Recently, most manufacturers of servohydraulic materials test equipment have developed digital control systems. Digital systems have several advantages over the more mature analog controllers, in particular, the availability of features that allow more realistic tests to be carried out. Also, the ability to interface and communicate with computers easily makes it possible to perform not only realistic but also very complex control and data acquisition tasks. However, the software required to define these complex tasks and communicate with digital controllers is demanding.
The development of digital controllers has been made possible by the tremendous advances in microprocessor technology. These developments have also given rise to computers with everincreasing capabilities at lower costs. The software architectures controlling these computers have also given rise to sophisticated developments in order to make the computers easier to use. Most computers now have some form of graphical user interface (GUI). The downside of most GUIs is that the development of application software is much more complex. In addition, most of these operating systems are not ideally suited for real-time control that is absolutely vital for automated fatigue testing.
The difficulties associated with developing software for specific fatigue tests may be somewhat alleviated by the development of suitable tools within an integrated architecture that allow the scientist/engineer to define the required test in the form of functional blocks. This type of general-purpose software can then take the test definition provided by the scientist and convert it into a form suitable for the digital controller.
A suitable test description paradigm is proposed in terms of general requirements; a test-description language with elements such as objects, functional blocks, time, events, and data presentation; and some specific requirements for a software development environment. From this, general-purpose software for automated fatigue testing can be developed and used at a high level of abstraction. In addition, the paper reviews the development of an integrated general-purpose program for automated fatigue testing that implements the functional blocks required but without the full test description language. The paper also uses the example of testing offshore structural components using realistic sea-state sequences, such as WASH, to illustrate the problems that must be solved.
Some implications of this approach in future fatigue testing applications are also discussed in the paper.