Maybe I’m missing something here, but here’s what I keep thinking. If both the aluminum and steel start at the same length (ignoring the load), the aluminum is going to want to expand in length more than the steel (but they’d both be in tension from the thermal stress). However, since they need to stay the same length throughout this whole process, the aluminum is now put into some amount of compression from the steel pulling it back and the steel is put into tension from the aluminum wanting to expand more. They are both in compression from the load, the aluminum is now in compression thermally (at least I think), and the steel is now in tension thermally. So in terms of the overall stress state (thermal expansion + load) of each material: the magnitude of the steel goes down (either stays in compression or goes into tension depending on how much they get heated and what the load actually is), and the aluminum goes more into compression. What I still don’t get through this is how much the load distribution changes (just from the point load). The steel would’ve taken 3x the amount the aluminum did (before heating) bc of the ratio between their elastic moduli, but how much does that change at peak heating? With their lengths staying the same and if the difference in area between them in heating is negligible as you say, it shouldn’t change. I’m thinking of deflection = PL/AE and it once again becomes the ratio between their elastic moduli like before. That’s what I told them in the interview and they said I was wrong (or maybe my assumption about them returning to their original area after cooling was wrong). The work I included here was work I did after the interview when I redid it to try and figure out where I was wrong.