Thixoforging of continuous fiber-reinforced AlSi/AlMg-alloys

High strength in combination with low density is the key features for lightweight constructions in automotive and aerospace applications. Tailor-made fiber reinforcements in light-metal matrices could help to achieve this goal. However, the integration of fibers with conventional casting-route manufacturing techniques like squeeze casting or diffusion bonding restricts the component geometry and results in elevated process cost due to long cycle times and the need of additional fiber coatings. In the center of competence for casting and thixoforging Stuttgart (CCT), new processes for manufacturing metal matrix composites are developed. Long-fiber reinforced Al–Si alloys and components are produced by thixoforging of laminates made of alternating metal matrix layers and carbon fiber fabrics. This paper illustrates the manufacturing technology and first experimental results with special focus on fiber penetration and infiltration behavior and also on the formation of fiber-matrix interface to analyze fiber damage by mechanical or chemical attack.     

轿车铝合金油泵壳体液态挤压工艺

采用液态挤压代替压力铸造及热模锻生产轿车铝合金油泵壳体,不仅克服了压铸件内部容易形成气孔和氧化夹杂的缺陷,而且减少了热模锻的投资及提高了材料利用率。本文介绍了铝合金油泵壳体液态挤压的模具结构及设计参数、技术经济分析。     

重组人EC-SOD包涵体的稀释复性及重折叠后蛋白的纯化

目的确定重组人ECSOD包涵体体外稀释复性和复性后蛋白纯化的适宜方法。方法通过对pH、温度、包涵体蛋白浓度、尿素和精氨酸浓度及氧化还原对比率的定性定量分析,研究重组人ECSOD包涵体体外稀释复性的基本条件。采用金属离子亲和柱(IMAC)和肝素亲和柱(Heparinsepharose)对复性蛋白进行纯化,比较纯化效率的差异。结果最佳复性条件为pH8.5,尿素浓度为1.5molL,精氨酸浓度大于0.3molL,GSH∶GSSG=4∶1;复性温度及包涵体蛋白终浓度越高,复性效率越低。IMAC和Heparinsepharose亲和柱均可用来纯化复性蛋白溶液,但Heparinsepharose纯化效率较高。结论确定了重组人ECSOD包涵体体外稀释复性的最佳条件及复性后蛋白纯化的方法。     

补强剂和共混工艺对PA/PVC/NBR三元共混弹性体性能的影响

在选择三元共聚尼龙（PA）、聚氯乙烯（PVC）、丁腈橡胶（NBR）为主体材料，制备PA／PVC／NBR（10／30／60）三元共混弹性体的工作基础上，进一步探讨了填料品种和用量，共混温度，加料顺序等因素PA／PVC／NBR三元共混弹性体的影响。试验结果表明：在PA／PVC／NBR（10／30／60）共混体系中，补强型填料的补强效果优于非补强型的填料，6种填料补强效果依次是：快压出炭黑＞半补强炭黑＞白炭黑＞活性重质，CaCO3＞陶土＞滑石粉，快压出炭黑的适宜用量是20－50份。在制备PA／PVC／NBR三元共混物时，适宜的共混温度是122－140℃，并且采用二段法混工艺制得的共混物性能优于采用一段法共混工艺。     

Theoretical Models for Binder Burnout

The kinetics of binder burnout, from a ceramic green body, are considered for the case of an "unzipping" binder which decomposes to produce a volatile monomer. The process is considered to fail if the concentration of monomer in the green body exceeds that in equilibrium with vapor at 1 atm (≅10⁵ Pa), when an internal bubble would be expected to form. Steady-state diffusional calculations and computer simulations explore the size and temperature dependence of the process and are in agreement. The model suggests that it is not feasible to burn out a large flat piece greater than about 3 mm thick, without going to very long times of burnout. The kinetics are significantly improved if porosity develops in the piece during the early stages of decomposition, as opposed to the retreat of the binder into the piece on a uniform front.     

Pullout behavior of polypropylene fibers from cementitious matrix

A comprehensive experimental investigation was performed to understand the pullout behavior of polypropylene fibers from a cementitious matrix. The effect of embedded length on the pullout characteristics, the development of the interfacial bond with age of curing of matrix and the effect of exposure to degrading environments, like seawater and salt water, on the interfacial bond between the fibers and cementitious matrix were studied. The aim of these experiments was to understand the properties of fiber/matrix interface, which are of primary significance in predicting the overall behavior of fiber-reinforced cement-based composites. Polypropylene fibers have a weak bond with cementitious matrix because of smooth surface of fibers, which does not allow for sufficient friction to develop between the two. In this study a new method to improve the frictional bond by means of mechanical indentations of fibers was also proposed. The bonding performance was characterized by means of pullout tests of the plain and modified fibers from a cementitious matrix. An optimum level of fiber modification for maximization of bond efficiency was determined experimentally.     

玻纤增强PA66／PP合金的特性及应用

介绍玻纤增强ＰＡ６６／ＰＰ合金的制备工艺及特性，与纯尼龙６６树脂相比，加工性能好，综合性能优异。该材料适用于中小型油浸式变压器的分接开关及其它绝缘部件。     

重组人白细胞介素-10在大肠杆菌中的表达及生物学活性分析

目的在大肠杆菌中表达重组人白细胞介素-10(Interleukin-10,IL-10),并检测其生物学活性。方法将IL-10基因重组到质粒pET11c中,转化BL21(DE),提取质粒,经酶切鉴定和测序分析;在25℃用低浓度的IPTG诱导表达,对包涵体IL-10稀释复性;经ELISA检测其含量,MC/9细胞增殖法检测其生物学活性。结果工程菌IL-10/pET11c/BL21诱导表达的目的蛋白以可溶性和包涵体两种形式存在,Westernblot鉴定证实为IL-10蛋白,两种形式的IL-10均具有一定的生物学活性。结论已成功地在大肠杆菌中表达了IL-10,为进一步纯化和制备IL-10的基因工程药物打下了基础。     

Mechanical properties of hybrid fiber-reinforced concrete at low fiber volume fraction

Concretes containing different types of hybrid fibers at the same volume fraction (0.5%) were compared in terms of compressive, splitting tensile, and flexural properties. Three types of hybrid composites were constructed using fiber combinations of polypropylene (PP) and carbon, carbon and steel, and steel and PP fibers. Test results showed that the fibers, when used in a hybrid form, could result in superior composite performance compared to their individual fiber-reinforced concretes. Among the three types of hybrids, the carbon-steel combination gave concrete of the highest strength and flexural toughness because of the similar modulus and the synergistic interaction between the two reinforcing fibers.     

A novel approach for fit analysis of thermal protective clothing using three-dimensional body scanning

The garment fit played an important role in protective performance, comfort and mobility. The purpose of this study is to quantify the air gap to quantitatively characterize a three-dimensional (3-D) garment fit using a 3-D body scanning technique. A method for processing of scanned data was developed to investigate the air gap size and distribution between the clothing and human body. The mesh model formed from nude and clothed body was aligned, superimposed and sectioned using Rapidform software. The air gap size and distribution over the body surface were analyzed. The total air volume was also calculated. The effects of fabric properties and garment size on air gap distribution were explored. The results indicated that average air gap of the fit clothing was around 25–30 mm and the overall air gap distribution was similar. The air gap was unevenly distributed over the body and it was strongly associated with the body parts, fabric properties and garment size. The research will help understand the overall clothing fit and its association with protection, thermal and movement comfort, and provide guidelines for clothing engineers to improve thermal performance and reduce physiological burden.