Using a standard specimen for crack propagation under plain strain conditions

R. Branco (CEMUC, Department of Mechanical Engineering, ISEC, Polytechnic Institute of Coimbra, Coimbra, Portugal)
J.M. Silva (Department of Aerospace Sciences, University of Beira Interior, Covilhã, Portugal)
V. Infante (Department of Mechanical Engineering, Technical University of Lisbon, Lisboa, Portugal)
F. Antunes (CEMUC, Department of Mechanical Engineering, University of Coimbra, Coimbra, Portugal)
F. Ferreira (División de Aeronáutica y Espacio, Altran, Miñano, Spain)

International Journal of Structural Integrity

ISSN: 1757-9864

Publication date: 1 November 2010



Stress state has a major influence on different phenomena, namely those involving diffusion and plastic deformation (like crack closure and high‐temperature fatigue crack growth, void formation or ductile fracture). The isolation of plane stress and plane strain states is crucial in fundamental studies of material behavior. The isolation of plane stress state is achieved with thin specimens, whilst the isolation of plane strain state is usually done increasing the thickness or introducing lateral grooves. The purpose of this paper is to propose a specimen geometry able to isolate the plane strain state, based on the standard M(T) geometry.


A numerical study was carried out aiming at obtaining a stress triaxiality parameter, h, as a function of different geometrical features of the specimen, such as the notch radius, notch depth and specimen thickness.


Results show that a pure plane strain state is achievable (i.e. 97 percent of specimen thickness has h>0.97) if a specimen with optimized geometrical features is used, which corresponds to a notch radius of 0.5 mm, a notch depth of 1 mm and a total specimen thickness of 12.56 mm.


This type of specimen geometry is a simple and efficient alternative to other common approaches used to obtain pure plain strain conditions for experimental purposes.



Branco, R., Silva, J., Infante, V., Antunes, F. and Ferreira, F. (2010), "Using a standard specimen for crack propagation under plain strain conditions", International Journal of Structural Integrity, Vol. 1 No. 4, pp. 332-343.

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