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[资源] 残余应力的实践测量方法

Practical Residual Stress Measurement Methods
Residual stresses are created by almost every manufacturing process, notably by casting,
welding and forming. But despite their widespread occurrence, the fact that residual
stresses occur without any external loads makes them easy to overlook and ignore. This
neglect can cause great design peril because residual stresses can have profound influences
on material strength, dimensional stability and fatigue life. Sometimes alone and sometimes
in combination with other factors, unaccounted for residual stresses have caused
the failure of major bridges, aircraft, ships and numerous smaller structures and devices,
often with substantial loss of life. At other times, residual stresses are deliberately introduced
to provide beneficial effects, such as in pre-stressed concrete, shot-peening and
cold hole-expansion.
Starting from early curiosities such as “Rupert’s Drops,” understanding of the character
and mechanics of residual stresses grew with the rise in the use of cast metals during
the Industrial Revolution. The famous crack in the Liberty Bell is due to the action
of residual stresses created during casting. Early methods for identifying the presence
of residual stresses involved cutting the material and observing the dimension changes.
With the passage of time, these methods became more sophisticated and quantitative.
Complementary non-destructive methods using X-rays, magnetism and ultrasonics were
simultaneously developed.
Modern residual stress measurement practice is largely based on the early historical
roots. However, the modern techniques bear the same relationship to their predecessors as
modern jet planes to early biplanes: they share similar conceptual bases, but in operational
terms the current measurement techniques are effectively “new.” They have attained a
very high degree of sophistication due to greatly increased conceptual understanding,
practical experience and much more advanced measurement/computation capabilities. All
these factors join to give substantial new life into established ideas and indeed to produce
“new lamps for old.”
Conceptual and technological progress has been a collective endeavor by a large group
of people. The list of names is a long and distinguished one. To paraphrase Isaac Newton’s
words, the present Residual Stress community indeed “stands on the shoulders of giants.”
A particular one of these giants that several of the contributors to this book were privileged
to know and learn from, was Iain Finnie, late Professor of Mechanical Engineering at the
University of California, Berkeley. Professor Finnie was a pioneer of the Slitting Method,
described in detail in Chapter 4 of this book. I join with the other authors in dedicating
this book to him as a sign of respect and of appreciation for his encouragement, teaching,
mentorship and personal friendship. Those of us who aspire to be researchers and teachers
can do no better than look to him for example.
On a personal note, I would like to express my sincere gratitude and appreciation to
all the chapter authors of this book. The depth of their knowledge and experience of their
various specialties and their generous willingness to share their expertise makes them a
true “dream team.” They have been extraordinarily patient with all my editorial requests,
both large and small, and have worked with me with grace and patience. Thank you, you
have been good friends!
I also would like to thank the staff at John Wiley & Sons for the support and encouragement
of this project, and for the careful way they have carried forward every step in
the production process.
And finally, more personally, I would like to acknowledge my late parents, Leonard
and Lilly Schajer, whose fingerprints are to be found on these pages. They followed the
biblical proverb “Train up a child in the way he should go: and when he is old, he will not
depart from it.” In keeping with their philosophy, the royalties from the sale of this book
have been directed to support students in financial need through the Leonard and Lilly
Schajer Memorial Bursary at the University of British Columbia. All book contributors
have graciously supported this endeavor and in this way hope to add to the available
shoulder-space on which the next generation may stand.

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2014-11-12 08:12:46, 5.49 M