8/13/2019 Computer Aided Design of Bolts

1/15

COMPUTER AIDED DESIGN OF BOLTS1John A. Akpobi and 2A.A. U h!"# h!

1Production Engineering Department, University of Benin, Benin City, Nigeria .2Mechanica Engineering Department, University of Benin, Benin City, Nigeria .

1E$ai%& a%'a()*ohni!+(ahoo.,o$

ABSTRACTThis work presents computer aided design software for the design of bolt used in joints. It was developed

using Microsofts Visual Basic object oriented programming techniques The software was incorporated with

graphical features to enable a visual presentation of solutions to problems. The software was then tested using a

number of benchmark e!amples. The results show that the software is highl" accurate fle!ible and efficient..

-!('o"d)& Computer!aided!design, "o t oading, o"#ects oriented programming, $oder"erg p ots, separation ine.

1. INTRODUCTION

Bo ts are machine e ements %hich are used in ho ding together machine parts. &hey are usua y emp oyedas fasteners and are fre'uent y encountered in machines.

(hen in use, they are su"#ected to stresses %hich arise from e)terna oads, temperature, and pressure

changes. Design for "o ts re'uires that the "o ts are safe y oaded to prevent fai ure %hi e in use.

* ot of comp e) computations are needed in the design of "o ts. &hus there is the need to design and

deve op soft%are that %i provide accurate and easy to interpret so utions to the designers.

&he soft%are deve oped in this %or+, is user!friend y and can hand e a variety of possi" e pro" ems in "o t

design.

n designing the a gorithm for this soft%are, the fo o%ing genera procedures for ana y-ing "o ts %ere considered

Determination of the area Determination of the def ection and def ection per unit oad for "o t and mem"ers

Determination of the resu tant oad and a so oad re'uired for separation to occur

Determination of the app ied tor'ue

Determination of the initia tension

Determination of the impact stress %hen the "o t is su"#ected to impact oads

Determination of the re'uired height of nut. Determination of the mean and varia" e stresses for "o ts underf uctuating oad and chec+ing for safety of oading.

Bo t fai ure ana ysis using $oder"erg p ots.

1

8/13/2019 Computer Aided Design of Bolts

2/15

n the area of deve oping soft%are for machine design, very itt e documented research e)ists. $ome of these

documented machine design soft%are inc ude the %or+s of *+po"i.and *rdey /2002 , %ho %or+ed on machine

vi"rations design, and, om"o. and *detona /2003 4 %ho %or+ed on "e ts and pu eys. 5o%ever, efforts have "een

made recent y to deve op more soft%are for the design of machine e ements, using o"#ect!oriented programming

Notation

# #rea $m % &

#r

'oot area $m % &

b (eflection per unit load for bolt $m)*&

d *ominal bolt diameter $m&

d r 'oot diameter of thread $m&

+ ,oungs Modulus $*)m % &

f -o efficient of thread co efficient

f c

-o efficient of collar co efficient

/ /orce caused b" impact $*&

h 0eight of nut $m&

1 f

2tress correction factor

3 3ength $m&

m (eflection per unit load for members $m)*& * 2afet" factor

r c

-ollar friction radius $m&

r m

Mean thread radius $m&

2 r

+ndurance load $*&

2 "

,ield point $*&

T c

-ollar torque $*m&

T f

Thread torque $*m&

4 +nerg" of Impact $5&

6 'esultant load $*&

6 7

Initial Tightening 3oad $*&

6 %

+!ternal load $*&

8 0eli! angle $radian&

9 :ne half of thread angle

; (eformation)deflection $m&

< c

-ollar torque $*m&

< m

Ma!imum shear stress $*)m % &

= 7

Initial temperature $1&

= %

/inal temperature $1&> 3inear e!pansion coefficient $)1&

2

8/13/2019 Computer Aided Design of Bolts

3/15

techni'ue. $ome of these %or+s addressed the design of some types of gears /he ica , and spur see /*+po"i, and

*iriohuodion, 20064 *+po"i, 1778 , design of 9o ing Bearings /*+po"i, 2001 , and : y%hee s / *+po"i and

;a%ani, 200< .

(e %ish to state that to the "est of our +no% edge there is no documented computer!aided design %or+ on "o ts.

&he authors %ou d have conducted a comparative assessment of our resu ts %ith any that %as avai a" e. But the resu ts

presented here are high y accurate as they %ere so utions to "ench mar+ e)amp es and pro" ems adopted from / 5a , et.

a ., 2001 .

2. DESIGN OF SOFT ARE MODEL

n deve oping this soft%are, %e considered the re evant design e'uations for "o t. &hese e'uations formed

the fundamenta princip es used in designing the soft%are. &he soft%are presented in this %or+ %as compi ed using

the o"#ect!oriented programming techni'ues of =isua Basic otterfried, 2002 . &he

design of "o ts is %e treated in some Machine Design te)ts /5a , et a , 20034 $hig ey and Misch+e, 20014 ?hurmi

and >upta, 2002

&hese fundamenta formu ae are presented as fo o%s

2.1. D!/%!,0ion

&his is ength added or removed %hen e)pansion or contraction ta+es p ace as temperature increases or

drops, or %hen pressure or force increases or decreases.

t@s va ue may "e found using any of the t%o e'uations sho%n "e o%

/3 #+

= /1

( )2 1 3 = /2

2.2. Ini0ia% bo%0 Load

&his arises as a resu t of the tightening of the "o ts "efore they are used. &his tightening may "e

done in any of three %ays

By an e)perienced mechanic

By using a tor'ue %rench

By using a theoretica e)pression

2.2.1 Estimation of oad %hen tightened "y a mechanic

16 1d = %here ? is a constant greater than 10000 "ut ess than 1

8/13/2019 Computer Aided Design of Bolts

4/15

2.2. Ca cu ation using the theoretica e)pression

( )( )

1 tan cos

1 tan cosn

m c cn

T 6

f r f r

f

= + +

/6

2. . R!)#%0an0 %oad

&he 9esu tant oad is defined as fo o%s

1 2

m6 6 6

m b = + +

/