Dynamic Behavior Of Materials Research Articles

Geometrical scaling law for laser-induced micro-projectile impact testing

Laser-induced micro-projectile impact testing (LIPIT) is a useful experimental method for exploring the dynamic behavior of materials at microscale. It has been a key issue to obtain a scaling law of launch velocity of LIPIT to simplify experimental design and improve experimental configuration. This paper obtains a geometrical scaling law of launch velocity for LIPIT with relative thick metallic film (30–80 µm thick aluminum) using dimensional analysis, experimental measurements, and numerical simulations. Firstly, the dimensional analyses of LIPIT with and without elastomer film configuration are performed, and the dimensionless parameters controlling the launch velocity of the micro-projectile are deduced, from which the geometrical scaling laws of launch velocity for the LIPIT are obtained. Then, the numerical simulation models of the LIPIT are established and validated by LIPIT experimental results, providing a numerical validation for the geometrical scaling laws. In addition, the influences of the dimensionless parameters on the dimensionless launch velocity of micro-projectiles are analyzed by numerical simulations, and the dimensionless formulas for predicting the launch velocities of micro-projectiles in a LIPIT are given, providing an effective method for analyzing and optimizing the LIPIT experiments.

In-situ monitoring of dynamic behavior of catalyst materials and reaction intermediates in semiconductor catalytic processes

Abstract Semiconductor photocatalysis, as a key part of solar energy utilization, has far-reaching implications for industrial, agricultural, and commercial development. Lack of understanding of the catalyst evolution and the reaction mechanism is a critical obstacle for designing efficient and stable photocatalysts. This review summarizes the recent progress of in-situ exploring the dynamic behavior of catalyst materials and reaction intermediates. Semiconductor photocatalytic processes and two major classes of in-situ techniques that include microscopic imaging and spectroscopic characterization are presented. Finally, problems and challenges in in-situ characterization are proposed, geared toward developing more advanced in-situ techniques and monitoring more accurate and realistic reaction processes, to guide designing advanced photocatalysts.

Variable-order fractional dynamic behavior of viscoelastic damping material

Abstract Viscoelastic damping material has been widely used in engineering machinery to absorb vibration and noise. Dynamic behavior of the viscoelastic damping material is mainly affected by temperature and frequency. Classical dynamic behavior equations of the viscoelastic damping material have complex structures with multiple and ambiguous parameters. So a novel variable-order fractional constitutive model (VOFC) is established based on the variable-order fractional operator. Then the viscoelastic dynamic equations are derived by Laplace transform of the VOFC model. The dynamic thermomechanical analysis tests by the three-point bending mode are carried out at variable temperatures and frequencies, and the frequency spectrum of the dynamic behavior, i.e. the loss modulus, storage modulus and loss factor are obtained. Against the test data, the VOFC model is compared with classical models such as the integer-order Maxwell model, constant fractional-order Kelvin-Voigt model, constant fractional-order Maxwell model and constant fractional-order standard linear solid model. The results show that the VOFC model can describe dynamic behavior of the viscoelastic damping material at different temperatures and frequencies more accurately. And the VOFC model has simpler structure and only two parameters with clearly physical meaning. Finally, a calculation software is designed and developed, which simplifies the process of predicting viscoelastic dynamic behavior in a wide frequency range.

Anisotropic peridynamics for homogenized microstructured materials

An anisotropic continuum-molecular model based on pair potentials for describing the linear static and dynamic behavior of periodic heterogeneous Cauchy materials is derived in the framework of peridynamic theory. Non-central pairwise actions are assumed as work-conjugates to specific pairwise deformation variables. A pairwise constitutive law, depending trigonometrically on the material fiber direction and preserving the elastic symmetries of the material, is properly defined. Based on this theoretical ground, a bond-based type continuum model with oriented material points, governed by six independent material micro-moduli, is obtained. Considering microstructured materials featuring periodic rigid massive blocks connected by soft elastic interfaces, the elastic potential functions of the continuum-molecular model are consistently identified in terms of geometrical and constitutive parameters of the microstructure. The identification is based on the formal analogy with the overall constitutive tensors of a homogeneous continuum obtained through continualization schemes and equivalent to the microstructured material. Consequently, the macroscopic elastic properties of the continuum-molecular model are described in terms of pairwise material properties, but its micro-moduli are also explicitly related to the specific properties of the linear elastic interfaces of the microstructured material. The accuracy of the proposed model in the static and dynamic response is successfully verified by comparison with high-fidelity finite element models of an auxetic tetrachiral block lattice considering different periodic cell orientations and elastic interface properties, as well as by comparison with analytical solutions for fully anisotropic elasticity.

Quasi-static and dynamic compaction of granular materials: A strain-activated statistical compaction model and its evaluation

The cold die compaction behaviors of granular material are investigated and a strain-activated statistical compaction model is developed to address its deformation mechanisms, namely particle rearrangement and deformation. The compaction equation is explicit in form and only contains four parameters. Its effectiveness is validated with multi-particle finite element simulation and experimental data. The results show that the compaction model can capture the main features of the nominal compression stress–strain curves of 2D/3D granular materials with different initial relative densities. The dependence of the four parameters in the compaction equation on the initial relative density are analyzed and corresponding quantitative statistical relationships are determined, which takes the same form for 2D and 3D granular materials. It is found that the difference in the quantitative statistical relationships between 2D and 3D granular materials cannot be neglected and the result of 3D multi-particle finite element model is more reasonable, which is verified by the existing experimental data of Al powder. Finally, the statistical compaction model can be applied to characterize the dynamic compaction behaviors of granular materials, and the stress behind the shock front and the shock speed predicted by the model agree well with the finite element results.

A modified discrete element method for concave granular materials based on energy-conserving contact model

The development of a general discrete element method for irregularly shaped particles is the core issue of the simulation of the dynamic behavior of granular materials. The general energy-conserving contact theory is used to establish a universal discrete element method suitable for particle contact of arbitrary shape. In this study, three dimentional (3D) modeling and scanning techniques are used to obtain a triangular mesh representation of the true particles containing typical concave particles. The contact volume-based energy-conserving model is used to realize the contact detection between irregularly shaped particles, and the contact force model is refined and modified to describe the contact under real conditions. The inelastic collision processes between the particles and boundaries are simulated to verify the robustness of the modified contact force model and its applicability to the multi-point contact mode. In addition, the packing process and the flow process of a large number of irregular particles are simulated with the modified discrete element method (DEM) to illustrate the applicability of the method of complex problems.

INVESTIGATION OF THE FRACTAL RESPONSE OF A NONLINEAR PACKAGING SYSTEM

The paper aims to obtain the cushion curves of a polymer foam commonly used in the protective packaging of fragile products and its fractal cushioning performance. First, the impact curves are obtained to evaluate the dropping damage of a critical component considering a fractal nonlinear dynamic packaging system model, more specifically a fractal cubic-quintic-heptic Duffing’s equation. Then, the two-scale fractal derivative transform is introduced to determine the packaging material fractal behavior due to the material molecular structure. The findings explain the dynamic response behavior of the porous cushion material, and the proposed fractal dynamic model sheds new light on the design and analysis of cushioning packaging systems.

Dynamic contact behaviors of saddle materials for suspension bridge

In order to prevent skid accidents of main cable of suspension bridge, dynamic contact behaviors between saddle materials and steel wires were explored in the present study. Dynamic contact tests of saddle materials were conducted employing the self-made dynamic contact test rig. Dynamic contact behaviors of the saddle material (transverse slip, longitudinal deformation, contact state, wear mechanism) in a friction cycle were investigated. Effects of transverse and longitudinal locations, friction cycles and saddle materials on the dynamic contact behaviors were presented. The results show that dynamic contact states between saddle specimen and steel wireexhibits the adhesion-gross slip-adhesion-gross slip state in a friction cycle. The transverse slip and longitudinal deformation of saddle specimen both decrease with increasing distance to the contact interface, decrease along the transverse sliding direction, and increase with increasing friction cycles. The ZG270-480 saddle material exhibits the largest average transverse slip and longitudinal deformation, while ZG275-485 saddle material shows the smaller values.

Algorithm-Driven Advances for Scientific CT Instruments: From model-based to deep learning-based approaches

Multi-scale 3D characterization is widely used by materials scientists to further their understanding of the relationships between microscopic structure and macroscopic function. Scientific computed tomography (CT) instruments are one of the most popular choices for 3D non-destructive characterization of materials at length scales ranging from the angstrom-scale to the micron-scale. These instruments typically have a source of radiation that interacts with the sample to be studied and a detector assembly to capture the result of this interaction. A collection of such high-resolution measurements are made by re-orienting the sample which is mounted on a specially designed stage/holder after which reconstruction algorithms are used to produce the final 3D volume of interest. The end goal of scientific CT scans include determining the morphology,chemical composition or dynamic behavior of materials when subjected to external stimuli. In this article, we will present an overview of recent advances in reconstruction algorithms that have enabled significant improvements in the performance of scientific CT instruments - enabling faster, more accurate and novel imaging capabilities. In the first part, we will focus on model-based image reconstruction algorithms that formulate the inversion as solving a high-dimensional optimization problem involving a data-fidelity term and a regularization term. In the last part of the article, we will present an overview of recent approaches using deep-learning based algorithms for improving scientific CT instruments.

A Modified Fractional-Order Derivative Zener Model for Rubber-Like Devices for Structural Control

AbstractFractional-order derivative (FD) models are widely used to describe the dynamic behavior of rubber-like materials. However, experiments have shown that FD models cannot reproduce the amplit...

High Strain Rate Behavior of Harmonic Structure Designed Pure Nickel: Mechanical Characterization, Microstructure Analysis and Modelisation

The development of new architecture metallic alloys with controlled microstructures is one of the strategic ways for designing materials with high innovation potential and, particularly with improved mechanical properties as required for structural materials [1]. Indeed, unlike conventional counterparts, metallic materials having so-called harmonic structure displays strength and ductility synergy. The latter occurs due to a unique microstructure design: a coarse grain structure surrounded by a 3D continuous network of ultra-fine grain known as “core” and “shell”, respectively. In the present study, pure harmonic-structured (HS) Nickel samples were processed via controlled mechanical milling and followed by spark plasma sintering (SPS), detailed in previous work [2]. In previous studies, the mechanical behavior under quasi-static loading at room temperature has been evaluated and showed the superior mechanical properties of HS pure Ni over the homogeneous conventional counterpart [3]. The present work aims at characterizing the mechanical properties of HS pure Ni under room temperature dynamic loading, through a Split Hopkinson Pressure Bar (SHPB) test, and the underlying microstructure evolution. A stopper ring was used to maintain the strain at a fixed value of about 20% (Fig. 1). Five samples (named B1 to B5) were impacted using different striker bar velocity (V0) from 14 m/s to 28 m/s, yielding strain rate in the range 4000-7000 s-1. Results were considered until a 10% deformation value, which is the deformation threshold for the constant strain rate assumption [4]. Figure 1: SHPB test mounting with a stopper ring The evolution flow stress with the strain rate for harmonic and conventional structure (CS) (using data from quasi-static and high rate experiments) makes it possible to identify two domains with a transition around 3000 s-1. First domain operating at low deformation rates is conventionally associated with the thermal activated movement of dislocation, whereas the second domain at high strain rates is associated with viscous drag. The non-deformed (INIT), and post-SHPB microstructure (B1 to B5), were investigated by EBSD (Fig. 2) and show that while strain rate increase, grains size within the core decrease. An in-depth analysis of grains and grain boundaries were made to highlight the thermal (such as dynamic recrystallization) or mechanical (such as grains fragmentation by dislocation) contribution within the “core” and “shell”. Figure 2: Cross section EBSD map of the initial sample from post-SPS process (INIT) One of the most widely used methods for determining dynamic behavior of materials is the SHPB technique developed by Kolsky [6]. A 3D simulation of SHPB test was created through ABAQUS in dynamic explicit. This 3D simulation allow taking into account all modes of vibration. An inverse approach was used to identify the material parameters from the equation of Johnson-Cook (JC) by minimizing the difference between the numerical and experimental data. The JC’s parameters were identified using B1 and B5 samples configuration. Predictively, identified parameters of JC’s equation shows good result for the others sample configuration (Fig. 3) (a)(b) Figure 3: 3D simulation assembly of SHPB test from ABAQUS (a) and output data of SHPB test from experiment and numerical test for the sample B4 (b) Furthermore, mean rise of temperature within the harmonic Nickel sample can be obtained through ABAQUS and show an elevation of about 35°C for all fives sample. At this temperature, thermal mechanism cannot be activated. Therefore, grains fragmentation within the core is mainly due to mechanical phenomena for a fixed final strain of 20%

Dynamic mechanical behavior of composite materials reinforced by graphene and huntite minerals

Abstract The aim of this study is to investigate the dynamic mechanical properties of composite materials reinforced by mineral experimentally. Graphene and huntite minerals were added to epoxy resin at different weight ratios (wt.-%) as 0.5 weight percent, 1 weight percent and 3 weight percent, to examine the effect of mineral types and percentages on the resulting dynamic mechanical properties. In addition, the effect of non-layered huntite unlike graphene, with a nano-sized grain structure, was investigated. Thus, glass transition temperature (Tg), storage modulus (E’), loss modulus (E”) and damping ratio (tan δ) values were determined and compared. Moreover, a tensile test was performed in order to explain the relation between stress and strain. It was seen that adding different minerals caused different results according to types and proportions. In general, adding minerals to the pure resin increased the storage modulus and loss modulus, whereas the damping ratio (tan δ) decreased compared to the pure resin.

Dynamic mechanical response and deformation behavior of a novel hierarchical cellular structure material – The thousands of eyes Bodhi

Natural cellular structures encourage researchers to seek new design inspirations for impact protection engineering materials. The thousands of eyes Bodhi (TEB) is a novel hierarchical cellular structure material, which includes the first order filled-cells, the second order novel-closed-cells, and the third order open-cells. In this study, dynamic compressive tests at different high strain rates in the longitudinal and transverse directions were conducted by a split Hopkinson pressure bar (SHPB), respectively. A high-speed camera was employed to capture the macroscopic deformation mechanisms and a scanning electron microscope (SEM) was employed to study the microscopic failure mechanisms. The dynamic mechanical response and strain rate effects of TEB samples in the transverse and longitudinal directions were investigated. The anisotropic behavior of TEB samples is observed under dynamic compression tests. The tests results show that the dynamic mechanical properties of TEB samples and dynamic deformation behavior of each order cellular structure exist a significant strain rate dependence. The TEB material dissipates the impact energy through the dynamic compression mechanisms of each order cellular structure which improves the energy absorption and impact resistance. Thus, it provides a bio-inspired template for the design of energy absorption and crashworthiness engineering materials.

Integrated energy performance of an innovative translucent photoluminescent building envelope for lighting energy storage

Novel, photoluminescent and translucent construction elements are considered for application on buildings’ envelope toward energy savings and avant-garde architectural expression. These elements allow natural light to pass through the envelope and charge the materials, which on their turn re-emit energy as visible light. By exploiting the intrinsic characteristics of these construction elements large amounts of energy could be saved in lighting applications. This work tackles the complex, dynamic behavior of photoluminescent materials by means of a novel, experimental and numerical methodology. Materials’ dynamic characteristics are firstly investigated by means of an in-lab experimental campaign. Secondly, coupled lighting and energy numerical simulations are carried out. Results show that translucent and photoluminescent envelope components could be able to reduce up to 40% building electricity consumption for lighting on an annual basis and depending on urban surroundings. In the best-case scenario, i.e. during the longest day of the year, the obtained electricity savings are around 80% for the photoluminescent–translucent envelope.

The direct impact method for studying dynamic behavior of viscoplastic materials

Equipping mathematical models of deformation of viscoplastic materials with the necessary parameters and constants requires comprehensive experimental data meeting the requirements of the problem being analyzed. For problems of evaluating strength of dynamically loaded structures, it is important to account for the strain rate effect on the yield surface radius. Experimental schemes for studying such an effect can be constructed based on the measuring rod technique. Such methods include, for instance, the well-known Kolsky method. The methodological limitations of the above experimental scheme necessitated the development of its alternative versions to widen the range of realized strain rates studied. The present paper gives the description and the results of numerical analysis of an experimental method implementing the socalled direct impact scheme that is also constructed based on the measuring bar technique. The method is used for determining deformation diagrams of viscoplastic structural materials loaded in high-rate compression with strain rates higher than those in the traditional Kolsky method. Using the Kolsky method and the direct impact method, deformation diagrams of copper S101 and aluminum alloy D16Т in the strain rate range of 1000 to 10000 s-1 have been obtained.

Electric field and frequency dependent scaling behavior of dynamic hysteresis in the epitaxial (Pb0.9La0.1)(Zi0.4Ti0.6)O3 films

Epitaxial (Pb0.9La0.1)(Zi0.4Ti0.6)O3 (PLZT) film was prepared with Pt as the upper electrode and La0.5Sr0.5CoO3(LSCO) as the bottom electrode on (001) STO substrate by radio frequency (RF) magnetron sputtering. The dynamic hysteresis scaling behavior of the film, including the variation of remanent polarization (P r), coercive field (E c), and loop area () with external field (E 0) and frequency (f) , was systematically studied. The evolution of scaling behavior in the PLZT film can be divided into two stages: minor loops and major loops, which are in the low and high E 0 regions, respectively. The scaling relations take form of and in minor loops and major loops, respectively. The results show that the domain structure and domain reversal play an important role in the dynamic hysteresis behavior of ferroelectric materials.

Dynamic mesoscale cracking modeling of energetic composite materials in Hopkinson bar test

Dynamic cracking behavior of energetic composite materials (ECMs) is very difficult to be modelled due to the complex microcrack evolution. The microcrack evolution in highly particle-filled composite materials presents asymmetrical characteristics under tension–compression. In this paper, a dynamic mesoscale viscoelastic model taking into account the microcrack growth is developed to simulate the center splitting phenomenon of the Octahydro-1,3,5,7-Tetranitro-Tetrazocine-based ECM Brazilian disc under dynamic loadings by means of the Hopkinson bar test. The microcrack evolution modeling fully considers cracking nucleation, growth and coalescence. The Mohr-Coulomb failure criterion is used to drive the crack propagation. The dynamic cracking formation in the test is captured well. The details of the cracking are analyzed for different loading conditions. The cracking initiation orientation is modelled with different precrack conditions. In addition, the effect of the failure criterion on the dynamic cracking condition is determined. Further, the heterogeneous failure surfaces are considered and compared with the unique failure surface condition.

Numerical Simulation of Detonation and Brisance Performance of Aluminized HMX Using Density‐Adaptive SPH

AbstractThe prediction of the brisance performance of the aluminized explosive detonation, which involves complicated multiphase and multiphysics flow, is a difficult problem to tackle. In this paper, the detonation and brisance performance of aluminized HMX explosives is investigated using the density‐adaptive smoothed particle hydrodynamics methodology. The ignition and growth model was incorporated in smoothed particle hydrodynamics to calculate the pressure generated by the detonation of aluminized explosive, and the after‐burning combustion model was used to obtain the released energy caused by the combustion of aluminium particles. The elastic‐perfectly plastic model and Tillotson equation of state were employed to predict the dynamic behavior of metal material. In addition, the density‐adaptive method is employed to deal with the multiphase interface with a large density ratio. Firstly, the equations of state and constitutive models are verified by two benchmark cases, namely three‐dimensional detonation of PBX 9501 explosive and three‐dimensional aluminium‐aluminium high‐velocity impact. Subsequently, the detonation velocity and peak pressure of aluminized HMX with different mass fractions of aluminium powder are investigated. In the end, the interaction between the steel confiner and the detonation of aluminized explosive is conducted in order to study the brisance performance of aluminized explosive. The numerical results obtained from smoothed particle hydrodynamics are in good agreement with the experimental data, which shows that the detonation and the ballistic performance of the condensed explosive can be captured by density‐adaptive smoothed particle hydrodynamics very well.

A modified rate-dependent peridynamic model with rotation effect for dynamic mechanical behavior of ceramic materials

As a mathematical expression of the dynamic mechanical behavior, the constitutive model plays an indispensable role in numerical simulations of ceramic materials. The current bond-based peridynamic constitutive models can accurately describe the dynamic mechanical behavior of partial ceramic materials under impact loading, however, the predicted value of the Poisson’s ratio is 0.25, which is not true for most of the known ceramic materials. Herein, based on the existing bond-based peridynamic constitutive model, the current study utilizes the description of tangential bond force and considers the influence of bond force on rotation to accurately predict the Poisson’s ratio of different types of ceramic materials, e.g., SiC and B4C. Moreover, a novel and comprehensive damage assessment criterion during tensile–shear​ and compressive–shear is established, and the rate-dependent bond-based peridynamic constitutive model is improved, which realized the optimization of the original model. Then, the improved rate-dependent bond-based peridynamic constitutive model is employed to conduct several numerical experiments, including frontal impact, edge-on impact and uniaxial compression experiments. The simulation results are compared with the classical finite element model and experimental results, demonstrating the superiority of the optimized model in terms of accuracy and versatility. The optimized model describes the damage behavior of different ceramic materials and provides theoretical bases for future work in penetration behavior of ceramics.

Influence of Non-Linearity in Losses Estimation of Magnetic Components for DC-DC Converters

In this paper, the problem of estimating the core losses for inductive components is addressed. A novel methodology is applied to estimate the core losses of an inductor in a DC-DC converter in the time-domain. The methodology addresses both the non-linearity and dynamic behavior of the core magnetic material and the non-uniformity of the field distribution for the device geometry. The methodology is natively implemented using the LTSpice simulation environment and can be used to include an accurate behavioral model of the magnetic devices in a more complex lumped circuit. The methodology is compared against classic estimation techniques such as Steinmetz Equation and the improved Generalized Steinmetz Equation. The validation is performed on a practical DC-DC Buck converter, which was utilized to experimentally verify the results derived by a model suitable to estimate the inductor losses. Both simulation and experimental test confirm the accuracy of the proposed methodology. Thus, the proposed technique can be flexibly used both for direct core loss estimation and the realization of a subsystem able to simulate the realistic behavior of an inductor within a more complex lumped circuit.