Future Systems for Industrial Technology, Consumer Goods and Building

Practical considerations also include how simply a technique can be implemented in large-scale production, how fast it works, and how much it costs. Ultrasound, for instance, is a good method for inspecting parts without a great deal of complexity and cost, i.e. very quickly and economically. An ultrasound probe, positioned in contact with the surface of the material through an interposed layer of gel or oil, emits ultrasound pulses. The ultrasonic waves traverse the material, which may be plastic, metal or ceramic. The test object’s opposite surface reflects the sound waves, which are recorded by the probe as echoes of the original pulse. Small defects in the material, such as pores, cracks or dirt particles, interfere with the propagation of the sound waves and can therefore be detected.

An examination with a single probe is time-consuming, because it must scan the entire length and width of the component. Researchers therefore developed a sensor array: They combined 64 probes into a single unit that is positioned in contact with the component. By designing such a phased array as a 2x32 configuration or as an 8x8 configuration, they can adapt its shape to the geometry of the component. The array just needs to be positioned properly in order to measure the component more quickly. If the component’s dimensions are small enough, such electronic scanning can completely replace any mechanical handling.

This approach is so promising that work has been under way for some time to perfect test modules with 128 probes. Present plans envision 2x64 and 1x128 configurations. This method, however, only works for simple geometries. As an example, it is not suitable for threaded components, because such complex geometries create too many reflections of the ultrasound signal. The bottom line is that, even in the development stage, it pays to design a product that will lend itself to testing by this efficient ultrasound system later in the production phase. If this is not feasible other methods are used, such as computer tomography, although this is more complex and costly.