This laboratory will serve as a wrap for the stress/stress laboratory courses. The main objective of the lab is to present the student with an engineering problem, in this case a design of a pop can (pressure vessel). The students will be presented with a hypothetical scenario where they will be working as design teams in charge of designing the next generation of pop can. First they would want to perform preliminary studies on the current design to characterize the features needed to be incorporated into the new design. They will have to perform the necessary test and analysis or use the knowledge base they have accumulated from their previous laboratory work. It is up to the students to define the parameters involved in the make up of a pop can then decided which ones should be analyzed.

The students will perform a strain gage measurement, which include the installation, set up, and analysis, in order to calculate the internal pressure of an unopened pop can. Other analysis such as leak before fracture, buckling, and yielding will also be explored.

Trace the life of a pop can from the manufacturing step to disposal. First the can itself had to be manufactured, filled or "bottled", delivered, consumed, then disposed. Discuss what conditions the can would be subjected to at each step of its life. Which conditions would warrant a further study and which would not.

Manufacturing

Delivery

Consume

Various sources published different value for the internal pressure of the beverage can. The bottler usually specify 30 psi as the pressure used. For the alcoholic beverage the pressure usually falls between 5 and 10 psi. The strain gage manufacturer present a value of approximately 50 psi. It is advisable to use the value from the gage manufacturer since there are many effects which make it impossible to determine the exact internal pressure using this strain gage set up.

The current impact extrusion process is capable of producing an aluminum can with the wall as thin as 0.001 inch. You and your fellow engineers are assigned the task of coming up with a new can design that use less material. At the same time, it must have the same functionality as the design in use today.

Before you start working on the new design, you are to conduct a preliminary study of the current design and test your experimental techniques. Various experiments will have to be conducted to compile the functionalities you are to incorporate in the new design. You also want to determine the limit as to how thin the current container design can be. Your supervisor required you to report the result of your preliminary study before proceeding further.

In addition to your full report, you are required to submit a one page summary containing the outline of your experiment(s) and the results. This would be an equivalent of the one page memo you have written in the past.

There are many aspects in the pop can design. Some of which you have studied such as fracture, buckling, and degradation. You are to applied your prior knowledge to this assignment. In addition, you will be performing an additional experiment for your analysis. Specifically, you will be exploring a common technique used to measure strains, i.e., pressure.

Prelab
Read page 17-23 in the Student Manual for Strain Gage Technology. Familiarize yourself with the strain gage installation procedures. You will be installing strain gage(s) to carry out your analysis.

Miscellaneous
Determination of the minimum possible wall thickness would require some kind of failure criteria. It is up to you to define what constitute a failure such as yielding, fracturing, etc. It is advisable that you calculate the principal stresses and the maximum shear stress. They are sometimes more convenient to use in a failure criterion.

Since this laboratory is a total hands on experiment, the student will have a certain degree of freedom as to what analysis should be performed beyond the required minimum. They are also free to choose the best report format for their hypothetical audience.

Plotting a simple average of the data hides statistical trend within a time set and may skew the overall trend of the data. Use curvefitting line to indicate trends in the data. Synergism means that the sum is greater than its parts taken separately. This must be shown in the graph and clearly stated in the report.