Applied Mechanics and Materials Vols. 246-247

Abstract: In order to reduce ring-liner interface friction power loss, this paper focuses on the structure parameters of the top ring, and investigates how the value of those parameters will influence top ring-liner friction power loss and the minimum thickness of oil film at top ring-liner interface. A mixed lubrication model is developed to simulate the effect of varying design parameters on ring-liner friction. Case study shows that ring-liner friction power loss will be reduced with decreased axial ring height and barrel height. This study provides a theoretical basis for design the top ring with reduced friction power loss at ring-liner interface.

Abstract: An increment transfer matrix equations based on step-by-step integration method and traditional transfer matrix method are deduced Combined with multi-mass model and Riccati method, the increment transfer matrix method is put forward, that can be directly used to analyze the dynamic response of the coupled bending and torsional vibrations of turbo-generator shafts with rub-impact. Taking a turbo-generator unit as example, the vibration character of rub-impact fault is analyzed when unit starts up. The research results show that rubbing will make vibration amplitude increase when the rotational speed is lower than the first critical speed; however, when the speed is higher than the first critical speed, rubbing will make the rotor mass unbalance reduce, thereby vibration amplitude will reduce slightly.

Abstract: For the purpose of construction an effective element model, the US- FE-LSPIM TRI3 element formulation, which is based on the concept of unsymmetric finite element formulation, is established. Classical linear triangle shape functions and FE-LSPIM TRI3 element shape functions are used as test and trial functions respectively. Classical linear triangle shape functions fulfill the requirements of continuity in displacement field for test functions. The FE-LSPIM TRI3 element shape functions synthesize the individual strengths of meshfree and finite element methods so they are more proper for trial functions. The element is applied in free vibration analysis of two dimension solids. Typical benchmark problems are solved. The results show that this element is more accurate and capable of good performances under both regular and irregular meshes.

Abstract: A complete system of vibration excitation with force feedback control for piezoelectric inertial exciter is presented. The vibration exciter is constructed and its dynamic model is established composed by piezoelectric stack, inertial mass and pretension institutions based on principle of inertia and reaction. The control system takes software program as the core part. The workflow of the digital step sine sweep control software for exciting force limit is recounted. Variety techniques are utilized to ensure real time and stability in the control process, including synchronization output and acquisition, extracting single tone information from waveform, model reference adaptive scaling control for amplitude of the output waveform. Some tests on a micro driving platform with high stiffness are carried out to verify the actual performance of the system. The results show that the piezoelectric inertial exciter and control system designed are very suitable for step sine sweep vibration excitation and exciting force control in high frequency range.

Abstract: Aiming at the nonlinear characteristics of the tool wear Acoustic Emission signal, tool wear state identification method is proposed based on local linear embedding and vector machine supported. The local linear embedding algorithm makes high dimensional information down to low dimension feature space through commutation, and thus to compress the data for highlighting signal features. This algorithm well compensates for the weakness of linear dimension reduction failing to find datasets nonlinear structure. In this paper, acoustic emission signal is firstly made by phase space reconstruction. Using local linear embedding method, the high dimension space mapping data points are reflected into low-dimensional space corresponding data points, then extracting tool wear state characteristics, and using vector machine supported classifier to identify classification of the tool wear conditions. Experimental results show that this method is used for the exact recognition of the tool wear state, and has widespread tendency.

Abstract: The strength of friction roller for endless-rope winch is analyzed, and the unit beam mechanics model for friction rollers is established, the flexural deformation equations are derived base on relevant theoretical analysis and calculate. Meanwhile, the variation curves of the flexural solution and compression stress along with the direction of friction roller width are obtained by MATLAB software. Thereby provides the theoretical basis for design and selection of friction roller.

Abstract: Based on the mould hydraulic vibration mathematics model in connection with the operation of actual hydraulic vibration equipment, analyzed the dynamic characteristic of the mould hydraulic vibration system with the MATLAB/Simulink module. Through the simulation on hydraulic cylinder's output displacement with different input signal, it can be seen that the system can be used to achieve non-sinusoidal vibration and provide a credible basis for research of mould hydraulic vibration system precisely. The experiments prove that the result is reliable.

Abstract: A metal-rolling process with chatter is chosen as the case for analysis. An isothermal, full film unsteady lubrication model is developed. The influences of time dependent variables such as back tension stress, variation on lubrication are investigated. By utilizing this model, roll forces and torque variation with respect to time can be successfully predicted. Chatter vibration in cold rolling due to unsteady lubrication phenomena is discussed. The current unsteady lubrication theory indicates that, when the nondimensional frequency of back tension stress variation is in a specific range, the roll force and torque variations can be significantly “amplified”.

Abstract: with the rapid development of ultraprecise process technology, the precision of instrument is being improved fast. Then instruments are more sensitive to the vibration of environment. This paper took advantage of the controlled character of MRF’s shear force, using actuators made of PZT,and put forward the double vibration isolation model based on MRF and piezoceramics. Through the theoretical analysis we arrival at a conclusion that the model has a good Isolation effect on both high frequency vibration and low frequency vibration especially ultralow frequency vibration.