Stress Analysis Applications to Service Failures of Traveling-Wave Tubes

1984 ◽  
Vol 106 (4) ◽  
pp. 533-537
Author(s):  
H.-Y. Yeh
Keyword(s):  
Stress Concentration ◽  
Traveling Wave ◽  
Elastic Stress ◽  
Electronic Device ◽  
Electrical Breakdown ◽  
Point Of View ◽  
Service Failures ◽  
Stress Concentration Factors ◽  
Traveling Wave Tubes ◽  
Element Technique

By utilizing the mathematical analogy between the electrostatic fields and the elastic stress field, the electrostatic stresses in high voltage electronic device such as Traveling Wave Tubes (TWT) can be obtained from finite element technique. A new point of view about the vacuum electrical breakdown from the theory of elastic stress concentration has been proposed. The elastic stress concentration factors may be used as a good reference figure for TWT design works.

Elastic Stress Concentrations for the Torsion of Hollow Shouldered Shafts Determined by an Electrical Analogue

1964 ◽  
Vol 15 (1) ◽  
pp. 83-96 ◽  
Author(s):  
K. R. Rushton
Keyword(s):  
Stress Concentration ◽  
Elastic Stress ◽  
Plastic Region ◽  
Stress Concentrations ◽  
Electrical Analogue ◽  
Shoulder Diameter ◽  
Concentration Factors ◽  
Stress Concentration Factors

SummaryThe elastic stress concentration factors for the torsion of solid and hollow shouldered shafts have been determined by means of a pure resistance electrical analogue. Fillet radii ranged from 0.05 to 1.0 times the diameter of the smaller shaft, and the shoulder diameter increased from 1.0 to 8.10 times the diameter of the smaller shaft. A comparison is made with the results of other techniques. A study has also been made of the formation of a plastic region in the neighbourhood of the fillet.

A simplified approach to calculating stresses due to radial loads and moments applied to branches in cylindrical pressure vessels (calculations to BS 5500, Appendix G)

1981 ◽  
Vol 16 (4) ◽  
pp. 217-226 ◽  
Author(s):  
M A Teixeira ◽  
R D McLeish ◽  
S S Gill
Keyword(s):  
Stress Concentration ◽  
Elastic Stress ◽  
Pressure Vessels ◽  
Geometrical Parameters ◽  
Local Loads ◽  
Simplified Approach ◽  
Concentration Factors ◽  
Stress Concentration Factors

Simplified charts are presented for elastic stress concentration factors due to radial loads and circumferential and longitudinal moments applied to circular branches normal to cylindrical pressure vessels. The charts are based on the procedures given in Appendix G of BS 5500. The assumptions implied in Appendix G and the limitations on the geometrical parameters ro/r and r/t are discussed. A modification to Appendix G is suggested which is slightly more restrictive than at present. Published results for stresses due to local loads on branches in cylindrical vessels are compared with the values given by the charts.

Analytical Methods for Preliminary Design of Anchor Flanges for Subsea Structures

2019 ◽  
Author(s):  
Sabesan Rajaratnam ◽  
T. Sriskandarajah ◽  
Daryl Clayton ◽  
Graeme Roberts ◽  
Vincent Loentgen ◽  
...  
Keyword(s):  
Stress Concentration ◽  
Plastic Strain ◽  
Elastic Stress ◽  
Limit Load ◽  
Preliminary Design ◽  
Time Saving ◽  
Linear Elastic ◽  
Stress Concentration Factors ◽  
Ultimate Load Carrying Capacity ◽  
Cost Implications

Abstract Anchor flanges are interface items which are used to connect pipelines to subsea in-line and end termination structures. They are forged and tend to be long-lead items; therefore, the design of an anchor flange should be completed at a very early project stage, possibly even during the tender phase. An optimised, analytical method for preliminary design would result in reduced design time overall and have beneficial cost implications. The analytical notch methods (i.e. Neuber’s and Glinka’s) that are presented utilise linear-elastic stress concentration factors to make realistic predictions of the ultimate load carrying capacity of an anchor flange in the non-linear regime. The linear-elastic stress concentration factor values are calculated with simple analytical formulae and graphs. The analytical notch methods are deployed to predict the anchor flange limit load and peak plastic strain and thereby ensure that the plastic strain remains within the allowable limits of design codes. The cost and time saving associated with the analytical notch methods, and the accuracy that is maintained, are assessed by comparison with the predictions results obtained from detailed finite element analyses.

Engineering Procedure for Calculation of Elastic Stress Concentration Factors of Bearing Pad Fretting Flaws

2009 ◽  
Author(s):  
Bogdan S. Wasiluk ◽  
Douglas A. Scarth
Keyword(s):  
Finite Element ◽  
Stress Concentration ◽  
Crack Initiation ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Elastic Stress ◽  
Elliptical Hole ◽  
Flat Bottom ◽  
Concentration Factors ◽  
Stress Concentration Factors

Procedures to evaluate volumetric bearing pad fretting flaws for crack initiation are in the Canadian Standard N285.8 for in-service evaluation of CANDU® pressure tubes. The crack initiation evaluation procedures use equations for calculating the elastic stress concentration factors. Newly developed engineering procedure for calculation of the elastic stress concentration factor for bearing pad fretting flaws is presented. The procedure is based on adapting a theoretical equation for the elastic stress concentration factor for an elliptical hole to the geometry of a bearing pad fretting flaw, and fitting the equation to the results from elastic finite element stress analyses. Non-dimensional flaw parameters a/w, a/c and a/ρ were used to characterize the elastic stress concentration factor, where w is wall thickness of a pressure tube, a is depth, c is half axial length, and ρ is root radius of the bearing pad fretting flaw. The engineering equations for 3-D round and flat bottom bearing pad fretting flaws were examined by calculation of the elastic stress concentration factor for each case in the matrix of source finite element cases. For the round bottom bearing pad fretting flaw, the fitted equation for the elastic stress concentration factor agrees with the finite element results within ±3.7% over the valid range of flaw geometries. For the flat bottom bearing pad fretting flaw, the fitted equation agrees with the finite element results within ±4.0% over the valid range of flaw geometries. The equations for the elastic stress concentration factor have been verified over the valid range of flaw geometries to ensure accurate results with no anomalous behavior. This included comparison against results from independent finite element calculations.

Reliable Ceramic Window Design for Electronic Devices

1992 ◽  
Vol 114 (3) ◽  
pp. 349-352
Author(s):  
Hsien-Yang Yeh
Keyword(s):  
Traveling Wave ◽  
Electronic Device ◽  
High Vacuum ◽  
Complex Nature ◽  
Circular Plates ◽  
Linear Elastic ◽  
Center Conductor ◽  
Elastic Fracture ◽  
Traveling Wave Tubes ◽  
Window Design

The effective operations of a high voltage vacuum electronic device, such as a traveling wave tube, depends on its ability to maintain high vacuum environments. However, during temperature tests, some tubes fail because of vacuum leaks through cracks in the ceramic window. It is believed that these leaks result from RF heating at the center conductor, which caused the ceramic to crack. To obtain a general understanding of the stress field in the window structure, a closed from analytical approach is imperative. However, due to the complex nature of the problem, only the first order engineering approximation is used in this preliminary study. The theory of linear elastic fracture mechanics and the existing solutions from elastic circular plates are useful for understanding the cause of ceramic window cracks. Some simple design references have also been developed for the design of reliable ceramic windows for traveling wave tubes.

Elastic-plastic finite element analysis of hollow tubes with axially loaded axisymmetric internal projections

1993 ◽  
Vol 28 (3) ◽  
pp. 187-196 ◽  
Author(s):  
S J Hardy ◽  
A R Gowhari-Anaraki
Keyword(s):  
Finite Element ◽  
Stress Concentration ◽  
Elastic Stress ◽  
Low Cycle Fatigue ◽  
Kinematic Hardening ◽  
Isotropic Hardening ◽  
Published Data ◽  
Elastic Plastic ◽  
Concentration Factors ◽  
Stress Concentration Factors

The finite element method is used to study the monotonic and cyclic elastic-plastic stress and strain characteristics of hollow tubes with axisymmetric internal projections subjected to monotonic and repeated axial loading. Two geometries having low and high elastic stress concentration factors are considered in this investigation, and the results are complementary to previously published data. For cyclic loading, three simple material behaviour models, e.g., elastic-perfectly-plastic, isotropic hardening, and kinematic hardening are assumed. All results have been normalized with respect to material properties so that they can be applied to all geometrically similar components from other materials which may be represented by the same material models. Finally, normalized maximum monotonic strain and steady state strain range, predicted in the present investigation and from previously published data, are plotted as a function of the nominal load for different material hardening assumptions and different elastic stress concentration factors. These plots can be used in the low cycle fatigue design of such geometrically similar components.

Updated Stress Concentration Factors for Filleted Shafts in Bending and Tension

1996 ◽  
Vol 118 (3) ◽  
pp. 321-327 ◽  
Author(s):  
S. M. Tipton ◽  
J. R. Sorem ◽  
R. D. Rolovic
Keyword(s):  
Finite Element ◽  
Stress Concentration ◽  
Maximum Stress ◽  
Elastic Stress ◽  
Equivalent Stress ◽  
Graphical Form ◽  
Fatigue Crack Nucleation ◽  
Wide Range ◽  
Concentration Factors ◽  
Stress Concentration Factors

Published elastic stress concentration factors are shown to underestimate stresses in the root of a shoulder filleted shaft in bending by as much as 21 percent, and in tension by as much as forty percent. For this geometry, published charts represent only approximated stress concentration factor values, based on known solutions for similar geometries. In this study, detailed finite element analyses were performed over a wide range of filleted shaft geometries to define three useful relations for bending and tension loading: (1) revised elastic stress concentration factors, (2) revised elastic von Mises equivalent stress concentration factors and (3) the maximum stress location in the fillet. Updated results are presented in the familiar graphical form and empirical relations are fit through the curves which are suitable for use in numerical design algorithms. It is demonstrated that the first two relations reveal the full multiaxial elastic state of stress and strain at the maximum stress location. Understanding the influence of geometry on the maximum stress location can be helpful for experimental strain determination or monitoring fatigue crack nucleation. The finite element results are validated against values published in the literature for several geometries and with limited experimental data.

Stress and Strength Analysis of Equal-Diameter Tees

1991 ◽  
Vol 113 (1) ◽  
pp. 55-63 ◽  
Author(s):  
J. Zhixiang ◽  
Z. Qingjiang ◽  
Z. Siding
Keyword(s):  
Finite Element ◽  
Stress Concentration ◽  
Stress Distribution ◽  
Maximum Stress ◽  
Elastic Stress ◽  
Stress Factors ◽  
Strength Analysis ◽  
Stress Distributions ◽  
Concentration Factors ◽  
Stress Concentration Factors

The elastic stress distribution of four models (β=Do/Di=1.07, 1.20, unreinforced and weld-reinforced) under five typical external loadings and the strength of six models (in addition to β=1.50) under internal pressure are investigated experimentally. The maximum stress factors are obtained. The influences of weld-reinforced structure on stress distribution and strength characteristics of tees are discussed. The finite-element predictions of unreinforced tees with β=1.07, 1.11, 1.15, 1.20 are carried out. The predicted stress distributions agree well with measured results. The relation between β and stress concentration factors under various loadings are obtained.

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