Journal of Pressure Vessel Technology
ISSN / EISSN : 0094-9930 / 1528-8978
Published by: ASME International (10.1115)
Total articles ≅ 4,227
Latest articles in this journal
Journal of Pressure Vessel Technology; https://doi.org/10.1115/1.4052397
Creep deformation behavior, creep strength property and microstructural evolution during creep exposure were investigated on Super 304H steel for boiler tube. In the high stress and lower temperature regime, creep rupture strength of Super 304H steel is higher than that of SUS304H steel. The slope of stress vs. time to rupture curve of Super 304H steel, however, becomes steeper with increase in creep exposure time and temperature, and the creep rupture strength of Super 304H steel becomes closer to that of SUS304H steel after the tens of thousands of hours at 700°C and above. In the short-term, at 600°C, creep rupture ductility increases with increase in creep rupture life. However, it tends to decrease after showing the maximum value and the creep rupture ductility decreases with increase in temperature. The complex shape of creep rate vs. time curves, with two minima in creep rate, was observed at 600°C. Several type precipitates of niobium carbonitride (Nb(C,N)), Z phase (NbCrN), and copper were observed in Super 304H steel, as well as M23C6 carbide and sigma phase observed in SUS304H steel. The change in slope of stress vs. time to rupture curve is caused by disappearance of precipitation strengthening effect during creep exposure. Accuracy of creep rupture life evaluation was improved by stress range splitting method which takes into accounts of the change in slope of stress vs. time to rupture curves was demonstrated.
Journal of Pressure Vessel Technology; https://doi.org/10.1115/1.4052399
Fluidelastic instability (FEI) is well known to be a critical flow-induced vibration concern for the integrity of the tubes in nuclear steam generators. Traditionally, this has been assumed to occur in the direction transverse to the direction of flow but the tube failures at San Onofre Nuclear Generating Station (SONGS) in Los Angeles proved that this assumption is not generally valid. A simple tube-in-channel theoretical model was previously developed to predict streamwise as well as transverse FEI in a parallel triangular tube array. This predicted that this array geometry was particularly sensitive to streamwise FEI for high mass-damping parameters and small pitch ratios, the conditions in which the SONGS failures occurred. The advantage of this simple modelling approach is that no new empirical data are required for parametric studies of the effects of tube pattern and pitch ratio on FEI. The tube-in-channel model has been extended to in-line square, normal triangular and rotated square tube arrays and the stability of these geometric patterns are analyzed for the effects of varying pitch ratio and the mass-damping parameter. The results are compared with the available experimental data and conclusions are drawn regarding the relative vulnerability of these different tube array geometries to streamwise FEI.
Journal of Pressure Vessel Technology; https://doi.org/10.1115/1.4052398
Accurate estimation of elastic-plastic fracture mechanics (EPFM) parameters for a crack in nuclear pipes was considered as an important factor for leak-before-break (LBB) design and evaluation. Yet few EPFM studies have been made to predict the crack opening displacement (COD) and J-integral of dissimilar metal welded pipes, which consist of two-layered materials (TLMs), due to the difficulty of complicate analysis encompassing both through-wall crack and internal surface crack in radial and circumferential directions. In this study, a series of finite element (FE) analyses to determine the typical EPFM parameters were carried out considering idealized complex-cracked pipes with TLMs. The analyses were elaborated through applying three loading conditions of axial tension, bending moment and internal pressure. Both J-integral and COD values were calculated by assuming two kinds of equivalent materials based on weighted average concepts as well as two different materials. The proposed equivalent schemes can be utilized in not only improvement to existing solutions but also more accurate detailed LBB assessment of complex cracked nuclear piping with TLMs.
Journal of Pressure Vessel Technology; https://doi.org/10.1115/1.4052401
Three-point bending specimen with fixed constraints (TPBSF) is a novel small specimen test technique, which can simultaneously obtain creep deformation and creep fracture data. However, the current researches are only focused on the small deformation theoretical analysis, which is contrary to the actual experiment results. In this study, the general deformation theory was introduced to analyze creep deformation behavior of TPBSF at the large deformation stage. Based on this theory, the equivalent stress and strain were analyzed. Then the feasibility and accuracy were verified by comparing with the experimental data of A7N01 aluminum alloy at 380 ?. The results show that the regressed creep parameters agree well with those from the uniaxial ones. It can be found that the equivalent stress obtained by the general deformation theory can be well used to life prediction analysis of A7N01 aluminum alloy.
Journal of Pressure Vessel Technology; https://doi.org/10.1115/1.4052393
In this paper, the pre-mixed type high pressure hydraulic sandblasting before portable nozzle structure optimized design calculation of cutting equipment, hydraulic sandblasting cutting using high-speed sand fluid jet to finish cutting operation, to improve the work efficiency of the device, this paper adopts the method of computational fluid dynamics, using the business software, numerical simulation of different nozzle type, nozzle length and Angle of the cone Angle of nozzle, the internal flow field of comparative analysis and calculation results, and to test the performance of the different nozzle, it is concluded that the cone shape nozzle structure is better, and working parameters of the type sprayer experiment, with the help of mathematical software to deal with the experimental data, the theoretical formulae of cutting depth, cutting target distance, transverse velocity and jet pressure were obtained, which provided a basis for the development of nozzle with high cutting efficiency and proved the accuracy and reliability of simulation results.
Journal of Pressure Vessel Technology; https://doi.org/10.1115/1.4052308
From previous combustion oscillation experiments using a simulated gas turbine combustor, oscillation frequencies around 350 Hz were measured in only natural gas-fired, and around 200 and 400 Hz were measured in the case of hydrogen-containing fuel. In this study, the axial gas column vibration mode was assumed, and the method to reproduce the change of oscillating frequency due to the difference of fuel was investigated. In the previous study, the temperature distribution in the combustor was divided into only two regions, and there were problems in terms of parameter estimation for modeling the flame dynamics. Therefore, the transfer matric method that incorporates a linear temperature gradient was employ. Also, the temperature distributions obtained from CFD and experiments were reduced to one dimension to reproduce the difference in combustion characteristics due to the difference in fuel composition; four methods were proposed, the axial representative temperatures. The Nyquist plot method was used to calculate up to 10 combinations of resonant frequency and growth rate simultaneously. And the oscillation frequency was determined in which the resonance frequency with the maximum growth rate was. As a result, the value of the oscillating frequency obtained was different depending on the method of creating the representative temperature distribution.
Journal of Pressure Vessel Technology; https://doi.org/10.1115/1.4052307
The objective of this paper is to evaluate the design collapse equations presented in chapter 8 and Annex F of the current standard ISO TR 10400 for casings under external pressure and axial tension. A nonlinear numerical model has been developed to analyze the performance of these equations to predict casing collapse under combined loads. Experimental tests have been performed with different diameters, d/h ratio and steel grade to calibrate the numerical model. The KT model has been assessed previously against different models by API Work Group and it has shown to be reliable to be used as design equations. However, the API Work Group included the KT model in the appendix F of the code as informative. The work done in this paper has confirmed the better performance of KT model for most of the cases analyzed. For combined loading, the API collapse equation results in a simple strength de-rating method, whilst the KT model has achieved similar behavior for low values of axial tension when comparing the experimental results. The axial tension for the casings into the well is likely to be lower than 40% of yield strength. Therefore, the KT model has shown to be more convenient to well design than API equations.
Journal of Pressure Vessel Technology, Volume 144; https://doi.org/10.1115/1.4051627
The local strains obtained from the best-known analytical approximations, namely, Neuber's rule, equivalent strain energy density method, and linear rule, were compared with those resulting from finite element analysis. It was found that apart from Neuber's rule with the elastic stress concentration factor Kt, all the aforementioned analytical methods underestimate the local strains for all notch root radius, strain amplitude levels, at room temperature and 550 °C. Neuber's rule with Kt slightly overestimates the maximum strains for lower notch root radius, namely, 1.25 mm, at high temperature. Based on the analytically and numerically obtained notch root strains, the fatigue lives were estimated using the Coffin–Manson–Basquin equation. Besides, a numerical assessment of fatigue lives was made based on Brown–Miller and maximum shear strain multi-axial fatigue life criteria. It was found that all these methods provide inaccurate fatigue life results for all notch root radius, strain amplitude level, and under both temperatures conditions. Therefore, a new method was suggested, for which only the applied strain amplitude is needed to calculate the fatigue life of notched components. It was revealed that the suggested method provides a good fatigue life prediction at a higher temperature loading state.
Journal of Pressure Vessel Technology, Volume 144; https://doi.org/10.1115/1.4051615
The purpose of this study was to propose low gas pressure effects on lifetime of natural gas high-density polyethylene (HDPE) pipes by thermal-oxidative aging. The new method to assess the lifetime of HDPE natural gas pipes is based on gas pressure testing. An approach to monitor oxidative induction time (OIT) has been used to predict lifetime. Natural gas HDPE pipes were used to evaluate the effects of low gas pressures on oxidative induction time. In order to emphasize the pressure effects, relatively low temperatures at 45, 55, 65, and 75 °C were utilized for the exposure. The low-pressure conditions were created using air at levels of 0, 0.1, 0.2, 0.3, and 0.4 MPa. The property of high density polyethylene pipes was effectively monitored using the low pressure OIT test. The results show that the aging reaction rate of high density polyethylene pipes increased exponentially with temperature and gas pressure according to the Arrhenius equation. Analytical models were developed to predict the aging reaction rate and lifetime of natural gas HDPE pipes.
Journal of Pressure Vessel Technology, Volume 144; https://doi.org/10.1115/1.4051688
This work reports results from a new finite element analysis (FEA)-based user programmable function (UPF) featuring true material constitutive behavior with proper algorithms for accurate stress analysis of swage autofrettage of high-strength thick-walled cylinders. This material model replicates an existing Bauschinger-effect characterization (BEC). This incorporates elastoplastic material behavior during loading. Reversed loading includes a reduced elastic modulus and nonlinear plasticity resulting from the Bauschinger effect (BE), both depending upon the maximum level of loading plastic strain. This case study identifies the difference in stress distributions based on two different material models, a bilinear kinematic hardening model, and the BEC model. Near-bore residual stresses for the BEC case are noteworthy and reported in detail, e.g., axial residual stress is tensile and hoop residual stress exhibits a distinct slope reversal, unlike hydraulic autofrettage. This indicates the possible need to re-assess the ASME pressure vessel code (correction for BE) regarding swage autofrettage.