it was about 45 min long, the guy asked me about why I was fit for the role, grilled me on my resume and asked a bunch of solid mechanics questions, thermo questions

Two technical interviews, then write up and discussed offer with HR. Interviews consisted of them introducing themselves, talking about the role in more detail, usually three technical questions, then a few minutes of you asking them questions. Entire interview process took more than a month but recruiter kept communication smooth.