Strength of Adhesive Contacts: Experiment and numerical simulation
Event details
| Date | 08.12.2017 |
| Hour | 12:15 › 13:15 |
| Speaker | Prof. Dr Valentin L. Popov, Technische Universität Berlin, Germany |
| Location | |
| Category | Conferences - Seminars |
Valentin L. Popov, Roman Pohrt, Qiang Li, Technische Universität Berlin, Germany
Abstract : The strength of an adhesive contact between two bodies can strongly depend on the macroscopic and microscopic shape of the surfaces. In the past, the influence of roughness has been investigated thoroughly. However, even in the presence of perfectly smooth surfaces, geometry can come into play in form of the macroscopic shape of the contacting region. Here we present numerical and experimental results for contacts of rigid punches with flat but oddly shaped face contacting a soft, adhesive counterpart. When it is carefully pulled off, we find that in contrast to circular shapes, detachment occurs not instantaneously but detachment fronts start at pointed corners and travel inwards, until the final configuration is reached which for macroscopically isotropic shapes is almost circular. For elongated indenters, the final shape resembles the original one with rounded corners. We describe the influence of the shape of the stamp both experimentally and numerically.
Numerical simulations are performed using a new formulation of the Boundary Element Method for simulation of adhesive contacts suggested by Pohrt and Popov. It is based on a local, mesh dependent detachment criterion which is derived from the Griffith principle of balance of released elastic energy and the work of adhesion. The validation of the suggested method is made both by comparison with known analytical solutions and with experiments. The method is applied for simulating the detachment of flat-ended indenters with square, triangle or rectangular shape of cross-section as well as shapes with various kinds of faults and to “brushes”. The method is extended for describing power-law gradient media.
Additionally, we discuss some implications of this work for simulations of material behavior, in particular adhesive wear.
Bio : Valentin L. Popov is full professor at the Berlin University of Technology, studied physics (1976-1982) and obtained his doctorate in 1985 from the Moscow State Lomonosov University. He worked at the Institute of Strength Physics of the Russian Academy of Sciences. After a guest professorship in the field of theoretical physics at the University of Paderborn (Germany) from 1999 to 2002, he has headed the department of System Dynamics and the Physics of Friction of the Institute of Mechanics at the Berlin University of Technology. His areas of interest include tribology, nanotribology, tribology at low temperatures, biotribology, the influence of friction through ultrasound, numerical simulation of frictional processes, research regarding earthquakes, as well as topics related to materials science such as the mechanics of elastoplastic media with microstructures, strength of metals and alloys, and shape memory alloys. He has published over 100 papers in leading international journals during the past 5 years. He is the author of the book "Contact Mechanics and Friction: Physical principles and applications" which appeared in three German, two English, Chinese, and Russian editions and co-author of the book on “Method of dimensionality Reduction in Contact Mechanics and Friction” which appeared in German, English and Chinese editions. He is the joint editor of international journals and regularly organizes international conferences and workshops over diverse tribological themes. He is a member of the Scientific Council of the German Tribological Society. He has intensively collaborated with many industrial corporations and possesses experience in implementing the results of scientific research in industrial applications.
Abstract : The strength of an adhesive contact between two bodies can strongly depend on the macroscopic and microscopic shape of the surfaces. In the past, the influence of roughness has been investigated thoroughly. However, even in the presence of perfectly smooth surfaces, geometry can come into play in form of the macroscopic shape of the contacting region. Here we present numerical and experimental results for contacts of rigid punches with flat but oddly shaped face contacting a soft, adhesive counterpart. When it is carefully pulled off, we find that in contrast to circular shapes, detachment occurs not instantaneously but detachment fronts start at pointed corners and travel inwards, until the final configuration is reached which for macroscopically isotropic shapes is almost circular. For elongated indenters, the final shape resembles the original one with rounded corners. We describe the influence of the shape of the stamp both experimentally and numerically.
Numerical simulations are performed using a new formulation of the Boundary Element Method for simulation of adhesive contacts suggested by Pohrt and Popov. It is based on a local, mesh dependent detachment criterion which is derived from the Griffith principle of balance of released elastic energy and the work of adhesion. The validation of the suggested method is made both by comparison with known analytical solutions and with experiments. The method is applied for simulating the detachment of flat-ended indenters with square, triangle or rectangular shape of cross-section as well as shapes with various kinds of faults and to “brushes”. The method is extended for describing power-law gradient media.
Additionally, we discuss some implications of this work for simulations of material behavior, in particular adhesive wear.
Bio : Valentin L. Popov is full professor at the Berlin University of Technology, studied physics (1976-1982) and obtained his doctorate in 1985 from the Moscow State Lomonosov University. He worked at the Institute of Strength Physics of the Russian Academy of Sciences. After a guest professorship in the field of theoretical physics at the University of Paderborn (Germany) from 1999 to 2002, he has headed the department of System Dynamics and the Physics of Friction of the Institute of Mechanics at the Berlin University of Technology. His areas of interest include tribology, nanotribology, tribology at low temperatures, biotribology, the influence of friction through ultrasound, numerical simulation of frictional processes, research regarding earthquakes, as well as topics related to materials science such as the mechanics of elastoplastic media with microstructures, strength of metals and alloys, and shape memory alloys. He has published over 100 papers in leading international journals during the past 5 years. He is the author of the book "Contact Mechanics and Friction: Physical principles and applications" which appeared in three German, two English, Chinese, and Russian editions and co-author of the book on “Method of dimensionality Reduction in Contact Mechanics and Friction” which appeared in German, English and Chinese editions. He is the joint editor of international journals and regularly organizes international conferences and workshops over diverse tribological themes. He is a member of the Scientific Council of the German Tribological Society. He has intensively collaborated with many industrial corporations and possesses experience in implementing the results of scientific research in industrial applications.
Practical information
- General public
- Free
Organizer
- Prof. Dr Brice Lecampion & Prof. Dr Katrin Beyer
Contact
- Prof. Dr Jean-François Molinari, LSMS