• Direct/residual Shear Machine

Direct/residual Shear Machine

ASTM D3080, AASHTO T236, BS 1377:7, NF P094 071-1/2, CEN-ISO/TS 7982-10


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The AUTOSHEAR machine is controlled by a microprocessor system which reads and processes horizontal force and displacement readings and manages the motor and safety limits via a closed-loop control system.The unit provides the following important features: 

 

Features Technical specifications
  • Microprocessor-controlled drive system
  • Large 240 x 128-pixel display
  • Test speed, direction and cycles (up to 10) programmable using the keyboard
  • Rapid approach and automatic positioning
  • Infinitely variable speed from 0.00001 to 11.00000 mm/min
  • Possibility to set different speed and direction (forward and reverse) in the residual shear test
  • Three analogue channels: one for load cell, and two for displacement transducers, 130,000-point resolution
  • Different protocols for downloading data to PC through RS-232 serial port
  • Standard load ring and dial gauges also compatible for manual recording
  • Automatic running of tests
  • Closed-loop control of test speed
  • Different calibration functions (linear and polynomial)
  • Language selection
  • Continuous monitoring and display of horizontal force, vertical and horizontal displacement
  • Maximum horizontal displacement limit (20 mm) controlled by mechanical and optical safety switch
  • Different recording modes, including linear, exponential (square root) and logarithmic
  • High capacity data memory (up to 1000 lines of data)
  • RAM memory with battery back-up with clock/calendar, operative even when theunit is switched off
  • Speed range: 0.00001 – 11.00000 mm (preset via firmware)
  • Maximum shear force: 5000 N
  • Maximum vertical load: 500 N or 5000 N using 10:1 lever-arm device
  • Speed drive ratio: stepper motor 1/10000 resolution
  • Horizontal travel: preset via firmware up to 20 mm
  • Displacement limits: controlled by optical safety switch
  • Maximum shear cycles: up to 10 (forward and reverse)
  • Digital: large 240 x 128 pixel display
  • Specimen sizes: 60 and 100 mm square; 50, 60, 63.5 and 100 mm diameter
  • Overall dimensions: 953 x 387 x 1180 mm (w x d x h)
  • Weight: 120 kg (approx.)

 

The design of the horizontal loading system provides rigid linear alignment of the loading ram, shear box and force measurement system, ensuring that the horizontal shearing force is transmitted along the shearing plane of the specimen. Techno-polymeric material of excellent quality and high resistance has been used for the carriage of the shear box. It offers excellent resistance to corrosion and wear and tear, and it is resistant to all chemicals found in soil specimens. The carriage is light- weight and easy to clean. The machine is supplied without load cell, transducers for horizontal and vertical displacement, shear box assembly and weights. All these items have to be ordered separately - see Accessories. The machine can also be fitted with mechanical (analogue) measuring devices. The microprocessor control system allows the machine to work as an automatic stand-alone unit: the test measurements (force and displacement) are directly displayed and stored in the unit memory according to pre-set recording modes. The PC is only required once the test is completed, to download the test data via the RS-232 port. The data can be processed using the Direct and residual shear Geo-Analysis templates - see Accessories.  
Detail of shear box carriage made of high resistance techno-polymeric material

 

Accessories
Electronic measuring devices  
27-WF0377/ST Load cell, 5 kN capacity, complete with adapters.
30-WF6207 Linear potentiometric transducer, 10 mm travel for vertical deformation, complete with mounting block.
30-WF6208 Linear potentiometric transducer, 25 mm travel for horizontal displacement, complete with mounting block.  
     
Data processing software    
30-WF6016/T2 Direct and residual shear Geo-Analysis templates conforming to BS 1377:7.  
30-WF6016/T9 Direct shear Geo-Analysis template conforming to ASTM D3080.  
     
Mechanical (analogue) measuring devices  
   
Shear box assemblies  
   
Weight set  

 

Example of a direct shear test processed with the 30-WF6016/T2 Geo-Analysis template (BS standard): the top plot shows shear stress versus horizontal displacement; the bottom plot shows change in specimen height versus horizontal displacement