156B Week 4

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

• • Done with (most) analysis, just waiting for ATA to confirm the corner frequencies

    • Finalizing aluminum plate: stock shape and machined shapes

      • Still need to finalize desired bolt pattern w/ ATA: size of holes, spacing, threaded vs. clearance

  • Purchased delrin

Accomplishments from Previous Week

• • Determined that we needed a second material (can't use only delrin for the impact head)

    • We need to get a harder material or get a much wider cross sectional area for delrin

    • Therefore, it was determined delrin can only be used for one of the impacting heads

  • Modal analysis finished on optimized plate; 100% higher frequency, 33% weight savings

    • NC program finished in HSMworks (pending Tom's input/need to move plate to fit in HAAS)

    • Considering rerunning optimization as a check with different BCs (bottom was fixed to simulate friction; discussion with ATA indicated friction damps, but can't force zero strain, so simply normal constraint is more accurate than fixed)

      • Results with optimized plate and normal constraint only were still close to optimization

  • General pricing for wood: very cheap (all wood will be easily <$75)

    • Tom has finish, wax, etc.

      • Also good ideas on wood assembly

    • Will buy some sandpaper (also cheap)

  • Cheap sound dampening foam found on Amazon (Does $66 sound better than $1,000? I think so)

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

• • Finalize design for the impacting heads- Roy

  • Make any corrections once ATA looks over the calculations we sent them- all

  • Begin presentation for week 5- all

  • First draft of report- all

  • Measure the coefficient of restitution of impact heads- all (somewhat related to below)

  • Build a model of system- all

    • Frame: Troy

    • Plate: Sam

    • Accelerometers: Leighy

    • MATH (parameter determination): Roy

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

• • After the half-sine is plotted, any ringing/vibration afterwards can be ignored

  • Not looking for a true half-sine, just for the general shape

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

  • Think about creating a 3-degree-of-freedom system (we are taking action to use it to bolster current results)

    • (via email) Gave some more info. on 3 DOF system (thanks!)

  • Think about creating a scale model (will be done for the proof of concept presentation)

  • Tom in person: a lot of machining/assembly input

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

• • Just got the peer review responses from the last presentation back

  • General comments asked to be more specific about the modal analysis

Risks and Areas of Concern

• • Highest risk is that the excitation surface will attenuate the response of the test article

Resources or Information Required but not Available

• • None-- All resources/info that we have have been answered by ATA

Schedule

• • Proof of Concept Presentation in 1 week

  • First draft of report due Friday of week 5

Budget (list amount spent and amount remaining)

• • Spent $30 on delrin

  • We have $1470 remaining to be spent on bearings, aluminum, steel

Progress on Report and Webpage

• • Report looks good so far, waiting for the comments from Michael for what we have turned in so far

  • Webpage is coming along as well