The following textbooks are intended for educational use, and are openly-licensed. 

Mechanics – “This is a calculus-based book meant for the first semester of a first year survey course taken by engineering and physical science majors.” Created by Ben Crowell of Fullerton College.

Multimedia Engineering Mechanics – Developed at University of Oklahoma. The book’s nine chapters cover topics like Stress/Strain, Torsion, Beam Deflections, and more. It’s part of a family of similar Ebooks, on topics like: Multimedia Engineering Dynamics, Multimedia Engineering Statics, Multimedia Engineering Mechanics of Materials, Multimedia Engineering 
Fluid Mechanics, and Multimedia Engineering Mathematics.

Another title is Engineering Thermodynamics – A Graphical Approach, by Israel Urieli of Ohio University.