Automobile collision imitation of fake people study development dynamics

Modern collision simulation software package consists of the pre-processing / post handler module and the numerical calculation module. The industrial use efficiency of the collision simulation software package depends not only on the computational programming efficiency, but also to a large extent, the quality, efficiency, and its user and coherence of the preceding / post-processing program module connected thereto. The PamGeneris preprocessing program module and PAM-View postparted program modules are currently available. Currently, both program modules are undergoing large-scale improvement and reconstruction to sufficiently guarantee the applicability and success of their industrial use. The PAM-Solid computing program includes PAM-CRASH car collision analysis programs, PAM-SAFE passenger safety analysis programs, PAM-STAM thin plate stamping procedures, and PAM-SHOCK shocks and high-speed response analysis programs. This article focuses on the PAM-Crash car collision analysis program.

Industrialized Automobile Collision Simulation started 12 years ago, the PAM-CRASH computing program was successfully collided with the front of VW Polo on the CRAY1 computer. Since then, all major automotive manufacturers are using collision simulations to facilitate design and manufacture competitive anti-collision cars. Moreover, collision simulation has been expanded to other industries, such as truck collisions, train collisions, containers fall, packaging structures and aircraft collisions.
The second step of logical is the simulation of the simulation method to passenger security. Such analog objects are passive safety devices, such as safe air bags, seat belts, and damping pads such as passenger models (fake people) when collisions.
The development of dummy test technology has led to the appearance of the fourth-generation fake man, and the 5th-generation fake man (the biological fake person) will also appear. Further, explicit finite element techniques have also been used in the processing technology, such as thin plate metal forming, thermoplastic composite housings, press forming and hydraulic forming, and the like. These processing processes can be dynamically analyzed and simulated for large-scale / large displacement and nonlinear materials for large amounts of thin shell finite element (up to more than 100,000).
Explicit thin shell simulation technology significantly success is further strengthening. First, the computing program is currently entered into large-scale parallel computers, allowing the design department to provide huge computing power. The second is to enter the calculation program to enter the cheap micrometer-level workstation, so that the small manufacturers can afford it.
The following aspects have enabled computing procedures to have large effects and effects on collisions and impact simulations in industrial problems: 1 directly read CAD data for grid production. 2 macro beam unit for concept design. 3 new material models, strain rate models, and injury sensitive models such as foam, composite materials and plastics.
Computer Simulation Next Development Includes the following major areas: 1 Connect the simulation package to the CAD system. 2 Develop more material models, more accurate unit equations and contact algorithms. 3Develop a larger calculation model. 4 The multi-physical quantity model (thermal effect and solid-liquid interaction). 5 Continue to enter a computing program to a large-scale parallel computer and a group of workstation.
First, the new progress of the algorithm
Although the industrial efficiency and stability of the modern explicit finite element collision simulation program have reached a considerable level, there is still a lot of improvement and development of the algorithm. The work that will now be described in this regard.
1.1 the contact simulation
It should be noted that in the collision simulation between correct and complete object touches simulation is a prerequisite for its success.
, it is worth noting that whether it is using a single processor (or shared storage parallel) program, or use large-scale distributed storage parallel programs, the contact simulation is always challenging and most complex programming tasks. . In the first case, in order to calculate simultaneously both efficient without losing accuracy and reliability of the contact treatment "rigid wall" or limit "the sliding contact surface" must be as reasonably possible. For the contact algorithm of the sliding contact surface, it has been proven to have a wide range of punishment compensation methods. Current development trends are efforts to make this approach as much as possible to understand the end users, including the need to overcome difficulties encountered in computational efficiency and accuracy. Comparison of airbag contact treatment in the application of the original and improved penalty compensation contact algorithm.
For large-scale parallel programming, the use of efficient automatic area dividing art will readily be able explicit finite element program in parallel together. Each parallel processor only needs to perform a small amount of communication with other processes to complete a large number of similar models. Since the determined contact area is not static (when the structure is deformed, the original area is connected to each other), the original area is quickly not applicable. If the original contact calculation is represented, the information is transmitted. The amount of large increments and extremely imbalanced workload are allocated. Therefore, the important work of the collision simulation program is a large-scale parallel interface is the effective parallelity of the contact algorithm.
1.2 grid independent variable algorithm
In the crash simulation configuration of the thin plate member and the main goal grid independent variable algorithm technique, the thin shell finite element mesh is close to the large deformation locally refined region automatically. This issue has been resolved in the stamping simulation of industrial metal sheets. The PAM-Stamp thin plate stamping simulation procedure adopts a program that can be uniform and automatically selecting thin shell mesh refinement and roughening.
Grid algorithm becomes difficult to be applied from a first reason for the crash simulation, selecting the grid must be treated into contact with a wide range of adaptability and rigid wall contact / impact compatible. While contact is the dominant mechanism of thin plate stamping, since the tool geometry used and the self-contained self-containement of the sheet is substantially non-existing, it is relatively simple. In collision simulation, self-contained contacts often appear, and it is more difficult to correct them to apply grid autism algorithm.
Since the mesh becomes less crash simulation algorithm adapted second reason even dangerous,It is limited to the plastic corners or in the collision zone. That is, in the actual calculation of the refined grid region its rigidity is smaller than the original thicker grid, and the plastic corners of unfinened grids may be added soft or decreased. The desascation area of the calculation resistance is calculated. Therefore, in order to avoid this limitation, the refinement standard must be seriously selected, and the original grid cannot be too thick.
Application examples of grid autism algorithm include the axial impact of thin-walled tank columns (Fig. 2A), a large-deformable plastic corner region in the S-shaped frame (Fig. 2B), the front of the passenger car collision (Figure 2C ) And metal sheet stamping (Figure 2D).
Design, calibration and confirmation of various material models have received more and more attention to aluminum alloys, plastics, foam materials, rubber and composite behavior. A model for describing these material behavior is included in the PAM-SOLID program.
Second, the following is highly introduced.
2. Elastoplastic / strain rate / injury model
The finite element method in the Pam-Solid program uses a variety of the sameness and anisotropic elastoplastic material and damage material model of the strain rate. Material stress - strain regular law, as shown in Figure 3. Figure 3A is a reactive and injury curve. In principle, the method can be applied to various materials. Basic unscrupulous stress - strain law. Number reduces material strength. The general description of the damage here is attributed to Lemaitre-ChBoche, which is applied to any material, such as metals, plastics, composites, and foam materials. At present, we work with Valenciennes University to use Gurson damage mode for tough metal to describe the nuclear process, growth and aggregation of material behavior. In different scale models, the effect of void or damage to stress is shown in Figure 3B. 2.2 Aluminum alloy
The plastic behavior of aluminum alloys can be described in Figure 4 using HILL (1990) non-quadratic yield functions that can be used for anisotropic material. This model has been used in the PAM-Stamp program and has been used for the aluminum plate deep rail.
2.3 Plastic
In the simulation of plastic, the plastic showed the elasticity of the first softened rehabilitation. First, the finite element model is used to simulate the softening stage (Fig. 5A) on the stress-strain curve in the tensile test, once the plastic stress σ drops below the precipitation modulus, the plastic instability (neck) is produced. When a plastic strain reaches a certain rupture limit, this instability quickly leads to a concentrated and test piece of the plastic strain. Next, modifications to the original plastic hardening curve (Fig. 5B) in order to strengthen the formation of higher plastic strain force, thereby limiting the planar stress condition σ Et of the neckline in the range of ε1 lt; ε lt; ε2. The initial neck is still developed as before, but now the finite element of the neck region isWhen stretched into the plastic strain ε2, the hardening of the material inhibits the neck injection. Thus, the neckline expands the finite element around it and gradually invades the entire test piece.
Other materials
For the description of the alley obstacles, pads, and mechanical dummy skin foams, the Pam-Solid software has a variety of models to simulate the rupture, compression, viscous deformation of these materials, and Rate-related behavior.
For rubber materials and similar to rubber materials, such as tires, engine brackets, and dummy components, there are also many superplasticity and quasi-non-compressed materials.
For the collision simulation of fiber reinforcing materials, models of susceptible damage materials. These models have also been extended to other composites.
Of course, all of these material models need further improvements. The new material model will continue to appear to meet the growing needs of the industrial sectors to improve their specific products.
Third, a conceptual collision design
A fun trend in collision simulation is that the industrial community is increasingly requires simple collision simulation means, especially the early stages of the design of transportation equipment. At present, the existing collision simulation practice emphasizes the final collision performance of the design structure in the final stage, that is, with a large number of finite element integral models (limited elevation 20,000 to 100,000, even more), the design structure is subjected to the final collision performance. However, when the collision performance of the design structure may not make the information and time required for a detailed collision verification model. Therefore, simplified methods are more popular.
One of the instances of concept collision design is a box column. Currently, the ESI Group is studying the image user interface required for this concept collision based on the power ultrastay software (PAM-Superfold) developed by the University of Valenciennes. In this interface, the user can enter the wall thickness and material characteristics of the box column. By power ultrastay software, the impact reactions under the circumference of the axial or deep bending in the unstable conditions are calculated. It is also possible to use another PAM-OPT program currently developed, and achieve the best response required by automatically changing a set of input optimized parameters and limiting variables. Then, the components of the determined thickness can be subjected to automatic finite element mesh, and the calculation verification is performed in the PAM-CRASH finite element software. Since the subsequent collision design process can put the collision component reaction curve into the collision program to specifically design three-dimensional beam / nonlinear elastic or integral beam unit model. Then thereafter form a transition from an early collision design to a structural node, which has a practical geometry, a cutoff point, and a connection. In this hybrid phase, the grid of the critical area can be refinered, while other parts of the structure can only be roughly simulated. In the final stage, the most fine model confirmed the overall design.
Four, security
In addition to the developed deformable impact obstacle (side hit and collision) model and various mechanical dummy models (composite III, European side strikes, American side hit, biological risks and children, etc., the human biomechanical model has also been developed. This work will be greater, because the simulation of the biological model of the human body is the only way to get a direct reaction of the collision event. The ESI Group has developed this type of model (such as head and lower leg). Leg initial models include bone, ligament, tendon and muscle model.
Fifth, conclusions
Collision simulation techniques and procedures can not only be successfully used for automotive collision simulation, but also in many other relevant areas. For example, buffer packaging materials designed for the drop of refrigerators, the falling of home appliances
fall test (such as small computers) to estimate the damage of sensitive components and collision simulation of hard landed for space detection. In addition, the tires react to the reaction when rolling the projections, and the impact reactions such as bridges, cranes, rails, containers, trains, vessels, trucks, tractors, and bicycles can be used. . In fact, the scope of application of collisions and impact simulation software is constantly growing.



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