151-0735: DYNAMIC BEHAVIOR OF MATERIALS AND STRUCTURES · 151-0735: Dynamic behavior of materials...

9/21/2015 1 1 Lecture #1 – Fall 2015 1 D. Mohr

151-0735: Dynamic behavior of materials and structures

by Dirk Mohr

ETH Zurich, Department of Mechanical and Process Engineering,

Chair of Computational Modeling of Materials in Manufacturing

151-0735: DYNAMIC BEHAVIOR OF

MATERIALS AND STRUCTURES

© 2015



Motivation

• Acquire knowledge and skills needed to predict the deformation and failure response of modern engineering structures under extreme dynamic loading conditions

Kinematics boundary conditions

Geometry Mesh

Element type

• Ingredients of FE Model of structure:

http://www.4teachers.de/?action=download&downloadtype=image&downloadid=1021&oldaction=keywordsearch&searchtype=images&searchstring=Puzzleteile



Potential Applications

• Passenger safety in vehicle accidents

Source:https://www.youtube.com/watch?v=uoENbWQFE_I&feature=player_detailpage

Video shown in class




• Passenger safety in vehicle accidents

Source:https://www.youtube.com/watch?feature=player_detailpage&v=n2Wxv9M-Hbw





• Manufacturing (machining, stamping, etc.)

Source: https://www.youtube.com/watch?feature=player_detailpage&v=Rn9iZsCHjrw






Source: https://www.youtube.com/watch?feature=player_detailpage&v=Rn9iZsCHjrw





• Defense

Source: https://www.youtube.com/watch?feature=player_detailpage&v=QfDoQwIAaXg





• Defense

Source: https://www.youtube.com/watch?v=MI_hu7stdQM





Source: Borja Erice

• Defense





Source: https://www.youtube.com/watch?v=AGUqMt9ijCk&feature=player_detailpage

• Public safety





Source: https://www.youtube.com/watch?feature=player_detailpage&v=NyRYUyPmWRs

• Machining (civil engineering)




Another application




Uncontained Engine Failure

• Rolls-Royce RB211-524 • Flight QF74 (Boeing 747-400)

• Rolls-Royce Trent 900 • Flight QF32 (Airbus A380)

… “Following the separation of the disc, the engine behaved in a manner different to that anticipated by the manufacturer during engine design and testing,” the ATSB says. The disc accelerated to a speed “in excess of its structural capacity” and burst into three main segments, which punctured the engine case. (source: aviationweek.com)



81 seconds into its launch

Columbia was traveling at Mach 2.46, at an altitude of 65,860 feet. The foam was calculated to have hit the orbiter at 700 – 800 feet per second (over 500 mph).

Columbia Space Shuttle



Challenge today: optimization of weigh-specific performance leads to multi-material structures

Example: BMW 5series (F10), source: http://m5carblog.blogspot.ch/2013/02/chassis.html

Multi-phase steels

aluminum

Hot-formed boron steels

Low strength steels



Example: 2016 Cadillac CT6 (source: www.autofieldguide.com)




Example: BMW i3 (source: http://blog.caranddriver.com)

Aluminum

Thermoplastic body panels

Carbon fiber composite




Example: Boeing 787 (source: http://metalpedia.asianmetal.com)




Example: 2016 Cadillac CT6 (source: www.autofieldguide.com)

Properties vary substantially among steel alloys

• Stiffness (E~200GPa) and density (~7800kg/m3) are similar, but strength and ductility may vary substantially among different steel alloys and heat treatments



Source: http://aluminium.matter.org.uk

Properties vary substantially among aluminum alloys

• Stiffness (E~70GPa) and density (~2700kg/m3) are similar, but strength and ductility may vary substantially among different aluminum alloys and heat treatments

http://www.google.ch/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&uact=8&ved=0CAcQjRxqFQoTCK2hktSqhcgCFcTTFAod6UkPfA&url=http://aluminium.matter.org.uk/content/html/eng/default.asp?catid%3D217%26pageid%3D2144417131&psig=AFQjCNH3-tc0LpwWP3y82qDmniMEGr-ddA&ust=1442828872709373



Source: https://www.cnde.iastate.edu

Properties vary substantially among composites • Stiffness, density, strength and ductility may vary substantially among

different composites



Scope of this Course

(1) Experimental: Material characterization for static and dynamic loading

• Split Hopkinson Pressure Bar Technique • Wave propagation in bars • SHPB systems

• Computational Plasticity • Rate-independent plasticity • Viscoplasticity • Return mapping schemes

• Ductile failure • Ductile fracture • Adiabatic shear banding

• Brittle failure • Anisotropic elasticity • Fracture of composites

• Advanced topics • Thermoviscoplasticity • Physical origin of rate dependent behavior • Equations of state • Fragmentation and Spalling

(2) Theoretical: Material model formulation for

plasticity and fracture

(3) Computational: Material model implementation

and application



Organization of this Course • Lectures (Prof. D. Mohr, [email protected], CLA F11.1) Mon 10-12 in LEE C-104

• Computer labs (Dr. B. Erice, [email protected], CLA F13.2) in CLA F2 (8 computers) • Need to work in pairs • Group “early birds”: Monday 1-3pm • Group “night owls”: Monday 6-8pm • Short report (pdf or hardcopy) from each lab is due at the beginning of

the computer lab of the following week; one report per student pair is sufficient;

• Project • Distributed by end of November • Report (about 20 pages) due 1 week before the first oral exam; one

report per student pair is sufficient • Oral presentation (20min) of project results during exam session

• Grading: • Reports from weekly computer labs will count towards 60% of grade; • Final report and project presentation will count towards 40% of grade.

mailto:[email protected]








Reading Materials

• Your notes taken during class

• Slides will be made available online after each lecture

• George T. Gray, “High-Strain-Rate Testing of Materials: The Split-Hopkinson Pressure Bar”: http://onlinelibrary.wiley.com/doi/10.1002/0471266965.com023.pub2/abstract

• J.C. Simo and T.J.R. Hughes, “Computational Inelasticity” (first three chapters): http://link.springer.com/book/10.1007%2Fb98904

• M.A. Meyers, “Dynamic behavior of Materials” (selected chapters): http://onlinelibrary.wiley.com/book/10.1002/9780470172278

• Scientific papers and other reading materials will be announced in upcoming lectures

http://onlinelibrary.wiley.com/doi/10.1002/0471266965.com023.pub2/abstract



http://link.springer.com/book/10.1007/b98904



http://onlinelibrary.wiley.com/book/10.1002/9780470172278





310 210 110 1 10 210 310 410

][ 1s

Universal testing machines SHPB Plate impact

Measurement of the stress-strain response at different strain rates



Kolsky bar system

Requirements: • Striker, input and output bar made from the same bar stock (i.e. same material, same diameter)

• Length of input and output bars identical • Striker bar length less then half the input bar length • Strain gages positioned at the center of the input and

output bars

striker bar

strain gage

strain gage

specimen input bar output bar

Launching system

L/2 L/2 L/2 L/2



Kolsky bar formulas

striker bar

strain gage

strain gage

specimen input bar output bar

Launching system

L/2 L/2 L/2 L/2

)(ttra

)(tre

)(tinc

)()( tA

EAt tra

s

s

)(2

)( tl

ct re

s

s

• Stress in specimen:

• Strain rate in specimen:

s

sl

s



Modern Hopkinson Bar Systems

striker bar

strain gage

specimen

input bar output bar

Launching system

L L

High speed camera

Features: • Striker and input typically made from the same bar stock (i.e. same material, same diameter)

• Small diameter output bar for accurate force measurement • Similar length of all bars • Output bar strain gages positioned near specimen end • Strains are measured directly on specimen surface using Digital

Image Correlation (DIC)

151-0735: DYNAMIC BEHAVIOR OF MATERIALS AND STRUCTURES · 151-0735: Dynamic behavior of materials...

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