Papers by Keyword: Size Effect

Abstract: The goal of this study is to analyze the material deformation behavior in the micron level by quasi-static and dynamic impact tests of hat shaped specimen. Three type of specimen with different shear ring thicknesses (800μm, 400μm, 50μm) were designed. The quasi-static and dynamic impact tests were performed by electronic universal testing machine and split Hopkinson pressure bar (SHPB) respectively. During the material deformation in the SHPB test, the value scope of strain is 0 to 9 while the value scope of strain rate is 0.001s-1 to 400000s-1. The size effect phenomenon on shear stress and failure strain with different shear ring thickness was investigated. The shear stress and failure strain of material increases with the decrease of shear ring thickness. And the size effect phenomenon was weakened with the increase of strain rate.

Abstract: Based on specimen size, which is the main reason of the shear fracture toughness of concrete, experimental research was carried out by 5 groups including 40 symmetrically loading specimens with different length and height. Through load and crack tip sliding displacement curve P-CTSD, load and strain curve P-ε and load and time curve P-t, the effects of length and height of specimens to shear fracture toughness were studied. Specimen stability is strengthened with increasing of length and weakened with increasing of height. Size effect of fracture toughness is weakened with increasing of length, is strengthened with the increasing of height. Fracture toughness increases with the increasing of length, decreases with the increasing of height. Research Background The size effect exists in parameters of concrete, such as concrete strength, modulus of elasticity, fracture toughness, fracture energy and so on [1-. In 1961, the theory of fracture mechanics was applied to concrete structure for the first time by Kaplan [. A vast majority of research work about concrete fracture mechanics was carried out by international scholars [6-. As the development of fracture theory of concrete, the size effect of fracture parameters became the focal point in theory study. Karihaloo [ pointed out that the size effect of concrete strength strengthens with the increasing of components size, however, the size effect weakens when crack length decreased relative to the size of specimens. Hu [3, 10, 11] accounted for the size effect by applying the theory of boundary effect and carried out the concept of local fracture energy which changes with width of fracture process zone. Based on the fictitious crack model, an analytical method [12, 13] for predicting the effective fracture toughness of concrete of three-point bending notched beams is proposed and the effects of initial seam height ratio and height on fracture parameters were carried out by Wu and Xu. At present, research on shear fracture toughness of concrete is immature and there are almost no papers about the size effect of shear fracture toughness of concrete. Aiming at the issue, this paper conducts a study on the size effect of shear fracture toughness of concrete by using symmetrically single-edge notched specimen.

Abstract: Research activities on gigacycle fatigue properties of materials have recently focused on the influence of specimen size used for ultrasonic fatigue tests. In order to increase the volume of material subjected to the maximum stress (risk volume) a new specimen shape with a Gaussian profile is proposed. An approximation of the Gaussian profile with an arc of circle is presented in the paper, in order to simplify the Gaussian specimen manufacturing process. The effect of the approximation is evaluated analytically and through a finite element analysis.

Abstract: Indentation hardness of homogeneous materials should be constant. However, at very small depths, the apparent hardness often increases with decreasing imprint size. The paper discusses various cases of this indentation size effect in metals and ceramics and explains the extrinsic and intrinsic reasons.

Abstract: Within the frame of average spin model the calculation of dependence of critical phase transition temperature in antiferromagnetic ultrathin films of different crystalline structure on their thickness has been carried out. I has been shown, that relative change of Neel temperature is subject to power law with exponent close to the experimental values.

Abstract: The 100 x 200 mm cylinder specimens are standard size to measure the compressive strength and modulus of elasticity. However, it is not enough for experimental data of mechanical properties of HPC about size effect. The aim of this study is to investigate the size effect of high performance concrete (HPC) using blast furnace slag (BS) for mechanical properties such as, compressive strength and modulus of elasticity. Therefore, in this study, Type A (100 x 200 mm cylinder specimens) and Type B (150 x 300 cylinder specimens) were prepared. Blast furnace slag is used as a replacement for ordinary Portland cement (OPC). The compressive strength, modulus of elasticity of harden concrete were determined in the laboratory.

Abstract: Eight concrete columns with various sizes confined by CFRP and four plain concrete columns as the control specimens were axially loaded to failure in order to investigate size effects in concrete columns confined by CFRP. Experimental results show that CFRP can increase considerably both the capacity and ductility of the concrete specimens. Furthermore, the peak stress of the unconfined concrete decreases with the size of the specimens increasing. Similarly, the peak stress of confined concrete decreases with the size of the specimens increasing when the lateral confining stresses are the same. Hence, the size effects should be considered in the stress-strain model of concrete confined by CFRP.

Abstract: In previous analysis and design of steel structure, connections (especially bearings) of construction membership in long-span structures are usually considered as rigid, partially released or entirely sliding. Practically, construction members mechanical property is always not idealized in rigid, released or entirely slide situation. In some cases, the joints are relevant in geometry deformation. In this paper, mechanical property of bearing will be researched considering bearings size effect and friction characteristic, and results will be statistically analyzed.

Abstract: With the development of modern constructional technique, more attention on the size effect is paid by academics and engineers. The normal section bearing capacity of Reinforced Concrete Column is analyzed by eccentrically compressed theory firstly. The size effect on normal section bearing capacity of reinforced concrete column is obtained by theoretical analysis and experimental summary. The size effect formula of concrete compressive strength is proposed. Finally, a research thinking of size effect on bearing capacity is suggested.

Abstract: 2-D pressure model in axial and radial direction was proposed to simulate response of copper subjected to micro laser shock peening (μLSP) according to the size effect in the propagation of shock wave induced by laser in microscale. Simulations under 1-D and 2-D pressure model were conducted respectively in order to explore the effect of pressure in radial direction. The results show that distribution of residual stress and plastic deformation in depth and width are obviously different, and response of copper under 2-D pressure model are more close to the experimental results. The pressure effect in radial direction in the propagation of shock wave shouldnt be ignored, and 2-D shock wave pressure model plays an important role in accurate simulation of μLSP.