DESIGN PHASE

What kind of analysis you need to do?

MIME Senior Design Projects - Spring 2013

Overview Design/Analysis Requirements Common Design Issues

Welds Fatigue Safety Quality

Design Requirements What type of analyses do I need?

Technical Analysis Description Examples

1 Static Analysis Calculate forces and moments for stationary components. Lifts, supports, structures, connections.

2 Dynamic Analysis Calculate s, v, a of moving components and the forces and torques needed.

All moving components such as gears, mechanisms, pulleys,

3 Power AnalysisCalculate the power needed to run the machine. Use the force and dynamic

4 Stress Analysis inclg FEACalculate stresses and compare with strengths to see if failure would occur.

Components under high forces, moments or torques such as support members.

5 Thermal Analysis Calculate temperature, temp changes, pressures, and possibly heat transfer.

Components including fluids where heat and temperature are involved.

6 Fluid Flow Analysis Calculate flow rate, speed, quantity, pressure, and possibly temperature.

Determine pump sizes, pipe diameters, flow measurement when you have fluids.

7 Process Analysis

Improve business activities in order to reduce overall costs, provide more efficient use of resources, and to better support and add value for customers.

Lean manufacturing, six sigma and total quality management.

8 Vibration Analysis Determine vibration frequency, and if vibration will be a problem.

Anything moving with a certain frequency. Also some electrical components.

9 Cost Analysis Determine the costs in the short run and long run, as well as ROI.

Determine if it is more cost effective to produce or to outsource a component.

Design Requirements Measure twice, cut once

Make sure you do adequate calculations and analysis

Tendency to build first, design later Works if you’re right the first time Costs material, effort, and time if you’re wrong

Anticipate use Anticipate misuse!

Design/Analysis FREE BODY DIAGRAM

FEA

Approximate Design/Calculations Is it a beam or a plate?

Design/Analysis - FEA Quality of input determines quality of

output “Magic” Black Box Factors

Solid model quality Correct boundary conditions Load accuracy Proper material selection Mesh quality Correct Failure Criteria

Design/Analysis - FEA Solid Model Quality

Balance simplicity/accuracy Use your intuition to include features that will

increase stresses Exclude trivial features

Correct Boundary Conditions Make sure your restraints accurately represent

real conditions Check degrees of freedom Check fastener/mating conditions in assemblies

Design/Analysis - FEA Load Accuracy

What type of loading? point load? distributed load? Am I missing loads? thermal? centripedal? What is the magnitude? 10lbs? 500lbs?

1,000,000lbs? Rationalize with intuition Determine with testing

Material Selection Did I select the correct material? Are my properties in the correct units?

FEA – What to expect?http://machinedesign.com/article/fe-update-expecting-too-much-from-fea-0710

Design/Analysis - FEA Mesh Quality

Make sure it is fine enough to accurately depict features

Affects processing time

Design/Analysis - FEA Correct Failure Criteria

Stress based: yielding or fracture? Excessive displacement Loss of function Corrosion Thermal degradation Fatigue

Remember that ductile and brittle materials fail differently and have different failure criteria!

Design/Analysis When in doubt, do some hand

calculations Mathcad and Matlab are very useful Shigley is very useful DANotes is a good resource as well:

http://www.mech.uwa.edu.au/DANotes/

Your basic calculations and FEA should support each other If they don’t, you should know why

Welds Strength of welds

Location- sharp corners? Loading- stress state of weld? Size Quality of weld! Fatigue

Fatigue Are their cyclic loads? Do fatigue analysis S/n approach used in Shigley

Safety Pinch points? Sanitation? Exposed wiring? Warnings?

Quality Deliverables should function well Make sure products are durable Double-check safety

References References:

What Kind of Analysis do you Need for your Project?, Dr. Kramer, MIME Dept.

Photo Credits: http

://www.msha.gov/Accident_Prevention/Tips/images/HandTools-Jacks.jpg

http://machinedesign.com/article/fe-update-expecting-too-much-from-fea-0710