CN-121156472-B - Ultrasonic welding method for automobile wire harness terminal

Abstract

The invention discloses an ultrasonic welding method of an automobile wire harness terminal, which belongs to the field of automobile manufacture and comprises the specific steps of collecting information of the terminal and a wire before welding starts, establishing a digital simulation model of each terminal, simulating a welding process and predicting welding defects, and II, dynamically scanning a contact surface and constructing a microcosmic contact resistance distribution diagram at the initial stage of compacting the terminal and the wire to identify a high contact resistance area.

Inventors

• PENG XIAOHU
• YANG WEIGUANG
• Peng Yinmao
• LIU XINGJUN

Assignees

• 南京鼎典科技有限公司

Dates

Publication Date

20260512

Application Date

20250828

Claims (5)

1. 1. The ultrasonic welding method for the automobile wire harness terminal is characterized by comprising the following specific steps of: I. Before welding starts, collecting various information of the terminals and the wires, establishing a digital simulation model of each terminal, simulating a welding process and predicting welding defects, wherein the specific steps of establishing the digital simulation model of each terminal are as follows: S1.1, acquiring various basic material performance parameters of a terminal and a wire by various methods of a durometer, a tensile testing machine and a microscope, then acquiring point cloud data of the terminal and the wire by using three-dimensional laser scanning or industrial CT, removing noise in original point cloud data based on a voxel downsampling criterion, and removing abnormal values in the noisy point cloud data; S1.2, according to the preprocessed point cloud data, the three-dimensional geometric dimensions and shapes of all terminals and wires are obtained, and based on the three-dimensional geometric dimensions and shapes of all terminals and wires, a digital simulation model of all the terminals and wires is built; S1.3, collecting surface roughness and oxidation layer resistance characteristics of a contact surface of a terminal and a wire by using a surface roughness meter or a resistivity meter, and then introducing the collected surface roughness and oxidation layer resistance characteristics into a digital simulation model of the corresponding terminal and the wire, so as to establish a complete terminal-wire simulation model; S1.4, calculating and setting simulation time according to main excitation frequency and highest effective frequency components of an ultrasonic welding head in simulation, calculating displacement of an end face of the welding head under preset simulation time according to amplitude, frequency and phase angle of ultrasonic welding in a digital simulation process so as to obtain a corresponding ultrasonic vibration boundary, and setting simulation boundary conditions of a corresponding terminal-wire simulation model according to material properties of each terminal and each wire; II. In the initial stage of compacting the terminal and the lead, dynamically scanning the contact surface, constructing a microcosmic contact resistance distribution diagram, and identifying a high contact resistance area; III, acquiring multi-source sensing data in the welding process in real time, performing fusion analysis on the acquired multi-source sensing data, and dynamically generating an ultrasonic energy output curve; IV, according to contact resistance distribution and real-time sensing data, ultrasonic energy is directionally put in, local plastic deformation is promoted, and an energy control strategy is optimized in real time; V, carrying out spectrum analysis on acoustic signals generated in the welding process, judging whether potential defects exist in welding spots in real time, and automatically triggering a self-repairing program according to a judging result; VI, monitoring the inherent mode of the welding head in real time, dynamically adjusting the driving parameters of the welding head according to the monitoring result, and reminding maintenance personnel to replace the welding head when fatigue or abrasion occurs to the welding head.
2. 2. The ultrasonic welding method for automotive wire harness terminals according to claim 1, wherein the step I of simulating the welding process, the specific step of predicting the welding defect is as follows: S2.1, applying normal compression and tangential relative sliding conditions to a terminal-wire contact interface in each terminal-wire simulation model according to the prior experience, and calculating interface friction heat flux generated by friction and adhesion-sliding conversion based on each applied condition; S2.2, calculating structural displacement, speed and acceleration response under preset ultrasonic excitation, and then superposing and solving transient heat conduction according to generated interface friction heat flux and material plastic dissipation transformed heat source to obtain a heat-force coupling state of a corresponding terminal-wire simulation model; S2.3, updating the flow resistance and softening of the material according to the latest thermal-force coupling state of the current simulation time step, carrying out integral treatment on contact compression and tangential work, calculating the interface energy density, and judging that weak welding trend exists in the simulation welding under the current parameters if the interface energy density is lower than a preset process threshold value; S2.4, monitoring the peak temperature of the interface and the neighborhood thereof, if the peak temperature is higher than the preset upper temperature limit, indicating that metal splashing or tissue overburning exists in the current welding process, and calculating the formation trend of unwelded-inclusion-pore communication in the current welding process according to the evolution relation of equivalent pore fraction along with plastic accumulation and rapid temperature rise; and S2.5, carrying out normalization weighting treatment on the three indexes of interface insufficient bonding, overheating and pore, generating a real-time defect risk score of the current welding simulation, and simultaneously carrying out real-time adjustment on each parameter of the welding process based on the real-time risk score.
3. 3. The ultrasonic welding method for the wire harness terminal of the automobile according to claim 2, wherein the specific step of identifying the high contact resistance region in step II is as follows: S3.1, carrying out rasterization scanning on a terminal-wire contact surface by utilizing current micro-excitation, establishing a group of scanning grids with two-dimensional coordinates on the contact surface based on a scanning result, setting an excitation time window and weight of each grid, and synchronously carrying out phase-locking integration on a measurement signal of each grid to obtain a coherent potential value corresponding to each grid; S3.2, correcting each measured coherent potential value through linear transformation by utilizing a preset transfer matrix, applying preset current disturbance to each grid, reading corresponding potential change, taking the obtained change value as a local incremental resistor, and carrying out convolution correction on each obtained local incremental resistor; S3.3, carrying out inversion processing on each corrected local increment resistance by using a Tikhonov inversion method, normalizing inversion results by using a steady statistic to obtain the relative resistance anomaly degree of each grid, calculating the resistance distribution condition of each grid, and setting a corresponding high resistance judgment threshold value; And S3.4, if the relative resistance anomaly degree is higher than a high resistance judgment threshold value, dividing the corresponding grids into a high contact resistance primary screening set, then processing each group of grids into a plurality of groups of connected grids through area opening operation and connected domain screening, and reserving the connected grids higher than a reserved area threshold value based on a preset reserved area threshold value so as to acquire a high contact resistance region in a microcosmic contact resistance distribution diagram.
4. 4. The ultrasonic welding method for automotive wire harness terminals according to claim 3, wherein the step III of dynamically generating an ultrasonic energy output curve comprises the steps of: S4.1, arranging a plurality of sensors on welding equipment, synchronously collecting the sensors according to fixed sampling frequency to obtain multi-mode sensing data, preprocessing the sensing data of different modes through denoising, smoothing and scale normalization, and dividing the continuously collected continuous multi-mode sensing data into a plurality of groups of sensing data sets by utilizing a sliding window; S4.2, inputting each group of sensing data sets into a one-dimensional convolution network, and carrying out convolution processing on the data in each group of sensing data sets through the convolution check of each convolution layer in the one-dimensional convolution network so as to extract local characteristic values of each sensor data; S4.3, transmitting the extracted local characteristic values to an LSTM network, identifying the dependency relationship among the local characteristic values through a gating mechanism of the LSTM network, simultaneously acquiring dynamic evolution data in the welding process in real time based on the identified dependency relationship, analyzing the current dynamic evolution data in real time through a Softmax classifier, and judging the welding physical state of a corresponding sensing data set in each sliding window; and S4.4, comparing the determined welding physical state with an expected process curve in real time, generating real-time control signals based on the comparison result, and outputting ultrasonic energy output curves corresponding to the control signals in each time period.
5. 5. The ultrasonic welding method for automotive wire harness terminals as claimed in claim 4, wherein the specific step of promoting the local plastic deformation of step IV is as follows: S5.1, collecting a current contact resistance distribution diagram and real-time data acquired by various types of sensors, and then fusing the contact resistance distribution diagram and a sensor data field to construct a corresponding joint state field so as to establish a hot zone-impedance composite distribution model of the welding state of a current welding interface; S5.2, dividing each generated set of welding spots into a plurality of groups of grids, calculating the joint state field strength of each grid unit, marking the corresponding grid unit as a priority compensation area if the joint state field strength is higher than a preset threshold value, and then calculating the ultrasonic energy weight of the ultrasonic head for each grid unit based on the marking result; s5.3, after the calculation of the ultrasonic energy weights is completed, the ultrasonic energy is concentrated and loaded in a corresponding high-resistance area according to the spatial distribution result of each ultrasonic energy weight by a modulation controller, then the ultrasonic energy is input into a material interface in the form of high-frequency shearing stress and friction work, and the oxide film on the surface of a welding spot is subjected to microcracking and cracking by the output ultrasonic energy; And S5.4, after the oxide film is broken, the ultrasonic energy continuously applies force to the corresponding welding spot surface, so that the contact point area of the welding spot surface is subjected to plastic deformation under the action of the ultrasonic energy, and micropores generated in the welding process are filled.

Description

Ultrasonic welding method for automobile wire harness terminal Technical Field The invention relates to the field of automobile manufacturing, in particular to an ultrasonic welding method for an automobile wire harness terminal. Background The automobile wire harness is used as a core component of an electric system of the vehicle, and the terminal welding quality of the automobile wire harness is directly related to the electric performance and safety of the whole vehicle. Although the traditional crimping and soldering process can meet the connection requirements to a certain extent, the traditional crimping and soldering process has the defects in the aspects of conductivity, fatigue resistance and production consistency. Ultrasonic welding is gradually becoming the mainstream technology for manufacturing automobile wire harness terminals because of its ability to achieve firm connection between metals at low temperatures, avoid residual contamination of flux, and ensure high conductivity. However, as the level of electronization and intellectualization of automobiles is continuously improved, the number of wire harness terminals is rapidly increased, and higher requirements are put on stability and controllability of welding quality. The ultrasonic welding process has the characteristics of high transient state, nonlinearity and multi-factor coupling, the welding spot defect is difficult to detect and repair in time, the traditional process control mode depending on experience and fixed parameters cannot meet the high reliability requirement of the modern automobile industry, and therefore, the invention becomes particularly important. The existing ultrasonic welding method for the automobile wire harness terminal cannot carry out systematic and closed-loop control on the welding process, cannot maintain stable welding quality under process fluctuation and material difference, is easy to cause energy waste, reduces energy efficiency utilization, is more dependent on manual experience, reduces welding spot strength and conductivity, and increases rejection rate caused by defects. Disclosure of Invention The invention aims to solve the defects in the prior art, and provides an ultrasonic welding method for an automobile wire harness terminal. In order to achieve the above purpose, the present invention adopts the following technical scheme: the ultrasonic welding method for the automobile wire harness terminal comprises the following specific steps: I. before welding starts, collecting various information of the terminals and the wires, establishing a digital simulation model of each terminal, simulating a welding process, and predicting welding defects; II. In the initial stage of compacting the terminal and the lead, dynamically scanning the contact surface, constructing a microcosmic contact resistance distribution diagram, and identifying a high contact resistance area; III, acquiring multi-source sensing data in the welding process in real time, performing fusion analysis on the acquired multi-source sensing data, and dynamically generating an ultrasonic energy output curve; IV, according to contact resistance distribution and real-time sensing data, ultrasonic energy is directionally put in, local plastic deformation is promoted, and an energy control strategy is optimized in real time; V, carrying out spectrum analysis on acoustic signals generated in the welding process, judging whether potential defects exist in welding spots in real time, and automatically triggering a self-repairing program according to a judging result; VI, monitoring the inherent mode of the welding head in real time, dynamically adjusting the driving parameters of the welding head according to the monitoring result, and reminding maintenance personnel to replace the welding head when fatigue or abrasion occurs to the welding head. As a further scheme of the invention, the specific steps for establishing the digital simulation model of each terminal in the step I are as follows: S1.1, acquiring various basic material performance parameters of a terminal and a wire by various methods of a durometer, a tensile testing machine and a microscope, then acquiring point cloud data of the terminal and the wire by using three-dimensional laser scanning or industrial CT, removing noise in original point cloud data based on a voxel downsampling criterion, and removing abnormal values in the noisy point cloud data; S1.2, according to the preprocessed point cloud data, the three-dimensional geometric dimensions and shapes of all terminals and wires are obtained, and based on the three-dimensional geometric dimensions and shapes of all terminals and wires, a digital simulation model of all the terminals and wires is built; s1.3, collecting surface roughness and oxide layer resistance characteristics of a contact surface of a terminal and a wire by using a surface roughness meter or a resistivity meter, and then introducing the collected su