PSI - Issue 28

Selda Oterkus et al. / Procedia Structural Integrity 28 (2020) 418–429 Author name / Structural Integrity Procedia 00 (2019) 000–000

421

4

  , t x





H   x



d s dV 



(5)

2.2. Non-ordinary state-based peridynamics

Fig. 2. Peridynamic forces in non-ordinary state-based peridynamics (Madenci and Oterkus, 2014).

As mentioned in the previous section, an assumption is made in ordinary state-based peridynamics regarding the direction of peridynamic forces being along the interaction direction. For non-ordinary state-based peridynamics, this assumption is relaxed so that interaction forces can be in arbitrary directions. Moreover, non-ordinary state based peridynamics is a suitable platform to incorporate classical material models in peridynamic framework. Peridynamic forces that the material points x and  x exert on each other in non-ordinary state-based peridynamics can be written as       1      t P x K x x x (6a)       1         t P x K x x x (6b) where  is the influence function,   P x is the first Piola-Kirchhoff tensor of the material point x , and   K x is the tensor of the material point x which is defined as         H dV          x K x x x x x (7)

with the symbol “  ” being the dyadic product. To calculate the first-Piola Kirchhoff tensor in peridynamic framework, it is essential to define the deformation tensor in peridynamic framework,   F x  which can be written as