153642 Bending

In the case of bending, the area under the load-deflection curve is used to estimate the energy-absorbing capacity or toughness of the material. Increase of the toughness also means improved performance under fatigue, impact, and impulse loading. The toughening mechanism provides ductility.

Another popular way to measure the toughness is characterized by the so-called toughness index, which is the area under the curve up to a specified deflection value. Three common codes for evaluating the bending toughness are

• American Concrete Institute (ACI) Committee 544 Toughness:

Index area of load-mid-span deflection curve to 1.9mm/area of curve up to first cracking.

• American Society of Testing & Materials (ASTM) C 1018:

I5 = Area of load-mid-span deflection curve to 3d/area of curve up to 8 (first cracking). I10 = Area of load-mid-span deflection curve to 5.5d/area of curve up to 8 (first cracking). I20 = Area of load-mid-span deflection curve to 15.5d/area of curve up to 8 (first cracking).

• Japan Toughness index = Area of load-mid-span deflection curve to 1/150 span.

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