A generalized Johnson parameter for pull-off decay in the adhesion of rough surfaces
AbstractThere is no simple theory at present to predict accurately the decay of pull-off in the adhesion of randomly rough surfaces. The asperity model of Fuller and Tabor has shown significant error in recent numerical investigations by Pastewka and Robbins of self-affine random roughness from micrometer to atomic scale which corresponds to low values of Tabor parameter. For sinusoidal contact, the Johnson parameter, originally introduced for the JKR regime (from JohnsonKendallRoberts) is the dominant parameter ruling the pull-off at intermediate Tabor values. Hence, we define a generalized Johnson parameter as the ratio between the adhesive energy to the elastic strain energy to flatten the surface in the case of multiscale roughness and find that it correlates very well with the data of Pastewka and Robbins spanning almost five orders of magnitude of reduction from theoretical strength, improving significantly with respect to other possible single parameter criteria. For the most important case in practice, that of low fractal dimensions, this suggests the product of amplitude and slope of the largest wavelength components of roughness dominate pull-off decay, and not small scales features like slopes and curvatures, as suggested by Pastewka and Robbins.A preprint can be found here.
Full reference: M Ciavarella and A Papangelo, A generalized Johnson parameter for pull-off decay in the adhesion of rough surfaces, Physical Mesomechanics, 20, 65-72, 2017.
PS. I have just noticed that a criterion proposed by Papangelo has been noticed by Prof. Steven Abbott who is very active in teaching and consultancy of "practical adhesion" of Pressure Sensitive Adhesive". His site seems quite interesting.
https://www.stevenabbott.co.uk/practical-adhesion/dahlquist.php
Best regards
NSF Summer Institute Short Course on Materiomics—Merging Biology and Engineering in Multiscale Structures and Materials
Location: Massachusetts Institute of Technology, LeMeridien Hotel (former Hotel@MIT)
Chair: Markus J. Buehler, Massachusetts Institute of Technology (mbuehler@MIT.EDU)
Dates: May 30 (Wednesday) morning to June 1 (Friday) evening, 2012
Course Objectives: Theme-based introduction into emerging science at the interface of engineering and biology
This exciting course will provide an introduction into the emerging science at the interface of engineering and biology, with a focus on the integration of multiscale modeling and experiment. Applying material design principles derived from biology—and specifically, the concept of developing diverse hierarchical structures composed of universal and simple design elements, used to derive sustainable and robust materials—is crucial for the next-generation engineering materials that are highly functional while satisfying multiple design constraints. This finds practical applications for example in regenerative medicine for de novo tissue growth, advanced carbon-based materials that are not only strong and tough, and self-learning material systems whose properties can be tailored by solely changing the structure without a need to introduce new building blocks.
This Summer Institute features experimental, computational and theoretical instructors from various areas of science, dealing with multiple length-scales, from nano to macro. Participants and instructors will engage in in-depth discussions on the frontiers, challenges, and opportunities in this emerging field referred to as materiomics. A unique feature of this short course is the participation of scientists from disparate fields that includes engineering mechanics, synthetic biology and architecture.
To make breakthroughs in this field, the introduction of dramatically new methods are critical, such as mathematical tools to understand and predict structure and hierarchies using geometric methods, folding of peptides, DNA, proteins or membranes or other structures, as well as the implementation of multiscale structures in diverse fields such as synthetic biology and architecture, which can be combined with new nanoscale engineering methods and chemistry. This Summer Institute will explore the application of these concepts towards the engineering design of materials from the bottom up and the application in high-impact areas of science and engineering.
Speakers include: Mary Boyce (MIT), Markus Buehler (MIT), Wing Kam Liu (Northwestern), Neri Oxman (MIT), Christine Ortiz (MIT), David Weitz (Harvard), David Kaplan (Tufts), Joyce Wong (Boston University), Pamela Silver (Harvard), Joanna Aizenberg (Harvard) and William Shih (Harvard).
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