Shape optimization of the fillet under a bolt’s head

2019 ◽  
Vol 54 (4) ◽  
pp. 247-253
Author(s):  
Andrea Sorrentino ◽  
Davide Castagnetti ◽  
Andrea Spaggiari ◽  
Eugenio Dragoni
Keyword(s):  
Shape Optimization ◽  
Stress Reduction ◽  
Ad Hoc ◽  
Optimization Procedure ◽  
Element Model ◽  
Critical Issue ◽  
Stress Concentrations ◽  
Lower Stress ◽  
Notch Radius ◽  
Head Height

The stress concentration in the fillet under a bolt’s head is a critical issue for the fatigue life of this component. Remembering the variable notch radius solution observed in many biological structures to lower stress concentrations due to normal loads, this work proposes, examines and optimizes a double circular arc fillet, not re-entering the head. The work implements an ad hoc shape optimization procedure that combines a genetic algorithm (the particle swarm optimization) and a parametric, axisymmetric finite-element model of the bolt: by focusing on an M12 bolt, the analysis focuses on two issues: first, the optimization of the radius of each arc in the fillet; second, the optimization of the bolt’s head height and head’s diameter in combination with the fillet radiuses. By comparing the proposed solution with the fillet geometries for the bolt’s heads from the literature, it appears a noticeable stress reduction, about 14% lower than the standard circular fillet, combined with an easy manufacturing.

scholarly journals An Efficient Contact Model for Rotating Mechanism Analysis and Design in Bridge Construction

2021 ◽  
Vol 16 (1) ◽  
pp. 57-76
Author(s):  
Shiping Huang ◽  
Yong Tang ◽  
Zhaoxun Yuan ◽  
Xiaopeng Cai
Keyword(s):  
Element Model ◽  
Critical Issue ◽  
Bridge Engineering ◽  
Contact Friction ◽  
Mechanism Analysis ◽  
Stress Concentrations ◽  
Bridge Construction ◽  
Surface Design ◽  
Analysis And Design ◽  
Nonlinear Stress

The rotation superstructure construction method is a widespread technique in bridge engineering. The critical issue for the successful application of this technique is the contact interface analysis and design for the rotating mechanism. A semi-analytical method predicated upon obtaining a uniform distribution of pressure on the slide plates within the interface is proposed. The surface design typically generates a nonlinear stress distribution. It leads to local damage and local asperity interlocking, which increase the contact friction dramatically during the rotation. In contrast, the proposed approach provides a surface that avoids stress concentrations and is expected to reduce the material cost of the slide plates. The proposed method is verified by the Finite Element Model. It can be used in a broad area involving contacting surface design, especially in the rotating mechanism design for bridge construction.

GPS Aided GEO Augmented Navigation Enabled Energy Efficient Routing for Mobile Ad-hoc Wireless Networks

2017 ◽  
Vol 2 (7) ◽  
pp. 5-8
Author(s):  
Neeraj Verma ◽  
Kuber Mohan
Keyword(s):  
Energy Efficient ◽  
Ad Hoc ◽  
Mobile Ad Hoc Network ◽  
Critical Issue ◽  
Ad Hoc Wireless Networks ◽  
Energy Utilization ◽  
Energy Efficient Routing ◽  
Network Nodes ◽  
Mobile Ad Hoc ◽  
Hoc Networks

Energy is a critical issue in Mobile Ad-hoc Network. Nodes in Network are working in presence of limited or less energy due to dynamic nature of nodes or infrastructure less network. MANET has no infrastructure so nodes in MANET work on dynamic routing. In this way, energy proficient routing is required for reducing energy utilization. Energy proficient routing plans can extraordinarily reduce energy utilization and augments the lifetime of the networks. Scalability of Ad Hoc Networks can be enhanced by using land data, for example, in LAR, GPSR etc. They utilize physical area data; regularly from GPS (Global Positioning System).GPS empowers a gadget to decide their position as in longitude, Latitude and Altitude by getting this data from the satellites. There has been significant effort in proposing energy efficient routing protocols with the help of GAGAN (GPS Aided GEO Augmented Navigation) which have accuracy to approx One meter in India or its neighbor countries. GAGAN is a route framework which is helped by both GPS and nearby telemetry information to possibly give quicker and more exact situating and navigational information.

Structural Shape Optimization Wth Error Control

1994 ◽  
Author(s):  
Pierre Duysinx ◽  
WeiHong Zhang ◽  
HaiGuang Zhong ◽  
Pierre Beckers ◽  
Claude Fleury
Keyword(s):  
Shape Optimization ◽  
Computer Aided Design ◽  
Adaptive Mesh Refinement ◽  
Error Control ◽  
Optimization Procedure ◽  
Adaptive Mesh ◽  
Structural Shape ◽  
Structural Shape Optimization ◽  
Design Variables ◽  
Recent Developments

Abstract A robust and automatic shape optimization procedure is presented in this paper, which incorporates recent developments in the field of computer-aided design (CAD) of mechanical structures, such as geometric modelling, automatic selection of independent design variables, sensitivity analysis using reliable mesh perturbation schemes, error estimation and adaptive mesh refinement. A numerical example is given to show the efficiency of the procedure.

Assessment of AASHTO Load-Spreading Method for Buried Culverts and Proposed Improvement

2021 ◽  
pp. 036119812110215
Author(s):  
Michael G. Katona
Keyword(s):  
Ad Hoc ◽  
Soil Depth ◽  
Free Field ◽  
Peak Stress ◽  
Element Model ◽  
Surface Load ◽  
Accuracy Evaluation ◽  
Simple Modification ◽  
Homogeneous Half Space ◽  
Order Of Magnitude

AASHTO’s ad hoc method (AAM) for predicting free-field soil stress under a rectangular loading area is a simple and very useful tool for the analysis of buried culverts subject to vehicular wheel loads. AAM assumes the surface load spreads with soil depth into an ever-increasing rectangular area whose dimensions are controlled by a constant spread angle θ usually taken as 30°, denoted as AAM-30°. Both simplified and comprehensive culvert analysis procedures utilize AAM predictions for adjusting pressure distributions acting on the culvert periphery. Also, AAM-30° is routinely used to determine the two-wheel soil interaction depth, in which the combined effect of both axial wheels need to be considered. To date, a thorough accuracy analysis of AAM-30° has not been published in the open literature. This paper provides a unique and rigorous evaluation of AAM-30° using an exact solution from an elasticity-based model (EBM) of a homogeneous half-space with rectangular surface load. One key discovery is the depth parameter called y*, which is the soil depth at which AAM-30° peak-stress prediction exactly matches the exact EBM solution. Moreover, it is shown that y* may be determined by a simple, yet accurate formula that only depends on the square root of the load area. However, the investigation reveals that AAM-30° significantly underestimates peak stress in the shallow-depth zone 0 <  y < ½ y* by as much as 31.3% of the applied surface pressure. As this is a large nonconservative error it cannot be ignored. Accordingly, a very simple modification is introduced called AAM-θ*, in which θ* is a spread angle that linearly increases to 30° at soil depth ½ y* and thereafter θ* remains constant at 30°. An accuracy evaluation of AAM-θ* reveals an order of magnitude increase in accuracy in which the small residual error is conservative, not nonconservative. The paper concludes with discussions on applying AAM-θ* to the analysis of buried culverts when using either simple or finite element model solution procedures.

A New Shaft Coupling Design for a High-Speed Rotor Wheel

1995 ◽  
Author(s):  
Tibor Kiss ◽  
Wing-Fai Ng ◽  
Larry D. Mitchell
Keyword(s):  
High Speed ◽  
High Stress ◽  
Critical Issue ◽  
Working Environment ◽  
Outer Diameter ◽  
Stress Concentrations ◽  
Coupling Region ◽  
Rotor Wheel ◽  
High Stress Concentration ◽  
Safety Margins

Abstract A high-speed rotor wheel for a wind-tunnel experiment has been designed. The rotor wheel was similar to one in an axial turbine, except that slender bars replaced the blades. The main parameters of the rotor wheel were an outer diameter of 10“, a maximum rotational speed of 24,000 RPM and a maximum transferred torque of 64 lb-ft. Due to the working environment, the rotor had to be designed with high safety margins. The coupling of the rotor wheel with the shaft was found to be the most critical issue, because of the high stress concentration factors associated with the conventional coupling methods. The efforts to reduce the stress concentrations resulted in an advanced coupling design which is the main subject of the present paper. This new design was a special key coupling in which six dowel pins were used for keys. The key slots, now pin-grooves, were placed in bosses on the inner surface of the hub. The hub of the rotor wheel was relatively long, which allowed for applying the coupling near the end faces of the hub, that is, away from the highly loaded centerplane. The long hub resulted in low radial expansion in the coupling region. Therefore, solid contact between the shaft and the hub could be maintained for all working conditions. To develop and verify the design ideas, stress and deformation analyses were carried out using quasi-two-dimensional finite element models. An overall safety factor of 3.7 resulted. The rotor has been built and successfully accelerated over the design speed in a spin test pit.

Robust Shape Optimization of Uncertain Dense Gas Flows Through a Plane Turbine Cascade

2011 ◽  
Author(s):  
Samuel J. Hercus ◽  
Paola Cinnella
Keyword(s):  
Robust Optimization ◽  
Shape Optimization ◽  
Flow Behavior ◽  
Computational Cost ◽  
Optimization Procedure ◽  
System Stability ◽  
Dense Gas ◽  
Turbine Cascade ◽  
The Mean ◽  
Inlet Conditions

A robust shape optimization procedure based on a multi-objective genetic algorithm coupled to a non-intrusive uncertainty quantification analysis was applied to a transonic inviscid flow of a dense gas over a plane turbine cascade. The goal was to simultaneously improve the mean turbine performance and the system stability under fluctuating thermodynamic inlet conditions. Despite an elevated computational cost, the optimization procedure was capable of generating a Pareto front of turbine geometries which improved the mean isentropic turbine efficiency μ(ηs) over the baseline profile, while limiting the solution variability in terms of the coefficient of variation of the power output CV(P2D). In addition to demonstrating an excellent parallel scalability over 1600 processors, the robust optimization revealed that variability of CV(P2D) depends more on the variation of inlet conditions than turbine geometry. A posteriori stochastic analyses on selected optimized turbine geometries allowed an investigation of flow behavior variability, as well as propositions for the improved selection of robust optimization cost criteria in future simulations.

Generation of Complex Energy Systems by Combination of Elementary Processes

2018 ◽  
Vol 140 (11) ◽  
Author(s):  
A. Toffolo ◽  
S. Rech ◽  
A. Lazzaretto
Keyword(s):  
Design Optimization ◽  
Ad Hoc ◽  
Energy Systems ◽  
Optimization Procedure ◽  
Thermodynamic Cycle ◽  
Energy System ◽  
Design Parameters ◽  
System Configuration ◽  
Complex Energy ◽  
Synthesis Design

The fundamental challenge in the synthesis/design optimization of energy systems is the definition of system configuration and design parameters. The traditional way to operate is to follow the previous experience, starting from the existing design solutions. A more advanced strategy consists in the preliminary identification of a superstructure that should include all the possible solutions to the synthesis/design optimization problem and in the selection of the system configuration starting from this superstructure through a design parameter optimization. This top–down approach cannot guarantee that all possible configurations could be predicted in advance and that all the configurations derived from the superstructure are feasible. To solve the general problem of the synthesis/design of complex energy systems, a new bottom–up methodology has been recently proposed by the authors, based on the original idea that the fundamental nucleus in the construction of any energy system configuration is the elementary thermodynamic cycle, composed only by the compression, heat transfer with hot and cold sources and expansion processes. So, any configuration can be built by generating, according to a rigorous set of rules, all the combinations of the elementary thermodynamic cycles operated by different working fluids that can be identified within the system, and selecting the best resulting configuration through an optimization procedure. In this paper, the main concepts and features of the methodology are deeply investigated to show, through different applications, how an artificial intelligence can generate system configurations of various complexity using preset logical rules without any “ad hoc” expertise.

Finite element modeling of guyed back spars in cable logging

2004 ◽  
Vol 34 (4) ◽  
pp. 817-828 ◽  
Author(s):  
Albert Saravi ◽  
C Kevin Lyons
Keyword(s):  
Finite Element ◽  
Normal Stress ◽  
Cross Section ◽  
A Priori ◽  
Element Model ◽  
Transverse Cross Section ◽  
Stress Fields ◽  
Stress Concentrations ◽  
Maximum Normal Stress ◽  
Tree Method

In this study a finite element model of a back spar system was developed with three guylines opposing the skyline strap tension. In this paper the allowable skyline strap tension is the tension in the skyline strap that results in the maximum normal stress on a transverse cross section of the tree being equal to an assumed allowable stress. An iterative routine was developed to find the allowable skyline strap tension, and this routine was found to converge rapidly from initial values that were below and above the allowable skyline strap tension. Two algorithms were developed for finding the maximum normal stress on a transverse cross section of a tree, method 1 and method 2. If the plane that the tree displaced in was known a priori, then method 2 could be used, and it was found to be less sensitive to mesh coarseness. If the plane that the tree displaced in was not known a priori, then method 1 had to be used with a less coarse mesh. It was found that the stress concentrations due to simplified cable connections were not significant for rigging configurations that allowed a larger rigging point displacement. The rigging configurations that allowed larger rigging point displacements have stress fields that are dominated by bending, while for rigging configurations that allow only small rigging point displacements, the stress fields are dominated by axial compression.

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