156B Week 2

Overview of Status of Analysis, Design, Fabrication, Tests, etc.

• • Closed-form solution relating impact velocity, masses, stiffnesses of materials to achieve desired impulse profiles

    • Modal analysis corrected for foam; cut included for impact head clearance

  • Considering alternative options for fixture plate construction: now very much on board with Tom's/Ian's thoughts on the matter

Accomplishments from Previous Week

• • Modal analysis redone to include plate mass

    • Also included cut needed for hammer clearance (swinging hammer would hit foam instead of aluminum sheet)

  • Side impact chosen

  • Closed-form solution for impact head-fixture plate interaction

    • Can determine materials+general geometry for impact head (delrin for short-duration profiles, spring for long duration)

    • Can determine impact velocity

  • More SolidWorks models: including impact head frame + axle now

Goals for Next Week (list names after each item). Use specific and measurable objectives.

• • Analyze aluminum fixture plate: make lighter+cheaper with high natural frequencies - Sam

  • Find more sources of (cheaper) open cell foam - Leighy

Sponsor Comments from Last Meeting and Actions Taken to Address these Comments (indicate date of comments and if via email or in person)

• • Sponsor meeting on Tuesday of Week 2 (progress report written by Monday, before meeting)

    • Anticipating comments on the following:

    • Side impact vs. vertical

    • Foam viability

    • Issues with foam tearing

    • Bolt pattern/mounting for test articles AND accelerometers

      • Use keenserts vs. just threading the material?

Instructor Comments from Last Meeting and Actions Taken to Address these Comments (indicate date of comments and if via email or in person)

• • All in person

  • Dr. Tustaniwskyj: Can do modal analysis of hammer impacting plate w/out damping and in time domain (done; analytical solution found)

    • Spring vs. material in hammer head (found necessary stiffnesses: one will be spring, two will be material of varying cross section etc.)

    • Worried about foam corrupting data (ATA has said if natural frequencies are low enough, this shouldn't be a problem)

  • Be more clear on specific deliverables (half sine pulse of 3 given amplitudes and durations; we will explain better in presentations/reports)

  • Tom/Ian: instead of solid aluminum plate, use two plates sandwiching some beams; tack weld together: lighter, cheaper, quicker

    • Tom: if attached to foam (vs. just laying on top), foam may tear after a few uses (will talk to ATA: determine if fixture plate should be attached to foam or just slide on top of it)

    • Ian: as long as data into fixture plate is correct, the rest doesn't matter: tune out friction/confounding variables by testing, i.e. if you expect to need 1.0kJ of energy to achieve profile, but output is too small, increase energy and make a note of it (this is along our train of thought)

Comments from Other Students in the Class (indicate date of comments and if via email or in person)

• • All in person (from 1st presentation feedback)

  • From first presentation: be more clear on FEA

    • Modal analysis does NOT have loads, need to explain that

    • Location/nature of BCs

  • Be more clear on specific deliverables (half sine pulse of 3 given amplitudes and durations)

Risks and Areas of Concern

• • EXPENSE: excluding dumpster diving, $1,500 will not be enough for impact head, arm, structure supporting it, fixture plate AND foam

  • Will ATA go for the side impact? If not, arresting method will need to be revisited

  • See concerns of instructors above

Resources or Information Required but not Available

• • None so far

Schedule

• • (See Gantt chart for dates/timeline, these are just the deliverables)

  • Finalize fixture plate design so materials can be purchased

    • Come up with scale model: for proof of concept

    • Determine if solid piece+pocketing or multi-piece+welding (multi-piece is more cost-effective, quicker to produce)

  • Finalize foam: talk to ATA about it

  • Determine impact head arm structure (single beam vs. truss-type structure)

    • Determine bearings needed for impact arm

    • May need to make two half axles that screw together (makes bearings easier; probably cheaper as well).

  • Add material damping to analysis

Budget (list amount spent and amount remaining)

• • Spent: $0

  • Remaining: $1,500

Progress on Report and Webpage

• • Analysis first, webpage after; After Tuesday ATA meeting, more updates to come + tons and tons and tons of analysis

    • Want to update info page first

  • Report status: not yet started; the good news is, we have good documentation, so inserting information will be less difficult