On a Perturbation Method for the Analysis of Unsteady Belt-Drive Operation

2004 ◽  
Vol 72 (4) ◽  
pp. 570-580 ◽  
Author(s):  
Michael J. Leamy
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Perturbation Method ◽  
Element Model ◽  
Contact Forces ◽  
Steady Solution ◽  
Belt Drive ◽  
Friction Forces ◽  
Direct Contrast ◽  
Validity Criteria

A perturbation method is presented for use in analyzing unsteady belt-drive operation. The method relies on the important assumption that for operating states close to steady operation, the friction state (i.e., whether the belt is creeping or sticking at any location on the pulley) is similar to that of the well-known steady solution in which a lone stick arc precedes a lone slip arc (Johnson, K. L., 1985, Contact Mechanics, Cambridge U.P., London, Chap. 8; Smith, D. P., 1999, Tribol. Int., 31(8), pp. 465–477). This assumption, however, is not used to determine the friction force distribution, and, in fact, the friction forces in the stick zone are found to be nonzero, in direct contrast to the steady solution. The perturbation analysis is used to derive expressions for the span tensions, the pulley tension distributions, the contact forces between the belt and the pulleys, and the angular velocity of the driven pulleys. Validity criteria are developed which determine bounds on the operation state for which the assumed friction state is upheld. Verification of response quantities from the perturbation solution is accomplished through comparison to quantities predicted by an in-house dynamic finite element model and excellent agreement is found. Additionally, the finite element model is used to verify the key assumption that a lone slip arc precedes a lone stick arc.

Detailed Finite Element Modeling of a High Capacity Mooring Steel Wire Rope: Calculation of the Stress Concentration Near the Connection

2020 ◽  
Author(s):  
Michaël Martinez ◽  
Sébastien Montalvo
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Stress Concentration ◽  
Finite Element Model ◽  
Steel Wire ◽  
High Capacity ◽  
Element Model ◽  
Wire Rope ◽  
Contact Forces ◽  
Life Assessment

Abstract The mooring of floating platforms is an important challenge for the offshore industry. It is an important part of the design engineering and, often, a critical point for the fatigue life assessment. A solution that could improve the fatigue life is to directly connect the mooring rope to the platform, without an intermediate chain. However this solution is not widespread and the behavior of a rope near such a connection is little known. The present paper proposes to better understand this behavior, thanks to a detailed finite element model of the rope. The study case is a steel wire rope directly connected to a floating wind turbine. A local finite element model of the rope has been built, where the wires are individually modeled with beam elements. One end of the rope is clamped, simulating the connection, while tension and cyclic bending oscillations are applied to the other end. A localized bending takes place near the connection, leading to stress concentration in the wires. The stress concentration and the local contact forces are calculated for each wire. These data are important entry parameters for a local failure or fatigue analysis. This latter is however not presented here. Despite IFPEN experience in the development of local finite element models of steel wire ropes, it is the first time that such a high capacity rope (MBL = 12 500 kN) is modeled. This is challenging because of the large diameter of the rope and the large number of wires. However this modeling approach is very valuable for such ropes, because the experimental tests are rare and very expensive.

Finite Element Model of Schallamach Waves in Belt-Drives

2019 ◽  
Author(s):  
Mohammed Khattab ◽  
Tamer Wasfy
Keyword(s):  
Finite Element ◽  
Friction Coefficient ◽  
Finite Element Model ◽  
Wave Phenomenon ◽  
Coulomb Friction ◽  
Element Model ◽  
Belt Drive ◽  
High Fidelity ◽  
Stick Slip ◽  
Belt Drives

Abstract The objective of this study is to investigate if a high-fidelity finite element model can predict the Schallamach wave phenomenon in belt-drives. To this end a computational model which closely mimics a recently developed one-pulley experimental belt-drive apparatus, was created. The dynamic response predicted by the model is compared to the experiment results in order to demonstrate that the model can be used to predict the Schallamach wave phenomenon. Furthermore, the model is used to investigate the roles of Coulomb friction coefficient, adhesion, and torque direction on stick-slip instability effects.

Complex Eigenvalue Analysis Applied to an Aircraft Brake Vibration Problem

1995 ◽  
Author(s):  
Denis J. Feld ◽  
Dana J. Fehr
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Friction Force ◽  
Mode Shape ◽  
Element Model ◽  
Eigenvalue Analysis ◽  
Complex Eigenvalue ◽  
Friction Forces ◽  
Model Complex ◽  
Complex Eigenvalue Analysis

Abstract A conventional finite element model of an aircraft wheel and brake is extended to include forces responsible for friction-induced noise. Responses of aircraft brake vibration modes change the normal force across the brake friction interfaces, and consequently the friction forces. The resulting friction force variations are assembled in the form of a supplemental stiffness matrix and added to the finite element model. Complex eigenvalue analysis that includes the friction force variations provides frequency and mode shape information, as well as an assessment of the predicted mode stability. A predicted unstable vibration mode compares very well to operating mode shape data determined from instrumented tests. Hardware modifications to reduce a brake noise in an aircraft cabin were based on beneficial trends found from exercising the model. Implementation of the hardware modifications on the aircraft successfully suppressed the noise.

Can Syndesmosis Screws Displace the Distal Fibula?

2020 ◽  
pp. 193864002091209
Author(s):  
Nicholas G. Vance ◽  
Robert C. Vance ◽  
William T. Chandler ◽  
Vinod K. Panchbhavi
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Element Model ◽  
Contact Forces ◽  
Tibiofibular Syndesmosis ◽  
Distal Fibula ◽  
Element Analysis ◽  
Clear Space ◽  
Distal Tibiofibular Syndesmosis ◽  
Level I

Background. There has been historical debate as to whether the distal tibiofibular syndesmosis can be overtightened during operative fixation. We used finite-element analysis to determine if overtightening of syndesmotic screws can cause widening of the lateral gutter clear space in the ankle joint. Methods. A 3D finite-element model was constructed and analyzed using geometries from a computed tomography scan of a cadaveric lower leg. Starting 2 cm from the plafond, screw fixation was simulated at 5-mm increments to a distance of 5 cm from the plafond. The fibula was compressed 2 mm toward the tibia at each interval, and the change in distance between the lateral talus and distal fibula was measured. Results. Medial deflection of the fibula resulted in widening of the lateral clear space, which was proportional to the amount of deflection. The effect increased as screws were placed closer to the plafond, with 1.5 mm of widening at 2 cm (0.76 mm/mm) versus 0.7 mm at 5 cm (0.34 mm/mm). Conclusion. Our finite-element model demonstrated that overtightening of the distal tibiofibular syndesmosis with medial fibular displacement can cause widening of the lateral clear space. Clinical relevance. The results suggest that screws placed farther from the plafond widen the lateral clear space to a lesser degree, which may be advantageous during surgical fixation to prevent clear space widening and increased tibiotalar contact forces. Levels of Evidence: Level I

Characterization of the static behavior of micromirrors under the effect of capillary force, an analytical approach

2012 ◽  
Vol 226 (9) ◽  
pp. 2361-2372 ◽  
Author(s):  
Hamid Moeenfard ◽  
Ali Darvishian ◽  
Hassan Zohoor ◽  
Mohammad Taghi Ahmadian
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Perturbation Method ◽  
Capillary Force ◽  
Homotopy Perturbation Method ◽  
Element Model ◽  
Geometrical Parameters ◽  
Static Behavior ◽  
Homotopy Perturbation

In this article, the static behavior of micromirrors under the effect of capillary force is studied. The dimensionless equations governing the static behavior and the pull-in state of the micromirror under capillary force are obtained, and the effects of different geometrical parameters on the pull-in angle of micromirrors are investigated. The static behavior of micromirrors is studied both numerically and analytically using the homotopy perturbation method. It is observed that with increasing the instability number defined in this article, the rotation angle of the micromirror is increased and suddenly the pull-in occurs. The results of the presented model are then verified by comparing them with the results of finite element simulations performed in the commercial finite element model software ANSYS. The agreement between the results of finite element model and those of the proposed analytical model shows that homotopy perturbation method can be used as a fast and accurate tool for predicting mirror’s behavior under capillary force.

scholarly journals An improved spectral decomposition flexibility perturbation method for finite element model updating

2018 ◽  
Vol 10 (12) ◽  
pp. 168781401881492 ◽  
Author(s):  
QW Yang ◽  
BX Sun ◽  
C Lu
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Perturbation Method ◽  
Spectral Decomposition ◽  
Model Updating ◽  
Element Model ◽  
Singular Value ◽  
Finite Element Model Updating ◽  
Noisy Environment ◽  
Initial Method

Finite element analysis is the most powerful tool to predict the behavior of a structure in engineering practice. Generally, the initial finite element model must be corrected with experimental data due to its complexity. Thus, it is very necessary to study a finite element model updating method with high precision and high efficiency. To this end, this article presented an improved spectral decomposition flexibility perturbation method for structural finite element model updating. The improvements of the proposed method lie in two aspects. First, using the uniform correction model, the proposed method is more economical in computation than the initial method because the spectral decomposition and reorganization of elemental stiffness matrices can be avoided. Second, using the twice singular-value-truncation method, the proposed method has better performance than the initial method in combating data noise. A beam structure is employed to demonstrate the proposed method for model updating in a noisy environment. It was found that the result obtained by least squares estimate is seriously distorted and the result obtained by the first singular value truncation is also not entirely satisfactory. Only the result obtained by the second singular value truncation is the most stable and accurate. Overall, the improved spectral decomposition flexibility perturbation method is robust and effective in small modification case, large modification case, adjacent modification case, and multiple modifications case. The proposed method may be very useful for structural finite element model updating in the noisy environment.

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