Fracture mechanics equation

1. Dec 17, 2009

Denzil

I am having trouble understanding where the units to fracture energy come from when worked out with the following equation.

2$$\gamma$$$$_{ef}$$=$$\frac{K^{2}_{Ic}}{E}$$

fracture energy = fracture toughness/young modulus
i asked my teacher as this is part of my coursework but he was not able to work it out.

I dont understand how the division of Mpa with Mpa = J/m$$^{2}$$

any insight would be much appreciated

Last edited: Dec 17, 2009
2. Dec 17, 2009

ideasrule

Fracture toughness has units of Pa*sqrt(m), so its square has units of Pa^2 * m. Divide that by Pa and you get Pa*m, or N/m^2 * m=N/m. Can you now see why the units are equal to J/m^2?