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Introduction to Vehicle Crashworthiness Lecture -1 1

Office Phone: Office: Email: Office Hours:

CE 264 Non-linear Finite Element Modeling and Simulation

Web:

Pradeep Mohan (703)726-8538 Research 2, 302 E [email protected] 2:00 to 4:00 PM on Tuesdays and by appointment http://crash.ncac.gwu.edu/pradeep/

CE 264, Lecture 1

Slide #2

Objective 

What is Non-Linear FEM and why study it? 



FEM is a numerical analysis technique for obtaining approximate solutions to a wide variety of engineering problems for which an analytical solution does not exist

Non-linearities 

Safety Standards

CE 264 Non-linear Finite Element Modeling and Simulation

Material • Stress-strain behavior



Geometry • Change in geometry have a significant effect on the load deformation behavior

CE 264, Lecture 1

Slide #3

1

Federal Motor Vehicle Safety Standards (Part 571) 

“Active Safety / Crash Avoidance” - 100 Series 

Braking (ABS), electronic stability control (ESC), lighting and signalling



Crash Phase • Minimize risk of injury to occupants, combines the reciprocal aims of absorbing impact and ensuring a survival space   



Post-Crash Phase • Interior Trim Flammability and fuel system integrity 



301 – Fuel System Integrity

CE 264, Lecture 1

Slide #5

FMVSS 208 – New Regulation 



208 – Occupant Crash Protection 214 – Side Impact Protection 216 – Roof Crush Resistance

“Fire-related” - 300 Series 





30 mph ( 48 kph) into a fixed barrier 50th percentile Hybrid III dummy in front driver and passenger seats Uses dummy injury measures for regulation • Chest G’s 1M





CE 264, Lecture 1

Slide #46

Prototypes reqd. for crash testing

10000

80000



Difficult to conceive a vehicle design with today’s constraints of regulations and safety without any simulation at all Accurate and robust analytical tools using state state-ofof the-art in computational mechanics and computer hardware are indispensable for crash simulations The contribution of simulation lies in that it complements a testing facility by preventing unnecessary y work from being g done The ideal picture is indeed one of a design, heavily supported by analysis, resulting in building of only those prototypes that are almost certain to pass all final verification testing

Engineering Analysis Methods

100

50

Engineering Analysis

Classical methods

Signiificant cost savings

1985

FE Model Size (elem)

M Made possible by suupercomputers

Regulatory Requirements

Reduce Injuries & Fatalities

Year



Exact

Approximate

Numerical methods

Energy

Boundary Finite Finite Element Difference Elements

CAE: Uses Engineering analysis tools primarily FE, BE and FD methods Linear / Non-Linear: based on material, loading Static / Dynamic: Temporal variation in loading, boundary conditions Quasi Static /Transient are sub-cases of above

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