For operational safety the design of the aluminium pipe requires that the stress in the pipe wall should not exceed 50% of the yield strength of the material. (i) if the yield strength of the aluminium is 360 mpa and the pipe has a diameter of 1.5 m and a wall thickness of 25 mm, determine the maximum internal pressure the pipe can be allowed to tolerate. (ii) inspection techniques are unable to identify defects due to welding that are less than 1.5 mm long. for the pipe in (i) calculate the minimum fracture toughness of the aluminium that would be needed to accommodate cracks up to this length. (take y = 1.2 for this geometry) (iii) comment on why the fracture toughness value you calculated in (ii) should be higher in practice.