Papers by Keyword: Uniaxial Compression

Abstract: Two sets of cylinder specimens with a height to diameter ratio of 1.5 made of annealed technical copper and AK12pch silumin were tested for uniaxial compression to different degrees of plastic deformation. At the first stage of the experiments, the ends of the specimen were ground on skins of different grain sizes and polished. Then the micro-hardness of the ends of each sample was measured. Micro-hardness measurements were carried out by the Vickers method at three loads on the indenter: 0.196, 0.490, and 0.980 N. At the second stage, the samples were cut along the meridional section, each sample was poured with a compound based on epoxy resin into an individual mold so that the meridional section of the cut sample came out onto the surface of the mold. After the process of grinding and polishing the meridional section, the micro-hardness of the center of the section was measured under the same loads that were used for measurements at the ends. At the third stage, the dependences of the micro-hardness on the intensity of plastic deformation were made. A comparative analysis of the indicated dependences, made from the results of measurements at the ends of the specimen and the surface of their meridional sections, showed that friction at the ends of the specimen during compression has a significant effect on the position of the dependence “micro-hardness - plastic deformation”. The evaluation of hardening based on the micro-hardness of the ends leads to significant errors.

Abstract: Supermacroporous three-dimensional matrices based on poly-D,L-lactide or polycaprolactone were fabricated by thermally induced phase separation method and 3D printing technique. The morphology and mechanical properties of the resulting matrices were studied with the use of optical and scanning electron microscopy and the uniaxial compression test, respectively. All matrices were characterized with supermacroporous structure suitable for cell penetration. A significant increase in Young's modulus and tensile strength was established for both polymer matrices prepared by 3D printing technique.

Abstract: Most dielectric materials and heterogeneous dielectric structures are operated under mechanical loads. Therefore, the usage of acoustic monitoring of the presence of defects and the destruction of such materials is difficult because of the high ultrasound damping decrement in these materials. This article presents assess the influence of the location of steel inclusions relative to the loading axis.

Abstract: This article presents the results of a study of the effect of crack formation in concrete that occurs during uniaxial compression on the parameters of the electrical response under periodic impulse shock action. Researches were conducted on fibre-reinforced concrete samples and samples without reinforcement. It is shown that the method based on mechanoelectric transformations phenomenon can be equally applied to both unreinforced and fibre-reinforced concrete samples.

Abstract: This research studied the fabrication of graphene-reinforced aluminum composite via powder metallurgy and uniaxial pressing. The process started from mixing graphene with aluminum powder with various content of graphene (0.5, 1, 1.5, 2 and 4 wt.%) in acetone medium, followed by dispersion process at high frequency using an ultrasonic bath. The mixed composite powders were then formed into pellet and sintered at 600°C. The results showed that when graphene content in graphene reinforced aluminum composite is low (0.5wt.%, 1wt.% and 1.5wt.%), the hardness was enhanced. It was suspected that graphene could get into aluminum matrix and impede the grain growth of aluminum and dislocation movement. However, when excessive graphene content was added, graphene nanoplatelets tended to agglomerate, decreasing the hardness of composite. Similarly, the improvement of electrical and thermal conductivities was achieved with a low content of graphene. The well dispersion of graphene in aluminum matrix could facilitate the electron transport and to induce the pore reduction throughout the matrix.

Abstract: The hot working flow stress of as-cast and two different extruded magnesium alloys AZ31was examined by uniaxial compression tests. It was found that the hot deformation behavior was affected by the deformation conditions and initial microstructure. The peak flow stress was sensitive to deformation temperature and strain rate, and the value was decreased with decreasing the deformation rate or increasing the deformation temperature. The extruded samples, instead of as-cast samples, have better ductility at high strain rate and high temperature. The temperature increment for Mg alloy with different extrusion ratios was also investigated. These key features of the deformation behavior were explained in terms of twinning, dynamic recrystallization and grain rotation.

Abstract: In this paper the effect of the strain path change was studied in aluminum alloy containing 0,25% Mg. In metals alloys different metal forming processes can create strong crystallographic and morphologic texture. Both of them can cause direction dependency of the mechanical and other properties. The aim of this paper is to analyze how the effect of the increasing reduction of cold drawn wire appears as a result of the uniaxial compression performed in the direction opposite of drawing. Compression test were performed. Through the results of these tests the changes of the direction of deformations were analyzed qualitatively and numerically. These results provide the possibility to use uniaxial compression test to evaluate the mechanical behavior of cold drawn aluminum.

Abstract: Metal forming of magnesium alloys often performed at elevated temperature, because magnesium alloys exhibit peculiar stress-strain relation and inferior ductility compared to conventional metals at room temperature. In the present study, deformation behavior and formability of cast and extruded AZ31 magnesium alloys under uniaxial and biaxial compressions at room temperature and at elevated temperatures were investigated. The results revealed that the compressive stress-strain relation of AZ31 magnesium alloy changed not only with the initial texture but also with the deformation temperature. The temperature dependency of flow stress of the cast alloy was smaller than that of the extruded alloy probably because of less influence of pre-deformation. In addition, the influence of compressive deformation pattern upon flow stress of the extruded alloy remained even at elevated temperature to 523 K. The temperature dependency of compressive fracture was also discussed and it was found that the equi-biaxial condition improved the compressive formability at elevated temperatures.

Abstract: In previous study, the formation behavior of texture and microstructure in AZ80 magnesium alloy under high temperature deformation was investigated. It was found that the basal texture was formed at stress of more than 15-20MPa and the non-basal texture was formed at stress of less than 15-20MPa. This means that stress of 15-20MPa is the change point of deformation mechanism. Therefore, in this study, uniaxial compression deformation of AZ80 magnesium alloy was carried out at high temperature deformation (stress of 15-20MPa). Behaviors of microstructure and texture development are experimentally studied. The material used in this study is a commercial magnesium alloy extruded AZ80. The uniaxial compression deformation is performed at temperature of 723K and strain rate 3.0×10^-3s^-1, with a strain range of between-0.4 and-1.3. Texture measurement was carried out on the compression planes by the Schulz reflection method using nickel filtered Cu Kα radiation. EBSD measurement was also conducted in order to observe spatial distribution of orientation. As a result of high temperature deformation, the maximum value of the flow stress is observed at the true stress-strain curves, and the main component of texture and the accumulation of pole density vary depending on deformation condition.

Abstract: Five series of strain hardening ultra-high performance cementitious composites (SHUHPCC) incorporated with different types of fibers and hybrid fibers were produced. Three types of fibers (steel fiber, polyvinyl alcohol fiber and polyethylene fiber) were used as mono or hybrid reinforcement in SHUHPCC with the same volume fraction of 2%. The primary strengths, strain hardening and multiple cracking behaviors of hybrid fiber reinforced SHUHPCC under the uniaxial tensile are investigated. Test results show that the SHUHPCC containing PE fibers exhibited higher strain hardening capacity and lower first cracking strength than composites reinforced with mono PVA fiber or mono steel fiber. The composites containing PVA fibers or steel fibers have higher tensile strength and first cracking strength than the composite reinforced by mono PE fiber. Hybridization reinforcement with different fibers is able to make up defects of mono fiber reinforcement for SHUHPCC. The change laws of tensile strength and uniaxial compression strength of SHUHPCC with mono PE fiber and mono PVA fiber are opposite to each other.