High Intensity UV Light

Kelsey Payne, Ryan Reid, Travis Smith

May 2019

Overview

“Mechanics at Extreme Temperatures” is Dr. Berke’s lab. His experiments involve observing specimens at extreme temperatures (i.e. 1500°C) under various load states to simulate jets in hypersonic flight, reentry of spacecraft, and other aerospace applications.

At these temperatures, the specimens are too hot for strain gauges, so Dr. Berke uses Digital Image Correlation (DIC) to obtain stress and strain measurements. Pictures are taken of speckle patterns on the specimen from high-temperature rated paint successively. The movement of the speckle patterns is used by the DIC software to obtain the stress and strain on the specimen. However, taking pictures of the specimens is difficult due to the light they give off at high temperatures. Instead of taking pictures in the visible light spectrum, Dr. Berke filters his camera for UV light, which is outside the spectrum of light given off by the specimen.

The filters result in a large loss of light, making the images dark and difficult to use with the DIC software. The High Intensity UV Light team designed a light with a higher intensity to give brighter images, adjustable intensity to fine-tune the contrast of the images, and other features to allow Dr. Berke to use the light in as many different experiments as possible.

Requirements

Intensity. The design must emit UVA light at a 365 nm wavelength in order to be compatible with Dr. Berke's filters. We also set a minimum intensity goal of 45.9 mW/cm2 at a distance of 116.5 mm to ensure we were at least significantly brighter than both of Dr. Berke's current UV lights combined.

Power. The design must use a power source available in Dr. Berke's lab. Dr. Berke has several different power options from junction boxes in his lab. However, a normal 120 V wall outlet was preferred.

Weight. The light bulbs and housing must collectively weigh less than 5 lbs. Dr. Berke has experiments that take place in several different rooms, so being able to move the light is a must. In addition, the weight limit was set as a design constraint on the mount.

Stiffness. The ball joints of the mount must be stiff enough to remain in place over a period of at least 12 hours while supporting the light subsystem. The mount may be moved in precarious positions for different experiments, and any drift could mean the whole setup has to be redone. Therefore, even for long testing periods, the mount should not move.

Spatial. The design must fully illuminate a specimen inside the Gleeble test chamber while not interfering with the camera’s view and not casting any shadows. The Gleeble is a test environment for one of Dr. Berke's experiments that has a limited viewing area – specifically, an 8 in. diameter porthole. If the design can be used with a Gleeble experiment setup, it can be used with any other experiment setup.

Area. The design must illuminate a 3 in. diameter circle at a distance of 12 in. Dr. Berke has requested an area of this size to be illuminated by the design in order for the design to be used with some of his experiments.

Goals

Strobing. The design should be capable of emitting light for less than 61.2 µs at a frequency of 16.14 kHz. These specification come from Dr. Berke's camera's capture speed. Essentially, the design should be able to rapidly pulse. This goal would allow the design to reduce the exposure time of Dr. Berke's camera, resulting in clearer images

Dimming. The device should be dimmable down to 50% of the maximum intensity. An adjustable intensity would allow Dr. Berke to fine-tune the contrast of his images, resulting in the best quality pictures for the DIC software.

UVB. The device should have a secondary light array that emits UVB light at approximately 304 nm that is compatible with the primary power source and primary driver. Emitting UVB light would allow Dr. Berke to conduct experiments at higher temperatures, as UVB light is further removed from the range of light emitted by specimens at extreme temperatures.

Design

Solis - 365C

• The average intensity at 116.5 mm is 492.2 mW/cm2 (Req. 45.9 mW/cm2)
• The worst-case intensity at 116.5 mm with 99% confidence is 264.3 mW/cm2
• Weight 2.37 Lbs. (Req 5 Lbs.)
• Dimensions: 5 in. x 5 in. x 6.4 in.

DC20 Driver

• Intensity Adjustment 0%-100% (Req. 50%-100%)
• Maximum pulse frequency permitted is 1 kHz

75 mm Focal Length Lens

• The coverage area at 12 in. is a 4 in. diameter circle (Req. 3 in. diameter)
• The estimated intensity at 12 in the center of the area is 20.6 mW/cm2 (Req. 2.81 mW/cm2)

150 mm Focal Length Lens

• The coverage area at 24 in. is a 5 in. diameter circle (Req. 3 in. Diameter)
• The estimated intensity at 24 in. in the center of the area is 9.79 mW/cm2 (Req. 2.81 mW/cm2)

Mount

• Fully supports Solis for over 18 hours with zero appreciable drift (Req. 12 hrs.)
• The fully extended length is 21.4 in.
• Ball-joints rotate fully about their bases and lock in position
• Carriage bolt and handle-nut allows 360 degree in-plane rotation and locking

Tests

Intensity Test

Because we were unable to measure intensities greater than 40 mW/cm2, we were unable to directly confirm that the light met the intensity requirement. The purpose of this test was to obtain sufficient intensity data to later calculate the light's intensity at 116.5 mm.

Intensity Analysis

Using the data from the intensity test, the watt output of the light was calculated. This wattage was divided by the area of illumination at 116.5 mm to obtain the intensity. The worst-case intensity was 294.3 mW/cm2 with 99% confidence. The average intensity was 492.2 mW/cm2.

Drift Check Test

This test was designed to verify the design meets the stiffness requirement. The mount was fully extended with the light attached and a 300 g weight added to the end. The design was left for 20.5 hours and did not drift during that time.

Gleeble Test

This test was designed to verify the design meets the spatial requirement. This test confirmed that the design does not interfere with the camera when performing an experiment with the Gleeble.

Area Illumination Test

This test found the intensity distribution of the light with and without either lens. The Solis natively covers a 1.4 in. x 1.4 in. square area at 12 in. With the 75 mm lens, most of the intensity was distributed in a 4 in. diameter circle at 12 in. With the 150 mm lens, the intensity was distributed in a 5 in. diameter circle at 24 in

Dimmability Test

The intensity adjustment capabilities of the DC20 driver were tested and found to adjust the Solis365C from 0%-100% maximum intensity.

Acknowledgements

• Dr. Ryan Berke
• Mechanics at Extreme Temperatures Lab
• Blair Martin
• Cole Sorensen
• Spencer Wendel

Team Information

• Kelsey Payne
• Ryan Reid Email:reid.ryank@gmail.com
• Travis Smith