scholarly journals Healing of Internal Defects in a Compressive Stress Field Using the Plastic Properties of Materials

2021 ◽  
pp. 36-43
Author(s):  
V. I Bukhalov ◽  
M. N Perelmuter ◽  
A. L Popov
Keyword(s):  
Yield Strength ◽  
Contact Pressure ◽  
Healing Process ◽  
External Pressure ◽  
Cylinder Axis ◽  
Dimensional Solution ◽  
Initial Field ◽  
Elastoplastic Behavior ◽  
Compressive Stresses ◽  
First Case

Numerical simulation of defect healing process in the field of previously created compressive stresses is performed. Isotropic cylinders with small axisymmetrically located defects are used as samples. The pressure created the initial field of compressive stresses inside the cylinder. The defects were modeled as a small blind closed annular cavity or as a through annular cut located around the cylinder axis. In the first case, a numerical three-dimensional solution is considered. For the second defect, the plane stress state model was used. The problems were solved in both elastic and elastoplastic formulations with an ideally elastoplastic behavior of the material. The external pressure was varied from values significantly lower than the yield strength to the yield strength and (for the first problem) for values slightly exceeding it. Based on the results of the numerical solution, the radial displacements of the cavity sides parallel to the cylinder axis are obtained depending on the external pressure. We found the values of pressure at which the cylindrical surfaces of the void defect were in contact. For the blind cavity, at any external pressure, there were unhealed areas. Healing was assessed by the volume of the material filling the initial cavity at the initial residual stresses. The value of the newly formed contact pressure at a certain value of the compressive stresses was determined by the ratio of the height of the healed area to the cavity height. The evaluation of the healing effect for a through cut in the cylinder was performed by varying the size of the gap formed by the cut between the inner cylinder and the outer ring depending on the applied external pressure. When the gap is completely healed, the values of the maximal contact pressure in the notch zone are determined.

Mathematical Model Establishment and Analysis on the Pipe Deformation under External Pressure with the Ovality

2013 ◽  
Vol 760-762 ◽  
pp. 2263-2266
Author(s):  
Kang Yong ◽  
Wei Chen
Keyword(s):  
Mathematical Model ◽  
Theoretical Analysis ◽  
Yield Strength ◽  
Residual Stresses ◽  
Numerical Simulations ◽  
Significant Influence ◽  
External Pressure ◽  
Pipe Diameter ◽  
Axial Loads ◽  
The Stability

Beside the residual stresses and axial loads, other factors of pipe like ovality, moment could also bring a significant influence on pipe deformation under external pressure. The Standard of API-5C3 has discussed the influences of deformation caused by yield strength of pipe, pipe diameter and pipe thickness, but the factor of ovality degree is not included. Experiments and numerical simulations show that with the increasing of pipe ovality degree, the anti-deformation capability under external pressure will become lower, and ovality affecting the stability of pipe shape under external pressure is significant. So it could be a path to find out the mechanics relationship between ovality and pipe deformation under external pressure by the methods of numerical simulations and theoretical analysis.

Minimum Weight Design of Ring Stiffened Cylinders Under External Pressure

1961 ◽  
Vol 5 (03) ◽  
pp. 44-49 ◽  
Author(s):  
George Gerard
Keyword(s):  
Yield Strength ◽  
Minimum Weight ◽  
External Pressure ◽  
Compressive Yield Strength ◽  
Minimum Weight Design ◽  
Weight Design

Minimum weight analyses for unstiffened and ring-stiffened cylinders under external pressure are presented for designs based on stability and compressive yield-strength considerations. The results for both types of cylinders are compared in terms of a common set of parameters to establish the efficiency of the stiffening system. The results are then compared on a somewhat different basis to establish the relative efficiencies of various classes of materials. Finally, certain conclusions are drawn of particular pertinence to deep submersibles.

Effect of Steel Properties on Buckling Pressure of Corroded Pipelines

2017 ◽  
Vol 898 ◽  
pp. 741-748 ◽  
Author(s):  
Meng Li ◽  
Hong Zhang ◽  
Meng Ying Xia ◽  
Kai Wu ◽  
Jing Tian Wu ◽  
...  
Keyword(s):  
Finite Element ◽  
Yield Strength ◽  
Strain Hardening ◽  
Corrosion Damage ◽  
Element Model ◽  
External Pressure ◽  
Strain Hardening Exponent ◽  
The Finite Element Method ◽  
Collapse Pressure ◽  
Steel Properties

Due to the harsh environment for submarine pipelines, corrosion damage of the pipeline steels is inevitable. After the corrosion damage, pipelines are prone to failure and may cause serious consequences. The analysis of the effects of different steel properties on the collapse pressure of pipelines with corrosion defects is of importance for the option of appropriate pipeline and avoiding accidents. Based on the finite element method, the finite element model of the pipeline with defects under external pressure was built. Firstly, the accuracy of the numerical model was validated by comparing with previous experimental results. The effects of yield strength and strain hardening exponent on collapse pressure of pipelines with different sizes of defect were discussed in detail. Results showed that the yield strength and strain hardening exponent have different influences on collapse pressure: the collapse pressure increases with the increasing yield strength, and the collapse pressure decreases with the increasing strain hardening exponent.

Collapse of Thin-Walled Elliptical Tubes for High Values of Major-to-Minor Axis Ratio

1993 ◽  
Vol 115 (4A) ◽  
pp. 432-440 ◽  
Author(s):  
C. Ribreau ◽  
S. Naili ◽  
M. Bonis ◽  
A. Langlet
Keyword(s):  
Contact Pressure ◽  
Cross Section ◽  
External Pressure ◽  
Straight Line Segment ◽  
Minor Axis ◽  
Cross Sectional ◽  
Axis Ratio ◽  
Straight Line ◽  
Thin Walled ◽  
The Cross

The topic of this study concerns principally representative models of some elliptical thin-walled anatomic vessels and polymeric tubes under uniform negative transmural pressure p (internal pressure minus external pressure). The ellipse’s ellipticity ko, defined as the major-to-minor axis ratio, varies from 1 up to 10. As p decreases from zero, at first the cross-section becomes somewhat oval, then the opposite sides touch in one point at the first-contact pressure pc. If p is lowered beneath pc, the curvature of the cross-section at the point of contact decreases until it becomes zero at the osculation pressure or the first line-contact pressure p1. For p<p1, the contact occurs along a straight-line segment, the length of which increases as p decreases. The pressures pc and p1 are determined numerically for various values of the wall thickness of the tubes. The nature of contact is especially described. The solution of the related nonlinear, two-boundary-values problem is compared with previous experimental results which give the luminal cross-sectional area (from two tubes), and the area of the mid-cross-section (from a third tube).

scholarly journals Dental extraction in patients with HIV/AIDS: report of two cases

RSBO ◽  
2019 ◽  
Vol 16 (1) ◽  
pp. 51-06
Author(s):  
Mariane Cristina Sloniak ◽  
Sara Regina Barancelli Todero ◽  
Luciana Aparecida Lyra ◽  
Elenara Beatriz Fontana ◽  
Paulo Sérgio Batista ◽  
...  
Keyword(s):  
Oral Health ◽  
Periodontal Disease ◽  
Hiv Infection ◽  
Dental Treatment ◽  
Treatment Plan ◽  
Healing Process ◽  
Special Treatment ◽  
Individual Treatment ◽  
Dental Surgery ◽  
First Case

The oral health of patients with HIV infection is often compromised by caries and periodontal disease. Thus, many patients need to undergo oral surgical procedures. Case report: This article describes two cases of patients with HIV infection who had undergone exodontia due to prosthetic indications. Both patients had been hospitalized for treatment of respiratory complications from HIV infection and were referred for dental treatment. In the first case, the adult patient had generally good oral health. However, the treatment plan for the installation of a removable prosthesis required the removal of tooth 38 since it was fairly inclined to the mesial. The second patient had poor oral conditions due to advanced periodontal disease. Thus, all upper arch teeth were removed in a single session followed by the installation of an immediate total prosthesis. No postoperative complications were recorded and the healing process occurred without incident for both patients. Dental treatment of patients with asymptomatic HIV infection does not differ from that performed for any other patient in practice. Nevertheless, patients in advanced stages of disease may require special treatment and an individual treatment plan must be developed for even routine procedures. Conclusion: The dental care of these individuals often requires more rigorous clinical follow-up for maintaining oral health. The performance of dental surgery in patients with HIV infection does not require technical modifications, but does require a complete anamnesis.

scholarly journals Numerical study of TRIP transformation in 35NCD16 steel-effects of plate orientation and some criteria

2021 ◽  
Vol 16 (59) ◽  
pp. 444-460
Author(s):  
Mounir Gaci ◽  
Fedaoui Kamel ◽  
Lazhar Baroura ◽  
Amar Talhi
Keyword(s):  
Grain Boundary ◽  
Shear Deformation ◽  
Numerical Study ◽  
Elastic Behavior ◽  
The Finite Element Method ◽  
Elastoplastic Behavior ◽  
Mechanical Coupling ◽  
First Case ◽  
Martensitic Plate ◽  
The Impact

This study aims to analyze the effect of thermo mechanical coupling damage in the presence of a phase change (austenite/martensite) in 35NCD16 steel. The impact of increasing mechanical traction load, accompanied by a martensitic transformation on the scale of a single grain with boundary has been studied. The prediction transformation of induced plasticity (TRIP) was evaluated by taking into account the following parameters: twenty shear directions of the martensitic plates, two values of the shear deformation of the martensitic plates, energetic and thermodynamics criteria for getting in order the transformation of the martensitic plates, elastoplastic behavior of the two areas in the first case (martensitic plate and grain boundary) and elastic behavior for the grain boundary in the second case. The numerical calculation is carried out using the finite element method (FEM), implemented in the Zebulon calculation code. The developed approach is validated using the available experimental results reported in the literature. The numerical results showed that the estimation of TRIP given by the energetics criteria with the values of the shear deformation (γ0 = 0.16) are closer to the experiment results.

scholarly journals Dental extraction in patients with HIV/AIDS: report of two cases

RSBO ◽  
2019 ◽  
Vol 16 (1) ◽  
pp. 51
Author(s):  
Mariane Cristina Sloniak ◽  
Sara Regina Barancelli Todero ◽  
Luciana Aparecida Lyra ◽  
Elenara Beatriz Fontana ◽  
Paulo Sérgio Batista ◽  
...  
Keyword(s):  
Oral Health ◽  
Periodontal Disease ◽  
Hiv Infection ◽  
Dental Treatment ◽  
Treatment Plan ◽  
Healing Process ◽  
Special Treatment ◽  
Individual Treatment ◽  
Dental Surgery ◽  
First Case

Introduction and objective: The oral health of patients with HIV infection is often compromised by caries and periodontal disease. Thus, many patients need to undergo oral surgical procedures. Case report: This article describes two cases of patients with HIV infection who had undergone exodontia due to prosthetic indications. Both patients had been hospitalized for treatment of respiratory complications from HIV infection and were referred for dental treatment. In the first case, the adult patient had generally good oral health. However, the treatment plan for the installation of a removable prosthesis required the removal of tooth 38 since it was fairly inclined to the mesial. The second patient had poor oral conditions due to advanced periodontal disease. Thus, all upper arch teeth were removed in a single session followed by the installationof an immediate total prosthesis. No postoperative complications were recorded and the healing process occurred without incident for both patients. Dental treatment of patients with asymptomatic HIV infection does not differ from that performed for any other patient in practice. Nevertheless, patients in advanced stages of disease may require special treatment and an individual treatment plan must be developed for even routine procedures. Conclusion: The dental careof these individuals often requires more rigorous clinical follow-up for maintaining oral health. The performance of dental surgery in patients with HIV infection does not require technical modifications, but does require a complete anamnesis.

Collapse Resistance Under Combined External Pressure and Bending Deformation of Coated Linepipe

2020 ◽  
Author(s):  
Takahiro Sakimoto ◽  
Hisakazu Tajika ◽  
Tsunehisa Handa ◽  
Yoshiaki Murakami ◽  
Satoshi Igi ◽  
...  
Keyword(s):  
Yield Strength ◽  
Deep Water ◽  
Thermal Cycle ◽  
Bauschinger Effect ◽  
Heating Temperature ◽  
External Pressure ◽  
Compressive Yield Strength ◽  
Heat Cycle ◽  
Bending Deformation ◽  
Collapse Resistance

Abstract As offshore pipeline projects have expanded to deeper water regions with depths of more than 2 000 m, higher resistance against collapse by external pressure is now required in linepipe. Collapse resistance is mainly controlled by the pipe geometry and compressive yield strength. In UOE pipe, the compressive yield strength along the circumferential direction changes dramatically due to tensile pre-strain that occurs in pipe forming processes such as the expansion process. In order to improve the compressive yield strength of pipes, it is important to consider the Bauschinger effect caused by pipe expansion. As the mechanism of this effect, it is understood that internal stress is generated by the accumulation of dislocations, and this reduces reverse flow stress. Compressive yield strength is also changed by the thermal cycle associated with application of fusion-bond epoxy in pipe anti-corrosion coating by induction heating. In the typical thermal heat cycle of this coating process, the maximum heating temperature is from 200 °C to 250 °C. In this case, compressive yield strength increases as an effect of the thermal cycle, resulting in increased collapse resistance. Thus, for deep water application of UEO linepipe, it is important to clarify the conflicting effects of the Bauschinger effect and the thermal heat cycle on compressive yield strength. During installation of deep water pipelines by a method such as J-lay, curvature is imposed on the pipe axis, but the circumferential bending that leads to ovalization is determined by the interaction of the curvature of bending deformation. This bending deformation decreases collapse resistance. The interaction of external pressure and bending is also important when evaluating collapse. Against this background, this study discusses the collapse criteria for coated linepipe and their bending interaction against collapse based on a full-scale collapse test under external pressure with and without bending loading. The effect of the thermal heat cycle on linepipe collapse criteria is also discussed based on the results of tensile pre-strain tests with simulation of the thermal cycle and a collapse calculation by FEA.

Collapse of Worn Casing

1977 ◽  
Vol 99 (1) ◽  
pp. 208-214 ◽  
Author(s):  
C. E. Murphey
Keyword(s):  
Yield Strength ◽  
Lower Bounds ◽  
Wall Thickness ◽  
Axial Load ◽  
External Pressure ◽  
Upper And Lower Bounds ◽  
Percentage Reduction ◽  
Steel Tubes ◽  
Collapse Pressure ◽  
Severe Wear

Collapse tests were performed on one-in. dia steel tubes with flats milled on the exterior to simulate worn casing. External pressure and axial load were applied to the tubs having a range of wall thickness, yield strength, and degree of wear. Empirical correlation of the data and comparison with elastic collapse calculations indicate the percentage reduction in collapse pressure due to wear. This reduction is predictable within upper and lower bounds. While the milled external flat may not accurately simulate severe internal wear, the correlation is adequate for less than severe wear to give an indication of remaining strength.

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