CN105138751A - Structural dynamic boundary parameter determining method - Google Patents
Structural dynamic boundary parameter determining method Download PDFInfo
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- CN105138751A CN105138751A CN201510496600.6A CN201510496600A CN105138751A CN 105138751 A CN105138751 A CN 105138751A CN 201510496600 A CN201510496600 A CN 201510496600A CN 105138751 A CN105138751 A CN 105138751A
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Abstract
The present invention discloses a structural dynamic boundary parameter determining method. A design parameter of a to-be-designed boundary structure is determined. A dynamic finite element model of the to-be-designed boundary structure is built. A natural frequency and a vibration mode of the to-be-designed boundary structure are calculated. The determination of the design parameter of the to-be-designed boundary structure comprises determination of a parameter change range of bl-bu and a parameter changing step length of the design parameter of a to-be-designed boundary condition. When a relative error between a natural frequency of a target structure and the natural frequency of the to-be-designed boundary structure is not greater than a limit coefficient of the relative error, and a vibration mode of the target structure is closest to the vibration mode of the to-be-designed boundary structure, a design variable of the boundary condition is found out. The structural dynamic boundary parameter determining method provided by the present invention enables the lower-order natural frequency and the vibration mode of the designed boundary structure to be close to those of the target structure, and meets design requirements of a dynamic test on the boundary condition.
Description
Technical field
The invention belongs to Structural Dynamics field, being specifically related to a kind of method for determining testpieces boundary condition optimal design parameters.
Background technology
In the dynamic test of engineering structure, testpieces needs to carry out under fixture supports usually.But great majority test does not at present have the operating actual boundary condition of accurate simulation object construction, often design fixture by Static stiffness principle, cause the dynamics of plan boundary structure and object construction (as natural frequency, the vibration shape) to differ greatly, the test findings of mistake may be caused.
Therefore, need to provide a kind of new Structural Dynamics boundary design method, be close to constraint condition with the natural frequency required, with the Norm minimum of low order mode for optimization aim.Object is the dynamics enabling plan boundary structure farthest reflect object construction, and warranty test result is accurately credible.
Summary of the invention
In order to solve the problem, the invention provides a kind of Structural Dynamics boundary parameter defining method, determining the design parameter of border structure to be designed according to the boundary condition design parameter of object construction, mainly comprise the following steps:
S1, determine the boundary condition design parameter of object construction;
S2, set up the Dynamics Finite Element Model of object construction, calculate the eigenfrequncies and vibration models of described object construction;
S3, determine the design parameter of border structure to be designed, set up the Dynamics Finite Element Model of border structure to be designed, calculate the eigenfrequncies and vibration models of described border structure to be designed, the determination of the design parameter of described border structure to be designed comprises treats boundary condition design parameter determination parameter variation range b to described
l~ b
u, and Parameters variation step-length;
S4, repeated execution of steps S3, the relative error found out when the natural frequency of object construction and the natural frequency of border structure to be designed is not more than relative error when limitting coefficient, the vibration shape of object construction and the vibration shape of border structure to be designed closest to time boundary condition design variable.
Preferably, described boundary condition design parameter comprises the height and the width of testpieces xsect.
In such scheme preferably, the vibration shape of described object construction and the vibration shape of border structure to be designed closest to time computing formula as follows:
findb
Wherein,
for the vibration shape of object construction;
for the natural frequency of object construction;
for the vibration shape of plan boundary structure; f
rfor the natural frequency of border structure to be designed; M is the nominal modes of requirement; N is the exponent number of the natural frequency of requirement; η is relative error limit coefficient; b
lfor the lower limit of boundary condition design variable; b
ufor the upper limit of boundary condition design variable; N is the nodes of finite element model.
In such scheme preferably, described relative error limit coefficient η is 0 ~ 5%.
In such scheme preferably, the eigenfrequncies and vibration models of described calculating object construction comprises the front N rank natural frequency and front m first order mode that calculate object construction.
In such scheme preferably, the eigenfrequncies and vibration models of described calculating border structure to be designed comprises the front N rank natural frequency and front m first order mode that calculate border structure to be designed.
The method that the present invention relates to is simple, clear and definite, easy sequencing, design efficiency is higher, avoid design process repeatedly, save experimentation cost, can make the low price eigenfrequncies and vibration models of plan boundary structure and object construction close, meet the designing requirement of dynamic test to boundary condition, obtain more believable test findings.
Accompanying drawing explanation
Fig. 1 is Structural Dynamics boundary parameter defining method process flow diagram according to an embodiment of the invention.
Fig. 2 is cantilever beam structure schematic diagram embodiment illustrated in fig. 1.
Embodiment
For making object of the invention process, technical scheme and advantage clearly, below in conjunction with the accompanying drawing in the embodiment of the present invention, the technical scheme in the embodiment of the present invention is further described in more detail.In the accompanying drawings, same or similar label represents same or similar element or has element that is identical or similar functions from start to finish.Described embodiment is the present invention's part embodiment, instead of whole embodiments.Be exemplary below by the embodiment be described with reference to the drawings, be intended to for explaining the present invention, and can not limitation of the present invention be interpreted as.Based on the embodiment in the present invention, those of ordinary skill in the art, not making the every other embodiment obtained under creative work prerequisite, belong to the scope of protection of the invention.Below in conjunction with accompanying drawing, embodiments of the invention are described in detail.
In describing the invention; it will be appreciated that; term " " center ", " longitudinal direction ", " transverse direction ", "front", "rear", "left", "right", " vertically ", " level ", " top ", " end " " interior ", " outward " etc. instruction orientation or position relationship be based on orientation shown in the drawings or position relationship; be only the present invention for convenience of description and simplified characterization; instead of instruction or imply indication device or element must have specific orientation, with specific azimuth configuration and operation, therefore can not be interpreted as limiting the scope of the invention.
As shown in Figure 1, the invention provides a kind of Structural Dynamics boundary parameter defining method, determine the design parameter of border structure to be designed according to the boundary condition design parameter of object construction, mainly comprise the following steps:
S1, determine the boundary condition design parameter of object construction;
S2, set up the Dynamics Finite Element Model of object construction, calculate the eigenfrequncies and vibration models of described object construction;
S3, determine the design parameter of border structure to be designed, set up the Dynamics Finite Element Model of border structure to be designed, calculate the eigenfrequncies and vibration models of described border structure to be designed, the determination of the design parameter of described border structure to be designed comprises treats boundary condition design parameter determination parameter variation range b to described
l~ b
u, and Parameters variation step-length;
S4, repeated execution of steps S3, the relative error found out when the natural frequency of object construction and the natural frequency of border structure to be designed is not more than relative error when limitting coefficient, the vibration shape of object construction and the vibration shape of border structure to be designed closest to time boundary condition design variable.
In the present embodiment, described boundary condition design parameter comprises the height and the width of testpieces xsect, and Fig. 2 shows a cantilever beam structure, and the depth of section h of root 0.1m mono-section and width b is design variable.Target girder construction h=0.03m, b=0.01m.Now change sectional dimension h and b, make the front 3 rank natural frequencys of Design of Cantilever Beam border structure and object construction close, front 2 first order modes coincide.
In step s3, the determination of the design parameter of described border structure to be designed comprises and treats boundary condition design parameter determination parameter variation range b to described
l~ b
u, and Parameters variation step-length sets in advance, in the present embodiment, is that example is as parameter variation range b with h=0.02-0.04m, b=0.005-0.015
l~ b
uwith step-length 0.001 for rate of change, calculate the eigenfrequncies and vibration models of border structure to be designed respectively, such as, as h=0.021, b=0.006, calculate once the eigenfrequncies and vibration models of border structure to be designed, and substitute in step S4, first check that the relative error of the natural frequency of its natural frequency whether meeting object construction and border structure to be designed is not more than relative error and limits coefficient, if met, then calculate the vibration shape of object construction and the Vibration Mode Difference of border structure to be designed again, and preserve; Vibration Mode Difference corresponding to next h, b is calculated, until it is minimum to find out Vibration Mode Difference according to step-length 0.001.Should be understood that, the Vibration Mode Difference described in the present embodiment is simple difference not, and its concrete computation process is as follows.
The present embodiment sets up the Dynamics Finite Element Model of object construction and plan boundary structure respectively, and carries out model analysis, determines the front 3 rank natural frequencys of concern and front 2 first order modes.The vibration shape of described object construction and the vibration shape of border structure to be designed closest to time computing formula as follows:
findb
Wherein,
for the vibration shape of object construction;
for the natural frequency of object construction;
for the vibration shape of plan boundary structure; f
rfor the natural frequency of border structure to be designed; M is the nominal modes of requirement; N is the exponent number of the natural frequency of requirement; η is relative error limit coefficient; b
lfor the lower limit of boundary condition design variable; b
ufor the upper limit of boundary condition design variable; N is the nodes of finite element model.
According to Optimization Design, design parameter h and b of continuous adjusted design border structure, until the front 3 rank natural frequencys of plan boundary structure and object construction meet error requirements, front 2 first order modes are close.
Table 1 shows front 3 rank natural frequency comparing results.Visible, the eigenfrequncies and vibration models of plan boundary structure coincide with target structure height within the scope of designing requirement, meets engineering design requirements.
Table 1
| Exponent number | 1 | 2 | 3 |
| Object construction 1./Hz | 37.968 | 281.86 | 805.76 |
| Plan boundary structure 2./Hz | 38.470 | 284.20 | 797.59 |
| Relative error [(2.-1.)/1.] | 1.32％ | 0.83％ | -1.01％ |
Should be understood that, concrete limits of error setting is determined on a case-by-case basis, and for meeting the designing requirement of dynamic test to boundary condition, obtains more believable test findings, and general relative error limit coefficient η is no more than 5%.
In the present embodiment, the eigenfrequncies and vibration models of described calculating object construction comprises the front N rank natural frequency and front m first order mode that calculate object construction; And,
The eigenfrequncies and vibration models of described calculating border structure to be designed comprises the front N rank natural frequency and front m first order mode that calculate border structure to be designed.
Should be understood that, front N rank natural frequency and front m first order mode are the intrinsic parameter of structure, and the present embodiment is described above, shows front 3 rank natural frequencys and front 2 first order modes.
The method that the present invention relates to is simple, clear and definite, easy sequencing, design efficiency is higher, avoid design process repeatedly, save experimentation cost, can make the low price eigenfrequncies and vibration models of plan boundary structure and object construction close, meet the designing requirement of dynamic test to boundary condition, obtain more believable test findings.
Finally it is to be noted: above embodiment only in order to technical scheme of the present invention to be described, is not intended to limit.Although with reference to previous embodiment to invention has been detailed description, those of ordinary skill in the art is to be understood that: it still can be modified to the technical scheme described in foregoing embodiments, or carries out equivalent replacement to wherein portion of techniques feature; And these amendments or replacement, do not make the essence of appropriate technical solution depart from the spirit and scope of various embodiments of the present invention technical scheme.
Claims (6)
1. a Structural Dynamics boundary parameter defining method, determine the design parameter of border structure to be designed according to the boundary condition design parameter of object construction, it is characterized in that, comprising:
S1, determine the boundary condition design parameter of object construction;
S2, set up the Dynamics Finite Element Model of object construction, calculate the eigenfrequncies and vibration models of described object construction;
S3, determine the design parameter of border structure to be designed, set up the Dynamics Finite Element Model of border structure to be designed, calculate the eigenfrequncies and vibration models of described border structure to be designed, the determination of the design parameter of described border structure to be designed comprises treats boundary condition design parameter determination parameter variation range b to described
l~ b
u, and Parameters variation step-length;
S4, repeated execution of steps S3, the relative error found out when the natural frequency of object construction and the natural frequency of border structure to be designed is not more than relative error when limitting coefficient, the vibration shape of object construction and the vibration shape of border structure to be designed closest to time boundary condition design variable.
2. Structural Dynamics boundary parameter defining method as claimed in claim 1, is characterized in that: described boundary condition design parameter comprises the height and the width of testpieces xsect.
3. Structural Dynamics boundary parameter defining method as claimed in claim 1, is characterized in that: the vibration shape of described object construction and the vibration shape of border structure to be designed closest to time computing formula as follows:
findb
b
l≤b≤b
u
Wherein,
for the vibration shape of object construction;
for the natural frequency of object construction;
for the vibration shape of plan boundary structure; f
rfor the natural frequency of border structure to be designed; M is the nominal modes of requirement; N is the exponent number of the natural frequency of requirement; η is relative error limit coefficient; b
lfor the lower limit of boundary condition design variable; b
ufor the upper limit of boundary condition design variable; N is the nodes of finite element model.
4. Structural Dynamics boundary parameter defining method as claimed in claim 3, is characterized in that: described relative error limit coefficient η is 0 ~ 5%.
5. Structural Dynamics boundary parameter defining method as claimed in claim 1, is characterized in that: the eigenfrequncies and vibration models of described calculating object construction comprises the front N rank natural frequency and front m first order mode that calculate object construction.
6. Structural Dynamics boundary parameter defining method as claimed in claim 1, is characterized in that: the eigenfrequncies and vibration models of described calculating border structure to be designed comprises the front N rank natural frequency and front m first order mode that calculate border structure to be designed.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114813006A (en) * | 2022-06-29 | 2022-07-29 | 中国飞机强度研究所 | Vibration fatigue test method for airplane overhanging structure, supporting structure and readable medium |
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| CN104778377A (en) * | 2015-05-04 | 2015-07-15 | 中国矿业大学 | Composite beam bending vibration inherent frequency analytical method |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN103399971A (en) * | 2013-05-09 | 2013-11-20 | 南车株洲电力机车研究所有限公司 | Fan tower inherent frequency analyzing method based on conservation of mechanical energy |
| CN104778377A (en) * | 2015-05-04 | 2015-07-15 | 中国矿业大学 | Composite beam bending vibration inherent frequency analytical method |
Non-Patent Citations (1)
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| 高跃飞: "结构动力学边界条件优化设计及工程实现方法研究", 《中国优秀博硕士学位论文全文数据库 (博士) 基础科学辑》 * |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114813006A (en) * | 2022-06-29 | 2022-07-29 | 中国飞机强度研究所 | Vibration fatigue test method for airplane overhanging structure, supporting structure and readable medium |
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Application publication date: 20151209 |