Modeling / Analysis Services
Meeting your fatigue and fatigue crack growth needs
Fatigue Modeling
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AFMA offers consulting and modeling services in support of the creation of LCF and HCF (low and high cycle fatigue) design tools.
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We have experience in developing unified fatigue models that bring the effects of geometry, stress ratio, and thermal effects into a single fatigue parameter.
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Model based off of textbook fatigue principles (Basquin, Manson coffin, et al) with modifications tailored to your specific material and design needs.
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We will work with you to evaluate your existing database, guide / execute literature searches, and make recommendations for additional testing to ensure efficient and effective characterization at deg conditions.​
Fatigue Crack Growth
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In addition to fatigue crack growth testing, AFMA also offers data post processing services using in-house analysis software that conforms to ASTM E647 standards.
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New K gradient option (developed by FractureLab) based on driving a linear decrease of plastic zone size during threshold tests mitigates the likelihood of remote closure.
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Additional curve fitting using the NASGRO equation defines crack growth behavior from threshold to failure.
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In the case of a variable Region II, a "perturbed" NASGRO fitting routine developed by FractureLab may be used to better characterize the data.
Adjusted Compliance Ratio and Master Curves
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AFMA standard compliance test protocols include measurement of opening load and the incorporation of Adjusted Compliance Ratio (ACR) to account for the effects of remote closure and bring it in line with small crack data..
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Another approach to mitigate remote closure effects is the constant Kmax / decreasing DK test.
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Resulting variable-R curves are collapsed using the Walker Equation, creating an equivalent "master curve" normalized to R = 0, which can then be mapped to any positive stress ratio.