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The acoustic behaviour of screws under applied load was examined to develop an in-process monitoring system for endangered screw connections. In order to apply load to a screw, a hydraulic tensile testing machine was designed. Signals occurring during tensile tests were digitally recorded and analyzed using an acoustic emission (AE) technique. An increase of the AE-rate at the yield limit and weaker AE-activity during plastic deformation were found. The AE-signals contained dominant frequencies in two narrow frequency ranges, at 590 kHz and 1010 kHz, which made it possible to distinguish between friction processes in the screw thread and abrupt dislocation processes under load. The significance of the results for in-process monitoring of screws is illustrated.

For the on-line measurement of stress and energy distributions inside ball mills, two types of self-contained, autonomous grinding balls with fully integrated piezo-electric sensors and data-processing electronics are developed and fabricated. The basic model is designed for batchwise experiments on ball mills, where data registered in electronic memories are read out through cable connections to a processing circuit. The improved model contains additional data modulation circuits with a VHF microtransmitter, allowing on-line data retrieval. For the purpose of circuit miniaturization, hybrid and surface mount techniques (SMT) have been utilized. The instrumented balls are identical in size, mass and surface characteristics to the normal grinding balls, with the minimum outer diameter being 40 mm. Systematic experiments have shown that they are fully applicable in a realistic grinding environment where grinding media are presented. In addition to ball mill applications, the developed integration and measuring technique is generally suited for on-line data registration on free-moving objects or other industrial applications where accessibility of the measurand is insufficient.

An energy converting system that can function for years without maintenance is required for the drive of a left ventricular assist device (LVAD). To meet the requirements of safety, the energy converter should have a simple design with few moving elements. The design applied herein has only one moving part and thus has greater inherent safety than competing systems. The only moving part is the rotor unit, comprised of the impeller of a centrifugal pump, the rotor of an electric motor, and the rotor of an electric axial actuator. A reversal of flow of the transmitter fluid can be achieved with an axial shift of this rotor unit. This fluid acts on the outer surface of a blood chamber and enables it to draw in blood and to expel it. Valves direct the flow of blood. The energy converter performs a flow of 12 L/min at a motor speed of 6, 000 rpm against a pressure head of 115 mm Hg according to an output of the pulsatile blood pump of 5 L/min.

We examined the acoustic behaviour of screws under applied load to develop an in-process monitoring system for endangered screw connections. To apply load to a screw, a hydraulic tensile testing machine was designed. Signals occurring during tensile tests were digitally recorded and analysed using acoustic emission (AE) technique. We established an increase of fhe AE- rate at the yield limit and weaker A€-activity during the plastic deformation. The A€-signals contained dominant frequencies in two narrow frequency ranges, namely at 590 kHz and 1010 kHz and therefore we were capable of distinguishing between friction processes in the screw thread and abrupt dislocation processes under load. The significance of the results for in-process moniforlng of screws is illustrated. I. INTRODUCTION Carrying through a special technique for in-process re- pairing of a leaky flange in a pipe line a special sub- stance is pressed from the outside into the flange. A higher pressure is necessary than exists inside of the pipeline, so that the flange screws or flange bolts are more stressed than usual. Generalising this special problem a method for in-process monitoring of screws being loaded in a critical range is needed. We decided to use the phenomen of acoustic emission, i.e. the emission of sound waves (mostly in the ultrasonic range) by a solid as a response to mechanical strength, expecting that structural changes in the condition of a screw express themselves as acoustic signals. Several authors report examinations of steel specimens during tensile tests according to the AE behaviour, especially the AE-rate (l-81. They established an increase of the AE-rate in the region of the elastic limit, with an amplitude strongly depending on the material and some other parameters. But there are other studies, e.g. (9), in which the AE-rate and the elastic limit could not be brought into connection. In this paper we present the results of our experiments with common industrial screws of German standard DIN 931 studying the AE- rate as well as the frequency distribution depending on the load condition. Especially, we were taking into consideration the applicability of our results for the in- process monitoring of screws.

An economical approach to integrated active RC filter design is described. Complex filter networks are broken down into a small family of cascadable second-order filter building blocks consisting of tantalum thin-film RC networks and semiconductor, integrated, operational amplifiers. The same building blocks are used for any desired filter configuration such as low-pass, high-pass, or bandpass filters, all-pass networks, notch filters, etc. Therefore, they possess the uniformity necessary for high-production quantities and batch processing, and consequently, benefit from the economical advantages that go with these methods.