The 3 Point Bend Test provides values for the modulus of Elasticity, flexural stress, and flexural strain of a material. With the use of a universal testing machine, a load is applied to the middle of a specimen while two supports hold up the specimen. These two supporting pins are placed a set distance apart.
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The goal of this project is to design a Support Test Fixture capable of being used to conduct 3 point bend testing of specimens using the Testing Machine in E3. The supports must be adjustable have a span that is accurate to 0.1mm. It also needs to be machined in house.
How will the supports move?
2 Options:
Spring and Screw
· Spring joining two supports
· Screws on either side apply torque and cause spring to compress which causes the support to move inwards
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Rack and Pinion
· Linear Gear and Circular Gear
· Driving the pinion into rotation causes the support to move linearly
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The circular gear is rotated by the knob in this example of a 3 point bend test fixture. The only caveat is that we need a way to lock the supports in place. Otherwise, the gears can rotate back into a neutral position, effectively making the positional accuracy of the support a function of the number of teeth on the gear.
NEXT STEPS:
Develop ideas some more
Pick one
Do an initial design