Target Configurations for Plate-Impact Recovery Experiments

1992 ◽  
Vol 59 (2) ◽  
pp. 305-311 ◽  
Author(s):  
S. N. Chang ◽  
D.-T. Chung ◽  
Y.-F. Li ◽  
S. Nemat-Nasser
Keyword(s):  
Free Edge ◽  
Surface Velocity ◽  
Thin Plates ◽  
Longitudinal Momentum ◽  
Normal Velocity ◽  
Flyer Plate ◽  
Plate Impact ◽  
Tensile Stresses ◽  
The Impact ◽  
Momentum Trap

Normal plate impact recovery experiments have been perfomed on thin plates of ceramics, with and without a back momentum trap, in a one-stage gas gun. The free-surface velocity of the momentum trap was measured, using a normal velocity (or displacement) interferometer. In all recovered samples, cross-shaped cracks were seen to have been formed during the impact, at impact velocities as low as 27 m/s, even though star-shaped flyer plates were used. These cracks appear to be due to in-plane tensile stresses which develop in the sample as a result of the size mismatch between the flyer plate and the specimen (the impacting area of the flyer being smaller than the impacted area of the target) and because of the free-edge effects. Finite element computations, using PRONTO-2D and DYNA-3D, based on linear elasticity, confirm this observation. Based on numerical computations, a simple configuration for plate impact experiments is proposed, which minimizes the inplane tensile stresses allowing recovery experiments at much higher velocities than possible by the star-shaped flyer plate configuration. This is confirmed by normal plate impact recovery experiments which produced no tensile cracks at velocities in a range where the star-shaped flyer invariably introduces cross-shaped cracks in the sample. The new configuration includes lateral as well as longitudinal momentum traps.

scholarly journals Ultrasonic Detection of Spall Damage Distribution Subjected to Plate Impact Test with Different Thickness

2018 ◽  
Vol 183 ◽  
pp. 02029
Author(s):  
Naoya Nishimura ◽  
Toshihiro Ito ◽  
Takeru Watanabe
Keyword(s):  
Tensile Stress ◽  
Impact Test ◽  
Plate Thickness ◽  
Flyer Plate ◽  
Plate Impact ◽  
Target Plate ◽  
Damage Distribution ◽  
Spall Damage ◽  
The Impact ◽  
Different Thickness

Plate impact test on medium carbon steel were carried out to the target plate by impacting the flyer plate with one-third and two-thirds thickness of the target plate. The spall damage within the target plate was evaluated non-destructively with a low frequency scanning acoustic microscope as well as ultrasonic velocity and backscattering intensity. We observed the spall damage distribution by the B-and Cscan images. The distribution of spall damage through the plate thickness depends on the tensile stress area within the target plate. The difference of spall damage distribution was investigated by the plate impact test by flyer plate with different thickness. In the plate impact test by the flyer plate with 1/3 target plate thickness, the spall damage was generated by tensile stress area which superposed in the back surface side. On the other hand, in the case of 2/3 target plate thickness, the spall damage was detected at the impact surface side. By generating the spall damage in the different position through the target thickness, it will be possible to evaluate the accumulation of spall damage by reflection and transmission of the stress wave at the internal damage subjected to repeated impact.

Analysis of Combined Pressure-Shear Waves in an Elastic/Viscoplastic Material

1977 ◽  
Vol 44 (1) ◽  
pp. 79-84 ◽  
Author(s):  
A. S. Abou-Sayed ◽  
R. J. Clifton
Keyword(s):  
Fine Structure ◽  
Rear Surface ◽  
Surface Velocity ◽  
Normal Velocity ◽  
Free Surface Velocity ◽  
Viscoplastic Material ◽  
Time Profiles ◽  
Laser Velocity ◽  
Skewed Plates ◽  
The Impact

A numerical solution is presented for the case of symmetric impact of two skewed plates, modeled to represent 6061-T6 Aluminum. The main features of the solution are, except near the impact face, the same as in previous solutions based on a rate-independent theory. Free-surface velocity-time profiles are obtained for the target rear surface. These profiles indicate that the fine structure of the normal velocity should be resolvable by means of a laser velocity-interferometer.

Unusual Microstructure in Shock-Compacted Graphite

1970 ◽  
Vol 28 ◽  
pp. 474-475
Author(s):  
Lucien F. Trueb
Keyword(s):  
Mechanical Characteristic ◽  
Compression Wave ◽  
Gray Zone ◽  
Flyer Plate ◽  
Compacted Graphite ◽  
The Impact

Crushed and statically compressed Madagascar graphite that was explosively shocked at 425 kb by means of a planar flyer-plate is characterized by a black zone extending for 2 to 3 nun below the impact plane of the driver. Beyond this point, the material assumes the normal gray color of graphite. The thickness of the black zone is identical with the distance taken by the relaxation wave to overtake the compression wave.The main mechanical characteristic of the black material is its great hardness; steel scalpels and razor blades are readily blunted during attempts to cut it. An average microhardness value of 95-3 DPHN was obtained with a 10 kg load. This figure is a minimum because the indentations were usually cracked; 14.8 DPHN was measured in the gray zone.

scholarly journals Numerical simulation of variable thermal conductivity on 3D flow of nanofluid over a stretching sheet

2020 ◽  
Vol 9 (1) ◽  
pp. 233-243 ◽  
Author(s):  
Nainaru Tarakaramu ◽  
P.V. Satya Narayana ◽  
Bhumarapu Venkateswarlu
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Stretching Sheet ◽  
Three Dimensional ◽  
Variable Thermal Conductivity ◽  
Normal Velocity ◽  
Transfer Coefficients ◽  
Similarity Transformations ◽  
Frictional Coefficients ◽  
The Impact

AbstractThe present investigation deals with the steady three-dimensional flow and heat transfer of nanofluids due to stretching sheet in the presence of magnetic field and heat source. Three types of water based nanoparticles namely, copper (Cu), aluminium oxide (Al2O3), and titanium dioxide (TiO2) are considered in this study. The temperature dependent variable thermal conductivity and thermal radiation has been introduced in the energy equation. Using suitable similarity transformations the dimensional non-linear expressions are converted into dimensionless system and are then solved numerically by Runge-Kutta-Fehlberg scheme along with well-known shooting technique. The impact of various flow parameters on axial and transverse velocities, temperature, surface frictional coefficients and rate of heat transfer coefficients are visualized both in qualitative and quantitative manners in the vicinity of stretching sheet. The results reviled that the temperature and velocity of the fluid rise with increasing values of variable thermal conductivity parameter. Also, the temperature and normal velocity of the fluid in case of Cu-water nanoparticles is more than that of Al2O3- water nanofluid. On the other hand, the axial velocity of the fluid in case of Al2O3- water nanofluid is more than that of TiO2nanoparticles. In addition, the current outcomes are matched with the previously published consequences and initiate to be a good contract as a limiting sense.

Explosive Welding of SS304 and Al6061 Using Copper as Interlayer – Development of Trial Methodology and its Optimisation

2015 ◽  
Vol 830-831 ◽  
pp. 306-309
Author(s):  
Niraj Srivastava ◽  
Abhishek Upadhyay ◽  
Sandeep Kumar ◽  
Diva ◽  
Jaspreet Singh ◽  
...  
Keyword(s):  
Explosive Welding ◽  
Welding Process ◽  
Al Alloy ◽  
Flyer Plate ◽  
Trial Methodology ◽  
Al 6061 ◽  
Velocity Of Detonation ◽  
Copper Interlayer ◽  
Weldability Window ◽  
The Impact

This paper explains the technique of explosive welding for joining SS304 and Al 6061 using Copper interlayer. The joining was done in two stages. In the first stage SS304 (thickness: 20 mm) was joined to Copper (thickness: 3mm). Second stage involved joining of SS-Cu plate to Al 6061 (thickness: 8 mm).The paper presents detailed discussion on important parameters required for explosive welded process. The most important parameter is minimum and maximum flyer plate velocity required for creating the impact. Collision angle and angle of impact are also discussed. Another important parameter is the Velocity of detonation (VOD) of explosive to be used. The explosives used have VOD of the order of 2500 m/s and 1600 m/sec. Since the explosive welding process involves formation of jet between two surface, therefore surface conditions of the base and flyer plate like its flatness, roughness and cleanliness which are very critical for proper joining have been discussed in this paper. Chisel test (which is considered to be most rugged test) was conducted on the joint. The test confirmed successful joining.The paper explains how use of trimonite expands the weldability window in comparison to NGU when used for direct SS to Al alloy welding.It also compares the results obtained by use of two different powder explosives to obtain the same tri-layered plate via two different routes. The results are particularly interesting because both the explosives have substantial difference in their properties such as Velocity of Detonation, Gurney Characteristic Velocity, density and homogeneity which can be used as advantages from different angles of views.

Pure Design Method for Aerofoils in Cascade

1969 ◽  
Vol 11 (5) ◽  
pp. 454-467 ◽  
Author(s):  
K. Murugesan ◽  
J. W. Railly
Keyword(s):  
Exact Solution ◽  
Velocity Distribution ◽  
Design Problem ◽  
Design Method ◽  
Tangential Velocity ◽  
Surface Velocity ◽  
Normal Velocity ◽  
Blade Design ◽  
Blade Shape

An extension of Martensen's method is described which permits an exact solution of the inverse or blade design problem. An equation is derived for the normal velocity distributed about a given contour when a given tangential velocity is imposed about the contour and from this normal velocity an initial arbitrarily chosen blade shape may be successively modified until a blade is found having a desired surface velocity distribution. Five examples of the method are given.

Influence of Engine Cabin Simplification on Aerodynamic Characteristics of Car

2014 ◽  
Vol 1042 ◽  
pp. 188-193 ◽  
Author(s):  
Xing Jun Hu ◽  
Jing Chang
Keyword(s):  
Numerical Simulation ◽  
Aerodynamic Drag ◽  
Aerodynamic Characteristics ◽  
Thin Plates ◽  
Average Thickness ◽  
Two Dimensional ◽  
Engine Cooling ◽  
Aerodynamic Drag Coefficient ◽  
Simulation Results ◽  
The Impact

In order to analyze the impact of engine cabin parts on aerodynamic characteristics, the related parts are divided into three categories except the engine cooling components: front thin plates (average thickness of 2mm), bottom-suspension and interior panels. The aerodynamic drag coefficient (Cd) were obtained upon the combination schemes consisting of the three types of parts by numerical simulation. Results show that Cd by simulation is closer to the test value gained by the wind tunnel experiment when front thin plates were simplified to the two-dimensional interface with zero thickness. The error is only 5.23%. Meanwhile this scheme reduces grid numbers, thus decreasing the calculating time. As the front thin plates can guide the flow, there is no difference on the Cd values gained from the model with or without bottom-suspension or interior panels when the engine cabin contains the front thin plates; while only both bottom-suspension and interior panels are removed, the Cd value can be reduced when the cabin doesn’t contain the front thin plates.

Low-Velocity Impact on a Functionally Graded Circular Thin Plate

2006 ◽  
Author(s):  
Pantele Chelu ◽  
Liviu Librescu
Keyword(s):  
Plate Theory ◽  
Equation System ◽  
Functionally Graded ◽  
Low Velocity Impact ◽  
Thin Plates ◽  
Low Velocity ◽  
Alternative Analysis ◽  
Velocity Impact ◽  
Graded Material ◽  
The Impact

In this paper, an alternative analysis strategy based on a Wavelet-Galerkin scheme specially tailored to solve impact problems of functionally graded orthotropic thin plates subjected to low-velocity impact is presented. The plate considered to be circular, is assumed to be clamped on its lateral edge and has internal supports of rigid, elastic and viscoelastic types. The material properties of the plate are represented in the form of exponential functions of the thickness coordinate. A rigid spherical indenter impacts the plate. The study is based on the classical lamination plate theory (CLT). An advanced contact law of the Hertzian type is adopted. A nonlinear Volterra integral equation system is obtained in the following unknown functions: the impact force and the dynamic reaction forces at the rigid, elastic and viscoelastic internal point supports. Numerical simulations displaying the contact force, the transversal displacement and the penetration depth are graphically presented, and pertinent conclusions regarding the implications of incorporation of graded material systems are outlined.

scholarly journals Forecasting of Surface Currents via Correcting Wind Stress with Assimilation of High-Frequency Radar Data in a Three-Dimensional Model

2016 ◽  
Vol 2016 ◽  
pp. 1-12 ◽  
Author(s):  
Lei Ren ◽  
Stephen Nash ◽  
Michael Hartnett
Keyword(s):  
Data Assimilation ◽  
High Frequency ◽  
Three Dimensional ◽  
Hf Radar ◽  
Surface Velocity ◽  
Shear Stresses ◽  
Surface Currents ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
The Impact

This paper details work in assessing the capability of a hydrodynamic model to forecast surface currents and in applying data assimilation techniques to improve model forecasts. A three-dimensional model Environment Fluid Dynamics Code (EFDC) was forced with tidal boundary data and onshore wind data, and so forth. Surface current data from a high-frequency (HF) radar system in Galway Bay were used for model intercomparisons and as a source for data assimilation. The impact of bottom roughness was also investigated. Having developed a “good” water circulation model the authors sought to improve its forecasting ability through correcting wind shear stress boundary conditions. The differences in surface velocity components between HF radar measurements and model output were calculated and used to correct surface shear stresses. Moreover, data assimilation cycle lengths were examined to extend the improvements of surface current’s patterns during forecasting period, especially for north-south velocity component. The influence of data assimilation in model forecasting was assessed using a Data Assimilation Skill Score (DASS). Positive magnitude of DASS indicated that both velocity components were considerably improved during forecasting period. Additionally, the improvements of RMSE for vector direction over domain were significant compared with the “free run.”

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