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Reconciling the differences between tolerance specification and measurement methods

Description
Dimensional Metrology is the branch of science that determines length, angular, and geometric relationships within manufactured parts and compares them with required tolerances. The measurements can be made using either manual methods or sampled coordinate metrology (Coordinate measuring machines). Manual measurement methods have been in practice for a long time…

Dimensional Metrology is the branch of science that determines length, angular, and geometric relationships within manufactured parts and compares them with required tolerances. The measurements can be made using either manual methods or sampled coordinate metrology (Coordinate measuring machines). Manual measurement methods have been in practice for a long time and are well accepted in the industry, but are slow for the present day manufacturing. On the other hand CMMs are relatively fast, but these methods are not well established yet. The major problem that needs to be addressed is the type of feature fitting algorithm used for evaluating tolerances. In a CMM the use of different feature fitting algorithms on a feature gives different values, and there is no standard that describes the type of feature fitting algorithm to be used for a specific tolerance. Our research is focused on identifying the feature fitting algorithm that is best used for each type of tolerance. Each algorithm is identified as the one to best represent the interpretation of geometric control as defined by the ASME Y14.5 standard and on the manual methods used for the measurement of a specific tolerance type. Using these algorithms normative procedures for CMMs are proposed for verifying tolerances. The proposed normative procedures are implemented as software. Then the procedures are verified by comparing the results from software with that of manual measurements.

To aid this research a library of feature fitting algorithms is developed in parallel. The library consists of least squares, Chebyshev and one sided fits applied on the features of line, plane, circle and cylinder. The proposed normative procedures are useful for evaluating tolerances in CMMs. The results evaluated will be in accordance to the standard. The ambiguity in choosing the algorithms is prevented. The software developed can be used in quality control for inspection purposes.
ContributorsVemulapalli, Prabath (Author) / Shah, Jami J. (Thesis advisor) / Davidson, Joseph K. (Committee member) / Takahashi, Timothy (Committee member) / Arizona State University (Publisher)
Created2014
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Monitors-based measurement of sedentary behaviors and light physical activity in adults

Description
Having accurate measurements of sedentary behaviors is important to understand relationships between sedentary behaviors and health outcomes and to evaluate changes in interventions and health promotion programs designed to reduce sedentary behaviors. This dissertation included three projects that examined measurement properties of wearable monitors used to measure sedentary behaviors. Project…

Having accurate measurements of sedentary behaviors is important to understand relationships between sedentary behaviors and health outcomes and to evaluate changes in interventions and health promotion programs designed to reduce sedentary behaviors. This dissertation included three projects that examined measurement properties of wearable monitors used to measure sedentary behaviors. Project one examined the validity of three monitors: the ActiGraph GT3X+, activPAL™, and SenseWear 2. None of the monitors were equivalent with the criterion measure of oxygen uptake to estimate the energy cost of sedentary and light-intensity activities. The ActivPAL™ had the best accuracy as compared with the other monitors. In project two, the accuracy of ActiGraph GT3X+and GENEActiv cut-points used to assess sedentary behavior were compared with direct observation during free-living conditions. New vector magnitude cut-points also were developed to classify time spent in sedentary- and stationary behaviors during free-living conditions. The cut-points tested had modest overall accuracy to classify sedentary time as compared to direct observation. New ActiGraph 1-minute vector cut-points increased overall accuracy for classifying sedentary time. Project 3 examined the accuracy of the sedentary sphere by testing various arm elevation- and movement-count configurations using GENEActiv and ActiGraph GT3X+ data obtained during free-living conditions. None of the configurations were equivalent to the criterion measure of direct observation. The best configuration of the GENEActiv was: worn on the dominant wrist at 15 degrees below the horizontal plane with a cut-point <489 for each 15-second interval. The best configuration for the ActiGraph was: worn on the non-dominant wrist at 5° below the horizontal plane with a cut-point of <489 counts for each 15-second interval. Collectively, these findings indicate that the wearable monitors and methods examined in this study are limited in their ability to assess sedentary behaviors and light intensity physical activity. Additional research is needed to further understand the scope and limitations of wearable monitors and methods used to assess sedentary behaviors and light intensity physical activity.
ContributorsFlorez Pregonero, Argemiro Alberto (Author) / Ainsworth, Barbara E (Thesis advisor) / Buman, Matthew P (Committee member) / Hooker, Steven P (Committee member) / Keller, Colleen S (Committee member) / Swan, Pamela (Committee member) / Arizona State University (Publisher)
Created2017