Welding spot failure test method for inducing two failure forms

Abstract

The invention discloses a welding spot failure test method for inducing two failure forms. The welding spot failure test method comprises the following steps: S1, preparing a feature piece; s2, the feature part is connected with a fixing tool; s3, applying a load to the feature part by adopting a hammer head; and S4, observing and recording the failure behavior of the two welding spots induced after the load is applied to the feature piece. According to the method, two different welding spot failure modes can be induced, the sequence of welding spot failure occurrence is guaranteed, the test repeatability is good, meanwhile, base metal failure can be avoided, and a basis is provided for welding spot failure behavior research of ultrahigh-strength steel materials.

Description

Technical Field

[0001] The present invention relates to a weld failure behavior test of an ultra-high strength steel material, and more particularly to a weld failure test method that induces two failure modes. Background Art

[0002] The failure behavior of ultra-high strength steel welds has a significant impact on vehicle collision safety, and the failure load is closely related to the load state of the weld. In order to evaluate and verify the failure behavior of materials and components, the industry usually uses the hat beam axial crushing test (such as Figure 1 As shown), hat beam three-point bending test (as shown Figure 2 As shown), T-piece loading test (as shown Figure 3 As shown). In the test method of the hat beam axial crushing and hat beam three-point bending using ultra-high strength steel materials, the welds are less likely to fail, the parent material is more likely to fail, and the verification ability of the weld failure behavior is poor. When the T-piece is loaded, the weld at the connection between the two parts plays a role in load transfer, bearing shear, tension and bending moment, which can better reflect the actual stress of the weld, and the failure position is basically at the weld position, but the test repeatability is poor, the order of weld failure is not fixed, and the failure load is unstable.

[0003] In existing patent applications, such as Chinese patent application No. 202120763938.4, a solder joint strength test device is disclosed, which realizes the failure test of solder joints under different loads through a set of fixtures. This patented technology is only applicable to plate samples, not to components or feature parts.

[0004] Chinese patent application No. 202110976122.4 discloses a multifunctional fixture for steel plate resistance spot welding test specimens. This patented technology is also only applicable to plate specimens and is not applicable to components or feature parts.

[0005] Chinese patent application numbers 201922367493.3 and 202122668163.5 etc. proposed component solder joint failure test devices, which mainly involve component clamping methods, strength testing and other contents.

[0006] Chinese patent publication numbers CN104785947B (a method for determining the failure of spot welding joints under combined action), CN101739490B (a method and system for determining spot welding joint failure in finite element analysis), CN101261653B (a numerical simulation system for spot welding connection failure), and CN105699186A (a method for evaluating the variable angle mechanical properties of metal resistance spot welding joints) all only involve digital simulation methods for welding joint failure.

[0007] It can be seen that the currently disclosed methods are mainly aimed at the test methods of plate specimens and the numerical simulation methods of solder joint failure. There is no solder joint failure test method that can realize multiple failure modes on components or feature parts. Summary of the invention

[0008] In view of the defects existing in the prior art, the purpose of the present invention is to provide a weld failure test method that induces two failure forms, which can induce two different weld failure modes and ensure the order of weld failure. The test has good repeatability and can avoid failure of the base material, thereby providing a basis for the study of weld failure behavior of ultra-high strength steel materials.

[0009] To achieve the above object, the present invention adopts the following technical solution:

[0010] A solder joint failure test method for inducing two failure modes comprises the following steps:

[0011] S1. Prepare characteristic parts;

[0012] S2, connecting the characteristic part to the fixed tooling;

[0013] S3, applying a load to the characteristic part using a hammer;

[0014] S4. Observe and record the failure behaviors of the two welds induced by the load applied to the feature part.

[0015] Preferably, the characteristic parts include a hat beam, an L-shaped plate and a sealing plate;

[0016] One end of the hat beam is provided with two flanges and an extended edge, and is welded to the L-shaped plate;

[0017] The other end of the hat beam is welded to the sealing plate.

[0018] Preferably, the fixing tool comprises a first fixing tool and a second fixing tool;

[0019] The first fixing fixture is connected to the sealing plate by bolts;

[0020] The second fixing fixture is connected to the L-shaped plate via bolts.

[0021] Preferably, the hammer head is a semicircular rigid hammer head, and the position where the hammer head applies the load is on the hat beam at the center of the first fixing fixture and the second fixing fixture;

[0022] The ratio of the bending fillet R1 of the hat beam to the plate thickness T of the hat beam is set to R1 / T≥4 and the ratio of the radius R3 of the hammer head to the bending fillet R1 of the hat beam is set to R3 / R1≥10 to ensure that the base material does not fail in area 1. Area 1 is the area where the hammer head directly squeezes the hat beam to produce a large deformation;

[0023] The ratio of the bending radius R1 of the hat-shaped beam to the plate thickness T of the hat-shaped beam is set to R1 / T≥4, and the ratio of the notch radius R2 of the hat-shaped beam to the plate thickness T of the hat-shaped beam is set to R2 / T≥5 to ensure that the base material does not fail in area 2. Area 2 is the area where the hat-shaped beam is deformed as a whole and thus produces a large deformation in the area.

[0024] The width of the hammer head is D=100 mm;

[0025] The length of the hat beam is L=300 mm.

[0026] Preferably, the load application method of the hammer head is quasi-static pressurization or impact pressurization.

[0027] Preferably, there are four welding points between one end of the hat beam and the L-shaped plate, which are:

[0028] A welding point A between the elongated side and the outer side surface of the short side of the L-shaped plate;

[0029] A welding point B between the flange and the outer side surface of the long side of the L-shaped plate;

[0030] A welding point C and a welding point D between the other flange and the outer side surface of the long side of the L-shaped plate;

[0031] The solder joint A and the solder joint B are solder joints that induce failure behavior.

[0032] Preferably, the solder joint A is subjected to shear force, and the failure behavior of the solder joint A is shear failure;

[0033] The solder joint B is subjected to a bending moment, and the failure behavior of the solder joint B is a bending failure.

[0034] Preferably, the ratio of the height H1 of the hat beam to the width W1 of the hat beam is set to H1 / W1≥0.75;

[0035] The shear deformation that the weld spot A can withstand is small, and it fails first, while the bending deformation that the weld spot B can withstand is large, and it fails later. By setting the loading distance and / or initial energy of the hammer head, only the weld spots A and B are controlled to fail, while the weld spots C and D do not fail.

[0036] The present invention provides a method for inducing a weld failure test in two failure forms. By designing characteristic samples and loading methods, two different weld failure modes can be induced, and the order of weld failure can be guaranteed, while the failure of the parent material can be avoided. The sample preparation is simple, and the test repeatability is good, which provides a basis for the study of weld failure behavior of ultra-high-strength steel materials. The preparation cost of characteristic parts and fixtures is low, the test operation is convenient, the test repeatability is good, the precision is high, and it has broad application prospects in engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a schematic diagram of the existing hat beam axial crushing test;

[0038] Figure 2 It is a schematic diagram of the existing hat beam three-point bending test;

[0039] Figure 3 It is a schematic diagram of the existing T-piece loading test;

[0040] Figure 4 It is a schematic flow chart of the solder joint failure test method of the present invention;

[0041] Figure 5 Schematic diagram of a hat beam in a weld failure test method of the present invention;

[0042] Figure 6 yes Figure 5 Schematic diagram of the A direction, (a) is the schematic diagram of T and R2, (b) is the schematic diagram of R1, H1, and W1;

[0043] Figure 7 Schematic diagram of solder joint A to solder joint D in the solder joint failure test method of the present invention;

[0044] Figure 8 It is a schematic diagram of the implementation of the solder joint failure test method of the present invention;

[0045] Fig. 9 It is a schematic diagram of the failure prone area on the characteristic part in the solder joint failure test method of the present invention;

[0046] Fig.10 It is a curve schematic diagram of the load on the solder joint A in the solder joint failure test method of the present invention;

[0047] Fig.11 It is a curve schematic diagram of the load on the solder joint B in the solder joint failure test method of the present invention;

[0048] Fig.12 It is a schematic diagram of the principle of inducing failure of solder joints A and B in the solder joint failure test method of the present invention. DETAILED DESCRIPTION

[0049] In order to better understand the above technical solution of the present invention, the technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0050] Combination Figures 4 to 8 As shown, the present invention provides a solder joint failure test method that induces two failure modes, comprising the following steps:

[0051] S1. Preparation of characteristic parts:

[0052] The hat beam 1 and the L-shaped plate 2 are first processed by bending, wire cutting and other processing methods, and then one end of the hat beam 1 is connected to the L-shaped plate 2 by spot welding. The materials and thicknesses of the hat beam 1 and the L-shaped plate 2 can be combined according to the test requirements. The other end of the hat beam 1 is connected to the sealing plate 3 by welding.

[0053] Two flanges 101, 102 and an extended side 103 are provided on one end of the hat beam 1 for welding with the L-shaped plate 2. There are four welding points between one end of the hat beam 1 and the L-shaped plate 2, namely: welding point A between the extended side 101 and the outer side of the short side of the L-shaped plate 2, welding point B between one flange 102 and the outer side of the long side of the L-shaped plate 2, welding point C and welding point D between the other flange 101 and the outer side of the long side of the L-shaped plate 2. Among them, welding point A and welding point B are the welding points of concern, and welding point C and welding point D mainly play a role in structural strengthening.

[0054] The ratio of the bending radius R1 of the hat beam 1 to the plate thickness T of the hat beam 1 is R1 / T≥4; the ratio of the notch radius R2 of the hat beam 1 to the plate thickness T of the hat beam 1 is R2 / T≥5; the ratio of the height H1 of the hat beam 1 to the width W1 of the hat beam 1 is H1 / W1≥0.75.

[0055] The thickness of the sealing plate 3 is greater than 5 mm, and its function is to fix the hat beam 1 .

[0056] S2. Connect the feature parts with the fixed tooling:

[0057] The fixing fixture comprises a first fixing fixture 4 and a second fixing fixture 5 . The first fixing fixture 4 is connected to the sealing plate 3 via six bolts 6 , and the second fixing fixture 5 is connected to the L-shaped plate 2 via six bolts.

[0058] The bottoms of the first fixing fixture 4 and the second fixing fixture 5 are respectively connected to the test bench via four bolts 7 .

[0059] S3. Use hammer head 8 to apply load to the characteristic part:

[0060] The hammer head 8 is a semicircular rigid hammer head, the ratio of the radius R3 of the hammer head 8 to the bending fillet R1 of the hat beam 1 is R3 / R1≥10, the width D of the hammer head 3 is 100 mm, and the length L of the hat beam 1 is 300 mm.

[0061] The position where the hammer head 8 applies the load is on the hat beam 1 at the center position of the first fixing fixture 4 and the second fixing fixture 5 .

[0062] The load application method of the hammer head 8 is that the hammer head 8 slowly applies the load to realize quasi-static pressurization of the characteristic part, or the hammer head 8 is equipped with a certain weight and initial velocity to realize impact pressurization of the characteristic part.

[0063] S4. Observe and record the failure behavior of the two welds induced by the load applied to the feature:

[0064] During the test, the failure behaviors of the solder joints A and B are observed and recorded, and the load value applied by the hammer head 8 to the characteristic part and the displacement of the hammer head 8 are outputted through the test equipment.

[0065] The ultra-high strength steel base material has a low ability to resist plastic deformation. During the test, there are two places on the characteristic part where base material failure is likely to occur. The distribution diagram is shown in the figure. Fig. 9 As shown, the hammer head 8 directly squeezes the hat beam 1 to produce a large deformation in region 1, and the hat beam 1 is deformed as a whole in region 2, which in turn produces a large deformation in the region. By setting R1 / T≥4 and R3 / R1≥10, it can be ensured that the parent material does not fail in region 1, and by setting R1 / T≥4 and R2 / T≥5, it can be ensured that the parent material does not fail in region 2.

[0066] Inducing two weld failure modes: By setting the ratio of the height H1 to the width W1 of the hat beam 1 to H1 / W1 ≥ 0.75, and setting the overlap mode between the two flanges 101 and 102 of the hat beam 1 and the L-shaped plate 2, weld points A and weld points B can be induced to fail successively. During the test, the load on weld point A is as follows Fig.10 As shown in the figure, solder joint A is mainly subjected to shear force and can withstand the smallest shear deformation, so it fails first. The failure mode of solder joint A is shear failure. The load on solder joint B is as follows: Fig.11 As shown in the figure, solder joint B is mainly subjected to bending moment and can withstand greater bending deformation, so it fails later and the failure form of solder joint B is bending failure. Solder joints C and D mainly play a role in structural reinforcement. By setting a reasonable loading distance or initial energy of the hammer head, it can be controlled that only solder joints A and B fail, while solder joints C and D do not fail.

[0067] The judgment of weld failure follows a resistance spot welding failure prediction method based on multiple failure modes and their coupling effects (patent application number 202210751400.0), which includes the following steps:

[0068] A. Establish a prediction model: In the formula,

[0069] F s , F n , M t , M b They are shear strength, tensile strength, torsional strength and bending strength; f s , f n , m t , m b are the shear force, tension, torque and bending moment actually exerted on the weld respectively; α, β, γ and ζ are the coupling power exponents reflecting the influence of different welding material combinations and welding process conditions on the weld failure;

[0070] B. Prepare the first, second and third spot welding samples according to the spot welding combination to be judged;

[0071] C. Perform a shear test and a 90° tensile test on the first spot weld sample to obtain the shear strength and tensile strength respectively;

[0072] D. Use the third spot weld sample to perform a torsion test to obtain the torsion strength M t ;

[0073] E. Use the second spot weld sample to perform a peel test to obtain the bending strength M b ;

[0074] F. Use the third spot welded sample to carry out bending and torsion tests at different angles, and calculate the coupling power exponents γ and ζ;

[0075] G. Conduct tensile tests at different angles using the first spot welded specimen, and calculate the coupling power exponents α and β;

[0076] H. Use a computer to calculate and predict the spot welding combination to be judged based on the prediction model and the parameters obtained from each test in step CG: If the prediction model equation is established, it is judged to be failed.

[0077] like Fig.12 The failure induction principle of the two failure forms shown in the figure. As the test load continues to increase, as mentioned above, under the shear stress state, the shear deformation that solder joint A can withstand is small, and the damage value of the solder joint increases the fastest. When the damage value reaches 1, solder joint A fails. At this time, under the bending moment stress state, the damage value of solder joint B increases slowly, and the damage value does not reach 1. As the test load is further increased, the damage value of solder joint B will eventually reach 1, and solder joint B fails.

[0078] By reasonably setting the ratios of R1 / T, R3 / R1 and R2 / T, the damage accumulation rate of area 1 and area 2 on the feature part can be slowed down. When welds A and B fail, the damage values ​​of area 1 and area 2 are both less than 1, thereby avoiding base material failure on the feature part.

[0079] The weld failure test method of the present invention is based on Patent 202210751400.0, and further proposes to verify the validity of the spot welding failure constitutive model proposed in Patent 202210751400.0 at the scale of feature parts or components. At the same time, due to the low resistance of ultra-high-strength steel base material to plastic deformation, conventional methods such as hat-beam weld failure test are prone to base material failure, thereby affecting the evaluation of weld failure. The weld failure test method of the present invention designs a new hat-beam structure based on this characteristic of ultra-high-strength steel to avoid base material failure during the test.

[0080] Example

[0081] Taking the DP980 ultra-high strength steel weld with thickness T=1.5mm as an example, the failure test process of the DP980 characteristic weld is as follows:

[0082] 1) The hat beam and L-shaped plate are processed by bending and wire cutting, and the characteristic parts are formed after spot welding. The bending radius of the hat beam is R1 = 6mm, and the ratio of the plate thickness T is R1 / T = 4; the notch radius is R2 = 8mm, and the ratio of the plate thickness T is R2 / T = 5.33; the height is H1 = 55mm, the width is W1 = 70mm, and H1 / W1 = 0.79. Four spot welds are used to connect the hat beam and the L-shaped plate.

[0083] 2) The cap beam and the cover plate are connected by welding, and the characteristic parts and the fixing fixtures are connected by bolts. The thickness of the cover plate is 5mm; the hammer head radius R3 = 60mm, and the ratio of the hammer head radius R1 to the cap beam is R3 / R1 = 10; the hammer head width D = 100mm, and the cap beam length L = 300mm.

[0084] 3) Slowly apply load to the hammer head, and observe that when the hammer head displacement is 17mm, weld A fails first, and the failure mode is shear failure; when the hammer head displacement is 25mm, weld B fails, and the failure mode is bending failure. At this time, weld C and weld D are not observed to fail, and no base material failure is observed in area 1 and area 2 on the feature part.

[0085] Those skilled in the art should recognize that the above embodiments are only used to illustrate the present invention, and are not intended to limit the present invention. As long as they are within the spirit of the present invention, any changes or modifications to the above embodiments will fall within the scope of the claims of the present invention.

Claims

1. A solder joint failure test method inducing two failure modes, characterized in that: The following steps are involved: S1. Prepare characteristic parts; S2, connecting the characteristic part to the fixed tooling; S3, applying a load to the characteristic part using a hammer; S4. Observe and record the failure behaviors of the two welds induced by the load applied to the feature part.

2. The solder joint failure test method for inducing two failure modes according to claim 1, characterized in that: The characteristic parts include a hat beam, an L-shaped plate and a sealing plate; One end of the hat beam is provided with two flanges and an extended edge, and is welded to the L-shaped plate; The other end of the hat beam is welded to the sealing plate.

3. The solder joint failure test method for inducing two failure modes according to claim 2, characterized in that: The fixing tool comprises a first fixing tool and a second fixing tool; The first fixing fixture is connected to the sealing plate by bolts; The second fixing fixture is connected to the L-shaped plate via bolts.

4. The solder joint failure test method for inducing two failure modes according to claim 3, characterized in that: The hammer head is a semicircular rigid hammer head, and the position where the hammer head applies load is on the hat beam at the center of the first fixing fixture and the second fixing fixture. The ratio of the bending fillet R1 of the hat beam to the plate thickness T of the hat beam is set to R1 / T≥4 and the ratio of the radius R3 of the hammer head to the bending fillet R1 of the hat beam is set to R3 / R1≥10 to ensure that the base material does not fail in area 1. Area 1 is the area where the hammer head directly squeezes the hat beam to produce a large deformation; The ratio of the bending radius R1 of the hat-shaped beam to the plate thickness T of the hat-shaped beam is set to R1 / T≥4, and the ratio of the notch radius R2 of the hat-shaped beam to the plate thickness T of the hat-shaped beam is set to R2 / T≥5 to ensure that the base material does not fail in area 2. Area 2 is the area where the hat-shaped beam is deformed as a whole and thus produces a large deformation in the area.

5. The solder joint failure test method for inducing two failure modes according to claim 4, characterized in that: The width of the hammer head is D=100 mm; The length of the hat beam is L=300 mm.

6. The solder joint failure test method for inducing two failure modes according to claim 5, characterized in that: The load application mode of the hammer head is quasi-static pressurization or impact pressurization.

7. The solder joint failure test method for inducing two failure modes according to claim 4, characterized in that: There are four welding points between one end of the hat beam and the L-shaped plate, which are: A welding point A between the elongated side and the outer side surface of the short side of the L-shaped plate; A welding point B between the flange and the outer side surface of the long side of the L-shaped plate; A welding point C and a welding point D between the other flange and the outer side surface of the long side of the L-shaped plate; The solder joint A and the solder joint B are solder joints that induce failure behavior.

8. The solder joint failure test method for inducing two failure modes according to claim 7, characterized in that: The solder joint A is subjected to shear force, and the failure behavior of the solder joint A is shear failure; The solder joint B is subjected to a bending moment, and the failure behavior of the solder joint B is a bending failure.

9. The solder joint failure test method for inducing two failure modes according to claim 8, characterized in that: Setting the ratio of the height H1 of the hat beam to the width W1 of the hat beam to be H1 / W1≥0.75; The shear deformation that the weld spot A can withstand is small, and it fails first, while the bending deformation that the weld spot B can withstand is large, and it fails later. By setting the loading distance and / or initial energy of the hammer head, only the weld spots A and B are controlled to fail, while the weld spots C and D do not fail.

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