Extreme wet adhesion of a novel epoxy-amine coating on aluminum alloy 2024-T3

Amine-epoxy polymer systems are widely used, for example as matrix materials for structural composites employed in aerospace industry and in industrial coatings on metal substrates for corrosion protection. This work focuses on the investigation of different epoxy-amine coatings on the adhesion performance on aluminum AA-2024 substrates. Two different epoxies (Epikote 828 (aromatic) and Eponex 1510 (aliphatic)) and four different amines (1,8-diaminooctane, Dytek A, Jeffamine EDR148 and Jeffamine D230) as curing agent were used in different stoichiometric ratios. These different epoxy-amine coatings were characterized using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), tensile tests (pull-off) and water-uptake measurements. Pull-off tests in dry conditions showed comparable adhesion of the coatings. Surprisingly, pull-off results showed after water soaking a higher wet adhesion of the coatings prepared with Eponex 1510 as compared to coatings prepared with Epikote 828. Moreover, the combination of Eponex 1510-Jeffamine EDR148 coatings resulted in high adhesion values (∼7 MPa) with pull-off tests and these values did not change after immersion for two weeks in water. This combination shows extreme good wet adhesion performance as compared to any other epoxy-amine coating. Complete recovery was demonstrated of the adhesion of Eponex 1510-Jeffamine D230 coating after being immersed for two weeks in water and dried for two weeks. Furthermore, in contrast with Epikote 828 water uptake measurements showed almost nil water uptake for all coatings prepared with Eponex 1510. Optical microscopy investigations on the residues of the coatings after pull-off tests revealed adhesive failure in wet condition for Epikote 828, while coatings prepared with Eponex 1510 showed cohesive failure.     

基于SINUMERIK 828D数控系统的数控机床螺距误差与反向间隙的测量与补偿

探讨了数控机床螺距误差和反向间隙的形成原理。针对采用西门子SINUMERIK 828D数控系统的数控机床,给出了测量数控机床位置偏差的运动程序,介绍了螺距误差和反向间隙测量和补偿的方法和步骤。     

配置西门子828D系统数控机床的批量调试和存档

以西门子828D系统数控机床的调试为例,介绍配置西门子828D系统的数控机床的批量调试和存档步骤.     

Modeling of Constitutive Behavior for Epon 828/T-403 at High Strain Rates

Experimental results on the uniaxial compressive stress-strainbehavior of Epon 828/T-403 over a strain rate range from 1.1 × 10^–4 to 5.2 × 10³ s^–1were simulated using a viscoelastic viscoplastic constitutive modeldeveloped by Hasan and Boyce (1995). An optimal combination of materialparameters for the constitutive model was determined by curve-fittingthe experimental results. A comparison between the modeling andexperimental results shows that this model, with proper parameters, iscapable of capturing the strain-rate effects, as well as the typicalpolymeric compressive stress-strain behavior, of Epon 828/T-403, whichincludes the stages of linearly elastic, nonlinearly elastic, yield-like(peak) behavior, strain softening, and nearly perfect flow. For all thestress-strain behavior modeled over seven decades of strain rate span,the maximum error between modeling and experimental results is less than25%. The temperature increase induced by the dissipated plasticwork is also computed and found to be between 3 and8°C at these strain rates.     

土工膜粘合剂及其在三峡工程的应用

土工膜是９０年代为实现国家“火炬计划”填补国内空白而开发的一种复合防渗材料，葛洲坝粘合剂开发公司研制的ＬＤＪ－２４６－１胶首先应用于水口电站上下游围堰防渗材料粘接，防渗性能优异，总渗漏量仅１００Ｌ／ｍｉｎ，三峡工程一期土石围堰用以粘接土工膜，经受了长江洪峰的考虑，质量可靠，施工方便，以聚氨酯为主料的璜时得ＰＵ８２８土工膜粘合剂应用三峡左岸隔流堤拦砂子堤加高工程，粘接ＰＶＣ胶带达３００００ｍ＾２。     

ITU-T误码性能建议之一

对于用于传送广播电视节目的国家和城域干线网,误码性能是一个关键的传输性能指标。本文介绍了ITU-T的几个主要的误码性能建议,希望能对干线网传输系统的建设和维护有所帮助。     

运载火箭框环自动钻孔设备控制系统的设计

设计了一套基于西门子828D数控系统的运载火箭框环自动钻孔设备控制系统,用于在运载火箭框环侧面进行钻孔以及在短壳表面进行开孔。该控制系统主要由828D数控系统、S120伺服驱动器、伺服电机、变频器、主轴电机、光栅尺构成,实现全闭环驱动控制,极大地提升了钻孔及开孔的效率、精度及质量;同时,应用828D数控系统的柱面转换功能,实现旋转轴B与直线轴Y之间的圆弧插补,有效降低了设备硬件成本。经调试与应用显示:该钻孔设备的自动钻孔效率为15个/min,自动开孔效率为10 min/个。     

SINAMICS数字I/O数据交换技术在数控机床中应用

阐述了CK8011F数控车床双数控系统PPU260.2之间的数据通讯方法,通过PN/PN耦合器数据交换法、局域网数据交换法及SINAMICS数字I/O控制端子数据交换法等数据交换方案的对比分析,采用了数字I/O控制端子数据交换法,实现了机床双数控系统之间的数据通讯交换.     

Fifteen chemistries for autonomous external self-healing polymers and composites

This review aims at guiding both new and established researchers in the field of self-healing by providing a clear overview of the fifteen most important chemistries used in autonomous external self-healing systems until today, together with their healing potential for different matrix materials and types of mechanical damage. The described self-healing systems require no manual intervention or additional stimulus for the self-healing event to take place (autonomous) and utilize added healing agents to repair the damage (external). A range of recent developments is discussed with indication of their strengths and weaknesses. An attempt is also made to demonstrate the research opportunities that are still available for each described system and to find the areas that require further elaboration. As such, this review can help to point the reader in the directions these self-healing materials could follow in the future.