Applied Mechanics and Materials Vol. 684

Abstract: The finite element method combined with the singular element was adopted to study the effects of thickness ratio of the coating-matrix, elastic modulus ratio of the coating-matrix, and the ratio of ensile stress and shear stress on the coating top on the stress intensity of the interface crack on the coating-matrix. Through calculations, results show that elastic modulus ratio of the coating-matrix has little effect on stress intensity factor of interface crack, while the thickness ratio and the tensile stress and shear stress ratio on the coating top have a great effect on it, which should be controlled in the coating-matrix structure design.

Abstract: Logging while drilling (LWD) neutron instrument is a core equipment of the pulsed neutron logging technology, its anti-vibration performance has a direct impact on the measurement accuracy. For improving the anti-vibration performance, a reverse design method was proposed to avoid the resonance region due to increasing structural stiffness. The dynamic performance of the original instrument was analyzed, the weaknesses of its anti-vibration performance were determined and its topologies were improved. Moreover, the structural parameters of the instrument were optimized to raise the structural base frequency. The results show that the base frequency of the instrument increases high enough, the influence curves and surfaces of the base frequency with design variables provide a theoretical reference for the design of a LWD neutron instrument.

Abstract: Three-dimensional two-phase flow in the typical double downside 90°afterburning chamber of boron based ducted rocket is numerically simulated by means of Realizable turbulence model, one-step eddy-dissipation combustion mode1 and the ignition and combustion mode of boron particles of KING with considering the film moving effect in the high-speed flow. The results show that co-swirl and counter-swirl air in the double side of inlet enters into afterburning chamber to make mixture of air and gas more fully and combustion efficiency increases with the increase of swirl number. Boron particles and total combustion efficiency with co-swirl is higher than counter-swirl when the swirl number is less than 0.179. On the contrary, the counter-swirl is higher than co-swirl when the swirl number greater than 0.385, the co-swirl is balance to the counter-swirl when the swirl number is about 0.2; the ignition time of boron particles is reduced with swirling air, its minimum can be attained when swirl number is 0.385.

Abstract: Perforated casing eyehole stress concentration and sanding and compaction are the main reasons of casing abnormal damage during the exploitation. To understand the impact of reservoir sanding on perforated casing strength, fracture mechanics is applied to analyze the stress concentration of casing caused by perforating, while rock mechanics is applied to analyze the load of perforated casing of reservoir sanding limited bailed section, and on this basis, the impact of reservoir sanding on perforated casing strength is analyzed by the three-dimensional finite element model building. The analysis results show that the finite element solution and the theoretical solution of stresses of the perforated casing of reservoir sanding limited bailed section can be verified with each other. Under the same condition, the theoretical solution is bigger than the finite element solution, this is mainly due to the perforated casing additional bending stress effect is considered in the fracture mechanics theoretical analysis. It is conservative to estimate the perforated casing safety by finite element solution, while the theoretical solution is economical.

Abstract: A theoretical analysis is followed to calculate the dynamic stress intensity factors (DSIFs) in transversely isotropic piezoelectric bi-materials, due to existence of a permeable interfacial crack, near the edge of a circular cavity. The model is subjected to dynamic incident anti-plane shearing (SH-wave) and the formulation based on Green's function method. Conjunction and crack-simulation techniques are applied to obtain DSIFs at the crack’s outer tip. Calculations are prepared based on FORTRAN language program. A comparison is accomplished between the present model and another model with a crack emerging from the cavity edge to calibrate the program. Calculating results showed the influences of the physical parameters, the structural geometry and the wave frequencies on the dimensionless DSIFs and how those affected the efficiency of piezoelectric devices and materials.

Abstract: Conservedquantities of a growing elastic roddynamics are studied on the basis of Lagrange equation. Several of conserved quantities and their condition of existencearederived, which expanded the concept of conversation from the time to the space, i.e. arc coordinate.Lagrange equation is applied to analyzed energy integral and cyclic integral. First integrals are of practical significance in both theoretical and numerical analysis for a growing elastic rod dynamics.

Abstract: To assess the carrying capacity and reliability of the-Longtan Bridge, applied static load in the middle of the bridge step by step, then collected strain and deflection data of the beam. In order to understand the working principle of a bridge under dynamic loads, dynamic load test - Vehicle traffic test and fluctuation test t was performed, and vibration frequency data was collected. This paper described the basic principles of the bridge static and dynamic tests, and introduced the program of the experiment. Based on the test data, the static and dynamic mechanism of the bridge was discussed, the conclusion provides the basis for further study of bridge mechanism of the mechanical.

Abstract: Through the detailed investigation of Hejiacao landslide in Zhen'an county, this paper analysed the developing features and forming factors of the trench landslides, Meanwhile, it preliminarily discusses the mechanism of deformation and failures for the trench landslide. The investigation shows that: 1The trench landslide is special in shape, mainly in pushing type with low angle, and has characters of slow creep speed and long time. It mainly takes place in populated regions with serious damage; 2The trench landslide is controlled by many factors, such as trench terrain, poor lithology, hydrologic condition and human activities; 3The trench landslide experiences three phases: Deposition-crack, pushing-creep and final destruction in the process of forming and movement.

Abstract: In this paper, the static and dynamic mechanical viscoelastic behavior of NEPE propellant are studied. Under static conditions, five samples were subjected to constant-strain-rate monotonic loading with five different loading rates at room temperature. The dynamic mechanical analysis was employed for measurements of temperature and frequency dependence of the NEPE propellant by mean of BOSE-DMA-ELF3200 in frequency range from 1Hz to 16Hz. And get the dynamic mechanics temperature spectrum In the low temperature region, a single relaxation is observed in loss modulus-temperature Curves, which is glass transition relaxation. The results showed that NEPE propellant showed rate dependence and the same mechanical properties in the lower temperature and higher frequency.

Abstract: A new method to recycle radial tyre is studied, using Ultra-High Pressure Water jet to cut the tread rubber. The dynamic constitutive model of radial tyre material is builded, fitting model parameters with least square method. And the stress distribution law and dissociation characteristics of rubber block under impact are studied by finite element analysis.Through the SEM observation of cross section, the relationship is preliminarily discussed between stress distribution and micro-morphology of fracture interface and dissociation pathways. The split Hopkinson pressure bar apparatus is used to obtain the dynamic response law of material in a wide range of Strain Rate. The experimental results show that viscoelasticity of the rubber material is not fully reflected from the perspective of the stress wave propagation. The rubber material has a brittle transition and eventually forming fine powder. And the experimentally measured material crushing threshold is found agreed well with the numerical simulation results. It provides important mechanical foundation for further research on the mechanical force desulfurization of material.