Plastic Collapse Behaviors of Tubulars With Recess Patterns

2015 ◽  
Author(s):  
Haifeng Zhao ◽  
David Iblings ◽  
Aleksey Barykin ◽  
Mohamed Mehdi
Keyword(s):  
Empirical Relationship ◽  
External Pressure ◽  
Reduction Factor ◽  
Strength Reduction ◽  
Plastic Collapse ◽  
Strength Reduction Factor ◽  
Periodic Distribution ◽  
Collapse Strength ◽  
Post Buckling ◽  
Collapse Behavior

The collapse strength of tubulars with recess patterns machined into their walls is an important topic for oilfield downhole tools as it applies to perforating guns, prepacked sand screens, and perforated and slotted liners. This paper presents a study of the plastic collapse behavior of thick-walled tubulars (those with an outside diameter to thickness ratio of approximately 10) having different patterns of circular recesses (blind holes partially machined into the tubing wall) that are subjected to external pressure. An empirical relationship between the reduction in collapse strength and the periodic distribution of recesses was constructed to account for the weakening effects of recess diameter, recess depth, axial spacing, angular phasing, etc. This strength reduction factor was introduced into the Tamano formula to predict collapse strength of recessed tubulars. Applicability of this empirical formula was validated with the aid of nonlinear, post-buckling Finite Element Analyses (FEA). The modeling approach was verified by full-scale physical tests. However, results of the physical testing are not presented in this paper. The strength reduction factor in combination with the Tamano formula provides a simple way of parametrically predicting the collapse strength of tubulars having circular recess patterns.

Plastic Collapse Behaviors of Tubulars with Recess Patterns—Application in Hollow Carrier Perforating Guns

2016 ◽  
Vol 3 (1) ◽  
Author(s):  
Haifeng Zhao ◽  
David Iblings ◽  
Aleksey Barykin ◽  
Mohamed Mehdi
Keyword(s):  
Empirical Relationship ◽  
External Pressure ◽  
Reduction Factor ◽  
Strength Reduction ◽  
Oil Field ◽  
Plastic Collapse ◽  
Strength Reduction Factor ◽  
Periodic Distribution ◽  
Collapse Strength ◽  
Collapse Behavior

The collapse strength of tubulars with recess patterns machined into their walls is an important topic for oil field downhole tools, especially in hollow carrier perforating gun systems. This paper presents a study of the plastic collapse behavior of thick-walled tubulars (those with an outside diameter to thickness ratio of approximately ten) having different patterns of circular recesses (blind holes partially machined into the tubing wall) that are subjected to external pressure. An empirical relationship between the reduction in collapse strength and the periodic distribution of recesses was constructed to account for the weakening effects of recess diameter, recess depth, axial spacing, angular phasing, etc. This strength reduction factor was introduced into the Tamano formula to predict collapse strength of recessed tubulars. Applicability of this empirical formula was validated with the aid of nonlinear, postbuckling finite element analyses (FEA). The strength reduction factor in combination with the Tamano formula provides a simple way of parametrically predicting the collapse strength of tubulars having circular recess patterns.

Dynamic Instability of Soil-SDOF Structure Systems under Far-Fault Earthquakes

2015 ◽  
Vol 31 (4) ◽  
pp. 2419-2441 ◽  
Author(s):  
Faramarz Khoshnoudian ◽  
Ehsan Ahmadi ◽  
Mahdi Kiani ◽  
Mohammad Hadikhan Tehrani
Keyword(s):  
Soil Structure ◽  
Dynamic Instability ◽  
Reduction Factor ◽  
Strength Reduction ◽  
Strength Reduction Factor ◽  
Vibration Period ◽  
Collapse Strength ◽  
Fixed Base ◽  
Far Fault ◽  
Reduction Factors

A parametric study is devoted to investigating the dynamic instability of soil-structure systems under far-fault earthquakes. The superstructure and soil are simulated as a bilinear single-degree-of-freedom (SDOF) oscillator and based on the cone model concept, respectively. The results show that soil flexibility makes the system dynamically more unstable and that as the non-dimensional frequency increases, the collapse strength-reduction factor highly decreases. Moreover, increasing the aspect ratio leads to a lower collapse strength-reduction factor. However, its effect is found to be negligible. The effects of vibration period and post-yield slope on the collapse strength-reduction factor are the same as on the fixed-base condition. Additionally, comparison of collapse strength-reduction factors resulting from exact time history analyses with those proposed in FEMA 440 for the fixed-base condition shows a great underestimation with errors larger than 20% at approximately all cases and 60% at extreme cases. Finally, a formulation is calibrated using nonlinear regression analysis in order to estimate collapse strength-reduction factors of soil-structure systems.

scholarly journals Assessing Slope Stability of Clay-Dominated Sediments Based on Ionic Concentrations Using Liquid Limits

2021 ◽  
Vol 21 (5) ◽  
pp. 237-243
Author(s):  
Joongi Kim ◽  
Jongmuk Won
Keyword(s):  
Slope Stability ◽  
Numerical Simulations ◽  
Clay Minerals ◽  
Empirical Relationship ◽  
Friction Angle ◽  
Ionic Concentration ◽  
Reduction Factor ◽  
Strength Reduction ◽  
Numerical Results ◽  
Strength Reduction Factor

Clay minerals typically exhibit high specific surfaces with negative charges, which result in a sensitive response against the change in the ionic concentration of pore water. In this study, the liquid limits of kaolinite, illite, and bentonite were determined as functions of the ionic concentration, and the results were used to obtain the cohesion and friction angle based on the empirical relationship for evaluating slope stability through numerical simulations. The experimental and numerical results revealed increased liquid limits and a decreased strength-reduction factor as the ionic concentration increased. Based on the numerical results, the influence of ionic concentration on the slope stability of clay-contained soils was analyzed.

Influence of Wear Properties on Fretting Fatigue Life of a CK45 Alloy and the Al7175 Alloy

2008 ◽  
Vol 587-588 ◽  
pp. 971-975 ◽  
Author(s):  
M. Buciumeanu ◽  
A.S. Miranda ◽  
F.S. Silva
Keyword(s):  
Wear Resistance ◽  
Fatigue Life ◽  
Material Properties ◽  
Fatigue Behavior ◽  
Synergetic Effect ◽  
Fretting Fatigue ◽  
Reduction Factor ◽  
Strength Reduction ◽  
Strength Reduction Factor ◽  
Wear Properties

The main objective of this work was to study the influence of the wear properties of two commercial alloys (CK45 and Al7175) on their fretting fatigue behavior. It is verified the effect of material local degradation by wear on a fatigue strength reduction factor, namely the stress concentration factor, and on the overall fretting fatigue life of these materials. The fretting fatigue phenomenon is a synergetic effect between wear and fatigue. It is dependent on both the fatigue and the wear properties of the materials. Material properties promoting an increase in wear resistance should enhance fretting fatigue life.

Design of Pressure Vessels for Low-Cycle Fatigue

1962 ◽  
Vol 84 (3) ◽  
pp. 389-399 ◽  
Author(s):  
B. F. Langer
Keyword(s):  
Fatigue Strength ◽  
Pressure Vessel ◽  
Low Cycle Fatigue ◽  
Fatigue Curve ◽  
Pressure Vessels ◽  
Reduction Factor ◽  
Strength Reduction ◽  
Strength Reduction Factor ◽  
The Mean ◽  
Fatigue Evaluation

Methods are described for constructing a fatigue curve based on strain-fatigue data for use in pressure vessel design. When this curve is used, the same fatigue strength-reduction factor should be used for low-cycle as for high-cycle conditions. When evaluating the effects of combined mean and alternating stress, the fatigue strength-reduction factor should be applied to both the mean and the alternating component, but then account must be taken of the reduction in mean stress which can be produced by yielding. The complete fatigue evaluation of a pressure vessel can be a major task for the designer, but it can be omitted, or at least drastically reduced, if certain requirements can be met regarding design details, inspection, and magnitude of transients. Although the emphasis in this paper is on pressure vessel design, the same principles could be applied to any structure made of ductile metal and subjected to limited numbers of load cycles.

Strength reduction factor of self-centering structures under near-fault pulse-like ground motions

2020 ◽  
Vol 24 (1) ◽  
pp. 119-133
Author(s):  
Huihui Dong ◽  
Qiang Han ◽  
Xiuli Du ◽  
Canxing Qiu
Keyword(s):  
Ground Motions ◽  
Time History ◽  
Reduction Factor ◽  
Strength Reduction ◽  
The Self ◽  
Hysteretic Behavior ◽  
Hysteretic Model ◽  
Strength Reduction Factor ◽  
Vibration Period ◽  
Near Fault

Many studies on the strength reduction factor mainly focused on structures with the conventional hysteretic models. However, for the self-centering structure with the typical flag-shaped hysteretic behavior, the corresponding study is limited. The main purpose of this study is to investigate the strength reduction factor of the self-centering structure with flag-shaped hysteretic behavior subjected to near-fault pulse-like ground motions by the time history analysis. For this purpose, the smooth flag-shaped model based on Bouc-Wen model which can show flag-shaped hysteretic behavior is first described. The strength reduction factor spectra of the flag-shaped model are then calculated under 85 near-fault pulse-like ground motions. The influences of the ductility level, vibration period, site condition, hysteretic parameter, and hysteretic model are investigated statistically. For comparison, the strength reduction factors under ordinary ground motions are also analyzed. The results show that the strength reduction factor from near-fault pulse-like ground motions is smaller. Finally, a predictive model is proposed to estimate the strength reduction factor for the self-centering structure with the flag-shaped model under near-fault pulse-like ground motions.

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