IPC분류정보
국가/구분 |
United States(US) Patent
등록
|
국제특허분류(IPC7판) |
|
출원번호 |
US-0182314
(2008-07-30)
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등록번호 |
US-8155940
(2012-04-10)
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발명자
/ 주소 |
- Wang, Qigui
- Powell, Jr., Bob R.
- Jones, Peggy E.
- Chang, Cherng-Chi
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출원인 / 주소 |
- GM Global Technology Operations LLC
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대리인 / 주소 |
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인용정보 |
피인용 횟수 :
2 인용 특허 :
3 |
초록
▼
A system and method for predicting fatigue life in metal alloys for very high cycle fatigue applications. The system and method are especially useful for cast metal alloys, such as cast aluminum alloys, where a fatigue endurance limit is either non-existent or hard to discern. Fatigue properties, su
A system and method for predicting fatigue life in metal alloys for very high cycle fatigue applications. The system and method are especially useful for cast metal alloys, such as cast aluminum alloys, where a fatigue endurance limit is either non-existent or hard to discern. Fatigue properties, such as fatigue strength in the very high cycle fatigue region, are based on a modified random fatigue limit model, where the very high cycle fatigue strength and infinite life fatigue strength are refined to take into consideration the sizes of the discontinuities and microstructure constituents since the fatigue life scatter depends upon the presence of discontinuities and microstructure constituents. The sizes of the discontinuities and microstructure constituents that can initiate fatigue cracks can be determined with extreme value statistics, then input to the modified random fatigue limit model.
대표청구항
▼
1. A computer-implemented method of predicting very high cycle fatigue strength for a cast aluminum-based metal alloy, said method comprising: providing a computer-based system comprising an input, an output, a central processing unit and memory;introducing program code into at least one of said inp
1. A computer-implemented method of predicting very high cycle fatigue strength for a cast aluminum-based metal alloy, said method comprising: providing a computer-based system comprising an input, an output, a central processing unit and memory;introducing program code into at least one of said input, memory and central processing unit from a computer-readable medium having a non-transitory form of said program code embodied therein;operating said program code such that calculations made thereby are performed by said central processing unit;selecting an alloy where at least one fatigue crack initiation site is presumed or determined to be present therein and where said alloy is generally not possessive of an identifiable endurance limit;inputting into said system a size of discontinuity or microstructure constituent representative of said at least one fatigue crack initiation site;inputting into said system a finite life fatigue strength that corresponds to said alloy; and calculating with said program code an infinite life fatigue strength and said very high cycle fatigue strength using a modified random fatigue limit model which comprises using the equation ln(aiαNf)=C0+C1 ln(σa−σL)where ai is said size of discontinuity or microstructure constituent, Nf is fatigue life, C0 and C1 are constants, α is a constant substantially in the range of between one and ten, σa is an applied stress, and σL is a measure of said infinite life fatigue strength. 2. The method of claim 1, wherein said applied stress comprises said very high cycle fatigue strength in situations where said fatigue life is at least 108 cycles. 3. The method of claim 1, wherein a distribution of said infinite life fatigue strength substantially follows the equation P=1-exp(-σLσ0)β where P is the probability of failure at an infinite number of cycles, and σ0 and β are parameters for a distribution of said infinite life fatigue strength. 4. The method of claim 1, wherein at least one fatigue crack initiation site is determined by at least one of direct measurement and analytical prediction. 5. The method of claim 4, wherein said direct measurement comprises at least one of X-ray computed tomography, single and serial sectioning metallography and fractography. 6. The method of claim 1, wherein said size of said discontinuity or microstructure constituent follows a generalized extreme value distribution according to the equation: P=exp(-(1+c(ai-μa0))-1c) where c, a0 and μ are generalized extreme value parameters used to represent at least one of a shape and a scale of a probabilistic distribution function of ai. 7. The method of claim 6, wherein said extreme value distribution is used in conjunction with at least one of 2D metallographic techniques, fractographic techniques, X-ray computed tomography and computational simulation and modeling to estimate values representing a population of said size of discontinuity or microstructure constituent. 8. An article of manufacture comprising a computer-usable medium having computer-readable program code embodied therein for calculating at least one very high cycle fatigue property in an aluminum-based metal casting where an endurance limit associated with said metal casting is either not existent or not readily identifiable, said computer-readable program code in said article of manufacture comprising: computer-readable program code portion for causing a computer to determine an infinite life fatigue strength of said metal casting where at least one fatigue crack initiation site is presumed or determined to be present therein;computer-readable program code portion for receiving a discontinuity size representative associated with said at least one fatigue crack initiation site;computer-readable program code portion for calculating said at least one very high cycle fatigue property based on a modified random fatigue limit model wherein said computer-readable program code portion for calculating said at least one very high cycle fatigue property comprises using the equation ln(aiαNf)=C0+C1 ln(σa−σL)to effect said modified random fatigue limit model, where ai is said discontinuity and microstructure constituent size, Nf is fatigue life, C0 and C1 are empirical constants, α is a constant substantially in the range of between one and ten, σa is an applied stress and σL is a measure of infinite life fatigue strength; andcomputer-readable program code portion configured to output results calculated by said modified random fatigue life model to at least one of a machine-readable format and a human-readable format. 9. The article of manufacture of claim 8, wherein said computer-readable program code portion for calculating said at least one very high cycle fatigue property comprises using a generalized extreme value distribution in conjunction with a modified random fatigue limit model. 10. An apparatus for predicting fatigue life in an aluminum-based metal alloy where an endurance limit associated with the alloy is either not existent or not readily identifiable, said apparatus comprising: a device configured to acquire at least one of measured or predicted fatigue crack initiation site information; anda computing member configured to accept fatigue property data gathered from said device and further configured to calculate at least one of a very high cycle fatigue strength and an infinite fatigue life strength of the alloy in accordance to instructions provided by a computer-readable program, said program comprising: a code portion for causing said computing member to determine said at least one of a very high cycle fatigue strength and an infinite life fatigue strength of the alloy where at least one fatigue crack initiation site is presumed or determined to be present therein;a code portion for receiving at least one of a discontinuity size and a microstructure constituent size associated with said at least one fatigue crack initiation site;a code portion for calculating said at least one of a very high cycle fatigue strength and an infinite fatigue life strength based on a modified random fatigue limit model wherein said computer-readable program code portion for calculating said at least one of a very high cycle fatigue strength and an infinite life fatigue strength comprises using the equation ln(aiαNf)=C0+C1 ln(σa−σL)to effect said modified random fatigue limit model, where ai is said discontinuity and microstructure constituent size, Nf is fatigue life, C0 and C1 are empirical constants, α is a constant substantially in the range of between one and ten σa is an applied stress and σL is a measure of said infinite life fatigue strength; anda code portion configured to output results calculated by said modified random fatigue limit model to at least one of a machine-readable format and a human-readable format. 11. The apparatus of claim 10, wherein said program further comprises at least one extreme value statistical algorithm to estimate an upper bound initiation site size expected to occur in the alloy.
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