Metal Magnetic Memory (MMM) is an after effect which occurs as residual magnetization in parent metal or welded joint formed in the course of fabrication or due to irreversible change of the local magnetization state of parent metal/inspection object in zones of stress conventration or damage under loadings.

In general, MMM is an after effect which is directly correlated with the distribution of natural magnetic feilds and the accumulated stress-stran which has been experienced by the ferrous or paramagmetic material.

To asses the stress condition in determine the weak area in material based on established correlation between accumulated stress-strain state that has been expereinced by ferrous/paramagnetic material with the distribution of natural magnetic fields.