Achievement of ultimate values of the bulk and shear strengths of iron irradiated by femtosecond laser pulses

Shock-wave phenomena generated by femtosecond laser pulses in submicron iron film samples have been studied by the interferometric method with the application of frequency-modulated diagnostics in the picosecond time range. The splitting of the shock wave into the elastic and plastic waves with a compression stress of up to $27.5$ GPa behind the front of an elastic precursor has been detected. The corresponding maximum shear stress reaches $7.9$ GPa, which is even somewhat higher than the calculated ideal shear strength. The measured spall strengths reach $20.3$ GPa, which is also comparable to the calculated values of the ideal tensile strength.