Compliant Mechanism Design

Course Summary

Compliant mechanisms are mechanisms that derive at least some or all their motion from flexing of material. They can provide powerful solutions to tasks requiring high precision, compact footprints, reduced weight, performance in harsh environments including where lubrication is restricted, specific force-deflection properties, energy-storage capabilities and ease of manufacturability. Compliant mechanisms have been used from macroscale pointing mechanisms to microelectromechanical (MEMS) instruments and devices. While their potential is powerful, compliant mechanisms can be challenging to analyze and design as large deflections cause commonly-used linear equations to fail. This course addresses design methods for compliant mechanisms. It highlights where compliant mechanisms can be advantageous, particularly in deployable and space-related mechanisms. The course addresses fabrication and testing of compliant mechanisms, including guidelines for additive manufacturing compliant mechanisms.

Course Materials

A complete set of the course materials is provided to each attendee.

Who Should Attend

Anyone involved in the design, selection, or evaluation of systems which transfer motion, force, or energy. This can include:

• Engineers and personnel involved in design, testing, and manufacturing.
• Program managers, decision makers, analysts and anyone else desiring a working knowledge of the advantages and challenges of compliant mechanism design and application.

What You Will Learn

Attendees will learn:

• How to recognize when compliant mechanism designs can offer strong solutions.
• The nomenclature necessary to understand and recognize compliant mechanisms.
• Methods for designing and analyzing compliant mechanisms.
• How compliant mechanisms can be effectively fabricated and tested with an emphasis on guidelines for additive manufacturing.

Course Outline

1. Introduction to Compliant Mechanisms
   The advantages, challenges, and terminology of compliant mechanisms.
2. Flexibility and Deflection
   Changing the mindset from the traditional solution of ‘increase the stiffness’ to using flexibility and deflection to solve challenges.  A discussion of the fundamental relationships governing large-deflection behavior.
3. Pseudo-Rigid Body Modeling
   Methodology for designing compliant mechanisms including building block elements such as small-length flexural pivots, cantilevered beams, fixed-guided segments, initially curved cantilever beams, and pinned-pinned segments.
4. Finite Element Modeling
   Guidelines for modeling compliant mechanisms with FE software using nonlinear analysis.
5. Force-Deflection Relationships
   Introduction to using generalized coordinates with virtual work to determine force-deflection relationships.
6. Compliant Mechanism Material Selection
   Desirable material property combinations for compliant mechanisms and a review of commonly used materials for compliant mechanisms.
7. Failure Modes and Failure Prevention
   Common failure modes for compliant mechanisms including fatigue, stress relaxation, and creep. Methods to minimize or prevent these failure modes.
8. Fabrication and Testing
   Review of effective practices used to fabricate and test compliant mechanisms and guidelines to successfully creating compliant mechanisms using additive manufacturing.
9. Rigid-Body Replacement Synthesis for Compliant Mechanisms
   A compliant mechanism design approach using traditional mechanisms (rigid links and pins) and finding compliant equivalents.
10. Case Studies
    Scenarios where compliant mechanisms have been used including constant force mechanisms, parallel mechanisms, pointer mechanisms, bistable (and multi-stable) mechanisms, and origami-inspired compliant mechanisms.

Instructor

DR. TODD G NELSON

Dr. Todd G Nelson received his Ph.D. in Mechanical Engineering from Brigham Young University (BYU) where he studied origami-inspired mechanisms and compliant mechanisms under his advisor, Dr. Larry L. Howell. Combining principles from compliant mechanisms and the ancient art of origami has led to novel mechanisms and products which can be ultra-compact, deployable, scalable and fabricated from a single sheet of material. His research has implications for varied applications including medical implants, surgical tools, aerospace applications, automotive airbags, and deployable structures. Dr. Nelson enjoys teaching mechanism and machine design courses that lead to innovations in aerospace technologies and designs.