Normal Impact Angle Research Articles

Radial-mode abrasive waterjet turning of short carbon–fiber-reinforced plastics

ABSTRACTAn experimental study is carried out for single-pass radial-mode abrasive waterjet (AWJ) turning of a short carbon–fiber-reinforced polyetheretherketone (PEEK) specimen to understand the machining process and the effects of major process variables (feed speed, water pressure, abrasive mass flow rate, nozzle tilt angle, and rotational surface speed) on the major machining performance measures, that is, the depth of cut, material removal rate (MRR) and surface roughness. It is found that high water pressure, normal nozzle impact angle and high rotational speed with suitably selected feed speed and abrasive flow rate may be selected to achieve a high MRR without significantly compromising the surface roughness. Mathematical models for the three cutting performance measures are then developed for use in process control.

Solid-particle erosion behavior of cast alloys used in the mining industry

The erosive-wear response of five commercial ferrous-based cast alloys used for crushing was examined in this study. The microstructures of the alloys were modified to elucidate the effect of microstructural features on wear. Erosion tests were conducted using aluminum oxide particles (90–125 μm) at 70 m/s and a normal impact angle (90°). The worn surfaces were characterized by scanning electron microscopy and 3D non-contact laser profilometry. It is found that (i) a pearlitic structure exhibiting a greater plastic deformation than both bainitic and martensitic structures shows the greatest resistance to erosive wear at normal impact and (ii) the fracture characteristics of carbide and graphite particles plays an important role in determining the erosion wear behavior of the cast alloy matrices.

Laboratory simulation of the surface erosion of solar glass mirrors

During their functioning in concentrated solar power plant – CSP, Glass mirrors are exposed to several climate conditions that cause their degradation. Surface erosion is among mechanical degradation phenomena that can alter mirrors surface and cause a decrease of the overall performance of the CSP plant. Several parameters are influencing this degradation phenomenon, namely the impact speed, the impact angle and the erosive sand particles properties. In this study, we proceed by simulation tests to investigate the effect of surface erosion phenomenon on thin glass mirrors. In order to be representative of the natural degradation phenomenon, the inputs parameters are chosen according to collected data from two different sites in Morocco. Results of simulation tests analysis indicate that the loss in specular reflectance increases with the impact speed. By analyzing the effect of the impact angle, it was discovered that the maximum surface erosion is observed at normal impact angle of 90°. Concerning the effect of sand particles properties on optical degradation, it was found that this latter increases by increasing the sand particle’s size which increase the erosion surface rate. In addition, it was shown that the sand particle’s sharpness presents a precursor for surface erosion phenomenon.

Study of the Surface Damage of Glass Reflectors Used in Concentrated Solar Power Plants

Abstract Solar mirrors are exposed, during their operation in Concentrated Solar Power plants –CSP-, to climatic stress factors that cause their degradation and therefore a decrease in the global efficiency of the plant. Sandstorms are among parameters that cause a decrease of mirrors optical performances by generating surface erosion. The intensity and the gravity of this erosion phenomenon is function of climatic, geological parameters and mirrors surface nature. To evaluate the effect of these parameters on the optical performance degradation, two approaches were adopted, namely the natural aging tests in two different sites in Morocco, and the aging tests in controlled environment in a sandblasting chamber. The objectives are, by monitoring the stress factors in natural aging sites, to define aging tests under controlled environment that reproduce similar degradation phenomenon that those observed on mirrors exposed in natural aging sites. Degradations observed in both natural and controlled aging tests are compared and correlated to validate the methodologies and the hypotheses on the analysis of the degradation phenomenon. The aging tests in controlled environment permits the evaluation of the effect of each influencing parameter separately from the others on the mirrors surface erosion, and eventually accelerate the apparition of surface erosion on mirrors. Under controlled environment, tests show that glass mirrors present maximum surface erosion at normal impact angle and that the loss in specular reflectivity is directly related to the wind speed. Exposed mirrors in natural aging sites present low loss in reflectivity which doesn’t exceed 0.4% after 240 days of outdoor exposure. Concerning the effect of sand properties on erosion phenomenon, it was found that the sand hardness affect the roughness parameters, whilethe sharp forms influence on the impactsproperties(roughness parameters, impacts number, impacted area, impacts size diameter). By increasing the sand particle's size, the impacted area increase and the losses in relative specular reflectivity increase.

To study the Erosion Behavior of H.V.O.F. Coating of 16Cr5Ni at the Different Velocity of Slurry

This paper describes erosion characteristics of high velocity oxy fuel (H.V.O.F.) along with commonly used steels 16Cr5Ni in Turbine and studied the comparison the effect of erosion at Different Velocities of the slurry on Cr 2 O 3 and CrC-NiCr coating on steel. The four different ranges of velocity is taken i.e. 35m/s, 50m/s ,60and 70m/s. at normal impact angle and comparison regarding the erosion resistance was determined from the mass loss results. Higher erosion takes place at medium range of velocity i.e. at 50 m/s. Based on this experimental study coating was considered acceptable for the processes employed

Effect of friction stir processing on erosion–corrosion behavior of nickel–aluminum bronze

In the present investigation, effects of Friction Stir Processing (FSP) on Erosion–Corrosion (E–C) behavior of Nickel–Aluminum Bronze (NAB) were studied by weight-loss measurements and surface characterization using an impingement jet test system. After FSP, the initial coarse microstructure of the cast NAB was transformed to a fine structure, and the porosity defects were eliminated. In addition, different FSP structures were produced by each rotation rate. Microhardness measurements showed a marked increase in FSP samples depending upon the FSP parameters. E–C tests were carried out by erodent at kinetic energies about 0.45μJ and in 30°, 60° and 90° impact angles to simulate actual service conditions. The maximum weight-loss was observed in FSP samples and Scanning Electron Microscopy (SEM) results showed signs of brittle fracture mechanism in FSP samples. By gravimetric analysis, the degree of synergy was evaluated at 0.45μJ kinetic energy at normal impact angle and negative synergy result implies the presence of a protective film on all sample surfaces.

Effect of Boronizing on the Deformation Behaviour of a H320LA Sheet Steel

Abstract The effect of boronizing on commercial H320LA steel sheets of 1 mm and 2 mm thickness was evaluated. The boronizing treatments were carried out in a solid medium at 1173 K for 5 h using the powder pack method. The boride layers formed on the surface were characterized and microhardness measurements were conducted on the borides and the substrate. Mechanical properties and deformation behaviour were compared by bending, tensile, deep drawing, and ballistic tests. The ballistic behaviour was investigated impacting against lead alloy core projectiles of 358 ± 12 m/s velocity at normal impact angle. The microhardness of the boride layers was approximately 1225–1455 HV0.1. Bend tests revealed a sharp decrease in flexural strengths of the boronized specimens. Deep drawability was impaired, while ballistic properties of the plates were improved with boronizing treatment due to improved surface hardness.

Erosion Behaviors of Impeller Material FV520B in Centrifugal Compressor

To study the erosion behaviors and mechanism of impeller material FV520B in centrifugal compressor, the erosion experiments with polygonal alumina particles were carried out on the high-speed erosion testing system. Microstructure of the erosion zone was analyzed by SEM to reveal the erosion mechanism. An erosion model to calculate the erosion rate of FV520B was developed. The results showed that, FV520B exhibited the erosion characteristics of typical plastic materials, the highest erosion rate occurred at the impact angle of 24°, the lowest erosion rate occurred at normal impact angle. The velocity index at the impact angle 24° and 90° were 3.37 and 3.68, it grew as the impact angle increased. The erosion mechanism of FV520B was micro-cutting and deformation wear, at low impact angles, the erosion was dominated by micro-cutting wear, while at high impact angle greater than 60 °, the erosion was dominated by deformation wear. Also the predictions of the erosion model were in good agreement with the results of experiments, indicating that this model can be used to estimate the erosion rate of compressor impeller under different working conditions.

Effect of Nanoclay Addition on the Erosion Wear of Glass/vinylester Composites Using Taguchi's Orthogonal Array Technique

Nanoclay dispersed polymer composites possess high specific stiffness and strength measured in-plane. Such composites can withstand out-of plane low-energy impacts, wear, abrasion and erosion. This paper reports the effect of nanoclay addition on particle impact erosion behaviour of glass / vinylester composites using Taguchi's Orthogonal Array technique. Erosion tests were conducted using silica sand particles of size 177 to 595μm. The results showed that addition of nanoclay up to 3wt. % reduced the erosion rate of the composites. Impingement angle, particle size, stand- off-distance and velocity of impact showed decreasing order of significance and the erosion was in the range 292.5 to442.5mg/kg. Morphology of the eroded surface was examined using Scanning Electron Microscopy. Erosion rate was maximum at normal impact angles with crater formation.

KETAHANAN BALISTIK LEMBARAN BAJA PADA BERBAGAI SUDUT TEMBAK

Results of study on the performance of 0.4 mm mild steel plate when impacted by 4.5 mm diameter steel ogive-shaped projectile at 45o, 60o (oblique impact) and 90 o (normal impact) angles of attack are presented. The projectiles were fired at highest velocity using air riffle gun. The target-holding fixture was located at a distance of 2 m from the gun. Experimental results show that steel plate provides protection at 45o and 60o obliquity, but fails to provide protection at angle of attack of 90o (normal impact)

Effect of Impact Angle on Slurry Erosion Behavior and Mechanisms of Carburized AISI 5117 Steel

The paper reports the influence of carburizing on the slurry erosion behavior of AISI 5117 steel using a whirling-arm rig. The microstructure and hardness profile of the surface layer of carburized steel were investigated. For characterizing the slurry damage process and for better understanding of material removal at different angles, scanning electron microscope (SEM) images at different locations on eroded surface using stepwise erosion combined with relocation SEM were presented. The study is also focused on studying the erosion wear resistance properties of AISI 5117 steel after carburizing at different impact 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. The results showed that, carburizing process of steel increased the erosion resistance and hardness compared with untreated material for all impact angles. The erosion resistance of AISI 5117 steel increases by 75%, 61%, 33%, 10% at an impact angle of 30 deg, 45 deg, 60 deg, and 90 deg, respectively, as result of carburizing, i.e., the effectiveness of carburizing was the highest at low impact angles. Treated and untreated specimens behaved as ductile material, and the maximum mass loss appeared at impact angle of 45 deg. Plough grooves and cutting lips appeared for acute impact angle, but the material extrusions were for normal impact angles. The erosion traces were wider and deeper for untreated specimens comparing by the shallower and superficial ones for the carburized specimens. Chipping of the former impact sites by subsequent impact particles plays an important role in developing erosion.

On ultrahigh velocity micro-particle impact on steels – A multiple impact study

A computational model is presented to investigate the ultrahigh-velocity multiple particle impact process on steels. It uses a Monte Carlo framework to model the stochastic nature of the particle flow and the finite element (FE) method to model the individual particle impact process, while considering the thermal diffusion process. The model predictions show a reasonably good agreement with the corresponding experimental data using a high-tensile steel specimen at various conditions. A simulation study using the model is then conducted and shows that it is essential to consider thermal diffusion which causes the temperature at the impact site to rapidly cool down in a multiple particle impact process. As a consequence, the impact result is impact-sequence and impact-time dependent. The study reveals that inertia-induced fracture is the primary material removal mechanism at the normal impacts, while the thermal instability-driven failure, or specifically the adiabatic shear banding (ASB) induced failure, as well as the elongation-induced fractures are the two major material removal mechanisms at oblique impact angles. These failures occur at the pile-up lips (at normal and oblique impact angles) and the crater bottom (at oblique impact angles). It is the thermal-instability-driven failure that contributes to the higher material removal rate at oblique impact angles.

Erosion resistant titanium based PVD coatings on CFRP

Carbon fibre reinforced plastics (CFRPs) are intensively used in aerospace applications due to their good strength to weight ratio. However, when subjected to solid particle erosion, wear rates of CFRP are more than one order of magnitude higher than steel. Protective coatings produced by physical vapour deposition (PVD) can increase the lifetime of CFRP components. In this work magnetron sputtering was used to deposit various pure titanium and Ti/TiN multilayer thin films on epoxy and PEEK based CFRP substrates to increase their erosion resistance. Erosion testing was performed at 90° impact angle and the mass loss was monitored. It was found that coatings with a film thickness below 10μm failed due to a strong substrate influence. Coatings with a film thickness of 30μm could withstand the erosive wear several times longer. Ductile coatings made of pure titanium showed the lowest mass loss on both substrates. However, for coated CFR-PEEK no reduction of mass loss could be achieved because the polymer had a high erosion resistance at normal impact angle. In contrast, the mass loss of CFR-epoxy could be reduced by a factor of 5 after 10min of erosion testing which shows high potential of such coatings on CFRP.

Effect of Impact Angle on Slurry Erosion Behaviour and Mechanisms of Carburized AISI 5117 Steel

The paper reports a study of slurry erosion of carburized AISI 5117 steel using whirling-arm rig. The study is mainly focused on studying the erosion wear resistance properties of AISI 5117 steel after carburizing at different impact angles. The mechanisms of erosion wear at different impact angles are presented using SEM examination of eroded samples. In addition, the SEM images of eroded samples at different stages are presented for better understanding of erosion mechanisms 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 having a nominal size range of 250 – 355 μm was used as an erodent. The results showed that, carburizing process of steel increased the erosion resistance and hardness compared with untreated material for all impact angles. The erosion resistance of AISI 5117 steel increases by 70, 57, 60 and 36 % at an impact angle of 30o, 45o, 60o and 90o, respectively as result of carburizing, i.e. the effectiveness of carburizing was the highest at low impact angles. Treated and untreated specimens behave as ductile material, and the maximum mass loss appears at impact angle of 45o. Plough grooves and cutting lips appears for acute impact angle, but the material extrusions are for normal impact angles. The erosion traces are wider and deeper for untreated specimens comparing by the shallower and superficial ones for the carburized specimens.

Surface Fatigue of Al-Metal Matrix Composites at Impact Loading

Aluminium 6061 has proven to be a suitable alloy as a basis for producing metal matrix composites (MMC). These MMCs have a low specific weight combined with a relatively good specific stiffness and high specific strength. The hardness and compressive strength of Al composites can be increased by reinforcing bulk material with nano particles. However the ductility of such alloys is relatively low, therefore one of the applications for such light alloys could be wear applications. In many wear conditions such as erosive or abrasive wear at normal impact angles the surface wear resistance plays a significant role. The surface fatigue properties have not been widely studied for such nanoparticle reinforced aluminium composites. The nano-reinforced composite materials were produced by means of high-energy milling (HEM) of nano-sized reinforcement particles together with a metallic matrix powder, followed by hot pressing. By utilizing up to 6 wt% multiwalled carbon nanotubes (MWCNT) as reinforcement the hardness of Al6061 MMC has been increased from 45 HV10 up to 317 HV10, compressive yield strength from 58 MPa up to 660 MPa and indentation modulus from 60 GPa up to 90 GPa compared to hot pressed Al6061. Surface fatigue tests were conducted at impact (dynamic) loading conditions using a hardened steel sphere as indenter. The Wöhler-like curves are plotted to estimate the surface fatigue. The surface fatigue indents were photographed by the aid of light optical microscopy (LOM) and analysed by image analysis software and optical profilometry (OP).

Cavitation erosion and jet impingement erosion mechanism of cold sprayed Ni–Al2O3 coating

Abstract A composite coating was deposited on Inconel 600 substrate by cold spray method using pure Ni powder (60 wt.%) blended with α-Al2O3 (40 wt.%) as feedstock. It is expected to be applied to repair the bellows eroded by the liquid droplet erosion (LDE). Microstructure of the coating was observed using optical microscope (OM) and scanning electron microscopy (SEM). Microhardness of the coating was determined by Vickers hardness tester. Cavitation erosion (CE) experiments were carried out in the distilled water. Jet impingement erosion (JIE) experiments were performed in slurry containing 1 wt.% quartz particle with the flow velocity of 15 m/s at impingement angles of 30°, 60° and 90°, respectively. Cumulative mass loss vs. testing time was used to evaluate the erosion rate of the coating. The erosion mechanism was analyzed by OM, SEM, X-ray diffraction (XRD) and the microhardness measurement. The results show that the composite coating has compact microstructure and relatively high hardness. The resistance to CE of the coating is not as good as that of Inconel 600 substrate due to the weak bonds of the Al2O3 particles. However, the results of the JIE test indicate that the slurry erosion resistance of the coating is better than that of Inconel 600 at the impact angles of 30° and 60°, but not at the normal impact angle.

Erosion–corrosion behavior of plastic mold steel in solid/aqueous slurry

Erosion–corrosion behavior of a precipitation hardenable plastic mold steel (NAK80) has been investigated by using a rotated slurry erosion rig containing a slurry comprising 20 wt% Al2O3 particle and 3.5% NaCl solution. The erosion–corrosion rate and the synergism between erosion and corrosion have been determined under various conditions. The major environmental parameters considered are impact angle, impact velocity, and particle size. Post-test examination was conducted to identify the material degradation mechanism involved. The erosion–corrosion mechanisms of NAK80 mold steel at high-impact angles are dominated by the formation of impact pits, dissolution of metallic matrix, and plastic deformation fatigue spalling, whereas at low-impact angles, the mechanisms are dominated by the formation of impact pits, dissolution of metallic matrix, fatigue cracks, and cutting. The observed synergism between these mechanisms is much more accentuated at an oblique impact angle than that at a normal impact angle. At a given impact angle, the erosion–corrosion rate is found to increase with the impact velocity and the size of solid particles. The maximum peak of the erosion rates lies at oblique angles between 30° and 45°, whereas the maximum peak of the erosion–corrosion rates appears at 45°, and the erosion–corrosion rate is higher than the erosion rate alone at all angles examined. There is a positive synergism between erosion and corrosion for NAK80 mold steel in solid/aqueous slurry. The synergistic effect is 40–60% of the total weight loss. The contribution of synergism to the total weight loss depends upon the impact velocity; however, it is almost independent of the impact angle and particle size.

Solid particle erosion behaviour of ferrous and non-ferrous materials and correlation of erosion data with erosion models

The main objective of the present investigation was to study the erosion behaviour of ferrous and non-ferrous materials and also to examine the erosion model developed for normal and oblique impact angles by Hutchings. For this purpose, erosion studies of ferrous and non-ferrous materials have been conducted at different impingement angles (15–90°) and impact velocities (24–52 m/s). It was observed in this study that the erosion peak at about 60° impingement angle has been pronounced at higher impact velocity (52 m/s) for different materials. However at lower impact velocities, for different materials, the curves of steady state erosion rate versus impingement angle were rather shallow. A reasonable agreement between wear coefficients and hardness of the materials has been observed from one of the models developed by Hutchings. Erosion efficiency values (1.5–6%) indicate that microploughing will be the dominating wear mechanism. Scanning electron microscopy (SEM) study of eroded surface has revealed different wear mechanisms.

Studies on the role of microstructure on performance of a high strength armour steel

This investigation describes and analyses the experimental results pertinent to the ballistic performance of two apparently identical low alloy high strength steel plates against deformable lead projectiles at a velocity about 840 m/s. All the tests are carried out at normal impact angle, i.e. zero obliquity. One plate stopped all projectiles fired at it. However, the other plate failed to stop the projectiles at some locations. Both the plates were subjected to detailed analysis using standard metallurgical techniques to identify the cause of failure in one plate. The experimental results presented include the variation in the microstructure, hardness and retained austenite of the two target plates. The study concludes that the failure is caused by the decrease in resistance of the plate possibly due to higher retained austenite and coarser martensitic structure.

Erosion mechanisms of nodular and gray cast irons at different impact angles

The erosion behaviours of the nodular and gray cast irons were studied at an intermediate and normal impact angles via an experimental setup. Erosion tests were carried out at impact angles of 30°, 60° and 90° using angular hard particles. The particle velocity was controlled utilizing the gas pressure and was measured with rotating double discs. The results showed considerable weight loss variation as a function of the impact angles. The highest erosion rate occurred at an impact angle of 30° and then, two types of the cast irons exhibited the least resistance to erosion. While the rate was at an intermediate level at 60°, the lowest rate occurred at normal impact angle. It was found that the erosion rate of the nodular cast iron (NCI) was lower than that of the gray cast iron (GCI) at all impact angles. In all cases, the erosion appeared to have occurred by a ductile process. At oblique impact angles (30° and 60°), hard erodent caused plastic flow in relatively softer surface of nodular cast iron and material removal occurred by microcutting and microploughing. During the erosive wear progress for nodular cast iron, just below the eroded surface, even though the ends of which behaved as crack nucleation agents, the deformed graphite fines were not broken off from the surface in a short time. No remarkable changes were relatively observed in the wear mechanisms. At a normal impact angle, material loss from the nodular cast iron surface occurred via gauging. Deformation spreading was also observed beneath the surface under at all impact tests. As far as gray cast iron is considered, the erodent can cause plastic yielding in the target surface and material removal went on by major ploughing with microcracking and subsurface fatigue. At a normal impact angle, the erosive wear occurred by chipping and small-scale fracture.