A Method for Modifying Dynamic Properties of Undamped Mechanical Systems

1989 ◽  
Vol 111 (3) ◽  
pp. 403-408 ◽  
Author(s):  
Y. G. Tsuei ◽  
Eric K. L. Yee
Keyword(s):  
Dynamic System ◽  
Parametric Study ◽  
Dynamic Properties ◽  
Mechanical Systems ◽  
Force Response ◽  
Eigen Frequencies ◽  
Original Dynamic ◽  
Eigen Frequency

A method for the parametric study of the eigen frequencies and eigen vectors of a dynamic system is presented. The technique is based on the force response of the original dynamic system and gives a global picture for the behavior of the system with respect to the mass and stiffness parameters. It provides the sensitivity and feasibility of shifting the eigen frequency to a designed value; thus, it can be applied to the modal modification of a dynamic system. Because no iteration is required, the method is efficient.

scholarly journals Smart Mechanical Systems for Manufacturing in the Era of Industry 4.0: Condition-Based Predictive Maintenance and Dynamic System Modification for Small and Medium-Sized Enterprises

2021 ◽  
Vol 20 (2) ◽  
Author(s):  
Giovanni Carabin ◽  
Erich Wehrle ◽  
Renato Vidoni
Keyword(s):  
Dynamic System ◽  
Industry 4.0 ◽  
Industrial Revolution ◽  
Mechanical Systems ◽  
Predictive Maintenance ◽  
Condition Based Maintenance ◽  
Specific Target ◽  
New Class ◽  
Fourth Industrial Revolution ◽  
Potential Benefits

We are in the era of the fourth industrial revolution. Which highlights adaptability, monitoring, digitisation and efficiency in manufacturing as a result of the design of new smart mechanical systems. A central role in Industry 4.0 is played by maintenance and, within this framework, we define and review condition-based predictive maintenance. Thereafter, we propose a new class of smart mechanical systems that self-optimise utilising both condition-based maintenance and dynamic system modification. Akin to smart structures, smart mechanical systems will recognise and predict faults or malfunctions and, subsequently, self-optimise to restore desirable system behaviour. Potential benefits include increased reliability and efficiency while reducing cost without the requirement of highly skilled technicians. Thus, small and medium-sized enterprises are a specific target of such technology due to their increasing level of automatisation within Industry 4.0.

A Project in the Determination of the Moment of Inertia

2005 ◽  
Vol 33 (4) ◽  
pp. 319-338
Author(s):  
Ron P. Podhorodeski ◽  
Paul Sobejko
Keyword(s):  
Dynamic Properties ◽  
Equations Of Motion ◽  
Mechanical Systems ◽  
Moment Of Inertia ◽  
Educational Goal ◽  
Centre Of Mass ◽  
Comparison Of Results ◽  
Physical Testing ◽  
The Moment

Analysis of the forces involved in mechanical systems requires an understanding of the dynamic properties of the system's components. In this work, a project on the determination of both the location of the centre of mass and inertial properties is described. The project involves physical testing, the proposal of approximate models, and the comparison of results. The educational goal of the project is to give students and appreciation of second mass moments and the validity of assumptions that are often applied in component modelling. This work reviews relevant equations of motion and discusses techniques to determine or estimate the centre of mass and second moment of inertia. An example project problem and solutions are presented. The value of such project problems within a first course on the theory of mechanisms is discussed.

The Characteristics of Fuel Motion Which Affect Airplane Dynamics

1952 ◽  
Vol 19 (3) ◽  
pp. 381-388 ◽  
Author(s):  
E. W. Graham ◽  
A. M. Rodriguez
Keyword(s):  
Dynamic System ◽  
Mechanical Systems ◽  
Aircraft Dynamics ◽  
Rectangular Tank

Abstract Problems in aircraft dynamics such as stability and response of the rigid airplane may be affected by fuel motion in the tanks. Such problems also might arise in connection with missiles. In this paper the response of the fuel to simple harmonic motions of a rectangular tank in translation, pitching, and yawing is studied. Using the force and moment expressions, simple mechanical systems equivalent to the fuel are constructed. These systems respond to motions of the tank walls in the same fashion as the fuel, producing identical forces and moments. The use of such mechanical analogies should simplify in many cases the analysis of the complete dynamic system.

Active Synthesis of Discrete Systems as a Tool for Reduction Vibration

2013 ◽  
Vol 198 ◽  
pp. 427-432 ◽  
Author(s):  
Andrzej Dymarek ◽  
Tomasz Dzitkowski
Keyword(s):  
Force Feedback ◽  
Dynamic Properties ◽  
Vibration Reduction ◽  
Mechanical Systems ◽  
Discrete Systems ◽  
Mechanical Effect ◽  
Active Force ◽  
Active Synthesis ◽  
Proper Selection ◽  
Selection Of

The paper presents the problem of vibration reduction in designed discrete mechanical systems. The method of reduction has been based on active synthesis, which makes it possible to obtain the desired mechanical effect through the proper selection of dynamic properties of the system, including the calculation of the active force as a function of the system force feedback.

Modified HHT Method for Vehicle Vibration Analysis in Time Domain Utilisation

2013 ◽  
Vol 486 ◽  
pp. 396-405 ◽  
Author(s):  
Juraj Gerlici ◽  
Tomáš Lack
Keyword(s):  
Mechanical System ◽  
Time Domain ◽  
Vibration Analysis ◽  
Mechanical Systems ◽  
Dynamical Analysis ◽  
Vehicle Design ◽  
Negative State ◽  
Eigen Frequencies ◽  
Dynamical Properties

The analysis of mechanical systems (for example the mechanical systems of vehicles) vibration is permanently very topical. The vehicle dynamical properties are determined with the help of this analysis during a new vehicle design, or renewal of an older existing vehicle. The Eigen frequencies are characteristic for a vehicle construction. A vehicle mechanical system is excited with various types of loads in the operation and this is the reason why its individual parts oscillate. The aim of a dynamical analysis is not only to judge the influence of an excitation on the mechanical system, but also on the base of that analysis, to propose and to perform the construction changes of a vehicle for the detected negative state elimination or improvement.

Effects of Partially-Filled Containers in Dynamic Behavior of Tanker Trains Traveling on Curved Tracks

2008 ◽  
Author(s):  
Iman Hazrati Ashtiani ◽  
Davood Younesian ◽  
Mehrnoosh Abedi ◽  
Ebrahim Esmailzadeh
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Dynamic System ◽  
Dynamic Analysis ◽  
Parametric Study ◽  
Fluid Density ◽  
Moment Arms ◽  
Rail Irregularities ◽  
Curved Track ◽  
The Moment

Dynamic analysis of a partially-filled tanker train traveling on a curved track is studied in this paper. A partially-filled tanker is dynamically modeled when it is traveling along a real curved track. For three classes of tracks, rail irregularities are randomly generated by using Monte-Carlo simulation. An equivalent dynamic system is used to model sloshing motion of the fluid. Two derailment indexes i.e. derailment quotient and unloading ratio are obtained numerically as safety indicators. A parametric study is carried out to investigate how different parameters like the operational speed, fluid modeling, rail irregularities, and fluid density may affect the derailment potential. It is found that descending of the center of gravity and consequently reduction of the moment arms is more dominant than the oscillating forces due to sloshing motion.

scholarly journals Serviceability and flexural strength of lightweight floor made of cold formed steel joists.

2021 ◽  
Author(s):  
Quzzafi Rehman
Keyword(s):  
Finite Element ◽  
Flexural Strength ◽  
Ultimate Strength ◽  
Parametric Study ◽  
Finite Element Modelling ◽  
Dynamic Properties ◽  
Element Modelling ◽  
Floor Systems ◽  
Cold Formed Steel ◽  
Experimental Findings

The use of cold-formed steel (CFS) is becoming popular in residential and commercial building as a cost-effective alternative to traditional wood materials. CFS provides high strength-to-weight ratio, resulting in permitting lighter structure and longer spans. If proper design considerations are not made, this longer span and lighter structure can result in vibration serviceability issues that may affect building occupant comfort. The available design methods to calculate the dynamic properties of floor systems (i.e. Canadian Wood Council Method, CWC; Applied Design Council Design Method, ATC; and Eurocode, EC5) are used for the design of light-frame timber-based systems, CFS C-shape joists, and structural steel and concrete floor systems. The applicability of such methods to I-shape CFS joists is as yet unavailable. In addition, the North American Code for Cold-formed Steel structural Members (CSA-S136-07) provides specifications of ultimate and serviceability limit state design of C-shape joists rather than I-shape joists. As such, this research was divided into three parts. Part 1 presented the results of laboratory and field study on the vibration of a recently developed CFS I-shape joist called “iSPAN.” The main objective of the first part was to understand the dynamic characteristics of iSPAN floor system, recommend an adequate model for predicting the dynamic response and modal properties of floor systems, and correlate its results with engineered wood I-joists in order to aid the design process. Part 2 presented comparison between the experimental findings and available code provisions for the design of CFS joists at ultimate and serviceability limit states. The effect of web utility holes was also considered on the dynamic properties, and ultimate strength of iSPAN joists. Part 3 presented a finite-element modeling and its verification with the experimental findings of the tested samples. Also, part 3 extended the finite element modelling to analyse I- and C-shape CFS joists to determine their ultimate strength and serviceability, with and without the presence of utility holes in the webs. Since CSA-S137-07 does not provide design provisions for the edge-stiffened (i.e. lipped) holes, a practical-design-oriented parametric study, using the finite-element modelling, was conducted on CFS I- and C-shape members with circular, slotted and tri-slotted, edge-stiffened, holes under flexural loading. The optimized profile of the edge-stiffened holes was obtained using the elastic-buckling analysis. The post-buckling finite-element analysis was then utilized to determine member flexural strength as affected by utility hole geometry and web depth. Results showed that the edge-stiffened holes can significantly improve the flexural strength of CFS joists. The data generated from the parametric study was used to develop new design provisions to predict the flexural strength of such joists with the presence of edge-stiffened holes.

scholarly journals Study of running engines inertial and gyroscopic properties influence on the dynamic system engine – pylon – wing structural capabilities

2020 ◽  
Vol 23 (3) ◽  
pp. 63-72
Author(s):  
V. V. Ovchinnikov ◽  
Yu. V. Petrov
Keyword(s):  
Dynamic System ◽  
Fatigue Damage ◽  
Dynamic Properties ◽  
Elastic Beam ◽  
Aircraft Engine ◽  
Basic Structure ◽  
Elastic Vibration ◽  
Rigid Bodies ◽  
Practical Implementation ◽  
Structural Elements

A modern large-sized aircraft dynamic properties analysis, determined by the specificity of its layout scheme, demonstrates that the engines on under the wing elastic pylons lightly damped oscillations cause a number of undesirable phenomena, including intense accumulation of fatigue damage of the pylon-to-the-wing attachment, in fact in the area of engine installation in the pylon and the wing. The results of theoretical and experimental research show that with some engine attachment to the pylon structural modification it becomes possible to use the engines inertial and gyroscopic properties to absorb these oscillations. In this case, the motor tones damping coefficients increase by an order of magnitude or even more, so the gyroscopic coupling of elastic vibration tones is realized. With the rational choice of the additional parameters of elastic and dissipative bonds in the engine attachments it is possible to affect the aircraft wing and engines aero elastic vibrations effectively, which has a significant effect on the aircraft elements structural capabilities. A mathematical model of aero elasticity (MMAE) with respect to the kinetic moment of the engine rotors and specially designed units for attaching the engines to the pylons was developed in order to study the influence and the selection of rational elastic-dissipative parameters of the pylons-under-the-wing aircraft engine mounts. The method of predetermined basic forms is used for the aircraft with running engines on the pylons MMAE synthesis. The given forms are considered as the aircraft basic structure forms natural vibrations in the void. This work treats the engine nacelle and the rotor as absolutely rigid bodies, the elasticity of the rotor to the nacelle attachment is neglected. The pylon is modeled by an elastic beam, and the elastic and dissipative properties of the pylon-to-the-wing and the engine-to-the-pylon attachments are correspondingly by elastic-dissipative bonds. Schematic diagrams of the engine to the pylon attachments are proposed. The results of the study devoted to the influence of the proposed attachment points modifications on the load and integral strength characteristics of the main structural elements of the engine – pylon – wing dynamic system on the example of an An-124 aircraft are presented. The practical implementation of the proposed solutions aimed to reduce the level of fatigue damage to structural elements of the aircraft feasibility is proved.

scholarly journals Eigenfrequency spectrum of the reinforced concrete cantilever beam

2019 ◽  
Vol 91 ◽  
pp. 02031
Author(s):  
Pavel Morozovskiy ◽  
Ilya Kulish ◽  
Nikita Kryzhanovskii ◽  
Vladimir Filatov ◽  
Marina Romanovich
Keyword(s):  
Reinforced Concrete ◽  
Cantilever Beam ◽  
Software Package ◽  
Dynamic Loads ◽  
Building Structures ◽  
Eigen Frequencies ◽  
Eigenfrequency Spectrum ◽  
Eigen Frequency

For the calculation of building structures under the influence of external dynamic loads, it is necessary to know the eigen frequencies of the structures themselves in order to prevent such a phenomenon as resonance. Steel has distinctive properties from concrete, so its consideration is necessary to determine the eigen frequency of the whole structure. This article presents the calculation of the cantilever beam analytically and in the software package Abaqus for linear and volumetric problems with the interaction of concrete and reinforcement. Due to the reinforcement, the beam eigen frequencies differ from the eigen frequency of the conventional rigidly fixed rod, as evidenced by the results of the calculation.

scholarly journals Serviceability and flexural strength of lightweight floor made of cold formed steel joists.

2021 ◽  
Author(s):  
Quzzafi Rehman
Keyword(s):  
Finite Element ◽  
Flexural Strength ◽  
Ultimate Strength ◽  
Parametric Study ◽  
Finite Element Modelling ◽  
Dynamic Properties ◽  
Element Modelling ◽  
Floor Systems ◽  
Cold Formed Steel ◽  
Experimental Findings

The use of cold-formed steel (CFS) is becoming popular in residential and commercial building as a cost-effective alternative to traditional wood materials. CFS provides high strength-to-weight ratio, resulting in permitting lighter structure and longer spans. If proper design considerations are not made, this longer span and lighter structure can result in vibration serviceability issues that may affect building occupant comfort. The available design methods to calculate the dynamic properties of floor systems (i.e. Canadian Wood Council Method, CWC; Applied Design Council Design Method, ATC; and Eurocode, EC5) are used for the design of light-frame timber-based systems, CFS C-shape joists, and structural steel and concrete floor systems. The applicability of such methods to I-shape CFS joists is as yet unavailable. In addition, the North American Code for Cold-formed Steel structural Members (CSA-S136-07) provides specifications of ultimate and serviceability limit state design of C-shape joists rather than I-shape joists. As such, this research was divided into three parts. Part 1 presented the results of laboratory and field study on the vibration of a recently developed CFS I-shape joist called “iSPAN.” The main objective of the first part was to understand the dynamic characteristics of iSPAN floor system, recommend an adequate model for predicting the dynamic response and modal properties of floor systems, and correlate its results with engineered wood I-joists in order to aid the design process. Part 2 presented comparison between the experimental findings and available code provisions for the design of CFS joists at ultimate and serviceability limit states. The effect of web utility holes was also considered on the dynamic properties, and ultimate strength of iSPAN joists. Part 3 presented a finite-element modeling and its verification with the experimental findings of the tested samples. Also, part 3 extended the finite element modelling to analyse I- and C-shape CFS joists to determine their ultimate strength and serviceability, with and without the presence of utility holes in the webs. Since CSA-S137-07 does not provide design provisions for the edge-stiffened (i.e. lipped) holes, a practical-design-oriented parametric study, using the finite-element modelling, was conducted on CFS I- and C-shape members with circular, slotted and tri-slotted, edge-stiffened, holes under flexural loading. The optimized profile of the edge-stiffened holes was obtained using the elastic-buckling analysis. The post-buckling finite-element analysis was then utilized to determine member flexural strength as affected by utility hole geometry and web depth. Results showed that the edge-stiffened holes can significantly improve the flexural strength of CFS joists. The data generated from the parametric study was used to develop new design provisions to predict the flexural strength of such joists with the presence of edge-stiffened holes.

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