156B Week 6

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

• • Data from prototype testing last week has been processed

  • Aluminum plate and foam for final model on its way

  • Troubleshooting stiffness discrepancy between aluminum plate and impact head (some solutions in the works: altering impact mass => alters impact head stiffness => alters drop height/input energy, considering spring assist again)

Accomplishments from Previous Week

• • Data from prototype processed

  • First draft of report

  • First draft of webpage

  • Side frame design modeled on CAD

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

• • Order remaining parts-- Leighy

  • Finalize issues with maximum impact head stiffness - Troy/Roy

    • Ensure impact head does not need to exceed ~2e8 N/m stiffness

      • Use this for new impact mass, new maximum height, new spring energy (if spring assist to be used)

  • Polish frame design, wood slider, etc. (requires some of the above) - Sam

    • Basic beam analysis on frame: ensure no buckling occurs under weight, forces, etc.

  • Prep the aluminum plate for machining: face it, straighten anything un-straight, etc. - Sam/Troy (and a lot of Tom's help)

  • Plate optistruct: add strike zone plate, remove cyclic pattern constraint (now only have mirror symmetry about impact line of action) - Sam

    • POSSIBLY try to get stiffness to exceed 1e9 N/m (previous likely number was 8e8 N/m)

    • Low priority until aluminum plate is faced, drilled, and ready for final pocketing (final pocketing determined by the OptiStruct)

Sponsor 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 on 04/28

  • 80-20 aluminum for frame

    • standard hardware, shareable with other things, etc.

  • Demonstrate ideas for arresting mechanism for this upcoming Tuesday

    • On hold until report completed; being resumed this weekend/Monday

  • Ensure frame won't buckle under weight, loads, etc.

  • Some more thoughts on the modal analysis of the plates (esp. in OptiStruct context)

    • Soft springs to simulate foam BC instead of pure normal constraints (we knew this was a simplification)

      • Remember the first 6 modes will be rigid body-esque (the plate will move about the springs in an "arc" + up/down+twisting; ignore those! (ignore modes where there is insignificant strain in plate: those are rigid body type modes)

    • Maybe be more accurate with test article attachments (big holes in center of each OptiStruct result are a result of the specific rigid patterning we are using)

  • Safety first! Have a good procedure, build in safety, extra restraints on impact mass, extra outriggers to prevent wobblies

    • This was perhaps an hour long discussion; very serious and in-depth discussion

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 on 04/27

  • Needed clarification on the interdependence of stiffnesses of system (we have math we can show; it's hard to explain verbally)

  • Stop using the word "soft": use compliance (we will not forget that this time, thank you)

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

• • Have not gotten the peer reviews back yet

Risks and Areas of Concern

• • Budget-- ATA asked us to use 80-20; can be extremely expensive

    • We would find a ballpark for cost between 80-20 and plain carbon steel tube: they would weigh cost/benefit

  • Large changes to impactor design: need to drive down stiffness = less impact mass which = more energy will come from "v" instead of "m" (1/2mv^2 at bottom of swing from mgh and 1/2kx^2 of spring)

    • Requires more number crunching: more time to do non-manufacturing!

Resources or Information Required but not Available

• • ATA has been very helpful with all information/resources that we ask for.

  • Waterjetting: where? what cost? what timescale? (a bunch of flat tabs for the impactor frame: easier to waterjet than machine with mills)

    • There are DEFINITELY multiple on campus: one in SME or something

Schedule

• • Order remaining parts by end of week.

    • McMaster: adjustable feet, keenserts+tool, etc.

    • IMS: tons of steel tube, a bunch of steel plate to be waterjet, perhaps?

  • Ask ATA at our weekly Tuesday meetings for more money.

  • Update Gantt chart.

Budget (list amount spent and amount remaining)

• • $962.26 spent

  • $537.75 remaining

Progress on Report and Webpage

• • First draft of both are complete!

    • Need to fill out appendices: technical drawings, procedural manuals, spec sheets, etc. are a must!