Effect of Reinforcement on the Strength of Junctions Between Cylindrical and Conical Shells

1995 ◽  
Vol 117 (2) ◽  
pp. 135-141 ◽  
Author(s):  
A. Kalnins ◽  
D. P. Updike
Keyword(s):  
Failure Criterion ◽  
Failure Modes ◽  
Low Cycle Fatigue ◽  
Safety Margin ◽  
External Pressure ◽  
Cycle Fatigue ◽  
Conical Shells ◽  
Section Viii ◽  
Cyclic Service ◽  
Reinforcement Distribution

Two failure modes are addressed for cylinder-cone junctions under internal or external pressure: axisymmetric yielding and low-cycle fatigue. If the junction fails to meet the failure criterion of any one of the two modes, then it must be strengthened by reinforcement. It is shown in the paper that the degree to which a junction is strengthened depends on the distribution of the reinforcement. A placement of reinforcement on the cylinder alone, leaving the actual connection between the cylinder and cone unreinforced, adds strength with regard to axisymmetric yielding, but may not strengthen the junction sufficiently with regard to low-cycle fatigue. This means that the junction may appear reinforced, but is not strengthened. It is pointed out that the design rules of Section VIII, Div. 1 of the ASME B & PV Code (1992) set the need for reinforcement according to the failure criterion of low-cycle fatigue, while the distribution of the reinforcement is guided by the criterion of axisymmetric yielding. There is no assurance that the reinforced junction will meet the failure criterion of low-cycle fatigue. This means that the safety margin on the number of allowed cycles is less than that which is expected and that the junction may be unfit for cyclic service. It is also shown in the paper that a reinforcement distribution that requires minimum thicknesses for sections of both the cylinder and cone near the junction can satisfy criteria for both failure modes. This approach is already used in Code Case 2150 of Section VIII, Div. 1, for half-apex cone angles from 30 to 60 deg, and required in Div. 2 for cone angles from 0 to 30 deg. Its extension to angles from 0 to 60 deg for both internal and external pressure is recommended.

Technical Basis for Code Cases on Design of Ellipsoidal and Torispherical Heads for ASME Section VIII Vessels

1999 ◽  
Vol 122 (1) ◽  
pp. 55-59 ◽  
Author(s):  
Mahendra D. Rana ◽  
Arturs Kalnins
Keyword(s):  
Failure Modes ◽  
Low Cycle Fatigue ◽  
Plastic Collapse ◽  
Cycle Fatigue ◽  
Dimensional Changes ◽  
Division 1 ◽  
Section Viii ◽  
Technical Basis ◽  
Division 2 ◽  
Fatigue Criterion

ASME Boiler and Pressure Vessel (B&PV) Code Committees have approved Code Cases 2260 and 2261 on the design of ellipsoidal and torispherical heads for Section VIII Division 1 and Division 2 vessels, respectively. Burst and low-cycle fatigue failure modes have been considered. A rationale is provided for including the foregoing referenced failure modes, and not including other failure modes such as dimensional changes, plastic collapse, knuckle yielding, etc. The basis for the specified design formulas to satisfy the burst and low-cycle fatigue criterion is discussed. The paper also discusses limitations and other requirements that have been imposed in the Code Cases. [S0094-9930(00)01401-3]

Identification of Failure Modes Under Design Extension Conditions

2015 ◽  
Author(s):  
Naoto Kasahara ◽  
Izumi Nakamura ◽  
Hideo Machida ◽  
Hitoshi Nakamura ◽  
Koji Okamoto
Keyword(s):  
High Temperature ◽  
Nuclear Power ◽  
Failure Modes ◽  
Low Cycle Fatigue ◽  
External Pressure ◽  
Lessons Learned ◽  
Local Failure ◽  
Severe Accident ◽  
Mitigation Measures ◽  
Loading Mode

As the important lessons learned from the Fukushima-nuclear power plant accident, mitigation of failure consequences and prevention of catastrophic failure became essential against severe accident and excessive earthquake conditions. To improve mitigation measures and accident management, clarification of failure behaviors with locations is premise under design extension conditions such as severe accidents and earthquakes. Design extension conditions induce some different failure modes from design conditions. Furthermore, best estimation for these failure modes are required for preparing countermeasures and management. Therefore, this study focused on identification of failure modes under design extension conditions. To observe ultimate failure behaviors of structures under extreme loadings, new experimental techniques were adopted with simulation materials such as lead and lead-antimony alloy, which has very small yield stress. Postulated failure modes of main components under design extension conditions were investigated according three categories of loading modes. The first loading mode is high temperature and internal pressure. Under this mode, ductile fracture and local failure were investigated. At the structural discontinuities, local failure may become dominant. The second is high temperature and external pressure loading mode. Buckling and fracture were investigated. Buckling occurs however hardly break without additional loads or constraints. The last loading is excessive earthquake. Ratchet deformation, collapse, and fatigue were investigated. Among them, low-cycle fatigue is dominant.

Failure Analysis of Thinned Wall Elbows Under Excessive Seismic Loading

2002 ◽  
Author(s):  
Masaki Shiratori ◽  
Yoji Ochi ◽  
Izumi Nakamura ◽  
Akihito Otani
Keyword(s):  
Finite Element ◽  
Fatigue Damage ◽  
Failure Modes ◽  
Low Cycle Fatigue ◽  
Local Buckling ◽  
Seismic Loading ◽  
Cycle Fatigue ◽  
Finite Element Analyses ◽  
Residual Thickness ◽  
Limited Period

A series of finite element analyses has been carried out in order to investigate the failure behaviors of degraded bent pipes with local thinning against seismic loading. The sensitivity of such parameters as the residual thickness, locations and width of the local thinning to the failure modes such as ovaling and local buckling and to the low cycle fatigue damage has been studied. It has been found that this approach is useful to make a reasonable experimental plan, which has to be carried out under the condition of limited cost and limited period.

Piping Stress-Strain Correlation for Seismic Loading

1988 ◽  
Vol 110 (4) ◽  
pp. 444-450
Author(s):  
G. Stawniczy ◽  
W. R. Bak ◽  
G. Hau
Keyword(s):  
Pressure Vessel ◽  
Failure Modes ◽  
Low Cycle Fatigue ◽  
Seismic Loading ◽  
Evaluation Procedure ◽  
Test Results ◽  
Cycle Fatigue ◽  
Stress Strain ◽  
Safety Margins ◽  
Fatigue Evaluation

This paper establishes limits on piping material strains for ASME Boiler and Pressure Vessel Code Level D loadings that ensure a limitation of deformation and provide suitable safety margins. In establishing the strain limits, potential piping failure modes due to compressive wrinkling and low-cycle fatigue are considered. A stress-strain correlation methodology to convert linear, elastically calculated Code Class 2 and 3 equation (9)-Level D stresses to strains is established. This correlation is based on the fatigue evaluation procedure of the Code and is verified by comparison with test results. A detailed discussion of test results compared with the stress-strain correlation methodology is also presented.

Low Cycle Fatigue Behavior and Seismic Assessment for Elbow Pipe Having Local Wall Thinning

2010 ◽  
Author(s):  
Yoshio Urabe ◽  
Koji Takahashi ◽  
Kotoji Ando
Keyword(s):  
Fatigue Crack ◽  
Pipe Wall ◽  
Low Cycle Fatigue ◽  
Safety Margin ◽  
Seismic Loading ◽  
Cycle Fatigue ◽  
Wall Thinning ◽  
Erosion Corrosion ◽  
Technical Issues ◽  
Local Wall Thinning

One of the concerned technical issues in the nuclear piping under operation is pipe wall thinning caused by flow accelerated corrosion. Recently it has been reported that the elbow section is more suspicious on pipe wall thinning by erosion-corrosion. Some researchers including authors have been studied static and fatigue strength of elbows with local wall thinning. However, still more experiment and analysis data are needed to clarify the technical issues. Accordingly, further experiments and their evaluations were carried out by the authors. This paper presents the influences of size and location on fatigue life. Also as one of the application of the test results, safety margin of elbows with wall thinning against seismic loading is discussed. Low cycle fatigue tests were conducted using elbow specimens made of STPT410 steel with local wall thinning. The local wall thinning was machined on the inside of elbow specimens in order to simulate erosion/corrosion metal loss. The local wall thinning areas were located at three different areas, called extrados, crown and intrados. Eroded ratio (eroded depth/wall thickness) is 0.5 and 0.8 and eroded angle is 90deg. and 180deg..The elbow specimens were subjected to cyclic in-plane bending under displacement control (±20mm) without and with internal pressure of 3MPa. Obtained main conclusions are shown bellow. (1) Existence of local wall thinning in extrados does not have an important effect on fatigue life. Especially, fatigue crack does not initiate at the extrados where the extreme local wall thinning exists (eroded ratio = 0.8 and eroded angle = 180 deg.). (2) Regardless of existence of internal pressure, fatigue crack initiates at the crown where local wall thinning does not exist. (3) Even if the eroded ratio and the eroded angle reached up to 0.8 and 180 deg., the elbows with local wall thinning have high safety margin against seismic loading, comparing to ASME Boiler and Pressure Vessel Code Sec. III allowable seismic stress criteria.

Subsea Pipeline Lateral Buckling Design—Strain Concentration or Strain Capacity Reduction Factors

2018 ◽  
Vol 140 (3) ◽  
Author(s):  
M. Liu ◽  
C. Cross
Keyword(s):  
Concentration Factor ◽  
Low Cycle Fatigue ◽  
Safety Margin ◽  
Local Buckling ◽  
Cycle Fatigue ◽  
Lateral Buckling ◽  
Strain Concentration ◽  
Strain Capacity ◽  
Global Strain ◽  
Capacity Reduction

A strain concentration factor is typically incorporated in the higher-pressure and high-temperature (HPHT) pipeline lateral buckling assessment to account for nonuniform stiffness or plastic bending moment. Increased strain concentration can compromise pipeline low cycle fatigue and lateral buckling capacity, leading to an early onset of local buckling failure. In this paper, the philosophy of local buckling mitigation using the strain concentration factor is examined. The local buckling behavior is evaluated. Global strain reduction and evolution against buckling are analyzed with respect to varying joint mismatch level. The concept of a strain reduction factor (SNRF) due to joint mismatch is developed based on the global strain capacity reduction with reference to the uniform configuration. It is demonstrated that the SNRF in terms of strain capacity reduction is a unique characteristic parameter. As opposed to strain concentration, it is an invariant insensitive to evaluation methods and design strain demand level, hence more representative as a limiting design metric to maintain the safety margin. The rationale for its introduction as an alternative to the strain concentration factor is outlined and its benefits are established. The method for obtaining the SNRF and its application is developed. The discernible difference and scenarios for application of either factor are discussed, including low and high cycle fatigue, linearity and stress concentration, engineering criticality assessment (ECA), and lateral buckling. Additional causal factors giving rise to mismatch such as pipe schedule transition and buckler arrestor are also discussed. Iterations of finite element (FE) analyses are performed for a pipe-in-pipe (PIP) configuration in a case study.

Subsea Pipeline Lateral Buckling Design: Strain Concentration or Strain Reduction Factors

2017 ◽  
Author(s):  
M. Liu
Keyword(s):  
Concentration Factor ◽  
Low Cycle Fatigue ◽  
Safety Margin ◽  
Local Buckling ◽  
Reduction Factor ◽  
Material Strength ◽  
Cycle Fatigue ◽  
Lateral Buckling ◽  
Strain Concentration ◽  
Global Strain

Strain based design is normally applied for HPHT pipelines when the conventional stress based method becomes impractical. In addition to a design safety factor, a strain concentration factor is typically incorporated in the lateral buckling assessment to account for non-uniform stiffness or plastic bending moment due to geometry and material strength mismatch between adjacent pipe joints. Increased strain concentration can compromise pipeline low cycle fatigue and lateral buckling capacity, leading to an early onset of local buckling failure. In this paper, the philosophy of local buckling mitigation using the strain concentration factor is examined. The local buckling behaviour is evaluated in relation to strain concentration. Global strain reduction and evolution against buckling is analysed with respect to varying joint mismatch level derived according to a structural reliability analysis. The concept of a strain reduction factor due to mismatch is developed and proposed based on the global strain capacity reduction with reference to the uniform configuration. It is demonstrated that the strain reduction factor is a unique characteristic parameter. As opposed to strain concentrations it is an invariant insensitive to evaluation methods and the design strain demand level, hence more representative as a limiting design metric to maintain the safety margin. The use of the strain reduction factor is thus put forward in strain based lateral buckling design as an alternative to using the strain concentration factor. The method for obtaining the strain reduction factor and its application is developed. The rationale for its introduction is outlined and some of its benefits are established. The discernible difference and scenarios for application of either factors are discussed, including low and high cycle fatigue, linearity and stress concentration (SNCF from SCF for welds), ECA and lateral buckling. Additional causal factors giving rise to mismatch such as pipe schedule transition and buckler arrestor are also discussed. Iterations of FE analyses are performed for a pipe-in-pipe configuration in a case study.

Vibration Durability Assessment of Sn3.0Ag0.5Cu and Sn37Pb Solders Under Harmonic Excitation

2009 ◽  
Vol 131 (1) ◽  
Author(s):  
Y. Zhou ◽  
M. Al-Bassyiouni ◽  
A. Dasgupta
Keyword(s):  
Mechanical Engineering ◽  
Failure Modes ◽  
Narrow Band ◽  
Low Cycle Fatigue ◽  
Stress Test ◽  
Harmonic Excitation ◽  
Cycle Fatigue ◽  
Mechanical Cycling ◽  
Mechanical Durability ◽  
Vibration Tests

In this paper, the vibration durability of both SAC305 and Sn37Pb interconnects are investigated with narrow-band harmonic vibration tests conducted at the first natural frequency of the test, printed wiring board, using constant-amplitude excitation. A time-domain approach, reported by Upadhyayula and Dasgupta (1998, “Guidelines for Physics-of-Failure Based Accelerated Stress Test,” Proceedings, Reliability and Maintainability Symposium, pp. 345–357), was adapted in this study for the fatigue analysis. The test board consists of daisy-chained components, to facilitate real-time failure monitoring. The response of the test specimens was characterized, and accelerated fatigue tests were conducted at different loading amplitudes to obtain a mix of low-cycle fatigue (LCF) and high-cycle fatigue data points. The SAC305 interconnects were found to have lower fatigue durability than comparable Sn37Pb interconnects, under the narrow-band harmonic excitation levels used in this study. This trend is consistent with most results from broadband vibration tests by Zhou et al. (2006, “Vibration Durability Comparison of Sn37Pb vs. SnAgCu Solders,” Proceedings of ASME International Mechanical Engineering Congress and Exposition, Chicago, IL, Paper No. 13555), Zhou and Dasgupta (2006, “Vibration Durability Investigation for SnPb and SnAgCu Solders With Accelerated Testing and Modeling,” IEEE-TC7 Conference on Accelerated Stress Testing & Reliability, San Francisco, CA), and Woodrow (2005, “JCAA/JG-PP No-Lead Solder Project: Vibration Test,” Boeing Electronics Materials and Processes Technical Report) and from repetitive mechanical shock tests by Zhang et al. (2005, “Isothermal Mechanical Durability of Three Selected Pb-Free Solders: Sn3.9Ag0.6Cu, Sn3.5Ag and Sn0.7Cu,” ASME J. Electron. Packag., 127, pp. 512–522), but counter to findings from quasistatic, LCF, and mechanical cycling studies by Cuddalorepatta and Dasgupta (2005, “Cyclic Mechanical Durability of Sn3.0Ag0.5Cu Pb-Free Solder Alloy,” Proceedings of the ASME International Mechanical Engineering Congress and Exposition, Orlando, FL, Paper No. 81171). Failure analysis revealed two competing failure modes, one in the solder and another in the copper trace under the component. Thus solder fatigue properties extracted with the help of finite element simulation of the test article should be treated as lower-bound estimates of the actual fatigue curves.

A new failure criterion for materials exhibiting ratcheting during very low cycle fatigue

2007 ◽  
Vol 452-453 ◽  
pp. 380-385 ◽  
Author(s):  
A. Satyadevi ◽  
S.M. Sivakumar ◽  
S.S. Bhattacharya
Keyword(s):  
Failure Criterion ◽  
Low Cycle Fatigue ◽  
Cycle Fatigue
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