The Experts below are selected from a list of 483219 Experts worldwide ranked by ideXlab platform
Xiaoqing Zhang - One of the best experts on this subject based on the ideXlab platform.
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delamination prediction in composite laminates under low velocity Impact
Composite Structures, 2015Co-Authors: Shuchang Long, Xiaohu Yao, Xiaoqing ZhangAbstract:Abstract This paper presents a damage analysis process of composite laminates subjected to low-velocity Impact. Drop weight tests were carried out on specimens with two kinds of stacking sequence. Ultrasonic C-Scan was used to investigate the delamination area of each interface. Numerical models were built based on a damage model where cohesive contact method was involved. The efficiency of delamination modeling was discussed and the damage model was validated. The results of the FEM were found to agree well with experimental observation. According to the results, a prediction process of delamination shape was made for composite laminates under low-velocity Impact. The delamination area was found to distribute symmetrically around the Impact Point while the shape is related to the ply angles of the layers close to the interface. The prediction was proved to have good accuracy and efficiency.
Mark Costello - One of the best experts on this subject based on the ideXlab platform.
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practical assessment of real time Impact Point estimators for smart weapons
Journal of Aerospace Engineering, 2011Co-Authors: Mark Costello, Frank Fresconi, Gene CooperAbstract:There are numerous ways to estimate the trajectory and subsequent Impact Point of a projectile. Some complex methods are highly accurate and require a lot of input data while others are fairly trivial and less accurate but require minimal input data. Projectile Impact Point predictors IPPs have three primary error sources: model error, parameter error, and initial state error. While model error typically shrinks as model complexity increases, parameter and initial state errors grow with increasing model complexity. Since all input data feeding an IPP are uncertain to some level, the ideal IPP for an overall situation is not clear cut by any means. This paper examines several different projectile IPPs that span the range of complex nonlinear rigid projectile models to simple vacuum Point mass models with the intent to better understand relative merits of each algorithm in relation to the other algorithms and as a function of parameter uncertainty and initial state error. Monte Carlo simulation is employed to compute Impact Point statistics as a function of the range to the target for an indirect fire 155-mm spin stabilized round. For this specific scenario, results indicated neglecting physical phenomena in the formulation of the equations of motion can degrade Impact Point prediction, especially early in the flight. Adding uncertainty to the parameters and states induces Impact Point errors that dominate model error contributions. Impact Point prediction errors scaled linearly with parameter and state errors. All IPPs investigated converged to the actual Impact Point as the time at which the estimate took place approached the time of Impact.
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use of variable incidence angle for glide slope control of autonomous parafoils
Journal of Guidance Control and Dynamics, 2007Co-Authors: Nathan Slegers, Eric Beyer, Mark CostelloAbstract:Strictly speaking, most autonomous parafoil and payload systems possess only lateral control, achieved by right and left parafoil brake deflection. An innovative technique to achieve direct longitudinal control through incidence angle changes is reported. Addition of this extra control channel requires simple rigging changes and an additional servoactuator. The ability of incidence angle to alter the glide slope of a parafoil and payload aircraft is demonstrated through a flight-test program with a microparafoil system. Results from the flight-test program are synthesized and integrated into a six degree-of-freedom simulation. The simulation model is subsequently used to assess the utility of glide slope control to improve autonomous flight control system performance. Through Monte Carlo simulation, Impact Point statistics with and without glide slope control indicate that dramatic improvements in Impact Point statistics are possible using direct glide slope control.
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modified projectile linear theory for rapid trajectory prediction
Journal of Guidance Control and Dynamics, 2005Co-Authors: Leonard Hainz, Mark CostelloAbstract:In some smart weapons, estimation of the Impact Point of the shell at each computation cycle of the control law is an integral part of the control strategy. In these situations, the Impact Point predictor is part of the imbedded computing system onboard the projectile. Practical considerations dictate that the Impact Point predictor yield rapid yet reasonably accurate estimates. Common methods for rapid trajectory prediction are numerical integration of Point mass dynamic equations and evaluation of approximate closed-form solutions of the rigid-body projectile dynamic equations. These methods are shown to exhibit poor Impact Point prediction for long-range shots with high gun elevations characteristic of smart indirect fire munitions. Through modifications of projectile linear theory, a rapid projectile Impact Point predictor is proposed that eliminates the accuracy problems of the other methods while preserving low computational requirements. Typical results are provided for a short-range trajectory of a direct fire fin-stabilized projectile and a long-range trajectory for an indirect fire spin-stabilized round to substantiate these claims.
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model predictive control of a direct fire projectile equipped with canards
AIAA Atmospheric Flight Mechanics Conference and Exhibit, 2005Co-Authors: Douglas R. Ollerenshaw, Mark CostelloAbstract:Launch uncertainties in uncontrolled direct fire projectiles can lead to significant Impact Point dispersion, even at relatively short range. A model predictive control scheme for direct fire projectiles is investigated to reduce Impact Point dispersion. The control law depends on projectile linear theory to create an approximate linear model of the projectile and quickly predict states into the future. Control inputs are based on minimization of the error between predicted projectile states and a desired trajectory leading to the target. Through simulation, the control law is shown to work well in reducing projectile Impact Point dispersion. Parametric trade studies on an example projectile configuration are reported that detail the effect of prediction horizon length, gain settings, model update interval, and model step size.
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prediction of swerving motion of a dual spin projectile with lateral pulse jets in atmospheric flight
Mathematical and Computer Modelling, 2002Co-Authors: Bradley T Burchett, A Peterson, Mark CostelloAbstract:Using the linear theory for a dual-spin projectile in atmospheric flight, closed form expressions are obtained for swerving motion under the action of lateral pulse jets. Trajectory results generated by the linear theory equations and a fully nonlinear seven degree-of-freedom dual spin projectile model agree favorably. The analytic solution provides a relatively straightforward and computationally efficient means of trajectory estimation which is useful within smart weapon flight control systems. In order to accurately predict the Impact Point using the analytic solution, the dual-spin projectile linear model must be updated periodically. Terminal Impact Point prediction degrades rapidly as the linear model update interval is increased beyond a critical value. Control authority, as defined by the change in Impact location due to a pulse jet firing, steadily decreases as a function of projectile down range position.
C A C P Coelho - One of the best experts on this subject based on the ideXlab platform.
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effect of distance between Impact Point and hole position on the Impact fatigue strength of composite laminates
Composite Structures, 2017Co-Authors: R A M Santos, P N B Reis, Mario Santos, C A C P CoelhoAbstract:Abstract An Impact fatigue study was performed to evaluate the effect of the distance between the Impact Point and the hole on the fatigue life of glass fibre/epoxy laminates. For this purpose, experimental tests were carried out in square plates and for the distances of 0, 5, 10 and 20 mm, from the Impact Point. The results were compared with the ones obtained in plates without hole. It was possible to conclude that the fatigue life decreased, comparatively to the control samples, about 10.9%, 40%, 63.6% and 69.1% for the distances of 20 mm, 10 mm, 5 mm and 0 mm, respectively. Higher distances promote higher maximum loads and elastic restitution, but an opposite trend in terms of maximum displacement. For example, it was found for 20 mm a maximum load around 5.54 kN, a displacement of about 4.4 mm and an elastic energy of 59.2%, while for 0 mm these values were about 4.59 kN, 5.7 mm and 40.4%, respectively. In terms of multi-Impacts, the damage severity is also very influenced by the distance. For small distances the damage progresses quickly, while three stages can be found for the control samples and for the distance of 20 mm.
Shuchang Long - One of the best experts on this subject based on the ideXlab platform.
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delamination prediction in composite laminates under low velocity Impact
Composite Structures, 2015Co-Authors: Shuchang Long, Xiaohu Yao, Xiaoqing ZhangAbstract:Abstract This paper presents a damage analysis process of composite laminates subjected to low-velocity Impact. Drop weight tests were carried out on specimens with two kinds of stacking sequence. Ultrasonic C-Scan was used to investigate the delamination area of each interface. Numerical models were built based on a damage model where cohesive contact method was involved. The efficiency of delamination modeling was discussed and the damage model was validated. The results of the FEM were found to agree well with experimental observation. According to the results, a prediction process of delamination shape was made for composite laminates under low-velocity Impact. The delamination area was found to distribute symmetrically around the Impact Point while the shape is related to the ply angles of the layers close to the interface. The prediction was proved to have good accuracy and efficiency.
Kumar V Jata - One of the best experts on this subject based on the ideXlab platform.
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locating Point of Impact in anisotropic fiber reinforced composite plates
Ultrasonics, 2008Co-Authors: Tribikram Kundu, Samik Das, Steven A Martin, Kumar V JataAbstract:The conventional triangulation technique cannot predict the Point of Impact in an anisotropic composite plate because the triangulation technique assumes that the wave speed is independent of the direction of propagation which is not the case for anisotropic plates. An alternative method based on the optimization scheme was proposed by Kundu et al. [T. Kundu, S. Das, K.V. Jata, Point of Impact prediction in isotropic and anistropic plates from the acoustic emission data, J. Acoust. Soc. Am. 122, 2007, 2057-2066] to locate the Point of Impact in plates by analyzing the time of arrival of the ultrasonic signals received by the passive sensors attached to the plate. In this paper, that objective function is modified further to overcome the inherent difficulties associated with multiple singularities and to maximize the efficiency of the acoustic emission data for multiple receiving sensors. With this modified objective function the Impact Point on an anisotropic composite plate is predicted from the acoustic emission data. Experiments are carried out by dropping steel and ping pong balls on a graphite-epoxy composite plate and recording acoustic signals by passive transducers adhesively bonded to the plate at three different locations. The Impact Point is predicted by the proposed method and compared with the actual location of Impact.
