Dynamic constitutive relation of EMC over a broad range of temperatures and strain rates
In this paper, dynamic properties of EMC were studied sat different temperatures and different strain rates. Firstly EMC was investigated by quasi-static tests. Secondly a series of dynamic compressive experiments of EMC were conducted using the Split Hopkinson Pressure Bar (SHPB) at high strain rates. Corresponding measurements were conducted at temperatures ranging from 20°C to 200°C. The results indicate that the yield strength and flow stress of EMC increase remarkably with the increase of strain rate. However, the yield strength of EMC is almost unchanged with the increase of temperature which is ranging from 20°C to 200°C.
Some experiments with the split hopkinson pressure bar
Abstract A n application of the split Hopkinson pressure bar to the dynamic testing of materials is given whereby continuous records of the strain vs. time, strain rate vs. time, stress vs. time, and stress vs. strain may be simultaneously recorded. For many materials a nearly constant true plastic strain rate can be maintained for loading durations on the order of 100 μsec. The assumptions made in applying the method are checked experimentally. Three annealed face centred cubic metals—lead, aluminium, and copper, are tested both dynamically and at lower strain rates to determine their rate sensitivity. The results indicate that a single thermally activated mechanism is predominant. A possible mechanism of this type is the intersection of glide and forest dislocations. In aluminium, the previous strain rate history of loading is shown to affect the material's dynamic response only. A rapid annealing effect is also evidenced. Finally, the method is shown to be applicable to some non-metallic materials.
The Dynamic Compression Testing of Solids by the Method of the Split Hopkinson Pressure Bar
Abstract The mechanical behaviour of some metals (annealed copper, aluminium, magnesium, zinc and brass) and polymers (polymethylmethacrylate, polyethylene, polyvinyl chloride, polytetrafluoroethylene, polycaprolactam and a filled rubber) has been investigated experimentally for compressive loading cycles of 30 ∽sec duration. Cylindrical specimens, of comparable length and diameter, were sandwiched between two (elastic) rods and deformed under the action of a compressive stress wave induced into the free end of one of the rods by the detonation of an explosive pellet. Experimental measurements were made of the displacement-time relation for the free end of the other rod, using a parallel plate condenser microphone. The mechanical behaviour of the specimen is derived from an analysis of the displacement-time records; in the analysis allowance is made for the non-uniformity of stress and strain inherent in all dynamic testing work.