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The purpose of this review is to discuss the development and the state of the art in dynamic testing techniques and dynamic mechanical behaviour of rock materials. The review begins by briefly introducing the history of rock dynamics and explaining the significance of studying these issues. Loading techniques commonly used for both intermediate and high strain rate tests and measurement techniques for dynamic stress and deformation are critically assessed in Sects. 2 and 3. In Sect. 4, methods of dynamic testing and estimation to obtain stress–strain curves at high strain rate are summarized, followed by an in-depth description of various dynamic mechanical properties (e.g. uniaxial and triaxial compressive strength, tensile strength, shear strength and fracture toughness) and corresponding fracture behaviour. Some influencing rock structural features (i.e. microstructure, size and shape) and testing conditions (i.e. confining pressure, temperature and water saturation) are considered, ending with some popular semi-empirical rate-dependent equations for the enhancement of dynamic mechanical properties. Section 5 discusses physical mechanisms of strain rate effects. Section 6 describes phenomenological and mechanically based rate-dependent constitutive models established from the knowledge of the stress–strain behaviour and physical mechanisms. Section 7 presents dynamic fracture criteria for quasi-brittle materials. Finally, a brief summary and some aspects of prospective research are presented.

/pdf/a-review-of-dynamic-experimental-techniques-and-mechanical-2kstp2wfg4.pdf

A Review of Dynamic Experimental Techniques and Mechanical Behaviour of Rock Materials

Recent developments in the direct-current geoelectrical imaging method

Infrared thermography for condition monitoring – A review

The intensity of the infrared radiation emitted by objects is mainly a function of their temperature. In infrared thermography, this feature is used for multiple purposes: as a health indicator in medical applications, as a sign of malfunction in mechanical and electrical maintenance or as an indicator of heat loss in buildings. This paper presents a review of infrared thermography especially focused on two applications: temperature measurement and non-destructive testing, two of the main fields where infrared thermography-based sensors are used. A general introduction to infrared thermography and the common procedures for temperature measurement and non-destructive testing are presented. Furthermore, developments in these fields and recent advances are reviewed.

/pdf/infrared-thermography-for-temperature-measurement-and-non-2r2amijcr4.pdf

Infrared thermography for temperature measurement and non-destructive testing.

Infrared thermography transforms the thermal energy, emitted by objects in the infrared band of the electromagnetic spectrum, into a visible image. This feature represents a great potentiality to be exploited in many fields, but this technique is still not adequately enclosed in industrial instrumentation because of a lack of adequate knowledge; at first sight, it seems too expensive and difficult to use. The aim of the present paper is to shortly overview existing work and to describe the most relevant experiences devoted to the use of infrared thermography in three main fields, i.e. thermo-fluid dynamics, technology and cultural heritage, which have been performed in the department the authors belong to. Results may be regarded from two points of view, either as validating infrared thermography as a full measurement instrument, or as presenting infrared thermography as a novel technique able to deal with several requirements, which are difficult to perform with other techniques. This study is also an attempt to give indications for a synergic use of the different thermographic methods and sharing experiences in the different fields.

http://iopscience.iop.org/article/10.1088/0957-0233/15/9/R01/pdf

Recent advances in the use of infrared thermography

Non-destructive evaluation of aerospace materials with lock-in thermography

The aim of the present paper was to investigate the behaviour of glass fibres reinforced polymer (GFRP) under low velocity impact with infrared thermography. Several specimens were considered which include unidirectional E-glass fibres embedded in epoxy resin matrix with symmetrical stacking sequence [02/902]S. These specimens were impacted with modified Charpy pendulum by varying shape (ogival and hemispherical) and diameter (18 and 24 mm) of the hammer and the impact energy in the range 4–25 J. The side opposite to impact was monitored by infrared cameras. Sequences of images were acquired with starting and ending times set so as to include the evolution of thermal phenomena from thermo-elastic to thermoplastic phases. Infrared thermography was also used for non-destructive evaluation of specimens before and after impact. The obtained results show that on-line monitoring of the impact is useful for material characterization. In particular, it is shown that the onset of heat generation loci corresponds to the onset of impact damage. From the analysis of temperature maps it is possible to get information about damage threshold and extension. One main finding regards the relationship between the damaged area and the effective striking surface.

Impact damage in GFRP: New insights with infrared thermography

Nondestructive evaluation of carbon fibre reinforced composites with infrared thermography and ultrasonics

Lock-in thermography is employed for non-destructive control to evaluate several aspects of industrial interest: inclusions of spurious materials in both carbon-epoxy and glass-epoxy, impact damage and delaminations occurring around holes during drilling in carbon-epoxy, bonding improvements in Certran® after plasma treatments and steel modifications after welding. Phase images are analysed to find quantitative information for industrial characterization.

https://iopscience.iop.org/article/10.1088/0957-0233/13/10/311/pdf

Carosena Meola

Papers

Recent advances in the use of infrared thermography

Non-destructive evaluation of aerospace materials with lock-in thermography

Impact damage in GFRP: New insights with infrared thermography

Nondestructive evaluation of carbon fibre reinforced composites with infrared thermography and ultrasonics

Non-destructive control of industrial materials by means of lock-in thermography