TABLE OF CONTENTS As pointed out in Chapter 2, fatigue of welded joints is a quite complex problem. All theories and models have to be verified and corroborated by experimental data. As for the S-N model, this model is nothing else but curve-fitting between applied stress range and experimental lifetime data. A fracture mechanics model has to be based on experimental data to determine appropriate values for the parameters involved. When these parameters have been determined, the model can predict crack growth and critical crack size for similar material and environments. The only theory involved is the development of the stress intensity factor concept. In fact, all models discussed in this book are semi-empirical models. The number of cycles to crack initiation, crack path history, and final fatigue life must be measured for typical steel materials, joint types, and loading conditions. Model parameters must be chosen to fit the experimental facts. In this chapter a brief overview of the common testing techniques is given. Finally, some often-employed statistical methods used to deal with the scatter in experimental results are also described.
The objective of this chapter is that the reader learns how to plan and carry out experimental work primarily related to the S-N model and the fracture mechanics model. The reader will also gain some knowledge on measurements techniques and how to analyze the results. Hence, life testing and crack growth testing will be shown in some details. More details are found in Ref [1].
