Scattered light sensors are optical sensors commonly used in industrial applications. They are particularly well suited to characterizing surface roughness. In contrast to most geometric measuring devices, a scattered light sensor measures reflection angles of surfaces according to the principle of the so-called mirror facet model. Surfaces can be evaluated based on the statistical distribution of the surface angles, meaning the gradients. To better understand how the sensor behaves, it is helpful to create a virtual model. Ray-tracing methods are just as conceivable as purely mathematical methods based on convolution. The mathematical description is especially interesting because it promotes fundamental comprehension of angle-resolved scattered light measurement technology and requires significantly less computation time than ray-tracing algorithms. Simplified and idealized assumptions are accepted. To reduce the effort required to simulate the sensor, an attempt was made to implement an idealized mathematical model using Matlab® to be able to quickly generate information on scattered light distribution without excessive effort. Studies were conducted to determine the extent to which the results of modeling correspond to the transfer characteristics of a virtual Zemax sensor, on the one hand, and with the measurement results of the actual scattered light sensor, on the other hand.
Abstract. The angle-resolved scattered light sensor OS500 is an optical measuring device that is becoming more and more frequently used in industrial applications and for the characterization of surfaces in general as well as for measuring roughness and shape. The angle-resolved measurement principle allows the statistical distribution of the gradients of a surface, resulting from the reflectance of the light at the flank angles of the areas examined, to be measured and consequently enables the geometric surface texture to be evaluated. Thus the topography of surfaces is not measured; instead the gradients are evaluated. Since the scattered light sensor measures angles and not distances, the sensor is immune to out-of-plane vibrations in the direction of measurement. Another distinct characteristic of the scattered light sensor is the high degree of sensor dynamics, which when combined with the statistical analysis of the surface angles, allows even the finest changes in the surface structure to be detected. Accordingly, it makes sense to use the sensor to monitor processes in which the surfaces and their structures change only slightly during the manufacturing process. One such process is so-called vibratory finishing. This process and several other manufacturing processes geared towards sustainable manufacturing methods are being examined by the "Department of Mechanical and Aerospace Engineering" at the University of California, Davis (CA, USA). On the basis of a ray tracing model, simulations calculations, meaning only virtual measurements, will demonstrate the suitability of the sensor for monitoring manufacturing.
Processing of long-fibre reinforced thermoplastics with a discontinuous reinforcement of long glass fibres, especially by direct-processing, leads to inhomogeneous and anisotropic properties. Because of this, locally resolved characterisation of the material properties is necessary. Non-contact testing methods are required to derive these material properties. Locally resolving hysteresis measurement, full-field strain measurement techniques and thermoelastic stress analysis (TSA) are applied to an incremental step test and to a fatigue test. It is shown that there is good correspondence between the local TSA-signals and the locally measured values of the major strain. This correlation is valid not only for lower linear elastic load levels, but also up to nonlinear-viscoelastic levels. A model is presented to describe the correlation between the TSA-signal and the measured major strain.
In thermoelastic stress analysis (TSA) the temperature change induced in a solid material as a result of the thermoelastic effect is measured with an infrared detector. Common infrared detectors used in TSA have a nonlinear signal to temperature relation. If a measurement is calibrated with a calibration constant determined previously at a specimen with a different absolute temperature, as well as if the measured surface has a non-uniform absolute temperature, the sensors' nonlinear response will cause significant errors. The thermoelastic signal therefore has to be corrected by the amount of signal change caused by the sensors' nonlinear response. This can be done by applying a temperature correction term to the thermoelastic signal S. As the absolute temperature is necessary to calculate the temperature correction term the thermal signal S DC has to be calibrated against temperature. It was reported that the temperature correction term depends on the system settings applied when a measurement is performed, more precisely on the electronic iris. In this work, the thermoelastic signal is corrected by a direct calibration of the sensors' thermal signal S DC . Therefore the sensors' absolute temperature to signal relation is determined with respect to the sensors' exposure time (ET). Based on the found thermal signal to temperature relation, a formulation is given which shows that the uncalibrated thermal signal and the thermoelastic signal are linearly related and that the slope of this linear relation is independent of the camera settings applied when the measurement is performed. This linearity is used for a thermal correction of thermoelastic data calibrated against stress. To calibrate the thermoelastic signal against the load-induced temperature change the found thermal signal to temperature relation is implemented in the DeltaVision calibration file. The results of the thermoelastic signal calibrated against temperature are compared with a calibration against the physical properties of the measured material.
Due to an excellent ratio of high strength and low density, Ti-6Al-4V is suitable for many industrial applications, especially in the aerospace industry. However, Ti-6Al-4V is also characterized by a very low thermal conductivity and high chemical reactivity which is why the titanium alloy is considered to be a hard-to-cut material. Machining Ti-6Al-4V leads to high cutting temperatures, which leads to a rapidly progressing thermo-chemical induced tool wear. To reduce the thermal load and to enhance the cutting performance, suitable cooling strategies are a necessity. A novel, highly efficient cooling approach is to apply sub-zero metalworking fluids (MWF) at liquid state but at supply temperatures well below 0 °C. These sub-zero MWF inhibit high cooling effects due to their low supply temperature in superposition with a beneficial wetting behavior. In this work, the application of a sub-zero cooling strategy is investigated when milling Ti-6Al-4V. The influence of both down milling and up milling is investigated under a systematic variation of the cutting speed and feed per tooth. For comparison, the experiments are also conducted using a cryogenic CO2 cooling. The performance of both cooling strategies in dependence of the milling process is described on the basis of the occurring forces, the resulting tool wear, and the surface quality achieved. The results show that the sub-zero cooling can successfully improve the machinability of Ti-6Al-4V even at elevated cutting parameters and unfavorable cutting conditions. As a result, sub-zero milling clearly outperforms the cryogenic CO2 cooling, since less tool wear and an overall lower surface roughness are observed. Consequently, when using a sub-zero cooling strategy, higher metal removal rates, longer tool life, and better surface qualities are achievable.
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