A new push‐pull sample design for microscale mode 1 fracture toughness measurements under uniaxial tension. Issue 5 (3rd November 2017)

• Record Type: Journal Article
• Authors: Schwiedrzik, J.J.; Ast, J.; Pethö, L.; Maeder, X.; Michler, J.
• Is Part Of: Fatigue & fracture of engineering materials & structures. Volume 41:Issue 5(2018)
• Page Start: 991
• Page End: 1001
• Publication Date: 2017-11-03
• Subjects: fracture toughness -- micromechanics -- push‐pull design -- silicon -- single‐edge notch tension; Materials -- Fatigue -- Periodicals; Fracture mechanics -- Periodicals; 620.1123
• DOI: 10.1111/ffe.12741
• Languages: English
• ISSNs: 8756-758X

Abstract

Abstract: A sample geometry is proposed for performing microscale tensile experiments based on a push‐pull design. It allows measuring mode 1 fracture toughness under uniform far‐field loading. Finite element simulations were performed to determine the geometry factor, which was nearly constant for Young's moduli spanning 2 orders of magnitude. It was further verified that mode 1 stress intensity factor K I is nearly constant over the width of the tension rods and an order of magnitude higher than K II and KIII . Notched samples with different a / w ratios were prepared in (100)‐oriented Si by a combination of reactive ion etching and focused ion beam milling. The mode 1 fracture toughness K I, q was constant with a / w and in average 1.02 ± 0.06 MPa√m in good agreement with existing literature. The geometry was characterized and experimentally validated and may be used for fracture toughness measurements of all material classes. It is especially interesting when a uniaxial, homogeneous stress field is desired, if crack tip plasticity is important, or when positioning of the indenter is difficult.