Variations in the Postbuckling Behavior of Straight Pipes Due to Steel Grade and Internal Pressure

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Ngoan T. Do ◽  
Celal Cakiroglu ◽  
Mustafa Gul ◽  
Roger Cheng ◽  
Millan Sen ◽  
...  
Keyword(s):  
Internal Pressure ◽  
Failure Mode ◽  
Material Properties ◽  
Failure Modes ◽  
Experimental Studies ◽  
Equivalent Plastic Strain ◽  
Slope Instability ◽  
Structural Behavior ◽  
Discontinuous Permafrost ◽  
Bending Loads

Pipelines can be subjected to bending loads due to a variety of factors such as seismic activity, slope instability, or discontinuous permafrost. Experimental studies of Sen et al. [1–3] showed that pipelines can fail under bending loads due to pipe body tension side fracture which is a mostly overlooked failure mode in pipelines. Recent numerical studies on the structural behavior of cold bent pipes [4–6] also confirmed the likelihood of the pipe body tension side fracture. Furthermore, it was shown that both the material properties and the level of internal pressure can have a considerable effect on the failure mode of the pipe. In this current work, the parametric studies of internal pressure and material properties are extended to straight pipes using finite-element analysis. The differences in the structural behavior due to using stress–strain curves from test specimens in longitudinal and circumferential direction of the pipe are demonstrated. Using failure criteria based on the equivalent plastic strain, different failure modes corresponding to different levels of internal pressure and yield strength are shown on straight pipes.

Post-Buckling Failure Modes of X65 Steel Pipe: An Experimental and Numerical Study

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
Nima Mohajer Rahbari ◽  
Mengying Xia ◽  
Xiaoben Liu ◽  
J. J. Roger Cheng ◽  
Millan Sen ◽  
...  
Keyword(s):  
Internal Pressure ◽  
Cross Section ◽  
Failure Modes ◽  
Bending Test ◽  
Bending Load ◽  
Post Buckling ◽  
X65 Steel ◽  
Bending Loads ◽  
Buckling Failure ◽  
Longitudinal Strains

In service pipelines exhibit bending loads in a variety of in-field situation. These bending loads can induce large longitudinal strains, which may trigger local buckling on the pipe's compressive side and/or lead to rupture of the pipe's tensile side. In this article, the post-buckling failure modes of pressurized X65 steel pipelines under monotonic bending loading conditions are studied via both experimental and numerical investigations. Through the performed full-scale bending test, it is shown that the post-buckling rupture is only plausible to occur in the pipe wall on the tensile side of the wrinkled cross section under the increased bending. Based on the experimental results, a finite element (FE)-based numerical model with a calibrated cumulative fracture criterion was proposed to conduct a parametric analysis on the effects of the internal pressure on the pipe's failure modes. The results show that the internal pressure is the most crucial variable that controls the ultimate failure mode of a wrinkled pipeline under monotonic bending load. And the post-buckling rupture of the tensile wall can only be reached in highly pressurized pipes (hoop stress no less than 70% SMYS for the investigated X65 pipe). That is, no postwrinkling rupture is likely to happen below a certain critical internal pressure even after an abrupt distortion of the wrinkled wall on the compressive side of the cross section.

Numerical Analysis of High Pressure Cold Bend Pipe to Investigate the Behaviour of Tension Side Fracture

2012 ◽  
Author(s):  
Celal Cakiroglu ◽  
Amin Komeili ◽  
Samer Adeeb ◽  
J. J. Roger Cheng ◽  
Millan Sen
Keyword(s):  
Finite Element ◽  
High Pressure ◽  
Internal Pressure ◽  
Experimental Studies ◽  
Element Model ◽  
Combined Loading ◽  
Element Analysis ◽  
Bend Pipe ◽  
Bending Load ◽  
Bending Loads

The cold bend pipelines may be affected by the geotechnical movements due to unstable slopes, soil type and seismic activities. An extensive experimental study was conducted by Sen et al. in 2006 to understand the buckling behaviour of cold bend pipes. In their experiments, it was noted that one high pressure X65 pipe specimen failed under axial and bending loads due to pipe body tensile side fracture which occurred after the development of a wrinkle. The behaviour of this cold bend pipe specimen under bending load has been investigated numerically to understand the conditions leading to pipe body tension side fracture following the compression side buckling. Bending load has been applied on a finite element model of the cold bend by increasing the curvature of it according to the experimental studies conducted by Sen [1]. The bending loads have been applied on the model with and without internal pressure. The distribution of the plastic strains and von Mises stresses as well as the load–displacement response of the pipe have been compared for both load cases. In this way the experimental results obtained by Sen [1] have been verified. The visualization of the finite element analysis results showed that pipe body failure at the tension side of the cold bend takes place under equal bending loads only in case of combined loading with internal pressure.

scholarly journals Reinforced Concrete Dapped End Beams – State of the Art

2018 ◽  
Vol 1 (2) ◽  
pp. p44 ◽  
Author(s):  
Qasim M. Shakir
Keyword(s):  
Reinforced Concrete ◽  
Material Properties ◽  
Failure Modes ◽  
State Of The Art ◽  
Experimental Studies ◽  
Historical Review ◽  
High Strength ◽  
Self Compacting Concrete ◽  
Effective Depth ◽  
Future Work

This paper represents a historical review, on the experimental studies carried out to investigate the behavior of non-prestressed dapped end beams. The specimens discussed are made of normal, high-strength and self-compacting concrete and subjected to several systems of loading setup. Different values of the (shear span-to-effective depth) ratio that were adopted by researchers are discussed. Some specimens are full scale other are prototypes. Different methods and suggestions by previous studies to strengthen the dapped end. Different failure modes that have been recognized based on detailing, dimension and material properties of the dapped end beams. Several parameters that may affect the behavior of dapped end beams are reported. Many shown also, the conclusions that have been drawn from various studies. In addition, some suggestion for future work are proposed and to extend studies about the behavior of the dapped end beams. Finally, a comprehensive list of references is provided.

Failure Mode Attribution Analysis of PBL Shear Connector

2013 ◽  
Vol 351-352 ◽  
pp. 683-686
Author(s):  
Wen Jiang Zhang ◽  
Er Xia Du ◽  
Bei Zhan Liu ◽  
Shao Chong Yang
Keyword(s):  
Failure Mode ◽  
Material Properties ◽  
High Strength Concrete ◽  
Failure Modes ◽  
Steel Plate ◽  
High Strength ◽  
Shear Connector ◽  
Related Factors ◽  
Shear Connectors ◽  
Attribution Analysis

Investigation on PBL shear connectors failure modes and their related factors is conducted. On the basis of analysis on the detail mechanism of PBL shear connectors failure modes, the relations between the construction factors and failure modes are summarized. A reasonable way of failure mode is proposed for exerting the material properties of all components in PBL shear connector. As reference to construction and design of PBL shear connector, it is advised that the high strength concrete should be used, and the strength of steel plate should be not less than that of rebar. The position and posture of rebar cannot be ignored.

Design Equations for Preventing Buckling in Fabricated Torispherical Shells Subjected to Internal Pressure

1986 ◽  
Vol 200 (2) ◽  
pp. 127-139 ◽  
Author(s):  
G D Galletly
Keyword(s):  
Internal Pressure ◽  
Failure Mode ◽  
Failure Modes ◽  
Experimental Results ◽  
Design Equation ◽  
Test Results ◽  
Theoretical Predictions ◽  
The Subject ◽  
The Difference ◽  
Empirical Constants

Design rules to prevent buckling in thin fabricated torispherical shells subjected to internal pressure are not yet available in either the American or the British pressure vessel Codes. They are the subject of the present paper and some possible design equations are suggested. The equations were obtained from the buckling equations for perfect torispheres after considering all known experimental results on fabricated models. The empirical constants in the proposed design equations depend on the type of head construction used, i.e. whether crown and segment or pressed and spun. For both types of head the equations give a factor of safety of at least 1.5. The design equation proposed for the crown and segment heads was also checked on several large vessels which had failed in service. The safety factors found for these cases were all greater than 1.7, which means that the vessels would not have buckled if the design equation had been available at the time. The other failure mode of these torispherical heads, i.e. large axisymmetric deformations leading to through-thickness yielding, is also discussed briefly. Curves are given which show that, for 300 < D/t < 500, buckling controls the failure mode in some cases and axisymmetric yielding in others. Neither the American nor the British codes recognize that buckling can occur in this D/t range but the theoretical predictions have been confirmed by experiments. However, the amount of test data is limited and more work is needed on the topic. It is also shown in the paper that, for torispherical shells with D/t ratios in the range 300 < D/t < 500, the axisymmetric limit pressures, pDS, are lower than both the internal buckling pressures and the large deflection axisymmetric yielding pressures. From this, one would expect the failure modes to be axisymmetric in this D/t range. However, as some non-symmetric buckling failures have occurred, the limit analysis predictions for the failure mode are thus not always correct. One feature of the experimental results on stainless steel torispherical shells which are reviewed in the paper is the relatively poor buckling performance of the heads tested by Kemper in comparison with similar heads tested by Stanley and Campbell. As the values of the empirical constants in the design equations are controlled by the lowest test results, the higher bucking pressures obtained by Stanley/Campbell cannot be utilized unless an adequate explanation for the difference in the two sets of results is forthcoming.

Trial Model Tests With Simulation Material to Obtain Failure Modes of Pipes Under Excessive Seismic Loads

2016 ◽  
Author(s):  
Izumi Nakamura ◽  
Naoto Kasahara
Keyword(s):  
Failure Mode ◽  
Failure Modes ◽  
Experimental Studies ◽  
Shaking Table ◽  
Seismic Load ◽  
Seismic Loads ◽  
Steel Pipes ◽  
Piping Systems ◽  
Collapse Failure ◽  
Input Motion

Piping systems are one of the central components of NPP; It is well known that the major failure mode under seismic loads is likely to be fatigue failure. Other failure modes, however, such as ratchet-buckling failure, have been reported to occur under particular conditions. It is necessary to clarify the conditions that cause different failure modes of piping systems under very high seismic motion, but experimental studies with steel pipes are difficult to achieve, mainly due to the limitations of testing facilities and safety concerns. In order to overcome such difficulties, we propose a new experimental approach that uses pipes made of a simulation material instead of steel. Lead (Pb) pipes were used for the simulation material, and shaking table tests were conducted on lead elbow pipe specimens. Results showed that ratchet-collapse and overall deformation of pipe specimens were possible failure modes. The ratchet-collapse failure mode appeared to be affected not only by input acceleration level but also by the direction of gravity, the primary constant stress level of its own weight, and the frequencies of the input motion. The dynamic behaviors of pipes in the high inelastic region where a nearly fully plastic section was assumed were quite different from those in the elastic region, and those of the steel pipes in previous studies. We demonstrate that the proposed test approach is effective for qualitatively clarifying various kinds of failure behaviors with large plasticity under excessive seismic load.

Computational and experimental studies of the strength of full-scale samples of pipes with defects "metal loss" and "dent with groove"

2020 ◽  
Vol 10 (3) ◽  
pp. 226-233
Author(s):  
Dmitry A. Neganov ◽  
◽  
Victor M. Varshitsky ◽  
Andrey A. Belkin ◽  
◽  
...  
Keyword(s):  
Internal Pressure ◽  
Experimental Studies ◽  
Full Scale ◽  
The Other ◽  
Metal Loss ◽  
Calculation Methods ◽  
Reliable Operation ◽  
Sufficient Stability ◽  
Comparative Results ◽  
The Moment

The article contains the comparative results of the experimental and calculated research of the strength of a pipeline with such defects as “metal loss” and “dent with groove”. Two coils with diameter of 820 mm and the thickness of 9 mm of 19G steel were used for full-scale pipe sample production. One of the coils was intentionally damaged by machining, which resulted in “metal loss” defect, the other one was dented (by press machine) and got groove mark (by chisel). The testing of pipe samples was performed by applying static internal pressure to the moment of collapse. The calculation of deterioration pressure was carried out with the use of national and foreign methodical approaches. The calculated values of collapsing pressure for the pipe with loss of metal mainly coincided with the calculation experiment results based on Russian method and ASME B31G. In case of pipe with dent and groove the calculated value of collapsing pressure demonstrated greater coincidence with Russian method and to a lesser extent with API 579/ASME FFS-1. In whole, all calculation methods demonstrate sufficient stability of results, which provides reliable operation of pipelines with defects.

Combine Nanoprobing Technique with Difference Analysis to Identify Nonvisual Failures

2006 ◽  
Author(s):  
Cha-Ming Shen ◽  
Tsan-Cheng Chuang ◽  
Jie-Fei Chang ◽  
Jin-Hong Chou
Keyword(s):  
Failure Mode ◽  
Failure Modes ◽  
Electrical Characteristic ◽  
The Novel ◽  
Difference Analysis ◽  
Original Idea ◽  
Deductive Method ◽  
Complete Measurement

Abstract This paper presents a novel deductive methodology, which is accomplished by applying difference analysis to nano-probing technique. In order to prove the novel methodology, the specimens with 90nm process and soft failures were chosen for the experiment. The objective is to overcome the difficulty in detecting non-visual, erratic, and complex failure modes. And the original idea of this deductive method is based on the complete measurement of electrical characteristic by nano-probing and difference analysis. The capability to distinguish erratic and invisible defect was proven, even when the compound and complicated failure mode resulted in a puzzling characteristic.

Case Study and Fault Modeling for Wrong Redundancy Evaluation on DRAM Devices

2007 ◽  
Author(s):  
Martin Versen ◽  
Dorina Diaconescu ◽  
Jerome Touzel
Keyword(s):  
Failure Mode ◽  
Failure Modes ◽  
Fault Modeling ◽  
Mode Analysis ◽  
Root Cause ◽  
Failure Mode Analysis

Abstract The characterization of failure modes of DRAM is often straight forward if array related hard failures with specific addresses for localization are concerned. The paper presents a case study of a bitline oriented failure mode connected to a redundancy evaluation in the DRAM periphery. The failure mode analysis and fault modeling focus both on the root-cause and on the test aspects of the problem.

Methodology for Analysis of Schottky Diode Failures

2010 ◽  
Author(s):  
Bhanu P. Sood ◽  
Michael Pecht ◽  
John Miker ◽  
Tom Wanek
Keyword(s):  
Failure Mode ◽  
Schottky Diode ◽  
Failure Modes ◽  
Schottky Diodes ◽  
Failure Mechanisms ◽  
Forward Voltage ◽  
Fast Switching ◽  
Voltage Drops ◽  
The Common

Abstract Schottky diodes are semiconductor switching devices with low forward voltage drops and very fast switching speeds. This paper provides an overview of the common failure modes in Schottky diodes and corresponding failure mechanisms associated with each failure mode. Results of material level evaluation on diodes and packages as well as manufacturing and assembly processes are analyzed to identify a set of possible failure sites with associated failure modes, mechanisms, and causes. A case study is then presented to illustrate the application of a systematic FMMEA methodology to the analysis of a specific failure in a Schottky diode package.

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