A Master S-N Curve Representation of Subsea Umbilical Tube Weld Fatigue Data

2010 ◽  
Author(s):  
Pingsha Dong ◽  
Xinhua Yang
Keyword(s):  
Stress Ratio ◽  
Correction Term ◽  
Fatigue Loading ◽  
Nominal Stress ◽  
Stress Range ◽  
Fatigue Data ◽  
Range Parameter ◽  
Weld Fatigue ◽  
Curve Representation ◽  
The One

In this paper, some of the available duplex and super-duplex stainless steel umbilical tube fatigue data are analyzed using an equivalent nominal stress range parameter, which shares a great deal of similarity to the one used in the 2007 ASME Div 2 Code. The proposed fatigue parameter consists of nominal stress range, a size correction term RTt with RT being the tube radius and t being tube wall thickness, and a stress ratio term (1 − R) with R being applied stress ratio. With it, the available girth weld fatigue test data are shown to collapse into a narrow band. The equivalent nominal stress range parameter is also shown to be effective in correlating seam weld data collected from seam-welded umbilicals, but with a different slope in log-log based S-N plot. Coiling/uncoiling low-cycle effects can be addressed by introducing a pseudo elastic nominal stress definition. Miner’s rule can be used to combine both coiling/uncoiling effects with subsequent high-cycle fatigue loading.

Fatigue Life of Arenga Pinnata/Epoxy Composites

2015 ◽  
Vol 1102 ◽  
pp. 103-106 ◽  
Author(s):  
Abdul Hakim Abdullah ◽  
Muhd Faiz Mat
Keyword(s):  
Fatigue Life ◽  
Tensile Stress ◽  
Tensile Test ◽  
Stress Ratio ◽  
Fatigue Loading ◽  
Ultimate Tensile Stress ◽  
Epoxy Composites ◽  
Fatigue Properties ◽  
Material Fatigue ◽  
Fatigue Data

In this study, fatigue properties of unidirectional Arenga Pinnata fibre reinforced epoxy composites have been investigated under tension-tension fatigue loading. Composites were made at 25% by Arenga Pinnata fibre weight contents using hand lay-out technique. Tensile test was performed prior fatigue loading evaluation. The composites where then were cycled between 90%, 80%, 70% measured from ultimate tensile stress (UTS), with 10 Hz of frequency and stress ratio of R at 0.1. Tensile results indicated that the composites resist to deformation and this reaction denotes that the composites are a brittle material. Fatigue life of composite was improving as the cycled stress decreases. The fatigue resistance were calculated by employing analytical expression and compared with relevant fatigue data.

Damage accumulation near a hole under low cycle fatigue proceeding from measurements of local deformation response

2020 ◽  
Vol 86 (10) ◽  
pp. 46-55
Author(s):  
S. I. Eleonsky ◽  
Yu. G. Matvienko ◽  
V. S. Pisarev ◽  
A. V. Chernov
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Damage Accumulation ◽  
Stress Ratio ◽  
Low Cycle Fatigue ◽  
Accumulation Process ◽  
Stress Range ◽  
Cycle Fatigue ◽  
Deformation Response

A new destructive method for quantitative determination of the damage accumulation in the vicinity of a stress concentrator has been proposed and verified. Increase of damage degree in local area with a high level of the strain gradient was achieved through preliminary low-cycle pull-push loading of plane specimens with central open holes. The above procedure is performed for three programs at the same stress range (333.3 MPa) and different stress ratio values 0.33, – 0.66 and – 1.0, and vice versa for two programs at the same stress ratio – 0.33 and different stress range 333.3 and 233.3 MPa. This process offers a set of the objects to be considered with different degree of accumulated fatigue damages. The key point of the developed approach consists in the fact that plane specimens with open holes are tested under real operation conditions without a preliminary notching of the specimen initiating the fatigue crack growth. The measured parameters necessary for a quantitative description of the damage accumulation process were obtained by removing the local volume of the material in the form of a sequence of narrow notches at a constant level of external tensile stress. External load can be considered an amplifier enhancing a useful signal responsible for revealing the material damage. The notch is intended for assessing the level of fatigue damage, just as probe holes are used to release residual stress energy in the hole drilling method. Measurements of the deformation response caused by local removing of the material are carried out by electronic speckle-pattern interferometry at different stages of low-cycle fatigue. The transition from measured in-plane displacements to the values of the stress intensity factor (SIF) and the T-stress was carried out on the basis of the relations of linear fracture mechanics. It was shown that the normalized dependences of the stress intensity factor on the durability percentage for the first notch (constructed for four programs of cyclic loading with different parameters), reflect the effect of the stress ratio and stress range of the loading cycle on the rate of damage accumulation. The data were used to obtain the explicit form of the damage accumulation function that quantitatively describes damage accumulation process. The functions were constructed for different stress ratios and stress ranges.

Bayesian Inference Method for Failure Probability of Wall Thinning Pipe in Corrosion Rate Fluctuation Model

2008 ◽  
Author(s):  
Satoshi Okajima ◽  
Satoshi Izumi ◽  
Shinsuke Sakai
Keyword(s):  
Corrosion Rate ◽  
Failure Probability ◽  
Error Term ◽  
Correction Term ◽  
Operational Environment ◽  
Bayes Method ◽  
Wall Thinning ◽  
Rate Fluctuation ◽  
The One ◽  
Linear Bayes

To rationalize the inspection interval for the wall-thinning piping element, the linear-Bayes method was proposed in the previous paper. To derive the simple formula, the linear-Bayes method ignores the corrosion rate change against time. However, this change may be caused by the one of the operational environment. Therefore, without the sufficient monitoring of the environment, the linear-Bayes method may underestimate the failure probability. In this paper, the linear-Bayes method is extended for the wall-thinning model with the corrosion rate fluctuation, which imitates the unexpected change of the corrosion rate. The extension is carried out through following two approaches: the “correction-term” and the “error-term” approaches. The correction-term approach can evaluate the change of corrosion rate, however, it requires sufficient number of inspections. The error-term approach evaluates the failure probability conservatively.

The Prediction of Notch and Crack Effects

1966 ◽  
Vol 3 (03) ◽  
pp. 364-368
Author(s):  
Paul Kuhn
Keyword(s):  
Static Loading ◽  
Aircraft Design ◽  
Fatigue Loading ◽  
Engineering Structures ◽  
Service Experience ◽  
Small Load ◽  
Automobile Engines ◽  
Quantitative Understanding ◽  
The One ◽  
Reliable Methods

Historically, engineering structures have been designed for static strength, that is, for the one-time application of a large load. However, service loads, as a rule, are repeated loads, and a rather small load can break a structure if it is repeated very often; this phenomenon is known as the fatigue problem. Fatigue was for a while a serious problem in the design of automobiles. But automobile engines, for instance, are built by hundreds of thousands to one design. Service experience thus furnishes highly reliable information as to which parts are underdesigned, and the design methods can be improved by adding experience factors. In aircraft design, this avenue of approach can be used only to a very limited extent, largely because any failure in the air is likely to be catastrophic. Thus, strong efforts must be made to provide reliable methods of design by research rather than by developing factors derived from service experience. This paper briefly discusses two separate but related phases of aircraft fatigue research: The effect of notches under fatigue loading, and the effect of cracks under static loading. Quantitative understanding of notches under fatigue loading enables the designer to minimize the appearance of cracks. Quantitative understanding of cracks under static loading enables the designer to produce a structure which is safe when cracks do occur.

scholarly journals Stress–Dilatancy Relationship of Erksak Sand under Drained Triaxial Compression

Geosciences ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 353
Author(s):  
Katarzyna Dołżyk-Szypcio
Keyword(s):  
Stress Ratio ◽  
Triaxial Compression ◽  
Stable Condition ◽  
Compression Tests ◽  
Ultimate State ◽  
Dense Sand ◽  
The One ◽  
Two Parameters ◽  
Relationship Of ◽  
Triaxial Compression Tests

Analyzing the results of triaxial compression tests under drained conditions for Erksak sand published in the literature, the stress–dilatancy relationships were described using the frictional state concept. At all phases of shearing, the linear stress ratio–plastic dilatancy relationship can be expressed by the critical frictional state angle and two parameters of the frictional state concept. At failure, dense sand exhibits purely frictional behavior (α = 0, β = 1) and the stress ratio–dilatancy relationship may be correctly described by the Rowe, Bolton, and frictional state concept relationships. Very loose Erksak sand sheared under drained triaxial compression at the ultimate state reaches a stable condition, but the reached stress ratio is significantly smaller than the one at a critical state.

Sensitization of the SST Turbulence Model to Rotation and Curvature by Applying the Spalart–Shur Correction Term

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
Pavel E. Smirnov ◽  
Florian R. Menter
Keyword(s):  
Turbulent Flows ◽  
Turbulence Model ◽  
Transport Model ◽  
Correction Term ◽  
Computational Cost ◽  
Turbulence Models ◽  
Reynolds Stress Transport Model ◽  
Wide Range ◽  
Sst Model ◽  
The One

A rotation-curvature correction suggested earlier by Spalart and Shur (1997, “On the Sensitization of Turbulence Models to Rotation and Curvature,” Aerosp. Sci. Technol., 1(5), pp. 297–302) for the one-equation Spalart–Allmaras turbulence model is adapted to the shear stress transport model. This new version of the model (SST-CC) has been extensively tested on a wide range of both wall-bounded and free shear turbulent flows with system rotation and/or streamline curvature. Predictions of the SST-CC model are compared with available experimental and direct numerical simulations (DNS) data, on the one hand, and with the corresponding results of the original SST model and advanced Reynolds stress transport model (RSM), on the other hand. It is found that in terms of accuracy the proposed model significantly improves the original SST model and is quite competitive with the RSM, whereas its computational cost is significantly less than that of the RSM.

scholarly journals A re-examination of the adiabatic correction term for the hydrogen molecule

1976 ◽  
Vol 54 (4) ◽  
pp. 651-656 ◽  
Author(s):  
Huw O. Pritchard ◽  
Lutosław Wolniewicz
Keyword(s):  
Energy Level ◽  
Hydrogen Molecule ◽  
Vibrational Energy ◽  
Correction Term ◽  
Internuclear Separation ◽  
Vibrational Energy Level ◽  
The Difference ◽  
The One

The adiabatic coupling correction term [Formula: see text] has been evaluated by two methods, the one used by Kołos and Wolniewicz in 1964 and the one suggested by Kari, Chan, Hunter, and Pritchard in 1973. The difference between the two procedures for H2 amounts to 0.04 cm−1 and is almost independent of internuclear separation in the range R = 1.0–1.8 a.u. Thus, the method of computing the ΔR-term does not affect the vibrational energy level spacings.

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