超声振动聚合物界面摩擦生热仿真分析

采用ANSYS和LS-DYNA仿真分析超声振动聚合物界面摩擦生热过程,主要分析超声振幅、超声频率和摩擦因数对界面摩擦生热速率的影响规律。研究结果表明:界面摩擦生热能使聚合物温度升高,且生热是瞬态过程,超声振动作用时间0.164 45s,聚合物界面局部温度能升高到160.7℃,生热速率达到855.57℃/s。界面摩擦生热速率随着超声振幅、超声频率和摩擦因数的增加而增大,超声频率对聚合物界面摩擦生热速率的影响更显著。     

超声塑化生热及其参数对温度特性的影响

超声熔融塑化注射成型是一种新型的聚合物塑化方式,而聚合物超声熔融塑化过程中温度场分布、超声波频率和振幅对聚合物塑化的影响规律等问题有待进一步的研究。本文针对这些问题,通过仿真计算、实验验证的方法,研究了超声工具头端面和外圆柱面振动对聚合物的熔融塑化效果和不同超声波参数对聚合物的熔融塑化的影响。结果表明:熔池从工具头端面中心部位开始形成,并向轴向和径向扩展;工具头轴向振动的塑化作用为聚合物熔融塑化的主要能量来源,其效果远远大于径向振动的塑化作用;超声波振幅对聚合物的塑化效率比超声波频率影响更大。     

超声振动对PS熔体流变及黏弹行为的影响

采用Bagley入口校正等理论计算方法与实验结果相结合，讨论了超声振动对PS熔体流变及黏弹行为的影响。在口模入口处施加超声振动，降低了聚合物熔体的非牛顿性，改变其黏弹行为，使其在毛细管口模中流动时弹性形变及储能减小，形变松弛加快，黏度降低，从而使挤出加工中流动阻力变小，挤出效率得到提高。     

超声振动对聚合物结构性能的影响

介绍了聚合物挤出成型过程中的超声振动技术，并对挤出模头引入超声振动后对聚合物物理机械性能、相容性、结晶性能的影响进行了评述。     

注塑制品内应力计算的非线性黏弹性本构方程

在聚合物黏弹性理论的基础上，构建了新的注塑制品内应力计算的四元件串联力学模型，并推导了其瞬态黏弹性响应的非线性本构方程，给出了聚合物材料参数弹性模量和黏壶系数的计算公式，并对PS平板注塑制件脱模前的内应力进行了模拟计算。计算结果与固体高聚物的结构和力学性能的相关研究结论相一致，所建计算模型合理可靠。     

模温及熔体温度对不同材料的薄壁注塑制品熔接痕的影响

利用MoldFlow模拟了不同模温和熔体温度对结晶型聚合物PP、无规脆性聚合物PS、无规韧性聚合物PC成型的数码电视机支撑座熔接痕长度的影响。模拟结果表明：当模具温度低于材料的熔化温度时，升高模具温度能显著的缩短PP、PC熔接痕的长度，但不能明显的缩短PS熔接痕的长度；当模具温度升高到PS熔融温度时，PS熔接痕长度随模温的升高急剧缩短；当模具温度高于熔体注射温度时，熔接痕长度的改变量很小。升高熔体温度不能缩短PP熔接痕长度，能缩短PS、PC熔接痕长度，但熔体温度对熔接痕的影响远不如模温明显。升高模温和熔体温度都很难消除熔体以头-头的形式相遇形成的熔接痕。     

遗传算法在动态黏弹性模型参数拟合中的应用研究

为了研究聚合物材料弹性变形对微结构成型制品变形的影响,采用仿真分析手段对环烯烃类共聚物(TOPAS-COC)材料的滚动热压成型进行了模拟计算,并对TOPAS-COC聚合物材料黏弹性模型参数进行了拟合。通过比较改进的遗传算法和最小二乘法拟合的结果,发现遗传算法在寻找动态黏弹性模型参数中具有很好的寻优功能。利用平移原理获得参考温度下主曲线,将拟合得到的模型参数输入非线性有限元软件Abaqus中进行仿真模拟,正交实验结果表明,适当增加温度、减小预压紧量以及减小滚动速度可以降低弹性回复对微结构弹性变形的影响。     

有机锆交联AM/DMAM/AMPS三元聚合物流变动力学

以乳酸/丙三醇有机锆为交联剂,聚合物[一种耐高温的丙烯酰胺(AM)/N,N-二甲基丙烯酰胺(DMAM)/2-丙烯酰胺基-2-甲基丙磺酸(AMPS)三元聚合物]为稠化剂,获得了耐高温聚合物凝胶.研究了聚合物凝胶的流变学特性(黏弹性、触变性)及其交联流变动力学,获得了聚合物交联过程中黏度、黏弹性模量随时间的变化关系,并考察了剪切速率和温度对凝胶形成的影响,建立了交联流变动力学模型.结果表明,交联聚合物凝胶具有明显的黏弹性和触变性;在180℃、170 s^-1下剪切120 min后,黏度达176.8 mPa·s,获得了耐高温达180℃的凝胶;一级交联流变动力学模型可拟合聚合物的交联流变动力学过程,拟合的模型参数物理意义明确合理.     

超声防蜡降粘系统的试制及其对延长油田原油的作用

通过分析超声防蜡降粘机理,研究和设计了超声防蜡降粘用全波长纵向复合式压电超声换能器,并进行了性能测试和超声场的分析,做了超声防蜡降粘实验。根据四端网络法设计了一种夹心式全波长复合压电换能器,对加载后节面位置的变化进行了分析计算,并采用有限元模态分析方法分析了所设计换能器的固有频率和振型,还通过测试实验验证了换能器的各项参数满足设计要求。以所研制的换能器为核心搭建了超声防蜡降粘实验平台,通过实验分析了超声频功率、作用时间及原油含蜡量对超声作用效果的影响及规律。     

疏水缔合聚合物HAWP与芥酸酰胺丙基烯丙基溴化铵复合体系流变和界面性能研究（英文）

针对疏水缔合聚合物增黏和界面活性提高能力有限的问题，疏水缔合聚合物复合增效体系被提出，基于疏水缔合聚合物HAWP与阳离子表面活性剂芥酸酰胺丙基烯丙基溴化铵（EDAA）复配构筑了疏水缔合聚合物复合增效体系EDHA，首先借助扫描电镜、流变仪以及环糊精包合法研究了疏水缔合聚合物复合增效体系的增黏机理，然后从流变性和界面性能两方面探究了pH值、NaCl质量浓度和温度对复合增效体系流变性和降低界面张力能力的影响。研究结果表明复合增效体系通过疏水缔合作用与静电吸引作用协同增效。复合增效体系的黏度和黏弹性随着pH值增加先增大后减小，界面张力先减小后增大；复合增效体系的黏度、黏弹性随着NaCl质量浓度的增大逐渐变小，界面张力先上升后下降。随着温度的增加，复合增效体系的黏度和黏弹性逐渐变小，界面张力逐渐增大。     

超声微注塑机超声单元的设计与分析

提出一种基于超声驱动技术实现聚合物塑化和注射的超声微注射成型机。首先分析超声微注塑机整体结构及工作原理,然后进行超声注塑单元和超声振动模块结构设计,最后利用ANSYS软件进行超声振动模块模态分析和静力学分析,获得超声振动模块的振动频率及相应的纵向振型和超声振动模块的应力应变分布,针对分析结果进行材料强度刚度校核。结果表明,该超声电动微注塑机的超声振动模块能够获得满足需要的纵向振动,且其强度、刚度满足材料性能要求。     

聚合物两圆筒环槽切向流传热的简化计算

本文应用有限差分法对聚合物在两圆筒环槽间具有粘滞耗散热的切向流,简化为两平行平板拖动流而进行传热计算.首先得出熔融体拖动流顺流方向的温度分布,并导出两壁面处温度梯度的近似计算式,从而求出两壁面处的努塞尔准数Nu和换热系数α值.本文可供聚合物螺杆机械、剪切机头、以及模腔流道等具有耗散热传热计算时参考.     

Anisotropy of the high-power piezoelectric properties of Pb(Zr,Ti)O3

Piezoceramics are widely-used in high-power applications, whereby the material is driven in the vicinity of the resonance frequency with high electric fields. Evaluating material's performance at these conditions requires the consideration of inherent nonlinearity, anisotropy, and differences between individual vibration modes. In this work, the relation between electromechanical properties at large vibration velocity and the utilized vibration mode is investigated for a prototype hard piezoceramic. The nonlinear behavior is determined using a combined three-stage pulse drive method, which enables the analysis of resonant and antiresonant conditions and the calculation of electromechanical parameters. The deviations of coupling coefficients, compliances, and piezoelectric coefficients at high-power drive were found to be strongest for the transverse length vibration mode. Differences in the mechanical quality factors were observed only between the planar and transverse length modes, which were rationalized by the different strain distribution profiles and the contribution of different loss tensor components. In addition, the influence of the measurement configuration was investigated and a correction method is proposed. The differences between vibration modes are further confirmed by heat generation measurements under continuous drive, which revealed that the strongest heat generation appears in the radial mode, while transverse and longitudinal length modes show similar temperature increase. Piezoceramics are widely-used in high-power applications, whereby the material is driven in the vicinity of the resonance frequency with high electric fields. Evaluating material's performance at these conditions requires the consideration of inherent nonlinearity, anisotropy, and differences between individual vibration modes. In this work, the relation between electromechanical properties at large vibration velocity and the utilized vibration mode is investigated for a prototype hard piezoceramic. The nonlinear behavior is determined using a combined three-stage pulse drive method, which enables the analysis of resonant and antiresonant conditions and the calculation of electromechanical parameters. The deviations of coupling coefficients, compliances, and piezoelectric coefficients at high-power drive were found to be strongest for the transverse length vibration mode. Differences in the mechanical quality factors were observed only between the planar and transverse length modes, which were rationalized by the different strain distribution profiles and the contribution of different loss tensor components. In addition, the influence of the measurement configuration was investigated and a correction method is proposed. The differences between vibration modes are further confirmed by heat generation measurements under continuous drive, which revealed that the strongest heat generation appears in the radial mode, while transverse and longitudinal length modes show similar temperature increase.     

Ultrasonic welding of thermoplastics in the far-field

In far-field ultrasonic welding of plastic parts the distance between the ultrasonic horn and the joint is greater than 6 mm. This study investigated the farfield ultrasonic welding of amorphous (acrylo butadiene styrene and polystyrene) and semicrystalline (polyethylene and polypropylene) polymers. Far-field welding worked well for amorphous polymers. Weld strength improved substantially with increasing amplitude of vibration at the joint interface. Increasing the weld pressure and/or the weld time also resulted in higher weld strengths. Far-field ultrasonic welding was not successful for semicrystalline polymers. The parts melted and deformed at the horn/part interface with little or no melting at the joint interface. A model for wave propagation in viscoelastic materials, which was developed to predict the vibration amplitude experienced at the joint interface, indicates that increasing the length of the samples to a half a wavelength should improve the far-field welding of semicrystalline polymers by maximizing the amplitude of vibration at the joint interface.     

Ultrasonic characterization of the crystallization behavior of poly(ethylene terephthalate)

On the basis of the previous observations that the ultrasonic signals are sensitive to the crystallization of polymers (Tatibouet and Piché, Polymer 1991, 32, 3147), we have expanded our efforts to study the detail relationship between the ultrasonic signals and crystallization process in this work. The nonisothermal and isothermal crystallization of virgin poly(ethylene terephthalate) (PET) and PET samples after degradation were studied by using a specially designed pressure‐volume‐temperature (PVT) device, with which an ultrasonic detector was combined. The results showed that the evolution of the ultrasonic signals not only can be used to probe the crystallization process but also can qualitatively characterize the crystallization rate, crystallinity, crystallite size, and amorphous. DSC measurement was used to verify such results. Ultrasonic signals could be as a complementary tool to polymer chain movement and well be applied to characterize the crystallization behavior. Furthermore, the ultrasonic measurement has the potential use to characterize crystallization of products in‐line during processing (i.e., injection molding, micromoulding). © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Modeling the Embossing Stage of the Ultrasonic-Vibration-Assisted Hot Glass Embossing Process

Ultrasonic vibration technology has recently been applied in high-temperature forming processes, such as hot upsetting and hot glass embossing. Experimental research has delineated the effects of ultrasonic vibration on reducing required forces and improving the formability of materials. The purpose of this study was to construct a finite element model of the embossing stage of the ultrasonic vibration-assisted hot glass embossing process. Traditional hot embossing experiments in which the embossing speed and temperature were varied were performed to calculate the viscoelastic dissipation caused by ultrasonic vibration, and this value was then inputted into the simulation. The consistency of the force responses in the experiments and simulation indicated that the proposed model is valid. The findings indicate that the influences of parameters such as the vibration frequency, vibration amplitude, and embossing speed on the ultrasonic vibration-assisted hot glass embossing process must be investigated further.     

Degradation and in situ reaction of polyolefin elastomers in the melt state induced by ultrasonic irradiation

The degradation and in situ reaction with polystyrene (PS) of polyolefin elastomers in the melt state induced through high intensity ultrasonic wave were investigated. The effects of initial molecular weight of polyolefin elastomers, irradiation time, ultrasonic intensity, as well as reaction temperature on the ultrasonic degradation of polyolefin elastomers melt were studied using a “static” ultrasonic vibration system. The results show that the degradation occurs mostly at the tip of the ultrasonic probe, and little or no degradation was observed at the distance of 5 mm or greater from the tip of the probe. The intrinsic viscosity [η] of polyolefin elastomers near the tip of ultrasound probe significantly decreases with irradiation time in the first 100 s and tends toward a limiting value for all samples. The degradation rates increased with an increase in ultrasonic intensity and decrease in reaction temperature. The ultrasonic degradation kinetics of polyolefin elastomers in melt state follows the equation: [η]_t = [η]_∞ + Ae^?kt. The fitting results by this equation accord well with the experimental data. The feasible ultrasonic degradation mechanism is proposed based on the viscoelastic characteristic of polymer melt. FTIR analysis confirms that the copolymer forms under ultrasonic irradiation for PS/POE mixtures and in situ reaction of polymer in melt state can be induced by ultrasonic irradiation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Composite Polymers Transducers for Ultrasonic and Biological Applications

Ferrite polymer transducer and copolyesters are being used for ultrasonic generation to be used in technology and in biological applications like orthodontic treatment. The objectives of this study were to introduce a new piezoelectric composite polymers and to evaluate and compare their electric and mechanical properties with the widely used other materials. The resonance and antiresonance frequencies were measured for the materials in the radial mode. It is noticed that the resonance frequency decreased with increasing CoZn ferrite concentrations in polymers. The electromechanical coupling factor was determined to be of value 0.8 which is the highest value of the piezoelectric materials. It is very difficult to produce ceramic transducers in large sizes because they are fragile, thus the composite transducer could be an alternative. The ultrasonic wave velocity of the composite polymer is higher than that of other polymers and piezoelectric ceramics making them more attractive for many applications than ceramics. The Young's modulus of the composite polymer increased with increasing ferrite concentrations.     

气泡在高聚物熔体中振荡的超声波效应

报道了在高聚物熔体中进行发泡时，气泡的泡孔半径在合适的条件下会发生振荡，其机械振荡在熔体中进行传播时会产生机械波；系统的考察了影响气泡泡孔半径在高聚物熔体中进行振荡的若干因素；借助于数值计算可得到泡孔的振荡频率，其结论为泡孔的振荡周期很短(约为10^-7s)，频率很高(可达MHz数量级)，高聚物中的气泡在发泡过程中的高频振荡会有超声波产生。