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MSS
conceptual design of a carbon fiber composite aircraft and FEA of the wing,Contact: [email protected]
uav thesis is good for reference
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BUET
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CDR Format for MSC
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CRACKSCKS
CRACKS
Menu:
CRACKS
Description: This menu contains commands used for defining cracks for a J-integral or VCCT evaluation.
The concept of a crack is a crack tip for 2-D and a crack front in 3-D. For each crack you select if a J-integral calculation or a VCCT calculation is to be performed. The J-integral option corresponds to the Marc option LORENZI while VCCT corresponds to the VCCT option. Both are related to the energy release rate of the crack. J-INTEGRAL For 2-D, the J-integral is defined as a line integral along a path surrounding the crack tip. In the method used by MSC.Marc, this integral is transformed into an area integral where the area to be integrated over is the one enclosed by the line integration path. Only a part of this area is actually used for the integration, usually the outermost ring of elements. In this way, only results values at a distance from the crack tip are used and more accurate results can be obtained for the J-integral. To identify the integration area, the user defines a list of nodes inside the elements that are used for the integration. These nodes define the RIGID REGION which the menus below refer to. Only elements elements that are connected to a node in the rigid region contribute to the J-integral value calculated. This does not include elements with all nodes in the rigid region. The term rigid region comes region comes from the fact that you can evaluate the J-integral by shifting the nodes in the rigid region and calculate the change in strain energy energy in the elements elements connected to a node in the rigid region. For 3-D, the line integral becomes a surface integral over a surface surrounding the crack front (or a part of the crack front). The area integral becomes a volume integral and the rigid region is similarly defined as a list of nodes. By choosing the rigid region as a thin disk of of nodes perpendicular to the crack front, where the disk contains one node along the crack front, you can obtain local values of the J-integral along a crack front. The automatic search routines for the rigid regions are designed to create this type of rigid regions. Shell elements are not supported for the J-integral. VCCT For VCCT the energy release rate is evaluated using forces and displacements around the crack tip. There is no extra input needed apart from the crack tip or front for the energy release rate calculation.
The VCCT option supports crack propagation. It can be defined by releasing a predefined tied interface or through global remeshing. In the global remeshing case the user does not need to define the crack growth path, it comes as a part of the solution. The crack growth can be done as either fatigue style or direct growth. In the direct grow case the crack grows whenever the calculated energy release rate is larger than the user specified crack growth resistance (fracture toughness). The energy release rate calculation supports all solid and shell elements except higher order tetrahedral elements. The released tying style of crack growth supports all the mentioned element types, while remeshing is supported for 2D solid elements.
