Mechanoluminescence technique for real-time monitoring of cracks produced during application of loads on crystals

When a load is applied on to a crystal, then the fractomechanoluminescence (ML) emission takes place in the form of light pulses. The number of ML pulses and the time duration tc for the appearance of ML increase with increasing value of the load and the average ML intensity from a single ML pulse decreases with increasing value of the load. For a given value of the applied pressure, the total number NT of ML pulses, the total ML intensity IT and the time duration tc of ML emission increase with increasing size of the crystals. As the total ML intensity is directly related to the area of newly created surfaces, the pressure dependence of the total ML intensity indicates that initially the total area of newly created surfaces increases with increasing value of the applied load and later on it tends to attain a saturation value for higher values of the applied load. As the strain rate is maximum at a particular time after the application of load on to a crystal, the rate of the emission of ML pulses is maximum at a particular time after the application of load on to the crystals. The dependence of NT, IT, and tc on the applied pressure Po follows the following expressions, respectively NT = Mo V y [1 – exp{–δc (Po – Pf)}]