Dynamic Structural Integrity Assessment for Offshore Structures

2004 ◽  
Vol 126 (4) ◽  
pp. 358-363 ◽  
Author(s):  
W. Zhao ◽  
F. M. Burdekin
Keyword(s):  
Structural Integrity ◽  
Global Analysis ◽  
Offshore Structures ◽  
Crack Tip Opening Displacement ◽  
Offshore Structure ◽  
Opening Displacement ◽  
Structural Dynamic ◽  
Integrity Assessment ◽  
Crack Tip Opening ◽  
Cracked Members

The paper initially presents the results of a dynamic structural integrity assessment for fracture of cracked plate and tubular members under sinusoidal loading at different frequencies. The behavior of cracked members and joints in an offshore structure under wave loading (Stokes 5th order or gridded wave) is then examined. Global structural dynamic analyses of a whole offshore jacket were carried out as the first step, then, a set of sub-models of joints was selected from chosen locations and modeled with through thickness cracks under the loading extracted from the global analysis. The sub-model dynamic results were analyzed to obtain the fracture response in terms of variation of crack tip opening displacement (CTOD). Related values of K, J and their rates were also calculated. These results are used to give guidance on methods for design and assessment of structural integrity under dynamic loading.

Accuracy of the Double-Clip on Gauge Method for Evaluating CTOD of SE(T) Specimens

2014 ◽  
Author(s):  
Zijian Yan ◽  
Yifan Huang ◽  
Wenxing Zhou
Keyword(s):  
Fracture Toughness ◽  
Structural Integrity ◽  
Oil And Gas ◽  
Three Dimensional ◽  
Specimen Thickness ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Integrity Assessment ◽  
Crack Tip Opening ◽  
Edge Tension

The crack tip opening displacement (CTOD)-based fracture toughness has been widely used for structural integrity assessment and strain-based design of oil and gas pipelines. The double-clip on gauge method has been used to experimentally determine CTOD. In this study, three-dimensional (3D) finite element analyses of clamped single-edge tension (SE(T)) specimens are carried out to investigate the accuracy of the CTOD evaluation equation associated with the double-clip on gauge method. The analysis considers SE(T) specimens with ranges of crack lengths (0.3 ≤ a/W ≤ 0.7) and specimen thickness (B/W = 0.5, 1 and 2). Based on the analysis results, a modified CTOD evaluation equation based on the double-clip on gauge method is developed to improve the accuracy of the CTOD evaluation. This study will facilitate the application of the fracture toughness determined from the SE(T) specimen in the strain-based design of pipelines.

Analysis on Critical CTOD of Long-Term Used Penstock

2017 ◽  
Vol 741 ◽  
pp. 57-62
Author(s):  
Fumito Kawamura ◽  
Masazumi Miura ◽  
Ryuichiro Ebara ◽  
Keiji Yanase
Keyword(s):  
Fracture Toughness ◽  
Structural Integrity ◽  
Steel Structures ◽  
Chemical Compositions ◽  
Structural Components ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Critical Crack ◽  
Crack Tip Opening

Many studies have been conducted to characterize the fracture toughness of structural steels and their welded joints. However, most studies focus on newly developed steels, and the number of studies on the fracture toughness of long-term used steels in structural components is rather limited. Furthermore, a lack of data on the fracture toughness causes difficulties in evaluating the structural integrity of existing steel structures. In this study, CTOD tests were performed to characterize the fracture toughness of penstock that has been in service for 50 years. By measuring the critical crack tip opening displacement in conjunction with analysis for chemical compositions, the characteristics of fracture toughness were investigated.

Offshore Structural Steel Plates for Extreme Low Temperature Service With Excellent HAZ Toughness

2014 ◽  
Author(s):  
Katsuyuki Ichimiya ◽  
Kazukuni Hase ◽  
Shigeru Endo ◽  
Yusuke Terazawa ◽  
Takaki Fujiwara ◽  
...  
Keyword(s):  
Low Temperature ◽  
Main Property ◽  
Offshore Structures ◽  
Nucleation Site ◽  
Steel Plates ◽  
Crack Tip Opening Displacement ◽  
Offshore Structure ◽  
Opening Displacement ◽  
Low Temperature Toughness ◽  
Haz Toughness

The strength and the toughness required for steel plates used for offshore structures became higher as the installation areas move into arctic areas. The main property of offshore structure steel is the crack tip opening displacement (CTOD) property of weld joint, and CTOD testing is performed at the minimum design temperature of the structure. Thus, the demand for satisfying −40°C of CTOD test temperature specification has increased. For the improvement of HAZ toughness, coarse austenite grain is suppressed by TiN, and low-C, Ceq, Si, P, Nb design is adopted to decrease the formation of M-A constituents. Furthermore, by using Ca inclusion, which works as a pinning particle and a bainite nucleation site, very fine bainite microstructure are formed in HAZ and excellent low temperature toughness are achieved. The YP420 class plate with excellent low temperature toughness has been developed using these technology.

CTOD Evaluation for HAZ Toughness of Offshore Structure Steels with Heavy Thickness Based on API RP 2Z

2013 ◽  
Vol 634-638 ◽  
pp. 2916-2922
Author(s):  
Ting Miao ◽  
Zhang Mu Miao ◽  
Ling Hu ◽  
Xiang Kui Zhang ◽  
Wei Fang Qian
Keyword(s):  
Steel Structures ◽  
American Petroleum Institute ◽  
International Standards ◽  
Steel Plates ◽  
Crack Tip Opening Displacement ◽  
Offshore Structure ◽  
Opening Displacement ◽  
And Control ◽  
Crack Tip Opening ◽  
Haz Toughness

The CTOD (Crack Tip Opening Displacement) evaluation and control for HAZ (Heat Affected Zone) toughness of welded joints are the most effective measures to the security of steel structures. This paper address the problem of the newly developed offshore structure steel API 2W 50Z with heavy thickness of 100mm. In accordance with the American Petroleum Institute standard Recommended Practice 2Z (API PR 2Z), the CTOD tests of two critical positions of HAZ in three kinds of heat inputs were carried out in low temperature (-10°C). All of these CTOD testing and assessments are finished under the witness of American Bureau of Shipping (ABS). The result shows that all of the CTOD values are greater than the required value (0.38mm) in API RP 2Z. This indicates that the newly developed offshore structure steel (API 2W 50Z) meet the requirement of the toughness. Further, the CTOD testing and assessments in several international standards about weld joints of steel plates are also compared and discussed in this paper.

Development of YS 500MPa Class Thick Steel Plate With Weld Joint CTOD Property for Offshore Structures

2019 ◽  
Author(s):  
Yusuke Terazawa ◽  
Katsuyuki Ichimiya ◽  
Keiji Ueda ◽  
Satoshi Igi ◽  
Minoru Suwa ◽  
...  
Keyword(s):  
Weld Joint ◽  
Steel Plate ◽  
Plate Thickness ◽  
Offshore Structures ◽  
Nucleation Site ◽  
Crack Tip Opening Displacement ◽  
Offshore Structure ◽  
Opening Displacement ◽  
Thick Steel ◽  
Haz Toughness

Abstract Recently, the installation areas of offshore structures has expanded into deep sea areas, and as a result, strength and plate thickness of the steel plate required for the offshore structures have become higher. And the main property of offshore structure steel is the crack tip opening displacement (CTOD) property of multi-pass weld joint. Thus, the developed steel was designed to improve HAZ toughness of multi-pass weld joint. Firstly, in order to achieve both high strength of the base metal and good HAZ toughness, the TMCP technology was applied, and Ceq. was minimized. And to obtain fine HAZ microstructure, fine TiN and Ca(O,S) particles having pinning effect and nucleation site effect were used. Finally, to decrease the formation of brittle martensite-austenite constituent (M-A) in HAZ of multi-pass weld joint, Si content was decreased. By using above technologies, the YS 500MPa class thick steel plate with good weld joint CTOD property have been developed.

Steel Plates With Excellent HAZ Toughness for Offshore Structure

2013 ◽  
Author(s):  
Katsuyuki Ichimiya ◽  
Kazukuni Hase ◽  
Shigeru Endo ◽  
Masao Yuga ◽  
Kenji Hirata ◽  
...  
Keyword(s):  
Yield Stress ◽  
High Strength ◽  
Offshore Structures ◽  
Controlled Rolling ◽  
Steel Plates ◽  
Accelerated Cooling ◽  
Crack Tip Opening Displacement ◽  
Offshore Structure ◽  
Opening Displacement ◽  
The Matrix

In the field of offshore structure, the strength and the toughness required for steel plates used for oil resource development become higher as the installation areas of the structures move into arctic and deep water areas. High strength steel plates for offshore structures, which meet the low temperature specification, have been developed. Excellent properties of the steel plates have been achieved by micro-alloying, the latest controlled rolling and accelerated cooling technology. Excellent properties of weld joints have been also achieved by advanced metallurgical techniques, which are grain-refinement of the coarse grain heat affected zone (CGHAZ), reduction of Martensite-Austenite (M-A) constituent in inter-critically CGHAZ (ICCGHAZ), and improvement of the matrix toughness. These steels are designed for excellent weldability due to low weld cracking parameter (PCM) value up to 550 MPa class in yield stress, and also up to 101.6 mm in thickness with 420 MPa class in yield stress, and satisfying −40°C of crack tip opening displacement (CTOD) temperature specification for offshore structure.

An experimental and numerical investigation of fracture resistance behaviour of a dissimilar metal welded joint

2009 ◽  
Vol 223 (7) ◽  
pp. 1507-1523 ◽  
Author(s):  
M K Samal ◽  
K Balani ◽  
M Seidenfuss ◽  
E Roos
Keyword(s):  
Fracture Resistance ◽  
Structural Integrity ◽  
Damage Model ◽  
Crack Tip ◽  
Initial Crack ◽  
Element Formulation ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Integrity Assessment ◽  
Porous Plasticity

Dissimilar welds impose a challenge to the engineers concerned with the structural integrity assessment of these joints. This is because of the highly inhomogeneous nature of these joints in terms of their microstructure, mechanical, thermal, and fracture properties. Fracture mechanics-based concepts cannot be directly used because of the problems associated with the definition of a suitable crack-tip loading parameter such as J-integral crack tip opening displacement (CTOD), etc. Again, depending upon the location of initial crack (i.e. base, weld, buttering, different interfaces, etc.), further crack propagation can occur in any material. The objective of the current work is to use micro-mechanical models of ductile fracture for initiation and propagation of cracks in the bimetallic welds. The authors have developed a finite element formulation that incorporates the porous plasticity yield function due to Gurson—Tvergaard—Needleman and utilized it here for the analysis. Experiments have been conducted at MPA Stuttgart using single edge-notched bend (SEB) specimens with cracks at different locations of the joint. The micro-mechanical (Gurson) parameters of four different materials (i.e. ferrite, austenite, buttering, and weld) have been determined individually by simulation of fracture resistance behaviour of SEB specimens and comparing the simulated results with those of the experiment. In order to demonstrate the effectiveness of the damage model in predicting the crack growth in the actual bimetallic-welded specimen, simulation of two SEB specimens (with initial crack at ferrite—buttering and buttering—weld interface) has been carried out. The simulated fracture resistance behaviour compares well with those of the experiment.

Fracture Behaviour of Thin Sheet Stainless Steel

2012 ◽  
Vol 525-526 ◽  
pp. 549-552
Author(s):  
Nenad Gubeljak ◽  
Darko Jagarinec ◽  
Jožef Predan ◽  
John Landes
Keyword(s):  
Fracture Toughness ◽  
Stainless Steel ◽  
Crack Initiation ◽  
Driving Force ◽  
Crack Tip ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Crack Driving Force ◽  
Integrity Assessment ◽  
Crack Tip Opening

The differences in fracture behavior between the compact tension C(T) and the middle tensile M(T) specimens make structure integrity assessment uncertain. Two different types of specimens C(T) and M(T) specimens made from stainless steel have been used for fracture toughness testing at the room temperature by the principles of the ASTM 1820-05 standard procedure. Stable crack initiation and crack propagation occurred for the C(T) specimens at lower values of crack driving force than for the M(T) specimens. Crack tip opening displacement-CTOD has been directly measured on the surface of specimens by using a stereo-optical grading method. The critical crack tip opening displacement at crack initiation CTODi has been measured as a plastic Stretch Zone Width (SZW) during a post test fractographic inspection. Comparison between the CTOD-R curves of both types of specimens shows some difference between the C(T) and the M(T) specimens, but a more significant difference appeared in the crack driving force, as consequence of different constraint (triaxiality) of the C(T) versus the M(T) specimens. Therefore, the result obtained by test on laboratory C(T) specimens cannot be directly used as fracture toughness material properties in a structure integrity assessment, except as a conservative lower bound estimate.

Experimental Study on Fracture Toughness of Q460C the High-Strength Construction Steel at Low Temperature

2011 ◽  
Vol 71-78 ◽  
pp. 890-897 ◽  
Author(s):  
Yuan Qing Wang ◽  
Yun Lin ◽  
Yan Nian Zhang ◽  
Yong Jiu Shi
Keyword(s):  
Low Temperature ◽  
High Strength ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Three Point Bending ◽  
Function Fitting ◽  
Ductile Brittle Transition Temperature ◽  
Boltzmann Function ◽  
Fracture Appearance ◽  
Crack Tip Opening

Three point bending tests were carried out on 14mm-thick Q460C the high-strength structural steel at low temperature, and scanning electronic microscope of the fracture appearance was analyzed. The results showed that the obvious feature of brittle mechanism was shown on the three point bending specimen fracture whose testing took place at -40°C. And the crack tip opening displacement value of Q460C steel, which was less than that of Q235 steel, Q345 steel and Q390 steel at low temperature, tended to decrease with respect to the temperature reduction. Moreover, a Boltzmann function fitting analysis was applied to the experimental data, and the ductile-brittle transition temperature and the changing regularity were obtained.

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