I have designed and built a servo-hydraulic machine for a range of mechanical testing from coupon-scale material tests through to component scale structural testing. The project included elements of hydraulics, electronics, DAQ and control systems, structural design and MATLAB ‘SIMULINK’ programming.

The very low budget meant that much of the equipment had to be cannibalised from previous projects, which complicated the design process somewhat, especially concerning software-hardware compatibility issues.

From the outset the machine was designed with a modular form to both enable virtually any test configuration to be carried out, and also to facilitate future expansions of the system to enable larger scale, higher load and/or fatigue cyclic testing. The three main components described below were all designed, assembled, commissioned and then further developed by myself ‘in-house’:

Servohydraulic Test Machine

Hydraulics

Power pack, 17t actuator and G761 MOOG servo-hydraulic control valve.
Sized for future capacity for fatigue testing.
Cooling system sized to allow operation at peak Portuguese summer temperatures.
Switchable pumps (6 and 12 lpm) to allow match between demands of different test configurations and pump supply.
High level fluid filtering.

Steel Reaction Frame

Simple 'bolt-on' supports and jigs allow many test configurations.
Moveable cross beam to allowing various test scales.
Maximum safe working load 25t
First failure at cross beam bolts to avoid structural damage. Maximum of 0.05 mm deflection at maximum 25t load.

Control and Data Acquisition System

Custom written MATLAB SIMULINK software-based.
Load cells (Novatech 500kg and 6t)
Displacement sensors (Penny and Giles SLS190)
8 strain gauge or other sensor channels.
Software-tuneable PID control on displacement signal.
Time-load-displacement output to spreadsheet
Post-processing signal filtering.
Custom National Instruments based DAQ system (using older PCMIA NI DAQcards due to budget restrictions).
Custom ‘Control Box’ (5 and 9V regulated power supplies, Load cell x248 amplifier, Load and Position filters, MOOG valve ‘buffer’ circuit).
Multi-level safety systems: custom hydraulic pump cut-out and pressure dump with emergency stop buttons, position limit stops and safe-start systems (all both software and hardware activated).
Extremely accurate custom load, displacement and strain gauge calibration procedures.