Stresses in torispherical drumheads: A photoelastic investigation

1965 ◽  
Vol 1 (1) ◽  
pp. 69-82 ◽  
Author(s):  
H Fessler ◽  
P Stanley
Keyword(s):  
Stress Concentration ◽  
Stress Distribution ◽  
Elastic Stress ◽  
Yield Criterion ◽  
Uniform Stress ◽  
Stress Indices ◽  
Wide Range ◽  
Photoelastic Investigation ◽  
Bending Stresses ◽  
Von Mises

The dependence of the elastic stress distribution on the shape and thickness parameters in a wide range of torispherical drumheads has been examined using the photoelastic frozen-stress method. Peak principal stress indices are presented in the form of two contour systems; they have also been studied in terms of mean and bending stresses. An approximate approach to some of the practical problems of non-uniform stress gradients is suggested. Head distortions have been measured. A stress concentration factor based on the Maxwell-von Mises yield criterion is shown to be approximately equal to the conventional one.

Limit pressure for a spherical vessel with a circumferential slot at its junction with a radial cylindrical protruding branch

1987 ◽  
Vol 22 (4) ◽  
pp. 215-227 ◽  
Author(s):  
M Robinson ◽  
C S Lim ◽  
R Kitching
Keyword(s):  
Spherical Shell ◽  
Lower Bounds ◽  
Yield Criterion ◽  
Spherical Vessel ◽  
Non Linear Programming ◽  
Limit Pressure ◽  
Wide Range ◽  
Cylindrical Branch ◽  
Von Mises ◽  
Plastic Limit Pressure

One of the requirements of the two criteria method of safety assessment of a pressure vessel with a defect is an estimate of the plastic limit pressure. Here the defect is in a spherical shell close to its junction with a protruding radial cylindrical branch. The defect is assumed to be an axisymmetric circumferential slot of uniform depth on the outer surface of the shell. Lower bounds to the limit pressure are calculated for a wide range of geometries. The material is assumed to obey the von Mises yield criterion and a non-linear programming method is used to give optimum lower bounds. Data is supplied for spherical shell radius to thickness ratios from 25 to 100, nozzle radius to vessel radius ratios from 0 to 0.4, nozzle to vessel thickness ratios from 0.25 to 1.0 and ligament thickness to vessel thicknesses (ligament efficiencies) of 0 to 1. Slot widths vary from the significant to the infinitesimal, where it becomes a crack. Vessels of some proportions were shown to have their limit pressures reduced only a little by very low ligament efficiencies.

Stress Distribution Around Edge Slits in a Plate Loaded in Tension —the Effect of Finite Width of Plate

1962 ◽  
Vol 66 (617) ◽  
pp. 320-322 ◽  
Author(s):  
J. R. Dixon
Keyword(s):  
Stress Concentration ◽  
Stress Distribution ◽  
Flat Plate ◽  
Elastic Stress ◽  
Width Ratio ◽  
Finite Width ◽  
Two Dimensional ◽  
Finite Plate ◽  
Edge Slit ◽  
Plate Width

SummaryTwo-dimensional photoelastic tests have been carried out on uni-axially loaded flat-plate specimens with two collinear edge slits, to investigate the effect of finite plate width on the elastic stress distribution. It was found that the effect of slitlength/ plate-width ratio on the elastic stress concentration at the end of the edge slit of length l was virtually the same as that for a central slit of length 2l in a plate of the same width, and could be adequately expressed by existing theories.

Stress Concentration and Stress Intensity for Pressurized Eroded Autofrettaged Thick Cylinders With Bauschinger Effect

2010 ◽  
Author(s):  
Q. Ma ◽  
C. Levy ◽  
M. Perl
Keyword(s):  
Stress Intensity ◽  
Stress Concentration ◽  
Bauschinger Effect ◽  
Thermal Loading ◽  
Yield Criterion ◽  
Pressure Vessels ◽  
Short Cracks ◽  
Finite Element Package ◽  
Von Mises ◽  
Walled Cylinder

Our previous studies have shown that stress intensity factors (SIFs) are influenced considerably from the presence of the Bauschinger Effect (BE) in thick-walled pressurized cracked cylinders. For some types of pressure vessels, such as gun barrels, working in corrosive environment, in addition to acute temperature gradients and repetitive high-pressure impulses, erosions can be practically induced. Those erosions cause stress concentration at the bore, where cracks can readily initiate and propagate. In this study, The BE on the SIFs will be investigated for a crack emanating from an erosion’s deepest point in a multiply eroded autofrettaged, pressurized thick-walled cylinder. A commercial finite element package, ANSYS, was employed to perform this type of analysis. A two-dimensional model, analogous to the authors’ previous studies, has been adopted for this new investigation. Autofrettage with and without BE, based on von Mises yield criterion, is simulated by thermal loading and the SIFs are determined by the nodal displacement method. The SIFs are evaluated for a variety of relative crack lengths, a0/t = 0.01–0.45 emanating from the tip of the erosion of different geometries including (a) semi-circular erosions of relative depths of 1–10 percent of the cylinder’s wall thickness, t; (b) arc erosions for several dimensionless radii of curvature, r′/t = 0.05–0.4; and (c) semi-elliptical erosions with ellipticities of d/h = 0.5–1.5, and erosion span angle, α, from 6 deg to 360 deg. The effective SIFs for relatively short cracks are found to be increased by the presence of the erosion and further increased due to the BE, which may result in a significant decrease in the vessel’s fatigue life. Deep cracks are found to be almost unaffected by the erosion, but are considerably affected by BE.

Stress Distribution Around Two Dental Implant Materials with New Designs: Comparative Finite Element Analysis Study

2021 ◽  
Vol 4 (1) ◽  
pp. 19
Author(s):  
Faaiz Alhamdani ◽  
Khawla H. Rasheed ◽  
Amjed Mahdi
Keyword(s):  
Stress Distribution ◽  
Dental Implant ◽  
Cancellous Bone ◽  
Stress Level ◽  
The Other ◽  
Von Mises Stress ◽  
Uniform Stress ◽  
Element Analysis ◽  
Other Hand ◽  
Von Mises

Background: The introduction of modified thread designs is one of the research areas of interest in the dental implantology field. Two suggested Buttress and Reverse Buttress thread designs in TiG5 and TiG4 models are tested against a standard TiG5 Fin Thread design (IBS®). Purpose: The study aims to compare stress distribution around the suggested designs and Fin Thread design. Methods: Three dental implant models: Fin Thread design, and newly suggested Buttress and Reverse Buttress designs of both TiG5 and TiG4 models were tested using FEA for stress distribution using static (70N, 0°) and (400N, 30°) occlusal loads. Results: The main difference between the suggested Buttress design and Fin Thread design lies in the overload (400N, 30°) condition. Maximum Von Mises stress is less in Buttress design than Fin Thread design. On the other hand the level of Von Mises stress over the buccolingual slop of the cancellous bone in Fin Thread design liess within the lowest stress level. The suggested Reverse Buttress design, on the other hand showed almost uniform stress distribution in both TiG4 and TiG4 models with maximum Von Mises stress higher than the elastic modulus of cancellous bone in overload (400N, 30°) condition. Conclusion: The suggested TiG4 Buttress design might have a minor advantage of stress level in cases of stress overload. In contrast, Fin Thread design shows minimal stress over the buccolingual slop of the cancellous bone. The suggested Reverse Buttress design might be more suitable for the D1 bone quality region with the advantage of almost uniform stress distribution

Effect of Yield Criterion on Stress Distribution and Maximum Safe Pressure for an Autofrettaged Gun Barrel

2017 ◽  
Vol 67 (5) ◽  
pp. 504
Author(s):  
Amit Bhetiwal ◽  
Sunil Kashikar ◽  
Haribhau Markale ◽  
Shailendra Gade
Keyword(s):  
Stress Distribution ◽  
Yield Criterion ◽  
The Other ◽  
Uniform Thickness ◽  
Theoretical Weight ◽  
Gun Barrel ◽  
Von Mises Criterion ◽  
Tresca Criterion ◽  
Von Mises

<p>World artillery in the present scenario is changing its role from defensive to aggressive nature and is attempting to achieve higher penetration into enemy targets. Even for an autofrettaged gun barrel, higher ranges requirement leads to higher barrel weight and its associated demerits. The design of gun barrel is based on the choice of yield criteria. Tresca yield criterion provides conservative design for a ductile barrel material. On the other hand, more accurate von Mises criterion presents complexity. The two criteria to evaluate various parameters required for design of an autofrettaged gun barrel are compared. The methodology for evaluation of maximum safe pressure, based on von Mises criterion, for an autofrettaged gun barrel is also included in the paper. Based on case study included in the article, for an autofrettaged gun barrel or pressure vessel with uniform thickness, a theoretical weight reduction of approximately 16 per cent is feasible with von Mises criterion as compared to Tresca criterion.</p>

Stress Concentration in a Stretched Cylindrical Shell With Two Equal Circular Holes

1975 ◽  
Vol 42 (1) ◽  
pp. 105-109 ◽  
Author(s):  
P. Seide ◽  
A. S. Hafiz
Keyword(s):  
Cylindrical Shell ◽  
Stress Concentration ◽  
Stress Distribution ◽  
Circular Cylindrical Shell ◽  
Algebraic Equations ◽  
Linear Algebraic Equations ◽  
Wide Range ◽  
Circular Holes ◽  
Limiting Case ◽  
Infinite Set

In this investigation, the stress distribution due to uniaxial tension of an infinitely long, thin, circular cylindrical shell with two equal small circular holes located along a generator is obtained. The problem is solved by the superposition of solutions previously obtained for a cylinder with a single circular hole. The satisfaction of boundary conditions on the free surfaces of the holes, together with uniqueness and overall equilibrium conditions, yields an infinite set of linear algebraic equations involving Hankel and Bessel functions of complex argument. The stress distribution along the boundaries of the holes and the interior of the shell is investigated. In particular, the value of the maximum stress is calculated for a wide range of parameters, including the limiting case in which the holes almost touch and the limiting case in which the radius of the cylinder becomes very large. As is the case for a flat plate, the stress-concentration factor is reduced by the presence of another hole.

Some Problems Associated with Stress Concentration

1955 ◽  
Vol 59 (536) ◽  
pp. 551-561 ◽  
Author(s):  
H. L. Cox
Keyword(s):  
Stress Concentration ◽  
Stress Distribution ◽  
Stress Analysis ◽  
Elastic Stress ◽  
Fatigue Tests ◽  
Detailed Knowledge ◽  
Two Dimensional ◽  
Special Boundaries ◽  
The Third ◽  
Actual Strength

The theory of stress concentration is such a fascinating study that the whole of this lecture could be most happily devoted to discussion of the stress distribution round all sorts of special boundaries. At the same time the most detailed knowledge of elastic stress distribution is of little value unless we can be sure how the stresses computed will be reflected in the actual strength of the part. For that reason this paper is divided into three sections: the first deals with certain moderately simple cases of stress and load concentration and shows how the stress analysis is confirmed by static and fatigue tests: the second describes some investigations of special two–dimensional boundaries and indicates, some fairly general theoretical conclusions which can be drawn: in the third I shall try to review the possible reasons why, in practice, the best found conclusions are not always borne out.

Stress Distribution Around a Central Crack in a Plate Loaded in Tension ; Effect of Finite Width of Plate

1960 ◽  
Vol 64 (591) ◽  
pp. 141-145 ◽  
Author(s):  
J. R. Dixon
Keyword(s):  
Stress Concentration ◽  
Stress Distribution ◽  
Flat Plate ◽  
Elastic Stress ◽  
Width Ratio ◽  
Finite Width ◽  
Two Dimensional ◽  
Central Crack ◽  
Image Position ◽  
Plate Width

Summary:The purpose of the work was to investigate the effect of the finite width of plate on the elastic-stress distribution due to a central crack in a flat plate loaded in tension.The range of investigation: (i) Two-dimensional photoelastic tests were carried out on flat-plate specimens. The photoelastic specimens were geometrically similar to the 10 in. wide fatigue specimens used by Frost and Dugdale, with the central crack simulated by a slot bounded by holes of small radii, (ii) A theoretical solution of the problem was derived and compared with the present and other photoelastic results.It is shown that the effect of the crack-length/plate-width ratio on the elastic-stress concentration at the head of the crack can be expressed by the following formulae:

Analysis on Elastoplastic Stress Distribution in a Layered Cylindrical Vessel With Interlayer Gaps

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
Shugen Xu ◽  
Weiqiang Wang
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Stress Distribution ◽  
Elastic Stress ◽  
Cylindrical Vessel ◽  
Elastoplastic Model ◽  
Elastoplastic Stress ◽  
Calculation Results ◽  
Von Mises ◽  
Good Agreement

In this paper, the formulae for elastoplastic stress distribution in layered cylindrical vessel layers with gaps have been provided. These formulae are based on the modified Pimshtein formulae for the elastic stress of layers. Plane strain with ideal elastoplastic model of materials is adopted. A practice example is presented to show how the formulae can be used for elastoplastic stress calculation. The hoop, radial, axial, and Von Mises equivalent stresses are obtained. The calculation result showed that the stress state of layered cylindrical vessel is more complex than that of monobloc cylindrical shell due to the interlayer gaps. The stress distribution is discontinuous. Calculation results obtained theoretically were compared to those obtained by finite element method (FEM). It shows that the results from the proposed formulae are in good agreement with finite element results.

Shape Optimization of a Self-deployable Anchor Designed for Percutaneous Mitral Valve Repair

2012 ◽  
Vol 6 (1) ◽  
Author(s):  
Farhad Javid ◽  
Jorge Angeles ◽  
Damiano Pasini ◽  
Renzo Cecere
Keyword(s):  
Stress Concentration ◽  
Mitral Valve ◽  
Stress Distribution ◽  
Iterative Process ◽  
Von Mises Stress ◽  
Valve Repair ◽  
Percutaneous Mitral Valve Repair ◽  
Von Mises ◽  
Previous Iteration ◽  
Weight Coefficients

A new percutaneous annuloplasty technique for mitral regurgitation is proposed here. In this technique, inter-related anchors are first inserted around the annulus via a trans-septal catheter. The tethered wire passed through the anchors is then pulled to shrink the annulus and stop regurgitation. The anchors should withstand large deformation, applied during the delivery process, and should recover their original shape after being released inside the tissue. The shape of the anchors is, thus, optimized in an iterative process, to avoid stress concentration by minimizing the weighted rms value of the curvature along the anchor. The weight coefficients in each iteration are defined based on the stress distribution of the anchor obtained in the previous iteration. The procedure finally results in a structurally optimum anchor with a minimum in the maximum von Mises stress. This anchor is fabricated from Nitinol and tested in a cadaveric swine heart.

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