Papers by Keyword: Residual Strength

Abstract: The advantages of aluminum alloy are found expression in lightweight and high strength, while bamboo features in density and thermal insulation. It’s necessary to explore composition effect of bamboo-aluminum composite. Specimens were prepared by filling aluminum alloy hollow profile with bamboo blocks, and then stress-time curves were collected in process of compression. Its ultimate strength reached 56 MPa, and residual strength is about 40% of its ultimate strength. The bamboo-aluminum composite has good mechanical properties and reliability for structural components and is worthy of wide applications.

Abstract: Abstract: In this paper, experimental and finite element methods are integrated to carry out the research about residual strength of composite laminate structure with central and edge notch. First, the specimens with central and edge notch and the fixtures used in compression tests were designed and manufactured, and the tensile and compression residual strengths with different notch size were measured. Then, finite element analysis model of specimens with central and edge notch were established to predict the residual strength based on the average stress criterion and Hoffman criterion, the effect of the notch size on the residual strength is evaluated, the results were compared and found that the average stress model has higher prediction accuracy and notch size has a significant influence on the residual strength of composite laminate structure with central and edge notch.

Abstract: Mechanical resistance of building materials exposed to high temperatures, e.g. fire loading or explosion damage, is one of parameters that determine the safety of structures. The residual strengths determine load-bearing capacity of construction after exposure of extreme temperatures. Mechanical properties of materials exposed to high temperature (400°C and more) are primarily tested and determined at ambient temperature testing mode. It means, that the sample is exposed to high temperature loading and after cooling to the nature temperature T₀ = 20°C are tested in common used testing machines. These residual strengths are a valuable foundation for an assessment of the structure exposed to a temperature load. The paper presents the test results of mechanical properties at hot state compared to the test results at ambient temperature for four type of lightweight concretes exposed to several temperature levels T_max = 200°C, 400°C, 600°C, 800°C and T_max = 1 000°C.

Abstract: Plates are the important structural members finding applications in the field of structural engineering, ship technology and aerospace engineering. Holes are often provided in the plates for the purpose of services and aesthetics. Pitting corrosion can also induce holes on the plates, thereby inducing stress concentration and redistribution of stress around the hole. In this paper, the popular finite element software ANSYS is used for the static analysis of thin plates with holes. The influence of shape and size of the hole on the stress distribution of plate is also analysed. The study can form foundation for strength assessment of steel plates with holes, especially residual strength of plates subjected to pitting corrosion.

Abstract: Liquid-solid extrusion following vacuum pressure infiltration technique (LSEVI), which integrates melting, pouring, infiltration, and liquid-solid forming under high infiltration pressure, is a promising technique for the fabrication of metal matrix composite. LSEVI technology combines the advantages of both squeeze casting and gas pressure infiltration method. In this study, 2D carbon fiber reinforced AZ91D matrix composites (2D-C_f/Mg composites) were fabricated by LSEVI. Pyrolytic carbon (PyC) coating was deposited on surface of T700 carbon fiber by chemically vapour deposited (CVD) before fabrication. SEM observation indicated that the composites were well fabricated by LSEVI. The ultimate tensile strength of 2D-C_f/Mg composites fabricated by LSEVI was 390-410 MPa. Two kinds of failure behavior were found during tensile test: abrupt failure and progressive failure. The abrupt failure was characterized by a complete failure after the ultimate tensile strength (UTS) was reached. The progressive failure was a unique failure behavior with gradual damage after the UTS. In the case of progressive failure, the remaining strength after the UTS was 79% of the UTS. There was a remaining strength of 200 MPa under the strain of 0.1. Fracture surface morphology indicated that the remaining strength was attributed to the gradual breakage of the fiber bundles.

Abstract: Favourable experience with fibre reinforced concrete (FRC) resulted in its increasing use worldwide. The properties of fibre reinforced concrete are mostly influenced by the type and the amount of fibres. Our experimental study was directed to the possible improvements of the residual flexural strength and the properties of concrete exposed to high temperatures with different fibre cocktails including steel, micro polymer or cellulose fibres. The influence of type and amount of fibres on residual flexural strength in cold state were tested after 300, 500 or 800 °C temperature loading.

Abstract: Numbers of residential houses were damaged in some areas caused by earthquakes. The damages greatly affected the number of losses. Most of the houses in some countries are made of brick unreinforced masonry (URM) walls. Improving the structural performance of this kind of masonry has become important. For this reason, experimental study was conducted on the flexural performance of brick walls retrofitted with strapping band (polypropylene/pp-band). The walls were constructed using bricks produced manually with joint mortar ratio of 1 PC: 6 sand, that chosen to represent the actual field conditions of the communities in Indonesia. The aims of the study were to determine the out of plane flexural performance of the non-retrofitted and retrofitted brick masonry walls under cyclic loading by using some variations of the distance between pp-band. The walls were loaded to produce flexural bending that caused vertical and horizontal cracks. The results of the test showed that the retrofitted walls failed by large deformation. After crack, the strength reduced to about 25-50% of the crack load and then regained progressively as residual strength until 150% higher than the strength at crack load by large deformation due to the strapping band mesh. The wall with 10 cm pp-band distance should be used as optimum solution for retrofitting

Abstract: Corrosion defect in oil tubes is one main threat for the safety production of oil field. The corrosion defect in the tube will cause stress concentration and even lead to failure. The injection of CO₂ widely used during the recent years in oil fields, making the corrosion problems more severe. In this study a finite element model for the residual strength analysis of oil tube with corrosion defect was established by the programing language APDL. Based on the actual data of one oil well in Tahe oil field in China, the sensitivities of the axial length, circumferential width, radial depth of the corrosion defect, the internal pressure and axial force on the residual strength of the tube was examined in detail. The proposed method can be referred in the safety evaluation for oil tubes with corrosion defect.

Abstract: The paper discusses durability of glass and carbon fibers which are exposed to alkali environment of concrete. Mainly glass fibers are affected by the high alkali environment with pH of concrete exceeding 12.0. The degradation of fibers is reflected by decreasing of its tension strength, while the rate of decreasing is depended on exposition time and temperature. The paper briefly presents results of a large experimental investigation which should specify an influence of alkali ions concentration in a solution on reduction of the mechanical properties of fibers. Reference samples were immersed in a bath with distilled water and the others were stored at ambient air only.

Abstract: Tubular drive shafts are subjected to combined axial tension, torsional moment and bending moment. The structural integrity of the driveshaft is investigated by evaluating the change in strength, stiffness and the life of the driveshaft with the change in the crack length. A review of driveshaft failure analysis case histories identifies circumferential crack and arbitrarily oriented cracks to be critical. The singular stress field around a crack tip in a general shell structure is characterized by mixed mode membrane and bending stress intensity factors. Accurate determination of these stress intensity factors (less than 1%) are carried out by a subprogram named as 3MBSIF. The validation of Finite element model using ABAQUS and post processing subprogram 3MBSIF together is carried out using benchmarks, a set of standard test problems with known target solutions. Further SIFs are derived for cylindrical shell and the driveshaft under the action of bending moment. To quantify the change in the compliance of cylindrical shell and the driveshaft with change in crack lengths is studied by performing Modal Analysis. It was observed that the variation in frequency is higher for smaller crack angles.