Papers by Keyword: Ductility

Abstract: The aging of asphalt pavement gets serious in the course of service due to the large number of vehicles and high pavement temperature. A survey was conducted on urban road’s asphalt pavement in the city of Tianjin. By analyzing the extracted asphalt sample from asphalt pavement built in different years, it shows that asphalt’s softening point and viscosity increase but its penetration and ductility attenuate with the extension of service period. Of which, the ductility changes dramatically with its ductility attenuating fast in the early years of service and the attenuation of ductility tending to slow down later. The vertical difference of aging in different depth of pavement is marked and degree of aging tends to attenuate from the surface to the center.

Abstract: The microstructure and properties of Q&P steel were studied by means of tensile test, OM and SEM after simulating heat treatment process in salt bath furnace. The results showed that the main microstructure of Q&P steel was lath martensite and retained film austenite. With the increase of partitioning time, the morphology of the parallel martensite lath became clear and ordered. With the trivialness and disorder with massive martensite appearing, the yield strengths and tensile strength decreased initially and then increased. On the other hand, the elongation increased initially and then decreased. This was because of that the retained austenite is unstable at the beginning for low carbon content, and the carbide precipitated after a long partitioning time. Therefore, there was an optimum partitioning time to obtain the best properties combination. Under 250 quenching temperature and 350 partitioning temperature, partitioning time was 60s, the tensile strength and elongation were 1027MPa and 27%, respectively. The product of strength and elongation was up to 27729MPa·%.

Abstract: In this study, based on cast Ti-47.5Al-2.5V-1.0Cr (at. %) alloy with the directional lamellar microstructure, the influence of exposure at 750 in air on room temperature tensile ductility was investigated as a function of time, ranging from1hr to 300hr, in order to determine the onset exposure time for a significant reduction in RT ductility and the fracture mechanism for the exposed specimens. The results indicated that this alloy could still retain more than 2.0% of its ductility after exposure at 750 for 150hr, and its ductility decreased to 1.58% and ~1.0% even after exposure for 200hr and 300hr, respectively. High ductility for the directional lamellar microstructure could be retained after exposure for 150hr, which was attributed to its high crack origination and propagation resistance at specific lamellar orientation. And the fracture mechanism of the exposed specimen with this special structure would also be discussed.

Abstract: In order to research seismic behavior of flat columns under bilateral cyclic loading with different angles, pseudo-static tests are conducted, which includes three 1:2 scaled flat columns. The height-width ratio of the column section is 5. And the loading directions are 00, 250 and 450 respectively. By observation of the test phenomenon and analysis of the data, the seismic performance of the columns including stiffness, skeleton curves, hysteresis curves, ductility and energy dissipation are obtained. Moreover, finite element program ANSYS is employed to simulate the bearing capacity of specimens. The research shows that with the loading angles increasing from 0 to 45, the strength of the flat column decreased gradually, while the ductility and energy dissipation capacity increase, and the failure mode changed from compression-shear to compression-bending. P-Δ effect becomes evident at lager values of loading angle. The compression-shearing curve of flat column complies with a heart-shape curve.

Abstract: Concrete is usually described as a three-phase material, where matrix, aggregate and interface zones are distinguished. The beam lattice model has been applied widely by many investigators to simulate fracture processes in concrete. Due to the extremely large computational effort, however, the beam lattice model faces practical difficulties. Moreover, real fracture processes are 3D and not 2D. In our investigation, a new 3D lattice called generalized beam (GB) lattice is developed to reduce computational effort. Numerical results obtained by the model are in agreement to what are observed in tests. The 3D effects of the particle content on the peak load and ductility are discussed as well as the 3D fracturing phenomenon.

Abstract: Influence of the combined action severe deformation and a pulse current on a microstructure and mechanical behavior of long-size rods and strips with thin section out of Ti50Ni50 and Ti49.3Ni50.7 alloys is presented. Dependence of electroplastic effect on phase composition of the initial alloys is demonstrated. It is established, that electropulse postdeformation processing promotes acceleration of a stress relaxation at stages of recovery, polygonization and recrystallization in alloys.

Abstract: In order to enhance the seismic behavior of reinforced concrete (RC) columns more efficiently, a thought to strengthen concrete columns by using steel bar/wire mesh mortar （FS）was proposed. An experimental study including five RC square columns strengthened with FS and steel bar mat mortar (S), respectively, under constant axial loading and lateral cyclic loading was carried out. Seismic bearing capacity, ductility, failure modes and hysteretic characteristics of all columns were tested, and the effect of reinforcement ratio and strengthening method to the tested columns was analyzed. The results showed that the energy dissipation capacity of FS strengthened columns was 73% higher than that of the S strengthened column, though the reinforcement ratio of the former was only 3.02% higher than that of the latter.

Abstract: Square concrete-filled steel tubes (CFSTs) are gaining increasing usage in modern construction practice, offering improved mechanical properties and increased material efficiency compared with the individual steel and core concrete components. However, the cross-section slenderness of the encasing steel is, although more inflexible than a comparable hollow steel tube, restrained due to local buckling. A number of innovative kinds of reinforcement stiffeners have been put forward particularly for the square CFSTs with slender sections of encasing steel. To investigate the mechanical effect of the reinforcement stiffeners and compare them with traditional ones in practice, four square CFSTs welded with various reinforcement stiffeners and one reference CFST have been tested, and are presented in this paper. The mechanical behaviors such as the resistance, ductility and failure mode investigated during the test were also studied in the theoretical research, which was carried out to predict and summarize the comprehensive properties of the specimens.

Abstract: The experimental work on two full-scale precast concrete beam-column corner joints with corbels was carried out and their seismic performance was examined. The first specimen was constructed without steel fiber, while second specimen was constructed by mixed up steel fiber with concrete and placed it at the corbels area. The specimen were tested under reversible lateral cyclic loading up to ±1.5% drift. The experimental results showed that for the first specimen, the cracks start to occur at +0.5% drifts with spalling of concrete and major cracks were observed at corbel while for the second specimen, the initial cracks were observed at +0.75% with no damage at corbel. In this study, it can be concluded that precast beam-column joint without steel fiber has better ductility and stiffness than precast beam-column joint with steel fiber. However, precast beam-column joint with steel fiber has better energy dissipation and fewer cracks at corbel as compared to precast beam-column joint without steel fiber.

Abstract: Complex sheet metal components can be formed from lightweight aluminum and magnesium sheet alloys using superplastic forming technologies. Superplastic forming typically takes advantage of the high strain-rate sensitivity characteristic of grain-boundary-sliding (GBS) creep to obtain significant ductility at high temperatures. However, GBS creep requires fine-grained materials, which can be expensive and difficult to manufacture. An alternative is provided by materials that exhibit solute-drag (SD) creep, a mechanism that also produces elevated values of strain-rate sensitivity. SD creep typically operates at lower temperatures and faster strain rates than does GBS creep. Unlike GBS creep, solute-drag creep does not require a fine, stable grain size. Previous work by Boissière et al. suggested that the Mg-Y-Nd alloy, essentially WE43, deforms by SD creep at temperatures near 400°C. The present investigation examines both tensile and biaxial deformation behavior of ElektronTM 43 sheet, which has a composition similar to WE43, at temperatures ranging from 400 to 500°C. Data are presented that provide additional evidence for SD creep in Elektron 43 and demonstrate the remarkable degree of biaxial strain possible under this regime (>1000%). These results indicate an excellent potential for producing complex 3-D parts, via superplastic forming, using this particular heat-treatable Mg alloy.