scholarly journals A similarity method for predicting the residual velocity and deceleration of projectiles during impact with dissimilar materials

2017 ◽  
Vol 9 (7) ◽  
pp. 168781401770559 ◽  
Author(s):  
Qing Song ◽  
Yongxiang Dong ◽  
Miao Cui ◽  
Bin Yu
Keyword(s):  
Similarity Theory ◽  
Dynamic Pressure ◽  
Dissimilar Materials ◽  
Target Thickness ◽  
Low Velocity Impact ◽  
Time Data ◽  
Residual Velocity ◽  
Triangular Wave ◽  
Deceleration Time ◽  
Maximum Deceleration

A method for predicting the residual velocity and deceleration of a projectile during normal low-velocity impact on a 2024-O thin aluminium plate is developed based on the similarity theory. Geometric scaling, the dissimilar materials of the projectile and different target thicknesses are considered. By a similitude analysis, the simulation criteria between the modelling and prototype experiments are obtained. The dimensionless velocity and deceleration of a projectile can be predicted by the relationship equations with the dimensionless dynamic pressure, projectile density and target thickness. On the basis of experimental data, the dimensionless residual velocity relationship is obtained and verified. In the range of normalised target thicknesses of [Formula: see text] (where H is target thickness and [Formula: see text] is projectile diameter), the deceleration–time data during penetration is simplified as a triangular wave. Moreover, it can be characterised using the maximum deceleration, the time to the maximum deceleration and the period of the triangular wave. Through a simulation analysis, three dimensionless deceleration characteristics of the projectile are developed to replicate a prototype-like deceleration–time process in a scaled model.

Perforation of Steel Targets by Blunt Projectiles Using Smoothed Particle Hydrodynamics Method

2017 ◽  
Vol 14 (03) ◽  
pp. 1750044 ◽  
Author(s):  
Ruiyu Li ◽  
Yuxin Sun ◽  
Qiran Sun ◽  
Yayun Zhao ◽  
Jiangtuo Feng
Keyword(s):  
Particle Size ◽  
Strain Hardening ◽  
Smoothed Particle Hydrodynamics ◽  
Target Thickness ◽  
Orthogonal Experimental Design ◽  
Residual Velocity ◽  
Hardening Modulus ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Smoothed Particle Hydrodynamics Method

In this paper, perforations of 12[Formula: see text]mm thick Weldox 460E steel plates by 20[Formula: see text]mm diameter blunt projectiles are simulated based on Two-dimensional Smoothed Particle Hydrodynamics method (SPH), and the modified Johnson–Cook (MJC) material model is adopted. To describe the shear plugging process, the particle approximation between different materials is canceled, and only the particle contact model based on the principle of conservation of momentum is applied. Then the separation of projectile and plug is simulated successfully, which is consistent with the experimental observations. Furthermore, it can be found that the particle size has a great influence on the calculation by comparing the effects of the different SPH particle sizes on plugging calculations. In general, the smaller the particle size is, the greater the residual velocity of projectile is. The residual velocities are tending towards stability as the decrease of particle size. Taking computational efficiency and accuracy into consideration, 0.033 (size[Formula: see text][Formula: see text][Formula: see text]0.4[Formula: see text]mm) is the most appropriate dimensionless particle size. Then, the effect of target thickness on perforation is conducted, which shows that the target thickness has certain influence on the global deformation of target. Moreover, the sensitivity of MJC material constants on the residual velocity of projectile is also analyzed and discussed using orthogonal experimental design method and the range analysis method. The results indicate that the most sensitivity parameter is yield strength [Formula: see text], followed by strain hardening modulus [Formula: see text] and strain hardening exponent [Formula: see text].

Flutter Optimized Design for a Aircraft Horizontal Tail Base on Optimus Software

2014 ◽  
Vol 684 ◽  
pp. 58-63
Author(s):  
Da Qian Zhang ◽  
Xiao Dong Tan ◽  
Zi Lei Zhang ◽  
Xin Ping Fu
Keyword(s):  
Finite Element ◽  
Wind Tunnel ◽  
Similarity Theory ◽  
Dynamic Pressure ◽  
Unsteady Aerodynamics ◽  
Element Model ◽  
Scale Model ◽  
Optimized Design ◽  
Lattice Method ◽  
Doublet Lattice Method

Based on the similarity theory, the horizontal tail scale model is designed and manufactured. Subsonic doublet lattice method is used to calculate unsteady aerodynamics, V-g method is used to solve the flutter determinant. Optimus software is used to optimize the thickness of the skin. The constraint condition is the frequency, MAC value and flexibility, and the objective function is flutter dynamic pressure. Flutter velocity of horizontal tail model optimized decreased 6%,and flutter frequency increased greatly. Horizontal tail scale model was test in wind tunnel. The finite element calculate results was very close with wind tunnel results, which verify the correctness of the finite element model and optimization models.

Side Branch Interaction With Main Line Standing Waves and Related Component Load Definition

2009 ◽  
Author(s):  
Arthur Ruggles ◽  
Eric M. Moore ◽  
Michael Shehane ◽  
Bi Yao Zhang ◽  
John Sparger
Keyword(s):  
Standing Wave ◽  
Dynamic Pressure ◽  
Standing Waves ◽  
Side Branch ◽  
Main Line ◽  
Test Facility ◽  
Time Data ◽  
Resonant Amplitude ◽  
Acoustic Boundary Condition ◽  
Signal Features

Side branch resonance can cause standing waves in the main line. The main line standing wave modifies the acoustic boundary condition between the side branch and the main line. This interaction leads to drift in the side branch resonant frequency, and to sensitivity in the side branch and main line resonant amplitude as a function of branch position along the main line standing wave. In many cases the mainline standing wave is not stationary, leading to temporal modulation of the side branch frequency and amplitude. These features are examined using novel signal interrogation techniques that expose frequency and amplitude variation in time. Data from a low pressure air test facility are used to reinforce the theory and demonstrate the system behavior. Finally, the connection between the dynamic pressure signal features and methods for main line and branch component endurance prediction is developed. Components such as steam dryers, safety relief valves, and heat exchangers would be candidates for endurance prediction using these methods.

scholarly journals Validity and Applicability of the Scaling Effects for Low Velocity Impact on Composite Plates

Materials ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 5884
Author(s):  
Michele Guida
Keyword(s):  
Large Scale ◽  
Similarity Theory ◽  
Composite Plates ◽  
Element Model ◽  
Low Velocity Impact ◽  
Scaling Effects ◽  
Low Velocity ◽  
Velocity Impact ◽  
Impact Performance ◽  
Theoretical Predictions

As a result of the increasing use of composite materials in engineering fields, the study of the effect of scale on impact performance is essential for the design of large-scale structures. The purpose of this study was to develop a method capable of identifying a corrective factor that can be used to evaluate based on similarity theory the behavior of panels with the same material but with scaled geometry when subjected to low velocity impact. The field of investigation was applied based on the experimental results present in the bibliography and that refer to two flat sheets differing only in geometric scale and made by overlapping carbon/carbon unidirectional pre-impregnated epoxy 914 C-TS (6K) −5 34% sheets. Behavior outside the range of structural linearity was investigated for the scaled panels, and the theoretical predictions of the model, projected with each law of scale for each variable present in the dynamic impact process, were compared with the experimental data. A finite element model was thereby developed that validates the theory of scaling and its limits of applicability up to the limits of fracture.

scholarly journals Deceleration time of projectile penetration/perforation into a concrete target: Experiment and discussions

2018 ◽  
Vol 22 (1) ◽  
pp. 112-125 ◽  
Author(s):  
Yong Peng ◽  
Hao Wu ◽  
Qin Fang ◽  
Ziming Gong
Keyword(s):  
Rigid Body ◽  
Cutoff Frequency ◽  
Main Concern ◽  
Time Data ◽  
Complex Signals ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Reinforced Concrete Slabs ◽  
Time Histories ◽  
Deceleration Time

Deceleration time histories of the 25.3 mm diameter, 428 g projectile penetration/perforation into 41 MPa reinforced concrete slabs with thicknesses of 100, 200, and 300 mm, are discussed. An ultra-high g small-caliber deceleration data recorder with a diameter of 18 mm is employed to digitize and record the acceleration during launch in the barrel, as well as the deceleration during penetration or perforation into targets. The accelerometer mounted in the data recorder measures rigid-body projectile deceleration as well as structural vibrations. To validate these complex signals, a validation approach for the accuracy of the recorded deceleration time data is proposed based on frequency characteristic analyses and signal integrations, and three sets of whole-range deceleration time data are validated. As the deceleration of the rigid-body projectile is the main concern, a signal processing approach is further given to obtain the rigid-body deceleration data, that is, using a low-pass filter to remove the high-frequency responses associated with vibrations of the projectile case and the internal supporting structure. The first valley frequency from the spectrum analysis is determined to be the critical cutoff frequency. To verify the accuracies of the theoretical model and the numerical simulation in predicting projectile motion time histories, theoretical projectile penetration/perforation deceleration time models are given and numerical simulations are performed. The predicted projectile time histories consist well with the validated deceleration time test data, as do their corresponding velocity and displacement time curves.

Normal Deceleration Behavior of Passenger Vehicles at Stop Sign–Controlled Intersections Evaluated with In-Vehicle Global Positioning System Data

2005 ◽  
Vol 1937 (1) ◽  
pp. 120-127 ◽  
Author(s):  
Jun Wang ◽  
Karen K. Dixon ◽  
Hainan Li ◽  
Jennifer Ogle
Keyword(s):  
Global Positioning System ◽  
Accurate Estimation ◽  
Positioning System ◽  
Data Set ◽  
Passenger Vehicles ◽  
Stop Sign ◽  
Global Positioning ◽  
System Data ◽  
Deceleration Time ◽  
Maximum Deceleration

Deceleration characteristics of passenger cars are often used in traffic simulation, vehicle fuel consumption and emissions models, and intersection and deceleration-lane design. Most previous studies collected spot speed data with detectors or radar guns. Because of the limitations of the data collection methods, these studies could not determine when and where drivers began to decelerate. Therefore, the studies may not provide an accurate estimation of deceleration time and distance. Furthermore, most previous studies are based on outdated and limited data, and their conclusions may not be applicable to the current vehicle fleet and drivers. The normal deceleration behavior of current passenger vehicles is evaluated at stop sign–controlled intersections on urban streets on the basis of in-vehicle Global Positioning System data. This study determined that drivers with higher approach speeds decelerated over a longer time and distance. Higher initial deceleration rates were also associated with higher approach speeds. However, the collected data in this study did not indicate a clear relationship between the average and maximum deceleration rates and approach speeds. With second-by-second deceleration profile data, the authors found that most drivers reached their maximum deceleration rates about 5 s or less than 5 s before stopping, and the maximum deceleration rate (3.4 m/s2) recommended by AASHTO was applicable to most of the study drivers. This review verified several previous deceleration models with the current observations and found that the polynomial model developed by Akcelik and Biggs provides the best fit for the data set in this study. Finally, this study developed a new deceleration model based on the approach speeds and deceleration time.

Analytical and High-Resolution EM Study of Crystalline Phases formed at Metal-Ceramic Interface

1990 ◽  
Vol 48 (2) ◽  
pp. 426-427
Author(s):  
N. Merk ◽  
A. P. Tomsia ◽  
G. Thomas
Keyword(s):  
Cross Section ◽  
Dissimilar Materials ◽  
Ceramic Materials ◽  
Electron Micrograph ◽  
Scanning Electron Micrograph ◽  
Structural Applications ◽  
Metal Ceramic ◽  
The Subject ◽  
Ceramic Compounds ◽  
Scanning Electron

A recent development of new ceramic materials for structural applications involves the joining of ceramic compounds to metals. Due to the wetting problem, an interlayer material (brazing alloy) is generally used to achieve the bonding. The nature of the interfaces between such dissimilar materials is the subject of intensive studies and is of utmost importance to obtain a controlled microstructure at the discontinuities to satisfy the demanding properties for engineering applications . The brazing alloy is generally ductile and hence, does not readily fracture. It must also wett the ceramic with similar thermal expansion coefficient to avoid large stresses at joints. In the present work we study mullite-molybdenum composites using a brazing alloy for the weldment.A scanning electron micrograph from the cross section of the joining sequence studied here is presented in Fig. 1.

Interfacial structures of dissimilar materials joined by capacitor-discharge welding

1994 ◽  
Vol 52 ◽  
pp. 534-535
Author(s):  
C. P. Doğan ◽  
R. D. Wilson ◽  
J. A. Hawk
Keyword(s):  
Rapid Solidification ◽  
Fusion Zone ◽  
Dissimilar Materials ◽  
Solidification Process ◽  
Weld Interface ◽  
Capacitor Discharge ◽  
Fine Grained ◽  
Iron Aluminum ◽  
Conductive Ceramics ◽  
Capacitor Discharge Welding

Capacitor Discharge Welding is a rapid solidification technique for joining conductive materials that results in a narrow fusion zone and almost no heat affected zone. As a result, the microstructures and properties of the bulk materials are essentially continuous across the weld interface. During the joining process, one of the materials to be joined acts as the anode and the other acts as the cathode. The anode and cathode are brought together with a concomitant discharge of a capacitor bank, creating an arc which melts the materials at the joining surfaces and welds them together (Fig. 1). As the electrodes impact, the arc is extinguished, and the molten interface cools at rates that can exceed 106 K/s. This process results in reduced porosity in the fusion zone, a fine-grained weldment, and a reduced tendency for hot cracking.At the U.S. Bureau of Mines, we are currently examining the possibilities of using capacitor discharge welding to join dissimilar metals, metals to intermetallics, and metals to conductive ceramics. In this particular study, we will examine the microstructural characteristics of iron-aluminum welds in detail, focussing our attention primarily on interfaces produced during the rapid solidification process.

Modeling Within-Person Variance in Reaction Time Data of Older Adults

GeroPsych ◽  
2011 ◽  
Vol 24 (4) ◽  
pp. 169-176 ◽  
Author(s):  
Philippe Rast ◽  
Daniel Zimprich
Keyword(s):  
Reaction Time ◽  
Cognitive Aging ◽  
Reaction Times ◽  
Reaction Time Task ◽  
Reaction Time Data ◽  
Scale Model ◽  
Time Data ◽  
Time Task ◽  
The Mean ◽  
Second Wave

In order to model within-person (WP) variance in a reaction time task, we applied a mixed location scale model using 335 participants from the second wave of the Zurich Longitudinal Study on Cognitive Aging. The age of the respondents and the performance in another reaction time task were used to explain individual differences in the WP variance. To account for larger variances due to slower reaction times, we also used the average of the predicted individual reaction time (RT) as a predictor for the WP variability. Here, the WP variability was a function of the mean. At the same time, older participants were more variable and those with better performance in another RT task were more consistent in their responses.

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