Patent ID: 11913915
Assignee: SHENZHEN UNIVERSITY
Field: Measurement (Instruments)
Classification: CPC G | IPC G

Claim 5:
6. A uniaxial bidirectional synchronous control electromagnetic loaded dynamic shear test method, using the test apparatus as claimed in claim 1 to conduct the following operations:
placing a machined and ground test specimen on a base, horizontally placing a left stress wave loading bar in a fastening groove of a loading bar support, and ensuring that the left stress wave loading bar can freely slide left and right in the fastening groove; then, aligning and closely attaching a right loading end surface of the left stress wave loading bar with/to a lower section of a dynamic shear loading surface on the left of the test specimen; meanwhile, placing a left electromagnetic pulse generator on a left electromagnetic pulse generator support, and adjusting the two to an end of the left stress wave loading bar, such that a right stress wave output end surface of the left electromagnetic pulse generator aligns with and is closely attached to an incident stress wave loading end surface of the left stress wave loading bar;
horizontally placing a right stress wave loading bar in a fastening groove of a loading bar support, and ensuring that the right stress wave loading bar can freely slide left and right in the fastening groove; then, aligning and closely attaching a left loading end surface of the right stress wave loading bar with/to an upper section of a dynamic shear loading surface on the right side of the test specimen; meanwhile, placing a right electromagnetic pulse generator on a right electromagnetic pulse generator support, and adjusting the two to an end of the right stress wave loading bar, such that a left stress wave output end surface of the right electromagnetic pulse generator aligns with and is closely attached to an incident stress wave loading end surface of the right stress wave loading bar;
setting a normal pressure value according to test requirements; adjusting, by means of a servo-controlled normal hydraulic pressure loading system, a normal static pressure applied to an upper surface of the test specimen by a hydraulic pressure loading apparatus driving actuator according to a preset loading rate; when the normal pressure reaches a preset value and then remains stable, operating 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 with an amplitude and a duration according to test requirements, wherein the incident stress waves propagate towards the test specimen along the left and the right stress wave loading bars, so as to apply a dynamic shear load to the test specimen;
during loading, monitoring incident strain signals and reflected strain signals in the bars by means of strain gauges adhered to the left and the right stress wave loading bars in real time, wherein when strain signal data monitored by the strain gauges shows that the dynamic shear loads applied to the left and the right end surfaces of the test specimen with a single joint during dynamic shear loading are basically consistent, the granite specimen with a single joint is considered to reach a stress balance state during the dynamic shear loading process; according to one-dimensional strain wave propagation theory, the dynamic shear strength τ(t) of the test specimen under a normal pressure set according to test requirement can be calculated with strain data monitored by the strain gauges using the following formula:, τ
    ⁡
    
      (
      t
      )
    
  
  =
  
    
      
        E
        ⁢
        A
      
      
        2
        ⁢
        
          A
          s
        
      
    
    ⁢
    
      (
      
        
          ɛ
          
            left
            ⁢
            
              
            
            ⁢
            incident
          
        
        +
        
          ɛ
          
            right
            ⁢
            
              
            
            ⁢
            incident
          
        
        +
        
          ɛ
          
            left
            ⁢
            
              
            
            ⁢
            reflected
          
        
        +
        
          ɛ
          
            right
            ⁢
            
              
            
            ⁢
            reflected
          
        
      
      )
    
  

wherein E and A are an elastic modulus and a cross section area of the stress wave loading bar, respectively; As is an area of a shear surface 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.