Before revision: In the SI system, the unit of tensile toughness can be easily calculated by using area underneath the stress–strain (σ–ε) curve, which gives tensile toughness value, as given below: UT = Area underneath the stress–strain (σ–ε) curve = σ × εUT = F/A × ΔL/L = (N·m−2)·(unitless)UT = N·m·m−3UT = J·m−3 Toughest material An alloy made of almost equal amounts of chromium, cobalt and nickel (CrCoNi) is the toughest material discovered thus far.
After revision: In the SI system, the unit of tensile toughness can be easily calculated by using area underneath the stress–strain (σ–ε) curve, which gives tensile toughness value, as given below:    Toughest material An alloy made of almost equal amounts of chromium, cobalt and nickel (CrCoNi) is the toughest material discovered thus far.