Using measurements and testing to support analyses of welded structures exposed to fatigue

New Handbook

The purpose of this handbook is to show how theoretical calculations, together with measurements and rig testing can be utilized for designing more cost-efficient products.

In December 2010, a team of experts within the areas mentioned above, met to discuss how knowledge can be transferred between the different professional spheres. It was decided to start a working group to create a handbook usable for calculation engineers, measurement engineers and testing engineers.


The main objective should be to create a better understanding between these groups of engineers. 


The working group met 4-5 times a year to discuss the content of the handbook and the material produced.

The daily work of a mechanical designer is becoming more and more fragmented and complex. The areas he/she must cover is vast, and it may be difficult to deepen the knowledge in the many specialized fields and at the same time keep up with tight product development schedules.

Therefore, during the years, the mechanical designer´s profession has been split into several fields, each having specialized engineers. This handbook will cover the following:

  • Calculation Engineers (able to predict the future strength, durability and functionality of a structure).

  • Measuring Engineers (collects and present input data from the environment the product will experience in service or at a test site).

  • Test Engineers (making physical tests of components and whole structures).

A Calculation Engineer is familiar with material behavior in different aspects. In this handbook we will concentrate on fatigue assessment of welded steel structures.

The Measuring Engineer is highly specialized in all kind of measuring equipment and has a deep knowledge in areas like electricity and measuring gages.

The Test Engineer is also specialized, but in areas like test equipment, hydraulics and stress and strength.

Finally, the Mechanical Designer has an overall responsibility for the structure, also involving functionality, cost, fabrication, purchasing and so forth.

It is essential for these four different types of engineers to understand each other and the different challenges they meet.


This handbook is written to show ways to use the combined knowledge and methods in the most effective way.

The first chapter covers the most basic areas regarding fatigue strength of welded components.

In Chapter 2, the different theoretical analysis methods for assessing fatigue strength of welded components are displayed, compared and commented.

The function of different measuring equipment is explained in Chapter 3, together with tips and practical advices how to use the equipment.

The different ways of handling measured data, load cycle counting  methods and how to design a load spectrum is explained in Chapter 4.

Chapter 5 gives practical advices on how to plan and conduct measurements in different situations.

How the measured data can be used as input for stress and strength analyses is suggested in Chapter 6.

If, instead of measured data, the input data is in the form of MultiBody Simulations (MBS) or Power Spectral  Density (PSD) is covered in Chapter 7.

In Chapter 8, advices can be found how to test welded joints to define “joint classes” (FAT-values) according to different design standards.

In Chapter 9, suggestions are given on how to perform rig tests of components and entire structures.

A comprehensive example, showing the benefits from using both theoretical analyses, measuring and testing is presented in Chapter 10 through Chapter 13.

Chapter 14 is an appendix with references and an index.

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