1

Riveted Joints

ME2140 Machine Elements and Innovative DesignDr Hans GrayDr Udaya KahangamageDepartment of Mechanical Engineering

2

Riveted Joint

3

Rivets …

4

Applications …

5

Applications …

6

Heavy Machinery …

7

Heavy Machinery – Car Dumper

8

Steel Bridges …

9

Fourth Bridge - Scotland

10

Sydney Harbour Bridge

11

Sydney Harbour Bridge

12

Sydney Harbour Bridge

13

Airplanes

14

Airplanes

15

Ships

16

Buses

17

Outline…

UPK - Mech

Introduction Advantages of riveted joints Disadvantages of riveted joints Types of rivets & Types of riveted

joints Failure mechanism Strength calculations under static

loads

18

Learning Outcomes

UPK - Mech

At the end of this section, you should be able to:

Select appropriate joint type for a given application

Design the size of the rivets considering strength requirements

19

Introduction

UPK - Mech

Riveted joints have been widely employed in various engineering structures, such as ships, boilers, bridges, etc.

The use of riveted joints has considerably been reduced due to the rapid development of welding techniques

Rivets are the main kind of fasteners in light frames and thin sheet shells made of light metals and alloys such as aluminium

Light alloys are difficult to weld

20

Rivets

UPK - Mech

The material of the rivets must be tough and ductile

Usually made of steel, brass, aluminium or copper

When strength and a fluid tight joint is the main consideration, steel rivets are used

21

Types of Rivets

UPK - Mech

22

Riveted Joints

UPK - Mech

23

Riveted Joint – Cross Section

24

Advantages of Riveted Joints

UPK - Mech

Riveted joints have high resistance against vibrational loads.

Can join difficult to weld parts: Dissimilar metals Thin plates Joints that cannot be subjected to heating

Riveted joints can be dismantled by cutting off the rivet heads.

Quality control is easier

25

Disadvantages of Riveted Joints

UPK - Mech

Rivet holes weaken the working cross section of the joint.

More metal is required for the joint owing to the necessity of overlapping the joined plates

26

Types of Riveted Joints (1)

UPK - Mech

Riveted joints may be classified according to:

The purpose for which it is used Strong joints – strength is the prime

requirement Tight strong joints – strength & leak proof

Method of placing joining member (eg. Lap and Butt)

The type of rivets employed (eg. Solid and tubular)

The number of rows of rivets used (eg. Single, double, triple)

27

UPK - Mech

Types of Riveted Joints (2)

28

Design Tips

UPK - Mech

At least two rivets should be used for each joint to avoid relative turning motion

Avoid placing rivets in constricted areas

Arrange rivets in Zig-zag pattern when using 2 or more rows of rivets

Use equal diameter rivets in a particular joint

29

Failure of Riveted Joints (1)

A rivet joint may fail in the following ways:

Shear of the rivets

UPK - Mech

30

Failure of Riveted Joints (2)

UPK - Mech

31

Failure of Riveted Joints (3)

Crushing of the rivets and plates

UPK - Mech

32

Failure of Riveted Joints (4)

Rupture of the plate in the section weakened by the holes

UPK - Mech

Tearing of plate at edge Tearing of plate across the rows of rivets

33

Strength Calculation under Static Loads

UPK - Mech

The method of strength calculation is based on the following assumptions:

The force is uniformly distributed between all elements

There is no friction force between the elements to be joined

34

Tearing of plate at edge

This can be avoided by maintaining a margin, m = 1.5d

UPK - Mech

35

Tearing of plate across the rows of rivets

p= ptich of rivets d= diameter of rivet t= thickness of plate σt= permissible tensile

stress for the plate material

UPK - Mech

Tearing area per pitch length At= (p-d)t Pull required to tear off plate Pt = At * σt

= (p-d)t*σt

If the applied load P is smaller than Pt no tearing will occur.

36

Strength Calculation under Static Loads (2)

Shear strength of rivets

UPK - Mech

22

4

4dn

P

dn

P

areastressShear

rivettheonForce ss

If the joint is lapped by two straps ??

37

Strength Calculation under Static Loads (3)

Crushing strength

UPK - Mech

ccc ndt

P

areastressCrushing

rivettheonForce

38

Strength of a riveted joint

The strength of a joint is the maximum force, which it can transmit, without causing it to fail

Joint can fail by (i) tearing off the plate (Pt)(ii) shearing off the rivet (Ps) & (iii) crushing off the rivet (Pc)

The strength of a riveted joint is the smallest of

Pt, Ps, and Pc

For continuous joints as in the case of a boiler, the calculations are done for a pitch.

For small joints the calculations are done for the entire joint

UPK - Mech

39

Efficiency of Riveted Joints (1)

UPK - Mech

The ratio of the strength of the riveted joint to the strength of the plate section

40

Efficiency of Riveted Joints (2)

UPK - Mech

tpt cst P and P ,P ofleast

where, p = pitch length, t = thickness of plates, σt = tensile stress of plates

41

Example

UPK - Mech

A single riveted lap joint is made of 15mm thick plates with 20mm diameter rivets. Determine the strength of the joint, if the pitch of rivets is 60mm. Take [σt]= 120MPa, τ = 90MPa, and [σc]= 160MPa.

What is the efficiency of this riveted joint

42

Eccentrically loaded riveted joints

A = Cross-section area of each rivet x1, x2, x3 etc. = Distance of rivets from OY

y1, y2, y3 etc. = Distance of rivets from OX

UPK - Mech

An

AxAxx

...21

_

An

AyAyy

...21

_

cos222 FPFPR ss

43

UPK - Mech

44

Average Ratios and Dimensions of Riveted Joints

UPK - Mech