Modellierung und experimentelle Untersuchung von materialintegrierten Sensoren

The thesis is divided in a theoretical and an experimental part. In the theoretical part investigations on the foreign body effect of a sensor in a material in terms of mechanical, thermal and thermo-mechanical loads are done. The second part is based on experiments on the foreign body effect to prove the results of the first part. Therefore temperature and force sensors are integrated in epoxy resin, aluminum and steel

Modeling and experimental study of material integrated sensors

The thesis is divided in a theoretical and an experimental part. In the theoretical part investigations on the foreign body effect of a sensor in a material in terms of mechanical, thermal and thermo-mechanical loads are done. The second part is based on experiments on the foreign body effect to prove the results of the first part. Therefore temperature and force sensors are integrated in epoxy resin, aluminum and steel

Printed Sensors for Material Integrated Sensing: Functionalization of Semi-Finished Parts

A new and innovative approach is presented to integrate sensors in materials and set up “smart materials”. Semi-finished parts are functionalized by printed sensors and printed interconnects. These functionalized parts are then further processed to components. This is a new and simple approach to integrate sensors in a material. Two examples of printed sensors and the process of integration are presented. One is a printed sensor on carbon weaves, integrated in carbon fiber reinforced plastic. The other one is a sensor structure printed on an aluminum sheet and integrated during high pressure die casting. Besides the benefits of this technological approach, challenges are focused in the paper as well

Surface Integrated Printed Interdigital Structure for Process Monitoring the Curing of an Adhesive Joint

We present a printable interdigital structure, integrated into the surface of a component, to monitor the curing of two adhesively joint components during the fabrication process. In the factory of the future there is a need of new sensor concepts beside the information technological infrastructure. Monitoring of the fabrication enables automated control of the process which improves the quality of adhesive joints. In addition, the cost can be reduced by individually adapted curing times. We demonstrate that cure monitoring with the printed interdigital structure is possible. Two adhesives, a fast and a slow curing one, are analyzed to show the high potential of this process monitoring method

Experimental and Numerical Investigations in Shallow Cut Grinding by Workpiece Integrated Infrared Thermopile Array

The purpose of our study is to investigate the heat distribution and the occurring temperatures during grinding. Therefore, we did both experimental and numerical investigations. In the first part, we present the integration of an infrared thermopile array in a steel workpiece. Experiments are done by acquiring data from the thermopile array during grinding of a groove in a workpiece made of steel. In the second part, we present numerical investigations in the grinding process to further understand the thermal characteristic during grinding. Finally, we conclude our work. Increasing the feed speed leads to two things: higher heat flux densities in the workpiece and higher temperature gradients in the material

Low-Cost Thin and Flexible Screen-Printed Pressure Sensor

Commercial pressure sensors are often fabricated using well-established silicon micromachining technologies. The thickness and stiffness of silicon-based sensors make them in most cases unsuitable for the integration into materials and surfaces. We present a flexible pressure sensor fabricated by printing technology. Therefore, an intrinsically pressure sensitive ink is screen printed on interdigital electrodes on a thin and flexible foil substrate. The sensor shows sufficient sensitivity and is applicable in a wide pressure range from 0 to 2 MPa. The sensor can completely be fabricated using a low-cost screen printing process. It is very thin and flexible, making it possible to be applied on curved surfaces or to be integrated into materials in a minimal invasive way

Sensor integration in castings made of aluminum - new approaches for direct sensor integration in aluminum high pressure die casting

The use of sensors for detection, measurement and evaluation of mechanical and thermal loads is well known and essential for the implementation of »Structural Health Monitoring« (SHM). For this, sensors are mainly used for condition monitoring of mechanical loads and their impact to the castings state, which is a decisive advantage for safety-related components. The use of sensors on the surface of metallic components, in particular of cast metal components made of aluminum, is still limited to the use of strain gauges. They are usually applied on the surface of the cast metal components and get fixed by adhesives. The idea is, to integrate the sensors directly during the aluminum casting process. Since integrated sensors are naturally protected against chemical and mechanical influences, furthermore the load can be measured directly at the point of interest inside the component. Measurement data can be recorded and provide a good data basis for future calculations and dimensioning of components, which is known as »Data Mining« or »Industrial Data Space«. New technology and material combinations, which allow the fabrication of sensors capable of withstanding force and temperature during the integration process in aluminum casting, are investigated. In this paper, the design and fabrication of a strain gauge printed on an aluminum sheet is shown. These sensor sheets get integrated in aluminum during high pressure die casting (HPDC) in a way that a specimen is build up. The specimen is characterized in a fatigue bending test and the sensor data was read permanently during this test. It is shown that the new approach with printed thick film sensors on aluminum substrate sheets works properly to withstand the heavy thermal conditions during high pressure die casting. The fabricated sensor is able to sense the mechanical tiredness and detects the fatigue of the metal matrix. This a first step to use such material integrated sensors in structural health monitoring applications

Boundary Layer Separation and Reattachment Detection on Airfoils by Thermal Flow Sensors

A sensor concept for detection of boundary layer separation (flow separation, stall) and reattachment on airfoils is introduced in this paper. Boundary layer separation and reattachment are phenomena of fluid mechanics showing characteristics of extinction and even inversion of the flow velocity on an overflowed surface. The flow sensor used in this work is able to measure the flow velocity in terms of direction and quantity at the sensor’s position and expected to determine those specific flow conditions. Therefore, an array of thermal flow sensors has been integrated (flush-mounted) on an airfoil and placed in a wind tunnel for measurement. Sensor signals have been recorded at different wind speeds and angles of attack for different positions on the airfoil. The sensors used here are based on the change of temperature distribution on a membrane (calorimetric principle). Thermopiles are used as temperature sensors in this approach offering a baseline free sensor signal, which is favorable for measurements at zero flow. Measurement results show clear separation points (zero flow) and even negative flow values (back flow) for all sensor positions. In addition to standard silicon-based flow sensors, a polymer-based flexible approach has been tested showing similar results