Vibrations of a flexible membrane coupled to a liquid material sample during its phase transition to solid: modelling, validation and identification****

材料表征对于研发、制造工艺和质量控制至关重要，特别是对于农业食品、乳制品和生命科学行业中的软粘弹性材料。然而，经典的方法来确定其整体性能，如流变仪，主要是破坏性的，需要许多不同的样品来测试材料在不同的阶段，导致统计强度的损失。这些问题是通过一种受医学动态弹性成像启发的波传播方法来解决的，该方法由加拿大公司Rheolution开发，作为一种在线兼容技术来测量软固体材料的粘弹性，而无需任何先验知识。该专利技术包括测量双层系统对振动脉冲的自由响应，该系统由材料样品和柔性膜组成，固体圆柱体样品保持器的底部。它的响应进行比较的模型，其中唯一的未知数是试样的粘弹性参数的模拟，允许他们的识别由于误差最小化程序。然而，该模型未能再现极软固体和在液态和固态之间转变的材料的响应，这在Rheolution的目标市场中很重要。因此，本项目旨在为此类样本开发这种双层系统行为的模型。将进行实验，以了解系统的振动响应与这样的标本，并优化其设计。试样的粘弹性或流变行为，其与固体样品保持器的相互作用和其对膜的振动的影响，将导出并链接到现有的软固体材料的理论，以获得一个通用的模型，该系统与实验数据进行验证。然后，将制定算法来识别样品的粘弹性参数，并应用于典型材料。这种扩展技术将提高加拿大乳制品工业生产线的产量-允许更生态和更具成本效益的生产-并将有助于简单，更便宜和更准确地表征生物材料凝胶化或降解，用于药物输送或组织再生，从而提高加拿大人的健康。

Material characterization is primordial for R&D, manufacturing processes and quality control, in particular for soft viscoelastic materials in agri-food - dairy - and life sciences industries. However, the classical methods to identify their bulk properties, such as rheometers, are mainly destructive, needing many different samples to test a material at different stages, resulting in a loss of statistical strength. Such issues are solved by a wave-propagation method inspired by medical dynamic elastography and developed by the Canadian company Rheolution as an at-line compatible technique to measure, without any prior knowledge, viscoelastic properties of soft solid materials. This patented technology consists in measuring the free response to a vibrational impulse of a bi-layered system comprised of a material specimen and of a flexible membrane, bottom of a solid cylinder sample holder. Its response is compared to the simulation of a model in which the only unknowns are the specimen's viscoelastic parameters, allowing their identification thanks to an error minimization procedure. However, this model fails to reproduce the response for extremely soft solids and for materials transitioning between liquid and solid states, significant in Rheolution's targeted markets. Therefore, this project aims at developing a model of this bi-layered system's behavior for such samples. Experiments will be conducted to comprehend the system's vibrational response with such specimens and to optimize its design. The specimen's viscoelastic or rheological behavior, its interaction with the solid sample holder and its influence on the membrane's vibrations, will be derived and linked to the existing theory for soft solid materials to obtain a generalized model of this system to be validated with experimental data. Then, algorithms will be formulated to identify the sample's viscoelastic parameters and applied on typical materials. This extended technique will improve the yield of Canadian dairy industry production lines - allowing for more ecological and cost-effective production - and will help simple, cheaper and more accurate characterization of biomaterials gelation or degradation, for drug delivery or tissue regeneration, and thereby enhancing Canadians' health.**************************