EXPERIMENTAL STUDY ON PULSE SHAPING TECHNIQUES OF LARGE DIAMETER SHPB APPARATUS FOR CONCRETE

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JIANGBO WANG
WENFENG LI
LIZHI XU
ZHONGHUA DU
GUANGFA GAO

Abstract

THE CONSTANT STRAIN RATE LOADING AND DYNAMIC STRESS EQUILIBRIUM ARE PREREQUISITES FOR ENSURING THE EXPERIMENTAL DATA OF SPLIT HOPKINSON PRESSURE BAR (SHPB). IN ORDER TO ACHIEVE THIS REQUIREMENT, A PROPER PULSE SHAPER DIMENSIONS IS USED IN EXPERIMENT. FOR THIS PURPOSE, THE PULSE SHAPER DIAMETER, THICKNESS AND STRENGTH AND THE STRIKE BAR LENGTH AND ITS VELOCITY ON THE INCIDENT PULSE ARE STUDIED BY ∅80MM SHPB DEVICE. THEN, THE PARAMETERS EFFECTING THE TWO KEY INFLECTION POINTS AND THREE LOADING AREAS OF INCIDENT PULSE ARE DISCUSSED. IN ADDITION, AN IMPROVED METHOD FOR TWO TYPICAL NON-CONSTANT STRAIN RATE WAVEFORMS FOR CONCRETE EXPERIMENT IS OBTAINED BASED ON THE REGULAR OF PULSE SHAPING. MOREOVER, SHPB EXPERIMENTS ARE CONDUCTED FOR CONCRETE BY EMPLOYING DIFFERENT PULSE SHAPER DIMENSIONS. THE RESULTS SHOW THAT MORE VALID DATA CAN BE OBTAINED BY EMPLOYING THE PULSE SHAPER WITH LARGE THICKNESS WHEN THE STRAIN RATE IS NON-CONSTANT DURING THE EXPERIMENT. WHETHER OR NOT CONSTANT STRAIN RATE LOADING MAINLY AFFECTS THE DYNAMIC COMPRESSIVE STRENGTH, BUT HAS LITTLE EFFECT ON THE DYNAMIC MODULUS. THE CONCLUSIONS AND METHOD PROVIDE GUIDANCE FOR THE SELECTING PULSE SHAPER FOR CONCRETE SHPB EXPERIMENTS.

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