CN108956122B - Assembly quality detection method based on structural dynamics characteristics - Google Patents
Assembly quality detection method based on structural dynamics characteristics Download PDFInfo
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Abstract
The invention provides an assembly quality detection method based on structural dynamics characteristics, and belongs to the technical field of mechanical assembly processes. The method comprises the following steps: 1) selecting a plurality of test pieces with qualified assembly quality inspection to establish a reference set; 2) building a measuring environment and measuring the dynamic characteristic parameters of each test piece in a reference set; 3) determining an evaluation index according to the measured kinetic characteristic parameters; 4) according to the evaluation index determined in the step 3), counting the average value mu and the standard deviation sigma of the kinetic characteristic parameters of the test pieces in the reference set; 5) carrying out dynamic test on batch test pieces; 6) and (3) comparing the dynamic characteristic parameters of each test piece obtained in the step 5) with the evaluation indexes determined in the step 3) to obtain a test piece assembly quality inspection result. The invention evaluates whether the assembly quality of the assembly product is qualified or not from the dimension of dynamics, is a supplement to the existing assembly detection process, and is particularly suitable for the quality inspection of batch small and medium-sized assembly structures.
Description
Technical Field
The invention belongs to the technical field of mechanical assembly processes, and particularly relates to an assembly quality detection method based on structural dynamics characteristics.
Background
The assembly structure is the most common product structure in the mechanical field, a plurality of parts can be combined into a mechanical structure with complex structure and various functions through assembly, and the assembly quality and the performance after assembly have important influence on the performance of the mechanical product.
In order to ensure the quality of the assembled product, the assembled product is usually detected, and the traditional detection method mainly adopts methods such as static measurement and test run. The static measurement method can be used for better detecting the static performance of an assembly product, but cannot be used for detecting the dynamic performance of the product. The test run method is relatively comprehensive in detection, but the labor cost and the time cost are relatively high, and the best economic benefit of production is not met.
The mode is the natural vibration characteristic of the structure, and the free vibration of the linear structure can be decoupled into N orthogonal single-degree-of-freedom vibration systems, which correspond to N modes of the structure, and each mode has a specific natural frequency, a specific damping ratio and a specific mode shape. These modal parameters may be derived from a calculation or a trial analysis, a process of which is referred to as a modal analysis. Currently, modal analysis is widely applied to the fields of aerospace, automobiles, ships, civil engineering, machinery and the like.
The dynamic performance is an important component of the performance of mechanical products, and the traditional detection process rarely relates to the detection of the dynamic performance, so that the process method of the existing assembly detection link needs to be perfected, and the assembly quality detection method based on the structural fixed mechanical characteristics is provided.
Disclosure of Invention
The invention aims to provide an assembly detection method based on structural dynamics characteristics, aims to supplement and perfect the existing assembly detection process, solves the problem that the quality of the local assembly part cannot be detected in the assembly process in the existing assembly detection method, and provides a quick, convenient and accurate dynamic performance detection means for mechanical assembly products. The application object of the invention is a batch small and medium-sized assembly structure.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention provides an assembly quality detection method based on structural dynamics characteristics, which is characterized by comprising the following steps of:
1) selecting a plurality of test pieces with qualified assembly quality inspection to establish a reference set
Selecting a part of test pieces accounting for 10-20% of the total number of the test pieces from test pieces to be inspected for fine assembly, respectively performing static performance detection on all the selected test pieces after the assembly is completed, and taking the test pieces meeting the detection standard as qualified test piece reference sets for standby;
2) the method comprises the following steps of constructing a measuring environment and measuring dynamic characteristic parameters of test pieces in a reference set, and specifically comprises the following steps:
2-1) according to the appearance of the batch of test pieces to be inspected, establishing a measuring environment by determining the support conditions, the arrangement of the sensors and the excitation points; wherein the content of the first and second substances,
the supporting condition is selected from free support or fixed support, and the supporting condition meets the following requirements: the mode influence on each test piece is the same, and no extra measurement error is introduced;
the distributed sensors comprise acceleration sensors, force sensors and displacement sensors, and excitation equipment selects a vibration exciter or a force hammer; selecting different positions on a test piece for trial excitation, measuring the proportion of signal measurement values of various sensors to a measurement noise value when excitation is not performed, and selecting the positions with high signal-to-noise ratio as sensor arrangement points and excitation points;
2-2) according to the sensors and excitation distribution points determined in the step 2-1), exciting each test piece in the reference set established in the step 1), collecting data of each sensor, measuring initial dynamic characteristic parameters of different test pieces in the reference set, repeating excitation test for a plurality of times, averaging the obtained various dynamic characteristic parameters, and obtaining corresponding dynamic characteristic parameters after correction;
3) determining an evaluation index from the measured kinetic parameters
Selecting the kinetic characteristic parameter with the highest repetition degree and the smallest random measurement error as an evaluation index according to the corrected kinetic characteristic parameters of the test pieces in the reference set determined in the step 2);
4) according to the evaluation index determined in the step 3), counting the average value mu and the standard deviation sigma of the kinetic characteristic parameters of the test pieces in the reference set;
5) dynamic testing of batches of test pieces
Testing the dynamic characteristic parameters corresponding to the evaluation indexes determined in the step 3) on the rest of the pieces to be tested except the reference set in the batch by using the same measurement conditions according to the test environment established in the step 2);
6) comparing the dynamic characteristic parameters of each test piece obtained in the step 5) with the evaluation indexes determined in the step 3), and judging whether the dynamic characteristic parameters of the test piece to be tested are positioned in the (mu-3 sigma, mu +3 sigma) interval according to the Lauda criterion, if so, testing the assembly quality of the test piece to be qualified, otherwise, testing the assembly quality of the test piece to be unqualified.
The invention has the characteristics and beneficial effects that:
the invention introduces a dynamic characteristic testing means into a detection link after assembly, and is a supplement to the blank of the method for detecting the assembly quality based on the structural dynamic characteristic by utilizing the characteristics of easy performance, quick measurement and capability of reflecting the structural performance of the dynamic characteristic test.
1. The device is suitable for small and medium-sized assembly structures in various shapes, and the experimental device is flexible and adjustable and can be recycled.
2. Compared with the traditional trial cutting detection method, the method is quick and convenient to detect, and saves time cost and labor cost.
3. Through dynamic characteristic measurement, can just detect local assembly body in the assembling process, can discover some assembly problems in advance before the complete machine assembly is accomplished, improve the complete machine and examine the qualification rate.
Drawings
Fig. 1 is a schematic structural diagram of an assembled test piece according to an embodiment of the present invention.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.
Now, a test piece composed of two parts connected by bolts is used as a detection object in the embodiment of the present invention, as shown in fig. 1, the test piece is a typical test piece of a fixed connection assembly body, an upper part and a lower part are connected by four bolts 7, and the assembly quality inspection is mainly the contact quality of the bolt joint surface. The following examples are only preferred embodiments of the present invention and are not intended to limit the present invention.
The assembly quality detection method based on the structural dynamics characteristics comprises the following steps:
1) selecting a plurality of test pieces with qualified assembly quality inspection to establish a reference set
Selecting part of test pieces accounting for 10% -20% of the total number of the test pieces from test pieces to be inspected to carry out fine assembly, respectively carrying out static performance detection on all the selected test pieces after the assembly is finished, wherein the static performance detection comprises size precision detection, geometric precision detection, static rigidity detection and the like on the test pieces, and using the test pieces meeting the detection standard as qualified test piece reference sets for standby.
In the embodiment, the static performance detection comprises measuring the parallelism between the axis 3 of the circular hole in the part 1 and the bottom surface 4 in the part 2 and measuring the three-way static rigidity of the joint surface of the test piece, and taking the test piece of which the parallelism between the axis 3 of the circular hole and the bottom surface 4 and the bending static rigidity value both meet the detection standard value as a qualified test piece reference set.
2) The method comprises the following steps of constructing a measuring environment and measuring dynamic characteristic parameters of test pieces in a reference set, and specifically comprises the following steps:
2-1) according to the appearance of the batch of test pieces to be inspected, establishing a measuring environment by determining the support conditions, the arrangement of the sensors and the excitation points; wherein the content of the first and second substances,
the supporting conditions are freely supported or fixedly supported, and meet the following requirements: the modal impact is the same for each test piece, no additional measurement error is introduced, and the free support condition is usually chosen. The test piece is simulated to be freely supported by the sponge elastic cushion in the embodiment.
The distributed sensors comprise acceleration sensors, force sensors and displacement sensors, and excitation equipment selects a vibration exciter or a force hammer; different positions are selected on a test piece for trial excitation, the ratio of the signal measurement value of each sensor to the measurement noise value when no excitation is measured, the signal-to-noise ratio of all the sensors is usually required to be more than 100, and the positions with high signal-to-noise ratio are selected as the sensor arrangement point and the excitation point.
In the embodiment, 4 acceleration sensors 5 are arranged on the top, the side and the front of the test piece, and the excitation point 6 of the electromagnetic exciter is arranged on the right half part of the front of the test piece part 1, as shown in fig. 1.
2-2) according to the sensors and the excitation distribution points determined in the step 2-1), exciting each test piece in the reference set established in the step 1), collecting data of an acceleration sensor, a force sensor and a displacement sensor, so as to measure initial dynamic characteristic parameters of different test pieces in the reference set, including modal frequency, modal vibration mode, damping ratio, frequency response function amplitude and the like of each order, collecting and recording through data collection equipment, usually carrying out excitation testing for more than 3 times, averaging all the obtained dynamic characteristic parameters, and obtaining the corresponding dynamic characteristic parameters after correction.
3) Determining an evaluation index according to the measured kinetic characteristic parameters;
according to the corrected dynamic characteristic parameters of the test pieces in the reference set determined in the step 2), the dynamic characteristic parameters with the highest repetition degree and the smallest random measurement error are selected as evaluation indexes, and the dynamic parameters such as modal frequency, modal vibration type, damping ratio, frequency response function value and the like of each order can be selected but are not limited. In this embodiment, parameters of modal frequencies (except rigid body modes) of different orders are selected as evaluation indexes according to a test condition.
4) And 3) according to the evaluation indexes determined in the step 3), counting the average value mu and the standard deviation sigma of the kinetic parameters of the test pieces in the reference set. In the embodiment, the average value mu of the first 5-order modal frequency (excluding rigid body mode) in each reference set test piece is obtained1、μ2、μ3、μ4、μ5And standard deviation sigma1、σ2、σ3、σ4、σ5。
5) Carrying out dynamic test on batch test pieces;
and testing the dynamic characteristic parameters corresponding to the other pieces to be tested in the batch except the reference set and the evaluation indexes determined in the step 3) by using the same measurement conditions according to the test environment established in the step 2). In this embodiment, the first 5-order modal frequencies (rigid body modes excluded) of the remaining test pieces are tested.
6) Comparing the dynamic characteristic parameters of each test piece obtained in the step 5) with the evaluation indexes determined in the step 3), and judging whether the dynamic characteristic parameters of the test piece to be tested are positioned in the (mu-3 sigma, mu +3 sigma) interval according to the Lauda criterion, if so, testing the assembly quality of the test piece to be qualified, otherwise, testing the assembly quality of the test piece to be unqualified. In this embodiment, the modal frequency (excluding rigid body mode) value θ of each order obtained in step 5) of each test piece is calculated1、θ2、θ3、θ4、θ5Respectively and interval (mu)1-3σ1，μ1+3σ1)、(μ2-3σ2，μ2+3σ2)、(μ3-3σ3，μ3+3σ3)、(μ4-3σ4，μ4+3σ4)、(μ5-3σ5，μ5+3σ5) And comparing, if the test pieces are all located in the corresponding intervals, the test piece is qualified, otherwise, the test piece is unqualified.
The invention has the realization principle that the problem of assembly quality can be reflected on the measured dynamic characteristics, the evaluation index is formed by measuring the dynamic characteristic parameters of qualified assembly products and counting, and the assembly quality of the assembly products can be preliminarily judged by comparing the dynamic parameters of the assembly products to be tested with the database of the dynamic characteristic parameters of the qualified products.
Claims (2)
1. An assembly quality detection method based on structural dynamics characteristics is characterized by comprising the following steps:
1) selecting a plurality of test pieces with qualified assembly quality inspection to establish a reference set
Selecting a part of test pieces accounting for 10-20% of the total number of the test pieces from test pieces to be inspected for fine assembly, respectively performing static performance detection on all the selected test pieces after the assembly is completed, and taking the test pieces meeting the detection standard as qualified test piece reference sets for standby; the static performance detection comprises the detection of the dimensional precision, the detection of the geometric precision and the detection of the static rigidity of the test piece;
2) the method comprises the following steps of constructing a measuring environment and measuring dynamic characteristic parameters of test pieces in a reference set, and specifically comprises the following steps:
2-1) according to the appearance of the batch of test pieces to be inspected, establishing a measuring environment by determining the support conditions, the arrangement of the sensors and the excitation points; wherein the content of the first and second substances,
the supporting condition is selected from free support or fixed support, and the supporting condition meets the following requirements: the mode influence on each test piece is the same, and no extra measurement error is introduced;
the distributed sensors comprise acceleration sensors, force sensors and displacement sensors, and excitation equipment selects a vibration exciter or a force hammer; selecting different positions on a test piece for trial excitation, measuring the proportion of signal measurement values of various sensors to a measurement noise value when excitation is not performed, and selecting the positions with high signal-to-noise ratio as sensor arrangement points and excitation points;
2-2) according to the sensors and excitation distribution points determined in the step 2-1), exciting each test piece in the reference set established in the step 1), collecting data of each sensor, measuring initial dynamic characteristic parameters of different test pieces in the reference set, repeating excitation test for a plurality of times, averaging the obtained various dynamic characteristic parameters, and obtaining corresponding dynamic characteristic parameters after correction;
3) determining an evaluation index from the measured kinetic parameters
Selecting the kinetic characteristic parameter with the highest repetition degree and the smallest random measurement error as an evaluation index according to the corrected kinetic characteristic parameters of the test pieces in the reference set determined in the step 2);
4) according to the evaluation index determined in the step 3), counting the average value mu and the standard deviation sigma of the kinetic characteristic parameters of the test pieces in the reference set;
5) dynamic testing of batches of test pieces
Testing the dynamic characteristic parameters corresponding to the evaluation indexes determined in the step 3) on the rest of the pieces to be tested except the reference set in the batch by using the same measurement conditions according to the test environment established in the step 2);
6) comparing the dynamic characteristic parameters of each test piece obtained in the step 5) with the evaluation indexes determined in the step 3), and judging whether the dynamic characteristic parameters of the test piece to be tested are positioned in the (mu-3 sigma, mu +3 sigma) interval according to the Lauda criterion, if so, testing the assembly quality of the test piece to be qualified, otherwise, testing the assembly quality of the test piece to be unqualified.
2. The structural dynamics-based assembly quality inspection method according to claim 1, wherein the dynamics parameters include modal frequency, modal shape, damping ratio, frequency response function amplitude of each order.
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