MTF STU Trnava
MSPO2_6I · Introductory Lecture

Modeling and Simulation
of Forming Processes

An introduction to physical, mathematical and computational modeling of metal forming technologies.

Ing. Martin Necpal, PhD.
Faculty of Materials Science and Technology (MTF STU), Trnava
Slovak University of Technology in Bratislava
Winter Semester 2026/2027 · Wednesday 13:00–14:50 · Room T-032
Welcome

Today's Agenda (110 minutes)

TimeSegment
0:00–0:10Welcome & course introduction
0:10–0:25Course logistics
0:25–0:50Motivation — why simulate forming processes
0:50–1:15Overview of forming processes
1:15–1:45Modeling & simulation approaches
1:45–1:50Wrap-up & next steps

Software tools (DEFORM, Simufact, Abaqus, LS-DYNA...) are covered in detail next class.

Course Introduction

MSPO2_6I — Course Basics

  • Faculty of Materials Science and Technology (MTF), Trnava
  • 2nd degree (Master's) study level
  • Credits: 5
  • No prerequisites for registration
  • Lecture: 2 h/week (26 h/semester, full-time)
  • Seminar: 2 h/week (26 h/semester, full-time)
  • Consultations: 8 h (combined form)
  • Intended for: 2I-PPNV-PPNV, 2I-PPNV-RVS
Course Introduction

Timetable & Teaching Staff

  • Wednesday 13:00–14:50, room T-032
  • prof. Ing. Maroš Martinkovič, PhD. — course guarantor, lecturer
  • Ing. Martin Necpal, PhD. — instructor, lecturer
  • prof. Dr. Ing. Jozef Peterka — examiner, instructor, lecturer
  • Ing. Róbert Sobota, PhD. — instructor
Course Introduction

Assessment & Grading

  • Seminar assignment: max 20 points
  • Written exam: max 80 points
GradePoints
A92–100
B83–91
C74–82
D65–73
E56–64
FX0–55
Course Introduction

Learning Outcomes

  • Understand physical and mathematical modeling of forming technological processes
  • Prepare input data and define boundary conditions for selected forming-process cases
  • Operate simulation software used in forming technology
Course Introduction

Course Contents — 6 Topics

  • 1. Introduction to modeling — physical & mathematical modeling, classification, model creation today
  • 2. Simulation of mathematical models — numerical methods, simulation software
  • 3. Material models — elasticity, plasticity, strain, strain rate, strain hardening
  • 4. Preprocessing — preparing data for technological process modeling
  • 5. Postprocessing — sheet metal forming simulation examples
  • 6. Postprocessing — bulk forming simulation examples
Course Introduction

Recommended Literature

  • NECPAL, M.; SOBOTA, R. Modelovanie a simulácia procesov tvárnenia. Bratislava: Spektrum STU, 2023. — course textbook, based on DEFORM software
  • SPIŠÁK, E. Matematické modelovanie a simulácia technologických procesov: Ťahanie. TYPOPress, 2000.
  • MARKOPOULOS, A. P. Finite Element Method in Machining Processes. Springer, 2013.
  • DIXIT, P. M.; DIXIT, U. S. Modeling of Metal Forming and Machining Processes. Springer, 2010.
  • BÍLIK, J.; KAPUSTOVÁ, M.; RIDZOŇ, M. Teória tvárnenia. AlumniPress, 2015.
  • HRIVŇÁK, A.; PODOLSKÝ, M.; DOMAZETOVIČ, V. Teória tvárnenia a nástroje. Alfa, 1992.
Part 1

Motivation

Why do we model and simulate forming processes?

Motivation

What Simulation Gives Us

  • Prediction of material flow during deformation
  • Analysis of stress, strain and temperature distribution
  • Determination of required forming forces and energy
  • Early forecast of defects and failures
  • Improved part quality and reduced manufacturing cost
Motivation

Why Simulate Before You Build?

Physical trial-and-error tooling is expensive and slow — simulation replaces costly iterations on the shop floor with fast iterations on the computer.

Design typically accounts for only 5–15% of total production cost — yet decisions made at this early stage largely determine the cost of everything that follows.
Project phase Cost (%) Concept Design & simulation Tooling Production ~80–90% of cost committed here Cost committed Cost incurred (actually spent)
Decisions made during design and simulation commit most of the eventual production cost, long before that cost is actually spent on tooling and production.
Motivation

Simulation in the Design Chain

  • Modeling & simulation are integrated parts of product and process design
  • Used from product design through process planning to process control
  • Supports sustainable, resilient and cost-efficient process design
  • Reduces the number of physical trials and tooling iterations needed
Part 2

Overview of Forming Processes

Classification and key physical phenomena

Forming Processes

Bulk Forming Processes

  • Rolling — flat rolling, ring rolling, caliber rolling
  • Forging — open-die forging, closed-die forging
  • Extrusion
  • Drawing (bar / wire / tube drawing)

Large plastic strains, complex die–workpiece contact, often coupled with heat transfer (hot forming).

Billet (thick) Strip (thin, longer) roll ω roll ω
Flat rolling: counter-rotating rolls reduce workpiece thickness — the archetype bulk-forming operation.
Forming Processes

Sheet Metal Forming Processes

  • Deep drawing
  • Bending
  • Stamping
  • Stretch forming, incremental sheet forming

Thin-walled geometry, anisotropy, springback and forming-limit (necking/tearing) are the key concerns.

Punch force Blank holder Sheet blank Die
Deep drawing: a punch forces a clamped sheet blank into a die cavity, forming a cup-shaped part.
Forming Processes

Key Physical Phenomena

  • Elastic-to-plastic transition and large plastic deformation
  • Friction and contact between tool (die) and workpiece
  • Heat generation and transfer (deformation heat, friction heat)
  • Strain hardening / workhardening of the material
  • Anisotropy of sheet materials, springback after unloading
Part 3

Modeling & Simulation Approaches

From physical models to the Finite Element Method

Modeling Approaches

Two Modeling Philosophies

System approach

  • Treats the process as a system: die temperature, die stress, friction, ram speed, billet properties, etc.
  • Simplified geometry → fast, inexpensive overview of parameter influence

Mechanic-detailed approach

  • Detailed continuum-mechanics description of deformation
  • Basis for numerical (FEM) simulation — higher accuracy, higher cost
Modeling Approaches

Material Behavior: The Basics

  • Elastic response: linear stress–strain relationship, fully recoverable
  • Yield stress — onset of plastic deformation
  • Beyond yield: workhardening — stress increases at a decreasing rate
  • The yield stress and the workhardening (flow) curve are the two fundamental quantities defining plastic deformation of metals
  • Course topic 3 covers this in depth: elasticity, plasticity, strain, strain rate, strain hardening
Strain ε Stress σ Yield stress σᵧ Elastic Plastic (workhardening)
Beyond the yield stress, a metal keeps hardening — this flow curve is the core input every forming simulation needs.
Modeling Approaches

From Physical Model to Computer Model

  • Physical model — idealizes and abstracts the real system to fit an assumed physical theory (e.g. continuum mechanics, elastic solid)
  • Mathematical model — specifies governing equations (e.g. partial differential equations) plus boundary and initial conditions
  • Computational model — defines element type, mesh density and solution parameters (tolerances, iteration, convergence criteria)
  • A simulation model is only an approximation of reality — it must be validated and verified before its results can be trusted
Physical model idealized system idealize / formulate Mathematical model governing equations + BCs discretize Computational model mesh, solver, tolerances solve Simulation results validate & verify against reality
The chain from physical to computational model only earns trust once results are checked back against reality.
Modeling Approaches

Finite Element Method — The Core Idea

  • The system is discretized into a finite number of small elements
  • Physical variables (temperature, stress, strain, velocity) are computed for each element
  • An approximate governing equation is generated for every element
  • Assembling all element equations yields the behavior of the whole system
  • Accurate flow-stress / constitutive models are essential — they let FEM predict the strain–strain-rate–temperature path through the process
Continuous body discretize Finite element mesh
FEM discretizes a continuous body into a finite number of elements, each carrying its own approximate governing equation.
Modeling Approaches

Solver Types & Model Trust

Implicit vs. explicit FEM

  • Static-implicit — stable, good for slow/quasi-static forming
  • Dynamic-explicit — robust for severe contact & large deformation

Validation & verification

  • Validation: does the model represent the real physics correctly?
  • Verification: was the model implemented correctly?
  • Both are required before results can support decisions
Wrap-up

Next Steps

  • Next class: simulation software for forming technology — DEFORM, Simufact, Abaqus, LS-DYNA and how to choose between them
  • Course textbook: Necpal & Sobota, Modelovanie a simulácia procesov tvárnenia (2023) — examples built with DEFORM 12.1.1
  • Reading: review Chapters 1–2 of the course textbook before next lecture
  • Seminar work topic will be assigned once software setup is complete

Questions?

Ing. Martin Necpal, PhD. · martin.necpal@gmail.com

MTF STU Trnava