Laser welding of advanced high strength steels [Elektronische Ressource] / Essam Ahjmed Ali Ahmed

Shaker Verlag Gmbh

Informations

• Publié par: rheinisch-westfalischen_technischen_hochschule_-rwth-_aachen
• Publié le: 01 janvier 2011
• Nombre de lectures: 6
• Langue: English
• Poids de l'ouvrage: 3 Mo

Extrait

Laser Welding of Advanced High Strength Steels
Von der Fakultät für Maschinenwesen der Rheinisch-Westfälischen Technischen
Hochschule Aachen zur Erlangung des akademischen Grades eines
Doktors der Ingenieurwissenschaften
genehmigte Dissertation
vorgelegt von
Essam Ahmed Ali Ahmed
Berichter: Univ.-Prof. Dr.-Ing. Uwe Reisgen
Univ.-Prof. Dr.-Ing. Lorenz Singheiser
Tag der mündlichen Prüfung: 28.03.2011
„Diese Dissertation ist auf den Internetseiten der Hochschulbibliothek online verfügbar.“ zum Drucken:
- Drucker: HP5000
Essam Ahmed Ali Ahmed
Laser Welding of Advanced
High Strength Steels
Aachener Berichte Fügetechnik
Herausgeber: Prof. Dr.-Ing. U. Reisgen
Band 2/2011 Shaker VerlagBibliographic information published by the Deutsche Nationalbibliothek
The Deutsche Nationalbibliothek lists this publication in the Deutsche
Nationalbibliografie; detailed bibliographic data are available in the Internet at
http://dnb.d-nb.de.
Zugl.: D 82 (Diss. RWTH Aachen University, 2011)
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Dedicated to
EgyptAcknowledgments
The success of this research has been achieved due to the invaluable contributions of
various individuals. I would like to take this opportunity to acknowledge their efforts:
I would like to express my sincere appreciation to my adviser, Prof. Dr.-Ing. U. Reisgen for
his invaluable advice and exceptional guidance throughout the graduate study. His
constant encouragement and drive for excellence were a source of inspiration.
I would also like to thank the members of my advisory committee Dr.-Ing. M. Schleser and
Dr. O. Mokrov for giving me helpful suggestions and their support throughout my stay at
the RWTH Aachen University.
Great appreciations to Prof. Dr.-Ing. U. Dilthey and Dr.-Ing. V. Pavlyk (Eisenbau Krämer
GmbH, Kreuztal, Germany) for their special care in the early years at Welding and Joining
Institute. I cannot forget to own my great appreciations to Dr.-Ing. S. Olschok and Dr.-Ing.
L. Stein for their gentleness and facilitation of the experimental procedures for this
research.
I am grateful to all scientists (especially: A. Abdurakhmanov, A. Harms, A. Schmidt, A.
Zabirov and E. Rossiter), technicians and laboratories’s members of the Welding and
Joining Institute of the RWTH Aachen University for their help during this research.
I would like to gratefully acknowledge for the financial support of the Higher Education
Ministry (Egypt) and the Welding and Joining Institute of the RWTH Aachen University
(Germany).
I am owing to the cultural department and study mission of the Arab Republic of Egypt in
Berlin for the unbroken care and the financial support during my stay in Germany.
I owe a debt of gratitude to Dr.-Ing. S. Ataya and Dr. A. Hamada (Materials and
Metallurgical Engineering Department, Suez Canal University, Egypt) for continuous
advises and assistance during this research.
Finally, I dedicate this dissertation to my mother, sisters and brothers for their continual
encouragement and prayer and to the memory of my father and brother. I would like to
express my warmest gratitude to my beloved wife and my children for their patience,
sacrifice and endless love.

Essam Ahmed Table of contents I
Table of contents
Table of contents ................................................................................................................ I
List of figures ................................................................................................................... IV
List of tables .................................................................................................................... VII
Symbols and abbreviations .......................................................................................... VIII
Abstract ............................................................................................................................ XI
1 Introduction and objectives ....................................................................................... 1
1.1 Brief overview ......................................................................................................... 1
1.2 Objectives of the study ........................................................................................... 2
2 Literature review 3
2.1 Advanced high strength steels (AHSS) ................................................................... 3
2.1.1 Dual phase (DP) steels .................................................................................... 3
2.1.2 Transformation induced plasticity (TRIP) steels ............................................... 4
2.2 Tailor welded blanks (TWBs) .................................................................................. 7
2.2.1 Definition and history ........................................................................................ 7
2.2.2 Benefits ............................................................................................................ 8
2.3 Formability of AHSS ............................................................................................... 8
2.3.1 Elastic and plastic deformation ......................................................................... 8
2.3.2 Failure modes .................................................................................................. 9
2.3.3 Formability simulation .................................................................................... 10
2.4 Finite element method: Application in welding ...................................................... 11
2.4.1 Welding – induced temperature field .............................................................. 12
2.4.2 Welding – induced stresses ........................................................................... 13
2.4.3 Welding – induced distortions ........................................................................ 14
2.4.4 Numerical simulation of laser welding ............................................................ 14
2.5 Statistics: Application in Welding .......................................................................... 15
2.5.1 Response surface methodology (RSM) ......................................................... 16
2.5.2 e surface models .............................................................................. 16
2.5.3 Applications of response surface methodology in welding ............................. 17
3 Experimentation procedures, results and discussion .......................................... 19
3.1 Experimental Design ............................................................................................. 19
3.1.1 Base materials characterization ..................................................................... 19
3.1.1.1 Materials selection ................................................................................... 19
3.1.1.2 Chemical composition .............................................................................. 19
3.1.1.3 Microstructure .......................................................................................... 19 II Table of contents
3.1.1.4 Retained austenite content ...................................................................... 19
3.1.2 Description of the welding process ................................................................. 20
3.1.3 Mechanical characterization of base metals and welded sheets .................... 21
3.1.3.1 Welding induced – microstructures .......................................................... 21
3.1.3.2 Microhardness distribution ....................................................................... 21
3.1.3.3 Tensile test .............................................................................................. 22
3.1.3.4 Formability test (Erichsen test) ................................................................ 22
3.1.4 Effects of shielding gases (experiments: group B) ......................................... 23
3.2 Experimental results ............................................................................................. 24
3.2.1 Base materials characterization ..................................................................... 24
3.2.1.1 Chemical composition .............................................................................. 24
3.2.1.2 Base materials microstructure ................................................................. 24
3.2.2 Weldments characterization ........................................................................... 24
3.2.2.1 Welding induced - microstructure ............................................................ 24
3.2.2.2 Microhardness distribution .............