Procedure to Approximately Estimate the Uncertainty of Material Ratio Parameters due to Inhomogeneity of Surface Roughness

Roughness parameters that characterize contacting surfaces with regard to friction and wear are commonly stated without uncertainties, or with an uncertainty only taking into account a very limited amount of aspects such as repeatability of reproducibility (homogeneity) of the specimen. This makes it difficult to discriminate between different values of single roughness parameters. Therefore uncertainty assessment methods are required that take all relevant aspects into account. In the literature this is scarcely performed and examples specific for parameters used in friction and wear are not yet given. We propose a procedure to derive the uncertainty from a single profile employing a statistical method that is based on the statistical moments of the amplitude distribution and the autocorrelation length of the profile. To show the possibilities and the limitations of this method we compare the uncertainty derived from a single profile with that derived from a high statistics experiment.Comment: submitted to Meas. Sci. Technol., 12 figure

Scientific modeling of Optical 3D Measuring Devices based on GPU-accelerated Ray Tracing using the NVIDIA OptiX Engine

Scientific optical 3D modeling requires the possibility to implement highly flexible and customizable mathematical models as well as high computing power. However, established ray tracing software for optical design and modeling purposes often has limitations in terms of access to underlying mathematical models and the possibility of accelerating the mostly CPU-based computation. To address these limitations, we propose the use of NVIDIA's OptiX Ray Tracing Engine as a highly flexible and high-performing alternative. OptiX offers a highly customizable ray tracing framework with onboard GPU support for parallel computing, as well as access to optimized ray tracing algorithms for accelerated computation. To demonstrate the capabilities of our approach, a realistic focus variation instrument is modeled, describing optical instrument components (light sources, lenses, detector, etc.) as well as the measuring sample surface mathematically or as meshed files. Using this focus variation instrument model, exemplary virtual measurements of arbitrary and standardized sample surfaces are carried out, generating image stacks of more than 100 images and tracing more than 1E9 light rays per image. The performance and accuracy of the simulations are qualitatively evaluated, and virtually generated detector images are compared with images acquired by a respective physical measuring device.Comment: conferenc

Manufacturing of new roughness standards for the linearity of the vertical axis – Feasibility study and optimization

AbstractIn order to provide an alternative for the vertical axis calibration of stylus instruments which is usually performed based on step height standards, a new measurement standard geometry for the calibration of the linearity and research on its manufacturing is needed. For the manufacturing of these geometric measurement standards there is, according to the type of the measurement standard, a broad range of manufacturing processes that can be applied. New measurement standards for the roughness calibration were developed at the University of Kaiserslautern and an ultra-precision turning process was chosen for its manufacturing. The paper presents a feasibility study of the chosen manufacturing process. The aim of the investigations is to present the development of the standard and the qualification of the ultra-precision turning process for the manufacturing of calibration standards. An examination was performed in order to characterize the influences of different process parameters on the quality of the manufactured roughness standard

Alternative evaluation methods for roundness measurements

Requirements to roundness tolerances are a part of the geometrical product specifications. However, the definition for the roundness tolerance according to ISO 1101 considering radial deviations only is not sufficient to assure the functionality of many products. In addition, the form of roundness deviations along the circumference plays a significant rule for rotating machine components. Especially periodic deviations cause vibrations that lead to noise and wear. The Fourier analysis and the corresponding amplitude spectrum deliver information about the properties of the form derived from the magnitude of the different harmonics. This information presents a series of results depending on the harmonics. Therefore, a dedicated tolerance definition in most cases in from of a mathematical equation is used. The currently used tolerance definitions are not standardized and difficult to understand. Often, only one amplitude of the spectrum is significantly larger than the others are and effects functionality. In this case, an algorithm that detects the largest amplitude enables an easier tolerance definition

Kinematic simulation to investigate the influence of the cutting edge topography when ball end micro milling

During the ball end micro milling of material measures, the cutting edge topography is imaged on the machined workpiece. The influence of the chipping on the resulting surface quality is much more dominant than other kinematic effects. In this simulative study, a model is built that is able to predict the correlation between the cutting edge topography and the resulting workpiece topography. Thus, the mentioned correlation can be investigated without overlaying effects of material separation or measurement uncertainties, which are unavoidable in an experimental study. The model has been validated based on four artificial chippings

System identification and control parameter optimization for a stylus profiler with exchangeable cantilevers

Stylus instruments are widely used in production metrology due to their robustness. Interchangeable cantilevers allow a wide range of measuring tasks to be covered with one measuring device. When approaching the sample, the positioning of the stylus instrument tip relative to the measurement object has to be accomplished in a controlled way in order to prevent damages to the specimen and the stylus cantilever. This is achieved by a closed-loop control. We present a method for the objective description of the stylus cantilever dynamics with system-theoretical techniques and show a simple iterative approach to optimize closed-loop control parameters with boundary conditions