Dynamic true triaxial electromagnetic Hopkinson bar system and testing method

A method for using a dynamic true triaxial electromagnetic Hopkinson bar system to implement dynamic damage of solid materials and ultrasonic wave propagation tests, comprising the following test steps:

• step 1, before a static prestress and an impact load are applied, placing an ultrasonic probe at an incident end of each square bar in six directions;
• in the direction X+, the ultrasonic probe is an ultrasonic transmitter probe which emits an ultrasonic incident signal, wherein the ultrasonic signal propagates along the square bar in the direction X+, passes through a cubic test specimen, and then continuously propagates to the square bar in the direction X− as a transmitted ultrasonic signal, which is finally received by an ultrasonic receiver probe placed at the incident end of the square bar in the direction X−;
• recording and storing a complete ultrasonic signal in the direction X without application of the static prestress and the impact load;
• in the direction Y, utilizing an ultrasonic transmitter probe placed at the incident end of the square bar in the direction Y+ to emit an ultrasonic incident signal, wherein the ultrasonic signal propagates along the square bar in the direction Y+, passes through the cubic test specimen, and then continuously propagates to the square bar in the direction Y− as a transmitted ultrasonic signal, which is finally received by an ultrasonic receiver probe placed at the incident end of the square bar in the direction Y−;
• recording and storing a complete ultrasonic signal in the direction Y without application of the static prestress and the impact load;
• in the direction Z, utilizing an ultrasonic transmitter probe placed at the incident end of the square bar in the direction Z+ to emit an ultrasonic incident signal, wherein the ultrasonic signal propagates along the square bar in the direction Z+, passes through the cubic test specimen, and then continuously propagates to the square bar in the direction Z− as a transmitted ultrasonic signal, which is finally received by an ultrasonic receiver probe placed at the incident end of the square bar in the direction Z−;
• recording and storing a complete ultrasonic signal in the direction Z without application of the static prestress and the impact load;
• step 2, applying the static prestress, wherein a mode of applying the static prestress is provided by taking the direction X as an example:
• opening a high pressure oil pipe, filling a confining-pressure loading hydraulic cylinder in the direction X+ with oil by means of an oil inlet, and pushing a confining-pressure loading actuator in the direction X+ to move forward and contact a confining-pressure loading frame in the direction X+;
• continuously applying an oil pressure to push the confining-pressure loading actuator in the direction X+ to move forward and then transfers an axial pressure to the square bar in the direction X+ by means of a circular bulge in the direction X+, and then loading the axial pressure on the cubic test specimen, so that the cubic test specimen is under a precise static prestress in the direction X;
• similarly, the static confining-pressure loading principle in the directions Y and Z is the same as that in the direction X;
• step 3, under the action of the static prestress in the step 2, re-utilizing the ultrasonic transmitter probe placed at the incident end of the square bar in the direction X+ to emit an ultrasonic incident signal, and utilizing the ultrasonic receiver probe placed at the incident end of the square bar in the direction X− to receive the transmitted ultrasonic signal passing through the test specimen loaded with static prestress, recording and storing a complete ultrasonic signal in the direction X under the static prestress;
• in the direction Y, utilizing the ultrasonic transmitter probe placed at the incident end of the square bar in the direction Y+ to emit an ultrasonic incident signal, and utilizing the ultrasonic receiving probe placed at the incident end of the square bar in the direction Y− to receive the transmitted ultrasonic signal passing through the test specimen loaded with static prestress, recording and storing a complete ultrasonic signal in the direction Y under the static prestress;
• in the direction Z, utilizing the ultrasonic transmitter probe placed at the incident end of the square bar in the direction Z+ to emit an ultrasonic incident signal, utilizing the ultrasonic receiver probe placed at the incident end of the square bar in the direction Z− to receive the transmitted ultrasonic signal passing through the test specimen loaded with static prestress, recording and storing a complete ultrasonic signal in the direction Z under the static prestress;
• step 4, applying the impact load, wherein a mode of applying the impact load is provided by taking the direction X as an example:
• after the step 3 is completed, moving the ultrasonic transmitter probe and the ultrasonic receiver probe closely attached to the incident end of the square bars in the directions X+ and X−, respectively, then, placing an electromagnetic pulse generator in the direction X+ and an electromagnetic pulse generator support frame in the direction X+ at the incident end of the square bar in the direction X+ in the confining-pressure loading frame in the direction X+, wherein the electromagnetic pulse generator in the direction X+ is freely and closely attached to the incident end of the square bar in the direction X+, and is used to apply a dynamic stress pulse load in the direction X+ to the test specimen along the incident end of the square bar in the direction X+;
• and placing an electromagnetic pulse generator in the direction X− and an electromagnetic pulse generator support frame in the direction X− at the incident end of the square bar in the direction X− in the confining-pressure loading frame in the direction X−, wherein the electromagnetic pulse generator in the direction X− is freely and closely attached to the incident end of the square bar in the direction X−, and is used to apply a dynamic stress pulse load in the direction X− to the test specimen along the incident end of the square bar in the direction X−;
• similarly, after the same operations as those in the direction X are performed in the directions Y and Z, then utilizing a triaxial and six-directional synchronous-coordinated-control electromagnetic loading system to apply dynamic impact loads to the test specimen along the directions X, Y and Z;
• and
• step 5, after completing dynamic impact loading test, continuously remaining the static prestress in the directions X, Y, and Z unchanged, namely, not releasing the static prestress, then removing the electromagnetic pulse generator in the direction X+ and the electromagnetic pulse generator support frame in the direction X+, and placing the ultrasonic transmitter probe at the incident end of the square bar in the direction X+ in the confining-pressure loading frame in the direction X+, wherein the ultrasonic transmitter probe is freely and closely attached to the incident end of the square bar in the direction X+;
• similarly, after performing the same operations as those in the direction X+ in the directions X−, Y+, Y−, Z+, and Z−, all the electromagnetic pulse generators and the electromagnetic pulse generator support frames are removed away, and enabling the ultrasonic transmitter probes and the ultrasonic receiver probes to be freely and closely attached to the incident ends of the square bars, respectively;
• subsequently, under a state that the static prestress is not released, utilizing the ultrasonic transmitter probe placed at the incident end of the square bar in the direction X+ to emit an ultrasonic incident signal, utilizing the ultrasonic receiver probe placed at the incident end of the square bar in the direction X− to receive the transmitted ultrasonic signal passing through the impact loaded test specimen from the direction X, recording and storing a complete ultrasonic signal in the direction X after application of the static prestress and the dynamic impact load, respectively;
• in the direction Y, utilizing the ultrasonic transmitter probe placed at the incident end of the square bar in the direction Y+ to emit an ultrasonic incident signal, utilizing the ultrasonic receiver probe placed at the incident end of the square bar in the direction Y− to receive the transmitted ultrasonic signal passing through the impact loaded test specimen from the direction Y, recording and storing a complete ultrasonic signal in the direction Y after application of the static prestress and the dynamic impact load, respectively;
• in the direction Z, utilizing the ultrasonic transmitter probe placed at the incident end of the square bar in the direction Z+ to emit an ultrasonic incident signal, utilizing the ultrasonic receiver probe placed at the incident end of the square bar in the direction Z− to receive the transmitted ultrasonic signal passing through the impact loaded test specimen from the direction Z, recording and storing a complete ultrasonic signal in the direction Z after application of the static prestress and the dynamic impact load, respectively.