logging in or signing up AAPT v3 Mentor Download Post to : URL : Related Presentations : Share Add to Flag Embed Email Send to Blogs and Networks Add to Channel Uploaded from authorPOINT Insert YouTube videos in PowerPont slides with aS Desktop Copy embed code: (To copy code, click on the text box) Embed: URL: Thumbnail: WordPress Embed Customize Embed The presentation is successfully added In Your Favorites. Views: 147 Category: Sports License: All Rights Reserved Like it (0) Dislike it (0) Added: July 09, 2007 This Presentation is Public Favorites: 0 Presentation Description No description available. Comments Posting comment... Premium member Presentation Transcript A Comparative Study ofWood and Aluminum Baseball BatsAlan M. NathanUniversity of Illinois at Urbana-Champaigna-nathan@uiuc.eduhttp://www.npl.uiuc.edu/~a-nathan/pob: A Comparative Study of Wood and Aluminum Baseball Bats Alan M. Nathan University of Illinois at Urbana-Champaign a-nathan@uiuc.edu http://www.npl.uiuc.edu/~a-nathan/pob Introduction Some Basics Wood vs. Aluminum Some Examples Summary/Conclusions Slide2: Introduction: Description of Ball-Bat Collision violent collision forces large (andgt;8000 lbs!) time is short (andlt;1/1000 sec!) bat compresses ball kinetic energy potential energy lots of energy dissipated ball deforms bat vibrations! performance metric: ball exit speed vf Slide3: vball and vbat 'Collision efficiency' (eA) For superball on massive, rigid bat … eA 1 For baseball on typical bat … eA 0.2 Recoil of bat Energy dissipated in ball and bat What Does vf Depend On? vf = eA vball + (1+eA) vbat Recoil Energy of Bat: m/Meff: Recoil Energy of Bat: m/Meff Bat recoil depends on…. mass M mass distribution location of CM MOI ICM impact location (z) Energy Dissipation: The COR: Energy Dissipation: The COR Coefficient Of Restitution: 'bounciness' of ball in CM frame: Ef/Ei = COR2 massive rigid surface: COR2 = hf/hi 0.25 COR 0.5 ~3/4 CM energy dissipated! depends (weakly) on impact speed depends on surface the bat matters too! Slide6: Effect of Bat on COR: Vibrations COR depends strongly on impact location Slide7: Putting Everything Together... 'sweet spot' depends on collision efficiency recoil factor COR how bat is swung vf = eA vball + (1+eA) vbat Slide8: Aluminum vs. Wood Inertial Effects: mass and mass distribution recoil bat swing Dynamic Effects COR: the trampoline effect Slide9: Generic Wood-Aluminum Comparison Conclusion: Inertial effects seem to favor wood Slide10: Compressional energy shared between ball and bat Ball very inefficient (~25% restored) Wood Bat hard to compress little effect on COR Aluminum Bat compressible through 'shell' modes COR larger The 'Trampoline' Effect Slide11: Generic Wood-Aluminum Comparison Conclusion: Trampoline effect favors aluminum The Trampoline Effect: A Closer Look: The Trampoline Effect: A Closer Look Bending Modes vs. Shell Modes k R4: large in barrel little energy stored f (170 Hz, etc) andgt; 1/ energy goes into vibrations k (t/R)3: small in barrel more energy stored f (2-3 kHz) andlt; 1/ energy mostly restored Slide13: Tracking the Energy Example 1: Effect of Wall Thickness: Example 1: Effect of Wall Thickness k t3 t make wall thinner add mass to keep CM, ICM fixed Conclusion: thinner is better! Example 2: Redistributing the Mass: Example 2: Redistributing the Mass make wall thinner add mass at different locations Conclusion: barrel loading better! Example 3: “Corking” a Wood Bat (illegal!): Example 3: 'Corking' a Wood Bat (illegal!) Drill ~1' diameter hole along axis to depth of ~10' Smaller mass larger recoil factor (bad) higher bat speed (good) Is there a trampoline effect? Slide17: Not Corked DATA Corked COR: 0.445 0.005 0.444 0.005 Conclusions: no tramopline effect! corked bat is WORSE even with higher vbat Bat Research Center, UML, Sherwood andamp; amn, Aug. 2001 calculation Example 4: Ash vs. Maple (legal!): Example 4: Ash vs. Maple (legal!) (maple) 1.085 (ash) equal mass Rmaple = Rash/1.042 k ~ R4 kmaple = 0.92 kash more compression energy stored in maple Conclusion: B2 had no real advantage! Summary and Conclusions: Summary and Conclusions The physics of ball-bat collision is well understood There are significant differences between wood and aluminum mass distribution trampoline effect Wood bats cannot easily duplicate trampoline effect Aluminum bats work better! You do not have the permission to view this presentation. In order to view it, please contact the author of the presentation.
AAPT v3 Mentor Download Post to : URL : Related Presentations : Share Add to Flag Embed Email Send to Blogs and Networks Add to Channel Uploaded from authorPOINT Insert YouTube videos in PowerPont slides with aS Desktop Copy embed code: (To copy code, click on the text box) Embed: URL: Thumbnail: WordPress Embed Customize Embed The presentation is successfully added In Your Favorites. Views: 147 Category: Sports License: All Rights Reserved Like it (0) Dislike it (0) Added: July 09, 2007 This Presentation is Public Favorites: 0 Presentation Description No description available. Comments Posting comment... Premium member Presentation Transcript A Comparative Study ofWood and Aluminum Baseball BatsAlan M. NathanUniversity of Illinois at Urbana-Champaigna-nathan@uiuc.eduhttp://www.npl.uiuc.edu/~a-nathan/pob: A Comparative Study of Wood and Aluminum Baseball Bats Alan M. Nathan University of Illinois at Urbana-Champaign a-nathan@uiuc.edu http://www.npl.uiuc.edu/~a-nathan/pob Introduction Some Basics Wood vs. Aluminum Some Examples Summary/Conclusions Slide2: Introduction: Description of Ball-Bat Collision violent collision forces large (andgt;8000 lbs!) time is short (andlt;1/1000 sec!) bat compresses ball kinetic energy potential energy lots of energy dissipated ball deforms bat vibrations! performance metric: ball exit speed vf Slide3: vball and vbat 'Collision efficiency' (eA) For superball on massive, rigid bat … eA 1 For baseball on typical bat … eA 0.2 Recoil of bat Energy dissipated in ball and bat What Does vf Depend On? vf = eA vball + (1+eA) vbat Recoil Energy of Bat: m/Meff: Recoil Energy of Bat: m/Meff Bat recoil depends on…. mass M mass distribution location of CM MOI ICM impact location (z) Energy Dissipation: The COR: Energy Dissipation: The COR Coefficient Of Restitution: 'bounciness' of ball in CM frame: Ef/Ei = COR2 massive rigid surface: COR2 = hf/hi 0.25 COR 0.5 ~3/4 CM energy dissipated! depends (weakly) on impact speed depends on surface the bat matters too! Slide6: Effect of Bat on COR: Vibrations COR depends strongly on impact location Slide7: Putting Everything Together... 'sweet spot' depends on collision efficiency recoil factor COR how bat is swung vf = eA vball + (1+eA) vbat Slide8: Aluminum vs. Wood Inertial Effects: mass and mass distribution recoil bat swing Dynamic Effects COR: the trampoline effect Slide9: Generic Wood-Aluminum Comparison Conclusion: Inertial effects seem to favor wood Slide10: Compressional energy shared between ball and bat Ball very inefficient (~25% restored) Wood Bat hard to compress little effect on COR Aluminum Bat compressible through 'shell' modes COR larger The 'Trampoline' Effect Slide11: Generic Wood-Aluminum Comparison Conclusion: Trampoline effect favors aluminum The Trampoline Effect: A Closer Look: The Trampoline Effect: A Closer Look Bending Modes vs. Shell Modes k R4: large in barrel little energy stored f (170 Hz, etc) andgt; 1/ energy goes into vibrations k (t/R)3: small in barrel more energy stored f (2-3 kHz) andlt; 1/ energy mostly restored Slide13: Tracking the Energy Example 1: Effect of Wall Thickness: Example 1: Effect of Wall Thickness k t3 t make wall thinner add mass to keep CM, ICM fixed Conclusion: thinner is better! Example 2: Redistributing the Mass: Example 2: Redistributing the Mass make wall thinner add mass at different locations Conclusion: barrel loading better! Example 3: “Corking” a Wood Bat (illegal!): Example 3: 'Corking' a Wood Bat (illegal!) Drill ~1' diameter hole along axis to depth of ~10' Smaller mass larger recoil factor (bad) higher bat speed (good) Is there a trampoline effect? Slide17: Not Corked DATA Corked COR: 0.445 0.005 0.444 0.005 Conclusions: no tramopline effect! corked bat is WORSE even with higher vbat Bat Research Center, UML, Sherwood andamp; amn, Aug. 2001 calculation Example 4: Ash vs. Maple (legal!): Example 4: Ash vs. Maple (legal!) (maple) 1.085 (ash) equal mass Rmaple = Rash/1.042 k ~ R4 kmaple = 0.92 kash more compression energy stored in maple Conclusion: B2 had no real advantage! Summary and Conclusions: Summary and Conclusions The physics of ball-bat collision is well understood There are significant differences between wood and aluminum mass distribution trampoline effect Wood bats cannot easily duplicate trampoline effect Aluminum bats work better!