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Full-Text Articles in Engineering
Studies Of Dynamic Crack Propagation And Crack Branching With Peridynamics, Youn Doh Ha Ph.D., Florin Bobaru Ph.D.
Studies Of Dynamic Crack Propagation And Crack Branching With Peridynamics, Youn Doh Ha Ph.D., Florin Bobaru Ph.D.
Department of Engineering Mechanics: Faculty Publications
In this paper we discuss the peridynamic analysis of dynamic crack branching in brittle materials and show results of convergence studies under uniform grid refinement (m-convergence) and under decreasing the peridynamic horizon (δ-convergence). Comparisons with experimentally obtained values are made for the crack-tip propagation speed with three different peridynamic horizons.We also analyze the influence of the particular shape of themicro-modulus function and of different materials (Duran 50 glass and soda-lime glass) on the crack propagation behavior. We show that the peridynamic solution for this problem captures all the main features, observed experimentally, of dynamic crack propagation and branching, as well …
Evaluation Of Biological Cell Properties Using Dynamic Indentation Measurement, Guoxin Cao, Namas Chandra
Evaluation Of Biological Cell Properties Using Dynamic Indentation Measurement, Guoxin Cao, Namas Chandra
Department of Engineering Mechanics: Faculty Publications
Viscoelastic mechanical properties of biological cells are commonly measured using atomic force microscope (AFM) dynamic indentation with spherical tips. A semiempirical analysis based on numerical simulation is built to determine the cell mechanical properties. It is shown that the existing analysis cannot reflect the accurate values of cell elastic/dynamic modulus due to the effects of substrate, indenter tip size, and cell size. Among these factors, substrate not only increases the true contact radius but also interferes the indentation stress field, which can cause the overestimation of cell moduli. Typically, the substrate effect is much stronger than the other two influences …
Dynamics Of Fibrillar Precursors Of Shishes As A Function Of Stress, Luigi Balzano, Dario Cavallo, Tim B. Van Erp, Zhe Ma, Jan-Willem Housmans, Lucia Fernandez-Ballester, Gerrit W. M. Peters
Dynamics Of Fibrillar Precursors Of Shishes As A Function Of Stress, Luigi Balzano, Dario Cavallo, Tim B. Van Erp, Zhe Ma, Jan-Willem Housmans, Lucia Fernandez-Ballester, Gerrit W. M. Peters
Department of Engineering Mechanics: Faculty Publications
Shishes are fibrillar crystallites that can be created by deforming a polymer melt. The formation of shishes takes place when flow is strong enough to stretch molecules. In the early stages, bundles of stretched molecules with pre-crystalline order form metastable precursors whose stability depends on their size and, hence, on the stress level. We find that for a specific isotactic polypropylene, close to the nominal melting point, a stress larger than 0.10 MPa leads to stable fibrillar precursors that are partially crystalline immediately after flow. On the other hand, below 0.10 MPa, the aspect ratio of precursors tends to unity …
Crack Nucleation In A Peridynamic Solid, S. A. Silling, O. Weckner, E. Askari, Florin Bobaru Ph.D.
Crack Nucleation In A Peridynamic Solid, S. A. Silling, O. Weckner, E. Askari, Florin Bobaru Ph.D.
Department of Engineering Mechanics: Faculty Publications
A condition for the emergence of a discontinuity in an elastic peridynamic body is proposed, resulting in a material stability condition for crack nucleation. The condition is derived by determining whether a small discontinuity in displacement, superposed on a possibly large deformation, grows over time. Stability is shown to be determined by the sign of the eigenvalues of a tensor field that depends only on the linearized material properties. This condition for nucleation of a discontinuity in displacement can be interpreted in terms of the dynamic stability of plane waves with very short wavelength. A numerical example illustrates that cracks …