Konzepte für die Verschleißmessung von Seilen mit Sensorfäden

Within the scope of this doctoral thesis methods and concepts were examined detecting the wear of textile ropes. Ropes are employed in a variety of applications such as fixation of goods during transportation, on ships, and for sports such as climbing and sailing. To ensure the safety of ropes they are usually inspected by eye, but there is no clear criterion when a rope needs to be replaced. This inspection is expensive and time consuming by expert staff. A sensor system must not causes additional damage in a rope. Therefore, the only possibility was to use sensors which were braided together with other yarns in the rope. Eventually silver coated yarns were employed whose resistance is increased by straining and wear. Because of the very different application terms of ropes, only one concept could not satisfy all demands. Instead, different concepts were suitable for different cases. In very thin ropes, as for example parachute tethers, only a single sensor yarn was braided into the tethers. Very long and thick ropes required several sensor yarns and also the possibility to detect multiple breaks of a sensor yarn. Ropes are used predominantly outdoors. Therefore, it was important to know the behaviour of the sensor yarns as a function of temperature and humidity. The experiments showed that the sensor yarn changed its electric resistance permanently by repeated temperature cycles. Also air humidity affects the electric resistance. Therefore, no reliable information about the wear of a rope can be obtained from the measurement of the electrical resistance of a sensor yarn. Hence, it was concluded that the only reliable way of wear measurement is to employ sensor yarns which break at a given load. A break can be also detected a long time afterwards by an easy measurement of the electric resistance of the sensor yarn. It was found out that the strain of the rope at which the sensor yarn breaks is a function of the position where the sensor yarn was braided into the rope. Beside the measurement of the electrical resistance by contacts at both ends of a rope other methods were examined as for example measuring of the run time of an electric pulse or acoustic signal along the sensor yarn. In addition, wireless reading out textile transponder coils braided into ropes was investigated. For the fabrication of textile transponder coils a fully isolated contact between electrically conducting yarns was required. For these contacts a process was developed which allows generating such contacts by ultrasonic welding in less than 1 s. Such electric contacts can be integrated into the braiding process