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Title: Stress-strain properties and micro-structural change in metal deformed at strain rates of upto 10⁵ per second
Author: Haque, Md. Mohafizul
ISNI:       0000 0001 3531 1472
Awarding Body: Sheffield City Polytechnic
Current Institution: Sheffield Hallam University
Date of Award: 1983
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A ballistic test equipment has been designed, constructed and commissioned to facilitate firing of cylindrical projectiles at speeds varying from 30 to 300 m/s on to small cylindrical test specimen placed on to a rigid anvil. Compressed air was used to propel the projectile the speed of which before impact was measured using laserbeam interruption device. An IMACON high speed camera was used to continuously record the deformation-time history of the specimen and these records were then used to obtain the prevailing force, strain, stress and strain rate histories during the entire deformation process. The stress-strain curves over large strain ranges were obtained from tests carried out on specimen statically pre-strained to different levels. The effect of strain rate history on the pre-strained specimen was found to be negligibly small and hence ignored. The temperature rise during highspeed deformation and material inertia were assumed to have mutually cancelling effect on the deduced stress values. The effect of friction was found to be significant and appropriate corrections were introduced to account for this effect. Following the above procedure, the stress-strain characteristics of structural steel (En-8) at strain rates of up to 10⁵ per second at -30°C, room temperature and at 235°C have been established. The structural steel has shown a strong strain rate sensitivity within the strain rate range of about 10³ to about 10⁵ per second. Comparative studies showed that copper was more strain rate sensitive than aluminium and steel used in the present investigation. .There were no marked differences observed in the microstructures of the structural steel specimen deformed quasi-statically and dynamically at -30°C, room temperature and at 235°C. There was also no distinguishable micro-structural change observed in the structure of aluminium specimen deformed at low and high strain rates but mechanical twinning was observed in the microstructure of copper specimens deformed at high strain rates.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Structural engineering