Metal Forming: Formability, Simulation, and Tool Design

Description

Metal Forming: Formability, Simulation, and Tool Design focuses on metal formability, finite element modeling, and tool design, providing readers with an integrated overview of the theory, experimentation and practice of metal forming. The book includes formability and finite element topics, including insights on plastic instability, necking, nucleation and coalescence of voids.  Chapters discuss the finite element method, including its accuracy, reliability and validity and finite element flow formulation, helping readers understand finite element formulations, iterative solution methods, friction and contact between objects, and other factors. The book's final sections discuss tool design for cold, warm and hot forming processes. Examples of tools, design guidelines, and information related to tool materials, lubricants, finishes, and tool failure are included as well. Front Matter Copyright Dedication Contributors Preface Acknowledgements Introduction Further reading Formability Introduction Deformation-zone geometry Voids and void-growth mechanisms Fractography and fracture Uncoupled ductile damage criteria and fracture Link between uncoupled ductile damage and fracture mechanics Mode I-Tensile fracture Mode II-In-plane shear fracture Mode III-Out-of-plane shear fracture Graphical representation of the analytical framework for ductile damage Uncoupled ductile damage and the Lode parameter Uncoupled ductile damage criterion due to Isik (2018) Uncoupled ductile damage criterion due to Bao and Wierzbicki (2004) Coupled ductile damage criteria and fracture Micromechanics-based damage criteria Macromechanics-based approaches Experimental determination of the fracture loci Sheet metal forming Bulk metal forming Plastic instability Diffuse necking in uniaxial tension Localised necking in uniaxial tension Localised necking in biaxial tension and the forming limit curve Representation of the forming limit curve in principal strain space Factors influencing the forming limit curve Representation of the forming limit curve in space of effective strain vs stress triaxiality Experimental determination of the forming limit curve Process defects Rolling Forging Wrinkling in deep drawing Tube bending Metallurgy Crystalline structure Defects Material matrix Grain size Surface quality References Finite element simulation: A user’s perspective Introduction The finite element environment Mesh generation Structured vs unstructured meshes Mesh generation techniques Mapped meshing Sweeping Plastering Indirect meshing Grid-based meshing Nonlinearity in finite element modelling of metal forming Kinematics of large deformations Measures of strain Rate of deformation Measures of stress Finite element formulations Quasi-static finite element formulations Direct iterative method Newton-Raphson iterative methods Convergence criteria Finite element equations Pros and cons of quasi-static finite element formulations Dynamic finite element formulations Explicit integration using the central difference method Pros and cons of explicit dynamic formulations Errors in finite element analysis Modelling errors Analysis type Material models Fundamental physical phenomenon Material data Ductile damage Friction and heat transfer Description of tooling Machine tools Numerical errors Selection of elements Discretisation and mesh convergence Time step and convergence criteria Other factors Other errors Validation of finite element procedures Process-independent validation procedures Material flow Stress field Distribution of forces Convergence studies Process-dependent validation procedures Validation against theoretical solutions and technical data available in literature Validation against experimental and industrial observations and measurements References Finite element flow formulation Introduction Theoretical fundamentals Quasi-static equilibrium-A solid mechanics view Second extremum principle-An energy view Rates of energy Extremum principles Momentum balance equation-A fluid dynamics view Viscous fluids Differential momentum balance equation Discretisation by finite elements Iterative solution methods Direct iterative method Newton-Raphson iterative method Line search algorithms Explicit solution scheme Numerical integration Treatment of rigid zones Treatment of friction Contact between objects Linear contact algorithms Penalty-based contact algorithms Lagrange multiplier-based contact algorithms Contact between deformable objects Thermo-mechanical analysis Heat transfer equation Finite element discretisation Electro-thermo-mechanical analysis Extensions of the conventional finite element flow formulation Porous metals Ductile polymers Viscous flow Anisotropic metals Rotation between global axes and material axes Elastic effects References Introduction to the finite element solid formulation Introduction Theoretical fundamentals Discretisation by finite elements Implicit vs explicit integration procedures Rate-independent limit References Tool design Introduction Tools for compressive forming Open-die tools Impression-die tools (closed-die tools) Precision tools Conventional precision tools Precision tools with floating dies Precision tools with multidirectional dies Tools for tensile, combined tensile and compressive forming, and bending Conventional tools with single-station dies Multidirectional tools with single-station dies Progressive tools with multistation dies Tools for forming by shearing Combination tools Compound tools Fine blanking tools Tool materials Selection of tool materials Hardening and tempering Surface treatments and coatings Preheating of punches and dies Punches Punch dimensioning Punch design Dies Die dimensioning Lamé equations Monoblock Prestressed container-Stress rings Guidelines for dimensioning a prestressed container with one stress ring Guidelines for dimensioning a prestressed container with two stress rings Manufacture of die cores and stress rings Strip-wound container Die design Rod and tube extrusion dies Can extrusion dies Lubrication Tool failure Wear to out-of-tolerance conditions Catastrophic failure (fracture) Thermal softening and subsequent deformation of dies Insufficient polishing of the punches and dies Inaccurate dies that miss target dimensions Material choice for punches References Further reading Appendices Appendix A Algebraic decomposition of the stress triaxiality Appendix B Large elastic-plastic and rigid-plastic deformations Appendix C Mathematics for continuum mechanics Appendix D Force increment ratio that is necessary for an elastic element to yield (Yamada et al., 1968) Appendix E Basic cold forging processes Appendix F Calculation of deflections and stress distributions in the die core and stress rings Assembly of die and stress ring Operation of die and stress ring during the extrusion process Unloading before ejection of the workpiece Unloading after ejection of the workpiece Appendix G MATLAB computer program Listing of the MATLAB computer program Appendix H Fit recommendations (adapted from Fisher et al., 2008) References Index A B C D E F G H I K L M N O P Q R S T U V W