PSI - Issue 13

Sheikh Muhammad Zakir et al. / Procedia Structural Integrity 13 (2018) 1244–1249 Sheikh Muhammad Zakir et al. / Structural Integrity Procedia 00 (2018) 000–000

1245

2

develop laminated glass panels [1-4]. However, the dynamic mechanical behavior of glass is a very provocative task due to its brittle nature and it poses a lot of difficulties to maintain stress equilibrium before glass failure and crack initiation, in SHPB tests. Many researchers have utilized experimental and numerical techniques to understand the dynamic and static mechanical behavior of glass [5-8] and glass laminate [3, 4, 9]. Peroni et al. [7] studied experimentally the compression and tensile tests on cylindrical glass specimens of high optical purity and concluded that the ultimate tensile strength is rate sensitive in contrast to its ultimate compressive strength. However, X. Zhang et al. [8] conducted static and dynamic compression tests on annealed float glass and reported that it is rate sensitive to both compression and tensile loading. Philip Jannotti et al. [10] studied impact behavior of chemically strengthened and un-strengthened lithium aluminosilicate glass bars. They found in experimentation that in un-strengthened bar tensile cracking/damage developed because of reflected stress wave which is prevented by high compressive layer on the surface of strengthened glass bars, this makes them an appropriate interlayer candidate for use in laminated glass windows to impact loading. In our recent paper [11], the effect of scratch on annealed and chemically tempered aluminosilicate glass for bending load is investigated in both static and dynamic conditions. It was found that strengthened glass has better resistance to scratch and high flexural strength as compared to annealed glass. In this work, static and dynamic compression behavior of un-strengthened ALS glass is studied experimentally. The main focus of the research is to realize the influence of rate sensitivity on ultimate compressive strength and dynamic failure process of aforementioned glass. Static tests at strain-rate of 2.5×10 -4 s -1 and 2.5×10 -3 s -1 are completed first and strain-gauges were also pasted on cubic glass specimens to get static strength and the strain-time history. Dynamic compression tests at an average strain-rate of 650 s -1 are completed using modified SHPB combined with a high-speed camera. The high-speed images are utilized to examine the crack initiation and propagation and failure process of glass. The high-speed images are also linked with stress history during dynamic deformation process of the ALS glass. Form the tests data it was found that ALS glass is rate sensitive concerning its compressive strength. The high-speed images and the glass debris collected during tests are used to explain the fracture process and test results. From both static and dynamic compression tests, the compressive strength, failure strain, and energy absorption results for ALS glass specimens are also compared. Based on the test results a constitutive model for dynamic compressive failure of ALS glass can be realized. 2. Experimental procedure 2.1. Glass materials and specimens The ALS flat glass plates of thickness 8 mm with mirror surface finish were provided by TM glass China and a cubic shaped specimen of size 8 mm were cut form as-received glass plates to perform the static and dynamic compression tests. the specimens were ground and polished, cutting faces polished to achieve surface parallelism accuracy of 5 μm. the density and longitudinal wave speed of glass specimens were measured using water displacement method and ultrasonic testing system, respectively. The mechanical properties of ALS glass are listed in table 1. The value of Poisson’s ratio is taken from [10] and Rayleigh wave speed was calculated.

Table 1 The mechanical properties of un-strengthened ALS glass

Density (kg/m 3 ) 2545.64

Longitudinal wave speed (km/s)

Elastic modulus (GPa)

Poisson’s ratio (--)

Shear modulus (GPa)

Shear wave speed (km/s)

Rayleigh wave speed (km/s)

5.432

75.13

0.22

30.79

3.477

3.1724

2.2. Static compression experiments Static tests (figure 1) on glass specimens were completed using the electro-mechanical testing machine (CRIMS DNS-100) at two strain-rates of 2.5 × 10 -4 s -1 and 2.5 × 10 -3 s -1 , respectively. During the tests, the cross-head speed of 0.12 mm/min and 1.2 mm/min is maintained to compress the specimens at desired strain-rates. The compressive force is recorded by the machine inbuilt load cell and the strain history in specimens is measured through gauges pasted on