Applied Mechanics and Materials Vols. 477-478

Abstract: Flat ends in cylindrical pressure vessels are a certain alternative for commonly used in boilers dished ends. These ends can have different form and one of the admitted proposals is the plate with the internally introduced circumferential stress relief groove. In codes [1, the grooves of circular shape are recommended. Three parameters describe the groove configuration, namely the groove radius, the minimum endplate thickness under the relief groove and the chamfer angle. The respective formulas for calculations of the first two parameters are expressed in the form of inequalities. This means that a certain range of their variation is possible. The existing codes do not give the clear suggestion about the optimal choice of values of the groove parameters, leading to the minimal value of the stress concentration in the groove area. This is usually done by numerical analysis. The significant reduction of stress concentration is observed when changing the shape of the groove from the circular to the elliptical one, which is also shown in the paper.

Abstract: The limited time of usage and damage of rolling bearings is mainly attributed to the cyclic loads appearing during their work. As it is well-known these loads are distributed over the small contact area, which leads to the relatively high values of contact loads and stresses in the vicinity of the contact zone. This work is a proposal of the application of analytical formulas describing the stress distributions in the contact region and well-established multi-axial fatigue hypothesis in the estimation of fatigue loads of certain roller bearings. Additionally, the analytically calculated stresses are verified by means of the numerical results obtained with the use of finite element approximation.

Abstract: As a main coaxial cable connector, BNC connector, internal connections of which often takes the form of a clamping structure, is widely used in communication industry. Due to different production processes and standards, inadequate compaction or out-of-tolerance component size in BNC connector production may cause poor contact, lead to mismatch loss and influence the quality of signal transmission. Based on an actual BNC connector failure, this paper analyzes mismatch loss caused by poor contact of its components, mainly focusing on excessive contact of its PTFE components. Quantitative analysis is given on the cause and sizes of mismatch loss, as well as stress distribution, which provides reference for coaxial cable production and troubleshooting.

Abstract: Fatigue fracture occurred on one blade when a certain aero-engine was under test run. The fracture is observed to measure the crack length and the average distance between fatigue striations. The Paris formula is employed to calculate the fatigue propagation life of the two main fatigue propagation regions observed on the fracture. The results show that the rate of crack propagation present a tendency of regular increase, and the fatigue propagation life takes a very small ratio of the total fatigue life of the blade.

Abstract: Mobile heavy machines as unsprung vehicles exhibit low dissipation ability, hence the ride even at low speeds may give rise to intensive vibration, or even to the galloping effect due to enhanced vertical and angular vibration causing the road wheels to break away from the roadway. As these are mostly low-frequency vibrations, energy dissipation in wheel tires will reduce the vibration intensity in a minor degree only. As a result, the speed of a travel has to be reduced, which adversely affects the cost-efficiency of those machines. Observations of an unsprung machine during its forward ride lead us to formulate the hypothesis of reduced machines stability while it moves in the vertical plane of symmetry. The work [2] confirms the view that the vertical motion of an unsprung heavy machine while it moves forward is implemented under the condition of stability limit, mostly due to stiffness of the dynamic system in the horizontal direction. Mobile machines are dynamic systems, governed by nonlinear and often non-stationary differential equations of motion. Their stability is also dependent on the intensity of acting excitations.

Abstract: In the paper we have investigated the power of temperature influence to rectangular plates fundamental frequencies depending on subject to plates fixing and thermal conditions at plate edges. We have shown the power of thermal stresses influence to plate vibration process is directly connected not only to the initial plate temperature, geometry and material, but also to the type of boundary conditions. Thus, rigidly fixed edges enlarge the thermal stress effect.

Abstract: Buried pipelines are important lifeline engineering. During war conventional weapons blasting in the air would induce indirect ground shock, and the shock to the buried pipeline can lead to the paralyzed of urban economic and social function. And the numerical simulation of the dynamic damage of buried pipeline is complicated and time consuming, so this article using the equivalent static load method proposes analytic solution method of stress calculation of buried pipeline under ground shock. Through comparing the results calculated by analytic solution method and numerical solution, it shows that the analytical solution is feasible in engineering application.

Abstract: A large-scale earthquake simulation experiment about the unanchored cylindrical steel liquid storage model tanks has been completed. The fundamental frequency of the model tank with liquid inside was investigated based on the experimental data of the acceleration dynamic response. The seismic table test, the analysis methods are designed and conducted, and experimental results of the model tank were carefully measured. Furthermore, national design standard was used to calculate the fundamental frequency of the model tank system. The reasons for the existence of consistency and differences between the results obtained from experiments and national design standard were discussed.

Abstract: In-vehicle noise is composed of a variety of tonal (frequency-related) components and the tonal components play an important role in the improvement of sound quality for interior vehicle noise. Among them, gear whine noise is the key contributor to total in-vehicle noise and gain a lot of researchers interest. Through their effort, the spl (dBA) is relatively low. However, customers still perceive the tonal components and complain about the vehicle quality. Therefore a better understanding of how tonal components are perceived is necessary for automotive gear transmission designers. In this study, firstly, gear dynamic behavior is briefly introduced to get the gear noise spectrum. Secondly, human hearing mechanism to different tonal components is summed. Then loudness case studies are conducted. Finally, some basic design principles of controlling gear whine noise are proposed based on the results.

Abstract: The solid model of a turbocharger rotor was simulated for the rotordynamic analysis by use of finite element method.The dynamic equations for the solid model were deduced from the rotatory effects and gyroscopic inertia.The program was developed to determine the bending,torsional and their couplied vibration models.Calculations show that both the spin softening and stress stiffening effects have significant influence on the forward and backward whirl modes,and the torsional vibration frequency doesn’t change with the increase of rotor speed.The couplied bending-torsional vibration may be took place as excited.The accuracy of the solid model and the solution techniques have been demonstrated by comparison with other results.