re curve bow final pres

8/20/2019 Re Curve Bow Final Pres

1/20

Stress Analysis Using ANSYSStress Analysis Using ANSYS

The Composite Recurve Bow

ME 4! "ro#ect$ %all &!!!

"resente' (y) *osee$ +ason"ro,essor) -r. Craig /ee0s


2/20

"ro#ect 1oals"ro#ect 1oals

Create Model Using Pro E

Mesh, Constrain, and Apply StringDisplacement to Model

Obtain Displacement and Stress Solution

For Each Composite Bo Using A!S"S

Finite Element Analysis So#tare

Compare $esults


3/20

The Early BowThe Early Bow

%non to !eolithic hunters, clearly depicted in ca&e

paintings o# '(,((( B)C)

*n its simplest #orm, the bo consisted o# a single piece o#

ood slightly bent by the tension o# a bostringconnecting its to ends)

+he bo stores the #orce o# the archers dra as potential

energy, then trans#er-s it to the bostring as .inetic energy,

imparting &elocity and poer to the arro)

+he total amount o# potential energy that an archer couldstore in the bo as a #unction o# the bos length)

+he more energy stored per unit o# or. is contained ithin

the dra length)


4/20

The Early BowThe Early Bow

+he longer bos more massi&e armsaccelerated sloly, a longer botransmitted .inetic energy to the stringand arro at a loer &elocity)

+he shorter bos stored less energy

#or the same amount o# or. e/pendedin the dra, but transmitted the energyto the arro, at a higher &elocity)

*n sum, the shorter bo transmittedless total energy to the arro, but it didso at a higher &elocity)

Ma/imum range as attained by sti##

short bos shooting a &ery light arro) Ma/imum poer, at medium ranges,

as attained by a long bo dri&ing arelati&ely hea&y arro)


5/20

The Recurve Bow 2s Born.The Recurve Bow 2s Born.

+he recur&e bo has limbs

that cur&e #orard prier to

loading)

0hen loaded ith a stringthese limbs o##er a

mechanical ad&antages

o&er the traditional long

bos because the sting is

closer to the handlealloing #or a greater dra

length hich accounts #or

an increase in stored

energy)


6/20

The Early Composite BowThe Early Composite Bow

*t is common belie# thatcomposite bos are o#recent origin)

1oe&er, there ha&e beencomposite bos identi#iedto ha&e originated earlierthan 23(( B)C)

+hese ancient compositebos are belie&ed to be o#

Assyrian Origin) Made o# ood, bone4horn,

sine, thin strips o# birchbar., and glue)

/oo'

Bone or

3orn

Sinew

Thin Birch

Bar0


7/20

Composite MaterialsComposite Materials

Composite5 A solid material that results hen to or more

di##erent substances, each ith its on characteristics, are

combined to create a ne substance hose properties aresuperior to those o# the original components in a speci#ic

application)

+his is achie&ed by embedding #ibers o# one substance in a

host matri/ o# another)

Binding the #ibers together using an adhesi&e, the rigid#ibers impart structural strength to the composite, hile the

matri/ protects the #ibers #rom the en&ironmental stress

and physical damage and o##ers thermal stability)


8/20

"roce'ure"roce'ure

Created the solid model inPro Engineer using thead&anced modelingtechni6ue7 Sept Blend)

Because the bo issymmetric, only hal# thebo is modeled)

E/ported this #ile to A!S"Sas an *8*S #ile)

*mport #ailed partially bynot recogni9ing the solid,hence the model ascompleted using A!S"Smodeling techni6ues)


9/20

MeshingMeshing

Once all o# the areas

are segmented, the

entire &olume is

meshed)

A Beam as added

#rom the central node

at the top o# the bo

straight don to themidpoint o# the bo to

represent the string)


10/20

Mo'el with Constraints Applie'Mo'el with Constraints Applie'

A#ter meshing is complete the

constraints are applied

+he model as constrained in

All DOF #or the bottom threelayers to simulate a persons

hand gripping the bo)

+he bo itsel# as

constrained in the 9 direction

and also the rotational / and y

directions)

+he base point o# the string

as alloed to mo&e in the /

direction only ith rotational

#reedom in :)

Y

5


11/20

AnalysisAnalysis

+his pro;ects analy9es an A and Bcomparison beteen to composite

materials)Materials used7 8raphite Epo/y and 8lass

Epo/y+his comparison ill determine hich

epo/y yields less stress #or a standardi9eddisplacement on the bo string)


12/20

2nitial Stress 1enerate' %rom String2nitial Stress 1enerate' %rom String

0hen the string is attached to

the bo it generates an initialstrain and stress)

+his initial strain as

selected to be


13/20

AnalysisAnalysis

For the analysis section, a

displacement as gi&en tothe base string node)

+his displacement as based

on an a&erage persons dra

length o# 3> inches)

+his plot demonstrates the

displacement that occurs andthe resulting de#ormation o#

the bo)


14/20

-isplacement Results %or 1raphite Epo6y-isplacement Results %or 1raphite Epo6y

7-isplacement Y7-isplacement


15/20

Stress "lot %or 1raphite Epo6yStress "lot %or 1raphite Epo6y


16/20

-isplacement Results %or 1lass Epo6y-isplacement Results %or 1lass Epo6y

7-isplacement Y7-isplacement


17/20

Stress "lot %or 1lass Epo6yStress "lot %or 1lass Epo6y


18/20

1raphite Epo6y 8s. 1lass Epo6y1raphite Epo6y 8s. 1lass Epo6y

97-isplacement:97-isplacement:1raphite 1lass


19/20

1raphite Epo6y 8s. 1lass Epo6y1raphite Epo6y 8s. 1lass Epo6y

9Stress "lots:9Stress "lots:1raphite 1lass


20/20

ConclusionConclusion

+he ? displacement #or the graphite bo is less than that #or the

glass) Since the displacement o# the bo string as .ept

standard during the analysis, this leads me to belie&e that it ill

be hard to pull the graphite bo to its optimal length) +here illbe a greater resistance ith the graphite bo)

1oe&er, based on the stress plots the graphite bo distributes

the load better) +he glass epo/y stress analysis re&eals a more

concentrated load on the outside cur&ature area) +his leads me to

belie&e that the glass epo/y may #atigue and #ail o&er time in that

area)

1ence, i# you can stand a little more resistance the graphite epo/y

bo ould be a better choice)

re curve bow final pres

Documents