Probabilistic structural analysis to quantify uncertainties associated with turbopump blades

A probabilistic study of turbopump blades has been in progress at NASA Lewis Research Center for over the last two years. The objectives of this study are to evaluate the effects of uncertainties in geometry and material properties on the structural response of the turbopump blades to evaluate the tolerance limits on the design. A methodology based on probabilistic approach was developed to quantify the effects of the random uncertainties. The results indicate that only the variations in geometry have significant effects

Observation of Berry's Phase in a Solid State Qubit

In quantum information science, the phase of a wavefunction plays an important role in encoding information. While most experiments in this field rely on dynamic effects to manipulate this information, an alternative approach is to use geometric phase, which has been argued to have potential fault tolerance. We demonstrate the controlled accumulation of a geometric phase, Berry's phase, in a superconducting qubit, manipulating the qubit geometrically using microwave radiation, and observing the accumulated phase in an interference experiment. We find excellent agreement with Berry's predictions, and also observe a geometry dependent contribution to dephasing.Comment: 5 pages, 4 figures, version with high resolution figures available at http://qudev.ethz.ch/content/science/PubsPapers.htm

Design descriptions to support reasoning about tolerances

This thesis is concerned with the use of Artificial Intelligence techniques to support human designers. The thesis argues that support for human designers can be improved by adopting an Al-based rather than a geometry-based approach to engineering design. Design Support Systems (DSSs) are proposed as an effective means of delivering this improved support. Representing and reasoning about tolerance statements in design is introduced as a valid area to test these claims. Tolerance statements describe the allowable variations in the geometry of a designed artefact. Two distinct, but related problems involving the use of toler¬ ance statements in design are tackled, namely: tolerance combination (including the way tolerance distributions combine), and tolerance allocation. The problem of tolerance combination (and distribution) involves determining the necessary consequences of the application of known tolerance statements to one or more designed artefact features. Tolerance allocation concerns the assignment of tol¬ erance statements during the design process. Solutions to this second problem are essential before manufactured instances of designed artefacts can be tested for compliance with design descriptions. The use of an experimental DSS, the Edinburgh Designer System (EDS), to solve design problems is illustrated. The implementation of techniques to im¬ prove the support of tolerance combination and tolerance allocation is described and where possible has been tested using EDS. The way that design is situated within the product creation process is investigated and the derivation of parts list information from an EDS design description is demonstrated. The thesis con¬ cludes that the Al-based approach can improve support for human designers, but that further research will be required to demonstrate the effective delivery of this support through DSSs

The Implications of Tolerance Optimization on Compressor Blade Design

Geometric variability increases performance variability and degrades the mean performance of turbomachinery compressor blades. These detrimental effects can be reduced by using robust optimization to design the blade geometry or by imposing stricter manufacturing tolerances. This paper presents a novel computational framework for optimizing compressor blade manufacturing tolerances, and incorporates this framework into existing robust geometry design frameworks. Optimizations of an exit guide vane geometry are conducted. The single-point optimal geometry is found to depend on the manufacturing tolerances due to a switch in the dominant loss mechanism. Multi-point geometry optimization avoids this switch so that the geometry and tolerance optimization problems are decoupled

A Process Planning Method and Data Format for Achieving Tolerances in Stereolithography

When building parts in a stereolithography apparatus (SLA), the user is faced with many decis!ons regarding the setting of process variables. To 'achieve a set of tolera~ces as closely as pOSSIble, relationships between part geometry, tolerances, and process v~nables ~ust be understood quantitatively. This paper presents a method for SLA process plannIng that IS based on response surface methodology and multi-objective optimization, where the response surfaces capture these relationships. These response surfaces were generated by extensive design-of-experiment studies for a variety of geometries. An annotated STL data format is also presented that enables the inclusion of tolerance and surface information in fatetted representations. Application of the data format and process planning method is illustrated on one part.Mechanical Engineerin

Ultrasonic Polishing

The ultrasonic polishing process makes use of the high-frequency (ultrasonic) vibrations of an abradable tool which automatically conforms to the work piece and an abrasive slurry to finish surfaces and edges on complex, highly detailed, close tolerance cavities in materials from beryllium copper to carbide. Applications range from critical deburring of guidance system components to removing EDM recast layers from aircraft engine components to polishing molds for forming carbide cutting tool inserts or injection molding plastics. A variety of materials including tool steels, carbides, and even ceramics can be successfully processed. Since the abradable tool automatically conforms to the work piece geometry, the ultrasonic finishing method described offers a number of important benefits in finishing components with complex geometries