ABSTRACT
Dealing with fracture is inherently more complicated than applying linear elasticity. In fracture one is confronted with a limit state: how do materials and structures break (fail)? How can we capture the observed behavior in a useful and correct model? I am hesitant to use the term “theory” because this seems to imply that the construct stands as a rock, and can only be turned over by extremely new insights. A theory is more than a model. Somehow
the word implies that the insights are well developed and stand for eternity. Over the years I have learned that we have to be careful with this terminology, and if we are to qualify a model with words such as “theory” or “law” (which is another qualiªcation that one should use sparsely) it is very dependent on our ability to prove that the parameters used, and which provide the link to real-world behavior are properly deªned, and can be determined from well-deªned and independent experiments. The limitations of any approach should be known in as much detail as the phenomena that can be described. This attitude is quite lacking in modern science and engineering, to the point where a certain arrogance starts to affect progress in the ªeld.
