Gustavo Donato obtained his PhD in Naval and Ocean Engineering in the University of Sao Paulo, Brazil in 2008. Nowadays, he is employed as a researcher and assistant professor at FEI University Centre, Brazil, where he graduated in Mechanical Engineering in 2004 with First Class Honours. His research efforts are focused on innovative methodologies for accurate materials testing and characterisation, especially regarding fracture mechanics and fatigue fields. His central expectation is to be able to contribute with improvements in testing protocols to better support structural integrity assessments, avoiding accidents and providing safer engineering solutions for the whole society.

Gustavo is a member of the Brazilian Materials, Metallurgy and Mining Association (ABM) and investigates the mechanical behaviour of high performance structural carbon steels, duplex and superduplex stainless steels containing welds and cracks. Constraint-designed specimens and micromechanics approaches for describing fracture toughness and fatigue crack growth are some of the main topics being investigated by his group.

Relevance of constraint-designed specimens for the accurate assessment of materials' fatigue and fracture resistance

Accurate mechanical properties play a key role in design and failure assessments, especially considering fatigue and fracture phenomena (increasingly relevant in current high performance designs). From a materials science point of view, improved alloys and processing techniques are achieved day-by-day, which demands mechanical quantification.

Conventional testing (eg tension) provides geometry-independent properties (neglecting statistical aspects), since specimens are smooth with known (stable) stresses. Fatigue and fracture mechanics testing, conversely, usually employs cracked specimens thus providing geometry-dependent properties. Different thicknesses, crack depths and loading modes generate different stresses (due to varying stress constraint) and consequently strength.

Standards provide only general-purpose guidance. For example, using standard SE(B) or C(T) specimens (according to ASTME1820) to design petroleum pipelines usually reveals very conservative results, leading to unnecessary expense and material specification. Alternatively, nonstandard specimens can be constraint-designed under tension, with shallow cracks and adequate thickness to reproduce applications' real stress rate. This purpose-oriented testing deserves attention since it favours a precise coupling between material properties and design demands, providing safer engineering solutions for the whole of society.

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