bluuebunny/crossref_metadata_2025 huggingface dataset:
Impact Perforation of aluminum Cymat Foam
Authors: Elnasri Ibrahim , Zhao Han
Published: September 2018

The behavior of aluminum Cymat foam under impact perforation loading was studied using experiments and simulations. Measurements at 40 m/s were performed with an inverse perforation setup using a Split Hopkinson Pressure Bars system. Such measurement is missing in a classical free-flying penetrator–immobile–target scheme under impact loading and makes it possible to directly compare impact the perforation force–displacement curves with the static ones. Compared with quasi-static test perforation forces obtained under the same geometry and clamping system, a significantly enhanced perforation force was found under impact loading. Numerical simulations of the perforation test were developed using LS-DYNAfinite element code to provide the local information necessary to understand the unexpected enhancement in perforation force. The shock effect was found to be responsible for enhancement of the perforation force and revealed that the honeycomb model with appropriate tensile failure criteria was more suitable for model perforation of the foam than the Deshpande and Fleck model with volumetric failure strain criteria
Microspalling Process of an Explosively-Driven Metal Tin: Experiments and Numerical Simulations
Authors: Li Qingzhong , Wang Peng , Ren Guowu , Liu Wentao , Chen Yongtao
Published: September 2018

Shock-induced melting phenomenon in tin material attracts considerable attention recently. Particularly, under the strong explosively loading, the shock-induced melted tin with lower strength is the weak region where the dynamic damage and fracture commonly appear, resulting in the “micro-spallation” process. In the current work, three tin targets with different thicknesses are designed to investigate such micro-spallation phenomenon of shock-loaded pure tin. A new damage model considering the melting effect is proposed and the simulated results are compared with experimental measurements for the validation.
Predicting the high strain rate response of plasticised poly(vinyl chloride) using a fractional derivative model
Authors: Trivedi Akash , Siviour Clive
Published: September 2018

Polymers are frequently used in fields as diverse as aerospace, biomedicine, automotive and in-dustrial vibration damping, where they are often subjected to high strain rate or impact loading. Poly(vinyl chloride) (PVC), and its plasticised variants (PPVC), are just two examples of this broad category of materi-als. Since many polymers exhibit strong rate and temperature dependence, including a low temperature brittle transition, it is extremely important to understand their mechanical responses over a wide range of loading con-ditions.PVC with 60 wt% plasticiser is used in this study, as its highly rubbery nature lends itself well to being used in various load mitigation and energy absorption applications. It is challenging to obtain high strain rate data on rubbery materials using conventional techniques such as the split-Hopkinson (Kolsky) bar. Therefore, alternative approaches are required. Based on previous work developing a framework to predict high rate re-sponseusing a fractional derivative model, Dynamic Mechanical Analysis (DMA) experiments are conducted on the PPVC to construct a master curve of storage modulus. These data are used to part-calibrate a modified Mulliken-Boyce model which also takes into account specimen heating to derive stress-strain relationships at strain rates varying from 0.001 s_1 to 13 500 s_1. This model is further calibrated against experiments conducted in a previous study and shown to provide an excellent description of the behaviour at these rates.
Boundary Element Modeling of Dynamic Bending of a Circular Piezoelectric Plate
Authors: Igumnov Leonid , Markov Ivan , Konstantinov Alexandr
Published: September 2018

Accurate modelling of a coupled dynamic electro-mechanical response of circular piezoelectric plates under various loading conditions is of particular importance. Piezoelectric plates are not only basic structural elements, but with certain considerations can be conveniently fit for numerical simulation of piezoelectric sensors and transducers. In this work, a Laplace domain direct boundary element formulation is applied for dynamic analysis of three-dimensional linear piezoelectric moderately thick circular plates. Zero initial conditions, vanishing body forces and the absence of the free electrical charges are assumed. Weakly singular expressions of Laplace domain boundary integral equations for the generalized displacements are employed. Spatial discretization is based on the nodal collocation method. Mixed boundary elements are implemented. The geometry of the elements, generalized displacement and generalized tractions are represented with different shape functions: quadratic, linear and constant, accordingly. Integral expressions of the three-dimensional Laplace domain piezoelectric displacement fundamental solutions are used. After solving the problem on a set of Laplace transform parameter values, time-domain solutions are retrieved from the corresponding Laplace domain solutions by employing a numerical inversion routine. Numerical example is provided to show reliability and accuracy of the proposed boundary element formulation.
Analysis of Fracture Behaviour of Exploded Metal Cylinders with Varied Charge
Authors: Dong Xinlong , Yu Xinlu , Pan Shunjie
Published: September 2018

Explosively driven fragmentation of ductile metals cylinders is a highly complex phenomenon. In this work, the fracture characteristics of exploded TA2 titanium alloy cylinder with varied charge were investigated numerically and experimentally. The results show that the fracture surfaces of fragments lie along planes of maximum shear stress for either a higher or a lower detonation pressure, but their mechanism is different. The finite element analysis demonstrated that the equivalent plastic strain in the middle of the wall is always larger than that of inner and outer wall for metal cylinder during the stage of shock wave driven period. For the high explosive pressures, the micro-cracks originated firstly in middle zone of wall during the stage of shock wave driven, and extend to the inner and outer wall in the direction of maximum shear stress. Explosives which generate lower detonation pressures, the shear fracture of cylinder originated from the inner wall and propagate to the outer wall in an angle of 45° or 135° to radial, the crack begin at the stage of free expansion. The simulated analysis of the process of deformation and fragmentation for exploded metal cylinder agree with the experimental results.
Calibration of Johnson’s damage model by a Bayesian approach
Authors: Perrin Guillaume , Pillon Laurianne
Published: September 2018

A calibration of the Johnson’s damage model is proposed by using a Bayesian approach. A set of 3 parameters has to be adjusted. For this purpose, free surface velocities of 7 plate impact experiments leading to spallation in targets of tantalum are used. The resulting distributions of probability indicate several potential values for each parameters. Each of them used in an hydrocode leads to good agreement with reference free surface velocities.
Characterisation of the behaviour of welded aluminium structures under dynamic loading
Authors: Bornstein Huon , McDonald Brodie , Frain Emily , De Oliveira Damas Daniel , Yang Eric , Herzig Norman
Published: September 2018

The presence and quality of welds in metallic structures has the ability to influence their likelihood of failure under dynamic loading. This investigation focused on characterising the behaviour of a welded aluminium structure. Samples were taken from the parent metal, heat affected zone (HAZ) and the weld bead and high strain rate characterisation testing was performed to determine the Johnson-Cook (JC) strength and failure model parameters for each material. However, significant scatter was found in the data for the weld bead due to porosity within the samples. Additional tensile tests were performed using a rotating fly wheel machine with four larger samples, which were machined from the welded aluminium structure and contained HAZs on either side of the weld bead, located in the centre of the specimen. Three of the four samples had the weld bead ground flush to the level of the base plate. Digital image correlation was used to determine the surface strain within each region of the sample and identified significant strain localisation at the interface between the weld metal and the HAZ, as well as within the weld bead. Comparisons between the ground welded specimens and those with the weld reinforcement showed a different failure mode between the two specimens. For the ground specimens, the strain localisation in the weld bead initiated failure prior to the strain localisation occurring at the interface between the weld bead and HAZ. Sectioning of the welds indicated that the strain localisation in the weld bead may have been caused by significant levels of porosity within the weld bead. Preliminary numerical simulations of the ground specimens indicated that the force-time history could be well captured. However, as the strain localisation due to porosity is not captured using a JC model, in addition to the scatter in the characterisation data for the weld bead, failure was not accurately predicted numerically.
Development of boundary-element time-step scheme in solving 3D poroelastodynamics problems
Authors: Vorobtsov Igor , Belov Aleksandr , Petrov Andrey
Published: September 2018

The development of time-step boundary-element scheme for the three dimensional boundaryvalue problems of poroelastodynamics is presented. The poroelastic continuum is described using Biot’s mathematical model. Poroelastic material is assumed to consist of a solid phase constituting an elastic formdefining skeleton and carrying most of the loading, and two fluid phases filling the pores. Dynamic equations of the poroelastic medium are written for unknown functions of displacement of the elastic skeleton and pore pressures of the filling materials. Green’s matrices and, based on it, boundary integral equations are written in Laplace domain. Discrete analogue are obtained by applying the collocation method to a regularized boundary integral equation. Boundary element scheme is based on time-step method of numerical inversion of Laplace transform. A modification of the time-step scheme on the nodes of Runge-Kutta methods is considered. The Runge-Kutta scheme is exemplified with 2-and 3-stage Radau schemes. The results of comparing the two schemes in analyzing a numerical example are presented.
Experimental and numerical analyses of the dynamic failure processes of symmetric Taylor impact specimens
Authors: Couque Hervé
Published: September 2018

Failure processes encountered in the Taylor impact specimen are of two kinds, Mode II cracks initiating within adiabatic shear bands and tensile cracks. Because friction occurring with the single Taylor configuration influences the failure processes, it is necessary to use the symmetric loading procedure providing frictionless interfaces. Numerical simulations of the symmetric Taylor test have been conducted to reproduce the failure processes observed with a highly ductile nickel and a high strength tungsten alloy. Because the adiabatic shear failure process is occurring along a three dimension path, the 3D module of the hydrocode AUTODYN was used.
Laser-driven shock experiments to investigate mitigation ability of polymeric foams
Authors: Pradel Pierre , Malaise Frédéric , de Rességuier Thibaut
Published: September 2018

Polymeric foams are widely used in many industrial fields as thermal insulators, structural materials or shock wave mitigators. Polymeric foams would be valuable candidates to protect structures against intense mechanical stress wave loadings generated by laser irradiation or high velocity impact of very small debris. This article presents the results of laser-driven shock experiments performed on polymeric foams to investigate their mitigation ability. The targets consisted of thin aluminum front plate (250 μm-thickness), 1 mm and 2 mm-thick samples made of expanded polyurethane foam (320 kg/m3) or syntactic epoxy foam (624 kg/m3), and 12 μm-thick aluminum foil. The laser beam provided 20 J in 25 ns and was shot through water confinement of the front plate. The dynamic responses of the foams were investigated by measuring time-velocity profiles at the rear surface. Preliminary tests were performed on thin aluminum plate in order to calibrate the stress wave loadings. A dynamic explicit one-dimensional hydrocode was used to simulate the experiments and validate the calibration of pressure generated under laser irradiation. Then, the numerical simulations were used to analyze the velocity profiles recorded at the rear surface of both foams. The dynamic macroscopic response of the foams was described by a phenomenological compaction model. The model has been validated by numerical correlations with the experimental results. The input pressure (front aluminum plate) and the output one (fictitious PMMA plate placed behind foam samples) were compared by help of numerical simulations. The ratio between input and output pressures could achieve 75. Polyurethane foam better mitigated shock waves below 2 GPa, and epoxy foam was better above 2 GPa.
Structural Response and Stochastic Impact Modeling
Authors: Troian Renata , Dallali Manel , Lemosse Didier , Khalij Leila
Published: September 2018

The problem of the vulnerability of structures facing explosions came to the front line of the scientific scene in the last decades. Uncertainty of the environmental conditions and material properties have to be taken into account. The corresponding numerical models are very complex and depend on numerous parameters. Consequently, such models are cursed with issues which limit their use for real applications. Most of the existing approaches are based on a deterministic point of view, and are not able to represent the extreme sensitivity of a model towards uncertain parameters. That is why the uncertainty analysis is needed. The proposed research is devoted to the analysis of a structural behavior under an uncertain impact loading. Elasto-plastic Bernoulli beam model is used as structural model for the case simplicity, while the different formulation for impact itself are studied to simulate the wide range of possible types of impact. Model sensitivity is studied first. The influence of input parameters on structural behavior, that are the impact force, duration and position, as well as beam material are then considered. The obtained insights can provide the guidelines for modeling the structure under the explosive loading taking into account the uncertainties.
Blast loading of concrete pipes using spherical centrically placed C-4 charges
Authors: Kristoffersen Martin , Ove Hauge Knut , Valsamos Georgios , Børvik Tore
Published: September 2018

The Norwegian Public Roads Administration has initiated a large research project on a potential ferry-free coastal highway route E39 from Trondheim to Kristiansand. Parts of this route involve crossing somewide and deep fjords, where one of the suggested crossing alternatives is a Submerged Floating Tunnel (SFT)built in concrete. A major concern regarding an SFT is internal blast loading from accidents involving gas orfuel tankers, or from terrorist attacks. To assess the performance of tubular concrete structures exposed to blastloading, 1760 mm long plain concrete pipes with an internal diameter of 200 mm and pipe wall thickness of41 mm were loaded by spherical C-4 charges of various sizes up to 25 g. Pressure sensors in different directionsequidistant from the charge location recorded the blast pressure, while two high-speed cameras captured theevents. Using mass produced commercial off-the-shelf pipes ensures consistent geometry and material proper-ties. A wooden pallet was used as support for the pipes, and an electrically initiated blasting cap was used todetonate the C-4. A charge size of at least 13 g C-4 was needed to breach the pipe wall. Larger charge sizescaused longitudinal cracks and broke the pipe into oblong pieces. The test results were used for comparisonwith simulations using the explicit finite element solver EUROPLEXUS, intended for fast transient dynam-ics involving fluid-structure interaction. Both purely Lagrangian simulations and fully coupled fluid-structureinteraction simulations were carried out. While the former method is more efficient computationally, the lat-ter approach accounts for reflections and the confinement of the pipe. It can be difficult to predict the exactcharge size where through-thickness cracking occurs, but the qualitative results were encouraging for furtherwork. When accurate simulations of the experiments are obtained, the simulations will be extended to a fullcross-section of a submerged floating tunnel.
Numerical Simulations of Laser-Driven Cratering Experiments into Porous Graphite
Authors: Aubert Bertrand , Hebert David , Rullier Jean-Luc , Chevalier Jean-Marc , Berthe Laurent , Brambrink Erik , Lescoute Emilien , Videau Laurent , Franzkowiak Jean-Eloi , Jodar Benjamin , Loison Didier , Nivard Mariette
Published: September 2018

We present the results of an experimental campaign conducted on the LULI2000 laser facility. Semi-infinite targets of a commercial grade of porous graphite were submitted to high-power laser irradiation inorder to generate craters. A 15 ns pulse duration was used along with a focal spot diameter of 900 µm to deliver energies up to 750 J. Numerical simulations of these shots have been performed following a specificmethodology which can be divided in three steps. Firstly, the mechanical loading induced by the laser iscalibrated by simulating the same shot on a thin aluminum target of which free surface velocity is measured byPDV and line-VISAR. Secondly, the same shot is performed on a thin graphite target to validate the materialmodel of graphite. Thirdly, the craterization shot on semi-infinite target is simulated. Numerical results arecompared to experimental measurements of craters obtained using an interferometric profilometer.
Variations in Hardness with Position In One Dimensionally Recovered Shock Loaded Metals
Authors: Whiteman G. , Higgins D.L. , Pang B. , Millett J.C.F. , Chiu Y-L. , Jones I.P.
Published: September 2018

The microstructural and mechanical response of materials to shock loading is of the utmost importance in the development of constitutive models for high strain-rate applications. However, unlike a purely mechanical response, to ensure that the microstructure has been generated under conditions of pure one dimensional strain, the target assembly requires both a complex array of momentum traps to prevent lateral releases entering the specimen location from the edges and spall plates to prevent tensile interactions (spall) affecting the microstructure. In this paper, we examine these effects by performing microhardness profiles of shock loaded copper and tantalum samples. In general, variations in hardness both parallel and perpendicular to the shock direction were small indicating successful momentum trapping. Variations in hardness at different locations relative to the impact face are discussed in terms of the initial degree of cold work and the ability to generate and move dislocations in the samples.
Rate-dependent ductile fracture under plane strain tension: experiments and simulations
Authors: Grolleau Vincent , Lafilé Vincent , Roth Christian C. , Galpin Bertrand , Mahéo Laurent , Mohr Dirk
Published: September 2018

Among all other stress states achievable under plane stress conditions, the lowest ductility is consistently observed for plane strain tension. For static loading conditions, V-bending of small sheet coupons is the most reliable way of characterising the strain to fracture for plane strain tension. Different from conventional notched tension specimens, necking is suppressed during V-bending which results in a remarkably constant stress state all the way until fracture initiation. The present DYMAT talk is concerned with the extension of the V-bending technique from low to high strain rate experiments. A new technique is designed with the help of finite element simulations. It makes use of modified Nakazima specimens that are subjected to V-bending. Irrespective of the loading velocity, plane strain tension conditions are maintained throughout the entire loading history up to fracture initiation. Experiments are performed on specimens extracted from aluminum 2024-T3 and dual phase DP450 steel sheets. The experimental program includes quasi static loading conditions which are achieved on a universal testing machine. In addition, high strain rate experiments are performed using a specially-designed drop tower system. In all experiments, images are acquired with two cameras to determine the surface strain history through stereo Digital Image Correlation (DIC). The experimental observations are discussed in detail and also compared with the numerical simulations to validate the proposed experimental technique
Experimental Technique for Dynamic Fragmentation of Liquid-Driving Expanding Ring
Authors: Zhang Jia , Zheng Yuxuan , Zhou Fenghua , Liu Jun
Published: September 2018

Expanding ring experiment is an important method for dynamic fragmentation of solid under 1D tensile loading. Based on the split Hokinson pressure bar (SHPB), a liquid-driving experimental technology was developed for conducting expanding ring tests. The loading fixture includes a hydraulic cylinder filled with water, which is pushed by a piston connected to the input bar. As the water is driven, it expands the metallic ring specimen in the radial direction. The approximately incompressible property of the water makes it possible to drive the specimen in very high radial velocity by low velocity movement of piston, according to the large sectional area ratio of the cylinder to specimen. Using liquid-driving expanding ring device, 1060 aluminum rings (ductile materials)/PMMA rings (brittle materials) were fragmented and the fragments were recovered. Impact deformation of free-flying fragments was avoided through the use of “sample soft-capture” technology. The fragmentation process was observable by high speed camera through modifying the driving direction of the water. From the observations of the fracture morphology and the residual internal cracks of the recovered fragments, it is concluded that the fracture of the rings is caused by the circumferential tensile stress.
Experimental study of the dynamic behaviour of High Performance Concrete (HPC) under tensile loading
Authors: Lukić Bratislav , Saletti Dominique , Forquin Pascal
Published: September 2018

This paper presents the measurement results of the dynamic tensile strength of a High Performance Concrete (HPC) obtained using full-field identification method. An ultra-high speed imaging system and the virtual fields method were used to obtain this information. Furthermore the measurement results were compared with the local point-wise measurement to validate the data pressing. The obtained spall strength was found to be consistently 20% lower than the one obtained when the Novikov formula is used.
Effect of Strain Rate on Compressive Behaviour of Silicone Rubber
Authors: Tateyama Kohei , Yamada Hiroyuki , Ogasawara Nagahisa
Published: September 2018

The purpose of this study is to evaluate the effect of strain rate on compressive behaviour of silicone rubber. The silicone rubber which was used as biomimetic material was prepared as a specimen. The shape of specimen was cubic and each side length was 10 mm. In this study, a dynamic compressive test was performed using a drop-weight testing machine at the strain rate of approximately 101 s-1, which can be detect the compressive stress for a long time without any disturbance. For comparison, a quasi-static compressive test was performed using the universal testing machine at the strain rate of 10-4 to 10-1 s-1. In the deformation process of the silicone rubber, the flow stress did not increase at the early stage of deformation. When the strain reached 0.6, the flow stress was increased with increasing strain. This deformation process was considered to be due to rubber elasticity. It was confirmed that the silicone rubber showed an increase of the flow stress with increasing strain rate, which showed general behaviour of soft materials such as rubber. In the silicone rubber, the flow stress with respect to the strain rate could be simply expressed with the Cowper-Symonds constitutive equation.
Dynamic properties of reactor steels Kh16N15M3T1 and Kh13V2 under shock-wave loading of submicrosecond scale
Authors: Mokrushin Sergey S. , Mayorova Anna S. , Malyugina Svetlana N. , Pavlenko Alexander V. , Sagaradze Victor V. , Kataeva Natalya V. , Volkova Elena G.
Published: September 2018

Kh16N15M3T1 and Kh13V2 reactor steels were investigated. The study was carried out using a light-gas gun with the deformation velocities ranging from 4·104 to 3·106 s-1 and shock-loading pulses in 0.05-1 μs duration range. Dependences of the spallation strength and dynamic elastic limit in a wide temperature range are obtained. The recovered specimens were used to carry out the metallography analysis.
Static and dynamic behaviour of ECAPed copper alloy
Authors: Lee Yerim , Lee Keunho , Woo Sanghyun , Lee Changsoo , Park Leeju
Published: September 2018

The equal channel angular processing (ECAP) is a severe plastic deformation technique which can produce ultrafine-grained (UFG) alloy. This paper investigate the static and dynamic behaviour of ECAPed OFHC-Cu to evaluate possibility of its application to defence industries. Tensile tests were carried out at two different strain rate (10-3/s, 1/s) using digital image correlation (DIC) technique. High strain rate experiments were conducted using the split Hopkinson pressure bar (SHPB). The results were compared with forged OFHC-Cu and additional heat treated OFHC-Cu after processed by ECAP. Flow stress and strain sensitivity of ECAPed OFHC-Copper were increased compare to forged OFHC-Copper. After ECAPed copper heat treatment, the yield strength decreased with increasing of the average grain size. And numerical simulation of ECAPed copper shaped charge was performed using Autodyn hydrodynamic code.
A novel method for severe plastic deformation at high strain rate
Authors: Lanjewar Harishchandra , Kestens Leo , Verleysen Patricia
Published: September 2018

Severe plastic deformation (SPD) processing is defined as any method of forming under an extensive hydrostatic pressure that may be used to impart a very high strain to a bulk solid without any significant change in dimensions of the sample, producing exceptional grain refinement. Most of the SPD techniques employ very low processing speeds, however increased deformation rates are known to have a significant effect on the final microstructure. Most of the SPD processes operating at high rates do not impose hydrostatic pressures to the material and can therefore only be used for very ductile materials, while in others, the microstructural changes are limited to the surface layers of the material. To circumvent these restrictions a novel facility has been designed and developed where high hydrostatic pressures are maintained while a high shear deformation is imposed at high strain rates. The device combines the features of a high pressure torsion (HPT) unit with the principle of a torsional split Hopkinson bar (SHB) setup. A small ring-like sample, placed between two molds, is first subjected to a high, static pressure and subsequently to a high speed shear deformation upon release of torsional energy stored in a long bar. Although, the principle is rather straightforward, the design of the setup was extremely critical because of the high forces and energies involved. Tests have been performed on commercially pure aluminum. The material hardness increased in accordance with the microstructure and processing conditions; viz. annealed, only compressed and applied shear strain. Deformed grains departed from equiaxed shape and showed morphological texture in the direction of the shear even at very low strains indicating the presence of shear strains in the material. Further the material, or more specifically its mechanical properties and microstructure evolution is compared with conventional, statically deformed HPT samples.
Mechanical properties of high-density TRIP steel honeycomb structures with varying cell profiles under different loading conditions
Authors: Baumgart Christine , Weigelt Christian , Aneziris Christos G. , Krüger Lutz
Published: September 2018

As the mechanical properties of honeycomb structures are influenced by several parameters, detailed analysis is necessary before their potential application in transportation industry components. Previous Finite Element Model (FEM)-based numerical analysis demonstrated that variation in cell geometry affects the achievable strength level and, thus, the energy absorption capability. According to this FEM study, the Kagome geometry – an ordered sequence of hexagons and triangles – exhibits properties that are particularly promising when compared to the square-celled structures investigated to date. When the load is applied parallel to the channel axis (the out-of-plane direction), the increment of strength is comparatively low, whereas in the in-plane direction (loading orthogonal to the channel axis), the dissipated specific energy can reach almost double that of the square-celled structure. In this study, the results of static and dynamic compression tests – performed in the out-of-plane and in-plane modes – are presented to examine the influence of strain rate and loading direction on the characteristic deformation stages of squarecelled and Kagome structures. Particular attention is paid to deformation induced martensite formation in the cell wall material, indicating the TRansformation Induced Plasticity (TRIP) effect as a function of applied cell geometry, strain rate and loading direction.
Analysis of Dynamic Plastic Deformation process on an Electrolytic Tough - Pitch copper (Cu-ETP): From material characterization to models improvement
Authors: Mespoulet Jérôme , Beucia Bermane , Tingaud David , Hereil Pierre-Louis , Couque Hervé , Dirras Guy
Published: September 2018

This paper presents a comprehensive study of a direct impact compression loading on an Electrolytic Tough-Pitch copper (Cu-ETP). The aim of the study is to provide reliable experimental data in this dynamic loading using high-speed video camera records and real time projectile deceleration profiles. Test set-up has been optimized to ensure an efficient recovery of the samples after the Dynamic Plastic Deformation (DPD) process in the 103 to 104 s-1 strain rate range regime. Structural investigations have been made on post-mortem samples: microstructure investigations of recovered samples have shown more structural changes in terms of crystallographic texture and grain sizes. Post-mortem tensile tests have also been carried out to evaluate yield strength behavior of the Cu-ETP copper after the DPD process. Numerical simulations have been performed to evaluate the ability of empirical models to reproduce recorded signals. In-situ results (time evolution of strain, strain rate, temperature, etc.) given by the numerical analysis have contributed to enrich the post-mortem analysis.
Shear localization of fcc high-entropy alloys
Authors: Meyers Marc A. , Li Zezhou , Zhao Shiteng , Wang Bingfeng , Liu Yong , Liaw Peter K.
Published: September 2018

Dynamic behavior of the single phase (fcc) Al0.3CoCrFeNi and CoCrFeMnNi high-entropy alloys (HEAs) was examined. The combination of multiple strengthening mechanisms such as solid solution hardening, cutting forest dislocation, as well as mechanical nano-twinning leads to a high work-hardening rate, compared with conventional alloys. The resistance to shear localization was studied by dynamicallyloading hat-shaped specimens to induce forced shear localization. However, no adiabatic shear band could be observed for Al0.3CoCrFeNi HEA at a large shear strain ~1.1. Additionally, shear localization of the CoCrFeMnNi HEA was only found at an even larger shear strain ~7 under dynamic compression. It is therefore proposed that the combination of the excellent strain-hardening ability and modest thermal softening of these two kinds of high-entropy alloys gives rise to remarkable resistance to shear localization, which makes HEAs excellent candidates for impact resistance applications.
Study on the dynamic properties of AM-SLM AlSi10Mg alloy using the Split Hopkinson Pressure Bar (SHPB) technique
Authors: Nurel Bar , Nahmany Moshe , Stern Adin , Frage Nahum , Sadot Oren
Published: September 2018

Additive manufacturing by Selective Laser Melting of metals is attracting substantial attention, due to its advantages, such as short-time production of customized structures. This technique is useful for building complex components using a metallic pre-alloyed powder. One of the most used materials in AMSLM is AlSi10Mg powder. Additively manufactured AlSi10Mg may be used as a structural material and it static mechanical properties were widely investigated. Properties in the strain rates of 5×102–1.6×103 s-1 and at higher strain rates of 5×103 –105 s-1 have been also reported. The aim of this study is investigation of dynamic properties in the 7×102–8×103 s-1 strain rate range, using the split Hopkinson pressure bar technique. It was found that the dynamic properties at strain-rates of 1×103–3×103 s-1 depend on a build direction and affected by heat treatment. At higher and lower strain-rates the effect of build direction is limited. The anisotropic nature of the material was determined by the ellipticity of samples after the SHPB test. No strain rate sensitivity was observed.
Paradiplozoon yunnanensis n. sp. (Monogenea, Diplozoidae) from Sikukia gudgeri (Cyprinidae, Barbinae) in southwest China
Authors: Fan Li-xian , Meng Fei-yan , Bai Jun-ping , Xu Wei-jiang , Wang Xu
Published: September 2018

Paradiplozoon yunnanensis n. sp. (Monogenea, Diplozoidae) is described from the gills of Sikukia gudgeri Smith, 1931 (Cyprinidae) collected from Jinghong Basin, a tributary of the international Lancang-Mekong River. This is the first diplozoid species from S. gudgeri and its description increases the number of Paradiplozoon species recorded in China to 25. The new species is distinguished from congeners by a combination of morphological and molecular features. The anterior end of the median plate is thickened in the marginal area and a narrow rectangular trapeze spur connects to the anterior jaw through two separate anterior joining sclerites. The posterior end of the median plate sclerite is invaginated with a smooth strip-shaped posterior joining sclerite. Comparison of a newly obtained sequence of rRNA ITS2 with 18 other congeneric sequences from GenBank provides support for separation of the new species.
Sequential management of tibial fractures using a temporary unicortical external fixator
Authors: Russo Anne-Pauline , Caubere Alexandre , Ghabi Ammar , Grosset Antoine , Mangin Philippe , Rigal Sylvain , Mathieu Laurent
Published: September 2018

Introduction: The development of damage control orthopedics (DCO) procedures has led to the development of temporary unicortical external fixators (TUEFs) intended to limit deep infectious complications and facilitate early conversion to internal fixation.

Methods: A retrospective study was conducted in two French military trauma centers, including on patients being treated for tibial fractures with a TUEF (UNYCO® − Orthofix®) followed by an early conversion to intramedullary nailing.

Results: Eleven patients with an average age of 41 were included between September 2015 and June 2017. A total of 12 TUEFs were implanted for one closed fracture and 11 open fractures, including one type I, eight types II, and two Gustilo types IIIB. The indication of DCO was related to hemodynamic instability in three cases, to the severity of soft tissue lesions in eight cases, and to the context of treatment in one case. The conversion to IM nailing was made after an average of 7.6 days. No significant loss of reduction was observed until internal osteosynthesis, which was performed with “fixator in place” in ten cases. The coverage of Gustilo type III injuries was performed by free flap transfers at the same time as IM nailing. All the patients were reviewed with an average follow-up of 16.5 months. Bone union was achieved in all cases. Two IM nailing dynamizations were carried out, but no bone grafting was required. Two cases of pandiaphysitis were observed and treated without functional complications.

Discussion: Despite a limited number of patients, this study demonstrates the reliability of the TUEF to maintain the reduction of tibial fractures and facilitate early conversion to IM nailing. Unicortical fixation does not prevent septic complications related to the severity of soft tissue injuries.
Administration klinischer Studien in der Nuklearmedizin
Authors: Zippel Claus , Giesel Frederik , Kopka Klaus , Reil-Held Anette
Published: September 2018

Um innovative PSMA-Tracer zur Krebsdiagnostik und -therapie in der klinischen Versorgung etablieren zu können, werden in der nuklearmedizinischen Forschung und Entwicklung zunehmend prospektiv-klinische (Multicenter-)Studien initiiert. Neben medizinisch-pharmazeutischen und regulatorisch-rechtlichen Vorgaben sind dabei verstärkt administrativ-koordinierende Aspekte zu beachten. In diesem Artikel beleuchten wir am Beispiel des DKTK-PSMA-Multicenter-Trials „[68Ga]Ga-PSMA-11 in high-risk Prostate Cancer“, 1. welche administrativen Abteilungen bei nuklearmedizinischen (Forschungs-)Studien grundsätzlich zu involvieren sind, 2. warum es dafür eines administrativen Projektmanagements bedarf und welche Werkzeuge Studienleiter und Koordinatoren hierfür nutzen können sowie 3. welche Vorteile die organisationale Struktur und Plattform des Deutschen Konsortiums für Translationale Krebsforschung (DKTK) für die Initiierung und Durchführung künftig weiterer (multizentrisch-)klinischer Studien in der Nuklearmedizin bietet.
Kolumne – Auf der sicheren Seite
Authors: Schiewack Michael
Published: September 2018

Für viele ist die neue Datenschutzgrundverordnung –kurz DSGVO – schon jetzt das Unwort des Jahres. Michael Schiewack tickt da ein wenig anders. Er widmet sich der Neuerung mit voller Hingabe.
Aerobic Variables for Prediction of Alpine Skiing Performance – A Novel Approach
Authors: Nilsson Robert , Lindberg Ann-Sofie , Theos Apostolos , Ferguson Richard , Malm Christer
Published: September 2018

The aim of this study was to investigate the predictive power of aerobic test results and anthropometric variables on FIS-ranking of junior elite alpine skiers. Results from twenty-three male and female adolescent elite alpine skiers from two seasons were included in the multivariate statistical models. Physical work capacity was determined by V̇O2peak, blood lactate concentration ([HLa]b), and heart rate (HR) during ergometer cycling. Anthropometric variables were body stature, body weight and calculated BMI. No significant correlation between competitive performance and aerobic work capacity or anthropometric data was observed neither in male nor female adolescent skiers. Pre-season physical tests and anthropometric data could therefore not predict end-season FIS-ranking. The best regression (R2) and prediction (Q2) models of FIS slalom (SL) and giant slalom (GS) rank reached R2=0.51 to 0.86, Q2=−0.73 to 0.18, indicating no valid models. This study could not establish V̇O2peak and other included variables as predictors of competitive performance. When combining results from commonly used tests for alpine skiers, and applying multivariate statistical models, investigated tests seems of limited used for athletes, coaches, and ski federations. Performance-specific pre-season tests must be developed and validated for prediction of performance and guidance of exercise training.
Lysimachia Capillipes Inhibit Adipogenesis via Angiogenesis Inhibition
Authors: Li Xiumin , Xue Yu , Pang Liang , ShangGuan Zhaoshui , Pan Yutian
Published: September 2018

Obesity is a common and increasingly prevalent human condition due to unhealthy diet and less-exercise lifestyle. Development of obesity is associated with substantial modulation of adipose tissue structure. The expansion of adipose tissue is linked to the development of its vasculature, and modulation of angiogenesis may have the potential to impair adipose tissue development. In this study, we used obesity model of zebrafish fed by egg yolk to investigate the effect of Lysimachia capillipes on the obesity. The results showed that Lysimachia capillipes inhibited angiogenesis of adipose tissue in transgenic zebrafish Tg (Fli 1: EGFP), which was similar to surppressing effect of TNP-470, which was accompanied by decreased Oil Red O staining of the zebrafish. The treatment of Lysimachia capillipes reduced expression of MTP significantly, but modestly reduced expression of Ppar g, FABP10a, and CD36 level through ISH, which was accordant with the results by PCR analysis. The study proved that Lysimachia capillipes might possess novel therapeutic properties for prevention and treatment of obesity.
The Association between Genetic Polymorphisms and Simvastatin-Induced Myopathy: A Narrative Synthesis of Evidence
Authors: Li Xingang , Sun Shusen , Xu Xiaowei , Zhao Zhigang , Li Wei
Published: September 2018

Background and study aim Genetic polymorphisms may play a role in muscular injury associated with simvastatin, but results were inconclusive. This study aimed to summarize evidence from the literature investigating the effects of genetic polymorphism on simvastatin-induced myopathy.

Methods Studies regarding the association between genetic polymorphisms and simvastatin-induced myopathy were retrieved through electronic databases from February 1, 1990 to March 15, 2018. Two authors independently extracted data, including PMID, author, publication year, country, race, age, population characteristics, drugs, definition of case and control, gene, allele, SNP position, Hardy-Weinberg equilibrium, number of genotypes (case and control), minor allele frequency of cases and controls, association, study type and the Newcastle-Ottawa scale. Due to high heterogeneity in study design and outcome measurements among the included articles, a narrative synthesis of the evidence was conducted.

Results A total of 10 association studies were identified in this study, including SLCO1B1, ABCB1, GATM, HTR3B, HTR7, RYR2 and HLA-DRB1. The evidence linking myopathy to rs4149056 in SLCO1B1 is of high quality, and this association has been reproduced in randomized trials and clinical practice-based cohorts. As for other candidate genetic markers, the evidences are limited or controversial, and additional well-designed studies with larger sample sizes, are required to further elucidate this association.

Conclusion SLCO1B1 genotype is a useful biomarker for predicting an increased risk of simvastatin-induced myopathy.
Determination of Tofacitinib in Mice Whole Blood on Dried Blood Spots Using LC–ESI–MS/MS: Application to Pharmacokinetic Study in Mice
Authors: Dixit Abhishek , Mallurwar Sadanand Rangnathrao , Sulochana Suresh P , Zainuddin Mohd , Mullangi Ramesh
Published: September 2018

A simple, sensitive and rapid assay method has been developed and validated as per regulatory guideline for the estimation of tofacitinib on mice dried blood spots (DBS) using liquid chromatography coupled to tandem mass spectrometry with electro spray ionization in the positive-ion mode. The method employs liquid extraction of tofacitinib from DBS disk of mice whole blood followed by chromatographic separation using 5 mM ammonium acetate (pH 6.5):acetonitrile (20:80, v/v) at a flow rate of 0.60 mL/min on an X-Terra Phenyl column with a total run time 2.5 min. The MS/MS ion transitions monitored were m/z 313→149 for tofacitinib and m/z 316→149 for the internal standard (13C3,
15N-tofacitinib). The assay was linear in the range of 0.99–1980 ng/mL. The intra- and inter-day precision was in the range of 1.17–10.3 and 3.37–10.9%, respectively. Stability studies showed that tofacitinib was stable on DBS cards for one month. This novel method has been applied to analyze the DBS samples of tofacitinib obtained from a pharmacokinetic study in mice.
Anterior Cruciate Ligament Reconstruction Using Bone-Patellar Tendon-Bone Autograft with Remnant Preservation: Comparison of Outcomes According to the Amount of Remnant Tissue
Authors: Kim Sung-Jae , Choi Chong Hyuk , Chun Yong-Min , Kim Sung-Hwan , Lee Su-Keon , Jung Woo Seok , Jung Min
Published: September 2018

There has been controversy about whether remnant tissue of anterior cruciate ligament (ACL) has to be preserved in ACL reconstruction. The purpose of the study was to compare clinical outcomes between groups of patients who underwent ACL reconstruction with bone-patellar tendon-bone (BPTB) autograft divided according to amount of ACL remnant and investigate effect of remnant preservation on outcomes of ACL reconstruction. A total of 185 patients who underwent ACL reconstruction with BPTB autograft were retrospectively reviewed. Patients were divided into four groups according to proportion of length of remnant tissue of injured ACL covering part of reconstructed ACL to total length of reconstructed ACL: group A included 83 patients with no remnant, group B consisted of 38 patients with remnant of < 1/3, group C consisted of 35 patients with remnant of 1/3 to2/3, and group D consisted of 29 patients with remnant of > 2/3. Primary outcome was International Knee Documentation Committee (IKDC) subjective score. Secondary outcomes were stability, range of motion, patient-reported outcomes determined by Lysholm knee scoring scale and Tegner activity scale, IKDC objective grade, and single hop for distance. Return to activity and near-return to activity were investigated. A minimum follow-up duration was 24 months. There was no statistically significant difference between four groups regarding postoperative anterior translation (p = 0.731), Lysholm knee score (p = 0.599), IKDC objective grade (p > 0.999), hop test (p = 0.878), and near-return to activity (p = 0.193). However, patients of group D had significantly better outcomes in IKDC subjective score (group A = 85.0 ± 5.9, group B = 84.9 ± 8.1, group C = 87.4 ± 6.4, group D = 89.2 ± 8.1, p = 0.017), Tegner activity scale (group A = 5.0 ± 1.1, group B = 5.2 ± 1.0, group C = 5.7 ± 1.3, group D = 5.9 ± 1.0, p = 0.001), and return to activity (group A = 25.3%, group B = 31.6%, group C = 45.7%, group D = 55.2%, p = 0.014). ACL reconstruction using BPTB autograft with remnant preservation did not provide better anterior stability compared with conventional ACL reconstruction. However, preservation of remnant of > 2/3 led to more improved activity-related clinical outcomes than no remnant preservation. In cases with substantial remnant tissue of injured ACL remaining, reconstruction of ACL while preserving as much remnant tissue as possible is recommended. This is a Level III, retrospective comparative therapeutic study.