Applied Mechanics and Materials Vol. 472

Abstract: Seismic vibrator is one of the most widely used equipments in exploration field. In recent years, with the development of exploration field, as well as the growing needs of high quality seismic data, the seismic vibrator's tonnage has increased a lot, which makes the stress of the vehicle frame very complicated in working state. And some local structure of the vehicle frame often appears crack phenomenon in working state. Therefore, the dynamic characteristic analysis is essential to the Seismic vibrator. In this paper, the finite element model of vehicle frame is established by ANSYS software. Through the modal analysis, the natural frequencies are obtained, and each vibration modes are analyzed. On the basis of the modal analysis, the modal neutral file of the vehicle frame is established. Using the data transfer function between ANSYS and ADAMS, the rigid-flexible coupling multi-body model is built for the dynamics simulation of the seismic vibrator. In this model, the stiffness and damping of air springs, hydraulic oil and soil are simulated by the spring-damper in the ADAMS software. The dynamic characteristics of vehicle frame under excited forces with different amplitude are obtained and analyzed. The stresses for some of the hot spots of the vehicle frame are extracted, which can be used to analyze the dynamic failure of the vehicle frame.

Abstract: Based on modal strain energy method, the paper discusses viscoelastic free layer damping sheet, establishes the finite element model of it and obtains the natural frequencies and loss factor. Then the paper calculates the loss factor of viscoelastic free layer damping structure with engineering empirical formula, and compares the result with that obtained by finite element method. By comparing the two results, it indicates that the finite element method is effective in analyzing this kind of problems.

Abstract: With changing strong nonlinear Duffing equation subject to harmonic excitation with damping in complex number field as an object, the amplitude frequency response equation of primary resonance of the system is obtained through parametric transformation with application of MLP method and modified method of multiple scales. In different approximation solution forms and different time scales, the two methods lead to the same amplitude frequency response equation. Thus, the two methods are mutually verifiable. Numerical analysis shows that for the strong nonlinear Duffing equation with damping in complex number field, the nonlinear stiffness coefficient is more than zero and the amplitude frequency response curve of primary resonance leans to the left, which is different from the weak nonlinear Duffing equation.Chinese books catalog: O321

Abstract: In rod's free vibration, its easy to obtain normal modes. However, if there is rigid body displacement, the problem will be much more complex. To solve these kinds of problems, single flexible body dynamics is needed. As the first part of the paper, considering rods rigid body displacement, the free vibration of tapered rod is discussed. By solving partial differential equation of rods free vibration, normal frequencies of tapered rod are obtained. As the second part of the paper, coupling vibration is discussed, in which process quasi-variational principle as the most important tool is used. Finally, first-order frequency of coupled vibration of rod is represented.

Abstract: In order to more accurately predict the vibration characteristics of drillpipe for rotary drilling rig, dynamic model of coupled axial and transverse vibrations was established based on Hamilton variation principle and finite element theory after discussing the vibration mechanism of drillpipe. The Newmark-β method was adopted to solve the dynamic equation and the simulated vibration responses of drillpipe were calculated. The results show that the axial models yield harmonic motion. The axial displacement is quite small and the maximum amplitude of the first section is about 6×10^-4 m. The transverse displacement is much larger than the axial displacement and the maximum transverse amplitude of the first section is about 0.03 m. The drillpipe of the first section of rotary drilling rig was tested. Comparing simulation results and test results, trends of the responses of axial displacement and transverse displacement have a good agreement and the simulation model is verified by the experiment.

Abstract: To describe the frequency distribution of the rotor blades and improve the optimization, resonance reliability of the rotor blades was analyzed in this paper. Considering the variety of rand-om variables, we jointly used finite element method and response surface method. The Campbell diagram was set up to describe blade resonance by analyzing the compressor rotor blade vibration characteristics. For the second-order vibration failure of the rotor blade, we considered the impact of random variables with the rotor blade material, the blade dimension and the rotor speed. The pro-bability distribution and allowable reliability of the second-order vibration frequency was calculated, and the sensitivity of the random variables influencing vibration frequency was completed. The res-ults show that the resonance reliability with the confidence level 0.95 of the rotor blade are = 0.99753 with the excited order =4 and =0.99767 with the excited order =5,and basically ag-ree with the design requirements when the rotor speed =9916.2, and the factors mainly affe-cting the distribution of the second-order vibration frequency of the blades include elastic modulus, density and the rotor speed, with the sensitivity probabilities 35.09%,34.56% and 24.15% respecti-vely.

Abstract: The present situation of damping capacity for magnesium alloys test techniques and its equipment were reviewed. Because there were many types of test equipment, So it pointed out the suitability of all testing equipment and schemes for damping testing of magnesium alloys. And based on the research results of dislocation damping mechanism of magnesium alloys. The author holds that test scheme for torsional deformation of torsion pendulum and test scheme for bending and shearing deformation of dynamic thermal mechanical analyzer meet high-precision test requirements for non-linear damping capacity of magnesium alloys. The study make great value for testing damping of magnesium alloys and reflecting their damping advantage.

Abstract: Gear transmission is one of the most important mechanical transmissions. It is widely used because of its high efficiency, compact structure, stable transmission ratio, etc. In general, the failure of gear transmission is mainly due to the failure of tooth. Tooth broken main failure mode of gear tooth is mainly due to the role of the tooth root bending fatigue. So, researching both tooth root bending fatigue strength and tooth surface contact fatigue strength are of great significance for the guarantee of gear life. Basing on romax this paper chooses a gear-bearing-rotor system as the research background to conduct parameter sensitivity analysis of gear contact and simulate the changes of tooth root bending stress and contact lines position in the whole meshing process of gear pair.

Abstract: Fracture line offset is the main defect in connecting rod fracture splitting processing, which seriously affects the using performance of connecting rod. In order to control this defect more effectively, the basic reason why this defect occurs was researched according to the theory of fracture mechanics, and the method of numerical simulation was used in this paper. The results show that when the applied load is nonparallel to the axis of a connecting rod, the first principle stress on the theoretical fracture surface is not perpendicular to the theoretical fracture line and the stress distribution is asymmetric on both sides of notches, which leads the type of fracture to turn into mixed mode I-II from mode I. As a result, the defect of fracture line offset occurs. Furthermore, the main factors leading to skew load were analyzed in actual production, and some effective measures were proposed to avoid the occurrence of this defect. This is significant in controlling the quality of connecting rod fracture splitting.

Abstract: A four-wheel rudimentary landing gear is studied numerically by detached eddy simulation (DES) based on the Spalart-Allmaras turbulence model. The surface sound pressure level and sound pressure spectra are calculated using the obtained unsteady flow field. The investigation shows that DES can describe the steady and unsteady properties in the flow around rudimentary landing gear. It can give reasonable results since the flow around the landing gear is a massive separated flow. The results prove the feasibility of DES type methods in massive separated unsteady flow field and aerodynamic noise prediction for landing gear, and can be used in the study of landing gear noise reduction.