This is a value stream map for a theoretical enterprise that I created in my ‘designing and improving operations’ course at Western Washington University. This mapping was done in Visio using standard icons and can be downloaded as a PDF by clicking the “Value Stream Map PDF” button. The Visio files containing the value stream map along with a legend of the icons used can be downloaded in a zipped file by clicking the “Visio Files” button.

I also performed a VSM for Subsonic Skateboards, a company I previously consulted for. This value stream map can be downloaded from the linked page

At Western Washington University I took a machine design class. I was interested in that class so I ended up going a little overboard on my project work in the sense that rather than answering all of the questions individually, I solved them parametrically. The first project was on shaft design. The attached shaft design file has the shaft design calculator, an automated CATIA V5 file, and other relevant project information. The second project was a gear design project that related to the shaft designed in project 1. For this project I manually derived most equations for values that were presented in the class graphically to allow for accurate and adaptable parameterization rather than taking values from charts. In the second project I also implemented a material database so that gear materials could be adjusted to inform design.

Though this calculators main intention was to estimate minimum require tank masses, it actually goes far beyond that. To obtain the minimum mass for a given laminate, the calculator performs pass/fail analysis structural analysis on the tank using 4 different failure criteria options: Maximum stress, maximum strain, tsai-hill, and tsai-wu. This analysis also includes residual stresses within the composite due to deviation between in process cure temperature and the test temperature.

In order to perform this test, many other properties need to be determined. These include mechanical properties for individual lamina in principle and global coordinate systems as well as properties for the entire laminate.

Before running the structural analysis, the code runs a probability of failure analysis to ensure that probability of success is above 99.9%. This analysis is based on a weibull model for which the weibull parameters have been empirically derived given in the linked document .

The current code assumes a common bulkhead tank with hemispherical caps for propellants and standalone tank for pressurant. I am currently developing in line fracture mechanics analyses of the tank liners to ensure that failure does not occur due to common flaws inherent to the process. This is difficult because critical stress intensity factors (Kc) are most often determined experimentally, and I do not have the resources to compile a database; a problem which I am actively looking to work around.

Future plans are to develop a parametric model for the tanks in Siemens NX using this analysis as a starting point. Then, FEMAP / Nastran will be used to optimize ply orientation. Though this is just a starting point, feel free to download and play around with it yourself!