預測鋁合金疲勞裂紋成長速率公式之探討

本研究是依據Mohanty等人的文獻中，所顯示的實驗值曲線圖，使用CorelDRAW 繪圖程式其中物件屬性之細節功能取得曲線圖形的各個曲線的點座標換算成數據代入曲線貼合法（Curve fitting）模擬成的ㄧ個多次方方程式，再用MATLAB polyfit的功能求出數據用Origin繪出曲線圖，然後與Mohanty等人實驗值及Paris model、Forman model的曲線分析比較，結果本研究所提出的多次方方程式能更準確預測鋁合金疲勞裂紋成長速率。本研究所得到的四次方程式使用在 Al 7020-T7 材料時del.K在10～30 MPa.m^1/2範圍內，最大誤差值為0.94%，使用在 Al 2024-T3材料時del.K在 5～30 MPa.m^1/2範圍內，最大誤差值為0.002%。

關鍵字

裂紋產生力量；恆定載荷；指數模型；疲勞裂紋成長速率

並列摘要

According to the experimental curves that Presented by Mohanty etal,for AI 7020-T7 and AI 2024-T3 the cures are converted to the data by using CorelDraw graphic program. Then, applying curve fitting method, the relationship between ranges stress intensity factor (del.K) and fatigue crack growth rate (da/dN) is simulated to a nonlinear polynomial with natural logarithms. The predicting relations are compared with experimental results, Paris model and Forman model. In this Study, the predicting formula with forthordor is applied to AI 7020-T7 for del.K between 10～30 MPa.m^1/2 the maximum error is 0.94%. For AI 2024-T3, and del.K between 5~30 MPa.m^1/2, the maximum error is 0.0024%.

並列關鍵字

Crack driving forces ； Constant amplitude loading ； Exponential model ； Fatigue crack growth rate

參考文獻

[1] Paris PC, Erdogan F. A critical analysis of crack Propagation law. J Basic

Eng 1963 85：528–34.

[2] Forman RG, Kearney VE, Engle RM. Numerical analysis of crack Propagation

[3] Mohanty JR. , Verma BB. , Ray PK. , Prediction of fatigue crack growth and

loading）.Int. J. Fatigue 2009 31：418-424.

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預測鋁合金疲勞裂紋成長速率公式之探討

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