The Efficacy of the Momentum Balance Method in Transverse Impact Problems

1995 ◽  
Author(s):  
Ahmet S. Yigit ◽  
Andreas P. Christoforou
Keyword(s):  
Permanent Deformation ◽  
Local Deformation ◽  
Balance Method ◽  
Impact Behavior ◽  
Momentum Balance ◽  
Transverse Impact ◽  
Balance Solution ◽  
Post Impact ◽  
The Difference ◽  
Impact Problems

Abstract An elastic-plastic contact law that incorporates local permanent deformation in the contact zone has been used to investigate the efficacy of the momentum balance method in transverse impact problems. The momentum balance solution is compared to the numerical solution of the same equations using the contact law. It is shown that the momentum balance method gives very good results for the post impact behavior of both the impacter and the beam. In certain cases, it is also shown to yield satisfactory results for the dynamic behavior during contact. It is demonstrated that the momentum balance method with an appropriate coefficient of restitution obtained from the contact law, is physically the same as using the contact law itself, with the difference that the local deformation is neglected.

The Efficacy of the Momentum Balance Method in Transverse Impact Problems

1998 ◽  
Vol 120 (1) ◽  
pp. 47-53 ◽  
Author(s):  
A. S. Yigit ◽  
A. P. Christoforou
Keyword(s):  
Permanent Deformation ◽  
Local Deformation ◽  
Balance Method ◽  
Impact Behavior ◽  
Momentum Balance ◽  
Transverse Impact ◽  
Balance Solution ◽  
Post Impact ◽  
The Difference ◽  
Impact Problems

An elastic-plastic contact law that incorporates local permanent deformation in the contact zone has been used to investigate the efficacy of the momentum balance method in transverse impact problems. The momentum balance solution is compared to the numerical solution of the same equations using the contact law. It is shown that the momentum balance method gives very good results for the post impact behavior of both the impacter and the beam. In certain cases, it is also shown to yield satisfactory results for the dynamic behavior during contact. It is demonstrated that the momentum balance method with an appropriate coefficient of restitution obtained from the contact law, is physically the same as using the contact law itself, with the difference that the local deformation is neglected.

Resolving the Unique Invariant Slip-Direction in Rigid Three-Dimensional Multi-Point Impacts at Stick-Slip Transitions

2018 ◽  
Author(s):  
Abhishek Chatterjee ◽  
Alan Bowling
Keyword(s):  
Single Point ◽  
Three Dimensional ◽  
Impact Behavior ◽  
Slip Direction ◽  
Stick Slip ◽  
Impact Forces ◽  
Post Impact ◽  
Impact Problems ◽  
Slip Transition ◽  
The Impact

This work presents a new approach for resolving the unique invariant slip direction at Stick-Slip Transition during impact. The solution method presented in this work is applicable to both single-point and multi-point impact problems. The proposed method utilizes rigid body constraints to resolve the impact forces at all collision points in terms of a single independent impact forces parameter. This work also uses an energetic coefficient of restitution to terminate impact events, thereby yielding energetically consistent post-impact behavior.

On the Use of Momentum Balance and the Assumed Modes Method in Transverse Impact Problems

1992 ◽  
Vol 114 (3) ◽  
pp. 364-373 ◽  
Author(s):  
H. Palas ◽  
W. C. Hsu ◽  
A. A. Shabana
Keyword(s):  
Degrees Of Freedom ◽  
Mass Matrix ◽  
Coefficient Of Restitution ◽  
Body Motion ◽  
Jump Discontinuity ◽  
Momentum Balance ◽  
Transverse Impact ◽  
Orthogonal Functions ◽  
Reaction Forces ◽  
Impact Problems

The objective of this investigation is to examine the validity of applying the assumed modes method and the generalized impulse momentum approach that involves the coefficient of restitution in the analysis of transverse impact in constrained elastic systems. A simple impact model that consists of a rotating beam which is subjected to a transverse impact by a mass (impact hammer) moving with a constant velocity is used. For the purpose of comparison and in order to check the validity of using the proposed technique, the transverse deformation of the beam with respect to the beam coordinate system is described using three different assumed sets of orthogonal functions. The different sets of modes are the clamped-free modes, pin-free modes, and a set of assumed harmonic functions. The system mass matrix that accounts for the coupling between the rigid body motion and the elastic deformation is identified and used with the Jacobian matrix of the kinematic constraints and the coefficient of restitution to define the algebraic generalized impulse momentum equations that describe the transverse impact. The series solution obtained using the generalized impulse momentum equations is used to define the generalized impulse, the jump discontinuity in the system reference and modal velocities, and the jump discontinuities in the generalized joint reaction forces. It is shown in this investigation, that by increasing the number of elastic degrees of freedom, the jump discontinuity in the angular velocity of the rod as well as the generalized impulse converge to zero regardless of the assumed complete set of modes used. The effect of the coefficient of restitution and the mass ratio on the jump in the system velocities and the generalized reaction forces is also examined.

A destructible headform for the assessment of sports impacts

2021 ◽  
pp. 175433712110559
Author(s):  
Ben Stone ◽  
Sean Mitchell ◽  
Yusuke Miyazaki ◽  
Nicholas Peirce ◽  
Andy Harland
Keyword(s):  
Human Subjects ◽  
Permanent Deformation ◽  
Human Head ◽  
Local Deformation ◽  
Resonance Excitation ◽  
Destructive Testing ◽  
Head Impacts ◽  
Resonance Frequencies ◽  
Hybrid Iii ◽  
Athletic Equipment

Commercially available headforms, such as the Hybrid-III and EN 960 headforms, have been used effectively to investigate the mechanics of head impacts. These headforms may result in accelerations that are unrepresentative of a human head in some impact scenarios. This may be important when considering impacts that produce areas of high pressure, since skull deformation and resonance excitation may influence the dynamic response. The National Operating Committee on Standards for Athletic Equipment (NOCSAE) headform may produce a more suitable response during these types of impacts due to the more representative skull component. However, permanent deformation may occur in some unprotected impact scenarios, resulting in the entire headform needing to be replaced. This paper outlines the development of a novel, modular and destructible headform (LU headform) that can be used in potentially destructive testing, where individual components can be replaced. The LU headform was modelled after a UK 50th percentile male. The inertial properties of the LU headform were within 6% of those observed in humans. The skull simulant properties were within the range of values reported for human tissue in two build orientations, but lower in one build orientation. The lowest and highest resonance frequencies observed in the headform model were within 5% of those observed in humans. Drop and projectile tests were conducted in line with previous cadaver tests with the observed accelerations within the range reported for post-mortem human subjects. The LU headform offers a practical means of simulating head dynamics during localised unprotected impacts or in protected impacts where local deformation and/or resonance frequency excitation remains possible.

Impact on Beams

1936 ◽  
Vol 3 (2) ◽  
pp. A55-A61
Author(s):  
H. L. Mason
Keyword(s):  
Historical Development ◽  
Contact Region ◽  
Local Deformation ◽  
Lateral Vibration ◽  
Transverse Impact ◽  
Concentrated Mass ◽  
Impact Theory ◽  
Inelastic Impact ◽  
Maximum Contact

Abstract This paper deals with transverse impact on beams the mass of which is of importance. Experimental results are presented for comparison with theory. Impacts which appear single to the eye are shown to consist in reality of several blows in quick succession. Section 1 of the paper traces the historical development of this subject by discussing the investigations of Young, Hodgkinson, Cox, Saint Venant, and Timoshenko. Section 2 treats a simplified system in which a concentrated mass strikes a smaller concentrated mass having a “soft” spring restraint. For elastic impact, theory predicts for the struck mass a path composed of sinusoidal elements separated by instantaneous blows. For inelastic impact it predicts a joint harmonic motion. Records of the paths of both masses were obtained experimentally. Section 3 of the paper uses Timoshenko’s method of combining local deformation of the contact region with lateral vibration of the beam. An experimental investigation of maximum contact pressure and of blow duration gives what is believed to be the first confirmation of this theory. Section 4 describes an experimental determination of flexural stresses in elastic and inelastic impact on a 3-in. I-beam by the use of a Westinghouse magnetic strain gage. The indication is that stresses may be higher than those calculated by the usual approximations.

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.

Post-Impact Behavior of a Droplet Impacting on a Permeable Metal Mesh with a Sharp Wettability Step

Langmuir ◽  
2019 ◽  
Vol 35 (39) ◽  
pp. 12711-12721 ◽  
Author(s):  
Uddalok Sen ◽  
Tamal Roy ◽  
Souvick Chatterjee ◽  
Ranjan Ganguly ◽  
Constantine M. Megaridis
Keyword(s):  
Impact Behavior ◽  
Metal Mesh ◽  
Post Impact

Impact and post impact behavior of fabric reinforced geopolymer composite

2016 ◽  
Vol 127 ◽  
pp. 111-124 ◽  
Author(s):  
Sneha Samal ◽  
Bohdana Marvalová ◽  
Iva Petríková ◽  
Katleen A.M. Vallons ◽  
Stepan V. Lomov ◽  
...  
Keyword(s):  
Impact Behavior ◽  
Post Impact

An Efficient Method for a Category of Contact/Impact Problems in Multibody Systems: Tree Topologies

2005 ◽  
Author(s):  
Michael J. Sadowski ◽  
Kurt S. Anderson
Keyword(s):  
Rigid Body ◽  
Dynamic Systems ◽  
Equations Of Motion ◽  
Momentum Balance ◽  
Unilateral Constraints ◽  
Constraint Forces ◽  
Rigid Body Dynamic ◽  
Tree Topologies ◽  
Contact Impact ◽  
Impact Problems

This paper presents an algorithm for the efficient numerical analysis and simulation of a category of contact/impact problems in multi-rigid-body dynamic systems with tree topologies. The algorithm can accommodate the jumps in structure which occur in the equations of motion of general multi-rigid-body systems due to a contact/impact event between bodies, or due to the locking of joints as long as the resulting system is a tree topology. The presented method uses a generalized momentum balance approach to determine the velocity jumps which take place across impacts in such multibody dynamic systems where event constraint forces are of the “non-working” category. The presented method does not suffer from the performance (speed) penalty encountered by most other momentum balance methods given its O(n) overall cost, and exact direct embedded consideration of all the constraints. Due to these characteristics, the presented algorithm offers superior computing performance relative to other methods in situations involving both large n and potentially many unilateral constraints.

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