PSI - Issue 14

6

Neelanchali Asija Bhalla et al. / Procedia Structural Integrity 14 (2019) 564–570 Neelanchali et al/ Structural Integrity Procedia 00 (2018) 000–000

569

Fig.5: Stress-Strain and Stress-Strain Rate plots for A-150 fumed silica dispersions

The high strain rate testing was conducted on SHPB apparatus. A pulse shaper was placed at the impacting surface of the IB, prior to each experiment. The advantage of using a pulse shaper is that it deforms slower than the bar material, thereby resulting in a near trapezoidal loading pulse (ε i ). For each experiment, a fresh pulse shaper was used. In the present study, the pulse shaper material used is Linatex rubber. Fig.4 and Fig.5 illustrate the results obtained from the mechanical testing of A-130 and A-150 FS dispersions, respectively, on SHPB. From both the Figures it is evident that as the triggering pressure of the striker bar increases, the specimen loading rate also increases. In the stress-strain rate plot only the loading part of the stress cycle is shown wherein both the specimen stress and strain rates continue to increase linearly. The specimen stress attained during the impact event is a measure of the resistance offered by the STF to the impact. It is observed that the peak specimen stress is 120 MPa for A-130 and 110 MPa for A-150 FS dispersions, respectively. It is also important to note that with the increase in specimen stress, the strain rate also exhibits an increasing trend, till a certain value of strain rate is attained. This value of the strain rate is termed as the limiting strain rate (LSR). The LSR value marks the initial fracture in the specimen which is seen in terms of the reduced reflected strain, causing a drop in the compressional strain rate of the specimen. From the experimental results, the LSR value was found to be 48000 s -1 for A-130 and 46800 s -1 for A-150 FS dispersions, respectively.

at 48000 s -1

10 15 20 25 30 35 40 45

0 5 Impact Toughness (J m -3 x 10 6 )

at 46800 s -1

A-130

A-150

Fig.6: Impact Toughness at Limiting Strain Rate for A-130 and A-150 Fumed Silica Dispersions