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Viscometric Techniques
Published in Nicholas P. Cheremisinoff, Polymer Mixing and Extrusion Technology, 2017
It is possible to measure transient start-up stresses of the material with this device. After a sufficiently long time and if the material is stable, the steady-state stress can be measured, at which point the viscosity can be determined as a function of shear rate. With many materials such as elastomers, both large times and equipment strains are needed. These conditions often result in slippage. To minimize slippage contact surfaces are usually knurled.
Conventional Viscometers and General Concepts
Published in Nicholas P. Cheremisinoff, An Introduction to Polymer Rheology and Processing, 1993
It is possible to measure transient start-up stresses of the material with this device. After a sufficiently long time and if the material is stable, the steady-state stress can be measured, at which point the viscosity can be determined as a function of shear rate. With many materials such as elastomers, both large times and equipment strains are needed. These conditions often result in slippage. To minimize slippage contact surfaces are usually knurled.
Machining engineering materials by turning
Published in David Salmon, Penny Powdrill, Mechanical Engineering Level 2 NVQ, 2012
A knurl is a straight or a diamond-indented pattern that provides a ‘thumb grip’ on the outside of screwed components. A knurl is put on a surface with a knurling tool that has two small HSS wheels that are forced on the workpiece's surface, reshaping it to form the pattern.
Adhesion testing of printed inks while varying the surface treatment of polymer substrates
Published in The Journal of Adhesion, 2021
Clayton Neff, Edwin Elston, Amanda Schrand, Nathan Crane
Fortunately, the surface roughness of printed substrates may achieve some of the same benefits of sandblasting. Conductive ink deposited on printed polymer substrates with undulated roughness shows ~30% increase in interfacial shear strength and altered the adhesive failure mode to cohesive failure when comparing smooth untreated ABS substrates. Conductive inks deposited on extrusion 3D printed ABS substrates with undulated roughness perpendicular to the applied force were hypothesized to have more mechanical interlocking and resistance to shear failure than those deposited parallel. However, no significant difference in shear strength was found between perpendicular and parallel extrusions. This may eliminate a trade-off between adhesion and electrical performance while depositing conductive inks onto extruded surfaces. The geometric freedom of extrusion or other AM processes could produce designed features or textures that could enhance adhesion of deposited conductive inks. A separate tool that scratched or knurled the surface could also produce adhesion promoting textures with mechanical interlocking features. These geometric effects could also be combined with chemical treatments.
Temperature measurement and machining damage in slotting of multidirectional CFRP laminate
Published in Machining Science and Technology, 2018
Souhir Gara, Samir M'hamed, Oleg Tsoumarev
Studying the influence of cutting conditions on the machining temperature, Liu et al. (2014) said that workpiece temperature increases with increasing spindle speed and depth of cut and added that axial cutting depth has more influence on the temperature variation followed by spindle speed and feed per tooth. In this context, Ghafarizadeh et al. (2015) have studied the end milling of unidirectional CFRP composite (referenced P2053 F-10 reinforced with 60% of fibers) with carbide ball end mill with chemical vapor deposition diamond coating made of two flutes. They concluded that the main source of heat generation is the frictional work and that cutting temperature increases linearly with the cutting speed over the interval [200; 375] m/min. Weinert and Kempmann (2004) observed, when drilling CFRP material with cemented carbide drill, that tool temperature raises with both increasing cutting speed and feed rate. By examining milling of CFRP laminate (T700/QY8911) 16 ply ([0/90]2s) with polycristalline diamond (PCD) knurled tool, Wang et al. (2016) concluded that the manufacturer must program the low cutting speed allowing lower temperature, the minimum feed rate allowing lower cutting efforts and the maximum radial depth of cut allowing high machining efficiency. They said that cutting speed has major effect on cutting temperature in milling of CFRP materials followed by the feed rate and depth of cut. Yashiro et al. (2013) noted that the temperature was elevated at higher cutting speeds and added that at 300 m/min, measured temperature did not exceed the glass transition temperature of the matrix resin.