Papers by Keyword: High-Strength

Abstract: The mechanical properties of high-strength reinforced concrete beams strengthened with FRP ( fiber reinforce polymer) are further investigated theoretically including it s failure mechanism and loadability,based on earlier theoretical works on RC beams. And the correlation equation of flexural capacity on the cross section of high-strength reinforced concrete beams strengthened with FRP is deduced according to different types of failure.The correlation equation is shown to be in good agreement with the experimental results, which can be referred to engineering application.

Abstract: A newly developed high-strength reaction-sintered silicon carbide (SiC), which has two or three times higher strength than conventional sintered SiC, is one of the most promising candidates for lightweight substrates of optical mirrors, because of its fully dense structure, small sintering shrinkage ( < 0.5 %), good shape capability, and low sintering temperature. In this paper, in order to improve the performance of the newly developed reaction-sintered SiC, the effect of the microstructure on the bending strength was investigated by focusing on a physical fracture model using observations from transmission electron microscopy and X-ray stress measurement. As a result, it was confirmed that the bending strength of the newly developed reaction-sintered SiC could be improved by reducing the size of residual silicon. The strengthening mechanism of the newly developed reaction-sintered SiC was assumed to be due to piled-up dislocations at the grain-boundary of residual silicon sites, based on Stroh’s fracture model of polycrystalline solids.

Abstract: According to preparation of noise-reducing concrete with the technology of exposed-aggregate, this paper exploits high performance roller compacted concrete used in tunnels. Based on optimizing proportion, exploiting special exposed-aggregate agent and corollary technology, it is necessary that the high strengthening and the stability in the Course of Using of the exposed-aggregate roller compacted concrete should be further studied. During the study on the properties of strength change of common strength grade exposed-aggregate roller compacted concrete pavement, it found that its strength varied from 38.6MPa to 19.2MPa when the depth of exposed-aggregate reached 3mm.This is the main reason that serious damage occurred in one tunnel pavement which is used less than one year. Consequently, this paper carried out experimental study of high strengthening. Furthermore, this paper have been optimized the parameters of exposed-aggregate roller compacted concrete. And the effect is relatively remarkable.

Abstract: This paper investigated solid freeform fabrication(SFF) and microwave sintering processes of high strength HA porous scaffold. A newly developed SFF method called motor assisted micro-syringe freeform fabrication system was introduced to construct HA scaffolds. Sintering conditions that influenced the phases, microstructure and mechanical strength of scaffolds were discussed. Study of microstructure images and strength test results showed that densification and grain size were found to play an important role in determining the mechanical properties of sintered porous scaffolds, and microwave sintering process could get a sintered scaffold with small grain size and uniform structure more rapidly at lower sintering temperature than that of the conventional sintering. The fabricated HA scaffolds with controlled architecture (interconnected macro pore of 200-400μm, micro pore of 1-10μm within the rods) and improved mechanical properties (45.2MPa, 56.2% porosity ) may find potential applications in bone tissue engineering.

Abstract: Two kinds of oil tank steels were fabricated by added B(B-steel) and Cu(Cu-steel) , and their microstructures, tensile and Charpy impact properties, undercooled austenite transformation were investigated. In this work,0.0016%B can improve hardenability distinctly. The B-steel was mainly composed of bainite at the cooling rate of 3°Cs^-1, but the Cu-steel completely consisted of bainite when the cooling rate exceed 20°Cs^-1. The steels manufactured by thermo-mechanical controlled process , test results indicated that the B-steel had the higher yield and tensile strength than the Cu-steel ,because their volume fractions and morphologies of bainite. The Cu-steel had the higher impact energy than the B-steel because of their higher effective grain size. Majority of the precipitation particles which were compounded of Nb and Ti existed as（Nb_x,Ti_(1-x)) (C_yN_(1-y)).

Abstract: Rock chips is a potential substitutable material for river sand, which can effectively solve the shortage problem of the river sand in concrete. At present most studies are about the rock chips concrete concentrate on the normal-strength concrete. The studies about rock chips as a substitution for river sand in C80 high-strength concrete were carried out. At first the basic physical properties of raw material are analyzed and the performance requirements of the concrete are confirmed. And then on the basis of the river sand concrete, the influence of the dosage of rock chips on the C80 high-strength concrete at the same water-binder ratio was studied. The particle size of rock chips larger than 4.75mm was considered as the coarse aggregate. The results showed that the C80 high-strength rock chips concrete can be prepared by increasing the dosage of superplasticizer and binder. The early age strength of high-strength rock chips concrete is higher than that of river sand concrete, while the contrary results of the long-term strength. Considering lots of fine powder in the rock chips, the coarse sand and rock chips are mixed to be used, the mixing ratio needs to be determined by experiments. In the high-strength concrete, the rock chips with good particle size distribution and with lower content of particle size larger than 4.75mm is better.

Abstract: Aiming at large and thick automobile die casting as well as combining with production practice, the main factors which influence the strength of gray iron in electric furnace are investigated and the smelting technology of electric furnace for thick and large gray iron with high strength is proposed in this paper. The result shows that the tensile strength of attached test specimen or hardness of casting can meet the application requirements greatly. This smelting technology provides reference for large and thick castings smelting under similar conditions.

Abstract: Three key points are discussed to manufacture 300Mpa cylinder block castings. The first one is the design of grey iron chemical composition. The chemical composition used for production is as follows: C: 3.20-3.30%, Si: 1.60-1.80%, Mn: 0.70-1.00%, S: <0.10%, P: <0.06%, Cu: 0.70-0.80%, Cr: 0.25-0.35%, Ni: 0.30-0.40%, Sn: 0.06-0.08%. The stream inoculation is adopted. Another key point is to increase the chilling effect of molding material. A kind of ceramic sand is used in the experiment. The ceramic sand is mainly composed of electric fusion bauxite. The material gives much stronger chilling effect. The tensile strength can be 20 MPa higher compared with ordinary silica sand. The third key point is to use the technology of synthetic cast iron. The 300 MPa cylinder block is successfully developed.

Abstract: High strength hull structural steel plate FH40 has been successfully developed by a 3500mm plate production line. Low-carbon micro-alloying niobium elements and TMCP (thermo-mechanical controlled processing) were employed to refine the grains and improve mechanical properties. This paper investigated the effects of TMCP process on the microstructure and mechanical properties of the rolled FH40 plate. Results indicate that the treatment could significantly improve the mechanical strength and impact toughness of the steel and the impact ductility was further enhanced after strain aging. The properties of plates remarkably satisfied with the requirements of the national standard of china and rules requirements by shipping classification associations.

Abstract: The application of vanadium-nitrogen alloy to develop a certain low carbon high strength H-beam steel was determined through the combination of theoretical study, product requirements and existing practical conditions. The specific rolling process was further defined through laboratory experiments. The developed low carbon high strength H-beam steel was trial produced and its properties were also analyzed. The results showed that the newly developed low carbon high strength H-beam steel had excellent mechanical properties and good weldability.