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41.
钢纤维聚合物混凝土抗压本构关系 总被引:2,自引:0,他引:2
钢纤维聚合物混凝土是由聚合物混凝土基体和钢纤维共同组成的纤维增强复合材料,它的力学行为不仅依赖于聚合物混凝土基体的行为,而且与钢纤维的掺量、分散特征以及钢纤维的几何尺寸有关,本文将基于损伤力学原理研究在不同纤维掺量下的钢纤维聚合物混凝土的全程压力-应变曲线及其本构模型。 相似文献
42.
M. M. I. HAMMOUDA I. G. EL-BATANONY H. E. M. SALLAM 《Fatigue & Fracture of Engineering Materials & Structures》2003,26(7):627-639
An understanding into the macro kinetic and kinematic behaviour of fretted surfaces is provided. Making use of a modified version of a previously developed in‐house two‐dimensional elastic–plastic finite element analysis numerically simulates flat contact pad fretting fatigue tests. Basic macro mechanics concepts are adopted to idealise two bodies with rough contact surfaces and loaded at two different sites with arbitrary axial loading profiles. A time scale factor is devised to recognise the earliest candidate out of the events possibly accommodated at each loading increment. The present analysis utilises a relevant experimental set up developed in the Structural Integrity Research Institute of the University of Sheffield as an application. Computational results accurate to within 1.2% and corresponding to one contact pad span and six constant normal loads acting individually with four amplitudes of two sinusoidal axial load cycles are presented. The present computations include (1) the development of the global and local normal and tangential reactions and relative sliding displacement acting along the fretting surfaces and (2) contact pad deformation, generated stress fields and plasticity development within the neighbouring region of the fretted area. 相似文献
43.
Anastasia Dobroskok Larissa Fradkin Gennady Mishuris 《Engineering Fracture Mechanics》2007,74(11):1719-1726
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. 相似文献
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LOW-CYCLE FATIGUE UNDER NON-PROPORTIONAL LOADING 总被引:4,自引:0,他引:4
X. Chen Q. Gao X.-F. Sun 《Fatigue & Fracture of Engineering Materials & Structures》1996,19(7):839-854
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. 相似文献
47.
Enhancement of hydrocyclone performance by controlling the inside turbulence structure 总被引:1,自引:0,他引:1
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. 相似文献
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49.
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·m1/2 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. 相似文献
50.
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. 相似文献