Papers by Keyword: Vibration

Abstract: Features of the piston reciprocating motion is a high commutation frequency, small displacement, the impact force. Requirements of the piston movement is able to adapt quickly to change. Reducing the resistance movement of the piston will be able to make more flexible movement of the piston .The seal with mating surfaces can reduce the resistance movement . The gap of mating surface of the piston rod formed hydraulic oil spill. Mating surface seal problem is that the oil leakage is larger。Piston movement way of hydraulic vibrator is a kind of variable frequency and variable amplitude, in the form of constant flow. The form of the oil cylinder and the piston movement is the same. The cylinder as the output component of hydraulic vibrator output movement is to reduce the leakage .

Abstract: Dynamic and static frequency of the rotor about diameter of 1.4m small horizontal axis wind turbine was tested by using PULSE16.1 structural vibration analysis system., through combining the data of static frequency to identify rotor Dynamic frequency using spectrum analysis method. The conclusions found that, at a yaw condition of constant rotor speed, vibration acceleration of axial movement, disc effect and first order vibration of rotor increased with the increase of the yaw angle. The reason was that yaw exciting force which generated by the yaw behavior increased with the increase of yaw angle. At a constant load yaw, vibration acceleration of axial float, disc effect increased with the increase of the yaw angle. At the yaw condition of constant load R=82Ω、R=118Ω and the yaw angle 25°,30°,the acceleration value sharp increased and occurred the machine resonance phenomenon due to the tower instability. First order symmetric and anti symmetric vibration acceleration of rotor decreased with the increase of the yaw angle. The reason was that after the wind turbine yaw, the speed decreased of rotor caused the centrifugal force of the blades decreased, the impact of the centrifugal load changed was far greater than yaw exciting force for the first order vibration acceleration. The study also found that vibration acceleration values of rotor first order anti symmetric was ​​greater than axial movement, disc effect and first order symmetric vibration acceleration values, which shows that stress concentration in root of blade was large and the blade fatigue damage was more serious. This paper related research results can provided a new analytical thinking for rotor fatigue damage or breakage occurred frequently in wind turbine operation process, and may provide a reference for the vibration characteristics of rotor in the process of yaw.

Abstract: The dynamic characteristics of the Polypropylene honeycomb (PPHC) sandwich composites have been investigated under various temperatures (30°,35°,40°,45°,50°,55°,60°, 65°,70°,75° and 80°C) and different orientations (0° and 90°) of the glass fibers in the composites. Since the thermal properties of the constituent materials (glass fiber, epoxy resin and PPHC core) of the PPHC sandwich composites are different and the in-plane effect of the composites varies with the two different orientations (0° and 90°) of the fibers, the variation of the loss factor under the various temperatures are also different for these orientations. A two stage layup technique has been used to fabricate the sandwich composite specimens. Impulse technique associated with the half power bandwidth method, has been used to evaluate the natural frequency and damping values of the sandwich composite under different temperatures.

Abstract: This study is based on the graduation design for undergraduate course. In the paper, finite element analysis software ANSYS had been used to create the finite element model of a cannon barrel. On this basis, the vibration modal analysis of the barrel was conducted. Through the model analysis, the natural frequency and modal shape of the cannon barrel was obtained. The situations of stiffness strength and elasticity deformation about each part of the barrel were got by analysis of the modal shape. By this way, we can verify the rationality of the barrel design .Also it can provide improvements of the weak place of the structure for people to improve the stiffness and shooting precision of the gun, in order to make the dynamics characteristics of the gun more reasonable.

Abstract: Ball bearing life test, once the failure specimen ball fatigue, if not timely shutdown, will lead to a series of chain reactions caused by the fault processing is not seasonable, serious word may also lead to the damage of equipment. Therefore the vibration test is very important to accurately determine the specimen failure, ball. In this paper, the vibration test for bearing fatigue testing machine, the test results to be real-time and accurate judgment sample ball failure.

Abstract: Power spectrum analysis is one of the important part of digital signal processing, various characteristics of the main signal in the frequency domain, is designed based on the limited data and extract the useful signal is submerged in the noise in the frequency domain. In this paper, the VB language to realize the power spectrum analysis can extract the useful signal was drowned in noise in frequency domain based on power spectrum, frequency structure and physical meaning analysis reflected the more obvious, monitoring and diagnosis in rotating machinery fault, power spectrum analysis is very wide.

Abstract: Based on the experimental study of response of the gravel cushion under the horizontal vibration loads, analyzed internal shear modulus changes process in the granular layer , which are the changing characteristics caused by the self-organization, particles movement and compacting degree. We simulated the response process of shear modulus in the granular layer by using the Poisson process, discussed the development of shear modulus after several vibration and established the model.

Abstract: In order to research the dynamic characteristics of drive roll, finite element model of the drive roll was set up by ANSYS/Workbench. The drive roll’s natural frequency and vibration mode concerned in reality were acquired based on modal analysis, deformation trend and size of each mode shape were analysed, then deformation of the weak positions about each mode was cleared, and some measures about improving its dynamic characteristics were proposed, all of these offered a support to strengthen drive roll’s damping property.

Abstract: Nickel-base superalloy GH4169 is a kind of alloy with high intensity, heat-stability and heat-fatigability, so that is often used to aerospace field, but which has poor machinability. The cutting force, plasticity deformation all present their particular characters which causes cutting vibration . The cutting vibration influence the surface roughness, the swing of the cutting force and tool wear. This article discusses the superalloy of GH4169 on the basis of cutting speed, cutting depth and feed per-tooth.

Abstract: Most large covering parts mold use panel board type joining together of hardened steel. The vibration and the milling force is more bigger when milling process the spell near joint. They affect spell near joint processing quality. Analyze of the dynamic milling force, vibration surface morphology change of the sensitivity of the joining together with the cross-correlation function for analyzing the sensitivity of the dynamic milling force of mold spell near joint surface morphology. Experimental study shows that the dynamic milling force and the surface morphology characteristic curve cross-correlation function absolute value can reach 0.952 when the tool path and splice joints into 90°.And the cross-correlation function absolute value of milling force and the surface morphology characteristic is larger than vibration signal one. When the tool path and the joint Angle is small, the milling force influence on the surface morphology is lesser, so process should try to choose the smaller Angle seam.