Thermal, microstructural and textural characterisation of gelatinised corn, cassava and yam starch blends

The functional properties of mixtures of maize, cassava and yam starches and their relationships with microstructural characteristics were investigated. Experiments were performed following the simplex‐centroid design with internal points and restrictions (upper limit) for yam starch proportion. The statistical model used (Scheffé canonical equation) was a powerful tool to predict the pastes behaviour within the limits of the experimental area. Polynomials with second level interactions were applied to obtain the surface response. Viscoelastic attributes of mixtures differed from those of individual starches. As shown by differential scanning calorimetry and microscopical observations, physical properties of the mixtures depended on the type of networks obtained. These networks varied upon yam, corn and cassava starch proportions as each one has a particular characteristic: gelatinisation temperature, granule size, swelling capacity and amylose/amylopectin ratio among others.     

Viscoelastic Characterization of Surimi Gel: Effects of Setting and Starch

Rheological properties of Alaska pollock surimi gels were affected by setting and addition of corn starch. Setting increased (p < 0.05) both elastic and loss moduli of gel in the absence of starch. However, in the presence of corn starch, setting decreased (p < 0.05) the elastic and loss moduli of the gels. In stress relaxation, the residual forces increased from 37.1 Newton (N) (nonsetting) to 51.8N (setting) in the absence of starch. However, in the presence of starch, the residual force decreased from 49.1N (nonsetting) to 39.0N (setting) which indicated an antagonistic effect between corn starch and setting. A Maxwell model was useful to quantify relaxation behavior of surimi gel and to evaluate the effects of changes in processing conditions.     

基于oldroyd-B本构模型的磨料流加工壁面滑移仿真分析

基于oldroyd-B粘弹性本构模型,应用POLYFLOW软件对流体磨料在圆管中的壁面滑移状态进行了模拟仿真。将得到的圆管中流体磨料的压力值与磨料流加工机床上测试点的压力值进行比较,得到二者的相对误差不超过5%,验证了模拟仿真的可行性。通过仿真可知,流体磨料在工件壁面上的滑移存在速度临界点。通过比较不同管道入口流量、流体磨料黏度和壁面滑移系数对壁面滑移速度的影响可知,当管道入口流量越大、流体磨料的黏度越高,以及壁面滑移系数越小时,加工过程中的壁面滑移速度越大。     

茧丝粘弹性及其对丝质的影响

从高分子物质的粘弹性建立茧丝纤维的四要素力学模型,讨论茧丝的粘弹性特征。通过有关理论和实验,分析制丝工程中张力、温湿度对丝质的影响。     

井巷围岩的延迟失稳机理分析

针对煤矿井巷围岩层状结构特征和流变特性,建立了围岩延迟失稳的粘弹性板屈曲模型,用粘弹性理论分析了具有层状（裂）结构特点的围岩延迟失稳特性,讨论了扰动载荷对围岩稳定性的影响以及冲击矿压发生的时间延迟问题,并进行了简单的实例计算,其结果对工程实践有一定的参考价值。     

受粘弹阻尼器控制的轴向移动弦系统动态特性分析

研究了用粘弹阻尼器控制的弦系统的动态特性,将分布传递函数方法用于粘弹材料结构,给出了受粘弹阻尼器约束的轴向率系统的传递函数。系统频率响应分析表明,由粘弹阻尼棒构成的阻尼器既能大大降低弦的振动幅值,又能够在较大的范围内调整系统的共振频率,从而使系统能更好地以满足预定要求。     

粘性弹耗能器恢复力模型的参数影响

首先在Kelvin-Voigt本构模型基础上,修正了振动频率对粘弹性材料剪切模量,损失模量的影响函数,其次,将环境温度 和剪切应变对上述模量的影响统一归为振动频率的转化系统;最后,由热力学第一定律导出了粘弹性耗能器疲劳温升模型。     

超音速流动中粘弹性圆柱壳的稳定性

基于薄壳的Karman-Donnell假设、空气动力学中的一阶活塞理论和粘弹性力学中的Boltzmann叠加原理,给出了超音速流动中粘弹性圆柱壳的数学模型。在空域上采用Galerkin方法,并在时域上通过引进新变量,将原来的积分－偏微分系统简化为高维微分系统。利用非线性动力学中的多种方法,考察了自由流动压对粘弹性圆柱壳稳定性的影响。发现气动粘弹性圆柱壳在径向周期激励下具有两种稳定的运动和两种不稳定的运动。     

Modeling of Constitutive Behavior for Epon 828/T-403 at High Strain Rates

Experimental results on the uniaxial compressive stress-strainbehavior of Epon 828/T-403 over a strain rate range from 1.1 × 10^–4 to 5.2 × 10³ s^–1were simulated using a viscoelastic viscoplastic constitutive modeldeveloped by Hasan and Boyce (1995). An optimal combination of materialparameters for the constitutive model was determined by curve-fittingthe experimental results. A comparison between the modeling andexperimental results shows that this model, with proper parameters, iscapable of capturing the strain-rate effects, as well as the typicalpolymeric compressive stress-strain behavior, of Epon 828/T-403, whichincludes the stages of linearly elastic, nonlinearly elastic, yield-like(peak) behavior, strain softening, and nearly perfect flow. For all thestress-strain behavior modeled over seven decades of strain rate span,the maximum error between modeling and experimental results is less than25%. The temperature increase induced by the dissipated plasticwork is also computed and found to be between 3 and8°C at these strain rates.     

孤岛油田东区原油流变性研究

重质高粘原油在地层条件下表现为非线性渗流,其流变性测试结果对于指导其油藏的开发具有重要意义。对孤岛油田东区重质高粘原油渗流流变性进行了研究。结果表明,该区含气原油为假塑性流体,地层条件下非线性渗流显著;脱气原油粘弹性较弱;注水开发时,油水井间的水驱速度应控制在0．885m/d以内。