Fatigue equation of structural materials and members under hot-wet environment and cyclic bending loads

2020 ◽  
Vol 12 (2-4) ◽  
pp. 119-125
Author(s):  
Zhanbiao Chen ◽  
Peiyan Huang ◽  
Xinyan Guo ◽  
Xiaohong Zheng ◽  
Yi Yang
Keyword(s):  
Structural Materials ◽  
Cyclic Bending ◽  
Bending Loads ◽  
Fatigue Equation

Comparative Assessment of Sacral Screw Loosening Augmented With PMMA Versus a Calcium Triglyceride Bone Cement

2010 ◽  
Author(s):  
Stewart D. McLachlin ◽  
Khalid Al Saleh ◽  
Kevin R. Gurr ◽  
Stewart I. Bailey ◽  
Chris S. Bailey ◽  
...  
Keyword(s):  
Bone Cement ◽  
Pedicle Screw ◽  
Interface Strength ◽  
Comparative Assessment ◽  
Screw Loosening ◽  
Cyclic Bending ◽  
Bone Interface ◽  
Screw Augmentation ◽  
Bending Loads ◽  
Instrumentation Failure

Instrumentation failure in the S1 pedicles as a result of the screw loosening created by large cyclic bending loads is well documented. Biomechanical studies have shown that pedicle screw augmentation with Polymethylmethacrylate (PMMA) can result in improved screw-bone interface strength [1].

Effects of Standoff Tolerances on the Fatigue Life of a Tool-Joint Pin

1966 ◽  
Vol 88 (2) ◽  
pp. 211-215 ◽  
Author(s):  
John Finke
Keyword(s):  
Fatigue Life ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Negligible Effect ◽  
Plastic Model ◽  
Cyclic Bending ◽  
Bending Loads ◽  
Tool Joint

A 4 1/2-in. API full-hole, tool-joint pin is stress-analyzed photoelastically over a range of standoffs. A three-dimensional plastic model is loaded to different values of makeup torque. At each torque a range of cyclic bending loads and a range of cyclic tensile loads are simulated. The results show that makeup torques must be raised for extreme hand-tight, shoulder-gap standoffs if a given pin tension is to be maintained. Maximum static root stresses are shown to be nearly independent of standoff if a constant pin tension is maintained. Further analysis indicates that the fluctuating pin-root stresses are also nearly independent of standoff if complete relieving of the shoulder compression loads is prevented. These considerations indicate that standoff has a negligible effect on the fatigue life of a tool-joint pin if relieving of the joint shoulders under operating conditions is prevented.

A Practical Criterion on Fatigue Crack Growth Rates at Notches and Its Application to Part-Through-Thickness Fatigue Cracks in Notched Plates Subjected to Cyclic Bending

2006 ◽  
Author(s):  
Hiroshi Matsuno
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Stress Field ◽  
Crack Growth ◽  
Growth Rates ◽  
Fatigue Cracks ◽  
Equivalent Stress ◽  
Cyclic Bending ◽  
Bending Loads ◽  
Crack Growth Rates

In the present paper, an equivalent stress ratio concept, which has hitherto been developed by author [1–3], is applied to problems of part-through-thickness fatigue crack growth in notched plates subjected to cyclic bending loads, and a criterion for estimating fatigue crack growth rates is derived on the basis of the concept. In order to take a great variety of practical notches into consideration, a bending stress field of a notched plate containing a part-through-thickness fatigue crack emanating from a notch root is simplified by the elementary beam theory, and the stress field is characterized in accordance with classification of notch morphology: (a) an unnotch type, (b) a transverse type notch such as a groove, a shoulder, a trapezoidal protuberance, etc., which is disposed along a width of a plate, and (c) a through-thickness type notch such as a circular and elliptical hole, a side-groove, etc. Experimental results on part-through-thickness fatigue cracks emanating from artificial flaws at notch roots in plates subjected to cyclic bending loads are analyzed. Growth rates of fatigue cracks in the notches are estimated based on the proposed criterion and the devised convenient method for calculating stress intensity factors, and they are compared with experimental ones.

Analysis of fatigue behaviour of drill pipe on pin-box connection

2020 ◽  
pp. 147509022095006
Author(s):  
Ozgur Ozguc
Keyword(s):  
Hot Spot ◽  
Drill Pipe ◽  
Oil And Gas Industry ◽  
Drill String ◽  
Load Level ◽  
Pipe Material ◽  
Hot Spot Stress ◽  
Cyclic Bending ◽  
Bending Loads ◽  
Sn Curve

Drilling is one of the costliest and risky activities in oil and gas industry due to complexity of interactions with downhole formation. Cyclic loads while drilling cause the initiation and growth of cracks in oil tubulars. This phenomenon, known as fatigue, results in permanent reduction of the failure-free service envelope of a certain tubular. Further, most of the drill string failures are triggered by fatigue, which results from repetitive cyclic bending loads and stresses in tensile or buckled drill strings. Fatigue is a cumulative and non-reversible condition induced by repetitive cyclic bending loads and tensile or buckled drill pipe stresses. Fatigue exists even though cyclic tension of the drill pipe material is much lower than static strength limit. Present work investigates fatigue capacity of the 4” WT38 drill pipe connection where cracks have been observed. In accordance with the geometry of connection, a hot spot stress from bending moment is calculated in the crack location in the first thread (upper) of the pin. The DNVGL-RP-C203 SN-curve B1 “in air” is used as relevant fatigue SN curve for the drill pipe thread location. Finite element method (FEM) is employed in modeling and analyzing of drill pipe on pin-box connections. With this method, various connections can be investigated relatively faster and cheaper compared with experimental tests. It is found that the fatigue failure may have been caused as a result of the cyclic load level and number of load cycles. A detailed discussion of the fatigue damage assessment concludes the paper.

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