CN111143943B - Method for calculating large deformation strength of pipe spring type undercarriage - Google Patents
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Abstract
The invention discloses a method for calculating large deformation strength of a tubular spring type undercarriage, which comprises the following steps of 1: calculating the internal force of the pipe spring type undercarriage; step 2: calculating the tensile stress sigma of the key section of the landing gear under the condition of limiting load Limiting And the tensile yield limit sigma of the material 0.2 Comparing; and 3, step 3: calculating the tensile stress sigma under the ultimate load condition of the key section of the undercarriage Extreme limit And to tensile stress sigma Extreme limit Performing plasticity correction; and 4, step 4: calculating the maximum shear stress tau of the key section of the undercarriage under the condition of ultimate load Extreme limit And the shear strength limit τ of the material b Carrying out comparison; and 5: calculating the resultant stress σ he And the tensile strength limit of the material sigma b Comparing; and 6: determine sigma he 、τ Extreme limit The invention solves the technical problem of strength calculation of the tube spring type undercarriage of the light-duty general aircraft, and can realize the coordination design of the buffering performance and the strength of the tube spring type undercarriage.
Description
Technical Field
The invention belongs to the technical field of strength design of undercarriage, and particularly relates to a calculation method for large deformation strength of a tubular spring type undercarriage.
Background
The universal aviation has the characteristics of flexibility, rapidness and high efficiency, and requires that the airplane has low production and use cost, simple outfield flight guarantee, and easily maintained and replaced parts. The landing gear of traditional aircraft needs corresponding hydraulic pressure receive and releases control system, fluid buffer, and the system is complicated, and fault probability such as oil leak is high, and the outfield maintenance is difficult, and purchase use cost is high, therefore the fixed landing gear of tube spring becomes the main landing gear form of general aircraft.
Due to policy limiting factors in China, the development requirement of light universal aircrafts is lacked for a long time, the universal aircrafts only have a few models of 5, 11, 12 and eagle series, and the design idea and the external field guarantee requirements of the landing gear are similar to those of the traditional large aircrafts. In recent years, a batch of light-weight general aircraft production enterprises appearing in China are all introduced with license assembly production and have no independent development capability. The development of a domestic tubular spring (plate spring) type landing gear is still blank.
The pipe spring type undercarriage is simple in structure, few in parts, and two conflicting design factors of buffering performance and strength are concentrated on the same part, and the two factors are difficult to balance on one part by a traditional strength analysis method, so that the undercarriage design becomes a technical difficulty of light universal aircraft design.
Disclosure of Invention
The purpose of the invention is as follows: a method for calculating the large deformation strength of a tube spring type undercarriage is provided to solve the technical problem of strength calculation of the tube spring type undercarriage of a light general-purpose aircraft.
The technical scheme of the invention is as follows:
a method for calculating the large deformation strength of a pipe spring type undercarriage comprises the following steps:
step 1: calculating the internal force of the pipe spring type undercarriage;
and 2, step: calculating the tensile stress sigma under the condition of limiting load of the key section of the landing gear Limiting And the tensile yield limit σ of the material 0.2 Making a comparison if σ Limiting ＜σ 0.2 Proceed to the operation of step 3 if σ Limiting of ＞σ 0.2 Adjusting the structural parameters of the tube spring type undercarriage, and repeating the steps 1-2 until sigma is reached Limiting of ＜σ 0.2 ；
And step 3: calculating the tensile stress sigma under the ultimate load condition of the key section of the undercarriage Extreme limit And to tensile stress sigma Extreme limit Performing plasticity correction;
and 4, step 4: calculating the maximum shear stress tau of the key section of the undercarriage under the condition of ultimate load Extreme limit And the shear strength limit tau of the material b Make a comparison if tau Extreme limit ＜τ b Proceeding the operation of step 5 if τ Extreme limit ＞τ b Adjusting the structural parameters of the tube spring type undercarriage, and repeating the steps 1-4 until the time is tau Extreme limit ＜τ b ；
And 5: calculating the resultant stress σ he And the tensile strength limit σ of the material b Making a comparison if σ he ＜σ b Proceed to the operation of step 6 if σ he ＞σ b Adjusting the structural parameters of the tube spring type undercarriage, and repeating the steps 1-5 until sigma is reached he ＜σ b ；
Step 6: determine sigma he 、τ Extreme limit Is less than 0.1, and if so, σ is determined he 、τ Extreme limit If not, adjusting the structural parameters of the tube spring type undercarriage and repeating the steps 1-6 until sigma is calculated as the strength calculation result he 、τ Extreme limit Are all less than 0.1.
When the internal force of the tube spring type undercarriage in the step 1 is calculated, the load loading method comprises the following steps: the load is applied in a manner that follows the point of action on the landing gear in translation, but not in rotation.
The material of the tube spring type landing gear in the step 1 is a linear elastic material.
Step 2, calculating the tensile stress sigma of the key section of the landing gear under the condition of limiting load Limiting The calculation formula is as follows:
wherein:
σ limiting : limiting the section normal stress under the load condition;
M y 、M z : limiting bending moments of the section in the y direction and the z direction under the load condition;
J y : moment of inertia in section y direction
R: maximum radius of the section;
N x : limiting the tensile load or the compressive load of the section under the load condition;
a: cross-sectional area.
Step 3, calculating the tensile stress sigma of the key section of the landing gear under the condition of the ultimate load Extreme limit The calculation formula is as follows:
wherein:
σ extreme limit : section normal stress under the condition of ultimate load;
M′ y ，M′ z : bending moment of the section in the y direction and the z direction under the condition of ultimate load;
J y : moment of inertia in the y-direction of the profile;
r: maximum radius of the section;
N′ x : tensile or compressive loading of the profile under extreme load conditions;
a: cross-sectional area.
Step 3 the tensile stress sigma Extreme limit Performing plasticity correction to obtain corrected tensile stress sigma After plastic correction Comprises the following steps:
wherein:
σ after plastic correction : the section normal stress after plastic correction;
σ extreme limit : section normal stress under the condition of ultimate load;
K p : and (4) plasticity correction coefficient.
Step 3, calculating the maximum shear stress tau of the key section of the landing gear under the condition of the ultimate load Extreme limit The calculation formula is as follows:
wherein:
τ extreme limit : profile shear stress under extreme load conditions;
Q y 、Q x : shear loads of the section in the directions of y and z under the condition of the limit load;
M x : section at extreme loadA torsional bending moment in the x-direction;
J y : moment of inertia in section y direction
R: maximum radius of the section;
a: cross-sectional area.
Step 5 said calculating the resultant stress σ he The calculation formula is as follows:
the invention has the beneficial effects that: the method for calculating the large deformation strength of the tube spring type undercarriage solves the technical problem of strength calculation of the tube spring type undercarriage of a light-duty general airplane, can achieve coordinated design of the buffer performance and the strength of the tube spring type undercarriage, ensures that the weight, the performance and the strength of the undercarriage meet design requirements, reduces test cost, improves model development efficiency, avoids repeated performance of a drop test and a strength test, and reduces development cycle.
Drawings
FIG. 1 is a flow chart of the method of the present invention.
Detailed Description
According to the method for calculating the large deformation strength of the pipe spring type undercarriage, before calculation, each section of the pipe spring type undercarriage is preliminarily determined, then the ground overload of the undercarriage is estimated according to the similar airplane, and the size of each section of the undercarriage is preliminarily designed according to the performance requirement.
In the initial stage of design:
1) the reference value of the ground overload coefficient can be 3.8;
2) the critical cross-sectional dimensions may be selected from the following references:
a) critical section-1: r is 20mm and R is 14mm
b) Critical section-2: r is 28mm, R is 14mm
c) Critical section-3: r20 mm, R14 mm includes the following steps:
the method for calculating the large deformation strength of the spring type undercarriage comprises the following steps:
step 1: calculating the internal force of the pipe spring type undercarriage, wherein during calculation, a load loading method comprises the following steps: because the biggest difference of tube spring formula undercarriage and traditional undercarriage lies in, and during the loading, undercarriage structure deflection is great, and consequently the load follows action point on the undercarriage and carries out the translation, but does not carry out the mode of rotation and apply, and the material of tube spring formula undercarriage is line elastic material.
Step 2: calculating the tensile stress sigma of the key section of the landing gear under the condition of limiting load Limiting And the tensile yield limit sigma of the material 0.2 Make a comparison if σ Limiting ＜σ 0.2 Proceed to the operation of step 3 if σ Limiting ＞σ 0.2 Adjusting the structural parameters of the tube spring type undercarriage, and repeating the steps 1-2 until sigma is reached Limiting ＜σ 0.2 ；
Calculating the tensile stress sigma of the key section of the landing gear under the condition of limiting load Limiting The calculation formula of (c) is:
wherein:
σ limiting : limiting the section normal stress under the load condition;
M y 、M z : limiting bending moments of the section in the y direction and the z direction under the load condition;
J y : moment of inertia in section y direction
R: maximum radius of the section;
N x : limiting the tensile load or the compressive load of the section under the load condition;
a: cross-sectional area.
And step 3: calculating the tensile stress sigma under the ultimate load condition of the key section of the undercarriage Extreme limit And to tensile stress sigma Extreme limit Performing plasticity correction;
calculating the tensile stress sigma under the ultimate load condition of the key section of the undercarriage Extreme limit The calculation formula is as follows:
wherein:
σ extreme limit : section normal stress under the condition of ultimate load;
M′ y ，M′ z : bending moment of the section in the y direction and the z direction under the condition of ultimate load;
J y : moment of inertia in the y-direction of the profile;
r: maximum radius of the section;
N′ x : tensile or compressive loading of the profile under extreme load conditions;
a: cross-sectional area.
For tensile stress sigma Extreme limit Performing plasticity correction to obtain corrected tensile stress sigma After plastic correction Comprises the following steps:
wherein:
σ after plastic correction : the section normal stress after plastic correction;
σ extreme limit : section normal stress under the condition of ultimate load;
K p : and (4) plasticity correction coefficient.
And 4, step 4: calculating the maximum shear stress tau of the key section of the landing gear under the condition of ultimate load Extreme limit And the shear strength limit τ of the material b Make a comparison if tau Extreme limit ＜τ b Proceeding with the operation of step 5 if τ Extreme limit ＞τ b Adjusting the structural parameters of the tube spring type undercarriage, and repeating the steps 1-4 until the time is tau Extreme limit ＜τ b ；
Calculating the maximum shear stress tau of the key section of the undercarriage under the condition of ultimate load Extreme limit The calculation formula is as follows:
wherein:
τ extreme limit : profile shear stress under extreme load conditions;
Q y 、Q x : shear loads of the section in the y direction and the z direction under the condition of the limit load;
M x : torsional bending moment of the section in the x direction under the condition of ultimate load;
J y : moment of inertia in section y direction
R: maximum radius of the section;
a: cross-sectional area.
And 5: calculating the resultant stress σ he And the tensile strength limit σ of the material b Making a comparison if σ he ＜σ b Proceed to the operation of step 6 if σ he ＞σ b Adjusting the structural parameters of the tube spring type undercarriage, and repeating the steps 1-5 until sigma is reached he ＜σ b ；
Calculating the resultant stress σ he The calculation formula is as follows:
and 6: determine sigma he 、τ Extreme limit Is less than 0.1, and if so, σ is determined he 、τ Extreme limit If not, adjusting the structural parameters of the tube spring type undercarriage and repeating the steps 1-6 until sigma is calculated as the strength calculation result he 、τ Extreme limit Are all less than 0.1.
Claims (8)
1. A method for calculating large deformation strength of a pipe spring type undercarriage is characterized by comprising the following steps: the method comprises the following steps:
step 1: calculating the internal force of the pipe spring type undercarriage;
step 2: calculating the tensile stress sigma of the key section of the landing gear under the condition of limiting load Limiting And the tensile yield limit σ of the material 0.2 Making a comparison if σ Limiting ＜σ 0.2 Proceed to the operation of step 3 if σ Limiting of ＞σ 0.2 Adjusting the structural parameters of the tube spring type undercarriage, and repeating the steps 1-2 until sigma is reached Limiting ＜σ 0.2 ；
And step 3: calculating the tensile stress sigma under the ultimate load condition of the key section of the landing gear Limiting of And to tensile stress sigma Limiting Performing plasticity correction;
and 4, step 4: calculating the maximum shear stress tau of the key section of the undercarriage under the condition of ultimate load Extreme limit And the shear strength limit τ of the material b Making a comparison if tau Extreme limit ＜τ b Proceeding the operation of step 5 if τ Extreme limit ＞τ b Adjusting the structural parameters of the tube spring type undercarriage, and repeating the steps 1-4 until the time is tau Extreme limit ＜τ b ；
And 5: calculating the resultant stress σ he And the tensile strength limit of the material sigma b Making a comparison if σ he ＜σ b Proceed to the operation of step 6 if σ he ＞σ b Adjusting the structural parameters of the tube spring type undercarriage, and repeating the steps 1-5 until sigma is reached he ＜σ b ；
And 6: determine sigma he 、τ Extreme limit Is less than 0.1, and if so, σ is determined he 、τ Extreme limit If not, adjusting the structural parameters of the tube spring type undercarriage and repeating the steps 1-6 until sigma is calculated as the strength calculation result he 、τ Extreme limit Are all less than 0.1.
2. The method for calculating the large deformation strength of the tube spring type landing gear according to claim 1, wherein the method comprises the following steps: when the internal force of the tube spring type undercarriage in the step 1 is calculated, the load loading method comprises the following steps: the load is applied in a manner that follows the point of action on the landing gear in translation, but not in rotation.
3. The method for calculating the large deformation strength of the tube spring type landing gear according to claim 1, wherein the method comprises the following steps: the material of the tube spring type landing gear in the step 1 is a linear elastic material.
4. The method for calculating the large deformation strength of the tube spring type landing gear according to claim 1, wherein the method comprises the following steps: step 2, calculating the tensile stress sigma of the key section of the landing gear under the condition of limiting load Limiting The calculation formula is as follows:
wherein:
σ limiting of : limiting the section normal stress under the load condition;
M y 、M z : limiting bending moments of the section in the y direction and the z direction under the load condition;
J y : moment of inertia in section y direction
R: maximum radius of the section;
N x : limiting the tensile load or the compressive load of the section under the load condition;
a: cross-sectional area.
5. The method for calculating the large deformation strength of the tube spring type landing gear according to claim 1, wherein the method comprises the following steps: step 3, calculating the tensile stress sigma of the key section of the landing gear under the condition of the ultimate load Extreme limit The calculation formula is as follows:
wherein:
σ extreme limit : section normal stress under the condition of ultimate load;
M′ y ，M′ z : bending moments in the y direction and the z direction of the section under the condition of ultimate load;
J y : moment of inertia in the y-direction of the profile;
r: the maximum radius of the section;
N′ x : tensile or compressive loading of the profile under extreme load conditions;
a: cross-sectional area.
6. The method for calculating the large deformation strength of the tube spring type landing gear according to claim 1, wherein the method comprises the following steps: step 3 the tensile stress σ Extreme limit Performing plasticity correction to obtain corrected tensile stress sigma After plastic correction Comprises the following steps:
wherein:
σ after plastic correction : the section normal stress after plastic correction;
σ extreme limit : section normal stress under the condition of ultimate load;
K p : and (4) plasticity correction coefficient.
7. The method for calculating the large deformation strength of the tube spring type landing gear according to claim 1, wherein the method comprises the following steps: step 3, calculating the maximum shear stress tau of the key section of the landing gear under the condition of the ultimate load Extreme limit The calculation formula is as follows:
wherein:
τ extreme limit : profile shear stress under extreme load conditions;
Q y 、Q x : shear loads of the section in the y direction and the z direction under the condition of the limit load;
M x : torsional bending moment of the section in the x direction under the condition of ultimate load;
J y : moment of inertia in section y direction
R: maximum radius of the section;
a: cross-sectional area.
8. The method for calculating the large deformation strength of the tube spring type landing gear according to claim 1, wherein the method comprises the following steps: step 5 said calculating the resultant stress σ he The calculation formula is as follows:
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| CN108090265A (en) * | 2017-12-08 | 2018-05-29 | 中国航空工业集团公司西安飞机设计研究所 | A kind of calculation method for stress of common frame of airframe under bending load |
| CN110362940A (en) * | 2019-07-19 | 2019-10-22 | 中国船舶科学研究中心（中国船舶重工集团公司第七0二研究所） | Complex load acts on lower offshore engineering structure ultimate bearing capacity calculation method |
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| CN108090265A (en) * | 2017-12-08 | 2018-05-29 | 中国航空工业集团公司西安飞机设计研究所 | A kind of calculation method for stress of common frame of airframe under bending load |
| CN110362940A (en) * | 2019-07-19 | 2019-10-22 | 中国船舶科学研究中心（中国船舶重工集团公司第七0二研究所） | Complex load acts on lower offshore engineering structure ultimate bearing capacity calculation method |
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| 风力机叶片结构强度复合材料力学分析方法研究;郭小锋等;《玻璃钢/复合材料》;20170528(第05期);全文 * |
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