A Study on the Creep Rupture Life Estimation of Internally Pressurized Welded Pipe Joints

2006 ◽  
Author(s):  
Tetsuo Teramae
Keyword(s):  
Crack Growth ◽  
Welded Joint ◽  
Rupture Life ◽  
Creep Rupture ◽  
Coarse Grained ◽  
Experimental Result ◽  
Fine Grained ◽  
Pipe Joints ◽  
Creep Rupture Test ◽  
Welded Pipe

A study had been conducted to establish the precise method estimating the creep rupture life of welded steam pipe joints used for thermal power plants. Firstly, basic creep data of 2.25CrlMo low alloy steel, such as rupture time, minimum creep strain rate, and creep crack growth rate, had been obtained on mother material, fine-grained heat affected zone (HAZ), coarse-grained HAZ, and weld metal. Secondly, internally pressurized creep rupture test had been conducted on the pipe specimens of mother material, seam welded joint and girth welded joint. Whereas girth welded pipe joints showed longer lives than those of mother material pipes, seam welded pipe joints showed shorter rupture lives. To clarify the effect of fine-grained HAZ on the rupture life of the seam welded pipe joint, an analytical study had been performed taking the difference of creep deformation between fine-grained HAZ and mother material into account. The analytical creep rupture life had agreed quite well with experimental one. Finally, internally pressurized creep rupture test had been conducted on the specimens of the seam welded pipe joints with a semi-elliptical notch introduced along the outer HAZ of weld line. Creep rupture life of these specimens was calculated as the sum of crack incubation time and crack growth time. It was shown that the calculated creep rupture life had agreed quite well with the experimental result.

Fatigue Crack Growth in Ultrafine-Grained Copper Obtained by ECAP

2014 ◽  
Vol 891-892 ◽  
pp. 1099-1104 ◽  
Author(s):  
Mandana Arzaghi ◽  
Christine Sarrazin-Baudoux ◽  
Jean Petit
Keyword(s):  
Crack Growth ◽  
Growth Rates ◽  
Fatigue Cracks ◽  
Deformation Texture ◽  
Coarse Grained ◽  
Fine Grained ◽  
Angular Pressing ◽  
Ultrafine Grained ◽  
Crack Growth Rates ◽  
Threshold Regime

The propagation of long fatigue cracks in ultra fine-grained (UFG) copper obtained by equal channel angular pressing (ECAP) is investigated in the mid ΔK range and in the near threshold regime. The crack growth rates in UFG copper are substantially faster than in coarse-grained (CG) copper. A huge influence of environment is observed, with growth rates faster of more than two orders of magnitude in air compared to vacuum. The crack growth mechanisms are discussed on the basis of microfractographic observations and the deformation texture.

Effect of Softening on Tensile Strength Limit in Girth-Welded Pipe Joints

2009 ◽  
Author(s):  
Houichi Kitano ◽  
Shigetaka Okano ◽  
Masahito Mochizuki
Keyword(s):  
Tensile Strength ◽  
Ultimate Tensile Strength ◽  
Weld Metal ◽  
Welded Joint ◽  
Fe Analysis ◽  
Strength Limit ◽  
Theoretical Approaches ◽  
Soft Interlayer ◽  
Pipe Joints ◽  
Welded Pipe

This paper discusses the ultimate tensile strength of girth-welded pipe joints with one or more soft interlayers, as determined by theoretical approaches and FE analysis. In FE analysis, the soft interlayer is assigned to be either the weld metal or heat-affected zone (HAZ). Based on the results of the FE analysis, an evaluation formula is proposed for the ultimate tensile strength of a welded joint including the soft interlayer.

Region-Specified Ratcheting Behavior of API X80 Welded Joint Under Uniaxial Cyclic Loading

2016 ◽  
Author(s):  
Hongsheng Lu ◽  
Yonghe Yang ◽  
Gang Chen ◽  
Xu Chen ◽  
Xin Wang
Keyword(s):  
Weld Metal ◽  
Base Metal ◽  
Heat Affected Zone ◽  
Welded Joint ◽  
Pipeline Steel ◽  
Coarse Grained ◽  
Strain Accumulation ◽  
Lower Strength ◽  
Fine Grained ◽  
Ratcheting Strain

Evaluation of mechanical performance of different regions can be difficult by using standard size samples due to the size limitation of weld metal and heat-affected zone (HAZ). At first, the microstructure of different regions was characterized and quantified by Scanning Electron Microscope, which indicate that the pipeline steel is a typical acicular ferrite steel. In this study the deformation behavior of different regions (base metal, weld metal and heat affected zone) in a welded joint of API X80 pipeline steel were studied by conducting uniaxial loading tests on miniature specimens with the cross section of 2×0.5mm and gauge length of 9mm. From the results of uniaxial tension in base metal and weld metal it is shown that the welding is overmatching. Compared to the base metal, the coarse grained HAZ exhibits a lower strength, while the fine grained HAZ exhibits a higher strength. Under near zero-to-tension cyclic stress loading, all regions of the welded joints exhibit progressive accumulation of plastic strain. Under the same stress level, the base metal shows the fastest ratcheting strain accumulation, which is the result of lower strength than other regions. This fact may indicate that the ratcheting behavior of the overall welded joint is highly dependence on that of base metal for the present case. But when under the same normalized stress level (σ = σ/σYS), the fine grained HAZ has the highest ratcheting strain accumulation, while the coarse grained HAZ has the lowest ratcheting strain accumulation, which reveals that the intrinsic resistance to ratcheting is yield strength dependent.

scholarly journals The Failure of Structural Metals Subjected to Strain-Cycling Conditions

1959 ◽  
Vol 81 (2) ◽  
pp. 203-208 ◽  
Author(s):  
R. W. Swindeman ◽  
D. A. Douglas
Keyword(s):  
Grain Size ◽  
Rupture Life ◽  
Thermal Strain ◽  
Coarse Grained ◽  
Fine Grained ◽  
Long Time ◽  
Structural Metals ◽  
Number Of Cycles ◽  
Cycles To Failure ◽  
Strain Cycling

Data showing the isothermal strain-cycling capacity of three metals, Inconel, Hastelloy B, and beryllium are presented. It is noted that at frequencies of 0.5 cycle per min the data satisfied an equation of the form Nαϵp = K, where N is the number of cycles to failure, ϵp is the plastic strain per cycle, and α and K are constants whose values depend on the material and test conditions. Data on Inconel are given to establish the effect of grain size, specimen geometry, temperature, and frequency. It is found that, at temperatures above 1300 F, grain size and frequency exert a pronounced effect on the rupture life. Fine-grained metal survives more cycles before failure than coarse-grained material. Long time cycles shorten the number of cycles to failure when the strain per cycle is low. Thermal-strain-cycling data for Inconel are compared to strain-cycling data at the same mean temperature. Good correlation is found to exist between the two types of tests.

Brittle and Ductile Creep Rupture Life Prediction of 1CrMoV Steel Notched Thick Plates

1990 ◽  
Vol 112 (3) ◽  
pp. 225-232 ◽  
Author(s):  
K. Ando ◽  
Y. Takeda ◽  
K. Takezoe
Keyword(s):  
Crack Initiation ◽  
Damage Mechanics ◽  
Notch Root ◽  
Rupture Life ◽  
Prediction Method ◽  
Creep Rupture ◽  
Material Behavior ◽  
Analytical Prediction ◽  
Crack Initiation Life ◽  
Creep Rupture Test

An analytical prediction method of brittle and ductile creep rupture life of 1CrMoV steel notched thick plate is proposed. Rupture time is evaluated as a sum of crack initiation life ti and crack growth life tp. In the case of ductile creep at high stresses, ti is evaluated by the creep deformation criteria. In addition, in the case of brittle creep at low stresses, ti is evaluated by Kachanov’s damage mechanics theory. Materials constants in Kachanov’s theory can be determined by the relatively short-term creep rupture test of notched specimen, etc., according to the present method. Creep rupture test, interrupted creep test, and micro-structural observation, have been used, which can explain the variety of material behavior, i.e., notch weakening at low stresses and notch strengthening at high stresses. In addition, in this analysis the analytically estimated creep crack initiation life corresponds to the time to creep void initiation just inside the notch root.

scholarly journals Twinning Assisted Crack Propagation of Magnesium-Rare Earth Casting and Wrought Alloys under Bending

2015 ◽  
Vol 828-829 ◽  
pp. 311-317 ◽  
Author(s):  
Petra Maier ◽  
Chamini Mendis ◽  
Martin Wolff ◽  
Sören Müller ◽  
Norbert Hort
Keyword(s):  
Rare Earth ◽  
Crack Initiation ◽  
Crack Propagation ◽  
Crack Growth ◽  
Coarse Grained ◽  
High Temperature Strength ◽  
Cast Material ◽  
Bending Tests ◽  
Fine Grained ◽  
Bending Modulus

Due to their high specific strength, good corrosion resistance and high temperature strength Magnesium alloys containing Rare Earth additions are promising candidates for structural and engine applications in the transportation industry. Also medical applications, like bone screws and nails, benefit from their moderate corrosion rate and biocompatibility. All applications need materials which show a high strength, ductility and fracture toughness in case a crack has formed during service to keep safety against rupture. In this study four extruded Mg10Gd based alloys modified with Nd and La have been 3-point-bend tested at low a deformation speed to evaluate the influence of the microstructure on crack growth. A comparison to the cast material (subjected to T4 to increase ductility and to reduce the dendritic microstructure) shows an increase in strength and ductility due to the fine grained microstructure as a result of recrystallization during extrusion. The maximum bending strength and outer strain to crack initiation is also strongly influenced by the alloying system itself. The influence of Nd and La to the binary alloy Mg10Gd is discussed in using tensile, compression and bending tests. The increase in strength results in reduced elongation to fracture in tension loading as well as the outer strain for the crack initiation during bending tests. Tensile tests are often discussed to be not a reliable method for determining the Young’s modulus of magnesium. Therefore resonance frequency damping analysis has been applied to determine the dynamic modulus of elasticity, which is compared with the flexural (bending) modulus. Crack growth is discussed using light microscopy and correlated with bending stress-strain curves. The crack growth rate of the extruded, fine grained material is many times higher than of the cast, coarse grained material. Crack propagation is mostly transgranular and assisted by twinning.

To the Question of Determining the Plasticity Zones of a Welded Joint of Large Diameter Pipes

2015 ◽  
Vol 763 ◽  
pp. 92-96
Author(s):  
Yuriy Ivanovich Pashkov ◽  
Mikhail Alekhsandrovich Ivanov ◽  
Yuriy Viktorovich Bezgans ◽  
Tatyana Vladimirovna Bezgans
Keyword(s):  
Plastic Deformation ◽  
Welded Joints ◽  
Arc Welding ◽  
Welded Joint ◽  
Large Diameter ◽  
Hydraulic Press ◽  
Welding Wire ◽  
Pipe Joints ◽  
Large Diameter Pipes ◽  
Welded Pipe

There was performed the analysis of a set of methodical solutions for determining of current and limit plasticity of welded joint zones at large diameter pipes. To determine the current plastic deformation of zones of pipes' welded joints it is offered to test the natural ring of a height of 80 mm, of a pipe with size 530x7,5 mm made of steel 17GS, welded by arc welding using a welding wire SV-08HM under a layer of flux AN-60. The ring samples are tested in the cone, the constructive dimensions of which match the cone used on the expander by the definite value of broadening on the hydraulic press with the force not less than 500 tons. The results of tests of ring samples of welded pipe with size 530х7,5 mm while their broadening by the cone. To determine the limit of plastic deformation of zones of a welded joint of large diameter pipes a method for testing a flat sample is proposed. The construction of the sample and the scheme of loading to determine the limit plasticity of welded pipe joints are proposed.

scholarly journals Experimental Investigation of Fatigue Crack Growth Behavior of the 2.25Cr1Mo0.25V Steel Welded Joint Used in Hydrogenation Reactors

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1159
Author(s):  
Yan Song ◽  
Mengyu Chai ◽  
Zelin Han
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Arc Welding ◽  
Welded Joint ◽  
Coarse Grained ◽  
Granular Bainite ◽  
Crack Growth Behavior ◽  
Shielded Metal Arc Welding ◽  
Secondary Cracks

In this work, the fatigue crack growth (FCG) behavior and fatigue damage mechanism of the 2.25Cr1Mo0.25V steel welded joint used in hydrogenation reactors were investigated. The multi-pass welding was carried out to manufacture the welded joint using the combined shielded metal arc welding (SMAW) and submerged automatic arc welding (SAAW) processes. The FCG behavior of different zones in the welded joint, including the base metal (BM), the heat-affected zone (HAZ) and the weld metal (WM), were studied by compact tension tests. Moreover, the acoustic emission (AE) technique was used to monitor AE signals generated from FCG process for further understanding FCG behavior and fatigue mechanisms. Additionally, the microstructures and fracture surfaces of different specimens were observed by optical microscopy (OM) and scanning electron microscopy (SEM). The results revealed that the microstructure of BM is fine granular bainite, while the WM shows coarser bainite grains. The HAZ exhibits the most significant inhomogeneity with large dispersion of grain size. FCG results showed that the HAZ exhibits much higher fatigue crack growth rate (FCGR) at low ΔK values, while the BM shows the most superior fatigue resistance. The AE technique is successful in monitoring and identifying damage evolutions during the FCG process. Moreover, an enhanced AE activity is observed in FCG of the WM specimen, which is attributed to the combined influence of the formation of numerous secondary cracks and coarse-grained microstructures.

scholarly journals Investigation on the validity of creep damage mechanics for the life time prediction of T92 welded joint

2019 ◽  
Vol 29 (3) ◽  
pp. 467-481 ◽  
Author(s):  
Xiao Wang ◽  
Xue Wang ◽  
Qiang Xu ◽  
Chuang Wang ◽  
Ya-lin Zhang ◽  
...  
Keyword(s):  
Damage Mechanics ◽  
Welded Joint ◽  
Rupture Life ◽  
Continuum Damage Mechanics ◽  
Creep Process ◽  
Continuum Damage ◽  
Creep Life ◽  
Fine Grained ◽  
Creep Time ◽  
The Continuum

This paper reports the damage evolution in ASME T92 welded joints during creep process. The creep test was conducted at 650℃ with applied stress of 90 MPa. The creep specimen was ultimately fractured at the fine-grained heat affected zones after creep for 1560 h. The metallographic results show that the cavity number and size in fine-grained heat affected zones increase with the creep time. The coalescence of creep cavities happened at the late stage of the creep life, which depending on the adjacent voids grows and propagates into the micro-crack. Besides, the deterioration in fine-grained heat affected zones of T92 steel welded joint with various creep time can be simulated based on the continuum damage mechanics with modified Kachanov-Rabotnov constitutive equation. The result of simulated creep rupture life is in good agreement with the experimental value, which indicates that the continuum damage mechanics can be used to predict creep life and evaluate creep deterioration in a T92 steel welded joint.

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