18391. According to Unwin’s formula, the relation between the diameter of rivet hole (d) and the thickness of plate (t) is given by (where d and t are in mm) September 14, 2025 by Admin [A]. d = t [B]. d = 1.6 t [C]. d = 2 t [D]. d = 6 t ✅ The correct answer is option D.