A load-free automobile ball hinge torque decay prediction method

Abstract

The application provides a load-free automobile ball hinge torque decay prediction method, relates to the automobile ball hinge design and research technical field, and obtains the torque mathematical model related parameters of the designed ball hinge through CAE simulation or manual calculation, carries out the ball pin seat material stress relaxation test according to the ball hinge related parameter information, obtains the material stress relaxation curve, obtains the product stress relaxation curve based on M=kdelta+c (the torque M is the principle of the first function of stress delta), that is, the product torque decay time and the torque value decaying to stability, can predict the ball hinge torque decay time period and the torque value decaying to stability when the ball hinge is researched, and solves the problems of long research period, low efficiency, high cost and the like of the traditional research ball hinge torque decay characteristics.

Description

Technical Field

[0001] This invention relates to the field of automotive ball joint design and development technology, and more specifically, to a method for predicting torque attenuation in an unloaded automotive ball joint. Background Technology

[0002] The ball joint is a key component of the automotive chassis, mainly composed of a metal ball pin, a plastic ball pin seat, and a metal ball pin sleeve. The ball pin and ball pin seat form a spherical friction pair, its primary function being to connect two components and enable force transmission and three-degree-of-freedom rotation between them. Torque performance is one of the key performance indicators of the ball joint; to achieve long-term, flexible, and stable operation, the ball joint torque must be maintained within a specific range. During assembly, the plastic ball pin seat is compressed by the ball pin sleeve and ball pin, creating contact stress between them, which generates frictional torque during operation.

[0003] Because the ball joint is made of plastic, it has stress relaxation characteristics. After a certain period of time, the ball joint will experience torque decay due to stress relaxation. In the past, to study the torque decay characteristics of ball joints, it was necessary to go through the process of product design, prototype manufacturing, product placement and torque testing, which had problems such as long cycle, low efficiency and high cost. Summary of the Invention

[0004] The purpose of this invention is to provide a method for predicting the torque decay of a ball joint in an unloaded vehicle. This method can predict the torque decay time period and the torque value at which the torque decays to a stable value during the development of the ball joint. It solves the problems of long time period, low efficiency and high cost in traditional research on the torque decay characteristics of ball joints.

[0005] The embodiments of the present invention are achieved through the following technical solution: a method for predicting the torque attenuation of an unloaded automotive ball joint, applied to the design and development of automotive ball joints, comprising the following steps:

[0006] S1. Ball joint design: determine the ball pin seat material, ball pin seat structure, ball joint contact stress, and ball pin seat wall thickness h. The relevant parameters of the torque mathematical model are obtained through CAE simulation or manual calculation: M=f(δ,S,X,u); the spherical contact stress is defined as δ, the spherical contact area as S, the spherical distribution position as X, and the friction coefficient as u. It is known that the torque M is a linear function of the stress δ. S2. Design and manufacturing of plastic compression test pieces; S3. Use a stress relaxation testing machine to conduct plastic compression relaxation tests to obtain the design contact stress level δ of the ball joint and the stress relaxation curve of the plastic specimen with the same wall thickness as the ball pin seat. S4. Based on the initial torque M and initial stress level δ determined by the ball joint design, and the stress relaxation curve of the specimen, obtain the product stress relaxation curve, i.e., the product torque decay time and the torque value at which it decays to a stable value, based on the principle that M=kδ+c (M is a linear function of stress δ).

[0007] Furthermore, in step S2, the compressed sample is circular, with a thickness h equal to the wall thickness of the ball pin seat, and a diameter of 10mm-100mm is acceptable. The sample is designed, and then the mold is opened for injection molding.

[0008] Furthermore, in step S3, the stress relaxation testing machine fixture is disc-shaped, and its area is more than twice that of the plastic specimen. The initial stress of the specimen is the initial stress δ designed by the ball joint.

[0009] Furthermore, when conducting stress relaxation tests on plastic specimens based on the actual initial stress of the designed ball joint product, the tests can be carried out at different ambient temperatures to obtain multiple stress relaxation curves.

[0010] The technical solutions of the embodiments of the present invention have at least the following advantages and beneficial effects: A method for predicting torque decay in unloaded automotive ball joints is proposed. This method obtains relevant parameters of the designed ball joint's torque mathematical model through CAE simulation or manual calculation. Stress relaxation tests are then conducted on the ball joint seat material based on these parameters to obtain the material stress relaxation curve. The product stress relaxation curve, i.e., the torque decay time and the torque value at which it stabilizes, is obtained based on the principle that torque M is a linear function of stress δ. This method allows for the prediction of the ball joint's torque decay time period and the torque value at which it stabilizes during the ball joint's development phase. It solves the problems of long cycles, low efficiency, and high costs associated with traditional methods for studying ball joint torque decay characteristics. Attached Figure Description

[0011] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 This is a schematic diagram of the structure of the automobile ball joint in the no-load automobile ball joint torque attenuation prediction method provided by the present invention; Figure 2 This is a schematic diagram of the stress relaxation testing machine performing a plastic compression relaxation test in step S3 of the no-load automotive ball joint torque attenuation prediction method provided by the present invention. Figure 3The stress relaxation curve of the plastic specimen with initial stress level δ in the method for predicting the torque decay of an unloaded automobile ball joint provided by the present invention; Figure 4 The attenuation curve of the torque M of the ball joint in the no-load automobile ball joint torque attenuation prediction method provided by the present invention; Icons: 1. Ball pin, 2. Ball pin seat, 3. Ball pin sleeve. Detailed Implementation

[0013] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0014] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0015] Reference Figures 1 to 4 As shown, in specific implementation, this embodiment provides a method for predicting the torque attenuation of an unloaded automotive ball joint, applied to the design and development of automotive ball joints, including the following steps: S1. Ball joint design: determine the material, structure, contact stress, and wall thickness h of ball pin seat 2. The relevant parameters of the torque mathematical model are obtained through CAE simulation or manual calculation: M=f(δ,S,X,u); the spherical contact stress is defined as δ, the spherical contact area as S, the spherical distribution position as X, and the friction coefficient as u. It is known that the torque M is a linear function of the stress δ. S2. Design and manufacturing of plastic compression test pieces; S3. Use a stress relaxation testing machine to conduct plastic compression relaxation tests to obtain the design contact stress level δ of the ball joint and the stress relaxation curve of the plastic specimen with the same wall thickness as the ball pin seat. S4. Based on the torque M and initial stress level δ determined by the ball joint design, and the stress relaxation curve of the specimen, obtain the product stress relaxation curve, i.e., the product torque decay time and the torque value at which it decays to a stable value, based on the principle that M=kδ+c (M is a linear function of stress δ).

[0016] More specifically, in step S2, the compressed sample is circular, with a thickness h equal to the wall thickness h of the ball pin seat 2, and a diameter of 10mm-100mm is acceptable. The sample is designed, and then the mold is opened for injection molding.

[0017] like Figure 2 As shown, in specific implementation, in step S3, the stress relaxation testing machine fixture is disc-shaped, and its area is more than twice that of the plastic specimen. The initial stress of the specimen is the initial stress δ designed by the ball joint.

[0018] When conducting stress relaxation tests on plastic specimens based on the initial design stress of the ball joint product, the tests can be carried out at different ambient temperatures (determined according to the actual storage environment temperature of the ball joint product) to obtain multiple stress relaxation curves.

[0019] In summary, after ball joint products are manufactured, they are left to stand for a period of time before customer assembly. The time it takes for the torque of different ball joints to decay to a relatively stable level varies. Previously, obtaining the torque decay time and the stable torque value for each ball joint required waiting until the ball joint development was completed, manufacturing a prototype, allowing it to stand for a period, and periodically testing the torque value. This method was inefficient and costly, severely impacting the ball joint development and promotion cycle. Therefore, based on the method proposed above, a method can predict the torque decay time and the stable torque level at the initial design stage. This allows for the prediction of the ball joint torque decay time period and the stable torque value during the ball joint development process.

[0020] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for predicting torque attenuation in an unloaded automotive ball joint, applied to the design and development of automotive ball joints, characterized in that... Includes the following steps: S1. Ball joint design, determine the material of ball pin seat (2), the structure of ball pin seat (2), the contact stress of ball joint, and the wall thickness h of ball pin seat (2); The relevant parameters of the torque mathematical model are obtained through CAE simulation or manual calculation: M=f(δ,S,X,u); the spherical contact stress is defined as δ, the spherical contact area as S, the spherical distribution position as X, and the friction coefficient as u. It is known that the torque M is a linear function of the stress δ. S2. Design and manufacturing of plastic compression test pieces; S3. Use a stress relaxation testing machine to conduct plastic compression relaxation tests to obtain the design contact stress level δ of the ball joint and the stress relaxation curve of the plastic specimen with the same wall thickness as the ball pin seat. S4. Based on the initial torque M and initial stress level δ determined by the ball joint design, and the stress relaxation curve of the specimen, obtain the product stress relaxation curve, i.e., the product torque decay time and the torque value at which it decays to a stable value, based on the principle that M=kδ+c (M is a linear function of stress δ).

2. The method for predicting the torque attenuation of an unloaded automotive ball joint according to claim 1, characterized in that, In step S2, the compressed sample is circular, with a thickness h equal to the wall thickness of the ball pin seat (2), and a diameter of 10mm-100mm is acceptable. The sample is designed, and then the mold is opened for injection molding.

3. The method for predicting the torque attenuation of an unloaded automotive ball joint according to claim 2, characterized in that, In step S3, the stress relaxation testing machine fixture is disc-shaped and its area is more than twice that of the plastic specimen. The initial stress of the specimen is the initial stress δ designed by the ball joint.

4. The method for predicting the torque attenuation of an unloaded automotive ball joint according to claim 3, characterized in that, When conducting stress relaxation tests on test specimens based on the actual initial stress of the designed ball joint product, the tests can be carried out at different ambient temperatures to obtain multiple stress relaxation curves.

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