Work-Energy Relationships for the Collinear Single Degree of Freedom Impact Model under the Case of Net Unbalanced Externally Applied Forces

2013 ◽  
Author(s):  
Jai P. Singh ◽  
Nicholas J. Carpenter
Keyword(s):  
Degree Of Freedom ◽  
Impact Model ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Energy Relationships ◽  
Applied Forces

The Effect of the Impact Model on Vibration Response of Discrete and Continuous Systems

2012 ◽  
Author(s):  
M. R. Brake
Keyword(s):  
Constitutive Model ◽  
Coefficient Of Restitution ◽  
Degree Of Freedom ◽  
Impact Dynamics ◽  
Impact Model ◽  
Single Degree Of Freedom ◽  
Elastic Plastic ◽  
Single Degree ◽  
Contact Models ◽  
The Impact

Impact is a phenomenon that is ubiquitous in mechanical design; however, the modeling of impacts in complex systems is often a simplified, imprecise process. In many high fidelity finite element simulations, the number of elements required to accurately model the constitutive properties of an impact event is impractical. As a result, rigid body dynamics with approximate representations of the impact dynamics are commonly used. These approximations can include a constant coefficient of restitution, an artificially large penalty stiffness, or a single degree of freedom constitutive model for the impact dynamics that is specific to the type of materials involved (elastic, plastic, viscoelastic, etc.). In order to understand the effect of the impact model on the system’s dynamics, simulations are conducted to investigate a single degree of freedom, two degrees of freedom, and continuous system each with rigid stops limiting the amplitude of vibration. Five contact models are considered: a coefficient of restitution method, a penalty stiffness method, two similar elastic-plastic constitutive models, and a dissimilar elastic-plastic constitutive model. Frequency sweeps show that simplified contact models can lead to incorrect assessments of the system’s dynamics and stability. In the worst case, periodic behavior can be predicted in a chaotic regime. Additionally, the choice of contact model can significantly affect the prediction of wear and damage in the system.

Kinematic comparison of single degree-of-freedom robotic gait trainers

2021 ◽  
Vol 159 ◽  
pp. 104258
Author(s):  
Jeonghwan Lee ◽  
Lailu Li ◽  
Sung Yul Shin ◽  
Ashish D. Deshpande ◽  
James Sulzer
Keyword(s):  
Degree Of Freedom ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Robotic Gait

Single-Degree-of-Freedom Based Pressure-Impulse Diagrams for Blast Damage Assessment

2014 ◽  
Vol 567 ◽  
pp. 499-504 ◽  
Author(s):  
Zubair Imam Syed ◽  
Mohd Shahir Liew ◽  
Muhammad Hasibul Hasan ◽  
Srikanth Venkatesan
Keyword(s):  
Damage Assessment ◽  
Structural Response ◽  
Blast Loading ◽  
Computational Effort ◽  
Degree Of Freedom ◽  
Negative Phase ◽  
Single Degree Of Freedom ◽  
Pressure Impulse ◽  
Single Degree ◽  
Structural Resistance

Pressure-impulse (P-I) diagrams, which relates damage with both impulse and pressure, are widely used in the design and damage assessment of structural elements under blast loading. Among many methods of deriving P-I diagrams, single degree of freedom (SDOF) models are widely used to develop P-I diagrams for damage assessment of structural members exposed to blast loading. The popularity of the SDOF method in structural response calculation in its simplicity and cost-effective approach that requires limited input data and less computational effort. The SDOF model gives reasonably good results if the response mode shape is representative of the real behaviour. Pressure-impulse diagrams based on SDOF models are derived based on idealised structural resistance functions and the effect of few of the parameters related to structural response and blast loading are ignored. Effects of idealisation of resistance function, inclusion of damping and load rise time on P-I diagrams constructed from SDOF models have been investigated in this study. In idealisation of load, the negative phase of the blast pressure pulse is ignored in SDOF analysis. The effect of this simplification has also been explored. Matrix Laboratory (MATLAB) codes were developed for response calculation of the SDOF system and for repeated analyses of the SDOF models to construct the P-I diagrams. Resistance functions were found to have significant effect on the P-I diagrams were observed. Inclusion of negative phase was found to have notable impact of the shape of P-I diagrams in the dynamic zone.

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