and mechanical properties of stainless austenitic steel AISI-321, the experiment was conducted where at the radial-shear rolling mill SVP-08 at 800 °C in several passes of the workpieces with a diameter of 30 mm rolled till a diameter of 13 mm with following cooling in water. The analysis of the microstructure of deformed samples showed the presence of equiaxed ultrafine-grained structure in the peripheral areas of the workpiece and the presence of elongated fibrous texture in the axial zone. The strength characteristics of the workpiece has increased more than 2 times, with a slight decrease of plasticity.
EBSD study of microstructure evolution of ferritic stainless steel during cold rolling and annealing
Authors: Zhang Chi , Xu Yijie , Zhang Liwen , Gu Yinlin
Published: September 2018

The microstructure and texture of ferritic stainless steels (FSSs), formed during cold rolling and annealing processes, determine the mechanical properties of final sheet, especially the deep drawing formability. In this work, aNb, Ti stabilized17%Cr FSS was cold rolled with the reductions of 20%~70% and annealed for periods at 700°C. EBSD technique was used to characterize the microstructure evolution and inhomogeneous deformation strain distribution of the sheet during cold rolling. Partially annealed sheets were also analyzed to observe the nucleation and growth of recrystallized grains. Special attentions were paid on the crystal orientation of the deformed grains and recrystallzed grains. The results infer that in-grain shear band was formed in the cold rolled sample with the reduction higher than 30%, associated with the formation of high deformation strains. And the recrystallized grains prefer to form at some unique grain boundaries and in-grain shear bands. The orientations of recrystallized grains relates to the deformed grains.
Influence of material damage during the forming process on the vibration fatigue behaviour of a clinched connection.
Authors: Maier Bernd , Klingler Markus , Böhm Sabine , Awiszus Birgit
Published: September 2018

This paper presents the results of an analysation of forming damage during the joining process on the fatigue failure behaviour of a clinched connection. The two joining partners out of aluminium, AlMg0.7Si on the punch side and AlMg3 on the die side, are clinched with a flat clinching system and the use of a preformed hole at the die side. By the use of two different geometry variants it could be shown, in fatigue Wöhler tests, that the fatigue failure behaviour is influenced by the material damage in the deformed material of the clinch. The material damage during the clinching process could be calculated with the help of FE-Simulations. So it was possible to show that more forming damage during the joining process causes less lifetime of the connection.
Investigation of a partial, inductive short-time heat treatment of thin metal sheets integrated into the forming process
Authors: Clausius Benjamin , Maier Petra
Published: September 2018

Flanging is a widespread method in the sheet metal working industry to connect same or different materials by forming. Especially the sealing technology makes high demands on the flanging process: a low sheet thickness of the inner eyelet is necessary for proper sealing. The outer edges of the neck rings are mostly manufactured by shear cutting. The quality of the cut surface and the level of the local strain hardening influence decisively the limit of the flanging process by possible cracking. This paper is focused on the dependencies of these factors regarding thin metal sheets of different materials with a thickness down to 100 μm. It could be shown that strain hardening has a stronger effect on the process limits compared to the notch effect of the sheet edges when using standard values for the clearance of the shear cutting tool. Furthermore, a process is investigated with a partial inductive short-time heat treatment of the most deformed edge area. Due to the low thickness of the material and low heat capacities related thereto, it is possible to integrate a recrystallization annealing as single step into the forming process. As a result, the strain hardening can be removed from the affected zone directly between two forming steps to increase the process limits.
Geometrical design of micro-textured DLC coatings toward lubricant-free metal forming
Authors: Shimizu Tetsuhide , Kan Hironori , Messaoudi Hamza , Vollertsen Frank , Yang Ming
Published: September 2018

To achieve a stable and high wear resistive functional surface under dry sliding friction, the present study proposes micro-textured diamond like carbon coatings fabricated by ionized physical vapour deposition (I-PVD) using metallic masks. To clarify the optimized geometrical dimensions under dry sliding friction, geometrical conditions of textured array patterns are varied by using metallic masks with different circular hole array patterns fabricated by picosecond pulsed laser processing. The effect of texturing on friction and wear properties is evaluated by ball-on-disk type friction tests for the condition of a constant DLC-coverage per unit area. Thereby, textured DLC pattern with diameters of 50 μm, 100 μm and 150 μm are applied. Within the first 10,000 laps stable and lower coefficient of friction is obtained with the smallest diameters of 50 μm. However, at further rotation of more than 40,000 laps, the wear of the smaller diameters becomes more pronounced due to the increase of stress concentration at the edge of the structure. Based on these findings, geometrical design of micro-textured DLC coating is discussed with regard to the suppression of three-body ploughing and the prevention of stress concentration.
Lubricant-free deep drawing using CO2 and N2 as volatile media injected through laser-drilled microholes
Authors: Zahedi Ehsan , Woerz Christoph , Reichardt Gerd , Umlauf Georg , Liewald Mathias , Barz Jakob , Weber Rudolf , Graf Thomas
Published: September 2018

Most metal forming processes use lubricants based on mineral oils as an intermediate medium to reduce friction and wear. To avoid the well-known drawbacks of oil lubrication, a novel and environment friendly lubrication system for deep-drawing processes was demonstrated at the University of Stuttgart. Liquid carbon dioxide and gaseous nitrogen are being used as volatile lubrication during the deep-drawing process, locally injected at high pressure through laser-drilled microholes. This new tribological system provides a significantly enlarged working range and at least 15% larger drawing depths compared to conventional oil lubrication.
Tensile properties and drawability of thin bimetallic aluminum-scandium-zirconium / stainless steel foils and monometallic Al-Sc-Zr fabricated by magnetron sputtering
Authors: Kovac Julien , Heinrich Lukas , Koehler Bernd , Mehner Andreas , Clausen Brigitte , Zoch Hans-Werner
Published: September 2018

Al-Sc-Zr alloys are interesting for the production of high strength micro components by micro deep drawing. These alloys show a good hardenability due to the formation of nanometer-scale spheroidal Al3(Sc, Zr) precipitates, which are highly coherent with the aluminum matrix. However, the formation of these precipitates in Al-Sc-Zr foils fabricated by conventional metallurgical methods dramatically reduces their ductility and drawability. In this work, magnetron sputtering was used to produce Al-Sc-Zr foils and Al-Sc-Zr / stainless steel bimetallic foils which are nearly free of these precipitates. Tensile tests were carried out to measure and compare the mechanical properties of monometallic Al-Sc-Zr foils and bimetallic Al-Sc-Zr / stainless steel foils deposited with varying plasma target powers and containing different volume fractions (layer thickness) of Al-Sc-Zr. Micro deep drawing was used to determine the drawability of selected monometallic and bimetallic foils. The results show that the density of monometallic Al-Sc-Zr foils can be improved significantly by increasing the DC target power and by using the high power impulse magnetron sputtering (HiPIMS) technology, resulting in foils with higher ductility. Bimetallic foils achieved higher strength and ductility than monometallic Al-Sc-Zr foils. Their mechanical properties vary with the target power and the volume fraction (thickness) of Al-Sc-Zr. The limit drawing ratio of HiPIMS deposited monometallic foil was 1.7 or 1.8 depending on the side of the foil facing the die, whereas a limit drawing ratio of 1.9 was observed for bimetallic foils.
Application of Cause-Effect-Networks for the process planning in laser rod end melting
Authors: Rippel Daniel , Schattmann Christine , Jahn Mischa , Lütjen Michael , Schmidt Alfred
Published: September 2018

In micro manufacturing, a precise configuration of manufacturing processes constitutes an essential factor for success. The continuing miniaturization of work pieces results in ever decreasing tolerances, whereas machines and processes become more and more specialized. As a result, a precise determination of each process result is important to guarantee the final product quality. Unfortunately, so called size effects often prevent the direct transfer of knowledge from the area of macro manufacturing. To cope with these effects, finite element simulations provide a suitable tool to simulate forming processes and their results in advance and to perform parameter studies in order to analyze the process and effect interdependencies. Unfortunately, these simulations usually require a rather long computing time, so that only simulations for a small subset of the available parameter range can be performed in a reasonable planning interval. In this context, this article presents an application of the method “Micro – Process Planning and Analysis” (μ-ProPlAn) for the configuration of laser rod end melting, which is used to create preforms for further forming processes. This method uses cause-effect networks, to combine expert knowledge with methods from artificial intelligence to estimate the result of laser melting processes quickly. For this purpose, the cause-effect networks are trained using a finite element simulation of the laser process using different process parameters and varying rod diameters. Results show a high accuracy for the prediction of the finite element simulation results. This article focusses on the validation of these cause-effect networks in comparison to the real laser rod end melting process and demonstrates how these models can be used to predict the resulting volume, eccentricity and the largest diameter of the solidified preform for different process configurations.