24.02.2009
Friction and Wear
Prepared by Suat Kadolu
(Based on P f Sahir A k L t
(B
d
Prof. S hi Arkans Lecture N t )
Notes)
17/02/2009
Friction
When two solid surfaces are pressed together, a force
parallel to the surfaces in contact is necessary to sli
pitch dia.
module
Pi
Pres. Angle
N
base dia.
add.dia
t
120
5
3.141592654
0.3490658504
24
112.76311449
125
Base circle
x
y
0 112.76311449
0
0.031415927 112.7074727 3.541975
0.062831853 112.54060224 7.0804545
0.094247780 112.2626678 10.611947
0.125663706 11
01.04.2009
Power Transmission
(Based on Prof. S. Arkans Notes)
Suat Kadolu
30.3.2009
Power Transmission
Ferquently, power is transmitted from a
prime mover (mechanical power
generator) to a working machine which
converts it to useful work.
Sometimes, po
18.03.2009
Rolling Contact Bearings
(Antifriction / Rolling Bearings)
Suat Kadolu
12 March 2009
Rolling Bearings
Locate the shaft in axial and radial
direction.
Load is transferred through rolling
contact rather than sliding contact.
Starting f i ti i t i
20.04.2009
Gears - 4
Suat Kadolu
14.4.2009
Forming of Gear Teeth
Various casting methods
sand, shell molding, investment etc.
Powder metallurgy
Extrusion
Cold forming and cold rolling
Machining followed by finishing
Heat treatment is applied for hardeni
25.03.2009
Rolling Bearings 3
Suat Kadolu
24.3.2009
Loading with adjusted and
preloaded bearings
Single row angular contact ball bearings
Tapered roller bearings
These can b assembled i X or O arrangement i pairs.
Th
be
bl d in
t in i
Direction of normal
23.03.2009
Rolling Bearings-2
Suat Kadolu
18/3/2009
Load vs Life
Experiments show that two groups of identical
bearings tested under different loads F1 and
F2 will have respective lives according to the
relation
L1 F2
=
L2 F1
a
Lives L1 and L2 are i
V-Belt Drives
Suat Kadolu
16-5-2013
Main Features
High speed ratio
Belt speeds: 5 m/s<V<50 m/s
Long Life
Quiet
Absorb shocks
Operating temperatures: 50 C<T<80 C
Belt Profiles
,b0,bw,hw,h,dw,min
and belt weight per
unit length defines
belt profile
dw
V-Be
06.03.2009
JOURNAL BEARINGS -2
Prepared by Suat Kadolu
3/03/2009
(Based on Shigleys Mechanical
Engineering Design)
Hydrodynamic Theory
Originated in the
p
lab. of Beauchamp
Tower (c.1880)
Oil flow out of the
lubricator hole
Plugs popped out
(high press
06.04.2009
GEARS
Suat Kadolu
2 April 2009
Types of Gears and Their Main
features
Transmit power
between
Comments
Spur gears
Parallel shafts
Teeth / to axis of rot.
Simplest, no thrust,
noisy, least expensive
Helical gears
Parallel and non-par.
Shafts. Tee
03.03.2009
JOURNAL BEARINGS
Prepared by
Suat Kadolu
22/02/2009
Sliding Bearings
In machines there are mating surfaces in
relative motion (sliding rolling or a
(sliding,
combination of both).
Bearing is a machine element which
supports a moving part (and
25.02.2009
LUBRICATION
Prepared by Suat Kadolu
(Based on Prof. Sahir Arkans Lecture
Notes)
20/02/2009
LUBRICATION
Consider two surfaces in contact and
having a relative sliding motion
Frictional forces arise, wear take place
Object of lubrication is to
10.04.2009
Gears - 3
Suat Kadolu
4 April 2009
Conjugate Action and Fundamental
Law of Gearing
When the contacting profiles are
designed in order to produce a
constant angular velocity ratio
during meshing, mating profiles
are said to have conjugate actio
11.03.2009
Tave=55+20/2
=65 C
=30 mPa.s
1st trial
S=0.1125
Temp. Rise varable=1.0258
2nd trial
S=0.075
Temp. Rise varable=0.8000
1
11.03.2009
Interpolate
between A and B
A
Tave=70 C
=24 mPa.s
B
Check Temp.
Rise:
S 0.09
S=0 09
Temp. Rise
Variable=0.89034
04.05.2009
Design of Spur and Helical
Gears
27.4.2009
Design of Helical and Spur Gears
Gear teeth fail due to bending (yielding or
fatigue) or due to wear
wear.
Wear is used as a general term for surface
failure, which is usually caused by pitting.
Pit
06.05.2009
Gear Design - 2
Suat Kadolu
5.4.2009
Surface Strength Geometry Factor I (ZI)
It is also called the pitting resistance geometry
factor by AGMA
AGMA.
c = C p
K vWt 1 1
+
F cos r1 r2
At pitch point
1 1
2
+ =
r1 r2 sin t
where
mG =
1
2
+
06.04.2009
Gears - 2
Suat Kadolu
2 April 2009
Overview-1
C
dg
dp
1
06.04.2009
Overview-2
Nomenclature for spur gear
2
06.04.2009
Nomenclature
Pinion: smaller of the two mating gears
Gear : larger of the two mating gears
G
l
f th t
ti
Thrust : force in the
Rolling Bearing Problem
Problem
The shaft in Figure 1 transmits the torque
applied from the belt-pulley to the helical gear at
rotational speed n=1000 rpm. Belt forces are FA=
2000 N and FB = 800 N. The pulley diameter is
300 mm where the minimum shaft d
07.05.2009
Gear Design - 3
May 6 2009
Suat Kadolu
Design of Straight Bevel Gears
Straight bevel gears are used if pitch line velocity is less than 5 m/s.
Otherwise spiral bevel gears should be used.
Tooth proportions, face width and minimum number of te
24.04.2009
Gears -5
Suat Kadolu
22.4.2009
Worm Gear Force Analysis
W x = W (cos n sin + f cos )
W z = W (cos n cos f sin )
W y = W sin n
f is the friction coefficient
1
24.04.2009
Let subscripts G and W indicate forces acting
against the worm and gear, r
11.03.2009
Journal Bearings Part 3
Suat Kadolu
March 9th 2009
Clearance
Optimum Design of Bearings
To be selected: grade of oil N P r c l
oil, N, P, r, c,l
To be monitored : (performance factors) T2,h0,Q, H
Poor selection leads to too thin film, insuf
METU Mechanical Engineering Department
ME 308 Machine Elements II
Spring 2015 - Term Project
Gearbox Design and Bearing Selection
Due Date: 17/04/2015
Burak Nebil BARUTU
Fulya EROL
Kerem Doruk KATLIOLU
al Merve TANIK
C-206
B-175
G-156
C-202
[email protected]
Prepared by: Fulya EROL
Room: B-175 Phone: 5256
E-mail: [email protected]
Solution:
Date: 04.03.2015 (updated on 13.03.2015)
ME 308 MACHINE ELEMENTS II
TUTORIAL 1
Power Transmission and Design of Gear Drives: TYPES and
KINEMATICS
Problem 1: Consider the
Prepared by:al Merve TANIK
Room:C-202Phone: 5270
E-mail:[email protected]
Solution 1:
Date: 18.03.2015
ME 308 MACHINE ELEMENTS II
TUTORIAL 2
Design of Gear Drives: SPUR GEARS
a.) Gears are produced with rack cutter. Therefore, N min = 18 (See Geometric
Lecture 7
Authentication
and
Access Control
01/06/16
ELE 467
1
Authentication and Authorization
There are two types of authentication,
entity authentication is to allow one party (the verifier)
to gain assurance that the identity of another (the
claimant)
Lecture 6
Public-Key Cryptography
This Week
Public Key Cryptography
Cryptography based on Factoring
Cryptography based on Discrete
Logarithm
Secret Sharing
Timestamping
One-Time Signatures
January 6, 20
ELE 467
2
Public Key Encryption
Plaintext
x
Encrypti
Lecture 11
PKI (Public Key Infrastructure)
SSL (Secure Socket Layer)
Definition
A public key infrastructure consists of
components necessary to securely distribute
public keys.
It consists of
Certificates
A repository for retriving certificates
A method o
Lecture 3
Introduction to Cryptography
01/06/16
ELE 467
1
This Week
The Role of Cryptography
Historic Examples of Simple Ciphers
Types of Cryptanalysis
Information Theory and Cipher Security
One-Time Pad
01/06/16
ELE 467
2
Cryptography
Cryptography is the
Prepared by: M.akr
Room: C-206 Phone: 7232
E-mail: [email protected]
Solution:
Date:06-10.03.2017
ME 308 MACHINE ELEMENTS II
TUTORIAL 1
Power Transmission and Design of Gear Drives: TYPES and
KINEMATICS
Problem 1: Design a simple gear train for a conveyo