The Superposition of Stress Concentration Factors

1962 ◽  
Vol 84 (1) ◽  
pp. 129-132 ◽  
Author(s):  
Frank W. Paul ◽  
Thomas R. Faucett
Keyword(s):  
Stress Concentration ◽  
Brittle Material ◽  
Mathematical Analysis ◽  
Concentration Factor ◽  
Close Agreement ◽  
Individual Factors ◽  
Test Results ◽  
Concentration Factors ◽  
Stress Concentration Factors ◽  
The Individual

A photoelastic study was made of the superposition of stress raising notches. Recent investigations [1, 2] have indicated that where one stress raising notch is placed in the region of maximum influence of a second notch the resulting stress concentration factor may be determined by taking the product of the concentration factors for the individual notches. Test results presented gave general although not precise agreement with this method of combination. The tests of reference [1] were performed on specific materials for static and repeated loads, and hence combine the effects of stress concentration with the sensitivity of the particular material. The tests of reference [2] run on a brittle material indicate the same general agreement. Normal practice for applying stress concentration factors separates the two effects, i.e., the actual concentration of stress and the sensitivity of the material to such concentration. It was believed that photoelasticity might yield a better verification of the method for combining superposed stresses as photoelastic methods have shown close agreement with theoretical factors of stress concentration. Results of the present investigation indicate that the product gives the combined concentration factor with the same degree of accuracy to which the individual factors are known. A mathematical analysis was made to determine the stresses across the section.

Investigation of Critical Stress Concentration Factor in Analytical Stress Based Forming Limit Criterion

2009 ◽  
Author(s):  
Kyle R. McLaughlin ◽  
Tugce Kasikci ◽  
Igor Tsukrov ◽  
Brad L. Kinsey
Keyword(s):  
Stress Concentration ◽  
Stress Concentration Factor ◽  
Failure Criterion ◽  
Concentration Factor ◽  
Critical Stress ◽  
Strain Path ◽  
Path Dependence ◽  
Forming Limit ◽  
Concentration Factors ◽  
Stress Concentration Factors

Tearing concerns in sheet metal forming have traditionally been predicted by comparing the strain state imposed on a material to its associated strain based Forming Limit Diagram. A shortcoming of this strain based failure criterion is that the Forming Limit Curves exhibit strain path dependence. Alternatively, a stress based failure criterion was introduced and shown analytically and numerically to exhibit less strain path dependence. In our past research, an analytical model was created to predict the stress based Forming Limit Curve. Inputs into the model include a material constitutive relationship, anisotropic yield criterion and a critical stress concentration factor, defined as the ratio of the effective stress in the base material to the effective stress in the necking region. This stress concentration factor is thought to be a material parameter, which characterizes a material’s ability to work harden and prevent the concentration of stress which produces the necking condition. In this paper, the critical stress concentration factors for steel and aluminum alloys were determined by comparing analytical model predictions and experimental data and found to be significantly different. A setup is then proposed to experimentally measure the critical stress concentration factors and initial results are presented.

Stress-Concentration Factors at a Doubly-Symmetric Hole

1966 ◽  
Vol 17 (2) ◽  
pp. 177-186 ◽  
Author(s):  
L. H. Mitchell
Keyword(s):  
Stress Concentration ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Infinite Plate ◽  
Concentration Factors ◽  
Stress Concentration Factors

SummaryThe stress-concentration factor is calculated for an infinite plate in tension containing a doubly-symmetrical hole whose boundary consists of parts of three intersecting circles. A suggestion is made for modifying the results to apply to a strip.

The Prediction of Three-Dimensional Stress Concentration Factors

1959 ◽  
Vol 63 (585) ◽  
pp. 549-551 ◽  
Author(s):  
I. M. Allison
Keyword(s):  
Stress Concentration ◽  
Mathematical Analysis ◽  
Three Dimensional ◽  
Stress Raiser ◽  
Two Dimensions ◽  
Two Dimensional ◽  
Torsional Loading ◽  
Loading System ◽  
Concentration Factors ◽  
Stress Concentration Factors

Two-Dimensional Stress concentration factors may be obtained more quickly and simply than the corresponding three-dimensional factors, either by experiment or mathematical analysis. It would be convenient to obtain information, for varying geometry in the two-dimensional case of a particular type of stress raiser, e.g. a shoulder, groove or hole, and use this either to predict the three-dimensional stress concentration factors or to extend the range of existing three-dimensional results. Clearly a comparison is only possible if the three-dimensional stress raiser embodies a plane of symmetry (which gives the geometry of the similar two-dimensional stress raiser), and if the loading conditions can be reproduced in both the two- and three-dimensional cases. The latter requirement restricts the correlation to the stress concentration factors obtained in tension and in bending. The three-dimensional torsional loading system has no plane of symmetry which can be simulated in two dimensions.

Stress Concentration Factors From Overlapping Stress Fields in Uniaxial Tension

1976 ◽  
Vol 98 (1) ◽  
pp. 332-339 ◽  
Author(s):  
H. T. Gencsoy ◽  
J. F. Hamilton ◽  
C. C. Yang
Keyword(s):  
Stress Concentration ◽  
Uniaxial Tension ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Substantial Effect ◽  
Stress Fields ◽  
Concentration Factors ◽  
Stress Concentration Factors ◽  
Stress Raisers ◽  
Resultant Stress

Standard transmission photoelastic techniques were used to determine the resultant stress concentration factors produced by multiple stress raisers in flat, rectangular bars under uniaxial tension. Observations were made on the overlapping stress fields due to various combinations and orientations of holes and semicircular grooves. Two cases of directly superposed discontinuities were also investigated. The results of this investigation indicate that the sizes and relative positions of the discontinuities had a substantial effect on the resultant stress concentration factor. In some cases the stress concentration factor would be decreased while in other cases it would be increased. In the case of superposed stress raisers considered in this investigation, the resultant stress concentration factor can be taken as the product of the individual stress concentration factors; this is in agreement with the results of other investigators. However, for other cases, much judgment and experience will be required to decide when this can be done. And even then this product should be considered only as the probable upper limit of the actual stress concentration factor.

A New Approach to Reducing the Stress Concentration Factors of Cross-Bores in Blocks Under High Pressure

2003 ◽  
Author(s):  
Mira K. Sahney
Keyword(s):  
High Pressure ◽  
Stress Concentration ◽  
Test Results ◽  
Element Analysis ◽  
New Approach ◽  
Standard Design ◽  
The Finite Element Analysis ◽  
Concentration Factors ◽  
Stress Concentration Factors ◽  
Fatigue Life Test

The fundamental design of high pressure joints such as crosses and tees has remained the same for many years. However, the introduction of commercially available high pressure equipment operating at 600 MPa and higher has demanded improved designs for these classic connections. This study presents a new design concept for reducing the stress concentration at intersecting crossbores. Both the finite element analysis and the fatigue test results from the standard high pressure design and the new design are compared. The new approach realizes a 17–25% reduction in the stress concentration factors and a 40% improvement in fatigue life test results when compared to the standard design.

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.

Torsional Stress Concentration Factors for Grooved Shafts

1967 ◽  
Vol 71 (673) ◽  
pp. 40-43 ◽  
Author(s):  
K. R. Rushton
Keyword(s):  
Stress Concentration ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Preliminary Investigation ◽  
Approximate Expression ◽  
Data Sheet ◽  
Analogue Computer ◽  
Torsional Stress ◽  
Concentration Factors ◽  
Stress Concentration Factors

SummaryThis paper describes a preliminary investigation of the torsional stress concentration factors for circular shafts containing grooves determined using an analogue computer. The range covered by this analysis is for grooves which increase in depth from a minimum of 0·05 of the diameter of the shaft, with radii which vary from 0·5 to 0·05 of the diameter at the minimum section. Results are presented in the form of a data sheet, and a comparison is made with the approximate expression of Neuber. An investigation is also made of the modifications to the stress concentration factor if the flank is not perpendicular to the centre-line of the shaft.

The Effect of a Large Hole on the Stress Concentration Factor of a Satellite Hole in a Tension Field

1999 ◽  
Vol 121 (3) ◽  
pp. 252-256 ◽  
Author(s):  
C. S. Sloan ◽  
M. D. Cowell ◽  
T. F. Lehnhoff
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Stress Concentration ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Hole Diameter ◽  
Element Analysis ◽  
Large Hole ◽  
Concentration Factors ◽  
Stress Concentration Factors

Stress concentration factors have been determined for large hole to small hole diameter ratios (D/d) of 10 to 50 for two holes in an infinitely wide tension-loaded panel. Finite element analysis was used to model the system of two holes in a plate that approximates the infinitely wide and tall case. Both the D/d ratio and edge to edge hole spacing were examined for hole placement along an axis perpendicular to the direction of the tension field. It was found for large D/d ratios that the stress concentration factor was only dependent on the distance between the hole edges divided by the large hole diameter. For the configurations analyzed, the stress concentration factors varied from approximately 3 to 11.

Neuber’s rule accounting for the material nonlinearity influence on the stress concentration of the laminated composites

2016 ◽  
Vol 36 (3) ◽  
pp. 214-225 ◽  
Author(s):  
Fathollah Taheri-Behrooz ◽  
Nima Bakhshi
Keyword(s):  
Stress Concentration ◽  
Stress Distribution ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Material Nonlinearity ◽  
Maximum Deviation ◽  
Linear Solution ◽  
Concentration Factors ◽  
Stress Concentration Factors ◽  
Neuber's Rule

Since holes comprise the necessary features of many structural components, a comprehensive understanding of the behavior of composite plates containing an open hole is a crucial step in their design process. In the present manuscript, an extensive numerical study has been conducted in order to investigate the effects of material nonlinearity on the stress distribution and stress concentration factors in unidirectional and laminated composite materials. To attain this objective, various models with different configurations were studied. In unidirectional composites, the maximum deviation of stress distribution around the hole (from the linear solution) happens in 45° lamina in which includes a high level of shear stress. However, the maximum difference in the stress concentration factor occurs in 15° lamina and is 15.1% at the onset of failure. In composite laminates, the maximum deviation of nonlinear stress concentration factor from the linear solution is reported 24.3% and it occurs in [+45/−45] s laminate. In the last section, Neuber’s rule is employed to find the stress concentration factors of the laminated composites, with a reasonable accuracy.

High Cycle Fatigue of Pipelines With Plain Dents: Simulations, Experiments and Assessment

2007 ◽  
Author(s):  
Se´rgio B. Cunha ◽  
Bianca C. Pinheiro ◽  
Ilson P. Pasqualino
Keyword(s):  
Stress Concentration ◽  
High Cycle Fatigue ◽  
Fatigue Tests ◽  
Test Material ◽  
Small Scale ◽  
Test Results ◽  
Cycle Fatigue ◽  
Concentration Factors ◽  
Stress Concentration Factors

The objective of this work is to propose a methodology for assessing the fatigue life of dented pipelines according to the current high cycle fatigue theory. The proposed methodology employs S-N curves obtained from tensile test material properties and includes an expression to estimate stress concentration factors for spherical dents. Finite element analyses are carried out to determine stress concentration factors for different pipe and dent geometries. Using the numerical results, an expression to estimate stress concentration factors of dented pipelines is developed. Additionally, fatigue tests are conducted with the application of cyclic internal pressure on small-scale dented steel pipe models. Different pressure levels are employed, resulting in failures ranging from around 6000 to more than 106 cycles, enabling the determination of the endurance limit and of the finite life behavior of dented pipes. Furthermore, the Goodman and Gerber criteria to account for the mean stress are evaluated in view of the experimental results. The fatigue test results are used to validate the proposed assessment methodology for the analyzed conditions.

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