Papers by Keyword: Mesoscopic

Abstract: In this paper, a new method mesoscopic been studied for metal material deformation to fracture process. In the polycrystalline material plastic flow process, mesoscopic structural features was obtained for translation - vortex by digital image correlation principle. A preliminary analytical method of material deformation is established. The behavior of plastic deformation of 7B04 high strength aluminum alloy was analyzed. Grain groups deformation, amount of rotation and the energy dissipation distribution were analyzed. An important deformation features is that micro cracks were bred in severe plastic strain region on mesoscopic scale. Based on the stress concentration, the formation of rotational deformation can be regarded as the beginning of an irreversible damage criterion. The Rotation of grain groups is the reason of the formation of microcracks.

Abstract: Monte Carlo method and the Fuller curve are used to calculate the amount of the aggregate of concrete. The programmer of generating mesoscopic concrete is written to simulate the cracking evolution through two-dimensional plane. In the mesoscopic concrete, the sample is described by a Tri-phase material which consists of aggregate, matrices and interface. Based on the model， a study on how the cracks generate, develop and cut through in the concrete. The results show that: the interface is the vulnerable part of the concrete, the determination of the parameter and the damage criterion of the interface element is the governing factor. During the cracking evolution, the interface element destroyed firstly, and then the crack expense along the edge of the aggregates, cutting through the concrete and damaged finally. Numerical simulation of mesoscopic concrete cracking evolution can be used to understand and describe the damage style and strength characters.

Abstract: Woven unit-cell geometry functions are presented for a balanced plain weave fabric. Based on the functions, a 3D geometrical model applying to a meshing preprocessor for 3D finite element is proposed. The geometry model takes into account the existence of the space between tows, the undulation of the tow, and the actual tow cross-section shape. The internal geometry of model is from micrographs of sectioned laminates, which is helpful to define the accurate and actual 3D geometrical model. The section shape of the yarn remains unchanged along the trajectory. This model can be easily identified using three parameters measured on a real fabric. An accurate hexahedral mesh developed using these geometry model is presented. This is an important point for 3D finite element simulation of fabric model, which is a powerful method to investigate the mechanical behavior and also the composites made from it.

Abstract: This paper aims to study the influence of aggregate shape and size on the tensile strength, compressive strength and fracture energy in mesoscopic modeling of concrete. For this purpose, several numerical models under three loading cases, uniaxial tension, uniaxial compression and bending resistance test are analyzed utilizing the software ABAQUS/Explicit. The mechanical responses and cracking behaviors well match the realistic situations of experiments. Various stress-strain curves and fracture patterns are presented and compared, which indicate that the aggregate size has very small effect on the tensile strength, compressive strength and fracture energy, and the effect of aggregate shape is a little more significant than that of the size.

Abstract: This paper presents a numerical strategy for realistic modelling of the internal material configuration and cracking of concrete on mesoscale. Polyhedron shapes resembling crushed rocks are adopted to represent the aggregate. A packing approach in which the particles are heaped up layer by layer is proposed for 3-D condition. A cubic representative volume element (RVE) is generated using the method. The cohesive approach, in which zero thickness cohesive elements are inserted into the ordinary finite element mesh along the potential cracking path, is adopted to model the cracking developing process. The cracking behaviours of created RVE under uniaxial tension are well simulated using the current approach.

Abstract: From micro perspective, crumb rubber concrete (CRC) is viewed as a composite consisting of mortar matrix, aggregates and rubber particle. In this paper, based on random aggregate model with different aggregate shape in planar, the mechanical properties of CRC using linear Mohr-coulomb constitutive relation are studied by nonlinear finite element method under uniaxial compression on mesoscopic. The number of random aggregates is calculated in two-dimension by Walraven formula. Circular random aggregate model, elliptic random aggregate model and polygonal random aggregate model are established. Stress-strain curves under varieties of conditions are derived and compared with the test results. The results show that the simulative stress-strain curve fit the reality very much. In the numerical analysis, the aggregate shape has little effect on the mechanical properties of CRC.

Abstract: In the paper, concrete on meso-level is taken as three phases composites consisting of aggregate、matrix and bond between matrix and aggregate. Model and arithmetic of Interface Element Method (IEM) is introduced and used to study the fracture characteristic and process of concrete under uniaxial load.

Abstract: The constitutive relation for open-celled metal foams with random characteristics of cells was constructed based on the mechanical behavior and the distribution of the cells, which implied the effect of the mesoscopic characteristics of the cells on the macroscopic behavior of the foam. The constitutive relation was able to represent the whole three phases of the stress-strain curve of the open-celled metal foam with merely one expression. Besides, the explicit expressions for the foam’s yield strain and yield stress were supplied. Experimental data was employed to check the constitutive relation. It was found that the constitutive relation was able to represent accurately the whole compression process of the foams, and the calculated yield points had a good agreement with the experimental results.