Pressure vessels are used in transportation for storage of gases and liquids. The pressure inside is multiple times higher than the pressure outside, so they are called "pressure vessels". Spherical shapes are ideal for pressure vessels since they have a uniform stress distribution in all directions. Rectangular or polygonal shapes can have a very high stress concentration in corners, which can result in weakness or premature wear and tear of the vessel. The most practical pressure vessels are cylindrical with welded elliptical ends. Many gases are stored at very high pressure in the liquid form. Pressure vessels are subjected to catastrophic failure, explosions due to temperature/pressure rise, or crack formations in the vessel metal. 
The pressure vessels are designed mainly to have high strength in both the circumferential (hoop strength) and axial directions. Also, a factor of safety ensures that the vessel is designed for higher loads than the actual working loads.
This SimCafe Structural Course was developed by Dr. Rajesh Bhaskaran, Swanson Director of Engineering Simulation at Cornell University in partnership with Ansys. It was last modified by Sebastien Lachnace-Barrett. It serves as an e-learning resource to integrate industry-standard simulation tools into courses and provides a resource for supplementary learning outside the classroom. The following course shows how to estimate the hoop, axial, and radial stresses in pressure vessels using Ansys Structural.
For more ways to learn, check out the Cornell edX course, A Hands-on Introduction to Engineering Simulations at ansys.com/cornell
Cornell University also offers a Fluid Dynamics Simulations Using Ansys online certificate authored by Dr. Rajesh Bhaskaran. Learn more here: https://ecornell.cornell.edu/fluiddynamics.
