An Energy-Based Coefficient of Restitution for Planar Impacts of Slender Bars With Massive External Surfaces

1998 ◽  
Vol 65 (4) ◽  
pp. 952-962 ◽  
Author(s):  
Y. Hurmuzlu
Keyword(s):  
Elastic Energy ◽  
Material Properties ◽  
Solution Method ◽  
Vibrational Energy ◽  
Scalar Function ◽  
Coefficient Of Restitution ◽  
Theoretical Development ◽  
Collision Process ◽  
Nondimensional Parameter ◽  
Multiple Collisions

A new method to solve the collision problems of slender bars with massive external surfaces is developed. The proposed solution accounts for the effect of impact induced vibrations and multiple collisions on the post-collision velocities of the impacting members. The approach is based on representing the vibrational energy of the bars during the collision process in terms of a nondimensional parameter, termed the elastic energy percentile. The elastic energy percentile is expressed as a simple scalar function of the drop angle and a nondimensional parameter, which encapsulates the bar geometry, material, and the stiffness of the contact surface. The elastic energy percentile is then used to develop a new momentum-based solution method. The method relies on a revised energetic coefficient of restitution that resolves the effect of impact induced vibrations on the post-collision velocities of the impacting bars. The assumptions used in the theoretical development and the outcomes predicted by the proposed method were verified by conducting a set of experiments using several bars with varying geometric and material properties.

SIMULATION OF DYNAMIC EVENT OF IMPACT USING EXPLICIT 3D FEM MODEL AND VALIDATION BY EXPERIMENT AND CONTACT MODELS

2021 ◽  
Vol 6 (3) ◽  
Author(s):  
Akshay Mallikarjuna ◽  
Dan Marghitu ◽  
P.K. Raju
Keyword(s):  
Material Properties ◽  
Permanent Deformation ◽  
Oblique Impact ◽  
Coefficient Of Restitution ◽  
Impact Behavior ◽  
3D Fem ◽  
Dynamic Event ◽  
Contact Models ◽  
Explicit Dynamic ◽  
The Impact

— In this study, an optimized method to simulate the dynamic 3D event of the impact of a rod with a flat surface has been presented. Unlike the 2D FEM based contact models, in this study both the bodies undergoing the impact are considered elastic(deformable) and simulation is the dynamic event of the impact, instead of predefined 2D symmetric contact analysis. Prominent contact models and plasticity models to define material properties in ANSYS are reviewed. Experimentation results of normal and oblique impact of the rod for different rods provided the coefficient of restitution. Experimental results of permanent deformation on the base for different impact velocity is derived out of a prominent impact study. The simulation results are in co-relation with experiment and both indentation and flattening models on the coefficient of restitution (COR) and permanent deformation of the base and rod after the impact. Thus, the presented 3D Explicit Dynamic simulation of impact is validated to analyze the impact behavior of the 2 bodies without any predefined assumptions with respect to boundary conditions or material properties.

Experiment Study on Collision of Graphite Dowel-Brick Structures

2013 ◽  
Author(s):  
Lie Jin ◽  
Libin Sun ◽  
Hongtao Wang ◽  
Haitao Wang ◽  
Xinxin Wu ◽  
...  
Keyword(s):  
Material Properties ◽  
Initial Velocity ◽  
Contact Time ◽  
Coefficient Of Restitution ◽  
Experiment Study ◽  
External Excitation ◽  
The Core ◽  
Central Collisions ◽  
Pile Up ◽  
High Temperature Gas

Graphite bricks have important applications in high temperature gas-cooled reactors (HTGRs), the core of HTGR is a pile-up of graphite bricks. So the vibrations and collisions between graphite bricks caused by external excitation have an important influence on structural stability of the core. The locations of bricks are fixed by various kinds of keys and dowels. The collision experiment, with tracks and small railcars as experimental devices and measurement system using optical method, was aimed at studying non-central collisions between two bricks. The passive one of the two bricks was equipped with a key or a dowel. Experiment’s results revealed how the coefficient of restitution and the contact time would change within the range of velocities of the active specimen. It was showed that the contact time would increase with the rise of initial velocity while the coefficient of restitution would rise up firstly and then decrease later in the same process. Besides, qualitative influence caused by different sizes of keys and dowels was briefly discussed, and material properties of graphite was not the dominate factor in the collision of dowel-brick structures experiment, while the velocity of active specimen just before collision and the fact that the collision is non-central have more significant effects on the collision results.

scholarly journals Coefficients of Restitution Based on a Fractal Surface Model

2003 ◽  
Vol 70 (3) ◽  
pp. 339-345 ◽  
Author(s):  
Chung-Jen Lu ◽  
Ming-Chang Kuo
Keyword(s):  
Surface Topography ◽  
Material Properties ◽  
Plastic Material ◽  
Coefficient Of Restitution ◽  
Surface Model ◽  
Fractal Surface ◽  
Normal Contact ◽  
Perfectly Plastic ◽  
Fractal Models ◽  
Elastic Perfectly Plastic

Equations of rigid-body mechanics provide a means to predict the post-collision behavior without recourse to highly complex, detailed analysis of deformations during contact. Before the prediction can be completed, the coefficient of restitution, which relates the rebound velocity to the incident velocity, must be estimated properly. The coefficient of restitution depends on the surface topography in addition to the material properties and incident velocity. Recent investigations showed that surface topography can be characterized properly by fractal models. This paper proposes a normal contact model for a fractal surface in contact with a rigid smooth half-space. The fractal surface is constructed based on the Cantor set and composed of elastic-perfectly plastic material. Asymptotic continuous expressions for the load-displacement relations during loading and unloading are derived. Based on these results, we study the effects of surface roughness, material properties and incident velocity on the coefficient of restitution.

scholarly journals A Higher-Order Thermomechanical Vibration Analysis of Temperature-Dependent FGM Beams with Porosities

2016 ◽  
Vol 2016 ◽  
pp. 1-20 ◽  
Author(s):  
Farzad Ebrahimi ◽  
Ali Jafari
Keyword(s):  
Differential Equations ◽  
Porous Material ◽  
Power Law ◽  
Material Properties ◽  
Solution Method ◽  
Equations Of Motion ◽  
Higher Order ◽  
Functionally Graded ◽  
Thickness Direction ◽  
Temperature Dependent

In the present paper, thermomechanical vibration characteristics of functionally graded (FG) Reddy beams made of porous material subjected to various thermal loadings are investigated by utilizing a Navier solution method for the first time. Four types of thermal loadings, namely, uniform, linear, nonlinear, and sinusoidal temperature rises, through the thickness direction are considered. Thermomechanical material properties of FG beam are assumed to be temperature-dependent and supposed to vary through thickness direction of the constituents according to power-law distribution (P-FGM) which is modified to approximate the porous material properties with even and uneven distributions of porosities phases. The governing differential equations of motion are derived based on higher order shear deformation beam theory. Hamilton’s principle is applied to obtain the governing differential equations of motion which are solved by employing an analytical technique called the Navier type solution method. Influences of several important parameters such as power-law exponents, porosity distributions, porosity volume fractions, thermal effects, and slenderness ratios on natural frequencies of the temperature-dependent FG beams with porosities are investigated and discussed in detail. It is concluded that these effects play significant role in the thermodynamic behavior of porous FG beams.

Coefficient of Restitution for Collinear Collisions of Elastic-Perfectly Plastic Spheres

1997 ◽  
Vol 64 (2) ◽  
pp. 383-386 ◽  
Author(s):  
C. Thornton
Keyword(s):  
Theoretical Model ◽  
Analytical Solution ◽  
Yield Stress ◽  
Impact Velocity ◽  
Contact Interaction ◽  
Material Properties ◽  
Coefficient Of Restitution ◽  
Normal Contact ◽  
Perfectly Plastic ◽  
Elastic Perfectly Plastic

Based on a simplified theoretical model for the normal contact interaction of two elastic-perfectly plastic spheres, an analytical solution is provided for the coefficient of restitution. The solution is expressed in terms of the ratio of impact velocity to yield velocity rather than in terms of material properties such as the yield stress which is difficult to reliably ascertain for many materials.

Towards Identification of Lower Scale Composite Material Properties From Higher Scale Experimental Data via Inverse Analysis of Coupled Multiscale Models

2015 ◽  
Author(s):  
Foteini Komninelli ◽  
Athanasios Iliopoulos ◽  
John G. Michopoulos
Keyword(s):  
Experimental Data ◽  
Composite Material ◽  
Material Properties ◽  
Synthetic Data ◽  
Theoretical Development ◽  
Micro Scale ◽  
Macro Scale ◽  
Periodic Microstructures ◽  
Fiber Matrix ◽  
Optimization Methodology

In the present paper we demonstrate the application of a multiscale inverse methodology for identifying material properties of the constituents of a selected composite material with long fibers embedded in a polymer matrix by utilizing macro-scale experimental data. Taking advantage of a computational homogenization technique for periodic microstructures, the proposed optimization methodology allows, for the determination of a considerable number of the elastic properties of the composite material at the micro-scale of the constituents and their interface zone. Our approach describes the theoretical development and numerical implementation of a multi-scale modeling chain of the composite, extending from the periodic microstructure represented by a suitable unit cell and subjected to appropriate periodic boundary conditions at the micro scale, to the composite lamina at the meso-scale, to the laminated, multi-axially loaded material at the macro-scale. By applying the proposed methodology, we have been able to accurately calculate several fiber, matrix properties by utilizing properly generated synthetic data of the macro-scale behavior of the composite laminate. Furthermore, in an effort to explore the potential of our method for identifying quantities that manifest only after manufacturing including damage quantities at the micro-scale, we have initiated an effort to explore the capability of determining fiber-matrix interfacial properties and have demonstrated initial success.

An Elastomeric Ejection System

1994 ◽  
Vol 67 (5) ◽  
pp. 892-903 ◽  
Author(s):  
I. S. Choi ◽  
C. M. Roland ◽  
L. C. Bissonnette
Keyword(s):  
Fatigue Life ◽  
Elastic Energy ◽  
Material Properties ◽  
The U.S ◽  
Selection Of

Abstract The ability of elastomers to store large quantities of energy, which can subsequently be recovered very quickly, makes them attractive materials for propulsion devices. Recently the U.S. Navy has developed a torpedo ejection system based on an elastomeric mechanical capacitor. The criteria governing selection of a material for this application include high elastic energy, sufficient fatigue life, minimal creep, and resistance to deterioration by seawater. This paper describes various approaches to obtaining these material properties.

Evaluation of Elastic-Plastic Rebound Properties of Coal Fly Ash Particles for Use in a Universal Turbine Deposition Model

2015 ◽  
Author(s):  
Steven M. Whitaker ◽  
Jeffrey P. Bons
Keyword(s):  
Experimental Data ◽  
Yield Stress ◽  
Material Properties ◽  
Coal Fly Ash ◽  
Impact Angle ◽  
Coefficient Of Restitution ◽  
Deposition Model ◽  
Mechanics Model ◽  
The Impact ◽  
Impact Models

Three particle impact models have been evaluated to determine their ability to predict particle material properties and restitution coefficients using experimental data for the coefficient of restitution of particles impacting a 410 stainless steel plate. The particles consisted of PMMA and three coal fly ashes: JBPS, Bituminous, and Lignite. Particle speeds ranged from approximately 20 to 120 meters per second, and the nominal impact angle was approximately 85 degrees. Flow temperatures for the ash particulate experiments were set at 295 K and 395 K. The impact models were applied to the experimental data via curve fitting to evaluate the yield stress of the particulate, which was known for the PMMA. For the ash particulate, a linear law of mixtures was used to approximate the modulus of elasticity and Poisson’s ratio for use in the yield stress determination. A Hertzian mechanics model was shown to over-predict the yield stress of the PMMA particulate, indicating that, for known material properties, they would under-predict the coefficient of restitution. A Plastic-JKR model and a finite element based model by Wu et al. showed good agreement between the calculated yield stress and known range of yield stress values for the PMMA particulate, indicating that the model would accurately predict restitution coefficients for particulate with known material properties (or could be used to accurately determine the material properties from experimental coefficient of restitution data). However, some questions remain as to the ability of these models to be used for non-spherical, conglomerate type particulate. A thorough overview of the impact process is provided, and the application of the results of the study to the development of a physics-based universal impact and deposition model is presented.

Effect of Finite Rotation on the Propagation of Elastic Waves in Constrained Mechanical Systems

1992 ◽  
Vol 114 (3) ◽  
pp. 384-393 ◽  
Author(s):  
Wei-Hsin Gau ◽  
A. A. Shabana
Keyword(s):  
Phase Velocity ◽  
Material Properties ◽  
Elastic Waves ◽  
Wave Motion ◽  
Coefficient Of Restitution ◽  
Wave Number ◽  
Harmonic Waves ◽  
Finite Rotation ◽  
Phase Velocities ◽  
The Impact

In structural systems, impact-induced longitudinal elastic waves travel with finite speeds that depend on the material properties. Using Fourier method of analysis, the exact wave motion can be described as the sum of infinite number of harmonic waves which have the same phase velocity. In this case the medium is said to be nondispersive, since the phase velocities of the harmonic waves are equal and equal to the group velocity of the resulting wave motion. In mechanism systems with intermittent motion, on the other hand, elastic members undergo finite rotations. In this investigation, the effect of the finite rotation, coefficient of restitution, and impact conditions on the propagation of the impact-induced waves in costrained elastic systems is examined. The system equations of motion are developed using the principle of virtual work in dynamics. The jump discontinuities in the system variables as the result of impact are predicted using the generalized impulse momentum equations that involve the coefficient of restitution. It is shown that the phase velocities of different harmonic waves are no longer equal, that is, dispersion occurs in perfectly elastic mechanism members as the result of the finite rotation. The analysis presented in this paper shows that the finite rotation has more significant effect on the phase velocity of the low frequency harmonics as compared to the high frequency harmonics. A rotation-wave number that depends on the material properties and the wave length is defined for each harmonic wave. It is shown that if the angular velocity of the elastic member becomes large such that the rotation-wave number of a mode exceeds one, the associated modal displacement is no longer oscillatory.

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