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In this paper, dynamic model of two stage power branch double wide helical gear planetary drive system based on complex, in-depth study of the natural vibration characteristic. Starting from the first star and second planetary gear around the sun wheel non equidistant arrangement in the respective gear train, calculating modal analysis of characteristics of the system, so as to understand the mechanism of the system vibration, to provide theoretical guidance for the design of underwater device two power branch double wide helical planetary composite transmission system. At the same time to improve the dynamic characteristics of the device structure of underwater engineering significance.

In the study of the dynamic characteristics of the system, should pay attention to the influence on the dynamic performance of the system mode change. Mode change is closely related with mutation phenomena of mode localization process, in the natural frequency with the change of parameters, with a large curvature are quickly turned to separate the two natural frequency curve in the close position. Mode change will lead to the drastic changes in the natural frequency and modal energy, the variation of system parameters is also the location of the influence degree mutation position. Based on the modal characteristics of unique two stage power branch double wide helical planetary composite transmission system, studied the mode change phenomena, reveal the modal system changes.

In the paper, for high-power marine overflow valve of low pressure big traffic problems, the design of the inside leaking mouth leaks in parallel structure ,that is suitable for the different oil and water flow, using additional flow beam, guiding type low pressure large flow overflow valve was developed and the experimental study, obtained the dynamic and static parameters of the valve. Invented the inside leaking and leaked mouth parallel connection structure, inside leaking and leaked mouth parallel connection is established the mathematical model of the overflow valve. Results show that compared with the traditional straight moving type overflow valve, the type overflow valve through a larger flow, has better dynamic and static performance and cavitation resistance.

This paper mainly consider the friction plate finite element modeling frictional contact conditions between the slices of components, friction plate assembly of the strength and stiffness of the. Through modal analysis of force and its distribution in different layers of friction plate assembly friction plate, a friction plate component analysis layers, friction plate by the effect of preload on the friction plate assembly strength, and in this state analysis of the friction plate stiffness. On the contact state under different friction plate layers, different pre tightening force under stress, stiffness were compared, the effect of contact on the stiffness and friction plate component strength.

Triangular cantilevers are usually used as small force sensors in the transverse direction. Analyzing the effect of a crack on transverse vibration of a triangular cantilever will be of value to users and designers of cantilever deflection force sensors. We present a method for prediction of location and size of a crack in a triangular cantilever beam based on measurement of the natural frequencies in this paper. The crack is modeled as a rotational spring. The beam is treated as two triangular beams connected by a rotational spring at the crack location. Formulae for representing the relation between natural frequencies and the crack details are presented. To detect crack details from experiment results, the plots of the crack stiffness versus its location for any three natural modes can be obtained through the relation equation, and the point of intersection of the three curves gives the crack location. The crack size is then calculated using the relation between its stiffness and size. An example to demonstrate the validity and accuracy of the method is presented.

The cantilevers of atomic force microscope (AFM) are mounted under a certain tilt angle, which is commonly assumed to have negligible effect on friction measurements in AFM. We present a theoretical study of the effect of the tilt angle on AFM based friction measurements. A method for correcting the friction coefficient between sample surfaces and AFM tips is also presented to minimize the effects of the tilt. The frictional forces between a silicon tip and a silicon surface at tilt angles ranging from 5 degrees to 25 degrees were measured. The results show that the measured friction coefficient increases with the tilt angle effectively, whereas the variation range of the corrected friction coefficient is within 10%.

Triangular cantilevers are used as small force sensors. Prediction of location and size of multiple cracks from experimental results will be of value to users and designers of cantilever deflection force sensors. We extend a method for prediction of location and size of multiple cracks in rectangular cantilevers to deal with triangular cantilevers in this paper. The cracks are assumed to introduce local flexibility change and are modeled as rotational springs. The beam is divided into a number of segments, and each segment is associated with a damage index, which can be calculated through the relationship between the damage index and strain energy of each segment and the changes in the frequencies caused by the cracks. The location of cracks can be obtained with high accuracy with sufficient segment numbers. The size of a crack can be calculated through the relationship between the crack size and its stiffness, which can be obtained from the damage index related to the crack. The maximum error in prediction of the crack position in the case of double cracks is less than 15%, and it is less than 25% in prediction of the crack size.