Yes, in Workbench Mechanical, the alpha and beta damping coefficients should have units of [s] and [s^-1] since they are of the following form: [C] = alpha * [M] + beta * [K]. This is reflected in two locations – in the Engineering Data (Damping Factor (alpha) and (beta)) and in WB Mechanical (Analysis Settings branch, under “Damping > Stiffness/Mass Coefficient). This should be corrected in future releases.