PSI - Issue 37

Nataliya Elenskaya et al. / Procedia Structural Integrity 37 (2022) 692–697 Nataliya Elenskaya / Structural Integrity Procedia 00 (2019) 000 – 000

694

3

3. Modelling of elastoplastic behavior Several gradient structures with different porosity fractions were generated for analysis. Compression and shear tests were simulated. The compressive load along the gradient action axis was specified through a 0.75 mm displacement of the top face of the structure. The shear load in the plane perpendicular to the gradient axis was specified by moving the top face of the structure by 1 mm along the X axis. The following elastic properties of PEEK were specified: Young's modulus 3800 MPa, E = Poisson's ratio 0.38.  = The plastic behavior of the structure was specified by the Johnson-Cook model:



   

   

   

p



(

)

( ) p 

  

 

n

.

(2)

,    p p

1 ln C

A B

= +

 +

 

p reference 



Here  is the flow stress,

132 MPa A = is the yield stress at reference temperature and reference strain rate,

10 MPa B = is the strain hardening coefficient,

0,7 n = is the strain hardening exponent,

p  is true strain,

0,034 C = is the coefficient of strain rate hardening, p  is the strain rate, p

reference  is the reference strain rate (Chen et

al., 2016). Finite element models with specified properties and loading conditions were calculated in Abaqus. An analysis of the results was performed by assessing deformations of the structure under the influence of the applied force. In compression tests of additively fabricated PEEK specimens fracture occurs at deformations greater than about 6% (Rahman et al., 2015). Fig. 2-4 show the maximal principal strain field at the step when the strain values in some parts of the structure exceed the assumed critical value after which the fracture process will occur.

a)

b)

( ) 01 , , G x y z  during а) compression load, with the total compression of the model is

Fig. 2 Maximal principal strain fields for the structure

0,42 mm; b) shear load, with the displacement of the upper face of the structure 0,46 mm ;