The interview process began with 3 phone screening interviews, each 30 min in length, spread out over a span of a month. These consisted of 15 minutes of technical questions, followed by 15 minutes of back and forth discussion about the company in general, during which time I was able to ask questions. Each of the 3 interviews focused on a different sub-field of engineering related to my area of expertise, and thus were conducted by existing employees of Exponent who are also experts in that area.
A final, full day interview was scheduled for a month after my most previous phone interview. This was an all day affair consisting of six 30 minute interviews with various people, each one similar to the phone interviews (in the sense that it was half technical questions and half relaxed discussion). In addition, I was asked to give a 45 minute technical presentation on my PhD research. The interviewers asked technical questions throughout, resulting in a total time of 60 minutes.
The hiring manager stressed that the technical presentation was the most important part of the whole process, and can ruin an otherwise perfect candidate. This is consulting after all, so communication is of utmost importance. They expect you to be able to clearly communicate not only *what* your research is, but *why* it matters, to an audience full of non-experts. The hiring manager specifically said "if you give the same presentation you gave for your PhD defense, you will fail the interview." You need to tailor your presentation to tell a narrative story, not just show a bunch of equations and expect your audience to care by default.