Analysis of dent resistance of cold-rolled steel coil considering interlaminar effect
Abstract : Aiming at the problem of contact deformation of multi-layer materials in cold-rolled steel coil packaging , the dent resistance of the steel coil packaging system was analyzed and studied ; a steel coil packaging system considering the interaction between layers was established The mechanical model of the steel coil was calculated and analyzed, and the finite element simulation of the dent resistance model of the steel coil was carried out by using HYPERMESH and ANSYS/LS - DYNA ; finally, the impact test of the dent resistance model was carried out to verify the limited The results of meta-simulation can provide a theoretical basis for the design of steel coil packaging process .
Key words : steel coil ; interlayer interaction ; dent resistance ; finite element ; impact test
CLC Number : TB487 ; TP3919 Document Identification Code : A Article Number : 1001-3563 ( 2012 ) 01-0058-04
Dent Resistance Analysis of Cold Rolled Steel Coil Considering Interlayer Effect
Abstract: For solving the multilayer contact deformation problem of cold rolled steel coil, dent resistance of steel coil packaging system was analyzed and studied. Mechanical model of steel coil packaging system consider ing interlayer effect was established and the strain and stress of the steel coil was calculated and analyzed. FEM simulationofdentresistanceofthesteelcoilwascarriedoutbyusing HYPERMESH and ANSYS／LS-DYNA． An impact test of the dent resistance model was carried out to verify the FEM simulation．The purpose was to providetheorybasisforsteelcoilpackagingprocessdesign．
Key words: steel coil; interlayer effect; dent resistance; FEM; impact test
Steel is an important material in industrial production . With the rapid growth of industrialization , the demand for steel is increasing , and the quality of steel is also greatly improved . Steel coil is an important transportation and storage method for steel . For cold-rolled sheets , galvanized sheets and other types of sheets, the finished sheets are coiled , packaged , and bundled to form a complete steel coil product . However, during the transportation and lifting of steel coils , some human or accidental factors will cause damage to steel coils . In particular, collisions , impacts, etc. on the surface of the coil often lead to damage to the inner protected plate layers . Steel coils are coiled from continuous plates that are hundreds of meters or even thousands of meters long . A small pit may cause the quality of several meters of plates to be unqualified , resulting in waste .
The dent resistance analysis of steel coil is different from the traditional dent resistance analysis . In the past practical engineering applications , the research on the dent resistance of plates mainly focused on single-layer plates . Zhang Yan of Shanghai Jiaotong University and others applied the flat shell theory to study the dent resistance of automobile bumpers ; Wei Yong and others of SAIC-GM-Wuling applied the finite element implicit algorithm to analyze and study the dent resistance of the door outer panel . However, these only consider the dent resistance of single-layer plates against external loads , while cold-rolled steel coils are made of external packaging plates and internal multi- layer plates . The interaction between them gradually weakens from the outside to the inside , which is very different from the analysis of the dent resistance of single-layer plates . Taking the cold-rolled steel coils of a steel company as the object , the dent resistance and related properties are analyzed .
and maintain shape when subjected to external loads is called dent resistance . It is an important index and characteristic to evaluate and reflect the surface quality and performance of the covering . Steel coil packaging is composed of outer cladding board , inner buffer flat paper , inner anti-rust paper , inner and outer corner protectors , straps, etc. The analysis of the dent resistance of the steel coil mainly considers the ability of the product sheet whose inner layer is protected against external loads under the condition of packaging protection.
Strength will cause plastic deformation and pit damage . fr a
Considering that the pit area is S , the force F is evenly distributed during the impact Mf =— ()
On the pit, the applied load can be approximated as q = —S . According to the theory of contact mechanics [ 3 ] , the contact stress is :
Because there is always a > sin a , we can get M' > M , M x 6 * 6 a , 6 a
Fig. 2 Equivalent mechanical model
of steel coil dent resistance
〉 " ', the stress value of the force F acting on point A of the plane model is greater than its value in the arc model , so it can be said that the safety factor of the plane model is lower than that of the arc model , and the critical load and The failure load is safer for the arc surface model and the real steel coil . At the same time , the planar model is also easier to operate in the impact test and modeling simulation , and the results obtained are more reliable .
2 Finite element simulation of dent resistance of steel coil packaging plate
Use Hypermesh+ Ls - dyna to jointly simulate and calculate the finite element model established by the plate model. Hypermesh performs mesh division, boundary conditions, and load settings . After the pre-processing is completed, export the k file and submit it to Ls-dyna for calculation . Simulation analysis of the impact of a 2- pound punch on the steel coil from a height of 80 inches , and reasonable suggestions for improvement .
200 mmX 200 mm square plate is only 1 ~ 2 mm, so choose to divide the two-dimensional shell element, and set the element property to * SECTION _ SHELL in Hypermesh . Material model * MAT_PIECEWISE_LINEAR " LASTICITY . _ Establish a loadcollector ( constrains) in which all nodes on the two opposite sides of the steel plate, flat paper, and tinplate stacks are set as full constraints.
Carry out three-dimensional mesh division on the punch, set the element attribute to * SECTION _ SOLID , then set the initial velocity of the punch, create a Loadcollector ( velocity ) , CONTROL CARD select * INITIAL_VELOCITY _ GENERATION , the test punch weighs 2 pounds, and the drop height is 80 inches, which is equivalent to setting the contact velocity to 1 m / s . The finite element model data are shown in Table 1 .
Table 1 Finite element model data
Tab. 1 Data of finite element model
part |
Number of nodes |
number of units |
|
shower |
Ch^ a^lc ademic |
Jou 226 E lectronic |
|
PE board |
3362 |
1600 |
|
flat paper |
3362 |
1600 |
|
plate |
11767 |
9600 |
Set the contact surface , the contact relationship is complicated during the drop process , and there may be contact in each part , so establish an automatic surface contact (* CONTACT _ AUTOMATIC _ SINGLE _ SUR - FACE ), set all parts as slave set, in the tab Set parameters such as contact surface FD , FS and VDC in , and select the default algorithm for contact algorithm .
The calculation results are shown in Figure 3. Under the action of impact , the center of the steel plate produces
Figure 3 Stress cloud diagram of steel coil finite element model
Fig. 3 Stress nephogram of steel coil FEM model
A clear pit with a depth of 0.562 mm was formed , and the maximum unit stress reached
340 MPa , but the bottom plate has no obvious damage .
3 Dent resistance test of steel coil packaging plate
At present , there is no unified test standard for the domestic plate dent resistance test , such as the diameter of the presser , the size of the test piece , the size of the blank holder force , and the test speed, etc. have not formed a standard [ 4 ] . In particular, the interaction between the inner and outer plates of the steel coil packaging , the different simulated working conditions , the nonlinear properties of the inner flat paper, etc. , will affect the reliability of the test . Based on these considerations , only a comparative evaluation method can be used for the dent resistance of steel plates , that is, under the same test conditions , according to the test results , it is believed that a certain plate has better dent resistance than another [ 5 ] .
The test object-group is 0.8 mm steel plate + flat paper + anti-rust paper + 60 tin-plated plates, the size is 200 mmX 200 mm, and the test is carried out with reference to the relevant requirements of GB - T 13448-2006 . Fix the sample on the fixture , pull the punch to a certain height and release it , and the punch will impact the plate sample when it falls , see Figure 4 . Pull the punch to different heights to test , observe and measure the diameter and depth of the pits formed on the plate , see Figure 5 .
It can be seen from figure 5 that the diameter of the pit caused by the impact of the 2 pound punch from the height of 80 inches is 5.84 mm , and the depth of the pit is 0,557 mm , which is consistent with the finite element calculation results , which is also The correctness of the mechanical model and finite element calculation of the dent resistance of cold-rolled steel coils is verified .
Fig. 4 Impact test photo
3F — pit depth
1 " Gang 7 Of 8 Of 10 Empty 3 0 £28 0 3 79
° 80 70 60 50 40 30
Punch height/inch
Figure 5 Measurement data of dent resistance test
Fig. 5 Measurement data of dent resistance test
4 Conclusion
Through the analysis of the dent resistance of the multi-layer steel coil plate model , a mechanical model of the dent resistance of the steel coil considering the interlayer effect was proposed , and the test and finite element simulation analysis were carried out to provide guidance for the design of the steel coil packaging and the selection of materials Provide theoretical guidance and data basis . There are many ways to improve the anti-dent performance of steel coil packaging plates , such as changing materials , increasing thickness or using buffer materials, etc. The best way is to propose a reasonable steel coil through the combination of laboratory research and factory experience . Roll packaging scheme .
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