''''It is true that "Nothing is more practical than a theory" Provided - however - That the assumptions on which the theory is founded Are well understood. - But, indeed, engineering experience shows that "Nothing can be more disastrous than a theory When applied to a real problem Outside of the practicailimits of the assumptions made", Because of an homonymous identity With the problem under consideration. " (J. T. P. ) The primary objective of this work is to present the theories of analytical and optical isodynes and the related measurement procedures in a manner com­ patible with the modem scientific methodology and with the requirements of modem technology pertaining to the usefulness of the stress analysis proce­ dures. The selected examples illustrate some major theses of this work and demonstrate the particular efficiency of the isodyne methods in solving the technologically important problems in fracture mechanics and mechanics of composite structures including new materials. To satisfy this objective it was necessary to depart from the common practice of presenting theories and techniques of experimental methods as a compatible system of equations and procedures without mentioning the tacitly accepted assumptions and their influence on the theoretical admissibility of analytical expressions and the reliability of the experimental or analytical results. It was necessary to design a more general frame of reference which could allow to assess the scientific correctness of isodyne methods and the reliability of experimental results.

The general objective of the Tenth Canadian Fracture Conference was to respond to progress in the engineering sciences - in particular with r- pect to rapidly developing new trends in the theory and methodology of researcr and designing - and to the resulting needs of practical engineering in the specific field of fracture mechanics and related areas of engineering mechanics. The basic underlying issue is the theory and practice of physical analytical and iconic (reduced) modelling of the actually involved physical processes and of the responses of physical bodies and systems to actual energy flow - a problem which is becoming dominant in all fields of the natural sciences. Accordingly, the theme of the CFCIO was "Modelling Problems in Crack Tip Mechanics", a well defined and limited subject, the scope of treatment of which can be as deep and as comprehensive as an in­ volved researcher wishes it to be.

The general objective of the Tenth Canadian Fracture Conference was to respond to progress in the engineering sciences - in particular with r- pect to rapidly developing new trends in the theory and methodology of researcr and designing - and to the resulting needs of practical engineering in the specific field of fracture mechanics and related areas of engineering mechanics. The basic underlying issue is the theory and practice of physical analytical and iconic (reduced) modelling of the actually involved physical processes and of the responses of physical bodies and systems to actual energy flow - a problem which is becoming dominant in all fields of the natural sciences. Accordingly, the theme of the CFCIO was "Modelling Problems in Crack Tip Mechanics", a well defined and limited subject, the scope of treatment of which can be as deep and as comprehensive as an in­ volved researcher wishes it to be.

''''It is true that "Nothing is more practical than a theory" Provided - however - That the assumptions on which the theory is founded Are well understood. - But, indeed, engineering experience shows that "Nothing can be more disastrous than a theory When applied to a real problem Outside of the practicailimits of the assumptions made", Because of an homonymous identity With the problem under consideration. " (J. T. P. ) The primary objective of this work is to present the theories of analytical and optical isodynes and the related measurement procedures in a manner com­ patible with the modem scientific methodology and with the requirements of modem technology pertaining to the usefulness of the stress analysis proce­ dures. The selected examples illustrate some major theses of this work and demonstrate the particular efficiency of the isodyne methods in solving the technologically important problems in fracture mechanics and mechanics of composite structures including new materials. To satisfy this objective it was necessary to depart from the common practice of presenting theories and techniques of experimental methods as a compatible system of equations and procedures without mentioning the tacitly accepted assumptions and their influence on the theoretical admissibility of analytical expressions and the reliability of the experimental or analytical results. It was necessary to design a more general frame of reference which could allow to assess the scientific correctness of isodyne methods and the reliability of experimental results.

The general objective of the Tenth Canadian Fracture Conference was to respond to progress in the engineering sciences - in particular with r- pect to rapidly developing new trends in the theory and methodology of researcr and designing - and to the resulting needs of practical engineering in the specific field of fracture mechanics and related areas of engineering mechanics. The basic underlying issue is the theory and practice of physical analytical and iconic (reduced) modelling of the actually involved physical processes and of the responses of physical bodies and systems to actual energy flow - a problem which is becoming dominant in all fields of the natural sciences. Accordingly, the theme of the CFCIO was "Modelling Problems in Crack Tip Mechanics", a well defined and limited subject, the scope of treatment of which can be as deep and as comprehensive as an in­ volved researcher wishes it to be.

The general objective of the Tenth Canadian Fracture Conference was to respond to progress in the engineering sciences - in particular with r- pect to rapidly developing new trends in the theory and methodology of researcr and designing - and to the resulting needs of practical engineering in the specific field of fracture mechanics and related areas of engineering mechanics. The basic underlying issue is the theory and practice of physical analytical and iconic (reduced) modelling of the actually involved physical processes and of the responses of physical bodies and systems to actual energy flow - a problem which is becoming dominant in all fields of the natural sciences. Accordingly, the theme of the CFCIO was "Modelling Problems in Crack Tip Mechanics", a well defined and limited subject, the scope of treatment of which can be as deep and as comprehensive as an in­ volved researcher wishes it to be.