Fracture mechanics is an important branch of materials science that delves into understanding the cracks in materials and how they propagate. This field has been instrumental in predicting material failure, especially in engineering materials subjected to applied stress. As we venture deeper into the micro and nanoscale realms, the traditional methods of studying fracture mechanics often fall short. Enter nanoindentation – a technique that has revolutionised our understanding of material properties at these scales.

Nanoindentation: A Brief Overview

Nanoindentation experiments involve precisely applying a sharp indenter into a material’s surface. The resultant force-displacement curve offers a treasure trove of information, revealing the material’s elastic modulus, hardness, and other intrinsic mechanical properties. But beyond these basic metrics, nanoindentation has opened doors to the world of small-scale fracture mechanics.

Fracture Toughness and the Microscale Challenge

Fracture toughness is a material’s resistance to crack propagation. At the microscale, materials often exhibit behaviours distinct from their macroscale counterparts. Factors like plastic deformation, elastic-plastic transitions, and stress intensity factor variations at the crack tip become more pronounced. Traditional testing methods, rooted in linear elastic fracture mechanics (LEFM), may not always capture these nuances.

A Quick History of Fracture MechanicsFracture mechanics roots back to the late 19th Century. Back then, structural steel became brittle at around 20°C. This was a problem when high-volume steel production began in the 1860s. Engineers like David Kirkaldy noticed this issue, but it wasn’t a big problem because fractures were contained within individual plates. However, in 1898, there was a significant brittle fracture in a water standpipe in New York. The problem got worse with the introduction of electric arc welding. Welded structures, like the Vierendeel Truss Bridge in Belgium, started to fail. The most notable were the fractures in the welded Liberty Ships, leading to the establishment of committees to investigate the issue.Initially, brittle fracture was viewed mainly as a metallurgical issue. The focus was on determining the transition temperature from ductile to cleavage behaviour. The Charpy test was introduced to assess this transition temperature. The concept of size effect in brittle fracture emerged slowly, with the first fracture test simulating a welded plate structure developed by Wells. The issue was primarily addressed by developing steels with lower transition temperatures. However, later improvements to increase steel strength led to issues with fast ductile fracture in certain applications, which required the application of elasto-plastic fracture mechanics.

Fast forward to today, and the field has evolved, integrating advanced techniques like nanoindentation to study material properties at scales previously deemed challenging.

Interested in Small-Scale Fracture Mechanics?

At Alemnis, we’ve been at the forefront of these exciting developments. Our commitment to pushing the boundaries of understanding has led to innovations that are shaping the future of materials science. For those intrigued by the intricacies of fracture toughness and keen to delve deeper, we invite you to explore our dedicated resource on the subject. Discover a world where the micro meets the macro, and where every indentation tells a story.


Cotterell, B. (2002). The past, present, and future of fracture mechanics. Engineering Fracture Mechanics 69. Available at