The Response of Mechanical Systems to Random Excitation

1957 ◽  
Vol 24 (2) ◽  
pp. 248-251
Author(s):  
W. T. Thomson ◽  
M. V. Barton
Keyword(s):  
Dynamic Response ◽  
Mechanical Systems ◽  
Random Excitation ◽  
Fixed Frequency ◽  
Harmonic Force ◽  
Instantaneous Values ◽  
Random Nature

Abstract Mechanical systems are not always excited by a harmonic force of fixed frequency and amplitude. Often the excitation input is of random nature, and the response of the system displays no orderly trends. Instantaneous values and phase are meaningless in such cases, and the problem must be treated statistically. It is the purpose of this paper to outline such an approach as related to the dynamic response of structures.

On the Comparison of the Dynamic Performance of Open-Loop and Closed-Loop Mechanisms

2014 ◽  
Author(s):  
Jahangir Rastegar ◽  
Dake Feng
Keyword(s):  
Dynamic Response ◽  
Dynamic Systems ◽  
Closed Loop ◽  
Dynamic Performance ◽  
Mechanical Systems ◽  
Open Loop ◽  
Actuation Devices

In general, mechanical systems with closed-loop mechanisms can achieve significantly higher operating speeds as compared to open-loop mechanisms such as robots performing identical tasks. In this brief paper, the reason for the superior dynamic performance of closed-loop mechanisms as compared to open-loop mechanisms performing identical tasks is shown to be the inherent dynamic response limitations of the actuation devices in open-loop dynamic systems. Several examples are provided.

Tuning the hygro-mechanical response of paper-based systems using glycerol

2020 ◽  
pp. 1045389X2094716
Author(s):  
Isaias Cueva-Perez ◽  
Roque Alfredo Osornio-Rios ◽  
Aurelio Dominguez-Gonzalez ◽  
Ion Stiharu ◽  
Angel Perez-Cruz
Keyword(s):  
Dynamic Response ◽  
Resonance Frequency ◽  
Mechanical Response ◽  
Water Solution ◽  
Low Cost ◽  
Mechanical Systems ◽  
Lumped Parameter Model ◽  
Glycerol Water ◽  
Energy Harvesters ◽  
Lumped Parameter

In recent years, the need for portable, low-cost, and eco-friendly devices for testing and monitoring has arisen. Paper-based devices have emerged as a response to these needs due to the properties induced by capillarity, flexibility, disposability, and biodegradability. In this work, the authors explored the possibility of tuning the hygro-mechanical response of paper-based cantilever beams using glycerol. A lumped-parameter model with non-linear stiffness is used to describe the dynamic response of the beams using three parameters. An experimental method based on resonance frequency tests is used to study the influence of glycerol on the dynamic response of four different beam configurations. The obtained results demonstrate that the resonance frequency of paper-based mechanical systems can be easily tuned by the imbibition of a glycerol–water solution. This study could lead to the development of tunable paper-based mechanical systems for specific applications such as energy harvesters and hygro-mechanical-based sensors.

Dynamics of a Multibody Mechanical System With Lubricated Long Journal Bearings

2004 ◽  
Vol 127 (3) ◽  
pp. 493-498 ◽  
Author(s):  
B. J. Alshaer ◽  
H. Nagarajan ◽  
H. K. Beheshti ◽  
H. M. Lankarani ◽  
S. Shivaswamy
Keyword(s):  
Dynamic Response ◽  
Mechanical System ◽  
Journal Bearing ◽  
Initial Conditions ◽  
Equations Of Motion ◽  
Mechanical Systems ◽  
Journal Bearings ◽  
Connecting Rod ◽  
Revolute Joint ◽  
Order Of Magnitude

Clearances exist in different kinds of joints in multibody mechanical systems, which could drastically affect the dynamic behavior of the system. If the joint is dry with no lubricant, impact occurs, resulting in wear and tear of the joint. In practical engineering design of machines, joints are usually designed to operate with some lubricant. Lubricated journal bearings are designed so that even when the maximum load is applied, the joint surfaces do not come into contact with each other. In this paper, a general methodology for modeling lubricated long journal bearings in multibody mechanical systems is presented. This modeling utilizes a method of solving for the forces produced by the lubricant in a dynamically loaded long journal bearing. A perfect revolute joint in a multibody mechanical system imposes kinematic constraints, while a lubricated journal bearing joint imposes force constraints. As an application, the dynamic response of a slider-crank mechanism including a lubricated journal bearing joint between the connecting rod and the slider is considered and analyzed. The dynamic response is obtained by numerically solving the constraint equations and the forces produced by the lubricant simultaneously with the differential equations of motion and a set of initial conditions numerically. The results are compared with the previous studies performed on the same mechanism as well a dry clearance joint. It is shown that in a multibody mechanical system, the journal bearing lubricant introduces damping and stiffness to the system. The earlier studies predict that the order of magnitude of the reaction moment is twice that of a perfect revolute joint. The proposed model predicts that the reaction moment is within the same order of magnitude of the perfect joint simulation case.

scholarly journals Dynamic response of reinforced concrete building from the effects of rail transport

2014 ◽  
Vol 9 (1) ◽  
pp. 69-78
Author(s):  
Ivo Demjan ◽  
Michal Tomko
Keyword(s):  
Reinforced Concrete ◽  
Dynamic Response ◽  
Dynamic Analysis ◽  
3D Model ◽  
Spectral Response ◽  
Random Excitation ◽  
Rail Transport ◽  
Reinforced Concrete Building ◽  
Load Spectra ◽  
Concrete Building

Abstract A 3D model of a reinforced concrete building and was created in software ANSYS. The dynamic analysis was focused on the spectral response of the object represented by a random excitation experiment found in records in the form of load spectra

scholarly journals Theoretical and experimental analysis of the exact receptance function of a clamped-clamped beam with concentrated masses

2020 ◽  
Author(s):  
Nguyen Viet Khoa ◽  
Dao Thi Bich Thao
Keyword(s):  
Dynamic Response ◽  
Numerical Simulations ◽  
Experimental Analysis ◽  
Arbitrary Point ◽  
Peak Position ◽  
Numerical Results ◽  
Experimental Results ◽  
Harmonic Force ◽  
Concentrated Masses

This paper establishes the exact receptance function of a clamped-clamped beam carrying concentrated masses. In this paper, the derivation of exact receptance and numerical simulations are provided. The proposed receptance function is convenient to apply for predicting the dynamic response at arbitrary point of the beam acted by a harmonic force applied at arbitrary point. The influence of the concentrated masses on the receptance is investigated. The numerical simulations show that a peak in the receptance decreases when there is a mass located close to that peak position. The numerical results have been compared to the experimental results has to justify the theory.

Dynamics of a Multibody Mechanical System With Lubricated Long Journal Bearings

2001 ◽  
Author(s):  
B. J. Alshaer ◽  
H. M. Lankarani ◽  
S. Shivaswamy
Keyword(s):  
Dynamic Response ◽  
Mechanical System ◽  
Journal Bearing ◽  
Initial Conditions ◽  
Equations Of Motion ◽  
Mechanical Systems ◽  
Journal Bearings ◽  
Connecting Rod ◽  
Revolute Joint ◽  
Order Of Magnitude

Abstract Clearances exist in different kinds of joints in multibody mechanical systems, which could drastically affect the dynamic behavior of the system. If the joint is dry with no lubricant, impact occurs, resulting in wear and tear of the joint. In practical engineering design of machines, joints are usually designed to operate with some lubricant. Lubricated journal bearings are designed so that even when the maximum load is applied, the joint surfaces do not come into contact with each other. In this paper, a general methodology for modeling lubricated long journal bearings in multibody mechanical systems is presented. This modeling utilizes a new method of solving for the forces produced by the lubricant in a dynamically loaded long journal bearing. A perfect revolute joint in a multibody mechanical system imposes kinematic constraints, while a lubricated journal bearing joint imposes force constraints. As an application, the dynamic response of a crank-slider mechanism including a lubricated journal bearing joint between the connecting rod and the slider is considered and analyzed. The dynamic response is obtained by numerically solving the constraint equations and the forces produced by the lubricant simultaneously with the differential equations of motion and a set of initial conditions numerically. The results are compared with the previous studies performed on the same mechanism as well a dry clearance joint. It is shown that in a multibody mechanical system, the journal bearing lubricant introduces damping and stiffness to the system. The earlier studies previous predict that the order of magnitude of the reaction moment is twice that of a perfect revolute joint. The proposed model predicts that the reaction moment is within the same order of magnitude of the perfect joint simulation case.

On the Dynamic Response of Actuation Devices in Nonlinear Dynamics Systems

2013 ◽  
Author(s):  
Jahangir Rastegar ◽  
Dake Feng
Keyword(s):  
Nonlinear Dynamics ◽  
Dynamic Response ◽  
Control Systems ◽  
Mechanical Systems ◽  
Inertial Load ◽  
Feed Forward ◽  
Feed Forward Control ◽  
Actuation System ◽  
Actuation Devices ◽  
Actuation Systems

This paper presents a study of the dynamic response of actuation devices used in mechanical systems with nonlinear dynamics such as robot manipulators. The study shows that the actuation forces/torques provided by actuation devices can be divided into two basic groups. The first group corresponds to the components of each actuator force/torque that is “actuator motion independent”. The dynamic response of this group is relatively high and limited only by the dynamic response limitations — for the case of electrically driven actuation systems — of the driving power amplifiers, electronics, computational and signal processing devices and components. The second group corresponds to those components of the actuator forces/torques that is “actuator motion dependent”. The dynamic response of this group is relatively low and dependent on the actuator effective inertial load and actuation speed. In all mechanical systems that are properly designed, the dynamic response of the first group is significantly higher than those of the second group. By separating the required actuating forces/torques into the above two groups, the dynamic response of such nonlinear dynamics systems may be determined for a given synthesized trajectory. The information can also be used to significantly increase the performance of control systems of such mechanical systems. When a feed-forward control signal is used, the performance of the system is shown to be significantly improved by generating each one of the group of components separately considering the dynamic response of the actuation system to each one of the groups of components. An example and practical methods of implementing the proposed feed-forward control for nonlinear dynamics systems are provided.

Dynamic response of a bi-axially pre-stressed bi-layered plate resting on a rigid foundation under a harmonic force

2019 ◽  
Vol 234 (3) ◽  
pp. 784-795
Author(s):  
Ahmet Daşdemir
Keyword(s):  
Mathematical Model ◽  
Dynamic Response ◽  
Three Dimensional ◽  
Dimensionless Frequency ◽  
Rigid Foundation ◽  
Layered Plate ◽  
Harmonic Force ◽  
Time Harmonic ◽  
Linearized Theory ◽  
Complete Contact

This study aims to investigate the forced vibrations caused by a time-harmonic force from a pre-stressed bi-layered plate resting on a rigid foundation under the action of a time-harmonic pointwise loading. Our investigation was conducted according to a piecewise homogeneous body model utilizing the three-dimensional linearized theory of elastic waves in initially stressed bodies. Throughout this study, we assumed that there is complete contact between the plate and the rigid foundation. The purpose of this study is threefold: the development of a mathematical model to investigate the dynamic response of the pre-stressed bi-layered plate, the analysis of the frequency response of the plate under consideration, and finally, demonstrating the relationship between the initial stress and the dimensionless frequency of the plate. We solved the mathematical model by employing the finite element method. We present our numerical results on the dynamic behavior of the plate. In particular, we have shown that an increase in the values of the aspect ratio of a plate under fixed thickness leads to a decrease in the normal stress resonance values.

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