PSI - Issue 50

V.G. Degtiar et al. / Procedia Structural Integrity 50 (2023) 40–49 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

42

3

Fig. 2. Typical patterns of large-scale roughness on ablated surfaces of C-C composites of the following types: (a) – KIMF; (b) – 4KMS; (c), (d) – 4KMS-L. 2. Electron microscopic and tomographic measurements of distributions of pores, shells and distributions of density over the volume of materials Since volume porosity of a material V P is related to its density  with the equation ) (1 V m P      (1) where m  - density of a monolith material, then carrying out tomographic measurements of the density distribution over volume of C-C composite samples, of which TPS elements are made, it is possible to form data on typical density distribution over volume of an element and, correspondingly, secondary roughness in the vicinity to a reference point. Stand fire tests, Kostin et al., showed that in a turbulent flow mode a relation of a gain of heat exchange Ts k versus the density of a C-C composite is an exponential function

a



   

   



(2)

Ts k k 

Tsn

n 

where a = 3 … 6 = const; Ts k ,

n  – nominal for the material gain of heat exchange and density. is negligible, in linear approximation it follows from (2)

( 

  )

Since the relation

n

n 

a

a





   

1          

1      

(

  )

(

  )

k

Tsn k k k  Ts







(3)

1  

a



n

n

Ts

Tsn

k

n 

n 

n 

Tsn

The gain of heat exchange can be presented as