Patent Application
20180253520
The invention generally relates to computer aided mechanical engineering analysis, more particularly to methods and systems for numerically simulating structural failure with clusters of bonded discrete elements representing a failed portion of the structure.
Continuum mechanics has been used for simulating continuous matter such as solids and fluids (i.e., liquids and gases). Differential equations are employed in solving problems in continuum mechanics. Many numerical procedures have been used, including but not limited to, finite element method (FEM), meshfree methods such as discrete element method (DEM), Smoothed-particle Hydrodynamics (SPH), and etc.
To numerically simulate structural failure, one of the prior art approach is based on combined FEM/DEM with discrete elements representing a failed portion of a structure. However, a problem/drawback associated with the prior art approach is that discrete elements would scatter in the failed portion hence not simulating realistic physical phenomena. Therefore, it would be desirable to have improved methods that can more realistically use discrete elements to represent a failed portion of a structure in a numerical simulation of a structural failure.
This section is for the purpose of summarizing some aspects of the 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 invention.
Methods and systems for numerically simulating structural failure with clusters of bonded discrete elements representing a failed portion of the structure are disclosed. A method of numerically simulating structural failure comprises: a computerized mesh model representing a structure is received in a computer system having an application module installed thereon. The computerized mesh model contains at least a plurality of finite elements (e.g., solid elements in three-dimension) with a subgroup of adaptive elements included therein. A corresponding cluster of discrete elements and connecting bonds for each adaptive element are created based on a set of predefined criteria. With the application module, the discrete elements and the connecting bonds are initially set to a state of pre-active, and connecting bonds are used for connecting discrete elements to one another within each cluster. Numerically-calculated structural behaviors are obtained by conducting a time-marching simulation for a predetermined duration in a plurality of solution cycles using the computerized mesh model with a special scheme for processing the adaptive elements and corresponding clusters of discrete elements.
According to another aspect, the special scheme comprises the following actions: (a) obtaining element deformations and global displacements of all of the finite elements; (b) determining which of the finite elements has failed in accordance with plastic strains that are derived from the element deformations; (c) deleting each failed adaptive element from the computerized mesh model and changing the state of the discrete elements and the connecting bonds in the corresponding cluster from pre-active to active; (d) updating the pre-active discrete elements to reflect the global displacements and the element deformations of each of the adaptive elements; (e) performing contact computations amongst all of the active discrete elements and the finite elements, no contact occur within each of the clusters; and (f) repeating actions (a)-(e) for next solution cycle until the predetermined duration has reached or the end of numerical simulation.
Other objects, features, and advantages of the 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 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 invention. However, it will become obvious to those skilled in the art that the 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, components, and circuitry have not been described in detail to avoid unnecessarily obscuring aspects of the 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 invention are discussed herein with reference to
Referring first to
Process 100 starts at action 102 by receiving a computerized mesh model representing a structure in a computer system (e.g., computer system 800 of
Whereas the examples shown have been in two-dimensional space, the invention does not limit to two-dimensional model. For example, a computerized mesh model can be a three-dimensional model comprising solid elements (e.g., hexahedral element 350 shown in
Next, at action 104, a corresponding cluster of discrete elements and connecting bonds are created for each adaptive element based on predetermined criteria. The discrete elements and the connecting bonds are initially set to a state of pre-active. Connecting bonds are used for connecting discrete elements to one another within each cluster. A set of predetermined criteria may include, but are not limited to, the number of discrete elements and locations of the discrete elements within corresponding adaptive element, size and shape of the discrete elements, a particular pattern of connecting bonds, material properties of the connecting bonds, etc. The locations of discrete elements are generally defined in an element local coordinate system, for example, an element local coordinate system (s-t) 420 for an example quadrilateral element 400 shown in
In addition, a global coordinate system (x-y) 410 used for defining the geometry of the computerized mesh model is also shown. Locations of the discrete elements can be defined in a local coordinate system as an s-t pair, for example, (0.5,0.5), (0.5, −0.5), etc.
Then, at action 106, numerically calculated structural behaviors are obtained by conducting a time-marching simulation using the computerized mesh model. Time-marching simulation is to numerically simulate structural behaviors for a predetermined time duration in a number of solution cycles. In other words, at each solution cycle, the structural behaviors at a particular time within the time duration are calculated and obtained. The particular time is an increment to the time at previous solution cycle. For processing adaptive elements and corresponding clusters of discrete elements in the time-marching simulation, a special scheme (details shown in process 110 of
At action 111, process 110 obtains local element forces, element deformations and global displacements of all finite elements including the adaptive elements in the computerized mesh model (e.g., via finite element method) at each solution cycle of the time-marching simulation.
At action 112, process 110 determines which of the adaptive elements has failed in accordance with plastic strains that are derived from the obtained element deformations at action 111 and a set of material failure rules. Next, at action 113, each failed adaptive element is deleted from the computerized mesh model and the state of the discrete elements and the connecting bonds in corresponding cluster are changed from pre-active to active at action.
Then, at action 114, the remaining of the pre-active discrete elements are updated to reflect the global displacements and the element deformations of each adaptive element. At the pre-active state, the connecting bonds are not assigned any forces.
At action 115, contact computations are performed amongst all of the active discrete elements and finite elements. No contact would occur within each cluster. In some embodiment, connecting bonds could subject to material failure. After such a failure of the connecting bonds, the discrete elements would become free of the constraint of a cluster.
Contact computations can be performed with a number of well-known techniques to detect contacts between two or more portions of a structure (represented by computerized mesh model). After each contact is detected, a corresponding contact force is then calculated and applied to the portions involved in the contact.
Finally, at action 120, process 110 repeats actions 111-115 for the next solution cycle until the time duration has reached and the time-marching simulation ends thereafter.
According to one aspect, the 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 usable storage 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. Software and data transferred via communications interface 824. 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 program medium”, “computer readable medium”, “computer recordable medium” and “computer usable medium” are used to generally refer to media such as removable storage drive 814 (e.g., flash storage drive), 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 invention as discussed herein. In particular, the computer programs, when executed, enable the processor 804 to perform features of the 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., FEM and/or DEM 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. 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 analysis is reported to the user via the I/O interface 830 either in a text or in a graphical representation upon user's instructions.
Although the invention has been described with reference to specific embodiments thereof, these embodiments are merely illustrative, and not restrictive of, the invention. Various modifications or changes to the specifically disclosed exemplary embodiments will be suggested to persons skilled in the art. For example, whereas most of the examples have been described and shown as two-dimension quadrilateral element, other types of elements can be used, for example, three-dimensional solid elements (hexahedral and/or tetrahedral elements) to accomplish the same. Additionally, one particular pattern of cluster of discrete elements have been described and shown, other patterns may be used to achieve the same. 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.
