Bolt Failure
Failure locations
Under the bolt head (large
fillet will reduce failure)
First engaged thread (60 to 70%)
Thread to shank (solid section) transition
(smooth transition will reduce failure)
Failure in fastened members
Snowmobile suspension bol
Discontinuity in Cross Section
Discontinuity
Discontinuity
Stepped shafts
Ken Youssefi
Mechanical & Aerospace Engr., SJSU
Discontinuity in Cross Section
High
stress
Water filter fatigue failure
Bracket with screw holes
Ken Youssefi
Mechanical & Aerospace
Kinematic (stick or skeleton) Diagrams
A striped-down (simplified) drawing showing the essentials needed for
kinematics analysis. All links are numbered while the joints are lettered.
Mechanism to open and close a window
Ken Youssefi
Mechanical & Aerospac
Design Example
12
A rotating shaft is carrying 10,000 lb force
as shown. The shaft is made of steel with
A
R1
r (fillet radius) = .1d
R2
R1 = 2500, R2 = 7500 lb.
The critical location is at the fillet,
Calculate the alternating stress,
MA = 2500 x 12 = 30
Pressurized Cylinders
Pipes carrying pressurized gas or liquid.
Press or shrink fits
Hydraulic or
pneumatic
actuators
Pressurized
cylinders
Ken Youssefi
MAE dept.
1
Stresses in Pressurized Cylinders
Cylindrical pressure vessels, hydraulic cylinders, shaft
Design Project
ME 154 Mechanical Engineering Design | R. K. Yee & V. K. Viswanathan | 2017 Jan 30
San Jos State University | Department of Mechanical Engineering
The ME 154 Design Project is an opportunity to demonstrate that you can effectively apply wha
Failure Theories Static Loads
Static load a stationary load that is gradually applied having an unchanging
magnitude and direction
Failure A part is permanently distorted and will not function properly.
A part has been separated into two or more pieces (f
Compression Members
The failure of members in compression
are due either to the load exceeding the
strength (crushing) or due to buckling
under the load, because the applied load
is larger than the critical buckling load.
Long members are referred to as c
Mechanism Design
Graphical Method
Ken Youssefi
Mechanical &
1
Mechanism Synthesis
Design a mechanism to obtain a specified
motion or force.
Type Synthesis given the required performance,
what type of mechanism is suitable? Linkages, gears,
cam and follow
Force Analysis
Kinetic analysis has to be performed to design the shape and
thickness of the links, the joints and to determine the required
input torque/force and the resulting output torque/force.
A
Force analysis of a 4-Bar
Known:
B
4
2
2
The length o
Ken Youssefi
Mechanical Engineering Dept, SJSU
1
Complex Numbers and Polar Notation
x2 + 1 = 0, x2 + x + 1 = 0,
Euler (1777), i = -1
i2 = -1
x=?
OA = - OA
OA = i2 OA
O
A
A
i2 represents 180o rotation of a vector
i represents 90o rotation of a vector
r = x
Normal & Shear components of stress
Normal stress is perpendicular to the cross section, (sigma).
Shear stress is parallel to the cross section, (tau).
y
y
3D case
xy
yx
yz
x
zx
xz
z
Ken Youssefi
Second subscript
indicates the positive
direction of t
5/1/2017
Design Against Fatigue Failure I*
Fatigue Failure Theory (Part 1)
Professor Yee
ME 154
1
*Machine Design by Robert L. Norton
Introduction to Fatigue Failure
441 ft long
9000 tons carrying capacity
1940-1944, 2708 ships were
constructed.
Welding t
Mechanism Synthesis and Analysis
Synthesis design a mechanism to perform a
desired function
Analysis given a mechanism, perform kinematics
and kinetics analysis
Graphical techniques
Analytical methods
Mechanism
Machines are mechanical devices used to acco
Fatigue Failure
It has been recognized that a metal subjected
to a repetitive or fluctuating stress will fail at a
stress much lower than that required to cause
failure on a single application of load. Failures
occurring under conditions of dynamic loadin
1. How many degrees of freedom does the following mechanism have?
Answer: n=6
J1=6
J2=1
DOF=2
2. What is the linkage type?
L=5
S=2
P=2
Q=3.5
L+S>P+Q, so Double rocker
If link 2 is the input and link 4 is the output, what is the range of motion of link 2?
SITTING TO STANDING LIFT ASSIST CHAIR
PROJECT SUMMARY
Mechanical Engineering Design
San Jose State University
Dr. Raymond Yee
May 16, 2017
Team Members
Juan Serrano
Michael Dang Nguyen
Raul Gonzalez
Initially, the original design product that the team des
MIDTERM 1 REVIEW
Kinematic Fundamentals
1) Link sufficiently rigid body that has two or more nodes to connect to other links; can be of any geometric
shape but number of nodes is its most fundamental characteristic
2) Joint kinematic pair; connection betw
NAME _
San Jose State University
Department of Mechanical Engineering
ME154
Homework 5 Due Wed. Oct. 21
Fall 2015
1 - Consider the wise grip mechanism shown in the figure. If the applied force P = 15 lb., determine the
output force Q, both forces are in t
Exam 1 Topics
Degrees of freedom and kinematics diagram. Identify the type
of mechanism (path, motion, function). Label all links and
joints clearly. Use the equation to find DOF. Indicate the type
of joint; pin, slider, 2DOF joints (roller in slot), .
Various Fasteners
Non-permanent fasteners (threaded)
Machine screws (cap screws)
Bolt and Nut
Stud and Nut
Permanent fasteners
Welding
Bonding (adhesive, brazing, and soldering)
Rivets
Which method to select depends on the type of joint, the force to be
t
Acceleration Analysis
DOM Ch 7
San Jos State University | Dr. Yee | Spring 2017
Learning Objectives
Express the acceleration of a point in complex notation, and
determine the acceleration from any given velocity vector.
Express the relative acceleration b
Stress-Strain 1
San Jos State University | Dr. Yee | Spring 2017
Learning Objectives
Define stress, strain, and modulus-of-elasticity (Youngs
modulus), and apply their defining equations.
Interpret a stress-strain curve, including elastic and plastic
regi
Velocity Analysis
DOM Ch 6
San Jos State University | Dr. Yee | Spring 2017
Learning Objectives
Express the velocity of a point in complex notation, and
determine the velocity from any given position vector.
Express the relative velocity between two point
Stress-Strain - Thick Walled Cylinders
See MD Ch4 Section 4.17 & Ch10 Section 10.12
San Jos State University | Dr. Yee | Spring 2017
Learning Objectives
Describe thick-walled cylinder equations under internal and
external pressures.
Explain the concept of