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  • 學位論文

奈米結構之磁碟片在壓痕測試下之數值及實驗研究

Numerical and Experimental Study of Indentation on Nano-patterned Magnetic Disks

指導教授 : 莊嘉揚

摘要


為了使硬碟機能突破現有之磁錄密度限制,未來將可能利用奈米柱陣列媒體(Bit-patterned media,簡稱BPM)技術來達成,但此種磁碟片的設計卻可能會在運轉的時候遇到接觸上的問題,因此,探討這種奈米尺度結構的接觸力學問題,可以使我們進一步的了解接觸的現象,並針對磁碟片結構做出修正。 本研究先利用TI-950 TriboIndenter奈米壓痕試驗機台,量測並分析具有奈米柱陣列媒體之新型磁碟片試片的接觸行為,其中試片的表面奈米結構已由原子力顯微鏡(AFM)量測確認,發現傳統連續媒體之接觸剛度大於奈米柱陣列媒體之接觸剛度,且在奈米柱陣列媒體中有微量的塑性變形。 本研究使用有限元素法建構三維有限元素模型計算磁碟片與壓痕器之間的接觸力與下壓深度關係,並與奈米壓痕試驗結果相互比較,發現兩者的趨勢接近,進一步使用有限元素法分析奈米柱幾何參數對磁碟片接觸行為之影響;在所有參數固定,僅改變奈米柱寬度時,發現將奈米柱加寬將有利於塑性變形之減少;而所有參數固定,僅改變奈米柱高度時,發現填入類鑽碳(DLC)以降低奈米柱高度時,雖可以降低塑性變形,但無法完全消除之,除非可以將磁碟片完全平坦化,而移除材料以增加奈米柱之高度時,可以看到接觸壓力明顯降低,並在一臨界高度時,其接觸壓力將低於完全平坦化之奈米柱陣列媒體。 最後,本研究比較使用DLC完全平坦化之奈米柱陣列媒體以及傳統連續媒體之接觸性質,發現兩者結果相近,故可視平坦化為此種磁碟片設計的解決之道。

並列摘要


Bit-patterned media (BPM) is considered as a potential technology to increase recording areal density of magnetic recording; however, since the surface of BPM is discrete, it may confront more tribological challenges than conventional continuous media (CM). Consequently, it is a rather crucial issue of the contact phenomena on nano-structures. In this study, we conduct nanoindentation tests on a prototype disk sample, which contains both BPM and CM regions, by TI-950 TriboIndenter. The surface topography of the disk was measured by AFM, and is used to create finite element model. We repeated the nanoindentation tests multiple times, and confirmed the results were repeatable. The results show that CM has a larger rigidity than BPM, and that BPM has residual deformation after indention. We conduct three-dimensional (3D) static finite element analysis to study the contact behavior during nanoindentation tests on continuous and patterned elastic-plastic layered media. At first, we compared the numerical results with experimental results and found that those results are consistent. Secondly, we change the geometry properties of nano-bits in numerical model and study the influences on contact behavior. While changing the width of nano-bits, it shows that the plastic deformation in disk is reduced by increasing the width of nano-bits. While changing the height of nano-bits, the reduction of height of nano-bits by filling diamond-like carbon (DLC) can decrease the magnitude of plastic deformation, but it cannot eliminate residual deformation completely unless the disk is fully planarized with filling materials. Increase of the height of nano-bits by removing materials significantly reduces the contact pressure, and at a particular critical height, the contact pressure on nano-bits is lower than that of the fully planarized one. At last, we compared the contact behavior between the conventional continuous media and BPM planarized by DLC. The results show that the contact behaviors of those are very close. Therefore, we can regard the planarization as a method to solve the tribological problems of BPM in disk design process.

參考文獻


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