dmc spring 2015 project presentation
DESCRIPTION
Powerpoint presentation giving a brief description about sprockets and chainsTRANSCRIPT
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DMC Spring 2015 Project Presentation
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Clutch
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What is a clutch?
• A mechanical device that engages and disengages the power transmission
• Used whenever the transmission of power or motion must be controlled either in amount or over time
• In the simplest application, they connect and disconnect 2 rotating shaft
• The motions involved are rotary, linear clutches are also possible
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Types Of Clutches
• Friction clutchContact made by two discs - made
of metals • Positive drive clutch
Consists of two mating surfaces with interconnecting elements, such as
teeth, that lock together during engagement to prevent slipping
• Centrifugal clutch
Used where speed of the engine defines the state of the clutch
Friction Clutch
Centrifugal Clutch
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Mechanism Of a Clutch
• Clutch is engaged when pedal is released, meaning both rotating shafts are locked together and spin at same speed
• Clutch is disengaged when pedal is pressed, meaning the rotating shafts are unlocked and spin at different speeds
• Clutch is slipping when rotating shafts are locked but spinning at different speeds
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Major Types of Clutches by its Application
• Vehicular (general)These are the different designs of clutches
used in vehicles. They are based on one or more friction discs pressed tightly together or against a
flywheel using springs.• Automobile Powertrain
In modern car with manual transmission - operated by the left-most pedal using hydraulic or cable connection.
Automobile powertrain
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Major Types of Clutches by its Application (conti..)
• MotorcyclesWet clutch - riding in the same oil as
transmission - made of stack of alternating plain steel and friction plates• Automobile non-powertrain
Use clutches in the places other than the drive plain driving and driven members are separated by a silicone based fluid and a valve controlled by a bimetallic spring
Motorcycle Clutch
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Friction Clutch: Other Clutches and Applications
● Belt ClutchUsed on agricultural equipment, lawn mowers,
tillers, and snow blowers● Dog Clutch
Used in the automobile manual transmissions mentioned ● Hydraulic Clutch
The driving and driven members are not in physical contact
Belt Clutch Dog Clutch
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Other Clutches and Applications (cont..)
● Electromagnetic ClutchEngaged by electromagnet
● Over Running or Free Wheel ClutchExternal force rotates the driven member
faster than the driver, the clutch effectively disengages● Wrap - Spring Clutches
These have a helical spring typically wound with square cross section wire
Electromagnetic Clutch Free Wheel Clutch Wrap-Spring Clutch
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Referenceshttp://en.wikipedia.org/wiki/Clutchhttp://www.designworldonline.com/low-cost-load-control-with-clutches-and-brakes/http://www.gmnbt.com/free-wheel-clutches.htmhttp://engineeringhindustan.tradeindia.com/stationary-field-type-electromagnetic-clutches-293730.htmlhttp://www.custom-sportbike-parts.com/parts/hand-controls-hydraulic-clutch/http://en.wikipedia.org/wiki/Manual_transmissionhttp://www.obups.com/AC120/clutches.htmhttp://www.motorcyclejazz.com/clutch.htmhttp://www.wisegeek.com/what-is-a-powertrain.htmhttp://www.google.com/search?biw=1366&bih=667&noj=1&tbm=isch&q=car+clutches&revid=1506666678&sa=X&ei=-NExVeGfHcOwsASbuoDYCg&ved=0CCUQ1QIoAg
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Thank you
Have a Wonderful Summer Break Team Clutch
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Samantha HellerHunter LankowskiJason KimAlan NorteyMatthew TubmanXiao Le Zheng
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THE BASICS
A Spring is any elastic object that:Exerts forces and torquesAbsorbs energy that is later released
They are usually Metal
[1]
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TYPES OF SPRINGS
Torsion Bar Spring:
Helical Spring: A torsion bar wound into a helixSpring Index:
[2]
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DESIGNING THE SPRING CONSTANTHooke’s Law: F = kx, where: x is the deflection
k is the spring constant
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TORSION BARSEquations:
Torsional Stress:
Angular Deflection:
Hooke’s Law:Where K is the spring constant [Nm]
Effects of Curvature:
Static Loading:
Cyclic Loading:
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COILS AND DIFFERENT ENDS “Active” Turns = N
Total Turns = Nt
Nt = N + 2
(+2) accounts for each
end of the spring
The different ends of springs:
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DIFFERENT SHAPES OF SPRINGS
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APPLICATIONS OF SPRINGS
Cars and BikesPo-Go Sticks and Toys
Pens and Mechanical Pencils
Garage DoorsStaplersWatchesTrampolinesBedsAnd so much more…
[3]
[4]
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REFERENCES
[1] http://hyperphysics.phy-astr.gsu.edu/hbase/permot2.html
[2] http://www.fea-optimization.com/ETBX/spring_help.html
[3] http://toys.lovetoknow.com/History_of_the_Pogo_Stick
[4] http://leftbraincraftbrain.com/2015/03/10/10-ways-to-play-and-learn-with-springs/
All other photos and information is from:
Juvinall, Robert C., and Kurt M. Marshek. "Chapter 12: Springs."Fundamentals of Machine Component Design. 5th ed. New Jsersey: John Wiley & Sons, 2006. 497-530. Print.
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OUR VIDEO
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byEric Hernandez Faizan AhmedJordan Rafalko Angelo GuloEdgard Jimenez Andrew Spano
DMC Project:Threaded Fasteners
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● Definitions and Standard Geometry● Threads and Sizes● Types of Fasteners● Common Screw and Bolt Head Types● Power Screws
○ Efficiency○ Overhauling and Self-Locking
Topics
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Types of Fasteners
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Power Screws
● convert rotary motion of either the nut or the
screw to relatively slow linear motion of the
mating member along the screw axis
● aka linear actuators or translation screws
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EfficiencyEfficiency = work output/work input = (force*distance)/(2*pi*torque)
Conclusions from plot● Efficiency decreases with increasing
coefficient of friction● Efficiency approaches zero as lead angle
approaches zero● Efficiency approaches zero as lead angle
approaches 90 degrees
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Overhauling and Self-locking
Self-locking screws require a positive torque to lower a load
Overhauling screws require that a negative external lowering torque must be maintained to keep a load from lowering due to the low friction
If collar friction is neglected a screw is self locking if
A screw may be self-locking under static conditions, but it may overhaul during vibration
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References
Juvinall, Robert C., and Kurt M. Marshek. Machine Component Design. Singapore: J. Wiley & Sons, 2012. Print.
http://en.wikipedia.org/wiki/Screw_thread#Pitch_diameter
http://www.accuratescrew.com/TechTips/?TipNO=8
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Gears
By: Etebom obot, Mert kahyaoglu, Brandon Wagner, Eamonn Hennessey, Matt Sheleheda, Kyle Kourelakos
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HISTORY
One of the oldest pieces of equipment. Can be traced back to the 27th century BC
Used in water wheels and clocks
Used as a force multiplier
Most fundamental part of machinery
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Common uses
Vehicles
Trains
Clocks
Bicycles
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How gears work
Gears are used in transmitting power from one part of a machine to another.
Combination of different sized gears are used for increasing and decreasing speed
Angular velocity ratios are constant as gears rotate
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Load transmission
power is transmitted by force developed between contact and teeth
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Types of gears
Spur gear
Rack and pinion
Worm gear
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Spur gears
Most commonly used gear
Torque is transmitted from pinion to gear
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Rack and pinion
Used to convert rotational motion to translation
eg rotating steering wheel to turn
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Worm gear
Basically a screw on a gear
One directional in nature. Only worm can turn gear
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Design/Manufacturing
Gears are made out of different materials including cast iron and steel
Combinations of gears with different materials can be used to attain certain properties.
Gears made of cast iron are less expensive and quieter than ones made of steel.
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Why do we need gears
very efficient
Motors usually provide power at high speeds and low torque
Torque provided by motor can be amplified through larger gears to load.
Without gears it would be impossible to operate a car or any mechanical device efficiently.
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BrakesBy: Cynthia Ko, Jonathan Schwalm, Kolung Chan,Peter Tran, Trent Handlovsky
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What is a Brake?
It is a mechanical device which inhibits motion, slowing or stopping a moving object. It depends on friction in order to function. The main objective is to maximize the friction coefficient, and keep it uniform over a wide range of operating conditions, and at the same time minimize wear.
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History of Brakes
In 1902, Frederick Lanchester patented the disc brake that helped make stopping cars much easier. The first time it was used was in his 12 hp Lanchester motor car in 1903.
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Different kinds of Brakes There are different types of brakes, both between vehicles and within a vehicle. The brakes used to stop a vehicle while driving are known as service brakes, which are either a disc or drum brake. Vehicles also come equipped with other braking systems including anti-lock and emergency brakes.
● Disc Brakes● Drum Brakes● Emergency Brakes● ABS aka Anti-Lock Braking
System● Air brakes● Engine brakes● Exhaust Brakes● Parking brakes● Regenerative braking
○ Electric○ Hydraulic (experimental)
● Aircraft brakes (landing gear disc brakes, thrust reversers, air brakes that work by increasing drag, and drogue parachutes)
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Engine Brakes
● Typically used in trucks and other large vehicles● Slow the vehicle by “shutting off” engine cylinders● Cylinders still move and compress air but they stop
firing and do not provide additional positive energy● The cylinder compression of the shut off cylinders slows
the engine when it pushes the air out the exhaust valve● The brakes are engaged with a switch when needed● This is very loud
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Exhaust Brakes● Also works by slowing engine speed● Typically found in large vehicles● Usually connected to turbocharger● Limits exhaust flow to slow down
engine● These are generally quiet but still
mitigate normal brake wear on vehicles
● Ex: similar to taking a deep breath, closing your mouth most of the way, and trying to exhale
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Regenerative Brakes
● Used in vehicles that make use of electric motors.
● When the motor is run in one direction, it converts electrical energy into mechanical energy that can be used to perform work.
● When the motor is run in the opposite direction it becomes an electrical generator converting mechanical energy into electrical energy.
● This electrical energy can then be fed into a charging system for the car’s batteries.
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Conclusion
Brakes are an important feature for any kind of vehicle. They help inhibit motion and allow us to properly stop vehicles safely.
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BEARINGSAlexander Hobbs, Timothy Beyer, Brian Blaney, Pierre Pais, Timothy Pearson, Gerome David
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WHAT IS A BEARING? A component with contacting surfaces
through which a load is transmitted Keeps motion between two parts on the
desired axis and helps to prevent friction and wear between them
Widely used in machines which involve rotational motion Examples include vehicle gearboxes, bicycle
wheels , and industrial machinery Two major types: sliding and rolling element
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SLIDING BEARINGS Direct sliding of the loading on the support Two types:
Journal - support perpendicular loads to shaft axis
Thrust - generally flat and support parallel loads to the shaft axis
Withstand higher temperatures and contamination better than rolling element bearings
Examples of sliding bearings
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ROLLING ELEMENT BEARINGS
Contain balls or rollers which separate the bearing and its force member
Sliding friction is replaced with rolling friction Lower starting friction, good for large loadings Can reduce cost by making extensive lubrication
unnecessary in certain applications Requires shielding of ball bearings to prevent
contamination
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IMPORTANT PROPERTIES FOR BEARING MATERIALS Important properties
Mechanical Conformability (low modulus of elasticity) Indentation softness Low shear strength Sufficient fatigue strength for repeated loadings
Thermal Good heat conductivity Thermal coefficient of expansion similar to housing
Metallurgical Compatible with journal material to resist welding,
seizing Chemical
Corrosion resistance
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COMMON BEARING MATERIALS
Babbitt Tin Base Lead base
Copper Alloys Copper lead Leaded bronze Tin bronze Aluminum bronze
Aluminum Silver
A babbitt bearing
Aluminum bearing
Copper alloy bearing
Silver bearings
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PETROFF’S EQUATION FOR BEARING FRICTION
Quick method of estimating reasonable coefficients of friction for bearings Where:
= viscosity n = rotating speed P = bearing load R = shaft radius c = radial clearance
Linear bearing
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BEARING SELECTION Must take into account loading, lubrication,
operating environment, speed of rotation, cost, and other factors
Bearing life varies greatly with the intensity of shock and axial loadings
Individual fatigue life has a skewed Weibull distribution
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WORKS CITED (IMAGES)"Aluminum Anti-Frction Bearings." Odessa Babbitt Bearing Company. N.p., n.d. Web. 28 Apr.
2015. <http://www.obbco.com/babbitt-bearings/aluminum-bearings.html>."Bearings." LinearBearings.com. N.p., n.d. Web. 28 Apr. 2015. <http://www.linear--
bearing.com/CNC-Bushing-16mm-Linear-Bearing-Open-Sliding-Unit.htm>."BL Bearings - Bearings, Chains, Sprockets, Bushings." BL Bearings - Bearings, Chains,
Sprockets, Bushings. N.p., n.d. Web. 28 Apr. 2015. <http://www.bearingslimited.com/>."Copper Alloy Bearing Promotion." Alibaba.com. N.p., n.d. Web. 28 Apr. 2015.
<http://www.alibaba.com/copper-alloy-bearing-promotion.html>.Juvinall, Robert C., and Kurt M. Marshek. Fundamentals of Machine Component Design. 5th ed.
Hoboken, NJ: John Wiley & Sons, 2012. Print.Repairpal.com. N.p., n.d. Web. 28 Apr. 2015.
<http://repairpal.com/images/managed/content_images/encyclopedia/CM_Steering_Suspension/Front_Wheel_Bearing_Set_08.11.png>.
"Silver Bearings." The Silver Institute. N.p., n.d. Web. 28 Apr. 2015. <https://www.silverinstitute.org/site/silver-in-industry/bearings/>.
"Submarine Main Propulsion Diesels - Chapter 3." Maritime.org. N.p., n.d. Web. 29 Apr. 2015. <http://maritime.org/doc/fleetsub/diesel/chap3.htm>.
Now for our video….
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Rivets and WeldingMuaz Billoo, Martin Mora, Allison Pelszynski,
Mike Czerhoniak, Benjamin Ratzersdorfer
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What are Rivets? Short metal pin or bolt used for holding
together two plates of metalWhen placed between two metals, hammers
or rivet guns generally used to fix them between the metals.
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Pros/Cons of RivetsStress analysis is the same as that of bolts Cheaper than screws
High Speed Riveting machines can assemble 1000 rivets/hour
Can be made from any ductile materialCannot provide an attachment as strong as a
bolt/screw with the same diameterSimple repair of electric appliances become
difficult
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What is Welding?To join together metal parts by heating their
surfaces to the point of melting Welding is generally accomplished through
the use of blow torches, or electric arcs.
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Pros/Cons of WeldingLiterally fusing two metals together to form a
single, homogeneous member With rivets, if the rivet fails then the metals
will have nothing to hold them togetherEither electric or gas powered
Riveting can be done with hammerIf one is not skilled in welding, they will leave
really bad trails on the metalsRelease of bright lights can damage a
person’s vision
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ImpactRobert NapoleonCharlene VanceNolan BarolinJack Kelliher
Joe ZevitsKhang Lam
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• Impact refers to an applied force that occurs over a short period of time when two or more bodies collide, causing a displacement
• It can be described by three types: gradual application of force, instantaneous application of the complete load value, and instantaneous application plus kinetic force of the object
What is impact?
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Slap experiment: Direct Impact forces
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Determining load application
• Load is slowly applied to an object such that it can be considered static.
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Static Impact
● Imagine a spring mass system.
● When load is rested on top of an object and there is no deflection.
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Dynamic Impact
● Spring mass system● Mass is suspended
above the spring, and is release on to spring creating deflection.
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Impact Factor
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Guidelines for the presentation
§ 4/29 W: Group 1~10§ Two parts§ Live presentation
Short lecture explaining the principle/concept, issues, examples, etc.2 Minutes, PowerPoint or PDF§ Video: 2 Minutes, <100 MB
Demonstration, experiment, lecture, story, examples, etc.Evaluation criteria:1. Understanding of the principle/concept2. Demonstration of the importance of the principle/concept3. Clarity of the presentation4. Technical aspect of the presentation5. Creativity
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14:650:342
Design of Mechanical Components
Brought to you by Juan Academy
Emily Lopez, Chris Fuscoletti, Diego Achury Triana, Juan Escobar, Christopher Gabrielski, Greg Smith
Surface Damage Presentation
*Slides inspired by Professor Lee
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Outline
Ch. 9■ Importance■ Types of Surface Damage■ Corrosion■ Cavitation Damage■ Wear
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■ Many materials ‘fail’ due to the effects of surface damage before breakage actually occurs.
■ Studying and preventing the various types of surface damage is a key importance in preserving the life expectancy of U.S. infrastructure
■ It is estimated that the U.S spends roughly $90 billion dollars annually repairing damages from Corrosion and Wear alone.
Importance
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Types of Surface Damage
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■ Materials chemical or electrochemical reaction with its environment that slowly deteriorates or erodes the material.
■ Most familiar type of corrosion is the rusting of metals
■ Pitting Corrosion is another form of corrosion which is normally undetectable because it is the forming of miniscule cavities in a metal that damage its structural integrity.
■ A few ways to increase a materials resistance to corrosion include painting, anodization, hot dip galvanization (coating the material in a layer of zinc)
■ Mostly corrosion occurs in metals, but can also happen with polymers and glass materials
Corrosion
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■ Explanation
○ Formation of gas bubbles or “cavities” in a liquid that with respect to a nearby solid
○ Creation and collapse of these bubbles on the solid creates pressure waves, which over time create plastic deformation and eventually failure
■ Possible Prevention
○ Modify liquid composition, velocity, flow pattern or static pressure
○ Increase surface hardness of the solid (Stainless steel is the most effective reasonable cost)
Cavitation Damage (Section 9.7)
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When the members are in sliding contactThe severity of wear can be reduced by using a lubricant (as an oil, grease, or solid film)
Types of Wear:● Adhesive Wear
○ Sliding metal surfaces increase pressure and temperature, causing welding of imperfections (peaks) as a result
● Abrasive Wear○ The term “wear” most often refers to abrasive wear, which is
due to the rubbing of abrasive particles on a surface. These particles are typically small and hard and have sharp edges—like grains of sand or particles of metal or metal oxide that rub off a wearing metal surface.
● Fretting○ Basically is the combination of abrasive wear and corrosion
film wear. Fretting happens when two surfaces are pressed together, experience slight relative motion.
Wear
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Analytical Approach to Wear
Where:
=Wear Depth t = Time K = Wear Coefficient H = Surface Hardness p = Surface Interface Pressure v = Sliding Velocity
Where:
W = Volume of Material Worn Away K = Wear Coefficient H = Surface Hardness F = Compressive Force S = Total Rubbing Distance
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SHAFTS
Miguel Ferrer, Lewis Beekman, Jesus Bravo, Dong Kwak, Akshita Kapasiawala,
Ryan Wilson
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Definition
Usually a long rotating member with a circular cross section that transmits power through its rotation.But it can also not have one or more of those traits, for example
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Types of SHAFTSSpindles- short small diameter
Axle- stationary, supports rotational members
Stub shafts- Connects multiple parts easily
Line shaft- connected between motor and multiple parts
Flexible shaft- transmits power between parts whose rotational axes are not aligned and or can move
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Universal Joint Very important in shaft applications.
Allow articulation between
Used in cars to allow the travel of drive wheels for suspension and steering.
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Properties of SHAFTSCritical Speed: and multiplesFor its only type of loading (dynamic):-SN curves are those standard for steel going through torsion.- Sn= 0.58*Sn’ = 0.29*Su
- S10^3=.9*.8*Su
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Maximum Torque Capacity
Different shaft geometries have different critical loadings that can be supported by each shaft.
Square Shaft Joint
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Materials
SHAFTS are commonly made from steel, aluminum, and titanium alloys, carbon fibers, and carbon-fiber/glass composites.
Steel’s strongest, carbon fiber is lightest, etc.Not only designed for strength but also max deflection.
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Keys
For SHAFTS to transmit power to other components, keys are necessary.
A shaft and its connected component have grooves in which a key is inserted. Keys help bind the pieces and transmit rotational power.
Different types of keys include:Square, gib-head, Pratt&Whitney keys
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Bearings
-Fits around a shaft locking it in it’s location andorientation
-allows rotation of the shaft at anincreased effeciency
-minimizes friction-reduce wear
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Failure-Incorrect meshing occurs in SHAFTS when they go through too much
lateral deflection (δst)., Too much torsional deflection ruins the cooperation between the key and grooves
-The surfaces that endure the most pressure may experience wear -Fracture only occurs though fatigue generally
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References-"Failure Analysis Of Machine Shafts - Maintenance Technology." Maintenance Technology. N.p., 16 July 2012. Web. 29 Apr. 2015.
-"Fundamentals of Machine Component Design Hardcover September 27, 2011." Fundamentals of Machine Component Design: Robert C. Juvinall, Kurt M. Marshek: 9781118012895: Amazon.com: Books. N.p., n.d. Web. 29 Apr. 2015.
-"Propeller Shaft Assemblies." Propeller Shaft Assemblies. N.p., n.d. Web. 29 Apr. 2015.
-"Torsion of Shafts." Torsion of Shafts. N.p., n.d. Web. 29 Apr. 2015.
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DMC Final ProjectFATIGUE
Nicole PaulinoDante LevariLouis Morales
Tyler SchiffShail Amin
Aakash Hathi
14:650:342 Section 1
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Definition❧ Fatigue is the weakening of a material caused by
repeatedly applied loads
❧ Fatigue fractures begin with a minute crack at a critical area of high local stress. This is almost always at a geometric stress raiser.
❧ Fatigue failure results from repeated plastic deformation, such as the breaking of a wire by bending it back and forth repeatedly.
❧ Fatigue failures typically occur after thousands or even millions of cycles of minute yielding that often exists only on a microscopic level.
❧ Fatigue failure can occur at stress levels far below the conventionally determined yield point or elastic limit.
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Example
-The engineer must focus attention on all potentially vulnerable locations such as holes, sharp corners, threads, keyways, surface scratches, and corrosion.
-Strengthening these vulnerable locations is often as effective as making the entire part from a stronger material.
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Fatigue Strength in Ductile Materials
❧ Moore’s Endurance Limit (S’n) is defined as the highest stress that a material can withstand for a given number of cycles without breaking. It is found experimentally with a Moore’s fatigue testing machine (shown in next slide).
❧ Endurance Limit (Sn). The equation for Sn is Sn=(S’n)(CL)(CG)(CS)(CT)(CR).
❧ CL is the Load Factor, CG is the Gradient Factor, CT is the Temperature Factor, CR is the Reliability Factor and CS is the Surface Factor.
❧ Each factor’s value can be determined by the type of loading and dimensions of specimen.
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Types of Fatigue Loads
❧ Rotating Bending (Moore testing)-maximum stresses on surface. Weakest point-fatigue start.
❧ Reversed Bending-One end of specimen fixed and free end is pushed up and down. Maximum stresses only at top and bottom. Fatigue strength usually slightly greater. Not the weakest point.
❧ Reversed Axial Loading-One end of specimen fixed and free end is pushed and pulled left and right. Maximum stresses entire cross section. Fatigue strength about 10% less. No reserve.
❧ Reversed Torsional Loading- Maximum stresses on surface. Shear stresses=fatigue starts. S_us=.8*S_u
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Fatigue Load Examples
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Fatigue Surface Treatments
❧ Surface treatments : It influences the Surface strength in comparison with the strength of the surface material, and The Surface Residual stress.
❧ There are 2 types of Surface treatments: 1) Mechanical Surface Treatments, and 2) Thermal and Chemical surface treatments.
❧ After the treatment: Surface strengthening, & compressive residual stresses substantially increases the load that can be carried.
❧ Mechanical Surface Treatments: cold-work the surface material, causing compressive residual stresses and, depending on the properties of the material, and often strengthening the surface against strain.
❧ Examples of Mechanical Surface Treatments: Shot peening, Cold rolling, and Coining
❧ Chemical Surface Treatments: The purpose of thermal and chemical surface-hardening treatments is usually to provide surfaces with increased resistance to wear; however, they also serve to increase fatigue strength.
❧ Examples of Chemical surface treatments: Induction Hardening, Carburising, and Nitriding.
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Avoiding Fatigue
❧ Stress concentrations should be avoided where possible; a design with smooth flowing lines is usually the optimum
❧ The tendency for surfaces to fail in fatigue can obviously be reduced by decreasing loads and decreasing sliding
❧ In general, increased surface hardness increases resistance to surface fatigue.
❧ Precise accuracy of surface geometry and extreme surface smoothness are highly beneficial.
❧ Surface porosity, or a pattern of minute depressions on one of the mating surfaces, may help by providing tiny reservoirs for holding lubricant.
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Questions?
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LUBRICATIONAkofa Elike-Avion
Bryan Stonkus
Kareem Soliman
Robert DeSimone
Yianni Frangos
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Definition• Any substance that reduces friction and wear• Usually a liquid (sometimes a solid)• Characterized by their viscosity
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Types of Lubriction• Hydrodynamic Lubrication – The lubricant separates the
moving surfaces. The surface wear is nonexistent in this condition.
• Mixed-Film Lubrication – The surfaces of each object are constantly lubricated and are intermittently in contact. Surface wear mildly occurs here.
• Boundary Lubrication – the surface contact is continuous and extensive, while the lubricant is constantly applied so that there is a continuous film on each object. Surface wear is mild to high in this condition.
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Ways to Supply Lubricant• Oil Ring – Usually in use with shafts with journal bearings. As
the shaft rotates, the oil ring supplies oil to the top of the journal bearing
• Oil Collar – Like the oil bearing, but a collar brings oil to the top of the shaft and has the lubricant flow through gravitational forces.
• Splash – Oil that is splashed due to rapidly moving parts is channeled into small reservoirs and is supplied to the bearings
• Oil Bath – Oil is supplied by submerging the journal bearing into an oil reservoir
• Oil Holes and Grooves – Oil is supplied to the bearings through holes and flows by either gravitational forces or pressure.
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Heat Dissipation
• Extremely important and useful quality of lubrication• Heat in bearings is generated through friction and the rate
at which the shafts are moving• Equilibrium Conditions – The rate at which heat is
generated through friction in the system is equal to the rate in which heat is being taken away.
• The temperature of the oil at thermal equilibrium depends on the effectiveness that the lubricant has at transferring internal heat to the outside environment
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Linear Motion Devices
Michael Han, Shaun Kenny, Krishna Yellayi, Rahul Upadhyay, Bryan Arcos, Matthew Kelsten
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Screw Jacks
• Roller-screw jack• Very similar to ball screws with
respect to backlash, torque, and efficiency
• Utilized when there are strict regulations placed upon axial stiffness, linear speed, and acceleration rates
• Very expensive to manufacture
• Machine screw jack• The leadscrew converts rotary
motion to linear motion• Rolling gears support the
mechanism and minimalize friction as the apparatus rotates
• Almost all machine screw jacks are installed with self-locking mechanisms in case of power failure
• Can weigh anywhere from 1 – 250 tons
• Drawbacks include low efficiency (usually around 25%) and can generate heat due to sliding between screw and drive nut
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Ball Screws
• Backlash• The overall precision of a ball screw
is dependent on the measured distance between the nut and the screw
• Average backlash range is .002-.013 in. often the nuts and preloaded so that there is so distance between the two.
• Machines threads• Threads are physically pre-machined
into the ball screw• Higher precision, but often
unnecessary• Compared to formed threads, which
have lower precision but also lower manufacturing cost
• Drive Torque• T = PL / 2(pi)E• T = torque input, lb-in.
P = Operating Load. lbL = Lead, in/revE = efficiency
• Life expectancy• Applied force, best when applied in
same axis as ball screw• Number and length of strokes
• Standard of 1 million inches of travel
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Applications
• Moon rover• Utilizes a screw jack to
vertically dig up samples from the moon’s surface
• Is easily stored when not being used
• Provides an efficient method to dig vertically into the ground
• CNC• Precise measurements and
placements using all previously mentioned devices to cut material into specific shapes
• 3D Printer
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Belt-Driven Linear Motion Devices
• Utilize a belt in their linear travel path as seen in model (B)
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Belt-Driven Linear Motion Devices Cont.
• Wheel and pulley system.
• Rotating wheel moves the belt to produce linear motion.
• Includes chain and cable drives, not limited to belts.
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Why Use Belt-Driven?
• When speed and acceleration are critical.
• Able to achieve high speed motion with long stroke lengths.
• Quiet, consistent, and smooth motion.
• Not as expensive as screw jacks.
• Valued in various applications including laser cutting, wielding, and packaging machining.
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Stepper (Step) Motors
• Device type: Actuator• An Actuator is a type of motor that is
responsible for moving or controlling a mechanism or system.
• Motors convert electrical energy into mechanical energy. A stepper motor converts electrical pulses into specific movements. The movement created by each pulse is precise and repeatable, which is why stepper motors are so effective for positioning applications.
• Comes in Rotational or Linear forms.
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Stepper Motor Design
• There are 4 coils with 90 angle between each other fixed on the stator. The way that the coils are interconnected, will finally characterize the type of stepper motor connection. In the above drawing, the coils are not connected together. The above motor has 90 rotation step. The coils are activated in a cyclic order, one by one. The rotation direction of the shaft is determined by the order that the coils are activated.
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Stepper Motors vs. Regular Motors
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SPROCKETS AND CHAIN
DMC Spring 2015Sarath Jaladi Adam Rupp
Mohanish Shinde Dylan Robertson
Kent Christian Dylan Bryan
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What are Sprockets and Chain?● Sprockets and Chain transmit
power● Sprockets are toothed wheels on
which chain rides● Similar to gears, different sized
sprockets may be chained together to increase or decrease speed and torque.
● Unlike gears, however, Sprockets that are chained together rotate in the same direction (depending on the side of the chain).
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Where are Sprockets and Chain Used?● Bicycles
o Derailleur sprockets for shifting. Takes advantage of gear ratio
equation to alter horsepower and speed.
● Continuous Tracks (Tank Treads)
o Distribution of weight and traction for heavy vehicles. Increased
mobility and toughness.
● Mechanical Power Transmission
o Continuous power transport between two drive shafts over
distance.
● Cinema
o Used to run film through movie projectors and cameras.
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Pros and Cons of Sprockets and Chain
Pros:● Less frictional loss than belts. No
slip.● Gear ratio is easily adjusted.● Eliminates gear trains.● All sprockets turn in the same
direction.● Lighter than an all gear system.● Allows for more tolerance than
gears.
Cons:● Requires lubrication to prevent wear.● Can be noisy due to metal contact
points and vibrations.● Chain breakage can lead to
catastrophic failure.● Sprockets wear out faster than either
pulleys or gears.● Idler sprockets may be needed to
gain maximum efficiency and reduce wear.
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Common Configurations
● Type A- No hub
● Type B- Hub on one side
● Type C- Hub on each side
● Type D- Bolt on plate attached to
hub
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Types of Chains● Roller Chain
o Most commonly used for power transmission
o Consist of a series of cylindrical roller links connected with plates and pin
● Inverted Tooth Chaino Also called a silent chain, for
relatively quiet operationo Toothed link plates connected with
pins
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Sprocket Dimensions
● Bottom Diameter: Diameter of the circle running tangent to the bottom of each tooth gap
● Caliper Diameter: Distance from the bottom of two tooth gaps nearly opposite each other, useful in sprockets with odd numbers of teeth
● Pitch Diameter: Diameter of the circle tangent to the points of contact between the chain and sprocket teeth
● Sprocket Diameter: Diameter of circle tangent to each tooth tip
● Face Width: Width of tooth tip
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Chain Dimensions and Terms● Roller Diameter: The outside diameter of
the chain roller. This diameter engages with the sprocket.
● Pitch: The average distance from one chain pin to the next pin.
● Inner Width: The dimension between the two inner plates. This dimension will be a little greater than the width of the sprocket teeth to allow for smooth engagement.
● Connecting Link: A special link designed to connect two free ends of a chain together.
● Offset Link: A modified connecting link that adds half of what a connecting link adds.
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BeltsRobert Kertz, Ani Thuppul, John Sengco,
Calen Fields, Brian Connolly, Kushal Darji
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Flat Belts
• Flat belts were often used for transmission of power from flywheels to other parts of machinery.
• Commonly seen in use as conveyor belts or parts of belt arrays.
• Types• Small Woven Endless Belts• Higher Power Flat Belts
Sources:http://machinedesign.com/basics-design/flat-belts 2 .http://en.wikipedia.org/wiki/Belt_(mechanical) 3 .http://www.wisegeek.com/what-is-a-flat-belt.htm
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V-Belt
• Sheaves (V-shaped grooves)• Wedging action (V shape)
provides more normal force, allowing greater torque
• Used to drive accessories in cars, internal comb. Engines
• Blowers, compressors, appliances, etc.
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Toothed Belt• AKA timing belts.• Since the drive is by means of teeth rather than friction, there is no slippage and
the driving and driven shafts remain synchronized. • Toothed belts are relatively lightweight, and can give efficient operation at speeds
up to at least 80 m/s (16,000 ft/min). • Their principal disadvantage is the higher cost of both the belt and the toothed
pulleys. • Typically used for driving an engine camshaft from the crankshaft.
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Roller Chains• The most widely used power transmission chain• The load is initially transferred to the chain by a driving
sprocket tooth• The load is then transferred to a bushing, then a pin, then a pair of link plates• The full load is then transferred through successive link plates along the tight side of the chain
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Torque = (P1 - P2)r
EquationsFlat Belt:
P1/P2 =
Where f is coefficient of friction and is angle of contact with the pulley
Pc = m’ = mWhere Pc is tension on belt due to rotation.
V-Belt:
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Example
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References• Juvinall, Robert C. (2012). Fundamentals of Machine
Component Design. John Wiley and Sons, Inc.• www.sudarshantools.com (image of V-belt)
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What is a Cam?▪A cam is a mechanical linkage whose purpose is to translate rotational motion into linear motion with specific timing.
▪The cam itself comes in many shapes but it is often an irregular cylinder.
▪The cam is paired with, and maintains contact with, a follower which provides the linear motion of the system.
▪Mass produced cams are made using chilled iron castings while high quality cams are made using billet steel in CNC milling machines.
A simple cam with a follower.
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History of the Cam▪Early cams were found in the 3rd century BC in ancient Greek water powered automata.
▪In Mesopotamia, the camshaft was first used in the early 13th century AD by Al-Jazari in his automata, water raising machines, and water clocks.
▪The cam and camshaft later appeared, and became more widely used, in the 14th century in European machines.
An Al-Jazari Automata
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Cams Today▪Today, cams are used in household appliances, industrial machinery, and high powered industrial tools.
▪The most common application is in internal combustion engines.
▪In automobiles, cams on a camshaft are responsible for translating the rotary motion of the engine into reciprocating motion to operate the poppet valves in the cylinder.
▪The timing cams provide in engines is crucial to gas and vapor intake and exhaust.
A high-quality automotive camshaft.
A 4-stroke engine with intake and exhaust controlled by cams and followers.
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Displacement of A Cam▪ Displacement diagrams relate angular position to the radial displacement experienced at that position.
▪ The rise is the motion of the follower away from the center of the cam.
▪ Dwell is the motion at which the follower is at rest.
▪ Return is the period of motion that the follower moves toward the cam center.
▪ C = L/(1-sin ∅)
▪ r = R – Lsin ∅/ (1 – sin ∅)
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Plate Cam
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Cylinder Cam
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Snail Cam● Used to gradually rise the follower then drop
suddenly, hence its second name: “Drop Cam”
● Can only turn in one direction or it will lock up
● Center of rotation is placed slightly off-center to ensure a smooth spin
● Examples: invented for use in watches○ was used to change the day presented on
the watch at the perfect time● Also used in bike chains: makes use of the
one possible direction
Mechanical representation of snail cam
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Linear Cam● Different from other cams in that it moves in a straight line
rather than rotational● versatile: can be cut into different shapes to determine
height of cam follower as well as operating several followers at once○ also utilizes a “return spring” to ensure a smooth follow
● Very prevalent cam
● Most common example is the pin tumbler lock
● Even used in a hole puncher
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Face Cam● Produces motion by using a follower
riding on the face of the disk● Has a groove cut or slot in which the
follower rides● Eliminates the need for a return
spring to keep the follower in contact with the control surface
● Example: Sash window lock○ Cam is mounted to the top of the
lower sash, while the follower is the hook on the upper sash
○ Cam is used to force the window shut
A sash window lock.
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Heart Shaped Cam● Allows the follower to rise and fall
with uniform velocity, giving it a smooth continuous motion
● Causes the follower to rise three times in one rotation
● Used to return the shaft holding the cam to a set position by pressure from a roller
● Examples:○ Used in stopwatches and
chronographs to return the recording hand to zero
○ Used to wind thread evenly on the bobbin in sewing machines
A heart shaped cam in a chronograph.
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Failure Theories and Reliability
Alex Weingarten, Chris Nazareno, Brandyn Merkle, Carlos Mora, Antonio Montanaro, Dan
Nemeth
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● Any materials behavior that renders a loaded member unsuitable for its intended function.o Static loading- deflection, buckling,
plastic distortion, and fracture.
Failure
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● Associated with shear stresses and involves slip along natural slip planes.
● Failure occurs when plastic deformation reaches an arbitrary limit.
Plastic Distortion
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● The separation or fragmentation of a member into two or more pieces.
● Normally constitutes a “pulling apart” associated with tensile stress.o Brittle fracture- occurs when conditions cause
instantaneous propagation to cause failure of one or more of the original cracks.
o Fatigue loading- initial cracks grow slowly until one reaches a critical size at which total fracture occurs.
Fracture Mechanics- Basic Concepts
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Brittle vs. Ductile Fracture
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● Buckling is a sudden sideways failure of a structural member under high compressive stress
● This stress at the point of failure is less than the ultimate compressive stress that the material is capable of withstanding.
● As a load is applied and increases large enough, the member will become unstable and buckles.
● Continual increasing of the load will cause unpredictable deformations○ Potential loss of the members carrying load
capacity
Buckling
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● Stress Intensity Factor (K)o Measure of the effective local stress at the
crack root. Expressed in Pa√m.● Critical Stress Intensity Factor (Kc, fracture
toughness)● Failure occurs when K > Kc ● Safety Factor SF defined as Kc/K
o or SF = (design overload)/(normally expected load)
c
Fracture Mechanics- Basic Concepts
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Stress Intensity Factor
Thin Plate Thick Plate Cylindrical Tube
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Maximum-Normal-Stress Theory● Failure when greatest tensile stress exceeds tensile strength of the
materialMaximum-Shear-Stress Theory● Failure when maximum shear stress exceeds shear strength of the
materialMaximum-Distortion-Energy Theory (Maximum-Octahedral-Shear-Stress Theory)● Equivalent Stress● Failure when σe > Syt
Mohr Theory and Modified Mohr Theory● Generally a modification of maximum-shear-stress theory, derived
including the effect of internal friction
Static Failure Theories
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Static Failure Theories
Maximum-Normal-Stress Theory
Maximum-Shear-Stress Theory
Maximum-Distortion-Energy Theory
Modified Mohr Theory
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● Reliability is a components ability to perform what is needed under certain conditions for a period of time.
● If 200 identical parts are tested and 4 fail, the parts are 98% reliable.
● Usefulness of reliability depends on having proper info on the statistical distribution of:o Loading applied to the partso significant strength of production runs of
manufactured parts
Reliability
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Reliability
μz = μx - μy
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Valve(s)(Not the Company)
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● “any device for halting or controlling the flow of a liquid, gas, or other material through a passage, pipe, inlet, outlet, etc.”-Dictionary.com
● Used throughout the world to control fluid or gas flow around systems● Found both in industrial settings as well as in the organic world (Heart Valve’s)● A great many types, we’ll only cover the most common or useful valve’s here
What is a Valve?
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Needle Valve
● Allow for very fine control of flow rate, results in very low flow rates as a trade-off● Flow rate is controlled by a ratio between the length of the needle and it’s own
diameter● With a very long needle, the change in diameter is very low, which allows for the
accuracy of flow● Needle valve’s are generally used in situations where exact control of flow is
important, like sampling systems of pressure gauges
● Also capable of function in a vacuum, and so are used to fill certain types of vacuum tubes as well as gas Lasers
● Not capable of quickly closing, make poor shut off valves
● Also difficult to tell if the valve is open at a glance, the small distances involved make it difficult to easily tell by sight alone
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Pressure Relief Valve● "Lets off steam" when safe pressures
are exceeded, then closes again when pressure drops to a preset level self-operating valve
● A helical or hydraulic pressure spring is used to maintain constant force acting on the backside of the valve disk or diaphragm
● When the force exerted by the process stream (i.e. fluid pressure) on the valve disk is greater than the constant force exerted by the spring, the valve opens until the fluid pressure falls below the preset value
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Ball Valve● They are wide duty valves, able to
transfer gases, liquids and liquids with suspended solids (slurries).
● Ball shaped disc within the valve is opened by a quarter turn of the actuator.
● Disc allows free flow or completely blocks flows.
● Maintains and regulates high volume, high pressure, and high temp flow
● Not designed to be gradually opened. Design Types
● Floating Ball- The upstream pressure helps create the seal by pushing the ball back against the rear or downstream seat.
● Trunnion-pin secures the ball so it doesn't dislodge; provide less friction between the ball and seal.
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Globe Valve● Advantages of the GLobe valve include
the speed with which it can be closed and opened, as well as the precision of control allowed for due to the use of a screw
● Disadvantages include a certain amount of head loss, a low flow coefficient, and its its inappropriateness for sterile applications
● Also known as a stop valve or a disk valve
● The valve functions via a movable plug set in a orifice of similar shape
● To open or close the valve, the plug is raised or lowered by turning the handle
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● Controls flow by compressing flexible interior piping
● Used mostly for solutions containing particulate matter
● Similar in function to how a kink in a hose reduces flow rate
● Inappropriate for high pressure situations
● Commonly used in situations containing particulate matter, such as clinical or chemical analyzers and a wide range of laboratory equipment
Pinch Valve
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Thanks! Any Questions?
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Team 1 Clutches https://www.youtube.com/watch?v=6WUW-uNVMy8
Team 2 Springs https://www.youtube.com/watch?v=zBrbWPy6hXY
Team 3 Screws https://youtu.be/jOVIom_8pEc
Team 4 Gears https://www.youtube.com/watch?v=-d4lmpB8mmE&feature=youtu.be
Team 5 Brakes https://www.youtube.com/watch?v=bGztsbHewec
Team 6 Bearings https://www.youtube.com/watch?v=vnsHKdFrUTo&feature=youtu.be
Team 7Rivets
/Weldingshttps://www.youtube.com/watch?v=yim_PULfrVw
Team 8 Impact http://youtu.be/BbZSiBoZ-xY
Team 9SurfaceDamage
https://www.youtube.com/watch?v=D6xILtd2sbQ
Team 10 Shafts http://youtu.be/7oIolLXgIYU
Team 11 Fatigue https://www.youtube.com/watch?v=dKleYzF9G3M&feature=youtu.be
Team 12 Lubrication https://www.youtube.com/watch?v=iEFbveEBeIk
Team 13 Linear motion device https://youtu.be/QcgX5tCcguM
Team 14 Chain and Sprockets https://www.youtube.com/watch?v=jAfCqfNhOQo&feature=youtu.be
Team 15 Belts https://www.youtube.com/watch?v=o9IO-Fy8E-I&feature=youtu.be
Team 16 Cams https://m.youtube.com/watch?v=7hRNGqj38R4
Team 17 Failure/reliability https://www.youtube.com/watch?v=PQaM4Z3iNiQ&feature=youtu.be
Team 18 Valves http://youtu.be/A05iLhcMDiA