Continuous Extruding Extending Forming of Semi-solid A2017 Alloy

Continuous extruding/ extending formiug process for A2017 alloy in semi-solid state was proposed through installing extending die at the outlet of shearing- cooling- rolling （SCR） machine. A series of experiments to produce fiat bar of A2017 alloy were carried oat. The forming process, metal flow behavior in die and microstructure and mechanical property of prodacts were investigated. It is shown that if the pouring temperature of melt was higher, the die was filled with semi-solid slurry with low solid fraction and periodical cracks would occur on the product surface ; If its pouring temperature was lower or the preheating temperature of die was lower, semisolid slurry would solidify rapidly and block the die after entering the cavity. The analysis of mass flow trace shows that the semi-solid slurry move forward layer by layer and fills the die extending cavity in radiation manner and the velocity of mass flow in the central area of extending cavity and exit of mould is the maximum, and then decreases gradually from the center to both sides of die wall. By inereasiug the die extending angle, the velocity of mass flow becomes more homogeneous. Under rational process control and die design, the A2017 fiat bar with transverse section of 10 × 50 mm and with good surface and fine equiaxed grains can be obtained by continuous extruding/extending forming process. The product＇s tensile strength and elongation are 420.5 MPa and 14.2% , respectively.

Experimental Study of Integration and Polyblends Performance for Improved Mixing-Extruding Machine

One improved mixing-extruding machine was introduced as the second-generation product of the mixing-molding integrated technology. In the extruding system,the conventional single screw extruder was substituted by a special conical twin-screw extruder,resulting in stronger feeding ability,more stable extrusion pressure,and better quality of products. The integrated mathematical model of mixing-extruding process was also established by theoretical derivation and optimization according to the experimental results.Then its accuracy was verified by the influences of the pressure of floating weight and the cooling water temperature of extruder on the mixing-extruding integrated process. The results showed that the changes of both parameters could give rise to the fluctuation of the temperature and apparent viscosity of polyblends, thus further influencing the screw rotation speed.

ANALYSIS OF SURFACE CRACK ON FORWARD EXTRUDING BAR DURING AXISYMMETRIC CUP-BAR COMBINED EXTRUSION PROCESS

In this paper, the kinematically admissible velocity field with surface crack on forward extruding bar is put forward during the axisymmetric cup-bar combined extrusion process, in accordance with the results of model experiments.On the basis of velocity field, the necessary condition for surface crack formation on the forward extruding bar is derived, with the help of upper bound theorem and the minimum energy principle. Meanwhile, the relationships between surface crack formation and combination of reduction in area for the part of forward and backward extursions relative residual thickness of billet (T/R0),frictional factor (m) or relative land length of ram and chamber are calculated during the extrusion process. Therefore, whether the surface crack on forward exturding bar occurs can be predicted before extruding the lower-plasticity metals for axisymmetric cup-bar combined extrusion process.The analytical results agree very well with experimental results of aluminium alloy LY12 (ASTM 2024) and LC4 (ASTM 7075).

Thermal and textural properties of extruded rice affect its cooking performances and the texture of the steamed extruded rice

Extruded rice has increasingly gained popularity in the market due to its convenience and acceptable texture.The objective of this study was to understand how the physicochemical,thermal,and textural properties of the extruded rice affected its cooking properties and texture of the cooked one.It was found that air trapped in the grains during extrusion reduced the transparency of extruded rice.More air trapped in the grains reduced the true density of the extruded rice,which in turn decreased the hardness of extruded rice.A looser internal structure of extruded rice grain,as indicated by the lower true density,resulted in a faster hydration and shorter optimum cooking time.Extruded rices showed two thermal-transition peaks,with peak 1 from 93.3℃ to 112.8℃ and peak 2 from 107.5℃ to 132.5℃.The increased hardness of extruded rice led to increases in its thermaltransition temperatures,longer optimum steaming time,and decreases in its water absorption and cooking loss,which resulted in an increase in the hardness and a reduction in the adhesiveness of the steamed one.This study provides insights into the key factors determining the eating quality of extruded rice,which is beneficial for food scientists in developing premium extruded rice.

Numerical simulation of upsetting-extruding process of dispersion strengthened copper welding electrode

The simulation of the upsetting-extruding process of dispersion strengthened copper welding electrode was carried out using Deform-2D finite element analysis software, and the characteristics of metal flow and the effect of different friction factors were analysed. The results show that the whole forming process consists of a forward extrusion and a backward extrusion. When the friction factor of the female die is 0.4, it is advantageous to the forward extrusion forming of the electrode work nose part, while the friction factor of the male die is only 0.1, it would be benefit to the backward extrusion forming of the electrode fit-up hole part. Addition of a scoop channel with 1.5 mm in depth and 4 mm in diameter at the bottom of the female die can avoid folds at the work nose. The rise in temperature is about 60 ℃ during the forming process.

Numerical Simulations of Polymer Melt Conveying in Co-Rotating Twin Screw Extruder

The 3 D non isothermal flow of non Newtonian viscous polymer melt in a co rotating twin screw extruder is modeled. The distributions of the velocity, temperature, pressure and the viscous dissipation in the flow domain are presented by using a fluid dynamics analysis package (Polyflow). The numerical results show that the temperatures are high in the intermeshing region and on the screw surface, the maximum pressure and the minimum pressure occur in the intermeshing region, and the flow rate is almost proportional to the screw speed.

响应面法优化香榧仁挤压-复形工艺

以香榧仁为原料,以复形率、整粒率以及二者的综合评分为评价指标,通过单因素试验和响应面试验优化挤压-复形香榧仁的制备工艺。结果表明:最佳挤压-复形工艺为香榧仁水分含量15%、挤压压力3MPa、挤压时间50s、复形时间5min。在此条件下,香榧仁复形率和整粒率分别为91.41%±2.39%、83.01%±1.86%,综合评分为88.05±1.17。微观结构分析结果显示,挤压-复形后的香榧仁组织结构更为疏松多孔。与炒制香榧仁相比,挤压-复形再烤制的成品去衣率更高、口感更为酥脆。

双螺杆捏合方式制备的三基发射药的流变性研究

为掌握三基发射药连续化捏合工艺中药料的流变特性,提高工艺模型的准确性,按照三基发射药代料配方制备了预混药料,使用双螺杆挤出机对预混药料进行捏合,并通过专用双料筒毛细管流变仪测试捏合后药料的流变特性。分别改变双螺杆挤出机的螺杆转速和捏合温度、药料的固含量和溶剂比,分析以上变量对三基发射药流变学参数的影响规律。结果表明:双螺杆捏合后,药料的本构方程与Carreau-Yasuda本构模型拟合程度较高;一定范围内,螺杆转速或捏合温度的提高会使捏合后的药料的剪切黏度降低;同时,螺杆转速的提高会使药料的停留时间减少,而过短的停留时间会导致捏合后的药料的黏度上升;固含量的增加或溶剂比的减小会使捏合后的药料的剪切黏度增大,而黏度增大会使药料的停留时间增长,一定程度上使药料受到更充分的捏合作用。

挤压型米线的研究进展

挤压型米线是以大米作为原料,经研磨并调配至一定水分含量后,挤压熟化成型后干燥而得到的米线。传统工艺生产的米线费力、耗时,在多步骤米线生产过程中会导致产品质量不一等问题。相比而言,挤压技术是一种集混合、加热、杀菌和成型于一体的食品加工技术。将挤压技术应用到米线加工中,具有营养成分损失少、微生物污染机会少、生产时间短、生产效率高和操作简便等优点。因此,我国米线加工业生产中,自动化的机械加工正逐步取代传统的手工作坊。挤压型米线质量主要受挤压型米线生产过程中原辅材料、加工工艺、挤压参数的影响。因此,本文阐述了挤压型米线的加工工艺及成型机制,综述了原辅材料、挤压参数对挤压型米线品质的影响规律,以期为挤压型米线加工工艺及关键点的控制提供理论依据。

带有反向螺纹的同轴变速单螺杆三维流场分析

为了改善单螺杆挤出机混炼性能,设计了一种装配内嵌式摆线齿轮减速器和反向螺纹元件的新型螺杆。使用Solid works软件建模,利用ANSYS和CFX软件分析新型同轴变速单螺杆挤出机的流道内三维流场变化,根据流道内的压力、速度矢量、截面速度等变化,探究物料在其流道内的剪切和混合情况。结果表明:在外部情况相同时,新型螺杆建压能力弱于传统螺杆,即新型螺杆的挤出效率较低;新型螺杆因为装配内嵌式摆线齿轮减速器使其混炼区域的速度降为传统螺杆的1/6,引起物料对流,加快压力场变化,使其速度流线更加混乱;新型螺杆因为装配有反向螺纹元件,使其混炼区域出现反向建压能力,在此作用下物料出现反向速度,出现回流现象。综上,摆线齿轮减速器和反向螺纹元件均延长了物料在流道内的停留时间,增加了物料的挤压剪切次数,从而增强了挤出机的混合分布能力和挤压剪切效果。

双螺杆挤出机齿轮箱效率计算

为提高齿轮箱的传动效率,降低功率损耗,提出了一种齿轮箱传动效率的仿真计算方法。基于KISSsys建立齿轮箱系统的传动模型,计算齿轮、轴承、轴封等损耗,并应用于双螺杆挤出机齿轮箱的传动效率分析,通过加载试验得到齿轮箱的效率数值,并与理论仿真计算的结果进行对比,结果表明仿真计算与试验结果的最大偏差为0.28%,提出的仿真计算方法能够很好的预测双螺杆挤出机齿轮箱的效率;并分析齿轮的压力角和润滑油类型对传动效率的影响,KISSsys分析结果显示齿轮压力角从20°增大到25°,齿轮的负载损耗降低了22.26%,传动效率提高了0.24%;使用聚乙二醇类合成润滑油,齿轮负载损耗平均降低了28.83%,轴承损耗平均降低了19.68%,传动效率平均提高了0.59%。

单螺杆挤出机连续挤出制备的超活化胶粉及其改性沥青的性能研究

采用单螺杆挤出机对废旧轮胎胶粉进行连续活化挤出以制备超活化胶粉,对超活化胶粉及其硫化胶性能进行研究,探讨超活化胶粉在沥青改性中的应用。结果表明:废旧轮胎胶粉活化时,芳烃油用量为8份制得的超活化胶粉的交联密度最小,其硫化胶的拉伸强度和拉断伸长率最大,活化效果较好;超活化胶粉的傅里叶变换红外光谱的1645 cm^(-1)处的吸收峰较废旧轮胎胶粉增强,超活化胶粉与沥青的相容性好,超活化胶粉掺量(质量分数)为47%的改性沥青未产生离析分层现象。

减速器推力轴承定位偏差影响轴系径向跳动异常分析

双螺杆挤出机是一种常用的塑料加工设备,在双螺杆挤出机减速器的生产制造过程中,出现了输出轴径向误差检测异常现象。输出轴转动两周,百分表指针检测数值从零点回到零点。本文从推力轴承结构方面对其进行分析,详细介绍了出现此种情况的原因及解决此问题的方案。

Methane aromatization in the absence of oxygen over extruded and molded MoO_3/ZSM-5 catalysts:Influences of binder and molding method

The influences of binder and molding method on the catalytic performance of methane aromatization in the absence of O2 over MoO3/ZSM-5 catalysts were investigated.SEM,NH3-TPD,FT-IR of adsorbed pyridine,N2 adsorption-desorption,cyclohexane adsorption and XPS were employed to characterize the physical and chemical properties of the catalysts.It was found that SiO2 was a suitable binder for the catalyst due to its appropriate weak acidity.The laminar catalyst comprising of an inert spherical core and a MoO3/ZSM-5 laminar shell with 0.1 0.2 mm in thickness showed a better catalytic performance than the extruded catalyst.The improved activity of the laminar catalyst could be attributed to the easy carbonization of Mo species and the quick removal of reaction products from the catalyst surface.

Effects of single and multi-stage solid solution treatments on microstructure and properties of as-extruded AA7055 helical profile

The effects of single-stage solution treatment(SST),enhanced solution treatment(EST),high-temperature pre-precipitation(HTPP)and multi-stage solution treatment(MST)on the microstructure,mechanical properties and corrosion resistance of the as-extruded 7055 aluminium alloy(AA7055)helical profile were investigated using differential scanning calorimetry(DSC),optical microscopy(OM),scanning electron microscopy(SEM),electron back-scattered diffraction(EBSD)and transmission electron microscopy(TEM).It was observed that EST and MST could promote the dissolution of the second-phase particles compared with the traditional SST,and the intergranular phases were distinctly discontinuously distributed after HTPP and MST.There was obvious difference in the main texture type and texture strength for the alloy after different solid solution treatments.HTPP could improve the corrosion resistance of the alloy by regulating the intergranular phases,but the mechanical properties were severely weakened.While the good corrosion resistance of the alloy could be obtained by MST without obvious strength loss.As a result,the MST is an ideal solid solution treatment scheme for AA7055.

Dynamic compressive property and failure behavior of extruded Mg-Gd-Y alloy under high temperatures and high strain rates

For the purpose of investigating the dynamic deformational behavior and failure mechanisms of magnesium under high strain rates,the Split Hopkinson Pressure Bar(SHPB)was used for investigating dynamic mechanical properties of extruded Mg-Gd-Y Magnesium alloy at ambient temperature(300 K),200℃(473 K)and 300℃(573 K)temperature.The samples after compression were analyzed by scanning electron microscope(SEM)and metallographic microscope.Dynamic mechanical properties,crack performance and plastic deformation mechanism of extruded Mg-Gd-Y Magnesium alloy along the extrusion direction(ED)were discussed.The results show that,extruded Mg-Gd-Y Magnesium alloy has the largest dynamic compressive strength which is 535 MPa at ambient temperature(300 K)and strain rate of 2826 s^(−1).When temperature increases,dynamic compressive strength decreases,while ductility increases.The dynamic compression fracture mechanism of extruded Mg-Gd-Y Magnesium alloy is multi-crack propagation and intergranular quasi-cleavage fracture at both ambient temperature and high temperature.The dynamic compressive deformation mechanism of extruded Mg-Gd-Y Magnesium alloy is a combination of twinning,slipping and dynamic recrystallization at both ambient temperature and high temperature.

Low cycle fatigue behavior of the extruded AZ80 magnesium alloy under different strain amplitudes and strain rates

Low cycle fatigue behavior of extruded AZ80 magnesium alloy was investigated under uniaxial tension-compression at different strain amplitudes and strain rates.The results show that the extruded AZ80 magnesium alloy exhibits cyclic hardening at strain amplitudes ranging from 0.4%to 1.0%,the asymmetry of hysteresis loops becomes increasingly obvious when the strain amplitude increases.Higher strain rates correspond to higher stress amplitudes,high mean stresses and short fatigue life.{10–12}extension twins play a role in the cyclic deformation under higher strain amplitudes(0.8%,1.0%).The relationship between total strain energy density and fatigue life can be described by the modified Morrow model.The effect of strain rate on the fatigue life can also be predicted by the model.

A comparison study of Ce/La and Ca microalloying on the bio-corrosion behaviors of extruded Mg-Zn alloys

The influences of Ca and Ce/La microalloying on the microstructure evolution and bio-corrosion resistances of extruded Mg-Zn alloys have been systematically investigated in the current study.Compared with single Ca or Ce/La addition,the Ca-Ce/La cooperative microalloying results in an outstanding grain refinement,because the fine secondary phase particles effectively hinder the recrystallized grain growth.The coarse Ca2Mg6Zn3 phases promote the formation of Ca3(PO4)2 or hydroxyapatite particles during the immersion process and accelerate the dissolution of the corrosion product film,which destroys its integrity and results in the deterioration of anti-corrosive performance.The Ce/La elements can be dispersed within the conventional Mg7Zn3 phases,which reduce the internal galvanic corrosion between Mg matrix and the secondary phases,leading to an obvious improvement of corrosion resistance.Therefore,the Ca-Ce/La cooperative microalloying achieves a homogenous fine-grained microstructure and improves the protective ability of surface film,which will pave a new avenue for the design of biomedical Mg alloys in the coming future.

Effects of Y content and temperature on the damping capacity of extruded Mg-Y sheets

The damping behavior of extruded Mg-xY(x=0.5,1.0,3.0 wt.%)sheets were investigated in detail concerning the effects of Y addition and temperature,and the relationship between damping capacity and yield strength was discussed.At room temperature(RT),with Y content increasing from 0.5%to 3.0%,the damping capacity(Q-1)significantly decreased from 0.037 to 0.015.For all the studied sheets,the relationship between strain amplitude and Q-1 fitted well with the Granato and Liicke(G-L)dislocation damping model.With temperature increased,the G-L plots deviated from linearity indicating that the dislocation damping was not the only dominate mechanism,and the grain boundary sliding(GBS)could contribute to damping capacity.Consequently,the Q-1 increased remarkably above the critical temperature,and the critical temperature increased significantly from 50℃ to 290℃ with increasing Y contents from 0 to 3.0wt.%.This result implied that the segregation of Y solutes at grain boundary could depress the GBS,which was consistent with the recent finding of segregation tendency for rare-earth solutes.The extruded Mg-IY sheet exhibited slightly higher yield strength(Rp0.2)and Q-1 comparing with high-damping Mg-0.6Zr at RT.At an elevated temperature of 325℃,the Mg-IY sheet had similar Q-1 but over 3 times larger Rp0.2 than that of the pure Mg.The present study indicated that the extruded Mg-Y based alloys exhibited promising potential for developing high-performance damping alloys,especially for the elevated-temperature application.

Effect of Replacing Fish Meal with Extruded Soybean Meal on Growth, Feed Utilization and Apparent Nutrient Digestibility of Juvenile White Shrimp(Litopenaeus vannamei)

Extruded soybean meal （ESBM） was evaluated as a protein source for partial replacement of fish meal （FM） in diets of juvenile Litopenaeus vannarnei. In the control diet （Diet 1）, FM protein was replaced with increasing dietary levels of ESBM （4.28%, 8.40%, 12.62%, 16.82%, and 25.26%） at 10%, 20%, 30%, 40%, and 60% levels （Diets 2 to 6, respectively）. An eight-week feeding trial was conducted on 720 juvenile shrimp （0.67 g ± 0.01 g mean initial Weight）, and nutrient digestibility of the six diets was determined. ESBM could replace 20% of FM without causing a significant reduction in growth of shrimp, but other dietary treatments strongly affected whole body composition. Crude protein content of the whole body fed Diet 6 was significantly lower than that fed Diet 2 （P〈0.05）, while crude lipid content of the whole body fed Diet 5 or 6 was significantly higher than that fed Diet 2 （P〈0,05）. Protein digestibilities of Diets 5 and 6 were significantly lower than that of Diet 1 （P〈0.05）. Digestibility of lipids ranged from 96.97% in Diet 6 to 98.34% in Diet 3, whereas dry matter digestibility decreased with increasing replacement level. This study indicates that 20% FM replacement with ESBM in the basic diet containing 40% protein and 30% FM is optimal for juvenile L. vannamei.