Integrated die-casting automobile rear floor torsional rigidity test fixture and method

Abstract

The application provides a kind of integrated die-casting automobile rear floor torsional rigidity test fixture and method, it is related to the field of automobile parts performance test, including marking constraint point, loading point and displacement collection point on automobile rear floor part, setting target load;Front end torsion applying assembly is installed at loading point, rear end displacement constraint assembly is installed at constraint point, vertical load of opposite direction, equal size or equivalent forming couple is respectively applied to front end torsion applying assembly by using quasi-static step loading mode, until target load is reached, record each level load holding time and displacement sensor data;The torsional rigidity and torsional deformation distribution of automobile rear floor part are calculated by obtaining data.The application makes the constraint state of part on test bench more close to its real installation state in whole vehicle, so that the test result can better reflect the torsional resistance of rear floor structure itself.The application can identify local weak area, improve test data stability and repeatability.

Description

Technical Field

[0001] This invention relates to the field of automotive component performance testing technology, and in particular to an integrated die-cast automotive rear floor torsional stiffness testing fixture and method. Background Technology

[0002] With the development of new energy vehicles and lightweight body technology, the traditional rear floor structure, which is made of multiple stamped sheet metal parts welded together, is gradually being replaced by an integrated die-cast rear floor structure. Integrated die-casting technology can integrate multiple components, connectors, and reinforcements in the traditional rear floor area into a single large die-cast aluminum alloy structural component. This reduces the number of parts, streamlines welding and assembly processes, improves manufacturing efficiency, and helps enhance the local rigidity and dimensional consistency of the vehicle body. Therefore, integrated die-cast rear floors have become one of the important directions for the development of body-in-white structures in new energy vehicles.

[0003] Traditional automotive parts are mostly assembled from multiple steel sheets. However, with the rise of die casting technology, large-sized castings produced using this technology integrate multiple sheets, combining various automotive components into a single part. Consequently, large-sized parts integrating multiple sheets lack rigidity testing methods.

[0004] Currently, there is a lack of unified standards and specifications for the boundary conditions of torsional stiffness of unibody die-cast aluminum alloy body parts, resulting in a lack of standardized methods for the load and constraint of individual parts.

[0005] Compared to traditional stamped and welded rear floors, integrated die-cast rear floors differ significantly in structural form, material properties, and testing methods. Traditional rear floors are typically welded from multiple thin-plate stampings, and their structural boundaries, connection methods, and local deformation characteristics are relatively easy to characterize through body-in-white assembly testing. In contrast, integrated die-cast rear floors are usually ultra-large aluminum alloy die-cast parts, characterized by large dimensions, complex shapes, interlaced stiffeners, significant local wall thickness variations, concentrated connection points, and uneven spatial distribution of casting defects. Their stiffness is influenced not only by the overall structural shape but also by local wall thickness, stiffener arrangement, connection point stiffness, die-casting process quality, and constrained boundary conditions.

[0006] During vehicle development, the rear floor area is a crucial load-bearing region for vehicle body torsional stiffness, rear-end collision safety, suspension mounting stiffness, battery pack installation stability, and overall NVH performance. Insufficient torsional stiffness in the rear floor can lead to excessive deformation of the rear of the vehicle under torsional loads, thereby affecting the stability of body joints, chassis mounting point reliability, rear suspension positioning accuracy, and overall vehicle handling stability. Therefore, a testing method capable of accurately evaluating the torsional stiffness of the integrated die-cast rear floor structure needs to be established during both the design and mass production verification phases.

[0007] Existing methods for testing the torsional stiffness of a vehicle body are mostly designed for the body-in-white assembly or traditional stamped and welded structures. They typically involve applying loads to the front and rear suspension mounting points of the entire vehicle or body-in-white, measuring the overall torsional angle of the vehicle body, and calculating the overall torsional stiffness of the vehicle.

[0008] This type of method is applicable to complete body-in-white structures. The original structure was an assembly composed of many parts; now, the rear floor is a single die-cast integrated component. Its stress and constraints differ from those of traditional steel assemblies, and it cannot be calculated using traditional methods. Since the integrated die-cast rear floor is only part of the body assembly, its test boundaries need to be simulated using specialized fixtures. If the fixture constraint method is inconsistent with the actual vehicle connection state, the loading path is inconsistent with the actual working conditions, or the displacement acquisition points are improperly arranged, the test results will not accurately reflect the torsional deformation characteristics of this component within the entire vehicle. Therefore, the lack of standardized testing procedures and data correction methods results in poor comparability and low repeatability of test results from different laboratories.

[0009] The closest existing technology typically uses a general-purpose component stiffness testing bench. The rear floor sample is fixed on the test bench, and force is applied through single-point or double-point loading. Stiffness is estimated by measuring the displacement at a few locations. While this method can obtain a certain force-displacement relationship, its fixtures are usually not designed exactly according to the actual vehicle mounting points, resulting in differences between the loading points and the actual force path of the rear floor. Furthermore, the displacement measurement points are insufficient to cover the entire deformation area of ​​large die-cast parts. Therefore, this method is prone to problems such as distorted test results, poor repeatability, and incomparability between results from different tests.

[0010] Therefore, for integrated die-cast automotive rear floor, a specialized torsional stiffness testing method needs to be developed to reproduce the actual vehicle installation boundary and torsional load input method as closely as possible under component-level testing conditions. By measuring displacement at multiple points, the overall deformation characteristics of the rear floor under torsional conditions can be obtained, thus providing a reliable basis for structural design optimization and mass production quality control.

[0011] Existing methods for testing the stiffness of automotive components typically include several basic steps: specimen fixation, loading, displacement measurement, and stiffness calculation. For traditional sheet metal welded structural parts, the basic testing requirements can usually be met by using general-purpose fixtures and conventional loading methods, as the structural stiffness is relatively uniform, the connection areas are dispersed, and local deformations are relatively easy to predict. However, for ultra-large, thin-walled aluminum alloy die-cast parts such as integrated die-cast rear floor panels, traditional testing methods have significant shortcomings.

[0012] First, existing general-purpose fixtures cannot accurately simulate the installation state of the rear floor in a real vehicle. The integrated die-cast rear floor is typically connected to the surrounding structure in the vehicle via the overlap surfaces of the left and right longitudinal beams, the mounting points of the rear subframe, and other body connection points. Its actual stress state depends on the location, stiffness, and assembly constraints of these connection points. If only simple clamping plates, ordinary supports, or non-real-vehicle connection points are used for fixation in the test, the stress boundary of the specimen will deviate from the overall vehicle condition. Once the boundary conditions change, the deformation mode and stiffness calculation results of the rear floor will also change significantly, rendering the test results unusable for guiding the overall vehicle design.

[0013] Secondly, existing loading methods cannot accurately reproduce the force transmission process of the rear floor under torsional conditions. During the torsion of the entire vehicle, the rear floor is usually subjected to the reverse displacement or reverse moment transmitted by the left and right longitudinal beams. If single-point loading is used or the loading position deviates from the actual force transmission path of the longitudinal beams, additional bending moments or local bending deformations can easily be introduced, causing non-torsional deformation components to be mixed into the test results, thus reducing the accuracy of torsional stiffness calculation.

[0014] Secondly, the existing number of data collection points is insufficient to comprehensively characterize the torsional deformation features of the integrated die-cast floor. Large die-cast flooring often exhibits variations in local stiffeners, mounting points, and wall thickness. Its deformation is not a simple rigid body torsion but a complex deformation involving local warping, local bending, and overall torsion. If only the displacement at the loading end or a few points is measured, it is impossible to determine the deformation differences between the middle section of the specimen, the constrained end, and the left and right structures, nor can weak areas of the flooring be identified. This affects the completeness of the stiffness evaluation and is detrimental to subsequent structural optimization.

[0015] Furthermore, existing testing procedures lack standardized methods for graded loading and repeated testing. For integral die-cast aluminum alloy parts, the material's elastic modulus is lower than that of steel, and large thin-walled structures may experience clamping gaps, contact adjustments, and minor nonlinear deformations in the initial loading stage. Applying a large load directly may cause test data to be affected by the initial gaps, or even cause local structures to enter an inelastic phase. If existing testing methods do not include pre-loading, graded loading, load stabilization, and repeated testing, the data fluctuations between different test batches are significant, resulting in insufficient repeatability and comparability.

[0016] Finally, existing technologies typically only provide a single stiffness value, lacking comprehensive analysis of multi-point displacement data, and thus failing to obtain further information on the deformation distribution and weak areas of the rear floor. For integrated die-cast rear floors, stiffness testing should not only serve as a pass / fail indicator but also contribute to structural design optimization. Therefore, the testing method should be able to output the overall torsional stiffness and also determine the structural deformation pattern based on the displacement differences at different measuring points, providing a basis for stiffener placement, local wall thickness adjustment, and connection point optimization.

[0017] Based on the above problems, the existing technology cannot meet the requirements of boundary authenticity, loading accuracy, measurement integrity and data repeatability for the torsional stiffness test of integrated die-cast floor components. There is an urgent need for a special test method designed for the characteristics of this type of structural component. Summary of the Invention

[0018] To address the technical problems existing in the prior art, this invention provides an integrated die-cast automotive rear floor torsional stiffness testing fixture and method. The technical solution is as follows:

[0019] An integrated die-cast automotive rear floor torsional stiffness testing fixture includes a front-end torsional application component and a rear-end displacement constraint component. The front-end torsional application component includes an inverted L-shaped plate with multiple screw holes on its top surface. The L-shaped plate includes a horizontal plate and a vertical plate, with a connecting plate between them. The multiple connecting plates are parallel and symmetrical to each other. The rear-end displacement constraint component includes a rectangular block, a semi-circular block, and a circular block. One end of the rectangular block is connected to the semi-circular block, and a circular block is provided on one side of the connection between the rectangular block and the semi-circular block.

[0020] Optionally, the length of the end connecting the rectangular block and the semicircular block is equal to the diameter of the semicircular block, and the axis of the rectangular block passes through the center of the semicircular block. The radius of the circular block is equal to the radius of the semicircular block, and the circular block and the semicircular block are concentrically set.

[0021] Optionally, a through hole is provided at the center of the circular block, and multiple screw holes are provided on the side wall of the rectangular block.

[0022] A method for testing the torsional stiffness of an integrated die-cast automotive rear floor, comprising the aforementioned integrated die-cast automotive rear floor torsional stiffness testing fixture, the method comprising:

[0023] S1. Prepare the rear floor parts of the car, mark the constraint points, loading points and displacement acquisition points on the rear floor parts of the car, and set the target load;

[0024] S2. Install a front-end torsion application component at the loading point, and connect the rear floor part of the car to the test bench through the front-end torsion application component. Install a rear-end displacement constraint component at the constraint point to constrain the translational degree of freedom of the rear floor part of the car, and connect the rear floor part of the car to the test bench through the rear-end displacement constraint component.

[0025] S3. Place displacement sensors at the displacement acquisition points;

[0026] S4. Apply vertical loads of opposite direction, equal magnitude, or equivalent force couple to the torsional application components on both sides respectively.

[0027] S5. Apply torsion to the front end to unload the component to zero load;

[0028] S6. Using a quasi-static graded loading method, apply vertical loads of opposite direction, equal magnitude, or equivalent force couple to the front torsional application components on both sides until the vertical load reaches the target load, and record the displacement sensor data when each load level is reached.

[0029] S7. Repeat S5 to S6 at least three times to calculate the torsional stiffness and torsional deformation distribution of the rear floor components of the vehicle using the obtained data.

[0030] Optionally,

[0031] The step of marking constraint points, loading points and displacement acquisition points on the rear floor component of the vehicle in S1 includes: there are two constraint points, one set on the left side of the rear subframe of the rear floor component of the vehicle, and the other set on the right side of the rear subframe of the rear floor component of the vehicle.

[0032] There are two loading points, which are respectively set at the overlap of the left longitudinal beam and the overlap of the right longitudinal beam of the rear floor part of the vehicle.

[0033] Three sets of displacement acquisition points are set up, with two displacement acquisition points in each set being symmetrical to each other. The three sets of displacement acquisition points are arranged longitudinally along the rear floor parts of the car.

[0034] In the first set of displacement acquisition points, one displacement acquisition point is set at the overlap of the left longitudinal beam of the rear floor part of the vehicle, and the other displacement acquisition point is set at the overlap of the right longitudinal beam of the rear floor part of the vehicle.

[0035] In the second set of displacement acquisition points, one is set on the left side of the middle section of the rear floor part of the car, and the other is set on the right side of the middle section of the rear floor part of the car.

[0036] In the third set of displacement acquisition points, one is set on the left side of the rear subframe of the rear floor component of the car, and the other is set on the right side of the rear subframe of the rear floor component of the car.

[0037] Optionally, the step S2, which involves installing a front-end torsion application component at the loading point to connect the rear floor component of the vehicle to the test bench, and installing a rear-end displacement constraint component at the constraint point to connect the rear floor component of the vehicle to the test bench, includes:

[0038] Two first fixed support arms are provided on one side of the top surface of the test bench, and the two first fixed support arms are arranged symmetrically. Two second fixed support arms are provided on the other side of the top surface of the test bench, and the two second fixed support arms are arranged symmetrically.

[0039] The top of a first fixed support arm is bolted to the bottom of the horizontal plate of the L-shaped plate of the front torsion application component, the top of the horizontal plate is bolted to the bottom wall of the left longitudinal beam overlap of a loading point of the rear floor part of the vehicle, and the outer wall of the vertical plate of the L-shaped plate is attached to the side wall of the left longitudinal beam overlap of a loading point of the rear floor part of the vehicle.

[0040] The top of the other first fixed support arm is fixedly connected to the bottom surface of the horizontal plate of the L-shaped plate of the front torsion application component by bolts. The top surface of the horizontal plate is fixedly connected to the bottom wall of the right longitudinal beam overlap of another loading point of the rear floor part of the vehicle by bolts. The outer wall of the vertical plate of the L-shaped plate is attached to the side wall of the right longitudinal beam overlap of another loading point of the rear floor part of the vehicle.

[0041] The top of a second fixed support arm is bolted to the rectangular block of the rear displacement constraint assembly, and the circular block of the rear displacement constraint assembly is bolted to the left side of the rear subframe at a constraint point of the rear floor part of the vehicle.

[0042] The top of the other second fixed support arm is bolted to the rectangular block of the rear displacement constraint assembly, and the circular block of the rear displacement constraint assembly is bolted to the right side of the rear subframe at another constraint point of the rear floor part of the vehicle.

[0043] Optionally,

[0044] The application of vertical loads in S4 to the torsional application components on both sides, which are in opposite directions and of equal or equivalent magnitude, forming a force couple, includes:

[0045] Two actuators are connected to the bottom wall of the test bench on one side where the first fixed support arm is located. The positions of the two actuators correspond to the positions of the two first fixed support arms, respectively.

[0046] Two actuators apply vertical loads that are opposite in direction, equal in magnitude, or equivalent to form a couple. The applied vertical loads are equal to the target loads and are perpendicular to the top surface of the test bench.

[0047] Optionally, in step S6, the quasi-static graded loading method applies vertical loads of opposite direction, equal magnitude, or equivalent force couples to the front-end torsional application components on both sides until the vertical load reaches the target load. The displacement sensor data recorded when each load level is reached includes:

[0048] Based on the target load, the number of loading stages n and the loading increment m per stage are set so that the actuator needs n loading stages to load from zero load to the target load, and the target load is nm.

[0049] Two actuators apply vertical loads that are opposite in direction, equal in magnitude, or equivalent to form a couple. The loads are applied n times, starting from zero load and continuing until the target load is reached. Data from each displacement sensor is recorded when the target load is reached at each level.

[0050] Optionally, the step S7, which involves calculating the torsional stiffness and torsional deformation distribution of the rear floor component of the vehicle using the obtained data, includes:

[0051] The formula for calculating the torsion angle θ of the rear floor components of a car is formula (1).

[0052] = (1)

[0053] S1 is the data of the displacement sensor at the overlap of the left longitudinal beam of the rear floor component, S2 is the data of the displacement sensor at the overlap of the right longitudinal beam of the rear floor component, and B is the distance between the displacement sensors at the overlap of the left and right longitudinal beams of the rear floor component, in meters.

[0054] Torsional stiffness of automotive rear floor components The calculation formula is formula (2).

[0055] (2)

[0056] M represents the torsional stiffness of the rear floor components of the vehicle, in N·m / °; F represents the torque applied by the actuator, in N·m; F represents the target load data, in N; and L represents the distance between the two first fixed support arms, in m.

[0057] The analysis of torsional deformation distribution of automotive rear floor components includes: comparing the data from each displacement sensor, and identifying the sensor with the highest data value where the deformation is greatest.

[0058] The beneficial effects of the technical solutions provided in the embodiments of the present invention include at least the following:

[0059] This invention employs a specialized constraint fixture that simulates the installation state of a real vehicle, making the constraint state of the integrated die-cast floor on the test bench more closely resemble its actual installation state in the vehicle. The fixture connection points, bolt specifications, assembly positions, and tightening states are all designed to closely resemble the actual vehicle connection scheme, thereby effectively reducing testing errors caused by inconsistent boundary conditions in traditional general-purpose fixtures and improving the authenticity and engineering applicability of the test results.

[0060] This invention applies reverse vertical loads to the left and right rear longitudinal beams or the overlapping area of ​​the longitudinal beams, subjecting the specimen to a torque action that more closely resembles the torsional condition of a complete vehicle. Compared with single-point loading or asymmetric loading methods, this invention can effectively reduce the interference of additional bending deformation on the torsional stiffness calculation, making the test results more reflective of the torsional resistance of the rear floor structure itself.

[0061] This invention utilizes multiple displacement sensors symmetrically arranged at the loading end, middle section, and constraint end to calculate not only the overall torsional stiffness but also the longitudinal torsional deformation distribution of the rear floor. This multi-point measurement method can identify local weak areas, providing data for subsequent stiffener placement, wall thickness optimization, and connection point design.

[0062] This invention employs a standardized testing process combining preloading, graded loading, load recording, and repeated testing. This eliminates the influence of fixture clearance and initial contact nonlinearity on test results, improving the stability and repeatability of test data. For large, thin-walled structural components with low elastic modulus and complex local structures, such as integrated aluminum alloy die-cast parts, this graded loading method effectively prevents the specimen from entering the inelastic deformation stage, ensuring the reliability of stiffness test results.

[0063] This invention establishes a complete testing and data processing method that can be used for the structural development, CAE simulation verification, sample validation, mass production consistency evaluation, and quality control of integrated die-cast flooring. The method features a clear operational process, well-defined testing boundaries, and standardized data calculation methods, making it highly valuable for engineering application. Attached Figure Description

[0064] 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.

[0065] Figure 1 A schematic diagram of the arrangement of displacement sensors in an integrated die-cast automotive rear floor torsional stiffness testing method provided by the present invention;

[0066] Figure 2 A schematic diagram of the front-end torsion application component of an integrated die-cast automotive rear floor torsional stiffness testing fixture provided by the present invention;

[0067] Figure 3 This invention provides a rear displacement constraint component for an integrated die-cast automotive rear floor torsional stiffness testing fixture.

[0068] Reference numerals: 1. Left longitudinal beam overlap of the rear floor component; 2. Right longitudinal beam overlap of the rear floor component; 3. Middle section of the rear floor component; 4. Left side of the rear subframe of the rear floor component; 5. Right side of the rear subframe of the rear floor component; 71. Horizontal plate; 72. Vertical plate; 81. Rectangular block; 82. Semi-circular block; 83. Circular block. Detailed Implementation

[0069] 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, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0070] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms “first,” “second,” and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, the terms “an,” “a,” or “the,” and similar terms do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms “comprising,” “including,” or “including,” and similar terms mean that the element or object preceding the word encompasses the element or object listed following the word and its equivalents, without excluding other elements or objects. The terms “connected,” “linked,” or “connected,” and similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect.

[0071] It should be noted that the terms "up", "down", "left", "right", "front", and "back" used in this invention are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0072] like Figures 1-3 As shown, an integrated die-cast automotive rear floor torsional stiffness testing fixture is provided, including a front-end torsional application component and a rear-end displacement constraint component. The front-end torsional application component includes an inverted L-shaped plate. In this embodiment, two L-shaped plates are preferred. The L-shaped plate includes a horizontal plate 71 and a vertical plate 72 vertically connected to one side of the bottom of the horizontal plate 71. The horizontal plate 71 has multiple screw holes. A right-angled triangular connecting plate connects the horizontal plate 71 and the vertical plate 72. One right-angled side of the connecting plate is connected to the bottom surface of the horizontal plate 71, and the other right-angled side is connected to the inner sidewall of the vertical plate 72. Preferably, there are two connecting plates, which are parallel and symmetrical to each other.

[0073] The rear displacement constraint assembly includes a rectangular block 81, a semi-circular block 82, and a circular block 83. Preferably, in this embodiment, the rectangular block 81, semi-circular block 82, and circular block 83 are in two sets. One end of the rectangular block 81 is connected to the semi-circular block 82. A circular block 83 is located on one side of the connection between the rectangular block 81 and the semi-circular block 82. The length of the end of the rectangular block 81 connected to the semi-circular block 82 is equal to the diameter of the semi-circular block 82, and the axis of the rectangular block 81 passes through the center of the semi-circular block 82. The radius of the circular block 83 is equal to the radius of the semi-circular block 82. The circular block 83 and the semi-circular block 82 are concentrically arranged; that is, half of the circular block 83 is located on one side of the semi-circular block 82 and coincides with it, while the other half of the circular block 83 is located on one side of the rectangular block 81. A through hole is formed at the center of the circular block 83, and multiple screw holes are formed on the sidewall of the rectangular block 81.

[0074] like Figures 1 to 3 As shown, an integrated die-cast automotive rear floor torsional stiffness testing method is provided, including:

[0075] S1. Prepare the rear floor parts of the car, mark the installation points on the rear floor parts, including constraint points, loading points and displacement acquisition points, and set the target load.

[0076] The constraint points are preferably two, one located on the left side 4 of the rear subframe of the rear floor component of the vehicle, and the other located on the right side 5 of the rear subframe of the rear floor component of the vehicle.

[0077] The loading points are preferably two, respectively set at the overlap of the left longitudinal beam of the rear floor component 1 and the overlap of the right longitudinal beam of the rear floor component 2;

[0078] At least three sets of displacement acquisition points are set, preferably three sets, with two displacement acquisition points in each set being symmetrical to each other, and the three sets of displacement acquisition points are arranged longitudinally along the rear floor part of the vehicle.

[0079] In the first set of displacement acquisition points, one displacement acquisition point is set at the overlap of the left longitudinal beam of the rear floor part of the vehicle 1, and the other displacement acquisition point is set at the overlap of the right longitudinal beam of the rear floor part of the vehicle 2; the displacement acquisition points do not coincide with the loading points, and the positions of the displacement acquisition points should be around the loading points.

[0080] In the second set of displacement acquisition points, one is set on the left side of the middle section 3 of the rear floor part of the car, and the other is set on the right side of the middle section 3 of the rear floor part of the car.

[0081] In the third set of displacement acquisition points, one is located on the left side (4) of the rear subframe of the rear floor component of the vehicle, and the other is located on the right side (5) of the rear subframe of the rear floor component of the vehicle. The displacement acquisition points do not coincide with the constraint points; the positions of the displacement acquisition points should be around the constraint points.

[0082] S2. Install a front-end torsion application component at the loading point and connect the rear floor part of the vehicle to the test bench through the front-end torsion application component. Install a rear-end displacement constraint component at the constraint point and connect the rear floor part of the vehicle to the test bench through the rear-end displacement constraint component.

[0083] The test bench is existing technology in this field, and its structure, function and principle will not be described in detail here.

[0084] Two first fixed support arms are provided on one side of the top surface of the test bench, and the two first fixed support arms are arranged symmetrically. Two second fixed support arms are provided on the other side of the top surface of the test bench, and the two second fixed support arms are arranged symmetrically.

[0085] The top of a first fixed support arm is fixedly connected to the bottom surface of the horizontal plate 71 of the L-shaped plate of the front torsion application component by bolts. The top surface of the horizontal plate 71 is fixedly connected to the bottom wall of the horizontal part of the overlap 1 of the left longitudinal beam of the loading point of the car rear floor part by bolts. The outer wall of the vertical plate 72 of the L-shaped plate is fitted and adapted to the side wall of the vertical part of the overlap 1 of the left longitudinal beam of the loading point of the car rear floor part.

[0086] The top of the other first fixed support arm is fixedly connected to the bottom surface of the horizontal plate 71 of the L-shaped plate of the front torsion application component by bolts. The top surface of the horizontal plate 71 is fixedly connected to the bottom wall of the horizontal part of the right longitudinal beam overlap 2 of the other loading point of the car rear floor part by bolts. The outer wall of the vertical plate 72 of the L-shaped plate is fitted and adapted to the side wall of the vertical part of the right longitudinal beam overlap 2 of the other loading point of the car rear floor part.

[0087] The top of a second fixed support arm is bolted to the rectangular block 81 of the rear displacement constraint assembly, and the circular block 83 of the rear displacement constraint assembly is bolted to the left side 4 of the rear subframe of the vehicle rear floor part.

[0088] The top of the other second fixed support arm is bolted to the rectangular block 81 of the rear displacement constraint assembly, and the circular block 83 of the rear displacement constraint assembly is bolted to the right side 5 of the rear subframe of the rear floor part of the vehicle at another constraint point.

[0089] S3. Place displacement sensors at the displacement acquisition points;

[0090] The sixth displacement sensor is located on the right side 5 of the rear subframe of the rear floor component of the vehicle; the fifth displacement sensor is located on the left side 4 of the rear subframe of the rear floor component of the vehicle; the fourth sensor is located on the left side of the middle section 3 of the rear floor component of the vehicle; the third displacement sensor is located on the right side of the middle section 3 of the rear floor component of the vehicle; the second displacement sensor is located at the right longitudinal beam overlap 2 of the rear floor component of the vehicle; and the first displacement sensor is located at the left longitudinal beam overlap 1 of the rear floor component of the vehicle.

[0091] S4. Apply vertical loads of opposite direction, equal magnitude, or equivalent force couple to the torsional application components on both sides respectively.

[0092] Two actuators are connected to one side of the test bench where the first fixed support arm is located. The positions of the two actuators correspond to the positions of the two first fixed support arms. The actuators are existing technology and convert the horizontal force into a vertical force on the test bench. This is existing technology and will not be described in detail here. The working principle, effect and implementation method of the actuators and the test bench are all existing technology and will not be described in detail here.

[0093] Two actuators apply vertical loads that are opposite in direction, equal in magnitude, or equivalent to form a couple. Preferably, the applied vertical load is equal to the target load, and the vertical load is perpendicular to the top surface of the test bench.

[0094] S5. Apply torsion to the front end to unload the component to zero load;

[0095] Control the two actuators to reduce the applied load to zero.

[0096] S6. Using a quasi-static graded loading method, apply vertical loads of opposite direction, equal magnitude, or equivalent force couple to the front torsional application components on both sides until the vertical load reaches the target load, and record the displacement sensor data when each load level is reached.

[0097] Based on the target load, the number of loading stages n and the loading increment m per stage are set so that the actuator needs n loading stages to load from zero load to the target load, and the target load is nm.

[0098] Two actuators are used to apply vertical loads that are opposite in direction, equal in magnitude, or equivalent to form a couple. The loads are applied n times, and each load is applied up to the level of the load. For example, the first load is m, and the second load is 2m.

[0099] Starting from zero load, the load is applied until the target load is reached, and the data from each displacement sensor is recorded when each level of load is reached.

[0100] S7. Repeat S5 to S6 at least three times, and calculate the torsional stiffness and torsional deformation distribution of the rear floor components of the vehicle using the obtained data:

[0101] The formula for calculating the torsion angle θ of the rear floor components of a car is formula (1).

[0102] = (1)

[0103] S1 is the data from the second displacement sensor, S2 is the data from the first displacement sensor, and B is the distance between the first and second displacement sensors, in meters.

[0104] Torsional stiffness of automotive rear floor components The calculation formula is formula (2).

[0105] (2)

[0106] M represents the torsional stiffness of the rear floor components of the vehicle, in N·m / °; F represents the torque applied by the actuator, in N·m; F represents the target load data, in N; and L represents the distance between the two first fixed support arms, in m.

[0107] The analysis of torsional deformation distribution of automotive rear floor components includes: comparing the data from each displacement sensor, and identifying the sensor with the highest data value where the deformation is greatest.

[0108] This solution can be used for design verification, process evaluation, structural optimization, and mass production consistency testing of rear floor assemblies for new energy vehicles, integrated die-cast rear floors, die-cast aluminum alloy rear body structural components, and similar large thin-walled die-cast structural components. In the sample preparation stage, an integrated die-cast automotive rear floor part that meets the dimensions, material, and process requirements of the drawings is first selected. The sample can be an integrated die-cast rear floor structural component for new energy vehicles, or an integrated aluminum alloy die-cast part including rear longitudinal beams, a rear subframe mounting area, the main body of the rear floor, reinforcing ribs, and surrounding connection areas. Before testing, burrs, oil stains, and impurities affecting clamping should be removed from the sample surface, and the sample should be checked for obvious cracks, severe shrinkage cavities, deformation, or machining defects. Subsequently, according to the assembly relationship of the sample in the vehicle, the actual vehicle mounting points are marked. The mounting points include the locations of constraint points, loading points, and displacement acquisition points. The mounting points are preferably selected from the actual connection points of the rear floor in the vehicle. The loading points are preferably selected from the overlapping areas of the left and right longitudinal beams or locations that can represent the torque input path of the rear floor. The displacement acquisition points are arranged along the longitudinal direction of the rear floor to cover the loading end, the middle area, and the constraint end.

[0109] The front-end torsion application component is used to mate with the overlapping areas of the left and right longitudinal beams or the front connection area of ​​the rear floor. Its connection hole positions, bolt specifications, and connection interfaces are made as consistent as possible with the actual vehicle connection scheme to ensure that the load can be input to the rear floor according to the force transmission path of the longitudinal beams in the actual vehicle. The rear-end displacement constraint component is used to simulate the fixed support boundary of the rear part of the rear floor in the whole vehicle, preferably through the rear subframe mounting point or the main mounting point of the rear floor for rigid connection. Each connection point is fastened with high-strength bolts of the same or matching specifications as the actual vehicle assembly. The bolt tightening torque is executed according to the actual vehicle assembly torque or the equivalent torque calibrated by test, so that a stable and reliable connection state is formed between the fixture and the specimen.

[0110] The front-end torsion application assembly and the rear-end displacement constraint assembly are preferably made of steel with significantly higher stiffness than the specimen material, such as Q235 steel or other structural steels that meet the stiffness requirements. The bodies of the front-end torsion application assembly and the rear-end displacement constraint assembly should have sufficient bending and torsional stiffness to ensure that their own deformation during loading is much smaller than the specimen deformation, thus avoiding a significant impact of the flexibility of the front-end torsion application assembly and the rear-end displacement constraint assembly on the test results. The connection interface between the front-end torsion application assembly and the rear-end displacement constraint assembly should ensure stable contact with the rear floor connection surface; if necessary, locating pins, limit blocks, or reference surface structures can be used to improve installation repeatability. Through the above design, this scheme can reproduce the boundary conditions of the integrated die-cast rear floor in the whole vehicle as closely as possible in component-level testing, solving the problem of boundary distortion in traditional general-purpose fixtures.

[0111] The two actuators are preferably connected to the test bench using a ball joint or other connection method that can release additional rotational constraints to reduce the effects of additional bending moments and eccentric loads during loading. This is existing technology and will not be elaborated here. By applying symmetrical reverse loading to the left and right, this invention can more realistically simulate the torque input to the rear floor by the left and right longitudinal beams under the torsional conditions of the whole vehicle.

[0112] The first and second displacement sensors are used to measure the left-right displacement difference at the input end of the torsional load; the third and fourth displacement sensors are used to monitor the torsional deformation and local warping of the main structure of the test piece; the fifth and sixth displacement sensors are used to verify the displacement state at the constraint end and assist in determining whether the boundary conditions are stable. Contact displacement sensors can be used, with a preferred measurement accuracy of not less than 0.01 mm. Laser displacement sensors, LVDT displacement sensors, or other high-precision displacement measurement devices can also be used depending on the required testing accuracy. All displacement sensors should be calibrated before the test, and the acquisition system should ensure synchronous acquisition across all channels to ensure that the displacement data accurately reflects the structural response under the same loading condition.

[0113] To ensure the integrated die-cast floor is in the elastic deformation stage and to reduce the impact of fixture gaps, connection gaps, and initial contact nonlinearity on the test results, preloading (step S4) is performed first. The preloading load can be determined according to the specimen size and structural stiffness. For example, it can be loaded to the target load or a lower load, held for a certain period of time, and then unloaded to zero load to eliminate connection gaps. In one embodiment, the load increment for each stage can be set to 250N, the target load can be set to 500N, or it can be adjusted according to the specimen's structural strength and elastic range. After each load reaches the target value, it is held for 30s, and all displacement sensor data are recorded after the force and displacement responses stabilize. After loading to the target load, it can be unloaded step by step to zero load, and the loading-unloading cycle can be repeated at least three times. The average of the multiple test results is taken as the final test result. Through graded loading and repeated testing, this invention can improve data stability and test repeatability.

[0114] In addition to calculating the overall torsional stiffness, this invention can also analyze the longitudinal torsional deformation distribution of the rear floor based on displacement data from multiple sets of symmetrically positioned measuring points at the loading end, mid-section, and constraint end. By comparing the differences in left and right displacements and the changes in torsional angles at different cross-sections, areas of concentrated deformation and localized weak points in the rear floor structure can be identified. For example, if the displacement difference at the mid-section measuring point is significantly greater than the trends at the loading and constraint ends, it indicates that there may be insufficient local stiffness in the main body of the rear floor; if the measuring points at the constraint end show significant displacement, it may indicate insufficient stiffness of the constraint boundary or loosening of the fixture connections. Through this multi-point displacement analysis method, this invention can not only output torsional stiffness values ​​but also provide direction for optimizing the rear floor structure.

[0115] This solution employs specialized constraint fixtures that simulate the actual installation state of a real vehicle, making the constraint state of the integrated die-cast floor on the test bench more closely resemble its actual installation state in the vehicle. The fixture connection points, bolt specifications, assembly positions, and tightening states are all referenced to the actual vehicle connection scheme as much as possible, thereby effectively reducing testing errors caused by inconsistent boundary conditions in traditional general-purpose fixtures, and improving the authenticity and engineering applicability of the test results.

[0116] This method applies reverse vertical loads to the left and right rear longitudinal beams or the overlapping area of ​​the longitudinal beams, subjecting the specimen to a torque action that more closely resembles the torsional condition of the entire vehicle. Compared with single-point loading or asymmetric loading methods, this invention can effectively reduce the interference of additional bending deformation on the torsional stiffness calculation, making the test results more reflective of the torsional resistance of the rear floor structure itself.

[0117] This solution utilizes multiple displacement sensors symmetrically arranged at the loading end, mid-section, and constraint end to calculate not only the overall torsional stiffness but also the longitudinal torsional deformation distribution of the rear floor. This multi-point measurement method can identify local weak areas, providing data for subsequent stiffener placement, wall thickness optimization, and connection point design.

[0118] This scheme employs a standardized testing process combining preloading, graded loading, load recording, and repeated testing. This eliminates the influence of fixture clearance and initial contact nonlinearity on test results, improving the stability and repeatability of test data. For large, thin-walled structural components such as integrated aluminum alloy die-cast parts, which have low elastic modulus and complex local structures, this graded loading method effectively prevents the specimen from entering the inelastic deformation stage, ensuring the reliability of stiffness test results.

[0119] This solution establishes a complete testing and data processing methodology, applicable to the structural development, CAE simulation verification, sample validation, mass production consistency evaluation, and quality control of integrated die-cast flooring. The methodology features a clear operational process, well-defined testing boundaries, and standardized data calculation methods, making it highly valuable for engineering implementation.

[0120] The following points need to be explained:

[0121] (1) The accompanying drawings of the embodiments of the present invention only involve the structures involved in the embodiments of the present invention. Other structures can refer to the general design.

[0122] (2) For clarity, the thickness of layers or regions is enlarged or reduced in the drawings used to describe embodiments of the invention, i.e., these drawings are not drawn to scale. It is understood that when an element such as a layer, film, region or substrate is referred to as being “above” or “below” another element, the element may be “directly” located “above” or “below” the other element or there may be intermediate elements.

[0123] (3) Where there is no conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other to obtain new embodiments.

[0124] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. The scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An integrated die-cast automotive rear floor torsional stiffness testing fixture, characterized in that, The device includes a front-end torsion application component and a rear-end displacement constraint component. The front-end torsion application component includes an inverted L-shaped plate with multiple screw holes on its top surface. The L-shaped plate includes a horizontal plate and a vertical plate, with a connecting plate between them. The multiple connecting plates are parallel and symmetrical to each other. The rear-end displacement constraint component includes a rectangular block, a semi-circular block, and a circular block. One end of the rectangular block is connected to a semi-circular block, and a circular block is provided on one side of the connection between the rectangular block and the semi-circular block.

2. The integrated die-cast automotive rear floor torsional stiffness testing fixture according to claim 1, characterized in that, The length of the end connecting the rectangular block and the semicircular block is equal to the diameter of the semicircular block, and the axis of the rectangular block passes through the center of the semicircular block. The radius of the circular block is equal to the radius of the semicircular block, and the circular block and the semicircular block are set concentrically.

3. The integrated die-cast automotive rear floor torsional stiffness testing fixture according to claim 1, characterized in that, A through hole is provided at the center of the circular block, and multiple screw holes are provided on the side wall of the rectangular block.

4. A method for testing the torsional stiffness of an integrated die-cast automotive rear floor, characterized in that, The method includes the integrated die-cast automotive rear floor torsional stiffness testing fixture according to any one of claims 1 to 3, wherein the method comprises: S1. Prepare the rear floor parts of the car, mark the constraint points, loading points and displacement acquisition points on the rear floor parts of the car, and set the target load; S2. Install a front-end torsion application component at the loading point, and connect the rear floor part of the car to the test bench through the front-end torsion application component. Install a rear-end displacement constraint component at the constraint point to constrain the translational degree of freedom of the rear floor part of the car, and connect the rear floor part of the car to the test bench through the rear-end displacement constraint component. S3. Place displacement sensors at the displacement acquisition points; S4. Apply vertical loads of opposite direction, equal magnitude, or equivalent force couple to the torsional application components on both sides respectively. S5. Apply torsion to the front end to unload the component to zero load; S6. Using a quasi-static graded loading method, apply vertical loads of opposite direction, equal magnitude, or equivalent force couple to the front torsional application components on both sides until the vertical load reaches the target load, and record the displacement sensor data when each load level is reached. S7. Repeat S5 to S6 at least three times to calculate the torsional stiffness and torsional deformation distribution of the rear floor components of the vehicle using the obtained data.

5. The method for testing the torsional stiffness of the integrated die-cast automotive rear floor according to claim 4, characterized in that, The step of marking constraint points, loading points, and displacement acquisition points on the rear floor component of the vehicle as described in S1 includes: There are two constraint points, one located on the left side of the rear subframe of the rear floor component of the vehicle, and the other located on the right side of the rear subframe of the rear floor component of the vehicle. There are two loading points, which are respectively set at the overlap of the left longitudinal beam and the overlap of the right longitudinal beam of the rear floor part of the vehicle. Three sets of displacement acquisition points are set up, with two displacement acquisition points in each set being symmetrical to each other. The three sets of displacement acquisition points are arranged longitudinally along the rear floor parts of the car. In the first set of displacement acquisition points, one displacement acquisition point is set at the overlap of the left longitudinal beam of the rear floor part of the vehicle, and the other displacement acquisition point is set at the overlap of the right longitudinal beam of the rear floor part of the vehicle. In the second set of displacement acquisition points, one is set on the left side of the middle section of the rear floor part of the car, and the other is set on the right side of the middle section of the rear floor part of the car. In the third set of displacement acquisition points, one is set on the left side of the rear subframe of the rear floor component of the car, and the other is set on the right side of the rear subframe of the rear floor component of the car.

6. The method for testing the torsional stiffness of the integrated die-cast automotive rear floor according to claim 5, characterized in that, The step S2, which involves installing a front-end torsion application component at the loading point to connect the rear floor component of the vehicle to the test bench, and installing a rear-end displacement constraint component at the constraint point to connect the rear floor component of the vehicle to the test bench, includes: Two first fixed support arms are provided on one side of the top surface of the test bench, and the two first fixed support arms are arranged symmetrically. Two second fixed support arms are provided on the other side of the top surface of the test bench, and the two second fixed support arms are arranged symmetrically. The top of a first fixed support arm is fixedly connected to the bottom surface of the horizontal plate of the L-shaped plate of the front torsion application component by bolts. The top surface of the horizontal plate is fixedly connected to the bottom wall of the left longitudinal beam overlap of the loading point of the rear floor part of the vehicle by bolts. The outer wall of the vertical plate of the L-shaped plate is attached to the side wall of the left longitudinal beam overlap of the loading point of the rear floor part of the vehicle. The top of the other first fixed support arm is fixedly connected to the bottom surface of the horizontal plate of the L-shaped plate of the front torsion application component by bolts. The top surface of the horizontal plate is fixedly connected to the bottom wall of the right longitudinal beam overlap of the loading point of the rear floor part of the vehicle by bolts. The outer wall of the vertical plate of the L-shaped plate is attached to the side wall of the right longitudinal beam overlap of the loading point of the rear floor part of the vehicle. The top of a second fixed support arm is bolted to the rectangular block of the rear displacement constraint assembly, and the circular block of the rear displacement constraint assembly is bolted to the left side of the rear subframe at the constraint point of the rear floor parts of the vehicle. The top of the other second fixed support arm is bolted to the rectangular block of the rear displacement constraint assembly, and the circular block of the rear displacement constraint assembly is bolted to the right side of the rear subframe at the constraint point of the rear floor parts of the vehicle.

7. The method for testing the torsional stiffness of the integrated die-cast automotive rear floor according to claim 6, characterized in that, The application of vertical loads in S4 to the torsional application components on both sides, which are in opposite directions and of equal or equivalent magnitude, forming a force couple, includes: Two actuators are connected to the bottom wall of the test bench on one side where the first fixed support arm is located. The positions of the two actuators correspond to the positions of the two first fixed support arms, respectively. Two actuators apply vertical loads that are opposite in direction, equal in magnitude, or equivalent to form a couple. The applied vertical loads are equal to the target loads and are perpendicular to the top surface of the test bench.

8. The method for testing the torsional stiffness of the integrated die-cast automotive rear floor according to claim 7, characterized in that, In step S6, a quasi-static graded loading method is used to apply vertical loads of opposite direction, equal magnitude, or equivalent force couples to the front-end torsional application components on both sides until the vertical load reaches the target load. The displacement sensor data recorded when each load level is reached includes: Based on the target load, the number of loading stages n and the loading increment m per stage are set so that the actuator needs n loading stages to load from zero load to the target load, and the target load is nm. Two actuators apply vertical loads that are opposite in direction, equal in magnitude, or equivalent to form a couple. The loads are applied n times, starting from zero load and continuing until the target load is reached. Data from each displacement sensor is recorded when the target load is reached at each level.

9. The method for testing the torsional stiffness of the integrated die-cast automotive rear floor according to claim 8, characterized in that, The calculation of the torsional stiffness and torsional deformation distribution of the rear floor components of the vehicle by obtaining the data in S7 includes: The formula for calculating the torsion angle θ of the rear floor components of a car is formula (1). = （1） S1 is the data of the displacement sensor at the overlap of the left longitudinal beam of the rear floor component, S2 is the data of the displacement sensor at the overlap of the right longitudinal beam of the rear floor component, and B is the distance between the displacement sensors at the overlap of the left and right longitudinal beams of the rear floor component, in meters. Torsional stiffness of automotive rear floor components The calculation formula is formula (2). （2） M represents the torsional stiffness of the rear floor components of the vehicle, in N·m / °; F represents the torque applied by the actuator, in N·m; F represents the target load data, in N; and L represents the distance between the two first fixed support arms, in m. The analysis of torsional deformation distribution of automotive rear floor components includes: comparing the data from each displacement sensor, and identifying the sensor with the highest data value where the deformation is greatest.

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