國家衛生研究院 NHRI:Item 3990099045/4505
English  |  正體中文  |  简体中文  |  全文筆數/總筆數 : 12145/12927 (94%)
造訪人次 : 857766      線上人數 : 803
RC Version 6.0 © Powered By DSPACE, MIT. Enhanced by NTU Library IR team.
搜尋範圍 查詢小技巧：
  • 您可在西文檢索詞彙前後加上"雙引號"，以獲取較精準的檢索結果
  • 若欲以作者姓名搜尋，建議至進階搜尋限定作者欄位，可獲得較完整資料
    •  進階搜尋
    主頁 ‧ 登入 ‧ 上傳 ‧ 說明 ‧ 關於NHRI ‧ 管理 到手機版


    請使用永久網址來引用或連結此文件: http://ir.nhri.org.tw/handle/3990099045/4505


    題名: Dynamic impact stress analysis of a bileaflet mechanical heart valve
    作者: Yuan, Q;Xu, LJ;Ngoi, BKA;Yeo, TJH;Hwang, NHC
    貢獻者: Division of Medical Engineering Research
    摘要: Background and aims of the study: Mechanical heart valves (MHV) are widely used to replace dysfunctional and failed heart valves. The bileaflet MHV is very popular due to its superior hemodynamics. At present, bileaflet MHVs account for about two-thirds of the prosthetic heart valve market: Since their introduction in 1977, the hemodynamics of bileaflet prostheses has been extensively studied. New technologies used to develop MHV include better design concepts, materials, manufacturing processes, and post-design verification. The study aim was to investigate the dynamic impact stress of a newly designed bileaflet MHV under normal physiological conditions. Methods: Pro/Engineer was used to generate a 3-D model of the designed valve. ANSYS 5.5 and LS-DYNA were used to calculate stress and deformation of the valve. Due to symmetry, a one-half orifice and one leaflet were modeled using the eight-noded hexahedral elements. When valve leaflets are in the fully closed position, the static contact stress between leaflet and orifice was predicated under typical heart valve closing pressure of 80 mmHg. To study the dynamic effects of the closing valve, LS-DYNA was used to simulate leaflet motion. Typical physiological pressure waveform was employed to initiate this leaflet motion. Two types of valve were investigated: Test valve A (size 19, flat leaflet); and test valve B (size 19, tapered leaflet 1.5degrees, with the same thickness at pivot as valve A). The non-invasive laser sweeping technique was used to measure leaflet closing velocity in a mock flow test rig. The closing velocity of test valve A was compared by experimental and computed results. The corresponding dynamic contact stress on the leaflet was obtained for different modes of loading, simulated under angular velocity; acceleration, and especially under representative pressure waveform. Results: The experimental closing velocity of test valve A was 1.07 +/- 0.05 m/s; the computed value was 1.130 m/s. During full closure, the leaflets showed a slight rebound, and this was also seen experimentally. For test valve B, the computed closing velocity was 1.039 m/s. In the dynamic impact analysis, the physiological pressure waveform was obtained at a normal heart rate of 70 beats/min from the mock flow test rig. Dynamic stress and displacement of the model valve were calculated as the valve was closing. The time step of calculation was determined by the wave propagation velocity and element size. With an inter-hinge distance of 4.966 mm based on the geometric design of the valve, maximum dynamic von Mises stress appeared near the hinge of the leaflet (26.92 MPa for valve A; 22.36 MPa for valve B). By varying the position of the hinge/pivoting axis (+/-10%), an optimized valve geometry could be obtained based on minimal impact stress on the valve leaflet. Conclusion: Based on closing velocity comparison of valve A, the calculated model and loading conditions were seen to be reasonable. Computational accuracy was satisfied. The tapering feature of the leaflet is designed especially for minimal impact stress at the leaflet contact areas upon impact with the inner walls of the BMHV. These points provide an optimum structure design for the Nanyang Technological University BMHV.
    日期: 2003-01
    關聯: Journal of Heart Valve Disease. 2003 Jan;12(1):102-109.
    Link to: http://www.icr-heart.com/journal/content/2003/jan/abstracts/article.php?id=147
    Cited Times(WOS): https://www.webofscience.com/wos/woscc/full-record/WOS:000180405900021
    Cited Times(Scopus): http://www.scopus.com/inward/record.url?partnerID=HzOxMe3b&scp=12244267075
    顯示於類別:[黃煥常(2000-2008)] 期刊論文

    文件中的檔案:

    檔案 描述 大小格式瀏覽次數
    ISI000180405900021.pdf147KbAdobe PDF737檢視/開啟


    在NHRI中所有的資料項目都受到原著作權保護.

    TAIR相關文章

    DSpace Software Copyright © 2002-2004  MIT &  Hewlett-Packard  /   Enhanced by   NTU Library IR team Copyright ©   - 回饋