Structural Shear Joints: Analyses, Properties And Design for Repeat Loading

238 Pages·2005·21.49 MB·English

by  George T. Hahn

STRUCTURAL SHEAR JOINTS
ANALYSES, PROPERTIES AND
DESIGN FOR REPEAT LOADING
George T. Hahn
Mechanical Engineering, Vanderbilt University
Kaushik A. Iyer
U.S. Army Research Laboratory
Carol A. Rubin
Mechanical Engineering, Vanderbilt University
WO o u s
D H E A D P 13 I. I H IN G L I M I T E D
0 2005 by ASME,Three Park Avenue, New York, NY 10016, USA (www.asme.org)
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Library of Congress Cataloging-in-Publication Data
Hahn, George T.
Structural shear joints : analyses, properties and design for repeat loading / George T. Hahn,
Kaushik Iyer, Carol A. Rubin.
p. cm.
Includes bibliographical references and index.
ISBN 0-7918-0238-8 (hardcover)
1. Shear (Mechanics) 2. Bolted joints. I. Iyer, Kaushik. 11. Rubin, Carol A. 111. Title.
TA417.7.SSH34 2005
621.8'82-dc22 2005016167
British Library Cataloguing in Publication Data
A catalogue record for this book is available from the British Library.
Woodhead Publishing ISBN-13: 978-1-84569-11 9-6
Woodhead Publishing ISBN-10: 1-84569-11 9-9
Cover graphic: Computed maximum principal stress contours in a butt joint with 0.6% interference
that is subjected to a remote tensile stress of 80 MPa
TABLE
OF CONTENTS
Preface vii
Acknowledgements ix
Introduction xi
SECTION 1. MECHANICAL BEHAVIOR OF SHEAR JOINTS AND
DESIGN CONSIDERATIONS
Chapter 1. BASIC FEATURES 3
1.1. Aspects of Shear Joints 3
1.2. Out-of-Plane Deformation, Microslip and Plasticity 6
1.3. Fasteners and the Fastener Load 8
1.4. The Bearing, Clamping and Adhesive Modes of Load Transfer 8
1.5. Stress Descriptors for Fatigue 11
Chapter 2. SHEAR JOINTS IN THE BEARING MODE 13
2.1. Stress Descriptors for Bearing Mode 13
2.2. Butt Joint 14
2.3. Doubler 19
2.4. Lap Joint 20
2.5. Lap Joints in the Adhesive-Plus-Bearing Mode 27
2.6. Multiple Rows of Fasteners 29
2.7. Biaxial Loading and Effects of the Free Edge 30
2.8. Fastener Stresses 33
Chapter 3. CLAMPING, INTERFERENCE, MICROSLIP AND
SELF-PIERCING RIVETS 41
3.1. The Clamped, Frictional or Slip-Resistant Mode of Butt and Lap Joints 41
3.2. Fasteners in the Clamping Mode 54
3.3. Hole Expansion, Squeeze and Interference 54
3.4. Contact Pressure, Microslip and Tangential Stress 59
3.5. Self-piercing Rivet 63
Chapter 4. FATIGUE OF SHEAR JOINTS 67
4.1. Stages of the Fatigue Process 67
4.2. Failure Modes and Locations 67
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iv Structural Shear Joints
4.3. Fatigue Strength of Panels 70
4.4. Fatigue Strength of Fasteners 80
4.5. Fretting Wear and Fatigue 81
Chapter 5. DESIGN CONSIDERATIONS FOR REPEATED LOADING 87
5.1. Mechanical Performance 87
5.2. Considerations for Joint Durability 87
5.3. Joint Type and Mode Selection 90
5.4. NDI and Fretting 91
5.5. Fail Safe Design 92
5.6. Generalizing Finite Element Results 92
SECTION 2. COMPILATION OF FINITE ELEMENT RESULTS
Chapter 6. LOAD TRANSFER IN SINGLE RIVET-ROW LAP JOINTS
(CONVENTIONAL AND COUNTERSUNK) 99
6.1. Summary of Load Transfer Models 99
6.2. Load Transfer Calculations for Single Rivet-Row Lap Joints 99
6.3. Summary and Important Points 104
Chapter 7. COMPILATION OF RESULTS FOR OPEN HOLE
PANELS AND BUTT JOINTS 107
7.1. Summary of Calculational Models for Open Hole Panels 107
7.2. Summary of Calculational Models for Butt Joints 107
7.3. Summary of Calculation Results for Open Hole Panels 107
7.4. Summary of Calculation Results for Butt Joints without Interference 107
7.5. Effects of Interference in Butt Joints 114
Chapter 8. COMPILATION OF RESULTS FOR LAP JOINTS 125
8.1. Summary of Calculational Models 125
8.2. Summary of Calculation Results 125
8.3. Summary of Calculation Results Including Interference and Clamping 129
Chapter 9. SINGLE RIVET-ROW LAP JOINTS UNDER BIAXIAL LOADING 151
9.1. Summary of Calculational Models for 2-D and 3-D Lap Joints under
Biaxial Loading 151
9.2. Summary of Calculation Results for Pinned Connections under Biaxial Loading 151
9.3. Summary of Calculation Results for Single Rivet-Row Lap Joints under
Biaxial Loading 151
Chapter 10. COMPILATION OF RESULTS FOR LAP JOINTS WITH
SEALANTS AND ADHESIVES 157
10.1. Summary of Calculational Models for for Single Rivet-Row Lap Joints
with Sealants and Adhesives 157
10.2. Summary of Calculation Results for Pinned Connections with Sealants
and Adhesives 157
Table of Contents V
Chapter 11. COMPILATION OF RESULTS FOR RIVETS 161
11.1. Summary of Calculational Models for Rivets 161
11.2. Summary of Calculational Results for Rivets 161
Chapter 12. DATA TABULATIONS 173
12.1. Summary Calculation Results for Single Rivet-Row Lap Joints 173
12.2. Summary Calculation Results for Double Rivet-Row Lap Joints 173
12.3. Summary Calculation Results for Rivet Installation Residual Stresses 174
12.4. Summary Calculation Results for Single Rivet-Row Joints Under
Biaxial Loading 174
12.5. Summary Calculation Results for Single Rivet-Row Joints With Sealant 175
12.6. Summary Calculation Results for Variation of Panel Thickness in
Wide Single Rivet-Row Joints 183
12.7. Summary Calculation Results for Joint Excess Compliance and Rivet Tilt 183
SECTION 3. CALCULATIONAL MODELS AND VALIDATION
Chapter 13. FINITE ELEMENT MODELS 189
13.1. 2D Models of Butt Joints, Attachment Joints and Open Hole Panels 189
3.2. 3D Models of Single Rivet-Row Lap and Butt Joints (Standard and
Countersunk Rivet Heads) 190
13.3. Double Rivet-Row Lap Joints (Standard and Countersunk Rivet Heads) 195
Chapter 14. THIN ADHESIVE LAYER ANALYSIS (TALA) FOR MODELING
SEALANTS AND ADHESIVES INSTALLED IN JOINTS 197
14.1. Development of A Thin Adhesive Layer Analysis (TALA) 197
14.2. Conversion of Adhesive Solid Element to Spring Element for 2-D Fem 197
14.3. Conversion of Stress-Strain Relationship to Force-Displacement Relationship
for Thin Adhesive Layer 200
14.4. Mechanical Behavior of Thin Sealant Layer 202
14.5. Shear Spring Dependence of Contact Pressure 205
Chapter 15. MATERIAL MODELS FOR THE FINITE ELEMENT CALCULATIONS
207
15.1. Materials Used in the Finite Element Calculations 207
Chapter 16. VALIDATION OF FINITE ELEMENT CALCULATIONS AND TALA 209
16.1. Finite Element Model Validation 209
16.2. Validation of The Thin Adhesive Layer Analysis (TALA) 210
Chapter 17. STRESS CONCENTRATION FACTORS IN MULTIPLE ROW JOINTS
217
17.1. Analyses of Multiple Row Joints 217
17.2. Estimating Fastener Loads in Multiple Row Joints 217
vi Structural Shear Joints
17.3. Estimating Fastener Loads with 3D Deformations 218
17.4. A Superposition Method for Estimating SCFs 221
17.5. Validation 223
Chapter 18. ANALYSIS OF FASTENER TENSION AND CLAMPING STRAIN 225
18.1. Nomenclature 225
18.2. Clamping Model 226
18.3. Fastener Tension and Clamping Strain Predictions 227
18.4. Summary of Procedure 229
APPENDIX A. SUMMARY OF CALCULATIONAL MODELS 231
APPENDIX B. STRESS CONCENTRATION FATOR-FATIGUE STRENGTH
(SCF-FS) ANALYSIS 241
APPENDIX C. ANALYSIS OF FRETTING WEAR AND FATIGUE 249
APPENDIX D. SYMBOLS, ABREVIATIONS AND UNITS 253
REFERENCES 257
INDEX
PREFACE
Engineers employ shear connections - riveted and bolted butt and lap joints - in a wide
range of structures and machines. Ordinary stress analyses of joints are unable to define the
features that ultimately govern fatigue and fretting and provide bases for design. Detailed
analyses have only become possible in the past decade with advances in finite element meth-
ods and computing capabilities. This text places into context the results of over 150 detailed,
2D and 3D finite element analyses of aluminum and steel shear connections.T he text exam-
ines the following joints, both single and multiple row, fasteners and modes of load trans-
mission:
butt joints bearing mode pins
lap joints clamped mode standard head fasteners
attachment joints adhesives mode countersunk fasteners
and doublers bearing mode with hole expansion self piercing rivets
interference fasteners
The analyses examine the fastener joint geometry, the adjacent region of the panel and the
important design variables. The text connects global features such as nominal stress, excess
compliance and fastener load, with the local conditions that affect fatigue and fretting.
Among the important local conditions are the contact pressures, interface slips, residual
stresses and the intensity and location of the stress concentrations. The text is divided into 3
sections designed for different audiences:
Section 1
Engineers and technicians seeking a better understanding of shear connections. The first
section introduces the different joints and identifies the important variables. It offers stress
contours and distorted meshes that complement easily grasped descriptions of the behavior
of panels and fasteners for the different modes of load transmission.
Engineers preparing to design shear connections resistant to fatigue.T he pros and cons of
the butt and lap joints for the different load transfer modes are discussed and a fail safe
strategy is identified in the first section. In addition, a simple and general FS-SCF (Fatigue
Strength-Stress Concentration Factor) analysis useful for preliminary design is identified
and validated. The analysis offers estimates of either the fatigue strengths of joints or the
vi i
viii Structural Shear Joints
joint geometry meeting a given fatigue strength requirement. Expressions for estimating the
bolt tension of clamped joints and the fastener load and SCF of multiple-row joints are
derived in appendices.
Engineers and technicians interested in fretting and in the fatigue strength of shear con-
nections. An extensive selection of fatigue strength measurements for riveted, bolted, and
bonded aluminum and steel joints is offered in the first section. The measurements are com-
pared with the forecasts of the FS-SCF estimation procedure. The contributions of fretting
wear and fretting fatigue are also examined.
NDE practitioners interested in knowing where to look for fatigue cracks and fretting dam-
age. The stress concentrations in shear joints are responsible for fatigue damage and crack ini-
tiation. The locations of the stress concentrations, which depend on the joint type and mode of
load transfer and are affected by hole expansion, are identified in the first section.
Section 2
Engineers and researchers wishing to access more finite element analysis findings. A
handbook-type, more detailed summary of the results of finite element calculations for fas-
teners and panels is presented in Section 2 of the book.
Section 3
Engineers and researchers seeking to perform finite element analyses of shear connec-
tions. To assist workers with computations, the finite element models, meshes, boundary con-
ditions and procedures used by the authors are described in Section 3. This includes TALA,
a Thin Adhesive Layer Analysis for modeling joints fastened with either adhesive alone, or
with rivets (or bolts) combined with a sealant or adhesive. Material models and parameters
employed in the calculations are listed. Validation of the finite element methods in the form
of comparisons with closed form analyses, other computations and measurements is pre-
sented.
ACKNOWLEDGEMENTS
The authors are indebted to John Wikswo of the Vanderbilt University Physics Depart-
ment who is responsible for inspiring the initial phases of the research endeavor described
in this book. The authors acknowledge the important contributions of the graduate students
who contributed to this research. In alphabetical order they are: former PhD students
Charoenyut Dechwayukul, Thongchai Fongsamootr, and Notsanop Kamnerdtong; and for-
mer MS students Khalid Al-Dakkan, Felicia Brittman, Yun Huang, and Charat Loha. They
also wish to thank Pedro Bastias, a former PhD student and colleague, who provided much
help and advice for the graduate students.
Computations were performed with the ABAQUS finite element program provided by
Abaqus, Inc. Most computations were performed on parallel systems in 3 major centers: the
National Center for Supercomputing Applications in Illinois (SGI Power Challenge Array),
Center for Advanced Computing at the University of Michigan in Ann Arbor (IBM SP) and
Department of Defense Major Shared Resource Center at the U.S. Army Research Labora-
tory in Maryland (IBM SP and SGI Origin).
Riveted lap joint specimens with and without a sealant were prepared Textron Aerostruc-
tures, Inc., Nashville, TN. with the help of Tom Warrion, Mike Floyd and Paul Nelson. Bill
Keller of PRC-DeSoto International, Inc. (formerly Courtalds Aerospace) provided the test
sealants. Bill King of Emhart Teknologies, Mt. Clemens, MI and Daniel Hayden of General
Motors Corp., Warren, MI provided assistance with fabrication and testing, respectively, of
the Self-piercing Riveted (SPR) joints.
Changchun Liu and Tuomas Wiste, graduate students at Vanderbilt University, and,
Shirleen Johnson of the graphic arts division at the U.S. Army Research Laboratory pro-
vided significant assistance with the drawings in this book.
The work was supported by the Air Force Office of Scientific Research, Vanderbilt Uni-
versity, The Royal Thai Government and the General Motors Collaborative Research Lab
(GMCRL) at the University of Michigan (Ann Arbor).
ix