scholarly journals Universal experimental relation for natural friquencies of transversal vibration of stubby free-free beams

2015 ◽  
pp. 42-51
Author(s):  
V. A. Chirikov ◽  
◽  
D. M. Dimitrov ◽  
K. P. Kostov ◽  
◽  
...  
Keyword(s):  
Transversal Vibration ◽  
Experimental Relation

Dynamic Stability of an Axially Moving Yarn with Time-Dependent Tension

2014 ◽  
Vol 900 ◽  
pp. 753-756 ◽  
Author(s):  
You Guo Li
Keyword(s):  
Differential Equation ◽  
Homotopy Perturbation Method ◽  
Time Dependent ◽  
Second Law ◽  
Order Ordinary Differential Equation ◽  
Vibration Equation ◽  
Transversal Vibration ◽  
First Order ◽  
Homotopy Perturbation ◽  
Axially Moving

In this paper the nonlinear transversal vibration of axially moving yarn with time-dependent tension is investigated. Yarn material is modeled as Kelvin element. A partial differential equation governing the transversal vibration is derived from Newtons second law. Galerkin method is used to truncate the governing nonlinear differential equation, and thus first-order ordinary differential equation is obtained. The periodic vibration equation and the natural frequency of moving yarn are received by applying homotopy perturbation method. As a result, the condition which should be avoided in the weaving process for resonance is obtained.

Effect of Ramp Angle on the Anti-Loosening Ability of Wedge Self-Locking Nuts Under Vibration

2018 ◽  
Vol 140 (7) ◽  
Author(s):  
Jianhua Liu ◽  
Hao Gong ◽  
Xiaoyu Ding
Keyword(s):  
Finite Element ◽  
Numerical Simulations ◽  
Production Technology ◽  
Material Properties ◽  
Threshold Value ◽  
Commercial Production ◽  
Experimental Results ◽  
Fe Method ◽  
Transversal Vibration

Recently, the wedge self-locking nut, a special anti-loosening product, is receiving more attention because of its excellent reliability in preventing loosening failure under vibration conditions. The key characteristic of a wedge self-locking nut is the special wedge ramp at the root of the thread. In this work, the effect of ramp angle on the anti-loosening ability of wedge self-locking nuts was studied systematically based on numerical simulations and experiments. Wedge self-locking nuts with nine ramp angles (10 deg, 15 deg, 20 deg, 25 deg, 30 deg, 35 deg, 40 deg, 45 deg, and 50 deg) were modeled using a finite element (FE) method, and manufactured using commercial production technology. Their anti-loosening abilities under transversal vibration conditions were analyzed based on numerical and experimental results. It was found that there is a threshold value of the initial preload below which the wedge self-locking nuts would lose their anti-loosening ability. This threshold value of initial preload was then proposed for use as a criterion to evaluate the anti-loosening ability of wedge self-locking nuts quantitatively and to determine the optimal ramp angle. Based on this criterion, it was demonstrated, numerically and experimentally, that a 30 deg wedge ramp resulted in the best anti-loosening ability among nine ramp angles studied. The significance of this study is that it provides an effective method to evaluate the anti-loosening ability of wedge self-locking nuts quantitatively, and determined the optimal ramp angle in terms of anti-loosening ability. The proposed method can also be used to optimize other parameters, such as the material properties and other dimensions, to guarantee the best anti-loosening ability of wedge self-locking nuts.

Study on the mechanism of preload decrease of bolted joints subjected to transversal vibration loading

2019 ◽  
Vol 233 (12) ◽  
pp. 2320-2329
Author(s):  
Hao Gong ◽  
Jianhua Liu ◽  
Xiaoyu Ding
Keyword(s):  
Finite Element ◽  
Comprehensive Evaluation ◽  
Evaluation Criteria ◽  
Bolted Joints ◽  
Cyclic Plasticity ◽  
Stress Release ◽  
Element Analysis ◽  
Transversal Vibration ◽  
Mechanical Products ◽  
As Stress

Sufficient preload in a bolted joint is key to ensuring the reliability of mechanical products; however, under vibration, preload decrease often occurs. The mechanism of preload decrease has not yet been fully clarified. In this study, finite element models of bolted joints with and without helix angles were constructed to study the mechanism of preload decrease under transversal vibration. Based on the finite element analysis results, a new cause of preload decrease, denoted as stress release and redistribution, was discovered and explained in detail. The mechanism of preload decrease caused by stress release and redistribution, cyclic plasticity deformation and rotation loosening is studied systematically, and the typical mode of preload decrease is proposed. Based on the preload decrease curve, more comprehensive evaluation criteria are established, quantified using three parameters to represent the locking behavior of bolted joints. Finally, experiments were conducted to verify the reliability of the preload decrease results.

Effect of the Ratio between Tension and Bending Vibration Loads on the Fatigue Behavior and Failure Mode of Titanium Alloy TA11

2014 ◽  
Vol 898 ◽  
pp. 27-32
Author(s):  
Nan Ma ◽  
Xin Ling Liu ◽  
Zhi Wang Qiu ◽  
Yu Huai He ◽  
Chun Hu Tao ◽  
...  
Keyword(s):  
Titanium Alloy ◽  
Failure Mode ◽  
Failure Modes ◽  
Fatigue Behavior ◽  
Tensile Force ◽  
Fatigue Properties ◽  
Bending Vibration ◽  
Transversal Vibration ◽  
Axial Tensile ◽  
Vibration Loads

This paper studied the effect of the ratio between the axial tensile force and the transversal vibration loads on the fatigue behavior and failure mode of the near alpha titanium alloy TA11, to simulate the service stress state applied on the engine blades, where a large centrifugal force is superimposed with bending vibration loads. The plate-like specimens were used in the fatigue tests by a special testing device which was designed and fabricated in the present research,where the vibration loads were applied by the electro-magnetic exciters. By experiments under various multi-axial fatigue loading cases with different ratios between the axial tensile force and the transversal vibration loads, the fatigue behavior and failure modes were observed and compared. Then, the energy based fatigue criteria were applied for correlation of the test results. The fatigue properties of titanium alloy TA11 under the specialized loading conditions are characterized and discussed. In addition, the experimental observations on the vibration behavior superimposed with different magnitude of axial tensile force are also helpful for understanding the real working conditions of the engine blades.

The ‘instantaneous’ elasticity of active muscle

1953 ◽  
Vol 141 (903) ◽  
pp. 161-178 ◽  
Keyword(s):  
Elastic Properties ◽  
Long Range ◽  
Linear Expansion ◽  
Thermal Coefficient ◽  
Active Muscle ◽  
Absolute Size ◽  
Rapid Fall ◽  
Experimental Relation ◽  
Coefficient Of Linear Expansion ◽  
Resting Muscle

When the tension of a muscle contracting isometrically is rapidly lowered, there is an immediate and proportional rise of temperature. This is not due to physiological shortening, which is a relatively slow process, but is directly connected with the fall of tension. A similar effect occurs in any material possessing a normal (positive) thermal coefficient of linear expansion. It is the opposite of what is observed in bodies with long-range rubber-like elasticity. The experimental relation, in active muscle, between the heat (∆ Q ) immediately produced and the rapid fall of tension (-∆ P ) is ∆ Q = 0∙018 l o (-∆ P ), where l o is the standard length of the muscle. The constant 0∙018 is considerably greater than for metals but about the same as for ebonite and wood. In resting muscle, in the range of moderate tensions, the constant is of the opposite sign, and its absolute size is five to ten times as great. Resting muscle, in this range, has rubber-like elastic properties. During active contraction, therefore, the contractile filaments possess normal and not long-range elasticity. The force exerted by active muscle is not of thermokinetic origin. Unlike resting muscle its entropy and its internal energy both decrease when its tension is rapidly lowered. The power of physiological shortening, at a rate depending on the tension, is not directly derived from elastic properties. In normal relaxation after an isometric contraction there is known to be a substantial production of heat. This is derived partly from elastic energy developed earlier during contraction, in the series elastic component: the balance is fully accounted for by the thermo­elastic heat resulting from the fall of tension.

Transversal Vibration Analysis of Vehicle Track System

2019 ◽  
Author(s):  
Pingxin Wang ◽  
Xiaoting Rui ◽  
Jianshu Zhang ◽  
Hailong Yu
Keyword(s):  
Natural Frequency ◽  
Vibration Analysis ◽  
Stability Control ◽  
Axially Moving Beam ◽  
Natural State ◽  
Beam Model ◽  
Tracked Vehicle ◽  
Transversal Vibration ◽  
Rubber Bushing ◽  
Axially Moving

Abstract The track is mainly composed of track shoes, track pins and rubber bushing elements. In order to suppress the transversal vibration of the upper track during the smooth running process of the tracked vehicle, it is necessary to study the important factors affecting the frequency characteristics of the kinematic chain and their interaction. Unlike the conventional chain drive system, the track in the natural state has a bending rigidity due to the action of the rubber bushing. Based on the dynamic theory of axially moving beam, the differential equation of transversal vibration of a beam element is established. The entire upper track is assumed to be a continuous multi-span axially moving Euler-Bernoulli beam with an axial tension. Based on the Transfer Matrix Method of Multibody System, the transfer equation is obtained. According to the boundary conditions, the natural frequency of the system is solved. The correctness of the beam model hypothesis is verified by experiments. The results show that the first-order natural frequency of the upper track increases with the increase of the tension and the decrease of the vehicle speed. Through frequency analysis, the main excitation source for the transversal vibration of the track is the polygon effect produced by the meshing of the track and the sprocket. This study provides a theoretical basis for the vibration analysis and stability control of the upper track on the tracked vehicle.

Temperature Field Analysis for Freezing Sealing Structure of Sodium Gate Valve in China Experiment Fast Reactor (CEFR)

2013 ◽  
Author(s):  
Lina Hu ◽  
Huajin Yu ◽  
Mingyu Lv
Keyword(s):  
Temperature Field ◽  
Fast Reactor ◽  
Nuclear Power ◽  
Large Scale ◽  
Gate Valve ◽  
Structure Design ◽  
Field Analysis ◽  
Power Station ◽  
Experimental Relation ◽  
Simulation Results

In order to achieve the localization of the large-scale sodium gate valve in fast reactor nuclear power station, this paper use fluid software FLUEN, using two different methods, analysis temperature field of sodium gate valve freezing sealing structure of CEFR. The first method is to establish air model; the second method is to making use of experimental relation to calculate surface coefficient of heat transfer to simulate temperature field of freezing sealing structure of sodium gate valve in CEFR. Compared with measuring results on-site, simulation results of the first method have error within 10%. Therefore, it is feasible that simulating temperature field of freezing sealing structure with this method. That will promote structure design of freezing sealing of sodium gate valve for large fast rector power plant.

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