Fatigue Loading Models

Using Finite Element Methods

Our focus is on two of the main types of cracking found in the Brown Gallery portrait set, being delamination and through-thickness (channelling) cracks.

Using the finite element method, we look to investigate initiation and propagation of both of these types of crack due to monotonic and low-cycle fatigue loading. Our goal with this is to examine the impact of cyclic changes in the environment (temperature and relative humidity) that reflect those found in the gallery that houses the panel paintings, since this is potentially the main cause of the damage to the paintings.

Schematic of a panel painting showing two of the main types of cracking, being delamination and through-thickness (channelling) cracks
Schematic of a panel painting showing two of the main types of cracking, being delamination and through-thickness (channelling) cracks
Schematic of a channelling crack in a thin film on a substrate, where the film (1) is of thickness h with tensile stress σ
Schematic of a channelling crack in a thin film on a substrate, where the film (1) is of thickness h with tensile stress σ

Finite Element Model of Monotonic Loading

For monotonic loading, we can impose scenarios that are characteristic of the average and extreme static conditions expected during prolonged periods of low/high moisture content to ascertain whether through-thickness (channelling) cracks or interface delamination is more likely to be the dominant failure mechanism.

The video below shows a finite element model of a channelling crack exposed to monotonic loading.

Finite Element Model of Cyclic Loading

Cyclic loading scenarios allow us to examine further fatigue loading models for delamination and through-thickness channelling that consider exposure to the variety of conditions that paintings may experience over time in their gallery environments. In particular, we are interested in obtaining crack initiation times in years and identifying whether channelling cracks or delamination cracks will grow more readily in the system.

The video below shows a finite element model of a channelling crack exposed to cyclic loading.