Matching Items (3)
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- All Subjects: Tolerance (Engineering)
- All Subjects: Universities and colleges--Honors courses.
- Genre: Academic theses
- Creators: Henderson, Mark
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 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.
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
Description
Mostly, manufacturing tolerance charts are used these days for manufacturing tolerance transfer but these have the limitation of being one dimensional only. Some research has been undertaken for the three dimensional geometric tolerances but it is too theoretical and yet to be ready for operator level usage. In this research, a new three dimensional model for tolerance transfer in manufacturing process planning is presented that is user friendly in the sense that it is built upon the Coordinate Measuring Machine (CMM) readings that are readily available in any decent manufacturing facility. This model can take care of datum reference change between non orthogonal datums (squeezed datums), non-linearly oriented datums (twisted datums) etc. Graph theoretic approach based upon ACIS, C++ and MFC is laid out to facilitate its implementation for automation of the model. A totally new approach to determining dimensions and tolerances for the manufacturing process plan is also presented. Secondly, a new statistical model for the statistical tolerance analysis based upon joint probability distribution of the trivariate normal distributed variables is presented. 4-D probability Maps have been developed in which the probability value of a point in space is represented by the size of the marker and the associated color. Points inside the part map represent the pass percentage for parts manufactured. The effect of refinement with form and orientation tolerance is highlighted by calculating the change in pass percentage with the pass percentage for size tolerance only. Delaunay triangulation and ray tracing algorithms have been used to automate the process of identifying the points inside and outside the part map. Proof of concept software has been implemented to demonstrate this model and to determine pass percentages for various cases. The model is further extended to assemblies by employing convolution algorithms on two trivariate statistical distributions to arrive at the statistical distribution of the assembly. Map generated by using Minkowski Sum techniques on the individual part maps is superimposed on the probability point cloud resulting from convolution. Delaunay triangulation and ray tracing algorithms are employed to determine the assembleability percentages for the assembly.
ContributorsKhan, M Nadeem Shafi (Author) / Phelan, Patrick E (Thesis advisor) / Montgomery, Douglas C. (Committee member) / Farin, Gerald (Committee member) / Roberts, Chell (Committee member) / Henderson, Mark (Committee member) / Arizona State University (Publisher)
Created2011
Description
Honors colleges have offered an academically rigorous option for growing numbers of diverse students. This study took place at a large, public university that required undergraduate students to complete a thesis to graduate from the honors college. In 2017, 97% of students who began the honors thesis prior to senior year completed it. Thus, the aim of this study was to help more students begin the honors thesis process early.
Thesis Launch was a six-week intervention that was designed to provide support for students in the critical early steps of thesis work such as brainstorming topics, examining professors’ research interests, reaching out to professors, preparing for meetings with potential thesis committee members, and writing a thesis prospectus. Thesis Launch offered web-based resources, weekly emails and text message reminders, and was supplemented by in-person advising options.
A mixed methods action research study was conducted to examine: (a) students’ perceptions of barriers that prevented beginning thesis work; (b) self-efficacy towards thesis work; (c) how to scale the intervention using technology; and (d) whether participants began the thesis early. Quantitative data was collected via pre- and post-intervention surveys, journals, and prospectus submissions. Qualitative data came from student interviews, journals, and open-ended questions on the surveys.
Quantitative data showed that after students participated in Thesis Launch, they had higher self-efficacy to work with professors, perceived fewer barriers to thesis work, and greater proportions of students began thesis work early. The qualitative data were complementary and showed that participants overcame barriers to thesis initiation, built self-efficacy, preferred an online intervention, and began thesis work early. Findings also showed that a primarily technology-based intervention was preferred by students and showed promise for scaling to a larger audience.
Thesis Launch provided a framework for students to begin work on the honors thesis and have mastery experiences to build self-efficacy. Strategies that fostered “small wins” and reflective efforts also assisted in this aim. Participants accomplished tasks tied to thesis work and customized their personal thesis timelines based on work begun during Thesis Launch. Finally, a discussion of limitations, implications for practice and research, and personal reflection was included.
Thesis Launch was a six-week intervention that was designed to provide support for students in the critical early steps of thesis work such as brainstorming topics, examining professors’ research interests, reaching out to professors, preparing for meetings with potential thesis committee members, and writing a thesis prospectus. Thesis Launch offered web-based resources, weekly emails and text message reminders, and was supplemented by in-person advising options.
A mixed methods action research study was conducted to examine: (a) students’ perceptions of barriers that prevented beginning thesis work; (b) self-efficacy towards thesis work; (c) how to scale the intervention using technology; and (d) whether participants began the thesis early. Quantitative data was collected via pre- and post-intervention surveys, journals, and prospectus submissions. Qualitative data came from student interviews, journals, and open-ended questions on the surveys.
Quantitative data showed that after students participated in Thesis Launch, they had higher self-efficacy to work with professors, perceived fewer barriers to thesis work, and greater proportions of students began thesis work early. The qualitative data were complementary and showed that participants overcame barriers to thesis initiation, built self-efficacy, preferred an online intervention, and began thesis work early. Findings also showed that a primarily technology-based intervention was preferred by students and showed promise for scaling to a larger audience.
Thesis Launch provided a framework for students to begin work on the honors thesis and have mastery experiences to build self-efficacy. Strategies that fostered “small wins” and reflective efforts also assisted in this aim. Participants accomplished tasks tied to thesis work and customized their personal thesis timelines based on work begun during Thesis Launch. Finally, a discussion of limitations, implications for practice and research, and personal reflection was included.
ContributorsEardley, Trisha Lynn (Author) / Buss, Ray (Thesis advisor) / Henderson, Mark (Committee member) / Johnson, Melissa (Committee member) / Arizona State University (Publisher)
Created2019