Applied Mechanics and Materials Vol. 307

Abstract: In this work the method of active synthesis of mechanical systems in accordance with the desired frequency spectrum has been formulated and formalised. Active synthesis of a proportional regulation system has been performed in accordance with the method formulated and a verification of the correctness of the results has been carried out.

Abstract: The motion path of grinding carriage about workpiece rotation angle in crankshaft tangential point tracing grinding is a complex curve. For such complicated movement curve, it’s necessary to find a proper path approximation method to meet the high requirement of speed and precision of path interpolation. Sectioned polynomial is effective to approach to complicated path which ensures the approximation precision with low-order polynomial. This paper presents a dynamic sectioned cubic polynomial approximation method based on approximation error which ensures the continuity of the neighboring sectioned cubic polynomial curves at their boundary points to realize the stable tangential point tracing grinding of crankshaft at high speed.

Abstract: This paper presents a numerical study of incompressible laminar natural convection in entrance region of two dimensional vertical and inclined channels using regularized lattice Boltzmann Bhatnaghar-Gross-Krook method. Individual distribution functions with lattice types D2Q9 and D2Q5 are considered to solve fluid flow and thermal fields, respectively. Rayleigh number and inclination angle are varied from 10e2 to 10e6 and 0 to 60°, respectively. Distribution functions are introduced to mimic Bernoulli’s equation for calculating pressure at the inlet. Predicted Nusselt numbers are compared with Nusselt numbers correlation. Averaged Nusselt numbers compare well with Nusselt number correlation of Bar-Cohen & Rohsenow.

Abstract: According to the physical principles of hydrostatics, we measure the gravitational acceleration by using the air specific heat ratio comprehensive instrument and an inverted test tube with a pressure sensor at the bottom of it. The experiment is simple and does not involve the measurement of time. The result is good.

Abstract: Machine tool vibrations have great impact on machining process. Dynamic parameters such as the modal frequencies and damping constant of their components are the essential technical information required in engineering analysis and design. In addition, this information is needed for numerical simulations and finite element modeling to predict the response of the structures to a variety of dynamic loadings. In this work, experimental modal testing of a cylindrical grinding machine has been performed to obtain the mode shapes and modal frequencies. A Fast Fourier Transform (FFT) Analyzer, Pulse lab shop was used to obtain the Frequency Response Functions (FRF) and subsequent extraction of modal data was performed using Me’scope modal analysis software. These modal parameters were then checked using finite element analysis software, Ansys which were found to comply with the experimental results

Abstract: Past experiences have shown that a local wind can considerably affect the performances of powerplant cooling towers and factory chimneys. In thermal powerplants, the performance of Rankin cycles would reduce if the temperature of its condenser increases. This issue is very important to powerplants located in countries with strong local winds. To remedy the mal-performance of a natural cooling tower in windy conditions, it is required to understand the physics of flow around cooling towers more clearly. One adverse physics is known as the wind covering problem which can drastically affect the natural draught through a cooling tower in windy conditions. In this paper, we focus on wind-covering problem and its adverse impact on a real natural draught cooling tower. Contrary to the past studies, we show that wind can generally affect either positively or negatively in cooling tower performances. Surprisingly, the positive and negative roles can simultaneously occur in most times. In this paper, we use computational fluid dynamics tool to quantify the positive and negative impacts of wind on natural draught flow through dry cooling towers.

Abstract: Aiming at the defects of fault diagnosis in the traditional method for sucker rod pump system, a new method based on support vector machine (SVM) pump fault diagnosis is proposed. Through studying the theory of invariant moment and the shape characteristics of pump indicator diagram, seven invariant moments is extracted from the indicator diagram as a pumping unit well condition of the characteristic parameters. Then these parameters are pretreatment, and it makes up seven eigenvector which are regarded as the input eigenvector of the SVM. The experiment indicates that the method can not only detect the fault of the pumping oil well but also can recognize the fault type of it, which is very effective for safety protection and fault diagnosis of the pumping oil.

Abstract: The offshore wind turbine (OWT) tower is the important support of the whole wind turbine components, it is necessary to design and research the tower reasonably in order to ensure reliable operation of the OWT. In this paper, 3MW OWT tower is chosen as the object of study. A gas-liquid-solid model of the OWT tower and its external environment is built using COMSOL Multiphysics software. Combined with the two-phase flow theory of gas-liquid, loads of the tower under the coupling action of wind and wave are computed, which provides a new direction for the load analysis of the tower. The results calculated by this method are closer to the physical truth, which provides a more reliable basis for analyzing the fatigue life of the tower further.

Abstract: The paper presents the problem of stability and vibration reduction in designed discrete mechanical systems. The method of stabilisation and 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.

Abstract: Abstract：Based on the actual situations of diesel engines, significance of dynamic balance for marine diesel engine crankshaft system is discussed and as well vibration monitoring and field dynamic balance system for diesel engine crankshaft system is constructed. The least square method is applied to fit fundamental frequency vibration signals of crankshaft system and the field dynamic balance strategy is designed on the basis of the influence coefficient method. The feasibility of the dynamic balance system is tested through experiments in the paper.