Study on the Mismatched Girth Welds of X80 Line Pipes

2006 ◽  
Author(s):  
Chuanjing Zhuang ◽  
Yaorong Feng ◽  
Chunyong Huo
Keyword(s):  
Fracture Resistance ◽  
Weld Seam ◽  
Limit Load ◽  
Defect Size ◽  
Weld Strength ◽  
High Grade ◽  
Critical Defect ◽  
Critical Defect Size ◽  
Girth Welds ◽  
Welding Procedure

X80 linepipes are going to be widely used for gas transmission pipelines in China. The welding procedure for girth weld is very critical to the safety of the X80 pipeline. In this paper, different welding procedures are employed to obtain three different mismatched girth welds, with which tests were carried out to analyze effect of mismatch on the properties of girth welds. Plastic deformation and critical defect size (δc) is calculated and discussed for the different mismatched girth welds utilizing both FAD and FEM methods. Overmatched or evenmatched girth weld is recommended for high grade linepipes because overmatched weld has the advantages of improving limit load and enhencing fracture resistance of pipe girth welds. But the increase of weld strength may reduce the resistance of the weld to HIC and SCC, as well as make the field weld operation more difficult. The level of mismatch shouldn’t be too high because too much weld seam strength will not only be a way of waste, but also decrease weld resistance to HIC cracks.

Effect of the Yield to Tensile Ratio, Y/T, on Structural Reliability of Linepipes

2003 ◽  
Author(s):  
Hugo A. Ernst ◽  
Jose´ A. Villasante ◽  
Alfonso Izquierdo
Keyword(s):  
Structural Reliability ◽  
Plasticity Theory ◽  
Defect Size ◽  
Defect Tolerance ◽  
Deformation Control ◽  
Critical Defect ◽  
Control Situations ◽  
Critical Defect Size ◽  
T Values ◽  
Lower Limits

The effect of the Yield (Y) to Tensile (T) ratio, Y/T, on the structural reliability of linepipes with longitudinal defects was studied in this work. A model based on elastic-plastic fracture mechanics (EPFM) and plasticity theory, was developed for that purpose. The analysis allows for load or deformation control situations. The results are shown in terms of curves of critical defect size vs. the controlling variable, i.e. load or deformation. For each one of the several materials studied, different cases with different Y/T values were considered. Even for the lower limits of experimental data, i.e. larger Y/T, the materials have adequate defect tolerance.

Investigation of the Improvements on Mechanical Properties and Thermal Performance of MgO-MgAl2O4 Composite Refractories by Additions of ZnO-Al2O3 to MgO

2012 ◽  
Vol 445 ◽  
pp. 530-535 ◽  
Author(s):  
Cemail Aksel
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Thermal Performance ◽  
Industrial Applications ◽  
Sem Analysis ◽  
Defect Size ◽  
Structural Variations ◽  
Factors Affecting ◽  
Critical Defect ◽  
Critical Defect Size

The variations and developments with the reasons on the mechanical properties of MgO-MgAl2O4 and MgO-ZnO-Al2O3 composite refractories were examined and thermal parameters affecting the durability of composites at high temperatures were investigated. The density, porosity, strength, modulus of elasticity, fracture toughness, fracture surface energy, critical defect size and mean MgO grain size values of composites were measured/calculated and evaluated. In addition, microstructural changes using XRD measurements and SEM analysis were examined. Thermal stress/shock parameters R and Rst that are used for determining high temperature performance of composites were calculated. The relationships between mechanical properties and structural variations for different compositions and the factors affecting this connection were investigated. With the additions of various amounts of ZnO-Al2O3 to MgO, significant improvements were achieved on both mechanical properties and R-Rst parameters of in-situ formed M-S-ZnAl2O4 composite refractories, compared to MgO-MgAl2O4 materials containing preformed spinel, by factors of up to 3.6 and 2.0, respectively. The important parameters increasing mechanical properties and thermal performance of M-S-ZnAl2O4 composites were determined as follows: i) formation of ZnAl2O4 phase leading to a high resistance to crack initiation and propagation, ii) propagation of microcracks formed in the structure for a short distance by interlinking to each other, iii) arresting or deviation of microcracks when reaching pores or ZnAl2O4 particles, and additionally iv) co-presence of both intergranular and transgranular types of cracks on fracture surfaces, and with the incorporations of ZnO-Al2O3, v) increase in density, vi) rise in critical defect size, and vii) a significant reduction in MgO grain size. The optimisation of M-S-ZnAl2O4 composite refractories that could be used for obtaining longer service life in industrial applications was performed.

Evaluation of the static cracking resistance of the metal calculating the critical defect size in bands of large compound support rolls

1990 ◽  
Vol 26 (2) ◽  
pp. 176-182
Author(s):  
O. N. Romaniv ◽  
Yu. A. Grushko ◽  
N. A. Adamova ◽  
A. N. Takach ◽  
T. Ra. Yus'kiv ◽  
...  
Keyword(s):  
Defect Size ◽  
Cracking Resistance ◽  
Critical Defect ◽  
Critical Defect Size ◽  
Large Compound

Critical Defect Size for Osteochondral Lesions of the Talus: Letter to the Editor

2012 ◽  
Vol 40 (9) ◽  
pp. NP23-NP24
Author(s):  
Charles P. Hannon ◽  
Christopher D. Murawski ◽  
Niall A. Smyth ◽  
John G. Kennedy
Keyword(s):  
Defect Size ◽  
Osteochondral Lesions ◽  
Letter To The Editor ◽  
Critical Defect ◽  
Critical Defect Size
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