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Emerging challenges to structural integrity technology for high-temperature applications

TU Shantung

《机械工程前沿(英文)》 2007年 第2卷 第4期   页码 375-387 doi: 10.1007/s11465-007-0066-y

摘要: Structural integrity technology has been widely used with great success for the design, manufacture and failure prevention of modern constructions such as chemical and petrochemical plants, power generation and energy conversion systems, as well as space and oceanic exploration. The modern needs of structural integrity technology are largely attributed to the increase of service temperature of the structures that results in the efficiency improvement in energy conversion and chemical processing technologies. Besides the needs arising from large-scale high-temperature plants, the high tech developments, such as micro chemo-mechanical systems and high-power electronics, provide new challenges to structural integrity technology. The present paper summarizes the recent technical progresses in large process plants and the aviation industry, micro chemo-mechanical systems, fuel cells, high-temperature electronics, and packaging and coating technologies. The state-of-the-art of structural integrity technology for high temperature applications is reviewed. Suggestions are provided for the improvement of current design and assessment methods.

关键词: manufacture     aviation industry     conversion     petrochemical     temperature    

Phase separation time/temperature dependence of thermoplastics-modified thermosetting systems

ZHANG Xiujuan, XU Yuanze, YI Xiaosu

《化学科学与工程前沿(英文)》 2008年 第2卷 第3期   页码 276-285 doi: 10.1007/s11705-008-0057-5

摘要: The cure-induced phase separation processes of various thermoplastics(TP)-modified thermosetting systems which show upper critical solution temperature (UCST) or lower critical solution temperature (LCST) were studied with emphasis on the temperature dependency of the phase separation time and its potential application in the cure time-temperature processing window. We found that the phase separation time/temperature relationship follows the simple Arrhenius equation. The cure-induced phase separation activation energy (ps) generated from the linear fitting of the Arrhenius equation is irrelevant to the detection means of phase separation time. We also found that (ps) is insensitive to TP content, TP molecular weight and curing rate, but it changes with the cure reaction kinetics and the chemical environment of the systems. With the established phase separation time-temperature dependence relation, we can easily establish the whole cure time-temperature transformation (TTT) diagram with morphology information which is a useful map for the TP/TS composites processing industry.

关键词: separation time-temperature     temperature dependency     cure-induced     separation activation     temperature    

Effects of temperature on pyrolysis products of oil sludge

LIU Jianguo, SONG Wei, NIE Yongfeng

《环境科学与工程前沿(英文)》 2008年 第2卷 第1期   页码 8-14 doi: 10.1007/s11783-008-0030-z

摘要: Temperature is the determining factor of pyrolysis, which is one of the alternative technologies for oil sludge treatment. The effects of final operating temperature ranging from 350 to 550°C on pyrolysis products of oil sludge were studied in an externally-heating fixed bed reactor. With an increase of temperature, the mass fraction of solid residues, liquids, and gases in the final product is 67.00%–56.00%, 25.60%–32.35%, and 7.40%–11.65%, and their corresponding heat values are 34.4–13.8 MJ/kg, 44.41–46.6 MJ/kg, and 23.94–48.23 MJ/Nm, respectively. The mass and energy tend to shift from solid to liquid and gas phase (especially to liquid phase) during the process, and the optimum temperature for oil sludge pyrolysis is 500°C. The liquid phase is mainly composed of alkane and alkene (C–C), and the gas phase is dominantly HC and H.

关键词: sludge treatment     corresponding     Temperature     liquid     process    

Field test on temperature field and thermal stress for prestressed concrete box-girder bridge

Baoguo CHEN, Rui DING, Junjie ZHENG, Shibiao ZHANG

《结构与土木工程前沿(英文)》 2009年 第3卷 第2期   页码 158-164 doi: 10.1007/s11709-009-0002-9

摘要: A field test was conducted to investigate the distribution of temperature field and the variation of thermal stress for a prestressed concrete (PC) box-girder bridge. The change of hydration heat temperature consists of four periods: temperature rising period, constant temperature period, rapid temperature fall period and slow temperature fall period. The peak value of hydration heat temperature increases with the increasing casting temperature of concrete; the relation between them is approximately linear. According to field tests, the thermal stress incurred by hydration heat may induce temperature cracks on the PC box-girder. Furthermore, the nonlinear distribution of temperature gradient and the fluctuation of thermal stress induced by exposure to sunlight were also obtained based on continuous in-situ monitoring. Such results show that the prevailing Chinese Code (2004) is insufficient since it does not take into account the temperature gradient of the bottom slab. Finally, some preventive measures against temperature cracks were proposed based on related studies. The conclusions can provide valuable reference for the design and construction of PC box-girder bridges.

关键词: box-girder bridge     field test     hydration heat     temperature field     temperature gradient     thermal stress    

Elevated temperature creep model of parallel wire strands

《结构与土木工程前沿(英文)》 2023年 第17卷 第7期   页码 1060-1071 doi: 10.1007/s11709-023-0981-y

摘要: Parallel wire strands (PWSs), which are widely used in prestressed steel structures, are typically in high-stress states. Under fire conditions, significant creep effects occur, reducing the prestress and influencing the mechanical behavior of PWSs. As there is no existing approach to analyze their creep behavior, this study experimentally investigated the elevated temperature creep model of PWSs. A charge-coupled camera system was incorporated to accurately obtain the deformation of the specimen during the elevated temperature creep test. It was concluded that the temperature level had a more significant effect on the creep strain than the stress level, and 450 °C was the key segment point where the creep rate varied significantly. By comparing the elevated temperature creep test results for PWSs and steel strands, it was found that the creep strain of PWSs was lower than that of steel strands at the same temperature and stress levels. The parameters in the general empirical formula, the Bailey–Norton model, and the composite time-hardening model were fitted based on the experimental results. By evaluating the accuracy and form of the models, the composite time-hardening model, which can simultaneously consider temperature, stress, and time, is recommended for use in the fire-resistance design of pre-tensioned structures with PWSs.

关键词: parallel wire strands     experimental study     elevated temperature creep model    

A review of low-temperature plasma-assisted machining: from mechanism to application

《机械工程前沿(英文)》 2023年 第18卷 第1期 doi: 10.1007/s11465-022-0734-y

摘要: Materials with high hardness, strength or plasticity have been widely used in the fields of aviation, aerospace, and military, among others. However, the poor machinability of these materials leads to large cutting forces, high cutting temperatures, serious tool wear, and chip adhesion, which affect machining quality. Low-temperature plasma contains a variety of active particles and can effectively adjust material properties, including hardness, strength, ductility, and wettability, significantly improving material machinability. In this paper, we first discuss the mechanisms and applications of low-temperature plasma-assisted machining. After introducing the characteristics, classifications, and action mechanisms of the low-temperature plasma, we describe the effects of the low-temperature plasma on different machining processes of various difficult-to-cut materials. The low-temperature plasma can be classified as hot plasma and cold plasma according to the different equilibrium states. Hot plasma improves material machinability via the thermal softening effect induced by the high temperature, whereas the main mechanisms of the cold plasma can be summarized as chemical reactions to reduce material hardness, the hydrophilization effect to improve surface wettability, and the Rehbinder effect to promote fracture. In addition, hybrid machining methods combining the merits of the low-temperature plasma and other energy fields like ultrasonic vibration, liquid nitrogen, and minimum quantity lubrication are also described and analyzed. Finally, the promising development trends of low-temperature plasma-assisted machining are presented, which include more precise control of the heat-affected zone in hot plasma-assisted machining, cold plasma-assisted polishing of metal materials, and further investigations on the reaction mechanisms between the cold plasma and other materials.

关键词: low-temperature plasma     difficult-to-cut material     machinability     hydrophilization effect     Rehbinder effect    

Real-time tool condition monitoring method based on temperature measurement and artificial neural network

《机械工程前沿(英文)》 doi: 10.1007/s11465-021-0661-3

摘要: Tool failures in machining processes often cause severe damages of workpieces and lead to large quantities of loss, making tool condition monitoring an important, urgent issue. However, problems such as practicability still remain in actual machining. Here, a real-time tool condition monitoring method integrated in an in situ fiber optic temperature measuring apparatus is proposed. A thermal simulation is conducted to investigate how the fluctuating cutting heats affect the measuring temperatures, and an intermittent cutting experiment is carried out, verifying that the apparatus can capture the rapid but slight temperature undulations. Fourier transform is carried out. The spectrum features are then selected and input into the artificial neural network for classification, and a caution is given if the tool is worn. A learning rate adaption algorithm is introduced, greatly reducing the dependence on initial parameters, making training convenient and flexible. The accuracy stays 90% and higher in variable argument processes. Furthermore, an application program with a graphical user interface is constructed to present real-time results, confirming the practicality.

关键词: tool condition monitoring     cutting temperature     neural network     learning rate adaption    

Effects of pressure and temperature on fixed-site carrier membrane for CO 2 separation from natural gas

Meng WANG, Dongxiao YANG, Zhi WANG, Jixiao WANG, Shichang WANG,

《化学科学与工程前沿(英文)》 2010年 第4卷 第2期   页码 127-132 doi: 10.1007/s11705-009-0231-4

摘要: In this paper, the effect of testing temperature on the performance of fixed carrier membrane for CO separation were studied. The blend composite membranes were developed respectively with a blend of PEI-PVA (polyetheleneimine-polyvinyl alcohol) as separation layer and PS (polysulfone) ultrafiltration membranes as the substrates. The permselectivity of the membranes was measured with CO/CH mixed gas. The effect of testing temperature on membrane separation performance was investigated. The results showed that both the permeances of CO and CH decreased with the increase of temperature, and the permeances decreased more quickly under low pressure than those under high pressure. At the feed pressure of 0.11MPa, the CO/ CH selectivity of PEI-PVA/PS blend composite membrane reduced along with temperature increment. Under the feed pressure of 0.21MPa, as well as 1.11MPa, the selectivity decreased with the increase of temperature.

关键词: temperature increment     high pressure     permselectivity     separation performance     temperature    

Investigation on the performance and detoxification of modified low temperature coal tar pitch

Fengyan SUN, Yu LIU

《结构与土木工程前沿(英文)》 2017年 第11卷 第3期   页码 315-321 doi: 10.1007/s11709-017-0386-x

摘要: In this paper, studies on the modification on the low temperature coal tar pitch extracted from coal tar residue in Inner Mongolia are conducted. First, the low temperature coal tar pitch in liquid state is solidified with a higher softening point by chemical crosslinking modification. The modified coal tar pitch can achieve the standard pavement performance requirements. Then, the effects of chemical crosslinking agent and physical modification additives on the mechanical performance and toxic properties of coal tar pitch are investigated. The detoxification mechanism is also studied, which further promote the applicability of modified low temperature coal tar pitch in the pavement constructions.

关键词: coal tar pitch     low temperature     modification     detoxification    

A review on the development of electrolytes for lithium-based batteries for low temperature applications

《能源前沿(英文)》 2023年 第17卷 第1期   页码 43-71 doi: 10.1007/s11708-022-0853-5

摘要: The aerospace industry relies heavily on lithium-ion batteries in instrumentation such as satellites and land rovers. This equipment is exposed to extremely low temperatures in space or on the Martian surface. The extremely low temperatures affect the discharge characteristics of the battery and decrease its available working capacity. Various solvents, cosolvents, additives, and salts have been researched to fine tune the conductivity, solvation, and solid-electrolyte interface forming properties of the electrolytes. Several different resistive phenomena have been investigated to precisely determine the most limiting steps during charge and discharge at low temperatures. Longer mission lifespans as well as self-reliance on the chemistry are now highly desirable to allow low temperature performance rather than rely on external heating components. As Martian rovers are equipped with greater instrumentation and demands for greater energy storage rise, new materials also need to be adopted involving next generation lithium-ion chemistry to increase available capacity. With these objectives in mind, tailoring of the electrolyte with higher-capacity materials such as lithium metal and silicon anodes at low temperatures is of high priority. This review paper highlights the progression of electrolyte research for low temperature performance of lithium-ion batteries over the previous several decades.

关键词: electrolyte     lithium-ion     low temperature     aerospace     solid-electrolyte interface    

Preparation of solar selective absorbing CuO coating for medium temperature application

HUANG Qunwu, WANG Yiping, LI Jinhua

《化学科学与工程前沿(英文)》 2007年 第1卷 第3期   页码 256-260 doi: 10.1007/s11705-007-0046-0

摘要: A new method of preparing CuO solar selective absorbing coating for medium temperature is presented. After pretreatment, brass was overlaid with CuO by chemical plating. The effects of reactant concentration, reaction temperature and reaction time on the absorptivity of CuO coating were investigated. The optimized condition of preparing CuO coating was obtained. The CuO coating was analyzed with X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). In order to prolong the period of use, the CuO coating was protected by TiO. The experiment shows that the TiO/CuO coating is more heat-resistant, acid-resistant, and wear resistant than CuO coating, without losing absorptivity markedly. The TiO coating can reduce emissivity and protect the CuO coating.

关键词: photoelectron spectroscopy     temperature     pretreatment     absorptivity     microscopy    

Temperature variation of concrete box girder bridge

Jian WANG, Zhi FANG,

《结构与土木工程前沿(英文)》 2009年 第3卷 第4期   页码 407-413 doi: 10.1007/s11709-009-0053-y

摘要: On the basis of theoretical analysis and measurement on site, the temperature gradients and its variation on concrete box girder bridges resulting from ambient temperature, solar radiation, and structural temperature fields were discussed. With the help of the heat transfer theory and finite element method (FEM), the heat flux of the surface of concrete box girder was carried out, and all the heat fluxes were described as the convection. The results were compared with that from field measurements, and a good correlation was found. It was revealed that the methods, the parameters, the boundary condition used in this paper were reasonable. Last, some conclusions were obtained, which could provide the basis for box girder design under solar radiation.

关键词: temperature     transfer     correlation     radiation     variation    

Modeling the gas flow in a cyclone separator at different temperature and pressure

Gujun WAN, Guogang SUN, Cuizhi GAO, Ruiqian DONG, Ying ZHENG, Mingxian SHI

《化学科学与工程前沿(英文)》 2010年 第4卷 第4期   页码 498-505 doi: 10.1007/s11705-010-0502-0

摘要: The gas flow field in a cyclone separator, operated within a temperature range of 293 K – 1373 K and a pressure range of 0.1 – 6.5 MPa, has been simulated using a modified Reynolds-stress model (RSM) on commercial software platform FLUENT 6.1. The computational results show that the temperature and pressure significantly influence the gas velocity vectors, especially on their tangential component, in the cyclone. The tangential velocity decreases with an increase in temperature and increases with an increase in pressure. This tendency of the decrease or increase, however, reduces gradually when the temperature is above 1000 K or the pressure goes beyond 1.0 MPa. The temperature and pressure have a relatively weak influence on the axial velocity profiles. The outer downward flow rate increases with a temperature increase, whereas it decreases with a pressure increase. The centripetal radial velocity is strong in the region of 0 – 0.25 below the vortex finder entrance, which is named as a short-cut flow zone in this study. Based on the simulation results, a set of correlations was developed to calculate the combined effects of temperature and pressure on the tangential velocity, the downward flow rate in the cyclone and the centripetal radial velocity in the short-cut flow region underneath the vortex finder.

关键词: cyclone separator     high temperature     high pressure     flow field     numerical simulation    

Temperature segregation and its impact on the quality and performance of asphalt pavements

Minkyum KIM, Pranjal PHALTANE, Louay N. MOHAMMAD, Mostafa ELSEIFI

《结构与土木工程前沿(英文)》 2018年 第12卷 第4期   页码 536-547 doi: 10.1007/s11709-017-0451-5

摘要: Temperature segregation is non-uniform temperature distributionacross the uncompacted asphalt mat during paving operations and mayhave detrimental effects on the quality and performance of asphaltpavements. However, many research studies conducted across the UShave reported mixed observations regarding its effects on the initialquality and long-term performance of asphalt pavements.?The objectiveof this study was to determine the effects of the temperature segregationon the density and mechanical properties of Louisiana asphalt mixtures.Seven asphalt rehabilitation projects across Louisiana were selected.A multi-sensor infrared bar (Pave-IR) system and a hand-held portablethermal camera were used to measure the temperature of asphalt mats.Field core samples were collected from various areas with varyingseverity levels of temperature segregation and tested for the density,fracture resistance (J ) by semi-circular bending(SCB), rut depth by wheel tracking, and dynamic modulus (|E*|) byindirect tension (IDT) devices.?Two distinctive patterns of non-uniformtemperature distribution were observed: a cyclic and irregular temperaturesegregations. Laboratory test results showed that highly temperaturesegregated asphalt pavements (i.e., temperature differentials ≥41.7°C) can have significantly lower densities and the mechanicalproperties than the non-segregated area, especially when the temperaturedifferentials are measured at compaction.

关键词: temperature segregation     temperature differential     pavement density     semi-circular bending     wheel tracking     dynamic modulus    

Effect of extrusion temperature on the physical properties of high-silicon aluminum alloy

YANG Fuliang, GAN Weiping, CHEN Zhaoke

《机械工程前沿(英文)》 2007年 第2卷 第1期   页码 120-124 doi: 10.1007/s11465-007-0021-y

摘要: Light-weight high-silicon aluminum alloys are used for electronic packaging in the aviation and space-flight industry. Al-30Si and Al-40Si are fabricated with air-atomization and vacuum-canning hot-extrusion process. The density, thermal conductivity, hermeticity and thermal expansion coefficients of the material are measured, and the relationship between extrusion temperature and properties is obtained. Experimental results show that the density of high-silicon aluminum alloys prepared with this method is as high as 99.64% of the theory density, and increases with elevating extrusion temperature. At the same time, thermal conductivity varies between 104-140 W/(m " K); with the extrusion temperature, thermal expansion coefficient also increases but within 13?10 (at 100?C) and hermeticity of the material is high to 10 order of magnitude.

关键词: coefficient     hermeticity     temperature     relationship     air-atomization    

标题 作者 时间 类型 操作

Emerging challenges to structural integrity technology for high-temperature applications

TU Shantung

期刊论文

Phase separation time/temperature dependence of thermoplastics-modified thermosetting systems

ZHANG Xiujuan, XU Yuanze, YI Xiaosu

期刊论文

Effects of temperature on pyrolysis products of oil sludge

LIU Jianguo, SONG Wei, NIE Yongfeng

期刊论文

Field test on temperature field and thermal stress for prestressed concrete box-girder bridge

Baoguo CHEN, Rui DING, Junjie ZHENG, Shibiao ZHANG

期刊论文

Elevated temperature creep model of parallel wire strands

期刊论文

A review of low-temperature plasma-assisted machining: from mechanism to application

期刊论文

Real-time tool condition monitoring method based on temperature measurement and artificial neural network

期刊论文

Effects of pressure and temperature on fixed-site carrier membrane for CO 2 separation from natural gas

Meng WANG, Dongxiao YANG, Zhi WANG, Jixiao WANG, Shichang WANG,

期刊论文

Investigation on the performance and detoxification of modified low temperature coal tar pitch

Fengyan SUN, Yu LIU

期刊论文

A review on the development of electrolytes for lithium-based batteries for low temperature applications

期刊论文

Preparation of solar selective absorbing CuO coating for medium temperature application

HUANG Qunwu, WANG Yiping, LI Jinhua

期刊论文

Temperature variation of concrete box girder bridge

Jian WANG, Zhi FANG,

期刊论文

Modeling the gas flow in a cyclone separator at different temperature and pressure

Gujun WAN, Guogang SUN, Cuizhi GAO, Ruiqian DONG, Ying ZHENG, Mingxian SHI

期刊论文

Temperature segregation and its impact on the quality and performance of asphalt pavements

Minkyum KIM, Pranjal PHALTANE, Louay N. MOHAMMAD, Mostafa ELSEIFI

期刊论文

Effect of extrusion temperature on the physical properties of high-silicon aluminum alloy

YANG Fuliang, GAN Weiping, CHEN Zhaoke

期刊论文