Papers by Keyword: Elastic Modulus

Abstract: Due to many different characteristics such as irregular polygon particle with pointed edges, rough surface and larger content of stone powder, machine-made sand has ignorable effects on the properties of concrete. As the basis for the design of concrete structures, the relations among the basic mechanical properties of concrete such as compressive strength, tensile strength, flexural strength and elastic modulus should be clearly understood. This paper summarizes the test data from the published references, and discusses the relations among these properties by statistical analyses compared with those of ordinary concrete. The results show that the axial compressive strength and the tensile strength can be prospected by the same formulas of ordinary concrete specified in current Chinese design code, but the prospected tensile strength should multiply a reducing coefficient when the strength grade of concrete is lower than C30. The elastic modulus of concrete with machine-made sand is larger than that of ordinary concrete, which should be prospect by the formula in this paper. Meanwhile, the formula of flexural strength is suggested.

Abstract: According to the related experimental standards, the finite element (FE) methodology to calculate the in-plane and out-of-plane moduli of hexagonal honeycombs (HHs) is designed by simulating the experimental loadings. Some simulations were carried out for the hexagonal honeycombs with different configuration parameters. The FE results are consistent with the theoretical ones, which verifies the reliability of FE methodology.

Abstract: Among different sterilization methods, heat-treatment of bone is recognized as one of the simple and practical methods to lower the human immunodeficiency virus (HIV) infection and overcome the risks of rejection and disease transfer from allograft and xenograft during bone transplantation. In order to best characterize the micro-structural mechanical property of bone after heat treatment, the nanoindentation technique was applied in this study to measure the localized elastic modulus and hardness for interstitial lamellae and osteons lamellae of bovine cortical bones at temperature 23°C (room temperature-pristine specimen), 37°C, 90°C, 120°C and 160°C, respectively. The elastic modulus (E) and hardness (H) of interstitial lamellae obtained higher values as compared with osteons lamellae which show that interstitial lamellae are more stiff and mineralized than osteons. Moreover, as a specimen pre-heat treated at 90°C, the E and H values of interstitial lamellae and osteons were closed to a pristine specimen. For a specimen pre-heat treated at 120°C, both interstitial lamellae and osteons obtained an increase in E and H values. As a specimen pre-heat treated at 160°C, the interstitial lamellae and osteons obtained a slight decrease in E and H values. These findings are correlated to results reported by other researchers [1, 2] that calcified collagen molecules starts to degenerate at about 120°C and complete at 160°C. Interestingly, when a specimen was pre-heat treated at 37°C, both interstitial lamellae and osteons obtained significant decreases in E values of 57% and 40%, respectively as compared to the pristine specimen; while in H values, there was a decrease of 27.4% and 15%, respectively. Thus, this paper will investigate the mechanical properties of bovine cortical bones under various temperature ranges by nanoindentation technique.

Abstract: The objective of this research is to present an identification method for elastic moduli of ground rock, through the first-order adjoint equation method using the measurements of the blasting vibration in tunnel excavation. Parameter identification is a minimization problem of the square sum of discrepancy between the computed and observed velocities. For the identification of these parameters, the magnitudes of the blasting force should be identified beforehand. In this study, propagation of an elastic wave is assumed because the amplitude of such a wave is infinitesimal. After the identification of the blasting force, the elastic moduli of three layers are identified simultaneously. We assume that the damping of vibration is linear. By applying the identification technique at the Ohyorogi tunnel site, we verify that the method is useful for tunnel excavation. Using measured data from actual tunnel excavation sites, the numerical identification method presented in this paper is shown to be useful for practical tunnel excavation.

Abstract: Functional vascular tissue engineering aims to produce blood vessels in vitro in a controlled environment named bioreactor. In order to control the growth and remodeling of vascular tissues, suitable measurements should be made on the construct in situ, i.e. during the growth. These measurements will feed the controller with information in order to take efficient control decisions. The non-destructive measurement of compliance or elastic modulus in vitro is a potential indicator of the vascular construct maturity. This work shows that compliance and elastic modulus are related: they can be estimated during the growth of constructs in a bioreactor, and thus provide useful feedback information to the controller.

Abstract: Diamond coatings were prepared on mono-crystalline silicon by hot filament chemical vapor deposition (HFCVD). Hardness, elastic modulus and other mechanical properties of the diamond were analyzed by nanoindenter. The results showed that the process parameters such as chamber pressure, substrate temperature, methane volume ratio have a greater impact on the mechanical properties of the diamond coating. The micro-hardness and elastic modulus of the coating would both decrease with too high or too low substrate temperature, chamber pressure or volume ratio of methane. The results showed that when the substrate temperature is 750°C, champer pressure is 2.5kPa and methane volume ratio is 2%, the diamond coatings have high micro-hardness and elastic modulus.

Abstract: Flat crush performance test, edgewise compressive properties test and sheering properties test of both ripple structure and latticed structure sandwich composites were performed respectively. Test value of elastic modulus was obtained. Contrastive analyzing the test value and calculated value, the correctness and feasibility of equivalent mechanical model were testified.

Abstract: This paper explores the properties of Fe40NiCrSiAl alloy treated by different methods. The hardness, elastic modulus and resistivity are tested. The results indicate that: after LSP to rolled Fe40NiCrSiAl alloy, the hardness increased 25.22%, the elastic modulus increased 7.17% and the resistivity decreased 39%. TEM photographs demonstrated that there appeared dislocations, martensite transformation and twin crystals inside the material after being treated by LSP. Twin crystals are the main reason attributing to the improvement of material electrical properties.

Abstract: Experiments were conducted to study the basic properties of steel fiber reinforced lightweight aggregate concrete (SFLAC) mixed with machine-made sand and expanded-shale. The effects of sand ratio and cement content on the cubic and axial compressive strengths, splitting and axial tensile strengths, flexural tensile strength as well as compressive and tensile elastic modulus of SFLAC are analyzed comparing with those of LAC in the same conditions. Data from the experiments shows that, the steel fiber has advantages to every mechanical properties of LAC especially to the tensile strengths, and also modifies the abruptness failure states of LAC into multi-cracked characteristics of SFLAC. The optimum mix proportion is suggested for getting better properties of SFLAC.

Abstract: Both natural and synthetic materials have been utilized to provide three dimensional scaffold environments ideal for bone repair. The biomechanical and biocompatibility characteristics of these scaffolds play a vital role in successful tissue engineering constructs. Polymer/carbonate apatite (CHA) composites have shown to improve cell adhesion and proliferation on the scaffold as well as increase elastic modulus, toughness and strength. The aim of this study is to prepare CHA- polylactic-co-glycolide (PLGA) composites in the form of microsphere, scaffold and disc and evaluate their physico-chemical properties, mechanical properties and in vitro bioactivity. 3-D porous cylindrical composite scaffolds were prepared using PLGA/CHA composites with varying PLGA/CHA ratios (30:70 and 50:50). The CHA was prepared by hydrolysis method and characterized using x-ray diffraction (XRD) and Fourier Transform Infrared spectroscopy (FTIR). The physico-chemical and mechanical properties of the composite scaffolds were evaluated using scanning electron microscopy (SEM), micro-computed tomography (μCT), XRD, FTIR, and thermogravimetry (TGA). Flexural strength was determined using Instron. In vitro bioactivity was determined by the formation of apatite on composite disc surfaces after immersion in simulated body fluid (SBF). SEM and μCT analyses showed high porosity and interconnectivity between microspheres in the composite scaffolds. In vitro bioactivity was observed by the development of an apatite layer on the surfaces of the composite scaffolds after immersion in simulated body fluid. The mechanical strength of the scaffolds was to be dependent on the PLGA-CHA ratio. The elastic modulus, toughness and strength values obtained for the composites were similar to those of reported bone substituted materials. Results from this study provided information on the fabrication of PLGA-CHA scaffolds and their properties that may be useful for their potential application in bone repair and as scaffolds in tissue engineering for bone regeneration.