CFETR COOL包层热-机械性能研究

超临界二氧化碳(sCO_(2))液态锂铅包层(COOL)是中国聚变工程实验堆(CFETR)的候选包层,其主要功能是增殖产氚、屏蔽中子辐射以及能量转换发电。COOL包层在正常运行工况下需要承受冷却剂压力、热应力、重力、电磁力等载荷。本文在不考虑重力和电磁载荷的情况下,采用ANSYS有限元方法对COOL包层扇段的赤道面外包层模块进行热-机械性能分析,结果表明,COOL包层在正常运行工况下,各类材料的最高温度不超过限值,并且结构应力能够满足ITER SDC-IC设计标准,分析结果可为包层优化设计提供重要参考和数据支撑。

成品革裁剪废料的纤维化及抄纸性能研究

成品革裁剪废料是一类特殊的皮革固体废弃物,本文通过对其进行纤维化处理,与一定比例的废纸浆混合抄造制备纸板,并对该皮-纸复合纸板的理化性能进行了研究。首先以纤维的分散状况为考察指标,对成品革裁剪废料的纤维化处理进行工艺优化,最佳纤维化工艺参数为:温度50～55℃,硫酸用量为5%,转速1000 r/min,反应时间1 h;然后以滑石粉、聚丙烯酰胺和松香为添加剂,按不同比例的皮纤维和纸纤维混合抄纸,并通过全自动拉力试验机、扫描电子显微镜(SEM)、热重分析(TGA)和差示扫描量热仪(DSC)对所得纸板的物理、机械和热性能进行表征。结果表明,皮-纸复合纸板展现出较好的性能,即混合纸板具有良好的纤维交织、较高的分解温度、较好的热稳定性。基于以上结果,本文所制备的复合纸板可望作为原料,生产诸如轻手袋、鞋盒等纸产品。

PVC/CaCO_3复合材料的结构与性能研究

研究了表面改性微米重质CaCO_3填充的聚氯乙烯(PVC)树脂所得PVC/CaCO_3复合材料的结构和热力学与机械性能。结果表明,改性微米重质CaCO_3的填充能明显提高PVC基复合材料的缺口冲击强度和维卡软化温度。当填充质量分数20%的改性微米重质CaCO_3后,PVC/CaCO_3复合材料的冲击强度为20.92kJ/m^2,比未加微米重质CaCO_3的提高了49.9%。扫描电镜(SEM)观察复合材料的表面形态,发现拉伸断面有拉丝现象。热失重-差示扫描量热分析发现,微米重质CaCO_3对PVC基复合材料分解有一定的抑制作用。

Microstructure characterization and mechanical properties of TC4-DT titanium alloy after thermomechanical treatment

Influence of thermomechanical treatments （mill annealing, duplex annealing, solution treatment plus aging and triple annealing） on microstructures and mechanical properties of TC4-DT titanium alloy was investigated. Results showed that thermomechanical treatments had a significant influence on the microstructure parameters and higher annealing and aging temperature and lower cooling rate led to the decrease of the volume fraction of primaryαand the size of prior-βand the increase of the width of grain boundary αand secondary α. The highest strength was obtained by solution treatment and aging due to a large amount of transformedβand finer grain boundaryαand secondaryαat the expense of slight decrease of elongation and the ultimate strength, yield strength, elongation, reduction of area were 1100 MPa, 1030 MPa, 13%and 53%separately. A good combination of strength and ductility has been obtained by duplex annealing with the above values 940 MPa, 887.5 MPa, 15%and 51%respectively. Analysis between microstructure parameters and tensile properties showed that with the volume fraction of transformedβphase and the prior-βgrain size increasing, the ultimate strength, yield strength and reduction of area increased, but the elongation decreased. While the width of grain boundary α and secondary α showed a contrary effect on the tensile properties. Elimination of grain boundaryαas well as small prior-βgrain size can also improve ductility.

Thermal-mechanical properties of short carbon fiber reinforced geopolymer matrix composites subjected to thermal load

Short carbon fiber preform reinforced geopolymer composites containing different contents of α-Al2O3 filler （Cr（a-Al2O3）/geopolymer composites） were fabricated, and the effects of heat treatment temperatures up to 1 200 ℃ on the thermal-mechanical properties were studied. The results show that the thermal shrinkage in the direction perpendicular to the lamination of the composites gradually increases with the increase of the heat treatment temperatures from room temperature （25 ℃ ） to 1000 ℃. However, the composites in the direction parallel to the lamination show an expansion behavior. Beyond 1 000℃, in the two directions the composites exhibit a larger degree of shrinkage due to the densification and crystallization. The mechanical properties of the composites show the minimum values in the temperature range from 600 to 800 ℃ as the hydration water of geopolymer matrix is lost. The addition of α-Al2O3 particle filler into the composites clearly increases the onset crystalline temperature of leucite （KAlSi2O6） from the amorphous geopolymer matrix. In addition, the addition of α-Al2O3 particles into the composites can not only help to keep volume stable at high temperatures but also effectively improve the mechanical properties of the composites subjected to thermal load to a certain extent. The main toughening mechanisms of the composites subjected to thermal load are attributed to fiber pulling-out.

Influence of addition of B_2O_3 on properties of Yb^(3+)-doped phosphate laser glass

The three host glasses doped with Yb 3+ were prepared by means of conventional melt quenching technology, and the influence on physical and spectral properties of phosphate glass due to addition of B2O3 was investigated and compared with silicate glass. The results show that due to the existence of OH- impurities which induce the non-radiative route, the fluorescence lifetime of phosphate glass is shorter, so silicate glass has better spectral properties than phosphate glass. Silicate glass has more excellent thermal-mechanical properties than phosphate glass, but with the addition of B2O3, thermal-mechanical properties of phosphate glass are improved greatly without fluorescence quenching effect, and this kind of borophosphate glass will be the candidate to be used in high average power solid state laser.

Transformation of β to α phase of isotactic polypropylene nucleated with nano styrene butadiene rubber-based β-nucleating agent under microwave irradiation

This paper investigates the effect of microwave irradiation on theβtoαphase transformation of theβ-nucleated isotactic polypropylene(iPP).Ten microwave irradiation cycles was applied to the iPP and iPP modified with 0.3 wt%and 0.5 wt%β-NA,and the data at 2nd,4th,6th,8th and 10th irradiation were reported.As expected,the sample temperature was found to increase with the irradiation time,by more than 130°C,due to high frequency of microwave processing.This was the major factor that induced theβ-phase transformation and structural change.Both the differential scanning calorimetry(DSC)and X-ray diffraction(XRD)results indicated thatβ-phase was mainly transformed toα-phase and partially converted to the amorphous section.It was reflected as 1)the reduction of the enthalpy ofβ-crystal melting(ΔHmβ),2)the increased enthalpy ofα-crystal melting(ΔHmα),3)the decreasedβ-crystalline phase fraction(Kβ)and 4)the decrease of the overall degree of crystallinity(Xall).Under impact force,neat iPP showed a slight increase in the impact strength with the irradiation time,due to the increase of amorphous region.For theβ-iPP,it decreased due to the reduction of theβ-phase content.

Effect of low temperature thermo-mechanical treatment on microstructures and mechanical properties of TC4 alloy

The effects of low temperature thermo-mechanical treatment （LTTMT） on microstructures and mechanical properties of Ti-6Al-4V （TC4） alloy were studied by optical microscopy （OM）, tensile test, scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. The experimental results confirm that the strength of TC4 alloy can be improved obviously by LTTMT processing, which combines strain strengthening with aging strengthening. The effect of LTTMT on the alloy depends on the microstructure of the refined and dispersed a＋fl phase on the basis of high dislocation density by pre-deformation below recrystallization temperature. The tensile strength decreases with the increase of pre-deformation reduction. The optimal processing parameters of LTTMT for TC4 alloy are as follows： solution treatment at 900 ℃ for 15 min, pre-deformation in the range of 600-700 ℃ with a reduction of 35%, finally aging at 540 ℃ for 4 h followed by air-cooling.

Anti-seismic behavior of HRB400 reinforced steel bars

The properties of anti-seismic HRB400 steel bars with 25 mm diameter were systematically investigated. The results showed that the properties of the HRB400 reinforced steel bars had been greatly enhanced comparing with HRB335 steel bars, i.e. coordination of strength and ductility, strain-aging sensibility, low temperature impact toughness, weld ability and high strain low cycle fatigue. The ductile-brittle transit temperatures of hot-rolled and strain-aged steel bars were evaluated as –17 °C and ?8 °C respectively, and the low temperature impact toughness of HRB400 steel bars remains to be improved. Transmission electron microscopy (TEM) and electron diffraction showed little vanadium existed in ferrite as VN, most of which existed in pearlite as alloy cementite which resulted in the declination of impact toughness. Methods were suggested to improve the anti- seismic properties of steel bars.

Elevated-temperature mechanical properties and thermal stability of Al-Cu-Mg-Ag heat-resistant alloy

The elevated-temperature mechanical properties and thermal stability of Al-Cu-Mg-Ag heat-resistant alloy were studied by tensile test, transmission electron microscopy(TEM) and scanning electron microscopy(SEM), respectively. The results show that with the increase of Ag content, the tensile strength and yield strength increase, which is attributed to the increase of the precipitations number and the decrease of the size. The same conclusions are drawn in the study of increasing Mg content. The alloy possesses excellent thermal stability. At 100-150 °C, the strength of the under-aged alloy increases at the initial stage, and after reaching the peak strength, it remains the same. The secondary precipitation of the under-aged alloy occurs in the process of exposure at 150℃, and it distributes diffusely after thermal exposed for 20 h. Then, the tensile strength decreases gradually with increasing the thermal exposure time at 200-250 °C. The strength of the peak-aged alloy decreases gradually, and the precipitation grows up, but the number decreases gradually with prolonging the exposure time at 100-250 °C. The strength of two kinds of alloys decreases with elevating of exposure temperature.

Heating and Cooling Performance of Earth-Tube Heat Exchanger in a Mechanical Ventilated Farrowing House

Earth tempering of stable air has attracted great attention as a sustainable air conditioning method in pig houses. At summer time air cooling of income air strongly reduces heat stress and required ventilation rate. At winter time heating costs can be reduced. The effect of air condition using geothermal energy was investigated in a farrowing house. Underneath the foundation of the farrowing house 88 non perforated ribbed tubes （diameter： 20 cm） were piped in a depth of 1.6-2.0 m. Over a period of 12 month following data were recorded at hourly intervals and analyzed： outside air temperature, as well as air temperature in the air supply duct and in the compartments. Incoming air （supply duct） was heated up to 20 ℃ during winter time and in summer time cooled by up to 15 ℃ compared to the outside air temperature. In contrast to the outside air diurnal variation, temperature fluctuations of the incoming air were reduced by 90%. Due to cooling of the incoming air at summer time the stable inside temperature could be limited to maximal 29 ℃（maximum outside temperature was 35℃）. Earth-tube heat exchangers with non perforated ribbed tubes were very efficient for air conditioning in farrowing houses. They were a cost effective supplement for sustainable cooling and heating of farrowing houses.

Thermo-mechanical and Experimental Analysis of Double Pass Line Heating

The present investigation deals with process analysis of oxy-acetylene flame assisted double pass line heating for varying plate thickness, oxy-acetylene flame as the heat source for multi pass line heating to achieve 3-D bending of plates with varying thicknesses was studied. The oxy-acetylene flame was modeled as the moving heat source in the FEM analysis. The transient thermal histories were predicted taking into account the temperature dependent thermo-mechanical properties. A comparative study between single pass and double pass line heating residual deformation was also carried out. The temperature distribution and residual detbrmations predicted by the numerical model developed in the present work compared fairly well with those of the experimental ones.

Thermo-mechanical properties of bowl-shaped grinding wheel and machining error compensation for grinding indexable inserts

In order to meet the technical requirements of grinding the circumferential cutting edge of indexable inserts, thermo-mechanical properties of bowl-shaped grinding wheel in high speed grinding process and the influence of dimension variations of the grinding wheel on machining accuracy were investigated. Firstly, the variation trends of the dimension due to centrifugal force generated in different wheel speeds were studied and the effect of stress stiffening and spin softening was presented. Triangular heat flux distribution model was adopted to determine temperature distribution in grinding process. Temperature field cloud pictures were obtained by the finite element software. Then, dimension variation trends of wheel structure were acquired by considering the thermo-mechanical characteristic under combined action of centrifugal force and grinding heat at different speeds. A method of online dynamic monitoring and automatic compensation for dimension error of indexable insert was proposed. By experimental verification, the precision of the inserts satisfies the requirement of processing.

Effects of induction heat treatment on mechanical properties of TiAl-based alloy

The effects of rapid heating cyclic heat treatment on mechanical properties of a TiAl based alloy (Ti 33Al 3Cr) were studied by means of an induction heating machine. The results show that: 1) fine fully lamellar microstructure with colony size of about 50 μm and lamellar spacing of about 0.12 μm can be obtained; 2) the compression mechanical properties can be improved to a large extent and the best comprehensive compression mechanical properties can reach the yield stress 745 MPa, the large flow stress 1 672 MPa and the compression ratio 19.4%; and 3) the compression fracture at room temperature after induction heat treatment and aging is still typical cleavage fracture.

Perturbation to Noether-Lie Symmetry and Adiabatic Invariants for Mechanical Systems in Phase Space

Based on the concept of adiabatic invariant,the perturbation to Noether-Lie symmetry and adiabatic invariants for mechanical systems in phase space are studied.The criterion of the Noether-Lie symmetry for the perturbed system is given,and the definition of the perturbation to Noether-Lie symmetry for the system under the action of small disturbance is presented.Meanwhile,the Noether adiabatic invariants and the generalized Hojman adiabatic invariants of the perturbed system are obtained.

Effect of Mg addition on mechanical and thermoelectrical properties of Al-Al_2O_3 nanocomposite

The effects of Mg addition on mechanical thermo-electrical properties of Al.Mg/5%Al2O3 nanocomposite with differentMg contents （0, 5%, 10% and 20%） produced by mechanical alloying were studied. Scanning electron microscopy analysis （SEM）,X-ray diffraction analysis （XRD） and transmission electron microscopy （TEM） were used to characterize the produced powder. Theresults show that addition of Mg forms a predominant phase （Al.Mg solid solution）. By increasing the mass fraction of Mg, thecrystallite size decreases and the lattice strain increases which results from the atomic penetration of Mg atoms into the substitutionalsites of Al lattice. The microhardness of the composite increases with the increase of the Mg content. The thermal and electricalconductivities increase linearly with the temperature increase in the inspected temperature range. Moreover, the thermalconductivity increases with the increase of Mg content.

Research on new-style seal-filling hydrogel material for coalmine fire zone

The present seal form is restricted by itself, so pilot study in new-style seal-filling hydrogel by choosing acrylamide as absorb-water performance monomer with binary solution hybrid method was carried out. The feasibility of using new-style seal-filling hydrogel to build hermetic wall rapidly was indicated from results. Gelling time of seal-filling hydrogel was influenced by gelling temperature, initiator concentration and accelerator content. Gelling time decreased by 1/3～1/2 times as gelling temperature increased by each 10℃. Gelling time was proportional to 1/2 power of initiator concentration, and was linear of accelerator content with one power. Addition, deformation rate of seal-filling hydrogel depended on monomer content, cross linking agent concentration, accelerator content. And staggered change of elastic modulus was come forth, its demar cation points generally appeared at the value of 50% of vertical deformation.

Optimizing consolidation behavior of Al 7068-TiC nanocomposites using Taguchi statistical analysis

The fabrication of high strength Al 7068？5%TiC （mass fraction） nanocomposite was studied by mechanical alloying and hot pressing routes. Considering densification importance and grain growth effects, hot pressing process conditions for producing bulk nanocomposite were optimized using statistical Taguchi method based on compressive strength achievement. The Taguchi results indicate that 30 min hot pressing under pressure of 500 MPa at 385 °C provides high compressive strength and hardness of 938 MPa and HV 265, respectively. More interestingly, analysis of variance proves that the applied pressure is the most influential factor for hot pressing of the nanocomposite. The contribution percentages of factors in hot pressing terms are as follows： applied pressure （61.3%）, exposed temperature （29.53%） and dwelling hot pressing time （4.49%）.

Semisolid lead-antimony alloys for cars batteries

The application of semisolid process was investigated on Pb-Sb alloys that are normally used for metallic parts in car batteries, in order to increase their mechanical properties and corrosion resistance.The semisolid behaviour of a Pb-4%Sb alloy was analysed by means of rheological and calorimetry differential scanning experiments.The alloy was melted, treated by ultrasound to obtain the semisolid state and then poured into permanent moulds.Some of these samples were also heated in semisolid temperature range and injected in thixo-casting apparatus.Both poured and injected samples were characterized by metallographic analysis, mechanical test and electrochemical corrosion experiments.The results show an improvement of mechanical and corrosion resistance with respect to samples obtained by conventional casting technique.

Study on Varying Metallic Properties of Straight and Elbow Pipes of Main Steam Piping after Long-Time Service

The mechanic properties, lasting strength and microstructural properties of straight and elbow pipesof 12CrMo, 10CrMo910 and 12CrlMoV low alloy steel main steam piping system after long-time service weretested and studied. The testing results showed that, for straight and elbow pipes of mainsteam piping under theconditions of high temperature and high pressure, the numerical operating performance indexes of their metalchanged with little difference, generally both within 5%, and the Values of elbow were higher than those ofstraight pipes. These phenomena proved that the aging processes of pipe metal at different positions are thesame. And the cause for higher numerical performance indexes of elbow and higher failure rate at elbow posi-tion during operation of steam pipes were investigated.