共查询到20条相似文献,搜索用时 265 毫秒
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利用ANSYS软件对受口模入口处周期性振动的压力驱动的非牛顿幂率聚合物熔体在“Y”型异型材挤出口模内的流动过程进行了三维等温数值模拟。研究了入口压力的振动参数对流场压力和速度的影响情况。结果表明:流场中压力和速度的振动频率与入口压力的振动频率相等,而流场压力和速度的振幅随入口压力振幅的增大或者频率的降低丽增大,亦即低频高幅的振动容易得到较大的振动幅值。研究还表明流场速度的振动滞后于压力,且速度振动的衰减也比压力的衰减慢。 相似文献
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振动强化对金属粉末注射成型中模腔压力的影响 总被引:5,自引:0,他引:5
介绍金属粉末振动辅助注射成型设备的原理、结构及其应用,利用自制的模腔压力传感器对振动力场强化金属粉末注射成型过程中模腔压力的变化历程进行实时采集。试验结果表明,振动力场可以改变熔体在模具内的流动方式;在试验研究的范围内,不同径向位置处的模腔最大压力随振动振幅、频率的增加而减小,从而可以在不影响制品性能的条件下降低注射成型中的压力,以拓宽金属粉末注射成型的适用范围。 相似文献
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借助流变测量和连续介质理论,不依赖已有的本构关系,对平行叠加正弦振动条件下高分子熔体经毛细管的动态挤出过程进行了理论分析。以低密度聚乙烯(LDPE)为原材料,实验测量LDPE熔体在一定振动频率和振幅下毛细管入口压力、体积流量和挤出胀大的瞬态值,即可得到动态成型过程中高分子熔体剪切应力、剪切速率和表观粘度的变化规律:随振幅和频率的变化,LDPE熔体的表观粘度呈非线性变化趋势;在不同的振幅和频率下动态挤出LDPE熔体,跟稳态挤出时一样,壁面剪切应力与壁面剪切速率也成非线性比例关系。 相似文献
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注射成型中模腔内振动剪切流动的理论模型 总被引:3,自引:1,他引:2
采用Leonov本构模型,首次研究了在注射成型中模腔内聚合物熔体的振动剪切流动时所产生的振动剪切应力。结果表明,振动剪切应力的振幅随着聚合物熔体的粘度,振动频率和应变振幅的增加而增加,随着熔体温度的增加而减小。 相似文献
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振动注射成型中模腔冷却过程的研究 总被引:2,自引:0,他引:2
研究了振动注射成型中模腔内聚合物溶体产生的振动剪切热,并研究在振动作用下模腔内物料的冷却过程。结果表明,模腔内熔体的温升速率随着振动频率、应变振幅及振动剪切速率的增加而增加,随熔体温度的增加而减少。由于振动剪切换,使振动注射成型需要更长的冷却时间。 相似文献
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聚合物动态挤出流变行为研究 总被引:30,自引:5,他引:25
本文论述聚合物材料毛细管动态流变行为的测量原理,介绍了自行研制成功的用于合物熔体挤出的毛细管动态流变仪。在该仪器上对LDPE进行了实验研究,发现熔体的粘度与振动源的频率、振幅呈非线性关系。在振动必场作用下LDPE熔体的粘度减小,随振动频率的变化有一最小值。这对矣合物动态塑化挤出工艺过程控制具有十分重要意义。 相似文献
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振动力场作用下聚合物挤出压力的时频特性研究 总被引:1,自引:0,他引:1
利用小波分析原理对实测的振动力场作用下LDPE、LLDPE熔体挤出压力进行5尺度Daubechies5小波分析,发现振动强度二因子振幅、频率分别对聚合物熔体挤出压力变化的周期性特征产生不同影响. 相似文献
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采用自行研制的压力振动注射装置,在不同熔体温度、振动频率、振动压力下得到等规聚丙烯(IPP)振动注射试样。运用广角X射线衍射测试方法对样条表层晶体结构进行了表征。测试结果表明当熔体温度上升到230℃时出现β晶型,β-IPP含量随振动频率和振动压力的上升而增加。试样拉伸性能随振动压力增加而提高,引入振动会引起断裂伸长率的降低,但随振动频率的增加,断裂伸长率有上升趋势。运用极图表征IPPα晶型特征晶面取向情况,在相对的低频、低温、高压条件下,α(040)晶面法向有较好的流动方向择优取向;而在高频、高温、低压情况下,α(040)晶面法向有较好的法向方向择优取向。 相似文献
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In this article, under shearing vibration and pressure vibration, the rheological behavior of HDPE, ABS, and PS melts and the mechanical properties of molded parts are studied. The experimental results show that, under the vibration condition, the apparent viscosity of the polymer melt decreases with an increasing of the vibration frequency and amplitude applied. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1587–1592, 2002 相似文献
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采用毛细管动态流变仪,选用PELD、PP、PS和PA等典型物料,研究了毛细管动态挤出下各聚合物熔体的非线性流变行为。结果表明,不同物料的流变行为对振动力场的响应特性有较大差异,只有在一定的振幅和频率下振动力场才能有效降低熔体的黏度。实验首次发现,PP、PS和PA存在窄的振动参数区域,在此区域内,熔体的动态表观黏度值大于相应的稳态值,出现“加振变黏”现象。这一新的发现表明,并非“只要引入振动就一定有利于聚合物材料的成型加工”,必须考虑不同分子结构的聚合物材料对振动的不同响应规律。 相似文献
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利用非仿射瞬态网络结构本构模型来分析正弦脉动流场中的聚合物熔体第一、第二法向应力差系数的变化规律,以及振动参数(振动频率和振幅)对聚合物熔体的影响作用。结果表明,在实际加工中可以通过增加振幅或振动频率来降低聚合物熔体的弹性,此模型还可以预测到最佳振幅或最佳振动频率。 相似文献
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BACKGROUND: A low‐frequency vibration‐assisted injection‐molding (VAIM) device was developed to explore the morphology of high‐density polyethylene (HDPE) injection moldings. Scanning electron microscopy, wide‐angle X‐ray diffraction and differential scanning calorimetry were used to characterize structure‐property relationships of final products prepared under different VAIM processing conditions (vibration frequency and vibration pressure amplitude) with conventional injection molding for comparison. RESULTS: It was found that increasing the vibration frequency at constant vibration pressure amplitude was beneficial for obtaining ‘shish‐kebab’ structures in the core region of VAIM specimens, and increasing the vibration pressure amplitude at constant vibration frequency was a prerequisite for achieving HDPE specimens with large‐scale lamellas, more pronounced orientation and high crystallinity. CONCLUSION: Both preferred orientation lamellas and increased crystallinity allow one to obtain strong injection moldings with the application of the melt vibration technique. Copyright © 2009 Society of Chemical Industry 相似文献
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Li Youbing Gao Xueqin Yuan Shaoyan Yuan Yi Zhang Jie Ke Wenti Shen Kaizhi 《Polymer International》2005,54(1):240-245
This paper introduces a novel melt vibration‐injection molding. The effect of mid‐frequency melt vibration on mechanical properties was introduced, and SEM, WAXD and DSC investigations had been employed to provide evidence for explaining the relationship between mechanical properties and morphology of vibration‐injection‐molded specimens. The results show that the effect of vibration frequency is very different from that of vibration pressure amplitude. At a given vibration pressure amplitude, the increase of vibration frequency is beneficial for obtaining preferential orientation, more perfect lamellae and enhanced mechanical properties. For a given vibration frequency, increase of vibration pressure amplitude is a pre‐requisite for the achievement of a large‐scale lamella, more pronounced orientation, increase of cyrstallinity and high strength of high‐density polyethylene, but part of the toughness is lost. Copyright © 2004 Society of Chemical Industry 相似文献
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Wu Hong-wu Zhang Shao-dan Qu Jin-ping Xu Hai-hang 《Polymer-Plastics Technology and Engineering》2013,52(2):123-127
Using an online measure system consisted of a high sensitivity pressure sensor, a spiral channel mold and a data collecting/analysis series. The cavity pressure and flow length response under different injection pressure, injection velocity, mold temperature and different vibration condition was measured and analyzed in this study. The results show that the cavity pressure and flow length increased with the increase of injection pressure, injection velocity and mold temperature. In vibration assisted injection molding (VAIM), the cavity pressure and flow length increased as a result of imposing vibration. The change of amplitude and frequency in VAIM had more distinct effect on flow length than injection pressure. The results also indicate that the measure system established in this study can accurately monitor and record the changes of cavity pressure, and could be used in the study of melt's filling capacity in injection molding process. 相似文献