About the distribution of forces in permanent magnets

Different methods can be proposed to determine the global force on magnets (equivalent models, Maxwell stress tensor, virtual work principle, etc.). The same value is obtained whatever the method while the local force distribution differs. This problem (i.e. different local force distributions on permanent magnets) has not yet been solved, even though the determination of the physical distribution of forces is a crucial point, both for practical applications and for theory. Thus, the different methods which allow the calculation of the local force distribution in permanent magnets are described and compared. Evidence is given that only the method based on the virtual work principle provides reliable results