Papers by Keyword: Compressive Property

Abstract: Two new AZ31 nanocomposites containing Al2O3 nanoparticle reinforcement were fabricated with different reinforcement integration methods using solidification processing followed by hot extrusion. Each nanocomposite had similar composition (Al and Zn contents), microstructure (grain and intermetallic particle sizes, Al2O3 nanoparticle distribution) and hardness. However, the first nanocomposite had better overall tensile properties compared to the second nanocomposite. Also, the second nanocomposite exhibited better overall compressive properties compared to the first nanocomposite. On the whole, the second nanocomposite was more deformable in tension and compression than the first nanocomposite. The effect of reinforcement integration method on the tensile and compressive properties of the AZ31- Al2O3 nanocomposites is investigated in this paper.

Abstract: In the coming decades, the need for reconstructive surgery of bones is predicted to increase with the ageing of the population as well as the increase of injuries needing traumatologic treatments. Therefore, there is still a constant search for tissue engineering and bone substitute materials. Xenografts, synthetic hydroxyapatitite, bioactive glasses and other bone substitutes have widely been studied. When bone defects are filled using bioceramics in granules, their utilization is limited to small size defects, because the injected granules do not give immediate support against the biomechanical loading of the bone. The aim of this study was to evaluate the preliminary biomineralization and the compression strength of experimental injectable bone cements modified with calcium ceramics. Our studies have focused on the development of injectable composites of bone cements, i.e. in situ curable resin systems containing impregnated Ca ceramics. The polymerized bone cement composites aspire to simulate as closely as possible the mechanical and structural properties properties of bone. The present compressive strength of our inorganic-organic bone cements are >65 up to ~180 MPa. These cements are slightly porous from their outermost surface and showed preliminarily osteoconductivity of some degree.

Abstract: Artificial neural network (ANN) is an intriguing data processing technique. Over the last decade, it was applied widely in the chemistry field, but there were few applications in the porous NiTi shape memory alloy (SMA). In this paper, 32 sets of samples from thermal explosion experiments were used to build a three-layer BP (back propagation) neural network model. According to the registered BP model, the effect of process parameters including heating rate ( ), green density ( ) and particle size of Ti ( d ) on compressive properties of reacted products including ultimate compressive strength ( v D σ ) and ultimate compressive strain (ε ) was analyzed. The predicted results agree with the actual data within reasonable experimental error, which shows that the BP model is a practically very useful tool in the properties analysis and process parameters design of the porous NiTi SMA prepared by thermal explosion method.

Abstract: Biodegradable polymers (e.g. poly-ε-caprolactone, PCL) have been studied largely for tissue engineering applications. The aim of this study was to evaluate the composite fabrication technique on PCL modified with the phosphate salts (i.e. NaH2PO4, Na2HPO4, KH2PO4, or K2HPO4) as well as to determine the compression strengths thereof. The chemical structure and morphology of composites were analyzed using FTIR and SEM/EDX. The influence of a plain phosphate salt in different quantities on the hydrophilic properties of PCL was evaluated by measuring the water contact angle. The results of this study indicated that the addition of phosphate salts led to an improvement in compression strength of PCL composites. According to the results of preliminary biomimetic mineralization, Na2HPO4 seems to increase the bioactivity of PCL.

Abstract: Nb-Si based in-situ composites have great potential for the application of high temperature structure components. In this paper, the influence of microstructure on the compression behavior of Nb-Si in-situ composite forged at high temperature was studied. The alloy with nominal composition of Nb-12Si-24Ti-4Cr-4Al-2Hf was consumable arc-melted, and then isothermal forged at 960°C. Scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) and X-ray diffraction (XRD) were used to characterize the microstructure, composition and phases. The compressive behaviors at 1250°C were carried out by Gleeble thermo-mechanical simulator. The results showed that the microstructures were inhomogenous in the different sections of the ingot, and no evident directional texture formed, and the main phases were niobium solid solution, Nb5Si3 and Ti5Si3. However, no macro-elements segregation in the ingot was observed. The compression strength was in the range of 140-360MPa. BSE observation showed that irregular-shaped Nb5Si3 and Ti5Si3 phases distributed in Nb solid solution and the size of Nb5Si3 in three tested samples was 10μm. Large size of eutectoid texture existed in the sample with strength of ~140MPa. On the contrary, in the sample with higher strength of 360MPa, eutectoid structures were hardly detected. The results suggested that the strength decreased gradually with size increase of eutectoid structure.

Abstract: Quartzite microcrystallite glass ceramics is one of the most promising machinable ceramic materials due to its many outstanding properties. The density of quartzite microcrystallite glass ceramics is smaller than the aluminum alloy and its thermal conductivity approaches to the zirconia and its elastic module is also very small; All these advantages meet the requirements for structural components to work at higher temperature; Compressive properties of quartzite microcrystallite glass ceramics had been studied at room temperature and 500°C in this paper; The specimens had been aged at 1000°C for 5, 10, 20, 30 hours, respectively. Through SEM observations of the fracture surface of the specimens, the microstructural changes had been determined; The tests showed: the compressive property of the machinable glass ceramic declined as the ageing time increasing; but the compressive property of the specimen aged for 10 hours was inferior to that aged for 20 hours; Then compressive property declined as the ageing time increasing. The SEM observation indicated that with the extend of ageing time, the grains grew bigger and microporous and microcracks increased in the specimens; Comparing the compressive property at room temperature with that at 500°C, one found that the change of compressive property was very small when the ageing time was the same; With the extend of ageing time, the curve of the compressive property changed from smooth curves to broken lines.

Abstract: This paper presents a study of heat treatment on the quasi-static and dynamic compressive properties of the open cell aluminum alloy foams in as-fabricated (F), age-hardened (A) and T6-strengthened (T6) conditions. Although the strain rate and heat treatment of foams are different, all exhibit similar deformation behavior in the subsequent deformation. The yield stress of foams at different strain rates are improved by heat treatment, all exhibit some strain rate sensitivity. However, the densification strain of foams is not sensitive to heat treatment.

Abstract: Spacer method is excellent technique of processing porous metals with well-controlled pore characteristics such as porosity (up to 90%) and pore size (as small as several hundred micrometers). Compressive properties of porous aluminum fabricated by the spacer method are investigated. They were subjected to monotonic compression tests at room temperature, and showed less fluctuated flow stress during their compressive deformation than conventional porous aluminum alloy, reflecting their homogeneous pore characteristics. Also, shortening behavior of the porous aluminum fabricated by the spacer method during cyclic compression was significantly differed from that of conventional porous aluminum alloy. Therefore, it can be concluded that the homogeneity of pore characteristics is responsible for compressive properties of porous metals. Monotonic compression tests on porous copper specimens with various porosities, which were made by the spacer method, were also conducted. The yield stress of the porous copper with high porosity (or low relative density) depended on the relative density more strongly than that of the porous copper with low porosity (or high relative density). It is presumed that porous metals with high porosity and ones with low porosities have different deformation mechanisms.

Abstract: Porous Ti51Ni(49-x)Mox (x=0, 0.7, 1.0, 1.2) shape memory alloys were successfully fabricated by the self-propagating high-temperature synthesis (SHS) method. The effect of Mo content on microstructures, transformation characteristics and compressive properties of porous TiNiMo alloys was investigated systemically. It has been found that Mo doping into porous TiNi alloys will induce R phase transformation. A small amount of Mo addition (0.7at.%) improves compressive properties of porous TiNiMo alloy due to Mo solution strengthening and the obvious ductile fracture is observed on the fracture photography. However, the compressive strength and compressive strain of porous TiNiMo alloys with excessive Mo content decrease sharply and the failure manner turned into brittle fracture mode, which results from a large amount of Ti2Ni and Ti4Ni2O phases precipitated at grain boundary. Porous Ti51Ni48.3Mo0.7 alloy with suitable transformation temperature and high compressive strength is very promising for use as biomaterial and damping material.

Abstract: The hybrid materials with Al-Mg alloy and its composites reinforced with SiC and Al2O3 particles were prepared by conventional powder metallurgy method. The Al-5wt%Mg and composite mixtures were compacted under a pressure of 400MPa and sintered at 873K for 5h. The obtained hybrid materials with Al-Mg/SiCp composite showed the higher relative density than those with Al-Mg/Al2O3 composite after compaction and sintering. In the composite side of hybrid materials, the SiC particles were densely distributed compared to the Al2O3 particles. The hybrid materials with Al-Mg/SiC composite showed higher micro-hardness than those with Al-Mg/Al2O3 composite. The mechanical properties were evaluated by the compressive test. The hybrid materials revealed almost the same value of 0.2% proof stress with Al-Mg alloy. However, their compressive strength was lower than that of Al-Mg alloy, resulting from the fracture occurring along the microinterface between matrix and reinforcements in the macro-interface.