IPC분류정보
국가/구분 |
United States(US) Patent
공개
|
국제특허분류(IPC7판) |
|
출원번호 |
US-0182314
(2008-07-30)
|
공개번호 |
US-0030537
(2010-02-04)
|
발명자
/ 주소 |
- Wang, Qigui
- Powell, JR., Bob R.
- Jones, Peggy E.
- Chang, Cherng-Chi
|
출원인 / 주소 |
- GM GLOBAL TECHNOLOGY OPERATIONS, INC.
|
대리인 / 주소 |
|
인용정보 |
피인용 횟수 :
0 인용 특허 :
0 |
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
▼
What is claimed is: 1. A method of predicting very high cycle fatigue strength for a metal alloy, said method comprising: 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 identi
What is claimed is: 1. A method of predicting very high cycle fatigue strength for a metal alloy, said method comprising: 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 a size of discontinuity or microstructure constituent representative of said at least one fatigue crack initiation site; inputting a finite life fatigue strength that corresponds to said alloy; and calculating an infinite life fatigue strength and said very high cycle fatigue strength using a modified random fatigue limit model. 2. The method of claim 1, wherein said modified random fatigue limit model 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 in the range of between one and ten, σa is an applied stress, and σL is a measure of said infinite life fatigue strength. 3. The method of claim 2, wherein said applied stress comprises said very high cycle fatigue strength in situations where said fatigue life is at least 108 cycles. 4. The method of claim 2, wherein a distribution of said infinite life fatigue strength substantially follows the equation P = 1 - exp ( - σ L σ 0 ) 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. 5. The method of claim 1, wherein said finite life fatigue strength comprises the fatigue strength at a fatigue life of up to ten million cycles. 6. The method of claim 1, wherein said metal alloy comprises a cast metal alloy. 7. The method of claim 6, wherein said cast metal alloy comprises a cast aluminum alloy. 8. The method of claim 1, wherein said metal alloy comprises a wrought non-ferrous alloy. 9. 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. 10. The method of claim 9, wherein said direct measurement comprises at least one of X-ray computed tomography, single and serial sectioning metallography and fractography. 11. The method of claim 2, wherein said size of said discontinuity or microstructure constituent follows a generalized extreme value distribution according to the equation: P = exp ( - ( 1 + c ( a i - μ a 0 ) ) - 1 c ) 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. 12. The method of claim 11, 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. 13. An article of manufacture comprising a computer-usable medium having computer-readable program code embodied therein for calculating at least one of very high cycle fatigue strength and infinite life fatigue strength in a 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 fatigue strength based on a modified random fatigue limit model; and computer-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. 14. The article of manufacture of claim 13, wherein said computer-readable program code portion for calculating at least one of said very high cycle fatigue strength and 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 in the range of between one and ten, σa is an applied stress and σL is a measure of said infinite life fatigue strength. 15. The article of manufacture of claim 14, wherein said computer-readable program code portion for calculating said fatigue strength comprises using a generalized extreme value distribution in conjunction with a modified random fatigue limit model. 16. An apparatus for predicting fatigue life in metal alloys 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; and a 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; and a code portion configured to output results calculated by said MRFL model to at least one of a machine-readable format and a human-readable format. 17. The apparatus of claim 16, 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. 18. The apparatus of claim 16, 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 in the range of between one and ten, σa is an applied stress and σL is a measure of said infinite life fatigue strength.
※ AI-Helper는 부적절한 답변을 할 수 있습니다.