Fatigue life of high-pressure hydrogen storage vessel with design pressure of 45 MPa and 99.9 MPa was investigated. The feasibility of improving fatigue life with crack grinding strategy was verified. First, fatigue assessment with fracture mechanics and S-N curve method was performed. The result indicates crack grinding is beneficial to the fatigue life of cracked hydrogen storage vessel. Then, slow strain rate tensile test of 4130X steel in 100 MPa hydrogen environment was performed. A fracture criterion that maximum principal stress equals the ultimate strength of 4130X was suggested for failure in 100 MPa hydrogen environment. At last, numerical burst pressure simulation was performed. The results suggested that burst pressure of hydrogen storage vessel with grinding groove was not influenced by crack grinding. The outcome of this work suggests a grinding strategy that repairs immediately upon crack detection for hydrogen storage vessel.

Current selection criteria for autofrettage pressure in hoop-wrapped composite vessels are inadequately defined, critically lacking consideration of axial structural safety and fatigue life requirements. To address this, the axial structure safety of the vessel during the autofrettage process within the respective selection range chosen by different criteria was analyzed. Results clarified the axial burst risks within conventional selection ranges. A safety criterion constraining pressure between the hydrostatic test and the liner axial burst limits was established. Fatigue analysis using fracture mechanics revealed that the mechanism of the autofrettage process enhances fatigue life of vessels by reducing crack-tip stress intensity factors due to residual stresses. The results also indicate that under axial structural safety constraints, the maximum fatigue life of vessels after autofrettage is only 12100 cycles, which is significantly lower than the design requirement of 37540 cycles. This demonstrates that current autofrettage processes fail to ensure processing safety and adequate fatigue life. To resolve this, an improved method imposing axial constraint to reduce stress and enhance liner axial capacity was proposed, and its feasibility was validated through numerical simulations. By enhancing axial load-bearing capacity, this approach expands the autofrettage pressure range, introducing higher residual stress that extends fatigue life to meet design requirements.

Rupture disk is an important safety relief device whose bursting at set pressure is essential to protect pressure equipment. However, the existing standards and research still lack the system regularity study of the pressure rise rate on the burst pressure. And the range of the pressure rise rate is not sufficient. In this paper, a test platform with an adjustable pressure rise rate is developed, which can achieve 0-950 MPa/s pressure rise rate load. A series study of conventional domed rupture disk is conducted based on this platform. The results show that the burst pressure error is up to 44.69% with increasing pressure rise rate, significantly affecting the burst pressure. The change of burst pressure is generally an increasing trend. It is divided into three stages, showing a trend of first fast, then slow and finally fast. The reasons for the failure of the regularity of the rupture disk under different pressure rise rates are revealed from the three aspects of burst pressure, deformation behavior, and fracture morphology.

This work proposed a technique reference on the determination of autofrettage pressure for ultra-high pressure valve. The detailed numerical autofrettage process for a valve body with 340 MPa design pressure was established, where material's Bauschinger effect was considered by a Chaboche kinematic hardening model. Validating autofrettage test was conducted at 600 MPa and 650 MPa hydraulic pressure. The effectiveness of autofrettage result was verified by the surface strain consistency with numerical calculation as well as the existence of plastic strain unraveled by electron backscatter diffraction (EBSD) characterization.

This paper focused on experimental research on the bursting pressure of steam generator (SG) tubes with typical uniform thinning defects. Bursting tests of Inconel-690 SG tubes with uniform thinning defects were carried out at 350 °C, and the regularity of the test results was analyzed. Based on the results, the prediction formula for the bursting pressure of the defective SG tubes was regressed using the least square method. Results show that the depth of the defects in the tubes is the main factor affecting the bursting pressure of SG tubes. The bursting pressure is negatively correlated with the depth of the defects. The defect length is a secondary factor, and its influence gradually weakens as the defect length increases. This paper provides a data set of the bursting pressure of the Inconel-690 SG tubes with uniform defects at 350 °C, which can serve as support for related research.

Hoop-wrapped vessels with metal liners (Type II vessels) are susceptible to the risks of brittle fracture and fatigue failure in high-pressure hydrogen environments. However, there is limited research concerning fitness-for-service (FFS) assessments of Type II vessels. An FFS assessment was conducted on a specific Type II vessel designed for high-pressure hydrogen storage. The mechanical properties of the liner material 4130X were obtained through in situ mechanical testing in a hydrogen environment. Based on the measured data, the stress distribution within the Type II vessel under different working conditions was determined using a finite element analysis by ANSYS Workbench 2019 R2 software. A leak-before-burst (LBB) analysis and a brittle fracture assessment of the Type II vessel were performed using the failure assessment diagram (FAD) methodology. The results indicate that the measured fracture toughness of 4130X under high-pressure hydrogen is 46 MPa·m0.5, which is significantly lower than the 178 MPa·m0.5 required for LBB failure for the studied vessel. However, the vessel remains in a safe state when the crack depth is under 3.03 mm. Furthermore, the remaining fatigue life of a Type II vessel containing a crack was calculated. The relationship between the non-destructive testing (NDT) capability requirement and the inspection interval for this type of vessel was explored, providing references for establishing inspection schedules for Type II vessels.

This paper compares the difference and accuracy of bursting pressure prediction based on the flow stress sigma(f) prediction method, plastic collapse prediction method, and ductile damage model prediction method in Inconel 690 steam generator tube (SGT) with volume defect. The tensile and smooth tube bursting tests determine the parameters required for the three prediction methods. The three methods predict the bursting pressures for four deep volume defects in SGT. The results are compared and analyzed with the experimental data. The results show that the ductile damage model prediction method is the best to predict the SGT bursting pressure error with volume defects simulating the structure's deformation and damage failure process.

As a safety relief device for pressure vessel, bursting disc is widely used in various pressure equipment for its simple structure, strong airtightness, large emission capacity, wide adaptability, sensitive overpressure response and other characteristics, which plays an important role in ensuring the safety of pressure equipment in complex environment. With the development of society and economy, pressure vessel is developed towards the direction of extreme and lightweight. In this paper, a semi-empirical formula for calculating the bursting pressure of ultra-high pressure bursting disc design is presented. The non-uniform thinning of the wall thickness after pre-arch deformation of ultra-high pressure bursting disc is measured. The theoretical calculation formula of nonuniform thinning wall thickness after deformation of bursting disc is established based on the hypothesis that the bursting disc is spherical after deformation. In order further simplify the calculation formula and process of semi-empirical formula, test data of different materials, bursting pressure and deflection height are selected to establish the correlation between the deflection height of bursting disc and the strain hardening index of material. The semi-empirical formulations of the designed blasting pressure are simplified, and the numerical simulation and experimental verification of the blasting pressure of the bursting disc are carried out by using experimental method to verify the accuracy of the calculation results of the semi-empirical formula and simplified formula of the designed blasting pressure.

2.25Cr-1Mo-0.25 V steel has been widely used to manufacture hydro-processing equipment operating under harsh environments for its good creep performance. Warm bending, a common fabricating process of 2.25Cr-1Mo-0.25 V steel ring shells, inevitably changes the creep property of 2.25Cr-1Mo-0.25 V steel, but its detailed effect still remains obscure. In this work, we experimentally investigated the impact of warm bending on the microstructure and creep behavior of 2.25Cr-1Mo-0.25 V steel. First, a series of creep rupture tests were carried out at 482 °C and 350 MPa, in which test materials were extracted from an actually fabricated ring shell and its raw plate. Thereafter, the microstructures of test materials were semi-quantitatively analyzed by various characterization techniques, such as electron backscatter diffraction (EBSD) and three-dimensional high-resolution X-ray computed tomography (3D μ-XCT). Finally, warm forming induced microstructural degradation as well as their implication for creep was discussed in detail. Creep rupture tests showed that warm bending leads to a significant decrease in creep lifetime at the surface region of virgin plate but a slight decline at the central region of virgin plate. An inhomogeneous creep resistance distribution was thereby revealed along the thickness direction of the ring shell, which could not be completely eliminated by subsequent tempering at 705 °C for 8 h. Moreover, microstructural observations demonstrated that warm deformation leads to multiple microstructural deterioration, including carbide coarsening, ferrite matrix softening, void defect increasing, etc. Their combined action appears to accelerate the creep fracture behavior of 2.25Cr-1Mo-0.25 V steel. This work will contribute to the long-term safety and integrity assessment of 2.25Cr-1Mo-0.25 V steel structures.

为掌握玻璃纤维/环氧乙烯基酯树脂复合材料经湿热老化后的力学性能,采用真空辅助注射成型技术,制作玻璃纤维/环氧乙烯基酯树脂复合材料层合板,并根据复合材料压力容器在服役过程中的受力特点,利用水切割技术将层合板制成弯曲和剪切试样.考虑到压力容器的使用工况,对试样进行浸泡加速老化试验,分析了在不同温度和周期下复合材料的质量和力学性能变化.结果表明,随着浸泡时间的增加,复合材料的弯曲和剪切性能逐渐降低.相比于浸泡时间的影响,温度对复合材料性能的影响更显著,如在 90℃水中浸泡 6 周后,复合材料的剪切强度、弯曲强度以及弯曲模量降为初始值的 1/2.

蒸汽发生器传热管的局部微振磨损缺陷会导致其承压能力降低.研究了含不同微振磨损缺陷的Inconel 690 蒸汽发生器传热管的爆破压,采用数值模拟方法分析了微振磨损缺陷对传热管爆破压的影响规律,并进一步研究得到了含瓦片状缺陷及防振条磨损缺陷的传热管爆破压估算公式.研究表明,基于缺陷分类的爆破压预测结果更为精确,且所建立的降质传热管爆破压估算公式是合理且保守的.

In this paper, a minimum toughness assessment method of exempting postweld heat treatment (PWHT) based on the master curve method is proposed to replace the current method of determining whether to perform PWHT by material thickness. Reference temperature to prevent fracture (T0-required) for structure to be exempt from PWHT at minimum design metal temperature (MDMT) was obtained by using the master curve method under presumed stresses and flaw size. A series of exemption curves were generated for the steels used in pressure vessels with yield strength of 300 similar to 550 MPa, and the method was corrected for low-stress conditions. Then the feasibility of this method was verified by an engineering example. A SA-738Gr.B welded joint in the example was taken as the research object, the experiment showed that the weld metal was the worst part of the fracture toughness of the joint. The results of research objects which were exempted from PWHT by the proposed method are consistent with ASME Code Case N-841, which proves that this method is feasible in assessing the exemption from PWHT.

This work presents a novel strategy to model the coexistence of HELP & HEDE mechanisms. The proposed method accounts for ductile and brittle damage with a competitive fracture criterion to describe the competition effect between HELP & HEDE mechanisms. The cooperation aspect is addressed by a dislocation-enhanced hydrogen accumulation model, which agrees with the HELP-mediated HEDE mechanism. The tensile, fracture toughness, and threshold stress intensity factor tests are simulated in different hydrogen environments. The results demonstrate that the proposed method reproduces the hydrogen-dependent ductile to brittle transition phenomenon. Under different hydrogen conditions, the dominating damage mechanism and degradation trends agree with experimental observations. Furthermore, for the investigated 4130 steel, the predicted value of fracture toughness and threshold stress intensity factor match the experiment results. The difference in damage kinetics inherent in the two test methods is captured, which supports the rationality of the proposed strategy for HELP and HEDE interaction.

The fast progress in artificial intelligence has increased the need for wearable electronics. Herein, a piezoresistive pressure sensor consisting of three layers has been proposed. The soft sensing film has been fabricated by filling PDMS (polydimethylsiloxane) with Ag-graphene by a simple mixing method, which possesses low cost and excellent sensing properties, including high sensitivity, high conductivity, and quick response to different pressures. Furthermore, the characterizations were performed by using a scanning electron microscope to study the microstructure and surface morphologies of the Ag-graphene-PDMS film to explore its internal working mechanism. Moreover, the single sensor and sensor array were tested for many applications. The results showed that the fabricated pressure sensor effectively identified various human movements and distinguished pressures with different values and positions. As a result, this sensor has a wide range of applications, including smart wearable technologies and soft robotics.

文章在回顾过程装备与控制工程专业发展历程的基础上，辨析了新经济形势下该专业存在的问题，并提出“四位一体”的专业升级模式及具体举措。该模式的实施，有助于提高学生的工程实践能力、创新能力及跨界整合能力，同时有助于提升本专业的影响力。

In this work, a practical numerical model with few parameters was proposed for the prediction of environmental hydrogen embrittlement. The proposed method adopts hydrogen enhanced plasticity-based mechanism in a fracture strain model to describe hydrogen embrittlement. Fracture toughness degradation of three commercial steels SA372J70, AISI4130 and X80 in high pressure hydrogen environment were investigated. Firstly, governing equations for hydrogen distribution and material damage evolution was established. Hydrogen enhanced localized flow softening effect was coupled within fracture strain dependency on stress triaxiality. Then, the numerical implementation and identification process of model parameters was described. Model parameters of the investigated steels were determined based on experiment results from literatures. Finally, with the calibrated model, fracture toughness reduction of the steels was predicted in a wide range of hydrogen pressure. The prediction results were compared with experimental results. Reasonable accuracy was reached. The proposed method is an attempt to reach balance between physical accurate prediction and engineering practicality. It is promising to provide a simplified numerical tool for the design and fit for service evaluation of hydrogen storage vessels.

With the fast development of electronic skin, there is a great demand for wearable sensing devices. Herein, a piezoresistive sensor has been fabricated comprising a conductive film of Polydimethylsiloxane (PDMS)-carbon nanotubes (CNTs) sandwiched by two protection films of PDMS. A simple and low-cost manufacturing method has been proposed to wrap CNTs inside the flexible PDMS to obtain a soft sensor with excellent conductivity, high sensitivity, and fast response to various pressures. Additionally, films with different percentages of CNTs were compared. The results show that the film with 7% CNTs has higher conductivity and sensitivity. Moreover, the surface morphologies and microstructures of the superior PDMS-CNTs film were studied by scanning electron microscope, and sensing properties of the pressure sensor were tested. Furthermore, applications of single sensor and sensor array were studied. The results exhibit that the as-prepared pressure sensor successfully detected different human motions and recognized Morse code and words, indicating that the portable sensor can be potentially applied in wide areas such as smart devices and flexible robotics.

目前对于采用金属内胆纤维环向缠绕的气瓶疲劳寿命影响因素研究多集中于气瓶的结构参数和工艺参数,对初始存在裂纹的探究较少.对某工作压力30 MPa的金属内胆碳纤维环向缠绕储氢气瓶进行研究,采用基于断裂力学的疲劳裂纹扩展法,结合有限元分析,对其临界疲劳循环次数进行计算,探究不同自紧压力,以及相同自紧压力下不同初始裂纹深度对金属内胆纤维环向缠绕储氢气瓶临界疲劳循环次数的影响.结果表明:(1)气瓶的临界疲劳循环次数随自紧压力的增大而增大;(2)随初始裂纹深度的减小而增加,且深度越小,临界疲劳循环次数增量越大.

为研究GB/T 34019标准与ASMEⅧ-3标准在计算压力容器临界裂纹扩展寿命时的差异,采用ANSYS软件建立不同设计压力和直径的4130X钢制瓶式容器,并利用自编的MATLAB疲劳计算程序计算临界裂纹循环次数,考察了应力强度因子和疲劳失效判据对容器设计疲劳寿命评价的影响.分析结果表明,在容器设计压力40～90 MPa、公称直径406～720 mm的研究范围内,对于指定的内壁轴向裂纹,GB/T 34019方法计算得到的应力强度因子值比ASMEⅧ-3大,但由于GB/T 34019采用的断裂韧度判据比ASMEⅧ-3失效评定图法(FAD)的双参量判据更宽松,导致GB/T 34019计算得到的疲劳寿命更长.因此认为,采用ASMEⅧ-3的应力强度因子解和双参量判据进行疲劳裂纹扩展分析相对保守.

In order to prevent the brittle fracture accident, minimum design metal temperature of ferrite steel should be limited. After the minimum design metal temperature curve in American Society of Mechanical Engineers VIII-2 (2007) was proposed, much related research has been done in recent years. In this paper, firstly the theoretical basis of four methods used to determine the minimum design metal temperature was introduced. Secondly, the mechanical properties of Q345R was measured by tensile test, Charpy v-notch impact test and fracture toughness test Thirdly, minimum design metal temperature curve of Q345R that determined by four methods were obtained. There are obvious difference between the curves of Q345R that determined by four methods. It can be concluded that low temperature fracture toughness of Q345R is underestimated when classifying Q345R into exemption curve A in American Society of Mechanical Engineers VIII-2 (2007).