Luggage pull rod service life evaluation method and system based on multi-degree-of-freedom fatigue test
By using multi-degree-of-freedom fatigue testing, the connection structure and material information of the bag and its handle were analyzed, a heat map was constructed, and influencing factors were configured. This solved the problem of inaccurate life assessment results in existing technologies and achieved a more reliable life assessment.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ZHEJIANG ZHENGTIAN TOURISM PROD CO LTD
- Filing Date
- 2026-02-03
- Publication Date
- 2026-05-15
AI Technical Summary
Existing methods for assessing the lifespan of luggage handles are mostly based on fatigue tests with a single degree of freedom or simplified working conditions. These methods fail to reflect the multi-directional stress state under real-world usage scenarios, resulting in insufficient reliability of lifespan assessment results.
By analyzing the connection structure and material information of the bag and the handle, multi-degree-of-freedom analysis is performed to construct a multi-degree-of-freedom coordinate heat map, configure thermal influence factors, set test machine parameters to simulate load, and generate life assessment results.
This improves the reliability of luggage handle life assessment results, enabling it to more accurately reflect the actual fatigue failure patterns and meet the needs of design optimization and life prediction.
Smart Images
Figure CN122046705A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of pull rod evaluation technology, specifically to a method and system for evaluating the lifespan of luggage pull rods based on multi-degree-of-freedom fatigue testing. Background Technology
[0002] As a key load-bearing component in luggage products, the pull rod withstands frequent stretching, retraction, and multi-directional external forces. Its structural reliability and service life directly affect the overall safety and user experience of the luggage. In actual use, the pull rod not only needs to withstand vertical tensile and compressive loads, but also is subjected to multi-degree-of-freedom coupled forces such as pushing, dragging, turning, tilting, and lateral forces and torsional loads caused by uneven road surfaces, exhibiting complex fatigue evolution characteristics. However, existing methods for assessing the lifespan of luggage pull rods are mostly based on fatigue tests of a single degree of freedom or simplified working conditions. They typically only perform axial reciprocating tension or simple loading tests on the pull rod, which is difficult to comprehensively reflect the multi-directional stress state of the pull rod in real-world usage scenarios and its coupled effects. At the same time, the setting of existing test parameters relies heavily on experience or fixed standards, lacking specific analysis of differences in luggage structure, pull rod material properties, and connection methods, leading to deviations between test conditions and actual usage. Under the above circumstances, the life assessment results of the tie rod obtained based on traditional test methods are often difficult to accurately reflect its true fatigue failure law. The reliability and engineering guidance significance of the assessment results are limited, and it is difficult to meet the actual needs of luggage products in terms of design optimization, quality control and life prediction. Summary of the Invention
[0003] This application provides a method and system for evaluating the lifespan of luggage handles based on multi-degree-of-freedom fatigue testing, which solves the technical problem that the lifespan evaluation process of luggage handles does not match the actual use conditions in the prior art, resulting in insufficient reliability of the lifespan evaluation results.
[0004] The first aspect of this application provides a method for evaluating the lifespan of a luggage handle based on multi-degree-of-freedom fatigue testing, the method comprising:
[0005] The connection structure between the bag and the handle is analyzed, along with the design link distribution and material information of the handle. A multi-degree-of-freedom (DOF) analysis of the stress during use is performed, and a multi-DOF coordinate heatmap is constructed. Based on the multi-DOF coordinate heatmap, the lifespan correlation of each degree of freedom is analyzed, and thermal influence factors for each degree of freedom are configured. The testing machine parameters are set according to the thermal influence factors, and a load simulation is performed on the handle of the bag to be tested to obtain a test simulation dataset. Based on the test simulation dataset and the multi-DOF coordinate heatmap, the load-bearing capacity of each degree of freedom is evaluated, the thermal decay relationship of each degree of freedom is predicted, and a lifespan assessment result is generated.
[0006] A second aspect of this application provides a luggage handle life assessment system based on multi-degree-of-freedom fatigue testing, the system comprising:
[0007] The module comprises the following components: Connection Structure Analysis Module: This module analyzes the connection structure between the bag and the pull rod, including the design link distribution and material information of the pull rod. It performs multi-degree-of-freedom (DOF) stress analysis and constructs a multi-DOF coordinate heatmap. Lifetime Correlation Analysis Module: Based on the multi-DOF coordinate heatmap, this module performs lifetime correlation analysis for each degree of freedom and configures the thermal influence factors for each degree of freedom. Load Simulation Module: Based on the thermal influence factors, this module sets the testing machine parameters and performs load simulation on the pull rod of the bag under test, obtaining a test simulation dataset. Lifetime Assessment Module: Based on the test simulation dataset and the multi-DOF coordinate heatmap, this module assesses the load-bearing capacity of each degree of freedom, predicts the thermal decay relationship of each degree of freedom, and generates a lifetime assessment result.
[0008] One or more technical solutions provided in this application have at least the following technical effects or advantages:
[0009] First, the connection structure between the bag and the handle is analyzed, along with the design link distribution and material information of the handle. A multi-degree-of-freedom (DOF) analysis of the stress during use is performed, and a multi-DOF coordinate heatmap is constructed. Next, based on the multi-DOF coordinate heatmap, the lifespan correlation of each degree of freedom is analyzed, and thermal influence factors for each degree of freedom are configured. Then, the testing machine parameters are set according to the thermal influence factors, and a load simulation is performed on the bag handle to be tested, obtaining a test simulation dataset. Finally, based on the test simulation dataset and the multi-DOF coordinate heatmap, the load-bearing capacity of each degree of freedom is evaluated, the thermal decay relationship of each degree of freedom is predicted, and lifespan assessment results are generated. This solves the technical problem in existing technologies where the lifespan assessment process for bag handles does not match actual usage conditions, leading to insufficient reliability of lifespan assessment results, and achieves the technical effect of improving the reliability of bag handle lifespan assessment results. Attached Figure Description
[0010] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0011] Figure 1 A schematic diagram of the process for evaluating the lifespan of a luggage handle based on multi-degree-of-freedom fatigue testing, provided in an embodiment of this application.
[0012] Figure 2 This is a schematic diagram of the life assessment system for luggage handles based on multi-degree-of-freedom fatigue testing provided in an embodiment of this application.
[0013] Explanation of reference numerals in the attached diagram: 11 Connection structure analysis module, 12 Lifetime correlation analysis module, 13 Load simulation module, 14 Lifetime assessment module. Detailed Implementation
[0014] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.
[0015] Example 1, as Figure 1 As shown, this application provides a method for evaluating the lifespan of luggage handles based on multi-degree-of-freedom fatigue testing, wherein the method includes:
[0016] The connection structure between the bag and the trolley is analyzed, along with the design link distribution and material information of the trolley. A multi-degree-of-freedom analysis of the forces exerted during use is conducted, and a multi-degree-of-freedom coordinate heat map is constructed.
[0017] In this embodiment, the assembly structure information of the bag and the pull rod is first obtained, including the connection method between the pull rod body and the bag base, the installation position and constraint form of the locking mechanism, and the connection structure between the handle and the pull rod. Simultaneously, the design link distribution parameters and material information of the pull rod are obtained. The design link distribution parameters include the length, cross-sectional shape, wall thickness variation, and connection transition structure of each section of the pull rod. The material information includes the type of metal or composite material, elastic modulus, yield strength, fatigue limit, and density parameters. Based on the above structural and material information, a three-dimensional digital force model of the pull rod-bag system is established, and boundary constraints consistent with actual usage conditions are defined in the model. Subsequently, combined with typical load conditions of the bag under actual use scenarios such as dragging, lifting, turning, going up and down stairs, and emergency stops, a multi-degree-of-freedom force analysis is performed on the pull rod. The multi-degree-of-freedom includes at least the tensile and compressive degrees of freedom along the pull rod axis, the lateral bending degree of freedom perpendicular to the axis, the torsional degree of freedom around the axis, and the overturning rotation degree of freedom of the base connection. Under multi-degree-of-freedom coupled loading conditions, the three-dimensional digital force model is subjected to force simulation calculations to obtain the stress distribution, strain distribution, and equivalent stress amplitude at each structural position of the tie rod under different degrees of freedom loads. Finally, the simulated force response results for each degree of freedom are mapped according to spatial coordinates. Using the spatial position coordinates of the tie rod as the coordinate axis and the equivalent stress amplitude, strain energy density, or fatigue damage index as color-level mapping values, a multi-degree-of-freedom coordinate heatmap is constructed to intuitively characterize the distribution of mechanical hotspots of the tie rod under multi-degree-of-freedom loading conditions.
[0018] Furthermore, the connection structure between the bag and the trolley handle is analyzed, along with the design link distribution and material information of the trolley handle. A multi-degree-of-freedom analysis of the forces exerted during use is conducted, and a multi-degree-of-freedom coordinate heatmap is constructed, including:
[0019] A three-dimensional digital model of the pull rod-bag structure is established to identify the geometric features and material information of the pull rod body, locking mechanism, pull rod-bag base connection, and handle grip area. Based on road spectrum data of actual user scenarios, the six-degree-of-freedom stress state of the pull rod under dragging, turning, bumping, and emergency stopping conditions is analyzed. According to the six-degree-of-freedom stress state, the three-dimensional digital model is subjected to stress simulation mapping to obtain the stress-strain response of each structural space under six-degree-of-freedom loads. A multi-degree-of-freedom coordinate heat map is generated with spatial coordinates as the horizontal and vertical axes and equivalent stress amplitude or damage density as the color scale value. The heat map dynamically represents the distribution and evolution trend of mechanical hotspots of the pull rod throughout its entire life cycle.
[0020] Preferably, based on the design drawings, BOM data, or 3D scanning results of the luggage and pull rod, a 3D digital model of the pull rod-luggage structure is established. In the model, key structural units such as the pull rod body, telescopic segments, locking mechanisms, pull rod-luggage base connection, and handle grip area are geometrically characterized and partitioned. Simultaneously, corresponding material property parameters, including material type, elastic modulus, yield strength, and fatigue performance parameters, are associated with each structural unit. Secondly, road spectrum data reflecting actual user scenarios is collected. This road spectrum data includes at least information on speed changes, impact intensity, and direction distribution under typical road conditions such as smooth roads, rough roads, steps, and speed bumps. Based on this, the six-degree-of-freedom force states of the pull rod under dragging, turning, bumping, and sudden stopping conditions are analyzed, including axial tension / compression, lateral bending, torsion, and overturning rotation. Then, based on the six-degree-of-freedom stress state, the multi-degree-of-freedom load conditions are mapped to a three-dimensional digital model. Multi-degree-of-freedom stress simulation analysis is performed on each structural spatial node to obtain the corresponding stress, strain, and equivalent damage response parameters. The response parameters are then normalized and visualized according to spatial coordinates to generate a multi-degree-of-freedom coordinate heatmap with spatial coordinates as the horizontal and vertical axes and equivalent stress amplitude or damage density as the color scale value. The multi-degree-of-freedom coordinate heatmap is used to dynamically characterize the distribution of mechanical hotspots in different structural regions of the tie rod throughout its entire life cycle and their changing trends with load cycles.
[0021] Furthermore, the six degrees of freedom include: tensile and compressive degrees of freedom along the axis of the tie rod, two transverse bending degrees of freedom orthogonal to the axis, torsional degrees of freedom about the axis, and two overturning rotation degrees of freedom of the base connection.
[0022] The six degrees of freedom are used to describe the complete force state of the luggage handle during actual use. Specifically, they include: tensile and compressive degrees of freedom along the handle's axis, which characterize the axial tensile and compressive loads generated during lifting, retraction, and bearing the weight of the luggage; two lateral bending degrees of freedom orthogonal to the handle's axis, corresponding to the forward and backward bending loads experienced by the handle during left and right turns and dragging on uneven surfaces, reflecting the bending deformation characteristics of the handle under lateral forces; torsional degrees of freedom about the handle's axis, characterizing the torsional load generated on the handle's cross-section when the user rotates the luggage or when the luggage is eccentrically loaded; and two overturning rotation degrees of freedom located at the connection between the handle and the luggage base, corresponding to the overturning rotation of the handle relative to the luggage base in the forward and backward and left and right directions, respectively, depicting the rotational coupling force state of the base connection under dragging, sudden stop, and obstacle crossing conditions. Through comprehensive modeling and analysis of the above six degrees of freedom, a complete characterization of the multi-directional and multi-form load coupling effects of the handle during actual use is achieved.
[0023] Furthermore, constructing a multi-degree-of-freedom coordinate heatmap also includes:
[0024] A time dimension is introduced into the multi-degree-of-freedom coordinate heatmap to construct a four-dimensional spatiotemporal heatmap, which characterizes the migration and diffusion of thermal distribution with the number of cycles and identifies the propagation path of damage from high-risk areas to low-risk areas. The distribution of composite materials is identified based on material information, and the ply angle and fiber orientation information of the tie rod in the heatmap are analyzed. Based on the number of stress cycles, the interlayer shear stress concentration area and the fiber-matrix interface debonding risk area of the tie rod material are marked.
[0025] A time dimension is introduced into the multi-degree-of-freedom coordinate thermogram, using the number of cycles or the equivalent fatigue load step as a time scale. The thermogram results obtained under different loading stages are correlated temporally to construct a four-dimensional spatiotemporal thermogram containing both spatial and temporal dimensions. This thermogram characterizes the migration, diffusion, and superposition evolution of the thermal distribution of the tie rod under multi-degree-of-freedom load cycles over time. By comparing the positional changes of high-color-level regions in the thermogram at different times, the propagation path of damage from the initial high-risk area to adjacent structural areas or low-risk areas is identified, thus depicting the temporal evolution characteristics of fatigue damage. Simultaneously, based on the material information of the tie rod, the distribution of composite materials in its structure is identified. The corresponding ply angles, fiber orientations, and interlaminar interface positions are superimposed and displayed in the multi-degree-of-freedom coordinate thermogram. Combined with the thermal changes under different loading cycles, areas prone to interlaminar shear stress concentration and fiber-matrix interface debonding risk areas in the composite material structure are marked to assist in the analysis of the potential failure modes and damage evolution mechanisms of the tie rod under multi-degree-of-freedom fatigue loads.
[0026] Furthermore, the multi-degree-of-freedom coordinate heatmap employs a multi-layer rendering rule, wherein the base layer displays the safety margin distribution of the material's yield strength or fatigue limit; the overlay layer displays the stress / strain amplitude ratio in real-time testing; and the warning layer marks areas approaching the failure threshold in a flashing or highlighting manner for visual monitoring of damage evolution.
[0027] The multi-degree-of-freedom coordinate heatmap employs a multi-layer rendering rule, including a base layer, an overlay layer, and an early warning layer. The base layer, based on the material parameters corresponding to each structural region of the tie rod, calculates the safety margin between the material's yield strength or fatigue limit and the current load level in the multi-degree-of-freedom coordinate space, and displays it visually in a continuous color gradient to characterize the basic safety reserve distribution at different spatial locations of the tie rod. The overlay layer displays the ratio between the stress amplitude or strain amplitude collected in real-time during the test and the corresponding material limit value. It is overlaid on the base layer in a semi-transparent manner to reflect the actual stress level changes in each structural region of the tie rod under the current loading state. The early warning layer, according to a preset failure threshold judgment rule, identifies spatial regions where the safety margin or stress / strain amplitude ratio is close to the failure threshold, and displays them through flashing, highlighting, or color-changing methods, thereby achieving visual monitoring and risk warning of the fatigue damage evolution process of the tie rod.
[0028] Based on the multi-degree-of-freedom coordinate heatmap, lifetime correlation analysis is performed for each degree of freedom, and thermal influence factors for each degree of freedom are configured.
[0029] Furthermore, based on the aforementioned multi-degree-of-freedom coordinate heatmap, lifetime correlation analysis is performed for each degree of freedom, and thermal influence factors for each degree of freedom are configured, including:
[0030] High stress concentration areas, fretting wear areas, and material interface transition areas in the multi-degree-of-freedom coordinate thermogram are identified as critical life control points. Based on the coordinate distribution of these critical life control points, the fatigue damage parameters of each coordinate node under multiaxial non-proportional loads are calculated using the critical plane method, establishing a mapping relationship between loads of each degree of freedom and local damage. Based on this mapping relationship, a thermodynamic influence factor matrix H is configured, where matrix elements h... ij This represents the contribution weight of the load of the i-th degree of freedom to the cumulative damage of the j-th spatial coordinate node.
[0031] Preferably, in the multi-degree-of-freedom coordinate thermogram, the equivalent stress amplitude, strain amplitude, and their gradient as a function of the number of cycles are statistically analyzed for each spatial coordinate node. Coordinate nodes whose equivalent stress amplitude exceeds a certain proportion of the material fatigue limit or whose damage density growth rate exceeds a preset threshold within a preset cycle interval are marked as high stress concentration areas. Coordinate nodes where local stress amplitude fluctuates repeatedly during load reversal or amplitude fluctuation are marked as fretting wear areas. Coordinate nodes located at the interface of different materials, different structural units, or different connection forms and where stress continuity changes abruptly are marked as material interface transition areas. The set of the above coordinate nodes is determined as the set of critical life control points. For each critical life control point, the stress-time history of that coordinate node under individual loads of each degree of freedom and combined loads of multiple degrees of freedom is extracted, and the stress-time history is converted into the corresponding normal stress components, shear stress components, and principal stress direction variation information. Based on this, using the critical plane method, a plane search is performed on the stress-time history under each load condition to determine the critical plane that causes the shear stress amplitude or equivalent damage parameter to reach its extreme value. The corresponding fatigue damage parameter is calculated on this critical plane to characterize the local fatigue damage degree of that coordinate node under multiaxial non-proportional load conditions. Then, the fatigue damage parameters obtained under each degree of freedom load condition are compared and analyzed to calculate the damage parameter increment ΔD caused by the change of the i-th degree of freedom load while keeping other degrees of freedom loads constant. ij , where ΔD ij This represents the damage contribution value of the i-th degree of freedom load to the j-th critical lifetime control point. The damage contribution values at each critical lifetime control point are normalized to obtain the relative contribution ratio of each degree of freedom load to the cumulative damage at different spatial coordinate nodes. Finally, a thermodynamic influence factor matrix H is constructed based on the normalized damage contribution ratio, where the matrix elements h... ij The weighting coefficient is used to represent the cumulative fatigue damage of the i-th degree of freedom load to the j-th spatial coordinate node under unit cycle conditions; the thermodynamic influence factor matrix H serves as the basis for the amplitude configuration, phase combination and cycle ratio setting of each degree of freedom load in the multi-degree-of-freedom fatigue test, and is used for subsequent test loading spectrum generation and life assessment analysis.
[0032] The parameters of the testing machine are set according to the thermal influence factor, and the load simulation is performed on the pull rod of the bag to be tested to obtain the test simulation dataset.
[0033] Furthermore, based on the aforementioned thermal influence factor, the testing machine parameters are set, and a load simulation is performed on the pull rod of the bag to be tested to obtain a test simulation dataset, including:
[0034] Based on the thermodynamic influence factor matrix, the load amplitude weight, phase configuration, and cycle ratio of each degree of freedom are determined to generate a non-proportional loading spectrum. The parameters of the testing machine are set according to the non-proportional loading spectrum, and a six-degree-of-freedom coupled load is applied through the testing machine. During the testing process, the strain field, displacement field, temperature field, and micro-vibration signal of the key parts of the tie rod are collected in real time to construct a multi-physics field fusion test simulation dataset.
[0035] Preferably, the thermodynamic influence factor matrix H obtained from the aforementioned lifetime correlation analysis is read, where the matrix elements h ij The contribution weight of the load of the i-th degree of freedom to the damage accumulation of the j-th critical spatial coordinate node is characterized; for each degree of freedom, the distribution of the contribution weight on all critical coordinate nodes is statistically analyzed to determine the relative importance of each degree of freedom in the overall fatigue damage, and it is converted into the corresponding load amplitude weighting coefficient w. i Based on the load amplitude weighting coefficient w i The basic load amplitudes of each degree of freedom are weighted and adjusted. Simultaneously, considering the phase relationship of the multi-degree-of-freedom loads in actual operating conditions, phase differences and synchronous or asynchronous loading modes are set between different degrees of freedom loads. A corresponding cycle number ratio is allocated according to the damage contribution ratio of each degree of freedom, thereby generating a non-proportional loading spectrum containing load amplitude, phase relationship, and cycle ratio parameters. This non-proportional loading spectrum is converted into control parameter commands recognizable by the testing machine. The parameters of the multi-degree-of-freedom execution unit of the testing machine are set according to the load amplitude weights, phase configuration, and cycle ratio. A six-degree-of-freedom coupled load is applied to the pull rod of the suitcase under test by the testing machine. This six-degree-of-freedom coupled load includes at least tensile and compressive loads along the pull rod axis, bending loads in two orthogonal directions, torsional loads around the axis, and overturning moment acting on the connection between the pull rod and the suitcase base. The loads can be synchronously or asynchronously excited according to a preset phase difference to simulate the multi-degree-of-freedom force state of the pull rod under actual dragging, turning, bumping, and emergency stop conditions.
[0036] During the loading process of the testing machine, strain sensors, displacement sensors, temperature sensors, and micro-vibration sensors are arranged in key parts such as the locking mechanism area, base connection area, and handle connection area of the tie rod to collect data on the local strain changes, overall displacement response, temperature rise, and micro-vibration characteristics of the tie rod in real time. The collected multi-source sensor data are synchronously processed according to a unified timestamp to form a multi-physics field fusion dataset containing strain field, displacement field, temperature field, and micro-vibration signal. This dataset serves as the test simulation dataset for subsequent multi-degree-of-freedom load assessment, thermal attenuation analysis, and life prediction.
[0037] Based on the experimental simulation dataset and the multi-degree-of-freedom coordinate heatmap, the load-bearing capacity of each degree of freedom is evaluated, the thermal decay relationship of each degree of freedom is predicted, and the life assessment results are generated.
[0038] Furthermore, based on the experimental simulation dataset and the multi-degree-of-freedom coordinate heatmap, the load-bearing capacity of each degree of freedom is assessed, the thermal decay relationship of each degree of freedom is predicted, and a lifetime assessment result is generated, including:
[0039] The experimental simulation dataset is mapped onto the multi-degree-of-freedom coordinate thermogram, and the damage thermodynamic state of each coordinate node is updated. The damage fatigue evolution analysis of the coordinate nodes is performed according to the updated thermodynamic time sequence relationship, and the decay trajectory of the thermogram color value under the load of each degree of freedom is predicted. Using structural failure, functional failure and appearance failure as multiple judgment criteria, the reliability evaluation of each dimension of the tie rod is performed based on the decay trajectory, and the life assessment result is generated.
[0040] Preferably, based on the strain field, displacement field, temperature field, and micro-vibration signals collected during the experiment, and according to the correspondence between the sensor placement positions and the spatial coordinate nodes in the three-dimensional digital model, the stress amplitude, strain amplitude, and damage increment of each coordinate node under the current cycle stage are calculated. This is then corrected by incorporating the aforementioned thermodynamic influence factors to adjust for damage contributions from different degrees of freedom loads, thereby updating the damage thermodynamic state of each coordinate node and obtaining a thermographic data sequence that dynamically changes with the number of cycles. Based on the updated thermographic data sequence, according to the relationship between thermodynamic color value and time or the number of cycles, damage fatigue evolution analysis is performed on each coordinate node, extracting the thermodynamic color value decay curves of key coordinate nodes under each degree of freedom load condition. By performing trend fitting or threshold extrapolation on the decay curves, the number of cycles or equivalent service time corresponding to when the thermodynamic color value reaches a preset failure threshold under the continuous action of different degrees of freedom loads is predicted, thereby obtaining the thermodynamic decay relationship and remaining life prediction results under the action of each degree of freedom load.
[0041] Based on the aforementioned thermal decay relationship, the reliability of the pull rod is evaluated according to multiple failure criteria. These failure criteria include at least: a structural failure criterion, used to determine whether the pull rod body, connecting parts, or key load-bearing structures have fractured, undergone significant plastic deformation, or lost their load-bearing capacity; a functional failure criterion, used to determine whether the pull rod exhibits a failure of its stepless locking function, an abnormally increased extension resistance exceeding a preset threshold, or cracks on the pull rod surface with a length or width reaching a preset size threshold, or significant fading, which affect normal use; and an appearance failure criterion, used to determine whether the pull rod or handle exhibits wear, coating or covering peeling, aging of rubber or elastic materials, powdering, or flaking that affect the product's appearance quality.
[0042] By comprehensively evaluating the tie rod across multiple dimensions, including structural reliability, functional reliability, and appearance reliability, based on the triggering time or number of cycles of each failure criterion in the thermal decay trajectory, the following steps are taken: Recording the number of cycles or equivalent service time corresponding to the first triggering of each structural, functional, and appearance failure criterion in the thermal decay trajectory, and using these as the failure thresholds for the corresponding reliability dimensions; comparing and analyzing the failure thresholds for different reliability dimensions, and selecting the number of cycles or equivalent service time that first reaches the failure threshold as the effective service life of the tie rod according to preset life determination rules; simultaneously, outputting the remaining life ratio and failure type identifier for each reliability dimension to characterize the structural, functional, and appearance reliability status of the tie rod under multi-degree-of-freedom fatigue loads, ultimately generating a life assessment result including effective service life, main failure modes, and reliability assessment level.
[0043] Furthermore, mapping the experimental simulation dataset to the multi-degree-of-freedom coordinate heatmap and updating the damage thermal state of each coordinate node includes:
[0044] A damage status file is established for each coordinate node in the multi-degree-of-freedom coordinate thermogram to record the material information, initial damage value, accumulated cycle count, and material performance degradation parameters of the coordinate node. The experimental simulation dataset is received, and the damage increment is corrected based on the current cycle damage increment value, combined with a multi-degree-of-freedom thermodynamic influence factor. This thermodynamic influence factor represents the weight difference in the contribution of different degrees of freedom loads to the damage of the coordinate node. Based on the load amplitude and phase relationship of each degree of freedom under the current loading mode, the corrected effective damage increment is obtained. The corrected effective damage increment is added to the historical damage accumulation value of the corresponding coordinate node, updating the total damage value and remaining lifetime percentage of the coordinate node. The color scale value is recalculated based on the updated damage value and remaining lifetime percentage, updating the thermodynamic color value of the coordinate node in the multi-degree-of-freedom coordinate thermogram.
[0045] First, a damage state profile is established for each spatial coordinate node in the multi-degree-of-freedom coordinate thermogram. This profile is stored in a data structure, recording the material type, material mechanical parameters, initial damage value, accumulated cycle count, and degradation parameters reflecting the degree of material performance degradation. The initial damage value characterizes the node's initial state before the test, and the material performance degradation parameters describe the changes in properties such as elastic modulus, fatigue strength, or fracture toughness under cyclic loading as damage accumulates. Second, the test simulation dataset is received. At the end of each loading cycle or a preset cycle step, the basic damage increment value for each coordinate node under the current cyclic condition is calculated based on the strain amplitude, stress amplitude, and temperature change information collected in the test simulation dataset. Based on this, a multi-degree-of-freedom thermodynamic influence factor is introduced to correct the basic damage increment value. This thermodynamic influence factor characterizes the weight differences of different degrees of freedom loads on the damage accumulation of the coordinate node under the current loading mode. Specifically, the basic damage increment value is weighted and corrected according to the amplitude ratio, phase relationship, and synchronous or asynchronous loading characteristics of each degree of freedom load in the current loading mode, resulting in the effective damage increment corresponding to each coordinate node. Then, the effective damage increment is added to the historical damage accumulation value of the corresponding coordinate node to update the total damage value of the coordinate node, and the corresponding remaining life percentage is calculated based on the preset damage-life mapping relationship. The remaining life percentage characterizes the remaining load-bearing capacity of the coordinate node relative to its design life under the current multi-degree-of-freedom fatigue load. Finally, based on the updated total damage value and remaining life percentage, the color scale values of each coordinate node in the multi-degree-of-freedom coordinate heatmap are recalculated and updated. When the damage value of a coordinate node is within a preset safe range, it is displayed in a cool color; when the damage value enters a warning range, it is displayed in a warm color; and when the damage value reaches or exceeds a danger threshold, it is displayed in a bright warning color. Simultaneously, the corresponding timestamp or cycle number is recorded for the color scale change process to form the damage evolution history of each coordinate node as it evolves with the loading cycle, which is used for subsequent fatigue evolution analysis and life prediction.
[0046] In summary, the embodiments of this application have at least the following technical effects:
[0047] First, the connection structure between the bag and the handle is analyzed, along with the design link distribution and material information of the handle. A multi-degree-of-freedom (DOF) analysis of the stress during use is performed, and a multi-DOF coordinate heatmap is constructed. Next, based on the multi-DOF coordinate heatmap, the lifespan correlation of each degree of freedom is analyzed, and thermal influence factors for each degree of freedom are configured. Then, the testing machine parameters are set according to the thermal influence factors, and a load simulation is performed on the bag handle to be tested, obtaining a test simulation dataset. Finally, based on the test simulation dataset and the multi-DOF coordinate heatmap, the load-bearing capacity of each degree of freedom is evaluated, the thermal decay relationship of each degree of freedom is predicted, and lifespan assessment results are generated. This solves the technical problem in existing technologies where the lifespan assessment process for bag handles does not match actual usage conditions, leading to insufficient reliability of lifespan assessment results, and achieves the technical effect of improving the reliability of bag handle lifespan assessment results.
[0048] Example 2 is based on the same inventive concept as the bag handle life assessment method based on multi-degree-of-freedom fatigue testing in the previous examples, such as... Figure 2 As shown, this application provides a luggage handle life assessment system based on multi-degree-of-freedom fatigue testing, wherein the system includes:
[0049] Connection Structure Analysis Module 11: Analyzes the connection structure between the bag and the pull rod, as well as the design link distribution and material information of the pull rod, performs multi-degree-of-freedom analysis of the stress during use, and constructs a multi-degree-of-freedom coordinate heat map; Lifetime Correlation Analysis Module 12: Based on the multi-degree-of-freedom coordinate heat map, performs lifetime correlation analysis for each degree of freedom and configures the thermal influence factors for each degree of freedom; Load Simulation Module 13: Sets the test machine parameters according to the thermal influence factors, performs load simulation on the pull rod of the bag to be tested, and obtains the test simulation dataset; Lifetime Assessment Module 14: Based on the test simulation dataset and the multi-degree-of-freedom coordinate heat map, performs load assessment for each degree of freedom, predicts the thermal decay relationship of each degree of freedom, and generates lifetime assessment results.
[0050] Furthermore, the connection structure parsing module 11 is used to perform the following method:
[0051] A three-dimensional digital model of the pull rod-bag structure is established to identify the geometric features and material information of the pull rod body, locking mechanism, pull rod-bag base connection, and handle grip area. Based on road spectrum data of actual user scenarios, the six-degree-of-freedom stress state of the pull rod under dragging, turning, bumping, and emergency stopping conditions is analyzed. According to the six-degree-of-freedom stress state, the three-dimensional digital model is subjected to stress simulation mapping to obtain the stress-strain response of each structural space under six-degree-of-freedom loads. A multi-degree-of-freedom coordinate heat map is generated with spatial coordinates as the horizontal and vertical axes and equivalent stress amplitude or damage density as the color scale value. The heat map dynamically represents the distribution and evolution trend of mechanical hotspots of the pull rod throughout its entire life cycle.
[0052] Furthermore, the connection structure parsing module 11 is used to perform the following method:
[0053] The six degrees of freedom include: tension and compression degrees of freedom along the tie rod axis, two transverse bending degrees of freedom orthogonal to the axis, torsion degrees of freedom around the axis, and two overturning rotation degrees of freedom of the base connection.
[0054] Furthermore, the connection structure parsing module 11 is used to perform the following method:
[0055] A time dimension is introduced into the multi-degree-of-freedom coordinate heatmap to construct a four-dimensional spatiotemporal heatmap, which characterizes the migration and diffusion of thermal distribution with the number of cycles and identifies the propagation path of damage from high-risk areas to low-risk areas. The distribution of composite materials is identified based on material information, and the ply angle and fiber orientation information of the tie rod in the heatmap are analyzed. Based on the number of stress cycles, the interlayer shear stress concentration area and the fiber-matrix interface debonding risk area of the tie rod material are marked.
[0056] Furthermore, the lifetime correlation parsing module 12 is used to perform the following method:
[0057] High stress concentration areas, fretting wear areas, and material interface transition areas in the multi-degree-of-freedom coordinate thermogram are identified as critical life control points. Based on the coordinate distribution of these critical life control points, the fatigue damage parameters of each coordinate node under multiaxial non-proportional loads are calculated using the critical plane method, establishing a mapping relationship between loads of each degree of freedom and local damage. Based on this mapping relationship, a thermodynamic influence factor matrix H is configured, where matrix elements h... ij This represents the contribution weight of the load of the i-th degree of freedom to the cumulative damage of the j-th spatial coordinate node.
[0058] Furthermore, the load simulation module 13 is used to perform the following method:
[0059] Based on the thermodynamic influence factor matrix, the load amplitude weight, phase configuration, and cycle ratio of each degree of freedom are determined to generate a non-proportional loading spectrum. The parameters of the testing machine are set according to the non-proportional loading spectrum, and a six-degree-of-freedom coupled load is applied through the testing machine. During the testing process, the strain field, displacement field, temperature field, and micro-vibration signal of the key parts of the tie rod are collected in real time to construct a multi-physics field fusion test simulation dataset.
[0060] Furthermore, the life assessment module 14 is used to perform the following methods:
[0061] The experimental simulation dataset is mapped onto the multi-degree-of-freedom coordinate thermogram, and the damage thermodynamic state of each coordinate node is updated. The damage fatigue evolution analysis of the coordinate nodes is performed according to the updated thermodynamic time sequence relationship, and the decay trajectory of the thermogram color value under the load of each degree of freedom is predicted. Using structural failure, functional failure and appearance failure as multiple judgment criteria, the reliability evaluation of each dimension of the tie rod is performed based on the decay trajectory, and the life assessment result is generated.
[0062] Furthermore, the life assessment module 14 is used to perform the following methods:
[0063] A damage status file is established for each coordinate node in the multi-degree-of-freedom coordinate thermogram to record the material information, initial damage value, accumulated cycle count, and material performance degradation parameters of the coordinate node. The experimental simulation dataset is received, and the damage increment is corrected based on the current cycle damage increment value, combined with a multi-degree-of-freedom thermodynamic influence factor. This thermodynamic influence factor represents the weight difference in the contribution of different degrees of freedom loads to the damage of the coordinate node. Based on the load amplitude and phase relationship of each degree of freedom under the current loading mode, the corrected effective damage increment is obtained. The corrected effective damage increment is added to the historical damage accumulation value of the corresponding coordinate node, updating the total damage value and remaining lifetime percentage of the coordinate node. The color scale value is recalculated based on the updated damage value and remaining lifetime percentage, updating the thermodynamic color value of the coordinate node in the multi-degree-of-freedom coordinate thermogram.
[0064] Furthermore, the connection structure parsing module 11 is used to perform the following method:
[0065] The multi-degree-of-freedom coordinate heatmap employs a multi-layer rendering rule. The base layer displays the safety margin distribution of the material's yield strength or fatigue limit; the overlay layer displays the stress / strain amplitude ratio in real-time testing; and the warning layer marks areas approaching the failure threshold with flashing or highlighting for visual monitoring of damage evolution.
[0066] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.
Claims
1. A method for evaluating the lifespan of luggage handles based on multi-degree-of-freedom fatigue testing, characterized in that, The method includes: The connection structure between the bag and the trolley is analyzed, as well as the design link distribution and material information of the trolley. A multi-degree-of-freedom analysis of the stress during use is performed, and a multi-degree-of-freedom coordinate heat map is constructed. Based on the multi-degree-of-freedom coordinate heatmap, lifetime correlation analysis of each degree of freedom is performed, and thermal influence factors of each degree of freedom are configured. The parameters of the testing machine are set according to the thermal influence factor, and the load simulation is performed on the pull rod of the bag to be tested to obtain the test simulation dataset. Based on the experimental simulation dataset and the multi-degree-of-freedom coordinate heatmap, the load-bearing capacity of each degree of freedom is evaluated, the thermal decay relationship of each degree of freedom is predicted, and the life assessment results are generated.
2. The method for evaluating the lifespan of luggage handles based on multi-degree-of-freedom fatigue testing according to claim 1, characterized in that, This study analyzes the connection structure between the bag and the trolley handle, as well as the design link distribution and material information of the trolley handle. It then performs a multi-degree-of-freedom analysis of the forces exerted during use and constructs a multi-degree-of-freedom coordinate heatmap, including: Establish a three-dimensional digital model of the pull rod-bag structure, and identify the geometric features and material information of the pull rod body, locking mechanism, pull rod-bag base connection and handle grip area; Based on road spectrum data from actual user scenarios, the six-degree-of-freedom force state of the tie rod under dragging, steering, bumping, and emergency stop conditions is analyzed. Based on the six-degree-of-freedom stress state, the three-dimensional digital model is subjected to stress simulation mapping to obtain the stress-strain response of each structural space under six-degree-of-freedom load. A multi-degree-of-freedom coordinate heat map is generated with spatial coordinates as the horizontal and vertical axes and equivalent stress amplitude or damage density as the color scale value. The heat map dynamically represents the distribution and evolution trend of mechanical hotspots of the tie rod throughout its entire life cycle.
3. The method for evaluating the lifespan of luggage handles based on multi-degree-of-freedom fatigue testing according to claim 2, characterized in that, The six degrees of freedom include: tension and compression degrees of freedom along the tie rod axis, two transverse bending degrees of freedom orthogonal to the axis, torsion degrees of freedom around the axis, and two overturning rotation degrees of freedom of the base connection.
4. The method for evaluating the lifespan of luggage handles based on multi-degree-of-freedom fatigue testing according to claim 2, characterized in that, Constructing a multi-degree-of-freedom coordinate heatmap also includes: By introducing a time dimension into the multi-degree-of-freedom coordinate heatmap, a four-dimensional spatiotemporal heatmap is constructed to characterize the migration and diffusion patterns of thermal distribution with the number of cycles, and to identify the propagation path of damage from high-risk areas to low-risk areas. Based on the material information, the distribution of composite materials is identified, and the information on the overlay angle and fiber orientation of the tie rod in the thermogram is analyzed. Based on the number of stress cycles, the interlayer shear stress concentration area and the fiber-matrix interface debonding risk area of the tie rod material are marked.
5. The method for evaluating the lifespan of a luggage handle based on multi-degree-of-freedom fatigue testing according to claim 3, characterized in that, Based on the multi-degree-of-freedom coordinate heatmap, lifetime correlation analysis is performed for each degree of freedom, and thermal influence factors for each degree of freedom are configured, including: Identify high stress concentration areas, fretting wear areas, and material interface transition areas in multi-degree-of-freedom coordinate thermograms as key life control points; Based on the coordinate distribution of the key life control points, the fatigue damage parameters of each coordinate node under multi-axis non-proportional loads are calculated using the critical plane method, and the mapping relationship between each degree of freedom load and local damage is established. Based on the mapping relationship between the loads of each degree of freedom and local damage, a thermodynamic influence factor matrix H is configured, where the matrix elements h ij This represents the contribution weight of the load of the i-th degree of freedom to the cumulative damage of the j-th spatial coordinate node.
6. The method for evaluating the lifespan of a luggage handle based on multi-degree-of-freedom fatigue testing according to claim 5, characterized in that, Based on the aforementioned thermal influence factors, the testing machine parameters are set, and a load simulation is performed on the pull rod of the bag to be tested to obtain a test simulation dataset, including: The load amplitude weights, phase configurations, and cycle ratios for each degree of freedom are determined based on the thermodynamic influence factor matrix, and a non-proportional loading spectrum is generated. The parameters of the testing machine are set according to the non-proportional loading spectrum, and a six-degree-of-freedom coupled load is applied through the testing machine. During the testing process on the testing machine, strain field, displacement field, temperature field and micro-vibration signals of key parts of the tie rod are collected in real time to construct a multi-physics field fusion test simulation dataset.
7. The method for evaluating the lifespan of a luggage handle based on multi-degree-of-freedom fatigue testing according to claim 6, characterized in that, Based on the experimental simulation dataset and the multi-degree-of-freedom coordinate heatmap, the load-bearing capacity of each degree of freedom is assessed, the thermal attenuation relationship of each degree of freedom is predicted, and a lifetime assessment result is generated, including: The experimental simulation dataset is mapped onto the multi-degree-of-freedom coordinate heatmap, and the damage thermal state of each coordinate node is updated. Damage fatigue evolution analysis of coordinate nodes is performed based on the updated thermo-temporal relationship to predict the decay trajectory of thermographic color value under load of each degree of freedom. Using structural failure, functional failure, and appearance failure as multiple judgment criteria, the reliability of the tie rod in various dimensions is evaluated based on the attenuation trajectory, and the life assessment result is generated.
8. The method for evaluating the lifespan of a luggage handle based on multi-degree-of-freedom fatigue testing according to claim 7, characterized in that, Mapping the experimental simulation dataset to the multi-degree-of-freedom coordinate heatmap and updating the damage thermal state of each coordinate node includes: A damage state file is established for each coordinate node in the multi-degree-of-freedom coordinate thermogram to record the material information, initial damage value, accumulated number of cycles, and material property degradation parameters of the coordinate node. The test simulation dataset is received, and the current cycle damage increment value is corrected by combining the multi-degree-of-freedom thermodynamic influence factor. The thermodynamic influence factor represents the weight difference of the load contribution of different degrees of freedom to the damage of coordinate nodes. Based on the load amplitude and phase relationship of each degree of freedom under the current loading mode, the corrected effective damage increment is obtained. The corrected effective damage increment is added to the historical damage accumulation value of the corresponding coordinate node, and the total damage value and remaining lifetime percentage of the coordinate node are updated. The color gradation value is recalculated based on the updated damage value and the percentage of remaining lifespan, and the thermochromatic value of the coordinate nodes in the multi-degree-of-freedom coordinate thermogram is updated.
9. The method for evaluating the lifespan of a luggage handle based on multi-degree-of-freedom fatigue testing according to claim 4, characterized in that, The multi-degree-of-freedom coordinate heatmap employs a multi-layer rendering rule. The base layer displays the safety margin distribution of the material's yield strength or fatigue limit; the overlay layer displays the stress / strain amplitude ratio in real-time testing; and the warning layer marks areas approaching the failure threshold with flashing or highlighting for visual monitoring of damage evolution.
10. A luggage handle life assessment system based on multi-degree-of-freedom fatigue testing, characterized in that, The system is used to implement the method for evaluating the lifespan of a luggage handle based on multi-degree-of-freedom fatigue testing as described in any one of claims 1-9, the system comprising: Connection Structure Analysis Module: Analyzes the connection structure between the bag and the trolley, as well as the design link distribution and material information of the trolley, performs multi-degree-of-freedom analysis of the stress during use, and constructs a multi-degree-of-freedom coordinate heat map; Lifetime correlation analysis module: Based on the multi-degree-of-freedom coordinate heatmap, perform lifetime correlation analysis for each degree of freedom and configure the thermal influence factors for each degree of freedom; Load simulation module: Set the testing machine parameters according to the thermal influence factor, perform load simulation on the pull rod of the bag to be tested, and obtain the test simulation dataset; Lifetime assessment module: Based on the experimental simulation dataset and the multi-degree-of-freedom coordinate heat map, the load-bearing capacity of each degree of freedom is assessed, the thermal decay relationship of each degree of freedom is predicted, and the lifetime assessment results are generated.