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A current trend in mechanical testing technologies is to equip researchers and industrial practitioners with the facilities for non-destructive characterisation of the deformation and fracture processes occurring on different scales. The synergistic effect of such a combination of destructive and non-destructive techniques both widens and deepens existing knowledge in the field of plasticity and fracture of materials and provides the feedback sought to develop new non-destructive testing approaches and in situ monitoring techniques with enhanced reliability, accuracy and a wider scope of applications. The macroscopic standardised mechanical testing is still dominant in the research laboratories and industrial sector worldwide. The present paper reviews multiple challenges commonly faced by experimentalists, aiming at enhancing the capability of conventional mechanical testing by a combination of contemporary infrared thermography (IRT), rapid video imaging (RVI) with non-contact strain mapping possibilities enabled by the digital image correlation (DIC) method, and the acoustic emission (AE) technique providing unbeatable temporal resolution of the stochastic defect dynamics under load. Practical recommendations to address these challenges are outlined. A versatile experimental setup uniting the unique competencies of all named techniques is described alone with the fascinating possibilities it offers for the comprehensive characterisation of damage accumulation during plastic deformation and fracture of materials. The developed toolbox comprising practical hardware and software solutions brings together measuring technologies, data, and processing in a single place. The proposed methodology focuses on the characterisation of the thermodynamics, kinematics and dynamics of the deformation and fracture processes occurring on different spatial and temporal scales. The capacity of the proposed combination is illustrated using preliminary results on the tensile and fatigue behaviour of the fcc Inconel-625 alloy used as a representative example. Dissipative processes occurring in this alloy are assessed through the complex interplay between the released heat, acoustic emission waves, and expended and stored elastic energy.

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Hydrogen is receiving growing interest as an energy carrier to facilitate the shift to a green economy. However, hydrogen may cause the significant degradation of mechanical properties of structural materials, premature strain localisation, crack nucleation, and catastrophic fracture. Therefore, mechanical testing in hydrogenating conditions plays a vital role in material integrity assessment. Digital image correlation (DIC) is a versatile optical technique that is ideally suited for studying local deformation distribution under external stimuli. However, during mechanical testing with in situ electrochemical hydrogen charging, gas bubbles inherent to hydrogen recombination are created at the sample surface, causing significant errors in the DIC measurements, and posing significant challenges to researchers and practitioners utilising this technique for testing in harsh environments. A postprocessing technique for the digital removal of gas bubbles is presented and validated for severe charging conditions (−1400mV vs. Ag/AgCl) under monotonic and cyclic loading conditions. Displacement fields and strain measurements are produced from the filtered images. An example application for measuring the crack tip opening displacement during a slow strain rate tensile test is presented. The limitations of the technique and a comparison to other bubble mitigation techniques are briefly discussed. It was concluded that the proposed filtering technique is highly effective in the digital removal of gas bubbles during in situ electrochemical hydrogen charging, enabling the use of DIC when the sample surface is almost completely obscured by gas bubbles.