抄録
A new expression method for tear toughness is proposed. The second half of the load-displacement curve after the peak load (stress) is curve-fitted by a cosine curve. The maximum stress σmax and displacement for fracture λ are defined as a doubled amplitude value and half of the wave length of the cosine curve, respectively. The tear toughness is expressed by the combination of these values and indicated in the logσmax -logλ chart. The UEp (Unit crack propagation energy) is also exhibited as a straight line with a gradient of －1 in the chart. The ‘logσmax -logλ expression’ is superior to the conventional UEp-based evaluation since a mutual balance between strength and ductility from the chart can be shown in the chart. The present logσmax -logλ chart is available for making direct comparison of tear toughness for various kinds of cast aluminum alloys from very brittle die-cast ADC12 to ductile squeeze-cast AC4CH aluminum alloys. Tear tests with the aid of present evaluation method will be useful for developing cast and die-cast aluminum alloys with improved toughness.
