Multibody Simulation Approach Research Articles

Modelling and numerical simulation of high-speed railway slab track structure

In terms of maintenance and structural behavior, slab track proves to be an advantage over conventional ballasted track due to increasing train speed, axle load, and traffic density. Since the vibration, noise, and risk of derailment, all accelerate as train speed increases, an in-depth investigation of track dynamics becomes essential for identifying the fundamental cause of the problem. In this paper modelling and numerical simulation of high-speed railway slab track structure has been studied using finite element method. Using the multi-body simulation approach and the finite element method a model of the 3D slab track system is developed. The slab track model has rail, rail pad, and concrete slab, HBL, and subgrade layers. In order to determine the fundamental frequency and the mode shapes associated with it, a modal analysis is carried out. Dynamic response, or acceleration against frequency curves derived via harmonic response analysis, is the result of the numerical simulation. The dynamic reaction of the structure of a high-speed slab track is studied, and the effect of elastic materials on reducing vibration is investigated. The results suggest that a layer of elastic material, like a slab of mat, inserted between a layer of concrete slab and a layer of HBL is capable of lowering the amount of vibration response of the track.

Railway track inspection and maintenance priorities due to dynamic coupling effects of dipped rails and differential track settlements

Abstract Each year, there can be three to six millions of service train axles running over an open plain track. In fact, these trains could impose a variety of dynamic loading conditions depending on the wheel and rail maintenance levels. Inevitably, the risk of high-intensity dynamic loading conditions by wheel-rail interactions due to wheel or rail irregularity cannot be disregarded. Imperfection of rail tracks could lead directly to the exceedance of permissible stress of a track component and later amplify rapid track deterioration rates causing cracking in sleepers and failure of track substructure. Practical railway track irregularities can be typically classified into short wave length (high frequency) and long wave length (low frequency) defects, of which previous researchers had studied each in isolation. This paper is the first to study the influence on railway track inspection and maintenance priorities caused by the coupling of wave lengths between dipped rail joint and differential track settlements. To study the dynamic coupling effects, P1 and P2 forces are evaluated at the track irregularity together with rail/sleeper contact force, ballast pressure and bending moments of sleepers using dynamic multi-body simulation approach. It is found that some patterns of coupling irregularity could cause a significant reduction in dynamic impact factors whilst some are associated with an increase in the wheel/rail impact force. The insight has then been integrated to establish track performance indicators that are paramount for prioritising track inspection and maintenance.

The application of multi-body simulation approach in the kinematic analysis of beetle leg joints

Locomotion of insects is exceptionally efficient and this efficiency is partially due to the kinematics within leg joints, which in different movement scenarios depends on their inner contacting conditions. The investigation of functionality of the leg joints can potentially provide new innovative problem solutions in robotics. The previously published information about the shape of the joints is not sufficient, because without knowledge about the movements of the articulating surfaces within the joint, the kinematics cannot be understood. To understand the joint movements, we have performed motion tracking experiments in the beetle Pachnoda marginata (Scarabaeidae, Cetoniinae) in different locomotory scenarios. We aimed at understanding the range of motion within single leg joints depending on their function in the entire leg movement scenario. For this purpose, we combined the motion analysis of living beetles with the results of the simulation of a multi-body system. The results of the multi-body simulation allowed the kinematic characterization of articulating joints by their degrees of freedom and the identification of the rotation axes. The simulated range of motion predicted by the limitations of the exoskeleton of the joints partially matched those obtained from the motion analysis of the living beetle. We showed that the range of motion of the single leg joints depends strongly on the type of the beetle locomotory scenario. It is also concluded that the simulation of multi-body systems is a powerful tool for the kinematic analysis of insect tribological systems.

Investigation on pitch system loads by means of an integral multi body simulation approach

In modern horizontal axis wind turbines the rotor blades are adjusted by three individual pitch systems to control power output. The pitch system consists of either a hydraulic or an electrical actuator, the blade bearing, the rotor blade itself and the control. In case of an electrical drive a gearbox is used to transmit the high torques that are required for blade pitch angle adjustment. In this contribution a new integral multi body simulation approach is presented that enables detailed assessment of dynamic pitch system loads. The simulation results presented are compared and evaluated with measurement data of a 2 MW-class reference wind turbine. Major focus of this contribution is on the assessment of non linear tooth contact behaviour incorporating tooth backlash for the single gear stages and the impact on dynamic pitch system loads.

Multibody Interactions, Phase Behavior, and Clustering in Nanoparticle-Polyelectrolyte Mixtures.

We present the results of a computational study of the interactions, phase-behavior and aggregation characteristics of charged nanoparticles (CNPs) suspended in solution of oppositely charged polyelectrolytes (PEs). We used an extension of the mean-field polymer self-consistent field theory (SCFT) model presented in our earlier work ( Macromolecules , 2014 , 47 , 6095 - 6112 ) to explicitly characterize the multibody interactions in such systems. For dilute-moderate particle volume fractions, the magnitudes of three and higher multibody interactions were seen to be weak relative to the contributions from pair interactions. On the basis of such results, we embeded the pair-interaction potentials within a thermodynamic perturbation theory approach to identify the phase behavior of such systems. The results of such a framework suggested that the gas and FCC crystal phases were thermodynamically stable, whereas the fluidlike phase was metastable in such systems. To complement the parameters studied using SCFT, we used a recently developed multibody simulation approach to study the aggregation and cluster morphologies in CNP-PE mixtures. For low particle charges, such systems mainly exhibited clusters arising from direct contact aggregation between CNPs. However, for higher particle and PE charges and low PE concentrations, large regions of PE-bridged clusters were seen to form. We present a morphological phase diagram summarizing such results.

Overview and Design of self-acting pitch control mechanism for vertical axis wind turbine using multi body simulation approach

Awareness about wind energy is constantly growing in the world. Especially a demand for small scale wind turbine is increasing and various products are available in market. There are mainly two types of wind turbines, horizontal axis wind turbine and vertical axis wind turbines. Horizontal axis wind turbines are suitable for high wind speed whereas vertical axis wind turbines operate relatively low wind speed area. Vertical axis wind turbines are cost effective and simple in construction as compared to the horizontal axis wind turbine. However, vertical axis wind turbines have inherent problem of self-start inability and has low power coefficient as compare to the horizontal axis wind turbine. These two problems can be eliminated by incorporating the blade pitching mechanism. So, in this paper overview of various pitch control systems is discussed and design of self-acting pitch mechanism is given. A pitch control linkage mechanism for vertical axis wind turbine is modeled by multi-body approach using MSC Software. Aerodynamic loads are predicted from a mathematical model based on double multiple stream tube method. An appropriate airfoil which works at low Reynolds number is selected for blade design. It is also focused on commercialization of the vertical axis wind turbine which incorporates the self-acting pitch control system. These aerodynamic load model will be coupled with the multi-body model in future work for optimization of the pitch control linkage mechanism. A 500 Watt vertical axis wind turbine is designed and it is planned to implement the self-acting pitch control mechanism in real model.

Experimental verification of a dynamic model of a tube roll in terms of subcritical superharmonic vibrations

The non-idealities in a rotor-bearing system may cause undesirable subcritical superharmonic resonances that occur when the rotating speed of the rotor is a fraction of the natural frequency of the system. These resonances arise partly from the non-idealities of the rotor and partly from the non-idealities of the bearings. The superharmonic vibrations of complex rotor-bearing systems can be studied accurately by combining a detailed rotor and bearing model with a multibody simulation approach. The complex rotor-bearing system under investigation is a tube roll of a paper machine supported by a hard-bearing-type balancing machine. Resonances affect the quality of end product and therefore have to be studied in detail. Non-idealities of the rotor-bearing system are measured from the existing structure and the parameters of the real structure are emulated as accurately as possible in the simulation model. The simulation model is verified using the results from experimental modal analysis and the measurement results for the subcritical superharmonic response of the roll. The analogy between the simulation and experimental results of the studied system is substantial.

Pilot study on proximal femur strains during locomotion and fall-down scenario

The most common and severe type of fracture among the elderly is known as a proximal femur fracture. Aging-related bone loss is one of the major contributing factors to increased likelihood of bone fracture. Specific exercises can be used to strain bones and increase bone strength to counter the effects of bone loss. The flexible multibody simulation approach can be used as a non-invasive method for estimating bone strains caused by physical activity. This method was recently used to analyze the strain of locomotion in regard to human femur and tibia leg bones. The current study focuses on strain analysis of the femoral neck. The research test person was a clinically healthy 65-year old Caucasian male. The computed tomography was used to build a geometrically accurate finite element model of the femur with inhomogeneous material properties derived from the voxel data. The anthropometric data was used to model the musculoskeletal system of the test person. The multibody skeletal model was utilized to estimate loading on the femoral neck during walking, which represents a routine daily activity. The flexible multibody simulation results were compared to strains that occurred during a simulated fall onto the greater trochanter of the femur. The fall simulation was made entirely using finite element software. Results from the finite element analysis were compared with the previous study showing that the test person does not belong to the high-risk hip fracture group. Finally, the estimated strains gathered from the walking simulation were compared to the strain values from the simulated fall-down scenario.

A full body musculoskeletal model based on flexible multibody simulation approach utilised in bone strain analysis during human locomotion

Load-induced strains applied to bone can stimulate its development and adaptation. In order to quantify the incident strains within the skeleton, in vivo implementation of strain gauges on the surfaces of bone is typically used. However, in vivo strain measurements require invasive methodology that is challenging and limited to certain regions of superficial bones only such as the anterior surface of the tibia. Based on our previous study [Al Nazer et al. (2008) J Biomech. 41:1036–1043], an alternative numerical approach to analyse in vivo strains based on the flexible multibody simulation approach was proposed. The purpose of this study was to extend the idea of using the flexible multibody approach in the analysis of bone strains during physical activity through integrating the magnetic resonance imaging (MRI) technique within the framework. In order to investigate the reliability and validity of the proposed approach, a three-dimensional full body musculoskeletal model with a flexible tibia was used as a demonstration example. The model was used in a forward dynamics simulation in order to predict the tibial strains during walking on a level exercise. The flexible tibial model was developed using the actual geometry of human tibia, which was obtained from three-dimensional reconstruction of MRI. Motion capture data obtained from walking at constant velocity were used to drive the model during the inverse dynamics simulation in order to teach the muscles to reproduce the motion in the forward dynamics simulation. Based on the agreement between the literature-based in vivo strain measurements and the simulated strain results, it can be concluded that the flexible multibody approach enables reasonable predictions of bone strain in response to dynamic loading. The information obtained from the present approach can be useful in clinical applications including devising exercises to prevent bone fragility or to accelerate fracture healing.

Flexible Multibody Simulation Approach in the Analysis of Friction Winder

The main objective of this study was to model and simulate a multi-flexible-body three-dimensional model for researching the Multi – rope Friction Winder system. By introducing the multi-flexible-body dynamics method, a multi-flexible-body virtual prototype of the winder is been builded with the RecurDyn software package. Kinematics and dynamics characteristic date are obtained by computer-aided dynamic simulation of virtual Multi – rope friction winder. The result is in accord with theoretical analysis. The research work will provide a powerful tool and useful method for the design of economic and credible elevator system. The approach can be generalized to analysis other flexible drive fields.

Analysis of dynamic strains in tibia during human locomotion based on flexible multibody approach integrated with magnetic resonance imaging technique

Bone is known to adapt to the prevalent strain environment while the variation in strains, e.g., due to mechanical loading, modulates bone remodeling, and modeling. Dynamic strains rather than static strains provide the primary stimulus of bone functional adaptation. The finite element method can be generally used for estimating bone strains, but it may be limited to the static analysis of bone strains since the dynamic analysis requires expensive computation. Direct in vivo strain measurement, in turn, is an invasive procedure, limited to certain superficial bone sites, and requires surgical implementation of strain gauges and thus involves risks (e.g., infection). Therefore, to overcome difficulties associated with the finite element method and the in vivo strain measurements, the flexible multibody simulation approach has been recently introduced as a feasible method to estimate dynamic bone strains during physical activity. The purpose of the present study is to further strengthen the idea of using the flexible multibody approach for the analysis of dynamic bone strains. Besides discussing the background theory, magnetic resonance imaging is integrated into the flexible multibody approach framework so that the actual bone geometry could be better accounted for and the accuracy of prediction improved.

Flexible multibody simulation approach in the analysis of tibial strain during walking

Strains within the bone tissue play a major role in bone (re)modeling. These small strains can be assessed using experimental strain gage measurements, which are challenging and invasive. Further, the strain measurements are, in practise, limited to certain regions of superficial bones only, such as the anterior surface of the tibia. In this study, tibial strains occurring during walking were estimated using a numerical approach based on flexible multibody dynamics. In the introduced approach, a lower body musculoskeletal model was developed by employing motion capture data obtained from walking at a constant velocity. The motion capture data were used in inverse dynamics simulation to teach the muscles in the model to replicate the motion in forward dynamics simulation. The maximum and minimum tibial principal strains predicted by the model were 490 and −588 microstrain, respectively, which are in line with literature values from in vivo measurements. In conclusion, the non-invasive flexible multibody simulation approach may be used as a surrogate for experimental bone strain measurements and thus be of use in detailed strain estimations of bones in different applications.

A COMPARATIVE APPROACH TO THE NC AXIS DYNAMIC BEHAVIOUR MODELLING

the metalworking industry interest in high speed and high accuracy machining has asked the machine-tools builders to focus attention on one topic in particular: the dynamic behaviour of the feed axes. The paper presents a comparative approach of the ball screw based NC axes dynamic behaviour modelling. An analytical approach and a multi body simulation approach are presented and discussed. Theoretical results are compared with experimental results.

Multi-body simulation approach for fault diagnosis of a reel

This study introduces a simulation approach that can be utilized in the detection of abnormalities in the behaviour of machines. The approach is based on the utilization of a detailed multi-body simulation model. In this study, the approach to detect abnormalities is applied to the study of a reel. The reel under investigation is used at the finishing end of the papermaking process and it consists of a number of subsystems including hydraulics, electrical drives, and mechanical parts. In the reel, mechanical parts are coupled by joints, contacts, and friction. The symptoms of the faults are generated using the variables which can be measured from the reel. When using a traditional component level monitoring method, the faults in the process often cannot be recognized. However, in the proposed multi-body simulation approach, the supervision of a machine can be focused on the functionality of the entire process, whereas detection of faults can be carried out without the use of additional instrumentation. When the multi-body simulation approach is used, the modelling of a machine can be carried out in a straightforward and systematic manner including the dynamic coupling between the subsystems of a machine.

Multibody Approach for Model-Based Fault Detection of a Reel

In order to improve the recognition of faulty situations, model-based fault detection can be used together with signal processing methods. In this study, faults and abnormalities of a reel are studied by employing the multibody simulation approach. The reel under consideration consists of a number of subsystems, including hydraulics, electrical drives, and mechanical parts. These subsystems are coupled by joints, friction forces, and contact forces. Using the multibody simulation approach, the complete model of the reel can be obtained by coupling different subsystems together. Three well-known multibody formulations, a method of Lagrange multipliers, an Augmented Lagrangian method, and a method based on projection matrix R, are briefly described and compared in order to find out the most efficient method for simulating the studied reel. Although this study is focused on the simulation of fault scenarios, the introduced multibody simulation approach can be utilized in real-time simulation. This makes it possible to apply the model to an existing reel.

A Simple Solvation Model Along with A Multibody Dynamics Strategy (MBO(N)D) Produces Stable DNA Simulations that are Faster than Traditional Atomistic Methods

We are developing solvation strategies that complement the speed advantage of MBO(N)D (a multibody simulation approach developed by Moldyn) for simulating biomolecular systems. In this report we propose to approximate the effect of bulk waters on DNA by using only a thin layer of waters proximate to the surface of DNA (which we will call the ‘thin shell approach’ or TSA). We will show that the TSA combined with substructuring (the grouping of atoms into rigid or flexible bodies) of the Dickerson dodecamer produces good comparisons with standard atomistic methods (over a nanosecond trajectory) as judged by a variety of DNA specific geometric (e.g., CURVES output) and dynamics (power spectra) properties. The MBO(N)D method, however, was faster than atomistic by a factor of six using the same solvation strategy and factor of 70 when compared to fully solvated atomistic system. The key to the speed of MBO(N)D is in its ability to use large time steps during dynamics. By keeping only a shell of molecules of water proximate to the dodecamer, we limit artifacts due to surface tension at the water-vacuum interface. These proximate waters are fairly immobile as compared to those in bulk and therefore do not severely limit the time step in the simulation. The strengths and limitations of this solvation approach, and future directions, will also be discussed.