Automatic Shear Testing Machine

This microprocessor-based advanced model is a stand-alone machine, driven by a high-resolution stepper motor with epicyclical reduction gear with reduced backlash.

A pneumatic closed-loop system with a high-performance pressure regulator is incorporated for the automatic application of vertical pressure, with the main advantage that manual loading of dead weights is eliminated. Techno-polymeric material of high quality and 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 microprocessor system reads and processes the force, vertical pressure and displacement readings, and manages the motor, the pressure valve, the safety system and the test steps through the closed-loop system. It has a scratchproof membrane keyboard and a large monochromatic graphic display. The machine is supplied complete with the following electronic transducers

• ± 5 kN capacity load cell, bi-directional type (compression and tension),nominal sensitivity 2 mV/V, accuracy ± 0.03%
• 10 mm displacement transducer, 1 kOhm nominal resistance, ± 0.25% linearity, 0.002 mm repeatability
• 25 mm displacement transducer, 1 kOhm nominal resistance, ± 0.25% linearity, 0.002 mm repeatability
• 1000 kPa pressure transducer, 0.1 kPa accuracy, nominal sensitivity 2 mV/Vt.

The Shearmatic unit, along with the ACE Automatic oedometer and Autotriax 2, Automatic Triaxial test system, makes up a unique equipment for providing complete automation of a Consolidation, Shear and Triaxial Soil Mechanic laboratory.

Features:

• Automatic pneumatic application of pre-set consolidation steps (up to 50).
• Automatic test management from consolidation to failure.
• No dead weights or lever-arm required.
• Infinitely variable speed from 0.00001 to 11.00000 mm/min.
• Linear connection between shear box, drive unit and load cell for transmission of the horizontal force along the shearing plane, instead of the classic “swan neck”.
• High-resistance techno-polymeric carriage.
• Possibility to set different speeds and travel (forward and reverse) in the residual shear tests.
• Each single step of vertical pressure can be applied instantaneously or by means of a linear ramp over a pre-set time interval.
• Automatic test termination:
  - When a pre-set horizontal load or displacement is reached
  - After a pre-set duration of the shear stage (from 1 minute to about 7 days) 
• Safety micro switch:
  - Optical for zero and end of travel
  - Mechanical for maximum horizontal displacement
• Application of vertical load:
  - Pneumatic piston with a high-resolution regulator, motor-driven via Automax electronic board with closed-loop control via a 10 bar pressure transducer Input channels:
  - One for a load cell transducer with130,000-point resolution
  - Two for potentiometric displacement transducers
• 3 calibration modes for transducers:
  - 1st step linear
  - 2nd degree polynomial
  - Up to 10 steps linearization
• Data recording:
  - Consolidation stage: vertical pressure and displacement
  - Shear stage: horizontal force and displacement; vertical pressure and displacement
• Recording mode:
  - Linear, exponential (square root) and logarithmic
  - At pre-set intervals of recorded data
• Recorded data capacity:
  - 2000 lines of data
• Blocks of memory:
  - Up to 25
• Communication protocol:
  - Selectable via RS-232 serial port:
  - ASCII for use with Windows Hyper Terminal or CONTROLS for use with 82-Q0800/TRM

Shearmatic layout
	Set up of the consolidation steps  Each row of this table represents a pressure step which is defined by: Initial pressure (set point) that is equal to the pressure of the previous step Pre-set time to pass from initial to final pressure For example, rows 3 and 4 of this table mean that: The pressure will be increased instantaneously (time = 0) from 100 to 300 kPa The pressure of 300 kPa will be maintained for the time of consolidation (in this case 500 minutes).
	Direct shear test This screen shows the status of and information about the test, and displays real-time values of: - Horizontal force - Vertical pressure (maintained constant) - Horizontal displacement - Vertical displacement