scholarly journals An Interactive Tool for Automatic Predimensioning and Numerical Modeling of Arch Dams

2017 ◽  
Vol 2017 ◽  
pp. 1-12 ◽  
Author(s):  
D. J. Vicente ◽  
J. San Mauro ◽  
F. Salazar ◽  
C. M. Baena
Keyword(s):  
Computer Aided Design ◽  
Complex Geometry ◽  
Design Procedure ◽  
Software Tool ◽  
Gravity Dams ◽  
Detailed Model ◽  
Arch Dams ◽  
Double Curvature ◽  
Aided Design ◽  
Mass Volume

The construction of double-curvature arch dams is an attractive solution from an economic viewpoint due to the reduced volume of concrete necessary for their construction as compared to conventional gravity dams. Due to their complex geometry, many criteria have arisen for their design. However, the most widespread methods are based on recommendations of traditional technical documents without taking into account the possibilities of computer-aided design. In this paper, an innovative software tool to design FEM models of double-curvature arch dams is presented. Several capabilities are allowed: simplified geometry creation (interesting for academic purposes), preliminary geometrical design, high-detailed model construction, and stochastic calculation performance (introducing uncertainty associated with material properties and other parameters). This paper specially focuses on geometrical issues describing the functionalities of the tool and the fundamentals of the design procedure with regard to the following aspects: topography, reference cylinder, excavation depth, crown cantilever thickness and curvature, horizontal arch curvature, excavation and concrete mass volume, and additional elements such as joints or spillways. Examples of application on two Spanish dams are presented and the results obtained analyzed.

scholarly journals The Influence of Exposure Energy Density on Porosity and Microhardness of the SLM Additive Manufactured Elements

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2304 ◽  
Author(s):  
Janusz Kluczyński ◽  
Lucjan Śnieżek ◽  
Krzysztof Grzelak ◽  
Janusz Mierzyński
Keyword(s):  
Computer Aided Design ◽  
Complex Geometry ◽  
Final Analysis ◽  
Machine Building ◽  
Layer By Layer ◽  
Laser Melting ◽  
Measurement Results ◽  
Computer Aided ◽  
Exposure Energy ◽  
Aided Design

Selective laser melting (SLM) is an additive manufacturing technique. It allows elements with very complex geometry to be produced using metallic powders. A geometry of manufacturing elements is based only on 3D computer-aided design (CAD) data. The metal powder is melted selectively layer by layer using an ytterbium laser. This paper contains the results of porosity and microhardness analysis made on specimens manufactured during a specially prepared process. Final analysis helped to discover connections between changing hatching distance, exposure speed and porosity. There were no significant differences in microhardness and porosity measurement results in the planes perpendicular and parallel to the machine building platform surface.

A Computational Geometry for the Blades and Internal Flow Channels of Centrifugal Compressors

1983 ◽  
Vol 105 (2) ◽  
pp. 288-295 ◽  
Author(s):  
M. V. Casey
Keyword(s):  
Computational Geometry ◽  
Computer Aided Design ◽  
Design Procedure ◽  
Internal Flow ◽  
Geometrical Shape ◽  
Parametric Form ◽  
Centrifugal Compressors ◽  
Flow Channels ◽  
Computer Aided ◽  
Aided Design

A new computational geometry for the blades and flow passages of centrifugal compressors is described and examples of its use in the design of industrial compressors are given. The method makes use of Bernstein-Bezier polynomial patches to define the geometrical shape of the flow channels. This has the following main advantages: the surfaces are defined by analytic functions which allow systematic and controlled variation of the shape and give continuous derivatives up to any required order: and the parametric form of the equations allows the blade and channel coordinates to be very simply obtained at any number of points and in any suitable distribution for use in subsequent aerodynamic and stress calculations and for manufacture. The method is particularly suitable for incorporation into a computer-aided design procedure.

Design of a Novel Statically Balanced Mechanism for Laparoscope Holders With Decoupled Positioning and Orientating Manipulation

2015 ◽  
Vol 8 (1) ◽  
Author(s):  
Chin-Hsing Kuo ◽  
Shao-Jung Lai
Keyword(s):  
Computer Aided Design ◽  
Parallel Mechanism ◽  
Design Procedure ◽  
Theoretical Formulation ◽  
Surgical Incision ◽  
Total Potential ◽  
Physical Prototype ◽  
Aided Design ◽  
Insertion Length ◽  
Kinematic Properties

This paper presents a novel mechanism concept of laparoscope holders used for minimally invasive surgery (MIS). The mechanism is made of a parallelogram linkage and a parallel mechanism, which, respectively, serve as a robotic positioning arm and an orientating wrist of the holder. Due to its special geometry, the mechanism possesses several interesting kinematic properties. First, the laparoscope, which is held by the end-effector, can illustrate a remote center-of-motion (RCM) kinematics at the surgical incision point. Second, the position of the RCM point is solely defined by the parallelogram, whereas the orientation and insertion length of the laparoscope are governed by the parallel mechanism. Such an arrangement suggests a decoupled positioning and orientating manipulation for the holder, which is clinically helpful in laparoscopic MIS. Third, the overall mechanism including the parallelogram linkage and the parallel mechanism can be statically balanced at any configuration within the workspaces by using common linear springs. In other words, no electrical actuation or mechanical locks are required for making the laparoscope rest at any position and orientation. The design procedure for static balancing is detailed in the paper, and the theoretical formulation of the statically balanced mechanism is verified by a numerical example and computer simulation. The computer-aided design (CAD) model of the holder is constructed for evaluating its workspace and a physical prototype using commercial springs is built up and tested. It shows that the prototype that uses nonideal (commercial) springs can be statically balanced within the overall workspace, since the shortage/overshoot of the potential energy in the positioning mechanism and orientating mechanism, which are theoretically 6.8% and 5.1% of their total potential energies in maximum, are fully compensated by the friction effect.

Human-Centric Design

1998 ◽  
Vol 120 (07) ◽  
pp. 60-62 ◽  
Author(s):  
Mark Morrissey
Keyword(s):  
Computer Aided Design ◽  
Phase 1 ◽  
Software Tool ◽  
Project Teams ◽  
User Interactions ◽  
Collaborative Project ◽  
Cad System ◽  
The United Kingdom ◽  
Virtual Prototyping Technology ◽  
Aided Design

This article reviews that advances in manikin software have enabled engineers to consider a fuller spectrum of user interactions with virtual products. It has been 15 years since Sammie—a computer model of a human or manikin—emerged from the research labs of Nottingham University in the United Kingdom, promising human-factors (HF) engineers a supporting software tool to improve the study of human elements of product design. Although Sammie incorporated accurate anthropometric data and representative joint constraints, the software was very difficult to use, could not import models from a computer-aided-design (CAD) system, and was not dynamic. After phase 1 of the collaborative project, Rolls-Royce and VSEL expanded their study to evaluate the use of virtual reality for the design and layout of larger and more complex machinery spaces. This second collaborative effort had several objectives: to understand how virtual-prototyping technology could help designers better visualize complex designs, design for ease of assembly and maintenance much earlier, train maintenance engineers, and enhance communications between disparate project teams, customers, and suppliers.

Computer Aided Design of Mixed Flow Turbines for Turbochargers

1979 ◽  
Vol 101 (3) ◽  
pp. 440-448 ◽  
Author(s):  
N. C. Baines ◽  
F. J. Wallace ◽  
A. Whitfield
Keyword(s):  
Mass Flow ◽  
Computer Aided Design ◽  
High Speed ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Design Procedure ◽  
Mixed Flow ◽  
Computer Aided ◽  
Design Calculations ◽  
Aided Design

The paper describes a comprehensive computer aided design procedure and its use to investigate mixed flow turbines for automotive turbocharger applications. The outside dimensions of rotor and casing as well as blade angles are determined from one-dimensional design and off design calculations, the detailed blade shape from quasi-three-dimensional analysis and mechanical stressing and vibration programs, and geometric data are presented as outside views and sections of the rotor by a graphics subroutine. The procedure consists of a series of separate programs rather than a single program, so that the designer’s intervention at each stage of the process can be applied. Two mixed flow rotors were designed, manufactured and tested in a specially designed high speed dynamometer. The first was intended to achieve a substantial increase in mass flow over the reference radial rotor without loss of efficiency, while the latter was intended as a direct replacement of the reference radial rotor, but should give more favorable pulse performance when operating in conjunction with an engine due to changes in the operating map viz: a) lower tip speeds for best efficiency, and b) flatter mass flow characteristics. Both effects were predicted by analysis and confirmed by tests.

Sign in / Sign up

Export Citation Format

Share Document