NDT ( UT ) Level II

A: Keep forcing the probe and you’ll chase disappearing echoes, fail sensitivity checks, and burn time on a retest. Excess pressure thins the couplant layer, breaking acoustic coupling so energy never enters the part. Relieving pressure and restoring a consistent film recovers transmission without changing calibrated variables.

A: Chasing setup errors here risks scrapping good material or missing a real defect. A planar lamination reflects sound at its depth, killing the backwall while leaving near-surface response intact. The other explanations would affect the entire sound path, not a discrete zone.

A: Set the wrong range and you’ll clip echoes or misread depth, then fail calibration on the spot. The pulse travels down and back, doubling the distance to 100 mm. Dividing by wave speed gives an order-of-magnitude check that keeps the gate where physics says it should be.

A: Cranking gain masks real geometry with grass and leads to false calls that won’t survive review. Gain should stay tied to reference sensitivity; moving the probe or changing angle alters insonification without corrupting the noise floor.