Chassis component bench fatigue load determination method

Abstract

The present application relates to a kind of chassis parts rack fatigue load determination method, the method specifically is: S1: the fatigue damage cloud atlas of chassis parts structure in all virtual road surface is obtained;S2: key road surface is obtained;S3: the sensitive coefficient of all passages under key road surface is extracted;S4: selecting key passage, in the far end of key passage, constraint is established in attachment point, fixed amplitude load is loaded at key passage, and the fixed amplitude load is derived from road spectrum.The present application is based on vehicle road life calculation and component structure stress characteristics, the present application proposes the concept of passage load sensitive coefficient, can maximum limit guarantee the damage mechanism of chassis parts rack and road is consistent, i.e. damage position is consistent, the damage proportion of each road surface is consistent, and load amplitude is close to road spectrum.

Description

Technical Field

[0001] This invention relates to the field of automotive computer-aided design technology, specifically to a method for developing equivalent load spectra of component fatigue damage on a test bench based on vehicle road loads. Background Technology

[0002] Product development in the automotive industry typically follows a V-shaped process, which involves decomposing the performance of the entire vehicle, systems, and components step by step, and then conducting tests and verifications in reverse order. This aims to mitigate vehicle performance risks through small-scale early testing, with component bench testing being the most cost-effective and readily implemented method by suppliers. Currently, chassis component bench test loads are primarily simulated by OEMs using virtual test tracks. Random load spectra on various virtual road surfaces are obtained through multibody dynamics simulation. OEMs then provide these random load spectra to component suppliers, who conduct structural design and bench verification tests according to the OEM's durability requirements. Once passed, the components are delivered to the OEM. However, chassis components often have numerous load channels at their attachment points, making it difficult to apply random load spectra using actuators. Therefore, component bench testing cannot reproduce the random load spectra required by the OEM for the virtual road surface. In such cases, load equivalence is necessary, transforming the random load spectra of all channels into single-channel or a few-channel fixed-amplitude load spectra. However, the equivalent load spectrum of components on test benches in the industry is usually obtained empirically. For example, for a triangular control arm, the function of which is to provide longitudinal and lateral support, the component supplier defines a resultant direction for the longitudinal and lateral forces. All vehicle models use the same resultant force angle. When applying load equivalence, only the load in the direction of the resultant force is considered, and a single-channel load pseudo-damage equivalence is performed, which is considered to be consistent with road load damage. As chassis integration increases and electrification becomes more widespread, chassis loads become heavier and the loads on chassis components become more complex. The traditional empirically defined single-channel pseudo-damage load equivalence method is difficult to fully cover the random load damage mechanism of the road spectrum. Summary of the Invention

[0003] The purpose of this invention is to provide a method for determining the bench fatigue load of chassis components, so as to solve the problem that the traditional empirically defined single-channel pseudo-damage load equivalent method is difficult to fully cover the road spectrum random load damage mechanism.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] A method for determining the fatigue load on a chassis component test bench, the method specifically comprising:

[0006] S1: Based on the virtual test field, obtain fatigue damage cloud maps of chassis component structures on all virtual road surfaces;

[0007] S2: Obtain critical road surfaces. The method for obtaining critical road surfaces is as follows: Based on the fatigue damage cloud maps of all virtual road surfaces, the virtual road test damage results are superimposed to obtain the damage results. The unit with the greatest damage degree in the chassis component structure is extracted, and the virtual road surfaces are sorted in ascending order based on the damage degree of the unit when driving on a single virtual road surface. Then, the top N virtual road surfaces in the sorted sequence are selected as critical road surfaces, where 0 < N ≤ N max N is a natural number. max This represents the total number of virtual road surfaces;

[0008] S3: Extract the sensitivity coefficients of all channels under the critical road surface. The sensitivity coefficient is defined as the maximum load amplitude of a certain channel under the critical road surface multiplied by the stress of the unit force of that channel acting on the unit with the greatest damage in the chassis component structure described in S2.

[0009] S4: Select a key channel, and under test conditions, establish constraints at the far end attachment point of the key channel of the chassis component structure. Apply a fixed-amplitude load at the key channel so that the fixed-amplitude load is equivalent to the random load in the virtual road surface, thereby obtaining the fatigue load of the chassis component structure.

[0010] The constant-amplitude load is derived from the road spectrum. The key channel is defined as follows: all sensitivity coefficients are sorted in ascending order, and the channel corresponding to the first M sensitivity coefficients in the sorted sequence is selected, where 0 < M ≤ M. max M is a natural number. max This represents the total number of sensitivity coefficients.

[0011] Based on the above technical means, by extracting the unit with the greatest damage in the chassis component structure, and selecting key road surfaces and key passages according to the damage degree of the unit, the fixed-amplitude load obtained through the road spectrum is applied to the key passages. This can ensure that the damage mechanism of the chassis component test bench and the road is consistent to the greatest extent, so that the damage ratio of each road surface is consistent, thereby maximizing the damage caused to the chassis component structure by the equivalent random load of the road spectrum.

[0012] Furthermore, the constant-amplitude load mentioned in S4 is the maximum load amplitude in the road spectrum.

[0013] Furthermore, the peak and trough values ​​of the constant-amplitude load can be scaled proportionally according to the required number of cyclic loading cycles.

[0014] Furthermore, S1 specifically refers to:

[0015] S11: In accordance with the vehicle road test specifications, virtual test field technology is used to calculate and extract the attachment point loads of chassis components on various virtual road surfaces;

[0016] S12: Obtain the stress distribution of chassis component structures under unit force at the attachment point;

[0017] S13: Based on S11 and S12, the time-domain load spectrum of all positions of the chassis component structure under random load spectrum is obtained. Finally, load statistics are performed, and the fatigue damage cloud map of the chassis component structure is obtained based on the damage superposition of fatigue life curves.

[0018] Furthermore, the relationship between the degree of damage to the chassis component structure on the critical road surface and the degree of damage to the chassis component structure on all the virtual road surfaces is as follows:

[0019] I 关键 ≥I 全部 50%;

[0020] Where I 关键 This indicates the degree of damage to chassis components on the critical road surface.

[0021] I 全部 This indicates the degree of damage to the chassis components and structure across the entire virtual road surface.

[0022] Furthermore, when the directions of two key channels correspond to the directions of two forces at the same loading point, the two key channels are merged, and the direction of the merged channel is the resultant force direction.

[0023] Furthermore, when the directions of the force and torque of two key channels correspond to the same loading point, an extension rod is added to merge the force and torque of the two key channels.

[0024] The beneficial effects of this invention are:

[0025] This invention uses virtual test field technology to obtain the unit with the greatest damage to the chassis component structure. Then, by obtaining the channel load sensitivity coefficient, the key channel is obtained. Then, a fixed-amplitude load obtained through the road spectrum is applied to the key channel. This can ensure that the damage mechanism of the chassis component test bench and the road is consistent to the greatest extent, that is, the damage location is consistent, so that the damage proportion of each road surface is consistent, thereby maximizing the damage caused to the chassis component structure by the equivalent road spectrum random load. Attached Figure Description

[0026] Figure 1 This is a flowchart of the method described in this embodiment;

[0027] Figure 2 This diagram illustrates the relevant concepts of component structural loads in this embodiment. Detailed Implementation

[0028] The following description, with reference to the accompanying drawings and preferred embodiments, illustrates the implementation of the technical solution of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be understood that the preferred embodiments are only for illustrating the present invention and not for limiting the scope of protection of the present invention.

[0029] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0030] This embodiment proposes a method for determining the fatigue load of chassis components on a test bench, such as... Figure 1 As shown, the specific method for determining this is as follows:

[0031] S1: Obtain fatigue damage cloud maps of chassis component structures on all virtual road surfaces;

[0032] The calculation of fatigue damage cloud maps for chassis components involves the following three steps:

[0033] S11: After the chassis component structural design is completed, in accordance with the vehicle road test specifications, virtual test track technology is used to calculate and extract the attachment point loads of the chassis components on various virtual road surfaces, such as... Figure 2 As shown, each attachment point has 6 degrees of freedom, that is, 6 load channels.

[0034] S12: The modal frequencies of chassis components are usually very high, and resonance will not occur in road tests. For constrained components, the static method can be used, and for unconstrained components, the inertial release method can be used to calculate the stress distribution of the chassis component structure under the action of a unit force at the attachment point.

[0035] S13: Input the results of S11 and S12 into the fatigue calculation software. Assuming that the stress of the chassis component structure at any time under the random load spectrum is the linear superposition of the stress distribution of each channel load multiplied by the corresponding channel unit force, the time-domain spectrum of the load of the chassis component structure at all positions under the random load spectrum can be obtained. Finally, load statistics are performed, such as the rainflow method, and damage superposition based on the fatigue life curve, to obtain the fatigue damage cloud map of the chassis component structure.

[0036] S2: Based on the fatigue damage cloud maps of the chassis component structure obtained in S1 across all virtual road surfaces, the fatigue damage results of the component structure in virtual road tests are calculated by superimposing the data according to the number of cycles for each road surface in the road test specifications. The unit with the most damage in the chassis component structure is extracted, and the virtual road surfaces are sorted in ascending order based on the degree of damage of this unit when driving on a single virtual road surface. The top N virtual road surfaces in the sorted sequence are then selected as the critical road surfaces, where 0 < N ≤ N. max N is a natural number. max The total number of virtual road surfaces is considered as the critical road surface. In this embodiment, the relationship between the damage level of the chassis component structure on the critical road surface and the damage level of the chassis component structure on all the virtual road surfaces is as follows:

[0037] I 关键 >I 全部 50%;

[0038] Where I 关键 This indicates the degree of damage to chassis components on critical road surfaces;

[0039] I 全部 This indicates the degree of damage to the chassis components across the entire virtual road surface.

[0040] S3: Extract the sensitivity coefficients of all channels under the critical road surface. The sensitivity coefficient is defined as the maximum load amplitude of a certain channel under the critical road surface multiplied by the stress of the unit force of that channel acting on the chassis component structure with the greatest damage in S2. The larger the sensitivity coefficient, the greater the contribution of the channel load to the road spectrum damage of the chassis components.

[0041] S4: Select a key channel. Under test conditions, establish constraints at the far-end attachment point of the key channel. Apply a fixed-amplitude load at the key channel. The fixed-amplitude load is derived from the road spectrum. The key channel is defined as follows: sort all sensitivity coefficients in ascending order, and select the channel corresponding to the first M sensitivity coefficients in the sorted sequence, where 0 < M ≤ M. max M is a natural number. max This represents the total number of sensitivity coefficients.

[0042] In short: After calculating the sensitivity coefficients of all channels, sort them according to their values, and select the one or several channels with the highest sensitivity coefficients as critical channels. The number of critical channels depends on whether channels can be combined. Typically, component test benches use single-actuator loading. Multiple critical channels should be combined as much as possible. For example, for forces in two directions at the same loading point, the resultant force direction should be taken. For forces and moments, extension rods can be added to achieve simultaneous loading of forces and moments. Test bench conditions should constrain the far-end attachment points of critical channels as much as possible, applying a fixed-amplitude load at the critical channel. The maximum load amplitude in the spectrum is recommended, and the peak and trough values ​​of the fixed-amplitude load should be scaled proportionally according to the required number of cycles. If it is the resultant force of two forces, or a combination of force and moment, the peak and trough values ​​of the maximum load amplitude should be taken simultaneously for both channels for combined loading. That is, when the directions of force and moment at the same loading point correspond to two critical channels respectively, extension rods can be added to achieve the merging of the force and moment of the two critical channels.

[0043] The above embodiments are merely preferred embodiments provided to fully illustrate the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention.

Claims

1. A method of determining a fatigue load for a chassis component bench, the method comprising: The method is specifically: ​ S1: based on a virtual test field, obtaining a fatigue damage cloud atlas of a chassis component structure on all virtual road surfaces; S2: Obtain the key road surface, the acquisition method of the key road surface is: based on the fatigue damage cloud atlas of all virtual road surfaces, superimposed to obtain the virtual road test damage result, extract the unit with the largest damage degree in the chassis component structure, and arrange the virtual road surface in ascending order based on the damage degree of the unit when driving on a single virtual road surface, then select the virtual road surface with the top N sequence as the key road surface, wherein 0 max , N is a natural number, N max represents the total number of virtual road surfaces; S3: extracting a sensitive coefficient of all channels under a key road surface, the sensitive coefficient being defined as a maximum load amplitude of a channel under the key road surface multiplied by a stress of a unit force of the channel acting on a most damaged unit of the chassis component structure in S2; S4: selecting a key channel, establishing a constraint at a distal attachment point of the key channel of the chassis component structure under a bench test condition, loading a constant amplitude load at the key channel, making the constant amplitude load equivalent to a random load in the virtual road surface, and further obtaining a fatigue load of the chassis component structure; The constant-amplitude load is derived from a road profile, and the key channels are defined as follows: all the sensitive coefficients are arranged in ascending order, and the channels corresponding to the sensitive coefficients with the top M ranks in the sequence are selected, 0 max M is a natural number, and M max represents the total number of the sensitive coefficients.

2. The determination method of claim 1, wherein: The constant amplitude load in S4 is a maximum load amplitude in a road spectrum.

3. The determination method according to claim 2, characterized in that: According to the number of cyclic loads, the peak and valley values of the constant amplitude load can be scaled proportionally.

4. The determination method of claim 1, wherein: The S1 is specifically: S11: according to a vehicle road test specification, using a virtual test field technology, calculating and extracting an attachment point load of a chassis component on each virtual road surface; S12: obtaining a stress distribution of a chassis component structure under a unit force at an attachment point; S13: based on S11 and S12, obtaining a load time domain spectrum of all positions of the chassis component structure under a random load spectrum, finally performing load statistics, and based on a fatigue life curve, damage superposition, obtaining a fatigue damage cloud atlas of the chassis component structure.

5. The determination method of claim 1, wherein: The relationship between the damage degree of the chassis component structure on the key road surface and the damage degree of the chassis component structure on all the virtual road surfaces is: I 关键 ≥I 全部 • 50%; where I 关键 represents the degree of damage of the chassis component structure on the critical road surface; I 全部 represents the damage degree of the chassis component structure on all the virtual road surfaces.

6. The determination method of claim 1, wherein: When the directions of two key channels correspond to the directions of two forces of the same loading point, the two key channels are combined, and the direction after combination is the direction of the resultant force.

7. The determination method of claim 1, wherein: When two key channels correspond to the directions of a force and a torque of the same loading point, respectively, an extension rod is added to realize the combination of the two key channels of the force and the torque.

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