Patent ID: 11921088
Assignee: SHENZHEN UNIVERSITY
Field: Measurement (Instruments)
Classification: CPC G | IPC G

Claim 9:
10. A test method for a thermal-stress-pore pressure coupled electromagnetic loading triaxial Hopkinson bar system, using the system according to claim 1 to conduct a test, and comprising the following steps:
first, a servo-controlled axial pressure loading system is used to synchronously control the left axial pressure loading cylinder and the right axial pressure loading cylinder to boost the pressures of the two axial pressure loading cylinders and drive the left axial pressure loading piston and the right axial pressure loading piston to move rightwards and leftwards respectively, so as to push the left stress wave loading bar and the right stress wave loading bar to apply axial pressures to the test specimen at a preset loading rate, respectively; when the axial pressure reaches a preset value, stopping loading and using the servo-controlled axial pressure loading system to maintain the axial pressure stable;
second, using servo-controlled confining pressure loading system to pump anti-wear hydraulic oil into the confining-pressure loading cylinder at a preset rate by means of a confining-pressure loading cylinder oil inlet; when the hydraulic oil flows out from the confining-pressure loading cylinder air outlet, which means that the confining-pressure loading cylinder is already full of the anti-wear hydraulic oil, tightening the sealing plug of the confining-pressure loading cylinder air outlet to seal the confining-pressure loading cylinder air outlet, and continuously applying the confining pressure; when a pressure value on the oil pressure gauge reaches a preset confining pressure value, stopping loading and using the servo-controlled confining pressure loading system to maintain the confining pressure stable, such that a circumferential confining pressure applied to the test specimen by means of an impermeable rubber sleeve maintains stable at a preset value; third, using the pore pressure loading system to apply a pore pressure to the test specimen by means of the left pore pressure pipe and the right pore pressure pipe; when a pressure difference between the pore pressures in the left pore pressure pipe and the right pore pressure pipe maintains stable at a preset value, activating the thermal control system, and driving the intelligent thermal control thermocouple and thermal sensor to heat at a preset rate; when the temperature of the hydraulic oil in the confining-pressure loading cylinder rises to a preset temperature, braking the thermal control system to maintain the temperature of the oil in the hydraulic cylinder at the preset experimental temperature by two hours, so that the temperature inside the test specimen wrapped in the high temperature resistant anti-wear rubber sleeve is uniform and maintains constant at the preset temperature, so as to complete the condition of applying the coupled effect of a static axial pressure, a confining pressure, a pore pressure, and a temperature to the test specimen; and
fourth, operating, according to a test design, an electromagnetic pulse generation control system to drive the left electromagnetic pulse generator and the right electromagnetic pulse generator to synchronously generate and output incident stress waves; subsequently, enabling the incident stress waves to propagate towards the test specimen along the left and the right stress wave loading bars respectively, and loading a dynamic impact to the test specimen, so as to achieve a thermal-stress-pore pressure coupled electromagnetic loading triaxial Hopkinson bar test,
during dynamic impact loading, an incident strain signal and a reflected strain signal in the stress wave loading bars are monitored in real time by means of the resistance strain gauges adhered at central positions of the left and the right loading bars; when the strain signal data monitored by the strain gauges shows that during the thermal-stress-pore pressure coupled electromagnetic loading triaxial Hopkinson bar test, the dynamic compression loads applied to left and right ends of the test specimen are consistent, the dynamic impact loading process of the test specimen can be considered to reach a stress balance state; according to one-dimensional strain wave propagation theory, a dynamic compression strength σ(t), a dynamic compression strain rate {dot over (ε)}(t), and a dynamic axial strain ε(t) of the test specimen can be calculated with the strain data monitored by the strain gauges using the following formulas:, σ
      ⁡
      
        (
        t
        )
      
    
    =
    
      
        
          E
          ⁢
          A
        
        
          2
          ⁢
          
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              incident
            
          
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              left
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              reflected
            
          
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              right
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              reflected
            
          
        
        )
      
    
  

  
    
      
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        .
      
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              left
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wherein E, C, and A are elastic modulus, compressional wave velocity, and cross-sectional area of the stress wave loading bar, respectively; As is a cross-sectional area of the test specimen; Ls is a length of the test specimen; εleft incident and εleft reflected are the incident strain signal and the reflected strain signal monitored on the left stress wave loading bar by the strain gauge, respectively; and εright incident and εright reflected are the incident strain signal and the reflected strain signal monitored on the right stress wave loading bar by the strain gauge, respectively.