A rectangular bar 30-mm wide and 24-mm thick made of aluminum ...
    E = 70 GPa
    α = 23.0 × 10^-6/°C

... and two rectangular copper bars 30-mm wide and 12-mm thick ...
    E = 120 GPa
    α = 16.0 × 10^-6/°C

... are connected (in the longitudinal direction) by two smooth 11-mm diameter pins.