CN112611554A - Virtual simulation method for predicting falling of ball hinge under impact working condition - Google Patents
Virtual simulation method for predicting falling of ball hinge under impact working condition Download PDFInfo
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Abstract
The invention relates to the technical field of automobile virtual performance, in particular to a virtual simulation method for predicting falling of a ball hinge under an impact working condition, which comprises the following steps: s1 testing to obtain mechanical characteristic curves of different types of ball hinges; s2, inputting the mechanical characteristic curve after data processing into the ball hinge virtual grid model to perform test condition simulation in S1, and performing benchmarking verification on a simulation result and the mechanical characteristic curve; s3, carrying out suspension subsystem trolley test and simulation verification on the ball hinge virtual grid model subjected to part verification calculation, outputting a failure result, and returning to S2 when the failure result is out of a preset error range; and when the S4 failure result is within the precision range, adding the ball hinge virtual grid model into the whole vehicle virtual model for simulation, comparing the simulation result with the 25% offset test result of the whole vehicle, and returning to S3 when the comparison result is outside the preset error range. The method can predict the hinge failure of the vehicle under the front 25% offset collision condition, and better guide the design of the matching safety performance of the suspension system.
Description
Technical Field
The invention relates to the technical field of automobile virtual performance, in particular to a virtual simulation method for predicting falling of a ball hinge under an impact working condition.
Background
The Chinese insurance automobile safety index C-IASI is tested and evaluated from four aspects of crashworthiness and maintenance economy index, in-vehicle passenger safety index, out-vehicle pedestrian safety index and vehicle auxiliary safety index, the in-vehicle passenger safety index comprises a front 25% offset collision test, a side collision test, a roof strength test and a seat whip test, wherein the front 25% offset collision has important significance on the safety of in-vehicle passengers. Due to the fact that the front 25% of offset collision rigid obstacle avoidance and the body offset rate are small, most of front ends of longitudinal beams of the body cannot participate in effective deformation energy absorption, collision energy cannot be effectively dissipated, and parts on a collision side and connecting pieces are largely out of work. Since the amount of intrusion of the vehicle body is an important research index for developing crash resistance, the yaw attitude and the strength of the rim are significant factors affecting the amount of intrusion of the upper and lower vehicle bodies, and the rim is connected to a knuckle by a bolt, and the knuckle is connected to chassis members such as a tie rod and a swing arm by a ball joint. Therefore, whether the ball hinge is broken or not in the chassis area controls the deflection posture of the tire in the collision process, and the different deflection postures of the tire lead to different collision load transmission modes, thereby directly influencing the vehicle body crashworthiness rating. Therefore, the ball hinge failure needs to be predicted in the vehicle model development process.
The ball hinge that car front suspension system part knuckle is connected includes and swing arm between the ball hinge, and between the tie rod ball hinge and stabilizer bar and the stabilizer bar connecting rod between the ball hinge, and the main structural element of ball hinge is bulb, bulb round pin and bulb shell, and ball hinge is in the in-service use in-process, and bulb round pin are integrated into one piece, have seted up the bulb shell in the bulb shell and have held the bulb. When the ball pin moves to the limit position of the upper edge of the ball head shell in the axial direction in the collision process, the ball hinge is easy to pull out and lose efficacy, and when the ball hinge swings due to stress, the ball pin swings to any position and contacts the upper edge of the ball head shell, the ball pin is easy to press out and lose efficacy.
In an LS-DYNA simulation environment, the conventional simulation means usually uses hinge keywords to simulate different types of spherical hinges on a chassis, hinge keyword cards provide failure load thresholds in six directions to simulate fracture mechanics behaviors of the spherical hinges, but the numerical simulation output hinge load fluctuation of vehicle collision is large, amplitude oscillation easily exceeds the threshold boundary, and unreal failure is caused, so that the conventional simulation method is difficult to accurately simulate the mechanics behaviors of hinge failure.
Disclosure of Invention
The invention aims to provide a virtual simulation method for predicting falling of a ball hinge under an impact working condition, and the virtual simulation method is used for solving the problem that the existing simulation method cannot simulate pressure-disengaging failure and pull-disengaging failure.
In the scheme, the virtual simulation method for spherical hinge falling under the prediction impact working condition comprises the following steps:
step S1, using a pull-out clamp to fix various spherical hinges of a vehicle chassis to respectively perform multiple pull-out tests, using a press-out clamp to fix various spherical hinges of the vehicle chassis to respectively perform multiple press-out tests, obtaining pull-out test mechanical characteristic curves of various spherical hinges after the pull-out tests, and obtaining press-out test mechanical characteristic curves of various spherical hinges after the press-out tests;
step S2, obtaining a plurality of ball hinge three-dimensional models, carrying out grid discretization on the ball hinge three-dimensional models to obtain ball hinge virtual grid models, carrying out average processing on the data of the pull-off test mechanical characteristic curve and the pressure-off test mechanical characteristic curve, inputting the data into an ineffective spring unit in the ball hinge virtual grid models, carrying out thermal expansion pre-tightening processing on the ball head part in the ball hinge virtual grid models to obtain ball hinge virtual simulation models, carrying out zero-part-level verification calculation on the test conditions in the step S1 by the aid of the ball hinge virtual simulation models to obtain simulation results, and comparing the simulation results with the pull-off test mechanical characteristic curve and the pressure-off test mechanical characteristic curve to carry out benchmarking verification;
step S3, carrying out trolley test and simulation verification on the ball hinge virtual grid model subjected to the part level verification calculation, outputting a comparison result of the trolley test and the simulation verification, and returning to the step S2 when the comparison result is out of a preset error range;
and S4, when the comparison result in the step S3 is within the preset error range, adding the ball hinge virtual grid model into the whole vehicle virtual model, comparing the simulation failure result of the whole vehicle virtual model with the 25% offset test result of the whole vehicle, and when the comparison result is outside the preset error range, returning to the step S3.
The beneficial effect of this scheme is:
the method comprises the steps of respectively carrying out a pull-off test and a press-off test for each ball hinge type for multiple times, carrying out averaging treatment after the tests are completed, avoiding errors caused by single test result contingency, endowing rigidity and failure characteristics in different freedom directions to failure spring units in a ball hinge grid model by using a pull-off test mechanical characteristic curve and a press-off test mechanical characteristic curve, enabling the ball hinge to have real rigidity in three freedom directions, carrying out thermal expansion pre-tightening treatment on a ball head virtual grid model in the ball hinge virtual grid model, enabling the ball head part not to jump in a ball head shell, and ensuring stability of load output of the ball hinge; and (3) performing simulation verification on the parts of the ball hinge endowed with mechanical properties, then performing suspension subsystem level verification, adding the ball hinge successfully verified by the suspension subsystem level verification into the whole vehicle virtual model to perform front 25% offset collision simulation, comparing the ball hinge failure result of the whole vehicle virtual simulation model with the ball hinge failure result of the real vehicle test, and performing the step S3 again when the error of the comparison result is out of the preset error range. The virtual solution of the ball hinge failure is applied to a 25% offset collision simulation test on the front side of the vehicle, the collision resistance result of the vehicle body can be accurately simulated by predicting the hinge failure, and the design of the matching safety performance of a suspension system is better guided.
Further, in step S2, the ball hinge three-dimensional model includes a ball head housing, a ball head and a ball head pin, the ball head is located in the ball head housing, the ball head and the ball head pin are independent of each other, when the mesh is discretized, the ball head housing, the ball head and the ball head pin mesh are discretized to obtain a ball head housing virtual mesh model, a ball head virtual mesh model and a ball head pin virtual mesh model, the independent ball head virtual mesh model and the ball head pin virtual mesh model are connected through a failure spring unit, and the pull-off test mechanical characteristic curve and the press-off test mechanical characteristic curve in step S1 are provided to a failure spring unit material card after being engineered.
The beneficial effects are that: because the ball pin virtual grid model of the hinge structure in the existing simulation is simulated by using the key words of the hinge, whether the hinge is invalid or not is judged by using a single invalid load, and the vibration of the numerical simulation load easily causes a non-true invalid result, so that the falling of the ball hinge under the impact working condition cannot be well predicted.
Further, in step S2, the ball head virtual grid model is given an elastic material, and thermal expansion of the ball head virtual grid model is realized through keywords in LS-DYNA to achieve a pre-tightening effect with the ball head shell, and after a preset time, the elastic ball head material is converted into a rigid material to complete the gap pre-tightening effect of the filled ball head shell virtual grid model.
The beneficial effects are that: because in the actual ball hinge, there is the plastic layer structure in order to reduce the noise when moving between bulb and the bulb shell inner wall, because the size of this plastic layer structure is very little, very difficult when the simulation modeling, if do not carry out the simulation modeling to this plastic layer structure, the simulation can arouse the beat of bulb department to arouse that simulation result and actual have great error. Therefore, according to the technical scheme, the problem that a plastic layer structure between the ball head and the ball head shell cannot be modeled in a simulation mode is solved through material conversion and expansion processing within the preset time, and the error of a simulation result caused by the jumping of the ball head during simulation is prevented.
Further, the failure spring unit defines mechanical failure characteristic parameters in three freedom directions in Mat196 material card in LS-DYNA software, and the failure characteristic parameters are derived from the pull-off test and the press-off test in the step S1.
The beneficial effects are that: and defining mechanical failure characteristic parameters for the ball hinge from three freedom directions, so that the simulated virtual grid model of the ball hinge is consistent with the real failure mode of the ball hinge in small offset collision.
Furthermore, each part of the ball head shell virtual grid model, the ball head virtual grid model and the ball pin virtual grid model defines the geometric properties and the mechanical properties of the model according to preset requirements.
The beneficial effects are that: by endowing the ball head shell virtual grid model, the ball head virtual grid model and the ball head pin virtual grid model with mechanical characteristics, the ball hinge simulation can reach real strength.
Further, the definition of the mechanical characteristics is performed by inputting material parameters of the processed pull-off test mechanical characteristic curve and the pressure-off test mechanical characteristic curve into a Mat196 material card in LS-DYNA software, and the parameters proposed from the processed pull-off test mechanical characteristic curve and the pressure-off test mechanical characteristic curve comprise: both linear section stiffness values and failure displacements.
The beneficial effects are that: because the hinge failure is a nonlinear elastic process, the rigidity value and the failure displacement of a linear section are obtained from a pull-off test mechanical characteristic curve and a press-off test mechanical characteristic curve and are given to a ball hinge grid model, the simulated ball hinge grid model has real rigidity before failure, a fracture parameter based on the physical quantity of the failure displacement is provided, and the fluctuation quantity of the displacement parameter is more stable than the physical quantity of a load in LS-DYNA numerical simulation.
Further, in the part-level simulation of the ball hinge, the suspension subsystem-level simulation and the whole vehicle-level simulation, the mechanical characteristic curve of the pull-off test and the mechanical characteristic curve Y of the press-off test processed in three freedom directions are scaled within the range of +/-20% through the real test benchmarking result to match the real test result, so that the axial rigidity of the ball hinge and the bending rigidity in two directions are kept consistent with the real test in the time period before failure, the fixed value of the rigidity in the material card is derived from the linear section slope of the scaled mechanical characteristic curve of the pull-off test and the scaled mechanical characteristic curve of the press-off test, the failure displacement parameter is scaled within the range of +/-20% through the displacement corresponding to the first peak value of the mechanical characteristic curve of the pull-off test and the mechanical characteristic curve of the press-off test as reference, and the failure displacement parameter is adjusted according to the suspension system-level and the whole vehicle-level benchmarking, when the collision load enables the relative displacement generated by the ball pin virtual grid model and the ball head virtual grid model to exceed the allowable failure displacement parameters, the ball hinge fails.
The beneficial effects are that: the actual engineering failure condition represented by the ball hinge on the mechanical characteristic curve is the point at which the rigidity value begins to decline, so that the corresponding rigidity value is obtained according to the linear section of the mechanical characteristic curve, the displacement corresponding to the first peak value of the mechanical characteristic curve is taken as failure displacement, the mechanical characteristic curve and the failure displacement are scaled, and comprehensive optimization parameters are provided for the virtual grid model of the ball hinge.
Drawings
FIG. 1 is a flowchart of a first embodiment of a virtual simulation method for predicting falling of a ball hinge under an impact condition according to the present invention;
FIG. 2 is a virtual grid model of a swing arm ball hinge in a first embodiment of a virtual simulation method for predicting falling of a ball hinge under an impact condition according to the present invention;
FIG. 3 is a card diagram of Mat196 failure material parameter addition in the first embodiment of the virtual simulation method for ball hinge falling under the prediction impact condition of the present invention;
FIG. 4 is a graph showing mechanical characteristics of a hinge pull-out test after a swing arm ball pull-out test in an embodiment of the present invention;
FIG. 5 is a graph showing mechanical characteristics of a swing arm ball press-out test according to an embodiment of the present invention;
FIG. 6 is a schematic diagram illustrating a displacement of a ball stud after a swing arm ball press-out test according to an embodiment of the present invention;
FIG. 7 is a diagram of a virtual grid model of a ball stud according to an embodiment of the present invention;
FIG. 8 is a diagram of a virtual grid model of a ball head according to an embodiment of the present invention;
FIG. 9 is a diagram of a virtual grid model of a ball head housing according to an embodiment of the present invention;
FIG. 10 is an exploded view of a pull-off clamp according to one embodiment of the present invention;
FIG. 11 is a front view of a medium pressure release clamp in accordance with an embodiment of the present invention;
fig. 12 is an enlarged structural view of the limiting plate and the holding frame in fig. 11.
Detailed Description
The following is a more detailed description of the present invention by way of specific embodiments.
Reference numerals in the drawings of the specification include: the clamping device comprises a base 1, an upper pressing die 2, a clamping column 3, a through hole 4, a clamping piece 5, an opening 6, a bottom plate 7, a waist plate 8, an inclined plane plate 9, a limiting plate 10, a clamping plate 11, a pressing hole 13 and a bayonet 14.
Example one
The virtual simulation method for predicting the falling of the ball hinge under the impact working condition, as shown in figure 1, comprises the following steps:
step S1, using an axial pull-out clamp to clamp a plurality of ball hinges of a vehicle chassis, then using an electronic universal testing machine to respectively perform a plurality of axial pull-out tests on the plurality of ball hinges, using a press-out clamp to clamp the plurality of ball hinges of the vehicle chassis, then using the electronic universal testing machine to respectively perform a plurality of press-out tests on the plurality of ball hinges, wherein the types of the ball hinges comprise a swing arm ball hinge, a steering tie rod ball hinge and a tappet ball hinge, the times of the tests can be set according to actual test results, in the first embodiment, the times of the tests are three, namely, the swing arm ball hinge is respectively subjected to three pull-out tests and press-out tests, the steering tie rod ball hinge is respectively subjected to three pull-out tests and press-out tests, the tappet ball hinge is respectively subjected to three pull-out tests and press-out tests, and one ball hinge is used for each test, and obtaining a pull-off test mechanical characteristic curve through a plurality of pull-off tests of each type of ball hinge, and obtaining a press-off test mechanical characteristic curve through a plurality of press-off tests of each type of ball hinge.
Step S2, obtaining three-dimensional models of a plurality of ball hinges, carrying out grid discretization processing on the three-dimensional models of the ball hinges by using finite element preprocessing software to obtain virtual grid models of the ball hinges, inputting the averaged mechanical characteristic curves of the pull-off test and the averaged mechanical characteristic curves of the pull-off test into the material cards of the ineffective spring units in the virtual grid models of the ball hinges, and the ball head virtual grid model is subjected to thermal expansion pre-tightening treatment, the material of the ball head virtual grid model is converted from an elastic material into a rigid material within a preset time, the ball head is expanded to a real thickness size after the preset time, and (4) performing part-level verification calculation through the test condition in the ball hinge virtual simulation model reproduction step S1 to obtain a simulation result, and comparing the simulation result with a pull-off test mechanical characteristic curve and a press-off test mechanical characteristic curve to verify the standard.
In step S2, the ball hinge three-dimensional model includes a ball head housing, a ball head and a ball head pin, the ball head is located in the ball head housing; when the virtual grid model of the ball hinge is processed, firstly, the ball shell, the ball head and the ball pin grid are discretized to establish a virtual grid model of the ball shell, a virtual grid model of the ball head, a virtual grid model of the ball pin and a failure spring unit for connecting the ball pin part and the ball head part, the virtual grid model of the ball head and the virtual grid model of the ball pin are mutually independent, taking the swing arm ball hinge as an example, the virtual grid model of the swing arm ball hinge comprises the virtual grid model of the ball pin shown in fig. 7, the virtual grid model of the ball head shown in fig. 8 and the virtual grid model of the ball shell shown in fig. 9.
In step S2, the thermal expansion of the virtual ball head grid model is realized by using keywords in LS-DYNA to achieve a pre-tightening effect with the virtual ball head shell grid model, the keywords used in the pre-tightening process of the virtual ball head grid model and the virtual ball head shell grid model define parameters smaller than actual CAD at the initial moment of the simulation model, the ball head is high in strength grade due to the use of a material 40CrMo, and is generally difficult to deform under an actual collision condition, and a shell unit in software is used to endow a rigid body material with mechanical properties represented by the rigid body material during actual modeling, specifically: dividing and defining parameters smaller than the CAD diameter by the size of the ball head virtual grid model, so that the ball head virtual grid model is not interfered with the ball head shell virtual grid model, predefining an elastic material MAT-1 by the ball head virtual grid model material, and setting the thickness t to be 1 mm; setting a THERMAL EXPANSION parameter of the ball virtual grid model by using a keyword MAT _ ADD _ THERMAL _ EXPANSION, setting an EXPANSION ratio parameter by using a node set defined by all balls and using THERMAL loading; using a keyword LOAD _ THERMAL _ VARIBLE, after 5ms, converting the material of the ball head virtual grid model from an elastic material into a rigid material within 5ms, namely preset time, and finishing the pre-tightening effect of filling the gap of the ball head shell virtual grid model; and expanding the spherical head virtual grid model and the spherical head shell virtual grid model TO a real thickness dimension after 5ms by using a keyword DEFORMABLE _ TO _ RIGID _ AUTOMATIC, so that real contact stress exists between the spherical head virtual grid model and the spherical head shell virtual grid model, and pre-tightening the spherical head virtual grid model and the spherical head shell virtual grid model is realized.
In step S2, each discrete unit of the virtual ball stud grid model, and the virtual ball shell grid model is provided with a mechanical property by providing a thickness and a rigid material, the virtual ball stud grid model is mainly made of 42CrMo, has a yield strength of 1000Mpa or more, hardly deforms during a collision, and has a mechanical property close to a rigid body, so that a 2mm shell unit is used to represent a characteristic profile of the virtual ball stud grid model to provide a rigid material. The virtual grid model of the ball head shell is connected to the position of the swing arm and is simulated by a 2mm second-order tetrahedron unit, so that a real material is endowed. Because the physical phenomenon that the ball head is separated from the ball head shell needs to be simulated, the ball head virtual grid model and the ball head pin virtual grid model are taken as two independent parts during modeling, as shown in fig. 2, the two parts are respectively as follows: a virtual ball head pin grid model and a virtual ball head grid model are characterized in that a virtual ball head grid model and a virtual ball head shell grid model meet the requirement of a solid 42CrMo material, a 2mm shell unit is used for representing the characteristic outline of the virtual ball head grid model, a failure spring unit is connected between the virtual ball head pin grid model and the virtual ball head shell grid model, the failure spring unit is endowed with mechanical characteristics by endowing length, section diameter and rigid material, the length of the failure spring unit is 3mm, the diameter is consistent with the diameter of a real ball head pin at the position, as shown in figure 3, the endowment of the mechanical characteristics is carried out by inputting material parameters of a pull-off load curve and a press-off load curve into a Mat196 material card, the mechanical connection between the virtual ball head grid model and the virtual ball head pin grid model is endowed with mechanical characteristics through the failure spring unit, and a parameter package provided from the processed pull-off test mechanical characteristic curve and the press-off test mechanical characteristic curve Comprises the following steps: both linear section stiffness values and failure displacements.
Step S3, performing trolley test and simulation verification on the ball hinge virtual grid model after the part-level verification calculation, that is, putting the three ball hinge virtual grid models into a trolley at the suspension frame system level, performing test and simulation comparison, outputting a comparison failure result, and outputting a comparison result of the trolley test and the simulation verification, when the comparison result is outside a preset error range, returning to step S2, that is, displaying the test in the front 25% offset collision trolley model, and outputting a failure result, where the suspension subsystem is a test trolley on the test trolley that includes three ball hinge front suspension subsystem parts, and the specific structures of the front suspension frame system and the test trolley are the prior art, and are not described herein.
And S4, when the comparison result in the step S3 is within the preset error range, adding the ball hinge virtual grid model into the whole vehicle virtual model, comparing the simulation failure result of the whole vehicle virtual model with the 25% offset test result of the whole vehicle to obtain the whole vehicle result, and when the whole vehicle result is outside the preset error range, returning to the step S3.
Performing equivalent stress calculation on a complete vehicle virtual grid model and a ball hinge virtual grid model which are endowed with mechanical characteristics by an LS-DYNA analysis and comparison test mechanical characteristic curve and a mechanical characteristic curve output by simulation, in the part-level simulation, the suspension subsystem-level simulation and the complete vehicle-level simulation of the ball hinge, when a collision load is transmitted to a failure position of the ball hinge virtual grid model, the material type is a Mat196 spring failure unit, the mechanical characteristic curve of a processed pull-off test and the mechanical characteristic curve Y value of a press-off test in three directions are zoomed within a range of +/-20% through a real test benchmarking result to match a real test result, the axial rigidity and the bending rigidity in two directions of the ball hinge are kept consistent with a real test in a time period before failure, and the fixed value of the rigidity in a card is derived from linear sections of the mechanical characteristic curve of the processed pull-off test and the press-off test, and the failure displacement is used as a reference through the displacement corresponding to the first peak value of the pull-off test mechanical characteristic curve and the pressure-off test mechanical characteristic curve, and the calibration test result is zoomed in the range of +/-20% of the failure displacement value.
When a pressure head presses the ball stud to perform a pressure release test, the process that the ball stud is released from the ball shell when being stressed shows that a small bending radian is generated, and because the abscissa of the bending stiffness displacement curve of the degree of freedom input into the Mat196 card is an arc value, the moving displacement of the ball stud needs to be converted into the bending radian, as shown in fig. 6, the specific calculation process is as follows:
the loading displacement is deta L-L1, wherein L-R sin25, L1R sina, R60/cos 25;
thus, if sina ═ R sin25-deta L/R, i.e. a ═ arc sin { (R sin25-deta L)/R }, then the angle of rotation is b ═ 25-a;
and (3) calculating the moment: from the figure, d1 is R cosa, and the moment is M F d 1.
According to a large number of different real vehicle collision tests, the failure modes of the ball hinge obtained through observation are divided into two types, namely pull-off failure and press-off failure, in order to obtain failure load curves under the two failure modes, a universal testing machine is adopted to respectively carry out failure tests on the three types of chassis ball hinges with different specifications, in order to eliminate fluctuation of test curves caused by manufacturing factors of ball hinge parts, each type of ball hinge is tested for three times, and after the tests, the load curves obtained by the three tests are arithmetically averaged and output one. Thus, the three types of ball hinges for the chassis were summed and two types of tests were performed for a total of 18 tests.
Taking a swing arm ball hinge as an example, a pull-out test and a press-out test are carried out. When the tensile speed of the pull-off test is 250mm/min, the pull-off load curve diagram 4 of the swing arm ball hinge is shown, and the results of three tests are averaged into a pull-off test mechanical characteristic curve by adopting an arithmetic mean method. When the pressing speed of the pressure release test is 250mm/min, the pressure release load curve diagram 5 of the swing arm ball hinge is shown, and the results of three tests are averaged into a pressure release test mechanical characteristic curve by adopting an arithmetic mean method.
The pulling-off clamp comprises a base 1, wherein a pressing hole 13 is formed in the center of the base 1, a clamping mechanism is detachably connected to the base 1, the clamping mechanism can be detachably connected through a plurality of bolts, the clamping mechanism comprises a pressing piece and clamping pieces 5 which are matched and customized according to the size of a spherical hinge shell in pairs, the pressing piece presses the clamping pieces 5 on the base 1 for limiting, and the clamping pieces 5 can be clamped below clamping grooves of the spherical hinge shell.
The pressing piece comprises an upper pressing die 2, the upper pressing die 2 is in the same shape as the base 1, the upper pressing die 2 and the base 1 are in a cylindrical shape, the upper pressing die 2 is detachably connected with the base 1 through a plurality of bolts, for example, four penetrating threaded holes are formed in the upper pressing die 2, threaded connecting holes corresponding to the threaded holes in one-to-one mode are formed in the base 1, and the upper pressing die 2 is detachably connected with the base 1 through bolts or screws; a limiting groove for accommodating the clamping piece 5 is formed in the side wall, facing the base 1, of the upper pressing die 2, an opening 6 communicated with the limiting groove is formed in the upper pressing die 2, and the opening 6 extends along the radial direction of the upper pressing die 2; a through hole 4 which is communicated with an opening 6 and penetrates through the bottom of the limiting groove is formed in the center of the upper pressing die 2, the diameter of the through hole 4 is smaller than that of the clamping piece 5, a clamping column 3 for clamping a testing machine from the lower part is integrally formed on the bottom of the base 1, threads are preset on the outer side wall of the clamping column 3, and the clamping column 3 is in threaded connection with the testing machine; the clamping mechanism is matched with a cylindrical sleeve which is in threaded connection with the ball stud, the cylindrical sleeve is used for clamping the testing machine above, the testing machine can be an existing microcomputer-controlled electronic universal testing machine of CTM8010 type, and the specific structure of the testing machine is not described herein.
The radial cross section of each clamping piece 5 is arc-shaped, the axial cross section of each clamping piece 5 is L-shaped, the two clamping pieces 5 can be combined into a circular ring, a bayonet 14 is arranged on any one clamping piece 5, a movable gap is preset between each clamping piece 5 and the spherical hinge, and the movable gap between each clamping piece 5 and the spherical hinge can be set to be 0.5mm-1 mm.
Before a pull-off test is carried out, the bottom of a ball head shell is abutted against a pressing hole 13, two clamping pieces 5 are clamped outside the ball head shell, a steering tie rod of a ball hinge extends out of a bayonet 14, a ball head pin extends out of a through hole 4, an upper pressing die 2 covers the clamping pieces 5, and finally the upper pressing die 2 is fixed on a base 1 through a screw, the installation process of the ball hinge between a transverse stabilizer bar and the transverse stabilizer bar is consistent with that of the ball hinge, as shown in fig. 3, the installation process of the ball hinge between a steering knuckle and a swing arm is consistent with that of the ball hinge, as shown in fig. 4; before a pull-off test is carried out, a clamping piece 5 is clamped below a limiting groove of a ball head shell of a ball hinge from the outer side wall of the ball head shell, a ball head pin of the ball hinge is clamped into the limiting groove from an opening 6, the ball head pin is kept in a through hole 4, a cylindrical sleeve is screwed on the ball head pin, a steering tie rod extends out of the opening 6, and an upper pressing die 2 is fixed on a base 1 through a bolt; clamping the cylindrical sleeve from the upper part by a testing machine, clamping the clamping column 3 from the lower part by the testing machine, starting the testing machine, and respectively pulling the ball hinge upwards and downwards by the testing machine until the ball head falls off from the ball head shell to finish a test; after the test is finished, the testing machine is stopped, the clamping mechanism is taken down, the bolt is unscrewed, and the ball hinge and the clamping piece 5 are taken out for the next test.
A press-off clamp is shown in figures 11 and 12, a base 1 and a clamping piece 5 are different in specific shape and structure, the base 1 comprises a bottom plate 7, a waist plate 8 and an inclined plate 9, the bottom plate 7, the waist plate 8 and the inclined plate 9 enclose a triangular space, one end of the waist plate 8 is welded on the bottom plate 7, the inclined plate 9 is inclined at an angle of 45-60 degrees, one end of the inclined plate 9 is welded on the bottom plate 7, and the other end of the inclined plate 9 is welded with the other end of the waist plate 8.
The radial section of each clamping piece 5 is arc-shaped, the axial section of each clamping piece 5 is L-shaped, the two clamping pieces 5 can form a C shape, and a movable gap is formed between the clamping end surface of each clamping piece 5 and the spherical hinge and can be set to be 1 mm; the pressing piece further comprises two limiting plates 10 for pressing the clamping piece 5, the limiting plates 10 are detachably connected with the inclined plane plate 9 through bolts, the limiting plates 10 are located in the middle of the inclined plane plate 9, clamping grooves for containing and limiting the clamping piece 5 are formed in the limiting plates 10, and the clamping grooves are L-shaped; the inclined plane plate 9 is detachably connected with a clamping plate 11 through a bolt, the clamping plate 11 is located on the inclined plane plate 9 above the limiting plate 10, and the clamping plate 11 is in a long strip shape and is not shown in the figure.
When a press-off test is carried out, a ball head shell of the ball hinge is placed in a pressing hole 13 of the inclined plane plate 9, a steering transverse pull rod part, a swing arm part or a transverse stabilizer rod part faces the lower part of the inclined plane plate 9, the cambered surface of the clamping piece 5 is pressed on the outer side wall of the ball head shell from two sides of the swing arm, the clamping piece 5 is clamped through a limiting plate 10, and the limiting plate 10 is fixed on the inclined plane plate 9 through a bolt; when the steering transverse pull rod part, the swing arm part or the transverse stabilizer bar part faces the upper part of the inclined plane plate 9, the swing arm is pressed through the clamping plate 11, and the clamping plate 11 is fixed on the inclined plane plate 9 through bolts; screwing a cylindrical sleeve on the ball stud, integrally forming a stress head on the end part of the cylindrical sleeve, matching the cylindrical sleeve with a pressure head 15, wherein the pressure head 15 comprises an integrally formed large section and a small section, the small section is provided with an external thread, and the pressure head 15 is fixed on a testing machine through the small section; placing the base 1 on a testing machine, enabling the stress head to be located right below a pressure applying part of the testing machine, applying pressure to the pressure head through the pressure applying part of the testing machine until the ball head is separated from the ball head shell, and completing the test; after the test is completed, the cylindrical sleeve, the clamping piece 5, the clamping plate 11 and the limiting plate 10 are taken down to prepare for the next test.
Compared with the existing mode of carrying out ball hinge modeling through keywords, the embodiment carries out mechanical property endowing modeling on the ball hinge alone, carries out a front 25% offset collision simulation test on the ball hinge endowed with the mechanical property, compares a simulated failure result with a whole vehicle test result, endows the ball hinge with the mechanical property again when an error of the comparison result is out of a preset error range, can accurately obtain the failure condition of the ball hinge under the collision working condition, ensures that the intrusion amount of a vehicle body is more real in the front 25% offset collision simulation test of the vehicle, and has more accurate evaluation on the safety index of a passenger of the vehicle under the front 25% offset collision working condition.
Example two
The difference with the first embodiment is that in the press-off test, aiming at the ball hinge between the steering knuckle and the swing arm, the swing arm on the ball head shell of the ball hinge has a certain angle, and the swing arm is easy to incline towards one side of the ball head pin in the test process, so that the press-off test is interfered. Install infrared emission tube on the lateral wall of pressure head, infrared ray transmission line of infrared emission tube is just being located the connecting hole on the central line between the spacing block on the swing arm, install infrared receiving tube on the inclined plane board, infrared receiving tube is located the inclined plane board of limiting plate top department, infrared receiving tube signal connection has the controller, controller signal connection has the pneumatic cylinder, the pneumatic cylinder is installed on the lateral wall of inclined plane board towards the waist board, the piston rod of pneumatic cylinder is just to the connecting hole, the welding has spacing post on the piston rod tip of pneumatic cylinder, infrared receiving tube installs on the lateral wall of spacing post, with the infrared ray that can receive the connecting hole of passing.
When carrying out the pressure and taking off the experiment, infrared light is launched by infrared transmitting tube, it is the ball hinge between knuckle and swing arm to show promptly when infrared light is received to infrared receiving tube, the pressure is taken off the experiment and can be received the interference of swing arm, let infrared receiving tube send interference signal to the controller, interference signal is the signal of telecommunication when infrared light is received to infrared receiving tube promptly, drive spacing post by controller control pneumatic cylinder and insert the connecting hole in, carry on spacingly to the swing arm through spacing post, prevent the interference among the experimentation.
And because the horizontal pull rod or stabilizer bar of other ball hinge can shelter from infrared receiving tube, then need not fixed horizontal pull rod or stabilizer bar this moment, needn't every ball hinge all carry out spacing fixed except that the stopper, and carry on spacingly when needs are fixed automatically, practice thrift the loading and unloading time among the test process, promote test efficiency.
The foregoing is merely an example of the present invention and common general knowledge of known specific structures and features of the embodiments is not described herein in any greater detail. It should be noted that, for those skilled in the art, without departing from the structure of the present invention, several changes and modifications can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicability of the patent. The scope of the claims of the present application shall be determined by the contents of the claims, and the description of the embodiments and the like in the specification shall be used to explain the contents of the claims.
Claims (7)
1. A virtual simulation method for predicting falling of a ball hinge under an impact working condition is characterized by comprising the following steps:
step S1, using a pull-out clamp to fix various spherical hinges of a vehicle chassis to respectively perform multiple pull-out tests, using a press-out clamp to fix various spherical hinges of the vehicle chassis to respectively perform multiple press-out tests, obtaining pull-out test mechanical characteristic curves of various spherical hinges after the pull-out tests, and obtaining press-out test mechanical characteristic curves of various spherical hinges after the press-out tests;
step S2, obtaining a plurality of ball hinge three-dimensional models, carrying out grid discretization on the ball hinge three-dimensional models to obtain ball hinge virtual grid models, carrying out average processing on the data of the pull-off test mechanical characteristic curve and the pressure-off test mechanical characteristic curve, inputting the data into an ineffective spring unit in the ball hinge virtual grid models, carrying out thermal expansion pre-tightening processing on the ball head part in the ball hinge virtual grid models to obtain ball hinge virtual simulation models, carrying out zero-part-level verification calculation on the test conditions in the step S1 by the aid of the ball hinge virtual simulation models to obtain simulation results, and comparing the simulation results with the pull-off test mechanical characteristic curve and the pressure-off test mechanical characteristic curve to carry out benchmarking verification;
step S3, carrying out trolley test and simulation verification on the ball hinge virtual grid model subjected to the part level verification calculation, outputting a comparison result of the trolley test and the simulation verification, and returning to the step S2 when the comparison result is out of a preset error range;
and S4, when the comparison result in the step S3 is within the preset error range, adding the ball hinge virtual grid model into the whole vehicle virtual model, comparing the simulation failure result of the whole vehicle virtual model with the 25% offset test result of the whole vehicle to obtain a whole vehicle result, and when the comparison result of the whole vehicle result is outside the preset error range, returning to the step S3.
2. The virtual simulation method for ball hinge falling under the prediction impact working condition according to claim 1, characterized in that: in the step S2, the ball hinge three-dimensional model includes a ball head shell, a ball head and a ball head pin, the ball head is located in the ball head shell, the ball head and the ball head pin are independent from each other, when the grid is discretized, the ball head shell, the ball head and the ball head pin are discretized to obtain a ball head shell virtual grid model, a ball head virtual grid model and a ball head pin virtual grid model, the independent ball head virtual grid model and the ball head pin virtual grid model are connected through a failure spring unit, and the pull-off test mechanical characteristic curve and the press-off test mechanical characteristic curve in the step S1 are provided to a failure spring unit material card after being engineered.
3. The virtual simulation method for ball hinge falling under the prediction impact working condition according to claim 2, characterized in that: in the step S2, the ball head virtual grid model is given with an elastic material, and thermal expansion of the ball head grid is realized by keywords in LS-DYNA to achieve a pre-tightening effect with the ball head shell, and after a preset time, the elastic ball head material is converted into a rigid material to complete the pre-tightening effect of filling the gap between the ball head shell.
4. The virtual simulation method for ball hinge falling under the prediction impact working condition according to claim 3, characterized in that: the failure spring unit defines mechanical failure characteristic parameters in three freedom directions in Mat196 material cards in LS-DYNA software, and the failure characteristic parameters are derived from the pull-off test and the press-off test in the step S1.
5. The virtual simulation method for ball hinge falling under the prediction impact working condition according to claim 4, characterized in that: and each part of the ball head shell virtual grid model, the ball head virtual grid model and the ball head pin virtual grid model defines the geometric properties and the mechanical properties of the materials of the models according to preset requirements.
6. The virtual simulation method for ball hinge falling under the prediction impact working condition according to claim 5, characterized in that: the definition of the mechanical characteristics is carried out by inputting material parameters of a processed pull-off test mechanical characteristic curve and a processed press-off test mechanical characteristic curve by a Mat196 material card in LS-DYNA software, and the parameters proposed from the processed pull-off test mechanical characteristic curve and the processed press-off test mechanical characteristic curve comprise: both linear section stiffness values and failure displacements.
7. The virtual simulation method for ball hinge falling under the prediction impact working condition according to claim 6, characterized in that: in the part-level simulation of the ball hinge, the suspension subsystem-level simulation and the whole vehicle-level simulation, the mechanical characteristic curve of the pull-off test and the mechanical characteristic curve Y of the press-off test processed in three freedom directions are scaled within a range of +/-20% through a real test scaling result to match the real test result, so that the axial rigidity and the bending rigidity in two directions are kept consistent with the real test in a time period before failure, the rigidity fixed value in a material card is derived from the linear section slope of the scaled mechanical characteristic curve of the pull-off test and the scaled mechanical characteristic curve of the press-off test, the failure displacement parameter is scaled within a range of +/-20% through the displacement corresponding to the first peak value of the mechanical characteristic curve of the pull-off test and the first peak value of the mechanical characteristic curve of the press-off test as a reference according to the suspension bracket system-level and the whole vehicle-level scaling test result, when the collision load enables the relative displacement generated by the ball pin virtual grid model and the ball head virtual grid model to exceed the allowable failure displacement parameters, the ball hinge fails.
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