Quality requirements of welded joints depend on the form of application, e.g. in the space or fly industry weld errors are not allowed. [1] Science try to gets good quality welds. There are many scientific articles describing the weld test, e.g. hardness, [2] [3] [4] tensile tests. [3] The weld structure can be examined by optical microscopy [3] [4] [5] and scanning electron microscopy. [6] [4] [5] [3] The computer finite element method (FEM) is used to predict the shape of the flash and interface and others, not only for rotary friction welding (RFW), [7] but also for friction stir welding (FSW), [8] [9] linear friction welding (LFW), [10] FRIEX, [11] and others. Temperature measurements are also carried out for scientific purposes e.g. by use thermocouples [4] [5] or sometimes thermography, [7] [5] mentions about measurements are generally found in research materials and journals.
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