| 摘要: | 粉末冶金技術能夠以低成本實現外形複雜之小型齒輪的量產,此優勢使得粉末冶金齒輪的重要性受到矚目;但由於粉末冶金齒輪具有空孔性之結構,此特徵將可能導致其具有較低之齒根疲勞強度,若要將粉末冶金齒輪作為傳動件使用,則須對其齒根疲勞強度作出充分的檢驗. 本研究針對粉末冶金正齒輪的齒根疲勞強度進行檢測,並以疲勞曲線呈現其結果,試驗樣本之成分為Fe-4Ni-0.5Mo-1.5Cu-0.6C;主要的實驗方式是單齒齒根疲勞試驗,另輔以齒輪對運轉試驗為驗證,確保實驗結果能忠實呈現齒輪在一般使用狀況下的強度.疲勞曲線與可靠度的計算,是採韋伯分布與ASTM E 739-91線性疲勞數據統計分析兩種方法進行,齒根應力則是依ISO 6336-3標準規範計算. 實驗結果顯示兩種試驗所得之疲勞曲線互為平行,如此可透過較有效率的單齒齒根疲勞試驗,推測齒輪於真實狀況下的強度表現.本研究亦將材料為Fe-1.75Ni-0.5Mo-1.5Cu-0.6C且經淬火之粉末冶金齒輪作為對照,比較該齒輪與本試驗齒輪的疲勞強度,發現該齒輪之強度整體而言較低,但當循環數越接近無限壽命區時,兩齒輪之強度則越趨接近;另外,本研究亦觀察到齒輪經運轉後,產生了點蝕與刮傷的齒面疲勞破壞. Powder metallurgy technology or PM technology plays an important role in gear manufacturing in recent years because it is cost-saving and efficient to produce small gears with complex shapes. However, the tooth root fatigue strength of the PM gear is reduced because it is porous. In order to use the PM gear for the power transmission, it is necessary to explore the tooth root fatigue strength of the PM gear for gear design. In order to determine the tooth root fatigue strength of the PM gear, a fatigue test for single tooth of a spur gear was conducted. The fatigue test results were also verified by a running test for the spur gear pair on a back-to-back test rig under real operational conditions. The composition of the testing spur gear is Fe-4Ni-0.5Mo-1.5Cu-0.6C. The test results are shown as S-N curves calculated based on Weibull distribution and ASTM E 739-91 standard. The corresponding tooth root stress is calculated based on ISO 6336-3 standard. The S-N curves obtained from the single tooth fatigue test and the running test are parallel. It means the tooth root fatigue strength under real operational conditions can be also estimated from the single tooth fatigue test, which is more time-saving and cost-saving to conduct. The available fatigue strength of a quenched PM gear with composition Fe-1.75Ni-0.5Mo-1.5Cu-0.6C is also compared with that of the test gear in the study. The tooth bending strength of the quenched gear is lower than that of the test gear, but it becomes closer to that of the test gear, in the range of high loading cycles. From the running test results, pitting and scuffing were also found on the tooth flanks. |
