1. Master thesis
Advanced CAE Methodologies
for new AHSS material
application in body in white
Academic tutor:
Giovanni Belingardi
Author:
Mohammad Sharif Nategh
Company Tutors:
Rosanna Brun
Alessandro Agnello

2. What is Advanced High Strength Steels?
• In 1994, a consortium of 35 sheet steel producers began the Ultra-Light
Steel Auto Body (ULSAB) program to design a lightweight steel auto body
structure that would meet a wide range of safety and performance
targets. One of the major success of the ULSAB was a group of new steel
types and grades called Advanced High-Strength Steels (AHSS). The AHSS
family had unique microstructures to achieve strength and ductility
combinations that were never-before realized.
• Advanced High Strength Steels (AHSS) contribute dramatically to the
lightweight automotive design.

3. Future of AHSS
• The successes of AHSS have motivated steel companies to continue research on both new types and grades of AHSS and to
then bring these new steels to production.
• The results was Introduction of 1st and 2nd generation of AHSS grades that contain a broad range of grades with different
properties.
• Recently there has been increased funding and research for the development of the “3rd Generation” of AHSS that is under
developed in the companies. These are steels with improved strength-ductility combinations compared to present grades,
at lower costs.

4. Dual Phase (DP) Steel
• DP steels consist of a ferritic matrix containing a hard martensitic
second phase in the form of islands.
• The DP steel exhibits higher initial work hardening rate, higher
ultimate tensile strength than a similar yield strength HSLA.

5. 3rd Generation of DP600
• In this thesis the material and mechanical characteristics of a 3rd generations of
DP600 which is nominated DP600HD is analyzed and compared to other grades of
commonly used steels in automotive industries for car body production and the
virtual simulation of stamping process with FEM methodology in an advanced CAE
software is performed in order to certify the theoretical analysis.
• The aim of this project was finding the possibility of production of car body parts
with this new material and substitution of current grades with new one and
simultaneous development of new processes and equipment to produce and form
this new material .

6. Comparison of DP600HD and commonly used
grades of steels
•DP600HD and DP600
•DP600HD and Mild steels or low carbon steels.
•DP600HD and IF (interstitial-Free) steels.
•DP600HD and BH-steels.
•DP600HD and HSLA Steels.

7. DP600HD and DP600
• Rp0.2 higher spring back
• Rm resistance against necking
• Total elongation higher formability
• r-value Disadvantage for cup drawing, hole expansion
• n-value help distribute deformation more uniformly and reduce local thinning
 the strength and formability are increased simultaneously

8. DP600 and DP600HD
 The area under a flow stress curve
determines the forming energy
requirement.
 An FLD is a map of strains that indicate the onset
of critical local (through thickness) necking for
different strain paths, represented by major and
minor strains.

9. Front Floor
Material propose
From DP600 th. 0.8mm
To DP600HD th. 0,8mm
Plastic strainThinning
min max
-0,432 0
3% limit+0,05/-0,20 limit
Virtual check on:
• Formability
• Dimensional analysis
Dimensional
min max
-2,954 +2,831
-1/+1 limit
0 +0,654 -2,552 +1,994-0,387 0 0 0,546
Virtual forming Simulation - case study 1

10. Inner rail Panel _Up
Material propose
From DP600 th. 0.8mm
To DP600HD th. 0,7mm
Plastic strainThinning
min max
-0,223 0
3% limit+0,05/-0,20 limit
Virtual check on:
• Formability
• Dimensional analysis
Dimensional
min max
-2,967 +0,927
-1/+1 limit
0 +0,299 -2,482 +1,123-0,222 0 0 0,281
Virtual forming Simulation - case study 2

11. Virtual forming Simulation - case study 2
Weight reduction in new proposals Maximum Press Force requirement For
Normal Production and new proposals
with considering thickness reduction

12. DP600 and DP600HD conclusion
• DP600HD totally has better thinning results and surface deformation
becomes more uniformly distributed because of higher work hardening
capability and increasing of forming limit curve (FLD).
• DP600HD has better formability and lower limit for bend radius(r/t)
Because of higher total elongation.
• For DP600 HD higher springback may occur in the zone with higher
deformation because of higher n-value and higher yield strength but total
result of springback in the case studies and analysis show improvement.
• Press force requirement is expected to be same because of similarity in
hardening curve.
• In DP600HD the capability of hole expansion and cup drawing may
decrease because of reduction in r-values.

13. Most important result of project
It should mention that what is worked in this thesis is
not only for one special material and can consider as a
sample study for every new generations of AHSS
materials and extend the sample of study and
conclusion to other materials by just changing the data.

14. Thank you for your attention!
Mohammad Sharif Nategh
October 2015