Evaluation Of Dynamic Characteristics Research Articles

Evaluation of Dynamic Tensile Characteristics of Polypropylene Composites with Temperature Variation

This article suggests two useful methods to obtain true stress—strain curves with the variation of the strain rate ranging from 0.001 to 200/s using a finite element technique and optimization for two typical polymers: a polypropylene; and a polypropylene composite. The polypropylene is adopted as a core material of a vehicle’s instrument panel and the polypropylene composite sustains the passenger-side air bag module (PAB module) as a structural member. Their dynamic tensile characteristics are important to predict deformation modes of the PAB module which undergoes high speed deformation during air bag expansion. Since the polymers are temperature sensitive materials, the dynamic tensile tests were performed at the three levels of temperature: the low temperature (—30°C); the room temperature (21°C); the high temperature (85°C). During tensile tests of two polypropylene composites, the gage region in the specimen of the polypropylene composite elongates uniformly while that of the polypropylene does not elongate uniformly. In the case of the polypropylene, experimental stress—strain curves were modified by enforcing the load response calculated by finite element analysis coincident with that of the experiment. In the case of the polypropylene composite, experimental stress—strain curves were scaled by applying change rate of the gage length. Stress—strain curves of both cases provide excellent performance in their numerical response with the finite element analysis. The material properties obtained are indispensible to estimate the high speed deformation mode during air bag expansion at both normal and harsh operating conditions.

1118 二成分系サーモサイフォンの伝熱流動特性と定量的性能評価(GS-6 伝熱流動(1))

1118 二成分系サーモサイフォンの伝熱流動特性と定量的性能評価(GS-6 伝熱流動(1))

Dynamic Formulation and Performance Evaluation of the 6-d.o.f. Parallel Structure Seismic Simulator

This paper presents the dynamic formulation and performance evaluation of the 6-d.o.f. parallel structure seismic simulator. By means of the principle of virtual work and the concept of link Jacobian matrices, the inverse dynamic model of the seismic simulator is set up. Then, a series of new dynamic performance indices with obvious physical meanings have been proposed. The dynamic performance index combining the acceleration, velocity and gravity terms of the dynamic equations has been achieved by decoupling the inverse dynamics in an exhaustive way. By using the index, it is possible for us to evaluate the performance in different directions. The index has been applied to the dynamic characteristic evaluation of the 6-d.o.f. parallel structure seismic simulator in the numerical simulation. Conclusions and results are provided at the end of the paper.

Dynamic formulation and performance evaluation of the redundant parallel manipulator

The dynamic formulation and performance evaluation of the redundant parallel manipulator are presented in this paper. By means of the principle of virtual work and the concept of link Jacobian matrices, the inverse dynamic model of the redundant parallel manipulator is set up. It consists of six linear consistent equations with eight unknown quantities. Then, the optimum solution of the actuating torques is achieved by employing the Moore-Penrose inverse matrix. It is with minimum norm and least quadratic sum among the possible actuating torque vectors. A series of new dynamic performance indices with obvious physical meanings have been proposed in the paper. By decoupling the inverse dynamics in the exhaustive way, a novel dynamic performance index combining the acceleration, velocity and gravity terms of the dynamic equations has been presented to evaluate the dynamic characteristic of the redundant parallel manipulator. With the index, it is possible to control the performance in the different direction. The index has been applied to the dynamic characteristic evaluation of the redundant parallel manipulator in the simulation. It is general and can be used for the dynamic performance evaluation of other types of parallel manipulators.

Experimental Identification of the Nonlinear Parameters of an Industrial Translational Guide for Machine Performance Evaluation

Prediction of machine dynamics at the design stage is a challenge due to lack of adequate methods for identifying and handling the nonlinearities in the machine joints, which appear as the nonlinear restoring force function of relative displacement and relative velocity across the joint. This paper discusses identification of such a nonlinear restoring force function for an industrial translational guide for use with the Nonlinear Receptance Coupling Approach (NLRCA) to evaluate machine dynamic characteristics. Translational guides are among the most commonly used joints in machine tools. Both parametric and nonparametric techniques have been employed to identify the nonlinearities. A novel parametric model based on Hertzian contact mechanics has been derived for the translational guide. A nonparametric method based on two-dimensional Chebyshev polynomials is also used. The models derived from the two techniques, i.e., parametric and nonparametric, are fitted to the experimental data derived from static and dynamic tests to get the restoring force as a function of relative displacement and relative velocity across the joint. The nonlinear representation obtained from both techniques is later converted into the describing function representation which is needed for evaluation of machine dynamic characteristics using the NLRCA. The describing function representations obtained from the two approaches are compared. The design of experiments for evaluating the nonlinearities in such industrial machine tool joints is a challenge, requiring careful alignment and calibration, because they are typically very stiff. This constrains the dynamic experiments to be carried out at high frequencies (e.g. 2000—7000 Hz) where the experimental readings are very sensitive to errors in geometry and calibration.

Understanding and Evaluation of Driver and Vehicle Dynamic Characteristics based upon Jerk Information

Understanding and Evaluation of Driver and Vehicle Dynamic Characteristics based upon Jerk Information

In Vivo Evaluation of Dynamic Characteristics of the Normal, Fused, and Disc Replacement Cervical Spines

In vivo human and biomechanical study. To quantify the in vivo kinematic and kinetic variations in the normal, fused, and disc replacement cervical spines. Clinical and cadaveric studies have reported the motions and forces after an anterior cervical decompression and fusion (ACDF) or implantation of a cervical artificial disc replacement (CADR). However, there is no current study that describes the in vivo dynamic data of these 2 groups and compares them with that of a normal group. Ten normal subjects, 10 patients treated with an ACDF (C5-C6), and 10 patients having CADR (C5-C6) performed full flexion to extension motions under fluoroscopic surveillance. Kinematic data were obtained from the fluoroscopic images. Kinetic data were derived based on an inverse dynamic model of the entire cervical spine. Even though the range of motion was larger for the normal group than for the ACDF group, the intersegmental rotations at the adjacent C6-C7 and C4-C5 levels in the ACDF group were 13.4 degrees and 8.8 degrees compared with 3.7 degrees and 4.8 degrees in the normal group, respectively, during the neck motion from 20 degrees flexion to 15 degrees extension. The difference at the C3-C4 level was 1 degree on average. Both the transverse contact forces and the soft tissue forces in the ACDF group were significantly larger than those in the normal group. The vertical forces in the ACDF group were smaller than those in the normal group, but there were no statistical differences. The CADR group exhibited kinematic and kinetic results similar to the normal group. In terms of restoring the normal dynamic motion of the cervical spine, CADR may be an alternative to the ACDF.

ひきつれ効果に着目したヒト肌の動特性評価

ひきつれ効果に着目したヒト肌の動特性評価

地盤・建物系の高密度強震観測の展開と建物動的挙動の検討

地盤・建物系の高密度強震観測の展開と建物動的挙動の検討

Dynamic characteristics evaluation of Masjed Soleiman Dam using in situ dynamic tests

The responses to forced vibrations, ambient vibrations, and large explosives were measured for Masjed Soleiman Dam, the highest embankment dam in Iran. Based on the results of these tests, the first 23 modal frequencies of the dam were measured and the related mode shapes for the first 16 modes were identified. A modal analysis of the dam body was also performed. The effects of reservoir water level variation, the rigidity and flexibility of the foundation and abutments and their depths and inertial properties, and the effect of material properties on the dynamic characteristics of the dam body were investigated, and the first eight modes of the dam body were identified. A comparison of the results of the numerical analysis with those from the tests indicates the best fit in lower modes occurs when the complete mass foundation is considered, whereas in higher modes the massless foundation model is a better fit.Key words: embankment dam, forced vibration test, ambient vibration test, explosion, modal properties.

Measurement of Finishing Errors for Evaluation of Dynamic Characteristics of NC Machine Tools

Efficient development of method for performance evaluation of machine tools has been regarded as the most important issue to enhance accuracy and quality for users and manufacturers. Recently, a method of accuracy evaluation for machine tools has been studied as interests on precision machine tools have rapidly increased. From this point of view, the circular interpolation test of machine tools is recognized as the most useful method to identify the dynamic accuracy of NC machine tools by ISO, ANSI/ASME and others. In this paper, we studied and developed a formal measurement system with a grid encoder to analyze the final accuracy of NC machine tools. We analyzed the servo system error and the geometric error of NC machine tools through measuring the dynamic error signals by using this system. We verified the experimental result and enhanced the reliability by means of comparing the characteristics of the developed system with the kinematical ball-bar system.

Evaluation of dynamic response characteristics of seismically isolated bridges in Chile

AbstractA complete renovation of the Pan‐American Highway from La Serena to Puerto Montt, Chile, has been recently completed, including the construction of several long‐span bridges, with different structural systems. Most of them have some sort of seismic protection, such as high‐damping rubber bearings, friction bearings or energy dissipation devices. Ambient vibration tests have been conducted on seven of these bridges to obtain their natural frequencies, modes of vibration, and equivalent damping, under small amplitude vibrations. In two of them local accelerometer networks have been installed for continued monitoring of their seismic behavior and a number of earthquakes have already been recorded. The seismic records show clearly the beneficial effect of the isolation and energy dissipation devices in the longitudinal direction. Analytical models with different degrees of complexity have been developed to reproduce the recorded behavior under ambient vibration and moderate earthquakes. This paper presents some of the data obtained and summarizes the research done by the authors over the last 10 years at the University of Chile on the seismic protection of bridges. Copyright © 2005 John Wiley & Sons, Ltd.

Application of the wavelet transform to health monitoring and evaluation of dynamic characteristics in gear sets

Application of the wavelet transform to health monitoring and evaluation of dynamic characteristics in gear sets

An evaluation of dynamic lip-tooth characteristics during speech and smile in adolescents.

This retrospective study was conducted to measure lip-tooth characteristics of adolescents. Pretreatment video clips of 1242 consecutive patients were screened for Class-I skeletal and dental patterns. After all inclusion criteria were applied, the final sample consisted of 50 patients (27 boys, 23 girls) with a mean age of 12.5 years. The raw digital video stream of each patient was edited to select a single image frame representing the patient saying the syllable "chee" and a second single image representing the patient's posed social smile and saved as part of a 12-frame image sequence. Each animation image was analyzed using a SmileMesh computer application to measure the smile index (the ratio of the intercommissure width divided by the interlabial gap), intercommissure width (mm), interlabial gap (mm), percent incisor below the intercommissure line, and maximum incisor exposure (mm). The data were analyzed using SAS (version 8.1). All recorded differences in linear measures had to be > or = 2 mm. The results suggest that anterior tooth display at speech and smile should be recorded independently but evaluated as part of a dynamic range. Asking patients to say "cheese" and then smile is no longer a valid method to elicit the parameters of anterior tooth display. When planning the vertical positions of incisors during orthodontic treatment, the orthodontist should view the dynamics of anterior tooth display as a continuum delineated by the time points of rest, speech, posed social smile, and a Duchenne smile.

Application of the wavelet transform to health monitoring and evaluation of dynamic characteristics in gear sets

This paper deals with health monitoring and evaluation of dynamic characteristics in gear sets. The wavelet transform (WT) is the method used for the time-frequency analysis. The dynamic characteristics of both steel and sintered gears were measured using a power circulating gear testing machine and were analysed in the time-frequency domain using continuous and discrete WTs. Furthermore, health monitoring of gear sets was carried out and tooth surface failure by pitting was diagnosed using WTs. The vibration acceleration characteristics of the gearbox could be divided into two different behaviours above and below the tooth mesh frequency. A failed tooth could be found by a change in WT intensity of the vibration acceleration, taking the tooth meshing into consideration. Since the discrete WT is able to provide the signal with the component of tooth mesh frequency, it was found to be superior to the continuous WT. In the case of failure at the dedendum surface of a driven gear, the amplitude of the vibration acceleration with the component of tooth mesh frequency became larger as after meshing of the failed tooth. Therefore, not only the vibration of the gear sets but also the condition of tooth meshing would have to be taken into consideration to diagnose failed teeth.

Calculation of Journal Bearing Dynamic Characteristics Including Journal Misalignment and Bearing Structural Deformation©

A detailed journal bearing analysis for accurate evaluation of film dynamic characteristics is presented. The new formulation is based on a local perturbation of the oil film at each computational node that captures the important effects of journal misalignment and bearing structural deformation in rotor dynamics and engine NVH applications. The new algorithm is an extension to the classical approach of evaluating film dynamic characteristics based on journal eccentricity perturbation. The governing equations for the oil film pressure, stiffness, and damping are solved using a finite difference approach and their output is validated with numerical results from the literature.

Ambient Vibration measurements and finite element modelling for the Hong Kong Ting Kau Bridge

The Ting Kau Bridge in Hong Kong is a cable-stayed bridge comprising two main spans and two side spans. The bridge deck is supported by three towers, an end pier and an abutment. Each of the three towers consists of a single reinforced concrete mast which reduces its section in steps, and it is strengthened by transverse cables and struts in the transverse vertical plane. The bridge deck is supported by four inclined planes of cables emanating from anchorages at the tower tops. In view of the threat from typhoons, the dynamic behaviour of long-span cable-supported bridges in the region is always an important consideration in their design. This paper is devoted to the ambient vibration measurements of the bridge for evaluation of dynamic characteristics including the natural frequencies and mode shapes. It also describes the modelling of the bridge. A few finite element models are developed and calibrated to match with the field data and the results of subsequent structural health monitoring of the bridge.

504 がたを含む連続体系の非線形振動特性の評価 : 新たな寸法の衝突板による評価

504 がたを含む連続体系の非線形振動特性の評価 : 新たな寸法の衝突板による評価

A Study on the Dynamic Modeling of a Magnetic Levitation Vehicle

There is growing in interest in the modeling and simulation of the dynamic behavior of advanced vehicles, including maglev-type systems. This paper demonstrates the application of DADS, a program especially suited for the analysis of multibody mechanical systems, to the dynamic modeling and simulation of a maglev system. A brief description is made of the modeling requirements of magnetically levitated systems along with a summary of some of the related capabilities of DADS. As a case study, an analysis of a vehicle based on the UTM01 system is presented. This paper shows that the presented modeling technique is applicable to the dynamic characteristics evaluation and control-law design of maglev-type vehicles.

C107 腹部大動脈用分岐人工血管の力学的評価シミュレータの開発

C107 腹部大動脈用分岐人工血管の力学的評価シミュレータの開発