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SUMMARY:Indentation of a viscoelastic half-space - Dr J Greenwood\, CUED (
 Emeritus)
DTSTART:20150501T130000Z
DTEND:20150501T140000Z
UID:TALK58029@talks.cam.ac.uk
CONTACT:Ms Helen Gardner
DESCRIPTION:The behaviour of a sphere indentation with a prescribed load c
 ycle is well understood through the use of Radok’s principle to study in
 creasing load and Ting’s explanation of the behaviour under decreasing l
 oad: a straightforward account is given in Johnson’s Contact Mechanics. 
 The theory will be reviewed\, and Ting’s surprising explanation that\, d
 espite the intrinsic visco-elastic memory effect\, all the loading-unloadi
 ng behaviour which occurred before the current configuration should be ign
 ored will (hopefully!) be clarified. Detailed results for the standard lin
 ear solid will be given\, both for a sphere and for a conical indenter.\nW
 hat happens with a prescribed displacement cycle has not been studied befo
 re\; and turns out to be more difficult. For with a load cycle\, the essen
 tial relationship between the time  during loading and the time   during u
 nloading such that the contact radii   are equal can be found without worr
 ying about the displacements: they may be found later. But with a displace
 ment cycle\, despite the superficial duality between stress  strain\, we c
 annot simply interchange the two hereditary integrals \n \; 	    or their 
 force/area equivalents: we have to worry about displacement and force toge
 ther. Embarrassingly\, only a step-by-step solution has been found.  Resul
 ts will be described both for a flat-ended indenter…which simply separat
 es from the indented material…and for  a sphere.\n\nps.   and not a Lapl
 ace transform in sight!\n
LOCATION:Oatley Seminar Room\, Department of Engineering
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