CN104785947A - Method for judging failures of spot-welded joint under recombination action - Google Patents

Abstract

The invention provides a method for judging failures of a spot-welded joint under the recombination action. The method includes the following steps that firstly, a sample is prepared; secondly, a double-U-type spot-welded sample test is carried out; thirdly, an edgefold stripping test is carried out; fourthly, a torsion test is carried out; fifthly, a welding spot nugget diameter test is carried out; sixthly, failure criteria parameter processing based on resultant force is carried out; seventhly, failure criteria parameter processing based on stress is carried out. By means of the method for judging failures of the spot-welded joint under the recombination action, the failure conditions of the welding spot can be accurately predicted, and the simulation precision of car collision is improved.

Description

Judge the method that tack-weld lost efficacy under compound action

Technical field

The present invention relates to the defeat technique of resistance spot welding, specifically a kind of method judging that tack-weld lost efficacy under compound action.

Background technology

In the manufacture of each parts of automobile, owing to having, quality is light in spot welding, good reliability, stable performance and the advantage such as easily to be automated, in the monocoque body of Modern Car, as topmost auto-body assembly process means.The quality of these solder joints directly can affect the properties of vehicle body, as intensity, anti-impact compressive property, fatigue behaviour etc.Constantly expand along with advanced high-strength steel application ground and go deep into, its resistance spot welding performance receives the extensive concern of people, and the Joint Strength of advanced high-strength steel has important impact to vehicle performance.

In recent years, along with developing rapidly of finite element technique, Automobile Design transforms the designs of modeling, static and dynamic analysis and virtual reality by original experience, analogy, Static Design just gradually.Numerical simulation not only can get rid of the contingency in experimentation, neatly comprehensive study and analysis are carried out to the various influence factors in pinpoint welding procedure, save production cost and the time, the study mechanism that also can be resistance spot welding process provides effective theory analysis means, helping the clear and definite research direction of experimenter, providing guidance for improving vehicle safety performance.The simulation precision of solder joint not only will embody the simulation requirements of vehicle body crash-worthiness index, also truly should reflect the failure conditions of solder joint.

For vehicle collision simulation, traditional spot welding simulation adopts first carries out car load simulation, and then it is stressed to check solder joint, cannot judge the failure conditions of solder joint in collision process like this.Although a large amount of work has been done in the research of foreign scholar's butt welding point failure mechanism aspect, the concrete acquisition methods for solder joint failure simulation and solder joint failure criterion has still retained, and not yet has clear and definite method and step.And domestic researcher is also confined to study dissimilar solder joint unit to the discussion of thin-walled parts collision simulation Accuracy mostly, the research for the physical simulation method of solder joint failure is deep not enough, leaves many problems needing to solve.Therefore the present invention is directed to this situation, system is carried out to the solder joint failure simulation in vehicle collision simulation and comprehensively studies, propose the concrete acquisition methods of solder joint failure criterion, thus reference can be provided for the design and development of native country Automobile Enterprises.

In numerical simulation, solder joint failure criterion is mainly divided into two kinds: a kind of is based on the inefficacy of making a concerted effort (Resultantbased failure), another kind of solder joint failure criterion is the failure behaviour describing solder joint by the solder joint failure parameter that stress represents, is called the inefficacy (stress based failure) based on stress.

Based on the failure criteria of power such as formula (1), when FC >=1, solder joint is judged as and lost efficacy as shown in the formula (1):

$\mathrm{FC}=\sqrt{{\left(\frac{\max (N_{\mathrm{rr}},0)}{N_{\mathrm{rrF}}}\right)}^2+{\left(\frac{N_{\mathrm{rs}}}{N_{\mathrm{rsF}}}\right)}^2+{\left(\frac{N_{\mathrm{rt}}}{N_{\mathrm{rtF}}}\right)}^2+{\left(\frac{M_{\mathrm{rr}}}{M_{\mathrm{rrF}}}\right)}^2+{\left(\frac{M_{\mathrm{ss}}}{M_{\mathrm{ssF}}}\right)}^2+{\left(\frac{M_{\mathrm{tt}}}{M_{\mathrm{ttF}}}\right)}^2}---\left(1\right)$

In RST three-dimensional coordinate, N in denominator _rrrepresent the pulling force along R positive direction; N _rsrepresent the shearing force along S positive direction; N _rtrepresent the shearing force along T positive direction; M _rrrepresent moment of torsion; M _ssrepresent the moment of flexure along S positive direction; M _ttrepresent the moment of flexure along T positive direction.

Another kind of stress failures criterion uses stress as solder joint failure parameter, describes the failure behaviour of solder joint.Shown in (2), use the shear stress τ of solder joint respectively, axially positive tensile stress sigma _nwith bending stress σ _brepresent the actual bearer situation of solder joint.Similar with formula (1), when f >=1 in formula (2), solder joint is considered to lose efficacy.

$f={\left(\frac{{\mathrm{\σ}}_N}{S_N}\right)}^{n_N}+{\left(\frac{{\mathrm{\σ}}_B}{S_B}\right)}^{n_B}+{\left(\frac{\mathrm{\τ}}{S_S}\right)}^{n_S}---\left(2\right)$

The present invention utilizes series of experiments to determine failure parameter in above two kinds of failure criterias (denominators namely in formula (1) and (2)), carrys out the failure conditions of judging point plumb joint under compound action with this.

Summary of the invention

For solving the technical problem existed in prior art, the invention provides a kind of method judging that tack-weld lost efficacy under compound action, specifically instruct the acquisition methods of failure parameter in failure criteria, criterion is applied in simulating car collision, can Accurate Prediction solder joint failure situation, improve the simulation accuracy of car crass.

The invention provides a kind of method judging that tack-weld lost efficacy under compound action, it is characterized in that, it comprises the following steps:

Step 1, carry out sample preparation;

Step 2, carry out double-U-shaped spot-welding sample test;

Step 3, carry out flanging disbonded test;

Step 4, carry out torsion test;

Step 5, carry out the test of nugget diameter;

Step 6, carry out based on make a concerted effort failure criteria parameter processing;

Step 7, to carry out based on the process of stress failures criteria parameter.

Preferably, described step 1 is welded double-U-shaped spot-welding sample, flanging peel test specimen, torsional specimen and test nugget size sample, the size of welding parameter and welding electrode used therein head is identical with the welding procedure on actual production line with standard, makes every effort to the solder joint on sample and the phase of solder joint on physical unit together.

Preferably, described step 2 comprises the following steps:

Step 201, sample welding are complete can start the test of double-U-shaped spot-welding sample, double-U-shaped spot-welding sample is fixed on the fixture of double-U-shaped spot-welding test by four pins, fixture rotates to the position of double-U-shaped spot-welding test 0 °, again fixture is fixed on cupping machine by latch, start to carry out tension test, till solder joint failure;

Step 202, complete U-shaped spot-welding test 0 °, U-shaped spot-welding test 30 ° can be carried out;

Step 203, complete U-shaped spot-welding test 30 °, U-shaped spot-welding test 60 ° can be carried out;

Step 204, complete U-shaped spot-welding test 60 °, U-shaped spot-welding test 90 ° can be carried out.

Preferably, described step 3 comprises the following steps:

Step 301, complete U-shaped spot-welding test after, can flanging disbonded test be carried out;

Step 302, by the test in step 301 in triplicate, namely test three groups of flanging peel test specimens, record three groups of failure force, average; Obtain failure load by flanging disbonded test, can moment of flexure be calculated.

Preferably, described step 4 comprises the following steps:

Step 401, complete flanging disbonded test after, can torsion test be carried out;

Step 402, by the test in step 401 in triplicate, namely test three groups of torsional specimens, record three groups of failure force, average, obtain failure load by torsion test, can moment of torsion be calculated.

Preferably, described step 5 comprises the following steps:

Step 501, in solder joint center, butt welding point cross section is polished, polishing and corrosion, corrosion employing 4% nitric acid alcohol;

Step 502, at solder joint cross section after treatment, feature that can be different from mother metal portion of tissue according to nugget district, adopts the three-dimensional microscopic system of the super depth of field to measure the nugget size of solder joint.

The present invention compared with prior art, has following apparent substantive distinguishing features and advantage: criterion applies in simulating car collision by the present invention, can Accurate Prediction solder joint failure situation, improves the simulation accuracy of car crass.

Accompanying drawing explanation

Fig. 1 is double-U-shaped spot-welding sample tension test schematic diagram, wherein Fig. 1 (a) is double-U-shaped spot-welding sample 0 ° of tension test schematic diagram, Fig. 1 (b) is double-U-shaped spot-welding sample 30 ° of tension test schematic diagrames, Fig. 1 (c) is double-U-shaped spot-welding sample 60 ° of tension test schematic diagrames, and Fig. 1 (d) is double-U-shaped spot-welding sample 90 ° of tension test schematic diagrames.

Fig. 2 is flanging disbonded test schematic diagram.

Fig. 3 is torsion test schematic diagram.

Detailed description of the invention

The present invention judges that the method that tack-weld lost efficacy under compound action comprises the following steps:

Step 1, carry out sample preparation, concrete steps are as follows:

Step 101, double-U-shaped spot-welding sample, flanging peel test specimen, torsional specimen and test nugget size sample to be welded, the size of welding parameter and welding electrode used therein head is identical with the welding procedure on actual production line with standard, make every effort to the solder joint on sample and the phase of solder joint on physical unit with, reduce error as much as possible.

Step 2, carry out double-U-shaped spot-welding sample test, concrete steps are as follows:

Step 201, sample welding are complete can start the test of double-U-shaped spot-welding sample, double-U-shaped spot-welding sample is fixed on the fixture of double-U-shaped spot-welding test by four pins, fixture rotates to the position of double-U-shaped spot-welding test 0 °, again fixture is fixed on cupping machine by latch, as shown in Fig. 1 (a), start to carry out tension test, till solder joint failure.According to the load that testing machine collects, determine the failure force of double-U-shaped spot-welding test 0 °.In triplicate, record three groups of failure force, average.

Step 202, complete U-shaped spot-welding test 0 °, U-shaped spot-welding test 30 ° can be carried out; Double-U-shaped spot-welding sample is fixed on the fixture of double-U-shaped spot-welding test by four pins, fixture rotates to the position of double-U-shaped spot-welding test 30 °, again fixture is fixed on cupping machine by latch, as shown in Fig. 1 (b), start to carry out tension test, till solder joint failure.According to the load that testing machine collects, determine the failure force of double-U-shaped spot-welding test 30 °.In triplicate, record three groups of failure force, average.

Step 203, complete U-shaped spot-welding test 30 °, U-shaped spot-welding test 60 ° can be carried out.Be fixed on the fixture of double-U-shaped spot-welding test by double-U-shaped spot-welding sample by 4 pins, fixture rotates to the position of double-U-shaped spot-welding test 60 °, then is fixed on cupping machine, by fixture as shown in Fig. 1 (c) by latch.Start to carry out tension test, till solder joint failure.According to the load that testing machine collects, determine the failure force of double-U-shaped spot-welding test 60 °.In triplicate, record three groups of failure force, average.

Step 204, complete U-shaped spot-welding test 60 °, U-shaped spot-welding test 90 ° can be carried out.Be fixed on the fixture of double-U-shaped spot-welding test by double-U-shaped spot-welding sample by 4 pins, fixture rotates to the position of double-U-shaped spot-welding test 90 °, then is fixed on cupping machine, by fixture as shown in Fig. 1 (d) by latch.Start to carry out tension test, till solder joint failure.According to the load that testing machine collects, determine the failure force of double-U-shaped spot-welding test 90 °.In triplicate, record three groups of failure force, average.

Step 3, carry out flanging disbonded test, concrete steps are as follows:

Step 301, complete U-shaped spot-welding test after, can flanging disbonded test be carried out.Be fixed on the fixture of double-U-shaped spot-welding test by flanging peel test specimen by four pins, fixture rotates to the position of double-U-shaped spot-welding test 90 °, then is fixed on cupping machine by fixture by latch, as shown in Figure 2.Start to carry out tension test, till solder joint failure.According to the load that testing machine collects, determine that flanging peels off failure force.

Step 302, by the test in step 301 in triplicate, namely test three groups of flanging peel test specimens, record three groups of failure force, average; Obtain failure load by flanging disbonded test, can moment of flexure be calculated.

Step 4, carry out torsion test, concrete steps are as follows:

Step 401, complete flanging disbonded test after, can torsion test be carried out.Torsional specimen is fixed on the fixture of torsion test by 2 pins, as shown in Figure 3.Again fixture is fixed on cupping machine by latch, starts to carry out tension test, till solder joint failure.According to the load that testing machine collects, determine torsional failure power.

Step 402, by the test in step 401 in triplicate, namely test three groups of torsional specimens, record three groups of failure force, average, obtain failure load by torsion test, can moment of torsion be calculated.

Step 5, carry out the test of nugget diameter, concrete steps are as follows:

Step 501, in solder joint center, butt welding point cross section is polished, polishing and corrosion, corrosion employing 4% nitric acid alcohol;

Step 502, at solder joint cross section after treatment, feature that can be different from mother metal portion of tissue according to nugget district, adopts the three-dimensional microscopic system of the super depth of field to measure the nugget size of solder joint.

Step 6, carry out based on make a concerted effort failure criteria parameter processing, concrete steps are as follows:

Step 601, after completing above-mentioned test, just can calculate the parameter based on making a concerted effort needed for failure criteria.For based on the solder joint failure criterion of making a concerted effort, shown in (1), in denominator, maximum failure pulling force N _rrFobtain by the double-U-shaped spot welding of step 201 0 ° test, maximum failure shears force N _rsF, N _rtFcan be obtained by the double-U-shaped spot welding of step 204 90 ° test, maximum failure moment M _ssF, M _ttFcan be obtained by the disbonded test of step 3 flanging, maximum failure moment of torsion M _rrFcan be obtained by step 4 torsion test.

Step 7, carry out based on the process of stress failures criteria parameter, concrete steps are as follows:

Step 701, experimentally result, just can calculate based on stress failures criterion desired parameters.For the solder joint failure criterion based on stress, shown in (2), the parameter determined is needed to be denominator S _n, S _band S _sand index n _n, n _band n _s.Denominator S _n, S _band S _sobtained by formula (3), (4), (5) respectively:

$S_N=\frac{N_{\mathrm{rrF}}}{A}---\left(3\right)$

$S_B=\frac{\sqrt{M_{\mathrm{ssF}}^2+M_{\mathrm{rrF}}^2}}{Z}---\left(4\right)$

$S_S=\frac{M_{\mathrm{rrF}}}{2Z}+\sqrt{\frac{N_{\mathrm{rsF}}^2+N_{\mathrm{rtF}}^2}{A}}---\left(5\right)$

In step 702, formula (3), (4) and (5), the calculating of A and Z is such as formula (6) and (7), and in formula, d is the nugget size of solder joint, by step 5 gained:

$A=\frac{{\mathrm{\πd}}^2}{4}---\left(6\right)$

$Z=\frac{{\mathrm{\πd}}^2}{32}---\left(7\right)$

Step 703, based on stress failures criterion desired parameters except above-mentioned denominator S _n, S _band S _s, also have index n _n, n _band n _s.N _n, n _band n _sfor stress exponent, test (step 202) by double-U-shaped spot welding 30 ° respectively, (step 203) is tested in double-U-shaped spot welding 60 ° and torsion test (step 4) is obtained by least square method.

Vehicle is in collision process, after the solder joint of connection metal thin plate is subject to strong shock, whether it lost efficacy can affect the distortion of vehicle body thin-wall member and the ability of energy-absorbing strongly, and solder joint failure directly can destroy the integrality of structure in collision process, thus change the pipeline of impact force, and then make the energy absorbing components such as front longitudinal according to the deformation pattern distortion of design, therefore can not can cause the reduction of vehicle Impact Resisting Capability.Consider that solder joint comes off to lose efficacy and has so important impact to automotive SBC, must study the failure mechanism of solder joint thus avoid the vehicle body crash-worthiness caused because of solder joint failure to reduce in the crash-worthiness design of car load.

Implementation process of the present invention, for DP1180 Plate Welding of the same race, has carried out the test of the 0 ° of tension test of double-U-shaped spot-welding sample, the 30 ° of tension tests of double-U-shaped spot-welding sample, the 60 ° of tension tests of double-U-shaped spot-welding sample, the 90 ° of tension tests of double-U-shaped spot-welding sample, flanging disbonded test, torsion test and nugget size for DP1180.

Following preparation is done: the fixture of double-U-shaped spot-welding sample test and torsion test is designed before test.Get out standard-sized sample, and weld.

Result of the test is as table 1 ~ table 4, and result of calculation is as table 5.

Table 1 double-U-shaped spot-welding sample result of the test table

Table 2 flanging disbonded test result table

Table 3 torsion test result table

Table 4 nugget size table with test results

Table 5 DP1180 failure parameter result of calculation table

N rrF(N)	N rsF(N)	N rtF(N)	M rrF(Nm)	M ssF(Nm)	M ttF(Nm)
						7879.1	26659.9	26659.9	73.8862	49.1003	49.1003
S N(Mpa)	S B(Mpa)	S S(Mpa)	n N	n B	n S
						201.0	2030.5	2029.1	0.4831	10.5457	1.5495

Claims (6)

1. judge the method that tack-weld lost efficacy under compound action, it is characterized in that, it comprises the following steps:

Step 1, carry out sample preparation;

Step 2, carry out double-U-shaped spot-welding sample test;

Step 3, carry out flanging disbonded test;

Step 4, carry out torsion test;

Step 5, carry out the test of nugget diameter;

Step 6, carry out based on make a concerted effort failure criteria parameter processing;

Step 7, to carry out based on the process of stress failures criteria parameter.

2. the method that under judgement compound action according to claim 1, tack-weld lost efficacy, it is characterized in that, described step 1 is welded double-U-shaped spot-welding sample, flanging peel test specimen, torsional specimen and test nugget size sample, the size of welding parameter and welding electrode used therein head is identical with the welding procedure on actual production line with standard, makes every effort to the solder joint on sample and the phase of solder joint on physical unit together.

3. the method that under judgement compound action according to claim 1, tack-weld lost efficacy, it is characterized in that, described step 2 comprises the following steps:

Step 201, sample welding are complete can start the test of double-U-shaped spot-welding sample, double-U-shaped spot-welding sample is fixed on the fixture of double-U-shaped spot-welding test by four pins, fixture rotates to the position of double-U-shaped spot-welding test 0 °, again fixture is fixed on cupping machine by latch, start to carry out tension test, till solder joint failure;

Step 202, complete U-shaped spot-welding test 0 °, U-shaped spot-welding test 30 ° can be carried out;

Step 203, complete U-shaped spot-welding test 30 °, U-shaped spot-welding test 60 ° can be carried out;

Step 204, complete U-shaped spot-welding test 60 °, U-shaped spot-welding test 90 ° can be carried out.

4. the method that under judgement compound action according to claim 1, tack-weld lost efficacy, it is characterized in that, described step 3 comprises the following steps:

Step 301, complete U-shaped spot-welding test after, can flanging disbonded test be carried out;

Step 302, by the test in step 301 in triplicate, namely test three groups of flanging peel test specimens, record three groups of failure force, average; Obtain failure load by flanging disbonded test, can moment of flexure be calculated.

5. the method that under judgement compound action according to claim 1, tack-weld lost efficacy, it is characterized in that, described step 4 comprises the following steps:

Step 401, complete flanging disbonded test after, can torsion test be carried out;

Step 402, by the test in step 401 in triplicate, namely test three groups of torsional specimens, record three groups of failure force, average, obtain failure load by torsion test, can moment of torsion be calculated.

6. the method that under judgement compound action according to claim 1, tack-weld lost efficacy, it is characterized in that, described step 5 comprises the following steps:

Step 501, in solder joint center, butt welding point cross section is polished, polishing and corrosion, corrosion employing 4% nitric acid alcohol;

Step 502, at solder joint cross section after treatment, feature that can be different from mother metal portion of tissue according to nugget district, adopts the three-dimensional microscopic system of the super depth of field to measure the nugget size of solder joint.