CN109766633A - A kind of structural fatigue computation processing method for spot welding junction in finite element algorithm - Google Patents
A kind of structural fatigue computation processing method for spot welding junction in finite element algorithm Download PDFInfo
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- CN109766633A CN109766633A CN201910024802.9A CN201910024802A CN109766633A CN 109766633 A CN109766633 A CN 109766633A CN 201910024802 A CN201910024802 A CN 201910024802A CN 109766633 A CN109766633 A CN 109766633A
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- 238000003466 welding Methods 0.000 title claims abstract description 42
- 238000004422 calculation algorithm Methods 0.000 title claims abstract description 8
- 238000003672 processing method Methods 0.000 title claims description 5
- 238000000034 method Methods 0.000 claims abstract description 39
- 229910000679 solder Inorganic materials 0.000 claims abstract description 18
- 238000007619 statistical method Methods 0.000 claims abstract description 4
- 230000008569 process Effects 0.000 claims description 6
- 238000004364 calculation method Methods 0.000 claims description 5
- 238000006243 chemical reaction Methods 0.000 claims description 3
- 241000239290 Araneae Species 0.000 claims description 2
- 230000008901 benefit Effects 0.000 abstract description 3
- 238000011426 transformation method Methods 0.000 abstract description 2
- 230000035882 stress Effects 0.000 description 24
- 238000004458 analytical method Methods 0.000 description 10
- 238000013461 design Methods 0.000 description 4
- 238000005516 engineering process Methods 0.000 description 3
- 239000000463 material Substances 0.000 description 3
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- 229910052751 metal Inorganic materials 0.000 description 3
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- 238000004088 simulation Methods 0.000 description 3
- 239000000155 melt Substances 0.000 description 2
- FGRBYDKOBBBPOI-UHFFFAOYSA-N 10,10-dioxo-2-[4-(N-phenylanilino)phenyl]thioxanthen-9-one Chemical group O=C1c2ccccc2S(=O)(=O)c2ccc(cc12)-c1ccc(cc1)N(c1ccccc1)c1ccccc1 FGRBYDKOBBBPOI-UHFFFAOYSA-N 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 239000004411 aluminium Substances 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 230000009514 concussion Effects 0.000 description 1
- 230000006378 damage Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 230000006355 external stress Effects 0.000 description 1
- 230000035800 maturation Effects 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
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Abstract
The invention discloses a kind of technical methods that the structural fatigue that spot welding junction is handled using Finite Element is calculated.Had using this method relative to traditional algorithm and operates convenient, the advantages that data processing is rapid, and computational accuracy is high.This method includes that solder joint hexahedron connects (ACM) modeling method, stress coordinate transformation method, the calculating generation method of power and torque in the present invention, and uses power of the present invention and Calculating Torque during Rotary method to spot welding remaining life statistical method flow chart.
Description
Technical field
The present invention relates to a kind of using Finite Element Algorithm to the processing method of spot welding junction structural fatigue, it is more specific and
Speech, be related to it is a kind of by finite elements numerical method come research and analysis structural member under external stress loading single spot welding with it is more
The fatigue at spot welding position and the evaluation method of remaining life.
Background technique
Currently, computer-aided engineering (CAE) technology has been widely used for structure design, analyzes, and simulation waits work
In, help analysis project Shi Jinhang assessment and design.And technology of the Finite Element as maturation the most a kind of in CAE analysis,
It has been used to a variety of business analysis softwares, such as ABAQUS, ANSYS, NASTRAN etc..
Initial conception of the invention is based in finite element program, and usual each solder joint is by a CBAR unit generation
Table, and two shells are connected by shell unit.These power (unit power) are transmitted by these CBAR units, they be used to count
It calculates and melts the structural capacity at core in spot welding, and between adjacent metal shell, be often unfolded along all strong points of each solder joint.
Then these stress are passed through spot welding and are used for the prediction of fatigue life based on S-N method (entire life).
Recent, this method has been allowed to be suitable for different finite element analysis codes, and different divisions connects
Connection technology (mainly so-called " face contact method ") Lai Daibiao spot welding.As nonetheless, its principle of operation is still,
For example, section power and torque be used to derive stress, and it is used for S-L fatigue mechanisms.
If using CBAR(or CBEAM) unit, each solder joint must be by a single CBAR rigid element connection 2
Shell unit plate, and perpendicular to the two.CBAR unit must adequately it is hard so that the rigidity at junction to CBAR characteristic not
It is sensitive.In fact, this can be by assigning CBAR unit and just same elasticity modulus realization (for the solder joint of rigid material
For), and the size of cross section should be approximately equal to the size that kernel representation is melted in spot welding.Shell is located at the middle plane of sheet metal,
And it is equal to CBAR element length.Such distribution of shell is exactly equal to the half of plate thickness.Do not have simultaneously at the edge of solder joint
It is necessary to carry out reinforcing grid dividing.The simulation of plate is uniquely needed to be correctly to transmit load using housing unit
Information is to boundary element.In fact, when the size of shell unit is very big, the diameter that generally more than 2 times of solder joints melt core, or
It is extraordinary (optimal combination rigidity) in 10mm or so.Since single-point is corrected, the gradually refinement of grid will lead to connector
Place's grid becomes increasingly complex, this will run counter to desire.
Summary of the invention
The invention discloses the processing methods that Welding Area domain fatigue life is handled in structure finite element calculates, and specifically include
Spot welding territory element and nodal analysis method generation method, the coordinate conversion side of each region of spot welding stress and torque in calculating process
The calculation method of method, stress and torque and spot welding damage and service life statistical method etc..
The extracting method of another aspect according to the present invention, coordinate transformation method and stress of the present invention and torque is only
Feature is generated suitable for spot welding region Modelon Modeling proposed by the invention, spot welding model described in other non-present invention is simultaneously uncomfortable
With.
According to another aspect, the spot welding fatigue statistics for giving inventive algorithm is executed in computer systems.Such as pass through
The life appraisal of computer-aided engineering (finite Element Analysis) execution design object function.The group generated at random is to be based on
The statistics and assessment realized in computer systems.
It checks in conjunction with attached drawing to embodiment of the present invention following detailed description, other purposes of the invention, feature and advantage
It will become significant.
Detailed description of the invention
The ACM of Fig. 1 solder joint is indicated.
Fig. 2 hexahedral element and equivalent bar unit.
Fig. 3 power is converted into local coordinate system from global coordinate, and then converts to the geometry of opposite elemental area
On center.
Fig. 4 is in the ACM connection of a separate unit.
The typical spot welding cross section Fig. 5.
Fig. 6 spot welding coordinate system.
Fig. 7 spot welding power calculating-schematic diagram.
Fig. 8 spot welding analytic process summary.
Specific embodiment
Two solder joints of journey can be modeled in the solder joint present invention of three ply board, are shared using CBAR unit with intermediate plate same
Node is combined using CBAR unit with solder joint, is also another mode for different attribute setting according to their diameter.
Equivalent simulation CBAR unit is also possible in other finite element softwares, for example, B31 unit.Note that in addition to
Except the power transmitting of each solder joint, in destination file, the available thickness of plate is also necessary.It it may be necessary to finger
Determine the destination file that these forms are requested in finite element input.
The details of the code and engagement conception of supporting spot welding finite element analysis also can provide elsewhere, but need one at this time
It is a little to explain, it herein include so-called " face contact method "
A pair of of disadvantage is a little welded with only with simple CBAR method to simulate:
1, it can have the tactic pattern for being intended to generate overall stiffness, such that solder joint rigidity is too small, thus vibrate
Mistake is generated in mode, etc.；
Unit 2, CBAR are required perpendicular to thin plate, this makes grid dividing more difficult, because needing at the flange of solder joint opposition
More or less consistent mesh.
" the face contact method " that the present invention uses has been attempted to handle one or two problem below, comprising:
1, load distribution is into grid for increasing " spider " unit of a rigidity
2, using CWELD unit
3, it indicates that solder joint melts core using an individual hexahedral element, passes through the method for multi-point constraint or equivalent unit
It is connected to plate up.
Single hexahedral element option is most praised highly, and such connection (ACM) is adopted in finite element program
It can be identified to CHEXA and RBE3 unit, or can be identified using C3D8 and DCOUP3D unit, Fig. 1 illustrates one
A example:
Note that hexahedral element (for example, CHEXA) must create in this way, if sequence of the node number in input storehouse
For G1, G2 ... G8, then G1-G4 is then associated with list 1, and G5-G8 is associated with list 2.When defining 3 tables
Single solder joint, then two hexahedral elements will shared 4 nodes in intermediate list.
Each lattice point power or multinode bonding force (equivalent force) from the node of hexahedral element will be used.
No matter which kind of mode is used, these power can all be converted into given power and torque and be applied on equivalent bar unit (Fig. 2),
These bar units are connected (Fig. 3) with the geometric center of face G1-G1 and G5-G8 in the coordinate system of equivalent bar.The seat of bar unit
Mark system is defined to Z axis in the center of fiqure of face G1-G1 and G5-G8, and X-axis is parallel to G1-G2 as far as possible.
Note that the prediction in toe of weld service life will be inaccurate if based on multiple spot bonding force is in electric welding.The common practice
It is to be calculated with hexahedral element using lattice point power in finite element solution procedure.
The advantage of these methods of the invention is:
The connection of 1 these types easily can divide software using business automatically to establish；
2 can create connection without having consistent dividing elements in flange.This means that sheet metal component can be independent stroke
Point, and spot welding can be moved easily；
The global stiffness of 3 models is more real using this Model Establishment, and can pass through the cross section of adjusting spot welding unit
Product is converted.(the long-pending ratio with practical spot welding cross-sectional area of cell cross-section need to be known, and as the contact area factor)；
4 these methods meet the needs of other laws (such as NVH) and promote General Model use.
The shortcomings that other general algorithms, is, although it is than being easier to implement using CBAR unit, and global stiffness or
Perhaps more preferable, but be easy to produce more concussion property in local stiffness, this, which will lead to, promotes the inconsistent of result in analysis of fatigue
Property:
The application of 1 connection the result is that may be divided independent by " independent to divide ".The position connecting with shell unit is to power
The fatigue life for having very important influence with torque, and therefore influencing；
It, as a result can be very poor if 2 MPC or RBE3 units are connect with the unit on flange angle；
It is connect if 3 MPC or RBE3 units share isolated node with neighbouring spot welding, it as a result can be excessively poor.
ACM method still can successfully apply (Fig. 4), if it is considered that if these factors.For example, across flange
During, at least need using three units, and it is best the result is that when be connected on each shell line have one solely
Vertical shell unit.It should also be noted that different modeling strategies has the characteristics that different, best calculated result is obtained, is needed
To use different S-N curves.
The introduction of step in detail below in fatigue mechanisms:
The recovery of power and torque
Dash area represents " nugget " of spot welding in Fig. 5.Example using local coordinate system as finite element solving, solder joint use
Buckstay CBAR unit is connected in the middle plane of the two plates of thin shell element.The length of bar unit is 0.5(s1+s2), this
In S1 and S2 be shell 1 and 2 thickness.Point 3 is on the axis of nugget and on the interface of two shells.For example, point 1
0.5 s1.All power and torque all think in the coordinate system of Fig. 6.This is a cartesian coordinate system, and Z axis runs through from point
1 arrives point 2.The setting of this point and Rupp et al. and CBAR unit setting in local coordinate system are all different, but more
It is easy.Global coordinate and the relationship of local coordinate system are as described in Figure 6.
The consistency of spot welding power and CBAR power in local coordinate system is as follows:
Here, s1 and s2 is respectively the thickness of shell surface 1 and 2.
Stress calculation
In order to run fatigue mechanisms, it would be desirable to which Stressing history, they calculate the power and torque put from every three
Time sequencing load history.The time history (FX, FY, FZ, MX, MY, MZ) of power and torque can be permanent by time series
It is obtained in the loop cycle of the spectrum type of tentering value or the acquisition of time step payload generator or these load；
Required stress is the structural stress of two versions and spot welding and nugget；
The structural stress of plate is the inner surface radial direction stress along the perimeter of two plate nuggets；
The radial stress of nugget depends on the principal stress of the nugget circumferential direction on a section, and two plates connect herein
It closes, based on nominal shear stress and normal stress (Fig. 7) in nugget that point.
Structural stress in plate is shear stress (FX, FY), the function of axis (FZ) and moment of flexure (MX, MY), and passes through knot
Structure unit transmits on (for example, CBAR) to plate, while changing with angle change.For example, for plate 1:
(from the contribution of moment of flexure, and including an empirical coefficient)
Also there is a similar equation in plate 2.
The calculating of empirical coefficient depends on 9 one group of material properties.Below it is typical steel spot welding numerical value:
Below it is typical aluminium spot welding numerical value:
Stress calculation in the nugget periphery of point 3 is as follows:
Shear stress:
Method corresponding force:
Then, it is formed according to the stress of shear stress and normal stress, we can calculate the complete maximum principal stress of nugget
(Absolute Maximum Principal stress):
Although the point in most of good design structures, which is welded in usual condition, will not undergo huge torsional load, once in a while point
Weldering can fail easily, be because of torsional fatigue.Torsional fatigue will be modeled separately as an apparent failure mode, it depends on
Circumference shear stress in each plate.Its calculating is as follows:
Note that Torsi on meter is option (based on torsion attribute is calculated) and needs additional materials attribute.
Analytic process summary
Spot welding analytic process of the present invention is summarized as follows shown in Fig. 8, based on information provided by payload generator, analysis engine
Power is created on three calculating points (plate 1, plate 2, nugget) and the time of torque (FX, FY, FZ, MX, MY, MZ) is gone through
Journey.It derives from time series, constant amplitude perhaps time step payload generator or from the week based on these three load
Phase circulation.
Claims (7)
1. a kind of structural fatigue computation processing method for spot welding junction in finite element algorithm, for using finite elements
The statistical method of fatigue life at spot welding is handled in algorithm, which is characterized in that the described method includes:
It is constructed based on coverboard structural unit included in commercial finite element software and is modeled at the exclusive structure spot welding of the present invention
Method；
Spot welding stress and torque conversion method are handled by the modeler model；
By after converting stress and torque result count the stress of spot welding all directions and the calculation method of torque；
The method that the stress and torque result calculated assesses spot-welded structures remaining life using fatigue statisic.
2. coverboard structural unit according to claim 1, which is characterized in that the cell type for being included includes CBAR mono-
Member, CBEAM unit, CWELD unit, " spider " unit, CHEXA unit, RBE3 unit, C3D8 unit and DCOUP3D are mono-
One of member is a variety of.
3. modeling method at exclusive structure spot welding according to claim 1, it is characterised in that use a kind of six face of solder joint
Body connection method (ACM).
4. spot welding stress according to claim 1 and torque conversion method, it is characterised in that by cell node stress transfer
Onto bar unit, then it is further continued for being transferred to the center of body unit by bar unit.
5. the calculation method of spot welding stress and torque according to claim 1, which is characterized in that overall calculating process includes
Nominal shear stress and method corresponding force.
6. the statistical method of spot-welded structures remaining life according to claim 1, it is characterised in that united using rain-flow counting
Meter method.
7. method described in -6 is a unified whole and indivisible program operation process according to claim 1, wherein
Any single claim can not represent object and feature of the present invention.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN111898307A (en) * | 2020-08-20 | 2020-11-06 | 哈尔滨工业大学 | Grading simplification method of fatigue simulation model of welding spot containing multi-strand wire |
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| JP2015001409A (en) * | 2013-06-13 | 2015-01-05 | 株式会社Ihi | Fatigue life evaluation method of structure |
| CN104573392A (en) * | 2015-01-27 | 2015-04-29 | 湖南大学 | Spot-weld fatigue life predicting method |
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|---|---|---|---|---|
| US20090211366A1 (en) * | 2003-05-12 | 2009-08-27 | Nihon University | Fatigue life estimating method for spot welded structure |
| JP2015001409A (en) * | 2013-06-13 | 2015-01-05 | 株式会社Ihi | Fatigue life evaluation method of structure |
| CN103995919A (en) * | 2014-04-17 | 2014-08-20 | 中国航空工业集团公司沈阳飞机设计研究所 | Method for calculating and analyzing fatigue life of airplane structure welding spots |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111898307A (en) * | 2020-08-20 | 2020-11-06 | 哈尔滨工业大学 | Grading simplification method of fatigue simulation model of welding spot containing multi-strand wire |
| CN111898307B (en) * | 2020-08-20 | 2022-08-02 | 哈尔滨工业大学 | Grading simplification method of fatigue simulation model of welding spot containing multi-strand wire |
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Application publication date: 20190517 |