Analysis of the dynamic response of a fluid-supported circular elastic plate impacted by a low-velocity projectile

2000 ◽  
Vol 214 (5) ◽  
pp. 719-727 ◽  
Author(s):  
W Huang ◽  
Y Li ◽  
W Chen
Keyword(s):  
Dynamic Response ◽  
Elastic Plate ◽  
Impact Force ◽  
The Other ◽  
Sound Waves ◽  
Low Velocity ◽  
The Impact ◽  
First Time ◽  
Transverse Deflection ◽  
Clamped Edges

In this paper, the dynamic response of a thin circular elastic plate supported by a fluid on one side and impacted by a low-velocity projectile on the other side is analysed for the first time. A semi-analytical method is put forward, a non-linear Volterra integral equation governing the impact force is deduced and a linear numerical method is used to solve the equation and calculate the transverse deflection of the plate. The presence of the fluid not only lowers, on account of increased inertia, the natural frequency of the plate vibrating in vacuum but also dampens its transverse vibration owing to the energy carried off in the form of sound waves. As a numerical example, the transverse deflection of a solid circular plate with clamped edges impacted centrally by a low-velocity sphere and the impact force are computed, and the results are discussed.

Linear Analysis Method for the Dynamic Response of a Winkler Foundation-Supported Elastic Plate Subjected to Low Velocity Projectile Impact

1994 ◽  
Vol 116 (1) ◽  
pp. 67-70 ◽  
Author(s):  
Wei Huang ◽  
Yida Zou
Keyword(s):  
Dynamic Response ◽  
Elastic Plate ◽  
Impact Force ◽  
Winkler Foundation ◽  
Analysis Method ◽  
Low Velocity ◽  
Arbitrary Boundary ◽  
Linear Viscoelastic ◽  
The Impact ◽  
Transverse Deflection

This work considers the dynamic response of an elastic plate with arbitrary boundary shape supported by a linear viscoelastic Winkler foundation, and impacted by a low velocity projectile. A nonlinear Volterra integral equation on impact force F (t) is deduced, and an effective numerical method is used to solve the equation and calculate the transverse deflection of the plate. The presence of the foundation in our problem has the effect of damping the transverse vibration of the plate owing to the absorbed energy. As a practical example, the transverse deflection of a square plate with simply supported edges impacted centrally by a sphere and the impact force are computed numerically.

Fractality of Simulated Fracture

2009 ◽  
Vol 409 ◽  
pp. 154-160 ◽  
Author(s):  
Petr Frantík ◽  
Zbyněk Keršner ◽  
Václav Veselý ◽  
Ladislav Řoutil
Keyword(s):  
Numerical Model ◽  
Elastic Plate ◽  
Model Simulation ◽  
Element Model ◽  
The Other ◽  
Particle Model ◽  
Discrete Element Model ◽  
Fractal Nature ◽  
Discrete Elements ◽  
The Impact

The paper is focussed on numerical simulations of the fracture of a quasi-brittle specimen due to its impact onto a fixed rigid elastic plate. The failure of the specimen after the impact is modelled in two ways based on the physical discretization of continuum: via physical discrete elements and pseudo-particles. Advantages and drawbacks of both used methods are discussed. The size distribution of the fragments of the broken specimen resulting from physical discrete element model simulation follows a power law, which indicates the ability of the numerical model to identify the fractal nature of the fracture. The pseudo-particle model, on the other side, can successfully predict the kinematics of the fragments of the specimen under impact failure.

scholarly journals A place too crowded to study: The impact of student cohort growth on the probability of university dropout

2019 ◽  
Vol 9 (2) ◽  
pp. 189-212
Author(s):  
Andrea Diem ◽  
Stefan C. Wolter
Keyword(s):  
Significant Relationship ◽  
Negative Influence ◽  
The Other ◽  
University System ◽  
Pronounced Increase ◽  
The Us ◽  
University Dropout ◽  
The Impact ◽  
First Time ◽  
Course Of Study

Introduction: This study examines the influence of major fluctuations in the number of students enrolling at university on the probability of dropout or a switch to a different course of study. Findings from the US show that a pronounced increase in student numbers leads to more dropouts. Materials and methods: This article provides an analysis of this relationship for the first time outside the US and for an entire university system. We use administrative data for all the students who started studying at Swiss universities between 1980 and 2001. Results: The results suggest a significant relationship between positive cohort growth and the probability of dropout. A reduction in student numbers, on the other hand, does not increase the probability of persistence. Discussion: Despite the negative influence of a big cohort on the probability of persistence, no statistically significant relationship exists, by contrast, between the change in student numbers and the probability of a student switching to a different course of study.

Impact Damage Detection in GFRP Laminates through Ultrasonic Imaging

2012 ◽  
Vol 585 ◽  
pp. 337-341 ◽  
Author(s):  
H. Rama Murthy Naik ◽  
J. Jerald ◽  
N. Rajesh Mathivanan
Keyword(s):  
Impact Energy ◽  
Ultrasonic Testing ◽  
Energy Levels ◽  
Low Velocity Impact ◽  
Image Processing Technique ◽  
Sound Waves ◽  
Low Velocity ◽  
Immersion Method ◽  
Pulse Echo ◽  
The Impact

Composite materials are increasingly used in aerospace, naval and automotive vehicles due to their high specific strength and stiffness. In the area of Non destructive testing, ultrasonic C-scans are used frequently to detect defects in composite components caused during fabrication and damage resulting from service conditions. Ultrasonic testing uses transmission of high frequency sound waves into a material to detect imperfections or to locate changes in material properties. The most commonly used ultrasonic testing technique is pulse echo and through transmission wherein sound is introduced into a test object and reflections (echoes) are returned to a receiver from internal imperfections. Under low-velocity impact loading delaminating is observed to be a major failure mode. This report presents the use of above two techniques to detect the damage in glass fiber reinforced plastic (GFRP) laminates. Pulse echo is used to locate the exact position of damage and through transmission is used to know the magnitude of damage in composite. This paper work will be carried out on two different thicknesses and at impact energy levels varying from 7 to 53J. The ensuring delamination damage will be determined by ultrasonic C-scans using the pulse-echo immersion method for through transmission. Delamination areas were quantified accurately by processing the raw image data using a digital image processing technique. Based on the data obtained, correlation will be established between the delamination area and the impact energy.

Dynamic Response and Shear Demand of Reinforced Concrete Beams Subjected to Impact Loading

2019 ◽  
Vol 19 (08) ◽  
pp. 1950091 ◽  
Author(s):  
Wuchao Zhao ◽  
Jiang Qian
Keyword(s):  
Dynamic Response ◽  
Impact Loading ◽  
Parametric Study ◽  
Shear Failure ◽  
Impact Force ◽  
Rc Beams ◽  
Local Response ◽  
Shear Demand ◽  
The Impact ◽  
Peak Impact Force

Reinforced concrete (RC) beams under the impact loading are typically prone to suffer shear failure in the local response phase. In order to enhance the understanding of the mechanical behavior of the RC beams, their dynamic response and shear demand are numerically investigated in this paper. A 3D finite-element model is developed and validated against the experimental data available in the literature. Taking advantage of the above calibrated numerical model, an intensive parametric study is performed to identify the effect of different factors including the impact velocity, impact mass and beam span-to-depth ratio on the impact response of the RC beams. It is found that, due to the inertial effect, a linear relationship exists between the maximum reverse support force and the peak impact force, while negative bending moments also appear in the shear span. In addition, the local response of the RC beams can be divided into a first impact stage and a separation stage. A shear plug is likely to be formed near the impact point at the first impact stage and a shear failure may be triggered near the support by large support forces. Based on the simulation results, simplified methods are proposed for predicting the shear demand for the two failure modes, whereas physical models are also established to illustrate the resistance mechanism of the RC beams at the peak impact force. By comparing with the results of the parametric study, it is concluded that the shear demand of the RC beams under the impact loading can be predicted by the proposed empirical formulas with reasonable accuracy.

Vibration Analysis of Different Micro-Beams with Laser Ablation

2013 ◽  
Vol 462-463 ◽  
pp. 428-431
Author(s):  
Liang Cai Xiong ◽  
Quan Sheng Zhou ◽  
Peng Chen
Keyword(s):  
Laser Ablation ◽  
Dynamic Response ◽  
Vibration Analysis ◽  
Laser Excitation ◽  
Impact Force ◽  
Laser Doppler Vibrometer ◽  
Impact Response ◽  
Vibration Velocity ◽  
Laser Shock ◽  
The Impact

The dynamic response of different micro-beams after laser excitation experiments have been investigated in this paper. The impact force that induces the vibration of micro-beams is the interaction of focused pulse laser and tested beams. The impact response of micro-beams after being excited is measured by Laser Doppler Vibrometer. Different beams such as cantilever beam, L-shaped beam are employed in our experiments. Comparisons of the vibration velocity and its frequencies of different beams have also been performed. Experimental results show that the mechanical effects of laser shock do really exist and can be utilized.

Finite Element Analysis of a Single-Layer Reticulated Dome under Impact Loading

2010 ◽  
Vol 163-167 ◽  
pp. 327-331 ◽  
Author(s):  
Liang Zheng ◽  
Zhi Hua Chen
Keyword(s):  
Finite Element ◽  
Dynamic Response ◽  
Impact Force ◽  
Impact Load ◽  
Residual Deformation ◽  
Time History ◽  
Single Layer ◽  
Element Analysis ◽  
Deformation Stage ◽  
The Impact

Finite element model of both the single-layer Schwedler reticulated dome with the span of 50m and a Cuboid impactor were developed, incorporating ANSYS/LS-DYNA. PLASTIC_KINEMATIC (MAT_003) material model which takes stain rate into account was used to simulate steel under impact load. The automatic point to surface contact (NODES TO SURFACE) was applied between the dome and impact block. Three stages of time history curve of the impact force on the apex of the single-layer Scheduler reticulated dome including the impact stage, stable stalemate stage, the decaying stage were generalized according to its dynamic response. It must be pointed out that the peak of the impact force of the single-layer reticulated dome increase with the increase of the weight and the velocity of the impact block, but the change of the velocity of the impact block is more sensitive than the change of weight of the impact block for the effect of the peak of the impact force, and a platform value of the impact force of the single-layer reticulated dome change near a certain value, and the duration time of the impact gradually increase. Then four stages of time history curve of the impact displacement were proposed according to the dynamic response of impact on the apex of the single-layer reticulated dome based on numerical analysis. Four stages include in elastic deformation stage, plastic deformation stage, elastic rebound stage, free vibration stage in the position of the residual deformation.

Dynamic Response Analysis of Control Rod Drive Mechanism Under the Stepping Impact Force for Nuclear Power Plants

2012 ◽  
Author(s):  
Xiaoyao Shen ◽  
Yongcheng Xie
Keyword(s):  
Dynamic Response ◽  
Nuclear Power ◽  
Power Plants ◽  
Structural Integrity ◽  
Impact Force ◽  
Response Analysis ◽  
Control Rod ◽  
Drive Mechanism ◽  
Finite Element Software ◽  
The Impact

The control rod drive mechanism (CRDM) is an important safety-related component in the nuclear power plant (NPP). When CRDM steps upward or downward, the pressure-containing housing of CRDM is shocked axially by an impact force from the engagement of the magnetic pole and the armature. To ensure the structural integrity of the primary coolant loop and the functionality of CRDM, dynamic response of CRDM under the impact force should be studied. In this manuscript, the commercial finite element software ANSYS is chosen to analyze the nonlinear impact problem. A nonlinear model is setup in ANSYS, including main CRDM parts such as the control rod, poles and armatures, as well as nonlinear gaps. The transient analysis method is adopted to calculate CRDM dynamic response when it steps upward. The impact loads and displacements at typical CRDM locations are successfully obtained, which are essential for design and stress analysis of CRDM.

Dynamic Response and Damage Mechanism of Two-Core Composite Sandwich Panels under Low-Velocity Impact

2013 ◽  
Vol 405-408 ◽  
pp. 2810-2814
Author(s):  
Chang Liang Li ◽  
Da Zhi Jiang ◽  
Jing Cheng Zeng ◽  
Su Li Xing
Keyword(s):  
Dynamic Response ◽  
Contact Force ◽  
Impact Energy ◽  
Sandwich Structures ◽  
Sandwich Panels ◽  
Damage Mechanism ◽  
The Other ◽  
Foam Core ◽  
Transverse Impact ◽  
Low Velocity

Dynamic response and damage mechanism of two-core sandwich panels with foam and honeycomb cores and glass fiber/epoxy composite sheets under low-velocity transverse impact are investigated. The emphasis is focused on the contact force response and crash mechanism of the two-core sandwich panels. Effects of configurations, impact energy levels and types of the cores on the dynamic response are investigated. A modified drop-test experiment is carried out to obtain contact force history of the two-core sandwich structures under different impact energies. The experimental results show that the 10:10 configurations for both honeycomb and foam core sandwich structures under lower impact energy absorb more impact energy than the other two structures. However, under higher impact energy, the honeycomb core sandwich structures of 15:5 configuration absorbs a little more impact energy than the other two, while for the foam core sandwich structures the 5:15 configuration shows a little better impact resistance. Results also show that when impact energy is low foam core sandwich structures do better in absorbing impact energy than the honeycomb ones.

Dynamic Response of Sandwich Panels With a Flexible Core Under Simultaneous Low-Velocity Impacts of Multiple Small Masses

2006 ◽  
Author(s):  
K. Malekzadeh ◽  
M. R. Khalili
Keyword(s):  
Dynamic Response ◽  
Plate Theory ◽  
Sandwich Panels ◽  
Shear Deformation Theory ◽  
Core Layer ◽  
Contact Forces ◽  
Low Velocity ◽  
The Face ◽  
The Impact ◽  
Flexible Core

Dynamic response of sandwich panels with a flexible core under simultaneous low-velocity impacts of multiple small masses has investigated in this paper. The contact forces between the panel and the impactors are treated as the internal forces of the system. Shear deformation theory is used for the face sheets while three dimensional elasticity is used for the soft core. The fully dynamic effects of the core layer and the face-sheets are considered in this study. The results in multiple mass impacts over sandwich panels are presented based on proposed improved higher-order sandwich plate theory (IHSAPT). As no literature could be found on the impact of multiple impactors over sandwich panels, the present formulation is validated indirectly by comparing the response of two cases of double small masses and single small mass impacts based on Olsson’s wave control principle.

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