The testing of fracture toughness becomes problematic when only limited amount of material is available that hinders the production of typical beam specimens to be tested in bending. Here we explore fracture toughness testing methodologies that allow for small discs and plates having surface cracks to be tested in biaxial flexure using the Ball-on-3-balls (B3B) set-up, or sawed notches as in the Compact Tension geometry. The B3B-K_Ic test has shown to be versatile and account for a very small overestimation of the K_Ic-value in the order of 0.8–1.25% due to in-plane crack mispositioning, and a maximum of 4% if a worst-case scenario of additional out-of-plane mispositioning is assumed. The geometrical factor in the standard SCF method, derived by Newman and Raju, resulted in an overestimation of ∼8% of the K_Ic-value compared to the new calculation by Strobl et al. for materials with Poisson’s ratio <0.3.

当只有有限数量的材料可用时，断裂韧性的测试就成问题了，这种材料阻碍了典型的弯曲弯曲试样的生产。在这里，我们探讨了断裂韧性测试方法，该方法允许使用3球上球（B3B）装置或紧凑张力几何形状中的锯切缺口在双轴挠曲中测试具有表面裂纹的小圆盘和板。B3B- K _Ic测试已被证明是通用的，并说明了对K _Ic的很小的高估由于面内裂纹错位，该值大约为0.8–1.25％，如果假设最坏的情况是附加平面外错位，则该值最大为4％。与Strobl等人的新计算相比，Newman和Raju推导的标准SCF方法中的几何因子导致K _Ic值的高估了约8％。泊松比<0.3的材料。