Simulation of the effects of different substrates, temperature,and substrate roughness on the mechanical properties of Al_2O_3 coating as tritium penetration barrier

Residual thermal stress in the system is a serious problem that affects the application of tritium permeation barrier coatings in fusion reactors. The stress not only determines the adhesion between coating and substrate, but also changes the properties of the material. In this study,finite element analysis was used to investigate the relationship between the residual thermal stress and the mechanical properties of Al_2O_3 tritium penetration barrier systems. Moreover, the residual thermal stress influenced by factors such as different substrates, temperature, and substrate roughness was also analyzed. The calculation showed that the hardness and elastic modulus increased with increasing compressive stress. However, the hardness and elastic modulus decreased with increasing tensile stress. The systems composed of Al_2O_3 coatings and different substrates exhibited different trends in mechanical properties. As the temperature increased, the hardness and the elastic modulus increased in an Al_2O_3/316 L stainless steel system; the trend was opposite in an Al_2O_3/Si system.Apart from this, the roughness of the substrate surface in the system could magnify the change in hardness and elastic modulus of the coating. Results showed that all these factors led to variation in the mechanical properties of Al_2O_3 tritium permeation barrier systems. Thus, thedetailed reasons for the changes in mechanical properties of these materials need to be analyzed.

Gaseous Penetration of Pr into PbTiO_3 Ceramics and Their Electric Properties

The gaseous Pr-penetration is a new method to modify ceramics, which is expected to be a promising method for producing new conductor ceramic materials. The gaseous penetration of Pr into PbTiO_3 ceramics and their improved electric properties were reported. Through XRD, EPMA and SEM analysis,it is confirmed that the gaseous penetration makes Pr enter into PbTiO_3 ceramics, and the new compound of Pr_2Ti_2O_7 is formed by the penetration of Pr in the gaseous state. The formed new Pr_2Ti_2O_7-PbTiO_3 ceramic materials have a significant change in electric properties. The room temperature resistivity decreases from 2.0×10^(10) Ω·m to 9.487 Ω·m. The grain resistance and the grain boundary resistance decrease with increase in temperature, and the PTCR effect disappears. The tendency of transition to a conductive body is manifest.

The Microstructures and Properties of SiC/Al_2O_3/Al-Si Composites Prepared by Reactive Penetration

The composition, microstructures and properties of SiC /Al-2O-3/Al-Si composites formed by reactive penetration of the molten aluminum into the preforms of SiO-2 and SiC were investigated. The composition of the composites was measured by X-ray diffraction (XRD). The microstructures of the composites were also measured by scanning electron microscopy (SEM) and optical microscopy. In addition, the factors affecting the properties of the composites were discussed.The experiments show that the mechanical properties of the composites depend on their relative densities and the sizes of the fillers“SiC grains".The denser the SiC/Al-2O-3/Al-Si composites,the higher their bending strength.As the filler “SiC grains" become fine,the bending strength of the composites increases.

Condition Assessment of August A. Busch Bridge Deck Using Portable Seismic Property Analyzer and Ground Penetrating Radar

Ground penetrating radar (GPR) and the portable seismic property analyzer (PSPA) have been extensively used in the past two decades for monitoring, quantifying, and mapping the deterioration of bridge decks. Using PSPA and GPR ensures regular monitoring of bridge conditions, leads to the early detection of deterioration. This research is to address the condition of August A. Busch bridge deck owned by the Missouri Department of Conservation. Visual inspection, GPR, and PSPA data were acquired on the bridge deck. Over 90% of the bridge deck was in fair to good condition with an average compressive strength of over 2500 psi. GPR data showed no indication of significant deterioration. The overall bridge deck was determined to be in fair to good condition.

Tree-Based Solution Frameworks for Predicting Tunnel Boring Machine Performance Using Rock Mass and Material Properties

Tunnel Boring Machines(TBMs)are vital for tunnel and underground construction due to their high safety and efficiency.Accurately predicting TBM operational parameters based on the surrounding environment is crucial for planning schedules and managing costs.This study investigates the effectiveness of tree-based machine learning models,including Random Forest,Extremely Randomized Trees,Adaptive Boosting Machine,Gradient Boosting Machine,Extreme Gradient Boosting Machine(XGBoost),Light Gradient Boosting Machine,and CatBoost,in predicting the Penetration Rate(PR)of TBMs by considering rock mass and material characteristics.These techniques are able to provide a good relationship between input(s)and output parameters;hence,obtaining a high level of accuracy.To do that,a comprehensive database comprising various rock mass and material parameters,including Rock Mass Rating,Brazilian Tensile Strength,and Weathering Zone,was utilized for model development.The practical application of these models was assessed with a new dataset representing diverse rock mass and material properties.To evaluate model performance,ranking systems and Taylor diagrams were employed.CatBoost emerged as the most accurate model during training and testing,with R2 scores of 0.927 and 0.861,respectively.However,during validation,XGBoost demonstrated superior performance with an R2 of 0.713.Despite these variations,all tree-based models showed promising accuracy in predicting TBM performance,providing valuable insights for similar projects in the future.

Developments of mucus penetrating nanoparticles

Mucus can effectively protect the exposed mucosal surfaces due to its adhesive and viscoelastic properties.Most foreign particulates are efficiently trapped in mucus layers via steric obstruction and adhesion.Trapped particles are typically removed from the mucosal tissue within seconds to a few hours depending on their location sites.This article focuses on describing the tenacious mucus barrier properties,the strategies to investigate the interaction of nanoparticles with the mucus as well as the novel developments of mucus penetrating nanoparticles.

Effect of weld microstructure on weld properties in A-TIG welding of titanium alloy

Conventional TIG welding is known as its low productivity and limited weld depth in a single pass. Activating TIG welding (A TIG) can greatly improve the penetration when compared with the conventional TIG welding. The effects of five kinds of activating fluxes with single component (NaF, CaF 2, AlF 3, NaCl or CaCl 2) on penetration, microstructure and weld mechanical properties during the TIG welding of titanium alloy Ti 6Al 4V were studied. Compared with the conventional TIG welding, the experimental results show that the fluxes can greatly improve the penetration at the same welding specifications. This is because of the constriction of anode spots and the change of surface tension grads. Among them the effect of flux NaF is the best in the weld tensile strength, and the effect of flux CaF 2 on the weld bend intension is the best. The appearance of inferior crystal grains and the structure of trident crystal grains are the main reasons that the performance of weld with fluoride is improved. These experimental results can be used as an aid for selecting suitable activating flux for titanium alloy.

Linear Shaped Charge Cutting Property and Charge Cutting Mechanism of Mg-Gd-Y-Zn Alloy

The linear shaped charge cutting technology is an effective technology for aircraft separation.It can separate invalid components from aircrafts timely to achieve light-weight.Magnesium alloy is the lightest metal material,and can be used to cast effective light-weight components of an aircraft construction.However,the application study of the linear shaped charge cutting technology on magnesium alloy components is basically blank.In response to the demand for the linear separation of magnesium alloys,the Mg-12Gd-0.5Y-0.4Zn alloy is selected to carry out the target shaped charge cutting test.The effects of the shaped charge line density,cutting thickness,and mechanical properties on the cutting performance of the alloy are studied.The shaped charge cutting mechanism is analyzed through the notch structure.The results show that the linear shaped charge cutting performance is significantly affected by the penetration and the collapse.The higher the linear density is,the stronger the ability of the linear shaped charge cutter is,and the greater the penetration depth is,which is advantageous.However,the target structure will be damaged when it is too large(e.g.,4.5 g·m^(-1)).Within 12 mm,when the cutting thickness of the target increases,the penetration depth increases.The lower the tensile strength is,the greater the penetration depth is,and the more conducive the penetration depth to the shaped charge cutting is.When the elongation(EL)increases to 12%,the collapse of the target is incomplete and the target cannot be separated.When the tensile strength of the Mg-Gd-Y-Zn alloy is less than 350 MPa,the EL is less than 6.5%,the cutting thickness is less than 12 mm,and the linear shaped charge cutting of the magnesium alloy can be achieved stably.

不同风化程度花岗岩的动态力学特性及抗侵彻性能

风化会使岩石材料孔隙发育,严重影响其工程性能,研究风化作用对花岗岩力学特性及抗侵彻性能的影响,对侵彻战斗部毁伤效能评估及地下工程防护能力分析具有重要意义。选用两种不同风化程度的花岗岩为研究对象,基于试验法系统分析其物理特性、静/动态压缩性能及抗侵彻性能的差异。结果表明:风化作用会造成花岗岩中黑云母和斜长石含量降低,孔隙率增加、内部组织变松散,缺陷加剧;风化作用将导致花岗岩抗压强度劣化、应变率效应降低,破坏模式从脆性破坏向弱剪切破坏转变;三轴围压作用下,两种花岗岩的静、动态抗压强度随围压的增大显著提升,且中风化花岗岩的抗压强度对围压的作用更敏感;高速(873~1040 m/s)侵彻条件下,两种风化花岗岩的抗侵彻性能差异较小,无量纲侵深不超过3倍弹长,岩石靶中不存在明显的侵彻弹道区,但有明显的压碎区,压碎区长度约为弹径的5~8倍。

改性硫铝酸盐水泥砂浆力学性能及耐久性能研究

过快的流动度损失和后期不稳定的强度发展限制了硫铝酸盐水泥工程中的进一步应用。因此以葡萄糖酸钠作为缓凝剂,掺入硅灰制备成改性硫铝酸盐水泥砂浆,并对其工作性能、力学性能和抗氯离子渗透性能开展了系统研究。研究结果表明:葡萄糖酸钠掺量0.4%可有效延长硫铝酸盐水泥砂浆凝结时间,提高砂浆流动性和抗氯离子渗透性能;硫铝酸盐砂浆工作性能、力学性能和抗氯离子渗透性能均随硅灰掺量的增加先提高后降低,硅灰最优掺量为20%。

光束倾角对激光深熔焊304不锈钢焊缝力学性能及熔池流动的影响

在激光深熔焊接中光束倾角会直接影响匙孔形态,光束倾角对熔池流动也具有一定的影响.采用激光深熔焊接白板试验结合“半三明治”熔池流动直接观测试验,以激光倾角作为变量,研究其对304不锈钢激光深熔焊接焊缝力学性能及熔池流动的影响.结果表明,在焊缝的力学性能上,不同激光倾角对焊缝上、中部的影响差异性较小,对下部的影响较大,焊缝底部拉伸件出现较多气孔缺陷,正激光入射角下的焊缝抗拉强度和断后伸长率小于负激光入射角.正激光入射角下“上小下大”的匙孔形貌使其底部易产生涡流,不利于气泡的排出,且匙孔坍塌频率较负激光入射角大,导致熔池稳定性较差,焊缝气孔缺陷的形成概率呈现为正激光入射角高于负激光入射角态势.

基于PLC的橡胶树皮非线性力学性能探测装置设计与试验

为了获取橡胶树皮结构力学特性参数,解决机械化采胶装备研发中采胶深度精准探测和耗皮厚度精准控制技术无可靠依据提供参考的问题,设计一种基于可编程序逻辑控制器(programmable logic controller, PLC)的橡胶树皮非线性力学性能测量的试验装置,实现橡胶树皮力学特性的自动化连续探测和数据采集,以及树皮厚度的高精低损测量。并应用于热研7-33-97和PR107两个品系的15龄、20龄、25龄橡胶树上进行树皮力学性能试验研究,建立刺入过程中刺入力随刺入深度变化的数学模型。结果表明:该装置工作性能稳定,不同品系、不同树龄的树皮刺入力随刺入深度的变化曲线形态相近,均呈高-低-高的趋势变化,并与树皮结构分层特性高度相关;相同树龄下,热研7-33-97和PR107两个品系的刺入力情况差异不明显,同品系的大树龄比小树龄刺入力更大,在1.0 mm针刺下,刺入力最大峰值可达48.5 N。该试验装置满足橡胶树皮结构力学特性参数的探测需求,并为机械化采胶装备的研发提供理论基础。

连续纤维增强高孔隙复合材料的抗侵彻性能研究

为开展连续纤维增强高孔隙复合材料的侵彻防护性能,首先,用二级轻气炮发射Q235钢质弹丸,对连续纤维增强高孔隙复合材料开展弹道侵彻实验,计算了弹道极限,归纳和分析了其损伤的形态和模式,并将这种复合材料的侵彻防护性能与其他材料进行了比较;然后,对弹道侵彻连续纤维增强高孔隙复合材料进行了数值模拟,比较了剩余速度、损伤的形态和范围,模拟结果与实验结果吻合较好;进而通过观察有限元模拟的弹孔形态、应力分布和损伤分布等方式,对侵彻过程的损伤机理进行了分析。研究结果可为复合材料在防热、冲击防护与承受外载荷等多功能一体化的应用提供参考依据。

La_2Ti_6O_(15)-CeTi_(21)O_(38)-PbTiO_3 ceramics formed in gaseous penetration of La-Ce into PbTiO_3 and their electric properties

The gaseous penetration of La-Ce into PbTiO3 ceramics is reported. The compounds of La2Ti6O15 and CeTi21O38 are formed and the new La2Ti6O15-CeTi21O38-PbTiO3 ceramics are prepared by the penetration of La and Ce in the gaseous state. The new ceramic materials have a significant change in electric properties. The room temperature resistivity decreases from 2.0×1010 to 0.248 Ω. m, and the grain resistance exhibits an obvious PTCR effect with the change of temperature. However, the grain boundary resistance decreases rapidly with increase in temperature. The change rule of the total resistance is similar to that of the grain boundary, and the PTCR effect disappears and the tendency of transition to a conductive body is manifest. The XPS analysis suggests that the particles that are Pb, Ti, La and Ce in La2Ti6O15-CeTi21O38-PbTiO3 ceramics all change their valence and lead to decreasing resistivity, and the bound energy peak values of elements in La2Ti6O15-CeTi21O38-PbTiO3 ceramics are also reported. The La2Ti6O15-CeTi21O38-PbTiO3 ceramics have a better thermal stability in high temperatures through TG-DTA analysis.

探地雷达技术在土壤性质探测应用中的研究进展

探地雷达(Ground Penetrating Radar,GPR)作为一种快速、无损的中小尺度近地传感技术,因其具有信息量大、分辨率高、空间连续性好等优点在土壤性质探测中得到广泛应用。在系统介绍探地雷达在探测土壤性质原理的基础上,概述了正演模拟方法与目前应用广泛的土壤介电模型,归纳了探地雷达技术在土壤性质(土壤含水量、土壤质地、土壤层次、土壤压实、土壤盐分)探测中的应用研究现状。并讨论了该技术在实地应用中存在的问题与局限性:实地探测影响因子复杂,难以分离,数据解译复杂且具有主观性,大部分研究仅停留在定性或半定量阶段等。最后针对探地雷达在土壤学领域的应用情况,提出了其不足与展望:随着信号处理技术的不断发展与理论研究的日益成熟,探地雷达在土壤特性探测中仍然是一个有潜力的工具。旨在为探地雷达在土壤性质探测应用中的研究提供参考。

胡萝卜联合收获挖掘部件运动及力学特性分析

针对胡萝卜联合收获机挖掘铲入土困难、挖掘壅土造成夹持不准、挖掘阻力大等问题,开展了胡萝卜挖掘部件运动及力学特性研究。构建了挖掘部件入土特性及与土壤互作力学特性的数学模型,理论解析了入土角、入土行程、挖掘阻力及挖掘部件结构间的关联关系。借助EDEM离散元仿真软件,分析了挖掘铲的入土行程及铲土互作力学特性,并进行田间验证试验。结果表明:土壤壅起高度、挖掘阻力均与入土角度成正比,最终入土角为14°~22°时,胡萝卜收净率≥98%,破损率为≤1.5%,壅土现象不显著,满足收获要求。

海洋环境下玄武岩纤维混凝土的抗侵蚀及力学性能

基于纤维混凝土契合当前海洋环境下混凝土服役的实际需求以及玄武岩纤维混凝土在海工类建筑物中的应用仍处于探索阶段。针对玄武岩纤维掺入海工混凝土后抗氯离子渗透性能以及力学抗裂性能的变化情况与作用机制展开研究;采用体积外掺法将长度为12,18,24 mm的玄武岩纤维分别以0.1%,0.2%,0.3%的体积掺量掺入海工混凝土中,就各纤维变量对混凝土电通量与混凝土拉压力学性能的影响展开分析。结果表明:混凝土电通量随着纤维掺量的增大呈现先降后增趋势,提升混凝土抗氯离子侵蚀性能的最佳掺量为0.1%~0.2%;不同尺寸纤维相同掺量下混凝土抗氯离子性能与纤维长度成正比;混凝土立方体抗压强度处于正增长趋势的纤维区间为0.1%~0.2%;0.2%掺量下的18 mm纤维,对混凝土劈裂抗拉强度提升幅度最大,0.3%掺量下的12 mm纤维混凝土劈裂抗拉强度提升最小;当掺入0.2%体积纤维时,18,24 mm玄武岩纤维混凝土拉压比增益最大,体积掺量为0.3%时,12 mm玄武岩纤维混凝土拉压比增益最大。

内掺水泥基渗透结晶型防水材料混凝土配合比设计及性能研究

试验研究了不同掺量水泥基渗透结晶型防水材料(CCCW)对混凝土保水性、力学性能、抗渗性能、抗氯离子渗透性能及凝结时间的影响,并采用扫描电镜观察分析其微观形貌。试验结果表明:适量的CCCW能明显改善混凝土的保水性及力学性能,当CCCW掺量为0.8%时效果最佳;CCCW的掺入对混凝土的抗渗性能以及抗氯离子渗透性能也有提升,当CCCW掺量为1.0%时,抗渗压力比升高趋势更明显,电通量最低,随着CCCW掺量增加,混凝土凝结时间有所缩短;SEM照片显示CCCW的掺入能促进裂缝与空隙处的水化反应,生成枝蔓状结晶体,使得混凝土更加致密,提高了混凝土的力学性能与抗氯离子渗透性。

锤击打桩桩周岩土体力学特性试验研究

为研究打桩前后桩周黏性土和泥岩力学性质的变化,在打桩前后分别进行标准贯入试验,分析了桩周黏性土与泥岩经打桩扰动后的力学特性,探讨了桩周岩土体力学性质变化的影响因素,提出了减小扰动、保证桩周岩土体力学性质的工程措施。研究表明:锤击打桩导致桩周泥岩力学性质降低,桩周泥岩产生损伤;黏性土随打桩产生的超静孔隙水压力逐渐消散,其力学性质28d后基本恢复,但不同黏性土的消散速率不同,力学性质恢复存在差异;泥岩打桩损伤后很难恢复,打桩前后同深度处以标贯锤击数表征的力学性质最大差异超过2倍;若存在软弱夹层,会加剧打桩对泥岩的影响;地下水、软弱夹层、打桩扰动是影响桩周泥岩力学性质的关键因素。

掺贝壳骨料混凝土的性能及固碳效果研究

将废弃贝壳制成再生粗、细骨料,研究了贝壳骨料等质量部分替代天然骨料对混凝土力学性能和抗氯离子渗透性能的影响,并依托福建泉港海岸修复工程,分析了掺贝壳骨料混凝土的固碳性能。结果表明:随着粗、细贝壳掺量的增加,试件的抗压、抗折和劈裂抗拉强度均先增大后减小;在粗贝壳掺量一定的情况下,增加细贝壳掺量对试件的抗氯离子渗透性能影响不大;当细贝壳掺量一定时,随着粗贝壳掺量的增加,试件的抗氯离子渗透性能下降;综合考虑力学性能和抗氯离子渗透性能,推荐粗、细贝壳的最佳掺量均为40%,据此可估算出福建泉港海岸修复工程中贝壳骨料生态贝藻礁可固碳1657 t,可清理陆地堆积废弃贝壳0.035 km^(2),生态环境效益显著。