# Strain Rate Dependencies and Competitive Effects of Dynamic Strength of Some Engineering Materials
## 2 Materials and Methods
### Materials  
The two batches of specimens for comparative research were made of ceramic and refractory brick. The bricks were bought at a building materials store. The ceramic brick was M150 grade, corresponding to a strength of at least 15 MPa for compression and 27 MPa for bending, according to standard GOST530-2012 [25]. The refractory (firedx) bricks were SHB-5 grade, corresponding to a compressive strength of at least 15 MPa, according to standard GOST390-2018 [26]. The density was 1641 kg/m\({}^{3}\) for the ceramic brick material and 2053 kg/m\({}^{3}\) for the refractory brick material. We followed specified standards for all other technical data regarding the grades of bricks under consideration. The specimens were cut from the block of brick using a diamond core drill bit. The cylindrical specimens each had a diameter of 18 mm and a height of 16 mm. Forty specimens of each material were selected for compression (20 specimens) and splitting tensile (20 specimens) tests. The other batch of specimens was made of mortar. The mortar was prepared based on a mixture of cement, sand (fraction of up to 2 mm) and water with the mix proportions 1:2.5:0.45, respectively. The cement was Portland cement type CEM I with a strength class of 32.5 in accordance with standard GOST31108-2016 [27]. According to the Russian technical regulation SP 82-101-98 [28], the mixture should provide the compressive strength of a mortar of at least 20 MPa. The mortar was cured for 28 days. After that, the mortar had density of 2361 kg/m\({}^{3}\). The limestone was purchased from a store with rocks for building and decoration. The material had a density of 2819 kg/m\({}^{3}\) and a longitudinal elastic wave speed of 5462 m/s. Dry, saturated and frozen states of the limestone and mortar were considered. Specimens for the tests were made in the form of a cylinder with a diameter of 20 mm and a length of 15 mm. The water saturation of the specimens was provided by placing the specimens in water for two weeks. The full saturation was 5% for the limestone and 6% for the mortar. Freezing of the specimens was achieved by placing the water-saturated specimens in a freezer at \(-\)15 to \(-\)10 \({}^{\circ}\)C for two days, after which the specimens were immediately tested. Ninety-six specimens of each material were selected for compression (16 specimens for each state) and splitting tensile (16 specimens for each state) test. Commercially pure titanium Grade 4 (99.1%) and electrotechnical pure copper M1 (99.9%) with coarse-grained (CG) and ultrafine-grained (UFG) structures were also considered in this study. The materials initially had a CG structure. UFG structures were produced by equal-channel angular pressing (ECAP) [29]. A UFG structure can lead to a significant increase in yield strength and tensile strength. However, the dynamic behavior of materials with such a structure is still little studied. The specimens each had the form of a cylinder with a diameter of 8 mm and a length of 4 mm. A more detailed description of the parameters of the materials can be found in [30] for copper and in [31] for titanium. In this paper, the results were used for an individual consideration of the competition effect of yield strengths. Six specimens of each material were selected for compression tests. Road bitumen with a penetration index of 60-90 mm (BND 60/90), polymer-bitumen binder with a penetration index of 60 (PBB 60) and rubber-bitumen binder (RBB) are discussed in this work. These materials were chosen in order to explore the dynamic behavior of the bitumen grades used for a roadway in northwestern Russia. PBB and RBB are modifications of BND bitumen due to the addition of polymer and rubber powders in order to reduce irreversible deformations and the brittleness temperature of the bitumen binder, depending on road conditions [32; 33]. The specimens were prepared at an asphalt-concrete plant, ABZ No. 1, in St. Petersburg, Russia. Cylindrical specimens each with a diameter of 19 mm and a length of 14 mm were used.