bluuebunny/crossref_metadata_2025 huggingface dataset:
Fracture and Fatigue Properties of High Strength Ferritic Steel Welds in High Pressure Hydrogen
Authors: Ortolani Matteo , Bortot Paolo , Connolly Matthew , Buck Zackary
Published: November 2024

High strength ferritic steels are very commonly used for construction of pressure vessels for hydrogen storage and transportation, thanks to the combination of affordable cost and availability of material for construction. As hydrogen becomes more and more important as a carbon-neutral energy vector, the number and size of installations for hydrogen storage are expected to grow, and large vessels fabricated by welding are among the possible solutions to meet this increasing demand of storage capacity.

Ferritic steels suffer from hydrogen assisted cracking, and therefore safe design requires reliable knowledge of their fracture and fatigue properties when exposed to pressurized hydrogen environment. Thankfully, this information is today available for most commonly used steel grades ([1], [2]).

However, these known design curves are specific for wrought products, whose microstructure is achieved by precise heat treatment conditions, typically, quenching and tempering. Welding, however, inevitably produces a local transformation of the material’s microstructure, and a gradient of properties in the volume surrounding the solidified pool. Therefore, fabricating any high strength steel pressure equipment that includes welds, requires characterization of the fracture and fatigue properties of the different microstructural regions.

Previous work from the same authors ([3]) demonstrated the variable performance of high strength steel welds in gaseous hydrogen, and thus the effect of welding parameters. This paper expands the previously published information, presenting new experimental findings on the FCGR behavior of welded joints made from a low a carbon weldable high strength steel, P690 QL2 ([4]).
Validity of Toughness Measurements From Miniature Specimens Failing in Different Fracture Modes
Authors: Ortner Susan , Sanchez Marcos , Echols John , Cicero Sergio , Chekhonin Paul
Published: November 2024

Using 0.16T (4 mm thick) compact tension specimens to determine toughness in reactor pressure vessel steels permits the ductile to brittle transition temperature to be derived from small amounts of material and allows more effective use of surveillance specimens. Achieving validity in the toughness measurements requires more care in specimen manufacture, load train alignment and test temperature selection than when larger specimens are used. This is particularly evident in the shapes of precrack fronts, which appear more sharply asymmetric on smaller specimens. Questions have also been raised as to whether the failure mechanisms are the same in miniature and large specimens. This work, performed within the FRACTESUS project, presents toughness measurements and detailed fractography on both a homogeneously brittle base metal and a relatively ductile, inhomogeneous weld. The fractography shows that, even in a ductile weld metal exhibiting clear shear lip, brittle fracture initiates within the part of specimen experiencing small scale yielding, so long as the toughness measurement is valid. Similarly, although the precrack front asymmetry appears more marked in smaller specimens, as long as the deviation from planarity is within the ASTM limits, the asymmetry does not affect the location of the initiation site. For materials showing a variety of fracture modes, the fracture modes observed at the initiation sites are consistent with those observed in larger specimens. Where data are available, the stress and strain conditions at the initiation sites are also found to be consistent in 0.16T and larger specimens. These fractographic observations support the thesis that toughness measurements made on miniature compact tension specimens reflect the same material characteristics and failure mechanisms as those on larger specimens. The limitations on specimen geometry and loading identified by the ASTM Standard are sufficient to ensure that transition temperature values derived from miniature compact specimens are valid for materials failing via a variety of fracture modes.
Stress Analysis of Explosion-Welded Stainless Steel to Aluminum Cryogenic Transition Joints
Authors: Ok Ali
Published: November 2024

Transition joints are commonly used to connect components built from two dissimilar metals. In cryogenic applications, aluminum to stainless steel transition joints are often used to connect aluminum vessels and heat exchangers to stainless steel piping. Such transition joints have been built using different technologies. In this paper, explosion-welded transition joints will be considered and modeled.

All piping transition joints must be designed to accommodate stresses due to pressure and other piping loads and forces. Explosion-welded stainless steel to aluminum cryogenic transition joints typically utilize multiple intermediate material layers for better bonding (depending on the manufacturer’s process) and to accommodate the differential thermal expansion/contraction between the aluminum and stainless steel outer layers. Considering aluminum alloys have thermal expansion coefficient approximately twice those for steels, consideration shall be given to the operating temperature of the joint to evaluate the thermal stresses occurring at the interlayers.

ASME PVP2023-105205 paper discusses the qualification methods and requirements for explosion-welded parent plate and transition joint design but the thermal stress effect on the transition joints due to the differential thermal expansion/contraction in the materials was not discussed in the paper. This paper includes thermal stresses occurring on the joint due to the differential thermal expansion/contraction and its impact on transition joint design. Finite Element Analysis (FEA) is used to understand the effect of the joint geometry and material composition on internal stresses due to the combination of pressure, piping loads, and differential thermal expansion/contraction within the joint.
Expanded PTFE Gasket Material Performance Variation With Thickness
Authors: Bausman Anita , Wilson Jeffery
Published: November 2024

Polytetrafluoroethylene (PTFE) is an excellent gasket material, chemically, but it has relatively poor mechanical performance. As a result, much effort has gone into improving the mechanical performance of PTFE-based gasket materials. Methods to improve mechanical performance include the addition of fillers (glass fibers, glass microspheres, silica, barium sulfate, carbon, etc.) and the manipulation of the microstructure (micro-cellular, expanded, restructured, etc.). These various forms of PTFE materials can have widely varying mechanical performance. PTFE materials that are chemically the same will have significantly different mechanical performance if the manufacturing process and microstructure are different. An example is the performance of amorphous, virgin PTFE sheet compared to the performance of fibrillated, expanded PTFE (ePTFE) sheet. The thickness of a gasket material is another structural difference that results in different mechanical performance.

This paper is an extension of PVP2022-84765, PTFE Gasket Material Performance Variation with Thickness [1], which investigated barium sulfate filled, restructured PTFE’s mechanical performance. This paper explores the difference in the mechanical performance of common expanded PTFE (ePTFE) materials that are often considered to be functionally the same by end users. The mechanical performance of each material is compared for different thicknesses using the Hot Blowout, Thermal Cycling test (HOBTC, ASTM WK61856 Rev 10-9-2020). [2] The authors selected these thicknesses for performance review because of their usage in industry. ePTFE sheet is most commonly used on vessel and equipment flanges. The thinner thicknesses considered in this paper, 1.5 mm (1/16 inch), is most commonly used in piping flanges. The two thicker sizes reviewed for this paper are 3 mm (1/8 inch) and 6 mm (1/4 inch). Because ePTFE is so conformable, it is often used on problematic flanges with irregularities in the flange faces. Hence, the 6 mm (1/4 inch) thickness is more commonly seen with ePTFE applications than with other forms of sheet PTFE gasketing. Very little test data on 6 mm (1/4 inch) thick ePTFE exists. Leakage testing is according to the Room Temperature Tightness test (ROTT, ASTM F2836) [3]. The authors primarily used lab tests for HOBTC and ROTT data with some comparison to publicly available data. HOBTC and ROTT lab tests were performed on an amtec TEMES fl.ai1 test fixture at the authors’ company. This data will demonstrate to the end-user how different the mechanical behavior can be of the same ePTFE gasket material whose only obvious difference is how thick it is.
Analysis and Treatment of Pipeline Vibration Driven by Turbine-Driven Boiler Feed Water Pump
Authors: Wang Chengwen
Published: November 2024

Boiler feed pumps in thermal power plants are normally powered by electric motors, but turbine-driven pumps are also used to reduce operating costs.

However, during the first startup phase, a steam-driven boiler feed pump pipeline encountered unexpected serious vibration. The vibration gradually worsened as the turbine speed rised during the acceleration stage to the rated speed of 3000 rpm. The entire concrete floor kept vibrating due to the severe vibration of the pump inlet pipeline, even with reinforced support. It had been discovered through a series of vibration measurements that the pressure control valve in the reflux pipeline, which has a labyrinth pressure reduction construction, was the primary cause of the vibration. Resonance was brought on by the pressure drop waves that travelled through the fluid and had an impact on the pump’s intake and exit pipelines. Furthermore, the vibration frequency didn’t change with speed, showing frequency locking. When the swing check valve of the pump outlet pipeline was opened normally and the return pipeline was no longer working, the entire system returned to normal. In order to achieve this goal and ensure the construction progress, viscous dampers were added to the pipeline system to absorb vibration, allowing the pump to smoothly reach the rated speed.
Expanded PTFE Gasket Material Performance Variation Comparing Solid to Jointed Constructions
Authors: Bausman Anita , Wilson Jeff
Published: November 2024

Polytetrafluoroethylene (PTFE) is an excellent gasket material. Expanded PTFE (ePTFE) achieves better mechanical performance compared to plain PTFE by a highly fibrillated microstructure. However, between the fibers of the ePTFE, there are air voids. To achieve superior sealing, the microstructure must be adequately compressed to close these voids and reduce permeation leakage through the gasket material itself. During this compression, the ePTFE dimensions shrink in contrast to most PTFE sheet materials that radially expand when compressed. This ePTFE behavior is problematic where a gasket with a joint is needed, for example on industrial column body flanges larger than available ePTFE sheets. Care must be taken to make a leak-free ePTFE joint on such gaskets.

Industry experience with the common dovetail joint has been poor using ePTFE materials. However, joints are sometimes needed. The authors investigated the leakage and mechanical performance of ePTFEs as solid rings without joints, industry-standard dovetail jointed rings, and Engineered Interference Tortuous Path (EITP) jointed rings. Data was collected according to the EN13555 leakage test at room temperature [1]. A preliminary investigation of pressure performance at temperature was made using the first step of the Hot Blowout Thermal Cycling (HOBTC, ASTM WK61856 Rev 10-9-2020) test (no thermal cycles this test round) [2]. Lab tests were performed on an amtec TEMES fl.ai1 test fixture at the authors’ company.
Tensile Strain Capacity of an X70 Pipe With Internal and External Semi-Elliptical Crack Under Bending and Tension
Authors: Yu Xinping , Park Dong-Yeob , Wang Xin
Published: November 2024

This paper studies an in-depth examination of the tensile strain capacity (TSC) of an X70 pipeline containing an internal or external semi-elliptical crack when exposed to bending or tension. Comprehensive TSC evaluations were conducted through finite element analyses, incorporating initiation and ductile tearing criteria for different crack depths and magnitudes of internal pressure. During the analyses, crack-tip opening displacement (CTOD) and J-integral were calculated, taking into account the crack’s depth and the magnitude of the internal pressure. The finite element results enabled a precise estimation of crack driving forces for both CTOD and J-integral, with respect to the remote strain of the pipeline. The findings revealed that, in bending scenarios, both internal and external cracks exhibited lower values of CTOD and J-integral compared to tension conditions, resulting in a slightly higher tensile strain capacity. The disparities observed in CTOD and J-integral values between bending and tension conditions were relatively minor, suggesting that material and pipe properties may exert a more pronounced influence on their behavior than the specific loading condition in the pipeline. TSC calculations using initiation and ductile tearing methods indicated no significant differences for either external or internal cracks, under both bending and tension conditions. This study provides valuable insights into the TSC assessment of full-scale pipelines with semi-elliptical cracks, highlighting the significance of considering the specific loading conditions in such evaluations.
Indicators for Coke Drum Replacement Due to Bulge-Induced Damage
Authors: Araque Vivas Egler Dubin , Park Stephen Michael
Published: November 2024

Replacement of coke drums is a major project that requires a significant investment and at least 3 or 4 years of planning. One of the leading causes of drum replacement has been the cost associated with repairs and unexpected shutdowns due to bulge-induced damage. An assessment of the total area of bulge-induced damage in 10 coke drums from two refineries (Sites A and B) that are conducting replacement projects is shown as an example of parameters that can be identified and tracked over the life span of the vessel.

The Local Plastic Strain Indicator, abbreviated as LPSI, is used as a methodology to quantify and track the evolution of bulged areas and surface damage found during laser mapping and remote visual inspections. LPSI identifies and ranks bulges prone to local failures using plastic strain calibrated against bulges that developed internal or external bulge-induced damage. The LPSI is the ratio of the plastic strain found at the point being analyzed to the calibrated strain limit found at points where through-wall cracks occurred due to bulging, in a percentage form.

Using LPSI to find the surface area of the drum cylinder that is bulged is a novel concept. Results show how total bulged area and the area with elephant skin surface damage increases over time, reaching the point where repairs are required to stop bulge growth and maintain safe operations. Eventually the accumulated bulging, surface damage, and amount of repairs required reach the point where the cost and potential for unexpected shutdowns leads to vessel replacement. Examples are provided to assist refiners in understanding how to assess their own drums.
A Finite Element Method to Simulate Non-Destructive Evaluation Testing of Downhole Tools Subject to Shock and Random Vibration
Authors: Ghosh Pritha , Sisak Ryan
Published: November 2024

A downhole tool typically encounters shock and vibration under different circumstances, including tool handling, tool transportation and tool operation. The aim of this work is to present a finite element analysis (FEA) method that can simulate non-destructive evaluation tests conducted on downhole tools subject to shock and random vibration. The downhole tool assembly is rigged up to the vibration test table and subjected to a shock signal or a random vibration signal as expected in well conditions. A corresponding three-dimensional finite element model of a downhole tool is developed with component geometry details and relevant interactions between the components, accounting for inertia of components and structural material properties. The method involves a two-part analysis of the finite element model: response spectrum and transient dynamic analysis for shock and random vibration. This simulation predicts the mechanical response of the tool used to determine failure within its operating range. The unique contribution of this work is that the analysis approach can capture the effects of the response of the tool assembly similar to non-destructive shock and random vibration testing. Comparisons of frequency response tests and structural integrity inspection from simulations versus testing on the downhole tool establish the fidelity of the FEA method as well as additional insights to the load path of the inner components of the tool assembly. The FEA method thus provides an alternative digital identification of the potential failure under shock and random vibration in downhole tool assemblies that is cost-effective and time-efficient, to reveal potential structural integrity issues of downhole tools in early design stages and identify critical components in the tools that need to be monitored during their physical testing.
Discussion on the Design Life and Ultimate Service Life Determination Criteria of Pressure Vessels in China
Authors: Chen Xuedong , Fan Zhichao , Xu Shuangqing , Chen Wei , Dong Jie
Published: November 2024

China is a big user of pressure vessels, with more than 4.97 million stationary pressure vessels in service by the end of 2022, among which pressure vessels in the process industry with high cost, many consumables, high technical difficulties, long production and procurement cycles. Therefore, the need for their long-term service is urgent. The design life of pressure vessels is the intended use time determined by the designer according to the design conditions and construction specifications to maintain the structural integrity or target function, and is a key parameter to balance safety and economy. The service life of the pressure vessels is the actual service time to maintain the structural integrity or target function under the actual service conditions, and changes with the actual service conditions. Reasonably extending the service life of pressure vessels in use is one of the important tasks of coordinating safety and development.
A Continuum Damage Coupled Unified Constitutive Model for Creep-Fatigue Damage Evaluation of Modified Grade 91 Tube Sheet Structures Under Flexible Loading Conditions
Authors: Islam Nazrul , Hossain Md. Sumon
Published: November 2024

The Grade 91 tube-sheet structure is a critical integral part of Sodium Fast Reactors (SFR) developed by the Japan Atomic Energy Agency. Life evaluation of such a component is complex because of its geometry with the numerous holes and combined creep-fatigue loading conditions at elevated temperatures. The Sodium in the SFR tube sheets is flowed at the operating temperature varied from 650°C and 250°C for hot and cold transients. For these components, the creep-fatigue damage evaluation is commonly performed using simplified approaches such as the Stress Redistribution Locus (SRL) method or non-unified constitutive models where creep and plastic strains are not coupled. However, understanding the behavior of Grade 91 steel under fatigue, creep and creep-fatigue loading conditions and its constitutive model based on these phenomena are important to properly predict the component responses. Hence, this study developed a 3D FE model of the tube-sheet component, utilized the advanced damage coupled unified constitutive model (UCM-CDM) of Mod. Grade 91, formulated by the author earlier, to analyze the creep-fatigue strength of the tube sheet under combined flexible loading. The damage estimation using the UCM-CDM model is compared with other commonly used non-unified models, and the robustness of the UCM-CDM model is discussed.
The Effects of Model Thickness on the Variation of Localised Stress Fields in Four-Point Bending Tests: A CPFE Study
Authors: Kuo Brandon , Taherijam Masoud , Abdolvand Hamidreza
Published: November 2024

Hydrogen embrittlement is one of the principal mechanisms leading to the degradation of engineering materials used in the core of nuclear reactors. This mechanism plays a major role in deciding when to replace the Zr-2.5Nb pressure tubes used in the core of CANDU nuclear reactors. The presence of localised stress fields in CANDU pressure tubes affects the diffusion of hydrogen atoms toward cracks, scratches, and other imperfections. These high-stress regions, in which the hydrogen accumulates, serve as the nucleation sites for hydrides. In this study, an in-house crystal plasticity finite element model was used to study the effects of model thicknesses on the distribution of stresses. This was done to provide a road map for comparing the results obtained from electron backscatter diffraction measurements (EBSD) to those calculated by CPFE modelling. It is shown, that within the ROI, the variation of von Mises stresses changes significantly with model thickness, while the hoop and hydrostatic stresses are only slightly affected. In all cases, the hydrostatic stresses were more pronounced at the midpoint of the sample. Additionally, it was found that to minimise the impact of the boundary conditions on the stresses at the free surface a thickness of 500 μm was found to be optimal.
ASME CC N-900 Revision Discussion (No.2) Revisit of Fabrication Strain Limitation of Pipe Fittings
Authors: Shibukuwa Kenichi , Wen Jie , Takanashi Masahiro , Funasaki Kenji
Published: November 2024

In 2019, ASME Section III and JSME published a remarkable code case (ASME CC N-900[1]/JSME NC1 CC-008[2]) regarding seismic design codes for piping by using elastic-plastic analysis. As shown in PVP2023-107170[3] “Seismic Design Method of Crossover Piping Across Building Isolation Boundary”, while it would be clear that this code case using elastic-plastic analysis allows for a reasonable seismic design of the piping, there are few examples of actual seismic design work using this code case. The reasons why the seismic evaluation method based on elastic-plastic analysis of piping has not been widely applied to actual design works include the limited applicability (especially, fabrication strain limitation of pipe fittings) of ASME CC N-900.

In this paper, a review of the fabrication strain limits for pipe fittings has been performed, and it is reported that the residual strain in the fabrication process of pipe fittings is small and has little effect on the ductility and fatigue strength of pipe fittings.
Mechanical Responses and Assessment of Fatigue Life for Submarine Suspended Pipelines
Authors: Zhang Yi , Shuai Jian , Shuai Yi , Liu Qianqian , Lv Zhiyang , Shi Lei , Jiang Lumeng , Jiang Yuanliang
Published: November 2024

As an essential component for the transportation of oceanic oil and gas supplies, it is crucial to ensure the efficient operation of submarine pipelines. The fatigue failure of submarine pipelines occurs frequently under the combined effects of currents, waves and soil. Firstly, a pipe-soil interaction suspended pipeline model was developed, which could be used to simulate the mechanical behavior of pipes and the dynamic response of the combined loads of waves and currents. Then, the effects of soil properties, current direction and suspended length on the stress distribution and dynamic mechanical response of submarine suspended pipelines were investigated. In addition, the vibration characteristics of suspended pipelines affected by soil were revealed. At last, according to the vortex-induced resonance evaluation and fatigue life assessment method, the critical length of suspended pipelines for the Bohai sea was determined. The results show that the stress change in the center of the suspended section reaches the most significant for the pipeline with a length of less than 20m. When the suspended length exceeds 20m of the pipeline, the connection between the suspended section and the buried section shows the most dramatic stress fluctuations. Meanwhile, the cumulative damage of the submarine suspended pipeline entering the soil becomes the maximum, and fatigue failure often occurs in this position. The results are expected to provide an important theoretical basis in safe operation and repair decision of submarine pipeline.
A Lightweight Model of Automatic Pixel-Level Detection for Weld Defects
Authors: Qian Weichao , Dong Shaohua , Ren Qingying , Chen Lin
Published: November 2024

Pipeline transportation serves as the primary method for conveying oil and gas, with welding being the predominant means of connecting pipelines. Nevertheless, weld defects frequently occur at circumferential welds due to various factors including the welding process and environmental conditions. Failures due to these welding defects threaten the safety of pipeline transportation, and X-ray inspection is used to visually detect defects. While manual inspection has traditionally been employed for X-ray defect detection, it suffers from inefficiency and subjectivity. As computer vision techniques have advanced, methods leveraging deep learning have emerged for weld defect detection. However, the practical application of deep learning methods is constrained by their size, limiting their effectiveness in industrial detection tasks. To address these challenges, this paper proposed a lightweight pixel-level automatic detection network for weld defects based on an encoder-decoder structure. Firstly, a lightweight global feature extraction block utilizing self-attention was introduced to enhance detection performance by extracting more discriminative features within defect areas. Subsequently, a high-low level feature fusion block was incorporated to mitigate feature loss resulting from downsampling. Additionally, the depthwise separable convolution was employed to further reduce network size. Our method demonstrated superior detection performance compared to other advanced methods, as evidenced by qualitative comparison and quantitative analysis, with dice coefficient (DICE) and intersection over union (IoU) scores of 0.881 and 0.789, respectively. Moreover, our network exhibited significantly reduced size compared to other advanced detection methods. Thus, the proposed detection network holds considerable promise for effectively detecting weld defects.
Strain-Rate-Dependent Parameters of Lithium as a Plasma Facing Material for Magnetized Target Fusion Application
Authors: Miao Yu , Sexsmith Michael , Hartono Soegi , Preston Claire , Tsai Benjamin , Dick Jean-Sebastien , Sirmas Nick
Published: November 2024

Lithium is an ideal plasma facing material for fusion plasmas due to its low atomic mass, ability to breed tritium fuel and its gettering characteristics. Liners made of lithium are used as magnetic flux conservers, which can be compressed for Magnetized Target Fusion (MTF) applications. Lithium has been extensively examined in the literature aiming at its mechanical properties for its various applications, and yet the knowledge about its mechanical properties is insufficient for the MTF application in two aspects. First, most of the available studies focus on the quasi-static loading cases. Second, the tests in those studies were commonly performed via uniaxial tensile test where the stress state was not representative for the compression loading scenario.

In this paper, we present an approach to estimate parameters that govern lithium’s behavior at high strain rates up to 500 s−1. In our approach, a series of drop-piston experiments were combined with ANSYS LS-DYNA simulation to determine the material parameters. The bi-linear strain hardening model and Johnson-Cook material model were considered in our studies where the former one accounts for the plastic stress-strain relationship and the latter one describes the plastic stress-strain relationship with the strain-rate effects. In our drop-piston experiments, we use high-speed camera imaging and a feature tracking algorithm to record the velocity and extract the piston impact time. A bi-linear strain hardening model was initially used to estimate plastic behavior of lithium. The strain-rate dependent material parameters were then determined using a reverse engineering approach with the help of numerical simulations that reproduce the tests. A series of numerical simulations with different combinations of material parameters were computed to establish the combination of material parameters that best fit the test results.

The proposed material model will be used in the lithium compression experiments for MTF applications, which accounts for the hardening behavior at different strain rates.
Benchmark Analysis on Pipe Support Structures for Establishing Inelastic Seismic Design
Authors: Nakamura Izumi , Takito Kiyotaka , Shimazu Ryuya , Okuda Yukihiko , Sakai Michiya , Otani Akihito , Watakabe Tomoyoshi , Okuda Takahiro , Shibutani Tadahiro , Shiratori Masaki
Published: November 2024

A new seismic design procedure which evaluates the inelastic behavior of piping system by detailed finite element method (FEM) analysis has been developed in Japan (the JSME CC); however, the inelastic behavior is only considered for pipe body in the JSME CC, and the evaluation of inelastic behavior of pipe support structure is still not included.

To clarify the current analytical accuracy of inelastic analysis of pipe support structures and to develop an analytical guideline to reasonably include the inelastic behavior of pipe support structure in the seismic design of piping system, a series of benchmark analysis on pipe support structures has been launched in 2022. The benchmark analysis of pipe support structures consists of mainly two stages; the first stage is the analysis of pipe support structures themselves, and the second stage is the analysis of piping system with inelastic pipe support structure.

As of January 2024, the first stage of benchmark analysis is in progress. It is confirmed that there are some variabilities in modeling of support structures, stress-strain relationship, and boundary conditions. The load-deflection relationships also show variability even when the support structures are in the elastic region. The effect of these variations to the response of piping system model is remained as future tasks.
Environmental Effect on Fatigue Life of Stainless Steel for Superimposed Waveforms Simulating High-Cycle Thermal Fatigue
Authors: Kamaya Masayuki
Published: November 2024

The degree of fatigue life reduction due to a pressurized water reactor (PWR) environment depends on strain rate. The environmental effect is negligibly small when the strain rate is sufficiently large. In general, the environmental effect is not considered in fatigue life assessments of high-cycle thermal fatigue, which has been observed at mixing tees of nuclear power plant piping systems. Although frequency of strain fluctuation caused by thermal striping is relatively high, it was found that the main source of fatigue damage was a relatively low-frequency strain fluctuation superimposed on the high-frequency strain fluctuation. In this study, to investigate the environmental effect on the high-cycle thermal fatigue, fatigue tests were conducted for superimposed waveforms in which high-frequency strain superimposed on the low-frequency strain fluctuation. Five loading patterns were tested in the PWR water environment using Type 316 stainless steel specimens. Also, tests in air were conducted for the same loading patterns. It was revealed that the degree of the environmental effect of the superimposed waveforms depended on the strain rate of high-frequency strain fluctuation rather than that of low-frequency strain fluctuation. It was concluded that, even though the high-cycle thermal fatigue failure was brought about by the low-frequency strain fluctuation, the environmental effect did not necessarily have to be considered in the fatigue assessment.
Vortex Shedding Characteristics of Concentric Circular Rod Bundle Arrangements
Authors: Huang Zhengfeng , Wang Heng , Lv Hong , Zhu Guorui
Published: November 2024

The concentric circular arrangement of bundles is widely used in the nuclear industry. The study of the vortex shedding characteristics of concentric circular arranged bundles can provide a reference for the design, manufacturing and maintenance of this type of heat exchanger. This research aims to thoroughly investigate the vortex shedding characteristics of concentric circular arranged bundles under different arrangement patterns (approximately triangular arrangements, approximately square arrangements, and transitional arrangements) and different Pitch-to-diameter ratios (1.25, 1.5, 1.75, and 2.0). Through numerical simulation, the lift coefficient was monitored to obtain data on vortex shedding, and the vortex shedding frequency was obtained using Fourier transformation. The study reveals that the most significant vortex shedding phenomenon occurs in the approximately square arrangement, followed by the approximately triangular arrangement, and finally the transitional arrangement. The approximately triangular arrangement exhibits flow characteristics similar to those of the equilateral triangle arrangement, and the difference in lift coefficient does not exceed 3%. Pitch Ratio is identified as a major factor influencing vortex shedding. The increase in Pitch Ratio significantly enhanced the vortex shedding. Moreover, the vortex shedding in the bundles is greatly influenced by neighboring tubes, resulting in a diminished manifestation of vortex shedding. The research results provide certain reference significance for the engineering practice of selecting arrangement methods and pitch-to-diameter ratios in concentric circular tube bundle heat exchangers.
The Safety Assessment of Tanker Truck due to Collision in Rollover Accidents
Authors: Feng Heyi , Xu Xiaodong , Deng Guide , Kang Xiaopeng , Li Yongquan , Jia Guodong
Published: November 2024

Tanker truck is an important way to carry fuel and hazardous materials in land transportation. In recent years, many tanker truck rollover accidents occurred, some of them are severe, causing casualties and significant economic losses. Therefore, it has come to public’s attention that how to avoid such accidents. This study performs the safety assessment of tanker truck due to collision in rollover accidents. The critical speed of the truck is determined using a multibody dynamic analysis software, ADAMS CAR. Then the collision analysis that study the structural response of tanker hitting on ground, curbstone, and concrete blocks are performed using ANSYS/LS-DYNA. The material parameters are obtained through experiments using specimens manufactured by a cut-off plate from a tanker involved in a rollover accident. The overturn analysis results show that the critical speed of the tanker truck is 39.46 km/h. The results of tanker hitting on the ground show that this process would cause significant deformation at connection joints of heads and tanker body, but it does not cause tanker failure. On the other hand, the tanker body is more likely to fail when concrete block that happens to hit on tanker next to baffles.
Prediction of Burst Pressure for Type IV High-Pressure Hydrogen Storage Vessel Based on Adaptive Meshing Method
Authors: Li Fanding , Chen Xuedong , Fan Zhichao , Xu Peng , Tao Jiahui , Wang Zhe
Published: November 2024

With the growth of the hydrogen energy industry, cost-effective and highly reliable high-pressure hydrogen storage technologies have gained increasing attention. High-pressure hydrogen storage vessels with plastic inner liners and composite materials (Type IV hydrogen vessels) have inherent advantages such as high hydrogen storage density, corrosion resistance, and excellent fatigue performance, making them one of the most advanced high-pressure hydrogen storage methods. Burst pressure is a critical performance indicator for Type IV hydrogen storage vessels. Due to the complex structure of Type IV high-pressure hydrogen storage vessels, material property variations in different parts, multiple failure modes for composite materials, and substantial influencing factors, experimental testing for structural design and performance optimization is challenging, time-consuming, and expensive. The numerical simulation method is an adequate way to reduce development costs. With the progressive damage method, burst pressure can be precisely predicted. However, the finite element model has an excessively high degree of freedom, resulting in low computational efficiency.

In response to the need for precise and efficient performance simulation of Type IV high-pressure hydrogen vessels, this paper proposed a framework to effectively reduce the resources needed for finite element calculations on multiple layup schemes based on an adaptive meshing method. Finite element models that include the fiber orientations and geometric details on dome parts and cylinder part are established. Various damage modes are considered and coupled with the progressive damage method. Comparative analysis of different meshing methods has been carried out to study the influence of meshing parameters on the calculation speed. With data processing and programmable finite element software, a burst pressure prediction method for Type IV hydrogen storage vessels based on adaptive meshing is proposed. Burst tests have been further taken, which indicate that the numerical results match the experiment well. Meanwhile, the adaptive meshing method significantly improves calculation speed and with satisfying accuracy. In conclusion, the framework proposed in this paper offers valuable insights into data collection speed for Type IV hydrogen storage vessels with complex layup schemes and advances the utilization of numerical simulation in the domain of hydrogen energy storage and transportation equipment.
The Development of Hydrogen Energy Equipment Safety Certification in China
Authors: Li Jun , Li Jiepu , Guan Chenxi , Zhang Songsong , Li Xiang , Liu Xu
Published: November 2024

In recent years, the hydrogen energy industry in China has experienced rapid development, leading to intensified research and development efforts in hydrogen energy equipment. As the cornerstone of the entire hydrogen energy industry chain, hydrogen energy equipment has experienced significant advancements. However, hydrogen energy equipment certification is still in its preliminary exploration stage, and the corresponding certification system lacks maturity, hindering the subsequent industrialization and reliability of hydrogen energy equipment in China. This article initiates with an introduction to the concepts of product certification and safety certification, elucidating the model and necessity of safety certification for hydrogen energy equipment. It subsequently provides a brief overview of the current state of safety certification for hydrogen energy equipment, touching on standards, technical specifications, inspection, testing capabilities, and other relevant aspects. Several issues are identified within the safety certification of hydrogen energy equipment in China: (1) The foundational theories pertaining to hydrogen energy equipment are inadequate, leading to the incompleteness of relevant product standards and technical specifications; (2) Scarcity of safety certification type test devices and a deficiency in certification institutions possessing international certification capabilities. (3) Limited safety certification projects for hydrogen energy equipment in China. In light of these challenges, targeted suggestions are proposed for the future development of hydrogen energy equipment safety certification in China. These recommendations aim to guide the standardization and systematization of hydrogen energy equipment, ensuring its high-quality development and secure operation. The ultimate goal is to establish a robust safety certification system for hydrogen energy equipment in China.
Preparation and Properties of the Low-Cost Heat-Resistant Rubber Material for Trenchless Rehabilitation of Thermal Pipelines
Authors: Wang Zhongzhen , Li Yao , Yasin Sohail , Zheng Ce , Hu Peiyu , Zhang Liang , Shi Jianfeng
Published: November 2024

Trenchless rehabilitation technology is a pipeline repair technology with the advantages of high construction efficiency and low impact on the environment. It is currently used in the repair of drainage pipelines and oil pipelines. Thermal pipelines transport hot water or hot steam from heat sources to buildings. They are an essential part of urban heating systems. With the increase in elapsed service life, thermal pipeline failure occurs frequently, so it is necessary to apply trenchless rehabilitation technology to repair thermal pipelines to improve the speed and efficiency of repair. However, the temperature of the conveying medium in thermal pipelines can reach 100°C, and plastic materials such as polyethylene (PE), commonly used in trenchless repair technology, cannot withstand the high working temperature. There are heat-resistant rubber materials with excellent properties, but the prices are too high to be widely used in trenchless rehabilitation technology. Therefore, this study analyzed the material temperature resistance and mechanical property requirements for applying trenchless rehabilitation technology to thermal pipelines. Using natural rubber (NR) and ethylene propylene diene monomer (EPDM) rubber as the matrix, the low-cost heat-resistant rubber material was successfully prepared by adding deep eutectic solvents (DES). The mechanical properties and heat aging resistance of the rubber material were tested. The results show that the rubber material has excellent mechanical properties and can meet the usage conditions of thermal pipelines. After aging at 150°C for 200 hours, the mechanical properties of the rubber material can still be maintained at a high level, meeting the long-term requirements of thermal pipelines. After economic analysis, the price of this rubber material was lower than 10 dollars per kilogram and can be applied in trenchless rehabilitation technology.
Analysis of the Tribological Behaviour of Titanium Fasteners Under Different Tightening Strategies
Authors: De Agostinis Massimiliano , Croccolo Dario , Fini Stefano , Mele Mattia , Olmi Giorgio , Scapecchi Chiara , Martini Jacopo
Published: November 2024

The present work aims at investigating the tribological behaviour of Ti6Al4V, M6 screws, applied to cast aluminium underhead and threads, when subjected to different tightening strategies. All tightenings have been performed in the dry condition, after degreasing of the cast parts by means of a commercial spray degreaser. Namely, a standard steady tightening operation at 20 rpm has been compared to a mixed high speed – standard speed strategy (200 rpm – 20 rpm), observing the tribological output in terms of underhead and thread friction coefficients at first tightening. All measurements have been performed by means of a tightening test bench that allows sampling the separate frictional contributions at the underhead and at the thread. For each specimen, force – torque diagrams have been plotted and observation of the underhead surfaces have been performed (before and after first tightening). The underhead and thread friction coefficients have been sampled at both 25% and 100% of the target tightening torque. The main outcomes of the study are: (i) the frictional behaviour of the Ti6Al4V screw, mating to aluminium substrates is nearly the same for both tightening strategies, in terms of average total coefficient of friction; (ii) in the case of mixed high – low speed strategy, a slightly better behaviour in terms of stick slip occurrence has been observed at first tightening, (iii) both processes allow achieving friction coefficients in the range suggested by the relevant standards.
Ultrasonic Phased Array Automatic Detection on Weld Seams of Plastic Liner in Type IV Hydrogen Cylinder
Authors: Miao Cunjian , Zhong Haijian , Teng Guoyang , Guo Weican , Tang Ping , Hu Jiansheng , Tao Yangji
Published: November 2024

On-board 70MPa Type IV hydrogen cylinders predominantly employ an injection-molded plastic liner with a welded design. During the welding sequence, parameters such as temperature, pressure, and duration, coupled with the quality of raw materials, can potentially instigate welding inconsistencies. These aberrations can subsequently compromise the impermeability of the plastic liner. Due to the plastic liner’s relatively thin thickness, the significant acoustic attenuation of the material, and the complex nature of defect formations, conventional ultrasonic inspection methods struggle to effectively detect defects within these liners.

An ultrasonic phased array automatic detection technique, tailored for the weld seams of Type IV hydrogen cylinder plastic liners, was introduced. By harnessing the capabilities of water wedge technology, it facilitates the deflection of ultrasonic beams and the transition of waveforms. Employing curved elements for intrinsic self-focusing and array elements for electronic focusing, this technique achieves bidirectional acoustic emission fields. Building upon the foundational insights from this acoustic field simulation, the phased array focusing principle, sensor orientation, array element number, pitch, and operational frequency, among other pivotal inspection determinants, were meticulously optimized and calibrated. A phased array multi-path imaging detection method for the liner’s weld seam was formulated, and an analysis was undertaken to evaluate the detection efficacy and sensitivity across various defect types.

Building on the aforementioned research foundation, a specialized ultrasonic phased array immersion C-scan automatic detection system, specifically designed for the weld seams of the plastic liner, was developed. Test sample of the plastic liner weld seam, integrated with artificial defects, were subjected to testing. The results demonstrated that this method could reliably detect artificial defects in the test sample. This methodology was also successfully implemented in the welding production line for inspection of actual plastic liner products, ensuring the integrity of the welding quality.