Introduction
Finite element method is initially applied to the structural strength calculation of the aircraft, with the rapid development and popularity of computer technology, and now the finite element method has been widely used in almost all Science and technology field.
Step
The basic steps of finite element analysis are usually:
first step forward. Define a solving model based on actual problems, including the following aspects:
(1) Define the geometric area of the problem: Approximate the physical properties and geometric areas of the domain based on actual issues.
(2) Defining unit type:
(3) Definition unit material properties:
(4) Define the geometric properties of the unit, such as length, area Waiting;
(5) Defining units of connectivity:
(6) Define the base function of the unit;
(7) Define boundary conditions:
(8) Define the load.
Section 2 Generalal Design: The unit is generally encapsulated into a total matrix equation (combination equation) of the entire discrete domain. The general dress is carried out in the adjacent unit node. State variables and their derivatives (if possible) continuity is established at the node. Solution of the Connection Future Group can be used directly, iterative method. The result is an approximate value of the state variable at the unit node.
third step processing: Analyze and evaluate the relevant criteria for the discovery. The post-processing user can easily extract information to understand the calculation results.
Basic Features
Finite element method and other method of solving the boundary value problem Approximate method is that its approximation is limited to relatively small subdomains. In the early 1960s, the image of CLOUGH, which proposed structural mechanics computing finite element concept, depicts it as: "finite element method = RAYLEIGH RITZ method + fragment function", that is, the finite element method is Rayleigh Ritz method. A localization. Unlike the solution (often difficult) Rayleigh Ritz method that meets the allowable function of the entire definition domain boundary condition, the finite element method defines the function on a simple geometry (such as a triangular or arbitrary quadrade in two-dimensional problem) ( Split functions) and does not consider complex boundary conditions of the entire definition domain, which is one of the reasons why finite element methods superior to other approximate methods.
Common Software
Finite element analysis Commonly used finite element software has ANSYS, SDRC / I-DEAS, etc.
Foreign software
Large-scale universal finite element business software: If ANSYS can analyze multidisciplinary issues, such as mechanical, electromagnetic, thermodynamics, etc .; Motor finite element analysis software Nastran et al.
There are also multiPhysics, CREO (Pro \ E), UG, Catia, etc. in three-dimensional structural design, CREO (PRO \ E), UG, Catia et al.
Domestic software
Domestic finite element software: FEPG, Scifea, Jifex, Kmas, FELAC, etc.
Development trend
The development of CAE software on the international CAE software can be seen from the development trend of finite element analysis:
1, seamless integration with CAD software
One of today's finite element analysis software The development trend is integrated with the general CAD software, that is, after the design of the CAD software completes the components and parts, the model can be directly transferred to the CAE software to divide and analyze the calculation, if the result is not The design requirements are met to design and analyze until satisfaction, thereby greatly improving design level and efficiency. In order to meet the requirements of engineers quickly solving complex project problems, many commercial finite element analysis software have developed interfaces with famous CAD software (such as Pro / ENGINEER, Unigraphics, SolidEdge, SolidWorks, Ideas, Bentley, and AutoCAD, etc.). Some CAE software adopts CAD modeling techniques in order to achieve seamless integration of CAD software, such as Adina software, due to entity modeling technology based on Parasolid kernel, CAD software with parasolid (such as Unigraphics, SolidEdge) SolidWorks) Realize truly seamless two-way data exchange.
2, more powerful grid processing capability
The basic process of solving the problem of finite element method mainly includes: analysis of discrete, finite element solution, post-processing three parts. Since the grid quality after the structure directly affects the solving time and the correctness of the solution, the software developers have increased their investment in grid processing, making the quality and efficiency of mesh generation. Big improvement, but in some aspects, it has not been improved. If the three-dimensional solid model is used to divide the model, the model is adaptive to the model according to the solution results, except for individual commercial software, most Analysis software still does not have this feature. Automatic hexahedral mesh division refers to a three-dimensional entity model program automatically divides the six-dimensional mesh unit. Most software can generate a six-dimensional unit using mapping, drag, sweeping, etc., but these functions can only model simple rule models. Applicable, for complex three-dimensional models can only be used to generate a four-sided unit unit with automatic tetrahedral mesh. For a four-sided body unit, if the intermediate node is not used, the incorrect result will occur in many problems, and if the intermediate node will cause a series of problems such as solving time, convergence speed, etc., people are urgently hoped to automatically The appearance of grid function. Adaptive grid division refers to a loop process of calculating error, re-dividing grid and recalculation based on finite element calculation results based on finite element calculation results. For many practical problems, in the entire solution, some areas of the model will have a large strain, causing unit distortion, resulting in solving can't be done or the result is incorrect, and therefore, mesh automatic re-division must be performed. Adaptive mesh is often a necessary condition for many engineering issues such as crack extension, thin plate forming and other large strain analysis.
3, from the process of solving linear problems to solve nonlinear problems
With the development of science and technology, linear theory is far from meeting design requirements, many engineering issues such as materials Destruction and failure, crack expansion, etc. Only by linear theory, it is not possible to solve it. It is necessary to solve nonlinear analysis. For example, thin plate forming requires simultaneous consideration of large displacement, large strain (geometric nonlinear) and plasticity (material nonlinear); Analysis of materials such as plastics, rubber, ceramics, concrete and geotechnical or need to consider the plasticity of the material, and the nonlinearity of the material must be considered. As we all know, the solution to nonlinear issues is very complicated. It not only involves many specialized mathematical problems, but also must master certain theoretical knowledge and solve skills, so they are also difficult. To this end, some foreign companies spend a large number of human and material development nonlinear solution analysis software such as Adina, Abaqus, etc. Their common feature is a highly efficient nonlinear solver, rich and practical nonlinear material library, and Adina also has two types of integration and explicit.
4, solving the development of a single structural field to the coupling field problem
finite element analysis method is used in the aerospace sector, mainly used to solve the problem of linear structure, practice prove It is a very effective numerical analysis method. And since theoretically, it has also been proven that the resulting solution can be approximately approximate as long as the unit used for discrete solution is sufficiently small. The finite element method and software used to solve the structural linear problem have been mature, the development direction is the solution of structural nonlinearity, fluid dynamics, and coupling field. For example, the heat problem caused by frictional contacts, the heat problem caused by plasticity during metal molding, the finite element analysis result of the structural field and the temperature field is required, ie the problem of "thermal coupling"; when the fluid is in the elut In the flow, the fluid pressure causes the elbow to deform, and the deformation of the tube is in turn affects the flow of fluid, which requires cross iteration of finite element analysis results for the structure field and flow field, so-called "flow solid coupling "The problem. Since the application of finite element is getting deeper, people pay more and more complex, and the solution of coupling fields must be the development direction of CAE software.
5, the program is open to the user's openness
With the improvement of commercialization, the software developers meet the needs of users in order to expand their market share, in software, Easy to use a large amount of investment, but because the user's requirements are very different, no matter what they work hard, it is impossible to meet all users' requirements, so a open environment must be given, allowing users to perform software according to their own actual situation. Expansion, including user-defined unit characteristics, user-defined materials (structural constitutive, hot structure, fluid constitutive), user-defined streaming boundary conditions, user-defined structural fracture judgments and crack expansion laws, etc. .Focus on finite element theoretical development, adopting the most advanced algorithm technology, expanding software performance, improving software performance to meet user growing demand, is the main attack target of CAE software developers, and its products continue Have the fundamental of the market, seek survival and development.
Analyze the new version
Abaqus 6.9 finite element release
Dasso system Simulia issued a finite element analysis new version
---- ---- Abaqus 6.9 Increases new features in fracture failure, high performance calculation, and noise vibration range
May 19, 2009, Message from Paris, France and Rodd Island, USA ---- Dasper System (DS) (Paris, European Exchange: # 13065,) is a 3D and product lifecycle management field (PLM) world leading solution provider; today announced: launch Abaqus 6.9, its technology lead Unified finite element analysis software set.
In order to evaluate the behavior of the real world, products and manufacturing processes, designers, engineers and researchers put Abaqus applications in including electronic, consumer goods packaging, aerospace, automobile, energy, and life sciences, etc. A wide range of industries. This release provides important new features, such as fracture failure, high performance computing, and noise and vibration. In addition, Simulia will continue to enrich the capacity of product sets in entity modeling, grid division, contact problems, materials, and multi-field coupling.
Auto Parts Supplier Donald Senior Engineering Consultant Frank Popielas said: "In order to meet the needs of today's rapid development, the early simulation simulation technology plays an important role. Abaqus 6.9 and high performance The synergy between computational clusters will help us minimize unit cost and maintain the best turnover time. "
Daren System Simulia Product Management Director Steve Crowley said:" Definition in new features Work closely with our customers, we have developed the most powerful finite element analysis software. In a unified finite element analysis environment, Abaqus 6.9 enables manufacturing companies to strengthen their nonlinear and linear analysis process.
Publishing focus:
Extension Finite Element (XFEM), implementation and providing a powerful tool for simulating crack extension of any path independent of the unit boundary. In an aerospace industry, XFEM can combine other capabilities of Abaqus to predict durability and damage tolerance of the aircraft composite structure. In the energy industry, it can help assess the sprout and growth of cracks in the pressure vessel.
Universal contact applications provide a simplified and highly automated way to define the contacts in the model. This capability provides a substantially effective improvement in a complex assembly of modeling, such as gear systems, hydraulic cylinders, or other components that require contact.
A new combined simulation method, the user can apply the implicit and explicit solver of Abaqus to a single analog simulation - making the calculation time greatly reduced. For example, automotive engineers can combine a representative mechanism of a vehicle model and a model consisting of tires and suspension systems to evaluate the durability of the vehicle running on rough roads.
Abaqus / CAE technology provides faster, more powerful grid division and powerful results visualization.
Enhanced performance, the AMS feature resolution significantly improved the efficiency of large-scale linear dynamics, such as automotive noise and vibration analysis.
A new viscous shear model can simulate non-Newtonian fluid, such as blood, binders, molten polymers, and other liquids in consumer products and industrial applications.
Application field
With the intensification of market competition, the product update cycle is more short, and the need for new technologies is more urgent, and finite element numerical simulation technology is to improve product quality. , Shorten the design cycle, improve the effective means of product competitiveness, so with the development of computer technology and calculation, the finite element method has received more and more extensive attention and application in engineering design and scientific research, has become a solution The effective way for complex engineering analysis calculation problem, from almost all design and manufacturing of automobiles to spaceplanes have been separated from finite element analysis, in mechanical manufacturing, material processing, aerospace, automotive, civil buildings, electronic appliances, national defense military Wide use of ships, railways, petrochemicals, energy and scientific research has enabled design levels in quality leaps.