Collaborative Research: Validated Complementarity Contact Conditions for Suction-Friction of Multiphasic Soft Materials

合作研究：验证多相软材料吸力摩擦的互补接触条件

• 批准号: 2224371
• 负责人: Timothy Truster
• 金额: $ 36.38万
• 依托单位: University of Tennessee Knoxville
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-01-01 至 2025-12-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2224371&HistoricalAwards=false
• 关键词: Collaborative; Research; Validated; Complementarity; Contact

This project will study adhesion and friction, and develop a physics-based contact model in various soft materials swollen by liquids. The ever-growing use of soft swollen materials in engineering and biomedical applications catalyzes demands for modeling of their mechanical behavior. Those materials experience large deformations and exhibit nonlinear mechanical response that depends on loading rate. In contact loading, rate-dependence stems primarily from liquid diffusion within soft solid network, viscous shearing of swelling liquid and viscoelastic deformation of the solid network. In recent studies, the rate-dependence of adhesion and friction were observed during the onset of peeling and sliding in synthetic and biological soft swollen materials. Current contact formulations lack a methodology to describe those observations. The research will fill this gap by exploring the mechanisms leading to rate-dependent and coupled physics of adhesion and friction, and by correcting current contact formulations accordingly. The physics-based contact formulation will enable modeling of friction-adhesion in numerous contact applications encountered in musculoskeletal joints; soft robots interacting with their environment; surgical cuts, suturing, and traumatic and ballistic impacts in soft tissues and surrogates; contact of flexible electronics with human skin; and other tough gel applications carrying significant mechanical loads. This novel contribution to contact mechanics will be discussed in graduate level courses and hands-on seminars for high school students. Finally, to ensure broad and quick dissemination of research products to the community, the formulation will be implemented in an open-source and widely used finite element code for soft materials.The specific goal of the research is to test a major hypothesis that in soft swollen materials, solid network controls the strength in both adhesion and friction, and therefore a modified effective traction-based formulation would resolve both rate-dependence and nonlocality in contact separation (peeling) processes. The PIs further hypothesize that the coupling of nonlocal adhesion (suction) and friction response is governed by the intrinsic relaxation time constants of the materials. Those hypotheses will be tested through novel computational and experimental efforts. In the computational program, a unified contact framework will be derived for the soft swollen material interfaces using the Variational Multiscale Discontinuous Galerkin method, which can weakly impose the entire range of loading and unloading of a material point along the interface without numerical tuning parameters. The experimental program will complement the computational framework with validation data to be obtained from bulk mechanical characterization, adhesion and friction tests on synthetic soft swollen material interfaces. Besides the global force-displacement responses, advanced laser and particle image velocimetry techniques will deliver full field characterization in the vicinity of interfaces. This time-resolved global and local data will enable robust validation of the modeling framework. After validation, this framework will deliver the first physics-based contact model that is fully parametrizable with measurable bulk and interface properties. This unified formulation will be achieved by exposing the transformative knowledge that local and nonlocal interfacial mechanisms act in tandem, with direct analogy to the behavior of bulk response (cohesion and suction) in soils and granular materials.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

本项目将研究各种软质材料被液体膨胀时的粘附和摩擦，并建立基于物理的接触模型。软膨胀材料在工程和生物医学应用中的日益增长的使用催化了对其机械行为建模的需求。这些材料经历了很大的变形，并表现出非线性的机械响应，这取决于加载速率。在接触加载中，速率依赖主要源于软固网内的液体扩散、膨胀液体的粘性剪切和固网的粘弹性变形。在最近的研究中，在合成和生物软膨胀材料的剥落和滑动开始时，观察到粘附和摩擦的速率依赖性。目前的接触公式缺乏描述这些观察结果的方法。该研究将通过探索导致速率依赖和耦合的粘附和摩擦物理的机制，并相应地纠正当前的接触公式来填补这一空白。基于物理的接触公式将使在肌肉骨骼关节中遇到的许多接触应用中的摩擦粘附建模；软体机器人与环境互动；手术割伤、缝合、软组织和替代物的创伤和弹道冲击；柔性电子产品与人体皮肤的接触；以及其他承载大量机械负荷的坚硬凝胶应用。这个对接触力学的新贡献将在研究生课程和高中学生的实践研讨会中讨论。最后，为了确保研究成果广泛、快速地传播到社区，该配方将在一个开源且广泛使用的软材料有限元代码中实施。该研究的具体目标是验证一个主要假设，即在软膨胀材料中，固体网络控制着粘附和摩擦的强度，因此一种改进的基于牵引力的有效配方将解决接触分离（剥离）过程中的速率依赖性和非局域性。pi进一步假设非局部粘附（吸力）和摩擦响应的耦合是由材料的本征松弛时间常数控制的。这些假设将通过新的计算和实验努力得到检验。在计算程序中，采用变分多尺度不连续伽辽金方法推导了软膨胀材料界面的统一接触框架，该框架可以在不需要数值调谐参数的情况下沿界面弱施加一个材料点的整个加载和卸载范围。实验程序将补充计算框架，验证数据将从合成软膨胀材料界面的整体力学特性、粘附和摩擦测试中获得。除了全局力-位移响应，先进的激光和粒子图像测速技术将提供界面附近的全场表征。这个时间解析的全局和局部数据将支持对建模框架进行可靠的验证。验证后，该框架将提供第一个基于物理的接触模型，该模型完全可参数化，具有可测量的体积和界面属性。这个统一的公式将通过揭示局部和非局部界面机制串联起作用的变革性知识来实现，直接类比土壤和颗粒材料中的体响应（内聚力和吸力）行为。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。