I love my MoM

Some mechanical-engineering programs, like ours here at the University of Utah, use the phrase “Strength of Materials” to refer to what the majority of other mechanical engineers more accurately refer to as “Mechanics of Materials” (often locally shortened to “MoM”).   The latter designation is more appropriate because this class typically is focused on an introduction to elementary elasticity with only very lightweight coverage of failure criteria (and almost never any post-failure theories, which are typically covered in upper-division and grad courses). Our University of Utah class, ME EN 3300, is locally called “Strengths” even though strength is barely covered (and only at an idealized level such as Tresca and von Mises criteria).

The following infographic furthermore shows that engineering textbooks appropriately and overwhelmingly favor MoM over Strengths (to see details, click to open in separate page and then zoom to fit the page):

LoveMom

Thanks go to Dr. Ashley Spear for stimulating this commentary/flame.

Simulation of sand/soil/clay thrown explosively into obstacles

Here are a couple of cool movies created by CSM researcher, Biswajit Banerjee, in preparation for our project review this week:

  1. Clods of soil impact a plate:  A major advantage of the Material Point Method (developed as part of this research effort) is that it automatically allows material interaction without needing a contact algorithm.
    FragmentsHittingPlateAreniscaDrained
  2. Extrapolated buried explosive ejecta. The sample is in a centrifuge to get higher artificial gravity, so the particles move to the side because of the Coriolis effect!
    CentrifugeRigidParticlesNoWall

PUBLICATION: Continuum effective-stress approach for high-rate plastic deformation of fluid-saturated geomaterials with application to shaped-charge jet penetration

StressSpaceVisualization

AUTHORS: Michael A. Homel · James E. Guilkey · Rebecca M. Brannon

ABSTRACT: A practical engineering approach for modeling the constitutive response of fluid-saturated porous geomaterials is developed and applied to shaped-charge jet penetration in wellbore completion. An analytical model of a saturated thick spherical shell provides valuable insight into the qualitative character of the elastic– plastic response with an evolving pore fluid pressure. However, intrinsic limitations of such a simplistic theory are discussed to motivate the more realistic semi-empirical model used in this work. The constitutive model is implemented into a material point method code that can accommodate extremely large deformations.Consistent with experimental observations, the simulations of wellbore perforation exhibit appropriate dependencies of depth of penetration on pore pressure and confining stress.

http://link.springer.com/article/10.1007%2Fs00707-015-1407-2

Bibdata:

@article{  year={2015},  issn={0001-5970},  journal={Acta Mechanica},  doi={10.1007/s00707-015-1407-2},  title={Continuum effective-stress approach for high-rate plastic deformation of fluid-saturated geomaterials with application to shaped-charge jet penetration},  url={http://dx.doi.org/10.1007/s00707-015-1407-2},  publisher={Springer Vienna},  author={Homel, Michael A. and Guilkey, James E. and Brannon, Rebecca M.},  pages={1-32},  language={English}  }

Linear algebra applied to sundials

CSM alumnus, Scot Swan, offers Sundials_and_Linear_Algebra,  which is a short (informal) writeup on the equations that are used for making standard horizontal dials.   Challenge: see if Scot’s write up is consistent with the calculator at http://www.anycalculator.com/horizontalsundial.htm.

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Undergraduate researcher applies binning to study aleatory uncertainty in nonlinear buckling foundation models

20150721_KatharinJensenAvatar

Sophomore undergraduate, Katharin Jensen, has developed an easily understood illustration of the effect of aleatory uncertainty, which means natural point-to-point variability in systems. She has put statistical variability on the lengths of buckling elements in the following system:

bistableSystem

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PUBLICATION: An efficient binning scheme with application to statistical crack mechanics

This paper has an algorithm that alleviates the computational burden of evaluating summations involving thousands or millions of terms, each of which is statistically variable.  It is a simple binning strategy that replaces the large (thousand or million-member) population of terms with a much smaller representative (~10 member) weighted population. This binning method typically gives ~500x computational efficiency boost.

10realizations

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Errata for two verification publications

computer-doh

This posting provides errata for an analytical solution that appeared in the following two publications:

Brannon, R. M. and S. Leelavanichkul (2010) A multi-stage return algorithm for solving the classical damage component of constitutive models for rocks, ceramics, and other rock-like media. Int. J. Fracture v. 163(1), pp. 133-149.

K.C. Kamojjala, R. Brannon, A. Sadeghirad, and J. Guilkey (2013) Verification tests in solid mechanics, Engineering with Computers, 1-21.

As pointed out by Dr. Andy Tonge, they both contain a the same transcription error that was not in the original unpublished working document where the details of the solution are archived.  The following excerpt from the original unpublished working document contains correct formulas:  PlasticityVerification2excerpt.   See the red comment boxes in this file for details.

Pyrrhonism (AKA fallibilism) is not contentious

Fallibilism goes beyond the simple recognition that everyone is fallible. It demands that any ethical and equitable quest for truth (or beauty) must be founded on a commitment (not just willingness) to SEEK OUT (not just be open to) alternative viewpoints, which might contradict those of other people (friend or foe) and might even run counter to one’s own cherished beliefs (including a belief in fallibilism itself)!

Graham_Hierarchy_of_Disagreement

Graham’s hierarchy of disagreement

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Tips for writing literature reviews

This posting aims to help graduate students write a good literature review for their qualifying exam, proposal, or thesis.

In the Department of Mechanical Engineering at the University of Utah, the qualifier examination is not a proposal, so there is no expectation that your Qual paper should propose new research.  Your literature review should, however, critically assess existing research in the subject area by pointing out specific limitations of (and, if applicable, errors in) existing published work.   The qualifier paper is meant to show that you can string together a coherent scholarly discussion.   The qualifier paper can have a fairly broad literature review as long as it still limits attention to mechanical engineering topics. The proposal document, on the other hand, should include a literature review that is more tightly related to your proposed research, as your aim is to convince the committee that your proposed work is (1) important to the field of Mechanical Engineering and (2) has not been done. The thesis document should include an updated literature review that suggests no one else has accomplished the same thing during the time you were working on it (or prior to your efforts, but inadvertently overlooked in your original literature review). The final thesis literature review should also thoroughly compare/contrast your own accomplishments with alternative approaches in contemporary literature.

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