Applied Mechanics and Materials Vols. 541-542

Abstract: The petroleum industry has been faced with the problem of flow-related erosion and corrosion during oil production and transportation for decades. In this paper, to characterize the flow behavior inside a pipe elbow, the RNG k-ε turbulence model with MUSCL discretization scheme is applied to the simulation. The calculation results are analyzed and conclusions can be drawn from these analyses: The simulations predicted value for the diametrical pressure coefficient is in excellent agreement with published correlation obtained from experimental data; The simulations indicate that the maximum wall shear stress occur near the inner corner wall, just downstream of the entrance to the elbow; At the entrance of the elbow, it is clear that the faster moving fluid starts out displaced towards the inner radius and the wall shear stress taking on its maximum value there; just downstream of 45°plane, the flow separates from the inner radius and a large separation vortex is formed that extends downstream.

Abstract: Fretting fatigue is an important failure mode of dovetail attachments in gas turbine engines. One of the most difficult challenges in carrying out experiments of components with actual geometry is the design of fixtures for the dovetail attachments since it can change the stress distribution under a given load. A circular arc dovetail attachment specimen with a tenon at each end respectively was designed and machined to simulate the fatigue damage that occurs in wide-chord fan blade attachments, so it can perform two dovetail attachment simulations at each time, and its related fixture was connected with the testing machine by two pins which were orthogonal to each other so as to eliminate additional bending moment. An Instron 8802 servo-hydraulic fatigue testing system was used to provide fatigue loads. Furthermore, Finite Element (FE) analysis based on the experimental configuration was carried out to obtain the stress distribution on the contact surface, crack initiation location and number of cycles to the fretting fatigue failure were predicted based on the FE results. The results show a good agreement with the experimental counterparts.

Abstract: Based on average loading assumption, a non-linear contact finite element model of coupling triple-diaphragm assembly configuration is established. In accordance with the result of diaphragm equivalent stress, the yield strength criterion and high cycle-stress fatigue life norm are adopted to calculate strength safety coefficient and fatigue life of coupling diaphragm. The durability of coupling diaphragm is proved enough numerically.

Abstract: This paper aims at the requirement of tracklayer gearing controlling racing power loss (for short racing loss), analyzed mechanism of generating racing loss of a high-power hydraulic retarder. By adding different number of baffle-plate equipment, racing loss was reduced. Using CFD technology, this paper studied contrastively the racing loss of hydraulic retarder in different condition, and compared with experiment result. The result indicated that the racing loss reduced obviously after fixing baffle-plate equipment, and the CFD simulation results agree well with the experimental results.

Abstract: There are many factors having effects on the cutting performance and useful time of cutting-tools, such as cutting-tools material, geometry parameters, structure and the optimization of cutting parameter, etc. But the condition of cutting-tools edge shouldnt be ignored. As is known to all, the micro gaps of cutting edge extend easily in the process of cutting, and accelerates the wear and damage of tools. As for the current situation of low passivation efficiency in edge, high loss of passivation and uncontrollability in blade shape, some improvements and new technology for applying to tools passivation are proposed based on the analysis and research about carbide tool passivation. Whats more, some exploration experiment will be done. The results show that those passivation technology can improve the processing efficiency of metal-cutting, cutting tool expectancy and reduce manufacturing cost.

Abstract: This study investigated the wear characteristics and anti-loosening characteristics of flank lock type precision locknut in the dynamic percussion vibration test. The experiment was conducted by using horizontal realistic dynamic percussion vibration test machine. The objective is to simulate the loosening condition of the locknut which was assembled in ball screw and machine tool spindle. Through this study, the wear resistance and anti-loosening characteristics of the precision locknut under the dynamic test were investigated by closely observing the roughness, flatness and tooth angle, seat surface and surface morphology before and after the test. The test results were used to calculate axial force ratio and anti-loosening ratio to understand the wear properties and anti-loosening properties of precision locknut under the dynamic conditions.

Abstract: The study investigated the variation of friction coefficient of a vertical assembly of flank lock type precision locknut at the different tightening speed by a torque and axial force test machine. The tightening speed is set at 4rpm, 6rpm and 8rpm, respectively. The lubricant is a type of 2TML. Surface morphology was observed before and after the test via an optical microscope. The experiment proceeded to five preloads to test and took the sixth as the experimental setting through the ISO 2320 specification. The study observed the variation of friction coefficient at the different tightening speed under a preload. The results show that the friction coefficient tends to be smaller when the tightening speed becomes faster. The increase of friction coefficient associates with the increase of anti-loosening ratio. For the surface morphology, it was found that the seat surface and the thread surface of the locknut generates the reaming, scraping and fatigue damage after the repeated tightening and loosening test.

Abstract: The tensile fatigue tests and S-N curve fitting results of the coupling bolt material 25CrMo were given in this paper. It has been proved that the high-cycle fatigue properties of the bolt material can be accurately described by the three-parameter exponential S-N curve model by comparing the fitting results based on different S-N curve models. The fatigue limit of the high-cycle P-S-N curve calculated by the traditional maximum likelihood method was proved to have a high probability of being higher than the accurate fatigue limit. Therefore, a modified method based on maximum likelihood method was proposed so as to calculate the high-cycle P-S-N curve more accurately. The P-S-N of 25CrMo calculated using the modified method was given in this paper.

Abstract: It is becoming a trend to achieve the purpose of energy conservation and emissions reduction that application of sailing navigation technology in large ocean-going ships. Two kinds of three-dimensional models of sail are presented in this paper, and they are made to do a structural calculation under the action of gravity with the ANSYS simulation software. Then the deflection of the sail under the action of gravity load and the distribution of its stress is concluded. A more reasonable design of sail structure can be selected.

Abstract: The similarity theory is in essence a method based on equation expression. In the application, the model is regarded to be similar to the prototype only if the similarity theorem can be met. But different physical objects have the same equation expression, so the model is always not similar to the prototype. To solve this problem, a new method which studies the similarity of mechanical components from the perspective of function and structure is put forward in this paper, based on the similarity theory and the ‘black box’ concept. The functional similarity criteria and structural similarity criteria derived from this method can accurately describe the similar properties of mechanical components under different similar requirements and can be used to set up the experimental model. Finally, a series of basic mechanical components are taken for example to verify the feasibility and superiority of this method. The method put forward in this paper can be applied to model test design and engineering test, etc. under different similar requirements.