Robust Mechanical Design Using Engineering Models

1995 ◽  
Vol 117 (B) ◽  
pp. 48-54 ◽  
Author(s):  
A. Parkinson
Keyword(s):  
Robust Design ◽  
Design Problem ◽  
Mechanical Design ◽  
Check Valve ◽  
Valve Design ◽  
Robust Designs ◽  
Linkage Design ◽  
Engineering Models ◽  
Transmitted Variation

This paper examines how engineering models can be used to develop robust designs—designs that can tolerate variation. Variation is defined in terms of tolerances which bracket the expected deviation of model variables and/or parameters. Several methods for robust design are discussed. The method of transmitted variation is explained in detail and illustrated on a linkage design problem and a check valve design problem.

Robust Mechanical Design Using Engineering Models

1995 ◽  
Vol 117 (B) ◽  
pp. 48-54 ◽  
Author(s):  
A. Parkinson
Keyword(s):  
Robust Design ◽  
Design Problem ◽  
Mechanical Design ◽  
Check Valve ◽  
Valve Design ◽  
Robust Designs ◽  
Linkage Design ◽  
Engineering Models ◽  
Transmitted Variation

This paper examines how engineering models can be used to develop robust designs—designs that can tolerate variation. Variation is defined in terms of tolerances which bracket the expected deviation of model variables and/or parameters. Several methods for robust design are discussed. The method of transmitted variation is explained in detail and illustrated on a linkage design problem and a check valve design problem.

Robust Compressor Blades for Desensitizing Operational Tip Clearance Variations

2014 ◽  
Author(s):  
Pranay Seshadri ◽  
Shahrokh Shahpar ◽  
Geoffrey T. Parks
Keyword(s):  
Robust Design ◽  
Total Pressure ◽  
Pressure Rise ◽  
Side Surface ◽  
Tip Clearance ◽  
Design Parameters ◽  
Compressor Blades ◽  
Robust Designs ◽  
Multi Objective ◽  
Mean And Variance

Robust design is a multi-objective optimization framework for obtaining designs that perform favorably under uncertainty. In this paper robust design is used to redesign a highly loaded, transonic rotor blade with a desensitized tip clearance. The tip gap is initially assumed to be uncertain from 0.5 to 0.85% span, and characterized by a beta distribution. This uncertainty is then fed to a multi-objective optimizer and iterated upon. For each iteration of the optimizer, 3D-RANS computations for two different tip gaps are carried out. Once the simulations are complete, stochastic collocation is used to generate mean and variance in efficiency values, which form the two optimization objectives. Two such robust design studies are carried out: one using 3D blade engineering design parameters (axial sweep, tangential lean, re-cambering and skew) and the other utilizing suction and pressure side surface perturbations (with bumps). A design is selected from each Pareto front. These designs are robust: they exhibit a greater mean efficiency and lower variance in efficiency compared to the datum blade. Both robust designs were also observed to have significantly higher aft and reduced fore tip loading. This resulted in a weaker clearance vortex, wall jet and double leakage flow, all of which lead to reduced mixed-out losses. Interestingly, the robust designs did not show an increase in total pressure at the tip. It is believed that this is due to a trade-off between fore-loading the tip and obtaining a favorable total pressure rise and higher mixed-out losses, or aft-loading the tip, obtaining a lower pressure rise and lower mixed-out losses.

scholarly journals Study of the nozzle check valve with respect to its operating characteristics

2018 ◽  
Vol 180 ◽  
pp. 02044 ◽  
Author(s):  
Roman Klas ◽  
Vladimír Habán ◽  
Pavel Rudolf
Keyword(s):  
Cfd Simulation ◽  
Check Valve ◽  
Operating Characteristics ◽  
Valve Design ◽  
Pressure Fields ◽  
Valve Disc ◽  
Unsteady Operation ◽  
Simulation Results ◽  
2D And 3D ◽  
Main Operating

Several modifications were developed when designing the nozzle valve. This study offers an assessment of the properties of new modifications of the nozzle valve design. The main operating characteristics, such as loss and flow coefficients, were determined using a CFD methods. Besides mentioned coefficients, the forces acting on the valve disc are also decisive for the behavior of the valve, both in its steady and unsteady operation. It is important to examine the possible simplification and matching of CFD simulation results from 2D and 3D geometries in terms of subsequent dynamic analysis of the valve. This will be taken into consideration by comparing the above-mentioned operating characteristics, by analyzing the forces acting on the valve disc and comparing the velocity and pressure fields.

A Model-Based Formulation of Robust Design

2005 ◽  
Vol 127 (3) ◽  
pp. 388-396 ◽  
Author(s):  
Khalid Al-Widyan ◽  
Jorge Angeles
Keyword(s):  
Covariance Matrix ◽  
Robust Design ◽  
Design Problem ◽  
Engineering Systems ◽  
Design Environment ◽  
Design Task ◽  
Model Based ◽  
Functional Relations ◽  
Design Variables ◽  
Environment Parameters

Laid down in this paper are the foundations on which the design of engineering systems, in the presence of an uncontrollable changing environment, can be based. The changes in environment conditions are accounted for by means of robustness. To this end, a theoretical framework as well as a general methodology for model-based robust design are proposed. Within this framework, all quantities involved in a design task are classified into three sets: the design variables (DV), grouped in vector x, which are to be assigned values as an outcome of the design task; the design-environment parameters (DEP), grouped in vector p, over which the designer has no control; and the performance functions (PF), grouped in vector f, representing the functional relations among performance, DV, and DEP. A distinction is made between global robust design and local robust design, this paper focusing on the latter. The robust design problem is formulated as the minimization of a norm of the covariance matrix of the variations in PF upon variations in the DEP, aka noise in the literature on robust design. Moreover, one pertinent concept is introduced: design isotropy. We show that isotropic designs lead to robustness, even in the absence of knowledge of the statistical properties of the variations of the DEP. To demonstrate our approach, a few examples are included.

scholarly journals Disposable miniature check valve design suitable for scalable manufacturing

2013 ◽  
Vol 203 ◽  
pp. 76-81 ◽  
Author(s):  
Anna I. Hickerson ◽  
Hsiang-Wei Lu ◽  
Kristina Roskos ◽  
Thomas Carey ◽  
Angelika Niemz
Keyword(s):  
Check Valve ◽  
Valve Design

Haptic Wrists: An Alternative Design Strategy Based on User Perception

2009 ◽  
Vol 9 (1) ◽  
Author(s):  
Javier Martín ◽  
Joan Savall ◽  
Iñaki Díaz ◽  
Josune Hernantes ◽  
Diego Borro
Keyword(s):  
Collision Detection ◽  
Design Problem ◽  
Force Feedback ◽  
Mechanical Design ◽  
Design Strategy ◽  
User Perception ◽  
Satisfactory Solution ◽  
Alternative Design ◽  
Three Degree Of Freedom ◽  
Mechanical Design Problem

A new three degree-of-freedom (3DOF) torque feedback wrist is being developed to be added to an existing 3DOF force feedback haptic device. It is difficult to find a satisfactory solution to the mechanical design problem, mainly because of the required large rotational workspace and severe weight constraints. This work proposes an alternative design strategy based on user perception, which allows simplification of the mechanics. The proposed approach consists of substituting the last rotational DOF of the wrist with a pseudohaptic DOF. Thanks to specially designed visuotactile cues, the pseudohaptic DOF is integrated with the active DOF into the same device, being able to generate free motion and collision detection perception to the user. This approach provides for simpler kinematics, lightweight designs, lower inertias, and less friction, which are key advantages for the inclusion of torque feedback into force feedback devices.

Development of Enertech’s Advanced Normally Open NozzleCheck Valves for Generation III+ Nuclear Power Plants

2014 ◽  
Author(s):  
Haykaz Mkrtchyan
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Reverse Flow ◽  
Flow Direction ◽  
Fluid Dynamic ◽  
High Capacity ◽  
Check Valve ◽  
Operating Conditions ◽  
Flow Conditions ◽  
Valve Design

Enertech introduced the first Normally Open NozzleCheck valves to the nuclear power industry nearly 20 years ago. This passive valve design was developed to address reoccurring maintenance and reliability issues often experienced by various check valve types due to low or turbulent flow conditions. Specifically, premature wear on the hinge pins, bushings and severe seat impact damage had been discovered in several applications while the systems were in steady state operating conditions. Over the last two decades, Enertech has continued to improve upon the design of the valve, with the culmination coming most recently in support of Generation III+ passive reactor requirements. This entirely new valve is designed with minimal stroke, ensuring quick closure under low reverse flow conditions which no other check valve design could support. Additionally, features such as first in kind test ports, visual inspection points, and the ability to manually stroke the valve in line have resolved many of the short comings of previous inline welded flow check valves. Most importantly, advanced test based methodologies and models developed by Enertech, allow for accurate prediction of NozzleCheck valve performance. This paper presents the development of Enertech’s advanced Normally Open NozzleCheck Valve for Generation III and III+ nuclear reactor designs. The Valve performance was initially determined by using verified and validated computational fluid dynamic (CFD) methods. The results obtained from the CFD model were then compared to the data gathered from a prototype valve that was built and tested to confirm the performance predictions. Enertech has fully tested and qualified the Normally Open NozzleCheck valve which is specifically designed for applications that require a high capacity in the forward flow direction and a quick closure during low reverse flow condition with short stroke to minimize the hydraulic impact on the system.

Robust Optimal Design for Worst-Case Tolerances

1994 ◽  
Vol 116 (4) ◽  
pp. 1019-1025 ◽  
Author(s):  
G. Emch ◽  
A. Parkinson
Keyword(s):  
Nonlinear Programming ◽  
Optimal Design ◽  
Worst Case ◽  
New Approach ◽  
Robust Designs ◽  
Design Variables ◽  
Robust Optimal Design ◽  
Programming Techniques ◽  
Engineering Models ◽  
Analytical Tools

Engineering models can and should be used to understand the effects of variability on a design. When variability is ignored, brittle designs can result that will not function properly or that will fail in service. By contrast, robust designs function properly even when subjected to off-nominal conditions. There is a need for better analytical tools to help engineers develop robust designs. In this paper we present a new approach for developing designs that are robust to variability induced by worst-case tolerances. An advantage of this approach is that tolerances may be placed on any or all model inputs, whether design variables or parameters. The method adapts nonlinear programming techniques in order to determine how a design should be modified to account for variability. We tested the method under relatively severe conditions on 13 problems, with excellent results. Using this approach, a designer can account for the effects of worst-case tolerances, making it possible to build robustness into an engineering design.

Using Engineering Models to Control Variability: Feasibility Robustness for Worst-Case Tolerances

1993 ◽  
Author(s):  
Gary Emch ◽  
Alan Parkinson
Keyword(s):  
Nonlinear Programming ◽  
Engineering Design ◽  
Test Cases ◽  
Worst Case ◽  
Robust Designs ◽  
Feasibility Robustness ◽  
Programming Techniques ◽  
Engineering Models ◽  
Analytical Tools ◽  
General Method

Abstract Engineering models can and should be used to understand the effects of variability on a design. When variability is ignored, brittle designs can result that fail in service. By contrast, robust designs function properly even when subjected to off-nominal conditions. There is a need for better analytical tools to help engineers develop robust designs. In this paper we present a general method for developing designs that are robust to variability induced by worst-case tolerances. The method adapts nonlinear programming techniques in order to determine how a design should be modified to account for variability. We show how this can be done with second order, or even exact, worst-case tolerance models. Results are given for 13 test cases that span a variety of problems. The method enables a designer to understand and account for the effects of worst-case tolerances, making it possible to build robustness into an engineering design.

Dynamic Non-Interference Constraints in Goal-Directed Geometry

1995 ◽  
Author(s):  
Stewart Coulter ◽  
Bert Bras ◽  
David Rosen
Keyword(s):  
Computer Aided Design ◽  
Preliminary Design ◽  
Design Tools ◽  
Multi Objective Optimization ◽  
Computational Framework ◽  
Linkage Design ◽  
Engineering Models ◽  
Aided Design ◽  
Dynamic Interference

Abstract Improvements in computer-aided design tools can significantly increase designer productivity. The ability to explore a variety of possible designs quickly and effectively is essential for a designer. In a previous paper, Goal Directed Geometry (GDG) was introduced as a computational framework for preliminary design, aiding the formulation of engineering models with geometric considerations, and the solution of these models with a multi-objective optimization package. The geometric considerations were limited to static noninterference constraints, introducing a metric and method for prevention of geometric interference between two subassemblies. In this paper, this metric and method are expanded to include the prevention of interference between moving subassemblies, or dynamic interference. Based on a series of repetitive static checks, this metric is intended to be accurate and simple for the designer to use. A case study is presented showing the GDG implementation for a linkage design problem, demonstrating the use of this metric. This parametric GDG model is then solved using an existing optimization program called DSIDES.

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