Nano- and Component Level Friction of Rubber Seals in Dispensing Devices

2009 ◽  
Author(s):  
Polina Prokopovich ◽  
Stephanos Theodossiades ◽  
Homer Rahnejat ◽  
Darren Hodson
Keyword(s):  
Silicon Nitride ◽  
Coefficient Of Friction ◽  
Friction Model ◽  
Polybutylene Terephthalate ◽  
Component Level ◽  
Fundamental Study ◽  
Rubber Ring ◽  
Nano Scale ◽  
Macro Scale ◽  
Scale Motion

In many drug dispensing devices, such as syringes and inhalers, a rubber ring is used as a seal. During device actuation the seal is subjected to friction which in turn causes it to deform. This can lead to suboptimal performance of the device and as a consequence variability in the delivered dose. Seal friction is complex, arising from adhesion of rubber in contact with a moving counterface, viscous action of a thin film of entrained fluid into the contact and ploughing of seal asperities. Therefore, the first step in the understanding of the conjunctional behaviour of rubber seals is the fundamental study of these friction mechanisms. A developed model can then be validated against measurements, prior to its use in a multi-body dynamic model of the inhaler valve to predict product performance, robustness and variability due to manufacturing tolerances. This paper undertakes two distinct studies. Firstly, a friction model for the rough elastomeric material, typically used for valve seals is developed. The model is then validated against measurements in nano-scale. Friction data is presented for nitrile rubber, using a silicon nitride AFM tip for nano-scale interactions. The validation is then extended to macro-scale motion of an instrumented trolley, incorporating an elastomeric surface sliding on a polymeric counterface. These tests are carried out for polybutylene terephthalate (PBT). Secondly, the validated friction model is used in an elastomeric seal model in-situ within the valve and in contact with a polymeric stem surface and subject to both global fittment deformation and canister pressure. Reasonable agreement is found between the measurements and model predictions for the nano-scale coefficient of friction of rubber against silicon nitride. Similarly, good agreement has been obtained for the mean coefficient of friction of rubber against PBT. In addition, the mechanism of adhesion between contacting surfaces of gasket and stem is taken into account.

Study on the Unhydrated Cement Grain/C-S-H Gel Interface in Cement Paste by Use of Nano-Scratch Technique

2013 ◽  
Vol 539 ◽  
pp. 84-88 ◽  
Author(s):  
Yue Mao ◽  
Wu Yao ◽  
Jing Xu
Keyword(s):  
Penetration Depth ◽  
Elastic Deformation ◽  
Cement Paste ◽  
Coefficient Of Friction ◽  
Comprehensive Analysis ◽  
Fundamental Study ◽  
Nano Scale ◽  
The Coefficient Of Friction ◽  
Deformation Ratio ◽  
Curing Age

Investigation at micro- and nano-scale is beneficial for the fundamental study of cement-based material as an extremely complex composite. This paper presents a preliminary exploration on the unhydrated cement grain/ C-S-H gel interface using nano-scratch technique. By comprehensive analysis of the penetration depth, the coefficient of friction, and the elastic deformation ratio, the interfacial width of different w/c ratio and curing age were obtained, which shows a tendency to increase with the curing age in the range of 1-4 um, while has no relation to the w/c ratio.

A Nano-Scale Multi-Asperity Contact and Friction Model

2002 ◽  
Author(s):  
George G. Adams ◽  
Sinan Mu¨ftu¨ ◽  
Nazif Mohd Azhar
Keyword(s):  
Friction Model ◽  
Real Contact Area ◽  
Asperity Contact ◽  
Adhesion Forces ◽  
Friction Forces ◽  
Dugdale Model ◽  
Nano Scale ◽  
Macro Scale ◽  
Asperity Contacts ◽  
Asperity Model

As surfaces become smoother and loading forces decrease in applications such as MEMS and NEMS devices, the asperity contacts which comprise the real contact area will continue to decrease into the nano scale regime. Thus it becomes important to understand how the material and topographical properties of surfaces contribute to measured friction forces at this nano scale. We have incorporated the single asperity nano contact model of Hurtado and Kim into a multi-asperity model for contact and friction which includes the effect of asperity adhesion forces using the Maugis-Dugdale model. Our model spans the range from nano-scale to micro-scale to macro-scale contacts. We have identified three key dimensionless parameters representing combinations of surface roughness measures, Burgers vector length, surface energy, and elastic modulus. Results are given for the normal and friction forces vs. separation, and for the friction coefficient vs. normal force for various values of these key parameters.

scholarly journals A Static Friction Model for Unlubricated Contact of Random Rough Surfaces at Micro/Nano Scale

Micromachines ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 368
Author(s):  
Shengguang Zhu ◽  
Liyong Ni
Keyword(s):  
Rough Surfaces ◽  
Static Friction ◽  
Friction Model ◽  
Elastic Contact ◽  
Nano Scale ◽  
Random Rough Surfaces ◽  
Proposed Model ◽  
Dissipation Mechanism ◽  
Rigid Plane ◽  
Contact Situation

A novel static friction model for the unlubricated contact of random rough surfaces at micro/nano scale is presented. This model is based on the energy dissipation mechanism that states that changes in the potential of the surfaces in contact lead to friction. Furthermore, it employs the statistical theory of two nominally flat rough surfaces in contact, which assumes that the contact between the equivalent rough peaks and the rigid flat plane satisfies the condition of interfacial friction. Additionally, it proposes a statistical coefficient of positional correlation that represents the contact situation between the equivalent rough surface and the rigid plane. Finally, this model is compared with the static friction model established by Kogut and Etsion (KE model). The results of the proposed model agree well with those of the KE model in the fully elastic contact zone. For the calculation of dry static friction of rough surfaces in contact, previous models have mainly been based on classical contact mechanics; however, this model introduces the potential barrier theory and statistics to address this and provides a new way to calculate unlubricated friction for rough surfaces in contact.

Identifying Product Scaling Principles: A Tool for Bioinspired Design and Beyond

2011 ◽  
Author(s):  
Angel G. Perez ◽  
Julie S. Linsey
Keyword(s):  
Scaling Laws ◽  
Initial Step ◽  
Nano Scale ◽  
Bioinspired Design ◽  
Macro Scale ◽  
Design By Analogy ◽  
Global Principles ◽  
Physical Principles

There are countless products that perform the same function but are engineered to suit a different scale. Designers are often faced with the problem of taking a solution at one scale and mapping it to another. This frequently happens with design-by-analogy and bioinspired design. Despite various scaling laws for specific systems, there are no global principles for scaling systems, for example from a biological nano-scale to macro-scale. This is likely one of the reasons bioinspired design is difficult. Very often scaling laws assume the same physical principles are being used, but this study of products indicates that a variety of changes occur as scale changes, including changing the physical principles to meet a particular function. Empirical product research was used to determine a set of principles by observing and understanding numerous products to unearth new generalizations. The function a product performs is examined in various scales to view subtle and blatant differences. Principles are then determined. This study provides an initial step in creating new innovative designs based on existing solutions in nature or other products that occur at very different scales. Much further work is needed by studying additional products and bioinspired examples.

Realization of Mechanical Properties Prediction from Nano- to Macro- Scale Structure: An Achievement of C-S-H Hydrated Phases

2019 ◽  
Vol 956 ◽  
pp. 332-341 ◽  
Author(s):  
Jia Fu
Keyword(s):  
Mechanical Properties ◽  
High Density ◽  
Theoretical Research ◽  
Step Method ◽  
Material Technology ◽  
Micro Scale ◽  
Nano Scale ◽  
Macro Scale ◽  
Mechanical Properties Prediction ◽  
Technology Modeling

The performance prediction of C-S-H gel is critical to the theoretical research of cement-based materials. In the light of recent computational material technology, modeling from nano-scale to micro-scale to predict mechanical properties of structure has become research hotspots. This paper aims to find the inter-linkages between the monolithic "glouble" C-S-H at nano-scale and the low/high density C-S-H at the micro-scale by step to step method, and to find a reliable experimental verification method. Above all, the basic structure of tobermorite and the "glouble" C-S-H model at nano-scale are discussed. At this scale, a "glouble" C-S-H structure of about 5.5 nm3 was established based on the 11Å tobermorite crystal, and the elastic modulus ​​of the isotropic "glouble" is obtained by simulation. Besides, by considering the effect of porosity on the low/high density of the gel morphology, the C-S-H phase at micro-scale can be reversely characterized by the "glouble". By setting different porosities and using Self-Consistent and Mori-Tanaka schemes, elastic moduli of the low density and high density C-S-H ​​from that of "glouble" are predicted, which are used to compare with the experimental values of the outer and inner C-S-H. Moreover, the nanoindentation simulation is carried out, where the simulated P-h curve is in good agreement with the accurate experimental curve in nanoindentation experiment by the regional indentation technique(RET), thus the rationality of the "glouble" structure modeled is verified and the feasibility of Jennings model is proved. Finally, the studies from the obtained ideal "glouble" model to the C-S-H phase performance has realized the mechanical properties prediction of the C-S-H structure from nano-scale to micro-scale, which has great theoretical significance for the C-S-H structural strengthening research.

Behavior Characteristics of Nano-Stage According to Hinge Structure

2007 ◽  
Vol 7 (11) ◽  
pp. 4146-4149 ◽  
Author(s):  
Hyun-Seong Oh ◽  
Sung-Jun Lee ◽  
Yong-Woo Kim ◽  
Deug-Woo Lee
Keyword(s):  
Optical Systems ◽  
Precision Machining ◽  
System Control ◽  
Nano Scale ◽  
Composite Joint ◽  
Ultra Precision ◽  
Probe Microscope ◽  
Motion Stage ◽  
Scale Motion ◽  
Behavior Characteristics

Nano-stages are used in many ultra-precision systems, such as scanning probe microscope (SPM), optical fiber aligners, ultra-precision cutting, measuring and optical systems. Generally, ultra-precision machining and measuring are achieved using a nano-scale motion stage actuated using Piezo-electric actuators (PZT), and the importance of and demands for the motion stage increase with the need to improve system performance and accuracy. However, it is difficult to find solutions because the performance and characteristics of nano-scale motion stages are determined by various factors, such as the hinge structure, actuator, and method of system control. This paper focuses on improving of leafspring and planar joint hinges, and suggests a composite joint hinge stage.

Granular chain escape from a pore in a wall in the presence of particles on one side: a comparison to polymer translocation

Soft Matter ◽  
2018 ◽  
Vol 14 (26) ◽  
pp. 5420-5427 ◽  
Author(s):  
Fereshteh Samadi Taheri ◽  
Hossein Fazli ◽  
Masao Doi ◽  
Mehdi Habibi
Keyword(s):  
Escape Behavior ◽  
Chain Polymer ◽  
Granular Chain ◽  
Nano Scale ◽  
Macro Scale ◽  
Polymer Translocation ◽  
Scale Experiment ◽  
A Chain

Macro-scale experiment and nano-scale simulation of a chain/polymer show the same escape behavior through the pore in the wall in the presence of particles.

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