Damage Mechanics
Vinh Van Nguyen; Trung Ngoc Nguyen; Chi Thuy Nguyen
Abstract
Information about the dynamic loading of a steel structure is important for its static design as well as for an assessment of its fatigue life. In the case of a hydraulic static-pile-pressing machine, these loads are mainly caused by vibrations and load sway, which occurs as a result of the slewing motion ...
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Information about the dynamic loading of a steel structure is important for its static design as well as for an assessment of its fatigue life. In the case of a hydraulic static-pile-pressing machine, these loads are mainly caused by vibrations and load sway, which occurs as a result of the slewing motion of the boom around the vertical axis and from the radial movement of the load’s suspension point. This paper presents the study of the dynamics of a hydraulic static-pile-pressing machine during the process of lifting and slewing a pile using a mounted crane. A six-degree-of-freedom non-linear spatial-dynamic model is employed and a non-linear mathematical model of the machine is formulated. To confirm the mathematical model, the comparison between the measured results and simulation results using the mathematical model shows that the mathematical model is reliable. These results can be used to optimize the machine design based on calculations of its dynamics, fatigue, life expectancy and stability from a dynamic point of view.
Damage Mechanics
E. Homaei; K. Farhangdoost; M. Akbari
Abstract
The aim of the study was to find the optimum combination of materials and thicknesses to provide a tough, damage resistant multi-layer system with numerical methods to restore the damaged teeth. Extended Finite Element Method (XFEM) was used to assess the critical loads for the onset of damage modes ...
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The aim of the study was to find the optimum combination of materials and thicknesses to provide a tough, damage resistant multi-layer system with numerical methods to restore the damaged teeth. Extended Finite Element Method (XFEM) was used to assess the critical loads for the onset of damage modes such as radial cracks and plastic deformation in dental prostheses, which consist of a brittle outerlayer (porcelain)/ metal (Au, Pd, Co)-core/ substrate (dentin) trilayer system. XFEM not only has the ability to model crack initiation process, but also could solve crack propagation problems. Generally speaking, porcelain layer shouldn't be thinner than 0.5 mm, as the stresses due to bending become tensile critically in porcelain undersurfaces and radial cracks would occur in low loads. Also, it could be concluded that XFEM in axisymmetric model could properly estimate crack initiation and propagation path. Yielding of metal core makes additional flexural stress at overlaying brittle surface and consequently, facilitates radial cracks. In dental applications, the optimum porcelain thickness would be between 0.75 and 1.25 mm. Furthermore, yield strength and stiffness of metal is better to be high sufficiently to prevent it from plastic deformation and ensuing radial cracks.
