جستجوی مقالات مرتبط با کلیدواژه « three-point bending test » در نشریات گروه « فنی و مهندسی »

In this study, a biodegradable composite by ML506 as matrix and kenaf fibers as reinforcement was designed, manufactured, and finally, its mechanical properties were investigated. The test samples were manufactured by the Vacuum-assisted resin transfer molding (VARTM) method. To determine the mechanical properties, a tensile test and three-point bending test were performed. Young modulus, yield stress, ultimate stress, maximum elongation, and toughness were obtained from the tensile test. Flexural strength and flexural chord modulus of elasticity were obtained from the three-point bending test. To determine the electrical properties, a dielectric constant test in X-band was performed. The loss tangent, as well as composite products, were obtained. The maximum tensile strength and tensile modulus were achieved in this research respectively equal to 62.42 Mpa and 4.43 Gpa. The flexural strength and flexural modulus were achieved in this research respectively equal to 99.19 Mpa and 5.619 Gpa. The dielectric constant and loss tangent of the samples produced in the X -band were 4.74 and 0.053, respectively. Finally, to validate the results in this research, the result of the tests were compared with the result of the other similar studies.

Because of the inherent structure of welded pipelines, the seam weld can be a potential source for initiation and propagation of crack that can eventually lead to failure of the structure. Due to the critical conditions in the welding region, the investigation of failure energy in gas transportation pipeline is very important for engineers and line designers. In this paper, the three-point bending test (according to the standard specimen of drop-weight tear test) was performed quasi-statically on the seam weld pipe and base metal of spiral seam weld pipe of API X65 steel from which force diagrams were extracted. The presence of sudden load drops in the force-displacement diagram of the specimen in the weld indicated the inhomogeneous structure of the weld. The diagrams of force-displacement, yield and ultimate force, amount of steady crack growth and fracture energy of the metal and seam weld specimens including initiation and propagation energy of crack were investigated and compared. Also, the ratio of the force drop to the ultimate force at the same displacement rate was investigated. The results showed that in seam weld compared to the base metal specimen, the yield force was higher and the ultimate force, the amount of steady crack, initiation and propagation energy of crack were lower. In addition, the lower ratio of force to ultimate force (at the same displacement) in the base metal also indicated a high resistance of the base to the crack propagation.

The welded zone of API X70 steel pipe, due to the inherent defects of welding, is a potential area for initiation and propagation of cracks which can eventually lead to damage of the structure. In this research, mechanical behavior of spiral seam weld was evaluated in API X70 pipe steel in three zones (base metal, HAZ and weld metal) using uniaxial tensile and three point bend (3PB) experiments. Three tensile specimens were used in each zone for measurement of mechanical properties. For studying the mechanical behaviour of the pipe, one specimen with 3PB geometry was tested for each zone. Specific values including yield, peak and final load for 3PB specimen were determined from load-displacement plots. The associated energy for each load plus initiation and propagation energies were calculated and the results were analyzed in relation to microstructure in each zone. With an analytical equation based on slip-line field analysis, yield strength was determined with 3PB specimen in each zone and compared with the result of uniaxial tensile experiment. From uniaxial tensile experiment, yield strength levels of 560, 514 and 507 MPa were found for base metal, HAZ and weld metal respectively and from 3PB experiment 604, 582, 575 MPa respectively. Keywords: Pipe line steel; API X70; Three point bending test; Spiral seam weld; Static fracture energy.