PSI - Issue 32

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

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Collectively, the provided data proves relevance of experimental study of the behavior of brittle materials under dynamic loads in presence of lateral compression compared to identical loading conditions in absence of lateral compression. The purpose of this study is to design and conduct an experiment assessing the fragmentation behavior of mica crystalline material under high velocity impact in constrained and non-constrained conditions.

Nomenclature N

number of fragments Feret ’s equivalent diameter sphericity coefficient

D f

C sph

C con convexity coefficient

2. Method and equipment The proposed experiment uses mica-crystalline material potassium fluorphlogopite as an object of impact. Potassium fluorphlogopite is a product of high-temperature remelting of nonferrous mineral oxide material with fluorsilicate potassium added to furnace charge. It has a density of 2.8 g/cm 3 and consists of three structural constituents: potassium fluorphlogopite (80-90%), accessory elements (5-10%) and glass phase (2-8%). The material has the follow ing crystal chemical formula: КMg 3 [Si 3 AlO 10 ]F 2 , and composition, weight %: SiO 2 – 39-43, Al 2 O 3 – 9-12, MgO – 27-30, K 2 О – 7-9, F – 9-12. Overall appearance of the structure consists of mutually perpendicular and parallel layers of various lengths (fig. 2, a). Compressive strength of potassium fluorphlogopite depends on the length of layers: at 50- 300 µm, this parameter varies within 50 to 10 MPa, respectively. A 23 mm steel ball (Steel 20) was used as a projectile. In order to create constrained conditions of lateral compression, a device for mechanical clamping of the sample was used as shown in fig. 2, b. a b

Fig. 2. (a) Structure of potassium fluorphlogopite, х150; (b) A sample in a clamping device.

Collection of destruction fragments was performed using a cellulose collector and by way of settlement to carbon scotch tape positioned at a distance of 0.5 m from the sample of mica-crystalline material at the moment of impact. Fragments within the range up to 1 mm have been analyzed. Parameters of destruction fragments have been established on the basis of images obtained by scanning electron microscopy (SEM) using X-ray spectral microprobe analysis with Hitachi S-3400N microscope and software