bluuebunny/crossref_metadata_2025 huggingface dataset:
The mechanical behaviours of the Ti-10V-2Fe-3Al alloy under the high-temperature and dynamic loading conditions
Authors: Li Lintao , Zhang Xiaoying , Li Zhiqiang , Wang Zhihua , Ma Wei
Published: September 2018

In this work, we develop a high-temperature dynamic testing technology for characterizing the properties of Ti-1023 alloy. The modified Hopkinson torsion bar system includes a high-temperature furnace subsystem and a water cooling subsystem. High-temperature dynamic tests of the alloy are performed. The dependence of the yield stress on the temperature and the shear strain rate is studied. The scanning electron microscopy observations show that the microstructural evolution makes up of two steps: the first one is caused by thermal loading and the second one by the mechanical loading. The high-temperature dynamic constitutive model is established based on the experimental results.
Experimental study of the mechanical strength and the failure of multi-sheet, multi-material spot-welded assemblies under pure and combined loading conditions
Authors: Chtourou Rim , Chaari Fahmi , Haugou Gregory , Leconte Nicolas , Markiewicz Eric , Zouari Bassem
Published: September 2018

Resistance Spot Welding (RSW) is widely used in the automotive industry thanks to its production convenience and cost effectiveness. Around four thousands spot welds are indeed employed to assemble the body-in-white. RSW of multiple sheets and combining multiple materials are increasingly realized. The Ultra-High-Strength Steels (UHSS) are particularly well suited for the entire range of structural parts requiring good crash resistance. However, the mechanical strength and the rupture of such new generation of RSW under multi-axial loadings is not yet well studied. The present work investigates the mechanical strength and the failure of a three-sheet spot welded assembly composed of two sheets of UHSS 22MnB5 and a third sheet of mild steel DX54D. An advanced experimental procedure is proposed for testing this assembly in pure and combined (tensile shear modes) modes I/II. Two types of specimen with different sheet thicknesses have been studied. The obtained results are analyzed to investigate the loading angle effect and the assembly configuration effect on the mechanical strength. Failure modes are also studied in relation with the increasing of the loading angle. Finally, the parameters of a macroscopic force-based failure criterion dedicated for FE crash modeling are identified.
Dynamic Tensile Behaviour of Strain-Hardening Cement-Based Composites (SHCC)
Authors: Curosu Iurie , Mechtcherine Viktor , Forni Daniele , Cadoni Ezio
Published: September 2018

The paper presents a part of an experimental campaign consisting of quasi-static and impact tensile experiments on three different types of strain-hardening cement-based composites (SHCC) as well as on their constitutive cementitious matrices [1]. The investigation on different SHCC types was intended for analysing the effect of matrix composition and fibre type on the strain rate sensitivity of the composites and for enabling the formulation of material design recommendations for impact resistant SHCC. The dynamic tests were carried out by means of a Modified Hopkinson Bar (MHB) installed in the DynaMat Laboratory in Lugano, Switzerland, which enabled the characterization of the dynamic material behaviour under direct tensile loading in terms of force-displacement relationships.
High Strain Rate Compaction of Porous Materials – Experiments and Modelling
Authors: Cotton Matthew , Maw John
Published: September 2018

Porosity can be found in many forms in common materials, either naturally occurring such as wood, or introduced by a manufacturing process. Applications for such materials include impact protection and energy absorption, which require a good understanding of their response to rapid loading. In order to increase confidence in simulations of porous materials under different loading conditions it is important to validate models with experimental data. To support this requirement experiments have been conducted to investigate the compaction behaviour of porous copper samples in the high strain rate regime. Gas gun plate impact trials with impact velocities in the range 100-300 m/s were used to achieve the conditions of interest. Simulations of the experiments were conducted with a focus on accurately modelling the material response in the region prior to complete compaction. This work will report on the experimental technique and the modelling approach employed to achieve good agreement with the data.
Experimental characterization of dynamic deformation behaviour for SCM440 steel at high strain rates
Authors: Lee Keunho , Lee Yerim , Woo Sanghyun , Lee Changsoo , Park Leeju
Published: September 2018

The dynamic deformation behaviours of SCM 440 steel were characterized at the strain rates from 10-3 s-1 to 106 s-1. The uniaxial tensile tests at different temperature of 25 °C, 350 °C, and 700 °C were performed by a hydraulic universal testing machine equipped with a heating stage, and the compressive tests were conducted by using a spilt Hopkinson pressure bar (SHPB) at room temperature. Material coefficients of the Johnson-Cook constitutive model considering temperature effects were obtained based on the stressstrain relations from the experimental tests. In addition, Taylor impact tests on the SCM 440 steel were carried out to evaluate the accuracy of the determined material coefficients and characterize the dynamic behavior at the ultra-high strain rates and high temperature, by comparison with numerical simulations.
Low energy shock response of a melt cast simulant material
Authors: Drouet David , Bailly Patrice , Pavier Julien , Eches Nicolas , Hanus Jean-Luc
Published: September 2018

To manufacture its insensitive munitions (MURAT MUnitions à Risque ATténué), NEXTER Munitions uses a melt cast explosives as an EIDS (Extremely Insensitive Detonating Substance). Unlike commonly used and well-documented EIDSs such as PBX, melt cast have a high volumetric matrix percentage. Moreover, in its life cycle, the ammunition can undergo severe loads, such as cannon firing, accidental shocks and terminal ballistics events. The objective of this paper is therefore to analyse, how these dynamic loads induce changes in the material (damage, cracking, de-cohesion), and then, to evaluate how these alterations influence the pyrotechnic properties of the melt cast explosive. To address the first point, we delimited the scope of the study in pressure and strain rate ranges which corresponds to the context of the ammunition. To safely explore this area, we have created an inert material that is morphologically and mechanically representative of the melt case explosive. It is used to setup and validate the experimental technic that will be applied to damage the melt cast explosive in the future. In this article the mechanical behaviour of the inert material is investigated under simple compression and passive confinement. This was done under the quasi-static and dynamic regimes thanks to a compression press and a Split Hopkinson Pressure Bars setup. Firstly, the results obtained show the emergence of a damage which increases with the loss of cohesion of the material during the test. This seems to be related to the extension strain. Then, for all tests, a strain rate dependent mechanical response is observed. Finally, the end of the test shows the material behaviour without cohesion. Then, a rate dependent ultimate shear criterion is deduced. To complete the interpretation these results, a model is proposed. It intends to be simple as it tries to describe the whole degradation of the material with a unique scalar parameter.
Challenges related to testing of composite materials at high strain rates using the split Hopkinson bar technique
Authors: Elmahdy Ahmed , Verleysen Patricia
Published: September 2018

The design of sample geometries and the measurement of small strains are considered the main challenges when testing composite materials at high strain rates using the split Hopkinson bar technique. The aim of this paper is to assess two types of tensile sample geometries, namely dog-bone and straight strip, in order to study the tensile behaviour of basalt fibre reinforced composites at high strain rates using the split Hopkinson bar technique. 2D Digital image correlation technique was used to study the distribution of the strain fields within the gauge section at quasi-static and dynamic strain rates. Results showed that for the current experiments and the proposed clamping techniques, both sample geometries fulfilled the requirements of a valid split Hopkinson test, and achieved uniform strain fields within the gauge section. However, classical Hopkinson analysis tends to overestimate the actual strains in the gauge section for both geometries. It is, therefore, important to use a local deformation measurement when using these 2 geometries with the proposed clamping technique.
High rate loading of hybrid joints in a Split Hopkinson Tension Bar
Authors: Ledford Noah , Paul Hanna , Isakov Matti , Hiermaier Stefan
Published: September 2018

Bonded joints are nowadays seen as one of the preferred joining methods in aerospace applications. However, the difficulty in certifying bond strength and the relatively low energy absorption capability of the joint are barriers to widespread adoption. The use of a hybrid joint, that is, the combination of a mechanical and a bonded joint, allows for a fail-safe design and offers improved performance of the joint. The quasi-static properties of hybrid joints have been investigated by a number of researchers. In contrast, the high rate loading regime has been only sparsely investigated. In this work, hybrid joints are tested in quasi-static and high rate loading in order to analyze their loading rate dependence. The hybrid joint studied is a composite-aluminum double lap shear joint with Sikaforce 7752 adhesive and Hi-Lite-315 countersunk titanium bolts. In order to quantitatively analyze the high rate behavior of the hybrid joints and their respective sub-components, additional tests are carried out on simply bonded and simply bolted specimens. The high rate characterization was performed with a Split Hopkinson Tension Bar. The main challenges for these tests are the relatively large specimen size and complex specimen geometry needed to properly characterize the joint behavior, which both are in contradiction with the assumptions of the classical Split Hopkinson Bar-analysis. In this paper we describe an approach to solve these challenges based on an elastic wave analysis of the system.
Comparison of Stress-induced Martensitic Transformation Under Tension and Compression in Fe-28Mn-6Si-Cr Shape Memory Alloy
Authors: Cao Bo , Iwamoto Takeshi
Published: September 2018

In the case of the NiTi alloy, some research works reported that the stress-strain curve differs significantly between tension and compression. It is considered that the difference in stress-induced martensitic transformation behavior may be observed under different loading modes in Fe-based shape memory alloy (Fe-SMA), which is less expensive compared with the widely-used NiTi alloy. In this study, both tensile and compressive tests of Fe-28Mn-6Si-5Cr shape memory alloy, which is one of Fe-SMA, are conducted under quasi-static and impact deformation at various strain rates. During deformation, it is attempted to evaluate the stress-induced martensitic transformation by measuring the volume resistivity as well as temperature for increasing a reliability of the alloy. Furthermore, from the results of volume resistivity at each strain rate, the strain rate sensitivity of stress-induced martensite under tensile and compressive tests is investigated. Additionally, the difference in stress-induced martensitic transformation under tension and compression is studied.
Dynamic behaviour of Al-Mg aluminum alloy at a wide range of strain rates
Authors: Kami Tsuyoshi , Yamada Hiroyuki , Ogasawara Nagahisa
Published: September 2018

The effect of strain rate on mechanical properties of Al-2.3wt.%Mg alloy (AA5021) and commercial pure aluminum (purity 99.7wt.%: A1070) was investigated at room temperature. The tensile tests were conducted at strain rates from 1.0×10−4 to 1.0×103 s−1. The universal testing machine was used for strain rate 1.0×10-4 to 1.0×10−1 s−1. For the strain rate 1.0×100 s-1, the servohydraulic testing machine, which was developed by our laboratory, was used. The impact strain rate 1.0×103 s−1 was obtained using the split Hopkinson pressure bar method. The pure aluminum showed positive strain rate dependence of material strength at the investigated strain rates. In contrast, the Al-2.3wt.%Mg alloy showed the negative strain rate dependence at strain rates from 1.0×10−4 to 1.0×100 s−1. However, Al-2.3wt.%Mg alloy showed the positive strain rate dependence at strain rates from 1.0×100 to 1.0×103 s−1. It was surmised that the effect of dislocation locking by the solute Mg atoms became negligible at strain rate of approximately 1.0×100 s−1. It was confirmed that material properties for the Al-Mg alloy at the strain rate of 1.0×100 s−1 were important, since the strain rate dependence changed negative to positive around this strain rate.
Ultrasonic Detection of Spall Damage Distribution Subjected to Plate Impact Test with Different Thickness
Authors: Nishimura Naoya , Ito Toshihiro , Watanabe Takeru
Published: September 2018

Plate impact test on medium carbon steel were carried out to the target plate by impacting the flyer plate with one-third and two-thirds thickness of the target plate. The spall damage within the target plate was evaluated non-destructively with a low frequency scanning acoustic microscope as well as ultrasonic velocity and backscattering intensity. We observed the spall damage distribution by the B-and Cscan images. The distribution of spall damage through the plate thickness depends on the tensile stress area within the target plate. The difference of spall damage distribution was investigated by the plate impact test by flyer plate with different thickness. In the plate impact test by the flyer plate with 1/3 target plate thickness, the spall damage was generated by tensile stress area which superposed in the back surface side. On the other hand, in the case of 2/3 target plate thickness, the spall damage was detected at the impact surface side. By generating the spall damage in the different position through the target thickness, it will be possible to evaluate the accumulation of spall damage by reflection and transmission of the stress wave at the internal damage subjected to repeated impact.
Nonlinear Spatial Localized Strain Waves
Authors: Erofeev Vladimir I. , Gerasimov Sergey I. , Malkhanov Alexey O.
Published: September 2018

A possible way of study of single waves in solids is discussed. The soliton is one of these waves without shape and parameters varying. Soliton deformation parameters are connected with the elastic moduli of the third order that allows defining values of these moduli by means of the measured solitondeformation parameters in various type waveguides made of the same material. The conditions under which a soliton can exist in a rod are analytically determined. For simultaneous excitation of loading in several wave guides two new energetic photosensitive structures (the mixtures are given) initiated by means of short light impulses of noncoherent light sources are proposed. Conditions of excitation of the waves on the basis of multipoint optical initiation loading impulses are described. As a technique for registration the shadowgraph visualization is proposed. It is discussed, how the problem connected to the use of energetic initiation structures consisting in the power background illumination can be solved. The shadow scheme with the use of a tiny dot explosive light source (Tbr ~41 kK) allows to carry out modelling experiments on research of slabbing actions, jet formations, fluffings, hydrodynamic instability during shock-wave loading of investigated samples, which makes it attractive for determination of parameters in equations-of-state for investigated materials, creation of numerical models and their validation. Some examples showing basic possibility of application of the declared techniques are included.
Numerical analysis of a testing technique to investigate the dynamic crack propagation in armour ceramic
Authors: Duplan Yannick , Forquin Pascal , Lukić Bratislav , Saletti Dominique
Published: September 2018

Ceramic materials are numerically studied to understand their fracturing behaviour upon dynamic conditions and impact loadings. During a ballistic impact of a projectile against a ceramic armour system, an intense fragmentation composed of numerous oriented cracks, develops in the target. It is the reason why the conditions of crack initiation, propagation and arrest in these materials need to be investigated. In the present work, a dynamic testing configuration has been developed in order to characterise the dynamic fracture toughness (K1,d), considering a single crack that propagates from the specimen notch tip. The “Rockspall” testing technique, which employs a two-notch specimen loaded in a spalling experiment, was used. Thanks to the reflection of a compression wave into a tensile load from the sample free-end, a single dynamic crack is triggered. The sample geometry is optimised by means of a series of FE numerical simulations involving an anisotropic damage model.
An Image-Based Impact Test for the High Strain Rate Tensile Properties of Brittle Materials
Authors: Fletcher Lloyd , Pierron Fabrice
Published: September 2018

Testing ceramics at high strain rates presents many experimental diffsiculties due to the brittle nature of the material being tested. When using a split Hopkinson pressure bar (SHPB) for high strain rate testing, adequate time is required for stress wave effects to dampen out. For brittle materials, with small strains to failure, it is difficult to satisfy this constraint. Because of this limitation, there are minimal data (if any) available on the stiffness and tensile strength of ceramics at high strain rates. Recently, a new image-based inertial impact (IBII) test method has shown promise for analysing the high strain rate behaviour of brittle materials. This test method uses a reflected compressive stress wave to generate tensile stress and failure in an impacted specimen. Throughout the propagation of the stress wave, full-field displacement measurements are taken, from which strain and acceleration fields are derived. The acceleration fields are then used to reconstruct stress information and identify the material properties. The aim of this study is to apply the IBII test methodology to analyse the stiffness and strength of ceramics at high strain rates. The results show that it is possible to identify the elastic modulus and tensile strength of tungsten carbide at strain rates on the order of 1000 s-1. For a tungsten carbide with 13% cobalt binder the elastic modulus was identified as 516 GPa and the strength was 1400 MPa. Future applications concern boron carbide and sapphire, for which limited data exist in high rate tension.
A testing technique to investigate the tensile behavior of propellant representative material
Authors: Viant Thibaut , Forquin Pascal , Saletti Dominique , Imbault Didier , Brunet Pierre , Moriceau Julien , Poirey Gilles
Published: September 2018

Propellants are energetic materials abundantly used to generate the propulsion of rockets, projectiles, or other objects. A wide range of stress-state and strain-rate has to be considered in view of predicting the mechanical behaviour of this material over its different life cycles. Propellant materials are usually studied through the use of propellant representative materials (PRM) when studied in a university laboratory. In the present work an experimental device was developed to investigate the dynamic tensile response of a PRM material. This device is based on the use of a pendulum that is employed to dynamically load the PRM sample on one end. The sample is attached to an instrumented Hopkinson bar on the other end. The data processing of Hopkinson bar point measurements combined to DIC (digital-imagecorrelation) measurements allows the stress and strain levels in the sample to be characterised. Finally these experimental results can be used to enhance the constitutive modelling of PRM materials.
A Wedge-DCB Test Methodology to Characterise High Rate Mode-I Interlaminar Fracture Properties of Fibre Composites
Authors: Ponnusami Sathiskumar A. , Cui Hao , Erice Borja , Pathan Mehtab V. , Petrinic Nik
Published: September 2018

A combined numerical-experimental methodology is presented to measure dynamic Mode-I fracture properties of fiber reinforced composites. A modified wedge-DCB test using a Split-Hopkinson Bar technique along with cohesive zone modelling is utilised for this purpose. Three different comparison metrics, namely, strain-displacement response, crack propagation history and crack opening history are employed in order to extract unique values for the cohesive fracture properties of the delaminating interface. More importantly, the complexity of dealing with the frictional effects between the wedge and the DCB specimen is effectively circumvented by utilising right acquisition techniques combined with an inverse numerical modelling procedure. The proposed methodology is applied to extract the high rate interlaminar fracture properties of carbon fiber reinforced epoxy composites and it is further shown that a high level of confidence in the calibrated data can be established by adopting the proposed methodology.
Research on phase transition and strength under ramp compression with graded density impactor
Authors: Tan Ye , Li Xuemei , Yu Yuying , Jin Ke
Published: September 2018

In our work, graded density impactors fabricated from 8 to 40 layers, are specifically designed to generate desired strain rates (on the order of 105~106 s-1) and thermodynamic path(shock loading-ramp loading-release). And experiments on phase transition and strength for metals (bismuth, LY12 Al) have been performed with light gas gun to peak pressure between 30 GPa and 50 GPa. Particle velocity at sample/window interface in these experiments are simultaneously traced by a distance interferometer system for any reflector, and a wave profile analysis is employed to explore the solidification transition and strength behaviour along elevated isentrope.
Experimental study on counterintuitive behavior of thin aluminium plates under free airblast loading
Authors: Xu Zixi , Liu Yan , Huang Fenglei
Published: September 2018

An experimental investigation of the counterintuitive behaviour in thin aluminium plates under fullfield test is presented in the paper. Special focus is placed on structural response and permanent deflection of the panels after the complex response. Thus, a series of tests with the plates varied in two kinds of thickness were conducted, where impulsive loading was generated by detonating the explosives at various standoff distances. As loaded impulsively, the vibration response was observed and the final configuration of each plate was measured and recreated. It is shown that all plates subjected to free air blast loading in such conditions exhibited plastic permanent deformation combined with distinct counterintuitive behaviour, as the plates deformed to the opposite direction of the incident wave. In addition, the characteristics of the permanent deflection can be divided into 2 typical deformation shapes, and the occurrences of which were correlated to the dimensionless parameter proposed in previous studies, confirmed to be an approximate indicator to describe the influence of loading conditions herein.
High Rate Characterization of Three DP980 Steels
Authors: Zhumagulov Amir , Abedini Armin , Rahmaann Taamjeed , Imbert José , Butcher Clifford , Worswick Michael , Malcolm Skye , Dykeman Jim , Ezzat Hesham
Published: September 2018

Advanced high strength steels (AHSS) are used extensively in the automotive industry in the ongoing effort to reduce vehicle weight. Their increased strength allows for the reduction of sheet thickness, and thus a reduction in mass, while offering formability and cost advantages when compared to other metal alloys typically considered for lightweight applications. DP980 steels are AHSS being considered for structural energy absorbing components; however, there is a lack of published information on their high rate behaviour. This paper presents the results of an experimental program that characterized three production DP980 steels from three different manufacturers at strain rates of 0.001, 1, 10, 100 and 1,000 s-1. An electro-mechanical frame was used for the quasi-static tests, the 1, 10, and 100 s-1 tests were carried out using a fast hydraulic apparatus and the 1,000 s-1 experiments were carried out using a tensile split Hopkinson bar. The quasi-static hardening response at strains higher than the uniform elongation of about 7% was obtained by using a shear test, thus avoiding the use of inverse modelling techniques. The results indicate that the DP980 steels are moderately rate sensitive, with one of the materials showing higher sensitivity than the others. One of the materials exhibited a yield point phenomenon that appears to affect the behaviour of the material at 100 and 1,000 s-1, however, the reasons for this behaviour remain an open question. The data was fit to modified Johnson-Cook and Cowper-Symonds model to account for rate sensitivity. The results presented in this paper provide a tool for modelling the dynamic behaviour of DP980 steels.
Experimental methodology for the measurement of plasticity on metals at high strain-rates
Authors: Sancho Alexander , Cox Mike J. , Aldrich-Smith Giles , Cartwright Tim , Davies Catrin M. , Hooper Paul A. , Dear John P.
Published: September 2018

An experimental methodology has been developed for the tensile characterisation of ductile isotropic metals at high strain-rate. This study includes the region beyond plastic instability or necking, which is rarely analysed for conventional applications. The research explores an imaging technique used to track the geometry of the specimen during tensile tests and calculate true local values of stress and strain by applying Bridgman theory [1]. To improve the quality of the images taken at high strain-rate an in-situ high speed shadowgraph technique has been developed, and to obtain better results from the images a sub-pixel accuracy edge detection algorithm has been implemented. The technique has been applied to an austenitic stainless steel. Its tensile behaviour has been assessed by testing round samples at strain-rates ranging from quasi-static to ~103 s-1. The results obtained with the proposed methodology have been validated by comparison with more conventional techniques such as video-extensometer and digital image correlation in the pre-necking region and good performance even at the highest strain-rate tested has been proved.
A Constant Acoustic Impedance Mount for Sheet-Type Specimens in the Tensile Split-Hopkinson Bar
Authors: Ganzenmüller Georg. C. , Langhof Timo , Hiermaier Stefan
Published: September 2018

This paper addresses a problem well-known amongst practitioners of the Split-Hopkinson Tension Bar method: attaching a flat test specimen made from sheet material to the cylindrical input-and output bars. To date, slotting the bar ends and gluing the specimens into these ends with high-strength adhesives is the gold standard. However, this approach is not universally applicable because some materials are difficult to bond, and the adhesion surface is limited by the bar diameter, meaning that only small width specimens can be tested. In contrast, the hitherto published mechanical clamping mechanisms typically introduce excessive additional mass into the Split-Hopkinson system which detrimentally affects wave propagation and thus causes errors in the stress-strain signals. We circumvent this problem by designing a mechanical clamping device which has the same acoustic impedance as the bar material and is suitable to securely attach specimens with a width larger than the bar diameter. The benefits of our new clamping device are demonstrated by reporting tensile stress-strain data for Polycarbonate at high strain rates. The data is free from unwanted oscillations and enables accurate determination of dynamic strength and stiffness.
Measurement of fracture energy of concrete at high strain rates
Authors: Rey-de-Pedraza V. , Gálvez F. , Cendón Franco D.
Published: September 2018

The Hopkinson Bar has been widely used by many researchers for the analysis of dynamic properties of different brittle materials and, due to its great interest, for the study of concrete. In concrete structures subjected to high velocity impacts, initial compression pulses travel through the material leading to tensile stresses when they reach a free surface. These tensile efforts are the main cause of concrete fracture due to its low tensile strength compared to the compressive one. This is the reason why dynamic tests in concrete are becoming of great interest and are mostly focused in obtaining tensile fracture properties. Apart form the dynamic tensile strength, which has been widely studied by many authors in the last decades, the dynamic fracture energy presents an increased difficulty and so not too much experimental information can be found in literature. Moreover, up to date there is not a clear methodology proposed in order to obtain this parameter in an accurate way. In this work a new methodology for measuring the dynamic fracture energy is proposed by using the Hopkinson Bar technique. Initial tests for a conventional concrete have been carried out and the results for the dynamic fracture energy of concrete at different strain rates are presented.
Comparison of dynamic tensile extrusion behaviour of WCu composites made by different processes
Authors: Park Leeju , Woo Sanghyun , Lee Yerim , Lee Keunho , Sun Yi Young
Published: September 2018

Composites with 60~90% of tungsten are used in liners of some specialty shaped charges. The penetration is enhanced by a factor against copper for homogeneous steel target. Tungsten powder based shaped charge liners are also especially suitable for oil well completion. In this study, WCu composites manufactured by different process are used for testing of dynamic tensile extrusion (DTE) behaviour. One samples were made by copper infiltrated method. The other samples were manufactured by metal injection molding methods with reduced tungsten copper composite powder. DTE tests were carried out by launching the sphere samples (Dia. 7.62mm) to the conical extrusion die at a speed of ~375m/s. The DTE fragmentation behaviour of tungsten copper composites after soft-recovered were examined and compared with each other.
Microstructure Based Failure Criterion For Ductile Materials
Authors: Fensin Saryu , Gray George , Bourne Neil , Hixson Robert
Published: September 2018

For ductile metals, the process of dynamic fracture occurs through nucleation, growth and coalescence of voids. The stress required to nucleate these voids is inferred from the velocimetry data (using the acoustic approach) and termed as the spall strength. This is a key parameter that is used to evaluate a material’s susceptibility to damage and failure. However, it is also well recognized that the dynamic parameters used to generate the shock state such as pulse duration, tensile strain-rate and peak stress coupled with material microstructure itself affect the material response in a complex manner. Yet, it is impossible to capture all this information by assessing only the spall strength measured from simple one-dimensional Photon Doppler Velocimetry measurements. Although, there exist widely used corrections proposed by Kanel et. al. that allow for the inclusion of some of these complexities into the measured spall strength but still does not take the microstructure into account. In this work, we propose another scheme for normalization of spall strength with a damage area to capture the complexities included in the damage and failure process especially pertaining to microstructure. We will also demonstrate the application of this scheme by applying to examples of materials such as Copper, Copper-24 wt%Ag, Copper-15 wt% Nb and additively manufactured 316L SS.
Investigating the Dynamic Tensile Response of Lean Duplex Stainless Steel and the Effects of Radial Waves Using the Recovered Plat-Impact Experiment
Authors: Ameri Ali A.H. , Brown Andrew D. , Quadir Zakaria , Hazell Paul J. , Logos Con , Escobedo-Diaz Juan P.
Published: September 2018

Lean Duplex Stainless Steel 2404 (LDX2404) is the newest commercial type of duplex stainless steels, recently introduced by Outokumpu®. This paper investigates the dynamic tensile failure (spall strength) of this new alloy under different peak stresses (4.5 GPa to 8.2 GPa) via the recovered plate-impact experiment using a single stage gas gun. The microstructural investigation for the as-received and soft recovered post-shock material conditions were accomplished using Electron Backscatter Diffraction (EBSD) and optical microscopy. The effect of the radial release waves and the effectiveness of using momentum trap rings on the spall strength and the spall damage during the impact experiment were studied. Results indicate that LDX2404 experienced spall damage for the entire range of tested peak stresses. The spall strength was not affected by the implementation of momentum trapping rings whereas; the damage content was highly influenced. The spall damage of LDX 2404 exists parallel to the phase boundary interfaces, which are normal to the impact direction. Grain orientation, based on Taylor factor values, was not controlling the voids nucleation and voids growth.
Effect of strain rate on the hydrogen embrittlement of a DP steel
Authors: Depover Tom , Elmahdy Ahmed , Vercruysse Florian , Verleysen Patricia , Verbeken Kim
Published: September 2018

Advanced high strength steels (HSSs), such as dual phase steels, are widely used in the automotive industry due to their excellent combination of strength and ductility. In certain applications, they might be exposed to hydrogen (H) which is known to be detrimental for the deformation. H embrittlement (HE) is still not fully understood. It might drastically reduce the energy absorbed in a crash event and limits the use of HSSs in car bodies. Although H diffusion is a highly time dependent phenomenon, so far, the combined effect of dynamic strain rates and electrochemical H pre-charging has not been studied. Therefore, a reproducible methodology has been developed. Tensile specimens were electrochemically H pre-charged and immediately tested in a split Hopkinson tensile bar setup. To distinguish between the effect of strain rate and HE, static tests have been conducted using the same procedure. Results show that the HE resistance decreased due to higher H amounts in the sample for all strain rates. The HE increased when slower strain rates were applied due to higher probability of H to diffuse to regions of stress concentration ahead of a crack tip and as such accelerating failure. At the highest strain rate considered (900 s-1), the material still lost about 10% of its ductility.
Structure of U-Zr-Mo alloy shell after explosive loading
Authors: Belyaev Dmitry , Aleksandrov Alexey , Zuyev Yuri , Kozlov Eugene , Svyatov Igor , Levi Catherine
Published: September 2018

This presentation describes investigation of a thick-wall spherical shell 48 mm in diameter from the alloy of uranium with molybdenum and zirconium, which survived after high-intensity explosive loading. Investigation was performed in the meridional section of the shell to obtain qualitative data on hardness and microhardness, metallurgical inclusions, damage, and also material microstructure. Structural changes are observed to widely present in the shell material. The localized damage observed both at R ≈ 12-14 mm and R ≈ 16-18 mm are the first and second converged spalls, respectively. What is more, in the southern sector the first spall was recompacted with the remelting of a large region of the material in the adjacent layers (region with the enhanced hardness for the first spall). Cracks of the second spall in the northern sector were also recompacted almost completely.
Additively manufactured penetrating warheads
Authors: Limido Jérôme , Deconinck Paul , Beaucamp Aurélien , Paintendre Frédéric , Hereil Pierre-Louis
Published: September 2018

Penetrating warheads have to both defeat thick and high strength targets and have high blast effects. Lattice structures could help to enhance blast effect and reduce the weight of the penetrators. Additive manufacture provides a method to produce this concept. This paper details a programme to evaluate the perforation performance of such a penetrator. This study implemented an approach based on the integration of virtual and physical tests. A mesoscale numerical approach based on explicit high order finite element (HOFEM) was first developed to optimize the lattice pattern. The dynamic behaviour of this material was then determined using the Split Hopkinson Pressure Bar (SHPB) technique and this was then used to fit a constitutive model in Impetus Afea Solver®. The modelling of the concrete penetration of small scale warhead was based on the advanced meshless approach coupled with HOFEM. The models developed enabled the determination, simultaneously, of the homogenised behaviour of the lattice material and also the global behaviour of the penetrators during and after the penetration. Seven ballistic tests against concrete targets were performed at Thiot Ingenierie to investigate the penetration capabilities of the additively manufactured penetrating warhead concept and especially when using a lattice pattern.
Fiber reinforced mortars based on free Portland-CSA binders under high stress rate
Authors: Coppola Luigi , Coffetti Denny , Crotti Elena , Forni Daniele , Cadoni Ezio
Published: September 2018

In this paper, dynamic behaviour of fiber reinforced mortars manufactured with innovative binders based on calcium sulphoaluminate cement (CSA), supplementary cementitious materials (SCMs), gypsum (G) and hydrated lime (CH) was investigated. Fly ash (FA) and ground granulated blast furnace slag (GGBFS) were used to develop sustainable Portland-free cementitious materials. Polypropylene structural fibers (1% by mortar volume) were used to reinforce the cementitious matrix. Fresh properties of mortars were evaluated in terms of workability and specific mass. In addition, elastic modulus, compressive and flexural strength were determined up 28 days from casting. The dynamic behaviour was studied by means of Split Hopkinson Tensile bar having 60 mm in diameter. Preliminary dynamic results reported in terms of stress versus crack opening displacement were evaluated and discussed.
The performance of armour steels with pre-layers against fragment simulating projectiles
Authors: van der Wal Rogier , Carton Erik , Hilvers Frits
Published: September 2018

Armour steels have proven to be promising solutions for protection against fragments from threat weapons. The area to cover for ship bulkheads is usually large, so cost of the raw material is an important driver. For new ships, additional mass can be compensated for in the design. Past research by TNO and other workers has shown that the ballistic limit V50 of armour steels against fragments is increased significantly by adding a front or pre-layer. This layer can be a variety of materials ranging from cardboard to glass. In TNO’s Laboratory for Ballistics Research a test program was conducted to study the effect of high pressure laminate, polymer and fire insulation pre-layers at the V50 and well above the ballistic limit. The high velocities are typically associated with fragments from relevant threats for warships. Fragment simulating projectiles were fired on armour steel plates of varying type and thickness with these pre-layers and measured the residual velocity and resulting hole sizes. The tests resulted in clear dependencies of the residual velocity as a function of impact velocity and pre-layer (type and thickness). Analysis of the data showed that there are several counteracting effects interacting when a pre-layer is applied to armour steel. The failure mechanism of the steel as well as the hardness and thickness of the pre-layer seem to influence the outcome of this interaction and hence the response of the steel to various pre-layers. The results of this research will be used in the design of fragment and blast resistant bulkheads for future naval ships.
Update: PET/CT und PET/MRT bei Tumoren des Kopf-Hals-Bereiches
Authors: Grosse Jirka , Hellwig Dirk
Published: September 2018

Die Positronen-Emissions-Tomografie (PET) mit 18F-Fluorodesoxyglukose (FDG) in Verbindung mit einer Computertomografie (CT) wird bei speziellen Indikationen in der Diagnostik bei Patienten mit Kopf-Hals-Tumoren eingesetzt. Die Einsatzmöglichkeiten umfassen die Suche nach einem okkulten Primärtumor bei zervikaler Lymphknotenmetastasierung mit zuvor inkonklusiver Diagnostik, das lokale Staging, die Beurteilung des Therapieansprechens nach Radio(chemo)therapie sowie Nachsorgeuntersuchungen, wenn zwischen therapieinduzierten Gewebealterationen und einem Tumorrezidiv differenziert werden muss. Der Erfolg einer Bestrahlung in Hochpräzisionslagerungstechnik (Stereotaxie) bzw. einer intensitätsmodulierten Strahlentherapie scheint durch die Bestimmung des Tumorvolumens unter Einbeziehung der PET/CT verbessert zu werden. Die kombinierte PET/Magnetresonanztomografie (MRT) bietet in diesem Indikationsfeld durch höhere anatomische Detailgenauigkeit Vorteile beim Staging hinsichtlich der Beurteilung des lokalen und lokoregionären Befundes, ist der PET/CT bei der Detektion pulmonaler Metastasen/Zweittumore jedoch deutlich unterlegen.

Auf dem höchstmöglichen Evidenzniveau einer randomisierten Studie wurde gezeigt, dass man bei Patienten mit lokal fortgeschrittenem Kopf-Hals-Tumor bei unauffälliger FDG-PET/CT nach Radiochemotherapie operative Eingriffe ohne Überlebensnachteil vermeiden kann. Die FDG-PET/CT bei Kopf-Hals-Tumoren konnte dadurch vom Gemeinsamen Bundesausschuss (G-BA) als notwendige Leistung für die Versorgung gesetzlich Versicherter anerkannt werden.
Update PET in der Pädiatrischen Onkologie
Authors: Roll Wolfgang , Dirksen Uta , Weckesser Matthias
Published: September 2018

Die PET/CT wird bei vielen kindlichen Tumorentitäten eingesetzt und hat beim Hodgkin-Lymphom bereits Eingang in nationale und internationale Leitlinien gefunden. Die PET ermöglicht eine semiquantitative Messung der metabolischen Tumoraktivität und damit eine frühe Beurteilung des Therapieansprechens sowie der Vitalität von Tumorrestgewebe oder eines Rezidivs. Für verschiedene Fragestellungen stehen unterschiedliche metabolische und molekulare Marker zur Verfügung.

In dieser Übersichtsarbeit werden Indikationen für PET im Kindesalter sowie die besonderen Anforderungen in der Durchführung und Befundung dargelegt. Abschließend wird die Bedeutung der neuen PET/MRT für die Diagnostik kindlicher Tumore diskutiert.
Somatostatinrezeptor-PET
Authors: Haug Alexander
Published: September 2018

Die SSTR-PET/CT ist Goldstandard in der Bildgebung von G1-/G2-NET. Sie hat eine signifikant höhere diagnostische Genauigkeit als die CT, erlaubt eine zuverlässige Primär- und Rezidivdiagnostik, und hat dadurch einen signifikanten Einfluss auf das therapeutische Management von Patienten mit NET. Eine Therapie mit kalten SSA muss für die SSTR-PET nicht unterbrochen werden. Die SSTR-PET/MRT kann sicherlich noch nicht als Standard angesehen werden, kann aber insbesondere bei Leber- und Knochenmetastasen hilfreich sein. Neue Entwicklungen in Richtung antagonistische SSA sind vielversprechend.
Frühmobilisation bei Strecksehnenverletzungen – Aktiv statt passiv
Authors: Jensen Carina
Published: September 2018

Im Haushalt oder im Beruf passiert es schnell, dass man sich in die Hand schneidet. Muss die Strecksehne eines Fingers genäht werden, weil sie verletzt oder gerissen ist, erfordert das ein adäquates Nachbehandlungsschema. Ordnet der Chirurg eine aktive Frühmobilisation an, eignet sich das Short-Arc-Motion-Konzept. Wie Handtherapeuten dabei vorgehen, erläutert Carina Jensen.
Umwelt- und personenbezogene Faktoren der ICF – Vom hemmenden zum fördernden Kontext
Authors: Janssen Christina
Published: September 2018

Die Umgebung eines Klienten kann ihn im Alltag unterstützen oder behindern. Dazu tragen die sogenannten Kontextfaktoren wie Angehörige, Technologien oder die Persön-lichkeit bei. Identifizieren Ergotherapeuten diese umwelt- und personenbezogenen Faktoren, können sie das Rehaergebnis positiv beeinflussen.
Schiff ahoi!
Authors: Tülsner Jens , Herrfurth Ramona
Published: September 2018

Die heutigen Einsatzmöglichkeiten von Fachkrankenpflegern sind breit. Verschiedene Disziplinen innerhalb und außerhalb des Krankenhauses sind dabei jedem
bekannt, der sich gedanklich mit einer Veränderung seines beruflichen Umfelds beschäftigt. Mancher denkt auch über die Landesgrenzen hinaus, bezieht das nähere
oder weitere Ausland in die Überlegungen für einen neuen Schritt mit ein. Dieser Artikel macht mit einem weiteren, weitgehend unbekannten Einsatzgebiet
vertraut: Haben Sie schon einmal daran gedacht, auf einem Kreuzfahrtschiff zu arbeiten?
Sport nach Knie- und Hüftendoprothetik
Authors: Boettner Friedrich , Kasparek Maximilian F. , Rueckl Kilian , Liebau Christian
Published: September 2018

Mit der Einführung neuer Materialien in die Hüft- und Knieendoprothetik sowie der Verbesserung der Prothesenverankerung im Knochen scheinen die Voraussetzungen
für eine stärkere Belastung künstlicher Endoprothesen erfüllt. Die Empfehlungen hinsichtlich der sportlichen Betätigung nach Implantation einer Knie- oder
Hüftprothese sind in den letzten 20 Jahren jedoch den implantattechnischen Verbesserungen nicht angepasst worden. Gerade in der Hüftendoprothetik erlaubt die
heute bevorzugte Verwendung von unzementierten Implantaten sowie der Einzug von hoch vernetztem Polyethylen einen deutlich aktiveren Lebenswandel, ohne dass
erhöhte Lockerungsraten und Komplikationen befürchtet werden müssen. Die hier vorgestellte Veröffentlichung fasst den gegenwärtigen Kenntnisstand aus der
Literatur zusammen.
Which Antimicrobial Agent is Likely to be the Best for Treating Clostridium difficile Infections? A Bayesian Network Meta-Analysis of Randomized Clinical Trials
Authors: Sridharan Kannan , Sivaramakrishnan Gowri
Published: September 2018

Background Vancomycin, metronidazole, fidaxomicin, teicoplanin, fusidic acid and bacitracin have been recommended for the treatment of Clostridium difficile infections (CDI). We conducted a Bayesian network meta-analysis comparing all the antimicrobial agents used in CDI.

Methods Electronic databases were searched for randomized controlled trials comparing antimicrobial agents used for CDI. Risk of bias was assessed. Random effects model was used to derive the mixed treatment comparison estimates. Odds ratio with 95% confidence intervals was used as effect estimate.

Results Seventeen studies were included in this meta-analysis. Teicoplanin was observed to perform better than vancomycin, metronidazole, fusidic acid and bacitracin to achieve the symptomatic cure. Teicoplanin was also associated with higher rates of bacteriological cure than vancomycin and metronidazole. Fidaxomicin is associated with significantly higher rates of symptomatic cure than vancomycin, bacitracin and metronidazole and is similar to teicoplanin.

Conclusion To conclude, teicoplanin and fidaxomicin have been observed to perform better than other antimicrobials for the treatment of CDI. We recommend conducting high quality randomized controlled clinical trials evaluating teicoplanin and fidaxomicin with other standard interventions for the management of CDI.
Cannabis auf Rezept – Wunderpflanze Hanf
Authors: Herz Mona
Published: September 2018

Seit März 2017 können Ärzte Cannabisblüten oder -extrakte Patienten verordnen, die an einer schwerwiegenden Erkrankung leiden. Das Gesetz legitimiert die Hanftherapie, wenn diese den Krankheitsverlauf verbessern und Symptome lindern kann. Doch nicht jeder ist für den Medizinalhanf geeignet.