scholarly journals Compatibility Between API Equations and Design Limits Plots for Ellipse and Circle of Plasticity

2021 ◽  
Author(s):  
Juan Manuel Romero ◽  
Jan Aage Aasen
Keyword(s):  
Axial Stress ◽  
Recent Change ◽  
American Petroleum Institute ◽  
Horizontal Axis ◽  
Main Body ◽  
Mathematical Relationship ◽  
Horizontal Shift ◽  
Industry Standard ◽  
Tension And Compression ◽  
Von Mises

Abstract This paper presents a methodology to superimpose the American Petroleum Institute (API TR 5C3 2018) uniaxial and triaxial limits on tubular design limits plots. Complications due to a recent change of axis are resolved, producing practical design limits plots that avoid the horizontal shift of the API vertical limits, currently done by the industry. The commonly used slanted ellipse is compared against an adaptation of the circle of plasticity in the form of a horizontal ellipse, showing the convenience of this last one with examples. After the new collapse formulation was made part of the main body of standard API TR 5C3 (2018), the horizontal axis on the standard industry well tubular design limits plot changed. The present study evaluates this redefinition of the horizontal axis. One consequence of this modification is a difficulty plotting the API tension and compression limits. The API horizontal limits (uniaxial burst and collapse) are found to be independent of load case, while the API vertical design limits (uniaxial tension and compression) are dependent on inside and outside tubular pressures. The approaches used by commercial software and industry publications to solve this challenge are reviewed. A new design methodology is developed to link API uniaxial limits to the triaxial theory. The main objective of the study is to establish a mathematical relationship between API tubular design limits and the von Mises triaxial theory (API TR 5C3 2018). A methodology that allows plotting the API uniaxial force limits on the design limit plot is developed. The study also shows that the results obtained from the industry standard slanted ellipse are identical to those obtained from the horizontal ellipse and circle. One important difference is that the slanted ellipse is based on zero axial stress datum while the horizontal ellipse/circle uses neutral axial stress datum. The horizontal ellipse/circle is well suited for calculations involving buckling, it is compatible with the information used in field operations and its formulations are less complicated than the tilted ellipse. Therefore, attention is called to it.

API Equation Design Limits Plot for Ellipse and Circle of Plasticity

2021 ◽  
pp. 1-12
Author(s):  
J. M. Romero ◽  
J. A. Aasen
Keyword(s):  
Axial Stress ◽  
Recent Change ◽  
American Petroleum Institute ◽  
Horizontal Axis ◽  
Main Body ◽  
Mathematical Relationship ◽  
Horizontal Shift ◽  
Industry Standard ◽  
Tension And Compression ◽  
Von Mises

Summary In this paper we present a methodology to superimpose the American Petroleum Institute (API) uniaxial and triaxial limits on tubular design limits plots (API TR 5C3 2018). Complications caused by a recent change of axis are resolved, producing a practical design limits plot that avoids the horizontal shift of the API vertical limits, which is currently the industry standard. The commonly used slanted ellipse is compared against an adaptation of the circle of plasticity in the form of a horizontal ellipse, showing the convenience of this last one with examples. After the current official collapse formulation was made part of the main body of standard API TR 5C3 (2018), the horizontal axis on the standard industry well tubular design limits plot changed. The present study evaluates this redefinition of the horizontal axis. One consequence of this modification is a difficulty plotting the API tension and compression limits. The API horizontal limits (uniaxial burst and collapse) are found to be independent of load situation, whereas the API vertical design limits (uniaxial tension and compression) are dependent on inside and outside tubular pressures. The approaches used by commercial software and industry publications to solve this challenge are reviewed. A new design methodology is developed to link API uniaxial limits to the triaxial theory. One main objective of the study is to establish a mathematical relationship between API tubular design limits and the von Mises triaxial theory (API TR 5C3 2018). A methodology that allows plotting the API uniaxial force limits on the design limits plot is developed. The study also shows that the results obtained from the industry standard slanted ellipse are identical to those obtained from the horizontal ellipse and circle. One important difference is that the slanted ellipse is based on the zero axial stress datum, whereas the horizontal ellipse/circle uses the neutral axial stress datum. The horizontal ellipse/circle is well suited for calculations involving buckling, compatible with the information used in field operations, and its formulations are less complicated than the tilted ellipse. Therefore, attention is called to the use of the horizontal ellipse/circle in well tubular design.

scholarly journals The elastic limit of metals exposed to tri-axial stress

1932 ◽  
Vol 137 (833) ◽  
pp. 559-574 ◽  
Keyword(s):  
Shear Stress ◽  
Axial Stress ◽  
Maximum Shear Stress ◽  
Internal Surface ◽  
External Pressure ◽  
Stress System ◽  
Axial Tension ◽  
Tension And Compression ◽  
Von Mises ◽  
Similar Kind

The numerous investigations which have been carried out since the opening of the present century into the elastic breakdown of metals have resulted in the formulation of several hypotheses concerning the conditions of stress and strain necessary for its occurrence. The methods generally employed in the investigations have consisted in the application of combinations of tension and compression with torsion, and of bending with torsion, to solid bars and thin tubes, and of tension and compression combined with internal and external pressure to thin tubes; so that the stress system produced in the metal was essentially bi-axial in character, the third principal stress being either very small or zero. The results of these experiments have given general support to the shear stress hypothesis of Guest, although with deviations which in some cases are not insignificant. Experiments employing a tri-axial stress system, in which the relation to each other of the component stresses could be varied, have been comparatively few in number. Tests by Turner on thick walled cylinders of mild steel exposed simultaneously to internal pressure and axial tension, were inconclusive, possibly owing to the irregularity of the tubes. Those by Cook and Robertson, also on thick-walled tubes of varying dimensions, showed a reasonably constant value of the maximum shear stress at the instant of elastic breakdown at the internal surface; this stress was, however, considerably higher than the shear stress observed in the uni-axial state of stress in a simple tensile test of the same material, a result confirmed in more recent tests of a similar kind by the author. The newer hypotheses of Haigh and of von Mises require an effect of this kind; but it has been suggested by the author that the observed effect may nevertheless be associated more directly with the non-uniform character of the stress distribution, rather than as an indication of the inapplicability of the hypothesis which regards failure as due to the existence of a critical value of the shear stress.

scholarly journals Comparison of Load Carrying Capacity of Three and Four Lobed Polygonal Shaft and Hub Connection for Constant Grinding Diameter

2016 ◽  
Author(s):  
Ravi Bhatta ◽  
Wendy Reffeor
Keyword(s):  
Carrying Capacity ◽  
Power Transmission ◽  
Axial Stress ◽  
Von Mises Stress ◽  
Load Carrying Capacity ◽  
Interference Fit ◽  
Bending Load ◽  
Load Carrying ◽  
Von Mises ◽  
Conformal Contact

Polygonal shafts are used in power transmission as alternatives to keyed and splined shafts. They are designed using DIN standards. This research explores the loading strength of the standardized three lobed (P3G) and four lobed (P4C) polygonal shafts and hubs manufactured from the same stock size, subjected to torsional bending load at various fits. Due to complex conformal contact (nonlinear model) between the shaft and the hub, there is no analytical solution and, therefore, Finite Element Method had been used to determine the stresses, after validating experimentally and using the DIN standard. From the analysis, it was found that the hub experienced greater stress than the shaft in all cases and the major stress in a polygonal shaft and hub connection is the contact stress. The clearance fit was found to be the most detrimental fit and the interference fit to be the most suitable for larger power transmission. Owing to its small normal axial stress and hub displacement, the P4C clearance fit has its use in low power transmission where a sliding fit is a requirement. The maximum von Mises stress was located below the surface for P4C and P3G clearance fit, suggesting failure from pitting and fretting on these shafts. All of the stresses were found to be higher in P4C than P3G for similar loading. Therefore, for general use, the P3G profile with an interference fit is recommended.

The effects of shape memory alloys’ tension–compression asymmetryon NiTi endodontic files’ fatigue life

2018 ◽  
Vol 232 (5) ◽  
pp. 437-445 ◽  
Author(s):  
MR Karamooz-Ravari ◽  
R Dehghani
Keyword(s):  
Finite Element ◽  
Shape Memory ◽  
Numerical Models ◽  
Equivalent Stress ◽  
Element Model ◽  
Niti Shape Memory Alloy ◽  
Element Analysis ◽  
Tension And Compression ◽  
Von Mises Equivalent Stress ◽  
Von Mises

Nowadays, NiTi rotary endodontic files are of great importance due to their flexibility which enables the device to cover all the portions of curved canal of tooth. Although this class of files are flexible, intracanal separation might happen during canal preparation due to bending or torsional loadings of the file. Since fabrication and characterization of such devices is challenging, time-consuming, and expensive, it is preferable to predict this failure before fabrication using numerical models. It is demonstrated that NiTi shape memory alloy shows asymmetric material response in tension and compression which can significantly affect the lifetime of the files fabricated from. In this article, the effects of this material asymmetry on the bending response of rotary files are assessed using finite element analysis. To do so, a constitutive model which takes material asymmetry into account is used in combination with the finite element model of a RaCe file. The results show that the material asymmetry can significantly affect the maximum von Mises equivalent stress as well as the force–displacement response of the tip of this file.

Leading Practices for the Prevention of Mechanical Damage

2006 ◽  
Author(s):  
Mark Hereth ◽  
Bernd Selig ◽  
John Zurcher ◽  
Keith Leewis ◽  
Rick Gailing
Keyword(s):  
Common Ground ◽  
Mechanical Damage ◽  
Recent Change ◽  
American Petroleum Institute ◽  
Performance Excellence ◽  
Time Data ◽  
Natural Gas Pipelines ◽  
Time Period ◽  
Additional Detail ◽  
The Common

Practices that are used by pipeline operators to prevent mechanical damage are examined in this paper. A set of practices specific to pipeline operations is presented. The practices were initially developed by a group of subject matter experts working under the auspices of the American Petroleum Institute and the Association of Oil Pipelines (API/AOPL) Performance Excellence Team. The practices drew upon the work started within the Common Ground Initiative in the late 1990s and continued by the Common Ground Alliance. The practices presented were reviewed again in preparation of this report. The practices build upon practices defined by Common Ground Alliance (CGA), largely by providing greater specificity and ensuring completeness and follow through in communication and documentation. A subset of these practices became the foundation of the standard, API 1166 Excavation Monitoring and Observation. The paper also provides an overview of historical safety performance for the period 1995 through 2003; with a specific focus on mechanical damage related incidents including the additional detail available in the recent change in Pipeline and Hazardous Materials Safety Administration (PHMSA, US-DOT) Incident Reporting. This period was selected because it represented the time period where there was a heightened interest in preventing damage to pipelines as described above. The large majority of mechanical damage related incidents result in an immediate impact; a small portion occur at some later point in time. Data for the nine-year period indicate that approximately 90 percent of the incidents result in an immediate impact. This is significant in that it underscores the importance of prevention of damage. The experience of hazardous liquid pipelines has shown a continuing decrease in numbers of annual incidents. The experience of natural gas pipelines has not shown a decreasing trend; in fact, it is relatively flat for the period of study. While the heightened awareness and strong commitment to dedication are known to have had an impact on damage prevention through numerous stories and vast experience shared by a variety of stakeholders, it is prudent to be concerned that the performance may be reaching a “plateau”.

Improving Prediction of Limit Bending Load for Wall-Thinned Pipes by Reconsidering the Effect of Biaxiality

2015 ◽  
Author(s):  
Kosuke Mori ◽  
Toshiyuki Meshii
Keyword(s):  
Finite Element Analysis ◽  
Large Strain ◽  
Axial Stress ◽  
Plastic Instability ◽  
Failure Criteria ◽  
Von Mises Stress ◽  
Element Analysis ◽  
Crack Penetration ◽  
Bending Load ◽  
Von Mises

In this paper, a failure criterion applicable to large-strain finite element analysis (FEA) results was studied to predict the limit bending load Mc of the groove shaped wall-thinned pipes, under combined internal pressure and bending load, that experienced cracking. In our previous studies, Meshii and Ito [1] considered cracking of pipes with groove shaped flaw (small axial length δz in Fig. 1) was due to the plastic instability at the wall-thinned section and proposed the Domain Collapse Criterion (DCC). The DCC predicted Mc of cracking for small δz by comparing the von Mises stress σMises with the true tensile strength σB. However, it was indicated that the predictability of Mc was not necessarily sufficient. Thus, in this work, attempts were made to improve the accuracy of Mc prediction with a perspective that multi-axial stress state might affect this plastic instability. As a result of examination of the various failure criteria based on multi-axial stress, it was confirmed that the limit bending load of the groove flawed pipe that experienced cracking could be predicted within 5 % accuracy by applying Hill’s plastic instability onset criterion [2] to the outer surface of the crack penetration section. The accuracy of the predicted limit bending load was improved from DCC’s error of 15% to 5%.

Flow and Fracture Behavior of NiAl in Relation to the Brittle-Toductile Transition Temperature

1990 ◽  
Vol 213 ◽  
Author(s):  
R.D. Noebe ◽  
R.R. Bowman ◽  
C.L. Cullers ◽  
S.V. Raj
Keyword(s):  
Transition Temperature ◽  
Flow Behavior ◽  
Polycrystalline Materials ◽  
Compression Tests ◽  
Dislocation Glide ◽  
Von Mises Criterion ◽  
Tension And Compression ◽  
Ductile Behavior ◽  
Von Mises ◽  
Increasing Temperature

ABSTRACTNiAl has only three independent slip systems operating at low and intermediate temperatures whereas five independent deformation mechanisms are required to satisfy the von Mises criterion for general plasticity in polycrystalline materials. Yet, it is generally recognized that polycrystalline NiAl can be deformed extensively in compression at room temperature and that limited tensile ductility can be obtained in extruded materials. In order to determine whether these results are in conflict with the von Mises criterion, tension and compression tests were conducted on powder-extruded, binary NiAl between 300 and 1300 K. The results indicate that below the brittle-to-ductile transition temperature (BDTT) the failure mechanism in NiAl involves the initiation and propagation of cracks at the grain boundaries which is consistent with the von Mises analysis. Furthermore, evaluation of the flow behavior of NiAl indicates that the transition from brittle to ductile behavior with increasing temperature coincides with the onset of recovery mechanisms such as dislocation climb. The increase in ductility above the BDTT is therefore attributed to the climb of <001> type dislocations which in combination with dislocation glide enable grain boundary compatibility to be maintained at the higher temperatures.

New Triaxial Connection Safety Factor for Tubular Design

2021 ◽  
pp. 1-11
Author(s):  
Malcolm A. Goodman
Keyword(s):  
Finite Element Analysis ◽  
Safety Factor ◽  
American Petroleum Institute ◽  
Von Mises Stress ◽  
Element Analysis ◽  
Threaded Connections ◽  
Shear Component ◽  
Physical Tests ◽  
The Mean ◽  
Von Mises

Summary The American Petroleum Institute (API) equation for internal leak of API connections is uniaxial because it ignores axial force and external backup pressure. The ISO 13679 (2002) standard for qualification of premium connections is biaxial at best. It includes tension/compression but ignores backup pressure for both internal and external leak tests. For tubular design, this paper introduces a new fully triaxial safety factor for threaded connections with dependence on thread shear and hydrostatic pressure. Triaxial hydrostatic behavior is modeled with the mean normal stress, and thread shear behavior is modeled with the shear component of the von Mises stress. A leak line for use like the pipe body ellipse is proposed for quick leak assessment. Leak ratings and correlation with finite element analysis (FEA) results are presented for an example case of a 7-in.35-ppf N80 long-thread-casing (LTC) connection. The new triaxial safety factor with two connection constants applies to all types of threaded connections, including tubing, casing, and drillpipe, so long as the two constants are evaluated with appropriate but simple physical tests.

Biaxial Specimen Design for Structures Subjected to Multi-Axial Loads

2014 ◽  
Vol 891-892 ◽  
pp. 1633-1638 ◽  
Author(s):  
Nayeem Tawqir Chowdhury ◽  
Wing Kong Chiu ◽  
John Wang
Keyword(s):  
Axial Stress ◽  
Tensile Load ◽  
Complex Loading ◽  
Effective Area ◽  
Dominant Mode ◽  
Model Material ◽  
Biaxial Testing ◽  
Failure Theory ◽  
Strain Invariant ◽  
Von Mises

The ability to optimise structures requires a thorough understanding of the loadsthat they are subjected to. Many composite materials in use today are subjectedto complex loading patterns that exhibit multi-axial stress and straincharacteristics. It is not sufficient to model material data for thesestructures based purely on uniaxial information. Unlike the well understoodfailure criteria of materials when subjected to uniaxial loads; biaxial failureenvelope has not been defined with sufficient experimental data particularly inthe tensile load region. There has not been any standard specimen geometrydefined for biaxial testing. Also the effective area when subjected to loadingis not as easily known as is the case in uniaxial loading. Thus biaxial testspose a greater level of difficulty when establishing failure stresses for thematerial. The authors look at establishing a specimen geometry that is suitablefor use preliminarily in isotropic materials. These specimen geometries must beable to ensure failure at the anticipated gauge region. Investigation into thefirst quadrant of the biaxial failure envelope under tension-tension is lookedat with insight into matrix failure as the dominant mode of failure. Numerical resultsand preliminary experimental results for FM355 epoxy specimens are presentedand compared with existing failure models such as Von Mises criterion and thefailure criterion used in Strain Invariant Failure Theory.

Yield Pressure Measurements and Analysis for Autofrettaged Cannons

2002 ◽  
Author(s):  
John H. Underwood ◽  
David B. Moak ◽  
Michael A. Audino ◽  
Anthony P. Parker
Keyword(s):  
Residual Stress ◽  
Yield Strength ◽  
Yield Criterion ◽  
Axial Stress ◽  
Design Procedure ◽  
Pressure Vessels ◽  
Pressure Measurements ◽  
Strain Rate Effects ◽  
Axial Residual Stress ◽  
Von Mises

Yield pressure corresponding to a small permanent OD strain was measured in quasi-static laboratory tests of autofrettaged ASTM A723 steel cannon pressure vessels. Yield pressure was found to be a consistent ratio of the yield strength measured from specimens located in close proximity to the area of observed yielding. Yield pressure measurements for dynamic cannon firing with typically a 5 ms pressure pulse duration gave 14% higher yield pressures, attributed to strain rate effects on plastic deformation. Calculated Von Mises yield pressure for the laboratory test conditions, including the Bauschinger-modified ID residual stress and open-end vessel conditions, agreed with measured yield pressure within 3–5%. Calculated yield pressure was found to be insensitive to the value of axial residual stress, since axial stress is the intermediate value in the Von Mises yield criterion. A description of yield pressure normalized by yield strength was given for autofrettaged A723 open-end pressure vessels over a range of wall ratio and degree of autofrettage, including effects of Bauschinger-modified residual stress. This description of yield pressure is proposed as a design procedure for cannons and other pressure vessels.

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