ME311 Machine DesignW Dornfeld04Sep2014Fairfield UniversitySchool of EngineeringLecture 1: Intro To Design; Units; FBDs; Stress & Mohr’s CircleWhat’s Machine Design all about?“Design” is used to refer to lots of different activities, but relating to engineering, it usually means one of two things:1. Industrial Design= Applied Art; concerns asthetics, ergonomics, useability2. Machine Design= Creating the mechanisms and structures to perform a function.Design Phases/ActivitiesA. Deciding» Requirements » Components» Concepts » Materials» Constraints » Appearance» Back Of Envelope Calcs » Patents / StandardsB. Sizing» Strength » Detailed Analysis» Life » Cost» Appearance » Factor of Safety» Dimensions (Overall & Parts)Starts with “Someone needing something to do some function”The “something” is the machine.C. Realizing» Drawings » Manufacturing» Configuration » Tolerances» Finishes » Support / RepairDesign Phases/ActivitiesDecidingSizingRealizinghttp://www.phillipsplastics.com/case_studiesDesign ClassificationsA. Integrated Design=Use “Off the Shelf” components (catalog items; standard structural shapes; etc.) to build a mechanism.Ex: Popular Mechanics-like things; Processing equipmentB. Custom Design=Totally unique, self-designed components and structureEx: Automobiles; consumer products; leading-edge technologyC. Mixed Design=Vendors slightly modify their partsEx: Medium production items; Agricultural equipmentExamples of Integrated Designhttp://misumiusa.com/technical/techSeminar.aspxhttp://develop3d.com/images/articles_fullwidth/Chaise_longue_FW.jpghttp://diydrones.com/profile/JeffZikahttp://www.acomputerportal.com/3D_printers.htmlhttp://www.seriouswheels.com/mno/Maserati-MC12-Studio-FA-Top-Off-1280x960.htmExample of Custom DesignExamples of Mixed Designhttp://www.stanneconsignmentauction.net/photos/06190953.JPGhttp://www.atomiczombie.com/StreetFoxSuspensionTadpoleTrike.aspxhttp://www.tjsnow.com/special.htmhttp://hamptonroads.com.nyud.net/node/251081Design Components• McMaster-Carr• Grainger• MisumiMore Design Components• Motors• Flywheels• Hydraulics• Pneumatics• Pulleys & Belts & Chains• Brakes & Clutches• Etc…To use any of these components, you need to know:1. That they exist, 2. How they work, and 3. How to “size” them for your application.Design Concept ActivityHow many different ways can you think of to attach a pin to a plate?Design RequirementsA. Function= The device must perform the duty for which it is intended.B. Durability= The device must operate without failing for the intended lifetime.ME311 PhilosophyLearn the Building Blocks of Design(not a lot of synthesis, but at least some of the ingredients)> Free Body Diagrams – because if you get the loads wrong, the stress and deflection analyses will be wrong.> Simple Analyses – most everything will be considered a beam; you must keep your FEA honest and know how design parameters affect the strength.> Failure Mechanisms – learn them so you can avoid them.> Mechanical Components – what is available, how do they work and break?Failure Modes• Yield• Fracture – Elastic and Brittle• Excess deflection• Buckling• Fatigue• Wear• CorrosionTechniques• Analyzing real hardware (not lab stuff) and recognizing assumptions via the Reverse Engineering project.• Mistake Reduction> Drawing sketches with accurate proportions> Making correct FBDs> Showing your intermediate calculations (not just calculator =)> Automating analyses with Excel, MathCad, Matlab, etc.> Showing and checking units> Asking “Does that make sense?”• Use the Web> Tutorials and solved problems• Build confidence level> Read the practice problems; do the homeworkNOT ME311 PhilosophyAcademic Honesty Basically, if you submit something that is someone else’s work (whether it is a classmate, a friend, or from the Web) and do not reference the source, that is academically dishonest.Collaboration in the learning of this material is encouraged, and that applies to discussions of homework and of assigned team projects. But if you complete your homework, and in discussion with a colleague discover an error which you then correct (but not by copying from the colleague), you should state that you corrected it.Class exams are intended to represent your individual work. It is dishonest to get help from other students or anyone else, including Chegg.You’re flunked!Catch 22 Two requirements to be an engineer:1. Knowledge of technical subjects2. Ethical behaviorTwo characteristics of people who would cheat on an exam:1. __________________ (Don't know the material)2. __________________ (Lack of Ethics)Conclusion:If you find that you can’t learn this material and that you do not possess enough personal honesty or integrity to be an engineer, then you need to transfer to some other field of study. The sooner, the better.This also applies to just copying the homework solutions and handing that in as completed homework. If you are inclined to do that, consider at least being honest and just printing it out and handing it in. Then I don’t need to waste my time figuring out that you are giving me a copy of my work and not yours.How to survive succeed at ME3111. Read the material for each week beforeclass. 2. Then the examples and activities we do in class will make sense.3. Also, you will be able to answer the weekly quizzes.4. Do the homework first without hints or solutions.UnitsEnglish MetricMass f=ma; w=mg; m=w/g1kg = 2.205 lbm(1g = 9.807 m/s2)Length1 in. = 25.4mm1m = 39.37 in.Force1lbf = 4.448N1N = 0.2248lbfPressure(or Stress)1 psi = 6894.8Pa = 6.9 kPa1 ksi = 6.9 MPaPower1HP = 6600 = 745.7 W1W = 12/4.3861sinlbfSo, what does a kilogram weigh?22160025.011inlbmNPa ≈=psipsiPaPammNMPa 1458.6894000,000,1112===~10 Atm211smkg ×=slbin.sNmWhat is the pressure of a dollar bill?m = 0.984gram, 66.3mm x 156.0mmElementary Load Building BlocksFrom DAWrightat U of Western Australia___________________See HamrockFig. 2.4Free Body Diagrams• Disassemble and/or cut apart• Draw all known and unknown loads and reactions• Balance Forces (V & H) and Moments on each piece• Internal loads on each side of a connection are equal and opposite• We need Forces and Moments to get stresses and deflectionsFBD for Lever AssemblyBeam Shear & MomentProcedure:Step 1: Compute the reaction forces and momentsStep 2: Break beam into segmentsStep 3: Compute shear forces and moments for