Surrogate-Based Optimization Using an Open-Source Framework: The Bulbous Bow Shape Optimization Case

Shape optimization is a very time-consuming and expensive task, especially if experimental tests need to be performed. To overcome the challenges of geometry optimization, the industry is increasingly relying on numerical simulations. These kinds of problems typically involve the interaction of three main applications: a solid modeler, a multi-physics solver, and an optimizer. In this manuscript, we present a shape optimization work-flow entirely based on open-source tools; it is fault tolerant and software agnostic, allows for asynchronous simulations, and has a high degree of automation. To demonstrate the usability and flexibility of the proposed methodology, we tested it in a practical case related to the naval industry, where we aimed at optimizing the shape of a bulbous bow in order to minimize the hydrodynamic resistance. As design variables, we considered the protrusion and immersion of the bulbous bow, and we used surrogate-based optimization. From the results presented, a non-negligible resistance reduction is obtainable using the proposed work-flow and optimization strategy.

Virtual Model of Gear Shaping—Part I: Kinematics, Cutter–Workpiece Engagement, and Cutting Forces

Gear shaping is, currently, the most prominent method for machining internal gears, which are a major component in planetary gearboxes. However, there are few reported studies on the mechanics of the process. This paper presents a comprehensive model of gear shaping that includes the kinematics, cutter–workpiece engagement (CWE), and cutting forces. To predict the cutting forces, the CWE is calculated at discrete time steps using a tridexel discrete solid modeler. From the CWE in tridexel form, the two-dimensional (2D) chip geometry is reconstructed using Delaunay triangulation (DT) and alpha shape reconstruction. This in turn is used to determine the undeformed chip geometry along the cutting edge. The cutting edge is discretized into nodes with varying cutting force directions (tangential, feed, and radial), inclination angles, and rake angles. If engaged in the cut during a particular time-step, each node contributes an incremental force vector calculated with the oblique cutting force model. Using a three-axis dynamometer on a Liebherr LSE500 gear shaping machine tool, the cutting force prediction algorithm was experimentally verified on a variety of processes and gears, which included an internal spur gear, external spur gear, and external helical gear. The simulated and measured force profiles correlate closely with about 3–10% RMS error.

A Design System for Six-Bar Linkages Integrated With a Solid Modeler

This paper presents a design system for planar and spherical six-bar linkages, which is integrated with a solid modeler. The user specifies a backbone 3R chain in five task configurations in the sketch mode of the solid modeler and executes the design system. Two RR constraints are computed, which constrain the 3R chain to a single degree-of-freedom six-bar linkage. There are six ways that these constraints can be added to the 3R serial chain to yield as many as 63 different linkages in case of planar six-bar linkages and 165 in case of spherical six-bar linkages. The performance of each candidate is analyzed, and those that meet the required task are presented to the designer for selection. The design algorithm is run iteratively with random variations applied to the task configurations within user-specified tolerance zones, to increase the number of candidate designs. The output is a solid model of the six-bar linkage. Examples are presented, which demonstrate the effectiveness of this strategy for both planar and spherical linkages.

Assessment of the Effects of Anisotropy in TRIGA Based on 3D-AGENT Methodology

The neutronics characterization of The University of Utah TRIGA reactor core focused at evaluating the effects of anisotropic neutron scattering is based on 3D AGENT methodology. The AGENT methodology is based on method of characteristics with exact modeling of geometry and material distribution in the reactor cores. This feature is unique to deterministic codes worldwide and is based on the originally developed R-function solid modeler. The anisotropic correction to neutron transport in 3D hexagonal and square reactors as implemented in AGENT, provides highly accurate solution with no limitations to core configuration or the degree of anisotropic scattering terms. In testing this new methodology on TRIGA type reactors, we conclude that the AGENT deterministic solution with P2 anisotropic scattering approximation provides fully comparable solution to the MCNP5 but with 93% CPU-time reduction.

Automatic Process Intermediate Model Generation in Process Planning

In process planning of machined part, three-dimensional process intermediate models are necessary for process design, documentation, and downstream applications including clamping design, NC programing, and process analysis. An automatic process intermediate model generation method is proposed in this paper for machined part represented in B-Rep solid model. Machining features are recognized and classified according to process type. Process plan is expressed in terms of machining features and feature surface modification operations in solid model. Local modification operations are applied to part model to move, replace or remove feature surface resembling machining process. Process intermediate models are generated automatically in a batch manner by applying geometry and topology modification operations directly on B-Rep model for each machining operation. The proposed algorithm is implemented in a CAPP tool developed in solid modeler ACIS.

Machining Feature Modeling and Process Intermediate Model Generation in Process Planning

In process planning of machined part, machining feature recognition and representation, feature-based generative process planning, and the process intermediate model generation are the key issues. While many research results have been achieved in recent years, the complete modeling of machining features, process operations, and the 3D models in process planning are still need further research to make the techniques to be applied in practical CAPP systems. In this paper, a machining feature definition and classification method is proposed for the purpose of process planning based on 3D model. Machining features are defined as the surfaces formed by a serious of machining operation. The classification scheme of machining features is proposed for the purpose of feature recognition, feature-based machining operations reasoning, and knowledge representation. Recognized from B-Rep representation of design model, machining features are represented by adjacent graph and organized by feature relations. The machining process plan is modeled as operations and steps, which is the combination and sequencing of machining feature’s process steps. The process intermediate models (PIM) are important for process documentation, analysis and NC programming. An automatic PIM generation approach is proposed using local operations directly on B-Rep model. The proposed data structure and algorithm is adopted in the development of CAPP tool on solid modeler ACIS/HOOPS.

Computing Geometric Transformations of Irregular Teeth Sets for Orthodontic Treatment

This research evaluates the feasibility of assisting orthodontists to treat irregularities in teeth by computing the geometric transformations to move each tooth to its ideal position. The intent is to help orthodontists craft a precise and specific treatment plan for each patient. The inputs for finding the transformations are the patient’s teeth mold and dental arch templates. A 3D laser scanner is used to generate a point cloud data representation of the patient’s teeth mold. A commercial solid modeler is used to construct a non-uniform rational B-spline surface from this point cloud. Transformations are then computed by establishing a multiple scan registration, matching the axis of the patient’s teeth model and dental arch templates, and computation of initial and final positions of the teeth. The steps in the process and the algorithms developed were implemented in the scripting language of the solid modeler. Details of the algorithms are provided, and a case study is presented to demonstrate the process.