scholarly journals Stochastic Natural Vibration Analyses of Free-Form Shells

2019 ◽  
Vol 9 (15) ◽  
pp. 3168
Author(s):  
Bingbing San ◽  
Yunlong Ma ◽  
Zhi Xiao ◽  
Dongming Feng ◽  
Liwei Yin
Keyword(s):  
Elastic Modulus ◽  
Shape Optimization ◽  
Shell Thickness ◽  
Natural Vibration ◽  
Natural Frequencies ◽  
Vibration Characteristics ◽  
Free Form ◽  
Probability Models ◽  
Geometric Imperfection ◽  
Natural Vibration Characteristics

This work investigates the natural vibration characteristics of free-form shells when considering the influence of uncertainties, including initial geometric imperfection, shell thickness deviation, and elastic modulus deviation. Herein, free-form shell models are generated while using a self-coded optimization algorithm. The Latin hypercube sampling (LHS) method is used to draw the samplings of uncertainties with respect to their stochastic probability models. ANSYS finite element (FE) software is adopted to analyze the natural vibration characteristics and compute the natural frequencies. The mean values, standard deviations, and cumulative distributions functions (CDFs) of the first three natural frequencies are obtained. The partial correlation coefficient is adopted to rank the significances of uncertainty factors. The study reveals that, for the free-form shells that were investigated in this study, the natural frequencies is a random quantity with a normal distribution; elastic modulus deviation imposes the greatest effect on natural frequencies; shell thickness ranks the second; geometrical imperfection ranks the last, with a much lower weight than the other two factors, which illustrates that the shape of the studied free-form shells is robust in term of natural vibration characteristics; when the supported edges are fixed during the shape optimization, the stochastic characteristics do not significantly change during the shape optimization process.

Study on the Natural Vibration Characteristics of Flexible Missile With Thrust by Using Riccati Transfer Matrix Method

2015 ◽  
Vol 83 (3) ◽  
Author(s):  
Gangli Chen ◽  
Xiaoting Rui ◽  
Fufeng Yang ◽  
Jianshu Zhang
Keyword(s):  
Transfer Matrix ◽  
Transfer Matrix Method ◽  
Matrix Method ◽  
Natural Vibration ◽  
Natural Frequencies ◽  
Compressive Force ◽  
Vibration Characteristics ◽  
Mode Shapes ◽  
Engine Thrust ◽  
Natural Vibration Characteristics

Due to the mass consumption and engine thrust of a flexible missile during the powered phase flight, its natural vibration characteristics may be changed significantly. The calculation of natural frequencies and mode shapes plays an important role in the structural design of the missile. Aiming at calculating the natural vibration characteristics of the missile rapidly and accurately, a nonuniform beam subjected to an engine thrust is used to model the free vibration of the missile and Riccati transfer matrix method (RTMM) is adopted in this paper. Numerical results show that the natural frequencies of a typical single stage flexible missile are increased unceasingly in its powered phase, and its mode shapes are changed a lot. When the presented methodology is used to study the natural vibration characteristics of flexible missiles, not only the mass, stiffness, and axial compressive force distributions are described realistically but also numerical stability, high computation speed, and accuracy are achieved.

Analysis of Vibration Caused by Ball Bearing in a HDD Spindle System at Elevated Temperature

2006 ◽  
Vol 321-323 ◽  
pp. 1624-1628 ◽  
Author(s):  
D.K. Kim ◽  
G.H. Jang
Keyword(s):  
Elevated Temperature ◽  
Frequency Distribution ◽  
Natural Vibration ◽  
Ball Bearing ◽  
Natural Frequencies ◽  
Vibration Characteristics ◽  
Spindle System ◽  
Bearing Stiffness ◽  
Natural Vibration Characteristics

This research investigates the vibration caused by ball bearing in a HDD spindle system, specifically non-repeatable runout (NRRO), at elevated temperature by analyzing the characteristics of ball bearing and the natural vibration characteristics of the spindle system due to the effect of elevated temperature. It shows that the elevated temperature results in the decrease of bearing deformation in the spindle system, which reduces the bearing stiffness and the natural frequencies of the spindle system consequently. It has a significant effect on the amplitude and the frequency distribution of NRRO at elevated temperature.

scholarly journals Influence of Temperature on the Natural Vibration Characteristics of Simply Supported Reinforced Concrete Beam

Sensors ◽  
2021 ◽  
Vol 21 (12) ◽  
pp. 4242
Author(s):  
Yanxia Cai ◽  
Kai Zhang ◽  
Zhoujing Ye ◽  
Chang Liu ◽  
Kaiji Lu ◽  
...  
Keyword(s):  
Elastic Modulus ◽  
Natural Frequency ◽  
Natural Vibration ◽  
Damage Identification ◽  
Vibration Characteristics ◽  
Theoretical Formula ◽  
Influence Of Temperature ◽  
Simply Supported ◽  
Influence Of Temperature On ◽  
Natural Vibration Characteristics

Natural vibration characteristics serve as one of the crucial references for bridge monitoring. However, temperature-induced changes in the natural vibration characteristics of bridge structures may exceed the impact of structural damage, thus causing some interference in damage identification. This study analyzed the influence of temperature on the natural vibration characteristics of simply supported beams, which is the most widely used bridge structure. The theoretical formula for the variation of the natural frequency of simply supported beams with temperature was proposed. The elastic modulus of simply supported beams in the range of −40 °C to 60 °C was acquired by means of the falling ball test and the theoretical formula and was compared with the elastic modulus obtained by the three-point bending test at room temperature (20 °C). In addition, the Midas/Civil finite-element simulation was carried out for the natural frequency of simply supported beams at different temperatures. The results showed that temperature was the main factor causing the variation of the natural frequency of simply supported beams. The linear negative correlation between the natural frequency of simply supported beams and their temperature were observed. The natural frequency of simply supported beams decreased by 0.148% for every 1 °C increase. This research contributed to the further understanding of the natural vibration characteristics of simply supported beams under the influence of temperature so as to provide references for natural frequency monitoring and damage identification of beam bridges.

Study on Natural Vibration Characteristics Based on the Coupled Wave Theory of Spring Supported Elastic Pipes and Fluids

2020 ◽  
Author(s):  
Takeshi Tokunaga ◽  
Koji Mori ◽  
Hiroko Kadowaki ◽  
Takashi Saito
Keyword(s):  
Boundary Condition ◽  
Blood Vessel ◽  
Flow Velocity ◽  
Blood Vessels ◽  
Natural Vibration ◽  
Wave Theory ◽  
Vibration Characteristics ◽  
Elastic Pipes ◽  
Coupled Wave ◽  
Natural Vibration Characteristics

Abstract A gradient of a blood flow velocity on the surface of a blood vessel is one of the clinical medicine concerns from the view point of prevention of the arteriosclerosis. In previous study, we formulated a relationship between the pressure and a flow velocity based on the coupled wave theory of elastic pipes and Newtonian fluids [1]. In addition, a flow velocity distribution and a wall shear stress are estimated by using the blood pressure data, which are non-invasively obtained by the tonometry method. This method is quasi-analytical method to apply the coupled wave theory for industrial flow field inside steel pipes proposed by Urata [4] to blood vessel, and has the advantage of systematic estimator compared with the numerical calculation. However, the coupled wave theory has applied to the elastic pipes that were assumed to be infinitely long. In addition, a single wave was assumed to be dominant within the elastic pipes and the Newtonian fluids. Therefore, in order to apply various length vessels in clinical field, the boundary of the blood vessels that varies from site to site, and the natural vibration characteristics that depend on the boundary conditions, could not be reflected in the wall shear stress estimation. In general, in order to solve the forced vibration with the boundary condition, it is necessary to clarify natural frequency and natural mode as natural vibration characteristics of structure. In this study, we introduce the spring supported elastic pipes to the coupled wave theory and formulated a relationship between the natural vibration characteristics and the boundary conditions. In this proposed method, the spring-supported elastic pipe has a feature that can be treated as an arbitrary boundary condition of an artery by giving an appropriate spring coefficients. Therefore, it is easy to apply to various types of blood vessels clinically. By investigating the natural vibration characteristics of blood vessels that varies from site to site, it may be possible to clarify fluctuations of blood flow in response to blood pressure with some frequency-bands. In addition, natural angular frequencies and natural modes of the spring supported elastic pipes and the Newtonian fluids were estimated for general blood vessel based on the coupled wave theory. In the result, the natural angular frequencies and the natural modes that reflect the clinical vibration characteristics to some extent can be estimated. On the other hand, particular modes may not reflect boundary condition, and further examination of the relationship between natural vibration characteristics and boundary condition is needed.

Natural vibration characteristics of a clamped circular plate in contact with fluid

2005 ◽  
Vol 21 (2) ◽  
pp. 169-184 ◽  
Author(s):  
Myung Jo Jhung ◽  
Young Hwan Choi ◽  
Hho Jung Kim ◽  
Kyeong Hoon Jeong
Keyword(s):  
Circular Plate ◽  
Natural Vibration ◽  
Vibration Characteristics ◽  
Natural Vibration Characteristics

Comprehensive Dynamic Model and Vibration Characteristics of Step-Type Compound Planetary Gear Sets

2011 ◽  
Vol 308-310 ◽  
pp. 1923-1928
Author(s):  
Fu Chun Yang ◽  
Xiao Jun Zhou ◽  
Ming Xiang Xie
Keyword(s):  
Dynamic Model ◽  
Natural Vibration ◽  
Natural Frequencies ◽  
Planetary Gear ◽  
Vibration Characteristics ◽  
Vibration Modes ◽  
Shape Distribution ◽  
Type Compound ◽  
Planetary Gear Sets ◽  
Step Type

Step-type compound planetary gear sets are widely applied in vehicle systems. Comprehensive dynamic model of step-type compound planetary gear sets, which includes translational, rotational vibrations and static transmission errors, was established. Natural vibration characteristics of the system, such as natural frequencies and vibration modes, were analyzed. Belt shape distribution characteristics of its natural frequencies was researched. According to vibration characteristics of both central components and planets, natural vibration modes of the system are classified into three types: central components translational vibration and planets random vibration, central components rotational vibration and planets identical vibration, central components static and adjacent planets reverse vibration mode.

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