Papers by Keyword: Compressive Property

Abstract: As-cast AM60 magnesium alloy was solid dissolved with exercising different pressures (atmospheric-pressure, 3, 4 and 5 Gpa) to it and subsequently aged for 10 h at 200 °C under atmospheric-pressure. The aging alloys were characterized by optical microscope, and their compressive properties were investigated by a Gleeble-3500 hot-stimulation machine. The results show that, compared with exercising atmospheric-pressure during solution treatment, exercising high-pressure during this process causes that the α-Mg grains of the subsequent aging alloy are more fine and uniform, while the β-Mg17Al12 phases transform into fine particles and aggregate to form gobbets or strips. With increasing the pressure gradually, the compressive strength of the aging alloy increases up to 4 Gpa and then decreases, while the maximum plastic strain decreases up to 4 Gpa and then increases.

Abstract: Porous NiTi alloys were prepared by powder metallurgy method using NH₄HCO₃ as space-holder. The effect of sintering temperature on pore characteristic, phase composition and compressive property of porous NiTi alloys was studied by XRD, SEM, EDS and a universal testing machine. The results show with the increase of sintering temperature the porosity of porous NiTi alloys first increases and then decreases, but the content of NiTi phase, compressive strength and modulous of sintered products continuously increase. When sintered at 980°C for 2h, the porous NiTi alloys have higher porosity of 53.6%, better compressive strength of 173.7MPa and elastic modulous of 4.2GPa. The phases of sinter products are mainly composed by TiNi, Ti₂Ni, and TiNi₃ phases.

Abstract: The compression tests were carried out to investigate the compression behavior of steel fiber reinforced ultra high strength concrete(SFRUHSC). Cubic and axial compression specimens were tested at room tempreture, in terms of load control. The result shouwed that the compression strength of 150×150×150mm³and 100×100×100mm³ cubic specimens is 108.4MPa and 94.7MPa, while the 100×100×300mm³ axial specimens’ is 73.4MPa. The above data demonstrated that the different size effect from that of strength of steel fiber reinforced concrete(SFRC), namely the strength of 100×100×100mm is larger than that of 150×150×150mm³. Two kinds of compression specimens showed various fracture mode: ductile tension fracture of cubic specimens and the brittle shearing fracture of axial ones. But the steel fibers inside the specimens had been pulled out from the matrix.

Abstract: Dynamic compressive tests of plain concrete specimens (C30 and C40) are carried out on MTS, with the uniaxial strain rate ranging from 10^-5/s to 10^-2/s. The impacts of strain rates on concrete strength are studied systematically. The mechanical properties of compressive strength, elastic modulus and compressive stress-strain curve of concrete under different stain rates are also analyzed. The experiental relationships between strain rate and compressive strength of concrete are established. It is found that the compressive strength of concrete increases with the strain rate increasing. Modulus is also showing a growth trend, but the growth rate varies greatly; and the stress-strain curve under dynamic loads is similar to the one under static loads. These research achievements can provide us with a more accurate grasp of concrete actual working conditions and provide some guidance to structural design of concrete. These are important to build the dynamic damage constitutive models, too.

Abstract: This paper investigated the microstructures and compressive properties of hot-rolled Mg-Zr-Ca alloys for biomedical applications. The microstructures of the Mg-Zr-Ca alloys were examined by X-ray diffraction analysis and optical microscopy, and the compressive properties were determined from compressive tests. The experimental results indicate that the hot-rolled Mg-Zr-Ca alloys with 1% Ca are composed of one single a phase and those alloys with 2% Ca consist of both Mg₂Ca and a phase. The hot-rolled Mg-Zr-Ca alloys exhibit typical elongated microstructures with obvious fibrous stripe, and have much higher compressive strength and lower compressive modulus than pure Mg. All the studied alloys have much higher compressive yield strength than the human bone (90~140 MPa) and comparable modulus with the human bone, suggesting that they have a great potential to be good candidates for biomedical applications.

Abstract: In this paper, the influence of hydrothermal environment on the composite laminate plate with a hole is studied by experiment method. The test setup is design for prevent the bucking of the plate specimen, which is composed two main parts. The slide part limits the movement of the specimen along the load direction. Three types of ply stack composite laminate plate are tested. Results show that the strength of all the type of laminate plate in the hydrothermal environment reduces on the contrast to the room temperature and dry environment. But the reduction relatives the ply stack of laminate plate. [45/0/-45/90]_2S plate reduces smallest. [45/0/0₂/45/90/-45/0/45/902/-45/0]_S plate reduces most.

Abstract: The 3D needled C/SiC composites were fabricated by chemical vapor infiltration combined with liquid melt infiltration. The microstructure and compressive behavior of 3D needled C/SiC composites were investigated. The results indicated that the 3D needled C/SiC composites were composed of the layers of 0 ° non-woven fiber cloth, short fiber web, 90 ° non-woven fiber cloth, and needle fibers. The materials were composed of carbon fiber, PyC, Si, and SiC. SiC and Si were mostly distributed in the short fiber web layers. Local C/C units (local carbon fiber reinforced PyC) were formed in the fiber bundles of non-woven fiber cloth. A great deal of pores and cracks existed in the 3D needled C/SiC composites. The pores less than 10 μm were generally located in the non-woven cloth layers, while the big pores were in the short fiber web layers. The cracks were regularly presented in the Si and SiC region of the composites and were normal to the axial direction of the fiber bundles. The compressive strengths perpendicular and parallel to the non-woven fiber cloth were about 118±18 MPa and 260±41 MPa, respectively. The compressive fractography revealed stepwise fracture along fiber layers direction.

Abstract: A series of rigid polyurethane foams are synthesized via the reaction of isocyanate terminated polyimide prepolymers with polyether polyol. Deionized water and n-pentane are used for blowing agents. The prepolymers and polymers are characterized by conventional methods, and physical, mechanical and thermal properties are studied. The results show that in comparison to pure polyurethane foams, these rigid polymer foams exhibit improved thermal stability as well as good compressive property. SEM of the compressed body of rigid polyurethane-imide foams show that the destructive forms are open-type tear of the film and the breakdown of the cell body wall.

Abstract: Aluminum foams with low relative density, especially less than 0.1, persist unique physical, mechanical and acoustic properties. There is a need of this modern material for special applications and scientific research. However, preparation of this super-light metal foam is quite difficult for the cell size of the foams would increase with its porosity. In this study, carbon fibers are used as novel stabilize additive for aluminum foams and the influence of alloying elements on cell wall thickness and area of Plateau border are studied. The results indicate that the cell wall thickness and bubble coarsening rate of the foam would decrease much when Mg is added into the melt and the relative density of prepared foam can be as low as 0.08. Results of compressive tests reveal the fact that these aluminum foams show a lower compressive strength. The plastic deformation region of this new foam is long and it performs good energy absorption capacity.

Abstract: In this paper, the simulation of the commpress properties of Al foam was investigated by finite element methods. The simulation results show that the compressive yield strength of Al foam is consistent with the theoretical model of Gibson and Ashby. The yield strength of Al foam decrease with the increase of porosity, and the yield strength decreases significantly with the increase of porosity. The density of Al foam is proportional to the compressive strength. At a certain porosity, the ratio of sample size and the aperture have an extremely important effects on compressive behavior of aluminum foam. When 4 ≤ D / d <8, with the increase of the ratio of D / d, the plastic deformation plateau and the compressive strength of metal foam is increasing ; on the contrary ,when the ratio> 8, with the increase of the ratio, the plastic deformation plateau is decreasing, the compressive strength keeps constant.