Papers by Keyword: Frequency

Abstract: The purpose to optimize the ship structure is to obtain the minimum weight and the maximization of economic benefit. The way is to change the ship size, structure form, whole or partial structure layout under the condition of meeting the requirements of mechanical properties. The whole ship structure optimization model is established. Optimization is carried out by means of the Optimtoolbox in MATLAB, with the total mass of the ship as objective function, the requirements of the specification and the natural frequencies as constraint conditions. With sensitivity analysis,the thickness of bottom plate, deck, keelson, side keelson, superstructure bulkhead, hatch coaming and other components are selected as design variables. The results show that through optimization, better ship lightweight effect is obtained under the premise of guarantee hull structure strength, stiffness and dynamic characteristics. The bulk carrier structure is optimizaed.

Abstract: Liquid storage tanks are used to store of liquids. During earthquake activity the liquid exerts impulsive and convective pressures (sloshing) on the walls and bottom of tank. In the present paper, experimental and analytical study is taken up to obtain sloshing frequency of liquid contained in rectangular calculating of circular frequencies fluid in rectangular container. Analytical results of first natural frequency are compared with experiment.

Abstract: The paper describes a vibrations acceleration signals scanning and processing principle at technology head characteristic frequency reading during AWJ manufacturing process.

Abstract: This paper selects two typical micro-displacement control platforms,and conducts comparative analysis of strength of their flexible guiding mechanism.Stress expressions of flexible guiding mechanism are respectively derived to obtain the relationship between the maximum stress and geometric parameters and the relationship between tensile stress and bending stress.with moving the same displacement,the difference of stress of the two micro-displacement control platforms is small,and can be ignored.

Abstract:

Titanium and its alloys have been experiencing extensive development over the past few decades. They have found wide applications in the aerospace, biomedical and automotive industries owing to their good strength-to-weight ratio and high corrosion resistance. Machining performance is often limited by chatter vibrations at the tool-workpiece interface. Chatter is an abnormal tool behaviour which is one of the most critical problems in the machining process and must be avoided to improve the dimensional accuracy and surface quality of the finished product. This research aims at investigating chatter trends in the end milling process and to identify machine parameters that have effects on chatter during machining. The machine parameters investigated include axial feed rate, spindle revolute speed and depth of cut. In this research, experimental data was collected using sensors to analyze the existence of chatter vibrations on each processing condition. This research showed that the combination of the machine parameters, feed rate and spindle speed within certain proportions has an influence on machine vibrations during end milling and if not managed properly, may lead to chatter.

Abstract: The distinctive paper is devoted to problem of identification the dynamic characteristics of mathematical models based on the measured dynamic characteristics of real constructions. It is describes a problem of discrepancy of measured and modeling eigen pairs. It is shown that the problem is systemic. The creation and verification processes of mathematical (finite element) models used in the design constructions need some work and adjustments. For a reliable analysis of the construction ways are suggested to overcome the identified gaps using adaptive procedures.

Abstract: This paper presents a novel non-destructive method to locate and size damages in frame structures, performed by examining and interpreting changes in measured vibration response. The method bases on a relation, prior contrived by the authors, between the strain energy distribution in the structure for the transversal vibration modes and the modal changes (in terms of natural frequencies) due to damage. Using this relation a damage location indicator DLI was derived, which permits to locate cracks in spatial structures. In this paper an L-frame is considered for proving the applicability of this method. First the mathematical expressions for the modes shapes and their derivatives were determined and simulation result compared with that obtained by finite element analysis. Afterwards patterns characterizing damage locations were derived and compared with measurement results on the real structure; the DLI permitted accurate localization of any crack placed in the two structural elements.

Abstract: Using the convex model theory, the reliability-based analysis of frequency of the vibration control problem of structures with Interval parameters is discussed. Based on the theory of perturbation method, reliability analysis, and PNET method, the method of reliability-based analysis of eigenvalues of closed-loop vibration control systems with uncertain parameters is studied. And the distribution function of the random eigenvalues will not be computed other than their means and variances. The standard deviations of eigenvalues of the uncertain closed-loop systems can be used to estimate the reliability of frequency. The numerical results show that the present method is effective.

Abstract: Mechanical suspension test rig is much cheaper, but is can not meet the requirements of the suspension in-depth study. The reason is that the frequency and amplitude of the bench is immutable. According to the requirements of practical use, the frequency and amplitude control equipment is designed to arbitrarily change the vibration frequencies of the left and right wheels,and it can change the vibration amplitude of the wheels with a range of 5~12mm. It can meet the suspension test requirements.

Abstract: Keyword extraction is important for information retrieval. This paper gave a hybrid keyword extraction method based on TF and semantic strategies for Chinese document. A new word finding method was proposed to find the new word not exist in the dictionary. Moreover the semantic strategies were introduced to filter the dependent words and remove the synonyms. Experimental results show that the proposed method can improve the accuracy and performance of keyword extraction.