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 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.

To address the difficulty in accurately monitoring and predicting the prestress loss of long‑distance prestressing strands in large‑scale structures due to duct friction，anchor deformation，and stress relaxation，a comprehensive prediction method integrating fiber optic sensing measurement data and machine learning is proposed，based on a liquefied natural gas storage tank project.This method uses fiber optic sensing technology to conduct long‑term monitoring of long‑distance prestressing strands in actual engineering，obtaining prestress loss data.Based on the measured data，a numerical simulation dataset of long‑term prestress loss is established.Multiple machine learning algorithms are used to construct prediction models，and the SHAP interpretability algorithm is further introduced to analyze the prediction basis and key influencing factors of the models.Experimental and simulation results show that the total losses of the circumferential and vertical prestressing strands of the storage tank are approximately 390 MPa and 320 MPa，respectively.The average percentage errors of the six established machine learning models in both the training set and the test set are below 3.5%，among which the XGBoost model has the smallest error，achieving 1.19% on the test set.Through SHAP analysis of multiple influencing factors，the length of the prestressing strand has the most significant effect on long‑term loss，followed by the elastic modulus of concrete，the elastic modulus of the prestressing strand，and the tensioning control stress.The research shows that machine learning models can accurately predict prestress loss and analyze the important factors causing prestress loss.This study is of great significance for the accurate evaluation of the service performance of prestressed structures.

Rectangular tangential nozzles are often used as special process interfaces in petrochemical equipment（such as multiphase flow cyclone separators），but their structural strength design has not been clearly specified in design codes such as GB/T 150.The finite element limit load analysis method was used to calculate the pressure‑bearing capacity of cylindrical shells with rectangular tangential nozzles，and the weakening effects of rectangular tangential nozzles with different dimensionless structural parameters（width‑to‑diameter ratio W/D_i，diameter‑to‑thickness ratio D_i/T，and thickness ratio t/T） on the strength of the cylindrical shell were investigated.It was found that the cylindrical shell with a square tangential nozzle having a side length ratio of 1 has the maximum pressure‑bearing capacity.Therefore，a limit load reduction factor reflecting the strength reduction of the cylindrical shell due to the provision of a square tangential nozzle was defined.The influences of the three dimensionless structural parameters W/D_i，D_i/T，and t/T were studied，and regression analysis was performed on the limit load reduction factor based on a large number of numerical calculations.This is helpful for the strength design or safety assessment of cylindrical shells with square tangential nozzles.It was also found that for the same opening area，the pressure‑bearing capacity of the cylindrical shell structure with a square tangential nozzle is significantly lower than that with a circular tangential nozzle.In other words，the strength weakening effect of a square tangential nozzle on the cylindrical shell is significantly greater than that of a circular tangential nozzle.Therefore，from a strength perspective，using a circular tangential nozzle is more reasonable than using a square tangential nozzle.

A 2507 duplex steel （S25073） U‑shaped tube reboiler in a chemical plant experienced a leakage during operation.After disassembly，it was discovered that the U‑shaped bend exhibited severe corrosion and perforation，resulting in the failure of the reboiler.To address the above issues，various methods such as macroscopic inspection，microscopic morphology analysis，chemical composition analysis，metallographic analysis，mechanical property analysis，residual stress analysis，and heat exchange vibration analysis were employed to investigate the causes of failure.The results show that inadequate circulation of the liquid phase material at the U‑shaped bend causes the corrosive medium to evaporate and concentrate，thereby increasing the risk of corrosion.Meanwhile，residual stress in the U‑shaped bend region reaches up to 231 MPa.Under the combined effect of these two factors，the heat exchange tube corrodes and failes at the U‑shaped bend.The straight pipe section do not experience significant corrosion because the concentration effect of the liquid phase material is not obvious and the residual stress is low，ensuring that the corrosion resistance still met the requirements.Based on the analysis of the failure causes，suggestions for improving the selection of the reboiler under this operating condition are proposed.After the actual operation under the working conditions，it has been verified that the reboiler with the improved selection performes well under the same conditions.This case shows that in the design of heat exchange with corrosion tendency，apart from the conventional calculation of heat transfer，vibration analysis and strength calculation，the corrosion problem caused by local concentration should be paid more attention.

To overcome the problems of strong magnetic force interference，low transduction efficiency，and poor detection performance existing in current electromagnetic acoustic surface wave transducers when detecting structural defects in ferromagnetic metals，a novel electromagnetic acoustic surface wave transducer based on a U‑type pulsed electromagnet with high conversion efficiency and strong adaptability，as well as a corresponding detection method，were designed and developed.Finite element numerical simulation was used to optimize the transducer configuration and verify the feasibility of the detection method.A pulsed electromagnet‑type electromagnetic acoustic testing system was established.The effects of pulse number，excitation voltage，and defect size on the transducer performance were analyzed，and the performance differences between this transducer and existing electromagnetic acoustic transducers were compared.The results show that the pulsed electromagnet‑type transducer has significantly better near‑surface defect detection capability in DH36 low‑alloy carbon steel compared to existing electromagnetic acoustic transducers.This study provides a new method for addressing near‑surface defects in ferromagnetic metals.