Learning from Objects: the use of advanced numerical methods to exploit a complete set of information from experimental data, for the Mona Lisa’s Digital-Twin

International audienceThe approach to wooden artefacts of historical importance, and panel paintings in particular, is a task that requires a multidisciplinary approach based on experimental observation of the artwork and advanced techniques to make these data actually useful for the knowledge and preservation of the object. This study illustrates how a series of scientific observations and instrumental analyses can be used to construct a numerical simulation that allows a deeper understanding of the physical structure and behaviour of the object itself, namely to construct a hygro-mechanical predictive model (a “Digital-Twin”) of Leonardo da Vinci's Mona Lisa panel. Based on specific request from the Louvre Museum, a group of experts with different and complementary skills cooperated and are still cooperating to construct a complete set of experimental observation and non-invasive tests; so, the integration of the collected data made the construction possible of the panel’s Digital-Twin. This paper also specifically examines how the Digital-Twin can be used to compare two framing conditions of the panel; although the two experimental configurations are not inherently comparable, the comparison is made possible by the introduction of a technique of projection of the fields obtained as results of the two analyses, named the Projected Model Comparison (PMC), which has been developed specifically for this research

Integration of experimental and numerical methods to study the mechanical risk conditions for the conservation of unique art pieces: the case of the Mona Lisa

International audienceThe engineering approach to analyse the hygromechanical behaviour of a panel painting requires a deep knowledge of its actual physical structure, including size, shape, wooden material's anatomy and character- istics, and responses to extemal actions such as forces or hygrothermal fluctuations. In fact, each panel is unique, different from all the others, because of numerous factors, in- cluding the intrinsic variability of the wood, the "cut" of the boards, the construction technique of the artwork, the succession of environments in which it has been main- tained, the irreversible processes developed during its existence, and the conservation interventions it has undergone over the centuries. Based on our experience, only a systematic set of experimental investiga- tions, conceived and implemented specifi- cally for the individuai artwork, can provide the information necessary to understand its conservation needs. However, experimen- tal investigations alone are not sufficient for a complete assessment of the artwork: numerical simulations integrated with the experimental tests can greatly improve the level of knowledge and provide more ex- tensive and deeper information. Moreover, following such an approach, the simulation can make it possible to explore situations of risk or modifications of the conservation situation in a totally non-invasive and risk- free way. The wooden panel ofLeonardo da Vinci's Mona Lisa has been studied by an intemational team with the aim of analysing and possibly improving its conservation conditions by combining a comprehensive set ofnon-invasively obtained experimental data with an advanced numerical modelling. The development of a Digital Twin of the pane I has hence provided a sound knowl- edge of the mechanical characteristics and behaviour ofthe panel, including the assess- ment of the risk of propagation of an ancient crack, and the evaluation of a new framing configuration