Increasing Impact Angle Research Articles

Impact dynamics of metallic nano particles in collision with graphene nano sheets

In this paper impact of metallic nanoparticles on graphene sheets was investigated via non equilibrium molecular dynamics (NEMD) approach. Upon unique feature of graphene to absorb motion energy of the materials impacted on it, systems based on graphene can be an appropriate solution for the purpose of damping. The proposed model was validated by available experimental data and simulation. It was demonstrated that mechanics of impact is not a multidimensional problem, therefore it can be studied by molecular dynamics. Effect of velocity of the particles, impact angle and number of the graphene sheets on the coefficient of restitution of the metallic nanoparticles was researched. Contrarily to macro systems, it was observed by increasing the velocity of impact, coefficient of restitution decreased. Also by increasing impact angle, coefficient of restitution changed with the formula: e(theta)=0.418(theta)^2-0.045(theta)-0.396. By increasing the graphene sheets, the coefficient reduced significantly. Negative coefficient of restitution was observed for some cases, which was reported also on other works about nanostructures. It was shown a single graphene layer can withstand 3.64 times more than a 20 layer graphene sheet toward impacting.

Construction of erosion mechanism maps for pipeline steels

Oil and gas industry spends millions of dollars every year dealing with problems caused by erosion. Erosion is a complex phenomenon and in order to recommend ways to mitigate its effect, it is essential to have a full understanding of the tribo-mechanisms involved. In the present study, erosion tests were conducted on AISI 1018, AISI 1080, API X42, API X70 and API X100 steels using aluminum oxide as erodent. Particle velocities and attack angles employed were as follows: 36, 47, 63 and 81ms−1 at 30°, 45°, 60° and 90°, respectively. Erosion rate decreases with increasing impact angle and increases with increasing particle velocity. Several mechanisms are found to be responsible for the behavior of these steels under the experimental conditions employed in this work. Heavy plastic deformation and fracture, ploughing, delamination and different forms of metal cutting are identified as operative mechanisms during erosion. Empirical erosion mechanism maps are constructed showing the variation in erosion regimes, as a function of impact angle and normalized velocity.

On the oblique collision of gaseous molecules with graphene nanosheets

In this paper, normal and tangential coefficients of restitution for gaseous molecules colliding with layerwise (single and few layers) graphene nanosheets were calculated using non-equilibrium molecular dynamics method. The normal and tangential coefficients of restitution depend on impact angle, velocity and landing position of projectiles. These parameters were evaluated computationally by implementation of several operations. Some differences were observed between proposed problem and macro-scale nature. The most notable difference was proportionality between the restitution coefficients and impact velocity, while in the case of macro-scale systems, they have inverse relation. Number of layers of graphene substrate does not contribute significantly to the normal and tangential coefficients of restitution. On the other hand, except for hydrogen, where its normal coefficient of restitution is approximately unity, the normal coefficient of restitution for other gasses increases as impact angle increases. Furthermore, tangential coefficients of restitution reduce with impact angle. These results can offer additional insights for further understanding the impact mechanisms and bombardment-related phenomena in low-dimensional materials. Presented results could be utilised to optimise some applied operations such as porosity generation via bombardment of layered nanostructures, gas detection process, thermal management and pressure sensor applications.

Analyzing the effect of wall roughness on gas–particle flow in confined channels based on a virtual-wall-group concept

Present work aims to develop a particle history effect model for describing the effect of wall roughness on particle–wall collision in confined flow channels. To solve the real distribution function of roughness angle, the effective distribution function is scrutinized with a virtual testing method, and a further virtual-wall-group concept is proposed to investigate the effect of particle motion experience. It is found that roughness angle distribution should be described by a particle history effect–probability distribution function. Rebound angle is rebuilt according to the coordinate rotation operation. Multiple collisions are divided into two types, namely Type I induced by negative rebound and Type II led by positive rebound. Besides, a new probability function is derived to distinguish multiple collisions from a single collision. A set of modified algorithm for multi-collision is built and applied to simulate the particle–rough wall collision, and the predictions are evaluated by the measurements. It reveals that a typical peak can be seen in the probability distributions of both types of multiple collisions, and the effect of wall roughness decreases with the increase of impact angle. The simulated results of confined planar gas–particle flow are good in accordance with the measured data.

The effect of test parameters on the impact resistance of a stainless steel/rubber/composite hybrid structure

In the present study, high velocity impact tests were carried out on stainless steel/rubber/composite hybrid plates. The projectile velocity, impact angle, number of impacts, sample temperature, and prior ageing were used as variables in order to investigate the effect of test parameters on the impact behaviour of the samples.In general, the energy absorption and the damage behaviour of the studied hybrid structure were rather immune to the changes in the test parameters. Only the impact angle showed a stronger effect with increasing plastic deformation and dissipated energy with increasing impact angle. Similar but not as strong effect was found with increasing sample temperature. In addition, the effect of increasing impact angle on the damage size was found to be stronger than the effect of increasing impact energy at a constant impact angle. The repeated impact studies showed that the structure does not lose its ability to withstand dynamic loading even when there is a gradually progressive damage. The results support the potential of the studied steel/rubber/composite hybrid structure to be implemented in real life applications.

Stepwise Erosion as a Method for Investigating the Wear Mechanisms at Different Impact Angles in Slurry Erosion

In the present work, stepwise erosion technique was carried out to investigate in detail the influence of impact angle on the erosion process of AISI 5117 steel. The number of impact sites and their morphologies at different impact angles were investigated using scanning electron microscope (SEM) examination and image analysis. The tests were carried out with particle concentration of 1 wt. %, and the impact velocity of slurry stream was 15 m/s. Silica sand—which has a nominal size range of 250–355 μm—was used as an erodent, using whirling-arm test rig. The results have shown that the number of craters, as expected, increases with the increase in the mass of erodent for all impact angles and this number decreases with the increase of the impact angle. In addition, the counted number of craters is larger than the calculated number of particles at any stage for all impact angles. This may be explained by the effect of the rebound effect of particles, the irregular shape for these particles, and particle fragmentation. The effect of impact angle based on the impact crater shape can be divided into two regions; the first region for θ ≤ 60 deg and the second region for θ ≥ 75 deg. The shape of the craters is related to the dominant erosion mechanisms of plowing and microcutting in the first region and indentation and lip extrusion in the second region. In the first region, the length of the tracks decreases with the increase of impact angle. The calculated size ranges are from few micrometers to 100 μm for the first region and to 50 μm in the second region. Chipping of the former impact sites by subsequent impact particles plays an important role in developing erosion.

Effect of impact angle and velocity on erosion of API X42 pipeline steel under high abrasive feed rate

The cost of erosion attack to the global oil and gas industry has drawn significant attention amongst researchers in recent years. Erosion is a complex phenomenon and in order to recommend ways to mitigate its effect it is essential to have a full understanding of the tribo-mechanisms involved. In the present study erosion tests were conducted on API X42 steel using aluminum oxide as erodent. The extent of material degradation is a function of the properties of abrasive particle, target material, erodent velocity, abrasive feed rate, attack angle and environment. In this study, erosion tests were carried out under high mean abrasive feed rate of 160gmin−1. Particle velocities and attack angles employed were as follows: 36ms−1, 47ms−1, 56ms−1 and 81ms−1 at 30°, 45°, 60° and 90°, respectively. Similar to erosion at low abrasive feed rate, it is found that erosion rate decreases with increasing impact angle and increases with increasing particle velocity. However, under the present experimental conditions, it is found that the velocity exponent (n) in the erosion rate equation (E=kVn) decreases with increasing abrasive particle angle of incidence. Contrary to common understanding for low particle feed rate tests, this finding suggests that the “n” value is mechanism dependent. Several mechanisms are found to be responsible for the behavior of API X42 steel under the experimental conditions used in this work. Heavy plastic deformation and fracture, ploughing and metal cutting are identified as operative mechanisms during erosion of API X42 pipeline steel.

Effect of Feed Rate and Impact Angle on the Erosive Wear of High Velocity Oxy-fuel Sprayed Coating Under High Temperature Conditions

In the present investigation erosive wear behavior of EWAC 1006 Co-base alloy deposited by high velocity oxy-fuel (HVOF) spraying process was investigated. The microstructure, porosity and hardness of the coating was evaluated. The effect of impact angles of 30°, 60° and 90° and erodent feed rate of 1, 3, 5 g/min on the erosive wear were evaluated. All erosive wear tests were conducted at high temperature (450°C) against erodent velocity of 40 m/s. The erosive wear was found to decrease with the increase in impact angle of the erodent and increase with the increase in erodent feed rate. The erosive wear of the coating was 3-4 times lower than the substrate. Analysis of the scanning electron microscope images revealed cutting and lip formation as the material removal mechanisms in these coatings under erosive wear conditions used in this investigation.

Experimental Study on Cement Clinker Particles under Impact Force

In order to further study the impact crushing mechanism of cement clinker, the impact experiment has been carried out at different impact angles. Impact crushing curves, acoustic emission signal and peak impact force and impact fracture morphology have been systematically studied. It is shown that each impact crushing curve includes an inertia peak and an actual impact peak. AE signal directly reflects the crack initiation and propagation during the process of impact experiment. With the increase of impact angle, the average value of peak impact force decreases. The peak impact force value reaches the minimum at 75 °. The experiment results will offer a successful alternative to the low – energy grinding of cement clinker.

Influence of impact angle on the interaction between Co55 nanocluster and Cu (0 0 1) substrate: Ionized cluster beam deposition

Using a classical molecular dynamics method, the influence of impact angle was studied on the ionized cluster beam (ICB) deposition. A many-body tight binding potential was employed to simulate the interactions among the atoms, in which the Co55 (55atoms/cluster) nanocluster with the total energy of 110eV was deposited on a Cu (001) substrate, whose temperature was set at 300k. The quantitative of kinetic energy of the cluster, maximum temperature substrate, cluster center of mass and diffusion area of the cluster were proposed to evaluate the interacting mechanism nanocluster and substrate. Also, the influence of impact angle was investigated on the Co–Co and Cu–Co radial distribution function and the adhesion between cluster and substrate. The simulation data demonstrated the decrease of the maximum temperature substrate with the increase of impact angle. The results indicated the decrease in the maximum depth penetration with the increase in the impact angle. The thin film formed by Co55 nanocluster with the impact angle of 30° had the minimum adhesion with the substrate.

STEPWISE EROSION AS A METHOD FOR INVESTIGATING THE WEAR MECHANISMS AT DIFFERENT IMPACT ANGLES IN SLURRY EROSION

In the present work, stepwise erosion technique was carried out to investigate in detail the influence of impact angle on the erosion process of AISI 5117 steel. The impact sites number and their morphology at different impact angles were investigated using SEM examination and image analysis. In addition, the SEM images of eroded surface using stepwise technique were used presented for better understanding of material removal at different angles. The tests were carried out with particle concentration of 1 wt %, and the impact velocity of slurry stream was 15 m/s. Silica sand has a nominal size range of 250 – 355 µm was used as an erodent, using whirling-arm test rig. The results showed that the number of craters as expected increases with the increase in the mass of erodent for all impact angles and that this number decreases with the increase of the impact angle. In addition, the counted number of craters is larger than the calculated number of particles for all impact angles and at any stage. The effect of impact angle based on the impact crater shape can be divided into two regions; the first region for θ ≤ 60o and the second region for θ ≥ 75o. In the first region the length of the tracks decreases with the increase of impact angle. The calculated size ranges from few micrometers to 100 micrometer for the first region and to 50 micrometers in the second region. Chipping of the former impact sites by subsequent impact particles plays important role in developing erosion.

Effect of Impact Angle on Erosion Wear Behaviours of SiC<sub>p</sub>/Cast Iron Surface Composite

The slurry erosion wear performances of the SiCp/cast iron surface composite, which was prepared by infiltrating molten cast iron into SiC particles preforms, were studied on self-made slurry inject erosion wear machine. The results show that the erosion wear rate of the SiCp/cast iron surface composite would be the lowest at impact angle of 30°, and the largest at impact angle of 60°. The erosion wear rate increases gradually when impact angle is changed from 30° to 60°, and then decreased with increasing the impact angle. The erosion wear mechanism of the SiCp/cast iron surface composite is dominated by cutting and grooving at low impact angle, and by fatigue spalling and cutting at high impact angle. For the gray cast iron, the erosion wear rate of would be increased gradually with the increase of impact angle, reaching the peak value at 90°, which indicates the typical characteristics of brittle material in slurry erosion wear process.

High Temperature Erosive Wear Study of NiCrFeSiB Flame Sprayed Coatings

In the present work erosive wear behavior of NiCrFeSiB coating deposited by flame spraying process was studied. The microstructure, porosity and hardness of the coatings have been evaluated. The high temperature (150, 300 and 450 °C) erosive wear behavior of these coatings was studied under 30, 60 and 90° impact angles against 30, 45 and 60 m/s velocity. The erosive wear was found to increase with the increase in velocity of the erodent and decrease with the increase of impact angle. The erosive wear resistance of the coating is higher than the substrate. The erosive wear of the coating was 4–5 times lower than the substrate. Scanning Electron Microscopy (SEM) analysis was carried out to determine the material removal mechanisms. The ductile fracture and platelets were revealed as the material removal mechanisms in these coatings.

Penetration depth for yaw-inducing bursting layer impacted by projectile

In order to accurately estimate the anti-penetration capacity of yaw-inducing bursting layer with irregular barriers on surface impacted by projectile, the theoretical model of attack angle and angular velocity for projectile impacting on irregular barrier was achieved according to the macroscopic relation of contact force versus contact time, in which the main factors such as the relative geometrical characteristics of projectile and irregular barrier, material property and impact velocity of projectile influencing on yaw-inducing effectiveness were considered. On the basis of considering synthetically the influences of attack angle, impact velocity, impact angle of projectile and uncontrolled free surface of target, the theoretical formulation of penetration depth for bursting layer with irregular barriers on surface impacted by projectile was presented by expressing the stress of an optional point on the nose of projectile according to the relation of stress versus velocity. The theoretical results indicate that in the case of oblique impact embodying effect of attack angle, the penetration depth is reduced with the increase of impact angle, attack angle or angular velocity, and penetration trajectory is also deflected obviously. The effectiveness of angular velocity influencing on penetration depth is increased with impact velocity increasing. The theoretical results are in good agreement with test data for low impact velocity.

Analysis of the influence of independent variables used for reconstruction of a traumatic brain injury incident

Traumatic brain injuries contribute to a high degree of morbidity and mortality in society. To study traumatic brain injuries researchers reconstruct the event using both physical and FE models. The purpose of these reconstructions is to correlate the brain deformation metric to the type of injury as a measure for prediction. These reconstructions are guided by a series of independent variables which all have influence upon the outcome variables. This research uses a combination of physical and FE modelling to quantify how independent variables such as velocity and impact vector (angle) contribute to the resulting variance in brain deformation metrics. The results indicated that using a Hybrid III neck controls the rotational acceleration response from an impact. Also, it was found that strain rate and product of strain and strain rate were more sensitive to changes in impact angle. Linear acceleration decreased with increasing impact angle, while brain deformations did not follow this trend, which suggests that peak linear acceleration may not be the only factor in the production of larger brain deformations.

Parametric effects on the erosion–corrosion rate and mechanism of carbon steel pipes in oil sands slurry

In this paper, the parametric effects, including the sand concentration, slurry flow velocity and impact angle, on erosion–corrosion (E–C) of X65 steel in oil sands slurry were investigated using an impingement jet loop system by weight-loss test, polarization curve measurements and surface characterization. The mechanism of the steel E–C was determined. It was found that erosion components, including pure erosion and corrosion-enhanced erosion, are the dominant contributors to E–C of the steel, while the contribution of corrosion components is slight. With the increase of the sand concentration and slurry flow velocity, the E–C rate of the steel increases. However, an increasing impact angle would decrease the E–C rate of the steel in oil sands slurry. When the potential of the steel is relatively negative, erosion is dominant, especially at high flow velocities. At positive potentials, corrosion of steel is important in E–C process, especially at low flow velocities. An E–C map is built to illustrate mechanistically the E–C process depending on the steel potential and slurry flow velocity.

Material deformation and removal due to single particle impacts on ductile materials using smoothed particle hydrodynamics

Smoothed particle hydrodynamics (SPH) was used to simulate the impact of single angular particles on Al6061-T6 targets, and the implications for solid particle erosion were discussed. The results of the simulations were verified by comparison to measurements obtained from impact experiments performed using a gas gun which was specifically designed to accelerate angular particles without disturbing their orientation with respect to the target. Both the simulations and the experiments showed that an increase in impact angle and initial orientation of the particle altered the deformation mechanism of the target material, as noted by other investigators. For impact angles close to normal, a significant amount of target material was extruded and piled up at the edge of the impact craters, due to the limited strain hardening of Al6061-T6. However, for certain combinations of incident parameters, the particle machined the surface and a chip was removed. With appropriate constitutive and failure parameters, SPH was demonstrated to be suitable for simulating all of the relevant damage phenomena, including crater formation, material pile-up and chip separation.

Stress and System Energy in Erosion Process for Brittle Materials

Erosion tests on high strengh refractory castables were carried out using SiC grains at impact angles of 30°,45°,60°,and 90° with the velocity of 5m/s.In order to study the variation in stress and system energy with impact angles during solid particle erosion process,a single particle erosion model was designed by means of three-dimensional explicit dynamic software ANSYS/LS-DYNA according to experiment parameters. The Johnson-Holmquist brittle ceramic model was employed to model the failure of target material. The impact angles varied from 15° to 90° in increments of 15°.The simulation results were compared with erosion rate values from experiments. The results show that the variation trends of both the maximum stress of targets and system total energy loss are in a good agreement with experiment data,which increaes with increasing impact angle. The variation of erosion rate as a function of impact angle can be explained by the variation of the maximum stress of target material. The rule “the maximum erosion of typical brittle material occurs at 90°” is confirmed by the view of energy analysis.

Crashworthiness Simulation Analysis of Light Sport Aircraft Fuselage Structure

In recent years, light sport aircraft, which not only serve the purpose of personal recreation but also act as a means of transportation for medium and short distance travel, have rapidly gained popularity in the general aviation industry worldwide. The FAA established regulations for this new category of airplanes in 2004. However, the crashworthiness requirements for this type of airplane have not been clearly specified. This study used the finite element method to investigate the effect of the impact angle and speed of the LSA fuselage structure on passenger safety during a crash event. We used sink speed defined by NASA AGATE, ASTM and FAR as parameters. The passenger compartment reducing rate defined by MIL-STD-1290A was used for a safety boundary condition. The results show that the maximum cockpit reducing rate of the airplane impact angle is 30o. When the impact angle increases, owing to the engine mount and fire wall’s reinforced structure, this type of airplane can sustain a greater vertical drop speed. When the impact angle is about 80°~90°, the maximum impact speed the fuselage that can be sustained is 33 m/s. This work also completed a simulation of safe and unsafe ranges for light sport aircraft at various impact angles and vertical drop speeds during impact.

Effect of SiC Particle Sizes on Erosion Wear Behaviour of SiC/Epoxy Resin Composite

The effect of SiC particles sizes on erosion wear behaviour of SiC/epoxy resin composite was studied on self-made slurry erosion wear tester. The results show that the erosion wear rate of SiC/epoxy resin composite would be decreased with the increase of SiC particle sizes. With the increase of impact angle, the erosion wear rate would be increased first, and then decreased, it would be peak value when the erosion wear test was carried out at 60° impact angle. When SiC particles were mixed with different sizes, the erosion wear rate of SiC/epoxy resin composite would be lowest. The erosion wear mechanism of SiC/epoxy resin composite was analyzed by observation of worn surface morphology.