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lecture 4 - IED Lecture 4 Class Goals Your Mini Project...

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Unformatted text preview: IED Lecture 4 Class Goals Your Mini Project Status Functional Analysis Mathematical Modeling Acceptance Criteria IED Your Mini Project Status Use data from 1 page Memo Start listing concepts Tech Memo due Friday on your design and methodology 2-3 minute oral Status Report Friday IED Functional Analysis Engineering Analysis Engineering Calculation Designers cannot just create and build it Might get lucky once in a while but not the way to keep a job IED Engineering Analysis/Calculations Motivation ... why do calculations? Approaches, Basic Steps, and Characteristics Examples Assessment IED Why Do It ? Helpful for developing a physical understanding of the problem Predictive ... it can save you lots of time and energy ... often easier than making multiple prototypes or conducting repeated experiments IED Why Do It ? Serves as a validation of your knowledge ... is analysis consistent with physical testing? When properly documented, engineering analysis and calculations help others understand your decisions IED Why Do It ? An important part of being a real engineer! IED Approaches - Quick and Simple Sometimes referred to as "back of the envelope" Provides a quick order of magnitude feel for the problem Not very accurate IED Approaches - Eng Approximation Calculator & paper, equation solvers, spreadsheets Used for preliminary estimates of important parameters (i.e., design specs) and evaluating design trade-offs Accurate enough for most practical engineering application IED Approaches - Complex May involve finite element or advanced design optimization codes Requires significant investment in time and effort Used where accuracy is critical and prototypes or testing are expensive IED Example Analysis Needed In-Home Elevator IED Types of Analysis Motor sizing Dynamic system Gear tooth stress Shaft deflection Tolerance stack-up Brake stopping force Cost Example Modeling Needed In-Home Elevator IED Calculations and Modeling May involve technical material beyond what you have had at RPI so far IED expects you to use what you know and maybe a little more, but not entire courses You may need to investigate to see if equations can be understood quickly IED Some Characteristics 1 Analysis starts with appropriate application of first principles, research of previous test data, and known engineering relationships (e.g. standards) IED Some Characteristics 2 Usually requires iteration ... with many unknown variables ... which makes it "open-ended" ... like design itself IED Some Characteristics 1 2 IED Mathematics primarily involves algebra, trigonometry, or geometry Few derivations or proofs, but maybe some calculus and statistics Some Characteristics 1 Use representative or actual data IED Simple Steps 1. 2. 3. 4. 5. Establish design goals. Define simplifying assumptions, constraints and parameters. Clarify and explore functional relationships. Pick a starting point and make computations. Iterate and verify results ... do a sensitivity analysis. Establishing Design Goals and Clarifying Parameters External Noise Factors Difficult to Control System Inputs User Settings Product or Process Output Response Performance Parameters Design Control Factors Engineering Parameter Settings Some Basic Principles Pertinent to Mechanical Engineering Conservation of Mass and Energy Newton's Laws of Motion Ideal Gas Equation Machine Failure Theories IED Documenting Eng Calculations 12 Questions to Consider: 1. 2. 3. 4. What is the problem you are attempting to solve? What are the design targets and constraints? What are the unknowns? What basic principles apply ? IED Documenting Eng Calculations 12 Questions to Consider: 1. 2. 3. 4. IED What assumptions are you making? What are the formulas and parameters? What are representative values for all parameters? What happens when parameters change? Did you perform a sensitivity analysis? Documenting Eng Calculations 12 Questions to Consider: 1. 2. 3. 4. IED Did you provide references for formulas, assumptions, and data. Did you show all work leading to your results. Do the numbers seem reasonable? Are results consistent with tests? Assessment Criteria for Engineering Analysis / Calculation Emphasis Preliminary Analysis Relevancy ... does it help solve a real problem? Appropriateness of basic principles and assumptions IED Assessment Criteria for Engineering Analysis / Calculation Emphasis Final Calculation Accuracy of calculated results Documentation and clarity of communication IED Acceptance Criteria How do you know you are done ? Should the customer be happy then ? Usually a target number has been achieved IED Validation and Verification Often used interchangeably Validation Are we building the right system? Does the system meet the expectations of the customers? Related Terms: Acceptance Tests, & User Tests IED Validation and Verification Verification Are we building the system right? Does the system meet the requirements and specifications? IED Test is one of the tools Review or Inspection Requirements or specifications Design documents Software (source codes) Modeling and Simulation Virtual tests instead of testing a physical prototype IED Validation by Tests Usability tested by (selected) users Operations of a system under the real operational environment IED Customer's LAN configuration, such as firewall settings, for a networked product Mini Project Popcorn Opener Used to open microwave bags Fast acting Cheap IED IED Popcorn Opener - Needs Open a bag Not effected by steam Lightweight Can be easily cleaned IED Popcorn Opener - Metrics Open a bag Not effected by steam Lightweight Can be easily cleaned IED 3 to 5 lbs 212 deg F 1 to 3 lbs Waterproof in sink, i.e. (Low pressure) Popcorn Opener - Calculations What can be calculated today ? Do we know the property of the glue used to keep bag closed ? IED Popcorn Opener - Calculations The popcorn bag itself will likely have to be tested to get the parameters to meet 3 to 5 lbs is only a guess But what can be calculated ? IED Popcorn Opener - Calculations F = ma How will this force be created ? Motors and gears ? Pneumatics (compressed air) ? There are calculations to determine what size motor to use, etc. IED Popcorn Opener - Calculations These calculations may go hand in hand with the concepts you are considering ! IED ...
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