A Novel Optical Technique for Measuring the Coefficient of Restitution of Microparticle Impacts in a Forced Flowfield

2012 ◽  
Author(s):  
C. J. Reagle ◽  
J. M. Delimont ◽  
W. F. Ng ◽  
S. V. Ekkad ◽  
V. P. Rajendran
Keyword(s):  
Impact Velocity ◽  
Fundamental Property ◽  
Impact Angle ◽  
Coefficient Of Restitution ◽  
304 Stainless Steel ◽  
Wall Material ◽  
Free Jet ◽  
Stainless Steel Coupon ◽  
Novel Method ◽  
Impact Angles

Erosion and deposition in gas turbine engines are functions of particle/wall interactions and Coefficient of Restitution (COR) is a fundamental property of these interactions. COR depends on impact velocity, angle of impact, temperature, particle composition, and wall material. The current study attempts to characterize the fundamental behavior of sand at different impact angles. A PIV system is used in the Virginia Tech Aerothermal Rig to measure velocity trajectories of microparticles. A novel method is used that solves for impact velocity in a forced flowfield by numerical methods. Two sizes of Arizona Test Dust and one of Glass beads are impacted into a 304 Stainless Steel coupon. Free jet velocity is 27m/s at room temperature. Impact angle varies from almost 90 to 25 degrees depending on particle. Mean results compare favorably with trends established in literature. This utilization of this technique to measure COR of microparticle sand will help develop a computational model and serve as a baseline for further measurements at elevated, engine representative air and wall temperatures.

Analytical Study of the Oblique Impact of a Rod with a Flat Using an Elasto-Plastic Contact Model

2015 ◽  
Vol 801 ◽  
pp. 25-32
Author(s):  
Ozdes Cermik ◽  
Hamid Ghaednia ◽  
Dan B. Marghitu
Keyword(s):  
Impact Velocity ◽  
Contact Force ◽  
Analytical Study ◽  
Initial Conditions ◽  
Permanent Deformation ◽  
Oblique Impact ◽  
Coefficient Of Restitution ◽  
Contact Model ◽  
Impact Angles ◽  
The Impact

In the current study a flattening contact model, combined with a permanent deformation expression, has been analyzed for the oblique impact case. The model has been simulated for different initial conditions using MATLAB. The initial impact velocity used for the simulations ranges from 0.5 to 3 m/s. The results are compared theoretically for four different impact angles including 20, 45, 70, and 90 degrees. The contact force, the linear and the angular motion, the permanent deformation, and the coefficient of restitution have been analyzed. It is assumed that sliding occurs throughout the impact.

Experimental Impact of a Pendulum With the Sand

2009 ◽  
Author(s):  
Seunghun Lee ◽  
Dan B. Marghitu
Keyword(s):  
Impact Velocity ◽  
Frictional Force ◽  
Granular Media ◽  
Stopping Time ◽  
Impact Angle ◽  
Resistance Force ◽  
Force Velocity ◽  
Static Resistance ◽  
Impact Angles ◽  
Resistance Forces

In this paper, a compound pendulum impacting a granular media is studied and the influences of initial impact velocity and impact angle are examined. The resistance forces are studied as the sum of a dynamic frictional force (velocity dependent) and a static resistance force (depth dependent). The penetrating angle is increasing with initial impact velocity as expected. However, the stopping time is decreasing with initial impact velocity for all initial impact angles in our system.

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.

Study on the Erosion Wear Behaviors of the PMMA Plates Impacted by Air Flow Containing Sands

2013 ◽  
Vol 631-632 ◽  
pp. 366-370
Author(s):  
Ting Xie ◽  
Gang Liu ◽  
Peng Fei Wang ◽  
Yan Guo Yin
Keyword(s):  
Impact Velocity ◽  
Impact Angle ◽  
Erosion Wear ◽  
Micro Cutting ◽  
Erosion Mechanism ◽  
Erosion Mechanisms ◽  
Impact Angles ◽  
The Impact ◽  
Erosion Volume ◽  
Sand Size

The polymethymethacrylate (PMMA) plate was adopted as the test samples. The effects of impact angle, impact velocity, sand size on the erosion wear of the PMMA plates were experimentally investigated. The erosion mechanisms were also analyzed. The results showed that, the erosion volume increased nonlinearly with the increase of impact velocity, the inflection point appeared at around 13 m/s, and then the erosion volume increased rapidly. The erosion volume decreased nonlinearly as the impact angle increased. In our experiments, under the impact angle less than 60°, the smaller sand size could result in higher erosion wear. However, at 90°, the erosion volume by larger sands produced higher erosion. In fact, the erosion mechanism depends on the impact angle, at small impact angles, the main erosion mechanism is micro-cutting, and the erosion mechanism will mainly be impacting fatigue at large impact angles. At the medium impact angles, the erosion mechanism is the combination of the micro-cutting and impacting.

Predicting the Coefficient of Restitution for Particle Wall Collisions in Gas Turbine Components

2013 ◽  
Author(s):  
Sukhjinder Singh ◽  
Danesh Tafti
Keyword(s):  
Experimental Data ◽  
Plastic Deformation ◽  
Gas Turbine ◽  
Impact Velocity ◽  
Impact Angle ◽  
Coefficient Of Restitution ◽  
Energy Losses ◽  
Velocity Impact ◽  
Fine Particulate ◽  
Wall Interaction

Jet engines often operate under hostile conditions and are increasingly exposed to fine particulate matter such as sand, ash and dirt. Large amounts of fine particulate ingestion, sand in particular, can damage different engine components through deposition and erosion. The extent of damage depends on the particle-wall interaction, which is further governed by particle velocity, impact angle, particle size, particle material, target material and target surface roughness. Coefficient of restitution, which is the ratio of rebound velocity to impact velocity, encapsulates the effect of all the energy losses occurring during a collision. The current work presents a new model which predicts the energy losses and hence coefficient of restitution for a particle-wall collision. The current work combines elastic plastic deformation and adhesion theories of particle-wall interaction. Plastic deformation losses and adhesion losses are calculated separately based on impact parameters: impact velocity, impact angle, particle/wall material properties. These losses combine together to give the net energy loss during a collision and hence coefficient of restitution. The main objective of this study is to develop a collision model for sand particle interaction in gas turbine components, so the results are compared with available experimental data on coefficient of restitution for sand particles. The coefficient of restitution predictions are also compared with existing experimental data on a wide range of particle sizes and materials. Model predictions are found to be in good agreement with experiments.

High Velocity Oblique Impact and Coefficient of Restitution for Head Disk Interface Operational Shock

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Raja R. Katta ◽  
Andreas A. Polycarpou ◽  
Jorge V. Hanchi ◽  
Robert M. Crone
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Impact Damage ◽  
Element Model ◽  
Oblique Impact ◽  
Coefficient Of Restitution ◽  
Energy Losses ◽  
Elastic Plastic ◽  
Impact Angles ◽  
Operational Shock

With the increased use of hard disk drives (HDDs) in mobile and consumer applications combined with the requirement of higher areal density, there is enhanced focus on reducing head disk spacing, and consequently there is higher susceptibility of slider/disk impact damage during HDD operation. To investigate this impact process, a dynamic elastic-plastic finite element model of a sphere (representing a slider corner) obliquely impacting a thin-film disk was created to study the effect of the slider corner radius and the impact velocity on critical contact parameters. To characterize the energy losses due to the operational shock impact damage, the coefficient of restitution for oblique elastic-plastic impact was studied using the finite element model. A modification to an existing physics-based elastic-plastic oblique impact coefficient of restitution model was proposed to accurately predict the energy losses for a rigid sphere impacting a half-space. The analytical model results compared favorably to the finite element results for the range from low impact angles (primarily normal impacts) to high impact angles (primarily tangential impacts).

Effective hydrogen diffusivities of AISI 304 stainless steel with Ni or Au coating

2020 ◽  
Vol 62 (6) ◽  
pp. 593-596
Author(s):  
Krittayot Wannapoklang ◽  
Sirichai Leelachao ◽  
Anchaleeporn W. Lothongkum ◽  
Gobboon Lothongkum
Keyword(s):  
Stainless Steel ◽  
Hydrogen Diffusion ◽  
304 Stainless Steel ◽  
Phase Identification ◽  
Aisi 304 Stainless Steel ◽  
Aisi 304 ◽  
304 Austenitic Stainless Steel ◽  
Hydrogen Assisted Cracking ◽  
Stainless Steel Coupon ◽  
Effective Hydrogen

AbstractMetallic coatings which provide a hydrogen diffusion barrier are thought to reduce hydrogen assisted cracking on stainless steel. The influence of a metallic layer on the hydrogen migration of AISI 304 stainless steel was investigated using a commercial electroplating layer of Ni and Au on a thin stainless steel coupon. Phase identification was performed using an X-ray diffractometer to determine the average thicknesses, measured from back-scattered scanning electron images. Regarding the ASTM G148-97 practice, the effective hydrogen diffusivities of AISI 304 austenitic stainless steel, nickel and gold were measured as 7.07 × 10-13, 2.72 × 10-14 and 9.64 × 10-16 m2 × s-1, respectively. In this work, a gold layer was found to be most effective for the prevention of hydrogen diffusion when compared with untreated and Ni-plated 304 stainless steel.

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