CN103559361B - A kind of optimization method of component strength and stress analysis method thereof - Google Patents

Abstract

The invention discloses a kind of stress analysis method of component, comprise the following steps: finite element analysis is carried out to component, obtain the linear stress distribution of unit and the sideline load at two ends; Inserting first, second node respectively region of stress concentration is inside and outside, is three subelements by this dividing elements; According to the force and moment of unit respectively with the principle equal with resultant moment of making a concerted effort of three subelements, obtain three subelements sideline load separately; Substitute the linear stress distribution of this unit with the multistage linear stress distribution of three subelements, obtain the stress analysis value of this unit.The present invention adopts the linear load of the original unit of piecewise linearity load diatibution matching to distribute, the analysis result correction that larger unit size is tried to achieve and actual conditions more close, significantly enhance component stress analyze precision; Can increase work efficiency simultaneously.On this basis, the present invention also provides a kind of optimization method of component strength.

Description

A kind of optimization method of component strength and stress analysis method thereof

Technical field

The present invention relates to the structure member design of the industries such as boats and ships, ocean platform, aviation and vehicle, be specifically related to optimization method and the stress analysis method thereof of component strength.

Background technology

Finite element analysis (FEA, FiniteElementAnalysis) be a kind of modern computing method, it adopts the method for mathematical approach to simulate actual physical system (geometry and load working condition), utilize simple and interactional element (i.e. unit), remove with the unknown quantity of limited quantity the real system approaching unlimited unknown quantity.Finite element analysis is utilized to carry out detailed mechanical analysis to structural member (component), component can be obtained under real use state as far as possible really by force information, thus safety evaluation can be carried out in the design phase to the various problems that may occur, and carry out corresponding design parameter amendment.Record according to interrelated data, the structural design defect of a new product has more than 60% can eliminate in the design phase, and therefore, the such analysis means of finite element analysis is performed meritorious deeds never to be obliterated.At present, finite element analysis has been widely used in the field of engineering technology of different subject, to guarantee the working strength of component.

When carrying out finite element analysis, for the component that physical dimension is larger, larger size of mesh opening (unit size) usually can be adopted to carry out modeling, to improve the efficiency of analytical calculation.But, for (the region that the rigidity of structure being generally component changes greatly, region that the stress gradient on component changes greatly, also be region of stress concentration), because its stress distribution generally shows as nonlinear Distribution, therefore, adopt larger unit size to carry out finite element analysis, the nonlinear Distribution situation of the stress of this unit can not be described well, specifically refer to following example.

Component shown in Fig. 1 is a kind of tee T welding joint, wherein, and the long 3000mm of base plate 11, wide 1000mm; The long 1000mm of riser 12, high 500mmm; The thickness of slab t of base plate 11 and riser 12 is 5mm; The base of riser 12 is welded on the right-hand member end face of base plate 11, and the height of weld seam 13 is 5mm.The right-hand member of this tee T welding joint is fixed, and left end loads, and adopts Shell Finite Element to carry out finite element analysis.When the length of setup unit is 100 × t=500mm, riser 12 is divided in order to the unit of two as shown in Figure 2 (A1, A2), the linear load distribution in the stress distribution on unit A1 as shown in Fig. 4 cathetus Z1.

But, in said structure, base plate 11 and weld seam 13 position of riser 12 necessarily have obvious stress and concentrate, that is, in fact the stress distribution in this region should show as obvious nonlinear Distribution, obviously, there is a certain distance with actual conditions in the linear load distribution in Fig. 4 shown in Z1.In order to obtain relatively accurate result, when carrying out finite element analysis, when stress evaluation carries out for thin portion structure (particularly region of stress concentration), usually need refinement Local grid.For the structure shown in Fig. 1, when the length of setup unit is 12.5 × t=62.5mm as shown in Figure 3, unit A1 is divided in order to 8 unit, by obtaining the curve in Fig. 4 shown in Z2 after finite element analysis, curve Z2 just can show the non-linear stress distribution situation of the root of weld well.

As can be seen here, in the finite element analysis process of component, the Influence on test result that unit size counter stress is analyzed is comparatively large, especially more obvious at region of stress concentration.Although can obtain relatively accurate result by the mode of tessellated mesh, this processing mode workload is large, and solution efficiency is low, realizes more loaded down with trivial details.

In view of this, be urgently optimized design for existing finite element method, to improve efficiency and the precision of component finite element analysis, improve the strength reliability of component further.

Summary of the invention

For above-mentioned defect, the technical matters that the present invention solves is a kind of stress analysis method providing component, to guarantee the precision that component stress is analyzed, effectively improves work efficiency simultaneously.On this basis, the present invention also provides the component strength optimization method of a kind of this stress analysis method of application.

The stress analysis method of component provided by the invention, comprises the following steps:

Finite element analysis is carried out to component, obtains the linear stress distribution of each unit and the sideline load at these unit two ends;

In the region of stress concentration of the described unit of stress concentration portion position, inserting first node, insert Section Point outward at region of stress concentration, is three subelements by this dividing elements;

According to the force and moment of described unit respectively with the principle equal with resultant moment of making a concerted effort of three described subelements, determine three described subelements sideline load separately;

Substitute the linear stress distribution of this unit with the multistage linear stress distribution of the sideline load composition of three described subelements, obtain the stress analysis value of this unit.

Preferably, corresponding unit is divided into first, second, and third subelement by described first node and Section Point successively, wherein, the stress distribution of described 3rd subelement is for all to carry, and sideline load ff3=(f1+f2)/2, wherein, f1 and f2 is the sideline load at these unit two ends.

Preferably, sideline, the two ends load ff1 of described first subelement and ff2 is obtained by following formulae discovery:

$\begin{array}{c}\mathrm{ff}1=\frac{({l1}^2+l1\·l2+L^2)}{2\·l1\·(l1+l2)}\·f1+\frac{({l1}^2+l1\·l2-L^2)}{2\·l1\·(l1+l2)}\·f2;\\ \mathrm{ff}2=\frac{[{(l1+l2)}^2-L^2]}{2\·{(l1+l2)}^2}\·f1+\frac{[{(l1+l2)}^2+L^2]}{2\·{(l1+l2)}^2}\·f2;\end{array}$

Wherein, L is the length of described unit, and l1 is the distance between sideline load that described first node and this unit are larger, and l2 is the distance between described Section Point and first node.

Preferably, the stress analysis value σ of described first node _s1with the stress analysis value σ of Section Point _s2obtain respectively by following formulae discovery:

$\begin{array}{c}{\mathrm{\σ}}_{s1}=\frac{\mathrm{ff}1}{t}+\frac{6\·\mathrm{mm}1}{t^2};\\ {\mathrm{\σ}}_{s2}=\frac{\mathrm{ff}2}{t}+\frac{6\·\mathrm{mm}2}{t^2};\end{array}$

Wherein, t is the component thickness that described unit is corresponding, and mm1, mm2 and mm3 are respectively the sideline load moment of first, second, and third subelement, and mm3=(m1+m2)/2;

$\begin{array}{c}\mathrm{mm}1=\frac{({l1}^2+l1\·l2+L^2)}{2\·l1\·(l1+l2)}\·m1+\frac{({l1}^2+l1\·l2-L^2)}{2\·l1\·(l1+l2)}\·m2\\ \mathrm{mm}2=\frac{[{(l1+l2)}^2-L^2]}{2\·{(l1+l2)}^2}\·m1+\frac{[{(l1+l2)}^2+L^2]}{2\·{(l1+l2)}^2}\·m2\end{array};$

Wherein, m1 and m2 respectively with the sideline load moment of this unit.

Preferably, described first node is positioned at the marginal position of described region of stress concentration.

Preferably, l2 >=l1, l1 are the distance between sideline load that first node and this unit are larger, and l2 is the distance between Section Point and first node.

Preferably, l2 ﹤ 1.5l1.

Preferably, described component is tee T welding joint.

Present invention also offers a kind of optimization method of component strength, comprise the following steps:

Step 1, carries out three-dimensional modeling to component;

Step 2, imports finite element analysis software by the three-dimensional modeling data of component and carries out initial analysis, obtain the stress distribution of each unit;

Step 3, adopts the method for claim 1 to carry out stress analysis, obtains the stress analysis value of corresponding units;

Step 4, compares the judged result obtaining front member and whether meet design requirement by described stress analysis value and designing requirement, when described judged result is for meeting design requirement, assert that the project organization of this component is reasonable, exiting; Otherwise the structure of amendment component, goes to step 1.

In the stress analysis method of component provided by the invention, after finite element initial analysis is carried out to component, for the unit of stress concentration portion position, first node is inserted at stress distribution gradient visibility point, Section Point is inserted in the unconspicuous position of stress distribution gradient, adopt the original linear load distribution of piecewise linearity load diatibution matching, the analysis result can tried to achieve larger unit size revise and actual conditions more close, obviously reliably improve component stress analyze precision; In addition, this method determines the distribution of load more one by one after not needing division unit, substantially increase work efficiency simultaneously.

In preferred version of the present invention, first node is positioned at the edge of region of stress concentration, 1.5l1 ﹥ l2 >=l1, l1 is the distance between sideline load that first node and this unit are larger, l2 is the distance between Section Point and first node, the mode of this selection node, analysis result closer to actual conditions, from improving analysis precision further.

Accompanying drawing explanation

Fig. 1 is a kind of structural representation of typical tee T welding joint;

Fig. 2 is for adopting existing general finite element analysis method with the dividing elements schematic diagram of larger unit size to the welding joint of tee T shown in Fig. 1;

Fig. 3 is for adopting existing general finite element analysis method with the single-row division schematic diagram of less unit size to the welding joint of tee T shown in Fig. 1;

The stress distribution contrast schematic diagram that Fig. 4 obtains for adopting the dividing elements method shown in Fig. 2, Fig. 3.

The stress analysis Method And Principle schematic diagram that Fig. 5 is the component described in embodiment;

The stress analysis method flow diagram that Fig. 6 is the component described in embodiment.

Embodiment

Core of the present invention is to provide a kind of stress analysis method of component, after optimal design is carried out on the basis of general finite element analysis, can guarantee the precision of stress analysis on the one hand, can effectively increase work efficiency simultaneously.Carry out the structural design of component on this basis, the needs of engineering reality can be met preferably.Technical scheme of the present invention is described in further detail, so that those skilled in the art understand better below in conjunction with explanation the drawings and specific embodiments.

Without loss of generality, the detailed introduction for technical solution of the present invention is still carried out for the element structure shown in Fig. 1.

Component strength optimization method described in present embodiment comprises the following steps:

Step 1: three-dimensional modeling is carried out to component (tee T welding joint).Three-dimensional modeling adopts the Three-dimensional Design Software of existing maturation to complete, such as Pro/Engineer, SolidWorks etc.

Step 2: the three-dimensional modeling data of component is imported finite element analysis software (as: LUSAS, MSC.Nastran, Ansys, Abaqus, LMS-Samtech, Algor, Femap/NXNastran, Hypermesh, COMSOLMultiphysics, FEPG etc.) in, and adopt larger unit size to carry out stress and strain model, finite element analysis software is utilized to carry out initial analysis to the stress distribution of above-mentioned component, obtain the stress distribution of each unit, wherein, the linear distribution of stress distribution as shown in Z1 in Fig. 4 of the unit of stress concentration portion position, seif-citing rate concentrated position distally, stress (load) reduces gradually.

In this embodiment, the length setting of unit is 100 × t=500mm, for side (dividing as separatrix using the thickness of slab center of riser 12) wherein, riser 12 is divided altogether in order to first module A1 and second unit A2 two unit, and base plate 11 is divided altogether in order to B1 ~ B6 six unit.

Step 3: the stress distribution for the unit of stress concentration portion position is revised, obtains the multi-line section stress distribution of corresponding units, and then obtains the stress analysis value of corresponding units.

Step 4: above-mentioned stress analysis value and designing requirement are compared the judged result obtaining front member and whether meet design requirement, when described judged result is for meeting design requirement, assert that the project organization of this component is reasonable, exiting; Otherwise the structure (as revised the size of riser 12, the height of amendment weld seam 13 or width etc.) of amendment component, then, forwards step 1 to and re-starts analysis.

In the above-mentioned methods, step 3 is the committed step of technical solution of the present invention, is below described in further detail.

As shown in Figure 6, the stress analysis method of the component described in the specific embodiment of the invention, comprises the following steps:

Step 21: carry out finite element analysis to component, obtains the linear stress distribution of each unit and the sideline load at these unit two ends.

For the stress distribution of unit A1 (linear load distribution as shown in Figure 5), wherein, the length of unit is L, and left end corresponds to weld seam position in Fig. 4, and right-hand member corresponds to free end in Fig. 4, left end load (stress) is maximum, magnitude of load is f1, and right-hand member load (stress) is minimum, and magnitude of load is f2, therefore, that this unit is F1=(f1+f2 with joint efforts) × L/2.

Step 22: on the unit A1 of stress concentration portion position, two nodes are inserted in the length L direction along unit successively, and these two nodes are defined as a first node J1 and the second two node J2 respectively.Unit A1 is divided into first, second, and third totally three subelements Z1, Z2, Z3 by a first node J1 and the second two node J2 successively, wherein, first node J1 is positioned at the region of stress concentration on component, stress distribution gradient in this region is obvious, the distance of first node J1 and unit left end sideline load is l1, the length being equivalent to the first subelement Z1 is l1, and the sideline load at two ends is respectively ff1 and ff2.Section Point J2 is positioned at outside the region of stress concentration on component, and the stress distribution gradient in this region is not obvious.Distance between Section Point J2 and first node J1 is l2, and the length being equivalent to the second subelement Z2 is l2, and the sideline load at two ends is respectively ff2 and ff3.So, the length l3=(L-l1-l2 of the 3rd subelement Z3), the stress distribution on the 3rd subelement Z3 is horizontal linear distribution, namely thinks that the load ff3 on the 3rd subelement Z3 is evenly distributed, ff3=(f1+f2)/2.

Like this, the F2 that makes a concerted effort of first, second, and third subelement is:

$F2=(\mathrm{ff}1+\mathrm{ff}2)\·\frac{l1}{2}+(\mathrm{ff}2+\mathrm{ff}3)\·\frac{l2}{2}+\mathrm{ff}2\·l3;$

Step 23, the F2 that makes a concerted effort in view of power F1=tri-subelements of, unit, therefore,

$(f1+f2)\·\frac{L}{2}=(\mathrm{ff}1+\mathrm{ff}2)\·\frac{l1}{2}+(\mathrm{ff}2+\mathrm{ff}3)\·\frac{l2}{2}+\mathrm{ff}3\·l3.$

Equal with the resultant moment of three subelements according to the moment of unit again, can obtain:

$\begin{array}{c}f2\·\frac{L^2}{2}+(f1-f2)\·\frac{L^2}{6}=\\ \mathrm{ff}3\·l3\·(l1+l2+\frac{l3}{2})+(\mathrm{ff}1-\mathrm{ff}2)\·\frac{{l1}^2}{6}+(\mathrm{ff}3-\mathrm{ff}2)\·\frac{l2}{2}\·(l1+\frac{2\·l2}{3})+\mathrm{ff}2\·\frac{{(l1+l2)}^2}{2}\end{array}$

Tried to achieve by above-mentioned two equatioies:

$\begin{array}{c}\mathrm{ff}1=\frac{({l1}^2+l1\·l2+L^2)}{2\·l1\·(l1+l2)}\·f1+\frac{({l1}^2+l1\·l2-L^2)}{2\·l1\·(l1+l2)}\·f2\\ \mathrm{ff}2=\frac{[{(l1+l2)}^2-L^2]}{2\·{(l1+l2)}^2}\·f1+\frac{[{(l1+l2)}^2+L^2]}{2\·{(l1+l2)}^2}\·f2\end{array}---\left(1\right)$

Step 24, in like manner: establish m1, m2 to be respectively the sideline load moment of unit A1;

Mm1, mm2 and mm3 are respectively the sideline load moment of first, second, and third subelement Z1, Z2 and Z3, and mm3 horizontal distribution also equals (m1+m2)/2;

The same, have:

$\begin{array}{c}\mathrm{mm}1=\frac{({l1}^2+l1\·l2+L^2)}{2\·l1\·(l1+l2)}\·m1+\frac{({l1}^2+l1\·l2-L^2)}{2\·l1\·(l1+l2)}\·m2\\ \mathrm{mm}2=\frac{[{(l1+l2)}^2-L^2]}{2\·{(l1+l2)}^2}\·m1+\frac{[{(l1+l2)}^2+L^2]}{2\·{(l1+l2)}^2}\·m2\end{array}---\left(2\right)$

Like this, the analytic value of the non-linear stress distribution of first node J1 and Section Point J2 is respectively:

$\begin{array}{c}{\mathrm{\σ}}_{s1}={\mathrm{\σ}}_{m1}+{\mathrm{\σ}}_{b1}=\frac{\mathrm{ff}1}{t}+\frac{6\·\mathrm{mm}1}{t^2}\\ {\mathrm{\σ}}_{s2}={\mathrm{\σ}}_{m2}+{\mathrm{\σ}}_{b2}=\frac{\mathrm{ff}2}{t}+\frac{6\·\mathrm{mm}2}{t^2}\end{array}---\left(3\right)$

In above introduction, with the explanation of unit A1 exemplarily property, other unit, as similar in A2, B1, B2 and A1, no longer repeat to introduce.

Method provided by the invention, uses the principle of sectional linear fitting, and by the linear distribution on larger unit, it fits to piecewise linearity distribution, then obtains the analytic value of non-linear stress distribution.When carrying out finite element analysis to large scale structure, can first analyze with larger size of mesh opening, after the stress distribution obtaining unit, adopt formula (1) and (2) to revise, then redefine actual non-linear stress distribution analytic value according to formula (3), do not need to repartition unit, solution efficiency is high, meanwhile, the result obtained and actual stress distribute more close, and analysis precision is obviously improved.

Through pilot production, result is compared to the factor of stress concentration SCF of the root of weld in above-mentioned example as follows:

(1) general finite element analysis is adopted, the SCF=6.25 tried to achieve when setting the unit size shown in Fig. 2;

(2) the theoretical reference value SCF=2.79 adopting solid element to try to achieve;

(3) adopt method provided by the invention, ask the SCF=2.82 obtained.

Obviously, above-mentioned comparing result shows, adopts method provided by the invention, significantly improves the efficiency in FEM (finite element) calculation process and precision, can guarantee the working strength of component, expands the applicability of Finite Element Method in engineer applied.

The above is only the preferred embodiment of the present invention; it should be pointed out that for those skilled in the art, under the premise without departing from the principles of the invention; can also make some improvements and modifications, these improvements and modifications also should be considered as protection scope of the present invention.

Claims (9)

1. the stress analysis method of component, is characterized in that, comprise the following steps:

Finite element analysis is carried out to component, obtains the linear stress distribution of each unit and the sideline load at these unit two ends;

Length direction along the described unit of stress concentration portion position inserts first node and Section Point successively, first node is inserted in the region of stress concentration of the described unit of stress concentration portion position, inserting Section Point outward at region of stress concentration, is three subelements by this dividing elements;

According to the force and moment of described unit respectively with the principle equal with resultant moment of making a concerted effort of three described subelements, determine three described subelements sideline load separately;

Substitute the linear stress distribution of this unit with the multistage linear stress distribution of the sideline load composition of three described subelements, obtain the stress analysis value of this unit.

2. the stress analysis method of component according to claim 1, it is characterized in that, corresponding unit is divided into first, second, and third subelement by described first node and Section Point successively, wherein, the stress distribution of described 3rd subelement is for all to carry, and sideline load ff3=(f1+f2)/2, wherein, f1 and f2 is the sideline load at described unit two ends.

3. the stress analysis method of component according to claim 2, is characterized in that, sideline, two ends load ff1 and the ff2 of described first subelement are obtained by following formulae discovery:

$ff1=\frac{(l{1}^2+l1\·l2+L^2)}{2\·l1\·(l1+l2)}\·f1+\frac{(l{1}^2+l1\·l2-L^2)}{2\·l1\·(l1+l2)}\·f2;$

$ff2=\frac{\[{(l1+l2)}^2-L^2\]}{2\·{(l1+l2)}^2}\·f1+\frac{\[{(l1+l2)}^2+L^2\]}{2\·{(l1+l2)}^2}\·f2;$

Wherein, L is the length of described unit, and l1 is the distance between sideline load that described first node and this unit are larger, and l2 is the distance between described Section Point and first node.

4. the stress analysis method of component according to claim 3, is characterized in that, the stress analysis value σ of described first node _s1with the stress analysis value σ of Section Point _s2obtain respectively by following formulae discovery:

${\mathrm{\σ}}_{s1}=\frac{ff1}{t}+\frac{6\·mm1}{t^2};$

${\mathrm{\σ}}_{s2}=\frac{ff2}{t}+\frac{6\·mm2}{t^2};$

Wherein, t is the component thickness that described unit is corresponding, and mm1, mm2 and mm3 are respectively the sideline load moment of first, second, and third subelement, and mm3=(m1+m2)/2;

$mm2=\frac{\[{(l1+l2)}^2-L^2\]}{2\·{(l1+l2)}^2}\·m1+\frac{\[{(l1+l2)}^2+L^2\]}{2\·{(l1+l2)}^2}\·m2;$

Wherein, m1 and m2 is respectively the sideline load moment of this unit.

5. the stress analysis method of component according to claim 1, is characterized in that, described first node is positioned at the marginal position of described region of stress concentration.

6. the stress analysis method of component according to claim 5, is characterized in that, l2 >=l1, l1 are the distance between sideline load that first node and this unit are larger, and l2 is the distance between Section Point and first node.

7. the stress analysis method of component according to claim 6, is characterized in that, l2 ﹤ 1.5l1.

8. the stress analysis method of the component according to claim 1 to 7 any one, is characterized in that, described component is tee T welding joint.

9. the optimization method of component strength, is characterized in that, comprises the following steps:

Step 1, carries out three-dimensional modeling to component;

Step 2, imports finite element analysis software by the three-dimensional modeling data of component and carries out initial analysis, obtain the stress distribution of each unit;

Step 3, adopts the method according to any one of claim 1 to 7 to carry out stress analysis, obtains the stress analysis value of corresponding units;

Step 4, compares the judged result obtaining front member and whether meet design requirement by described stress analysis value and designing requirement, when described judged result is for meeting design requirement, assert that the project organization of this component is reasonable, exiting; Otherwise the structure of amendment component, goes to step 1.