Papers by Keyword: Elastic Modulus

Abstract: Elastic modulus of a coating is an important property for design and use of the coating. At present, many methods have been put forward to evaluate the coating elastic modulus. However, each methods has special property, which make the elastic moduli from them are different. In the study, elastic modulus of a porous Ti coating has been evaluated by three-point bending test and indentation method. The results show that the coating elastic moduli from the two different methods agree well, which can reflect the uniformity of the pore structures of the porous coating. Meanwhile, the little deviations among the different test points of indentation method could reflect the uniformity of the coating structure partly.

Abstract: Every material is structured in its unique way and has its own recognizable microstructure. There are a number of approaches in establishing the relationship between mechanical properties and microstructure of a material, but none of them is universal and correlation free, probably because of luck of attention to the sub-grain structure. The possibility of calculating the hardness number using only geometric sizes of microstructural formations is discussed in this paper, where the grain is meant to be a container of the two most frequently occurred shapes in the microstructures globula and lamellae.

Abstract: Four materials Ti_xTa_1-xCN-20%Co of two chemical composition (x=0.9 and 0.95) and two high energy milling methods have been prepared. Nanoardness and elastic modulus for microstructure as a whole and both phases (matrix and hardmetal grain) were obtained (Tab. 1). Instrumented indentation was cerried out on the nanoindentation equipment TTX NHT (CSM instruments). Single load mode was used. Maximum applied loads of 20 and 50 mN for individual phases and 300 mN and 400 mN for microstructure as a whole were used.

Abstract: The influence of microstructural variations on the macro/microhardness, nanohardness and Young`s modulus of liquid phase sintered silicon carbide (LPS SiC) has been observed. In order to modify the microstructures some samples were further heat treated at 1850°C for 5 hours to promote grain growth. The depth-sensing indentation tests of SiC materials were performed at several peak loads in the range 10-400 mN. For a better assessment, the indentation values of hardness and Young`s modulus modulus of SiC matrix were also compared to the hardness and Elastic modulus of individual SiC grains. The comparison of macro/micro and nanohardness showed that nanohardness was significantly higher, generally by 6-7 GPa. The nanohardness of individual plate-like SiC grains was around 2 GPa higher than nanohardness of SiC matrix.

Abstract: The paper gives a brief overview of various energy approaches and possibilities they offer. Most of it is illustrated on examples from depth-sensing indentation. Components of contact work are listed, and the relationships between these components and material characteristics are given. Also the solution of impact problems is shown, based on the law of energy conservation. Finally, the role of surface energy and adhesion is mentioned.

Abstract: Biological tissues belong to the group of materials highly dependent on its micro structure. A variety of results may be found in the study of human teeth whose local composition and mechanical characteristics show considerable variations. The article deals with the measurement of elastic micromechanical characteristics in the root part of human tooth dentin. An extracted tooth was analyzed in two typical directions, i.e. longitudinal (from the tooth crown-neck to the root) and transverse (in the middle of the root part). Values of the modulus of elasticity in walls of the tooth root in the longitudinal and transverse directions were identified by means of nanoindentation. The development of the modulus of elasticity was measured in several parallel rows proceeding from the outer edge of the tooth root towards the root canal. The values measured in the dentin part of the tooth root ranged around ~17 GPa (cement-dentin boundary), ~23 GPa (middle part of dentin) and ~14 GPa (dentin-root part interface). In the longitudinal section, the value of the modulus of elasticity was almost constant in the majority of tested volume (~18 GPa) with some deviations in peripheral part (end of the root) due to changes in microstructural orientation from sagittal plane. The differences revealed a low degree of anisotropy of dentin.

Abstract: A fire can cause serious damage to steel framed buildings so most of countries have fire regulations specifying fire resistance for structural elements. Fire resistance generally has been evaluated by a limited size testing facility. However, the size of columns and beams are different based on various conditions. Especially, the height of column and boundary condition are the main factors that govern the fire resistance of structural elements. To make a basic database for the H-section made of an ordinary grade structural steel, SM 400, an analysis was conducted by using mechanical and thermal properties with a proper theory. The fact findings suggested that the fire resistance for longer and fixed to fixed column were required a new guide line for covering of fire protective materials.

Abstract: Surface quality of an upper hook, an important fishing net-weaving machine component manufactured from stainless steel, was improved by systematically investigating the effects of sputtering coating factors using experimental design. Three factors of MoN coating on upper hooks including DC current, operating pressure, and Ar/N₂ ratio were studied and optimized for maximum elastic modulus. It was found that the three coating factors affected the elastic modulus of the MoN coating on upper hooks. In addition, the optimal operating condition for MoN coating that produced a maximum elastic modulus was obtained at DC current of 0.35 A, operating pressure of 0.01 mbar, and Ar/N₂ ratio of 1.5.

Abstract: In this paper, the mechanical properties and permeability of the concrete with steel slag coarse aggregates were investigated by comparing with the concrete with crushed limestone coarse aggregates. Results show that the concrete with steel slag aggregates shows similar strength with the concrete with crushed limestone aggregates at the age of 28 days, but it shows a little higher strength especially splitting tensile strength at the age of 90 days. Steel slag coarse aggregates tend to have limited influence on the elastic modulus and permeability of concrete. The results at different water to cement ratios are similar.

Abstract: Due to vehicle load, shrinkage, creep, temperature and other factors, the strength and stiffness degenerate increasingly for the pre-stressed concrete continuous beam bridge in service. The problem, such as cracking, excessive deflection in the mid-span caused by the deterioration of the elastic modulus and pre-stress, has a direct impact on the usability, durability and security. To solve the problem mentioned above, according to the monitored deflection of the bridge in service at different time, the elastic modulus and the effective pre-stress are evaluated by establishing the inversion analysis model based on the inversion theory.