Methods and apparatus for predicting the failure of a component, and for determining a grain orientation factor for a material

• US 7,480,601 B2
• Filed: 01/18/2006
• Issued: 01/20/2009
• Est. Priority Date: 10/26/2000
• Status: Expired due to Term

• Current Assignee: Vextec Corporation
• Original Assignee: Vextec Corporation
• Inventors: Tryon, Robert G. III
• Primary Examiner(s): Rodriguez; Paul L
• Assistant Examiner(s): GUILL, RUSSELL L
• Application Number:
  US11/335,021
• Publication Number:
  US 20060206295A1
• Time in Patent Office: 1,098 Days
• Field of Search: 703/6, 703/7, 703/8, 703/2, 703/13, 702/181, 702/182
• US Class Current: 703/7
• CPC Class Codes: G06F 2111/08 Probabilistic or stochastic CAD
• CPC Class Codes: G06F 30/23 using finite element methods [FEM] or finite difference methods [FDM]

Abstract

The invention provides a method and apparatus for predicting the failure of a component using a probabilistic model of a material'"'"'s microstructural-based response to fatigue. The method predicts the component failure by a computer simulation of multiple incarnations of real material behavior, or virtual prototyping. The virtual prototyping simulates the effects of characteristics that include grain size, grain orientation, micro-applied stress and micro-yield strength that are difficult to simulate with real specimens. The invention provides an apparatus for predicting the response of a component to fatigue using the method.

Claims

1. An apparatus comprising:

a central processing unit (CPU)

an output device for displaying simulated fatigue results;

an input device for receiving input;

and a memory,

the CPU, memory, input device and output device being connected to one another via a bus, and the memory comprising;

instructions for predicting a probability of failure of a component, the instructions comprising;

obtaining a Finite Element Model (FEM) of the component;

analyzing said FEM to obtain stresses at nodes of said FEM;

determining a Representative Volume Element (RVE) for at least one of said nodes;

building a microstructure-based failure model for at least one said RVE and including the microstructure-based failure model in the RVE;

simulating a component life using at least one RVE microstructure-based failure model, said simulating producing a result related to component life;

performing said simulating a plurality of times to produce results related to component life;

using the results to predict a probability of failure for said component; and

instructions for displaying a result from said predicting.

2. The apparatus of claim 1, wherein said microstructure-based failure model comprises fatigue failure modeling information.

3. The apparatus of claim 1, wherein each said microstructure-based failure model comprises at least one random variable and wherein probabilistic methods are used to provide values for said at least one random variable.

4. The apparatus of claim 1, wherein said instructions for simulating further comprise:

establishing an RVE life for each said RVE; and

using each said RVE life to produce the result related to said component life.

5. The apparatus of claim 1, wherein said at least one RVE microstructure-based failure model was ascertained following steps comprising:

identifying a material microstructure in said RVE;

characterizing how damage interacts with said microstructure to provide at least one damage mechanism; and

creating a failure model for said material microstructure based on said at least one damage mechanism, said creating comprising;

finding a sequence in which said at least one damage mechanism works to damage said material microstructure;

getting for each said at least one damage mechanism one of a group of models consisting of;

a crack nucleation model, a short crack growth model, and a long crack growth model; and

linking said models to produce said RVE microstructure-based failure model based on information from said identifying, characterizing, and finding.

6. The apparatus of claim 5, wherein said characterizing further comprises:

determining said material microstructure'"'"'s mechanical characteristics; and

determining said material microstructure'"'"'s bulk elastic material characteristics.

7. The apparatus of claim 5, wherein said finding comprises:

determining how many of said at least one damage mechanism are crack nucleation mechanisms;

determining how many of said at least one damage mechanism are short crack growth mechanisms;

determining how many of said at least one damage mechanism are long crack growth mechanisms; and

developing a strategy for linking said crack nucleation, short crack growth, and long crack growth mechanisms.

8. The apparatus of claim 1, said instructions for simulating further comprising:

determining an RVE life for each said RVE, said determining an RVE life comprising;

evaluating a statistically determined number of nucleation sites within said RVE utilizing probabilistic methods.

9. The apparatus of claim 8, wherein said probabilistic methods comprise Monte Carlo (MC) methods.

10. The apparatus of claim 1, said instructions for identifying further comprising:

identifying a subset of said nodes as significant nodes based on said stresses.

11. The apparatus of claim 10 wherein instructions for identifying a subset of said nodes comprise:

obtaining a statistical distribution of said stresses at said nodes,

and wherein said instructions for simulating a component life further comprise establishing an RVE life for each RVE using probabilistic methods comprising Monte Carlo methods.

12. The apparatus of claim 10, wherein said component has regions of similar geometric detail and said simulating further comprises adding a spatial correlation for said regions.

13. The apparatus of claim 1, wherein said component has regions of similar geometric detail and said simulating further comprises adding a spatial correlation for said regions.

14. The apparatus of claim 1, wherein said building comprises:

receiving information indicative of a selected material microstructure in said RVE;

receiving pre-determined failure modeling information for said selected material microstructure, wherein the pre-determined failure modeling information includes modeling information for one or more damage mechanisms for the selected material microstructure.

15. The apparatus of claim 14, wherein said pre-determined failure modeling information for the selected material microstructure includes modeling information for at least one mechanical characteristic of the selected material microstructure, and further includes modeling information for at least one bulk elastic material characteristic of the selected material microstructure.

16. The apparatus of claim 14, wherein said pre-determined failure modeling information comprises crack nucleation modeling information, short crack growth modeling information, and long crack growth modeling information.

17. The apparatus of claim 14, wherein receiving information indicative of selected material microstructure in said RVE comprises receiving information indicative of a component material, and wherein the selected material microstructure is selected from a plurality of available material microstructures associated with the component material.

18. The apparatus of claim 1, wherein said performing said simulating a plurality of times comprises:

performing said simulating a first time using a first selected material microstructure of a plurality of available material microstructures associated with at least one component material;

and further comprises

performing said simulating a second time using a second different selected material microstructure of the plurality of available microstructures associated with the at least one component material.

19. A method, performed on a computer, for determining a grain orientation factor for a material, the method comprising:

obtaining one or more equations that relate a stress direction to a slip direction for one or more respective potential slip systems of the material;

simulating a grain orientation of said material, said simulating comprising, for each grain of a defined number of grains;

using probabilistic methods to generate a slip plane normal angle for each of the potential slip systems in the grain;

inputting said normal angles into said equations to obtain a potential orientation factor for each of the potential slip systems; and

selecting the minimum potential orientation factor as a grain orientation factor for said grain;

repeating said simulating for the defined number of grains thereby obtaining a plurality of grain orientation factors;

creating a statistical distribution of said plurality of grain orientation factors to determine the grain orientation factor for said material and

displaying at least the grain orientation factor for the material on an output device of the computer.

20. The method of claim 19, wherein said probabilistic methods comprise Monte Carlo methods.

21. The method of claim 19, wherein the obtaining one or more equations comprises:

for a given potential slip system,

identifying, based on a crystal structure of the material, each other symmetrically related potential slip system; and

deriving a relationship between the slip direction in the given potential slip system and a slip direction in each of the other symmetrically related potential slip systems.

22. An apparatus for determining a grain orientation factor for a material, the apparatus comprising:

a central processing unit (CPU);

an output device for displaying at least the grain orientation factor;

an input device for receiving input;

and a memory,

the CPU, memory, input device and output device being connected to one another via a bus, and the memory comprising;

instructions for receiving input;

instructions for obtaining one or more equations that relate a stress direction to one or more respective potential slip systems of the material;

instructions for simulating the grain orientation factor of said material, said simulating comprising, for each grain of a defined number of grains;

using probabilistic methods to generate a slip plane normal angle for each of the potential slip systems in the grain;

inputting said normal angles into said equations to obtain a potential orientation factor for each of the potential slip systems;

and

selecting a minimum potential orientation factor as a grain orientation factor for said grain;

instructions for repeating said simulating for the defined number of grains thereby obtaining a plurality of grain orientation factors;

instructions for creating a statistical distribution of said plurality of grain orientation factors to determine the grain orientation factor for said material.

23. The apparatus of claim 22, wherein said probabilistic methods comprise Monte Carlo methods.

24. The apparatus of claim 22, wherein the instructions for obtaining one or more equations comprise:

for a given potential slip system,

instructions for identifying, based on a crystal structure of the material, each other symmetrically related potential slip system; and

instructions for deriving a relationship between the slip direction in the given potential slip system and a slip direction in each of the other symmetrically related potential slip systems.

25. A method, performed on a computer, for predicting the failure of a component made from a material, the method comprising:

obtaining a Finite Element Model (FEM) of a component;

analyzing said FEM to obtain stresses at nodes of said FEM;

identifying a subset of said nodes as significant nodes based on said stresses;

determining a Representative Volume Element (RVE) for at least one of said significant nodes;

developing an RVE microstructure-based failure model for at least one said RVE, said developing comprising;

identifying a material microstructure in said RVE;

characterizing how damage interacts with said material microstructure to provide at least one damage mechanism, wherein the at least one damage mechanism includes stress and fatigue; and

creating a failure model for said material microstructure based on said at least one damage mechanism, said creating comprising;

finding a sequence in which said at least one damage mechanism works to damage said material microstructure;

getting for each said at least one damage mechanism one of a group of models consisting of;

a crack nucleation model, a short crack growth model, and a long crack growth model; and

linking said models to produce said RVE microstructure-based failure model based on information from said identifying, characterizing, and finding;

simulating a component life using at least one RVE microstructure-based failure model, said simulating producing a result related to said component life;

performing said simulating a plurality of times to produce results related to component life;

preparing statistics using said results;

comparing said statistics to a probability of failure (POF) criterion to determine whether said performing predicted failure for said component and

displaying an indication of whether the failure was predicted on an output device of the computer.

26. The method of claim 25, wherein the RVE comprises a grain orientation factor for the material.

27. A method, performed on a computer, for predicting the failure of a component, the method comprising:

obtaining a Finite Element Model (FEM) of a component;

analyzing said FEM to obtain stresses at nodes of said FEM;

identifying a subset of said nodes as significant nodes based on said stresses;

determining a Representative Volume Element (RVE) for at least one of said significant nodes;

developing an RVE microstructure-based failure model for at least one said RVE;

simulating a component life using at least one RVE microstructure-based failure model, said simulating producing a result related to said component life;

performing said simulating a plurality of times to produce results related to component life;

preparing statistics using said results;

comparing said statistics to a probability of failure (POF) criterion to determine whether said performing predicted failure for said component; and

displaying an indication of whether the failure was predicted on an output device of the computer.

28. The method of claim 27, wherein said performing said simulating a plurality of times comprises performing said simulating a first time using a first selected material microstructure of a plurality of available material microstructures associated with at least one component material, and further comprises performing said simulating a second time using a second different selected material microstructure of the plurality of available microstructures associated with the at least one component material.