In response to the significant risks associated with hydrogen storage cylinders under extreme fire conditions，this study adopts a method combining fire accident analysis with fire test data to systematically evaluate key parameters such as the burst pressure of hydrogen storage tanks.The results show that the pressure‑bearing capacity of hydrogen storage tanks decreases significantly under fire exposure：For a tank with a nominal working pressure（NWP） of 35 MPa，the burst pressure drops from 122.7~126.0 MPa at room temperature to 41.1~53.5 MPa；For a 70 MPa NWP tank，it drops from 209.8~226.8 MPa at room temperature to 98.9~112.3 MPa.The time from fire exposure to tank explosion ranges from 9 to 22 min.When the pressure relief setting of the tank is close to its burst pressure，the damage tolerance is low，resulting in a high risk of explosion under fire conditions.After fire exposure and subsequent cooling，the tanks still exhibit relatively high residual strength，approximately 2.09~3.37 times the NWP.It is recommended that，with the objective of “pressure release first”，the safety threshold for tank burst strength under fire conditions be further refined，and that standardized testing methods for post‑fire residual strength be established.This study provides a technical basis for the comprehensive safety assessment of hydrogen storage tanks in fire scenarios.

Creep is a major damage mechanism for high‑temperature components in nuclear power plants，and the temperature‑ and time‑dependent stress intensity limit S_t is an important material parameter for creep assessment.In the ASME Code，safety factors are directly applied to the three criteria for determining the stress intensity limit S_t，but the implied failure probability and conservatism of this method have rarely been reported.To quantify the failure probability of S_t，functional expressions for the failure probability corresponding to each criterion were derived in this study based on creep data of Alloy 617，combined with the relationship between each S_tcriterion and the average creep rupture life equation.The failure probabilities of the three criteria for S_t of Alloy 617 were calculated，and the effects of safety factors（1.0，1.25，1.5） on the failure probabilities were discussed.The results show that the stress intensity limit S_t of Alloy 617 exhibits a relatively low failure probability（at 750 ℃，10⁻⁹~10⁻⁵；at 850 ℃，10^-8~10^-5；at 950 ℃，10^-8~10^-4），indicating a high level of conservatism.The minimum stress for the onset of tertiary creep criterion and the minimum creep rupture stress criterion play a controlling role in S_t，depending on the stress level.The findings can provide a theoretical basis for the probabilistic evaluation of material parameters related to high‑temperature strength assessment.

To address the leakage risk in the double‑cone seal structure of high‑pressure vessels and the difficulty of directly measuring the gasket contact pressure，an indirect contact pressure monitoring method based on bolt load measurement is proposed.A mechanical model of the double‑cone seal structure is established，and a linear mapping relationship between the bolt load and the average gasket contact pressure is derived.Based on plate and shell bending theory，the deflection angle of the flat cover is introduced to develop an analytical calculation method for the contact pressure that accounts for non‑uniform radial distribution.A leakage simulation test bench for the double‑cone seal is constructed，where washer‑type sensors and pressure‑sensitive paper are used to obtain the bolt load and contact pressure，respectively，and the proposed method is verified through finite element simulations.Experimental and simulation results show that within the internal pressure range of 0~4 MPa，the error between the analytically calculated average contact pressure and the measured values is less than 16%；in the simulation under a high‑pressure condition of 15 MPa，the error is only 0.8%~2.6%.The radial distribution of the gasket contact pressure exhibits a pattern of “high at both ends and low in the middle”，and the theoretically calculated distribution is in strong agreement with the results obtained from pressure‑sensitive paper measurements and simulations.This method enables accurate inversion of the gasket contact pressure state by monitoring the bolt load，confirming the validity of the model and providing an effective technical approach for the safety monitoring of double‑cone seal structures.

To meet the lightweight requirements of deep‑sea vehicles and address the issues of high residual stress and poor reliability associated with traditional welded internal ribbed heads，a new configuration of spiral‑ribbed ellipsoidal head suitable for integrated manufacturing is proposed.Through axial compression tests and finite element simulations，the compressive and buckling performance of four types of 6061-T6 aluminum alloy heads，namely without ribs，with transverse ribs，with longitudinal ribs，and with spiral ribs，was systematically compared.The overall formability was verified by spinning simulation and trial production.The results show that the structure with longitudinal internal ribs exhibits the best mechanical performance，with its ultimate compressive strength and critical buckling pressure increased by 8.7% and 5%，respectively，compared to the structure without ribs.The structure with spiral internal ribs，while maintaining good mechanical performance，can achieve overall forming with non‑deformed internal ribs and high filling quality by means of the spinning process.In contrast，structures with transverse internal ribs and longitudinal internal ribs are prone to forming defects.The structure with longitudinal internal ribs has the most outstanding load‑bearing capacity，while the structure with spiral internal ribs has a significant advantage in integrated forming，balancing mechanical performance and forming feasibility.This study provides new ideas for high‑performance design and integrated manufacturing of pressure components for deep‑sea equipment.

To implement GB/T 4732.3—2024 Pressure vessels design by analysis-Part 3：Formulae method，this paper systematically elaborates on the development practice and key considerations of the fixed tubesheet heat exchanger module in the SW7 software.The research focuses on several issues not mandated by the standard but of significant engineering significance，and conducts theoretical modeling，formula derivation，and functional expansion.The main contents include：Expanding the mechanical models to include the tubesheet embedded welding structure and the flat cover with a central nozzle opening，enhancing the engineering applicability of the software；Incorporating the effects of thermal bending deformation caused by temperature differences across the tubesheet thickness and the differential thermal expansion between the tubesheet and flange materials，achieving refined analysis of thermal loads；Based on the deformation coordination relationship of the flange-bolt-gasket system，proposing a method for determining a single bolt preload load that meets sealing requirements under multiple operating conditions；Innovatively proposing a nonlinear analysis theory for the variable‑stiffness elastic foundation plate，revealing the coupling mechanism by which tubesheet bending leads to a reduction in the axial stiffness of peripheral heat exchange tubes；Improving the stress evaluation system for key components such as the channel shell and shell‑side shell ends，and the flat cover，while clarifying the priority conditions for stability checks of heat exchange tubes and the criteria for selecting strength theories under biaxial stress states.SW7 software is not only a programmatic implementation of the new analysis and design standard，but also a beneficial supplement and engineering extension to the standard content.The release of its trial version is expected to promote the advancement of industry technical level.

To address the lack of high‑temperature irradiation performance data for the austenitic stainless steel 316H，the material used for the reactor pressure vessel of a fourth‑generation high‑temperature gas‑cooled microreactor，at the design operating temperature of 550 ℃，a research plan involving irradiation damage tests and aging tests was proposed.The SRIM software was used to simulate the trajectories and irradiation damage defects of energetic ions （He²⁺） incident on the material.Combined with high‑temperature irradiation tests under different cumulative irradiation doses （0.005，0.05，0.5 dpa） and an irradiation aging test at 650 ℃ for 100 h，the evolution laws of the material's high‑temperature damage behavior and aging behavior with microstructure were established.The results show that at the design temperature of 550 ℃，316H exhibits good irradiation resistance.The irradiation damage layer is approximately several micrometers thick，and the damage mainly manifests as microvoids and dislocations.After aging at 650 ℃ for 100 h，carbides precipitate along grain boundaries，with C and Mo elements enriching at the grain boundaries and Cr element depleting near the grain boundaries，presenting a certain risk of failure.This study provides a reference for subsequent engineering implementation of in‑reactor irradiation tests.

This study focuses on the application of expansion technology to rupture disc safety relief devices for high‑pressure hydrogen storage vessels，using ultra‑high purity （UHP） AISI 316L austenitic stainless steel.Internal inclusions act as hydrogen traps and corrosion initiation sites，directly influencing the material's susceptibility to hydrogen embrittlement as well as the triggering accuracy and reliability of the rupture disc.Currently，the industry lacks a systematic evaluation and comparison of cleanliness and inclusion control for such materials.In this study，a systematic quality assessment was carried out by comparing materials produced by different manufacturers using vacuum induction melting combined with vacuum arc remelting （Material A），as well as the argon‑oxygen decarburization process followed by VAR （Material B）.Innovatively，this study employed a combination of microscopic characterization techniques including metallographic microscopy，scanning electron microscopy，and energy‑dispersive X‑ray spectroscopy，coupled with thermodynamic calculations to simulate the evolution of inclusions during cooling.This approach revealed the characteristics and distribution patterns of inclusions resulting from different processes and sources.The results indicate that among the evaluated samples，Material B produced by China Factory A exhibited the best cleanliness，with both inclusion density and area fraction significantly lower than those of the other samples.This finding is in strong agreement with the thermodynamic simulation predictions，confirming the reliability of the adopted methodology.The results provide important guidance for the selection and process optimization of ultra‑high purity 316L stainless steel used in critical hydrogen‑containing rupture disc safety components，and also offer a reference framework for the quality assessment and control of similar high‑cleanliness materials.

To address issues such as dimensional deviations，ovality，and uneven wall thickness that are prone to occur during the cold rolling forming of small‑diameter thin‑walled duplex stainless steel pipes，a finite element simulation method was employed to study the influence of Pilger cold rolling process parameters （rolling speed，rotation angle，and feed amount） on the forming dimensions of S32750 duplex stainless steel pipes.The results show that when the rolling speed is 70 cycles/min，the ovality and wall thickness unevenness of the pipe are significantly better than those at the other three speeds；among the four rotation angles，except for 60°，the other angles cause significant oval deformation in the pipe，resulting in poorer forming quality；however，at a 60° rotation angle，localized high deformation zones repeatedly appear in the sample，which may lead to uneven wall thickness；as the feed amount increases，the deviation of the pipe's forming dimensions from the target dimensions and its ovality gradually increase，and the forming quality decreases accordingly.Therefore，it is recommended that the combination of 70 cycles/min rolling speed，60° rotation angle，and 2 mm feed amount be adopted as the optimal process parameters.Through influence weight analysis，it was found that the feed amount has a greater impact on the ovality and outer diameter deviation of the pipe during cold rolling forming，while the rolling speed has a more significant influence on the wall thickness unevenness.The study provides theoretical guidance for the rolling production of small‑diameter thin‑walled duplex stainless steel pipes.

To investigate the applicability of gas metal arc welding （GMAW） in high‑temperature molten salt storage tank engineering，two welding process tests，with and without pulse application，were conducted on 347H stainless steel.The microstructure of the welded joints was observed using optical microscopy and scanning electron microscopy，and their mechanical properties were evaluated.The results show that the welded joint without pulse application exhibited slag inclusion defects，while the welded joint with pulse application showed no slag inclusion，porosity，or other defects；the weld microstructure mainly consisted of columnar and dendritic austenite and precipitated phases.In contrast，the welded joint with pulse application exhibited high‑temperature tensile properties at 565 ℃ （R_m≥139 MPa，R_p0.2≥360 MPa） and low‑temperature impact properties at -196 ℃ （≥31 J） that met the requirements of GB/T 150—2024 and related manufacturing engineering technical specifications.This study provides theoretical and experimental support for the reliable application and quality assurance of GMAW welding technology in the manufacturing field of stainless steel pressure vessels.

In view of the tendency in the analysis and design of heat exchanger tube sheets to overemphasize technical means while neglecting engineering factors，this paper，based on previous research results combined with three failure cases and relevant engineering experience，identifies the issues worthy of attention in modeling，including non‑pressure‑bearing structural members and the distortion of actual operating conditions.In some cases，the absence of baffles，tie rods，spacer tubes and partition plates in the tube bundle model will lead to analysis results inconsistent with engineering practice.In the analysis and discussion of the cases，analytical models improved to varying degrees are proposed.The synergistic complementarity of finite element secondary analysis technology，conventional design technology and engineering auxiliary technology to the analysis and design technology is a better handling countermeasure.Through the discussion of 7 points of understanding across 3 topics—including the content and integrity of analysis and design，the concept and verification of the analytical model，and the objective resources and subjective awareness of analysis and design—the necessity of adopting the dual criteria of stress and displacement in the analysis and design of tube bundles is put forward.It is suggested that in analysis and design，the cultivation of engineering literacy and the conscious improvement of individual skills should be strengthened.