The Optimization of Thermocouple Galvanometer System Dynamics When Measuring Temperature Transients

1973 ◽  
Vol 6 (9) ◽  
pp. 384-388
Author(s):  
W. H. McKenzie ◽  
A. H. Richards
Keyword(s):  
System Dynamics ◽  
Natural Frequency ◽  
Time Constant ◽  
Exponential Type ◽  
Natural Frequencies ◽  
Low Voltage ◽  
Damping Ratio ◽  
Dynamic Performance ◽  
Ultra Violet ◽  
Dimensional Parameter

When using thermocouples directly connected to ultra-violet galvanometers for recording temperature transients, the low-voltage outputs necessitate the use of galvanometers with low natural frequencies. This puts a limitation on the overall dynamic performance. In a particular application, the user has to select the damping resistor for the galvanometer and the work describes how this is done so that the system is optimised for minimum integrated errors during a transient. The transient considered was of an exponential type which occurs frequently in practice and it is shown that the correct damping ratio and hence damping resistor for the galvanometer depends upon the non-dimensional parameter defined by the product of the natural frequency of the galvanometer and the time constant of the exponential. The results show that the usual value of damping ratio of 0·64 based on minimum sinusoidal distortion has to be modified for best dynamic performance. However, if the non-dimensional parameter is sufficiently large, higher values of damping can be used, which produce a large trace with acceptably small errors.

scholarly journals Dynamic Characteristics of Blade with Viscoelastic Damping Block Based on Complex Eigenvalue Method

2018 ◽  
Vol 2018 ◽  
pp. 1-16
Author(s):  
Jiao Wang ◽  
Yue-hao Zhang ◽  
Tao Yu ◽  
Qing-kai Han
Keyword(s):  
Differential Equations ◽  
Force Field ◽  
Natural Frequency ◽  
Dynamical Equation ◽  
Natural Frequencies ◽  
Damping Ratio ◽  
Constitutive Law ◽  
Viscoelastic Damping ◽  
Complex Eigenvalue ◽  
Eigenvalue Method

A novel method for vibration suppression is proposed, adding a viscoelastic damping block to the root of the blade. The dynamical equation for a rotational viscoelastic damping block-blade (VE-blade) in a centrifugal force field and aerodynamic force field is established to calculate the dynamical natural frequency and responses of the VE-blade. Complex modulus model is applied to represent the constitutive law of viscoelastic material and shear force acting on the VE-blade formulates the effect of viscoelastic damping at the root interfaces. The dynamical equation of the system is established and the Galerkin method is used to discretize the partial differential equations to a 3-DOF system so as to compute the dynamic natural frequencies and responses of the VE-blade. Then the differential equations of motion with 3-DOF are numerically solved by using complex eigenvalue method. A cantilever VE-blade is simplified according to testing the first three natural frequencies of the real blade to obtain geometric parameters of cantilever beam. The effects of various parameters including thickness, storage modulus, loss factor of viscoelastic damping block, and rotating speed on natural frequency and modal damping ratio of VE-blade are discussed in detail.

Modification of Stiffness for Shifting Natural Frequencies of Damped Mechanical Systems

1991 ◽  
Author(s):  
Eric K. L. Yee ◽  
Y. G. Tsuei
Keyword(s):  
System Dynamics ◽  
Mechanical System ◽  
Natural Frequency ◽  
Degrees Of Freedom ◽  
Natural Frequencies ◽  
Original System ◽  
Force Response ◽  
Modal Coupling ◽  
Response Equation ◽  
Final Equation

Abstract A method for shifting the natural frequency of a damped mechanical system to a desired value is discussed. The solution is derived from the force response equation of the original system. The final equation contains only the degrees of freedom connected to the modifying parameter. Iterations are required but the solution converges rapidly. Modal coupling effects and sensitivity for shifting a frequency are also derived. Modification of stiffness is used as an example for shifting the natural frequency. Numerical results indicate that the method is effective for system dynamics modification.

Determining Structural Modes of HSK Tool System Based on FEM and EMA

2010 ◽  
Vol 139-141 ◽  
pp. 1479-1484 ◽  
Author(s):  
Chun Gen Shen ◽  
Gui Cheng Wang ◽  
Shu Lin Wang ◽  
Gang Liu
Keyword(s):  
Modal Analysis ◽  
Natural Frequency ◽  
Damping Ratio ◽  
Dynamic Performance ◽  
Experimental Modal Analysis ◽  
Operating Conditions ◽  
Data Sets ◽  
Linear Elastic ◽  
Computational Data ◽  
Experimental Findings

In this research, we computationally analyzed the structural modes of an HSK63E type tool system and verified the results with experimental modal analysis (EMA). The computation was implemented using the finite element method (FEM) based on a linear-elastic theory, with which we computed the natural frequency and obtained the modal shapes under both free and operating conditions. With the method of experimental modal analysis, we also obtained structural modal parameters including the natural frequency, modal shapes and damping ratio under the same free and operating conditions. The computational data were compared with the experimental findings. The reasonable agreement between the two data sets indicated the validity and provided a theoretical basis for using computational methods for determining the natural characteristics and influencing factors of HSK tool system. With this validated FEM model, further analyses were performed to evaluate the unique dynamic performance of the HSK tool system, and to apply dynamic optimum design to other types of HSK tool system.

scholarly journals Free vibration analysis of isotopic rectangular plate with one edge free of support (CSCF and SCFC plate)

2014 ◽  
Vol 3 (1) ◽  
pp. 30 ◽  
Author(s):  
Stanley I Ebirim ◽  
J C Ezeh ◽  
M Owus Ibearugbulem
Keyword(s):  
Aspect Ratio ◽  
Free Vibration ◽  
Natural Frequency ◽  
Natural Frequencies ◽  
Shape Function ◽  
Ritz Method ◽  
Dimensional Parameter ◽  
Fundamental Natural Frequency ◽  
Aspect Ratios ◽  
Significant Difference

The paper presents a theoretical formulation based on Ibearugbulems shape function and application of Ritz method. In this study, the free vibration of simply supported plate with one free edge was analyzed. The Ibearugbulems shape function derived was substituted into the potential energy functional, which was minimized to obtain the fundamental natural frequency. Aspect ratios from 0.1 to 2.0 with 0.1 increments were considered. The values of fundamental natural frequencies of the first mode were determined for different aspect ratio. For aspect ratio of 1.0, the value of non-dimensional parameter of fundamental natural frequency obtained was 23.86. Comparison was made for values of non-dimensional parameter of fundamental natural frequencies obtained in this study with those of previous research works. It was seen that there is no significant difference between values obtained in this study with those of previous studies. Keywords: fundamental natural frequency; Ibearugbulems shape function; CSCF plate; Ritz method; SCFC plate.

Influence of Bearing Configuration on Spindle Modal Characteristics

2014 ◽  
Author(s):  
Jun Hong ◽  
Guanghui Liu ◽  
Xiaohu Li ◽  
Wenwu Wu ◽  
Shaoke Wan ◽  
...  
Keyword(s):  
Natural Frequency ◽  
Machine Tools ◽  
Test Bench ◽  
Natural Frequencies ◽  
Dynamic Performance ◽  
Radial Deformation ◽  
Spindle System ◽  
Modal Characteristics ◽  
Spindle Bearing ◽  
Simulation And Experiment

Since bearing configuration has significant influence on the spindle modal characteristics which can reflect the dynamic performance of spindle system in machine tools, so it would be of extraordinary importance and necessity to analyze the spindle modal characteristics through simulation and experiment when it comes to designing spindle system. In this paper, the number and span of bearings, the spacer of bearing set and the overhang of spindle are considered as the main designing parameters of the spindle system. Firstly, a coupled spindle-bearing model is established considering the radial deformation of the bearing inner ring caused by interference fits of spindle assembly, as well as the centrifugal and thermal deformations. Based on the model, the modal characteristics of different bearing configurations are analyzed. Secondly, a spindle test bench is designed and constructed. Finally, modal characteristics of the spindle system are tested with different bearing configurations. From the simulation and experimental results, it’s indicated that there is a correlation between the natural frequency and the number of bearings. The using of short spacer inside the bearing set can increase spindle natural frequency slightly. Besides, the first natural frequency of the spindle system rises with the bearing span, whereas the second one tends to decrease. And shortening the overhang of spindle can also increase its natural frequencies, which can be taken into account in spindle design.

scholarly journals Investigation of Gas Nitriding Effect on Damping Ratio of Steel 1.7225 and Cutting Vibration of Indexable End Mill Made from It During the Straight Groove

2021 ◽  
Author(s):  
Abbas Rahi ◽  
Mahdi Hosseinpour ◽  
Behrouz Mahdikhani ◽  
Elham Inanloo
Keyword(s):  
Natural Frequency ◽  
Natural Frequencies ◽  
End Milling ◽  
Damping Ratio ◽  
End Mill ◽  
Gas Nitriding ◽  
Hardening Process ◽  
Tool Performance ◽  
Cutting Vibration ◽  
Low Stiffness

Abstract End-milling is a cutting technology that removes material from machined workpieces by end mill and is widely used to manufacture parts. Moreover, this process is prone to vibration due to low stiffness. Also, nitriding is a surface hardening process with lots of effects on mechanical properties. This study investigated the effect of gas nitriding on a nitrided end mill in comparison with an unnitrided end mill and showed significant improvement in vibration peak and RMS during end milling. To clarify the reason for this improvement this article carried out a modal test to show how nitriding affected the natural frequency and damping ratio of the nitrided and unnitrided samples and showed that tool rigidity remained the same while damping ratio increased so we claimed nitriding improved damping ratio without change of tool rigidity. For verifying this claim we modeled, meshed, and analyzed for obtaining tool natural frequency both for nitrided and unnitrided tool and compared with extracted natural frequencies from each tool FFT diagram during straight grooving. We showed that the natural frequencies were the same with less than 3 percent change so we concluded that nitriding led to better tool performance by increasing the damping ratio without any significant change in the tool stiffness.

scholarly journals Effects of Elliptical Hole on the Correlation of Natural Frequency with Buckling Load of Basalt Laminates Composite Plates

2020 ◽  
Vol 27 (1) ◽  
pp. 216-225
Author(s):  
Buntheng Chhorn ◽  
WooYoung Jung
Keyword(s):  
Free Vibration ◽  
Natural Frequency ◽  
Natural Frequencies ◽  
Basalt Fiber ◽  
Orientation Angle ◽  
Elliptical Hole ◽  
Composite Plates ◽  
Buckling Load ◽  
Mode Shapes ◽  
Geometric Ratio

AbstractRecently, basalt fiber reinforced polymer (BFRP) is acknowledged as an outstanding material for the strengthening of existing concrete structure, especially it was being used in marine vehicles, aerospace, automotive and nuclear engineering. Most of the structures were subjected to severe dynamic loading during their service life that may induce vibration of the structures. However, free vibration studied on the basalt laminates composite plates with elliptical cut-out and correlation of natural frequency with buckling load has been very limited. Therefore, effects of the elliptical hole on the natural frequency of basalt/epoxy composite plates was performed in this study. Effects of stacking sequence (θ), elliptical hole inclination (ϕ), hole geometric ratio (a/b) and position of the elliptical hole were considered. The numerical modeling of free vibration analysis was based on the mechanical properties of BFRP obtained from the experiment. The natural frequencies as well as mode shapes of basalt laminates composite plates were numerically determined using the commercial program software (ABAQUS). Then, the determination of correlation of natural frequencies with buckling load was carried out. Results showed that elliptical hole inclination and fiber orientation angle induced the inverse proportion between natural frequency and buckling load.

scholarly journals A Vibration-Based Structural Health Monitoring System for Transmission Line Towers

Electronics ◽  
2019 ◽  
Vol 8 (5) ◽  
pp. 515 ◽  
Author(s):  
Long Zhao ◽  
Xinbo Huang ◽  
Ye Zhang ◽  
Yi Tian ◽  
Yu Zhao
Keyword(s):  
Structural Health Monitoring ◽  
Transmission Line ◽  
Natural Frequency ◽  
Health Monitoring ◽  
Structural Changes ◽  
Natural Frequencies ◽  
Transmission Tower ◽  
Health Monitoring System ◽  
Wind Speeds ◽  
Before And After

In this paper, we present a vibration-based transmission tower structural health monitoring system consisting of two parts that identifies structural changes in towers. An accelerometer group realizes vibration response acquisition at different positions and reduces the risk of data loss by data compression technology. A solar cell provides the power supply. An analyser receives the data from the acceleration sensor group and calculates the transmission tower natural frequencies, and the change in the structure is determined based on natural frequencies. Then, the data are sent to the monitoring center. Furthermore, analysis of the vibration signal and the calculation method of natural frequencies are proposed. The response and natural frequencies of vibration at different wind speeds are analysed by time-domain signal, power spectral density (PSD), root mean square (RMS) and short-time Fouier transform (STFT). The natural frequency identification of the overall structure by the stochastic subspace identification (SSI) method reveals that the number of natural frequencies that can be calculated at different wind speeds is different, but the 2nd, 3rd and 4th natural frequencies can be excited. Finally, the system was tested on a 110 kV experimental transmission line. After 18 h of experimentation, the natural frequency of the overall structure of the transmission tower was determined before and after the tower leg was lifted. The results show that before and after the tower leg is lifted, the natural frequencies of each order exhibit obvious changes, and the differences in the average values can be used as the basis for judging the structural changes of the tower.

Vibration of Beams with a Single Delamination under Axial Loading

2011 ◽  
Vol 675-677 ◽  
pp. 477-480
Author(s):  
Dong Wei Shu
Keyword(s):  
Free Vibration ◽  
Natural Frequency ◽  
Analytical Solutions ◽  
Axial Load ◽  
Natural Frequencies ◽  
Axial Loading ◽  
Composite Beams ◽  
Mode Shapes ◽  
Equilibrium Conditions ◽  
Monotonic Relation

In this work analytical solutions are developed to study the free vibration of composite beams under axial loading. The beam with a single delamination is modeled as four interconnected Euler-Bernoulli beams using the delamination as their boundary. The continuity and the equilibrium conditions are satisfied between the adjoining beams. The studies show that the sizes and the locations of the delaminations significantly influence the natural frequencies and mode shapes of the beam. A monotonic relation between the natural frequency and the axial load is predicted.

Theoretical Analysis and FEM Simulation of Piezoelectric Vibrator Used in Ultrasonic EDM System

2013 ◽  
Vol 694-697 ◽  
pp. 3020-3024
Author(s):  
Hong Bing Wang ◽  
Zhi Rong Li ◽  
Chun Hua Sun
Keyword(s):  
Theoretical Analysis ◽  
Natural Frequencies ◽  
Dynamic Performance ◽  
Three Dimensional ◽  
Fem Simulation ◽  
Model Analysis ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Piezoelectric Vibrator ◽  
Working Frequency

The dynamic performance of the piezoelectric vibrator used in ultrasonic EDM machine in natural frequencies has a great effect on machining precision. Firstly, Through theoretical analysis the dynamic characteristics of the piezoelectric vibrator is obtained. Then the three-dimensional model of the piezoelectric vibrator is constructed by using PRO/E software, and model analysis is carried by using FEM software. Through theoretical analysis and FEM simulation, the appropriate working frequency and mode of the piezoelectric vibrator was found, and the piezoelectric vibrator was fabricated. Experimented results show that the model analysis of frequency is accord with that of FEM.

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