Prediction of System Natural Frequencies Using an Explicit Finite Element Code With Application to Belt-Drives

2004 ◽  
Author(s):  
Tamer Wasfy ◽  
Michael Leamy ◽  
Rick J. Meckstroth
Keyword(s):  
Finite Element ◽  
Multibody Systems ◽  
Natural Frequencies ◽  
System Response ◽  
Finite Element Code ◽  
Frequency Range ◽  
Harmonic Force ◽  
Explicit Finite Element ◽  
Belt Drives ◽  
Time Histories

A time-accurate explicit finite element code is used to predict the natural frequencies of a typical class of flexible multibody systems — automotive accessory belt-drives. The system considered consists of a belt, two pulleys, and a tensioner. Two techniques are used to find the system natural frequencies: (a) applying a sharp impulse to the system and extracting the system natural frequencies from the resulting displacement/strain time-histories via an FFT; and (b) applying a harmonic force to the system and sweeping through a frequency range, while at the same time, monitoring for large system response. In the present paper a comparison between these two techniques is presented for a typical accessory drive. Also, recommendations are offered on how to best use each technique to efficiently extract the system’s natural frequencies.

Asperity Spring Friction Model With Application to Belt-Drives

2003 ◽  
Author(s):  
Tamer M. Wasfy
Keyword(s):  
Finite Element ◽  
Coulomb Friction ◽  
Friction Model ◽  
Belt Drive ◽  
Finite Element Code ◽  
Time Step ◽  
Stick Slip ◽  
Normal Contact ◽  
Belt Drives ◽  
Coulomb Friction Model

An asperity spring friction model that uses a variable anchor point spring along with a velocity dependent force is presented. The model is incorporated in an explicit timeintegration finite element code. The friction model is used along with a penalty-based normal contact model to simulate the dynamic response of a two-pulley belt-drive system. It is shown that the present friction model accurately captures the stick-slip behavior between the belt and the pulleys using a much larger time-step than a pure velocity-dependent approximate Coulomb friction model.

Modeling the Dynamic Frictional Contact of Tires Using an Explicit Finite Element Code

2005 ◽  
Author(s):  
Tamer M. Wasfy ◽  
Michael J. Leamy
Keyword(s):  
Finite Element ◽  
Frictional Contact ◽  
Time Integration ◽  
Friction Model ◽  
Finite Element Code ◽  
Normal Contact ◽  
Explicit Finite Element ◽  
Beam Elements ◽  
Coulomb Friction Model ◽  
Stiffness And Damping

A time-accurate explicit time-integration finite element code is used to simulate the dynamic response of tires including tire/pavement and tire/rim frictional contact. Eight-node brick elements, which do not exhibit locking or spurious modes, are used to model the tire’s rubber. Those elements enable use of one element through the thickness for modeling the tire. The bead, tread and ply are modeled using truss or beam elements along the tire circumference and meridian directions with appropriate stiffness and damping properties. The tire wheel is modeled as a rigid cylinder. Normal contact between the tire and the wheel and between the tire and the pavement is modeled using the penalty technique. Friction is modeled using an asperity-based approximate Coulomb friction model.

Study on the collapse of tapered tubes subjected to oblique loads

2008 ◽  
Vol 222 (11) ◽  
pp. 2025-2039 ◽  
Author(s):  
P Hosseini-Tehrani ◽  
S Pirmohammad ◽  
M Golmohammadi
Keyword(s):  
Finite Element ◽  
Cross Section ◽  
Numerical Models ◽  
Point Of View ◽  
Finite Element Code ◽  
Energy Absorber ◽  
Explicit Finite Element ◽  
Bending Deformation ◽  
Oblique Loading

In this work, several antisymmetric tapered tubes with an inner stiffener under axial and oblique loading are studied and optimum dimensions of the tapered tube are derived from a crashworthiness point of view. The importance of detecting these dimensions is optimizing the weight while the crashworthiness of tube is not damaged. By using an internal stiffener, crashworthiness is improved against oblique loads, and the sensitivity of tubes with respect to oblique loads and bending deformation is diminished. The numerical models have been developed using the explicit finite element code LS-DYNA. The crashworthiness of the optimized tapered tube is compared with that of an octagonal-cross-section tube which is known as the best energy absorber model in the literature. It is shown that an optimized tapered tube has an average of 29.3 per cent less crushing displacement in comparison with octagonal-section tube when both tubes have the same weights and the same peaks of crushing load. Finally, the orientation of loading is changed and the best orientation is proposed.

Airbag Tire Modeling by the Explicit Finite Element Method

1997 ◽  
Vol 25 (4) ◽  
pp. 288-300 ◽  
Author(s):  
S. R. Wu ◽  
L. Gu ◽  
H. Chen
Keyword(s):  
Finite Element ◽  
Computational Procedure ◽  
Ford Motor Company ◽  
Feasibility Trial ◽  
Closed Volume ◽  
Finite Element Code ◽  
Explicit Finite Element ◽  
Shell Elements ◽  
Concept Model ◽  
Tire Modeling

Abstract An explicit finite element code FCRASH has been applied to both static and dynamic tire modeling. The computational procedure for predicting tire loads has been investigated. The typical tire model used in the simulation consists of a tire and rim. The tire is defined by membrane elements and the rim by rigid body with shell elements. The tire and rim form a closed volume. The airbag functionality in FCRASH, an explicit finite element code developed by Ford Motor Company, has been employed to simulate the test and to monitor the pressure and volume changes in the tire. Three static tire models (Taurus spare tire, P145/75R12, and P225/60R16) have been studied and the force-deflection curves are compared with test data. All of them exhibit a very good agreement. The standard spindle test for the P145/75R12 tire at three different speeds (10, 20, and 30 mph) is also simulated. The prediction of vertical and horizontal forces at 30 mph shows an excellent agreement with the test. The results for 20 and 10 mph are also reasonably good. The simulations for complex road conditions and full vehicle over bumps with a concept model are also performed as a feasibility trial. The CPU time used in both HP735 and CRAY computers for all these cases are comparable with other major CAE jobs. The experiments show that the explicit finite element code has a lot of advantages and strong potential to perform durability road load analysis with affordable computer costs.

A Bodner Type of Material Model for the Description of Foam Properties

2001 ◽  
Author(s):  
Yuzhao Song ◽  
Ziqi Chen
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Automobile Industry ◽  
Material Model ◽  
Finite Element Code ◽  
Foam Material ◽  
Element Analysis ◽  
Explicit Finite Element ◽  
Compression Strain ◽  
Foam Properties

Abstract A unified constitutive equation has been used to represent Foam material. It can describe the large compression strain, compression strain rate, tension strain and the bottom out behavior of various foams. The material has been incorporated into LS-DYNA, an explicit finite element code widely used in the automobile industry. An example is given to show an application of the material model in a low speed impact finite element analysis.

A Diagnosis of Failure of a Compressor Blade

1987 ◽  
Author(s):  
J. A. Kubiak ◽  
J. M. Franco ◽  
A. Carnero ◽  
A. Rothhirsch L ◽  
J. Aguirre R.
Keyword(s):  
Finite Element ◽  
High Cycle Fatigue ◽  
Natural Frequencies ◽  
Welded Joint ◽  
Compressor Blade ◽  
Finite Element Code ◽  
Cycle Fatigue ◽  
Start Up ◽  
Load Conditions

The methodology and the procedure of diagnosis of a cracked stationary blade of a compressor due to high cycle fatigue is presented. The natural frequencies of the blades and a stator row were measured and an analysis of the casing vibrations during start-up and under load conditions of the compressor was conducted in a search for the cause of the failure. Using finite element code the natural frequencies and the vibratory stresses of the stator row blades (vanes) were computed. The computed maximum vibratory stresses in the vane were concentrated in the location of the crack which originated from the welded joint. It was concluded that the welded joint requires modification.

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