Journal of Shenyang Institute of Technology uses MCA method to study the effect of different coatings on three-point bending of steel plates Xu Yue \ Li Jinquan \ Tang Yujing2, Huang Dewu1 (1. Institute of Mechanical Strength of Shenyang Institute of Technology, Shenyang 110016, Liaoning, China; 2Sujia, Shenyang Tun District Labor Park Management Office) Three-point bending calculation simulation test of steel plates with coatings of different shapes, and research on the deformation and fracture process, so that the performance of the coating can be more deeply understood and provide a theoretical basis for the design.
; Cell; Three-point bending; Coating: O316: A coating technology is a popular technology today. The coating has been widely used in aviation, chemical industry and other industries due to its beautiful appearance to improve mechanical properties and prevent corrosion. However, because the coating is very thin, especially when it is subjected to impact load, damage, or shedding, the commonly used finite element method is difficult to describe and calculate. In recent years, in the case of discontinuous media, the research on discrete methods has made considerable progress, of which the "moving somatic automata" or MCA (Movable Cellular Automata) method is the most prominent. This method divides the simulated sample into a series of automatons. Under the load, not only can the interaction between them be studied, but also the changes in their position and direction, that is, the dynamic evolution of the somatic cell.
In this paper, the MCA method is used to simulate four samples with different structural coatings to observe the fracture process and performance changes of the four samples.
1 The mathematical model and theoretical basis of the MCA method The displacement involved in the traditional finite element only refers to the relative displacement caused by the deformation, and the deformation must be continuous without rigid body displacement. However, the MCA method is used to study the cell The interaction between them not only allows relative displacement between body cells and rigid body displacement between body cells, but also allows relative rotation between body cells, that is, it can describe a series of simulated sample body cells The whole dynamic evolution process from loading to fracture. In order to describe the dynamic process between each somatic cell, the adjacent somatic cell must introduce the overlapping parameter between the somatic cell, such as.
Xu Yue et al .: Using the MCA method to study the effect of different coatings on the three-point bending of steel plates. The change of the relationship between adjacent pairs of somatic cells depends on the relative movement between the somatic cells. The dynamic evolution of the interaction between somatic cells is determined by the following formula.
a) Translation: where jtk is the number of adjacent somatic cells; 0ij is the relative rotation angle between somatic cells j; qj (ji) is the contact point between the center of somatic cell i (j) and somatic cell j (i) The distance between; fj is the tangential force; S ((j, ik (jt)), C (ij, ik (jt)) are parameters related to H and 9, respectively, here are 1, / j (A, j7) is the total normal force between cells.
For the strain between body cells ij, AX is the strain increment and V / is the normal component of the relative velocity Vj. The shear strain of the j unit cell and the j cell is VSj, which is the relative tangential velocity, and its value is: V / j = k / jrij, where Vj = Vj is the relative rotation of the neighboring soma that rotates around the centroid of the soma Movement effect rotation speed, as in the MCA method, the stress intensity is used as a criterion for discriminating the link-unlinked between somatic cells.
When the model is loaded, the specimen will be damaged, and the damage will continue to accumulate to produce cracks and eventually fracture instability. At this time: when the body cells i, j are the same material, Kj = 1, in most cases, the body cells i, j are different materials, at this time, 1, the value of the value and the bonding structure between the materials , The size of the cell size and many other factors.
2 The establishment of the sample model The entire modeling process is carried out on the MCA software. The test device is divided into three parts: punching body, sample and supporting block. The approximate size of the sample model is 0.4 The structure of the sample The sample (a) is made of steel, the surface coating is ceramic, and the rectangle is combined with the sample surface, the coating thickness is Q02m. The sample (b) is made of steel , The surface coating is ceramic, which is combined with the surface of the sample with a rectangular tooth shape, the thickness of the coating is the sample (c), the material is steel, the surface coating is ceramic, and the angle tooth shape is combined with the surface of the sample, the coating The thickness is Q02m. The sample (d) is made of steel with double coating on the surface, the upper layer is soft ceramic, and the lower layer is ceramic. They are combined with the surface of the sample in a rectangular shape. The total thickness of the coating is 0.02m. The upper punch and the bottom The material parameters of the supporting table 1 support block adopt the same size of cells. When modeling, you need to enter the relevant characteristic parameters of the test material (Table 1), which represents the elastic limit, ey2 represents the yield limit, X represents the strain at the yield limit, e represents the strength limit, X represents the coating 1 coating 2 sample Punch body support block material ceramic soft ceramic steel corundum Poisson's strain at the limit of elastic modulus strength limit.
3 Calculation results and analysis 3.1 Analysis of specimen fracture process In the traditional finite element method, only the stress state of the independent unit is studied, while the MCA method can study the stress state of the independent somatic cell 71994-2015ChinaAcademicJournalElectronic1, and can also be studied into The interaction relationship between the somatic cells and the adjacent somatic cells at different time steps, as the loading continues, when some somatic cells satisfy the relationship)> 'The four models start to destroy and From the comparison diagram of the final fracture, we can see that the evolution process of crack initiation and propagation can be studied in detail by analyzing the changes of each cell at different time steps. If the wire segment is connected between the center of the two units, it means that the pair of somatic cells are still connected to each other by a certain valence bond, and there is no line segment connected, indicating that the pair of somatic cells has been disconnected. The fracture process of the four samples is different. Sample (a), sample (b), sample (c), the surface of the three samples began to produce micro cracks at very close steps, and sample (d) used the least number of steps, that is, the first crack, because The material of the uppermost layer of sample (d) is lower in strength than the first three samples; of the four samples, sample (c) is the earliest to break, and the crack is in a zigzag shape, because the angle tooth coating is prone to produce at the sharp corner. With large stress concentration, the crack passes through the sharp corners of the angular tooth coating. The second fracture is the sample (a), the crack is diamond-shaped, along the direction of maximum shear stress. Next is the sample (b), the crack is funnel-shaped, the crack passes through the corner end of the rectangular tooth coating, and the rectangular tooth coating of the sample (b) plays a role in strengthening the sample. The final fracture is the sample (d). The crack is funnel-shaped, and the fracture damage is the most serious, because it is a double coating, the first layer of coating is very soft, and the first layer is destroyed first, resulting in one unloading of the pressure.
Journal of Shenyang Institute of Technology 3.2 Comparison of different sample loading curves Through simulation calculations, we obtained Fy-Y curves for four different samples (, 6). Where Fy is the vertical pressure of the punch, and Y is the vertical displacement of the punch. As can be seen from the figure, the four samples not only have different maximum values ​​of Fy, but also the area enclosed by the Fy-Y curve and the coordinate axis. Very different. Different Fy means that the resistance of the four samples is different, the sample (C) has the largest Fy, and the other three samples are relatively close.
Fy-Y curve comparison chart of three single-coated samples. The area under the curve of the F.-Y curve comparison chart of sample (a) and sample (d) is related to the work done by the punch on the sample. The area value can be estimated by using formula (4): where S and i take 1 ~ 4. SiS2S3S4 are the curve 132 () and the area of ​​the double coating curve and the coordinate axis (), respectively, through the calculation of formula (5) The results show that compared with the sample (a), the absorbed energy of sample (b) is reduced by 7.4%, while the sample (c) (d) is increased by 20.9% and 73.2 *. In terms of fracture, the double coating is better than the single coating, and the rectangular tooth coating is better than the other two single coatings. The angular tooth coating significantly improves the resistance of the component. Therefore, when designing the coating, the performance and quality of the component can be improved by changing the material and shape of the coating.
4 Conclusion â‘ The MCA method can intuitively and truly simulate the fracture process of coated steel plates with different structures.
â‘¡The MCA method provides us with a new method for designing coatings.
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