PSI - Issue 14

Tulsi Chouhan et al. / Procedia Structural Integrity 14 (2019) 883–890 Author name / Structural Integrity Procedia 00 (2018) 000–000

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by both the specimens were in the nearby range of 0.15 to 0.26, respectively. The damage behavior of these specimens was a mix of brittle and ductile damage, indicating higher sintering temperature requirements or generation of oxide on the powder due to enormous milling time.

300

1785 /s 2390 /s 2910 /s 3025 /s

300

(b)

1920 /s 2145 /s 2770 /s 3012 /s

(a)

200

200

100

100

Sress (MPa)

Stress (MPa)

0

0

0

0.1

0.2

0.3

0 0.05 0.1 0.15 0.2 0.25 0.3

Strain

Strain

150

150

1525 /s 2475 /s 2840 /s 3200 /s

(d)

(c)

2303 /s 2812 /s 3140 /s

100

100

50

50

Stress (MPa)

Stress (MPa)

0

0

0

0.1

0.2

0.3

0

0.1

0.2

0.3

Strain

Strain

Fig. 2. Stress-strain plots for dynamic high strain rate compressive loading of (a) Al as received; (b) Al milled 24 hours; (c) Al containing 33 % rock salt; and (d) rock salt containing specimen boiled in water for 1 hour.

Fig. 2 (c) depicts the compressive high strain rate behavior of Al specimen containing 33 % rock salt (by weight). A sharp rising stress curve followed by continuously dropping stress with an increasing strain may be noted. The constant rate of stress drop after attaining peak clearly indicates the ill-effect of rock salt. Also, compared to Al as received the peak stress attained is significantly lower (Fig. 2(a)). The rate of adiabatic heat induced thermal softening is significantly higher for the specimen containing rock salt. The stress variation for this set of the specimen was noted typically lower in the range of 120 MPa to 141 MPa, for the strain rate variation in the range of 1525 /s to 3200 /s, respectively. It may be noted that the strain rate attained by the rock salt containing Al specimen were highest of all, for identical incident energy. The specimens containing salt were kept in boiling water for one hour to dissolve the salt content. This limited period in boiling water resulted in reduced salt content as revealed by lower density (Table 1). On high strain rate loading of these low densities Al specimens, much lower peak stress was recorded. Boiling in water resulted in a crack generation on the cylindrical surface of many of the specimen, indicating excess rock salt content. Only those specimens which were intact after one hour of boiling were tested on SHPB. The resulting stresses for identical incident energy were in the range of 63 MPa to 80 MPa for the strain rate range of 2303 /s to 3140 /s, respectively.