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A challenge to Mr. Koenemann
I am sure that several of you have followed Mr. Koenemann's posts with some interests. For some it might be entertainment, and for others it might be like watching a car wreck. In any case, several iMechanicians have attempted to convince Falk that his theories do not make sense. We have all failed miserably at that task. I am perhaps a bit slower than most, but it is clear to me that Mr. Koenemann will not be convinced by any physical or mathematical arguments. So I am left with the ultimate arbiter of all theories, experimental measurement and observation.
So I am posting the following challenge to Mr. Koenemann.
Ultimately a theory is only as good as its predictions. So, Mr. Koenemann, I offer you a challenge. I will use the theory of elasticity to make a prediction, and you can use your theory to make your prediction for the result of an experimental test. The test will be as follows. Someone will make a thin circular plate with two small bars, to be used for gripping, on opposite sides. They will place this structure in a tensile testing machine and pull on it. They will measure the change in length of lines through the center of the circle, in both the parallel and perpendicular directions to the loading axis. You and I will make our predictions and send them to one another. We will find two other individuals to perform the experiment and they will send the results to both of us. We will post all of our findings on this blog.
If you have any confidence in your theory then you should accept this challenge and we can proceed to the first phase, our predictions.
- Chad Landis's blog
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There's enough to look at
There is no reason for a contest. I offer enough material for comparison. In my paper "Approach",
- p.2628 I propose an equation of state for solids which is material-independent, and I demonstrate by using data by Bridgman that it works, at least for the alkalies.
- on p.2636 I give a calculated example to show that for an isotropic material subjected to pure shear, the volume should remain constant.
- on p.2644-45 I give a calculated example to show that that for an isotropic material subjected to simple shear, the volume should dilate (Poynting effect).
- From the systematics of the theory, it can be predicted that dilatancy should be a common effect for anisotropic materials in pure or simple shear.
- on p.2644 Fig.11 I predict the eigendirections and the kinematics of simple shear, compared with reality in Figs.13 ff.
- on p.2647 Fig.15 I compare my prediction with the observed orientation of joints in shear zone rocks.
- on p.2648 Fig.16 I compare my predictions with the observed max stress orientation along the San Andreas Fault. The orientation expected by workers on this fault is at 45°, observed is ca.80°, my prediction is 80°, with correct asymmetry relative to sense of shear. (Research on why the orientation is nearly vertically on the fault is a very active research subject, google for 'SAFOD-project'. The high angle is not a special Californian fault feature. The same orientation
is found along the North Anatolian Fault, the Kenai Fault in Alaska, and a large fault in Japan for which I have seen the data.)
- on p.2648, Chapter 8, I derive the work done in pure and simple shear, elastic and plastic deformation. The prediction is that in the elastic field, simple shear should cost a little more than pure shear per chosen unit strain, whereas in the plastic field simple shear should cost substantially less than pure shear per chosen unit strain. The observed data are available at
http://www.elastic-plastic.de/experimentaldata.pdf.
Should Chad believe that these data are insufficient, he is invited to search for better ones. I am confident that the pattern will persist.
- on p.2652, Fig.17, I predict the orientation of cracks in solids in 3D, to the best of my knowledge absolutely correct. (Seen enough shear zones in my life.)
- on p.2653 I compare the calculated orientation with observed cracks in sea ice. Given some natural variation, the predictions are right on the mark.
- on p.2653 Fig.18, and on p.2654 in the text, I show that upon irreversible relaxation of the elastically loaded state, an unbalanced rotational momentum is released which will actually cause external body rotatation about a rotational axis close to the direction perpendicular to the shear plane. This unbalanced momentum is a prime candidate for the origin of turbulence in fluid flow, plus for a few other phenomena, such as sheath folds, which may not be known to engineers, but are well known among structural geologists working in large shear zones.
- on p.2659 I offer the interpretation that the reduced density in Prandtl boundary layers is due to the Poynting effect.
- on p.2662 ff (Chapter 12) I give a calculated example for the distribution of deformation in a technical experiment, namely a block with free lateral surfaces which is loaded vertically, as a function of shape (the vertical dimension varies from one unit to 30 units).
Altogether, there cannot be better predictions, excuse the satisfaction. Thus there should be enough meat to sink his teath in even for Chad Landis.
The critical deformation state to test the conventional theory is simple shear. I am fully confident that for sufficiently high symmetry conditions (orthorhombic or higher) the conventional theory will not fail obviously. It was the inconsistencies between the predictions and observations for simple shear – in the elastic (Poynting), plastic (SC-fabric, microfabric, energetic) and viscous (turbulence) field – that made me study continuum mechanics in the first place.
One can easily arrive at right results for the wrong reasons. But right answers don't matter. What matters is to ask the right questions, then the right answers will come by themselves.
Falk H. Koenemann
respected sir, if i applied
respected sir, if i applied an arbitrary force to a beam of infinite length at one of its two ends, will the same force act at the other end at infinity??? here the beam is horizontal and am applying the force in the direction of orientation of the beam.
thanks.