Bulk Metal Forming I - RWTH Aachen Metal Forming I Simulation Techniques in Manufacturing Technology ... Cold forming Advantages and Disadvantages of Cold Forming Cold Forming Advantages:

  • View
    236

  • Download
    12

Embed Size (px)

Text of Bulk Metal Forming I - RWTH Aachen Metal Forming I Simulation Techniques in Manufacturing Technology...

  • WZL/Fraunhofer IPT

    Bulk Metal Forming I

    Simulation Techniques in Manufacturing Technology

    Lecture 1

    Laboratory for Machine Tools and Production Engineering

    Chair of Manufacturing Technology

    Prof. Dr.-Ing. Dr.-Ing. E.h. Dr. h.c. Dr. h.c. F. Klocke

  • Seite 1 WZL/Fraunhofer IPT

    Lecture objectives

    Basic knowledge in metallurgy for a better understanding of the mechanisms during metal forming

    Elastic and plastic material behaviour and its influence on the process results in forming technology

    Mathematical models for a description of the elastic and plastic material behaviour

    Introduction of processes in cold and warm bulk forming as well as in forging

  • Seite 2 WZL/Fraunhofer IPT

    Forging8

    Warm Forming7

    Cold Forming6

    Recrystallisation5

    Flow Stress4

    Plastic Deformation3

    Elastic Deformation2

    Metallurgical Basics1

    Outline

  • Seite 3 WZL/Fraunhofer IPT

    Metallurgical Basics

    4 Basic Chemical Bonds

    + + + + + + + + + ++ + + + + + + + + ++ + + + + + + + + ++ + + + + + + + + +

    electron gas (e-)

    positive chargedmetal ions

    ionic bond

    metal bond

    +

    -

    -

    --

    -

    -

    --

    ---

    -

    --+

    ++

    ++

    ++

    ++

    +

    ++

    +

    metal bond

    ionic bond

    covalent bond

    Van-der-Waals bond

  • Seite 4 WZL/Fraunhofer IPT

    Metallurgical Basics

    The Metal Bond metal atoms basically emit electrons

    positive charged ions

    in pure metals no electron-absorbing atoms do existun-combined electrons (outer electrons) form an electron gas

    outer electrons in metals can freely movegood electrical and thermal conductivity

    in absolute pure metals all atoms are totally equalplastic deformation

    + + + + + + + + + +

    + + + + + + + + + +

    + + + + + + + + + +

    + + + + + + + + + +

    electron gas (e-)

    positive chargedmetal ions

    metal bond

  • Seite 5 WZL/Fraunhofer IPT

    Metallurgical Basics

    Lattice Types of an Unit Cell

    face-centred cubic(fcc)

    body-centred cubic(bcc)

    hexagonal(hex)

    examples:

    sliding planes:

    sliding directions:

    sliding systems:

    formability:

    -Fe, Al, Cu

    4

    3

    12

    very good

    -Fe, Cr, Mo

    6

    2

    12

    good

    Mg, Zn, Be

    1

    3

    3

    poor

  • Seite 6 WZL/Fraunhofer IPT

    Metallurgical Basics

    Atomic and Macroscopic View of Metal Structures

    idealcrystal

    structure

    special agglomeration of crystals

    section plane

    a

    crystal latticeunit cell

    2D Cutof the microstructure

    microstructure

    schematically photograph

    realcrystal

    structure

  • Seite 7 WZL/Fraunhofer IPT

    Forging8

    Warm Forming7

    Cold Forming6

    Recrystallisation5

    Flow Stress4

    Plastic Deformation3

    Elastic Deformation2

    Metallurgical Basics1

    Outline

  • Seite 8 WZL/Fraunhofer IPT

    Elastic Deformation

    Tensile Test Load-Displacement Diagram

    specimen 1

    specimen 2

    A1 = 2 A2

    follows:

    F1 = 2 F2

    relate force to cross section surface

    tensile specimen

    load

    displacement

    F1

    F2

    l1l1 = l2

  • Seite 9 WZL/Fraunhofer IPT

    Elastic Deformation

    Stress-Strain Curve of Elastic Behaviour

    00

    01l

    l 00 ll

    l

    ll

    ldl

    ldl

    d1

    0

    ====

    AF

    0

    =

    tanel

    el

    =

    stre

    ss

    strain

    F

    F

    Re

    el

    eel

    l0

    l

    lA0

    A

    engineering strain:

    engineering stress:

    For elastic behaviour:

    Eel

    el

    = Re

    E = Youngs Modulus

    specimenno. 1 no. 2

  • Seite 10 WZL/Fraunhofer IPT

    tensile test compression test shear test

    F

    F

    l0

    A0

    l1

    A1

    A0F

    F

    A1

    l1

    l0

    0AF=

    0AF=

    Elastic Deformation

    Stress Determination Depending on Load

    0AF=

    F

    Fa

    l

    q

    A0

    tensile stress compression stress shear stress

  • Seite 11 WZL/Fraunhofer IPT

    unloaded tensile-loaded

    - nominal stress - strainE - Youngs Modulus

    l0 l1

    s

    s

    Elastic Deformation

    Atomic Representation of Pure Elastic-Tensile Deformation

    00

    01el l

    l

    lll

    == Eel

    el

    =

    elastic strain based on tensile load

  • Seite 12 WZL/Fraunhofer IPT

    unloaded shear-loaded

    - shear angle - shear stressG - shear modulus - Poissons ratioE - Youngs modulus

    Elastic Deformation

    Atomic Representation of Pure Elastic-Shear Deformation

    )2(1

    Gel

    +

    == E

    elastic shearing based on shear load

  • Seite 13 WZL/Fraunhofer IPT

    Forging8

    Warm Forming7

    Cold Forming6

    Recrystallisation5

    Flow Stress4

    Plastic Deformation3

    Elastic Deformation2

    Metallurgical Basics1

    Outline

  • Seite 14 WZL/Fraunhofer IPT

    Plastic Deformation

    Stress-Strain Curve up to the Uniform Elongation

    AF

    0

    =

    stre

    ss

    strain

    engineering stress:(related to starting section)

    F

    F

    Rm

    Re ,se

    eelepl

    l0

    l

    lA0

    A

    load relieving reload

    AF

    =

    true tensile stress:(related to real section)

  • Seite 15 WZL/Fraunhofer IPT

    Plastic Deformation

    Strain Determination of an Idealized Upsetting Process

    00

    01

    00

    1

    0

    ll

    lll

    ldl

    ldl

    dl

    lxx

    ====

    0

    1

    0

    1

    0

    1 ln ;ln ;lnhh

    bb

    ll

    zyx ===

    0

    1ln1

    0ll

    ldl

    ldl

    dl

    l

    == =

    engineering strain (elastic)

    true strain (plastic)

    including of volume constancy

    )1( ln ll

    ll

    ln l

    ll ln

    lul

    ln ll

    ln 0

    0

    00

    0

    0

    x0

    0

    1 +=

    +=

    +=

    +=

    = xx

    const. 111000 == bhlbhl

    0 =++ zyx

    connection between true strain - engineering strain

  • Seite 16 WZL/Fraunhofer IPT

    Plastic Deformation

    Types of Plastic Deformation

    dislocation movement

    low energy required

    sliding

    high energy required

    before

    after

  • Seite 17 WZL/Fraunhofer IPT

    Plastic Deformation

    Sliding and Dislocation Movement

    dislocation movementsliding

  • Seite 18 WZL/Fraunhofer IPT

    Forging8

    Warm Forming7

    Cold Forming6

    Recrystallisation5

    Flow Stress4

    Plastic Deformation3

    Elastic Deformation2

    Metallurgical Basics1

    Outline

  • Seite 19 WZL/Fraunhofer IPT

    Flow Stress

    Flow Curve

    flo

    w s

    tres

    s

    effective strain

    required stress to breakthe strain hardening

    required stress for plastic deformation

  • Seite 20 WZL/Fraunhofer IPT

    Flow Stress

    Strain Hardening Depends on Dislocationsschematic diagramdislocation movement

    sliding planes

    dislocation origingrain boundary

    moving direction

    grain boundary

    piled up dislocations at boundary grainsdislocation structure of little-formed copper

  • Seite 21 WZL/Fraunhofer IPT

    Forging8

    Warm Forming7

    Cold Forming6

    Recrystallisation5

    Flow Stress4

    Plastic Deformation3

    Elastic Deformation2

    Metallurgical Basics1

    Outline

  • Seite 22 WZL/Fraunhofer IPT

    Recrystallisation

    Static Recrystallisation

    requirements:

    - v > 0

    - T > T Recrystallisation

    - impact time

    Schematic course of recrystallisation of cold formed structure

    du

    ctile

    yie

    ld A

    10,

    ten

    sile

    str

    eng

    th R

    m

    crys

    tal

    reg

    ener

    atio

    n

    large increaseof A10

    small decreaseof Rm

    temperature, C

  • Seite 23 WZL/Fraunhofer IPT

    RecrystallisationStress Curve of Cold Forming as a Result of Static Recrystallisation

    flo

    w s

    tres

    s

    effective strain

    anne

    alin

    g fo

    r re

    crys

    talli

    satio

    n

    vBr vBr

    vBr - effective strain at time of fracture

    annealing for recrystallisation increases effective strain and decreases flow stress

    anne

    alin

    g fo

    r re

    crys

    talli

    satio

    n

  • Seite 24 WZL/Fraunhofer IPT

    Recrystallisation

    Effective Strain and Temperature Influence the Grain Sizeg

    rain

    siz

    e

    effective strain

    range of recrystallisation

  • Seite 25 WZL/Fraunhofer IPT

    Recrystallisation

    Forming Temperature and Velocity Influence the Flow Stress

    forming temperature below recrystallisation temperature

    high forming velocity

    low forming velocity

    forming temperature above recrystallisation temperature

    effective strain

    flo

    w s

    tres

    s

  • Seite 26 WZL/Fraunhofer IPT

    Forging8

    Warm Forming7

    Cold Forming6

    Recrystallisation5

    Flow Stress4

    Plastic Deformation3

    Elastic Deformation2

    Metallurgical Basics1

    Outline

Related documents