Increasing Impact Angle Research Articles

Effects of flow velocity and impact angle on erosion-corrosion of an API-5 L X65 steel coated by plasma nitriding of hard chromium underlayer

In this study, the erosion-corrosion behavior of an API-5L-X65 steel coated by plasma nitriding of hard chromium underlayer has been investigated as a function of flow velocity (4, 5, 6, 7.5m s−1) and impact angle (30°, 45°, 60°, 90°) by a slurry of 3.5wt.% NaCl, and 3wt.%SiO2. The structure and microstructure of coating were characterized by X-ray diffractometry and scanning electron microscopy techniques. The maximum of mass loss was at the impact angle of 45° which the degradation slightly decreased with the increase of impact angle. However, the maximum degradation of the CrN coated samples occurred at normal impact angle. The analysis of erosion-corrosion mechanism showed the erosion process was more effective than corrosion.

Numerical study of oblique droplet impact on a liquid film

The dynamic characteristics of droplet obliquely impact on a liquid film are investigated numerically by using the Coupled Level Set and Volume of Fluid method (CLSVOF), with the impact angle ranging from 0° to 60°. The influence factors as film thickness and Weber number on the splashing formation and the crown evolution are also systematically investigated. Results showed that the crown radius on the behind side of the advancing droplet decreases as the impact angle increases, while the crown radius on the front side of the advancing droplet appears to be an opposite trend. Furthermore, the crown diameter is almost unchanged when the impact angle increases from 30° to 45°. However, when the impact angle increases to 60°, the crown lamella on the front side of the advancing droplet is completely suppressed. It is found that the crown height does not linearly change with the film thickness. With an increase in the film thickness, the right crown height first increases and then decreases, indicating the presence of a critical film thickness under the studied conditions. An increase in Weber number results in a transition from non-splashing to partial splashing and even to entire splashing.

High strength welding of NiTi and stainless steel by impact: Process, structure and properties

High strength solid-state welds are demonstrated between NiTi shape memory alloy (SMA) and 436 stainless steel (SS) through Vaporizing Foil Actuator Welding (VFAW) method. This process uses the rapid ablation of a foil in a lab-scale process that is similar to explosive welding. The welding process characteristics including collision speed and angle were estimated using an optical method, Photon Doppler Velocimetry (PDV). The local microstructure had strong spatial variation along the weld. The first area to impact, the center of the structure does not weld, as impact is at a normal inclination. This center region has the highest collision speed, but lowest angle; moving outward collision speed decreases and impact angle increases. This causes a progression of varied weld morphologies. Transmission Electron Microscopy shows that some regions that locally melted solidified as amorphous zones. This corresponds to the Thermo-Calc calculations which also predict a high glass forming potential in the resulting multi-component alloy. While the local structure is heterogeneous from varied features across the entire span of the weld (over millimeters) to thin amorphous layers, they exhibit much higher joint efficiency than traditional welding technologies. This work sets a foundation to design processes to harness this high joint strength available through impact welding with other weld morphologies.

Dynamic behaviors of nanoscale binary water droplets simultaneously impacting on flat surface

Dynamic wetting of nanoscale binary water droplets simultaneously impacting on flat copper surface is explored using molecular dynamics simulations (MDS). The spreading performance is described through the images of shape evolution and the temporal variations of radial spreading factor and dynamic contact angle. The corresponding spreading characteristic is separately assessed by the following five key aspects: impact velocity, impact direction, the potential depth between oxygen and surface atoms, the center distance of binary nanodroplets and nanodroplet diameter, respectively. Here, the simulated results show that the binary nanodroplets with a low impact velocity exhibit the advancing, receding and coalescing motion states and the fluid with the high impact speed spreading on the solid surface may develop into jet flow along the radial direction. For impact direction, the radial momentum will cause larger axial wetting length with the increase of impact angle. In addition, a wide motion regions of binary water droplets impingement from partial wetting to non-wetting are observed, which helps us better understand the feature of nanodroplet equilibrium. Besides, the influence of coupling strength on dynamics behavior is also considered. We find that the center distance of binary droplets is relatively small, which will be conducive to the jetting occurrence. The enhancement of momentum and mass transport of the colliding two equal-sized nanodroplets also boosts the jetting as the droplet diameter increases.

Sand particle erosion of cement mortar under sulfate and chloride attack and exposure to freeze–thaw cycles

The erosion behaviour of cement mortar subjected to sand particle blasting was investigated using the gas-blast method with different impact angles and sand particle fluxes. The corrosion regime under the action of freeze–thaw cycles was also investigated. The erosion rate of the cement mortar was measured and analysed under freeze–thaw cycles using two concentrations of corrosive solutions (8% and 10% mass fractions of salt solutions of sodium chloride and sodium sulfate). Moreover, with the support of scanning electron microscopy images, X-ray diffraction patterns and laser scanning confocal microscopy, the erosion mechanism at different impact angles and freeze–thaw cycles was investigated. The results showed that the erosion rate increased with increasing impact angle and decreased with an increase in sand particle flux. The erosion rate of the cement mortar was also found to first decrease and then increase with an increasing number of freeze–thaw cycles. The erosion damage of the cement mortar surface with significant mass loss was found to be due to two mechanisms – horizontal cutting and vertical pressing.

Simulation analysis of the effect of conical cap on the piercing performance of projectile

To study on the effect of conical cap on the piercing performance of projectile( Φ 150mm) when penetrating three-interval-layer steel target ( target thickness: 20mm+20mm+20mm, the center of distance between adjacent targets is 1.5m ), the FEA model of penetrating performance of the projectile with conical cap was built by using Ls-dyna, and the attitude change law, velocity change law and impacting acceleration change law of projectile in the process of piercing the targets were analyzed under the different impact velocity(500m/s, 600m/s, 700m/s, 800m/s) and impact angle(0°, 25°, 50°) condition. The simulation results show that: with the increase of impact velocity and impact angle, the time of the conical cap separating from the head of projectile and breaking is earlier, and the breakage of the cap is also more severity. Under the same impact angle and different impact velocity condition, the maximum axial acceleration variation of projectile penetrating into each target is inconsistent, which is closely related to the separation of the cap from the projectile and the breaking of the cap. After the cap separating from the head of projectile, the cap will impact on the target firstly, which can reduce the axial acceleration when the projectile penetrates the target. Under the same impact velocity condition, the residual velocity of the projectile decreased with the increase of impact angle; and under the same impact angle condition, the velocity change after the projectile penetrates the target gradually decreases with the increase of the impact velocity of projectile. The amount of kinetic energy change of projectile increases with the increase of impact velocity of the projectile, that is to say, the higher of the impact velocity, the more of the kinetic energy loss in process of projectile penetrating target.

Flow and heat transfer characteristics of droplet obliquely impact on a stationary liquid film

The flow and heat transfer characteristics of a droplet obliquely impact on a stationary liquid film is numerically studied by using a coupled level set and volume of fluid method (CLSVOF). The effects of impact angle, Weber number, and film thickness are analyzed. As compared with the normal impact, the flow features and surface heat flux distribution for oblique impact are asymmetric and where the secondary droplets only can be observed on one side. Corresponding mechanisms have also been interpreted. The maximum value of the local surface heat flux decreases and moves to the right with the increase in impact angle, while the minimum local surface heat flux on both sides increases as the impact angle increases. With a greater Weber number or a thinner film thickness, the maximum local surface heat flux is higher, while the minimum local surface heat flux on both sides appears to be an opposite trend. In addition, the impact angle has little effect on the average surface heat flux.

Investigation on slurry erosion of Al<SUB align="right">2O<SUB align="right">3 incorporated glass/epoxy composites

The jet erosion of fibre reinforced plastics (FRPs) has been reported in many literatures available, but very few have reported on their slurry erosion behaviour of FRPs. Furthermore, limited studies have paid attention on slurry erosion characterisation of filler incorporated FRPs. Hence, present study was focused on slurry erosion behaviour of alumina fillers incorporated glass/epoxy composites. The parameters considered were slurry concentration, contact angle and impact velocity. The experimental results reveal that increase in filler percentage increased the erosion resistance of glass/epoxy composites. The increase in slurry concentration and impact velocity has resulted in higher amount of erosion of studied composites. The material loss due to erosion increased with increase of impact angle till 45°, whereas further increase in impact angle caused reduction in wear. Erosion mechanisms were studied through SEM image of eroded samples. Worn surface analysis revealed that plastic deformation, matrix debonding with microcutting, microploughing, and pulverisation were dominant erosion mechanisms at 45° to 60° impact angle.

Investigation on slurry erosion of Al<SUB align="right">2O<SUB align="right">3 incorporated glass/epoxy composites

The jet erosion of fibre reinforced plastics (FRPs) has been reported in many literatures available, but very few have reported on their slurry erosion behaviour of FRPs. Furthermore, limited studies have paid attention on slurry erosion characterisation of filler incorporated FRPs. Hence, present study was focused on slurry erosion behaviour of alumina fillers incorporated glass/epoxy composites. The parameters considered were slurry concentration, contact angle and impact velocity. The experimental results reveal that increase in filler percentage increased the erosion resistance of glass/epoxy composites. The increase in slurry concentration and impact velocity has resulted in higher amount of erosion of studied composites. The material loss due to erosion increased with increase of impact angle till 45°, whereas further increase in impact angle caused reduction in wear. Erosion mechanisms were studied through SEM image of eroded samples. Worn surface analysis revealed that plastic deformation, matrix debonding with microcutting, microploughing, and pulverisation were dominant erosion mechanisms at 45° to 60° impact angle.

Effect of NiCr content on the solid particle erosion behavior of NiCr-Cr3C2 coatings deposited by atmospheric plasma spraying

Homogeneous coatings cannot meet the overall erosion-resistance requirements for an entire blade since materials present different erosion resistances at various impact angles. In this work, NiCr-Cr3C2 coatings with different NiCr contents were prepared on FV520B steels through atmospheric plasma spraying (APS) by using a double-channel powder feeder. The composition and microstructure of the as-sprayed coatings were examined by SEM, EDS, and XRD analyses, and microhardness was determined by microhardness tests. The erosion performance of NiCr-Cr3C2 coatings under different testing conditions (impact angle, solid particle size, solid particle velocity, and NiCr contents) were further evaluated with a gas–solid two-phase testing machine. Furthermore, the erosion wear mechanism of NiCr-Cr3C2 coatings with different NiCr contents at various impact angles was investigated. The results showed that the phase distribution inside the NiCr-Cr3C2 coatings became uneven with the increased NiCr content, leading to the fluctuation of microhardness. The erosion rate of 25 wt% NiCr-Cr3C2 coating initially increased and then decreased with increasing impact angle and solid particle size. The erosion rate was also improved rapidly with the increased erosion velocity for all impact angles. It was found that at low impact angles, the erosion resistance of NiCr-Cr3C2 coatings was increased with higher ceramic content because of the micro-cutting failure. By contrast, at medium and high impact angles, the erosion resistance of the coating could be improved by increasing metal content since coatings are eroded through fatigue spalling and rigid fracture.

Deposition of wet microparticles on a fiber: Effects of impact velocity and initial spin

Inertial deposition of wet microparticles on a fiber is numerically investigated by means of discrete element method, taking the effects of impact velocity and initial spin into consideration. Results indicate that the overall, normal and tangential coefficients of restitution remain zero as the impact velocity is lower than a critical value, beyond which these restitution coefficients will increase nonlinearly with increasing the impact velocity. As the impact angle increases, the normal critical impact velocity will show a parabolic decrease and the tangential critical impact velocity will increase linearly, different from dry collisions where the critical impact velocities almost keep constant. As the impact velocity increases, the capture efficiency of wet microparticles by the fiber decreases exponentially, meanwhile the deposit microstructures tend to be denser. It becomes much more complex if clockwise or anti-clockwise initial spins are encountered. The rotational coefficient of restitution will first decrease with increasing the rotational rate until reaching a minimum value, beyond which the rotational restitution coefficient will increase as the rotational rate increases further. However, the overall restitution coefficient changes slightly if the rotational rate is less than about 105 rad/s. The effect of clockwise spin on capture efficiency is found to be distinctly different from that of anti-clockwise spin, and it can be reasonably interpreted by their effects on the overall coefficient of restitution.

Erosion Characteristics of Electroless Deposited Ni-Fe-P Al-loys in 5% NaOH Slurry

Amorphous Ni-Fe-P alloy coating was prepared on thecopper substrate by electroless deposition. Silicon carbide particles were added into the suspension containing 5wt% NaOH to carry out erosion experiments on the coatings with the self-made erosion tester. The experimental results show that, due to the corrosion of the solution on the coating and the impact of SiC particles on the corrosion film and matrix metal, the maximum loss of coating quality occurs when the SiC particle size is 120 μιη at different impact angles. With the increase of impact angle, the mass loss of coating tends to increase. With the increase oftheslurry flow rate, the mass loss of coating increases.

Numerical Simulation of Erosion of Valve Sealing Surface by High Speed Water Flow Based on ALE Method

With the development of modern industry, more and more valves need to be serviced under severe working conditions. Due to the high-speed flushing of working media, the failure of valve sealing surfaces is not uncommon. Based on the ALE (Arbitrary Lagrange-Euler) algorithm, LS-DYNA is used to simulate the erosion of the valve sealing surface material Stellite21 by high-speed water flow, and the damage degree of grid unit is judged by the damage parameter D. At the same time, the parameters of Stellite21 in the Johnson-Cook material model were first calibrated. In this paper, the impact dynamics simulations of different impact angles and different impact velocities were carried out and the material behaviour under different operation parameters of water jet is studied. It is found that with the increase of impact velocity, the erosion rate of materials has a significant increase. As impact angle increases, the erosion damage rate increases first and then decreases, and material has the maximum erosion damage rate at the impact angle of about 40°.

Experimental Investigation on Slurry Erosion Behavior of 304L Steel, Grey Cast Iron, and High Chromium White Cast Iron

The materials used for the slurry transportation system experience erosion wear due to the impact of suspended solid particles. In the present experimental investigation, a large size slurry pot tester was used to investigate the slurry erosion behavior of steel 304L, grey cast iron, and high chromium white cast iron in the velocity range of 9.0–18.5 m/s. Experiments were conducted by rotating the wear specimens in the pot tester at 1% weight concentration of Indian standard sand. The erosion behavior of the three target materials was evaluated by varying the orientation angle from 15 to 90 deg and particle size from 256 to 655 µm. The erosion rate was found to increase with velocity having power index value varying between 2 and 3, which increases with an increase in impact angle and depends on the target material. The erosion rate of the material also increases with the increase in particle size with the power index varying between 0.8 and 1.4 depending on the target material. No significant change was noticed in the mechanism of erosion of the target materials with the variation in velocity in the present range of test conditions. Empirical correlations are proposed to estimate the total erosion rate of all the three materials as a contribution of cutting and deformation wear.

Crashworthiness analysis and design of composite tapered tubes under multiple load cases

Carbon fibre reinforced plastics (CFRP) are characterized by lightweight, high specific strength and stiffness, superior energy-absorbing capacity, and excellent design flexibility. Thus, use of CFRP thin-walled structure as crashworthy application can improve fuel economics and crashworthiness characteristics compared with their metal counterparts. In this study, we reported crushing behavior of several CFRP tapered tubes with various cross-sectional profiles and tapered angles under multiple load cases through numerical simulations. The influences of cross-sectional profiles, tapered angle and loading angle on crashworthiness of all configurations were explored by comparing their failure modes, load-displacement curves, crashworthiness indicators and energy-absorbing mechanisms. It was found that a positive correlation between total energy-absorbing capacity and the edge number of cross section profile was demonstrated, and the tapered tubes with circular profile showed the best total energy-absorbing capacity under both axial and oblique loadings. Besides, it was indicated that the energy-absorbing capacity of the tubes reduced in different degrees with increasing impact angle, and raising tapered angle of the tube was capable to mitigate this reduction degree. Further, the complex proportional assessment method (COPRAS) was adopted to effectively pick up the optimal configuration from all configurations concerned. It was found that H-6, which is the CFRP tapered tube with hexagonal profiles and tapered angle of 6°, was the best configuration, indicating its superiority in crashworthiness characteristics under multiple load cases. Finally, the CFRP tapered tube H-6 was further optimized by using a discrete optimization method to improve its crashworthiness characteristics, and the results showed that the SEAα was improved by 4.35% from the initial design. This study demonstrated that the proposed two-step process (firstly select the best optimal configuration based on COPRAS; then perform the discrete optimization) was fairly effective to obtain an optimal configuration for crashworthiness design of CFRP tapered tubes under multiple load cases.

Erosion behavior of a ship propeller material of QAl9-4 alloy

The erosion behavior of a QAl9-4 alloy as a ship propeller material was investigated. The effects of the solution, the impact angles and the sand content were considered. The test results demonstrate that the mass loss of the alloy in 3.5 wt% NaCl solution is 1.35 times that in tap water, due to the corrosive effect of Cl−. The mass loss of the alloy increases as the impact angle increases up to ~ 30° and consequently decreases as the impact angle increases. Also, this feature is typical for the ductile metal behavior. At the impact angle of 0°, this feature is associated with the predominant erosion mechanisms, such as shallow plowing and surface fatigue; at 30°, this feature is micro-cutting, deep plowing and surface fatigue; and at 45°, it becomes indentation accompanied by extruded lips. The mass loss and surface roughness of the alloy increase as the sand content increases under the testing conditions.

Effect of cenosphere filler surface treatment on the erosion behavior of epoxy matrix syntactic foams

Influence of cenosphere surface modification and volume fraction on the solid particle erosion of cenosphere/epoxy syntactic foams is investigated. Fly ash cenospheres are used as filler in both as received and silane surface modified configurations. Erosion behavior is studied at room temperature for different impact angles (30, 45, 60, and 90°) and velocities (30, 45, and 60 m/s). Neat epoxy shows the highest erosion rate compared with that of the syntactic foams. Results show a strong dependence of impact angle and velocity on erosion rate of syntactic foams. With increasing cenosphere content erosion rate decreases for all impact angles. Erosion rate decreases with increasing impact angle and with decreasing velocity. Good interfacial bonding of treated cenospheres enhances the erosion resistance. All the samples exhibit ductile erosive behavior, with maximum erosion at 30°. The velocity exponent and erosion efficiency parameters confirm the ductile behavior of syntactic foams. POLYM. COMPOS., 40:2109–2118, 2019. © 2018 Society of Plastics Engineers

Effects of pre-tension and impact angle on penetration resistance of woven fabric

High-strength woven fabrics made of polymeric yarns are widely used because of their low density and high toughness, as well as good resistance to high speed loading, particularly ballistic impact. However, their response to impact is complex, due to the woven architecture and rate-dependent behavior of their constituent yarns. This work aims at understanding the effect of applying pre-tension to a woven fabric subjected to normal and oblique impact. A new experimental setup is designed to facilitate application of pre-tension and prescription of specimen inclination. The fabric performance in terms of its ballistic limit is examined, and the variation of the in-plane force experienced by the fabric during impact is also measured. The fabric response for different pre-tensions and impact angles in terms of the ballistic limit is analyzed. In parallel, a numerical model that includes the geometrical features of woven fabric and incorporates the rate-dependent behavior of the yarns, is established. Results generated by the model correlate well with experiments, and yield useful insights into the mechanisms governing fabric behavior, and how pre-tension and impact obliquity influence them. The findings indicate that the fabric response is determined by four primary factors, all of which are affected differently by pre-tension and impact angle: (i) number of yarns involved in the deformation process (increases with pre-tension); (ii) degree of yarn mobility (reduces with pre-tension); (iii) yarn strain energy absorption capacity (decreases with pre-tension and impact obliquity); (iv) sliding of the projectile against the fabric (increases with impact angle). These combine such that the ballistic limit increases with pre-tension up to a critical value, after which it drops. In terms of impact obliquity, the ballistic limit increases with impact obliquity; this is because there is greater sliding of the projectile against the fabric as the impact angle increases, which offsets the decrease in strain energy absorption capacity associated with asymmetric deformation for oblique impact.

Numerical study of the internal flow and initial mixing of diesel injector nozzles with V-type intersecting holes

A V-type intersecting hole nozzle, in which each hole is formed by the coalescence of a pair of sub-holes, has been developed to improve fuel-air mixing for diesel engines. In this paper, a numerical study has been conducted to examine the effects of the V-type intersecting hole structure on the internal flow of a nozzle and the initial stage of the fuel-air mixing processes. With this aim, a multi-phase flow calculation has been implemented on seven V-type intersecting hole nozzles with impact angles ranging from 20° to 50° and a referenced cylindrical hole nozzle under injection pressures varying from 60MPa to 240MPa. The comparison was made in terms of mass flow, momentum flux, effective velocity, discharge coefficient, area coefficient and velocity coefficient. The three-fluid model, which was validated using X-ray experimental data of an Engine Combustion Network (ECN) Spray A injector, was employed to calculate the associated multi-phase flow. The main results show that use of a V-type intersecting hole in a nozzle eliminates cavitation, leading to higher mass flow and momentum flux. Correspondingly, for these V-type intersecting hole nozzles, the discharge coefficients are insensitive to injection pressure, but decrease with an increasing impact angle, and are 20–30% higher than those of the cylindrical hole nozzle. These higher discharge coefficients mainly result from very high area coefficients that are approximately 0.98 at all injection pressure conditions because of the non-cavitating nature of the in-nozzle flow. Moreover, the impact effect of a V-type intersecting hole results in a fan-shaped jet with a very large spreading angle (25–40°) at the dispersion plane and a relatively narrower angle (approximately 12°) at the impact plane. The jet spreading angles at both planes are wider than that of the cylindrical hole nozzle (approximately 7°), indicating a noticeable improvement in the initial fuel-air mixing. Additionally, an increase in the impact angle of a V-type intersecting hole nozzle promotes initial mixing in terms of yielding a wider jet spreading angle, in spite of a slightly lower effective velocity.

Solid particle erosion behaviour of cenosphere reinforced LM6 (Al-Si12) matrix alloy composites

Solid particle erosion of squeeze-cast LM6 (Al-Si12)/cenosphere composites was investigated at ambient temperature. Experiments were performed with different weight percentages (5%, 7.5%, 10% and 12.5%) of composites, having four velocities (48 m/s, 70 m/s, 82 m/s and 109 m/s), at impact angle (30°, 45°, 60° and 90°) and with silica sand as abrasive particle. The eroded surfaces were analysed using scanning electron microscopy (SEM). The results revealed that the particle velocity and impact angle affected the erosion behaviour of the composites. It was found that with the addition of reinforcement to the matrix, the erosion rate was increased at high particle velocities or upon increasing impact angle. The erosion mechanisms observed for the composites are micro ploughing and micro cutting at low impact angles, whereas at high impact angles the erosion of the composites is due to fracture.