DCPD Unit

The Bi-06-889 pulsed DCPD unit is intended for use with BiSS 2350, 2360 and 2370 Series Controllers for fully automated crack size measurement using the potential drop technique. Documentation provided with unit may be used to interface it with third party controllers as well.

The principle of operation of the Bi-06-889 DCPD unit is schematically described in the figure below. The circuit provides for parallel and simultaneous measurement of two potential drops, one across the crack and another across a reference resistance, in order to obtain non-dimensional estimates of potential drop per ampere of current passing through the circuit. Both values are estimated with 24-bit resolution in order to obtain precision readouts. A TTL-logic input to the unit is used to switch the current on and off. This scheme permits the elimination of errors due to thermal e.m.f. and signal offsets. Application software provided with the host Controller allows for selection of pulse duration and other settings. Note that use of this unit requires isolation of the specimen to preclude alternate current paths.

Applications:

• Fatigue crack growth
• Crack sizing
• Fracture toughness testing including J1c
• Crack closure studies
• Fatigue crack initiation

Features:

• Current up to 15 A
• Advanced filtering options
• Pulsed DCPD as a standard
• Advanced triggering including peak, trough and mid point of load cycle waveform input
• Variable DC offsets for removing standing voltages
• Two channels as standard to acquire reference and specimen potential drop
• Conforms to PD equations recommended by ASTM E647 and ASTM 1820
• Application software user interface includes specimen description, loading parameters, material properties, pump controls, test run/stop, graph display, and numeric readouts of several relevant test parameters. Test descriptions and test settings are available as panels accessed by clicking on relevant tabs or pull down menus.

Specifications :