Hot Stamping Process Simulation Using Integrated using Structural & CFD Analysis

Innovation Intelligence®

Hot Stamping Process Simulation Using

Integrated Structural and CFD Analyses

Hariharasudhan Palaniswamy, Subir Roy

May 7, 2015

Copyright © 2015 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.

Agenda

• Hot Stamping - Press Hardening process

• HyperForm

• HyperWorks™ Approach

• RADIOSS – Hot Stamping simulation

• Hot stamping simulation – Indirect Coupling

• Hot stamping – Simulation strategy

• Summary


Hot Stamping Process

• Stamping process with integrated Heat

treatment (Tempering)

• Heating the blank above 900oC

• Quick Forming

• Rapid cooling in tools

• Hot stamped parts Higher strength

significant contribution for weight reduction

• Part Metallurgy

• Part PropertiesAltan et al 2002

Garcia et al 2002

Altan et al 2002


Hot stamping Process

• Tailored gradient material properties at desired location from single blank through

localized Heating or in die differential Cooling

• New possibilities for energy management in Crash Design Innovations

• Part consolidation + weight reduction + Cost reduction

Ralf Hund 2013,

Ignacio Martin 2013,

(A) - Soft zone

UTS 450 – 700 Mpa

Elongation >= 15%

(B) - Hard zone

UTS 1300 – 1500 Mpa

Elongation >= 5%


• Interaction of various physical phenomena in the process

• Simulation tools used for process design should be able to model all the

phenomena to estimate various process parameters to achieve desired final part

properties

Hot stamping process


A Complete Solution for Sheet Metal Forming

• Product feasibility analysis with optimization

• Material Utilization / Cost analysis

• Die face design

• Virtual try-out with optimization

• Die stress analysis with optimization

• Modeling advanced stamping processes

• Press hardening

• Composite forming

HyperForm


HyperForm – Virtual Tryout (Incremental)

• Seamless integration with RADIOSS, the most

accurate solver in the marketplace

• Fully supporting LS-Dyna as an alternate

incremental solver

• Process oriented work flow for fast and intuitive

stamping model setup

• Blank - Metals or Composites, Shell or Solid

elements,

• Room or Elevated temperature

• Automated process for multi-stage transfer and

progressive die simulations

• Tube Bending and Tube Hydroforming model setup

• Optimization enabled for process design

• Efficient post processing tools with automated

reporting


HyperWorks™ Approach

• Coupled solution with solvers RADIOSS and AcuSolve

• RADIOSS – Non-linear finite element based structural and thermal analysis

solver

• AcuSolve - Incompressible fluid flow solver based on Galerkin Least Square

Finite element Method

• Direct coupling – Large models, Implicit – Explicit combination, High

computation cost and time – Not practical

• Indirect coupling – Efficient


RADIOSS – Hot stamping simulation

• New material model for Boron steels – Akerstorm 2006

• New time step integration method to significantly reduce quenching simulation time.

• Validation - Numisheet 2008 Benchmark problem


Hot Stamping simulation – Indirect coupling

• Example part – U Channel

• Initial forming simulation in RADIOSS – Predict blank temperature at start of

quenching.

Model setup

Predicted blank temperature –

end of forming


Hot stamping simulation – Indirect coupling

• Cooling simulation – Acusolve - Predict tool temperature during quenching

considering fluid flow in channels

• Step 1 – Steady state flow analysis for fluid velocity and pressure profile

• Step 2 – Transient Thermal analysis with inputs from step 1

Model setup

Predicted blank temperature

– end of forming

Punch – 348 K

Die – 348 K Blank – Initial Temperature

from RADIOSS forming run

Cooling channel- Fluid temperature 298 K and

flow rate 5 l/min



• Cooling simulation– Acusolve

0

100

200

300

400

500

600

700

800

900

0 1 2 3 4 5 6

To

ol s

urf

ace

te

mp

era

ture

(K

)

Time (sec)

Location 1

Location 2

Location 3

Tool temperature – Quenching 5 secs



• Quenching simulation– RADIOSS

• Tool temperature history – AcuSolve Cooling Run


Die – Temperature function of time from Acusolve run

Blank – 810 oC

Punch – Temperature function of time from Acusolve run





Constant Tool temperature – 348 K

Traditional simulation

Tool temperature – Variable with time from AcuSolve

Indirect coupled simulation

Martensite Volume

fraction

Martensite Volume fraction – Quenching 5 secs





• Traditional approach results in faster cooling and inaccurate final properties of

the formed part


Hot Stamping - Simulation strategy

Design criteriaSplits,

Wrinkles, thinning

Hardness, Tool

temperature, Cycle time

CAD InputDie face design

Detailed design

CAE RADIOSSRADIOSS + ACUSOLVE

• Thermo – Mechanical

simulation

• Tool temperature

assumed

• Thermal + Mechanical +

Fluid flow

• Minimal assumptions

Die face, Press

parameters

Cooling channel

size, location, fluid

flow rate, pressure

1. Forming Feasibility 2. Properties Feasibility


Summary

• New material model implemented in RADIOSS to model press hardening steel

and validated.

• Efficient approach that models all the physical phenomena in press hardening

has been proposed using Altair’s Solvers.

• RADIOSS – Mechanical, Thermal and Metallurgy

• AcuSolve – Thermal and Fluid flow

• New approach illustrated the tools effect (thermal and fluid flow) play a

significant role in heat loss and final part hardness.

• The proposed approach is the efficient way to model all the physical phenomena

in press hardening to predict accurate results.

Hot Stamping Process Simulation Using Integrated using Structural & CFD Analysis

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