SHIP VIBRATION PROBLEMS

2009 ◽  
Vol 65 (1) ◽  
pp. 23-28
Author(s):  
N. H. JASPER
2016 ◽  
Vol 1 (1) ◽  
Author(s):  
Wibowo H. Nugroho ◽  
Nanang J. H. Purnomo ◽  
Endah Suwarni

Ship vibration problems today's increasingly complex and often occurs in addition to the strict requirements of ship classification agencies for allowable levels of vibration so that passengers and crew more comfortable and secure. One method for reducing the influence of ship structural vibration is to minimize the response of the vibration by using damper. This paper describes the effect of the thickness of the damping layer made from cement material on the deck plate due to the harmonic load excitation. As cement is a common damper application on the ship deck.  A numerical modeling based on finite element analysis was applied in two-layer conditions, namely an overall and tiling coating. The results of this study indicate that thee minimum thickness of the cement layer has an optimum damping for the overall coating is approximately 8 mm and as for tile coating is approximately 15 mm.


1983 ◽  
Vol 27 (02) ◽  
pp. 103-112
Author(s):  
Peter Kaleff

A procedure is presented to determine the vibration frequencies and mode shapes of submerged structures. Hamilton's principle is used to formulate the problem, and general sequences of trial functions are introduced to permit the direct extremization of the corresponding energy functional. The fluid-structure interaction is accounted for by restricting the trial functions of the fluid to represent the flow around the immersed body imposed by each trial function of the structure. The trial functions for the fluid are built up from the contributions of triangular constant source elements distributed over the wetted surface of the structure, the accuracy of which in representing a flow is tested on an accelerated sphere. The structure is modeled with finite elements. The accuracy of the hydroelastic procedure is accessed on two examples as compared to experimental data: a cantilever plate and a freely floating ship.


2018 ◽  
pp. 44-47
Author(s):  
F.J. Тurayev

In this paper, mathematical model of nonlinear vibration problems with fluid flows through pipelines have been developed. Using the Bubnov–Galerkin method for the boundary conditions, the resulting nonlinear integro-differential equations with partial derivatives are reduced to solving systems of nonlinear ordinary integro-differential equations with both constant and variable coefficients as functions of time.A system of algebraic equations is obtained according to numerical method for the unknowns. The influence of the singularity of heredity kernels on the vibrations of structures possessing viscoelastic properties is numerically investigated.It was found that the determination of the effect of viscoelastic properties of the construction material on vibrations of the pipeline with a flowing liquid requires applying weakly singular hereditary kernels with an Abel type singularity.


2020 ◽  
Vol 25 (2) ◽  
pp. 29
Author(s):  
Desmond Adair ◽  
Aigul Nagimova ◽  
Martin Jaeger

The vibration characteristics of a nonuniform, flexible and free-flying slender rocket experiencing constant thrust is investigated. The rocket is idealized as a classic nonuniform beam with a constant one-dimensional follower force and with free-free boundary conditions. The equations of motion are derived by applying the extended Hamilton’s principle for non-conservative systems. Natural frequencies and associated mode shapes of the rocket are determined using the relatively efficient and accurate Adomian modified decomposition method (AMDM) with the solutions obtained by solving a set of algebraic equations with only three unknown parameters. The method can easily be extended to obtain approximate solutions to vibration problems for any type of nonuniform beam.


2019 ◽  
Vol 43 (4) ◽  
pp. 535-543 ◽  
Author(s):  
Shunxin Cao ◽  
Ruijun Zhang ◽  
Shuohua Zhang ◽  
Shuai Qiao ◽  
Dongsheng Cong ◽  
...  

Interaction and wear between wheel and rail become increasingly serious with the increase in elevator speed and load. Uneven roller surface, eccentricity of rollers, and the looseness of rail brackets result in serious vibration problems of high-speed and super-high-speed elevators. Therefore, the forced vibration differential equation representing elevator guide rails is established based on Bernoulli–Euler theory, and the vibration equation of the elevator guide shoes and the car is constructed using the Darren Bell principle. Then, the coupled vibration model of guide rail, guide shoes, and car can be obtained using the relationship of force and relative displacement among these components. The roller–rail parameters are introduced into the established coupled vibration model using the model equivalent method. Then, the influence of roller–rail parameters on the horizontal vibration of super-high-speed elevator cars is investigated. Roller eccentricity and the vibration acceleration of the car present a linear correlation, with the amplitude of the car vibration acceleration increasing with the eccentricity of the roller. A nonlinear relationship exists between the surface roughness of the roller and the vibration acceleration of the car. Increased continuous loosening of the guide rail results in severe vibration of the car at the loose position of the support.


2011 ◽  
Vol 189-193 ◽  
pp. 1914-1917
Author(s):  
Lin Ji

A key assumption of conventional Statistical Energy Analysis (SEA) theory is that, for two coupled subsystems, the transmitted power from one to another is proportional to the energy differences between the mode pairs of the two subsystems. Previous research has shown that such an assumption remains valid if each individual subsystem is of high modal density. This thus limits the successful applications of SEA theory mostly to the regime of high frequency vibration modeling. This paper argues that, under certain coupling conditions, conventional SEA can be extended to solve the mid-frequency vibration problems where systems may consist of both mode-dense and mode-spare subsystems, e.g. ribbed-plates.


Sign in / Sign up

Export Citation Format

Share Document