MEAM.Design - MEAM 247 - P3: Concentrate


Dates & Deadlines

11/8, 11:59 p.m. prelab deadline
11/9-10 LRSM for testing
11/10, 6:00 p.m. team formation deadline
11/22, 2:00 p.m. video submission deadline


Prelab

Send the answers to the following questions in an email to medesign@seas.upenn.edu entitled 247-P3-Prelab before 11:59 p.m. on Monday, November 8th:

1. What are the yield stress, young's modulus, and poisson's ratio for polycarbonate? Where did you get your values from?

2. What is the theoretical maximum load, P, that should be applied to the plate to ensure that we do not exceed the yield stress at any location in the plate?

Also, do not forget to sign up for a team, as explained below.


Background

In this lab we will use a number of different methods to examine how geometric features influence the stress and strain within a planar specimen. See here for more information concerning the underlying theory of plane stress and strain, net-section stress, stress concentrations for round holes, St. Venant's principle, and photoelasticity.


Experimental Procedures

1 Predictions (individual)

Based on the theory described in the Background section, use Matlab to plot the expected ($\sigma_y$) along one half of the H-H cross-section of the plate. Does the profile match your intuition? Save your plot for later comparison with the experimental data.


2 Finite-Element Analysis (individual)

Using SolidWorks, create a 3-dimensional model of the central region of the plate (W = 10 inches, t = 0.211 inches, L = 12 inches, hole radius = 0.5 inches centered in the plate), then follow the instructions posted here to set up and run a linear static analysis on the plate.
Save an image showing the mesh that you used.
Save a plot of the vertical stress, ($\sigma_y$), throughout the plate. Paying particular attention to the bisection line (H-H), do the finite-element model results match up with the theoretical prediction from part 1? Also examine the stress around the circumference of the hole to see if it matches with the theoretical predictions.
Save a plot of the maximum in-plane shear stress, ($\tau_{max}$), throughout the plate.
You may also want to investigate the animation options, which will produce video files that could be overlaid with the photoelastic results in part 4 below.


3 Strain Gauges (in your lab group)

To experimentally confirm the predicted stress at the midplane, a set of strain gauges have been distributed along the H-H cross section. You will see that we have placed gauges to measure both the X and Y components of strain at each point, thereby allowing you to use the plane stress equations above to find ($\sigma_x$) and ($\sigma_y$).
We will use the Instron testing machine to apply a moderate tensile load to the plate. It is critical that the maximum stress within the plate not exceed the yield point at any time.
Strain Gauge Data


4 Photoelastic Visualization (in your lab group)

With the polarized light source behind the polycarbonate plate, you can use either the video camera and/or DSLR fitted with a macro lens and polarizing filter to capture the state of stress within the plate during loading (recall that changing the orientation of the polarizing filter on the video camera will alter the viewing of the isoclinics). You should capture images and/or video of both the stress concentrations around the central hole as well as the distribution of stress caused by the loading condition. You will want to develop a method to keep track of the images and videos with respect to the strain and Instron data that you collect.
Photo and video archives (including Instron data files) for section: 101 | 102 | 103 | 104 | 105 | 106


5 Team Formation

For the remainder of the project, you will need to work within a team of three (note - it will likely be easier to work with people within your section, though this is not a steadfast rule). Add your name to a team here before 6:00 p.m. on November 10th. Those not listed on the page by the deadline will be randomly assigned.


6 Presentation of Results (in your team of 3)

Your team will be creating a short video highlighting the work you've done and the results of this lab. Within a maximum of one minute, your video should convincingly demonstrate the principles under investigation, and must show the results from all four of the above sections. Convincing comparisons between the theory, models, and experimental results will be particularly appropriate. It is highly recommended that you work as a team to lay out your video in storyboard form before actual creation. Resources for video production (including cameras and editing workstations) are available at the Vitale Digital Media Lab within the Van Pelt Library (more info here).
Once your video is complete, find a place to host it (YouTube, Vimeo, etc.), then send an email to medesign@seas.upenn.edu entitled 247-P3-Txx-Video (where "xx" is your team number) containing a link to your posted video. You must complete this before 2:00 p.m. on Monday, November 22nd.