Stress and Strain Determination
In Chap. 1 of this book, the term Technical Diagnostics has been introduced as the examination of symptoms and syndromes to determine the nature of faults or failures of technical objects. Their characteristics in different technological areas may be of
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Stress and Strain Determination Thomas Kannengiesser and Klaus-Peter Gru¨nder
Abstract
In Chap. 1 of this book, the term Technical Diagnostics has been introduced as the examination of symptoms and syndromes to determine the nature of faults or failures of technical objects. Their characteristics in different technological areas may be of very different nature. One of them is the reaction of technical objects to deform under loads. Those loads may be induced by external forces or thermal fields resulting in mechanical or thermal stresses, respectively. Another reason of deformation is the permanent presence of internal material forces mainly caused by material processing technologies at elevated temperatures such as welding, forging, rolling, or casting and referred to as residual stresses.
In Chap. 1 of this book, the term Technical Diagnostics has been introduced as the examination of symptoms and syndromes to determine the nature of faults or failures of technical objects. Their characteristics in different technological areas may be of very different nature. One of them is the reaction of technical objects to deform under loads. Those loads may be induced by external forces or thermal fields resulting in mechanical or thermal stresses, respectively. Another reason of deformation is the permanent presence of internal material
T. Kannengiesser (&) K.-P. Gründer (&) BAM Bundesanstalt für Materialforschung und— prüfung, Unter den Eichen 87, 12205, Berlin, Germany e-mail: [email protected] K.-P. Gründer e-mail: [email protected]
forces mainly caused by material processing technologies at elevated temperatures such as welding, forging, rolling, or casting and referred to as residual stresses. Stresses play a central role in failure mechanism analysis explicitly discussed in Chap. 3 of this book. In continuum mechanics, the term stress is tightly related to force vectors acting either locally via surface contact or more globally, e.g., centrifugal or gravitational, on the whole object volume. Their amount and direction per unit of area are the basis of stress definition and corresponding calculations. Experimental stress–strain analysis does not only serve the purpose of ascertaining material properties, but rather assumes growing prominence particularly as regards economical design and integrity of engineering systems. Since the level of and change in component loading as well as their impact on safety are dependent on a multitude of material, mechanical,
H. Czichos (ed.), Handbook of Technical Diagnostics, DOI: 10.1007/978-3-642-25850-3_5, Springer-Verlag Berlin Heidelberg 2013
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and thermal influencing factors (stiffness conditions, fabrication processes, load cycles) interfering with each other, it is often essential in fabrication and service to concomitantly measure the strains resulting from mechanical and thermal conditions and to determine the stresses based on the measured results. Depending on the required proof of the loadbearing capacity for a supporting structure and
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