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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
9/21/2015 2 2 Lecture #1 – Fall 2015 2 D. Mohr
151-0735: Dynamic behavior of materials and structures
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:
9/21/2015 3 3 Lecture #1 – Fall 2015 3 D. Mohr
151-0735: Dynamic behavior of materials and structures
Potential Applications
• Passenger safety in vehicle accidents
Source:https://www.youtube.com/watch?v=uoENbWQFE_I&feature=player_detailpage
Video shown in class
9/21/2015 4 4 Lecture #1 – Fall 2015 4 D. Mohr
151-0735: Dynamic behavior of materials and structures
Potential Applications
• Passenger safety in vehicle accidents
Source:https://www.youtube.com/watch?feature=player_detailpage&v=n2Wxv9M-Hbw
Video shown in class
9/21/2015 5 5 Lecture #1 – Fall 2015 5 D. Mohr
151-0735: Dynamic behavior of materials and structures
Potential Applications
• Manufacturing (machining, stamping, etc.)
Source: https://www.youtube.com/watch?feature=player_detailpage&v=Rn9iZsCHjrw
Video shown in class
9/21/2015 6 6 Lecture #1 – Fall 2015 6 D. Mohr
151-0735: Dynamic behavior of materials and structures
Potential Applications
• Manufacturing (machining, stamping, etc.)
Video shown in class
9/21/2015 7 7 Lecture #1 – Fall 2015 7 D. Mohr
151-0735: Dynamic behavior of materials and structures
Potential Applications
• Manufacturing (machining, stamping, etc.)
Video shown in class
9/21/2015 8 8 Lecture #1 – Fall 2015 8 D. Mohr
151-0735: Dynamic behavior of materials and structures
Potential Applications
• Manufacturing (machining, stamping, etc.)
Source: https://www.youtube.com/watch?feature=player_detailpage&v=Rn9iZsCHjrw
Video shown in class
9/21/2015 9 9 Lecture #1 – Fall 2015 9 D. Mohr
151-0735: Dynamic behavior of materials and structures
Potential Applications
• Defense
Source: https://www.youtube.com/watch?feature=player_detailpage&v=QfDoQwIAaXg
Video shown in class
9/21/2015 10 10 Lecture #1 – Fall 2015 10 D. Mohr
151-0735: Dynamic behavior of materials and structures
Potential Applications
• Defense
Source: https://www.youtube.com/watch?v=MI_hu7stdQM
Video shown in class
9/21/2015 11 11 Lecture #1 – Fall 2015 11 D. Mohr
151-0735: Dynamic behavior of materials and structures
Potential Applications
Source: Borja Erice
• Defense
Video shown in class
9/21/2015 12 12 Lecture #1 – Fall 2015 12 D. Mohr
151-0735: Dynamic behavior of materials and structures
Potential Applications
Source: https://www.youtube.com/watch?v=AGUqMt9ijCk&feature=player_detailpage
• Public safety
Video shown in class
9/21/2015 13 13 Lecture #1 – Fall 2015 13 D. Mohr
151-0735: Dynamic behavior of materials and structures
Potential Applications
Source: https://www.youtube.com/watch?feature=player_detailpage&v=NyRYUyPmWRs
• Machining (civil engineering)
Video shown in class
9/21/2015 14 14 Lecture #1 – Fall 2015 14 D. Mohr
151-0735: Dynamic behavior of materials and structures
Another application
Video shown in class
9/21/2015 15 15 Lecture #1 – Fall 2015 15 D. Mohr
151-0735: Dynamic behavior of materials and structures
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)
9/21/2015 16 16 Lecture #1 – Fall 2015 16 D. Mohr
151-0735: Dynamic behavior of materials and structures
Potential Applications
Video shown in class
9/21/2015 17 17 Lecture #1 – Fall 2015 17 D. Mohr
151-0735: Dynamic behavior of materials and structures
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
9/21/2015 18 18 Lecture #1 – Fall 2015 18 D. Mohr
151-0735: Dynamic behavior of materials and structures
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
9/21/2015 19 19 Lecture #1 – Fall 2015 19 D. Mohr
151-0735: Dynamic behavior of materials and structures
Example: 2016 Cadillac CT6 (source: www.autofieldguide.com)
Challenge today: optimization of weigh-specific performance leads to multi-material structures
9/21/2015 20 20 Lecture #1 – Fall 2015 20 D. Mohr
151-0735: Dynamic behavior of materials and structures
Example: BMW i3 (source: http://blog.caranddriver.com)
Aluminum
Thermoplastic body panels
Carbon fiber composite
Challenge today: optimization of weigh-specific performance leads to multi-material structures
9/21/2015 21 21 Lecture #1 – Fall 2015 21 D. Mohr
151-0735: Dynamic behavior of materials and structures
Example: Boeing 787 (source: http://metalpedia.asianmetal.com)
Challenge today: optimization of weigh-specific performance leads to multi-material structures
9/21/2015 22 22 Lecture #1 – Fall 2015 22 D. Mohr
151-0735: Dynamic behavior of materials and structures
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
9/21/2015 23 23 Lecture #1 – Fall 2015 23 D. Mohr
151-0735: Dynamic behavior of materials and structures
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
9/21/2015 24 24 Lecture #1 – Fall 2015 24 D. Mohr
151-0735: Dynamic behavior of materials and structures
Source: https://www.cnde.iastate.edu
Properties vary substantially among composites • Stiffness, density, strength and ductility may vary substantially among
different composites
9/21/2015 25 25 Lecture #1 – Fall 2015 25 D. Mohr
151-0735: Dynamic behavior of materials and structures
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
9/21/2015 26 26 Lecture #1 – Fall 2015 26 D. Mohr
151-0735: Dynamic behavior of materials and structures
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.
9/21/2015 27 27 Lecture #1 – Fall 2015 27 D. Mohr
151-0735: Dynamic behavior of materials and structures
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
9/21/2015 28 28 Lecture #1 – Fall 2015 28 D. Mohr
151-0735: Dynamic behavior of materials and structures
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
9/21/2015 29 29 Lecture #1 – Fall 2015 29 D. Mohr
151-0735: Dynamic behavior of materials and structures
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
9/21/2015 30 30 Lecture #1 – Fall 2015 30 D. Mohr
151-0735: Dynamic behavior of materials and structures
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
9/21/2015 31 31 Lecture #1 – Fall 2015 31 D. Mohr
151-0735: Dynamic behavior of materials and structures
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)