18.4 : 応力-ひずみ図 - 脆性材料

Brittle materials, under tensile stress, do not elongate much before rupturing, meaning their ultimate and breaking strengths are identical. Compared with ductile materials, they possess lower strain during rupture.

It occurs along a surface perpendicular to the load, indicating that normal stresses primarily cause the failure.

Brittle materials do not undergo noticeable necking under stress.

Most brittle materials have higher ultimate strength in compression than tension, mainly due to microscopic flaws like cracks or cavities, that weaken the material under tension.

Consider a stress-strain diagram for the concrete slab, an example of a brittle material.

Under tension, a linear elastic range is observed until the yield point, and then strain increases more rapidly than stress until the slab ruptures.

Under compression, concrete displays a larger linear elastic range, and rupture doesn't occur as stress hits its peak. Instead, stress decreases while strain continues to increase until rupture.

The modulus of elasticity, represented by the slope of the linear region, is equal in both compression and tension for most brittle materials.