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The objective of this study is to observe the thermoelastic coupling effect in a monocrystalline Cu-Al-Be shape-memory alloy. The orientation of the austenite crystal is measured by Microfocus X-ray texture analysis. Uniaxial cyclic loading is applied to the specimen at room temperature. Infrared thermography is used to capture temperature fields on the specimen surface. The approach consists in analysing the cyclic temperature oscillation of points located on the surface of the specimen. The study highlights first the significant difference between the thermoelastic couplings in austenite and martensite. Second the anisotropy of both phases, especially the martensite, is evidenced.

The checkerboard constitutes the best pattern for full‐field strain measurement because it maximizes image gradient. In the experimental mechanics community, employing this pattern is currently strongly limited because depositing it on the surface of specimens raises practical difficulties. A recent study shows, however, that it is technically possible by using a laser engraver. The present paper aims to push this solution forward by printing a checkerboard pattern on a thin polymeric film and then gluing the resulting laser‐engraved film on the specimen surface. The underlying idea is to separate the manufacturing process of this optical strain gauge on the one hand and its use on the other hand to help spread this strain measuring tool in the experimental mechanics community. The polymeric film employed here is the same as that used in the manufacturing process of classic electrical gauges, so one can rely on the know‐how of classic strain gauge bonding to glue this optical strain gauge on the specimen surface. The main difference between the proposed tool and classic electrical gauges is that the strain field beneath the polymeric support is measured instead of localized strain values. The paper is a proof of concept for this strain field measuring tool. The manufacturing and bonding processes are described in the paper. The localized spectrum analysis, a spectral technique developed for processing images of periodic patterns, is used to retrieve the strain fields from checkerboard images. Through two complementary examples, we show the ability of this new type of strain gauge to detect and quantify local details in the strain field beneath. A simplified 1D model is also proposed to assess the minimum width of the strain peak that can reliably be measured with this technique. [ABSTRACT FROM AUTHOR]

The context of the study is the preventive reinforcement of aluminium structures with bonded composite patches. The paper deals with stress relief in the substrate under tensile loading, as well as crack propagation in the adhesive during fatigue tests. For this purpose, temperature measurements are performed through the thickness of the specimen using an infrared camera. The procedure provides two types of information. First, thermoelasticity is used to study the relief in the aluminium substrate during cyclic loading: stress distribution, global relief, and progressive load transfer zone. Second, the study allows the tracking of patch disbond and characterization of mode-II crack propagation in the adhesive. A Paris law is determined for the design of bonded composite patches subjected to tensile fatigue loading. [ABSTRACT FROM AUTHOR]

This paper presents a calorimetric approach to the measurement of mechanical dissipation in specimens subjected to cyclic tensile tests. Mechanical dissipation, that is, the heat power produced by the material due to mechanical irreversibility, can potentially be deduced from the temperature changes captured on the specimen surface by infrared thermography. However, a difficulty arises for long-term cyclic tests: Results are easily skewed by any change in the specimen's environment. The problem is amplified by the fact that mechanical dissipation is in general small compared to the heat sources associated with thermomechanical couplings, making its estimation difficult. The paper proposes a simple procedure to extract a well-resolved estimation of mechanical dissipation by solving two key points specific to long-term cyclic tests: (a) the reduction of the parasitic effects associated with changes in the specimen's environment by using a specific device based on two references samples and (b) the choice of relevant thermal data acquisition parameters. A test is performed on a copper-based shape-memory alloy whose calorific response comprises three origins of heat sources: thermoelastic coupling, phase transformation, and mechanical irreversibility. The results obtained demonstrate the relevancy of the approach in extracting mechanical dissipation from the thermal response of the specimen subjected to long-term tensile tests in fatigue. [ABSTRACT FROM AUTHOR]

Shape memory alloys (SMAs) are promising mechanocaloric materials for the creation of innovative heating/cooling systems. The present paper proposes a simple concept of "porous" SMA material in the form of a two-dimensional (2D) "granular" system. The basic idea is to place SMA cylinders in parallel and in contact, thus creating a 2D granular material, with fluid circulation in the third dimension (i.e. in the longitudinal direction of the cylinders). The study is dedicated to the validation of the mechanocaloric character of such a material system subjected to confined compression. First, experiments were conducted using superelastic nickel-titanium rods of various diameters, enabling us to create different bidispersity levels for the granular medium. Infrared thermography was used to analyze the temperature changes within the cylinders. Second, air was used as the circulating fluid for the sake of concept validation. Comparison between different levels of bidispersity of the granular system showed that a nearly-monodisperse configuration could be advantageous to optimize the concept. • Superelastic SMA cylinders were placed in parallel to create a 2D granular system. • Ni–Ti rods of varying diameters were used to create bidisperse configurations. • Mechanocaloric response under confined compression was validated by IR thermography. • Air was used as a fluid circulating in the longitudinal direction of the SMA rods. • A nearly-monodisperse configuration appears to be a relevant compromise. [ABSTRACT FROM AUTHOR]