-New equipment Crack growth monitoring ASI, designers and manufacturers of ACPD and pulsed DC instrumentation for dynamic crack growth monitoring, have announced that, in addition to their range of ACPD units, they will continue to make available pulsed DC systems for those customers who have built up practical experience with that technique or who prefer that system for technical reasons.

The company's latest development in ACPD instrumentation includes multi-frequency, multi-channel systems designed on a modular basis and available in manual and computer controlled versions. A range of current output modules and voltage receiver modules cover the frequencies from 2.5 kHz to 80 kHz. These frequencies have been determined to be the most useful after many years of development. Each system is supplied with four frequencies, which may be selected at the ordering stage depending on the range of materials in the user's test programme. The frequency range may be extended by purchasing additional modules.

Using a standard IBM PC or

compatible the frequency changes and amplifier stage gains may be called up dynamically and data taken at chosen points on the test machine cycle at a rate of up to 4000 recordings per second. The system is designed for ease of use, with maximum testing flexibility in mind, and is suitable for crack initiation studies, corner crack testing, and long crack testing in a wide range of metallic materials. The dynamic capability of the system allows greater information to be obtained, and avoids the test disruption experienced with systems requiring the test cycle to be halted in order to take readings. Test machine control incorporation for delta K controlled testing is easily carried out and is aided by the long term stability of the instrument.

Interest in the technique is accelerating due to the availability of high gain, low noise amplifiers and the advantages of the skin effect exploited in the multi-frequency version which guarantees reliable results.

Advanced Scientific Instrumentation, Pensnett House, Pensnett Trading Estate, Kingswinford DY6 7PP, UK

ACPD crack monitoring unit from ASI

Precision modular cubes from Spindler & Hoyer, for optical NDT systems

Cubes simplify opto-mechanical construction Two models of precision machined cubes have been added to the Microbench range of modular components. Microbench allows opto-mechanical NDT systems to be built to individual specifications. ~The resultant construction can then be used as a prototype test bed, used in the laboratory as a complete instrument/system or cased and shipped as a finished equipment.

Machined cube model 06 1080 has four 25 mm apertures while model 06 1081 has 30 mm apertures. The cubes also have a series of threaded holes on all faces, making them compatible with other components in the range.

Using cubes, it is easy and inexpensive to tap into a system at 9 0 as well as continuing on axis.

A complementary component, the model 06 1060, is an angle plate which enables easy construction of configurations whose optical axes are set at an angle of 6 0 with respect to each other.

Spindler & Hoyer UK Ltd, 2 Drakes Mews, Crownhill, Milton Keynes, Bucks MK8 0ER, UK

56 NDT International February 1991