Force analysis and experimental study of pure aluminum and Al-5%Ti-1%B alloy continuous expansion extrusion forming process

The deformation zone of CONFORM extrusion was divided into primary gripping zone,gripping zone,conical expansion chamber zone,cylindrical zone and sizing zone of die,and corresponding force equilibrium equations were established using the Slab method.The deformation force formulae of CONFORM machine at any wrapping angle with an expansion chamber were obtained.Experiment on pure aluminum and Al-5%Ti-1%B alloy was conducted on the CONFORM machine self-designed.The resistance to deformation of Al-5%Ti-1%B alloy at the deformation temperature of 400℃ and the strain rate of 3.07 s-1 was measured to be 50 MPa using Gleeble-1500 thermal simulation machine.The calculation results of deformation forces for CONFORM process with an expansion chamber for pure aluminum and Al-5%Ti-1%B alloy were given.The experimental CONFORM radial force is in agreement with the radial force obtained by theoretical formula.

Extrusion force analysis of aluminum pipe fabricated by CASTEX using expansion combination die

To determine the extrusion force of pipe fabricated by continuous casting and extrusion (CASTEX) using an expansion combination die, the metallic expansion combination die was divided into diversion zone, expansion zone, flow dividing zone, welding chamber, and sizing zone, and the corresponding stress formulae in various zones were established using the slab method. The deformation zones of CASTEX groove were divided into liquid and semisolid zone, solid primary gripping zone, and solid gripping zone, and the formulae of pipe extrusion forces were established. Experiments were carried out on the self-designed CASTEX machine to obtain the aluminum pipe and measure its extrusion force using the expansion combination die. The experimental results of radial extrusion force for aluminum pipe are in good agreement with the calculated ones.

Texture evolution and mechanical anisotropy of an ultrafine/nano-grained pure copper tube processed via hydrostatic tube cyclic expansion extrusion

Texture evolution and mechanical anisotropic behavior of an ultrafine-grained(UFG)pure copper tube processed by recently introduced method of hydrostatic tube cyclic expansion extrusion(HTCEE)was investigated.For the UFG tube,different deformation behavior and a significant anisotropy in tensile properties were recorded along the longitudinal and peripheral directions.The HTCEE process increased the yield strength and the ultimate strength in the axial direction by 3.6 and 1.67 times,respectively.Also,this process increased the yield strength and the ultimate strength in the peripheral direction by 1.15 and 1.12 times,respectively.The ratio of ultimate tensile strength in the peripheral direction to that in the axial direction,as a criterion for mechanical anisotropy,are 1.7 and 1.16 for the as-annealed coarse-grained and the HTCEE processed UFG tube,respectively.The results are indicative of a reducing effect of the HTCEE process on the mechanical anisotropy.Besides,after HTCEE process,a low loss of ductility was observed in both directions,which is another advantage of HTCEE process.Hardness measurements revealed a slight increment of hardness values in the peripheral direction,which is in agreement with the trend of tensile tests.Texture analysis was conducted in order to determine the oriental distribution of the grains.The obtained{111}pole figures demonstrate the texture evolution and reaffirm the anisotropy observed in mechanical properties.Scanning electron microscopy micrographs showed that different modes of fracture occurred after tensile testing in the two orthogonal directions.

Processing of AM60 magnesium alloy by hydrostatic cyclic expansion extrusion at elevated temperature as a new severe plastic deformation method

Hydrostatic cyclic expansion extrusion(HCEE) process at elevated temperatures is proposed as a method for processing less deformable materials such as magnesium and for producing long ultrafine-grained rods. In the HCEE process at elevated temperatures, high-pressure molten linear low-density polyethylene(LLDPE) was used as a fluid to eliminate frictional forces. To study the capability of the process,AM60 magnesium rods were processed and the properties were investigated. The mechanical properties were found to improve significantly after the HCEE process. The yield and ultimate strengths increased from initial values of 138 and 221 MPa to 212 and 317 MPa, respectively.Moreover, the elongation was enhanced due to the refined grains and the existence of high hydrostatic pressure. Furthermore, the microhardness was increased from HV 55.0 to HV 72.5. The microstructural analysis revealed that ultrafine-grained structure could be produced by the HCEE process. Moreover, the size of the particles decreased, and these particles thoroughly scattered between the grains. Finite element analysis showed that the HCEE was independent of the length of the sample, which makes the process suitable for industrial applications.

Microstructure and mechanical properties of AZ31 alloy prepared by cyclic expansion extrusion with asymmetrical extrusion cavity

The microstructure,texture evolution and mechanical properties of AZ31 magnesium alloy were investigated during the cyclic expansion extrusion with the asymmetrical extrusion cavity(CEE-AEC)process.The results show that continuous dynamic recrystallization(CDRX)and discontinuous dynamic recrystallization(DDRX)occur during the CEE-AEC process.After 3 passes,the microstructures of the deformed samples are refined,and the average grain size of the alloys in asymmetrical cavity region is 6.9μm.The maximum intensities of the basal textures increase with the increase in the number of passes,and the basal textures are deflected during the deformation process.The basal texture of the alloys in asymmetrical cavity region is tilted by approximately±45°from the normal direction(ND)to the extrusion direction(ED).Grain refinement strengthening and texture deflection significantly improve the comprehensive mechanical properties of the deformed alloys.After 3 passes,tensile yield strength(TYS),ultimate tensile strength(UTS)and elongation-to-failure of the alloy in the asymmetric cavity region are 146 MPa,230 MPa and 29.7%,respectively.

Severe plastic deformation of commercially pure aluminum using novel equal channel angular expansion extrusion with spherical cavity

Equal channel angular expansion extrusion with spherical cavity(ECAEE-SC)was introduced as a novel severe plastic deformation(SPD)technique,which is capable of imposing large plastic strain and intrinsic back-pressure on the processed billet.The plastic deformation behaviors of commercially pure aluminum during ECAEE-SC process were investigated using finite element analysis DEFORM-3D simulation software.The material flow,the load history,the distribution of effective strain and mean stress in the billet were analyzed in comparison with conventional equal channel angular extrusion(ECAE)process.In addition,single-pass ECAEE-SC was experimentally conducted on commercially pure aluminum at room temperature for validation,and the evolution of microstructure and microhardness of as-processed material was discussed.It was shown that during the process,the material is in the ideal hydrostatic stress state and the load requirement for ECAEE-SC is much more than that for ECAE.After a single-pass ECAEE-SC,an average strain of 3.51 was accumulated in the billet with homogeneous distribution.Moreover,the microstructure was significantly refined and composed of equiaxed ultrafine grains with sub-micron size.Considerable improvement in the average microhardness of aluminum was also found,which was homogenized and increased from HV 36.61 to HV 70.20,denoting 91.75%improvement compared with that of the as-cast billet.

Microstructure and properties of Al-0.70Fe-0.24Cu alloy conductor prepared by horizontal continuous casting and subsequent continuous extrusion forming

A novel process for manufacturing A1-0.70Fe-0.24Cu alloy conductor was proposed, which includes horizontal continuous casting and subsequent continuous extrusion forming （Conform）. The mechanical properties, electrical conductivity and the compressed creep behaviour of the alloy were studied. The results indicate that the Conform process induces obvious grain refinement, strain-induced precipitation of AI7CuzFe phase and the transformation of crystal orientation distribution. The processed alloy has good comprehensive mechanical properties and electrical conductivity. Moreover, a better creep resistance under the conditions of 90 ~C and 76 MPa is shown compared with pure A1 and annealed copper, and the relationship between primary creep strain and time may comply with the logarithmic law. The enhanced properties are attributed to the grain refinement as well as the fine and homogeneously distributed thermally stable A1Fe and A17Cu2Fe precipitation phases.

Measurement and simulation of the two-phase velocity correlation in sudden-expansion gas-particle flows

In this paper the present authors measured the gas-particle two-phase velocity correlation in sudden expansion gas-particle flows with a phase Doppler particle anemometer （PDPA） and simulated the system behavior by using both a Reynolds-averaged Navier-Stokes （RANS） model and a large-eddy simulation （LES）. The results of the measurements yield the axial and radial time-averaged velocities as well as the fluctuation velocities of gas and three particle-size groups （30μm, 50μm, and 95μm） and the gasparticle velocity correlation for 30μm and 50μm particles. From the measurements, theoretical analysis, and simulation, it is found that the two-phase velocity correlation of sudden-expansion flows, like that of jet flows, is less than the gas and particle Reynolds stresses. What distinguishes the two-phase velocity correlations of sudden-expansion flow from those of jet and channel flows is the absence of a clear relationship between the two-phase velocity correlation and particle size in sudden-expansion flows. The measurements, theoretical analysis, and numerical simulation all lead to the above-stated conclusions. Quantitatively, the results of the LES are better than those of the RANS model.

金枪鱼亚微米-纳米级鱼骨粉的制备及其对鱼糜凝胶品质的影响

为促进金枪鱼骨的高值化利用,本研究基于挤压膨化技术高效制备亚微米-纳米级鱼骨粉,并探究其对鱼糜凝胶性能的影响。结果表明,挤压膨化制得的鱼骨粉化学结构及成分未发生变化,相比未挤压膨化的鱼骨粉,其平均粒径显著减小,达308.07 nm(59.41%为亚微米级、40.59%为纳米级)。与NaCl、CaCl_(2)、大米+淀粉、未经挤压膨化粉碎鱼骨粉等相比,挤压膨化鱼骨粉能最大程度提高鱼糜的质构特性和持水性,但对鱼糜的色差影响较大,需调控其添加量;通过流变特性、化学作用力、傅里叶红外光谱(FT-IR)、扫描电镜(SEM)等研究发现,挤压膨化鱼骨粉可有效改善鱼糜凝胶蛋白的凝胶特性、增强鱼糜凝胶的疏水相互作用和二硫键交联、提高鱼糜凝胶的β-折叠含量及降低α-螺旋含量,使得鱼糜凝胶形成更为致密的微观结构,其凝胶效果与纳米级鱼骨粉相似。此外,挤压膨化制备的亚微米-纳米级金枪鱼骨富含蛋白质、脂肪和其他天然营养成分,其可接受程度远高于CaCl_(2)、NaCl等无机凝胶剂。由此可见,挤压膨化法可高效、节能地制备亚微米-纳米级金枪鱼骨粉,该鱼骨粉可作为一种优良、天然的钙源鱼糜凝胶增强剂。本研究为高值化利用鱼骨及开发新型鱼糜制品提供了理论依据。

Thermal Expansion Behavior of La1-xSrxMn1-yCoyO3-δ Perovskites

The thermal expansion behavior of La1-xSrxMn1-yCoyO3-δ (x=0.2-0.4, y=0.1-0.3) perovskites in air has been investigated. The average linear thermal expansion coefficients increased with increasing Sr content up to 40 mole fraction or Co content up to 30 mole fraction. The expansion is generally attributed to an increase in the average cation radius as some of the cations in the perovskite are reduced in valence when oxygen ions are removed from the structure.

Rapid Expansion of Supercritical Solution of Poly (1,1,2,2- Tetrahy-droperfluorodecyl Acrylate)

Poly(1,1,2,2- tetrahydroperfluorodecyl acrylate) (poly (TA-N)) was synthesized in laboratory. The resulting morphology of rapid expansion of supercritical solution (RESS) sprays of poly(TA - N) was investigated. At apre - expansion temperature of 45℃), amorphous polymer was formed. At temperature around 60 ℃ to 80 ℃ , fibers were formed. Increase of temperature increasesparticle size slightly. At temperature of 105℃ , most of particles are spheres. The RESS is an attractive process. To apply the polymers desired for coating applications in an organic solvent - free process that is economically viable , and it will have implications for pollution prevention during polymer film

Microstructural Characteristics and Wear Performance of Plasma Sprayed Al_2O_3-13 wt. % TiO_2 Coating on the Surface of Extrusion Wheel

The conventional Al2O3-13 wt. % TiO2 composite ceramic coatings are fabricated by plasma spraying on the surface of extrusion wheel. The microstrueture, morphology and phase compositions of the substrate and coat- ing are investigated by using X-ray diffractometry （XRD） , scanning electron microsopy （SEM） and energy dis- persive spectroscopy （EDS）. Moreover, the microhardness of the substrate and the coating are investigated using Vickers mierohardness tester, the friction and wear behaviors of the substrate and the coating are investigated by using a block-on-ring tribometer under dry sliding conditions with the load of 245 N. The results show that both γ-Al2O3 and α-Al2O3 phases are observed in the as-sprayed coatings, the mian phase is γ-Al2O3. There are white particulates Al2O3 on its surface. The Al2O3-13 wt. % TiO2 coating possesses higher mierohardness which is about 1018HV and 1.6 times that of the substrate. The wear performance of coating is better than that of the substrate. In a practical application, the life of the extrusion wheel which is plasma sprayed Al2O3-13 wt. % TiO2 coating on the surface is 1.2 times that of the conventional extrusion wheel, and the life is about 330 h.

鲣鱼肉挤压膨化工艺研究

以鲣鱼碎肉为对象,以硫代巴比妥酸值、氮溶解指数、质构、色差和感官评分为指标,探究不同挤压参数对挤压样品品质特性的影响。在此基础上,通过3因素3水平正交试验确定最优挤压膨化工艺:物料水分质量分数为25%、末端温度为130℃、螺杆频率为15 Hz。据此参数制得样品的感官总评分最高,为8.4分。从鲣鱼碎肉和挤压膨化样品中共检出了36种挥发物,确定了以己醛为代表的14种气味活性物质。经挤压膨化后鲣鱼碎肉中挥发物总质量分数从666.46 ng/g提高至2646.13 ng/g,以己醛为代表的不良风味物质质量分数显著下降,而以呋喃类为代表的熟化风味物质开始生成。研究成果可为金枪鱼肉加工企业提供理论参考和方法借鉴。

Microstructure, mechanical properties and deformation characteristics of Al-Mg-Si alloys processed by a continuous expansion extrusion approach

In the present work,a double-pass continuous expansion extrusion forming(CEEF) process was proposed for an Al-Mg-Si alloy,in which the diameter of rods was gradually expanded.The microstructural evolution,mechanical properties and deformation characteristics were investigated by utilizing microstructural observations,mechanical testing and a finite element method coupled with a cellular automata model.The results showed that the strength and ductility of the double-pass CEEF processed Al-Mg-Si alloys were improved synchronously,especially in artificially aged alloys.The grain size of the processed Al-Mg-Si alloy rods was refined remarkably by continuous dynamic recrystallization(CDRX)and geometric dynamic recrystallization(GDRX),and the homogeneity of microstructure was gradually improved with increasing number of processing passes.The artificially aged alloy processed with double-pass CEEF and water quenching contained fine(sub)grains and high-density dislocations,which resulted in more needle-shaped β" precipitates and a larger precipitate aspect ratio than the as-received and air-cooled CEEF alloys owing to the different precipitation kinetics.The severe cumulate strain and microshear bands were found to accelerate CDRX and GDRX for grain refinement between adjacent positions of the parabolic metal flow due to the special temperature characteristics and la rge shear straining during the CEEF process.

喷头流道结构参数对高黏度含能材料直写成型3D打印挤出过程稳定性影响

为了研究直写成型技术(DIW)中挤出系统的喷头流道结构参数(锥角角度、出口直径、成型段长度)对含能材料挤出过程的流体流动影响,研究建立了基于Polyfow Extrusion模块的高黏度含能材料挤出模型,并采用直写成型3D打印工况的挤出实验对其进行了验证。研究通过所建立的模型分析了锥角角度范围90°~130°,出口直径0.75~2 mm以及成型段长度5~20 mm对高黏度含能材料挤出过程的影响。结果表明:采用Polyflow Extrusion模块可以较准确地模拟复合含能材料的流动行为,同时发现锥角为100°、喷头出口直径为1.5~1.75 mm时挤出成型过程相对稳定、挤出膨胀较小,且成型段的增长会在增大所需入口压强的同时减小出口膨胀效应。

AP-CMDB推进剂微观结构及药形尺寸对低温力学性能的影响

为研究溶剂压伸法制备的AP-CMDB推进剂低温发动机试验易产生碎药的原因,采用扫描电子显微镜(SEM)和能谱仪(EDS)观察了AP-CMDB推进剂样品的微观结构;通过测试样品的线膨胀系数,研究了AP颗粒与黏合剂体系的线膨胀匹配性;讨论了药形尺寸对推进剂低温抗冲强度的影响。结果表明,溶剂压伸法制备的APCMDB推进剂药柱中存在大量微孔和少量微裂纹,AP颗粒团聚明显,Al颗粒与黏合剂体系间出现严重的界面脱粘;AP颗粒与黏合剂体系间的线膨胀匹配性较差;壁厚1.5mm的单孔管状药柱的低温(-40℃)抗冲强度低于壁厚4.5mm的,套管结构药柱的低温(-40℃)抗冲强度低于单孔管状药柱的。AP-CMDB推进剂低温碎药的形成与其微观结构、力学性能及药形尺寸有关。

挤压膨化结合酶解制备低GI代餐粉及其体外消化率测定

以藜麦、燕麦、青稞、苦荞为主要原料,辅以薏仁、葛根、桑叶、菊粉、低聚果糖等,利用酶解植物性原料及挤压膨化工艺制备代餐粉。以分散性指数和感官评分为指标,通过单因素试验和Box-Behnken试验结合优化原料挤压膨化工艺,并对原料代餐粉、挤压膨化代餐粉和酶解挤压膨化代餐粉的品质、体外消化率和血糖生成指数进行测定。结果表明:酶解挤压膨化代餐粉的最佳挤压膨化工艺为挤压温度150℃,螺杆转速810 r/min,喂料速度340 r/min,该工艺下代餐粉的分散性指数98.81%,感官评分89分。三种粉品质差异显著,酶解挤压膨化代餐粉的分散性指数和感官品质最高,酶解挤压膨化代餐粉eGI值为51.56,属于低GI食物,可为低GI代餐粉的开发提供一定的参考。

UHMWPE隔膜挤出成型工艺的实验研究

研究了挤出成型工艺参数如螺杆转速、螺杆温度等对超高分子质量聚乙烯(UHMWPE)湿法隔膜加工过程中冻胶液压力及预制膜厚度的影响。结果表明:随着螺杆转速的增加,相同时间内冻胶液挤出量增加,导致冻胶液压力增加;挤出膨胀率随剪切速率的增加而增加,从而造成挤出胀大现象更加明显;随着熔融段温度梯度的增加,网前、网后压力及预制膜的厚度增加,制品厚度尺寸稳定性降低。

挤扩支盘桩在岩溶区桥梁中的应用及推广

为了研究挤扩支盘桩技术在岩溶区桥梁中的应用及推广,依据根基原理的多支点端承桩基础设计,采用了挤扩支盘桩技术。通过充分利用挤扩土的压硬特征,构建了高效的多支点端承桩基础系统,提高了桥梁在岩溶地区的稳定性和可靠性。在实际项目中,通过详细的地质勘察与设计优化,科学合理地设置支盘布局,以确保桥梁基础在复杂地质环境下的稳定性。施工过程中,采用实时监测技术进行动态调控,确保挤扩支盘桩的施工质量和效率。项目实施后的实测数据表明,节约了约40%的施工时间,降低了约20%的施工成本。

Tuning of band gaps for a two-dimensional piezoelectric phononic crystal with a rectangular lattice

In this paper, the elastic wave propagation in a two-dimensional piezoelectric phononic crystal is studied by considering the mechanic-electric coupling. The generalized eigenvalue equation is obtained by the relation of the mechanic and electric fields as well as the Bloch-Floquet theorem. The band structures of both the in-plane and anti-plane modes are calculated for a rectangular lattice by the planewave expansion method. The effects of the lattice constant ratio and the piezoelectricity with different filling fractions are analyzed. The results show that the largest gap width is not always obtained for a square lattice. In some situations, a rectangular lattice may generate larger gaps. The band gap characteristics are influenced obviously by the piezoelectricity with the larger lattice constant ratios and the filling fractions.