Is there a convention regarding frames around plots in engineering?
There is no convention or guide on this, at least none with appreciable universality. Having said that, one doesn't need a style guide for things like this. 

The intention is to be clear to the reader. Minimalism or any other aesthetic ideal is secondary. In engineering, the values on graphs are potentially of interest, not just the trend. So a reader could potentially want to know the value of y(x), and your graph of y vs x should make it as easy as possible for him/her to do so. The top and right  axes make it easier to read out values, because (a) you now have two sets of axes to check your value against, (b) a point on the top-right is as easy to read as a point on the bottom-left.

Given that, I wouldn't recommend removing the frame or the ticks on the frame.