DMC Spring 2015 Project Presentation

Clutch

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

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

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

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

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

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

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

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

Thank you

Have a Wonderful Summer Break Team Clutch

Samantha HellerHunter LankowskiJason KimAlan NorteyMatthew TubmanXiao Le Zheng

THE BASICS

A Spring is any elastic object that:Exerts forces and torquesAbsorbs energy that is later released

They are usually Metal

[1]

TYPES OF SPRINGS

Torsion Bar Spring:

Helical Spring: A torsion bar wound into a helixSpring Index:

[2]

DESIGNING THE SPRING CONSTANTHooke’s Law: F = kx, where: x is the deflection

k is the spring constant

TORSION BARSEquations:

Torsional Stress:

Angular Deflection:

Hooke’s Law:Where K is the spring constant [Nm]

Effects of Curvature:

Static Loading:

Cyclic Loading:

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:

DIFFERENT SHAPES OF SPRINGS

APPLICATIONS OF SPRINGS

Cars and BikesPo-Go Sticks and Toys

Pens and Mechanical Pencils

Garage DoorsStaplersWatchesTrampolinesBedsAnd so much more…

[3]

[4]

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.

OUR VIDEO

byEric Hernandez Faizan AhmedJordan Rafalko Angelo GuloEdgard Jimenez Andrew Spano

DMC Project:Threaded Fasteners

● Definitions and Standard Geometry● Threads and Sizes● Types of Fasteners● Common Screw and Bolt Head Types● Power Screws

○ Efficiency○ Overhauling and Self-Locking

Topics

Types of Fasteners

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

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

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

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

Gears

By: Etebom obot, Mert kahyaoglu, Brandon Wagner, Eamonn Hennessey, Matt Sheleheda, Kyle Kourelakos

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

Common uses

Vehicles

Trains

Clocks

Bicycles

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

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

Spur gears

Most commonly used gear

Torque is transmitted from pinion to gear

Rack and pinion

Used to convert rotational motion to translation

eg rotating steering wheel to turn

Worm gear

Basically a screw on a gear

One directional in nature. Only worm can turn gear

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.

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.

BrakesBy: Cynthia Ko, Jonathan Schwalm, Kolung Chan,Peter Tran, Trent Handlovsky

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.

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.

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)

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

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

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.

Conclusion

Brakes are an important feature for any kind of vehicle. They help inhibit motion and allow us to properly stop vehicles safely.

BEARINGSAlexander Hobbs, Timothy Beyer, Brian Blaney, Pierre Pais, Timothy Pearson, Gerome David

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

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

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

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

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

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

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

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….

Rivets and WeldingMuaz Billoo, Martin Mora, Allison Pelszynski,

Mike Czerhoniak, Benjamin Ratzersdorfer

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.

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

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.

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

ImpactRobert NapoleonCharlene VanceNolan BarolinJack Kelliher

Joe ZevitsKhang Lam

• 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?

Slap experiment: Direct Impact forces

Determining load application

• Load is slowly applied to an object such that it can be considered static.

Static Impact

● Imagine a spring mass system.

● When load is rested on top of an object and there is no deflection.

Dynamic Impact

● Spring mass system● Mass is suspended

above the spring, and is release on to spring creating deflection.

Impact Factor

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

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

Outline

Ch. 9■ Importance■ Types of Surface Damage■ Corrosion■ Cavitation Damage■ Wear

■ 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

Types of Surface Damage

■ 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

■ 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)

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

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

SHAFTS

Miguel Ferrer, Lewis Beekman, Jesus Bravo, Dong Kwak, Akshita Kapasiawala,

Ryan Wilson

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

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

Universal Joint Very important in shaft applications.

Allow articulation between

Used in cars to allow the travel of drive wheels for suspension and steering.

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

Maximum Torque Capacity

Different shaft geometries have different critical loadings that can be supported by each shaft.

Square Shaft Joint

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.

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

Bearings

-Fits around a shaft locking it in it’s location andorientation

-allows rotation of the shaft at anincreased effeciency

-minimizes friction-reduce wear

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

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.

DMC Final ProjectFATIGUE

Nicole PaulinoDante LevariLouis Morales

Tyler SchiffShail Amin

Aakash Hathi

14:650:342 Section 1

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.

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.

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.

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

Fatigue Load Examples

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.

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.

Questions?

LUBRICATIONAkofa Elike-Avion

Bryan Stonkus

Kareem Soliman

Robert DeSimone

Yianni Frangos

Definition• Any substance that reduces friction and wear• Usually a liquid (sometimes a solid)• Characterized by their viscosity

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.

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.

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

Linear Motion Devices

Michael Han, Shaun Kenny, Krishna Yellayi, Rahul Upadhyay, Bryan Arcos, Matthew Kelsten

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

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

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

Belt-Driven Linear Motion Devices

• Utilize a belt in their linear travel path as seen in model (B)

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.

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.

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.

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.

Stepper Motors vs. Regular Motors

SPROCKETS AND CHAIN

DMC Spring 2015Sarath Jaladi Adam Rupp

Mohanish Shinde Dylan Robertson

Kent Christian Dylan Bryan

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).

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.

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.

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

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

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

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.

BeltsRobert Kertz, Ani Thuppul, John Sengco,

Calen Fields, Brian Connolly, Kushal Darji

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

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.

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.

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

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:

Example

References• Juvinall, Robert C. (2012). Fundamentals of Machine

Component Design. John Wiley and Sons, Inc.• www.sudarshantools.com (image of V-belt)

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.

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

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.

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 ∅)

Plate Cam

Cylinder Cam

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

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

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.

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.

Failure Theories and Reliability

Alex Weingarten, Chris Nazareno, Brandyn Merkle, Carlos Mora, Antonio Montanaro, Dan

Nemeth

● Any materials behavior that renders a loaded member unsuitable for its intended function.o Static loading- deflection, buckling,

plastic distortion, and fracture.

Failure

● Associated with shear stresses and involves slip along natural slip planes.

● Failure occurs when plastic deformation reaches an arbitrary limit.

Plastic Distortion

● 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

Brittle vs. Ductile Fracture

● 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

● 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

Stress Intensity Factor

Thin Plate Thick Plate Cylindrical Tube

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

Static Failure Theories

Maximum-Normal-Stress Theory

Maximum-Shear-Stress Theory

Maximum-Distortion-Energy Theory

Modified Mohr Theory

● 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

Reliability

μz = μx - μy

Valve(s)(Not the Company)

● “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?

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

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

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.

Tesla Valve(Correct Direction)

Tesla Valve (Wrong direction)

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

● 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

Thanks! Any Questions?

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