These are projects posted by the students of Dr. Gove Allen at Brigham Young University. These students have taken one semester-long course on VBA and generally have had no prior programming experience

Thursday, December 11, 2014

Flexibility is Tough for Engineering Students

Compliant Mechanisms achieve part or all of their motion from the deflection of their members. Instead of rigid body engineering (i.e. pins, joints and rigid segments) compliant mechanisms use their deformation to accomplish the desired motion. Some benefits of this design method include reduced wear, lower friction, energy storage potential, lower assembly needs. Examples of compliant mechanisms are a bow, springs, trees, eels and virtually everything in nature.

One of the key challenges of incorporating compliant mechanisms into design is the rigorous mathematical sequence to analyze the design’s performance. Small angle approximations have been developed to simplify design, but these approximations are not appropriate for the range of motion found in many compliant mechanisms as they typically fall apart at a few degrees of deflection. Dr. Howell, Professor of Mechanical Engineering at BYU, teaches methods to evaluate the behavior of compliant mechanisms. One of his methods requires many inputs and iterations due to the evaluation of elliptic integrals.

For my project I built a user interface for one specific design case – a beam cantilevered at one end with an applied force at the other. An example of this condition would be a thin metal ruler clamped at one end and a point force applied on the other end. Dr. Howell provided an excel file with the elliptical integral functions built and I created the user form. This project enables his students, and others he distributes it to, to better understand the non-linear behavior of these systems as they change parameters. It gives them a simple system to improve their intuition. The graphs enable the user to learn: 
  1. the shape the beam will deflect to subject to the conditions entered, 
  2. the stress profile along the length of the beam and 
  3. the internal moment along the length of the beam.
Numerical outputs are given for further detail.

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