scispace - formally typeset
Search or ask a question

Showing papers by "Vadim V. Silberschmidt published in 2016"


Journal ArticleDOI
TL;DR: In this article, the microstructures and properties of SAC305 lead-free solder reinforced with graphene nanosheets (GNS) decorated with Ni nanoparticles (Ni-GNS).

100 citations


Journal ArticleDOI
TL;DR: In this paper, the effect of nano-reinforcement that was successfully introduced into a SAC305 lead-free solder alloy with different weight fractions through a powder-metallurgy route was quantitatively analyzed.

62 citations


Journal ArticleDOI
TL;DR: In this article, the authors focus on localisation of damage-related nonlinearities based on higher harmonic generation and show that cracks are particularly strong in the vicinity of damage, allowing not only for damage localisation but also for separation of crack induced nonlinearity from other sources of non linearities.

59 citations


Book
01 Jan 2016
TL;DR: In this paper, the authors reviewed various aspects of dynamic deformation, damage and fracture in composite laminates and sandwich structures in a broad range of application fields including aerospace, automotive, defense and sports engineering.
Abstract: Composite materials, with their higher exposure to dynamic loads, have increasingly been used in aerospace, naval, automotive, sports and other sectors over the last few decades. Dynamic Deformation, Damage and Fracture in Composite Materials and Structures reviews various aspects of dynamic deformation, damage and fracture, mostly in composite laminates and sandwich structures, in a broad range of application fields including aerospace, automotive, defense and sports engineering. As the mechanical behavior and performance of composites varies under different dynamic loading regimes and velocities, the book is divided into sections that examine the different loading regimes and velocities. Part one examine low-velocity loading and part two looks at high-velocity loading. Part three then assesses shock and blast (i.e. contactless) events and the final part focuses on impact (contact) events. As sports applications of composites are linked to a specific subset of dynamic loading regimes, these applications are reviewed in the final part. Examines dynamic deformation and fracture of composite materialsCovers experimental, analytical and numerical aspectsAddresses important application areas such as aerospace, automotive, wind energy and defence, with a special section on sport applications

46 citations


Journal ArticleDOI
TL;DR: In this paper, a micro-scale model with hexagonal arrays of fibres was built to compute effective elastic constants and yarn strength under different loading conditions, and the results generated by this model were used as input for a meso-scale modeling approach.
Abstract: Braided textile-reinforced composites have become increasingly attractive as protection materials thanks to their unique inter-weaving structures and excellent energy-absorption capacity. However, development of adequate models for simulation of failure processes in them remains a challenge. In this study, tensile strength and progressive damage behaviour of braided textile composites are predicted by a multi-scale modelling approach. First, a micro-scale model with hexagonal arrays of fibres was built to compute effective elastic constants and yarn strength under different loading conditions. Instead of using cited values, the input data for this micro-scale model were obtained experimentally. Subsequently, the results generated by this model were used as input for a meso-scale model. At meso-scale, Hashin’s 3D with Stassi’s failure criteria and a modified Murakami-type stiffness-degradation scheme was employed in a user-defined subroutine developed in the general-purpose finite-element software Abaqus/Standard. An overall stress–strain curve of a meso-scale representative unit cell was verified with the experimental data. Numerical studies show that bias yarns suffer continuous damage during an axial tension test. The magnitudes of ultimate strengths and Young’s moduli of the studied braided composites decreased with an increase in the braiding angle.

44 citations


Journal ArticleDOI
TL;DR: In this article, a stacking-sequence optimization method for composite laminates using a multicriteria objective function with buckling, strength and continuity constraint subject to in-plane normal compressive loads is presented.

39 citations


Journal ArticleDOI
TL;DR: The obtained material parameters allow us to identify time-dependent behaviour of BC hydrogel at high stress level with sufficient accuracy and allow combination of good accuracy in analytical description of viscoelastic behaviour of real materials and simplicity in solving boundary value problems.

36 citations


Journal ArticleDOI
TL;DR: In this paper, a high-speed camera is used to record the penetration of a gas-gun launched cylindrical mass with a hemispherical cap into a block of clay.

35 citations


Journal ArticleDOI
TL;DR: In this paper, a hybrid algorithm fully utilizing advantages of both SPH and FEM is proposed to simulate a metal-jet penetration into a double hull made of different materials, namely steel and SPS (Sandwich Plate System).

31 citations


Journal ArticleDOI
TL;DR: In this article, a crystal-plasticity theory was implemented in a finite-element (FE) modelling scheme to consider inherently anisotropic deformation of a single-crystal metal at micro-scale.

29 citations


Journal ArticleDOI
TL;DR: Unlike strain-rate softening behaviours in other materials, reorientation of nanofibres and kinematics of free-water flow dominate the softening behaviour of BC hydrogel at high strain rates.

Journal ArticleDOI
TL;DR: The feasibility of this setup for TM stressing was further verified with experimental and simulation methods; a temperature gradient in a solder seam was calculated as 1070 K/cm in this paper, and the microstructural evolution and mechanical properties of both plain and composite solder alloys were then studied under the condition of TM stressing.
Abstract: In this work, SAC305 lead-free solder reinforced with 0.1 wt. % fullerene nanoparticles was prepared using a powder metallurgy method. A lab-made setup and a corresponding Cu/solder/Cu sample for thermo-migration (TM) test were designed and implemented. The feasibility of this setup for TM stressing was further verified with experimental and simulation methods; a temperature gradient in a solder seam was calculated as 1070 K/cm. Microstructural evolution and mechanical properties of both plain and composite solder alloys were then studied under the condition of TM stressing. It was shown that compared to unreinforced SAC305 solder, the process of diffusion of Cu atoms in the composite solder seam was remarkably suppressed. After the TM test for 600 h, Cu/solder interfaces in the composite solder seam were more stable and the inner structure remained more intact. Moreover, the addition of fullerene reinforcement can considerably affect a distribution of Cu6Sn5 formed as a result of dissolution of Cu atoms during the TM test. Hardness data across the solder seam were also found notably different because of the elemental redistribution caused by TM.

Journal ArticleDOI
TL;DR: In this article, an elastic-plastic finite-element model was developed to obtain detailed mechanical information for thermoplastic polyurethane (PU) elastomers and the graphene oxide (GO) composite material with enhanced properties.
Abstract: Thermoplastic polyurethane (PU) elastomers are used as shoe-sole materials due to many excellent properties but their inelastic deformation is a serious deficiency for such applications. Hence, graphene oxide (GO) was introduced into the synthesized thermoplastic PU to produce a GO/PU composite material with enhanced properties. Plastic behaviour of this composite was assessed in cyclic tensile tests, demonstrating reduction of irreversible deformations with the addition of GO. Additionally, in order to evaluate mechanical performance of PU and the GO/PU composite under conditions of large-deflection bending typical for shoe soles, finite-element simulations with Abaqus/Standard were conducted. An elastic–plastic finite-element model was developed to obtain detailed mechanical information for PU and the GO/PU composite. The numerical study demonstrated that the plastic area, final specific plastic dissipation energy and residual height for PU specimens were significantly larger than those for the GO/PU composite. Besides, the addition of GO into the PU matrix greatly delayed the onset of plastic deformation in PU in a large-deflection bending process. The average residual height and final specific plastic dissipation energy for PU were approximately 5.6 and 17.7 times as large as those for the studied GO/PU composite. The finite-element analysis provided quantification of the effect of GO enhancement on the large-deflection bending performance of PU for regimes typical for shoe soles and can be used as a basis for optimization of real composite products.

Journal ArticleDOI
TL;DR: A holistic study combining mechanical testing and micro-morphological observations of BC hydrogel with analytical modelling of its relaxation behaviour based on fraction-exponential operators shows a good potential to use a fraction- expansion model to describe time-dependent behaviour of multi-layered hydrogels.
Abstract: Biological hydrogels, e.g. bacterial cellulose (BC) hydrogel, attracted increasing interest in recent decades since they show a good potential for biomedical engineering as replacements of real tissues thanks mainly to their good biocompatibility and fibrous structure. To select potential candidates for such applications, a comprehensive understanding of their performance under application-relevant conditions is needed. Most hydrogels demonstrate time-dependent behaviour due to the contribution of their liquid phase and reorientation of fibres in a process of their deformation. To quantify such time-dependent behaviour is crucial due to their exposure to complicated loading conditions in body environment. Some hydrogel-based biomaterials with a multi-layered fibrous structure demonstrate a promise as artificial skin and blood vessels. To characterise and model time-dependent behaviour of these multi-layered hydrogels along their through-thickness direction is thereby of vital importance. Hence, a holistic study combining mechanical testing and micro-morphological observations of BC hydrogel with analytical modelling of its relaxation behaviour based on fraction-exponential operators was performed. The results show a good potential to use a fraction-exponential model to describe such behaviour of multi-layered hydrogels, especially at stages of stress decay at low forces and of stress equilibrium at high forces.

Journal ArticleDOI
TL;DR: In this paper, a global shared-layer blending (GSLB) method is proposed to improve the blending properties of composite composite structures with multiple manufacturing constraints, with variables dealt with separately at different levels and manufacturing constraints divided and imposed in each step.

Journal ArticleDOI
TL;DR: In this article, the authors compared the Gurson-Tvergaard-Needleman (GTN) and extended finite element method (XFEM) to study the crack initiation and propagation processes in aluminium specimens with different notch shapes (V-shape, U-shape and square).
Abstract: Failures of components and structures are often related to the presence of notches of different shapes. Damage modelling techniques have been proven capable of modelling the crack initiation and propagation in ductile materials (such as Al alloys). The Gurson–Tvergaard–Needleman (GTN) method and extended finite-element method (XFEM) are compared against original experiments to study the crack initiation and propagation processes in aluminium specimens with different notch shapes (V-shape, U-shape and square). Two regimes are considered in this study: quasi-static and impact uniaxial tensile loading. Results show that the load-bearing capability predicted with the two methods is somewhat lower compared to experiments; still, the crack shapes were predicted correctly, with the exception of the square-notch case, for which XFEM was unable to predict the correct shape due to limitations in the model formulation. This study provides information useful for the design of components with stress raisers that are exposed to different loading regimes and shows limitations in both the GTN- and XFEM-based approaches that in many cases underestimate the load-bearing capacity.

Journal ArticleDOI
TL;DR: In this article, the effects of particles on the performance of polyarylene ether nitrile (PEN) composite systems with functionalized aluminum nitride (AlN) were investigated.
Abstract: Aluminum nitride (AlN) with high thermal conductivity was blended in polyarylene ether nitrile (PEN) to obtain a composite system. A ball milling process could provide AlN particles of smaller size with higher surface silylation for homogeneous particle distribution in polymeric matrix. Thermal, electrical, and mechanical behaviors of the produced composites were characterized to investigate the effects of particles on the performance of PENbased composites with functionalized AlN. The composite exhibited thermal conductivity of 0.779 W m 21 K 21 ,a dielectric constant of 7.7, dielectric loss of 0.032, electrical resistivity of 1.39 GX.cm, and break strength of 36 N when the fraction of functionalized AlN increased to 42.3 vol%. A fitted equation based on the improved Russell’s model could effectively predict a trend for thermal conductivity of the composite systems with consideration of interfacial resistance between AlN and surrounding PEN. POLYM. COMPOS., 00:000–000, 2015. V C 2015 Society of Plastics Engineers

Journal ArticleDOI
TL;DR: In this paper, the effect of through-thickness compression on in-plane tensile strength of glass/epoxy composites with random microstructure was investigated experimentally.

Journal ArticleDOI
TL;DR: In this paper, size-dependent crystal plasticity of metal single crystals is investigated using finite element method based on a phenomenological crystal-plasticity model, incorporating both first-order and second-order effects.

Journal ArticleDOI
TL;DR: In this article, the main strategies used to simulate the mechanical behavior of nonwoven materials that is defined by a structure of their fibrous networks and a mechanical behaviour of constituent fibres or filaments are reviewed.
Abstract: This paper reviews the main strategies used to simulate the mechanical behaviour of nonwoven materials that is defined by a structure of their fibrous networks and a mechanical behaviour of constituent fibres or filaments. The main parameters influencing the network structure of nonwoven materials are discussed in the first part. The second part deals with two main strategies employed in the analysis of mechanical behaviour of nonwoven materials using finite-element models based on continuous and discontinuous techniques. Both strategies have further subtypes, which are critically reviewed, and future trends in this area of research are discussed.

Journal ArticleDOI
TL;DR: In this article, the effect of reinforcement type, processing methods and reflow cycle on actual retained ratio of foreign reinforcement added in solder joints was systematically studied, and the morphology of prepared composite solder powder and solder pastes was examined; retained ratios of reinforcement (RRoR) added in composite solder joints after different reflow cycles were analysed quantitatively using an Inductively Coupled Plasma optical system (ICP-OES Varian-720).
Abstract: Purpose This paper aims to systematically study the effect of reinforcement type, processing methods and reflow cycle on actual retained ratio of foreign reinforcement added in solder joints. Design/methodology/approach Two kinds of composite solders based on SAC305 (wt.%) alloys with reinforcements of 1 wt.% Ni and 1 wt.% TiC nano-particles were produced using powder metallurgy and mechanical blending method. The morphology of prepared composite solder powder and solder pastes was examined; retained ratios of reinforcement (RRoR) added in solder joints after different reflow cycles were analysed quantitatively using an Inductively Coupled Plasma optical system (ICP-OES Varian-720). The existence forms of reinforcement added in solder alloys during different processing stages were studied using scanning electron microscope, X-ray diffractometry and energy dispersive spectrometry. Findings The obtained experimental results indicated that the RRoR in composite solder joints decreased with the increase in the number of reflow cycles, but a loss ratio diminished gradually. It was also found that the RRoR which could react with the solder alloy were higher than that of the one that are unable to react with the solder. In addition, compared with mechanical blending, the RRoRs in the composite solders prepared using power metallurgy were relatively pronounced. Originality/value Present study offer a preliminary understanding on actual content and existence form of reinforcement added in a reflowed solder joint, which would also provide practical implications for choosing reinforcement and adjusting processing parameters in the manufacture of composite solders.

Journal ArticleDOI
TL;DR: In this article, a 3D finite-element model of orthogonal micro-cutting of a single crystal of b.c. brass was implemented in a commercial software ABAQUS/Explicit using a user-defined subroutine VUMAT.
Abstract: In recent years thanks to enhancements in design of advanced machines, laser metrology and computer control, ultra-precision machining has become increasingly important. In micromachining of metals the depth of cut is usually less than the average grain size of a polycrystalline aggregate; hence, a cutting process can occur entirely within a single crystal. The respective effect of crystallographic anisotropy requires development of machining models that incorporate crystal plasticity for an accurate prediction of micro-scale material removal under such conditions. To achieve this, a 3D finite-element model of orthogonal micro-cutting of a single crystal of b.c.c. brass was implemented in a commercial software ABAQUS/Explicit using a user-defined subroutine VUMAT. Strain-gradient crystal-plasticity theories were used to demonstrate the influence of evolved strain gradients on the cutting process for different cutting directions.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated fracture behavior of fully-hydrated and freeze-dried bacterial cellulose (BC) hydrogel and found a significant role of interstitial water in fracture behavior.
Abstract: A growing interest in fibrous biomaterials, especially hydrogels, is due to a fact that they promise a good potential in biomedical applications thanks to their attractive biological properties and similar microstructure that mimics its in vivo environment. Since they are usually employed as a main load-bearing-component when introduced into body environment, a comprehensive understanding of their application-relevant mechanical behaviour, such as deformation and fracture, as well as structure-function relationships is essential. To date, deformation behaviour and mechanisms of hydrogels were well documented; still, a lack of understanding of their fracture behaviour, especially structure-function relationships, could complicate an evaluation of their applicability. Hence, this work carried out four types of test – uniaxial tension, single-notch, double-notch and central-notch fracture testing – to investigate fracture behaviour of fully-hydrated and freeze-dried bacterial cellulose (BC) hydrogel. Our results support a significant role of interstitial water – free and bonded water – played in fracture behaviour of the studied BC hydrogel.

Journal ArticleDOI
TL;DR: In this paper, a hybrid modeling approach combining smoothed particle hydrodynamics and continuum finite element analysis is proposed for micro-machining of f.c. single-crystal materials.
Abstract: In this study, micro-machining of f.c.c. single-crystal materials was investigated based on a hybrid modelling approach combining smoothed particle hydrodynamics and continuum finite element analysis. The numerical modelling was implemented in the commercial software ABAQUS/Explicit by employing a user-defined subroutine VUMAT for a crystal plasticity formulation to gain insight into the underlying mechanisms that drive a plastic response of materials in high deformation processes. The numerical studies demonstrate that cutting force variations in different cutting directions are similar for different f.c.c. crystals even though the magnitudes of the cutting forces are different.

Proceedings ArticleDOI
TL;DR: In this article, a non-contact imaging photoplethysmography (iPPG) system is proposed to detect pulsatile blood microcirculation in tissue, which employs a novel illumination source constructed of multiple high power LEDs with narrow spectral emission, which are temporally modulated and synchronised with a high performance sCMOS sensor.
Abstract: Non-contact imaging photoplethysmography (iPPG) to detect pulsatile blood microcirculation in tissue has been selected as a successor to low spatial resolution and slow scanning blood perfusion techniques currently employed by clinicians. The proposed iPPG system employs a novel illumination source constructed of multiple high power LEDs with narrow spectral emission, which are temporally modulated and synchronised with a high performance sCMOS sensor. To ensure spectrum stability and prevent thermal wavelength drift due to junction temperature variations, each LED features a custom-designed thermal management system to effectively dissipate generated heat and auto-adjust current flow. The use of a multi-wavelength approach has resulted in simultaneous microvascular perfusion monitoring at various tissue depths, which is an added benefit for specific clinical applications. A synchronous detection algorithm to extract weak photoplethysmographic pulse-waveforms demonstrated robustness and high efficiency when applied to even small regions of 5 mm2. The experimental results showed evidences that the proposed system could achieve noticeable accuracy in blood perfusion monitoring by creating complex amplitude and phase maps for the tissue under examination.

Journal ArticleDOI
TL;DR: In this article, the morphology of nano-and microstructures in primary and secondary shear zones of machining chips produced with two different machining methods: conventional and ultrasonically assisted turning.
Abstract: This work systematically studied morphology of nano- and microstructures in primary and secondary shear zones of machining chips produced with two different machining methods: conventional and ultrasonically assisted turning. Electron backscatter diffraction and transmission electron microscopy showed that chips had similar microstructures for both machining techniques. The nanostructure in secondary shear zones was less homogeneous than that in primary shear zones. In addition, a heavily deformed layer was formed in a subsurface of Ti-15V-3Cr-3Al-3Sn work-pieces, replicating the microstructure of secondary shear zones of the machining chips, and elongated nanocrystalline grains in this layer were aligned with a tangential direction of turning.

Journal ArticleDOI
TL;DR: In this paper, the authors examined the wear behavior of two different types of cutting inserts using UAT and conventional turning of Ti-15333 alloy and found that the KC5510 cutting inserts demonstrated better tool-life in UAT when compared to CP-500 inserts.

Journal ArticleDOI
TL;DR: In this article, the effect of morphological state of GO flakes on stiffness of nanocomposites with widely used micromechanical models, e.g. rule of mixtures, Hui-Shia and Halpin-Tsai, was investigated.
Abstract: In the last decade, graphene has emerged as one of the best-performing reinforcement materials for nanocomposites. Incorporation of graphene into polymer results in a nanocomposite with a new microstructure responsible for its enhanced features. A morphological state of graphene flakes is one of the factors that govern formation of this microstructure. Studies showed that graphene oxide (GO) flakes can be found either as fully exfoliated or intercalated in polymer-based nanocomposites. While traditional parameters are commonly taken into consideration in theoretical assessment of properties of composites by means of micromechanical models, the morphological state is often ignored. This research aims to investigate the effect of morphological state of GO flakes on stiffness of nanocomposites with widely used micromechanical models, e.g. rule of mixtures, Hui–Shia and Halpin–Tsai. Pure sodium alginate and nanocomposites on its basis reinforced with 1.0 and 2.5 wt% GO were used in the study. Parameters required for modelling were quantified with microstructural characterisation. Micromechanical models were adapted to account for the morphological state of intercalation observed in the characterisation study. Tensile experiments were employed to assess the adopted models, and the effect matrix stiffness, GO thickness, spacing of intercalates as well as the Poisson’s ratio and stiffness of inter-flake polymer layers were studied.

Journal ArticleDOI
TL;DR: In this article, a 2x2 twill weave T300 carbon fiber/epoxy composite flat-plate specimen is examined, using a combination of non-invasive analysis techniques.
Abstract: In this study the resultant ballistic dynamic response observed in a 2x2 twill weave T300 carbon fibre/epoxy composite flat-plate specimen is examined, using a combination of non-invasive analysis techniques. The study investigates deformation, damage and fracture following the impacts with both solid (steel) and fragmenting (ice) projectiles travelling with velocities of 70-90 m/s and 300-500 m/s, respectively. Digital image correlation was employed to obtain displacement data for the rear surfaces of the specimens in each experiment, and used to assess the effect of impact velocity and projectile material on the specimen’s response. 3D X-ray computed tomography was used to image and visualize the resultant internal cloud of damage and fracture, initiated by dynamic loading in each specimen. It was shown that solid projectiles led to greater localized deformation and, in some cases, penetration, whereas fragmenting projectiles destroyed on impact resulted in more distributed loading leading to major front-surface damage depending on the depth on indentation before fragmentation.

Book ChapterDOI
01 Jan 2016
TL;DR: In this paper, a crystal-plasticity modeling framework was implemented to simulate micromachining of a single-crystal metal, and a new shear strain-based criterion was proposed to control material removal.
Abstract: A crystal-plasticity modelling framework was implemented to simulate micromachining of a single-crystal metal. A new shear strain-based criterion was proposed to control material removal. This criterion was implemented in three different modelling techniques: element deletion, arbitrary Lagrangian–Eulerian (ALE) adaptive remeshing and smooth particle hydrodynamics (SPH) in a general-purpose finite-element software package ABAQUS. The three different modelling approaches were compared in terms of their computational accuracy and efficiency. Based on these studies, an optimized modelling strategy was proposed to simulate microscratching of single-crystal copper. The validity of the suggested methodology was corroborated through comparison between FE simulations and experimental data in terms of cutting forces, chip morphology and pile-up patterns in the work-piece.