CN110083922B - Method for preventing buckling failure in steel oval end socket - Google Patents

Method for preventing buckling failure in steel oval end socket Download PDF

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CN110083922B
CN110083922B CN201910327075.3A CN201910327075A CN110083922B CN 110083922 B CN110083922 B CN 110083922B CN 201910327075 A CN201910327075 A CN 201910327075A CN 110083922 B CN110083922 B CN 110083922B
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end socket
pressure
buckling
seal head
elliptical
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CN110083922A (en
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郑津洋
李克明
张泽坤
顾超华
徐平
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Zhejiang University ZJU
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Zhejiang University ZJU
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    • G06—COMPUTING; CALCULATING OR COUNTING
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    • G06F30/00—Computer-aided design [CAD]
    • G06F30/20—Design optimisation, verification or simulation

Abstract

The invention relates to the field of pressure vessels, and aims to provide a method for preventing buckling failure in an inner pressure of a steel oval end socket. The method comprises the following steps: determining the inner diameter, the inner height and the thickness of the preliminarily selected elliptical seal head and the yield strength of the material used by the seal head according to the process requirements; and if the calculated buckling pressure of the seal head is smaller than the internal pressure of the seal head under the process condition, the size or the material of the seal head is adjusted and then calculated again until the calculated buckling pressure is larger than the internal pressure of the seal head under the process condition. The invention has theoretical basis, simple formula format and convenient calculation; the method has comprehensive advantages in the aspects of accuracy, engineering practicability, calculation convenience and the like, not only covers the standard elliptical head commonly used in engineering, but also can be suitable for elliptical heads with other diameter-height ratios, and has relatively stronger engineering practicability.

Description

Method for preventing buckling failure in steel oval end socket
Technical Field
The invention relates to the field of pressure containers, in particular to a method for preventing buckling failure in an inner pressure of a steel oval end socket.
Background
The convex seal head is an important element of the pressure container and is widely applied to industries such as petroleum, chemical engineering, nuclear power and the like. Compared with a hemispherical end socket, the elliptical end socket is low in height and easy to form; compared with a disc-shaped end socket, the stress distribution of the oval end socket is more uniform; therefore, the elliptical seal head is one of the more convex seal heads applied to the current medium-pressure and low-pressure containers. Meanwhile, the number of the used inner pressure containers in the engineering is far larger than that of the outer pressure containers, so that the failure mode and the bearing capacity of the inner pressure oval end socket are more worth paying attention.
Because the transition region of the oval end socket bears the hoop compressive stress under the action of internal pressure, the oval end socket can be subjected to buckling failure, particularly the ultra-large and ultra-thin oval end socket. Buckling failure is an important failure mode that needs to be prevented by an internal pressure oval head. In order to prevent buckling failure of the internal-pressure elliptical head, the internal-pressure buckling pressure of the elliptical head needs to be predicted. Therefore, the buckling pressure prediction formula of the internal pressure elliptical seal head is established, and the method has important significance for preventing buckling failure of the elliptical seal head.
At present, formulas for predicting buckling pressure of the internal pressure steel oval end socket mainly comprise a Tovstik theoretical formula, a Galley elastic buckling pressure prediction formula, a Galley plastic buckling pressure prediction formula, a Roche & Alix elastic buckling pressure prediction formula and a Roche & Alix empirical formula.
(1) Tovstik theoretical formula
Tovstik gives a theoretical formula for calculating the elastic buckling pressure of the internal pressure elliptical seal head:
Figure BDA0002036013430000011
in the formula:
Figure BDA0002036013430000012
Dithe inner diameter of the elliptic end socket is in mm; e is the modulus of elasticity in MPa; h isiThe inner height of the oval end socket is in mm; pbIs the buckling pressure in MPa; t is the thickness of the oval end socket, and the unit is mm; v is the Poisson's ratio. However, this formula is only applicable to oval heads (D) of small heighti/2hiNot less than 3.3), and especially the standard elliptical seal head (diameter-height ratio) commonly used in engineering can not be predicted
Figure BDA0002036013430000013
) The buckling pressure.
(2) Galley elastic buckling pressure prediction formula
Galley calculates the elastic buckling pressure of the standard elliptical seal head by using a numerical analysis program, and obtains a prediction formula of the elastic buckling pressure of the standard elliptical seal head by fitting through parametric analysis:
Pb＝455E(Di/t)-2.5
the application range of the radius-thickness ratio of the formula is 750 < DiThe/t is less than 1500, but the diameter-thickness ratio is not wide in application range. Another big disadvantage is that the formula is only applicable to standard elliptical heads, and elliptical heads with other aspect ratios cannot be predicted.
(3) Galley plastic buckling prediction formula
Galley calculates the plastic buckling pressure of the standard elliptical head by using a numerical analysis program, and obtains a prediction formula of the plastic buckling pressure of the standard elliptical head by fitting through parametric analysis:
Pb＝10.4Sy(Di/t)-1.25
in the formula: syYield strength is given in MPa. The application range of the radius-thickness ratio of the formula is more than 600DiThe t is less than 1500, but the diameter-thickness ratio is not wider than the application range. In addition, the formula is only suitable for the standard elliptical seal head, and elliptical seal heads with other diameter-height ratios cannot be predicted.
(4) Roche & Alix elastic buckling calculation formula
A prediction formula of the elastic buckling pressure of the internal pressure oval seal head is given based on numerical calculation results of Roche R.L. and Alix M:
Figure BDA0002036013430000021
in the formula: keIs a coefficient related to the aspect ratio. When in use
Figure BDA0002036013430000022
When, Ke＝1。
Research shows that the internal pressure buckling of the steel oval end socket with the common size occurs after the material enters the plastic region, and the steel oval end socket belongs to plastic buckling, so that the buckling pressure of the steel oval end socket cannot be accurately predicted by an elastic buckling pressure prediction formula (Tovstik theoretical formula, Galley elastic buckling pressure prediction formula and Roche & Alix elastic buckling pressure calculation formula).
(5) Roche & Alix empirical formula
Roche R.L. and Alix M. based on the internal pressure buckling test results of 17 oval seal heads, an empirical formula for predicting the buckling pressure of the internal pressure oval seal head is given:
Figure BDA0002036013430000023
in the formula:
Figure BDA0002036013430000024
Sf＝(Sy+Su)/2；Sutensile strength is given in MPa.
The formula is obtained based on test results, lacks theoretical basis, and is more complicated to calculate.
Disclosure of Invention
The invention aims to solve the technical problem of overcoming the defects in the prior art and provides a method for preventing the internal pressure buckling failure of a steel oval end socket.
In order to solve the technical problem, the solution of the invention is as follows:
the method for preventing buckling failure in the steel oval end socket comprises the following steps:
(1) determining the inner diameter D of the preliminarily selected elliptical seal head according to the process requirementsiInner height hiAnd thickness t, and yield strength S of the material used for the closurey；
(2) The buckling pressure of the internal pressure steel oval end socket is calculated according to the following formula:
Figure BDA0002036013430000031
in the formula:
Sythe yield strength of the material used for the end socket is unit MPa; t is the thickness of the oval end socket in mm; diIs an ellipseThe inner diameter of the circular end socket is in mm; h isiThe inner height of the oval end socket is in unit mm; pbBuckling pressure P for closure headbIn MPa;
(3) as calculated buckling pressure P of the closurebAdjusting the size or material of the end socket if the internal pressure of the end socket is less than the internal pressure of the end socket under the process condition, and then calculating again by using the formula in the step (2);
(4) repeating the step (3) until the calculated buckling pressure P is obtainedbIs larger than the internal pressure of the end socket under the process condition.
In the invention, the diameter-thickness ratio of the elliptical seal head
Figure BDA0002036013430000032
It should satisfy:
Figure BDA0002036013430000033
in the invention, the diameter-height ratio of the elliptical seal head
Figure BDA0002036013430000034
It should satisfy:
Figure BDA0002036013430000035
in the invention, the yield strength S of the material of the elliptical seal headyIt should satisfy: s is more than or equal to 100y≤600。
Compared with the prior art, the invention has the beneficial effects that:
1. compared with the conventional elastic buckling pressure calculation formula, the internal pressure elliptical head plastic buckling pressure calculation method has higher accuracy; the method has comprehensive advantages in the aspects of accuracy, engineering practicability, calculation convenience and the like.
2. The invention not only covers the standard elliptical seal head commonly used in engineering, but also can be suitable for elliptical seal heads with other diameter-height ratios, and has relatively stronger engineering practicability.
3. The empirical formula in the prior art is mostly obtained based on test results, lacks theoretical basis and is relatively complicated in calculation, while the prediction formula provided by the invention is obtained based on numerical calculation result fitting of a nonlinear buckling analysis method and correction of the test results, has the theoretical basis, is simple in formula format and is convenient to calculate.
Drawings
Fig. 1 is a schematic cross-sectional view of an elliptical head.
Detailed Description
The implementation process of the invention is described below with reference to the accompanying drawings and specific examples:
taking the internal pressure steel standard oval end socket in fig. 1 as an example, the method for preventing the internal pressure buckling failure of the end socket product comprises the following steps:
(1) determining the inner diameter D of the preliminarily selected elliptical seal head according to the process requirementsiInner height hiAnd thickness t, and yield strength S of the material used for the closurey；
More preferably, the diameter-thickness ratio of the elliptical seal head
Figure BDA0002036013430000041
Satisfies the following conditions:
Figure BDA0002036013430000042
diameter-height ratio of elliptical seal head
Figure BDA0002036013430000043
Satisfies the following conditions:
Figure BDA0002036013430000044
yield strength S of material of elliptical headySatisfies the following conditions: s is more than or equal to 100y≤600。
(2) The buckling pressure of the internal pressure steel oval end socket is calculated according to the following formula:
Figure BDA0002036013430000045
in the formula:
Syyield strength of material used for end socketDegree, in MPa; t is the thickness of the oval end socket in mm; diThe inner diameter of the elliptic end socket is in unit mm; h isiThe inner height of the oval end socket is in unit mm; pbBuckling pressure P for closure headbIn MPa;
(3) as calculated buckling pressure P of the closurebAdjusting the size or material of the end socket if the internal pressure of the end socket is less than the internal pressure of the end socket under the process condition, and then calculating again by using the formula in the step (2);
(4) repeating the step (3) until the calculated buckling pressure P is obtainedbIs larger than the internal pressure of the end socket under the process condition.
Specific application examples are as follows:
(1) the internal pressure of the end socket is 0.80MPa under the process condition, and the internal diameter D of the preliminarily selected elliptical end socket is determinedi1800mm, inner height hi450mm and a thickness t 3 mm. The product-related data during the initial selection can be selected according to empirical data of the end socket product manufacture, so that excessive subsequent repeated calculation times are avoided. Wherein the ratio of diameter to thickness
Figure BDA0002036013430000046
Satisfy the requirement of
Figure BDA0002036013430000047
Aspect ratio
Figure BDA0002036013430000048
Satisfy the requirement of
Figure BDA0002036013430000049
In addition, the material used by the oval end socket is stainless steel S30408, and the yield strength S of the material is obtained through a tensile test performed in advancey385MPa, and satisfies 100 ≤ Sy≤600。
(2) The buckling pressure of the internal pressure steel oval end socket is calculated according to the following formula:
Figure BDA00020360134300000410
in the formula: diThe inner diameter of the elliptic end socket is in mm; h isiThe inner height of the oval end socket is in mm; pbIs the buckling pressure in MPa; t is the thickness of the oval end socket, and the unit is mm.
(3) The buckling pressure predicted value P of the elliptic seal head is obtained through calculationb0.92 MPa; the value is greater than the internal pressure of the end socket under the process condition by 0.80 MPa.
(4) And manufacturing the steel elliptical seal head according to the parameters used for calculation. And performing an internal pressure buckling test on the prepared end socket product to obtain a buckling pressure test value of the elliptic end socket of 1.30 MPa. Therefore, the buckling pressure predicted value P obtained by pre-calculating the end socket can be seenbWhen the internal pressure of the end socket is higher than the internal pressure of the end socket under the process condition, the actually prepared end socket product cannot be buckled and lose efficacy.

Claims (1)

1. A method for preventing buckling failure in steel oval end socket is characterized by comprising the following steps:
(1) determining the inner diameter D of the preliminarily selected elliptical seal head according to the process requirementsiInner height hiAnd thickness t, and yield strength S of the material used for the closurey；
(2) The buckling pressure of the internal pressure steel oval end socket is calculated according to the following formula:
Figure FDA0002527671240000011
in the formula:
Sythe yield strength of the material used for the end socket is unit MPa; t is the thickness of the oval end socket in mm; diThe inner diameter of the elliptic end socket is in unit mm; h isiThe inner height of the oval end socket is in unit mm; pbBuckling pressure P for closure headbIn MPa;
(3) as calculated buckling pressure P of the closurebAdjusting the size or material of the end socket when the internal pressure of the end socket is less than the internal pressure of the end socket under the process condition, and then utilizing the stepsCalculating the formula again in the step (2);
(4) repeating the step (3) until the calculated buckling pressure P is obtainedbThe internal pressure of the end socket is greater than that of the end socket under the process condition;
the diameter-thickness ratio of the elliptical seal head
Figure FDA0002527671240000012
Satisfies the following conditions:
Figure FDA0002527671240000013
diameter-height ratio of elliptical seal head
Figure FDA0002527671240000014
Satisfies the following conditions:
Figure FDA0002527671240000015
yield strength S of material of elliptical headySatisfies the following conditions: s is more than or equal to 100y≤600。
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CN111611680B (en) * 2020-03-30 2024-02-09 浙江大学 Manufacturing method of internal pressure steel elliptical head based on failure mode design
CN111400838B (en) * 2020-03-30 2023-10-31 浙江大学 Manufacturing method for preventing plastic collapse failure of inner-pressure steel elliptical head

Citations (1)

* Cited by examiner, † Cited by third party
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CN206160963U (en) * 2016-11-11 2017-05-10 国核华清（北京）核电技术研发中心有限公司 A appearance measuring device that lateral deflection song was experimental in was used for head

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN206160963U (en) * 2016-11-11 2017-05-10 国核华清（北京）核电技术研发中心有限公司 A appearance measuring device that lateral deflection song was experimental in was used for head

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