bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Investigation Into the Role of Mean Flame Stabilization on the Combustion Dynamics of High-Hydrogen Fuels in a Turbulent Combustor
Authors: Baraiya Nikhil A. , Ramanan Vikram , Baladandayuthapani N. , Vegad Chetankumar S. , Chakravarthy S. R.
Published: February 2021

A bluff-body turbulent combustor is mapped for its thermo-acoustic stability across variation in airflow rate, nondimensionalized as the Reynolds number (Re) and fuel composition. The combustor stability is evaluated for three fuels, namely, pure hydrogen (PH), synthesis natural gas (SNG), and syngas (SG). The combustion dynamics display markedly different behavior across the fuels, in the extent of the unstable region, as well as the observed dominant Eigenvalues. At low Re, SNG displays stable combustion, while SG exhibits high amplitude oscillations at the fundamental duct acoustic mode. As the Re is increased, SNG displays very high amplitude oscillations at the duct acoustic mode, while SG exhibit relatively low amplitude oscillations at the third harmonic. In the case of PH, high amplitude oscillations observed at higher Re at the first harmonic. These peculiarities are investigated in light of the role of mean flame stabilization. The combustion dynamics of the fuels is influenced by the global equivalence ratio, as well as the jet momentum ratio. These effects significantly demarcate the dynamics of SNG and SG combustion. This is seen manifested in the mean flame structure of flame at high amplitude oscillations, whereby result in SNG flame to be present in the wake, while the SG flame resides in the shear layer. The driving by the flame because of their mean stabilization is quantified by a spatial Rayleigh index. It confirms the presence of large driving regions for SNG compared to that of SG, results in the observed differences in amplitude of the oscillations.
Measurement Drift in 3-Hole Yaw Pressure Probes From 5µm Sand Fouling at 1050 °C
Authors: Turner Edward J. , Bogdan Matthew F. , O’Connell Tyler M. , Ng Wing F. , Lowe Kevin T. , Crook Loren , Stevenson Richard , Roberts James
Published: February 2021

The present paper focuses on the resilience of 3-hole pressure probes to hot sand fouling in turbomachinery environments. These probes are utilized inside jet engine hot sections for diagnostics and flow characterization. Ingestion of sand and other particulates pose a significant risk to hot section components and measurement devices in gas turbine engines. In this study, wedge, cylindrical, and trapezoidal probes were exposed to hot section turbine aerothermal conditions of 1050 °C and 65–70 m/s flow velocity and fouled with 0–5 µm Arizona Road Dust (ARD). Sand accumulated more rapidly on the surface of the trapezoidal and cylindrical probe geometries than on the surface of the wedge probe geometry. Probe calibrations following sand fouling were performed in an ambient temperature, open air, calibration jet at Mach 0.3 and 0.5. Calibration curves using nondimensional coefficients were used to assess probe error in yaw angle due to sand fouling. Probe error was based on each probe’s ability to accurately measure flow direction over a flow angle range of [−10 deg, 10 deg]. On average, the probes displayed greater error at Mach 0.5 than Mach 0.3. The wedge probe performed the best after sand fouling and displayed a maximum error of less than ±2 deg in yaw angle. In contrast, the cylindrical probe performed the worst after sand fouling and displayed maximum errors of more than ±8 deg in yaw angle. Transient response did not change notably with sand fouling.
Barriers for Industrial Sensor Integration Design—An Exploratory Interview Study
Authors: Juul-Nyholm Herle Bagh , Ebro Martin , Eifler Tobias
Published: February 2021

The transition to Industry 4.0 poses new challenges for sensor integration design. The foundation of any intelligent system is the data, and the data quality depends largely on the integration of the sensor generating it. In this study, the barriers for robust sensor system design are explored through an interview study among practitioners from different industrial contexts. The aim is to explore potential challenges within different contexts and suggest possible directions for research within the field of sensor integration design. Beyond the question of new sensing technologies, the study highlights an increasing challenge of physical integration tasks and illustrates the varying requirements for development support in different industry sectors.
An Investigation in the Numerical Approach to Solve the Heat Transfer Phenomenon in Gas Turbine
Authors: Kumar Sourabh , Amano Ryoichi S.
Published: February 2021

The gas turbine engine's extreme conditions need a robust design to produce efficient energy and for reliable operation. Flow and thermal analysis are essential for complex aerodynamic and thermodynamic interaction during turbine performance. There is a need to understand and predict the temperature to make the gas turbine engine efficient. This paper will outline the numerical methods applied for primary cooling methods in gas turbine blades. These include impinging leading-edge cooling, internal cooling in the midsection, and pin fin in the trailing edge. The main objective of this paper is to understand the numerical research done on improving gas turbine cooling. The emphasis will be on understanding the present computational fluid dynamics (CFD) techniques applied for gas turbine cooling and further development. This paper briefly outlines the new conjugate heat transfer–based CFD modeling techniques that have evolved over the years due to recent computing power development.
Net Zero Energy Model for Wastewater Treatment Plants
Authors: Qandil Mohammad D. , Abbas Ahmad I. , Salem Abdel Rahman , Abdelhadi Ahmad I. , Hasan Alaa , Nourin Farah Nazifa , Abousabae Mohamed , Selim Osama M. , Espindola Juan , Amano Ryoichi S.
Published: February 2021

The primary objective of this study is to achieve net-zero energy (NZE) wastewater treatment plants (WWTPs) by utilizing energy efficiency opportunities (EEO), combined heat and power (CHP) systems, and other renewable energy (RE) sources, e.g., solar, water, and wind powers. This study discusses an innovative energy solution for WWTPs in the United States, and one of the WWTPs with a flow capacity of 1.5 million gallons per day (MGD) was selected as a case study. An optimization tool, Hybrid Optimization of Multiple Energy Resources (HOMER) software, is used in this study to find the best energy system configuration to run the system. An energy audit for one WWTP was conducted in early 2020 and the report is used to do this study. The proposed EEOs were able to reduce WWTP energy consumption by about 11%. The excess anaerobic digester gas was utilized in a CHP system to cover about 42% of the facility’s consumption. Also, 3% of the utility energy consumption can be claimed by microturbines in the aeration tanks. Another two renewable energy systems, solar photovoltaic (PV) with 29% and water turbines with 15%, contribute to covering 100% of the WWTP energy consumption and achieving an NZE WWTP.
Information Exchange Patterns in Digital Engineering: An Observational Study Using Web-Based Virtual Design Studio
Authors: Thekinen Joseph , Grogan Paul T.
Published: February 2021

This paper performs an observational human subjects study to investigate how design teams use an information system to exchange, store, and synthesize information in an engineering design task. Framed through the lens of decision-based design, a surrogate design task models an aircraft design problem with 12 design parameters across four roles and six system-level functional requirements. A virtual design studio provides a browser-based interface for four participants in a 30-min design session. Data collected across 10 design sessions provide process factors about communication patterns and outcome factors about the resulting design. Correlation analysis shows a positive relationship between design iteration and outcome performance but a negative relationship between chat messages and outcome performance. Discussion explains how advances in information exchange, storage, and synthesis can support future design activities.
Quantification of the Complex Crack Geometry Effect on Fracture Resistance Using Strain-Based Finite Element Damage Analysis
Authors: Kim Seung-Jae , Ryu Ho-Wan , Kim Jin-Weon , Oh Young-Jin , Kim Yun-Jae
Published: February 2021

This paper examines the effect of complex crack geometry on the J-resistance curves obtained by strain-based ductile tearing simulation of complex cracked tension (CC(T)) specimens. The damage model is determined by analyzing the results of a smooth bar tensile test and a compact tension (C(T)) specimen toughness test on an SA508 Gr.1a low-alloy steel at 316 °C. The validity of the damage model and simulation method is checked by comparing the fracture test data for two CC(T) specimen tests. To investigate the effect of the complex crack geometry on the crack growth profiles and J-resistance curves, two geometric parameters (namely, the through-wall crack length and the surface crack depth) are systematically varied. It is found that the J-resistance curves for the CC(T) specimens with various through-wall crack lengths and surface crack depths are consistently lower than the corresponding 1 T C(T) J-resistance curves. The effect of the through-wall crack length upon the J-resistance curve is found to be less significant than that of the surface crack depth. Moreover, the J-resistance curve decreases continuously with increasing surface crack depth.
A Mobility Determination Method for Parallel Platforms Based on the Lie Algebra of SE(3) and Its Subspaces
Authors: Sánchez-García A. J. , Rico J. M. , Cervantes-Sánchez J. J. , López-Custodio P. C.
Published: February 2021

This contribution presents a screw theory-based method for determining the mobility of fully parallel platforms. The method is based on the application of three stages. The first stage involves the application of the intersection of subalgebras of Lie algebra, se(3), of the special Euclidean group, SE(3), associated with the legs of the platform. The second stage analyzes the possibility of the legs of the platform generating a sum or direct sum of two subalgebras of the Lie algebra, se(3). The last stage, if necessary, considers the possibility of the kinematic pairs of the legs satisfying certain velocity conditions; these conditions reduce the platform’s mobility analysis to one that can be solved using one of the two previous stages. Several examples are illustrated.
Dynamic Simulation-Guided Design of Tumbling Magnetic Microrobots
Authors: Xie Jiayin , Bi Chenghao , Cappelleri David J. , Chakraborty Nilanjan
Published: February 2021

The design of robots at the small scale is a trial-and-error based process, which is costly and time-consuming. There are few dynamic simulation tools available to accurately predict the motion or performance of untethered microrobots as they move over a substrate. At smaller length scales, the influence of adhesion and friction, which scales with surface area, becomes more pronounced. Thus, rigid body dynamic simulators, which implicitly assume that contact between two bodies can be modeled as point contact, are not suitable. In this paper, we present techniques for simulating the motion of microrobots where there can be intermittent and non-point contact between the robot and the substrate. We use these techniques to study the motion of tumbling microrobots of different shapes and select shapes that are optimal for improving locomotion performance. Simulation results are verified using experimental data on linear velocity, maximum climbable incline angle, and microrobot trajectory. Microrobots with improved geometry were fabricated, but limitations in the fabrication process resulted in unexpected manufacturing errors and material/size scale adjustments. The developed simulation model can incorporate these limitations and emulate their effect on the microrobot’s motion, reproducing the experimental behavior of the tumbling microrobots, further showcasing the effectiveness of having such a dynamic model.
Prototype Human Model for the Evaluation of a Crew Transportation Module
Authors: Evans D. , Jayaram U. , Jayaram S. , Angster S. , Pettit R.
Published: February 2021

This paper details the design and implementation of a prototype human model for use in evaluation of a Crew Transportation Module for a Reusable Launch Vehicle design. This human model allows the user to use a combination of immersive and non-immersive techniques for ergonomic evaluations. The human model presented in this paper has the following functionalities: free floating (each body part is uninfluenced by other body parts), scalable (the parametric nature allows for scaling of each individual body part), calibration of body parts (to account for error in the mounting of the tracking devices to the body parts), gripping methods, multiple body part tracking configurations, predefined sitting and standing postures, mouse-based manipulation of human model, and dynamic switching between first and third person views. The overall goal was to create a scaleable human model software system which could be easily included in any immersive or non-immersive graphics application. This human model was inserted into a MuSE™-based environment. The methods used to create this human model and its salient features as well as its shortcomings are discussed in this paper.
Numerical Simulation of Viscous Flow-Field in Cascade Using Thin-Layer Equations and AF Method
Authors: Xiao Yumin , Amano R. S.
Published: February 2021

In this paper an implicit 3-D solver for computations of a viscous flow has been developed and the computations of the flow between blade passage are presented. This method employs an AF (Approximate Factorization) method in which four techniques are incorporated to speed up convergence to the steady-state solutions: (1) body-fitted H-grid; (2) artificial viscosity; (3) implicit residual smoothing; and (4) local time-stepping. The two-dimensional pseudo-characteristic method was used to determine the inlet and outlet boundary conditions of the computational domain and the periodic boundary conditions were used at inter-boards. The validation cases include subsonic and transonic viscous flows in C3X cascade. Results for these turbine cascade flows are presented and compared with experiments at corresponding conditions. Computed pressure distributions on blade surfaces show good agreement with the published experimental data. This method was further applied to a three-dimensional case and demonstrated the code capability for predicting the secondary flow in a 3-D transonic flow-field. From these computations it was found that the proposed method possesses superior convergence characteristics and can be extended to unsteady flow calculations. Finally, it was observed that the three-dimensional calculation results show that the secondary flow mechanism in a transonic cascade seems to be quit different from those, in a subsonic case.
Slurry Residue Removal in Post Chemical Mechanical Polishing
Authors: Busnaina Ahmed A. , Moumen Naim
Published: February 2021

The megasonic cleaning process proved to be an essential process in cleaning silicon wafers after processes such as pre-oxidation, pre-CVD, pre-EPI, post-ASH and lately post-CMP. Current post-CMP cleans are contact cleaning techniques. These contact techniques have a low throughput and may cause wafer scratching. In addition, in contact cleaning, brush shedding which occurs under many operating conditions causes additional particulate contamination. There is a need for an effective post-CMP cleaning process. Megasonic cleaning provides the best alternative or compliment to brush clean.
Determination of Propane-Air Maximum Mixing Times
Authors: Brasoveanu Dan , Gupta Ashwani K.
Published: February 2021

The model of gaseous fuel and air mixing, developed by the authors2–3, is applied here to calculate maximum mixing times of propane and air. The degree of mixing is determined using the mass fraction of fuel while the rate of mixing is determined from the rate of this mass fraction. The values of both these parameters are local, i.e., measured within an infinitesimal element of fluid. An Eulerian representation is used. The model is based on the assumption that both fuel and air behaves like single chemical species. It is further assumed that pressure is low and only fuel and air are present within the fluid element. Under non-reacting conditions, the model is valid anywhere in the combustor. Under reacting conditions, the model is valid within those combustor regions where the fuel-air mixture is not flammable. The results of this analysis show that mixing times of propane and air are most reduced by high gradients of temperature and velocity, as long as these gradients act in phase. To a lesser degree, high gradients of pressure also help reduce mixing times. High initial pressure and temperature increase mixing time. Mixing with air penetration into the fuel flow is slower than with propane dispersion into the surrounding air. In general, the exact mixing time has to be determined numerically. Nevertheless, the analytical solutions included here provide maximum mixing times of propane and air under most conditions. These results provide important guidelines for the development of high intensity, high efficiency and low emission combustors.
Basic Models in Fire Development
Authors: Kim Hyeong-Jin , Lilley David G.
Published: February 2021

The ultimate goal of this study is to improve scientific understanding of fire behavior leading to flashover in structural fires. This document summarizes important information in five topic areas: burning rates, radiant ignition, fire spread rates, ventilation limit imposed by size of opening, and flashover criteria.

These are the main components related to the scientific understanding of the fire growth and flashover problem involved in real-world structural fires. Within each topic area, there are four subsections dealing with background, theory, comments, and references. Main components of the study are to develop improved mathematical simulations so as to improve the accuracy of theoretical calculation and to develop and extend the range of knowledge and modeling capability so as to extend the range of available experimental data.
Pool Fires and Radiant Ignition Capability
Authors: Lilley David G.
Published: February 2021

Radiation heat transfer is a primary reason for fire growth. Experimental data are needed to clarify the ignition potential and time required to ignite a particular “target” second item. The objective of the present contribution is to clarify how the size and material of a pool fire determine ignition distance capability, and exemplify realistic calculations related to real-world situations.
Constrained Kalman Filter in Structural Model Identification
Authors: Yang Y. , Zhang H. , Foliente G. C. , Ma F.
Published: February 2021

In this paper, a constrained Kaiman filter is developed for the purpose of estimating the parameters of nonlinear structural hysteresis model. In this method, a constrained method is incorporated into the extended Kalman filter to develop convergence stability, precision and speed. At the same time, a global weighted iteration technique is used to tackle the problem of arbitrary initial values. It can be found that this method is highly efficient in identification of inelastic structures from both clean data and noise-corrupted data.
A Web Based Micro Turning-Process Planning System With Considering Distributed Resources
Authors: Yang Xiaoming , Zheng Li , Zhang Zhihai , Liu Dacheng , Zhang Bopeng , Liu T. I.
Published: February 2021

A new and emerging agile manufacturing paradigm is attracting an increasing amount of attention from both the academic and industrial communities. Agile manufacturing makes use of modern information technology to form virtual enterprises, which agilely respond to the changing market demands. In recent years, Web related technology improves greatly the abilities to communicate and cooperate, The web technology enables the manufacturing resources, including information, facilities and so on, to be shared among geographically distributed partners. The significance of web technology to agile manufacturing is unquestionable. In this paper we develop a prototyping system to explore methodology of enhancing agility by use of Web based technology. A web-based micro-process planning system for turning has been developed. The engineers who are connected to the Internet at geographically distributed sites can use a standard browser to realize process parameter planning and optimization.
An Internet-Based Distributed Service Architecture
Authors: Han Charles S. , Kunz John C. , Law Kincho H.
Published: February 2021

This paper describes a distributed architecture that enables the delivery of design services over the Internet. The architecture of an individual service is three-tiered. The first tier is a common communication protocol interface. The middle tier is the common product model interface. The third tier is the core of the design service. Though fundamentally decoupled, methods in the communication layer and the product model layer have been formalized to enable the aggregation of services and the support of problem decomposition. In addition, with the standardization of the first two tiers, it is possible to rapidly deploy various design services, both new and legacy applications, that can be easily made accessible via the Internet. As examples of design services, the prototype implements a project manager service with a companion CAD package, services that incorporate two legacy applications (a building code analysis service and a service that generates and displays an accessible path for a given floor plan design using motion planning and animation techniques), and a disabled access service that takes advantage of the decomposable infrastructure.
Digital Library Support for Engineering Design and Manufacturing
Authors: Regli William C.
Published: February 2021

This paper describes our initial efforts to deploy a digital library to support engineering design and manufacturing. This experimental testbed, The Engineering Design Repository, is an effort to collect and archive public domain engineering data for use by researchers and engineering professionals.

CAD knowledge-bases are vital to engineers, who search through vast amounts of corporate legacy data and navigate online catalogs to retrieve precisely the right components for assembly into new products. This research attempts to begin addressing the critical need for improved computational methods for reasoning about complex geometric and engineering information. In particular, we focus on archival and reuse of design and manufacturing data for mechatronic systems. This paper presents a description of the research problem and an overview of the initial architecture of testbed.
Process-Centric Distributed Collaborative Design Based on the Web
Authors: Kim Hyun , Lee Jae Yeol , Han Sung-Bae
Published: February 2021

In this paper, we discuss a distributed collaborative design for embodying concurrent engineering. The concept of a process-centric collaborative design is proposed to progress collaboratively an engineering design. It is implemented in the PEDWorks (Process-centric Engineering Design Workspace) as a prototype system for the Web-based collaborative workspace to integrate design activities in a distributed and heterogeneous computing environment. The PEDWorks has a client/server architecture, which consists of server applications such as a process controller, a design board, a communication server and a CAD server, and the client browsers with a Web-based process-driven user interface. We have conformed to CORBA (Common Object Request Broker Architecture) standard to support interoperability between distributed objects and have used JAVA to support cross-platform and distributed user access to PEDWorks on the Web. PEDWorks enables design teams to define the design process collaboratively, execute it in a distributed environment, share design information and communicate with each other.
A Multi-Level Heuristic Search Algorithm for Production Scheduling
Authors: Yadav S. , Xu Y. , Xue D.
Published: February 2021

This paper introduces a multi-level heuristic search algorithm for identifying the optimal production schedule considering different levels of manufacturing requirements and constraints. In this multi-level heuristic search-based scheduling system, production requirements and constraints are represented at three different levels: task level, process level, and resource level. A task describes a manufacturing requirement. A process defines a method to achieve the goal of a task. A resource, such as a machine or a person, is a facility for accomplishing a required process. The scheduling system was implemented using Smalltalk, an object oriented programming language.
A Method for Qualifying High Density Data Acquisition Systems for Free Form Metrology
Authors: Ebenstein Sam E. , Kiridena Vijitha S. , Rodin Yelena M. , Smith Gregory H.
Published: February 2021

The Vehicle Perception Safety Research Team of the Ford Manufacturing & Vehicle Design Research Laboratory has developed artifacts, procedures and data analysis techniques to assist in evaluating systems used for the high-speed collection of geometric data. These systems are usually comprised of a non-contact sensor and a means of positioning the sensor relative to the part being inspected. They are usually used to collect data from sculptured or “free form” surfaces for reverse engineering or for applications in the emerging field of free form metrology. The evaluation procedure consists of acquiring data from three ceramic balls nominally 44.45 mm in diameter held by depressions in a flat plate. The data are then first analyzed using least square techniques to obtain observed radii of the balls and the location of their centers. Then free form metrology techniques are used to compare the data from each ball to an ideal sphere of the observed radius and center location. By combining the observed location and radii with a high resolution graphical representation of the quality of fit between the data and an ideal sphere, a good assessment of the system’s capability for collection of data for reverse engineering or for free form metrology is obtained. At the same time the technique graphically reveals any troublesome systematic or shape-related sources of error.
New Sampling Strategies for Form Evaluation of Free-Form Surfaces
Authors: Kim Doo Hwan , Ozsoy Tulga M.
Published: February 2021

New strategies to determine the location of the measurement points for form evaluation of free-form surfaces by using Coordinate Measuring Machines are investigated. The newly developed corrected length method locates the measurement points on constant curvature contour lines. The length and the rank of each contour line are used as parameters to control the distribution of the measurement points. The experimental results have shown that the proposed method is more robust than the known methods currently being used for form evaluation of free-form surfaces. The method also offers opportunities for developing more efficient probe-path generation strategies, since the measurement points are located on continuous paths formed by constant curvature contour lines.
Feature-Based Segmentation of CT-Contours for Reverse Engineering
Authors: Liu Shoubin , Ma Weiyin
Published: February 2021

This paper presents results on feature-based segmentation of contour data for creating a CAD model in the context of CT-based reverse engineering applications. After pre-processing of CT-scanning results, the geometry of an existing part is represented as a collection of complex raw CT-contours. The interested CT-contours representing a large surface area or the complete external or internal surfaces are first extracted from the raw CT-contours. A feature-based segmentation technique is then applied to subdivide the extracted CT-contours into individual surface features. Based on the input of an open seed contour, all contour segments belonging to the same surface feature of the user-entered seed contour are segmented from others layer by layer using a seed-growing approach. A turning angle map is used for the identification of candidate feature points on an individual contour. An elastic spline and an optimization algorithm are used in the seed-growing process. A surface model can then be further created from the segmented features.
Representation of Swept Volumes in a Parametric CAD System Using Trajectory Information From Virtual Environments
Authors: Wang Yong , Jayaram Sankar , Jayaram Uma , Lyons Kevin , Hart Peter
Published: February 2021

Swept volumes are the volumes created by a part moving in space during the process of assembly, disassembly, service, etc. Swept volumes represent important manufacturing, maintainability, and serviceability data. Several graphical and implicit modeling techniques are currently available to create and represent swept volumes as three-dimensional polygonal blobs. In this paper, we present a method for generating swept volumes from trajectory data created in a virtual graphics environment during an assembly/disassembly scenario. The individual instances can be edited in the virtual environment by swept instance removal and modification of position and orientation of instances. Using a synchronous link between the virtual environment and the CAD system, the trajectory information from the virtual environment is used along with the parametric model in the CAD system to create swept volume geometry directly in a parametric CAD system as a feature of the assembly. In addition, using the synchronous link, this swept volume (not just instances along the trajectory) can then be exported back to the original virtual environment and displayed. This method can handle any sweeping trajectory and does not restrict the geometry or the topology requirement of the sweeping object. The swept volumes generated this way are accurate, concise, and can be easily processed by CAD systems.
Offset Curves and Surfaces With Continued Fractions
Authors: Wen Manhong , Ting Kwun-Lon
Published: February 2021

This paper provides a new approach to approximate the offset of free-form curves and surfaces with continued fractions. The properties of continued fractions are introduced. The convergence of the approximation is proved and the relationship between accuracy and approximate step is established. It shows that the approximation converges fast and reliably, the error of approximation is easily estimated and controlled, and a unified algorithm can be used to generate the rational offset of non-rational and rational planar curves, spatial curves, and surfaces in CAD/CAM industry.
NURBS-Based Multi-Axis Toolpath for High Speed Machining
Authors: Cheng Kevin , Tang Sheng-Der
Published: February 2021

The NURBS-based toolpath has been considered as an important step forward in computer-aided manufacturing technology for high speed machining applications. Major CNC vendors have found that the NURBS toolpath provides the following benefits over the traditional line string toolpath: more accurate parts, reduced cycle time, improved surface quality, and drastically smaller part programs. This paper presents the technological advancements in the NURBS based toolpath project that Unigraphics Solutions’ CAM group has done since 1996. The NURBS toolpath generator has been implemented to a multi-axis surface milling module. Examples demonstrate the advantages of the NURBS toolpath over the conventional line string toolpath in high speed machining.
History-Independent Boundary Evaluation for Feature Modeling
Authors: Bidarra Rafael , Bronsvoort Willem F.
Published: February 2021

Most current feature modeling systems strongly rely on a history-based interpretation of the feature model, in order to maintain its evaluated boundary representation. This dependency on the model history is undesirable, as it forces the user of the modeling system to reason in terms of a strict chronological feature creation order. Moreover, re-evaluation of the boundary representation, as performed in such systems, has a computational cost proportional to the size of the model history. Such drawbacks suggest that current feature modeling systems are still too tied to conventional geometric modeling techniques.

In this paper, it is argued that to overcome the drawbacks mentioned above, a declarative feature model is required, whose structure is dynamically adapted as modeling operations create or modify relations among its features. Operations performed on this feature model can then be efficiently propagated to an evaluated non-manifold geometric representation, without invoking model history considerations. The paper describes how such a geometric model — the so-called Cellular Model — can be maintained throughout model evolution. For each modeling operation, this is achieved in two phases. First, the Cellular Model is incrementally re-evaluated. Second, the Cellular Model is interpreted, according to the feature information stored in its cellular entities and the current dependencies among the features. The advantages of the use of this history-independent boundary evaluation, implemented within the semantic feature modeling approach, are illustrated with some modeling examples.
A Process Planning Method for Improving the Build Performance in Stereolithography
Authors: West Aaron P. , Rosen David W.
Published: February 2021

A process planning method is presented in this paper to aid stereolithography users in the selection of appropriate values of build process variables in order to achieve specific goals and characteristics that are desirable in the end prototype. To accomplish this, user-defined input in the form of goal preferences and feature tolerances are used to control how the prototype will be built by way of process planning. The user inputs will be used to drive the creation of the process plan so that a prototype is produced, which reflects the intent of the operator. The process planning method is adapted from multi-objective optimization and utilizes empirical data, analytical models, and heuristics to quantitatively relate build process variables to goals of surface finish, accuracy, and build time. The objective is to render decision support by handling tradeoffs among conflicting goals quantitatively and give the user some degree of insight into what quality of prototype may ultimately be produced. The process planning method is demonstrated on a part with non-trivial geometric features.
Verification of the Thick Layered Free-Form Object Fabrication by Visual Simulation
Authors: Horváth Imre , Rusák Zoltán , Kuczogi György , Broek Johan J. , Vergeest Joris S. M.
Published: February 2021

The process of free-form thick-layered object manufacturing (FF-TLOM) has been developed with the aim of supporting physical concept modeling and rapid prototyping Of large sized, morphologically complex, dominantly free-form industrial engineering products. The FF-TLOM process involves the following activities: (i) morphological segmentation of the CAD model, (ii) tool profile generation, (iii) slicing the segments based on higher order shape approximation, and (iv) tool position and tool path calculation, (v) layer manufacturing, and (vi) assembly of the physical model. Due to the number of factors that influence the decisions, the otherwise highly automated computations must be accompanied by an in-process visualization. This paper proposes a ‘virtual prototyping’ for pre-implementation testing of the actual physical concept modeling and/or rapid prototyping process. It explains the operation of the developed calculation software tools and presents the results of the visualization tools. Based on the visualization of the process and the artifact, possible errors of the physical model can be explored and eliminated, furthermore, parameters of the process can be optimized.
Manufacturing Resource Modeling With Petri Nets
Authors: Kiritsis Dimitris , Xirouchakis Paul
Published: February 2021

The problem under consideration is the modeling of manufacturing resources like machine tools, setups and tools which affect the cost and batch delivery time estimation of machined parts. The proposed resource models are built upon Petri net models for process planning and scheduling with three methods: (i) an implicit modeling method where resources are modeled as a data structure which acts on a specific Process Planning Petri net (PP-net), (ii) a first explicit modeling method where resources, are modeled as separated Petri nets whose places are connected to PP-net transitions with adequate arcs and form a Process Planning Cost System (PPC-system) and (iii) a second explicit modeling method where a two-level Petri net model is proposed which allows the modular modeling of process plans and resources. In the later case, integration is achieved through an synchronization mechanism. The first two methods are used for the cost estimation of process plans of unique parts while the third one is used for delivery time and cost estimation of a batch of machined parts.
Robustness Optimization of FMS Under Production Plan Variations: The Case of Cyclic Production
Authors: Saitou Kazuhiro , Malpathak Samir
Published: February 2021

This paper discusses an extension of our previous work (Saitou, 1998) on robustness optimization of flexible manufacturing systems (FMS) that undergo forecasted production plan variations. The extension is made to a more general class of FMS performing “non-linear” or “cyclic” production that allows multiple operation types per one machine type. As in our previous work (Saitou, 1998), a configuration of an FMS is modeled as a colored Petri net and the associated transition firing sequence, and the robustness of FMS is defined as the insensitivity of production performances against variations in production plan. The optimization of the robustness of the colored Petri net model is formulated as a multi-objective optimization problem which minimizes production costs under multiple production plans (batch sizes for all jobs), and reconfiguration cost due to production plan changes. A genetic algorithm, coupled with a dispatching rule based on shortest imminent operation time (SIO), is used to simultaneously find an semi-optimal resource allocation and event-driven schedule of a colored Petri net. The resulting Petri nets are then compared with the Petri nets optimized for a particular production plan in order to address the effectiveness of the robustness optimization. The simulation results suggest that the proposed robustness optimization scheme should be considered when the products are moderately different in their job specifications so that optimizing for a particular production plan creates inevitably bottlenecks in product flow and/or deadlock under other production plans.
Towards Combining Digitization Techniques in the Generation of Reverse Engineering Data Sets
Authors: Rolls C. J. , ElMaraghy W. , ElMaraghy H.
Published: February 2021

Reverse engineering (RE), may be defined as the process of generating computer aided design models (CAD) from existing or prototype parts. The process has been used for many years in industry. It has markedly increased in implementation in the past few years, primarily due to the introduction of rapid part digitization technologies. Current industrial applications include CAD model construction from artisan geometry, such as in automotive body styling, the generation of custom fits to human surfaces, and quality control. This paper summarizes the principles of operation behind many commercially available part digitization technologies, and discusses techniques involved in part digitization using a coordinate measuring machine (CMM) and laser scanner. An overall error characterization of the laser scanning digitization process is presented for a particular scanner. This is followed by a discussion of the merits and considerations involved in generating combined data sets with characteristics indicative of the design intent of specific part features. Issues in facilitating the assembly, or registration, of the different types of data into a single point set are discussed.
Accuracy and Fitting-Time Minimization in the Reverse Engineering of Prismatic Features
Authors: Nassef Ashraf O. , Ashraf Ayman M. , Metwalli Sayed M.
Published: February 2021

In many years of industry, it is desirable to create geometric models of existing objects for which no such models are available. Reverse engineering transforms real parts into engineering models and concepts. This paper presents an approach for fitting three-dimensional prismatic features using real-coded genetic algorithms. The approach is compared with the Nelder Meade Simplex search method as a variant of the traditional direct search method. The results show the superiority of the real-coded genetic algorithms over the traditional direct search method with respect to accuracy. The paper also concerns with the minimization of the fitting time through minimizing the number of objective function evaluations. This is done by optimizing the genetic algorithms parameters such as the number of times for which the various cross-overs and mutations should be applied.
Data Reduction for Reverse Engineering of Free Form Surfaces
Authors: Vafaeesefat Abbas , ElMaraghy Hoda A.
Published: February 2021

The large amount of irregular and unstructured data collected by the laser scanner, often refered to as “cloud data”, presents a serious challenge in reverse engineering applications. Data reduction is essential for simplifying the process of creating surface models in order to remove redundancy, save space, and speed up the display and recognition tasks. In this paper, an algorithm which effectively reduces the data collected by laser scanners is presented. Data points are first organized into a large regular grid of data points which is then interpolated using the linear polynominal dual Kriging technique to form the initial surface. Next, the algorithm generates a subset of this grid (within the specified deviation) by identifying the knots that play important role in the Kriging interpolation. Finally, additional reduction is done by merging the rectangles of the grid where the tangent variation between two rectangles is insignificant. Since the final surface is usually represented by a set of connected rectangles, the surface segmentation and fitting procedures can be accomplished in a short period of time. Examples are used to show the efficiency and validity of the proposed algorithms.
Reverse Engineering of Standard Mechanical Elements
Authors: Hegazi Hesham A. , Metwalli Sayed M.
Published: February 2021

This paper presents a new procedure by which standard machine elements can be reverse engineered. Standard elements or components need not be scanned and identified as surface or solid model. The standard character is sufficient to be identified by few parameters. These parameters can be measured or deduced by calculations from certain geometric relations. The procedure presented herein is devoted to the reverse engineering of spur and helical gears. Other standard machine elements can be treated the same way. A computer aided reverse engineering (CARE) program is used to satisfy all geometric constraints, identify other dependent geometries and define production and inspection requirements. It allows the further check of the design appropriateness of material selection and loading conditions.
CAD of Disc Brakes by Multi-Objective Optimization
Authors: Metwalli Sayed M. , Hegazi Hesham A. , Abdel-Aal Usama M.
Published: February 2021

This paper is concerned with CAD techniques to solve the multi-objective problem of designing optimum disc brakes. The geometrical parameters affecting disk brake design such as the outer and inner disc diameters, disc thickness, pad thickness and pad angle are considered. A computer aided optimum design program is constructed with full graphics interface for automatic viewing and further detailing of the design construction. The design vector for optimizing disc brakes includes the outer disc diameters, diameter ratio, disc thickness, and pad angle. The multi-objectives formulation satisfies maximum attained torque; minimum actuating force; minimum thermal stresses; minimum temperature and minimum disc volume. A comparison with previous optimization results indicates a marked saving since previous results did not consider all design objectives and parameters.
A Sequential-Quadratic-Programming Algorithm Using Orthogonal Decomposition With Gerschgorin Stabilization
Authors: Teng Chin-Pun , Angeles Jorge
Published: February 2021

This paper introduces a new approach to sequential quadratic programming. Upon application of the Gerschgorin Theorem for the stabilization of the Hessian matrix and of the orthogonal-decomposition algorithm in the quadratic programming solution, this novel approach offers a faster computation and dispenses with a feasible initial guess.
Topology Synthesis of Two-Phase Compliant Actuators
Authors: Sigmund Ole
Published: February 2021

This paper describes how the topology optimization method can be used as a tool for the synthesis of two-phase compliant actuators. Two materials, one or both being active materials, are distributed in a design domain such that the work performed on an elastic workpiece is maximized. The two-material design is obtained by introducing two variables per element. One variable determines the relative density of material in the element and the other variable determines the material type. Examples demonstrate the design of thermal actuators and gripping mechanisms.
Smooth Surface Interpolation With Multiple Patches
Authors: Adhikary N. , Gurumoorthy B.
Published: February 2021

This paper addresses the problem of interpolating point data with multiple patches. The specific issue addressed in this paper is the continuity between the patches used for interpolation. The procedure described in this paper maintains continuity by introducing an intermediate patch between the two patches used for interpolating the point data. This patch is formed by several Bezier patches that maintain continuity with the corresponding Bezier patches obtained by repeated knot insertion in the two interpolating patches. The blending Bezier patches are then converted to a blending B-spline patch by knot removal. It is shown that C1 continuity is obtained across the junction between each interpolating patch and the blending patch. The continuity, across each blending patch and the interpolation performance in the blending patch is also discussed. The paper presents results, of implementation on some typical surfaces.
A Novel Approach for Decoupling of Dynamical Equations of Flexible Manipulators
Authors: Meghdari Ali , Fahimi Farbod
Published: February 2021

Recent advances in the study of dynamics of elastic multibody systems, specially the flexible manipulators, indicate the need and importance of decoupling the equations of motion. In this paper, an improved method for deriving elastic generalized coordinates is presented. In this regard, the Kane’s equations of motion for elastic multibody systems are considered. These equations are in the generalized form and may be applied to any desired holonomic system. Flexibility in choosing generalized speeds in terms of generalized coordinate derivatives in Kane’s method is used. It is shown that proper choice of a congruency transformation between generalized coordinate derivatives and generalized speeds leads to a series of first order decoupled equations of motion for holonomic elastic multibody systems. Furthermore, numerical implementation of the decoupling technique using congruency transformation is discussed and presented via simulation of a two degree of freedom flexible manipulator.