How to teach an undergraduate course without having taken that course formally before? I am in the final year of my PhD. My work was on using Finite element method to study tribology. It was completely modeling based. I developed various models and have gained quite expertise in modeling with the commercially available finite element code.

However, I come from materials engineering background and I don't have any formal education on statics, dynamics, continuum mechanics or finite element method. I had taken some advanced courses on mechanics. But, they did not cover the undergrad stuff and straightaway went for the modeling part or some applied stuff. 

Whatever theoretical I have learnt during my PhD, I have done that myself. So, it's neither structured or formalized. I read books, online videos, and I only concentrated on portions applicable for my research. As a result, I know how to model my problem statement which involves dynamic and transient behaviors. But know nothing about statics or quasi-static behaviors.

Now, I am asked to teach a short summer finite element analysis course to mechanical engineering undergrads from July to September (8 lectures ~ 12 hours). and I have no idea what and how to teach them. I have to teach theory and introduce modeling. How do I teach students who have more formal education than me on topics like statics, dynamics, continuum mechanics?
The more I think about this, the less I like it.  A summer course is SUPER ACCELERATED.  You blink, and the course is half over.  The opportunity to fix problems that arise is tiny.

I hope this is a low-credit course, as I really encourage you to stick to a workshop-style approach.  Teach by example.  This will essentially be a "getting started" guided tour.  Pick a problem, and walk the students through that problem during the summer session using a number of the tools you're trying to teach.

If you can find somebody that's taught this before, make that person your best friend.