Patent Application
20130325417
The present invention generally relates to computer aided engineering analysis, more particularly to methods and systems for conducting a numerical simulation of a structure having heat-affected zone, which is located in the vicinity of heat sources (e.g., welding).
Computer aided engineering (CAE) has been used for supporting engineers in many tasks. For example, in a structure or engineering product design procedure, CAE analysis, particularly finite element analysis (FEA), has often been employed to predict structural behavior (e.g., stresses, displacements, etc.) under various simulated loading conditions (e.g., static or dynamic).
FEA is a computerized method widely used in industry to numerically simulate (i.e., model and solve in a computer system) engineering problems relating to complex products or systems (e.g., cars, airplanes, consumer products, etc.) such as three-dimensional non-linear structural design and analysis. FEA derives its name from the manner in which the geometry of the object under consideration is specified. The geometry is defined by elements and nodal points. There are a number of types of elements, solid elements for volumes or continua, shell or plate elements for surfaces and beam or truss elements for one-dimensional structural objects. The geometry of each element is defined by nodal points, for example, a brick or hexahedral element comprising eight corner nodes.
FEA has been used for estimating automobile crashworthiness. Numerical simulation of an impact event (e.g., car crash) using FEA has been improved significantly with advent of computer technology. In recent years, attentions have been paid to numerically simulate structural behavior within a heat-affected zone (HAZ) near a heat source (e.g., a spotweld, a butt weld seam).
Heat-affected zone is the area of a material whose properties altered by high heat (e.g., welding). For example, use of Metal Inert Gas welding induces material strength reductions in the HAZ. As a result, lines of weakness are created in the vicinity of the heat sources for potential structural failure, particularly under crash loading. Material properties (e.g., stress-strain relationship) within the HAZ are altered comparing to those of the base material. In general, material properties within HAZ vary by the distance measured from a heat source location (i.e., the center of a spotweld).
Prior art approaches for modeling such effects have been to create several layers of finite elements 212a-212c surrounding a weld 210 in an exemplary FEA model shown in
It would, therefore, be desirable to have efficient numerical simulation methods of a structure containing HAZ using a FEA model.
This section is for the purpose of summarizing some aspects of the present invention and to briefly introduce some preferred embodiments. Simplifications or omissions in this section as well as in the abstract and the title herein may be made to avoid obscuring the purpose of the section. Such simplifications or omissions are not intended to limit the scope of the present invention.
Methods and systems for conducting numerical simulation of a structure having at least one heat-affected zone using a FEA model are disclosed. According to one exemplary embodiment of the present invention, a FEA model includes at least a group of finite elements representing a welded structural part that encompasses at least one HAZ is defined and received in a computer system having a FEA application module installed thereon. Each finite element in the group is configured with at least one integration point based on FEA. The group of finite elements is associated with a set of HAZ material properties representing structural behavior of the welded structural part inside and outside the HAZ. Corresponding material properties are then determined and assigned to each integration point by interpolating the associated set using the shortest heat-propagation distance between each integration point and the heat source locations (e.g., spotwelds' centroid). A numerical simulation of the structure can then be conducted using the FEA model with corresponding numerical material properties determined at each integration point. According to another aspect of the present invention, the parts in a FEA model that reference the HAZ constitutive model are automatically initiated and no other input is necessary. The present invention eliminates the need for the complex meshing techniques (e.g., the FEA mesh in
Objects, features, and advantages of the present invention will become apparent upon examining the following detailed description of an embodiment thereof, taken in conjunction with the attached drawings.
These and other features, aspects, and advantages of the present invention will be better understood with regard to the following description, appended claims, and accompanying drawings as follows:
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will become obvious to those skilled in the art that the present invention may be practiced without these specific details. The descriptions and representations herein are the common means used by those experienced or skilled in the art to most effectively convey the substance of their work to others skilled in the art. In other instances, well-known methods, procedures, and components have not been described in detail to avoid unnecessarily obscuring aspects of the present invention.
Reference herein to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the invention. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Further, the order of blocks in process flowcharts or diagrams representing one or more embodiments of the invention do not inherently indicate any particular order nor imply any limitations in the invention.
Embodiments of the present invention are discussed herein with reference to
Referring first to
Process 300 starts, at step 302, by defining and receiving a finite element analysis (FEA) model in a computer system (e.g., computer 800 of
It is noted that a fully-integrated 8-node hexahedral element can have eight integration points (not shown).
Referring back to step 304, a set of HAZ material properties is associated with the group of finite elements that represents a welded structural part. For example, part's structural behavior can be represented by a “yield stress”-versus-“effective plastic strain” relationship shown in
At step 306, after the set of HAZ material properties is associated with the group of finite elements, corresponding material properties are determined and assigned at each integration point by interpolating the associated set using the heat-propagation distance between each integration point and the closest heat source location.
Further, the heat-propagation distance between each integration point and one of the heat source locations accounts for the warping of the finite element, for example, four nodes of certain two-dimensional quadrilateral shell element may not be coplanar.
At step 308, a numerical simulation of the structure can then be conducted using the FEA model with corresponding material properties determined at respective integration points to represent structural behavior.
According to one aspect, the present invention is directed towards one or more computer systems capable of carrying out the functionality described herein. An example of a computer system 800 is shown in
Computer system 800 also includes a main memory 808, preferably random access memory (RAM), and may also include a secondary memory 810. The secondary memory 810 may include, for example, one or more hard disk drives 812 and/or one or more removable storage drives 814, representing a floppy disk drive, a magnetic tape drive, an optical disk drive, etc. The removable storage drive 814 reads from and/or writes to a removable storage unit 818 in a well-known manner. Removable storage unit 818, represents a floppy disk, magnetic tape, optical disk, etc. which is read by and written to by removable storage drive 814. As will be appreciated, the removable storage unit 818 includes a computer readable medium having stored therein computer software and/or data.
In alternative embodiments, secondary memory 810 may include other similar means for allowing computer programs or other instructions to be loaded into computer system 800. Such means may include, for example, a removable storage unit 822 and an interface 820. Examples of such may include a program cartridge and cartridge interface (such as that found in video game devices), a removable memory chip (such as an Erasable Programmable Read-Only Memory (EPROM), Universal Serial Bus (USB) flash memory, or PROM) and associated socket, and other removable storage units 822 and interfaces 820 which allow software and data to be transferred from the removable storage unit 822 to computer system 800. In general, Computer system 800 is controlled and coordinated by operating system (OS) software, which performs tasks such as process scheduling, memory management, networking and I/O services.
There may also be a communications interface 824 connecting to the bus 802. Communications interface 824 allows software and data to be transferred between computer system 800 and external devices. Examples of communications interface 824 may include a modem, a network interface (such as an Ethernet card), a communications port, a Personal Computer Memory Card International Association (PCMCIA) slot and card, etc.
The computer 800 communicates with other computing devices over a data network based on a special set of rules (i.e., a protocol). One of the common protocols is TCP/IP (Transmission Control Protocol/Internet Protocol) commonly used in the Internet. In general, the communication interface 824 manages the assembling of a data file into smaller packets that are transmitted over the data network or reassembles received packets into the original data file. In addition, the communication interface 824 handles the address part of each packet so that it gets to the right destination or intercepts packets destined for the computer 800.
In this document, the terms “computer recordable storage medium”, “computer recordable medium” and “computer readable medium” are used to generally refer to media such as removable storage drive 814, and/or a hard disk installed in hard disk drive 812. These computer program products are means for providing software to computer system 800. The invention is directed to such computer program products.
The computer system 800 may also include an input/output (I/O) interface 830, which provides the computer system 800 to access monitor, keyboard, mouse, printer, scanner, plotter, and alike.
Computer programs (also called computer control logic) are stored as application modules 806 in main memory 808 and/or secondary memory 810. Computer programs may also be received via communications interface 824. Such computer programs, when executed, enable the computer system 800 to perform the features of the present invention as discussed herein. In particular, the computer programs, when executed, enable the processor 804 to perform features of the present invention. Accordingly, such computer programs represent controllers of the computer system 800.
In an embodiment where the invention is implemented using software, the software may be stored in a computer program product and loaded into computer system 800 using removable storage drive 814, hard drive 812, or communications interface 824. The application module 806, when executed by the processor 804, causes the processor 804 to perform the functions of the invention as described herein.
The main memory 808 may be loaded with one or more application modules 806 (e.g., a finite element analysis application module) that can be executed by one or more processors 804 with or without a user input through the I/O interface 830 to achieve desired tasks (e.g., determining corresponding material properties at each integration point). In operation, when at least one processor 804 executes one of the application modules 806, the results are computed and stored in the secondary memory 810 (i.e., hard disk drive 812). The status of the time-marching engineering simulation (e.g., stress and failure of a finite element, etc.) is reported to the user via the I/O interface 830 either in a text or in a graphical form.
Although the present invention has been described with reference to specific embodiments thereof, these embodiments are merely illustrative, and not restrictive of, the present invention. Various modifications or changes to the specifically disclosed exemplary embodiments will be suggested to persons skilled in the art. For example, whereas numerical material properties have been shown and described as two sets of “yield stress”-versus-“effective plastic strain” curves in a X-Y diagram, other equivalent means for representing numerical material properties can be used for achieving the same, for example, a three-dimensional lookup table storing corresponding numbers reflecting the curves in the X-Y diagram. Additionally, whereas quadrilateral finite elements have been shown and described to demonstrate embodiments of the present invention, other type of finite elements can be used for achieving the same, for example, triangular elements. Further, whereas four integration points per membrane element have been shown and described, other numbers of integration points may be used, for example, two integration points through the thickness of the shell element. Finally, whereas welding has been shown and described as the heat source, other types of manufacturing process may cause similar material damage or degradation, for example, trimming or cutting a sheet metal. In summary, the scope of the invention should not be restricted to the specific exemplary embodiments disclosed herein, and all modifications that are readily suggested to those of ordinary skill in the art should be included within the spirit and purview of this application and scope of the appended claims.
