scholarly journals Response of a Tensegrity Simplex in Experimental Tests of a Modal Hammer at Different Self-Stress Levels

2020 ◽  
Vol 10 (23) ◽  
pp. 8733
Author(s):  
Leszek Małyszko ◽  
Andrzej Rutkiewicz
Keyword(s):  
Stress Level ◽  
Health Monitoring ◽  
Natural Frequencies ◽  
Dynamic Properties ◽  
Experimental Tests ◽  
Rotational Frequency ◽  
The Self ◽  
The Finite Element Method ◽  
Recorded Data ◽  
The Relationship

The natural frequencies and eigenmodes of the tensegrity simplex are determined experimentally in impact hammer tests. To study an effect of prestressing, the tests are carried out on a physical model 1.2 m high and 0.5 m diameter with build-in transducers for measuring actual values of forces in cables at 13 prestress levels. The recorded data for each pre-stress level from three three-axial accelerometers are combined to extract the first five natural frequencies and modes by means of the method of experimental modal analysis. It was experimentally confirmed that the first rotational frequency depends on the pre-stress level and its sensitivity to the self-stress state is high enough to be successfully used in vibrational health monitoring. A proprietary formula was proposed for the relationship between frequency and the pre-stress level to control the dynamic properties of the simplex. An excellent comparison between the experimental results of the frequency and the formula was obtained. A comparison of numerical results of the finite element method with truss element and experiment is also shown.

scholarly journals Influence of the flexibility of beams and slabs in static response and dynamic properties

2016 ◽  
Vol 9 (6) ◽  
pp. 842-855 ◽  
Author(s):  
J. R. BUENO ◽  
◽  
D. D. LORIGGIO ◽  
Keyword(s):  
Finite Element Method ◽  
Natural Frequencies ◽  
Dynamic Properties ◽  
Vibration Modes ◽  
Linear Regime ◽  
Static Response ◽  
The Finite Element Method ◽  
Standard Code ◽  
The Relationship ◽  
Brazilian Standard

Abstract This article examines numerically the flexibility influence of support beams in static response and dynamic properties of a symmetric plate formed by massive slabs of reinforced concrete in elastic linear regime, using the Finite Element Method. In the static response the variation of bending mo-ments and displacements are evaluated, which depend on the relationship between the flexibility of the slab and the beam. The evaluation of dynamic properties is held in undamped free vibration, through which the vibration modes and the values of the natural frequencies is obtained, which are compared with the limits of the Brazilian standard code for design of concrete structures. Results show that the response may show great variation due to the change in the relationship between bending stiffness of the slabs and the beams.

scholarly journals Overcoming Effects from Environmental Temperature on the Natural Frequencies of Cable-strut Structures

2020 ◽  
pp. 22-30
Author(s):  
Nasseradeen Ashwear ◽  
Haithem Elderrat ◽  
Mahmud A. Eljaarani
Keyword(s):  
Genetic Algorithm ◽  
Health Monitoring ◽  
Optimization Problem ◽  
Environmental Temperature ◽  
Natural Frequencies ◽  
Dynamic Properties ◽  
Environmental Variable ◽  
Mode Shapes ◽  
Stress Vector ◽  
Temperature Changes

The changes in dynamic properties such as natural frequencies and mode shapes are used in vibration health monitoring as tools for assessing the structures health status. They are, however, also affected by environmental conditions like wind, humidity and temperature changes. Of particular importance is the change of the environmental temperature, and it is the most commonly considered environmental variable that influences the vibration health monitoring algorithms. This paper discusses how cable-strut structures can be designed such that their first natural frequency is less sensitive to the temperature changes. The optimization problem is solved by using a genetic algorithm. The level of pre-stress can be regulated to achieve the solution, particularly when a symmetric self-stress vector is chosen.

A Dynamic Characteristic Analysis of Continuous Welded Rail Track under Different Longitudinal Stress

2011 ◽  
Vol 105-107 ◽  
pp. 1134-1137
Author(s):  
Yan Yun Luo ◽  
Hu Zhang ◽  
Yan Liu
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Natural Frequencies ◽  
Track Structure ◽  
Longitudinal Stress ◽  
The Finite Element Method ◽  
Rail Track ◽  
Continuous Welded Rail ◽  
The Relationship ◽  
Element Method

The paper presents a dynamic computational model and field test for analyzing the relationship between the rail natural frequencies and the longitudinal temperature stress by means of the finite element method. The essay use the infinite Timoshenko beam as the plane model to simulate continuous welded rail track structure and the rail model by means of the finite element method in order to its unit as a division of space elastomer. The test uses vertical incentive and horizontal incentive to encourage continuous welded rail track structure to get the rail natural frequencies. The measured data and the result of finite element analysis are compared, finds the results are consistent. The paper not only investigates the relationship between the rail’s dynamic characteristics and the longitudinal stress, but also provides a feasible method for test longitudinal stress of continuous welded rail track.

scholarly journals Dynamic instability of vibrations of thin-wall composite curvorine viscoelastic tubes under the influence of pulse pressure

2020 ◽  
Vol 164 ◽  
pp. 14013 ◽  
Author(s):  
Mirziyod Mirsaidov ◽  
Ismoil Safarov ◽  
Mukhsin Teshaev
Keyword(s):  
Natural Frequencies ◽  
Dynamic Instability ◽  
Boundary Effect ◽  
Stress And Strain ◽  
Thin Wall ◽  
Pipe Material ◽  
The Finite Element Method ◽  
Transverse Vibrations ◽  
Curved Rod ◽  
The Relationship

In this paper the results of a study of the dynamic characteristics of thin-walled composite curved viscoelastic pipes under the influence of internal pulsating pressures is presented. The relationship between stress and strain is described by the Aviary equations. Based on the principle of calculus of variations, the equations of the dynamics of curvilinear shells are obtained. The obtained integral and integro-differential equations are solved using the finite element method, the Mueller and Gauss methods. The results of calculations of the natural frequencies of the shell and the curved rod are compared. As a result of the calculation, it was found that, shell vibrations occur at higher frequencies than rod vibrations (manifestation of a boundary effect). With this difference, the natural frequency, which has no analogue in the rod model decreases. This is due to the fact that, in this case the transverse vibrations of the section itself become significant, the rod. Some mechanical effects were discovered when taking into account the rheological properties of the pipe material.

scholarly journals Experimental and Numerical Dynamic Properties of Two Timber Footbridges Including Seasonal Effects

2021 ◽  
Author(s):  
John Hallak Neilson ◽  
Aida Ibisevic ◽  
Hasanhüseyin Ugur ◽  
Jean-Marc Battini ◽  
Roberto Crocetti ◽  
...  
Keyword(s):  
Natural Frequencies ◽  
Dynamic Properties ◽  
Experimental Tests ◽  
Transverse Mode ◽  
Seasonal Effects ◽  
Finite Element Models ◽  
Good Correspondence ◽  
Damping Coefficients ◽  
Transverse Modes ◽  
Dynamic Analyses

AbstractThis paper deals with experimental and numerical dynamic analyses of two timber footbridges. Both bridges have a span of 35 m and consist of a timber deck supported by two timber arches. The main purpose is to investigate if the dynamic properties of the bridges are season dependent. To this end, experimental tests are performed during a cold day in winter and a warm day in spring in Sweden. The first bending and transverse mode frequencies increase 22% and 44%, respectively, due to temperature effects in the case of Vega Bridge. In the case of Hägernäs bridge, the corresponding values are 5% and 26%. For both bridges, the measured damping coefficients are similar in winter and spring. However, the damping coefficients for the first bending and transverse modes are different for both footbridges: about 1% for the Hägernäs bridge and 3% for the Vega bridge. Finite-element models are also implemented. Both numerical and experimental results show good correspondence. From the analyses performed, it is concluded that the connections between the different components of the bridges have a significant influence on the dynamic properties. In addition, the variation of the stiffness for the asphalt layer can explain the differences found in the natural frequencies between spring and winter. However, due to the uncertainties in the modelling of the asphalt layer, this conclusion must be taken with caution.

scholarly journals Research on the dynamics of railway car construction

2019 ◽  
Vol 20 (1-2) ◽  
pp. 142-146
Author(s):  
Jarosław Bednarz
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Structural Model ◽  
Natural Frequencies ◽  
Dynamic Properties ◽  
Structural Models ◽  
Transformation Model ◽  
Mode Shapes ◽  
The Finite Element Method ◽  
Modal Model

Nowadays, one of the basic criteria of the design of mechanical structures are dynamic properties of the object. They have a significant effect on the vibration, emitted noise, fatigue strength, controllability and stability of the structure. The structural models are most often use to describe the dynamics of the structures. These models are built in accordance with the principles of the finite element method . Structural model can be used to determine the modal model which is a collection of natural frequencies and corresponding mode shapes by an appropriate coordinate transformation model. The construction pro-cess is called the modal analysis . The article presented a method of conducting the experimental modal studies of railway car. The aim of the study was to identify the dynamic properties including the frequency and mode shapes of the object..

scholarly journals Latitude Determination and Error Analysis for Stationary SINS in Unknow-Position Condition

Sensors ◽  
2020 ◽  
Vol 20 (9) ◽  
pp. 2558
Author(s):  
Suier Wang ◽  
Gongliu Yang ◽  
Wei Chen ◽  
Lifen Wang
Keyword(s):  
Navigation System ◽  
Estimation Method ◽  
Experimental Tests ◽  
The Self ◽  
Measurement Unit ◽  
Test Results ◽  
Bias Estimation ◽  
Short Time ◽  
The Relationship

The initial geographic latitude information is the key to the self-alignment of the strapdown inertial navigation system (SINS), but how to determine the latitude when the latitude cannot be obtained directly or in a short time? The latitude determination (LD) methods are introduced, including magnitude method, geometric method, and analytical methods 1 and 2, to solve this situation only by the output of the SINS itself. Simulation and experimental test results validate the efficiency of these LD methods. In order to improve the accuracy of the LD, the error of the LD method is derived through comparative analysis. Based on the relationship between LD error and inertial measurement unit (IMU) bias. Partial bias estimation method is introduced and executed during latitude determination. After compensating the estimated IMU bias, the accuracy of the LD will be further improved. Latitude errors are also affected by the latitude where SINS is located. Comprehensive simulation and experimental tests verify the effectiveness of the method. The IMU determined latitude can not only be used to achieve the self-alignment of the SINS, but also to correct the navigation latitude of the long-term SINS, thereby improving the autonomy and positioning accuracy of the navigation system.

From Container to Claustrum: Projective Identification in Couples

2014 ◽  
Vol 4 (2) ◽  
Author(s):  
Tamara Feldman
Keyword(s):  
Psychological Health ◽  
Projective Identification ◽  
The Self ◽  
The Other ◽  
Intimate Partners ◽  
And Control ◽  
The Relationship ◽  
As If

This paper is a contribution to the growing literature on the role of projective identification in understanding couples' dynamics. Projective identification as a defence is well suited to couples, as intimate partners provide an ideal location to deposit unwanted parts of the self. This paper illustrates how projective identification functions differently depending on the psychological health of the couple. It elucidates how healthier couples use projective identification more as a form of communication, whereas disturbed couples are inclined to employ it to invade and control the other, as captured by Meltzer's concept of "intrusive identification". These different uses of projective identification affect couples' capacities to provide what Bion called "containment". In disturbed couples, partners serve as what Meltzer termed "claustrums" whereby projections are not contained, but imprisoned or entombed in the other. Applying the concept of claustrum helps illuminate common feelings these couples express, such as feeling suffocated, stifled, trapped, held hostage, or feeling as if the relationship is killing them. Finally, this paper presents treatment challenges in working with more disturbed couples.

The Relationship between Seeker and Spiritual Guide as portrayed in contemporary Western Sufi Autobiographies

2011 ◽  
Vol 5 (2) ◽  
pp. 297-332
Author(s):  
Kate Zebiri
Keyword(s):  
Life Writing ◽  
New Age ◽  
The Self ◽  
Individual Autonomy ◽  
Religious Authority ◽  
The Face ◽  
The Relationship ◽  
Insight Into ◽  
Continuity And Discontinuity

This article aims to explore the Shaykh-mur?d (disciple) or teacher-pupil relationship as portrayed in Western Sufi life writing in recent decades, observing elements of continuity and discontinuity with classical Sufism. Additionally, it traces the influence on the texts of certain developments in religiosity in contemporary Western societies, especially New Age understandings of religious authority. Studying these works will provide an insight into the diversity of expressions of contemporary Sufism, while shedding light on a phenomenon which seems to fly in the face of contemporary social and religious trends which deemphasize external authority and promote the authority of the self or individual autonomy.

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