Porosity in Spray-Formed Materials

2007 ◽  
Vol 534-536 ◽  
pp. 429-432 ◽  
Author(s):  
Volker Uhlenwinkel ◽  
N. Ellendt
Keyword(s):  
Surface Temperature ◽  
Theoretical Models ◽  
Impact Angle ◽  
The Past ◽  
Deposit Surface ◽  
Average Impact ◽  
Basic Understanding ◽  
Impact Angles ◽  
The Impact ◽  
Average Weighted Impact

Porosity in spray-formed materials is an important issue, but the formation of porosity is not completely understood. Many experimental results and some theoretical models have been presented in the past. Nevertheless, the prediction of porosity in a deposit is still not possible today. The paper will give some examples picked from literature, which show some general correlations between process parameters and porosity. These correlations can be helpful to form a basic understanding of the process. Finally it is necessary to know more about the conditions of the droplets and the deposit at the point of impingement. These impacting conditions have to be correlated to the porosity to improve the understanding of the process and to make a prediction possible. Determining the impact conditions is a challenge because usually they are not constant with time and some values are difficult to measure. Our experiments show a strong correlation between the surface temperature of the deposit and the porosity. For IN718 and U720 as-sprayed porosities below 1 vol.% were achieved if the deposit surface temperature is app. 1250 °C. The average impact angle weighted by the local particle mass flux is also an important parameter. The probability of low as-sprayed porosity is high if the average weighted impact angle is below 25° but decreases dramatically for higher impact angles.

Erosion-Abrasion Behavior of Eutectic Al-Mn Alloy Matrix Composites Reinforced with Al2O3 Particulates

2010 ◽  
Vol 152-153 ◽  
pp. 1054-1057
Author(s):  
Bing Liu ◽  
Xin Mei Li ◽  
Xiang Liu ◽  
Chun Yao Wang
Keyword(s):  
Solid Solution ◽  
Shear Stress ◽  
Impact Angle ◽  
Matrix Composites ◽  
Alloy Matrix ◽  
Abrasion Test ◽  
Wear Rates ◽  
Impact Angles ◽  
The Impact ◽  
Worn Surface

Effects of different impact angles such as 45°and 90°on the erosion-abrasion properties of eutectic Al-Mn alloy and its composites reinforced with Al2O3 particulates were studied by rotating erosion-abrasion test, and the microstructure and the worn surfaces were analyzed. The results show that the as-cast Al-Mn alloy is composed of aluminium-manganese solid solution, MnAl6 and Al11Mn4 phase, while the δ-Al2O3 particles are included in the composites besides the aforementioned microstructures. With elongating the erosion time, the wear rates of the Al-Mn alloy and its composites increase at the impact angle of 90°, whereas they firstly increase and then decrease , and there is a maximum at 45°. The distortion wear caused by the normal stress is dominant at 90°, which lead to the erosion pits on the worn surface. However, the cutting wear by the shear stress is predominant at 45°, which result in the ploughs.

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

2014 ◽  
Vol 136 (2) ◽  
Author(s):  
Y. M. Abd-Elrhman ◽  
A. Abouel-Kasem ◽  
S. M. Ahmed ◽  
K. M. Emara
Keyword(s):  
Rebound Effect ◽  
Impact Angle ◽  
Silica Sand ◽  
Slurry Erosion ◽  
Nominal Size ◽  
Erosion Mechanisms ◽  
Impact Angles ◽  
The Impact ◽  
Calculated Number ◽  
Number Of Particles

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.

Crashworthiness Simulation Analysis of Light Sport Aircraft Fuselage Structure

2011 ◽  
Vol 199-200 ◽  
pp. 48-53 ◽  
Author(s):  
Pu Woei Chen ◽  
Shu Han Chang ◽  
Yu Yang Hsieh ◽  
Tai Sing Sun
Keyword(s):  
Simulation Analysis ◽  
Impact Angle ◽  
General Aviation ◽  
Aviation Industry ◽  
Aircraft Fuselage ◽  
Passenger Safety ◽  
Engine Mount ◽  
Distance Travel ◽  
Impact Angles ◽  
The Impact

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.

scholarly journals Impact and Ricochet of a High Speed Projectile from a Plate

2021 ◽  
Vol 71 (6) ◽  
pp. 737-747
Author(s):  
Hussein Bassindowa ◽  
Bakhtier Farouk ◽  
Steven B. Segletes
Keyword(s):  
Titanium Alloy ◽  
High Speed ◽  
Computational Study ◽  
Incident Angle ◽  
Finite Thickness ◽  
Impact Angle ◽  
Projectile Velocity ◽  
Alloy Plate ◽  
Impact Angles ◽  
The Impact

A computational study of a projectile (either 2024 aluminum or TiAl6V4 titanium alloy) impacting a plate (either titanium alloy or aluminum) is presented in this paper. Projectile velocity (ranging from 250 m/s to 1500 m/s) with varying impact angles are considered. The presence of ricochet (if any) is identified over the ranges of the projectile velocity and impact angle considered. For the cases where ricochet is identified, the ricochet angle and velocity are predicted as functions of the incident angle and the incident velocity. The numerical results are compared with an analytical solution of the ricochet problem. The analytical solutions are from a model developed to predict the ballistic ricochet of a projectile (projectile) penetrator. The dynamics and the deformation of an aluminum (or a titanium alloy) projectile impacting on a finite thickness titanium alloy (or aluminum) plate are simulated. The current work is interesting in that it looks in the field of ballistics of different material combinations than are traditionally studied. The present simulations based on detailed material models for the aluminum and the titanium alloy and the impact physics modelling features in the LS-DYNA code provide interesting details regarding the projectile/plate deformations and post-impact projectile shape and geometry. The present results indicate that for no cases (for specified incoming velocities and impact angles considered) can an aluminum projectile penetrate a titanium alloy plate. The ricochet ‘mode predictions ‘obtained from the present simulations agree well with the ricochet ‘mode predictions’ given in an analytical model.

scholarly journals Neck Moment Characterization of Restrained Child Occupant at Realistic Nontest Standard Higher Impact Speed of 32.2 km/h

2014 ◽  
Vol 2014 ◽  
pp. 1-8
Author(s):  
S. Shasthri ◽  
V. Kausalyah ◽  
Qasim H. Shah ◽  
Kassim A. Abdullah ◽  
Moumen M. Idres ◽  
...  
Keyword(s):  
Interactive Effect ◽  
Impact Angle ◽  
Side Impact ◽  
Impact Speed ◽  
Child Restraint ◽  
Child Restraint System ◽  
Impact Angles ◽  
Child Occupant ◽  
The Impact

The effects of bullet vehicle crash impact angle, child restraint system design, and restraint harness slack at side impact speed of 32.2 km/h (20 mph) on moments sustained at the neck by a three-year-old child are investigated. Mathematical models are built using the response surface method based on simulation results whereby good fitness is achieved. The singular and cross interactive effect of each predictor on the neck moment are analyzed. The number of significant parameters affecting the neck moment is shown to be the largest for wide impact angles (ϕ≥60°) and the impact angle parameter is largely revealed to be the most sensitive. An ideal safe range for low neck moment has been established to be within ϕ angles 45° and 65°. It is further shown that the nature of all parameters effect on the neck moment is highly dependent on the impact angle range.

Erosion and its Effect on a Water-Cooled Turbine

1978 ◽  
Author(s):  
Max Freedman
Keyword(s):  
Impact Velocity ◽  
Gas Turbines ◽  
Mass Loss Rate ◽  
Impact Angle ◽  
Aluminum Specimen ◽  
High Impact Velocity ◽  
Short Time ◽  
Impact Angles ◽  
The Impact

Erosion tests were run to obtain data for designing a water-cooled gas turbine collection shroud. All tests utilized a coherent stream of water ejected from a static nozzle against stationary small block specimens. Twenty-one tests were run with aluminum specimens and 16 more tests with other materials. The impact velocity was varied from 165 to 270 m/s (540 to 890 fps). The impact angle was varied from 10 to 90 deg. The mass loss rate results generally show four erosion regions, which are consistent with the literature. A correlation between regions two and four was found. Aluminum specimen erosion rate was found to be unexpectedly high with impact angles of 10 deg and moderate-to-high impact velocity. No report of previous liquid erosion work at impact angles less than 30 deg was found; since it is expected that water-cooled gas turbines will operate at impact angles of about 15 deg, erosion in this low impact angle region should be studied. If the correlation between erosion regions two and four can be quantized, then very short-time tests could be used to predict long-term erosion at minimal cost.

Evaluating Impact Properties of Cement Clinker at Different Angle for Impact Indentation

2011 ◽  
Vol 492 ◽  
pp. 43-46
Author(s):  
Xiu Fang Wang ◽  
Yi Wang Bao ◽  
Yan Qiu ◽  
Xiao Gen Liu ◽  
Yuan Tian
Keyword(s):  
Impact Velocity ◽  
Impact Force ◽  
Surface Damage ◽  
Impact Angle ◽  
Cement Clinker ◽  
Damage Degree ◽  
Indentation Tests ◽  
Impact Angles ◽  
The Impact ◽  
Peak Impact Force

Spherical impact indentation tests with different impact angles (90°, 60°, 45°, and 30°) was carried out to understand the effect of impact angles on damage degree of cement clinker. A linear rail which can adjust angle to alter impact velocity was used to guide the slipping impact head to impact the sample. The different steel wedge was used to change the impact angle. It is found that the area of damage surface for cement clinker is most serious the peak impact force for surface damage decreases but the contact indentation becomes longer with decreasing impact angle when the impact angle is 45°. Under almost the same impact velocity, the smaller the impact angle, the higher the impulse, the longer contact time, and the peak impact force of 45° is maximum.

Analysis of Bloodstains Patterns at Sharp Impact Angles

2016 ◽  
Author(s):  
Mohammad Moshfeghi ◽  
Iman Rahimipetroudi ◽  
Nahmkeon Hur
Keyword(s):  
Crime Scene ◽  
Impact Angle ◽  
Equivalent Diameter ◽  
Glycerol Solution ◽  
Fluid Viscosity ◽  
Bloodstain Pattern ◽  
Droplet Sizes ◽  
Impact Angles ◽  
The Impact ◽  
Inclined Surface

Bloodstain pattern analysis is of tremendous value for the investigation of the evidence at the crime scene. Analyzing the bloodstain patterns provides an appropriate method for retracing the origin of blood droplets and also reconstruction of the crime scene. The patterns of the bloodstains on the floors and walls are determined by the impact conditions of blood drops such as droplet sizes, impact angles and velocities. The objective of this work is to study the bloodstain patterns on an inclined surface, in order to categorize the bloodstain shapes. The experiments have been carried out using a 38% glycerol solution at room temperature between 16° C∼21° C. The experiments have been done for three different droplet diameters, five different velocities and four different surface inclinations. The blood-mimicking fluid viscosity and density have been measured at the same temperature range with the experiments. The results have been investigated in terms of bloodstain shape and patterns and three different categories have been determined. In addition, a new mathematical formula has been derived based on the equivalent diameter of the bloodstains, which relates the bloodstain dimensions to the droplet Reynolds and Weber numbers. It has been shown that the proposed formula fits more accurately with the experimental results for high impact angle cases as compared to the classical formula.

scholarly journals An Experimental Study on the Oblique Collisions of Water Droplets With a Smooth Hot Solid

2012 ◽  
Vol 134 (7) ◽  
Author(s):  
Hitoshi Fujimoto ◽  
Ryota Doi ◽  
Hirohiko Takuda
Keyword(s):  
Surface Temperature ◽  
Impact Velocity ◽  
Solid Surface ◽  
Impact Angle ◽  
Alloy Surface ◽  
Inconel 625 ◽  
Normal Velocity ◽  
Inconel 625 Alloy ◽  
Secondary Droplets ◽  
The Impact

The motions of liquid droplets impinging on a solid substrate have been studied experimentally in fundamental research on various types of industrial applications, including spray cooling. The oblique collision of a single water droplet with a hot Inconel 625 alloy surface has been investigated by means of a two-directional flash photography technique that uses two digital still cameras and three flash units. The experiments were conducted under the following conditions. The preimpact diameter of the droplets was approximately 0.6 mm, the impact velocity was 1.9–3.1 m/s, and the temperature of the Inconel 625 alloy surface ranged from 170 °C to 500 °C. The impact angle of droplets on the solid surface was in the range 45 deg–90 deg. Experiments using 2.5 mm diameter droplets at an impact velocity of 0.84–1.4 m/s were also conducted at the surface temperature of 500 °C. At surface temperatures of 200 °C, 300 °C, and 400 °C, the droplet deforms into an asymmetric shape and moves downward along the tilted surface. Numerous secondary droplets jet upward from the deforming droplet as a result of the blowout of vapor bubbles into the atmosphere. At a surface temperature of 500 °C and a low Weber number Wen based on the normal velocity component to the solid surface, no secondary droplets are observed. The droplet rebounds off the solid without disintegrating. The droplet becomes almost axisymmetric in shape during the collision regardless of the impact angle. The dimensionless collision behaviors of large and small droplets were similar for the same Wen when the temperature was 500 °C. Using Wen, we investigated the deformation characteristics of droplets in oblique collisions.

Shock Pressure in Oblique Impact—A Theoretical Analysis

1974 ◽  
Vol 41 (1) ◽  
pp. 124-130 ◽  
Author(s):  
C. A˚ke Persson
Keyword(s):  
Shock Wave ◽  
Pressure Rise ◽  
Impact Angle ◽  
Oblique Impact ◽  
Shock Pressure ◽  
Elastic Media ◽  
Linear Elastic ◽  
Wave Velocities ◽  
Impact Angles ◽  
The Impact

The variation of shock pressure with the angle between the colliding surfaces in an oblique impact between two plane plates is analyzed theoretically. The analysis is carried out for small impact angles and the plate materials are assumed to behave like fluids (Case 1) and linear elastic media (Case 2). In the latter case the two extreme assumptions concerning the friction at the interface, no friction and no sliding, are treated. The results show that the shock pressure increases quadratically with the impact angle (except for some of the no sliding cases, where decreasing pressure can occur) and that the pressure rise is strongly dependent upon the ratio between the impact velocity and the shock wave velocities for the plate materials.

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