PSI - Issue 32

A.M. Ignatova et al. / Procedia Structural Integrity 32 (2021) 79–86 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

85 7

a

b

10 15 20 25 30 35 40

0 10 20 30 40 50 60 70 80 90 100

N

N

0 5

0

0,5

1

0

0,5

1

C con

C con

1

2

3

4

1

2

3

4

Fig. 9. Distribution of destruction fragments by convexity coefficient: ( а ) samples destroyed in non-constrained conditions, (b) samples destroyed in constrained conditions; 1 – at a velocity of 230 m/s, collision angle 90º; 2 – at a velocity of 120 m/s, collision angle 90 º; 3 – at a velocity of 230 m/s, collision angle 30º; 4 – at a velocity of 120 m/s, collision angle 30 º . Functions of fragment distribution by sphericity coefficient in non-constrained and constrained destruction conditions are also exponential, and they all correspond to normal distribution. There is a statistically significant difference between distributions of fragments in non-constrained and constrained impact conditions. In non constrained conditions, the range of average values of fragment sphericity coefficient is narrower and is within 0.70 0.79, compared to constrained conditions with the range of 0.53-0.84.

Table 1. Parameters of destruction fragments for various impact types.

Non-constrained conditions

Constrained conditions

Steel ball velocity 230 m/s

Steel ball velocity 120 m/s

Steel ball velocity 230 m/s

Steel ball velocity 120 m/s

Parameter

90 

30 

90 

30 

90 

30 

90 

30 

Impactor specific energy, J/cm 2 Average fragment size , μm Average fragment sphericity coefficient value Average fragment convexity coefficient value

269.41

73.34

269.41

73.34

5.15* (F 1.13 =4.32) 0.79± 0.02* (F 1.21 =3.09) 0.81± 0.005* (F 1.21 =4.04)

12.63* (F 1.16 =42.67) 0.70± 0.03* (F 1.23 =1.89) 0.77± 0.007* (F 1.23 =2.74)

7.42* (F 1.15 =1.75) 0.77± 0.01* (F 1.34 =1.46) 0.79± 0.006* (F 1.35 =2.03)

17.45* (F 1.2 =14.02) 0.70± 0.03* (F 1.26 =1.43) 0.76± 0.008* (F 1.27 =1.55)

15.06

71.45

22.93

27.23

0.53± 0.07 0.66± 0.02

0.84± 0.01 0.87± 0.003

0.84± 0.01 0.86± 0.003

0.68± 0.04 0.73± 0.01

*statistically significant differences vs. same parameters of loading in constrained conditions

The difference between ranges of average values of fragment sphericity coefficients points at various mechanisms of their splitting. It may be assumed that in constrained conditions, fragments forming as a result of dissipation of the ball’s energy with sphericity coefficient of 0.7 -0.8 become mixed with fragments forming as a result of fracture growth in peripheral areas of the sample, i.e. outside of the deformation localization area.