No abstract

During the initial stages of iterative design process, a quick CAE (Computer-aided Engineering) analysis of the CAD (Computer-aided Design) models is needed. To reduce the computational resources and time needed for such analysis, the models are often simplified by removing the irrelevant details and are abstracted by reducing the dimension, wherever appropriate. Thin-walled parts, such as sheet metal parts are often abstracted to a set of surfaces lying midway, called mid-surface. The mid-surface is expected to mimic the shape of the original solid, both geometrically and topologically. Widely-used methods of accessing the quality of the mid-surface are geometric. Hausdorff distance from the midsurface its original solid is computed to find the gaps and medial-ness. Accuracy of such methods depends on the sampling as well as on the complexity of the surface representation, making them computationally intensive and error-prone.This paper provides a topological method for verification, which is computationally simple and robust. A novel topological transformation relationship has been derived between a sheet metal part (solid) to its mid-surface (surface), in both directions (solid-to-surface and surface-to-solid) which can be used to compare the predicted vs actual entities. Simple as well as practical shapes have been tested to prove the efficacy of the newly-derived formulation.

Blade is the critical and extensively used component of aero-engine, which machining quality directly affects engine performance. Due to its flexibility, laser solid forming (LSF) from powders is widely used to synthesis novel materials, build three-dimensional parts, repair damage part and form surface coating in advanced manufacturing. To repair damaged parts or form surface coating, especially for aero-engine free-form surface blade, process of numerical control or robotic LSF is applied in industry. Nevertheless, on account of the complex geometry of the free-form surface, it's quite a challenge to generate proper laser beam paths according to the process requirements of LSF. To address this problem, a path generation method based on the differential geometry is presented. The generated paths can ensure the overlap requirements between deposited tracks as well as paths shifts between adjacent layers. The proposed method has been applied to two examples to verify their validity, and there exists a great potential for the applications in aeroengine manufacturing industry, especially in the LSF repair or surface coating of free-form surface blade.