CN112001082A - I-beam front axle lightweight method - Google Patents

I-beam front axle lightweight method Download PDF

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CN112001082A
CN112001082A CN202010861312.7A CN202010861312A CN112001082A CN 112001082 A CN112001082 A CN 112001082A CN 202010861312 A CN202010861312 A CN 202010861312A CN 112001082 A CN112001082 A CN 112001082A
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front axle
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赵礼辉
张泽强
刘新荣
杨振毅
冯金芝
郑松林
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University of Shanghai for Science and Technology
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Abstract

The invention provides a method for lightening an I-beam front axle, which comprises the following steps: collecting automobile load spectrum data to perform rain flow circulation counting, constructing a relation between load variation and frequency, and calculating load damage of each level and equating to maximum damage; calculating equivalent times according to the maximum damage, and obtaining a corresponding stress limit value under the target mileage of the user by combining the load variation and frequency relation and the stress life curve; constructing an I-beam optimization model, and acquiring constraint conditions of the I-beam optimization model, wherein the constraint conditions comprise the stress limit value; solving the I-beam optimization model according to the constraint conditions to obtain front axle I-beam section optimization parameters and obtain a light-weight front axle; and verifying the light-weight front axle. According to the lightweight method, the neutral surface is moved downwards by adjusting the thicknesses of the upper wing surface and the lower wing surface, so that the tensile stress of the whole cross section of the I-beam is reduced, most cross sections bear the action of the compressive stress, and the service life of the front axle is prolonged.

Description

I-beam front axle lightweight method
Technical Field
The invention belongs to the technical field of automobile part processing, and particularly relates to a method for lightening an I-beam front axle.
Background
The I-beam is an important bearing part on the front axle of the automobile and is generally formed by roll forging, fist parts at two ends of the I-beam are connected with the wheel end of the front axle, and the middle of the I-beam is symmetrically provided with a plate spring support for being connected with a plate spring. The I-beam in the prior art is of a front-back and left-right symmetrical structure, the front and back of two fist parts of the I-beam are respectively provided with a limiting boss, the upper surface of the I-beam is provided with two plate spring supports, and the plate spring supports are provided with mounting holes. The existing I-beam is heavy in structure, materials are not fully utilized, the overall stress of the I-beam is distributed unevenly, so that the local rigidity is large, and the lightweight of the whole vehicle is not realized easily. The existing front axle light weight method mainly achieves the purpose of light weight by adopting structure optimization design, adopting size reduction at the position with excessive strength, or adopting material optimization design of high-strength steel, magnesium-aluminum alloy and the like and adopting an advanced manufacturing process. However, due to the matching degree of the structural specificity of the front axle and the limit load, the adoption of the method only can be little effective, and the whole light weight design process is complicated, local and incomplete, the scheme is conservative and the cost is high.
Therefore, it is necessary to provide a method for reducing the weight of a front axle to reduce the complexity of the design process of the front axle and effectively improve the life of the front axle.
Disclosure of Invention
Aiming at the problems of complicated design process, partial and incomplete design, conservative scheme and high cost of the existing light-weight front axle, the invention provides an I-beam front axle light-weight method, which effectively reduces the complexity of the design process of the front axle and simultaneously reduces the cost.
In order to achieve the purpose, the invention provides the following scheme: the invention provides a method for lightening an I-beam front axle, which is characterized by comprising the following steps of:
collecting automobile load spectrum data, performing rain flow circulation counting, constructing a load range and frequency relation curve, and calculating equivalent times under a load spectrum;
and acquiring a stress life curve, acquiring the equivalent times of the user target mileage according to the corresponding relation between the equivalent times and the mileage under the load spectrum, and acquiring a corresponding stress limit value of the user target mileage according to the stress life curve.
Constructing an I-beam optimization model, and acquiring constraint conditions of the I-beam optimization model, wherein the constraint conditions comprise the stress limit value;
solving the I-beam optimization model according to the constraint conditions to obtain front axle I-beam section optimization parameters and obtain a light-weight front axle;
and verifying the lightweight front axle and analyzing the feasibility of the lightweight front axle.
Preferably, the acquisition process of the equivalent times under one load spectrum is as follows: carrying out rain flow counting circulation on the load spectrum data to obtain a relation curve of load variation and frequency; and calculating the load damage of each stage according to the load variation and frequency relation curve and the stress life curve and equating to the maximum damage, thereby obtaining the equivalent times under one load spectrum.
Preferably, the I-beam optimization model takes volume or mass as an objective function;
the constraint conditions of the I-beam optimization model further comprise deflection constraint and section size constraint.
Preferably, the method for obtaining the lightweight front axle comprises the following steps: and moving the neutral surface position of the I-beam downwards according to the section optimization parameters of the I-beam of the front axle to obtain the lightweight front axle.
Preferably, the method for moving down the position of the neutral plane of the I-beam comprises the following steps: and according to the front axle I-beam section optimization parameters, reducing the thickness of the upper I-shaped surface of the I-beam section and increasing the thickness of the lower I-shaped surface.
Preferably, the method for moving down the position of the neutral plane of the i-beam further comprises the following steps: and according to the section optimization parameters of the front axle I-beam, digging a groove on the upper I-shaped surface of the section of the I-beam to move the position of the neutral surface downwards.
Preferably, the verification content of the lightweight front axle comprises modal analysis, gantry fatigue analysis and simulation analysis.
The invention discloses the following technical effects: based on test field load spectrum and finite element simulation analysis, the invention discovers that the I-beam part of the front axle is a potential failure part through analysis, further establishes an I-beam optimization model, takes the volume or mass as a target function, takes stress, deflection and size parameters as constraint conditions, and adopts a multi-objective algorithm to solve. The neutral surface is moved downwards by adjusting the thickness of the upper wing surface and the lower wing surface, the tensile stress of the whole section of the I-beam is reduced, most of the section bears the action of the compressive stress, the service life of the front axle is prolonged, and the requirement of weight reduction is met, so that the optimization method is long in service life and low in cost. The invention innovatively adopts a method for reducing the overall stress condition of the I-shaped beam section of the front axle without changing other structures, so that the design process of the front axle is simple and the cost is reduced.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.
FIG. 1 is a flow chart of a method for lightening an I-beam front axle of the invention;
FIG. 2 is a schematic view of a test field loading spectrum in an embodiment of the present invention;
FIG. 3 is a schematic diagram showing the relationship between load variation and frequency according to the present invention;
FIG. 4 is a schematic diagram of the variable-range damage distribution under different loads according to the present invention;
FIG. 5 is a schematic diagram of an I-beam section optimization model;
FIG. 6 is a schematic cross-sectional view of an I-beam of a front axle with a thin upper I-shaped surface and a thick lower I-shaped surface according to an embodiment of the present invention;
FIG. 7 is a schematic cross-sectional view of an I-beam of a front axle trenched in an embodiment of the present invention;
FIG. 8 is a schematic cross-sectional view of an alternative front axle I-beam of the present invention in the form of a trough;
fig. 9 is a schematic cross-sectional view of an alternative embodiment of the i-beam of the present invention with the neutral plane down.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
As shown in fig. 1, the invention provides a method for lightening an i-beam front axle, which comprises the following steps:
s1, according to the requirement of the commercial vehicle durability specification, carrying out load spectrum collection in a certain test field, carrying out extreme load characteristic statistics on the test field load spectrum, carrying out finite element analysis, determining the extreme working condition of the front axle, obtaining a load and stress relation curve, further verifying the accuracy of a finite element model, and determining the part of the I-beam part, which is the front axle structure and needs to be improved. The resulting test field loading spectrum is shown in fig. 2.
S2, as shown in figure 3, carrying out rain current circulation counting on the load spectrum of the test field, and constructing a load variation range SRAnd frequency nRAnd calculating the fatigue life N corresponding to each stage of the transformation processf，i，
The calculation method comprises the following steps:
Figure BDA0002648226400000051
wherein: m is a reflectivity index; c is a material constant; sRLoad variation is carried out; n is a radical offThe fatigue life is considered.
Fatigue life N corresponding to each stage of variable rangef，iCalculating the damage d corresponding to the ith level load variation in the load spectrumi＝nR,i/Nf，iObtaining the rain flow course SR,iCorresponding damage distribution di. The obtained damage distribution of different load variation ranges is shown in figure 4;
according to the damage distribution diCalculating the total damage D, specifically:
D＝∑di (2)
equating total damage D to maximum damage D according to damage equivalence principlemaxAnd calculating equivalent times under a load spectrum according to the maximum damage, specifically:
neq＝ndmaxD/dmax (3)
wherein: n iseqRepresenting the equivalent times; n isdmaxRepresenting the maximum damage frequency, and obtaining the maximum damage frequency according to the corresponding relation between the load variation and the damage distribution; d represents total injury; dmaxIndicating the maximum damage.
Obtaining the equivalent times under the target mileage of the user according to the corresponding relation between the equivalent times and the mileage under one load spectrum, and combining the equivalent times under the target mileage of the user with a stress life curve to obtain a corresponding stress limit value [ sigma ] under the target mileage of the user, wherein the specific equivalent process comprises the following steps:
Figure BDA0002648226400000061
wherein: n iseqRepresenting the equivalent times; l is1The equivalent times correspond to mileage; l isUser' sTarget mileage for the user; n isUser' sAnd the equivalent times of the target mileage of the user.
S3, as shown in FIG. 5, establishing a front axle I-beam section optimization model, wherein the main section parameters are b1, b2, b3, h1, h2 and h3, wherein: b1 for upper airfoil width, b2 for lower airfoil width, b3 for web width, h1 for upper airfoil height,h2 represents the lower blade height, h3 represents the web height, and b1, b2, b3, h1 and h2 are respectively set as variables corresponding to X1，X2，X3，X4，X5H3 is set to a constant value;
therefore, the optimization model of the cross section of the I-beam is as follows:
F＝min f, (5)
f＝b1*h1+b2*h2+b3*h3 (6)
Figure BDA0002648226400000062
wherein: f represents the area of the cross section of the I-beam, namely the amount of the material used for the cross section of the I-beam; f represents a calculation formula of the cross section of the I-beam; s.t as a constraint; y isFirst stageIn order to optimize the minimum static deflection before, can calculate according to the size parameter of the I-beam; ximinAnd XimaxThe upper limit and the lower limit of the I-beam section size parameter aiming at the actual situation are respectively.
The objective function of the I-beam section optimization model is a volume (mass) function, and the constraint conditions are stress constraint, deflection constraint and size constraint respectively, and specifically comprise the following steps:
(1) stress restraint
And taking the bending stress born by the I-shaped beam to be less than the stress limit value [ sigma ] as one of the constraint conditions. Calculating values of the neutral layer and the inertia moment, and solving bending stress borne by the section of the I-beam;
neutral layer position H1 is:
Figure BDA0002648226400000071
the section moment of inertia I is:
Figure BDA0002648226400000072
bending positive stress σ:
Figure BDA0002648226400000073
wherein I is the moment of inertia, M is the bending moment, [ sigma ] stress limit.
(2) Deflection constraint
The deflection constraint is considered by static deflection, and the minimum static deflection under the given load condition is not more than the minimum static deflection before optimization and is taken as one of constraint conditions;
the static deflection w is:
Figure BDA0002648226400000074
the constraint conditions are as follows:
Figure BDA0002648226400000075
wherein, p is the maximum bending load in the middle of the upper section of the I-beam model, l is the length of the intercepted I-beam, E is the elastic modulus, and I is the inertia moment;
(3) cross sectional dimension constraint
The cross-sectional dimension constraints are as follows:
Ximin≤Xi≤Ximax，i＝1～5 (13)
and solving the I-beam optimization model through an NSGA-II algorithm to obtain front axle I-beam section optimization parameters, reducing the thickness of an upper I-shaped surface of the I-beam section through the I-beam section optimization parameters, increasing the thickness of a lower I-shaped surface, and moving down the position of a neutral surface to finally obtain the light I-beam, wherein the light I-beam is shown in figure 6. In addition, it is also possible to dig a groove in the upper H-shaped surface to move the neutral surface position downward, as shown in FIG. 7.
And S4, performing modal analysis, bench fatigue test and simulation analysis on the obtained lightweight front axle respectively, and further analyzing the feasibility of the lightweight front axle scheme.
The above-described embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solutions of the present invention can be made by those skilled in the art without departing from the spirit of the present invention, and the technical solutions of the present invention are within the scope of the present invention defined by the claims.

Claims (7)

1. A method for lightening an I-beam front axle is characterized by comprising the following steps:
collecting automobile load spectrum data, performing rain flow circulation counting, constructing a load range and frequency relation curve, and calculating equivalent times under a load spectrum;
and acquiring a stress life curve, acquiring the equivalent times of the user target mileage according to the corresponding relation between the equivalent times and the mileage under the load spectrum, and acquiring a corresponding stress limit value of the user target mileage according to the stress life curve.
Constructing an I-beam optimization model, and acquiring constraint conditions of the I-beam optimization model, wherein the constraint conditions comprise the stress limit value;
solving the I-beam optimization model according to the constraint conditions to obtain front axle I-beam section optimization parameters and obtain a light-weight front axle;
and verifying the lightweight front axle and analyzing the feasibility of the lightweight front axle.
2. The method for lightening the i-beam front axle according to claim 1, wherein the process for obtaining the equivalent times under one load spectrum is as follows: carrying out rain flow counting circulation on the load spectrum data to obtain a relation curve of load variation and frequency; and calculating the load damage of each stage according to the load variation and frequency relation curve and the stress life curve and equating to the maximum damage, thereby obtaining the equivalent times under one load spectrum.
3. The method for lightening an i-beam front axle according to claim 1, wherein the i-beam optimization model takes volume or mass as an objective function;
the constraint conditions of the I-beam optimization model further comprise deflection constraint and section size constraint.
4. The method for lightening an i-beam front axle according to claim 1, wherein the method for obtaining a lightened front axle comprises: and moving the neutral surface position of the I-beam downwards according to the section optimization parameters of the I-beam of the front axle to obtain the lightweight front axle.
5. The method for lightening an i-beam front axle according to claim 4, wherein the method for moving down the neutral plane position of the i-beam comprises: and according to the front axle I-beam section optimization parameters, reducing the thickness of the upper I-shaped surface of the I-beam section and increasing the thickness of the lower I-shaped surface.
6. The method for lightening an i-beam front axle according to claim 4, wherein the method for moving down the neutral plane position of the i-beam further comprises: and according to the section optimization parameters of the front axle I-beam, digging a groove on the upper I-shaped surface of the section of the I-beam to move the position of the neutral surface downwards.
7. The method for lightening an i-beam front axle according to claim 1, wherein the verification content of the front axle comprises modal analysis, bench fatigue analysis and simulation analysis.
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