?url_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Adc&rft.relation=http%3A%2F%2Fmiis.maths.ox.ac.uk%2Fmiis%2F236%2F&rft.title=Maximizing+Minimum+Pressure+in+Fluid+Dynamic+Bearings+of+Hard+Disk+Drives&rft.creator=Maki%2C+Kara&rft.creator=Ozlem%2C+Melih&rft.creator=Schwendeman%2C+Don&rft.creator=Please%2C+Colin&rft.creator=Phillips%2C+Joel&rft.creator=Case%2C+Michael&rft.creator=Heryudono%2C+Alfa&rft.creator=Bhalezcio%2C+Kishor&rft.creator=Atena%2C+Agegnehu&rft.creator=Witelski%2C+Tom&rft.creator=Sun%2C+Jiguang&rft.creator=Fehribach%2C+Joseph&rft.subject=Information+and+communication+technology&rft.description=We+focus+on+the+central+spindle+which+supports+the+rotating+magnetic+platters+which+hold+all+of+the+data.+The+spindle+must+operate+with+great+precision+and+stability+at+high+rotational+speeds.+Design+practice+has+converged+on+oil-lubricated+hydrodynamic+journal+bearings+as+the+most+common+choice+for+spindles.+That+is%2C+a+layer+of+viscous+oil+separates+a+rotating+shaft+(the+bearing)+from+the+fixed+outer+sleeve+(the+journal).+In+hard+drives%2C+it+is+very+important+for+the+shaft+to+be+centered+within+the+sleeve.+Plain+journal+bearings+(i.e.+both+surfaces+are+circular+cylinders)+are+unstable+to+perturbations+that+push+the+shaft+off-center.+It+was+found+that+this+stability+problem+can+be+overcome+by+cutting+diagonal+grooves+into+the+journal+in+a+pattern+called+a+herring-bone.+Another+consequence+of+this+design+is+that+very+high+pressures+are+generated+by+the+grooves+as+they+drive+the+oil+to+the+middle+of+the+bearing%2C+away+from+the+top%2Fbottom+ends+of+the+spindle.+This+pumping+action+generally+works+to+oppose+leakage+out+of+the+bearing.%0D%0A%0D%0AWe+examine+how+choices+for+the+groove+pattern+can+influence+the+key+properties+of+the+bearing.+The+focus+is+to+understand+the+effect+of+the+groove+geometry+on+the+pumping+action.+In+particular+the+undesirable+behavior+caused+by+the+low+pressures+created+near+the+top%2Fbottom+ends+of+the+bearing+which%2C+under+many+conditions%2C+may+result+in+the+pressure+becoming+negative%2C+relative+to+atmospheric+pressure.+Negative+pressure+can+result+in+cavitation+or%2C+when+it+occurs+near+an+air-oil+interface%2C+can+cause+air+to+be+ingested+and+hence+create+bubbles.+Any+bubbles+in+the+oil+can+corrupt+the+lubricating+layer+in+the+bearing+and%2C+as+they+are+created+and+collapse%2C+can+cause+significant+undesirable+vibrations.+The+negative+pressures+have+therefore+been+identified+as+one+of+the+key+problems+in+design+of+hard+disk+drive+bearings.%0D%0A%0D%0AWe+will+use+numerical+computations+and+some+analysis+to+show+that+by+modifying+the+groove+geometry+we+can+reduce+the+negative+pressure+while+retaining+good+stability+characteristics.&rft.date=2007&rft.type=Study+Group+Report&rft.type=NonPeerReviewed&rft.format=application%2Fpdf&rft.language=en&rft.identifier=http%3A%2F%2Fmiis.maths.ox.ac.uk%2Fmiis%2F236%2F1%2FHitachi_final.pdf&rft.identifier=++Maki%2C+Kara+and+Ozlem%2C+Melih+and+Schwendeman%2C+Don+and+Please%2C+Colin+and+Phillips%2C+Joel+and+Case%2C+Michael+and+Heryudono%2C+Alfa+and+Bhalezcio%2C+Kishor+and+Atena%2C+Agegnehu+and+Witelski%2C+Tom+and+Sun%2C+Jiguang+and+Fehribach%2C+Joseph++(2007)+Maximizing+Minimum+Pressure+in+Fluid+Dynamic+Bearings+of+Hard+Disk+Drives.++%5BStudy+Group+Report%5D+++++