User talk:Stress9/HW2

Templates: $$\displaystyle \clubsuit$$ Copyright violation / plagiarism: Completeness: Team contribution: Correctness: Artistic aspect: Comments: Overall rating:

 Note: The Overall rating: here is more of a "gut feeling" than a formal quantitative grading. Follow our list of criteria for formal grading and commenting. In case of a tie, let's favor new teams for the top-3 positions.

=EAS 4200C=

User:Eas4200c.f08/HW_report_table

General comments for HW2

 * the moment of inertia of a solid circular cross section must be integrated using polar coordinates, and NOT by adding the moments of inertia with respect to the principal directions, i.e., $$\displaystyle J= I_x + I_y$$.
 * the moment of inertial of the channel cross section must be computed at the centroid of that cross section; thus the centroid location must be computed first.

Specific comments on team HW2 reports
$$\displaystyle \clubsuit$$ Team Aero Copyright violation / plagiarism: No. Completeness: Yes, but did not detail how to do the approximation for moment of inertia in Pb.1.1, not as good as solution of Team Radsam; Best solution for Pb.1.1 is from Team Carbon. Team contribution: Yes (importance of stringers). Correctness: Almost overall, comparison of inertia between solid circular cross section and that of channel cross section appears correct, did compute location of centroid, result differs with that of Team Aero6 Check. Artistic aspect: Yes (nice figures). Comments: Good work (derivations, complete HW problems, appears to be correct), nice figures (color, pleasant). Overall rating: 8.9 / 10.

$$\displaystyle \clubsuit$$ Team Aero (Eelman) Should combine the archived version of Week3 Week4 into a single subpage to submit; see an example in Team Carbon. Copyright violation / plagiarism: No. Completeness: Yes, but did not detail how to do the approximation for moment of inertia in Pb.1.1, not as good as solution of Team Radsam; Best solution for Pb.1.1 is from Team Carbon. Team contribution: Yes, brief overview of Mohr circle; excellent photo of riveting of stringers to aircraft skin during aircraft construction. Correctness: Almost overall; Small error in computation of centroid location $$\displaystyle Y \sum A = \sum y A$$, and $$\displaystyle Y = \frac{0.176 a^3}{0.28 a^2}= 0.62857 a$$; Small error in the ratio (there should not be $$\displaystyle a^4$$ ) $$\displaystyle \frac{I_1}{I_2} = \frac{0.007162 a^4}{0.064442 a^4} = .11114 $$ or $$\displaystyle \frac{I_2}{I_1} \approx 9 $$ almost agreeing with the result in Team Aero, who gave $$\displaystyle \frac{I_2}{I_1} = 8.145. $$ Artistic aspect: Regular, no problem, nothing outstanding. Overall rating: 9.1 / 10.

$$\displaystyle \clubsuit$$ Team Aero6 Copyright violation / plagiarism: No. Completeness: Yes, but did not detail how to do the approximation for moment of inertia in Pb.1.1, not as good as solution of Team Radsam; derivation of moments of inertia (rectangle, circle, channel cross section). Team contribution: Yes, stringer cross section. Correctness: Almost overall, comparison of moment inertia between solid circular cross section and that of channel cross section appears fine, did compute location of centroid, but the result differs with that of Team Aero, perhaps due to computation with respect to the y axis not passing to the centroid. Artistic aspect: Yes, nice layout and figures, figure on shear strain wrong $$\displaystyle \gamma$$. Comments: Good work (derivations, complete HW problems, results differ with another team; need to check), nice figures (color, pleasant, error in Figure 11 on shear strain). Overall rating: 9.1 / 10.

$$\displaystyle \clubsuit$$ Team Carbon Copyright violation / plagiarism: No. Completeness: Yes, detail how to do the approximation for moment of inertia in Pb.1.1, very good. Team contribution: Yes (importance of stringers). Correctness: Almost, but inertia of channel cross section computed with respect to middle of vertical member instead of centroid; see Team Aero Team Aero6 Check. Pb.1.7 not complete as other teams; see Team Aero6. Artistic aspect: Yes, figures not as nice as other teams; see Team Radsam; Team Aero6 Comments: Good work (good classnotes, derivations, complete HW problems, excellent Pb.1.1 solution, other solution appears to be correct, except for moment of inertia of channel section not about centroid). Good combined HW wiki page for submission like Team Gator. Overall rating: 9.2 / 10

$$\displaystyle \clubsuit$$ Team Gator Copyright violation / plagiarism: No. Completeness: Yes, there are even quotations and photos of authors that I mentioned in class; excellent. Team contribution: Nothing outstanding. Correctness: Almost, detailed figure on shear flow for derivation of torque in thin-walled rectangular box beam, but no details on how to do the approximation for Pb.1.1; see Team Carbon. Did not derive polar moment of inertia by integration with polar coordinates, but use sum of I_x and I_y. Did not compute the centroid location of channel cross section. Artistic aspect: Nothing outstanding. Comments: Good, nothing outstanding. Good combined HW wiki page for submission like Team Carbon. Overall rating: 8.5 / 10.

$$\displaystyle \clubsuit$$ Team Radsam Copyright violation / plagiarism: No. Completeness: Yes, nice detailed how to do approximation for moment of inertia in Pb.1.1, nice explanation of maximizing I/b with good plots; the solution for Pb.1.1 appears better than that of Team Aero. Team contribution: OK, not outstanding. Correctness: Almost in general, except for the comparison of inertia between solid circular cross section and that of channel cross section, did NOT compute location of centroid of the channel cross section. Artistic aspect: OK, not outstanding. Comments: Good work (derivations, complete HW problems, good solution for Pb.1.1, except for one problem). Overall rating: 9 / 10.

$$\displaystyle \clubsuit$$ Team VQCrew Copyright violation / plagiarism: No. Completeness: Yes, but did not detail the approximation for the moment of inertia in Pb.1.1 as done in class; see the best solution by Team Carbon, figure on shear flow in Pb.1.1 not complete, but has other good figures (parabola); good derivation of moment of inertia by polar coordinates via computation of the Jacobian of coordinate transformation, but no geometrical interpretation as done by Team Aero6; did not compute the centroid of the channel cross section and the moment of inertia wrt to the y axis passing through the centroid; see Team Aero and Team Aero (Eelman); did not have a figure of a solid circular cross section and a channel cross section. Team contribution: Yes, good classnotes on stringers; excellent photo and figures. Correctness: Almost for the most part, but not for the problem of comparing the moment of inertia of a solid circular cross section and a channel cross section with the same area; did not compute the centroid location of the channel cross section. Artistic aspect: Nice latex equations, nice figures. Comments: Overall rating: 8.9 / 10.

=EML 4500=

User:Eml4500.f08/HW_report_table

General comments for HW2

 * only 2 teams did run the matlab code for the two-bar truss structure; these are Team Delta_6 and Team Lulz; please give them good grade for this problem, e.g., 100/100.
 * The other teams just copied from my web page, which showed the results, and presented the results as if they actually ran the matlab code; not much grade should be given to this part of the report, e.g, 20/100.
 * If they are honest in reporting that they could not run the matlab code because they could not find the necessary matlab functions from the book, they should get more points than those who pretended that they ran the code, e.g., 60/100.
 * At least one team did NOT do this part of the report; they get ZERO for this part of the HW2 report.


 * the weight for the classnotes is 80% and for the problem of running of the matlab code is 20%.

Specific comments on team HW2 reports
$$\displaystyle \clubsuit$$ Team Bike Copyright violation / plagiarism: No. Completeness: Almost; did not run the matlab code for two-bar truss system, but was honest enough to say that they got the result from my web page; compute all element internal forces; did set up the statics solution for the two-bar truss problem, but did not produce numerical results, and did not compare to FEM results. Team contribution: Nothing beyond lecture presentations. Correctness: Almost, got the Euler cut principle right; I have not seen many teams who who got this concept right and reported it; unfortunately, the figure on the assembly of the element stiffness matrices into the global stiffness matrix, while having nice colors, was actually WRONG; see Team Bottle. Artistic aspect: Nice, pleasant figures of FBDs. Comments: Equations completely in latex format, nice pleasant to read. Overall rating: 9.1 / 10.

$$\displaystyle \clubsuit$$ Team Bottle Copyright violation / plagiarism: No. Completeness: Team contribution: Correctness: Artistic aspect: Best image of assembly of element stiffness matrices into global stiffness matrix. Comments: Overall rating:

$$\displaystyle \clubsuit$$ Team Delta_6 Copyright violation / plagiarism: No. Completeness: Almost; did solve the two-bar truss system using statics to get axial forces, but did not compare to FEM results; did not compute the reactions for Element 2 in the two-bar truss system; did actually run the matlab code for two-bar truss system using the "missing" matlab codes from the book, potentially good work on this problem; on the other hand their HW report did not show the complete work; see Diana Guzman's e-mail; we need to see exactly what they did; the best report on this two-bar truss matlab problem is by Team Lulz, where all "missing" matlab codes were displayed in their HW2 report. Team contribution: Nothing beyond lecture presentations. Correctness: Almost, but wrong direction of axial force $$\displaystyle p_1^{(1)}$$ in figure for Element 1, and elsewhere; want to use the same positive convention as taught in class. Artistic aspect: Nice figures of FBDs, but erroneous positive convention; still use Words equations and tables. Comments: Equations not completely in latex format; use "zero" or character "o" instead of "theta"; nice figures. Overall rating: 9.0 / 10.

$$\displaystyle \clubsuit$$ Team Gravy Copyright violation / plagiarism: No. Completeness: Not quite; did not complete the matrices for the computation of the reactions; did NOT to the matlab problem of two-bar truss system. Team contribution: Some, but not significant. Correctness: OK, many errors; figures do not look right, particularly the blue forces with a cross bar; cryptic, not clear; local coordinates should be with tilder not overbar. Artistic aspect: Good equations in latex format, but use underbar (as in hand-written lecture presentation) instead of boldface (as it should be); good use of overhead arrow to designate vectors as in lecture presentations, but could use boldface characters, as it should be. Comments: See above on equations; Much better than their HW1 report; they also resubmitted an improved HW1 report; need to look into this report; have a sense of humour (talking about "baking a cake" using the "recipe" explained in class). Overall rating: 7.8 / 10.

$$\displaystyle \clubsuit$$ Team Lulz Copyright violation / plagiarism: No. Completeness: Not quite, did run the matlab code for two-bar truss system; but did NOT solve the two-bar problem using statics and compare the results to the FEM results. Team contribution: Nothing outstanding. Correctness: Ok. Artistic aspect: Figures not nice; coarse; hand-drawn. Comments: Most equations typed in latex format; good. Overall rating: 8.0 / 10.