Einstein demanded that conservation of energy-momentum should be valid in the general theory of relativity since energy-momentum is a tensor quantity
. This was represented as
To describe crack anisotropy a tensor quantity
called "crack tensor" can be used (Idziak and Stan-Kleczek, 2006).The crack tensor of rank "k" can be defined as:
Integration and addition are usually accomplished by transforming the material (convected) components of a tensor quantity
such as stress or strain and then performing the addition (20).