Showing papers in "Mechanics Based Design of Structures and Machines in 2011"
TL;DR: In this paper, the relationship between motor and transmission is investigated by introducing some easily calculated factors useful for comparing all the available motor-reducer couplings and selecting the best solution.
Abstract: The selection of a motor-reducer unit in electrical servo-systems has a profound impact on the dynamic performance of a machine. This choice must be made considering all the limits imposed by each component of the system and all the operational constraints. This article proposes a useful and practical methodology for the correct sizing of a motor-reducer unit. The relationships between motor and transmission are investigated by introducing some easily calculated factors useful for comparing all the available motor-reducer couplings and selecting the best solution. The article suggests an innovative approach for the selection of a motor-reducer unit that involves solving the problem with the use of graphs that would allow showing all the possible alternatives.
58 citations
TL;DR: In this article, a chain algorithm element is created from pseudo-rigid body segments and used in a chain calculation that accurately predicts the force deflection relationship of beams with large 3D deflections.
Abstract: A chain algorithm element is created from pseudo-rigid-body segments and used in a chain calculation that accurately predicts the force deflection relationship of beams with large 3-D deflections. Each chain element is made up of three superimposed pseudo-rigid-body models acting orthogonally in relation to each other. The chain algorithm can accurately and quickly predict large displacements and the force-deflection relationship of lateral torsional buckled beams. This approach is not intended to compete with finite element analysis, but rather is a supplement tool that may prove particularly useful in the early phases of design when many analysis iterations are required. The 3-D chain algorithm is demonstrated and compared to the finite element analysis for the nonlinear large-deflection, post-buckling path of a flexible beam undergoing lateral-torsional buckling.
39 citations
TL;DR: In this article, the parametric vibration and stability of the functionally graded ceramic-metal plate subjected to in-plane excitation is presented. And the variations of resonance solution, stability, and bifurcation characteristics were analyzed.
Abstract: The parametric vibration and stability of the functionally graded ceramic-metal plate subjected to in-plane excitation is presented. Based on the stress-strain relationship and nonlinear geometric equations of nonhomogeneous materials, the nonlinear partial differential equations of this problem were derived by using principle of virtual work. For the simply supported rectangular plate, the displacement function was assumed and the nonlinear Mathieu vibrations equation of parametric excitation was obtained by using Galerkin method. The principal parametric resonance was analyzed. The multiscale method is used to obtain the frequency-response equation of the steady-state movement. Based on the Lyapunov stability theory, the critical conditions of steady-state solutions were deduced. Numerical examples are provided to investigate the amplitude curves of functionally graded plate and the influences of different frequency and excitation amplitude. The variations of resonance solution, stability, and bifurcation characteristics were analyzed.
37 citations
TL;DR: In this paper, the maximum contact and fillet stresses in normal and high contact ratio spur gears are evaluated based on load sharing ratio using finite element method through single and multi-point loaded models as well as multi-pair contact model.
Abstract: Maximum contact and fillet stresses in normal and high contact ratio spur gears are evaluated based on load sharing ratio using finite element method through single- and multi-point loaded models as well as multi-pair contact model. The multi-pair contact model has been justified as an appropriate one for the present analysis as this model exclusively considers the influence of the loaded adjacent teeth and the Hertz contact deflections. A detailed parametric study on the load sharing ratio and the respective stresses has also been carried out to analyze the effect of addendum height, the pressure angle, gear ratio, teeth number, and tooth size. Finally, the importance of load sharing ratio and the critical loading points for maximum fillet and contact stresses in normal and high contact ratio spur gears is highlighted for the effective design.
34 citations
TL;DR: The solution is inspired from Particle Swarm Optimization (PSO) and combined with multibody system dynamics which also includes the consideration of robots' physical properties like mass, inertia, force, acceleration, etc.
Abstract: This paper addresses the problem of cooperative motion of a swarm mobile robotic system with the purpose of searching a target in a complicated environment. The solution is inspired from Particle Swarm Optimization (PSO) and combined with multibody system dynamics which also includes the consideration of robots' physical properties like mass, inertia, force, acceleration, etc. The entire robot swarm is mainly guided by this physical PSO and an independent obstacle avoidance module is active when robots encounter any conflicts during missions. This paper considers an artificial swarm mobile robot system to perform searching tasks and each member of the system may interact with its neighbors or the environment by limited local communication ability. Several groups of simulations are set up for the verification of the strategy and the results show that this method creates the desired behavior well. The simulation experiments also investigate the feature of fault tolerance of this strategy. Finally, a framewo...
31 citations
TL;DR: In this article, the authors studied the vibration suppression of an end-capped cylindrical shell structure with surface bonded macro fiber composite actuators and found that structural vibration was reduced by adopting a proper negative velocity feedback control algorithm in both resonance and non-resonance regimes.
Abstract: We studied the vibration suppression of an end-capped cylindrical shell structure with surface bonded macro fiber composite actuators. The dynamic characteristics of the cylindrical shell structure were first analyzed, and then a negative velocity feedback algorithm was applied to suppress the structural vibration at resonance and nonresonance vibration frequencies. The modal mass and stiffness matrix of the smart cylindrical shell structure were extracted for the controller design. An active controller was designed to suppress vibration of the smart structure, and the control performance was evaluated in resonance and nonresonance regimes. It was found that structural vibration was reduced by adopting a proper negative velocity feedback control algorithm in both resonance and nonresonance regimes.
30 citations
TL;DR: In this paper, the effects of constant rotating speed, crack length and orientation, and length-diameter ratio of the cylindrical shell on the free-vibration and buckling behaviors are investigated.
Abstract: Vibration, linear elastic buckling and dynamic stability behaviors of a cracked cylindrical shell with time-varying rotating speed are analyzed. Finite element method is used to obtain the system mass and stiffness matrix, and Bolotin's method is applied to explore the dynamic stability region. The effects of constant rotating speed, crack length and orientation, and length-diameter ratio of the cylindrical shell on the free-vibration and buckling behaviors are investigated. The stability characteristics of the cracked shell are also researched and the influences of crack length, crack orientation, rotating speed basic value, steady load factor, dynamic load factor and damping ratio are considered. Numerical examples show that crack length and orientation can affect the vibration, buckling and dynamic stability behavior of cylindrical shell significantly.
28 citations
TL;DR: An attempt at summarizing the state of the art in the field of robot hands is described, focused on the Gifu Hand series and its application.
Abstract: In this paper, an attempt at summarizing the state of the art in the field of robot hands is described. The survey is focused on the Gifu Hand series and its application. To create a standard robot hand that is used to study grasping and dexterous manipulation, the Gifu Hand has been developed. Authors study not only a mechanical structure of the robot hand but also control methods for dexterous and autonomous work that human hands perform. The robotics technology is applied to a haptic interface and to a hand rehabilitation systems and medical care.
28 citations
TL;DR: In this paper, the effects of plate thickness, stand-off distance, and material properties on the mid-point deflection, on the deformation profile and on the natural strain distributions are considered.
Abstract: The plastic responses of clamped mild steel, copper, and aluminum circular plates subjected to blast loads are investigated. In this way, extensive experimental results concerning the variations of central deflection and natural strain distributions are presented. The effects of plate thickness, stand-off distance, and material properties on the mid-point deflection, on the deformation profile and on the natural strain distributions are considered. Moreover, the influence of impulse on the mid-point deflection and strain distribution are demonstrated. The applied impulse imparted to the plate was obtained from the recorded motion of the ballistic pendulum. Using the obtained experimental input-output data, closed form mathematical models based on nondimensional analysis and Singular Value Decomposition method have been found. The comparisons of the closed form mathematical models of this work with those in literature illustrate the robustness and the efficacy of this approach.
28 citations
TL;DR: In this article, the singularity analysis of a symmetrical four degrees of freedom (DOFs) parallel manipulator, known as 4UPS + 1PS manipulator is studied.
Abstract: This paper addresses kinematics and singularity analysis of a novel symmetrical four degrees of freedom (DOFs) parallel manipulator, known as 4UPS +1PS manipulator. The manipulator consists of two rigid bodies, one movable (platform) and the other fixed (base), connected to each other by five serial chains (legs), four UPS-type active legs, and one PS-type passive leg where P, U, and S stand for prismatic, universal, and spherical joints, respectively. First, the inverse and direct position kinematics of the manipulator are investigated. The direct position kinematics leads to an even twelfth-degree polynomial in a single variable indicating that the manipulator has two sets of at most six assembly configurations which are symmetric with respect to each other. Through a numerical example it is shown that the polynomial is minimal. Then, the inverse and direct velocity kinematics problems are solved and singularity of the manipulator is analyzed using Jacobian matrices. Also the number and type of addition...
25 citations
TL;DR: In this paper, the nonlinear vibration of a cantilever beam with tip mass subjected to periodically varying axial load and magnetic field has been studied and the temporal equation of motion of the system containing linear and nonlinear parametric excitation terms along with nonlinear damping, geometric and inertial types of nonlinear terms has been derived and solved using method of multiple scales.
Abstract: In this paper, nonlinear vibration of a cantilever beam with tip mass subjected to periodically varying axial load and magnetic field has been studied. The temporal equation of motion of the system containing linear and nonlinear parametric excitation terms along with nonlinear damping, geometric and inertial types of nonlinear terms has been derived and solved using method of multiple scales. The stability and bifurcation analysis for three different resonance conditions were investigated. The numerical results demonstrate that while in simple resonance case with increase in magnetic field strength, the system becomes unstable, in principal parametric or simultaneous resonance cases, the vibration can be reduced significantly by increasing the magnetic field strength. The present work will be very useful for feed forward vibration control of magnetoelastic beams which are used nowadays in many industrial applications.
Abstract: A reliability-based robust design method for structural system with multiple failure modes is proposed. For arbitrarily distributed random variables, the perturbation method and the Edgeworth series expansion are employed to approximate the cumulative distribution function of each failure mode. On the relevancy of failure modes, the probability network evaluation technique is used to assess the reliability of the system. Reliability sensitivities of random variables are derived with the gradient method. A reliability-based optimization model is built through minimum reliability sensitivity of design variables. Numerical examples illustrate the method proposed facilitates the robust design of structural system.
TL;DR: The drilling orthopedic robot (DORO) is presented as a device for automatic bone drilling execution as well as its technical features and functional applications and the experimental results are shown for identification of the parameters of the drilling process, including the bone structure in part.
Abstract: In orthopedic surgery the manipulation “bone drilling” is used very often and it is performed by hand drilling, which causes a lot of problems—getting the big outlets, breaking the tendons or blood vessels, protecting the rear bone wall (which brings one more cutting of the tissue), overheating, and so on. Automatic bone drilling could successfully solve these problems. The drilling orthopedic robot (DORO) is presented as a device for automatic bone drilling execution as well as its technical features and functional applications. The experimental results are shown for identification of the parameters of the drilling process, including the bone structure in part.
TL;DR: In this paper, free vibrations of nonuniform rectangular plates varying in one or two directions are investigated and the effects of the spring foundation together with the orthotropy aspect ratio, truncation factor, and thickness variation on the natural frequencies of the plate are investigated.
Abstract: In this paper, free vibrations of nonuniform rectangular plates varying in one or two directions are investigated. The plate is orthotropic and resting upon a Winkler-type spring foundation. A set of admissible functions which are the static solutions of the tapered beam under arbitrary static load is adopted. By adopting Galerkin's method, the fourth-order differential equation governing the motion of such plates can be solved. The effects of the spring foundation together with the orthotropy aspect ratio, truncation factor, and thickness variation on the natural frequencies of the plate are investigated and discussed. Some results from the present study are compared with those from other literatures.
TL;DR: It is possible to construct a universal procedure, which is capable of generating the necessary structural matrices of a finite element by its extended code dncm, called the extended digital nomenclature code in the current paper.
Abstract: In recent research (Dmitrochenko and Mikkola, 2011), a digital nomenclature code in the form dncm was proposed for a systematic classification of topology of finite elements (given by the dimension d and the number of nodes n ) and their kinematics (described by the number of coordinates per node c and a so-called vectorization multiplier m ). The digital code allows the kinematics of simple finite elements to be enumerated by a few integers; allowing the elements to be reconstructed without the need of their graphical representations. More complicated elements possess a set of nodal coordinates X that formally correspond to some code dncm ; however, their kinematics require that an auxiliary element ( d η ς μ) to be created using different topology η and kinematics ς, μ with a different set of nodal coordinates . Then, a transformation T toward coordinates X leads to an element systematically denoted by code , which is proposed in the current paper and called the extended digital nomenclature code. Examp...
TL;DR: In this paper, the authors present the implementation of a sensorless torque control algorithm using a friction model developed for the Harmonic Drive (HD) reducers based on experiments, which can be obtained based on catalog data, without the need of identification.
Abstract: The paper presents the implementation of a sensorless torque control algorithm using a friction model developed for the Harmonic Drive (HD) reducers based on experiments. The friction model is developed to account for the temperature variation inside the gear, speed, type of bearing, amount and type of lubricant, etc. The objective is to develop the friction model, which can be obtained based on catalog data, without the need of identification. The model validity and the successful implementation of the sensorless torque control method have been confirmed through simulations and real-time experiments on a 5 d.o.f. chopsticks robot.
TL;DR: In this article, the exact buckling solutions of annular plates with an elastically restrained guided edge against translation were analyzed and the critical buckling load parameters for axisymmetric and asymmetric buckling modes were presented.
Abstract: This study deals with the exact buckling solutions of annular plates with an elastically restrained guided edge against translation. The classical plate theory is used to derive the governing differential equation for annular plate with elastically restrained guided edge against translation. The buckling mode may not be axisymmetric as previously assumed. In certain cases, an asymmetric mode would yield a lower buckling load. This is due to switching of mode. This work presents the critical buckling load parameters for axisymmetric and asymmetric buckling modes. Extensive data is tabulated so that pertinent conclusions can be arrived at on the influence of translational restraints, Poisson's ratio and other boundary conditions on the buckling of uniform isotropic annular plates. The numerical results obtained, are in good agreement with the previously published data. In this paper the characteristic equations are exact, therefore the results can be calculated to any accuracy. Comparison of studies demonst...
TL;DR: In this paper, the analytical solution to eight individual trusses is investigated and the validity of the results obtained by the analytical method is verified by the numerical arc-length technique.
Abstract: This paper investigates the analytical solution to eight individual trusses. They are two- and three-dimensional structures. In addition, explicit expressions for the tangent stiffness matrix, critical loads, bifurcation points and limit points as well as equilibrium paths are also assessed. Necessary discussions are provided for different values of effective parameters. As a final objective, the validity of the results obtained by the analytical method is verified by the numerical arc-length technique.
TL;DR: In this article, the effect of the non-conservativeness parameter on the critical buckling and flutter loads of a column for the inelastic stability analysis from the characteristic curves was investigated.
Abstract: This study performs the inelastic static and dynamic stability analyses of a column subjected to a nonconservative force using the finite element method. Based on the tangent modulus theory, the nonlinear compressive stress-strain and tangent modulus-stress relationships of an inelastic column are derived from the column strength curves given in two design codes. The extended Hamilton principle is employed to obtain the mass, elastic stiffness, and geometric stiffness matrices. Evaluation procedures for the critical values of buckling and flutter of the nonconservative systems are briefly introduced. In numerical examples, the influence of various parameters on the inelastic static and dynamic stability of the nonconservative systems is addressed as follows: (1) the effect of the nonconservativeness parameter on the critical buckling and flutter loads of the column for the inelastic stability analysis from the characteristic curves, (2) the variation of the effective length factor (K-factor) for inelastic columns with respect to the nonconservativeness parameter.
TL;DR: In this paper, a hybrid experimental-theoretical method is proposed to investigate the influence of unavoidable scatter in elastic moduli on the natural frequency and axial buckling load of composite plate using ellipsoidal and interval analyses.
Abstract: A hybrid experimental-theoretical method is proposed to investigate the influence of unavoidable scatter in elastic moduli on the natural frequency and axial buckling load of composite plate using ellipsoidal and interval analyses. The elastic moduli for material T300-QY8911 are quantified by use of the smallest ellipsoid or smallest hyper-rectangle based on a set of real experimental data. Then the bounds of the natural frequency of axial buckling load of composite plate in virtue of the obtained ellipsoid and hyper-rectangle are evaluated. Numerical examples are provided to illustrate the feasibility and validity of the proposed method.
TL;DR: In this paper, a test bench was designed and assembled to carry out impact tests on samples and components, which allowed simple and rapid adjustment of the test parameters such as the shot size and air pressure, with good repeatability of the results.
Abstract: A test bench was designed and assembled to carry out impact tests on samples and components. The system allows simple and rapid adjustment of the test parameters, such as the shot size and air pressure, with good repeatability of the results. Tests on steel and light alloys were carried out under both as-produced condition and on thin hard-coated samples. Significant reductions in dimple dimensions were seen after coating. FE models simulating the experiments overestimated the dimple depths, although the parameter trend was satisfactorily captured. The residual stresses from coating and shot peening determined numerically are believed to have been proven effective against fatigue.
TL;DR: In this article, a laminated cantilever composite beam is studied in frequency domain by using some popular model order reduction techniques, including component mode synthesis (CMS) and quasi-static model synthesis (QSM1, QSM2).
Abstract: In this study, a laminated cantilever composite beam is studied in frequency domain by using some popular model order reduction techniques. In the analyses, component mode synthesis (CMS) and quasi-static mode synthesis (QSM1, QSM2) methods are applied to semi-discrete finite element equations to obtain reduced order models for structural analyses. The performance of the model order reduction methods is compared. In addition, fiber orientation, stacking sequence, ply thickness, and its location effects on the number of modes of the methods and on the natural frequencies are investigated. Results reveal that the performance of the QSM2 method is found to be better than the others. It is observed that the fiber orientation, stacking sequence, ply thickness, and its location parameters affect the natural frequency values and the number of modes of the methods.
TL;DR: In this paper, a quasi-static proportional external load is considered and it is assumed that, during the response of the structure, local reverse unloading is ruled out and a holonomic analysis can be conducted.
Abstract: The aim of this paper is to present and investigate softening and hardening constitutive models derived from the general isotropic work softening and hardening hypothesis and to show their application to the step-by-step analysis of linearly elastic-perfectly plastic softening or hardening skeletal structures (trusses, beams, frames). A quasi-static proportional external load is considered and it is assumed that, during the response of the structure, local reverse unloading is ruled out and a holonomic analysis can be conducted. The analysis makes possible to study the response of the structure during the loading procedure and to determine those loading multipliers at which excessive deformations and displacements and the loss of equilibrium or stability occur.
TL;DR: In this paper, the authors deal with numerical and experimental investigations in the field of a rail vehicle dynamics and the sensitivity analysis of the influence of relevant wagon parameters on the coincidence of experimental measurements' and numerical simulations' results was examined.
Abstract: This paper deals with numerical and experimental investigations in the field of a rail vehicle dynamics. The sensitivity analysis of the influence of relevant wagon parameters on the coincidence of experimental measurements' and numerical simulations' results was examined. The aim of laboratory tests and computer simulations is the investigation of dynamic properties of leaf springs of two types mounted on a freight wagon. The goal of the computer simulations and experimental tests is the verification of the developed approach to the wagon multibody modeling. In future, verified wagon models can be used for studying the dynamics of complex vehicles in different driving situations or for various laboratory excitations.
TL;DR: In this paper, a steel ring with many small teeth was used to join an aluminum tube to an aluminum yoke to increase reliability and reduce manufacturing cost of a hybrid propeller shaft.
Abstract: Hybrid or aluminum tube structure requires reliable joining of the shaft to other components such as steel yoke and universal joint, which is often the most difficult task. Therefore, a reliable joining method between the aluminum tube and the steel yoke of a hybrid composite propeller shaft for automobile is required. In this work a press fitting method for joining of an aluminum tube to an aluminum yoke is devised by a steel ring with many small teeth to increase reliability as well as to reduce manufacturing cost of the hybrid propeller shaft rather than using other joining methods such as adhesively bonded or welded joints. The optimal shape and number of teeth of the steel ring were obtained experimentally for the maximum static torque capabilities and fatigue characteristics of the press fit joint, and was compared to the finite element analysis results. Finally, a design guideline for the press fit joint using a steel ring with many small teeth for joining the aluminum shaft to the steel ring was suggested. With the developed press fit joint, the static average shear strength of 70 MPa and fatigue strength of 21 MPa between the aluminum tube and the steel ring were realized, which were almost three times higher than that of the adhesively bonded joint.
TL;DR: In this article, the authors address the elastodynamics behavior of the McGill Schonflies motion generator (SMG), a four-degree-of-freedom parallel robot capable of producing motions proper for what is known as SCARA (selective compliance assembly robot arm) systems.
Abstract: The aim of this paper is to address the elastodynamics behavior of the McGill Schonflies motion generator (SMG). A SMG is a four-degree-of-freedom parallel robot capable of producing motions proper for what is known as SCARA (selective-compliance assembly robot arm) systems. Elastodynamics refers to the modal analysis of a mechanical system composed of a combination of rigid and elastic bodies. Modal analysis, in turn, pertains to the dynamic response of the system at hand when subjected to “small” disturbances that take the system away from a nominal posture under “small amplitude” displacements. The elastodynamics model involves two main ingredients, the n × n mass and stiffness matrices. The work reported here focuses on the formulation of the 20 × 20 mass matrix of the underlying mechanical system.
TL;DR: In this paper, the authors presented a method for optimally actuating a novel omnidirectional wheeled mobile platform with three driven ball wheels, which is designed for use in unstructured and congested environments such as those of highway maintenance and construction work sites.
Abstract: This paper presents a method for optimally actuating a novel omnidirectional wheeled mobile platform with three driven ball wheels. This platform, which will be integrated with a manipulator, is designed for use in unstructured and congested environments such as those of highway maintenance and construction work sites. The designed ball wheel mobile platform can move in all directions on the plane, instantaneously and isotropically. For accurate motion control with parametric uncertainty in the dynamic model, an adaptive controller is applied for trajectory tracking control of the three-ball wheel platform. Each ball wheel has two active drive mechanisms which makes the platform redundantly actuated for in-plane motion. As such, a pseudo-inverse method is used for redundancy resolution and optimal torque distribution. Simulation results demonstrate the effectiveness of the approach.
TL;DR: In this article, the forces produced by the muscles of the human leg during flexion, using a static optimization algorithm, accounting for the dynamics of muscle contraction, were compared with different cost functions.
Abstract: Several methods have been proposed to solve the “redundancy problem in biomechanics,” optimization techniques that are being most widely used. In posing the optimization problem, a variety of cost functions can be found in the literature, designed to meet various criteria, whether to minimize muscle fatigue, active or passive instant muscle strength, the level of muscle activation, or metabolic cost. The aim of this paper is to compare muscles forces generated by different cost functions. We have studied the forces produced by the muscles of the human leg during flexion, using a static optimization algorithm, accounting for the dynamics of muscle contraction.