Papers by Keyword: Bending Load

Abstract: The effect of defined preloading in the tensile and compressive regime on the near surface (residual) stress distributions, which result from laser surface hardening, is systematically studied in-situ, i.e. under the applied preload and after unloading. Samples made of steel grade AISI 4140 are defined surface hardened by means of a high-power diode laser (HPDL) system during uniaxial compressive elastic loading at-300 MPa as well as during uniaxial elastic tensile loading at 300 MPa using a custom designed 4-point-bending device, which can be mounted on an X-ray diffractometer. The results of X-ray stress analysis were compared to data derived for a sample state unaffected by any preload. Without external loading compressive residual stresses are induced inside the process zone that are balanced by tensile residual stresses outside this zone. The investigations show that external loading in the tensile and compressive regime has a strong impact on the resulting lateral residual stress distribution in loading direction. The results further indicate that undesirable tensile residual stresses outside the process zone can even be suppressed by using a defined appropriate preloading in the tensile regime.

Abstract: This paper mainly determined free chloride ion concentration of concrete beams of two kinds of water cement ratio (0.45and0.60) and bending load (0.00F_max, 0.30F_max, 0.45F_max and 0.60F_max) after 240 d in marine environment and compared the effect of different load conditions in the same water cement ratio on the free chloride ion concentration. The results show that the concentration of free chloride ion in tension zone of concrete increases with the increase of load level, the concentration of free chloride ion in compressed zone of concrete decreases with the increase of load level; under the same bending load level, the concentration of free chloride ion in concrete increases with water cement ratio.

Abstract: A damage limit prediction model was built due to fracture failure problems of aluminum alloy plates. Based on the global plastic collapse of the entire cross-section containing the defect, the relationships of crack width and depth of fracturing 7075 aluminum alloy plates with either shallow crack or deep crack was analyzed by using reference stress method. The damage limit curves of 7075 aluminum alloy plates with crack was drew, and safety zone of crack propagation under corresponding bending load was confirmed. Then the experimental verification was carried out, results show that calculated results are in good agreement with the test results during the shallow crack stage, while in the deep crack stage experimental results are slightly less than calculated results.

Abstract: Depending on the mechanical characteristics of casing located at the bending part of sidetrack horizontal well, the calculation model of casing collapsing strength under the effect of bending load is established, and corresponding theoretical formulae is derived. During the process of deducing formulas, the influence of bending load on the casing section out of roundness is ignored, which made the calculation formula benefits intuition and practicality comparing to the T.Tamano formula. The result of this paper is verified through the simulation value and laboratory test of casing used in the Jilin oilfield. It shows that the formula of this paper can meet the engineering commands; the axial load is significant to affect casing collapsing strength, and in the actual production process should be strictly controlled.

Abstract: The fatigue performance and durability of the reinforced concrete (RC) beams strengthened with fibre reinforced polymer (FRP) laminates is an advanced research topic in civil engineering. The crack propagation life is the dominant part of the whole fatigue life of the cracked RC members strengthened with FRP laminates under cyclic loads. In this paper, a theoretical and experimental study was conducted to investigate the rule of the fatigue crack propagation of the RC beams strengthened with carbon FRP (CFRP) under constant cyclic bending load. A total of 5 RC beams with sizes 1850×100×200mm strengthened with CFRP were tested. The results show that it is possible to divide the process of the crack propagation into three distinct phases, including crack initiation and then quickly propagation (Phase I), stable propagation and then rest (Phase II) and unstable propagation (Phase III). In accordance with Paris-Erdogan Law, a semi-empirical equation was developed to predict the crack propagation rate. The empirical coefficients of the equation were obtained from the fatigue test results. To validate this equation, the predicted fatigue life of crack propagation calculated by it is compared with the data obtained from tests. It shows the agreement is good.

Abstract: An analysis of fracture problems near crack tip for linear elastic orthotropic composite plate under bending and twisting is carried out. By solving the boundary value problem of partial differential equations and applying the method of undetermined coefficients, the two group expressions for bending moment, twisting moment and displacement near crack tip are derived. The formulae have certain practical and referential value in related fracture analysis.