| 摘要 |
PURPOSE:To improve accuracy by projecting ultrasonic waves of a wide frequency band into a spheroidal graphite cast iron and measuring the upper limit value of the frequencies of the ultrasonic waves transmitted through the cast iron, then determining the fracture toughness of an object to be measured from the upper limit value of the frequencies. CONSTITUTION:The ultrasonic waves X of, for example, an about 0.5-10MHz frequency band are projected from an ultrasonic probe 2 into the spheroidal graphite cast iron which is the object 1 to be measured. Only the high frequency bands of the ultrasonic waves transmitted through and reflected by the object 1 to be measured scatter and attenuate according to the grain sizes of the graphite 3 and the distance between the graphite 3 particles and, therefore, the fracture toughness is determined as a relative value by measuring the upper limit value of the frequencies and the normal fracture toughness is obtd. by a suitable calibration curve. The fracture toughness is, therefore, measured with good accuracy by a non-destructive method. |
