Composite test component and test method for analyzing influence of deformation and temperature on LME and collision performance

Abstract

The invention belongs to the technical field of LME test methods, and particularly relates to a composite test component and a test method for analyzing the influence of deformation and temperature on LME and collision performance. The method for testing the influence of the deformation on the LME comprises the following steps: sampling and testing at different deformation positions of a groove of a composite test component after thermal forming, and researching the influence of the deformation on the LME. According to the invention, the grooves with different thinning amounts are designed on the composite test component, so that the LME crack depths at different deformation amounts can be researched at the same temperature, and the LME crack depths at the same deformation amount can also be researched at different temperatures, so that systematic research on the LME crack depths is realized; and the n-shaped straight arm part is designed to be used for testing the collision performance, and after the hot-formed n-shaped straight arm and the flat plate are subjected to spot welding, the three-point bending performance is tested to be used for evaluating the collision performance of the part.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of LME test methods, and particularly relates to a composite test component for analyzing the influence of deformation and temperature on LME and crash performance and a test method. BACKGROUND

[0002] Compared with aluminum-silicon coating materials, domestic galvanized sheets have a significant cost advantage, saving about 1000 yuan per ton. In addition, galvanized sheets also have superior corrosion resistance and can effectively prolong the service life. However, during the hot forming process, when the liquid zinc in the galvanized layer contacts the substrate and is subjected to tensile stress, the liquid zinc will penetrate along the grain boundary, resulting in a decrease in the plasticity of the material and causing brittle fracture. This phenomenon is known as liquid metal embrittlement (LME).

[0003] Liquid metal induced embrittlement (LME) reduces the cold bending performance and tensile performance of steel sheets, and is a key factor restricting the application and promotion of zinc-based coatings. When the depth of microcracks in the base metal is greater than 10 μm, the fatigue life of hot stamping parts is reduced, but when the crack depth is less than 10 μm, the fatigue performance is not significantly reduced.

[0004] The key to reducing LME is to reduce the content of liquid Zn and the aggregation of Zn in the austenite grain boundary during hot forming. The formation of LME is closely related to the mold temperature and the degree of strain. If the mold temperature is too high, the penetration ability of liquid zinc will be significantly enhanced, thereby greatly increasing the crack depth. In addition, a higher strain rate will also increase crack formation. Therefore, during hot forming, the mold temperature and strain rate need to be strictly controlled to effectively suppress the occurrence of LME phenomenon. Currently, the direct hot forming process of galvanized sheets has not been mass-produced, and there is a lack of research on the forming temperature and deformation amount window. Currently, different deformation amounts and temperature conditions need to be set on different parts, which not only increases the complexity and cost of the experiment, but also may introduce errors due to differences in parts, affecting the accuracy and reliability of the research results. SUMMARY

[0005] In view of the above deficiencies in the prior art, the present application aims to provide a composite test component for analyzing the influence of deformation and temperature on LME and a test method.

[0006] To achieve the above purpose, the technical solution adopted is: A test method for the influence of deformation on LME, comprising the following steps: after hot forming, sampling and testing at different deformation amount positions of the grooves of the composite test component to study the influence of deformation on LME. Specifically, sampling and testing at different deformation amount positions of the first groove, the second groove, and the third groove of the composite test component to study the influence of deformation on LME.

[0007] A test method for the influence of forming temperature on LME, comprising the following steps: adjusting the forming temperature of a composite test component during hot forming, taking tests at the same deformation amount, and studying the influence of forming temperature on LME.

[0008] A test method for crash performance, after hot forming of a composite test component, spot welding the straight arm of the H-shaped straight arm with the flat plate at the lower opening, and testing the three-point bending performance, for evaluating the crash performance of the part, specifically, cutting the head and the straight arm part, and spot welding the flange edge of the H-shaped straight arm with the flat plate at the lower opening.

[0009] A composite test component in the shape of T, comprising a head and a straight arm connected to the head, wherein a plurality of grooves are provided on the head, the bottom of each groove is inclined, the depths of the plurality of grooves are different from each other, and the depths of the plurality of grooves are sequentially and continuously gradiently arranged, and the cross section of the straight arm is in the shape of H.

[0010] The beneficial effects of the above technical solutions are that: through the design of the T-shaped structure, good stability and easy-to-operate characteristics are provided, so that it can be effectively used in various test environments, the head grooves are used to provide a study of the forming temperature and deformation amount window, the continuous gradient arrangement of the groove depth can provide a display window for any value (corresponding to different deformation amounts) in the depth range, the straight arm H-shaped structure is used to test the three-point bending crash performance, which is not limited to T-shaped, but also L-shaped.

[0011] On the basis of the above technical solutions, the present application can also be improved as follows: Further, the grooves are provided in three, namely a first groove, a second groove and a third groove, the minimum and maximum thinning amounts of the first groove are 0% and 10% of the thickness of the composite test component respectively, the minimum and maximum thinning amounts of the second groove are 10% and 20% of the thickness of the composite test component respectively, and the minimum and maximum thinning amounts of the third groove are 20% and 30% of the thickness of the composite test component respectively.

[0012] Specifically, the thinning amount of the three grooves is 0-10%, 10-20%, and 20-30% of the thickness of the composite test component, that is, the thinning amount of one end of the first groove is 0% of the thickness of the composite test component, the thinning amount (depth) of the other end is 10% of the thickness of the composite test component, and the thinning amount (depth) continuously increases between the one end and the other end; the thinning amount (depth) of one end of the second groove is 10% of the thickness of the composite test component, the thinning amount (depth) of the other end is 20% of the thickness of the composite test component, and the thinning amount (depth) continuously increases between the one end and the other end; the thinning amount (depth) of one end of the third groove is 20% of the thickness of the composite test component, the thinning amount (depth) of the other end is 30% of the thickness of the composite test component, and the thinning amount (depth) continuously increases between the one end and the other end.

[0013] The beneficial effects of adopting the above technical solutions are that such a depth range setting can cover different degrees of damage that may occur to the component in actual use, from slight damage to moderate damage, and can comprehensively evaluate the performance change of the component under different damage states, providing more accurate basis for safety evaluation and maintenance of the component. The depth span of 10% at both ends of the groove is relatively appropriate, and a too small span will make the window too narrow due to limited space, and a too large span may damage the component.

[0014] Further, the U-shaped straight arm includes an upper horizontal plate, the ends of the upper horizontal plate are connected with side walls, the lower ends of the side walls are connected with flange edges, and a fillet is arranged between the horizontal plate and the side wall and between the side wall and the flange edge, the top edge and the bottom edge of the groove are provided with a fillet, and R1 of the fillet is K*T, wherein K is a proportionality coefficient, T is the thickness of the plate, when T≤1mm, K is 0.5-1.5, when 1

[0015] The beneficial effects of adopting the above technical solutions are that different R1 values are adopted for different plate thicknesses, which can promote plastic deformation of the plate, can not only avoid cracking due to stress concentration caused by too small R1 values, but also avoid that the thinning rate of the position to be sampled and tested during material forming cannot reach the preset value due to too large R1 values.

[0016] Further, the angle between the line connecting the top and the bottom of the groove and the horizontal plane is α1 of 60°-84°, and the angle between the side wall of the straight arm and the horizontal plane is α2 of 45°-84°.

[0017] The beneficial effects of the above technical solutions are that: if the angle is too small (<60°), the groove will be too flat, the effective deformation gradient interval will be too long, a larger component size will be required, and the local deformation amount will not change significantly; if the angle is too large (>84°), the groove will be too steep, similar to a step, and a continuous change in the deformation gradient cannot be formed, and the forming cracking problem caused by the too large friction coefficient is solved, the angle range ensures the continuity and significance of the deformation gradient, and the same applies to the straight arm part.

[0018] Further, the longitudinal section of the groove is V-shaped, U-shaped or trapezoidal.

[0019] Still further, an arc-shaped transition area with a radius R2≥10mm is arranged at the connection between the straight arm and the head.

[0020] The beneficial effects of the above technical solutions are that: the arc-shaped transition area with a specified radius is arranged at the stress concentration key area of the T-shaped structure, which can greatly reduce the stress concentration effect of the area in the forming and subsequent three-point bending test. This ensures that the damage occurs in the designed straight arm area in the crash performance test, rather than at the connection between the head and the straight arm, thereby ensuring the effectiveness and specificity of the crash test data and avoiding test failure caused by structural defects.

[0021] Further, the bottom slopes of the plurality of grooves are the same.

[0022] The beneficial effects of the above further technical solutions are that: the influence of the slope difference on the LME cracking condition is avoided.

[0023] Further, the plurality of grooves are arranged at intervals.

[0024] The beneficial effects of the above further technical solutions are that: the grooves arranged at intervals can avoid mutual interference, so that the test results of each groove are more independent and reliable.

[0025] Further, the groove is long strip-shaped, and the groove extends from the head to the straight arm.

[0026] The beneficial effects of the above further technical solutions are that: the head space is fully utilized.

[0027] Further, the material of the composite test component is a hot-formed galvanized sheet.

[0028] The beneficial effects of the above further technical solutions are that: the galvanized sheet is used as the material of the component, which enhances its corrosion resistance and durability, is suitable for use in various environments, and prolongs the service life.

[0029] Further, the head and the straight arm are an integrated structure.

[0030] The composite test component adopts a direct hot forming process, and the process includes blanking-heating-direct hot forming (including two processes of pre-cooling process and pre-alloying process)-laser cutting-shot blasting-point welding.

[0031] Compared with the prior art, the beneficial effects of the present application are that the present application provides a galvanized sheet hot forming T-shaped component with multi-directional test function, which can simultaneously study the forming temperature and deformation amount window, through designing grooves with different deformation amounts (corresponding to different depths) on the T-shaped component, the LME crack depth at different deformation amounts can be studied at the same temperature, or the LME crack depth at the same deformation amount can be studied at different temperatures, so as to realize systematic study of the LME crack depth, and a straight arm part is designed for crash performance test, after the hot forming of the several-character straight arm and the flat plate after point welding, the three-point bending performance is tested, which is used for evaluating the crash performance of the part.

[0032] The development of the GI galvanized hot forming material is to verify the material through T-shaped parts, simulate the stamping deformation process of the actual part, study the influencing factors of cracks of the galvanized steel sheet, establish the relationship among the part deformation amount (thinning), temperature (temperature before forming) and LME micro-cracks, and form the design reference of the GI galvanized hot forming part. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 It is a structure schematic view of the composite test component of the present application; Figure 2 It is a top view of the composite test component of the present application; Figure 3 It is a side view of the composite test component of the present application; Figure 2 It is a sectional view along A-A; Figure 4 It is an enlarged view of B of Figure 3 Figure 5 It is a sectional view along C-C; Figure 2 Figure 6 It is a side view of the composite test component of the present application; Figure 7 It is a structure view of the straight arm and the flat plate during the crash test; The figure marks are as follows: 1, head; 2, straight arm; 201, horizontal plate; 202, side wall; 203, flange edge; 3, groove; 301, first groove; 302, second groove; 303, third groove; 4, flat plate. DETAILED DESCRIPTION

[0034] The present application is described below in combination with examples, and the examples are only used for explaining the present application, and are not used for limiting the scope of the present application.

[0035] ​​In the description of the present application, it should be noted that the terms "vertical", "upper", "lower", "horizontal" and the like indicate the orientation or positional relationship shown in the drawings, which are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application.

[0036] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "set", "mount", "connected", "connected" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0037] Reference Figures 1-7 A test method for the influence of deformation amount on LME, comprising the following steps: sampling and testing at different deformation amount positions of the grooves 3 of the composite test member after hot forming to study the influence of deformation amount on LME, specifically sampling and testing at different deformation amount positions of the first groove 301, the second groove 302 and the third groove 303 of the composite test member to study the influence of deformation amount on LME.

[0038] A test method for the influence of forming temperature on LME, comprising the following steps: adjusting the forming temperature of the composite test member during hot forming, and testing at the same deformation amount to study the influence of forming temperature on LME.

[0039] A test method for crash performance, after hot forming of the composite test member, the straight arm 2 of the letter-shaped straight arm 2 is spot welded with the flat plate 4 at the lower opening, and the three-point bending performance is tested to evaluate the crash performance of the part, specifically, the head 1 and the straight arm 2 are partially cut, and the flange edge 203 of the letter-shaped straight arm 2 is spot welded with the flat plate 4 at the lower opening.

[0040] A composite test member, in the shape of T, comprising a head 1 and a straight arm 2 connected to the head 1, the head 1 is provided with a plurality of grooves 3, the bottom of each groove 3 is inclined, the depths of the plurality of grooves 3 are different from each other, and the depths of the plurality of grooves 3 are sequentially and continuously gradiently arranged, and the cross section of the straight arm 2 is in the shape of a letter.

[0041] In an optional embodiment, the grooves 3 are provided in three, namely a first groove 301, a second groove 302 and a third groove 303, the minimum and maximum thinning amounts of the first groove 301 are 0% and 10% of the thickness of the composite test member respectively, the minimum and maximum thinning amounts of the second groove 302 are 10% and 20% of the thickness of the composite test member respectively, and the minimum and maximum thinning amounts of the third groove 303 are 20% and 30% of the thickness of the composite test member respectively.

[0042] Specifically, the thinning amounts of the three grooves 3 are 0%-10%, 10%-20% and 20%-30% of the thickness of the composite test member respectively, that is, the thinning amount of one end of the first groove 301 is 0% of the thickness of the composite test member, the thinning amount of the other end is 10% of the thickness of the composite test member, and the thinning amount continuously increases between the two ends; the thinning amount of one end of the second groove 302 is 10% of the thickness of the composite test member, the thinning amount of the other end is 20% of the thickness of the composite test member, and the thinning amount continuously increases between the two ends; the thinning amount of one end of the third groove 303 is 20% of the thickness of the composite test member, the thinning amount of the other end is 30% of the thickness of the composite test member, and the thinning amount continuously increases between the two ends.

[0043] In an optional embodiment, the U-shaped straight arm 2 comprises an upper horizontal plate 201, the ends of the upper horizontal plate 201 are connected with side walls 202, the lower ends of the side walls 202 are connected with flange edges 203, and a round corner is arranged between the horizontal plate 201 and the side wall 202 and between the side wall 202 and the flange edge 203, the top edge and the bottom edge of the groove 3 are also provided with a round corner, and the R1 of the round corner is K×T, wherein K is a proportionality coefficient and T is the plate thickness, when T≤1mm, K takes a value of 0.5-1.5, when 1

[0044] In an optional embodiment, the included angle α1 between the line connecting the top and the bottom of the groove 3 and the horizontal plane is 60°-84°, and the included angle α2 between the side wall 202 of the straight arm 2 and the horizontal plane is 45°-84°.

[0045] In an optional embodiment, the longitudinal section of the groove 3 is V-shaped, U-shaped or trapezoidal.

[0046] In an optional embodiment, an arc-shaped transition zone is arranged at the connection between the straight arm 2 and the head 1, and the curvature radius R2 of the arc-shaped transition zone is ≥10mm.

[0047] In an optional embodiment, the bottom slopes of the plurality of grooves 3 are the same.

[0048] In an alternative embodiment, the plurality of grooves 3 are spaced apart.

[0049] In an alternative embodiment, the grooves 3 are elongated and extend from the head 1 towards the straight arm 2.

[0050] As a preferred embodiment, the material of the composite test member is hot- stamped galvanized sheet.

[0051] As a preferred embodiment, the head 1 and the straight arm 2 are integrated.

[0052] The composite test member is manufactured by direct hot stamping process, the process including blanking-heating-direct hot stamping including pre-cooling process, pre-alloying process, laser cutting, shot blasting and spot welding.

[0053] The above description is merely preferred embodiments of the present application, but not to limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method of testing the effect of the amount of deformation on LME, characterized in that, The method comprises the following steps: The method comprises the following steps:

2. A method of testing the effect of molding temperature on LME, characterized by, The method comprises the following steps: The method comprises the following steps:

3. A method of testing the crash performance of a vehicle, characterized in that The method comprises the following steps:

4. A composite test member characterized by, The head is provided with a plurality of grooves, the bottom of each groove is obliquely arranged, the depths of the plurality of grooves are different from each other, and the cross section of the straight arm is in the shape of a Chinese character 'jie'.

5. The composite test member of claim 4, wherein, The grooves are three, namely a first groove, a second groove and a third groove, the minimum thinning amount and the maximum thinning amount of the first groove are 0% and 10% of the thickness of the composite test member respectively, the minimum thinning amount and the maximum thinning amount of the second groove are 10% and 20% of the thickness of the composite test member respectively, and the minimum thinning amount and the maximum thinning amount of the third groove are 20% and 30% of the thickness of the composite test member respectively.

6. The composite test member of claim 4, wherein The straight arm in the shape of a Chinese character 'jie' comprises an upper horizontal plate, the two ends of the upper horizontal plate are connected with side walls, the lower ends of the side walls are connected with flange edges, and a round corner is arranged between the horizontal plate and the side wall and between the side wall and the flange edge, the top edge and the bottom edge of the groove are provided with round corners, and the R1 of the round corner is K*T, wherein K is a proportionality coefficient and T is the plate thickness, when T<=1mm, K is 0.5-1.5, when 1 7. The composite test member of claim 6, wherein The included angle between the line connecting the top and the bottom of the groove and the horizontal plane is alpha1, and alpha1 is 60-84 degrees, and the included angle between the side wall and the horizontal plane is alpha2, and alpha2 is 45-84 degrees.

8. The composite test member of claim 4, wherein The longitudinal section of the groove is in the shape of a V, a U or a trapezoid.

9. The composite test member of claim 8, wherein, The material of the multifunctional composite test member is a hot-formed galvanized plate.

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