Fracture Mechanics Units Question

Hi everyone,

I wanted to share an issue I ran into while working on stress intensity factor () calculations in Mathcad, and see if anyone has advice on how to resolve it. When I calculated , Mathcad returned results with strange units: ΔK(a0) = 6.013×10^6 lb / (ft^0.5·s^2). That term in the denominator makes no sense — stress intensity factor units should be something like ksi√in (force / length^1.5), with no time dimensions.

It seems that Mathcad is treating lb as pound-mass (lbm) instead of pound-force (lbf). Because of that, it introduces extra time units through when it tries to reconcile the dimensions. This appears to be why an is showing up in the denominator. Even after trying to redefine lb as lbf in my worksheet, Mathcad still seems to carry the time unit into the result. I can’t just delete the s^2 term — it keeps reappearing.

Has anyone else run into this issue where Mathcad sneaks in an term when working with fracture mechanics equations? How do you properly set up your units (lb, lbf, psi, ksi, etc.) so that comes out cleanly in ksi√in? Any tips, tricks, or best practices would be hugely appreciated.