4PB STAND ALONE SERVO PNEUMATIC FOUR POINT BENDING SYSTEM
This Servo-pneumatic Four Point Bending (4PB) System is a servo-pneumatic testing machine utilizing digital control of a high performance servo valve to provide accurate loading wave shapes up to 60Hz. The 4PB system can be operated in haversine or sinusoidal, controlled stain or sinusoidal controlled stress mode to determine the flexural stiffness/modulus and resistance to fatigue of asphalt beams of various sizes.
The 4PB System is underpinned by leading edge CDAS digital controller, TestLab software and a full complement of accessories… hardware and software in perfect unison.
CDAS Digital Controller: This compact Control and Data Acquisition System (CDAS) delivers unparalleled performance, real time control and ultimate versatility in acquisition. The CDAS provides excellent waveform fidelity from integrated acquisition and control functions, with low level sampling at speeds of up to 200,000 samples per second simultaneously on all channels (using up to 64x oversampling) gives superior low noise performance and resolution of 20 bit over the full dynamic input signal range (no auto ranging required).
TestLab Software: Developed with ultimate flexibility in mind, TestLab test and control software caters to all levels of operator experience. By use of pre-programmed “Method files”, an inexperienced operator can run a range of international test methods without the need for any programming. Moreover, a test “Wizard”, available with popular tests can guide the operator step by step based on a “recipe book” approach. Most importantly, the experienced engineer and/or researcher need not be constrained by the functions and analysis in the method files provided. The operator may, clone, modify and/or generate his/her own method file to suit their specific requirements. The Excel based data analysis offers the operator the flexibility to implement alternative analysis and customized reporting facilities.
TestLab allows for real time graphing of results and configurable real time transducer levels display with unprecedented clarity of results and analytical power.
The specimen is securely clamped using servo-motor driven ball screws to maintain the prescribed clamping force, to accommodate any compliance of the specimen between the clamping surfaces, during the test. The clamping force is controlled by regulating the motor current. Two switches located on the front of the device are used to activate and release the inner and outer specimen clamps.
The four specimen yokes provide backlash free rotation and translation at all load and reaction points. The clamping surfaces are 25mm wide, so as to distribute the stress between the clamps during loading. A specially designed tool is provided to accurately set the spacing of the four loading points according to the two most commonly used spans. Markings on the top clamp pads assist the operator to centre the beam laterally prior to clamping. It’s important for the centre line (neutral axis) of the specimen to be in line with the pivot points. For this reason, the system includes a set of (10mm) thick clamp pad spacers … to be used in conjunction with 50mm high specimens or set aside when testing 70mm high specimens.
The servo-pneumatic system uses a bottom loading pneumatic actuator coupled to a high performance servo valve, with PID closed-loop control and run time adaptive control to achieve/maintain the requested strain/stress for the duration of the test.
The test control system is computer based, using three sensors on the machine for control and/or data acquisition. A low profile, high performance stainless steel ring torsion load cell is used to measure and control the load and a co-axially mounted (LVDT) displacement transducer, on the actuator is used to position the centre cradle. An on-specimen (LVDT) displacement transducer is used to measure and control the deflection at the centre of the beam with respect to the outer load/reaction points, as prescribed in the relevant standards.
The Windows based, TestLab software provides a user interface that is as simple and efficient as possible and application software according to the following international standards: AASHTO T321, AST 03, EN12697-24 Annex D, EN12697-26 Annex B and ASTM-D7460
Robust four point loading frame
Backlash free rotation and translation on all load and reaction points
Fully configurable to suit a large range of testing applications
High performance servo-valveLong life pneumatic actuator
Digital Servo-pneumatic control 2 axis control and 8 channel data acquisition