STUDY ON DYNAMIC COMPRESSIVE MECHANICAL PROPERTIES AND FAILURE MODES OF HEAT-TREATED GRANITE

Abstract

DYNAMIC COMPRESSIVE PROPERTIES AND FAILURE MODES OF HEAT-TREATED GRANITE ARE EXPLORED BY USING THE IMPROVED SPLIT HOPKINSON PRESSURE BAR (SHPB). THE RESULTS SHOW THAT THE AMPLITUDE OF INCIDENT WAVE INCREASES WITH THE IMPACT VELOCITY OF STRIKER, AND THE SHAPES OF THE TRANSMITTED AND REFLECTED WAVES ARE CLOSELY RELATED TO THE FAILURE STATE OF THE SPECIMEN. THE STRESS-STRAIN CURVES FOR THE HEAT-TREATED SPECIMENS ABOVE 700OC ARE OBVIOUSLY DIFFERENT TO THOSE BELOW 500OC IN TERMS OF THE SLOPES FOR THE ASCENDING SEGMENT AND THE PEAK STRESS, INDICATING THAT THERE IS A TEMPERATURE THRESHOLD BETWEEN 500OC AND 700OC. UNDER THE SAME VELOCITY, THE STRAIN RATE DECREASES SLIGHTLY AND THEN INCREASES AS THE TEMPERATURE INCREASES. AT A CONSTANT TEMPERATURE, STRAIN RATE INCREASES LINEARLY WITH THE IMPACT VELOCITY. THE RELATIONSHIP BETWEEN ELASTIC MODULUS AND STRAIN RATE FOR THE HEAT-TREATED SPECIMEN OBVIOUSLY TENDS TO HAVE NO REGULARITY. IN ADDITION, BOTH PEAK STRESS AND PEAK STRAIN EXHIBIT STRAIN RATE SENSITIVITY, BUT DIFFERENT INCREASING RATES FOR DIFFERENT TEMPERATURES ARE DETECTED. BELOW 500OC, THE INFLUENCE OF TEMPERATURE ON PEAK STRESS AND PEAK STRAIN IS NOT EVIDENT, HOWEVER, THE INFLUENCE BECOMES REMARKABLE AT 700OC AND 900OC.