Advanced Materials Research Vol. 871

Abstract: Double Crossed Step-Down-Stress Accelerated Life Testing (DCSDS-ALT) discussed in this paper was implemented by switch down the double stresses alternately. Compared to constant stress test, step-stress test decreased specimen numbers, time and cost, and eventually well improve the accelerated testing efficiency. For pneumatic cylinder, the step-down-stress testing failure physics can be described as cumulative degradation model. By use of cumulative damage General Log-Linear relationship and Weibull assumption, the failure data obtained were equivalently converted to failure data under constant stress testing. Then the reliability specifications can be derived with better accuracy. The 5% of average lifetime estimation error and 1.85% of the characteristic lifetime error are very satisfying for pneumatic industrial lifetime prediction.

Abstract: This article studied the 13 m basic boom of SC50C hydraulic crawler crane, and made static analysis on crane basic boom by applying ANSYS, and obtains the stress distribution. Based on the features of the loads and structure of the crane basic boom, this paper sets up a finite element model of it, thus providing reference for the design and optimization of crane boom.

Abstract: The landing gear ground loading tests is a vital part before flight. As the motion of landing gear is three-dimensional motion,the traditional loading method cannot effectively simulate the pneumatic load on the ground. In order to simulate the load in the process of retraction/extension, a loading simulation system is proposed, including retractile system, position follow-up system and force servo loading system. This paper analyzes retraction/extension mechanism of the landing gear and builds up its mathematical model. A co-simulation model is developed in which the hydraulic system model and control system are built in software AMESim, the mechanical system of test platform model is built in software ADAMS. The results of the simulation confirm that the loading simulation system is feasible and provide the basis for building hardware platform.

Abstract: In this paper, a simulation model of the electrical transmission system with hydraulic coupler is established based on the analysis of the mechanical characteristics of the motor, the original characteristic curves of the hydraulic coupler and the torque equations of the pump wheel and the turbine. The starting and impact process of the system are simulated and the results reveal the mechanism of the characteristics of the starting process of the system and the isolation effect of the torsional vibration of the hydraulic coupler.

Abstract: In this paper, the penetration characteristic of tungsten penetrator was studied. Tungsten and aluminum was used as the material of the penetrator and target, respectively. Dimensions of the aluminum target were 100 X 100 X 5 (mm³). The penetrator with cylinder conical tip and flat tip was used in the impact test and simulation. The range of the initial velocity was from 400 to 1600 m/s. The angle of the incidence on the penetrator with cylinder cone tip was 0 ̊. The angle of the incidence on the penetrator with flat tip was 0 ̊, 30 ̊ , 60 ̊ . To obtain results of the simulation, AUTODYN 3D code was used. The residual mass and velocity was obtained to compare with results between the impact test and simulation.

Abstract: In this paper, both experimental and numerical studies were carried out for fully developed water and CTAC solution channel flows in order to understand the different distribution of Reynolds shear stress appeared in experiments and DNS. Quadrant analysis were carried out according to the categorization of turbulent fluid motions. The studies indicates that the elastic force of the additives' structures will cause the fluids moving back and forth in the wall-normal direction in experiment and the symmetric distribution of Reynolds shear stress in all quadrants. However, Giesekus model in DNS only applies the elastic force inhibiting the transverse fluctuations.

Abstract: This paper presents results obtained from the application of a computational fluid dynamics (CFD) code Fluent 6.3 to modelling of temperature in propane flames with air preheat. The study focuses on investigating the effect of air preheat temperature on the temperature of the flame. A standard k-ε turbulence model in combination with the Probability Density Function (PDF) model for Non Premix Combustion model and Eddy Dissipation Model (EDM) are utilized to represent the flow and temperature fields of the flame being investigated, respectively. The results of calculations are compared with experimental data of propane flame taken from literature. The results of the study showed that the combination of the standard k-ε turbulence model and PDF model is more capable of producing reasonable predictions of temperature, particularly in axial profile and rich fuel area of all two flames compared with those of EDM model. Both experimental works and numerical simulation showed that increasing the temperature of the combustion air significantly increases the flame temperature.

Abstract: In this paper, we study the planar Newtonian four-body problem with various choices of masses. We prove that there exist infinitely many periodic and quasi-periodic orbits with certain topological type, called retrograde orbits, that minimize the action functional on certain path spaces. On these orbits, two particles revolve around each other in one direction, while the other two particles travel on themselves orbits in opposite direction, respectively. Our proof is based on variational methods inspired by the work of Kuo-Chang Chen.

Abstract: For better understanding physical mechanism of radial disturbances, previously proposed to disturb the wake flow and vortex-induced vibration of risers, numerical simulations are carried out for the flow around the fixed cylinder with such disturbances at a Reynolds number of 100. After introducing disturbances, specific distributions of flow and vertical vorticity near cylinder surfaces are identified and related to different vortex patterns. The spanwise variation of free shear layers is discussed and physically explained. Different characteristics for the pressure on cylinder surfaces, frequency of vortex shedding and time history of lift are also analyzed and presented in detail.

Abstract: According to the integrate reciprocating compressors vibration problems occur in the process of operation, research the working principle of the unit, the incentive vibration element, establishes the physical model of the vibration excitation source. it is a guiding significance for the dynamic design, reform system, monitoring and operation management of the integrate reciprocating compressors.