Study Concerning the Effect of the Bushings' Deformability on the Static Behavior of the Rear Axle Guiding Linkages

2012 ◽  
Vol 245 ◽  
pp. 132-137 ◽  
Author(s):  
Vlad Totu ◽  
Cătălin Alexandru
Keyword(s):  
Rear Axle ◽  
Stationary Regime ◽  
Geometric Constraints ◽  
External Loading ◽  
Static Behavior ◽  
Compliant Joints ◽  
Rigid Model ◽  
The Difference ◽  
Guiding System ◽  
Multi Body

In this paper, we attempt to study the influence of the bushings (compliant joints) on the static behavior of the guiding system used for the rear axle of the vehicles. In fact, we are interested to determine the difference in behavior between the compliant model (with bushings) and the rigid model (bushings modeled as spherical joints) of the axle guiding mechanism. The static model, in which the car body is attached to ground, is a constrained, multi-body spatial mechanical system, in which the bodies are connected through geometric constraints, compliant joints, and force elements. The external loading is made by vertical forces applied to the wheels, in stationary regime. The study is made for the general groups of guiding mechanisms, with M=1 and M=2 degrees of mobility, by using the MBS (Multi-Body Systems) environment ADAMS of MSC Software.

scholarly journals Effect Of Rubber Damper Stiffness And Tire Pressure To Reduce Ground Reaction Load Factor On Main Landing Gear Using Multi-Body Simulation (MBS) Rigid Model

2019 ◽  
Vol 17 (2) ◽  
pp. 123
Author(s):  
Dony Hidayat
Keyword(s):  
Landing Gear ◽  
Load Factor ◽  
Tire Pressure ◽  
Initial Stage ◽  
Adams Software ◽  
Rigid Model ◽  
Contact Impact ◽  
The Difference ◽  
Multi Body ◽  
Rubber Damper

Landing Gear Drop Test (LGDT) utilizes the apparatus requiring a substantial time and cost. Virtual LGDT (vLGDT) using MSC ADAMS software is one of the solutions for initial stage to testing landing gear. From simulation with vsink 1.7 m/s and load 22000 N obtained contact/impact force that ensue in  MSC ADAMS was 73650 N, while from experimental was 73612 N. The difference between vLGDT and LGDT result is 0.05 %. To obtain ground reaction load factor below 3 in vsink = 3.05 m/s, the rubber damper should have stiffness in the range of 1900 - 2100 N/mm and for the tire pressure of  60 - 65 psi.

Introducing a Projection-Based Method to Compare Three Approaches Computing the Accumulation of Geometric Variations

2018 ◽  
Author(s):  
Vincent Delos ◽  
Santiago Arroyave-Tobón ◽  
Denis Teissandier
Keyword(s):  
Degrees Of Freedom ◽  
Mechanical Design ◽  
Geometric Constraints ◽  
Computational Time ◽  
Manufacturing Defects ◽  
Design Tolerance ◽  
Polyhedral Objects ◽  
The Difference ◽  
Bounded Sets ◽  
Accumulation Of Defects

In mechanical design, tolerance zones and contact gaps can be represented by sets of geometric constraints. For computing the accumulation of possible manufacturing defects, these sets have to be summed and/or intersected according to the assembly architecture. The advantage of this approach is its robustness for treating even over-constrained mechanisms i.e. mechanisms in which some degrees of freedom are suppressed in a redundant way. However, the sum of constraints, which must be computed when simulating the accumulation of defects in serial joints, is a very time-consuming operation. In this work, we compare three methods for summing sets of constraints using polyhedral objects. The difference between them lie in the way the degrees of freedom (DOFs) (or invariance) of joints and features are treated. The first method proposes to virtually limit the DOFs of the toleranced features and joints to turn the polyhedra into polytopes and avoid manipulating unbounded objects. Even though this approach enables to sum, it also introduces bounding or cap facets which increase the complexity of the operand sets. This complexity increases after each operation until becoming far too significant. The second method aims to face this problem by cleaning, after each sum, the calculated polytope to keep under control the effects of the propagation of the DOFs. The third method is new and based on the identification of the sub-space in which the projection of the operands are bounded sets. Calculating the sum in this sub-space allows reducing significantly the operands complexity and consequently the computational time. After presenting the geometric properties on which the approaches rely, we demonstrate them on an industrial case. Then we compare the computation times and deduce the equality of the results of all the methods.

scholarly journals A Constraint Solver for Flexible Protein Model

2013 ◽  
Vol 48 ◽  
pp. 953-1000 ◽  
Author(s):  
F. Campeotto ◽  
A. Dal Palù ◽  
A. Dovier ◽  
F. Fioretto ◽  
E. Pontelli
Keyword(s):  
Structure Prediction ◽  
Dimensional Space ◽  
Protein Structures ◽  
Empirical Evaluation ◽  
Geometric Constraints ◽  
Conformational Space ◽  
Loop Modeling ◽  
Geometric Properties ◽  
Constraint Solver ◽  
Multi Body

This paper proposes the formalization and implementation of a novel class of constraints aimed at modeling problems related to placement of multi-body systems in the 3-dimensional space. Each multi-body is a system composed of body elements, connected by joint relationships and constrained by geometric properties. The emphasis of this investigation is the use of multi-body systems to model native conformations of protein structures---where each body represents an entity of the protein (e.g., an amino acid, a small peptide) and the geometric constraints are related to the spatial properties of the composing atoms. The paper explores the use of the proposed class of constraints to support a variety of different structural analysis of proteins, such as loop modeling and structure prediction. The declarative nature of a constraint-based encoding provides elaboration tolerance and the ability to make use of any additional knowledge in the analysis studies. The filtering capabilities of the proposed constraints also allow to control the number of representative solutions that are withdrawn from the conformational space of the protein, by means of criteria driven by uniform distribution sampling principles. In this scenario it is possible to select the desired degree of precision and/or number of solutions. The filtering component automatically excludes configurations that violate the spatial and geometric properties of the composing multi-body system. The paper illustrates the implementation of a constraint solver based on the multi-body perspective and its empirical evaluation on protein structure analysis problems.

Fracture Mechanics of Bone

1993 ◽  
Vol 115 (4B) ◽  
pp. 549-554 ◽  
Author(s):  
J. W. Melvin
Keyword(s):  
Fracture Mechanics ◽  
Bone Fracture ◽  
Longitudinal Crack ◽  
Compact Bone ◽  
Plastic Zone Size ◽  
Geometric Constraints ◽  
External Loading ◽  
Specimen Thickness ◽  
Critical Crack ◽  
Critical Crack Length

This paper reviews the progress that has been made in applying the principles of fracture mechanics to the topic of fracture of long bones. Prediction of loading conditions which result in the propagation of fractures in bones has been of interest to the field of trauma biomechanics and orthopedics for over one hundred years. Independent verifications, by various investigators, of bone fracture mechanics parameters are reviewed and investigations of the effects of bone density and specimen thickness on the critical fracture mechanics parameters and of other factors such as critical crack length and plastic zone size in bovine femoral bone, and the effects of crack velocity on fracture mechanics parameters in bovine tibial bone are discussed. It took over ten years for the techniques of bone fracture mechanics to be applied to human compact bone, due primarily to geometric constraints from the smaller size of human bones. That work will be reviewed along with other continuing work to define the orientation dependence of the fracture mechanics parameters in bone and to refine the experimental techniques needed to overcome the geometric constraints of specimen size. A discussion is included of work still needed to determine fracture mechanics parameters for transverse and longitudinal crack propagation in human bone and to establish the effects of age on those parameters. Finally, a discussion will be given of how this knowledge needs to be extended to allow prediction of whole bone fracture from external loading to aid in the design of protective systems.

scholarly journals Electron-Induced Chemistry in the Condensed Phase

Atoms ◽  
2019 ◽  
Vol 7 (1) ◽  
pp. 33
Author(s):  
Jan Hendrik Bredehöft
Keyword(s):  
Gas Phase ◽  
Cross Sections ◽  
Condensed Phase ◽  
Theoretical Understanding ◽  
The Past ◽  
Long Time ◽  
The Difference ◽  
Molecule Interactions ◽  
Multi Body ◽  
Molecule Interaction

Electron–molecule interactions have been studied for a long time. Most of these studies have in the past been limited to the gas phase. In the condensed-phase processes that have recently attracted attention from academia as well as industry, a theoretical understanding is mostly based on electron–molecule interaction data from these gas phase experiments. When transferring this knowledge to condensed-phase problems, where number densities are much higher and multi-body interactions are common, care must be taken to critically interpret data, in the light of this chemical environment. The paper presented here highlights three typical challenges, namely the shift of ionization energies, the difference in absolute cross-sections and branching ratios, and the occurrence of multi-body processes that can stabilize otherwise unstable intermediates. Examples from recent research in astrochemistry, where radiation driven chemistry is imminently important are used to illustrate these challenges.

Study on the Difference of Frontal Impact Response among People of Different Sizes

2010 ◽  
Vol 34-35 ◽  
pp. 111-116 ◽  
Author(s):  
Li Bo Cao ◽  
Chong Zhen Cui ◽  
Ning Yu Zhu ◽  
Huan Chen
Keyword(s):  
Human Body ◽  
Injury Risk ◽  
Simulation Models ◽  
Restraint System ◽  
Frontal Impact ◽  
Occupant Restraint System ◽  
Impact Simulation ◽  
The Difference ◽  
Human Body Models ◽  
Multi Body

In this article, seven frontal impact simulation models with same restraint system and different human body models were established through the use of multi-body kinematics software MADYMO. The injuries in head, chest and femurs of different human models and the differences of these injuries were analyzed in detail. The weighted injury criterion was adopted to evaluate the overall injuries of different human body models. The results shows that the injury risk of smaller human body is much higher than the taller human body, and existing occupant restraint system that protects the 50th percentile American occupant well protects other size occupant poorly.

Multi-Body Dynamics Analysis of Anti-Backlash Gear System Based on ADAMS/ Flex

2014 ◽  
Vol 971-973 ◽  
pp. 1261-1265
Author(s):  
Yu Jun Cao ◽  
Nai Hui Yu ◽  
Zheng Yang ◽  
Jian Zhong Shang
Keyword(s):  
Dynamic Characteristics ◽  
Coupling Model ◽  
Gear System ◽  
Dynamics Analysis ◽  
Simulation Accuracy ◽  
Flexible Coupling ◽  
Torsion Spring ◽  
Body Dynamics ◽  
Rigid Model ◽  
Multi Body

Anti-backlash gear can improve the static transmission precision of system. Besides, the dynamic characteristics of anti-backlash gear system have a significant effect on the performance of overall mechanism, and the torsion spring preload of anti-backlash gear is an important factor to affect the dynamic characteristic. In order to study dynamic characteristics of the anti-backlash gear, a rigid-flexible coupling model of single-stage anti-backlash system was established based on ADAMS / Flex, and the simulation accuracy was compared with the pure rigid model. The effect of the torsion spring preload on frequency response of the anti-backlash system was studied by virtual sweep experiments.

scholarly journals Steering test of mid-size bus with flexible-body dynamics model

2018 ◽  
Vol 169 ◽  
pp. 01038 ◽  
Author(s):  
Jia-Shiun Chen ◽  
Hsiu-Ying Hwang
Keyword(s):  
Structural Vibration ◽  
Vehicle Body ◽  
Flexible Body ◽  
Simulation Test ◽  
Body Model ◽  
Vibration Responses ◽  
Flexible Body Dynamics ◽  
The Difference ◽  
Rigid Body Simulation ◽  
Multi Body

The object of this paper is to analyze the vehicle structural vibration responses during the step steering simulation test. With computer simulations, confirming the influence from the difference between configurations of components on mid-size electrical bus and tradition one could be possible. The difference of the vibration responses between flexible multi-body model and rigid one would be discussed. Since the wheel base of mid-size bus is longer than passenger car, the deformation of vehicle body more obviously influences the output of vibration response. The operating condition in practical driving can be expressed by flexible model, and the performance prediction of vehicle can be closer to the real vehicle behavior. The difference between the flexible body simulation and rigid body simulation is 1.17%, and the flexible body model is more practical.

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