Rain erosion evaluation systems
Rain erosion evaluation systems
Keywords: Precision-Optical Engineering, Optics, Tests, Water,Simulation
The effect of rain erosion on optical materials is of vital importance in the aerospace industry. Equipment for simulating drop impact is now commercially available from Cambridge University. Precision-Optical Engineering, a specialist in the design and manufacture of industrial electro-optic systems, is delighted to be involved in the distribution chain for the rain erosion evaluation units,and has been instrumental in securing commercial orders. Two system types,single impact jet apparatus (SIJA) and multiple impact jet apparatus (MIJA), are available.
The SIJA liquid jet technique for simulating drop impact was developed at the Cavendish Laboratory, University of Cambridge, UK about 40 years ago. The system allows a coherent jet of water with a reproducible front profile to be fired at a stationary specimen. It can be used to evaluate erosion effects, damage thresholds and adhesion strengths of coatings. Optical, infra-red and microwave transmitting window and dome materials travelling at high velocity through rain droplets, such as on an aircraft, are readily evaluated.
The system consists of a nozzle, filled with the liquid to be fired (usually water) and sealed with a neoprene diaphragm. A 0.22" lead slug is fired into the diaphragm from a converted air-rifle, producing a jet of water which then impinges on the sample.
The air-rifle is powered by a small gas reservoir and jet velocities up to 1,200ms–1 can be readily obtained. Higher velocity jets can be achieved with a more powerful gun system. The nozzle design and loading are critical to the success of the technique and have been developed by a succession of researchers at the Cavendish.
MIJA is an automated version that allows greater reproducibility of the jet velocity and jet contact profile. MIJA is controlled by a PC which allows impacts to be positioned accurately on a sample in a random pattern, rectangular grid, or a user-defined array.
Details available from: Precision-Optical Engineering. Tel: +44 (0)1462 440328; Fax: +44 (0)1462 440329; E-mail: sales@p-oe.co.uk;Web site: www.p-oe.co.uk/
