Crack redirection with thermal secondary loading

In the current paper crack redirection due to a strategic placing of a heat source in the vicinity of a crack tip is studied. Analysis suggests that for PMMA and considered temperature range the only factor responsible for the deviation of crack trajectory is thermal stress. The simulation of crack growth in PMMA under external tension and secondary heat loading shows that a moving heat source in the vicinity of a crack tip can serve as a pointer for the crack trajectory. In highly conductive materials, redirection can be possibly effected with low-power thermal dipoles.     

牙哈采油树腐蚀检查分析及对策

介绍塔里木牙哈凝析气田高温高压井口采油树腐蚀的现象，腐蚀机理及采取的措施，对其他油田采油树腐蚀的防治起到指导借鉴作用。     

混凝土多孔砖应用技术研究

在分析了多孔砖力学特点的基础上,通过分析和研究,找出克服由于设计、施工原因造成的混凝土多孔砖砌体强度下降的措施。     

LOW-CYCLE FATIGUE UNDER NON-PROPORTIONAL LOADING

A series of strain-controlled, low-cycle fatigue experiments have been conducted on 42CrMo steel under various loading paths including circular, square, cruciform, and rectangular paths. Present experiments have shown that there is additional hardening under non-proportional cyclic loading. Non-proportional cyclic additional hardening also results in a shorter life for multiaxial low cycle fatigue. A non-proportionality measure of strain path based on both a physical basis and macromechanical phenomena is proposed. The loading path effect on additional hardening is also described well. Low-cycle fatigue damage accumulation and the evolution process under non-proportional loading is analysed via the Continuum Damage Mechanics Model of Chaboche. A non-proportinality measure is introduced in the damage evolution equation and a modified Coffin-Manson type formula is derived. A novel fatigue life prediction approach based on the critical-plane concept of Brown and Miller is proposed.     

Enhancement of hydrocyclone performance by controlling the inside turbulence structure

A new hydrocyclone was designed with a winged core fixed below the vortex finder in this study. With the winged core, the turbulence structure characteristics inside the hydrocyclone, including time-averaged pressure, pressure fluctuation, relative pressure fluctuation characteristics, and distribution characteristics of the probability density of the turbulence pressure, were all positively controlled. By controlling the turbulence structure, the performance of the new hydrocyclone was improved effectively. Compared with the common hydrocyclone, the new hydrocyclone was featured with lower energy loss coefficient, higher reduced separation efficiency, higher separation sharpness and larger capacity.     

大庆油田深层岩石力学特性参数的试验研究

通过对岩石可钻性、硬度、抗压强度等参数的测量 ,对大庆油田深井不同深度、不同层位、不同岩性的具有广泛代表性的岩心进行试验。并通过线性回归分析 ,建立了适用性较广的钻井岩石力学特性参数预测模型 ,为深井钻头选型提供了依据。     

Effect of Lateral Cracks on Fracture Toughness Determined by the Surface-Crack-in-Flexure Method

The surface-crack-in-flexure (SCF) method uses a Knoop indenter to create small, semielliptical surface precracks in beam specimens. Lateral cracks may interfere with the primary median crack and cause errors of up to 10% in determination of fracture toughness, particularly for materials for which the fracture toughness is ∼3 MPa·m^1/2 or less. Although the residual-stress-damage zone is ground or polished away by hand by removing 4.5–5 times the indentation depth, this amount may not be sufficient to completely remove the lateral cracks in low-fracture-toughness materials. A series of tests were conducted on sintered alpha silicon carbide with different amounts of material removed after indentation. Once the lateral cracks were fully removed, the SCF results concurred with single-edged-precracked-beam and chevron-notched-beam data collected in accordance with ASTM Designation C1421. A simple remedy for the SCF method is to examine the outer ground surface for remnants of lateral cracks before fracture and to remove more material if necessary.     

New unified laws in fatigue: From the Wöhler’s to the Paris’ regime

Generalizations and unification of the celebrated Paris’ and Wöhler’s laws for fatigue crack propagation are derived by applying the recently developed quantized (or finite) fracture mechanics. In particular, three generalized Paris’, Wöhler’s or unified laws are proposed and compared, demonstrating their applicability for predicting the life time of structures containing from small (the Wöhler’s regime) to large (the Paris’ regime) propagating fatigue cracks.     

Prediction of fatigue behaviour in stress-concentrators of arbitrary geometry

A new method is outlined which aims to predict high-cycle fatigue behavior of components which fail from stress-concentrators. This involves examination of the stress field in the vicinity of the stress-concentrator, and comparison with stress fields for cracks at known stress intensities. Methods which are currently used for simple notch geometries can thus be generalised, making the approach applicable to stress concentrators of any geometry. The method of prediction is shown to be stable, providing a solution of good accuracy when compared to analytical methods for standard specimen geometries. Favourable comparisons with experimental data have been achieved both for standard notches and for a corner geometry which represents a typical component case.     

Stress analysis with arbitrary body force by boundary element method

Linear stress analysis without body force can be easily carried out by means of the boundary element method. Some cases of linear stress analysis with body force can also be solved without the domain integral. However domain integrals are generally necessary to solve the linear stress problems with complicated body forces. This paper shows that the linear stress problems with complicated body forces can be solved approximately without the domain integral. In order to solve these problems, the domain is divided into small areas using contour lines of body force. In these areas, the distributions of body force are assumed approximately to satisfy the Laplace equation.