Dynamic Response Of Materials Research Articles

Dynamic Mechanical Response and Fracture Properties of Rock-Like Materials with Parallel and Intersecting Flaws

Dynamic Mechanical Response and Fracture Properties of Rock-Like Materials with Parallel and Intersecting Flaws

Effect of impact spacing on the dynamic response of UHMWPE fiber composites under two-point high velocity impacts

The impact from multiple bullets leads to more severe damage to fiber composite laminates, and the dynamic response becomes more complex. However, current research has focused on studying the ballistic limit and single impact response of materials. In this study, an experimental method to investigate the dynamic response and damage modes of fiber composite materials under multi-point asynchronous impacts is proposed. The aim is to reveal the mechanisms behind the differences in ballistic limits and energy absorption of UHMWPE (Ultra-High Molecular Weight Polyethylene) fiber composite panels at different impact distances. Through CT scanning and DIC (Digital Image Correlation) techniques, the delamination area and dynamic response of the laminates were quantitatively analyzed. The results show that the ballistic limit of the second impact is increased by 3.05 % when the impact distance is 2.5 times the diameter of the bullet. The maximum difference of energy absorption compared to the first impact was only 3.7 % at an impact spacing of 5 times the diameter of the bullet, despite the interference in the damage region. From the perspective of energy absorption, the two impacts are independent. Multiple impact tests are critical for protective materials, and the results of this study provide important insights into UHMWPE fiber laminates in terms of multi-point impact.

Dynamic response and roughness control of surface materials on TC4 titanium alloy subjected to laser shock wave planishing

Abstract In this study, ABAQUS was used to predict the dynamic response of surface materials on TC4 titanium alloy during laser shock wave planishing (LSWP). The experiments were conducted to evaluate the simulations. The results indicate that during the initial stage of LSWP, the contact status between the contact foil and the micro-protrusion changes from the one-dimensional stress state to the one-dimensional strain state. This causes the high-amplitude tensile residual stress to converge at the center of the flattened micro-protrusion surface. When treating specimens with high surface roughness, the application of a thin contact foil can significantly lower the height of micro-protrusions and lift the bottom of micro-depressions. This improves the plastic flow of micro-protrusions and prevents the convergence of tensile residual stress. Using a thick contact foil can help extend the pressure pulse duration and prevent the overall surface profile subsidence when treating specimens with lower surface roughness. The outcomes of the experiment and the simulation agree rather well. Additionally, a thick contact foil can reduce the build-up of tensile residual stress by reducing the contact pressure.

Using graded density impactor to achieve quasi-isentropic loading with stress and strain-rate controlled

In gas gun experiments, a graded density impactor (GDI) is used to achieve quasi-isentropic loading. However, inconsistency between the designed and experimental loading profiles, mainly caused by by-products during preparation, limits the application of GDI for a long time. In this work, a kind of W/Ti GDI with advantages of a wide density range of 4.5–19.3 g/cm3 and high structural designability was designed and synthesized. Each of mid-layers of the W/Ti GDI was composed of W and Ti without the formation of an intermetallic compound, and had good parallelism and flatness. This provides a prerequisite for good agreement between the designed and experimental loading profiles. Due to the high designability of the GDI, quasi-isentropic loading with different stress-paths was achieved by controlling the structure of the GDI. Then, independently controlling peak stress and strain rates of loading was successfully achieved by changing the flyer velocity and the type of the W/Ti GDI. The W/Ti GDI has enormous application potential in studying the dynamic response of materials under quasi-isentropic loading with stress and strain rate controlled.

Controlling the motion of gravitational spinners and waves in chiral waveguides

In this paper we present a mathematical modelling framework for chiral phenomena associated with rotational motions, highlighting the combination of gyroscopic action with gravity. We discuss new ideas of controlling gravity-induced waves by a cluster of gyroscopic spinners. For an elementary gravitational spinner, the transient oscillations are accompanied by a full classification and examples, linked to natural phenomena observed in planetary motion. Applications are presented in the theory of chiral metamaterials, and of the dynamic response of such materials to external loads.

Effect of Hydrothermal Aging on Damping Properties in Sisal Mat-Reinforced Polyester Composites.

Hydrothermal aging is a matter of considerable concern for natural fiber-reinforced polymers; it can alter dimensional stability and induce microcracks and macro strain on the composite structure. This study applied a sorption kinetic model and examined the effects of water on the damping factor of sisal mat-reinforced polyester composites. The experimental data were fitted well using a Boltzmann sigmoid function, suggesting a promising first step toward kinetic water sorption modeling. Additionally, a damping test was carried out using the impulse excitation technique, highlighting the composite material's dynamic response under varying water absorption conditions. The result showed that damping exhibited sensitivity to water absorption, increasing significantly during the first 24 h of immersion in water, then remained steady over time, inferring a critical time interval. An empirical model proved satisfactory with the correlation coefficient for sorption rates and damping of sisal mat polymeric composites.

A Review of Numerical Simulation and Modeling in High Strain Rate Deformation Processes

Numerical simulation and modeling play a crucial role in understanding and predicting the behavior of materials subjected to high strain rate deformation processes. These processes involve rapid deformation and loading rates, typically encountered in scenarios such as impact events, explosive detonations, metal forming, and crash simulations. By employing advanced computational techniques, researchers and engineers can gain insights into complex material behavior under extreme loading conditions. This paper provides an overview of numerical simulation and modeling approaches used in studying high-strain rate deformation processes. It discusses the challenges associated with capturing dynamic material response, the development of constitutive models, and the use of finite element analysis and computational fluid dynamics. The paper also highlights the importance of material characterization, model validation, and sensitivity analysis for accurate and reliable simulations. Additionally, it explores the application of numerical simulations in optimizing material properties, designing protective structures, and improving the performance of impact-resistant materials. Overall, this review paper emphasizes the significance of numerical simulation and modeling as powerful tools for advancing the understanding and design of high-strain rate deformation processes.

Dynamic response of composite materials subjected to low velocity impacts in water: A numerical study

The damage tolerant design of marine composite structures for impacts is dependent on empirical data to ensure continuing seaworthiness. Impact studies on composite laminates are typically performed according to ASTM D7136 which was originally developed by the aerospace industry. The marine operating environment, however, is vastly different. Impact characterisation and damage prediction of underwater composite structures is hindered by the limited understanding on the effects of fluid-structure interaction of a surrounding water medium with the composite structure and impactor. A coupled Eulerian-Lagrangian (CEL) numerical model is presented in this work with the aim of advancing fundamental understanding of the effects of a fluid on the transient dynamic response of composite plates subjected to foreign body impact. The added mass effect of the water increased the peak impact force while reducing the free vibration frequency and peak displacement. The virtual added mass factor also reduced significantly with increasing laminate thickness. This work will pave the way in improving the damage tolerant design of underwater composite structures as will computationally efficient methods of simulating such events.

Experimental validation of multiferroic antennas in GHz frequency range

Various mechanical antennas have emerged to overcome the inherently narrower bandwidth and degraded efficiency in electrically small antennas. Among them, multiferroic antennas are expected to realize high-frequency applications and maintain their performance, even with significantly reduced sizes. However, experimental proof of such radiation from multiferroic or magnetoelectric coupling in the GHz range deserves further examination. This paper designs and fabricates a series of multiferroic antenna samples with mechanical resonances at around 3.5 and 6 GHz, and their radiation transmissions are tested at these resonances. Nickel, a magnetoelastic material, consistently exhibits magnetically induced radiation at both resonances. However, magnetic material consisting of Permalloy (Ni78Fe22), known for its much weaker magnetoelastic effects, still shows similar transmission behaviors at 3.67 GHz and enhanced power absorption at 6.42 GHz. Our results indicate that the dynamic response of magnetoelastic materials in the GHz band should differ from their response at the MHz and below bands. This evidence calls for further investigations of the source of magnetoelectric radiation.

Dynamic response of surface materials and topography control on TC4 titanium alloy subjected to laser shock imprinting

Laser shock imprinting (LSI) can improve the fatigue performance of workpieces by controlling the surface topography. In this paper, TC4 titanium alloy was treated with LSI. The dynamic response of the surface material at the imprinted area was investigated with finite element modeling (FEM), and the simulated results were evaluated by experiments. The results show that a special shape with the convex on both sides and concave on the center is formed, which may not be beneficial to the fatigue performance of the workpiece. Increasing the shock wave pressure will aggravate the residual stress difference (the compressive residual stress is at the non-direct contact area and the tensile residual stress is at the direct contact area) and this problem can be effectively solved by multiple impacts with a thicker contact foil. Multiple impacts with thin contact foils will cause irregular deformation (tilting) of micro-protrusions, whereas utilizing thicker contact foils for multiple impacts can flatten the micro-protrusion surface and prevent tilting. In the overlapping LSI experiment, with the increasing of the contact foil thickness (CFT), the height of the micro-protrusion decreases, and the “laser spot boundary effect” (LSBE) is effectively alleviated, which decreases the surface roughness.

Characterization of dynamic confinement response of potting materials at different strain rates and temperatures

A Kolsky compression bar was modified with an instrumented confining tube for characterizing dynamic confinement response of materials at various strain rates. A thin film polyvinylidene fluoride (PVDF) force transducer was designed and integrated to the confining tube for direct in-situ measurement of confining pressure when the specimen is subjected to dynamic axial compressive load such that the mean stress-volumetric strain response of the specimen material is able to be determined. An environmental chamber was also implemented to the Kolsky compression bar for characterizing dynamic confinement response of materials at different environmental temperatures. After careful calibration of the instrumental confining tube, five different potting materials (EPON 828, EPON 828 filled with glass microballoons (GMBs), Sylgard 184, Sylgard 184 filled with GMBs, and expanded polystyrene (EPS) foam) were characterized with the modified Kolsky compression bar at different strain rates and environment temperatures. The effects of strain rate and temperature on the mean stress-volumetric strain response were determined for all five potting materials. Experimental uncertainties were also presented.

Inertial effect on dynamic hardness and apparent strain-rate sensitivity of ductile materials

Indentation is a simple and one of the oldest small-scale test methods for characterizing the mechanical response of materials. Recently, there has been a growing interest in dynamic indentation due to its potential to characterize the mechanical response of small volume of materials at high strain-rates. Herein, we focus on understanding the synergistic effects of materials’ inherent strain-rate sensitivity and inertia on the scaling of dynamic hardness with indentation strain-rate. Specifically, we analyze the dynamic indentation response of ductile materials over a wide range of indentation velocities, utilizing both finite element calculations and an analytical cavity expansion model. The materials are assumed to follow isotropic elastic–viscoplastic constitutive relations, with the viscoplastic part described by either an overstress or a simple power-law model. Our results show that below a critical indentation strain-rate, the scaling of dynamic hardness with indentation strain-rate is the same as the viscoplastic constitutive description. Therefore, at these strain-rates, dynamic hardness can effectively characterize a material’s strain-rate sensitivity, provided its viscoplastic constitutive description is known beforehand. However, above the critical indentation strain-rate, the dynamic hardness increases rapidly with indentation strain-rate. This phenomenon indicates an apparent strain-rate sensitivity that exceeds the expected response of the viscoplastic constitutive description. Moreover, above the critical indentation strain-rate, the indentation depth acts as a natural length-scale, with higher hardness observed at greater depths due to increased inertial effects. In other words, above the critical indentation strain-rate, dynamic hardness cannot be taken as an intrinsic material property.

A hybrid polymer–water peridynamics model for ballistic penetration damage of soft materials

Numerically understanding the dynamic response of soft materials subject to high-speed penetration is crucial for advancing transdermal delivery technologies and analyzing injuries related to ballistics. Due to the complexity in material correspondence models and the difficulty of simulating high-speed impact damage problems using traditional mesh-based numerical techniques, precisely capturing mechanical behaviors of soft materials following ballistic penetration remains challenging. This work proposes a novel hybrid polymer–water model within the peridynamics (PD) framework to accurately clarify the complex damage process of soft materials subject to ballistic penetration. We propose the hybrid interactions comprising of water–water, polymer–polymer, and polymer–water interactions, which embodies the subscale nature of various components and captures the constitutive features of soft materials. A novel decomposition scheme for the deformation gradient is proposed to overcome the limitations in traditional non-ordinary state-based PD where only homogeneous particles are involved in the influence domain, extending the scope of PD theory to mixed material systems. The superior effectiveness and applicability of proposed model are demonstrated through compression, shear, fracture tests. Regarding to the case of high-velocity penetration, both motion profiles of projectile and pressure profiles of gelatin after penetration can be captured in line with physics awareness. The proposed model offers a reasonable and practical representation of soft material from the perspective of a particle-based approach and enhances the potential applications of PD framework for simulating large deformation and dynamic response of soft materials.

Uniaxial dynamic behavior of foam glass aggregate under oedometric (fully side restrained) condition at different compaction ratios

Foam glass aggregate (FGA) is considered as a lightweight and thermal insulation material. It has a wide granular size distribution nature that can influence the material's dynamic response when subjected to moving loads. Therefore, it is crucial to investigate the impact of different compaction ratios on the material's dynamic behavior. This study focused on examining the effects of varying compaction ratios (10%, 20%, 30%, and 40%) on dynamic parameters such as resilient stiffness (Mr) and accumulated plastic strains (ɛacc) of FGA. Uniaxial deviatoric stresses were applied to the material samples in a series to assess their influence on the material's behavior over multiple cycles. The results revealed the significant influence of increasing the compaction ratio to 40% on the material's behavior. At this compaction ratio, the ɛacc decreased to approximately 71%, 69%, and 86% for deviatoric stresses of 25 kPa, 100 kPa, and 200 kPa, respectively, after subjecting the material to 40,000 cycles. The increase in recoverable strains resulting from the material's fragile property under higher compaction energy led to a decrease in the Mr values of FGA samples as the compaction ratios increased. The lower boundary of Mr values for FGA ranged from 102 MPa to 189 MPa, while the upper boundary ranged from 150 MPa to 219 MPa under the selected deviatoric stresses. Although the interpretation of the shakedown criterion limitations yielded varying ranges for the colocation of FGA samples, it was found that FGA samples compacted at 40% exhibited robust characteristics suitable for constructing road embankments. This can be beneficial for infrastructure applications due to their excellent lightweight and thermal insulation properties.

Fluid–solid coupled simulation of hypervelocity impact and plasma formation

Previous theoretical and computational studies on hypervelocity impact have mainly focused on the dynamic response of the solid materials that constitute the projectile and the target, while the surrounding environment is often assumed to be a vacuum. In this paper, we consider impact events that occur in a fluid (e.g., gas) medium, and present a computational model that includes the dynamics, thermodynamics, and ionization of the surrounding fluid material. The model couples the compressible Navier–Stokes equations with the Saha equations to predict the onset and extent of ionization in the surrounding fluid. An extended level set method with two signed distance functions is employed to track the three material interfaces between the projectile, the target, and the ambient fluid. This method accommodates the large deformation, contact, and separation of the interfaces, while avoiding spurious overlapping of different material subdomains. The advective fluxes across material interfaces are computed by constructing and solving bimaterial Riemann problems, thereby taking into account the discontinuities in both state variables (e.g., density) and thermodynamic relations. The computational model is first verified for an infinite ideal plasma and a one-dimensional three-material impact problem. Next, the model is employed to analyze the impact of a tantalum rod projectile onto a soda lime glass (SLG) target in an argon gas environment. In different analyses, the impact velocity is varied between 3 and 6km/s, and the radius of the projectile is varied between 2.5 and 10mm. Each analysis starts with a steady-state fluid dynamics simulation that generates the shock-dominated hypersonic flow around the projectile. This flow field is then used as an initial condition to start the fluid–solid coupled impact simulation. The predicted maximum temperature and pressure within the SLG target agree reasonably well with published experimental data for a similar material (fused quartz). Within the ambient gas, the impact-generated shock wave is found to be stronger than the initial bow shock in front of the projectile. Behind this shock wave, a region of high pressure and temperature forms in the early stage of the impact, mainly due to the hypersonic compression of the fluid between the projectile and the target. The temperature within this region is significantly higher than the peak temperature in the solid materials. For impact velocities higher than 4km/s, ionization is predicted. This finding indicates that the ambient gas may be a nontrivial contributor to the plasma formed in terrestrial and atmospheric hypervelocity impact events.

Selected Papers from the International Symposium on Dynamic Response and Failure of Composite Materials, Draf2022

Selected Papers from the International Symposium on Dynamic Response and Failure of Composite Materials, Draf2022

Dynamic mechanical response and fracture mechanism of rock-like materials with concealed structural planes of different filling thicknesses

Structural planes are the primary variables determining the stability of rock masses. Numerous non-penetrating structural planes exist in nature and are concealed inside the slopes or underground rock formations. The concealed structural planes (CSP) pose a possible hazard to the construction safety of rock mass engineering, particularly for the rock mass subjected to dynamic load. Using rock-like materials, intact specimens and specimens with CSP of varying filling thicknesses are constructed in order to examine the dynamic mechanical response and fracture mechanism of rock masses with CSP. Single impact experiments and cyclic impact experiments are carried out at various speeds using the Split Hopkinson Pressure Bar experimental system (SHPB). The results demonstrate that the specimens' peak stress is negatively correlated with the filling thickness, and that as the reflection coefficient increases and the transmission coefficient decreases, the filling thickness increases. Also, the energy dissipation rate of the specimens is positively correlated with the increase in thickness of filling at impact velocities of 3.7 m/s and 4.5 m/s, with the rate showing an increasing trend followed by a decreasing trend at impact velocities of 5.5 m/s and 6.5 m/s. The main surface and internal cracks of specimens can be categorized into seven types, which are combined into three failure modes. As the filling thickness increases, the failure mode changes from transverse tensile failure to combined tensile and shear failure to bi-directional tensile failure under combined transverse and axial tensile action. The crack propagation behavior and the fracture mechanism from the interior to the exterior of the CSP specimens are investigated using the impact test results, finite element model, and mechanical theory analysis, which can be used as a reference to reveal the destabilization process of the rock mass with CSP.

Temperature dependence of dynamic response of liquid crystal materials

Most properties of liquid crystal (LC) materials will change with the change of temperature, which makes the performance of liquid crystal display (LCD) and other devices change. However, at low temperature, the properties of LC will mutate with the decrease of temperature, which directly leads to the defects of LC devices. This paper makes use of the developed homemade temperature control device to realize the construction of high temperature to low temperature environment, using precision LCR meter (Agilent E4980A) and self-built optical path, combined with LC cell capacitance model and dual-cell model, the dynamic response properties of LC materials with temperature change law was explored. The results show that the decay time τ d of the LC with positive dielectric anisotropy increases from 12.04 ms to 159.7 ms, and the rotational viscosity coefficient γ 1 increases exponentially from 12.04 mPa·s to 1582.45 mPa·s. While τ d of the LC with negative dielectric anisotropy increases from 13.10 ms to 408.1 ms, γ 1 also increases exponentially from 162.73 mPa·s to 7903.69 mPa·s. The conclusions presented in this paper provide some guidance for the improvement of low temperature properties of LC.

Suitability Analysis of Machine Learning Algorithms for Crack Growth Prediction Based on Dynamic Response Data.

Machine learning has the potential to enhance damage detection and prediction in materials science. Machine learning also has the ability to produce highly reliable and accurate representations, which can improve the detection and prediction of damage compared to the traditional knowledge-based approaches. These approaches can be used for a wide range of applications, including material design; predicting material properties; identifying hidden relationships; and classifying microstructures, defects, and damage. However, researchers must carefully consider the appropriateness of various machine learning algorithms, based on the available data, material being studied, and desired knowledge outcomes. In addition, the interpretability of certain machine learning models can be a limitation in materials science, as it may be difficult to understand the reasoning behind predictions. This paper aims to make novel contributions to the field of material engineering by analyzing the compatibility of dynamic response data from various material structures with prominent machine learning approaches. The purpose of this is to help researchers choose models that are both effective and understandable, while also enhancing their understanding of the model's predictions. To achieve this, this paper analyzed the requirements and characteristics of commonly used machine learning algorithms for crack propagation in materials. This analysis assisted the authors in selecting machine learning algorithms (K nearest neighbor, Ridge, and Lasso regression) to evaluate the dynamic response of aluminum and ABS materials, using experimental data from previous studies to train the models. The results showed that natural frequency was the most significant predictor for ABS material, while temperature, natural frequency, and amplitude were the most important predictors for aluminum. Crack location along samples had no significant impact on either material. Future work could involve applying the discussed techniques to a wider range of materials under dynamic loading conditions.

A WEIGHTED POWER-FORM FORMULATION FOR THE FRACTAL WARNER–GENT VISCOHYPERLASTIC MODEL

This paper elucidates how the two-scale fractal dimension transform, and a transformation method can be applied to replace the Warner–Gent equation that models the fractal dynamic response of porous viscohyperelastic materials with an equivalent power-form equation. Furthermore, this research work elucidates the advantages of modeling viscohyperlastic materials using the fractal Warner–Gent’s model since the values of the fractal dimension parameter unveil how the global molecular structure of viscohyperelastic materials varies as a function of the vibration frequency wavelength. Compared to the original one, the accuracy attained from the Warner–Gent power-form equivalent equation is examined by plotting the frequency–amplitude and time–amplitude curves obtained from the corresponding numerical integration solutions. It is found that both numerical integration solutions agree well since the root-mean-square-error (RMSE) values remain small.