Varying Impact Velocities Research Articles

Effect of abrasive particle hardness on interface response and impact wear behavior of TC17 titanium alloy

The impact wear behavior, dynamic response, and wear marks of TC17 titanium alloy in soft, hard, and mixed sand environments were studied. As the proportion of soft sand increased, the wear volume decreased significantly. At 75% and 100% of soft sand, ‘negative’ wear occurred, which indicated that the sand adhered to the surface of the specimen. However, no significant difference in peak impact force, impact return speed, and energy absorption was observed in different sand environments. Tests with varied impact velocities were also conducted. For different proportions of sand particles, the wear volume and wear rate varied with increase in impact velocity. An increase in impact velocity resulted in the increase in peak impact force and energy absorption, whereas the contact time and energy absorptivity decreased. However, no significant difference was observed in the peak impact force, impact return speed, and energy absorption under different proportions of sand particles when the impact velocity was a definite value. The main mechanism of TC17 titanium alloy was that hard sand particles were ploughed, extruded, and cut on the specimen surface; the soft sand particles were broken and adhered to the surface of the specimen to form a protective shell.

Synthesis and Erosion Wear Analysis of Short Bamboo Fiber Reinforced Epoxy Composites Filled with Ceramic Fillers

Hybrid natural fiber reinforced composites with ceramic fillers has been fabricated. Two ceramic fillers (Alumina and Silicon Carbide) have been used for the synthesis of composites and the samples have been fabricated with hand layup technique. 10% and 20% weight percentage of filler materials have been used for the different sets of composite samples. Erosion wear analysis of these composite samples has been carried out at different impingement angles (30,45,60,75, and 90) with varying impact velocities (48 m/s, 70 m/s, 82 m/s, and 109 m/s) and with varying erodent size (108, 125,150, 180µm). Results for the composites with and without filler have been compared. It has been observed that composites filled with particulate filler shows improvement in wear resistance properties as compared to composites without filler. Among the two fillers, Al2O3 has shown better resistance as compared to silicon carbide. A scanning electron microscope has been used to study the morphology of eroded surfaces and the mode of material removal.

Impact response of basalt textile reinforced concrete subjected to different velocities and temperatures

Basalt textile reinforced concrete (BTRC) specimens were tested at different impact velocities of 0.77 m/s, 2.31 m/s and 4.62 m/s and temperatures of −25, 0, 25, 50 and 100 °C to study possible influences on their impact resistance and failure patterns. The experimental results indicate that the impact velocity, temperature, the number of basalt textile layers and boundary conditions can significantly affect the impact responses. At a constant temperature, both the maximum impact force and the energy absorption exhibit apparent increase with increasing impact velocity. On the other hand, experimental data indicate that for the same impact velocity, the maximum impact force and absorbed energy decrease with temperature at span of −25 °C to 100 °C. Both the maximum impact force and the energy absorption of the specimens are improved as the number of basalt textile layers increased from four to six. All specimens are able to absorb most of the kinetic energy under impact velocity of 4.62 m/s, since the basalt textile is mainly pulled out from the matrix. Under the impact velocity of 4.62 m/s, the fixed boundary increases the peak impact force, but reduces energy absorption compared with free boundary condition at the room temperature (25 °C). Failure patterns are significantly affected by the varying impact velocities, but not the temperature and boundary conditions.

Towards the shortest possible contact time: Droplet impact on cylindrical superhydrophobic surfaces structured with macro-scale features

HypothesisRecently, it has been shown that the contact time of impacting water droplets on a superhydrophobic cylindrical surface decreases when its radius becomes comparable to that of the droplet, yet the correlation of this reduction with the impact velocity is unclear. Moreover, on a flat surface, experiments involving the addition of a single macrotexture, along with covering the surface with macroscopic cylindrical ridges (ribbed pattern), have been reported to shorten the contact time. Hence, a ribbed-curved surface with an additional macrotexture may logically lead to a very short contact time.ExperimentsSuch a surface was obtained by utilizing an extruder-type 3D printer and a copper wire was used as the additional macrotexture. The bouncing of water droplets of three different volumes on curved and ribbed-curved samples with two different diameters was investigated for varied impact velocities. FindingsFor the curved surfaces, a scaling model for the contact time reduction with respect to the impact velocity was found. Our data show that adding a wire to the peak of a cylinder containing both micro- and macro-scale roughness (wired ribbed-curved surfaces) yields the contact time even shorter than the inertial-capillary time scale, an unprecedented phenomenon.

An Experimental Investigation on Slurry Erosion Wear Characteristics of Brass Alloy

Material loss due to slurry erosion was a serious problem in many industrial applications like hydraulic turbines, slurry pumps, pipe lines, etc. where the ideal choice of engineering materials is a real challenge. Brass alloy was extensively used owing to its reasonable strength and ease of processing. Currently these alloys are also explored as candidate materials for propeller blade of torpedoes where major failure occurs due to slurry erosive wear. In the light of the above present investigation was aimed to study the slurry erosive wear behavior of brass with sand particles slurry. The studies were carried out at different sand concentration (16–28%), varying impact velocity (10-25m/sec), at different impingement angle (30°-75°) and varied impinging particle size (100-400 µm).The rate of material loss was found to be higher with increased sand concentration due to increased impinging action of sand particles. Increased impact velocity of slurry resulted in higher weight loss. Increased in impingement angle up to 60°, the wear rate increases; However beyond this the wear rate decreased. SEM studies were carried out on eroded surface to observe the mechanism of metal removal. The eroded surface also indicates that increased sand concentration, higher rotational speed and increased particle size resulted in severe damage on tested surfaces.

Numerical Study on the Ballistic Impact Response of Aramid Fabric- epoxy Laminated Composites by Armor Piercing Projectile

This paper presents the results from experiments and numerical simulations on the ballistic impact of 10mm thick aramid fabric-epoxy composite laminates by a 7.62mm armor piercing projectile at varying impact velocities. Post perforated residual velocity (RV), contact duration of projectile with the target and ballistic limit (BL) of composite were simulated using a finite element code HyperWorks-Radioss. Interaction of projectile with composite laminates was captured by high speed video. The predicted ballistic parameter from simulation compared well with the precision experimental results. The simulated energy and stress distribution during impact of projectile on composite laminate showed marked difference with variation in impact velocities (SV). The magnitude and duration of stress as well as the contact force was found to increase when projectile impacted at lower SV thus enhancing the extent of delaminating and the core damage area and the trend was reversed for higher SV. The findings corroborate the bullet inflicted damage of composite laminates experimentally determined by ultrasonic C-scan.

Numerical analysis of projectile penetration and perforation of plain and fiber reinforced concrete slabs

SummaryThe research presented in this paper deals with the numerical analysis of projectile impact on regular strength concrete (RSC), high‐strength concrete (HSC), and engineered cementitious composites (ECC) using the Lattice Discrete Particle Model (LDPM). The LDPM is chosen in this study as it naturally captures the failure mechanisms at the length scale of coarse aggregate of concrete, and its capabilities include the accurate depiction of both intrinsic and apparent rate effects in concrete, as well as fiber reinforcement effects. The model is used to predict the experimental impact response performed by four independent testing laboratories, and for each data set the model parameters are calibrated and validated using a combination of uniaxial compression, triaxial compression, uniaxial strain compression, and dogbone tests. In the first study, perforation experiments on RSC and HSC for varied impact velocities are carried out, and the exit velocity is compared with the available experimental data. The second study focuses on ECC, where multiple impact of steel and plastic fiber reinforced concrete panels are explored. A third investigation is performed on four RSC panels with varied thicknesses and subjected to the same impact velocity. In this instance, the model is used to predict the penetration depths for the different cases. Finally, in the last study, the response of large‐thickness infinite panels of sizes ranging from 300 mm to 700 mm under projectile impact is considered. Copyright © 2016 John Wiley & Sons, Ltd.

Study of Solid Particle Erosion Wear Behavior of Bamboo Fiber Reinforced Polymer Composite with Cenosphere Filler

AbstractIn this study, solid particle erosion (SPE) wear behavior of bamboo fiber‐reinforced epoxy composite with cenosphere filler was investigated. Cenosphere is an industrial waste of thermal power plants which is produced during burning of pulverized coals. The present composites consisting of varying weight percentage of fibers and cenosphere fillers were prepared by hand lay‐up technique. The erosion wear rates of these composites have been studied with varying impact velocities and impingement angles. The study reveals that addition of cenosphere filler to the bamboo–epoxy composite reduces its erosion wear rate. Morphologies of the eroded surface of composite samples were inspected by a scanning electron microscope to discuss the behavior of erosion wear. Both bamboo–epoxy composite with and without cenosphere filler show semiductile erosion wear behavior with maximum erosion rate at an impingement angle of 60°.

Numerical Simulation and Experimental Validation of Granite Powder Filled Jute Epoxy Composite for Slurry Jet Erosive Wear

Abstract In the polymer composite the benefits of utilizing the excellent wear resisting properties in terms of light weight structural design are immediately apparent. Hence, the focus of this study is to propose new sets of unfilled and particulate filled treated jute epoxy composites. Therefore, initially five different weight percentages of alkali treated jute epoxy composites are fabricated (10, 20, 30 40 and 50 wt.%) and studied their slurry erosive wear in experimentally at different operating conditions such as by varying impact velocity and impingement angle by keeping all other factors constant. The steady state erosion results for jute epoxy composites shows better wear resistant behavior for 40 wt.% jute fiber loading. Hence, for further fabrication of series of hybrid composite 40 wt.% jute fiber is kept constant and granite powder is varied in three different (8, 16 and 24 wt.%) weight percentages. The granite filler content in the jute epoxy composite played a major contribution for slurry erosion resistance. Finally, the obtained experimental results are compared with simulated model results by using a computational fluid dynamics tool. The eroded samples are observed through scanning electron microscope to study the wear mechanism.

Experimental study of a droplet impacting on a burning fuel liquid surface

A series of experiments were performed to study a single droplet impingement on a burning fuel liquid surface with varying impact velocity. The impact droplet diameter used in this experiment was around 2.2mm. The impacted liquid was alcohol with the burning surface. The impact process was recorded using a high-speed digital camera at 2000frames/s. The results show that three typical impact regimes appear, including splashing-injecting, splashing-injecting-secondary injecting and splashing-bubble, which are determined by the impact velocity. The maximum crater depth, width and the maximum jet height have a slight increase when the impact velocity ranges from 2.351m/s to 3.357m/s, but the maximum heights of the crown are almost constant. As the impact velocity is continuously increased to 3.513m/s, the maximum crater depth, width and the maximum crown height have a sharp decline. In addition, fire plume has evident influence on the loss rate of the impact velocity.

Effect of CFRP strengthening on the response of RC slabs to hard projectile impact

In this paper impact response of CFRP-strengthened RC panels under the impact of non-deformable projectiles has been presented. The control and CFRP-strengthened RC slab panels were tested under the strike of hemispherical nosed steel projectiles at varying impact velocities. The response of these panels was investigated experimentally as well as numerically. The damage of the slab panels was measured in terms of the penetration depth, formation of cracks, spalling and scabbing areas and fracture of CFRP sheet. This study presents a practical and efficient numerical method for analyzing the impact response of CFRP-strengthened RC structures using LS-DYNA. The CFRP strengthening was found to increase the ballistic limit velocity by 18%, perforation energy of RC slabs by 56.7%, reduce the front crater damage and contains the flying of concrete fragments from the rear face. The maximum impact force occurs at almost same penetration depth for the control and CFRP-strengthened slabs but the restraint provided by CFRP increased the penetration depth by about 1/19.3 of the thickness of slab.

Effect of Loading Rate on Dynamic Fracture Morphology of a Zr-Based Bulk Metallic Glass

Low-velocity plate impact experiments using a single-stage gas-gun are performed on Zr58.5Cu15.6Ni12.8Al10.3Nb2.8. Compressive fracture surfaces of the samples subjected to varying impact velocities and stress amplitudes are evaluated in order to study their loading rate dependence. Samples impacted at increasing loading rates, from increasing velocities of impact, show a larger extent of localized melting while those subjected to increasing stress show a transition from ductile to brittle fracture. These observations suggest that the mechanisms and morphology of fracture are strain-rate dependent. [doi:10.2320/matertrans.M2014467]

Exploring the applicability of equine blood to bloodstain pattern analysis.

Bloodstain pattern analysis (BPA) is the forensic application of the interpretation of distinct patterns which blood exhibits during a bloodletting incident, providing key evidence with its ability to map the sequence of events. Here, we explore the use of equine blood and investigate its suitability within the field of BPA. Blood is a complex fluid, and finding a suitable safe substitute to human blood that encompasses all of its characteristics has been the focus of many investigations. Animal blood has been concluded as the closest and therefore the most suitable alternate. However, it seems that currently only porcine blood is most prominently utilised.In this study, equine blood was investigated, using two different anti-clotting methods, where blood impacts were explored over a typical range of varying impact velocities upon a selection of commonly encountered surfaces. Key BPA parameters, such as the diameters of the resulting bloodstains, number of spines and area of origin were measured, which were subsequently applied into previously derived BPA equations.We find that defibrinated equine blood is a suitable alternative and offers the same conclusive outcomes to human blood. This gives bloodstain pattern investigators and researchers an additional choice of blood which can be of benefit when certain bloods are difficult to attain or when the activity involves the usage of a large quantity of blood. Additionally we explore the effect on BPA of aged blood, which revealed a significant decrease in stain diameter of up to 12.78 % when blood has been left for 57 days. A shelf life of no more than 12 days is recommended when blood is refrigerated at 4℃.

Reliability of double-wall containment against the impact of hard projectiles

Effectiveness of single or double-wall containment structures against a possible strike of projectiles, missiles or airplanes is well researched. However, how the uncertainties involved in the various design parameters influence the reliability of the containment is not very well known. In a double-wall containment structure, as name implies, there are two walls – an outer thick reinforced concrete (RC) wall and an inner thin steel shell/wall. In the present study, a simple probabilistic procedure based on Monte Carlo simulation technique is presented to study the reliability of double-wall containment structures against the impact of external hard projectiles on outer RC wall for varying impact velocities. In order to illustrate the proposed methodology, an idealized double-wall containment structure and a hard projectile were chosen. The probability of failure and the reliability indices of the selected double-wall containment structure were obtained for different striking velocities of the projectile and safety of the containment was correlated with the ballistic limit of the outer RC wall. The results of the study show that the double-wall containment is “safe enough” against the impact of the selected projectile if the projectile nominal velocity is less than 65% of the containment outer wall's nominal ballistic limit (VBL). Results also show that under the given uncertainties, if the nominal impact velocity is less than 65% of the nominal ballistic limit of the outer RC wall (i.e. 0.65VBL), failure probability of the containment is almost zero. However, when impact velocity is more than 0.90VBL, failure probability of the double-wall containment is quite high. It was also observed that a little change in the impact velocity over 0.90VBL may cause a phenomenal change in the containment reliability due to substantial change in the residual kinetic energy of the projectile. A number of sensitivity studies have also been carried out to obtain the results of practical interest.

Ballistic Performance of a Composite Metal Foam-ceramic Armor System

Composite Metal Foam is a low-weight, high-strength porous material capable of absorbing great amounts of energy under loading. In this report, Composite Metal Foam panels are manufactured using powder metallurgy technique and 2mm steel hollow spheres in a steel matrix and used in conjunction with a ceramic plate to fabricate a new light-weight composite armor system. This armor system is tested under ballistic loading using 7.62x51mm M80 and 7.62x63mm M2 AP projectiles at varying impact velocities for single and multi-impact scenarios. The material behavior, failure mechanism, and ballistic performance of the armor system are studied for optimization.

Effects of clamping design on the ballistic impact response of soft body armor

The effects of clamping on the ballistic impact performance of non-backed woven aramid fabrics is studied by considering several clamping configurations including 4-sided, 2-sided, circular, diamond, and corner-clamped frames. V50 velocities were estimated through several deterministic finite element impact simulations at varying impact velocities. Impacts occurring both directly on a yarn and the inter-yarn gap were considered. The different clamping configurations resulted in different fabric deformation, failure, and energy dissipating mechanisms. The circular frame resulted in the highest fabric V50 velocity. The V50 velocities were often sensitive to the precise projectile impact location relative to the principal yarns. Impact tests with fabrics clamped using four corner plates showed tearing at the corners. Fabrics clamped at their four corner points showed distinct deformation and failure mechanisms over three impact velocity regimes.

Ballistic Impact Response of Ceramic-Faced Aramid Laminated Composites Against 7.62 mm Armour Piercing Projectiles

Ballistic impact response of ceramic- composite armor, consisting of zirconia toughened alumina (ZTA) ceramic front and aramid laminated composite as backing, against 7.62 mm armor piercing (AP) projectiles has been studied. Two types of backing composite laminates i.e. Twaron-epoxy and Twaron-polypropylene (PP) of 10 mm and 15 mm thickness were used with a ceramic face of 4mm thick ZTA. The ceramic- faced and the stand alone composite laminates were subjected to ballistic impact of steel core 7.62 mm AP projectiles with varying impact velocities and their V50 ballistic limit (BL) was determined. A sharp rise in BL was observed due to addition of ceramic front layer as compared to stand alone ones. The impact energy was absorbed during penetration primarily by fracture of ceramic, deformation and fracture of projectile and elastic-plastic deformation of flexible backing composite layer. The breaking of ceramic tiles were only limited to impact area and did not spread to whole surface and projectile shattering above BL and blunting on impact below BL was observed. The ceramic- faced composites showed higher BL with Twaron-PP as backing than Twaron-epoxy laminate of same thickness. This combination of ceramic-composite laminates exhibited better multi-hit resistance capability; ideal for light weight armor. Defence Science Journal, 2013, 63(4), pp.369 -375 , DOI:http://dx.doi.org/10.14429/dsj.63.2616

Preliminary study on the effect of heated surfaces upon bloodstain pattern analysis.

Bloodstain pattern analysis (BPA) involves the interpretation of distinct blood patterns found at crime scenes following a violent act. In this paper, we explored for the first time the effects of surface temperatures upon blood impacting a horizontal surface (steel) with its implications in BPA explored. Specific surface temperatures were explored over the range 24-250°C which relate to the four major boiling regimes of liquid media; natural convection, nucleate boiling, transition boiling, and film boiling, where a series of blood drops tests were performed at varying impact velocities. Blood was found to separate into its components at temperatures of 50°C+, displayed as temperature induced blood rings, where a single secondary and a series of further inner rings are exhibited. This consequently led to the development of a new constant Cd heated expressing the decrease in spread factor (D(s)/D(o)) at the secondary ring.

Frontal Impact Response for Pole Crash Scenarios

Objective: Vehicle impacts with fixed roadside structures, such as poles, constitute a significant portion of road fatalities in North America. The purpose of this study was to evaluate occupant response in pole crash scenarios and compare the current vehicle kinematic–based injury metrics to occupant-based metrics to determine whether the vehicle metrics are representative of the injury levels sustained by an occupant. Methods: To better understand vehicle and occupant response during impact with a pole, frontal crash scenarios with 3 common pole types (a rigid pole, a rigid pole with a frangible base, and a deforming or energy-absorbing pole) were investigated at various impact velocities. A numerical model of a Hybrid III human surrogate was integrated with a numerical model of a mid-size sedan, including improvements to the vehicle and seat models, and implementation of an air bag and restraint system. The vehicle model was validated using the National Highway Traffic Safety Administration's (NHTSA) frontal crash data for varying impact velocities into a rigid wall. A numerical model of a high-energy-absorbing pole was developed and validated, along with a rigid pole and a previously developed breakaway pole, to examine the effects of pole compliance on the vehicle and occupant response. Occupant response was investigated at varying impact velocities with the poles aligned with the vehicle centerline. Offset impacts were then investigated with the energy-absorbing pole aligned with the driver-side crush structure. Results: The vehicle kinematic response metrics currently used to evaluate poles were compared to the currently accepted occupant injury response metrics and it was found, in general, that the occupant-based injury criteria predicted lesser injury than the vehicle kinematic response metrics for the same impact scenario. Specifically, the occupant impact velocity provided trends that differed from all other metrics. This can be attributed in part to the improvement in vehicle safety systems not accounted for by the vehicle-based metrics. Conclusions: For the same impact scenario, the breakaway pole resulted in the lowest predicted injury metrics for the vehicle occupant but was noted to be a potential threat to pedestrians and other nearby road users. The rigid pole resulted in the highest occupant injury predictions, whereas the energy-absorbing steel pole resulted in injury metrics below the threshold values, controlled the vehicle deceleration, and detached from the base only at higher velocity impacts. Appropriate evaluation of energy-absorbing poles requires consideration of the occupant response in addition to the current kinematic criteria.

Molecular dynamics study of nanodroplets: Initial compressed phase of collisions against a flat wall

Collisions of spherical nanodroplets against a flat wall are studied using molecular dynamics simulations. The initial compressed phase of the collisions is focused on to illuminate the elastic behavior of the droplet. The normal forces F z between the droplet and the wall are calculated at varying impact velocities u along the z-direction and fitted to a power law of the form F z ∝ ξ n , where ξ denotes a deformation. If u is less than 0.2 and ξ < 0.8, then the normal forces all together satisfy a power law with exponent n ≈ 1.5, corresponding to the Hertz law. However, if u is greater than 0.3, then the exponent n changes to around 2.0 ∼ 2.4.