Multiaxial Loading Fracture of Al 2 O 3 Tubes: I, Experiments

Alumina thin‐walled tubes were fractured in axial tension, hoop tension, balanced biaxial tension, balanced tension‐compression, and pure torsion using an electrohydraulic mechanical testing apparatus. A slight anisotropy in the axial and hoop uniaxial strengths indicated that the predominant defects were axially oriented, and probably fabrication‐related as opposed to machining flaws. A 10% weakening was observed in balanced biaxial tension as compared to uniaxial tension, whereas strength was insensitive to a balanced tension‐compression stress state. The strength in pure torsion was 16% higher than the axial strength. Stress state results suggest a weakening due to in‐flaw plane tensile stresses and more complex fracture‐initiation phenomena for stresses not oriented perpendicular to the dominant defects.