CN113722943B - Fatigue durability analysis method for engine cover of long-head truck - Google Patents
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Abstract
The application discloses a fatigue durability analysis method for a long-head truck engine cover, which comprises the following steps: establishing an engine cover finite element model; intercepting a front half frame, performing flexible treatment on the front half frame, and then assembling the front half frame and an engine hood to construct a frame-engine hood rigid-flexible coupling multi-body dynamics model; based on a response signal actually measured by a test field, acquiring the equivalent displacement of a frame of the test field by utilizing an iterative inverse strategy, and acquiring a fatigue load spectrum of the engine cover according to an equivalent displacement driving dynamics model; and (3) carrying out fatigue simulation analysis on the engine cover by applying a Miner linear accumulated damage theory in combination with the material properties of the engine cover and the distribution result of the stress field of the unit load. The application relates to the correlation between the fatigue simulation analysis of the engine cover and the road use scene of the user, overcomes the defect that the fatigue life of the engine cover structure cannot be accurately reproduced by the traditional method, and simultaneously effectively shortens the development period of enterprises and reduces the research and development cost.
Description
Technical Field
The application relates to the technical field of commercial vehicles, in particular to a fatigue durability analysis method for a long-head truck engine cover.
Background
The absolute advantages of the commercial vehicle, such as transportation distance, load capacity and ton oil consumption, are widely applied to the road transportation industry, but the fatigue damage problem is serious due to severe use environment and complex working conditions, and researches show that about 80% of failures in mechanical structures are caused by the fatigue damage.
The engine cover is not only affected by vibration of the power assembly in the running process of the vehicle, but also subjected to the action of alternating load on the road surface, and the sheet metal part of the engine cover is extremely easy to fatigue damage, so that the engine cover has important effects on the appearance of the vehicle body and vibration noise, and also has the effects of sun shading, rain shielding, heat insulation, sound insulation, air diversion and the like, and the fatigue damage of the engine cover can cause rainwater to pollute precise elements such as a spark plug, an electromagnetic valve and the like, so that the engine work is abnormal, and therefore, how to accurately predict the fatigue life of the engine cover and improve the fatigue durability performance of the engine cover are the problems to be solved in the current automobile industry.
Disclosure of Invention
This section is intended to outline some aspects of embodiments of the application and to briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section as well as in the description of the application and in the title of the application, which may not be used to limit the scope of the application.
The present application has been made in view of the above-described problems occurring in the prior art.
Therefore, the technical problems solved by the application are as follows: traditional fatigue durability check is excessively dependent on real vehicle road tests and bench tests, and the fatigue life of the engine cover structure cannot be accurately reproduced.
In order to solve the technical problems, the application provides the following technical scheme: establishing an engine hood finite element model according to a solid digital model, comparing a calculation mode with an experimental mode, and performing inertial release analysis on an engine hood to obtain unit load stress field distribution of the engine hood; intercepting a front half frame, performing flexible treatment on the front half frame, and then assembling the front half frame with the engine hood to build a frame-engine hood rigid-flexible coupling multi-body dynamics model; based on a response signal actually measured by a test field, acquiring the equivalent displacement of a frame of the test field by utilizing an iterative inverse strategy, and driving a dynamic model according to the equivalent displacement to acquire a fatigue load spectrum of the engine cover; and carrying out fatigue simulation analysis on the engine cover by applying a Miner linear cumulative damage theory according to the material properties of the engine cover and the distribution result of the unit load stress field.
As a preferable mode of the fatigue durability analysis method for a hood of a long-head truck according to the present application, wherein: the iterative equivalent displacement target signal comprises the steps of collecting acceleration signals of key areas of the vehicle frame and the engine cover, performing drift removal, deburring and filtering treatment on the collected signals, and taking the signals as iterative equivalent displacement target signals.
As a preferable mode of the fatigue durability analysis method for a hood of a long-head truck according to the present application, wherein: the frame-engine cover rigid-flexible coupling multi-body dynamics model is built by cutting the frame from a second cross beam, performing flexible treatment, assembling the frame with the engine cover and building the frame-engine cover rigid-flexible coupling multi-body dynamics model; according to the simplified thought of a seven-degree-of-freedom model of the vehicle, 4Z-displacement driving is respectively established at the positions of the hanging lugs of the frame plate springs and the rolling lugs, and the vertical, pitching and side-tilting stress characteristics of the cab are simulated; 1X-direction displacement drive is established at the second cross beam of the frame, and the longitudinal impact stress characteristic of the cab is simulated; 2Y-displacement drives are established at the same side of the frame, and the transverse and yaw stress characteristics of the cab are simulated; and establishing a corresponding Request point on the engine cover multisome model for outputting fatigue load spectrum of the engine cover.
As a preferable mode of the fatigue durability analysis method for a hood of a long-head truck according to the present application, wherein: the engine cover iterative inverse-solving frame equivalent displacement comprises the steps of generating red, white and powder noise signals at the frame equivalent displacement to drive a multi-body dynamics system to generate corresponding responses, selecting 12 acceleration signals of four suspension points of the engine cover as system response signals, and solving a system frequency response transfer function H (omega) based on the system response signals; according to the iteration step, the external load is reversely calculated, and the response signal approaches the expected signal; the initial signal x in the iterative step 0 (t) obtaining the response signal y of the system under the excitation as the excitation signal input system 0 (t) and is matched with the desired signal y Des (t) comparing, and correcting the initial signal by using the deviation value to obtain an input signal x of the next iteration 1 (t)。
As a preferable mode of the fatigue durability analysis method for a hood of a long-head truck according to the present application, wherein: the system frequency response transfer function H (ω) includes,
H(ω)＝G yx /G xx
wherein X (t) is a white noise time domain signal, Y (t) is a time domain response signal, X (omega) and Y (omega) are corresponding frequency values, G yx As a cross-power spectral density function of the input signal x (t) and the response signal y (t), G xx As a function of the self-power spectral density of the input signal.
As a preferable mode of the fatigue durability analysis method for a hood of a long-head truck according to the present application, wherein: the initial signal x 0 The formula of (t) includes that,
where a is a correction coefficient.
As a preferable mode of the fatigue durability analysis method for a hood of a long-head truck according to the present application, wherein: the input signal x of the next iteration 1 (t) comprises the steps of,
e 0 (t)＝y Des (t)-y 0 (t)；
x 1 (t)＝x 0 (t)+a·Δ 0 (t)
wherein e 0 (t) is response deviation, Δ 0 And (t) is a driving signal correction amount.
As a preferable mode of the fatigue durability analysis method for a hood of a long-head truck according to the present application, wherein: in the iterative process, when the relative damage value is between 0.8 and 1.2, the error requirement is met.
As a preferable mode of the fatigue durability analysis method for a hood of a long-head truck according to the present application, wherein: extracting the fatigue load spectrum of the engine cover comprises the step of driving the whole multi-body model to carry out Adams/car simulation analysis by taking test field equivalent displacement signal excitation obtained in the last iteration as an input condition to obtain the fatigue load spectrum of the fatigue durability analysis of the engine cover structure.
The application has the beneficial effects that: the application relates to the correlation between the fatigue simulation analysis of the engine cover and the road use scene of the user, overcomes the defect that the fatigue life of the engine cover structure cannot be accurately reproduced by the traditional method, and simultaneously effectively shortens the development period of enterprises and reduces the research and development cost.
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In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the description of the embodiments will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort to a person skilled in the art. Wherein:
FIG. 1 is a schematic flow diagram of a method for analyzing fatigue durability of a hood of a long-head truck according to an embodiment of the present application;
FIG. 2 is a diagram of a hood acceleration sensor arrangement for a method of fatigue durability analysis for a long-head truck hood, according to one embodiment of the present application;
FIG. 3 is a diagram of a frame-hood rigid-flexible coupled multi-body dynamics model for a method of fatigue durability analysis for a long-head truck hood, according to one embodiment of the present application;
FIG. 4 is a schematic diagram of an iterative path for a fatigue durability analysis method for a hood of a pick-up truck according to one embodiment of the present application;
FIG. 5 is a schematic diagram of iterative channel relative damage values for a fatigue durability analysis method for a hood of a pick-up truck according to an embodiment of the present application;
FIG. 6 is a simulated cloud image of fatigue of a truck hood according to one embodiment of the present application for a method of fatigue durability analysis of a long-head truck hood;
FIG. 7 is a schematic diagram of a test fatigue failure point of a truck hood test field for a method of analyzing fatigue durability of a long-head truck hood according to one embodiment of the present application.
Detailed Description
In order that the above-recited objects, features and advantages of the present application will be readily understood, a more particular description of the application will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings, in which the appended drawings are illustrated in a partial, but not all, embodiment of the application. All other embodiments, which can be made by one of ordinary skill in the art without undue burden on the person of ordinary skill in the art based on embodiments of the present application, are intended to be within the scope of the present application.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application, but the present application may be practiced in other ways other than those described herein, and persons skilled in the art will readily appreciate that the present application is not limited to the specific embodiments disclosed below.
Further, reference herein to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic can be included in at least one implementation of the application. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments.
While embodiments of the application have been illustrated and described in detail in connection with the drawings, the cross-sectional view illustrating the structure of the device is not to scale in order to facilitate the description, and the drawings are merely exemplary and should not be construed as limiting the scope of the application. In addition, the three-dimensional dimensions of length, width and depth should be included in actual fabrication.
Also in the description of the present application, it should be noted that the directions or positional relationships indicated by the terms "upper, lower, inner and outer" and the like are based on the directions or positional relationships shown in the drawings, are merely for convenience of describing the present application and simplifying the description, and do not indicate or imply that the apparatus or elements to be referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present application. Furthermore, the terms "first, second, or third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
The terms "mounted, connected, and coupled" should be construed broadly in this disclosure unless otherwise specifically indicated and defined, such as: can be fixed connection, detachable connection or integral connection; it may also be a mechanical connection, an electrical connection, or a direct connection, or may be an indirect connection via an intermediary, or may be a communication between two elements. The specific meaning of the above terms in the present application will be understood in specific cases by those of ordinary skill in the art.
Example 1
Referring to fig. 1 to 5, for one embodiment of the present application, there is provided a fatigue durability analysis method for a hood of a long-head truck, including:
s1: establishing a finite element model of the engine hood according to the entity digital model, comparing the calculation mode with the experimental mode, and performing inertial release analysis on the engine hood to obtain the unit load stress field distribution of the engine hood;
s2: intercepting a front half frame, performing flexible treatment on the front half frame, and then assembling the front half frame and an engine hood to construct a frame-engine hood rigid-flexible coupling multi-body dynamics model;
s3: based on a response signal actually measured by a test field, acquiring the equivalent displacement of a frame of the test field by utilizing an iterative inverse strategy, and acquiring a fatigue load spectrum of the engine cover according to an equivalent displacement driving dynamics model;
s4: and (3) carrying out fatigue simulation analysis on the engine cover by applying a Miner linear cumulative damage theory in combination with the material properties of the engine cover and the distribution result of the stress field of the unit load.
The steps S1 to S4 are specifically as follows:
(1) Making a road test scheme of a test field: based on the damage equivalent principle, the actual use mileage of the target user is related to the field-enhanced road surface of the test field, namely, the road surface combination of the test field is optimized, so that the pseudo damage value caused by the road of the test field combination is consistent with the pseudo damage value caused by the road of the actual user, and the road test program of the test field is shown in the table 1:
table 1: the program table is tested based on the equivalent test field route of the damage.
(2) Collecting and processing acceleration signals of an engine cover test field: as shown in fig. 2, which is a layout diagram of an acceleration sensor of an engine hood, signal acquisition is performed according to a test field road test scheme formulated in the step (1), acceleration signals of a vehicle frame and a key area of the engine hood are acquired on a durable road surface of the test field by a real vehicle, drift removal, deburring and filtering processing are performed on the acquired signals, and the acquired signals are used as target signals of iterative equivalent displacement in the step (5);
(3) Building a finite element model of an engine hood and performing modal alignment: establishing a finite element model of the engine cover, comparing a calculation mode with a test mode, as shown in a table 2, so as to verify the accuracy of the finite element model of the engine cover, and performing inertial release on the basis of the finite element model of the engine cover to obtain stress field distribution under the action of unit load of the finite element model of the engine cover, thereby providing necessary preparation for fatigue analysis in the step (7);
table 2: and comparing the model attitude test values of the engine cover.
| Modality | Vibration type | Computing modality/Hz | Test modality/Hz | Error of |
| 1 | First order bending | 9.79 | 10.8 | 9.4％ |
| 2 | First order torsion | 21.14 | 22.4 | 5.6％ |
(4) Establishing a rigid-flexible coupling multi-body dynamics model of a frame-engine cover: as shown in fig. 3, the frame is intercepted from the second cross beam for flexible treatment and is assembled with the engine hood, and a frame-engine hood rigid-flexible coupling multi-body dynamics model is built; according to the simplified thought of a seven-degree-of-freedom model of the vehicle, 4Z-displacement driving is respectively established at the positions of the lifting lug and the rolling lug of the frame plate spring, and the vertical, pitching and rolling stress characteristics of the cab are simulated; 1X-direction displacement drive is established at the second cross beam of the frame, and the longitudinal impact (acceleration, braking and the like) stress characteristics of the cab are simulated; 2Y-displacement drives are established at the same side of the frame, and the transverse and yaw stress characteristics of the cab are simulated; and establishing a corresponding Request point on the engine cover multisome model for outputting a fatigue load spectrum of the engine cover subsequently.
(5) Iterative inversion of the hood to frame equivalent displacement: as shown in fig. 4 to 5, for the rigid-flexible coupled multi-body dynamics model established in the step (4), the engine hood acceleration acquired by the durable road of the test field is taken as a desired signal, and based on the cyclic iteration principle, when the model converges and the simulation signal is consistent with the desired signal measured by the test field, the equivalent displacement excitation signal of the vehicle frame under the condition of accurately simulating the road surface impact of the test field is considered to be obtained. The method comprises the following specific steps:
(a) Generating red powder white noise signals at the equivalent displacement of the frame to drive the multi-body dynamics system to generate corresponding responses, and selecting 12 acceleration signals of four suspension points of the engine cover as system response signals to obtain a system frequency response transfer function H (omega), namely:
H(ω)＝G yx /G xx
wherein X (t) is a white noise time domain signal, Y (t) is a time domain response signal, X (omega) and Y (omega) are corresponding frequency values, G yx As a cross-power spectral density function of the input signal x (t) and the response signal y (t), G xx As a function of the self-power spectral density of the input signal.
(b) Since the multi-body model is a nonlinear system and the transfer function is linear, the inverse calculated excitation signal deviates from the actual load signal, so that an iterative step is required to be introduced in the process of inverse external load to reduce the error and enable the response signal to approach the desired signal. Solving an initial signal x in an iterative process 0 The formula of (t) is:
where a is a correction coefficient.
(c) Inputting the initial signal as an excitation signal into a system to obtain a response signal y of the system under the excitation 0 (t) and is matched with the desired signal y Des (t) comparing, correcting the initial signal by the deviation value to obtain the input signal x of the next iteration 1 (t), namely:
e 0 (t)＝y Des (t)-y 0 (t)；
x 1 (t)＝x 0 (t)+a·Δ 0 (t)
wherein e 0 (t) is response deviation, Δ 0 And (t) is a driving signal correction amount.
Further, performing iterative judgment, namely performing pseudo-damage value calculation on the acceleration signal according to a Miner criterion, dividing the damage value of the response signal obtained by iteration by the damage value of the expected signal to describe the difference degree of the two groups of data, and the difference degree is called a relative damage value; when the relative damage value is between 0.8 and 1.2, the error requirement can be considered to be met, and the iterated and reversely calculated frame equivalent displacement signal can simulate the real load condition of the test field.
(6) Extracting a fatigue load spectrum of the engine cover: and driving the whole multi-body model to carry out Adams/car simulation analysis by taking the equivalent displacement signal excitation of the test field obtained in the last iteration as an input condition, thereby obtaining a fatigue load spectrum of fatigue durability analysis of the engine cover structure.
(7) Hood fatigue durability analysis: based on the fatigue load spectrum of the engine cover obtained in the step (6), the fatigue life of the engine cover is analyzed in nCode fatigue simulation software by combining the material property and the inertia release stress result of the engine cover, and the fatigue durability performance of the engine cover is redirected to structural design.
The application aims to ensure the relevance between fatigue durability analysis and a real use scene of a user, and a test field durability road test scheme which accords with a typical user use scene is prepared based on a damage equivalent principle; establishing a finite element model of the engine cover according to the entity digital model, comparing the calculation mode with the experimental mode, and performing inertial release analysis on the engine cover to obtain the unit load stress field distribution of the engine cover; intercepting a front half frame, performing flexible treatment on the front half frame, and then assembling the front half frame and an engine hood to build a frame-engine hood rigid-flexible coupling multi-body dynamics model; obtaining the equivalent displacement of a frame of the test field by using a response signal actually measured by the test field through an iterative inverse method, and driving a dynamic model to further obtain a fatigue load spectrum of the engine cover; by combining the material properties of the engine cover and the distribution result of the stress field of the unit load, the fatigue simulation analysis is carried out by using the Miner linear accumulated damage theory; the fatigue durability check of the traditional method is over dependent on the real vehicle road test and the bench test, and the fatigue simulation analysis of the engine cover is correlated with the road use scene of the user, so that the defect that the fatigue life of the engine cover structure cannot be accurately reproduced by the traditional method is overcome, the development period of enterprises is effectively shortened, and the development cost is reduced.
Example 2
Referring to fig. 6 to 7, another embodiment of the present application is different from the first embodiment in that a verification test for a fatigue durability analysis method of a hood of a long-head truck is provided, and in order to verify and explain the technical effects adopted in the method, the embodiment uses the method of the present application to perform an experimental test based on an actual target user, and verifies the actual effects of the method by means of scientific demonstration.
Aiming at the fatigue failure problem of a long-head truck engine cover, the embodiment aims at using 150 ten thousand kilometers of target users, creates a test field road test program based on a damage equivalent principle, correlates fatigue durability analysis with a real use scene of the users, and provides an analysis method combining actual measurement road spectrum with virtual simulation; acquiring response signals by arranging sensors on a real vehicle in a test field, and acquiring equivalent displacement at a vehicle frame by adopting iterative reverse thought to perform joint simulation on Adams/car and Femfat-Lab, so as to acquire a fatigue load spectrum of the engine cover by means of a multi-body dynamics model; establishing a finite element model of an engine hood in HyperMesh of finite element software, comparing a calculation mode with a test mode, wherein the error of the calculation mode and the test mode is within 10%, thereby verifying the accuracy of the finite element model, and performing inertial release on the basis to obtain a stress field distribution result under the action of unit load; solving and calculating in nCode fatigue analysis software by combining material properties, engine cover fatigue load spectrum and unit stress field distribution results; and compared with the test result of the test field road, the fatigue simulation predicted failure point is higher in coincidence degree as shown in figure 7, so that the method has higher engineering application value.
It should be noted that the above embodiments are only for illustrating the technical solution of the present application and not for limiting the same, and although the present application has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solution of the present application may be modified or substituted without departing from the spirit and scope of the technical solution of the present application, which is intended to be covered in the scope of the claims of the present application.
Claims (3)
1. A fatigue durability analysis method for a hood of a long-head truck, comprising:
establishing an engine cover finite element model according to an entity digital model, comparing a calculation mode with an experimental mode, and performing inertial release analysis on the engine cover to obtain unit load stress field distribution of the engine cover;
intercepting a front half frame, performing flexible treatment on the front half frame, and then assembling the front half frame with the engine hood to build a frame-engine hood rigid-flexible coupling multi-body dynamics model;
based on a response signal actually measured by a test field, acquiring the equivalent displacement of a frame of the test field by utilizing an iterative inverse strategy, and driving a dynamic model according to the equivalent displacement to acquire a fatigue load spectrum of the engine cover;
carrying out fatigue simulation analysis on the engine cover by applying a Miner linear accumulated damage theory according to the material properties of the engine cover and the distribution result of the unit load stress field;
the response signal of the equivalent displacement includes,
collecting acceleration signals of key areas of the frame and the engine cover, performing drift removal, deburring and filtering treatment on the collected signals, and taking the signals as response signals of iterative equivalent displacement;
the establishment of the rigid-flexible coupling multi-body dynamics model of the frame-engine cover comprises the following steps of,
intercepting a frame from a second beam for flexible treatment and assembling with an engine hood, and constructing a frame-engine hood rigid-flexible coupling multi-body dynamics model;
according to the simplified thought of a seven-degree-of-freedom model of the vehicle, 4Z-displacement driving is respectively established at the positions of the lifting lug and the rolling lug of the frame plate spring, and the vertical, pitching and rolling stress characteristics of the cab are simulated;
1X-direction displacement drive is established at the second cross beam of the frame, and the longitudinal impact stress characteristic of the cab is simulated;
2Y-displacement drives are established at the same side of the frame, and the transverse and yaw stress characteristics of the cab are simulated;
establishing a corresponding Request point on the engine cover multi-body model for outputting a fatigue load spectrum of the engine cover;
the equivalent displacement includes the displacement of the piston rod,
generating red powder white noise signals at the equivalent displacement of the frame to drive a multi-body dynamics system to generate corresponding responses, selecting 12 acceleration signals of four suspension points of the engine cover as system response signals, and solving a system frequency response transfer function H (omega) based on the system response signals;
according to the iteration step, the external load is reversely calculated, and the response signal approaches the expected signal;
the initial signal x in the iterative step 0 (t) obtaining the response signal y of the system under the excitation as the excitation signal input system 0 (t) and is matched with the desired signal y Des (t) comparing, and correcting the initial signal by using the deviation value to obtain an input signal x of the next iteration 1 (t)；
The system frequency response transfer function H (ω) includes,
H(ω)＝G yx /G xx
wherein X (t) is a white noise time domain signal, Y (t) is a time domain response signal, X (omega) and Y (omega) are corresponding frequency values, G yx As a cross-power spectral density function of the input signal x (t) and the response signal y (t), G xx As a function of the self-power spectral density of the input signal;
the initial signal x 0 The formula of (t) includes that,
wherein a is a correction coefficient;
the input signal x of the next iteration 1 (t) comprises the steps of,
e 0 (t)＝y Des (tt)-y 0 (t)；
x 1 (t)＝x 0 (t)+a·Δ 0 (t)
wherein e 0 (t) is response deviation, Δ 0 And (t) is a driving signal correction amount.
2. The fatigue durability analysis method for a hood of a long-head truck according to claim 1, characterized in that: in the iterative process, when the relative damage value is between 0.8 and 1.2, the error requirement is met.
3. The fatigue durability analysis method for a hood of a long-head truck according to claim 2, characterized in that: extracting the hood fatigue load spectrum includes,
and driving the whole multi-body model to carry out Adams/car simulation analysis by taking the equivalent displacement signal excitation of the test field obtained in the last iteration as an input condition to obtain a fatigue load spectrum of the fatigue durability analysis of the engine cover structure.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110801517.0A CN113722943B (en) | 2021-07-15 | 2021-07-15 | Fatigue durability analysis method for engine cover of long-head truck |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110801517.0A CN113722943B (en) | 2021-07-15 | 2021-07-15 | Fatigue durability analysis method for engine cover of long-head truck |
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| CN113722943A CN113722943A (en) | 2021-11-30 |
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