Papers by Keyword: Young’s Modulus

Abstract: The Oliver–Pharr method has extensively been adopted for measuring hardness and Young’s modulus by indentation techniques. However, the method assumes that the contact periphery sinks in, which limits the applicability to the materials pile-up [1]. In this work, we characterize the pile-up (shape and height) in steel sheets with different mechanical properties and propose an improved methodology to calculate the real mechanical characteristics of steel sheets with significant pile-up. Pile-up correction of mechanical characteristics is based on ratio of pile-up height and contact depth. Pile-up height was measured by atomic force microscopy (AFM).

Abstract: This article deals with the usage of recycled concrete, which arises from the demolition of concrete structures. The work is focused on the development of mechanical properties (Young's modulus) depending on the microstructure of composite cement based materials with different percentage of fine ground recycled concrete as a partial substitute of the filler in the cement mixture, which under certain circumstances also functions as a binder component. To assess of the microstructure there were used images from the optical and scanning electron microscopy. There were used four mixtures of the cement pastes containing 0, 33, 50 and 67 wt. % of finely ground recycled concrete. Development of Young's modulus was measured by nondestructive method. The results showed that of the captured images of surfaces of individual mixtures with increasing amounts of fine ground recycled concrete is seen an increasing amount of pores, which results in a loss of cohesion of the cement matrix and decrease of the Young's modulus.

Abstract: Considering the size of the natural appearance of the micro alloy components of a SAC solder joint, AFM was used to investigate their mechanical properties in the form of their natural appearance. Contact-mode point-spectroscopy was done to determine the elastic modulus and tapping-mode point-spectroscopy was done to investigate the tip-sample power dissipation.The measured Young’s modulus values of the Cu, IML, Ag₃Sn and Sn components, were 125±9 GPa, 111±20 GPa, 67±11 GPa and 57±16 GPa, respectively. The dissipation measurements were accomplished by Si and diamond probes with different spring constants. The different characteristics of the results are discussed.

Abstract: Young’s moduli of coatings in the both perpendicular and horizontal directions were evaluated by the relative method, which are determined via establishing the relationship between the uncoated specimen and the coated specimen, with different coating positions during the loading tests. Compared with other traditional methods, the relative method is much simpler in both sample pretreatment and testing device. The validity and reliability of this method has been demonstrated by the beam specimens with CVD-SiC coatings, which will be applied to establish and improve a simple and reliable evaluation system for the anisotropy of coating modulus.

Abstract: Structural and mechanical behavior of thin hydroxyapatite (HA) films deposited via radio-frequency magnetron sputtering on AZ91D magnesium alloy was investigated. Nanoindentationwas employed to evaluate nanohardness and Young’s modulus of the uncoated and HA-coated AZ91 magnesium alloy. The HA-coated AZ91D magnesium alloy exhibited a higher hardness of 7.1 GPa and a higher modulus of 86 GPa compared withthe uncoated substrate revealing a strong load-bearing capacity.

Abstract: The viscoelastic properties of glass under different temperature are essential for the high-precision thermo-plastic-forming of glass. But it is exceptionally difficult to establish a quantitative relation between the thermal history and the viscoelasticity owing to the lack of constitutive model of glassy materials’ relaxation. The present work investigates the validity of Young’s modulus measurement in impulse excitation technology and then the viscosity predicted by Kelvin and Maxwell model. It is demonstrated that the classical Kelvin model, leads to the seemingly unphysical result that viscosity increases with temperature since the experimental loss rate of damped vibration increases with temperature. Although Maxwell model can be employed to explain the positive temperature dependence of loss rate, the magnitude is even smaller than the viscosity at glass transition temperature and is therefore also unreasonable. The further theoretical work suggests the intermediate zone of Kelvin and Maxwell model.

Abstract: Human cryopreserved allografts of pulmonary and aortic valves are routinely used as total valve replacement. For successful surgery it is needed to sufficiently preserve biomechanical properties and histological structures of allografts. However, it is not known how the mechanical properties of these allografts relate to their histological composition. The aim of our study was to compare the histological composition and mechanical properties of the valves. From allografts we prepared 2 valve cusps and samples of aorta or pulmonary trunk. In a previous study we had measured following parameters: ultimate stress, ultimate strain, Young’s moduli of elasticity, intima-media thickness, wall thickness, area fraction of elastin and area fraction of collagen in the whole wall. We found weak positive correlation between ultimate stress and Young’s modulus in small and large deformation with wall thickness in the valve cusps. In the arteries we found positive correlation between Young’s modulus in large deformation with intima-media thickness and ultimate strain with intima-media thickness and area fraction of collagen, and negative correlation between ultimate strain with area fraction of elastin. In our study we quantified also the other components of wall with mechanical significance, such as the fraction of smooth muscle cells and chondroitin sulfate, which belong to glycosaminoglycans. We did not find correlation between these components and mechanical properties of these valves. Therefore, it is recommended to perform both mechanical and histological analysis to further characterize cryopreserved allografts.

Abstract: Case study on copper-tungsten metal-matrix composite was performed. The influence of presence of an interface on the distribution of measured hardness and/or modulus was incorporated by a statistical distribution taking into account a progressive change of materials behavior as a function of depth of penetration. Unbiased (intrinsic) material properties (hardness and Young’s modulus) were then successfully extracted from the experimental grid indentation data.

Abstract: The Young’s modulus of Ti-Cr-Sn-Zr alloy varies with the composition of Cr, Sn and Zr, in which the elements act as β stabilizers. Some Ti-Cr-Sn-Zr alloys show very low Young’s modulus under 50GPa. The amount of Zr in alloys with very low Young's modulus increases with the decrease of Cr. We investigated the Young’s modulus and deformation behavior of Ti-xCr-Sn-Zr (x=0~1mass%) alloys containing a large amount of Zr. The quenched microstructure of Ti-Cr-Sn-Zr alloys changes from martensitic structure to β single-phase structure if the amounts of β stabilized elements are increased. The Ti-Cr-Sn-Zr alloys with compositions close to the transitional composition of microstructure from martensite to β phase show minimum Young’s modulus. The clear microstructural transition disappears and the minimum Young’s modulus increases if the amount of Cr becomes too small. In Ti-Cr-Sn-Zr alloys containing a large amount of Zr, Young’s modulus depends on β phase that is intermingled with martensite.

Abstract: The microstructure, phase composition and nanomechanical properties of AlCu2Si1Mg0.6 alloy was studied where partial melting of grain boundaries during quenching. It was assumed that the following two low-melting eutectics were present along the grain boundaries: α-Al+Cu₂Al+Mg₂Si and α-Al+Al₁₅(Fe,Mn)₃Si₂+Si. The measurements of nanohardness and the Young’s modulus in the sub micro volumes were carried out by means of the nanoindentation method using a NanoScan-4D scanning nanohardness tester. An algorithm offered is for calculating the additional pressure that occurs when the mechanical action on the metal having a partial melting of grain boundaries.