Increasing Impact Energy Research Articles

An improved nonlinear ultrasonic technique for detecting and monitoring impact induced damage in composite plates

An improved technique for sensing damage initiation and progression in thermoplastic resin composite plate specimens is presented in this study. The composite plate specimens are investigated by using a nonlinear ultrasonic (NLU) technique called Sideband Peak Count Index or SPC-I. The technique presented in this paper is an improvement from the previous SPC-I technique. This improved technique provides more reliable and consistent results and can monitor the damage progression over a wide range. In this paper the narrow band SPC-I technique is introduced to replace the conventional wide band SPC-I technique. The method implemented here is improved in three ways. First and foremost the narrow band SPC-I technique is introduced. Secondly, the non-permanently adhered gel coupled Lead-Zirconate-Titanate (PZT) transducers are used to reduce inconsistency in transducer adhesion and manufacturing. Lastly, higher sampling rate equipment is used for better signal resolution and peak counting. The experiments are performed on 4 sets of composite plate specimens fabricated using two composite fiber materials (Glass and Basalt) that have increasing levels of damage. The composite plate specimens were damaged by a falling weight impact machine with increasing impact energy (0 J, 10 J, 20 J and 30 J). The composite plate specimens were examined by propagating a narrow band chirp signal through the specimens using gel coupled transducers in a transmission mode setup. The received signals were recorded and analyzed using the NLU SPC-I technique. The modified SPC-I technique proposed in this paper can reliably and consistently detect both initiation and progression of damage in the composite plate specimens.

Experimental and numerical study on the dynamic response of steel-reinforced concrete composite members under lateral impact

This paper investigates the dynamic response of steel-reinforced concrete (SRC) composite members under lateral impact using experimental and numerical studies. A total of 11 specimens composed of structural steel encased in reinforced concrete were tested under drop hammer impacts. The dynamic responses of SRC members including damage observations, impact force, and mid-span displacement were obtained and analyzed with emphasis on the effect of impact velocity, boundary condition, and axial load. It was found that the specimens failed in a shear–flexural response and impact velocity played a significant role in determining the dynamic response of SRC members. It was also found that the amount of residual displacement was linearly proportioned to the displacement ductility. Followed by the experimental study, a finite element analysis (FEA) model was established and verified based on the test results. The distributions of impact energy among different components are obtained using FEA models. It was found that the energy dissipation was dominated by concrete rather than structural steel or reinforcement. However, with the increase in impact energy, the percentage of energy dissipation in the structural steel increases, meaning that encasing structural steel in concrete elements is an effective method to improve impact resistance.

Mechanisms and predictive models for the erosion process of super hard and brittle materials by a vibration-assisted slurry jet

The mechanisms under which vibration assistance improves the material removal process in slurry jet machining of super hard and brittle materials are seminally studied based on the erosive theories, viscous flow principles and particle dynamics under the effect of vibration. It is shown that brittle erosion by the impact of jet particles is dominant in the material removal, followed by a secondary erosive process driven by the vortices induced on a viscous crossflow. The vibration applied to the work surface perturbates the crossflow and promotes the forces to accelerate the particles on both the impact zone and within the crossflow layer, which allows particles to overcome the viscous restriction and move more freely in the suspending liquid. The number of the particles accumulated in the impact zone therefore is reduced or, if at the optimal condition, is eliminated, making a more efficient transfer of the impact energy to the target material. From this new understanding, process models are developed which can be used to guide the selection of process parameters for micro-machining such as hole piercing. The models are then assessed on the SiC polymorphs, 4H-SiC, with relatively softer SiC abrasives and shown to be able to predict the time required for creating a desired cavity geometry and the optimal vibration amplitude for an increased impact energy transfer efficiency.

Low-velocity impact response of Kevlar/epoxy aluminum laminates

In this experimental study, the low-velocity impact behavior of aluminum–Kevlar laminates (ARALL) was investigated. ARALL composites were prepared in two different configurations as aluminum–Kevlar–aluminum (AKA) and Kevlar–aluminum–Kevlar (KAK). The aluminum alloy used in the preparation of the samples was supplied as 5754 series 2 mm thick plates. Kevlar fabrics were supplied in a weight of 300 g/m2 and in twill weave type. Laminated composites with Kevlar twill fabrics were made through hand lay-up followed by the compression-molding process. [K]4 composite laminates were obtained by curing Kevlar/epoxy laminates under 100°C and 7 bar pressure for 180 min. Then, samples of size 100 × 100 mm were cut from the plates with a water jet. The cut specimens were bound together with two-component adhesive. An Instron Dynatup 9250 HV impact test device was used for impact tests. The energy profiling method was used, which expresses the impact energy and the corresponding absorbed energy. The increasing impact energy was performed on the two configurations of ARALL composites until perforation occurred. The perforation threshold of AKA samples was approximately 70% higher than that of KAK samples.

EXPERIMENTAL AND ANALYTICAL STUDY ON THE IMPACT BEHAVIOR OF STEEL–CONCRETE COMPOSITE SLAB

Concrete structures have been widely used for many years to resist impact loads. Steel–concrete composite structures may be considered efficient structures in the emerging modern construction field. Hence, the main objective of this research was to study the impact behavior of steel concrete composite slabs with different shear connectors and compare them with conventional slabs. Seven specimens of dimensions 500 × 500 × 50 mm were cast, which included plain cement concrete slabs, two reinforced cement concrete slabs with steel mesh and steel rebars as reinforcement, and four steel-concrete composite slabs with four different shear connectors: stud, tee, angle, and channel connectors. The composite action was achieved using a steel decking sheet welded with connectors on which the concrete layer was poured at the top. The test setup was fabricated with slots provided for specimens with simply supported end conditions and a mild steel drop weight. The specimens were impacted at the center of the span by dropping a steel mass from a free fall height of 1 m. The number of blows corresponding to the initial cracking and ultimate failure stages was recorded. The parameters that were used to compare the specimens were the impact energy absorbed, crack pattern, crack width, and increase in impact energy from the first blow to the last blow. The experimental results were very close to the analytical results obtained using ANSYS. The experimental and analytical results showed that the composite slabs with channel connectors performed better than the others, and it was proven that the composite slabs performed better under impact loading than conventional slabs.

Effect of Uniaxial Fatigue Aging and Fabric Orientation on Low Impact Velocity Response of Glass Fibers/Elium Acrylic Composite Laminates.

Impact resistance is one of the most critical features of composite structures, and therefore, its examination for a new material has a fundamental importance. This paper is devoted to the characterization of the fully recyclable thermoplastic ELIUM acrylic resin reinforced by glass fabric woven, which belongs to a new category of materials requiring advanced testing before their application in responsible elements of engineering structures. Its high strength, low weight as well as low production cost give excellent opportunities for its wide application in the automotive industry as a replacement of the thermoset-based laminates. The study presents an experimental work concerning the effect of damage due to low and high cyclic fatigue aging of two groups of specimens, first with the woven fabric orientations of [0°/90°]4 and secondly with [45°/45°]4, on the low impact velocity properties. The impact resistance was measured in terms of load peak, absorbed energy, penetration threshold and damage analysis. The low velocity impact results indicate that the uniaxial cyclic loading (fatigue aging) of the material leads to the reduction of impact resistance, especially at the high impact energy levels. Scanning Electron Microscopy (SEM) and Computed Tomography (CT) scan observations reveal that the damage area grows with the increase of both strain amplitude and impact energy.

Modelling the sputtering and reflection from a beryllium surface: atomistic analysis

Sputtering from plasma-facing surfaces upon particle impact can limit the lifetime of components in fusion devices, especially in the diverter region. Atomistic simulations of the processes associated with plasma–wall interactions allow for a detailed analysis of sputtering, reflection and adsorption. Most former works of beryllium sputtering by hydrogen isotopes were aimed mostly on the sputtering yield. We investigate the influence of impact energy and angle on sputtering, and analyze these quantities also for the outgoing particle. We model the sputtering by non-cumulative molecular dynamics simulations with a large number of trajectories for the various parameters. The underlying forces and energies are obtained from high-dimensional neural networks fitted to density functional calculations. We find a good agreement with the previously reported sputtering yields for perpendicular impact and a qualitative accordance with experimental data. In detail, the sputtering yield increases with increasing impact energy for angles of incidence larger than 45° with respect to the surface normal, while smaller angles show a maximal yield up to 100 eV. In cases where D reflection rather than sputtering occurs, a similar pattern is found for all angles, with the maximal reflection rate at 80°.

Experimental and analytical assessment of the hypervelocity impact damage of GLAss fiber REinforced aluminum

This article addresses the response of GLAss fiber REinforced aluminum to hypervelocity impacts of micrometeoroid analogs at impact velocities of 7 km/s and beyond. In relation, the damage modes of different GLAss fiber REinforced aluminum configurations have been exemplified. The GLAss fiber REinforced aluminum configurations comprised six to twelve variably thick aluminum layers and up to four plies of glass fiber reinforced epoxy per composite laminate. Hypervelocity impact experiments have been conducted with the help of a two-stage light-gas gun, wherein aluminum- and stainless steel projectiles were launched at velocities up to 7.15 km/s. Visual inspection of the damage area suggested the dissipation of impact energy in elastic-plastic deformation, petalling, delamination, debonding, tensile failure of fibers, and pyrolysis of epoxy. A prevailing damage mode was not apparent albeit. The quasi-isotropic ply orientation of S2-glass/FM94-epoxy laminates promoted the interference of shock- and rarefaction waves and suppressed the damage area of GLAss fiber REinforced aluminum. To discriminate between the impact performance of different GLAss fiber REinforced aluminum configurations, the energy dissipated in different damage modes of GLAss fiber REinforced aluminum has been assessed quantitatively. In terms of normalized energy, the cross-ply GLAss fiber REinforced aluminum dissipated higher energy in petal formation than in other primary damage modes. The normalized petalling energy was found to decline with the increase of impact energy. The outcomes of this study will help to optimize the GLAss fiber REinforced aluminum laminate, which will be employed as a bumper shield to prevent the fatal damage and the unzipping of a spacecraft pressure bulkhead.

Low-velocity impact behaviors of glass fiber-reinforced polymer laminates embedded with shape memory alloy

Shape memory alloy wires embedded glass fiber-reinforced polymer (SMA-GFRP) laminates have great potential in engineering applications. In this paper, low-velocity impact behaviors of SMA-GFRP laminates are investigated under different initial impact energies. Firstly, tensile tests are conducted on a single SMA wire and SMA-GFRP laminates to obtain their mechanical parameters. Then, finite element models are established to describe the mechanical behaviors of SMA-GFRP laminates. Finally, experiments and simulations are carried out to explore the low-velocity impact behaviors and damage mechanisms of SMA-GFRP laminates. The results show that, due to their excellent superelastic deformation and shape recovery ability, SMA wires can improve the damage tolerance and impact resistance of GFRP laminates. The damage patterns and mechanisms of SMA-GFRP laminates vary with the increase of initial impact energy. Under low and medium initial impact energies, deformation can be mostly recovered, while under high impact energy, laminates are almost penetrated and deformation cannot be recovered because of breakage of SMA wires. The damage area of laminates increases first and then decreases as the increase of impact energy. The findings provide a guidance for design and evaluation of SMA-GFRP laminates with low-velocity impact resistance.

Assessment of Impact Energy, Wear Behavior, Thermal Resistance and Water Absorption Properties of Hybrid Bagasse Fiber/CaCO3 Reinforced Polypropylene Composites

Abstract To harness the inherent advantages of both synthetic and natural reinforcements, mercerized bagasse fibers (BF) and particulate calcium carbonate (CaCO3) were utilized as a complementing reinforcement for the fabrication of bagasse fiber/calcium carbonate (BF/CaCO3) polypropylene composites. Two sets of composites were produced – one with mercerized BF/CaCO3 and the other with unmercerized BF/ CaCO3. The effect of reinforcement loading on the impact energy, wear behavior, thermal resistance and water absorption properties of the composites were studied. Results showed that the mercerized BF/CaCO3 hybrid reinforced polypropylene composites exhibited significant increase in impact energy and offered better resistance to weight loss during wear test. Similarly, the thermal resistance of the mercerized composites was higher than their corresponding unmercerized composites. Additionally, water absorption in mercerized composites was highly resisted than in unmercerized samples. These results indicated that mercerization treatment and reinforcement hybridization improved the impact energy, wear, thermal resistance and water ingress resistance of hybrid fiber/ particulate reinforced polypropylene composites.

In-plane quasi-static and out-of-plane dynamic behavior of nanofiber interleaved glass/epoxy composites and finite element simulation

Eight-ply glass/epoxy composites interleaved by electrospun Polysulfone (PSF) nanofibers were manufactured by vacuum-assisted hand lay-up method. The effect of nanofibrous interlaminar layers on the mechanical performance of laminated composites was investigated under both in-plane quasi-static and out-of-plane low-velocity impact (LVI) test conditions. Low-velocity impact responses of reference and nanofiber interleaved composite laminates were modeled by LS-Dyna finite element (FE) code for numerical simulations. The results of the quasi-static mechanical tests show that PSF nanofiber interleaving increases the tensile and compressive strength by 10.5% and 25.5%, respectively. PSF nanofibers played an important role in improving the impact damage resistance of composite laminates with increasing impact energy levels. The low-velocity impact tests results indicated that PSF nanofibers decreased the fiber breakage area at 20 J and 30 J energy levels by about 26% and 28%, respectively. Besides, PSF nanofiber interleaving improved damage threshold load values by 4.8%, 15.2%, and 23% at 10 J, 20 J, and 30 J energy levels, respectively. Experimental and FE simulation results were comparatively presented in terms of force–time, force–deflection, and energy-time curves. A good agreement was achieved between experimental and simulation results.

Effect of Tempering Condition on Microstructure, Mechanical Properties and Precipitates in AISI H13 Steel

The mechanical properties and microstructures, in particular precipitation in the AISI H13 steel, quenched and tempered from 773 K to 973 K for different periods, were systematically investigated by scanning electron microscopy, electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). The results indicate a sharp decrease in hardness at temperatures > 863 K during the first 2 h of tempering. Ultimate tensile strength and yield strength decrease, while elongation and impact energy increase with the increase of tempering temperature. The volume fraction of static recrystallization increases from the EBSD result. Regarding precipitates, the coarsening rate of M23C6 was much faster than that of MC and M2C and was verified by using the Ostwald ripening model. In addition, kinetic modeling of the softening of H13 during tempering from 863 K to 973 K was performed. This model was also applied successfully to predict the hardness of double-tempered H13 steel samples.

Effect of Rolling and Heat Treatment Process Tempering on the Microstructure and Mechanical Performance of Cr–Ni–Mo High‐Strength Ship Steel

The effects of rolling process and tempering temperature on microstructure and mechanical performance of experimental steel are studied. The results show that the yield ratio and elongation of the experimental steel are lower under noncontrolled rolling; under off‐line tempering after controlled rolling, the tensile and yield strength decrease slightly with the increase in quenching temperature, the yield ratio decreases and the elongation increases; under the condition of controlled rolling, ultrafast cooling (UFC), and off‐line tempering, the microstructure is fine martensite lath and a large number of fine precipitates, the steel has the highest strength and elongation. With the increase in tempering temperature, the tensile strength of the experimental steel decreases gradually, the elongation increases monotonously, the yield ratio and impact energy increase first, and then decrease. After comparison and analysis, it is found that the best performance can be obtained by direct online UFC after controlled rolling, and then tempering at 630 °C, that is, tensile strength 908 MPa, yield strength 863 MPa, yield ratio 0.95, elongation 21.41%, and impact energy 94 J at −100 °C.

Effect Analysis of Laser Shock Peening on Nickel-based Alloys by Laser Solid Forming

Laser solid forming has the advantages of rapid and complex shapes, but the stress caused by high temperature gradient changes during the forming process can easily lead to the deformation of parts and insufficient mechanical properties. This article focuses on laser solid forming GH4169 superalloy for laser shock peening. The influence of process parameters on surface morphology and toughness were analyzed. The mechanism of laser shock peening was analyzed. The results show: As the number of impacts increases, the depth gradually increases, and the increasing trend slows down. When the energy is small, the surface change cannot be observed. After 5J, as the energy increases, the depth of the pit increases. As the impact energy increases, the toughness of the material first increases and then decreases. The toughness of the material is the highest at 6J, reaching 65J/cm2. The action mechanism of laser shock peening has three main methods, one is fine-grain strengthening, the other is twinning and work hardening, and the third is stress strengthening.

Experimental and Numerical Study of Low-Velocity Impact and Tensile after Impact for CFRP Laminates Single-Lap Joints Adhesively Bonded Structure.

To investigate the mechanical behavior of the single-lap joints (SLJs) adhesively bonded structure of carbon fiber reinforced polymer (CFRP) laminates under the low-velocity impact (LVI) and tensile-after impact (TAI), tests and simulations were carried out. A finite element model (FEM) was established based on the cohesive zone model (CZM) and Hashin criterion to predict the damage evolution process of adhesive film, intra- and inter-laminar of the SLJs of CFRP laminates, and its effectiveness was verified by experiments. Moreover, three different overlap lengths (20 mm, 30 mm, and 40 mm) and four different impact energies (Intact joint, 10 J, 20 J, and 30 J) are considered in the present study. Finally, the effects of different impact energies and overlap lengths on the residual strength of SLJs after impact were discussed. The results divulged that numerical results of impact and TAI processes of SLJs were in good agreement with experiment results. During the impact process, the damage of the laminates was primarily fiber and matrix tensile damage, whereas the adhesive film was damaged cohesively; the areas of damage increased with the increase of impact energy, and the normal stress of the adhesive film expanded from the edge to the middle region with the increase of impact force. The influence of LVI on SLJs adhesively bonded structures was very significant, and it is not effective to obtain a higher impact resistance by increasing the overlap length. For the tensile process, the failure mode of TAI of the SLJs was interface failure, the surplus strength of the SLJs gradually decreased with the increase of the impact energy because of the smaller overlap length, the overlap length more than 30 mm, and the low energy impact has almost no effect on the residual strength of the SLJs.

Towards understanding performance enhancing mechanism of micro-holes on K9 glasses using ultrasonic vibration-assisted abrasive slurry jet

Abrasive slurry jet (ASJ) machining technology is highly desirable to meet the increasing demand for machining of micro-structures on difficult-to-machine materials, like ceramics and glasses. However, by employing the relatively low pressure ASJ with small abrasive particles usually results in W-shaped bottom surface of micro-hole while to use the relatively large abrasive particles involved in ASJ could eliminate the W-shaped profile but the bottom surface quality seems not to be good. In this paper, the ultrasonic vibration-assisted abrasive slurry jet machining of micro-holes on K9 glasses was proposed to enhance the machining performance. It is found that the effect of ultrasonic vibration on the particle trajectories and the resultant particle dynamic impact process in the stagnation zone significantly contributes to the performance enhancement of micro-hole, including the material removal rate and bottom surface morphology, rather than its effect on inducing the additional brittle erosion due to the less increase of particle impact energy. Further, the bottom surface quality has also found to be enhanced because the periodical vibration of the workpiece would affect the fluid streamlines in the stagnation where it not only enables more particles to participate the material removal process but also drives more after-impact particles to roll over and smooth the machined surface due to the viscous flow induced secondary or multiple particle impacts, and hence, resulting in a smoother surface.

Mathematical modeling of the percussion mechanism with a single impact energy increase

The present study aims to develop a mathematical model of the percussion mechanism with a single impact energy increase and determine the influence of the spring stiffness and the ratio of inertial and projectile masses on the main parameters of the destruction process. The method of mathematical modeling of the destruction process was applied. A mathematical model of the percussion mechanism with a single impact energy increase and a diagram for its solution in Matlab-Simulink have been developed; dependences of the main parameters of the desctrution process on the spring stiffness and the ratio of inertial and projectile masses have been obtained. The mathematical model of the percussion mechanism makes it possible to increase the energy of a single impact by three-five times in comparison with a freely falling projectile. The reactive component is not transmitted to the base machine.

Numerical Study on Dynamic Performance of End-anchored Rockbolt under Impact Loading

Abstract The numerical modelling for dynamic impact testing of end-anchored rockbolt is established in this paper. The dynamic response of rockbolt under impact loading condition is investigated considering the effects of different impact energy levels, anchoring length, bolt diameter, and material type. The results show that the stress characteristics of the anchoring section in end-anchored rockbolt could be divided into three stages with the impact time: impact initial stage, impact middle stage and impact final stage. The elongation of the rockbolt increases by about 30 mm for every 5kJ increase in impact energy. When the impact energy level increases, the energy absorption rate and maximum plastic strain both increase significantly. The impact energy is mainly dissipated by the plastic deformation of the free section and debonding section of end-anchored rockbolt. The free section plays a buffer role through its elastic deformation when the rockbolt is subjected to impact loading. It is remarkable that the energy absorption rate and anti-impact performance of the end-anchored rockbolt can be improved by increasing the bolt diameter and the bolt material strength.

Particle Impact Energy Variation with the Size and Number of Particles in a Planetary Ball Mill

To investigate the mechanical energy applying to the particles in a grinding process using a planetary ball mill, the impact energy of particles was estimated by simulating the behavior of the particles and grinding balls using the discrete element method (DEM) under different conditions of the size and number of particles, corresponding to their variations during milling. As the impact energy contributing to the particle breakage, we focused on the particle impact energy generated at particle-to-grinding ball/wall and particle-to-particle collisions. The particle size and the number of particles affected the level of particle impact energy at a single collision and the number of collisions of particles, respectively, resulting in an increase of the total impact energy of particles with decreasing particle size and increasing number of particles. The result suggests that milling conditions such as the size of grinding balls should be adjusted appropriately based on the variation of the size and number of particles so that the particles can receive large amounts of the impact energy during milling.

Investigation on mechanical properties of Al319– Al2O3 – TiO2 reinforced hybrid metal matrix composites

This development activity describes the assessment or manufacturing of mechanical characteristics of AMMCs. Al 319 was added with alumina and titanium dioxide by stir casting method. Alumina and titanium dioxide added with Al 319 in quantity of 2%, 4% and 6 wt%. In this development activity mechanical characteristics such as tensile and impact energy analysed. In parallel with improving quantity of Al2O3 and TiO2, value of hardness and tensile strength were increase and value of impact energy were diminish with enhancing quantity of alumina and titanium dioxide. The optical micrographs impart the varying distribution of alumina and titanium dioxide particles in Al 319 matrix. The present learning is expected that the developed composite will be advantages for light weight evolution in automotive components such as brake rotor.