Shared posts

25 Jan 04:30

Alien Observers

ALERT: Human 910-25J-1Q38 has created a Youtube channel. Increase erratic jerkiness of flying by 30% until safely out of range.
12 Jan 04:54

Decorative Constants

Arguably, the '1/2' in the drag equation is purely decorative, since drag coefficients are already unitless and could just as easily be half as big. Some derivations give more justification for the extra 1/2 than others, but one textbook just calls it 'a traditional tribute to Euler and Bernoulli.'
16 Aug 20:49

Dynamic crack propagation in elastoplastic thin-walled structures: Modelling and validation

by S. Mostofizadeh, M. Fagerström, R. Larsson


In this paper, a method to analyse and predict crack propagation in thin-walled structures subjected to large plastic deformations when loaded at high strain rates—such as impact and/or blast—has been proposed. To represent the crack propagation independently of the finite element discretisation, an extended finite element method based shell formulation has been employed. More precisely, an underlying 7-parameter shell model formulation with extensible directors has been extended by locally introducing an additional displacement field, representing the displacement discontinuity independently of the mesh. Of special concern in the paper has been to find a proper balance between, level of detail and accuracy when representing the physics of the problem and, on the other hand, computational efficiency and robustness. To promote computational efficiency, an explicit time step scheme has been employed, which however has been discovered to generate unphysical oscillations in the response upon crack propagation. Therefore, special focus has been placed to investigate these oscillations as well as to find proper remedies. The paper is concluded with three numerical examples to verify and validate the proposed model.Copyright © 2013 John Wiley & Sons, Ltd.

26 Jul 17:59

Social Media

The social media reaction to this asteroid announcement has been sharply negative. Care to respond?