A reduced-order FE model to aid the design of vibration-mitigating framing and mounting methods for paintings on display and during transportation

The risk of exposing artworks to a variety of vibration sources is becoming increasingly recognised and the effects of such exposure, together with the vulnerabilities of different materials and objects are becoming better understood. The impact is believed to be cumulative: changes may not be evident until the point of substantial damage or even catastrophic failure. This cumulative impact is an increasing issue in today’s world of essentially 24-hour museum operation, which leads to more frequent and greater vibration exposure and thus the need to understand, limit and mitigate vibration from all sources. To assess and manage the risks of such exposure and explore potential mitigation approaches, two NG CDP PhD projects are already being undertaken in Oxford (in collaboration with Tomasz Galikowski). While these projects are helping to understand the vibration levels to which paintings are exposed and their response to a range of vibration sources, they are also raising very important, practical questions about how – at the level of individual paintings – measures can be taken to mitigate the effects and which factors most influence the risk this exposure poses. For example, can how a painting is framed or mounted mitigate the impact of vibration or might it potentially make the situation worse, for varied vibration types? These sorts of question cannot be addressed with the methods used for the existing PhD projects which are – by necessity – based on a simplified paintings model. To start to address issues around the design of mounting/hanging systems and choices regarding the framing of paintings, a more detailed finite element (FE) model that accounts for the vibro-acoustic interaction of all components is needed. Previous work in heritage applications using FE methods has neglected vibro-acoustic interactions, has not incorporated all components of interest and does not consider the cumulative impact of multiple vibration or other mechanical sources. This project aims to develop a robust model of a painting to accurately account for the interaction of its components (frame, glazing, backboard, trapped air and hanging or packing system) when exposed to various forms of vibrational excitation. To improve the computational efficiency but retain sufficient accuracy, reduction methods will be used. The reduced FE-based model produced will make it possible to offer guidance as to how various changes to the overall framing and mounting of paintings might help mitigate the effects of exposure to all potential vibration sources (or might inadvertently make it worse). It will look at the cumulative effect of such exposure and can be used to help design mounting and packaging systems. The FE modelling will be supported by experimental validation working with mock-ups and mechanical testing etc. The resulting model will apply to both paintings on canvas and panel supports and can account for pre-existing damage. It could be extended to investigate other mechanical forces, including the effect of fluctuating RH or temperature, relevant to research to develop more sustainable approaches to controlling museum environments. The underlying code will be freely available so users can input their own painting parameters and relevant vibrational excitation sources and then output calculated values including velocities, accelerations, strains, estimated fatigue life, crack propagation and modal properties. While the underlying experimentation and modelling will be academically rigorous, the project is focused on the needs of heritage end-users presenting and safeguarding collections.