Method for on-line monitoring of rubber vulcanization degree based on ultrasonic array

Abstract

The present application belongs to the technical field of ultrasonic nondestructive testing, and relates to a rubber vulcanization degree online monitoring method based on an ultrasonic wave array, comprising the following steps: generating a stable acoustic coupling interface on the surface of the rubber to be measured; constructing a multi-path composite acoustic field in the interior of the rubber to be measured, which is composed of short-range high-density paths and long-range cross paths; forming a multi-channel synchronous acoustic wave response data set; calculating the signal waveform similarity of the multi-channel synchronous acoustic wave response data set originating from densely arranged adjacent probe pairs to obtain an acoustic homogeneity index; calculating the acoustic wave propagation speed to obtain an average propagation sound speed; generating a vulcanization state characteristic vector representing the coupling state of the micro-homogeneity and macro-rigidity in the current vulcanization process; and determining the absolute vulcanization degree in the interior of the current rubber material. The present application solves the problem that the process procedure based on a fixed time cannot adapt to the performance fluctuations between batches of raw materials, the slight differences in the equipment state, and the temperature gradient in the mold.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of ultrasonic nondestructive testing, and relates to a rubber vulcanization degree online monitoring method based on an ultrasonic array. BACKGROUND

[0002] The core challenge currently faced by the rubber product production field is how to perform online monitoring on the vulcanization process inside a sealing mold. Rubber vulcanization is a complex physical and chemical change process that occurs under high temperature and high pressure, and the material changes from sticky raw rubber to high-elasticity cooked rubber, and the internal microscopic cross-linking network structure and macroscopic mechanical properties thereof change dramatically and irreversibly. Due to the extremity of the production environment and the closed nature of the mold, it is extremely difficult to directly measure the real vulcanization state of the rubber, and it is difficult to maintain stable physical contact between the sensor and the dynamically changing rubber material, resulting in serious attenuation and distortion of the signal transmission, which is a key technical bottleneck that must be overcome to achieve effective online monitoring.

[0003] The current solution in the industry is to establish a fixed process procedure based on offline experiments, that is, to determine the standard vulcanization curve of a specific rubber material by using laboratory equipment such as a rheometer, to thereby preset a fixed temperature, pressure and time control scheme and apply it to batch production. In the production process, a thermocouple is usually installed on the mold to indirectly monitor whether the heating temperature meets the preset curve. This method is essentially an open-loop control mode, which assumes that all production conditions are completely consistent with the laboratory standard state, and accordingly infers that the vulcanization reaction has been completed at the predetermined time point.

[0004] Based on the above problems, the process procedure based on fixed time cannot adapt to the performance fluctuations between batches of raw materials, small differences in equipment state and temperature gradients inside the mold, and is extremely prone to causing under-vulcanization or over-vulcanization of the product, resulting in unstable quality. SUMMARY

[0005] To solve the above problems, the application provides a rubber vulcanization degree online monitoring method based on an ultrasonic array.

[0006] The rubber vulcanization degree online monitoring method based on an ultrasonic array comprises the following steps:

[0007] S1, deploying an active pressure-stable coupling type acoustic window array unit on the inner wall of a rubber vulcanization mold to generate a stable acoustic coupling interface on the surface of the rubber to be measured;

[0008] S2, based on the stable acoustic coupling interface, triggering the ultrasonic probe in the active pressure-stable coupling type acoustic window array unit in time to construct a multi-path composite acoustic field composed of short-range high-density paths and long-range cross paths inside the rubber to be measured;

[0009] S3, synchronously collect signals of the multi-path composite sound field passing through the rubber to be tested and received by the ultrasonic probe, to form a multi-channel synchronous sound wave response data set;

[0010] S4, calculate the similarity of signal waveforms in the multi-channel synchronous sound wave response data set originating from adjacent probe pairs arranged in dense parallel, to obtain an acoustic homogeneity index;

[0011] S5, extract the signal flight time in the multi-channel synchronous sound wave response data set originating from probe pairs arranged in large spacing and diagonal staggered, calculate the sound wave propagation speed, and obtain the average propagation sound speed;

[0012] S6, fuse the acoustic homogeneity index and the average propagation sound speed, to generate a vulcanization state feature vector representing the coupling state of micro-homogeneity and macro-rigidity in the current vulcanization process;

[0013] S7, map the position of the vulcanization state feature vector on the pre-labeled standard vulcanization trajectory curve, to determine the absolute vulcanization degree inside the rubber material.

[0014] Further schemes of the present application generate a stable acoustic coupling interface on the surface of the rubber to be tested, including the following steps:

[0015] The active constant pressure coupling type acoustic window array unit is adsorbed on the inner wall of the rubber vulcanization mold by the double-layer suspended magnetic adsorption and damping structure at the bottom of the active constant pressure coupling type acoustic window array unit, with a preset constant positive pressure;

[0016] The preset constant positive pressure acts on the pre-stress loaded viscoelastic coupling layer in the active constant pressure coupling type acoustic window array unit, so that the pre-stress loaded viscoelastic coupling layer actively compensates for the micro gap at the interface generated during the vulcanization process, to form a stable acoustic coupling interface.

[0017] Further schemes of the present application construct a multi-path composite sound field composed of short-range high-density paths and long-range cross paths inside the rubber to be tested, including the following steps:

[0018] The ultrasonic probes arranged in dense parallel are triggered in time division, to generate short-range high-density paths for detecting differences in local medium microstructure;

[0019] The transmit-receive ultrasonic probe pairs arranged in large spacing and diagonal staggered are triggered in time division, to generate long-range cross paths for reflecting overall macroscopic properties;

[0020] The short-range high-density paths and the long-range cross paths jointly constitute the multi-path composite sound field.

[0021] Further schemes of the present application form a multi-channel synchronous sound wave response data set, including the following steps:

[0022] Each time the time-sharing triggered emission ultrasonic probe, the data acquisition window of all receiving ultrasonic probes is started synchronously;

[0023] The electrical signal waveform recorded by each receiving probe in the respective data acquisition window is digitized;

[0024] The digitized electrical signal waveform is associated and integrated with the corresponding timestamp and probe position information to form a multi-channel synchronous acoustic response dataset.

[0025] In a further aspect of the application, an acoustic homogeneity index is obtained, comprising the following steps:

[0026] Two signal waveforms triggered by the same emission event and collected by a pair of receiving ultrasonic probes adjacent in physical position are screened out from the multi-channel synchronous acoustic response dataset;

[0027] The two signal waveforms are normalized and cross-correlated within a preset time window, and the peak value of the operation result is extracted as the acoustic homogeneity index.

[0028] In a further aspect of the application, an average propagation speed is obtained, comprising the following steps:

[0029] Signals recorded by the emission probe and receiving probes arranged in a large-mesh diagonal staggered pattern are screened out from the multi-channel synchronous acoustic response dataset;

[0030] The time difference between the emission of an ultrasonic pulse from the emission probe and the reception by the receiving probe is measured to obtain the signal flight time;

[0031] The average propagation speed is calculated based on the known geometric distance between the probe pairs and the measured signal flight time.

[0032] In a further aspect of the application, the absolute vulcanization degree of the current rubber material is determined, comprising the following steps:

[0033] The currently measured vulcanization state feature vector is projected onto a pre-calibrated standard vulcanization trajectory curve to obtain a mapping point, and the standard vulcanization trajectory curve is a continuous path described by the vulcanization state feature vector in a two-dimensional coordinate system under standard process conditions for a specific rubber compound;

[0034] The arc length from the starting point of the pre-calibrated standard vulcanization trajectory curve along the curve path to the mapping point is calculated;

[0035] The arc length is compared with the total arc length of the pre-calibrated standard vulcanization trajectory curve to obtain a normalized position, and the normalized position is determined as the absolute vulcanization degree.

[0036] In a further aspect of the application, a double-layer suspended magnetic adsorption and damping structure, comprising the following steps:

[0037] The outer shell is equipped with a high-temperature resistant magnet assembly, which is used to adhere to the inner wall of the rubber vulcanizing mold and generate a preset constant positive pressure.

[0038] The inner housing that supports the ultrasonic probe;

[0039] A high-damping elastomer connecting the outer shell and the inner shell is used to stably transmit a preset constant positive pressure from the outer shell to the inner shell and isolate the mechanical vibration of the rubber vulcanizing mold.

[0040] A further aspect of this invention involves generating a sulfidation state feature vector characterizing the coupling state between microscopic homogeneity and macroscopic rigidity in the current sulfidation process, comprising the following steps:

[0041] The acoustic homogeneity index, calculated in real time, is used as the first dimension component.

[0042] The average propagation speed of sound calculated in real time is used as the second dimension component;

[0043] Construct a two-dimensional vector consisting of the first and second dimension components as the sulfurization state feature vector.

[0044] A further aspect of the present invention involves the generation of a pre-calibrated standard vulcanization trajectory curve, comprising the following steps:

[0045] For the same rubber compound as the rubber to be tested, perform a complete vulcanization process under standard process conditions;

[0046] Throughout the complete vulcanization process, steps S1 to S6 are continuously executed to obtain a series of vulcanization state feature vectors that evolve over time.

[0047] A series of vulcanization state feature vectors are connected in a two-dimensional coordinate system to form a pre-calibrated standard vulcanization trajectory curve.

[0048] In summary, the present invention has the following beneficial technical effects:

[0049] 1. By establishing a continuous and stable acoustic measurement interface inside the mold and combining it with multipath acoustic field detection technology, direct, continuous, and high-precision penetrating monitoring of the true physicochemical state inside the rubber can be achieved. This fundamentally overcomes the limitations of traditional methods that rely on external parameters for indirect inference, making the monitoring results no longer affected by fluctuations in the external environment and minor differences in process conditions. This direct measurement method can capture the complete dynamic process of the material from microstructural homogenization to the formation of macroscopic mechanical properties in real time.

[0050] 2. By acquiring and integrating dual key indicators characterizing microscopic uniformity and macroscopic rigidity, the vulcanization endpoint can be accurately determined, thereby significantly improving the quality and consistency of rubber products. The production process can end based on the actual state of the material rather than a fixed process time, effectively avoiding under-vulcanization and over-vulcanization problems caused by batch differences in raw materials or process fluctuations, achieving a high level of quality control and high batch-to-batch stability.

[0051] 3. The redundant heating time required in traditional processes to ensure complete vulcanization has been completely eliminated, allowing for faster production cycles and significantly improved equipment utilization. Energy consumption is directly reduced due to the decrease in ineffective heating time, and the reduced product performance degradation caused by avoiding over-sulfurization also lowers the scrap rate. This direct optimization of production efficiency and cost control enhances the company's competitiveness in the market. Attached Figure Description

[0052] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. The drawings are used to provide a further understanding of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0053] Fig. 1 A flowchart illustrating an embodiment of this application is disclosed.

[0054] Fig. 2 Structural schematic diagrams of embodiments of this application are disclosed. Detailed Implementation

[0055] 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 embodiments of the present invention, not all embodiments. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0056] The following is in conjunction with the appendix Figs. 1-2 A preferred description of the present invention is provided below.

[0057] See attached document Fig. 1 This invention proposes an online monitoring method for the degree of rubber vulcanization based on an ultrasonic array, comprising the following steps:

[0058] S1. Deploy an active voltage-stabilized coupling acoustic window array unit on the inner wall of the rubber vulcanizing mold to generate a stable acoustic coupling interface on the surface of the rubber to be tested.

[0059] S2. Based on a stable acoustic coupling interface, the ultrasonic probe in the active voltage-stabilized coupling acoustic window array unit is triggered in a time-division manner to construct a multi-path composite acoustic field inside the rubber under test, which is composed of short-range high-density paths and long-range cross paths.

[0060] S3. Synchronously acquire the signal received by the ultrasonic probe after the multi-path composite sound field passes through the rubber under test, forming a multi-channel synchronous acoustic response dataset.

[0061] S4. Calculate the signal waveform similarity of the multi-channel synchronous acoustic response data sourced from densely parallel adjacent probe pairs to obtain the acoustic homogeneity index.

[0062] S5. Extract the flight time of signals from the large-spacing diagonally staggered probe pairs in the multi-channel synchronous acoustic response data, calculate the acoustic propagation speed, and obtain the average propagation speed of sound.

[0063] S6. By integrating the acoustic homogeneity index and the average propagation speed, a sulfurization state feature vector is generated that characterizes the coupling state between microscopic homogeneity and macroscopic rigidity in the current sulfurization process.

[0064] S7. Map the position of the vulcanization state feature vector on the pre-calibrated standard vulcanization trajectory curve to determine the absolute degree of vulcanization inside the current rubber material.

[0065] In one embodiment of the present invention, step S1 includes the following steps:

[0066] An active voltage-stabilized coupling acoustic window array unit is deployed. Through the double-layer suspended magnetic adsorption and damping structure at the bottom of the acoustic window array unit, the acoustic window array unit is adsorbed onto the inner wall of the rubber vulcanizing mold with a preset constant positive pressure. The preset constant positive pressure acts on the pre-stressed viscoelastic coupling layer inside the acoustic window array unit, so that the viscoelastic coupling layer actively compensates for the small gaps at the interface caused by thermal expansion and contraction and phase changes during the vulcanization process. As a result, a stable acoustic coupling interface is generated on the surface of the rubber under test to eliminate the fluctuation of the interface sound energy transmission.

[0067] Specifically, through a pre-deployed, actively voltage-stabilized, coupled acoustic window array unit, its bottom double-layer suspended magnetic adsorption and damping structure adsorbs the acoustic window array unit with a preset constant positive pressure at a predetermined monitoring position on the inner wall of a rubber vulcanizing mold. The rubber vulcanizing mold is an industrial metal mold used for molding rubber products under high temperature and pressure. The acoustic window array unit is a composite sensor module integrating a magnetic adsorption structure, a vibration damping structure, a sensor probe array, and an acoustic coupling layer, automatically maintaining stable acoustic contact with the object being measured in harsh industrial environments. The double-layer suspended magnetic adsorption and damping structure, a component of the acoustic window array unit, consists of an outer adsorption shell, an inner probe-bearing shell, and a high-damping elastomer connecting the two. It converts external magnetic force into stable internal pressure and isolates external vibration interference.

[0068] The preset constant positive pressure is a pressure value designed and calibrated in advance based on experimental data. The preset constant positive pressure is set according to the following formula: , The constant positive pressure, expressed in Pa, represents the preset constant positive pressure. It is based on the statistical average of the minimum pressure required to achieve an interfacial acoustic impedance matching fluctuation of less than 2% under vulcanization conditions of 15 different rubber formulations at 160℃. The constant positive pressure is usually set to 20 kPa, which allows the viscoelastic coupling layer to fill the interfacial gaps without damaging the surface of the rubber under test or affecting its normal vulcanization reaction. The rubber under test refers to the rubber compound placed in the rubber vulcanization mold that has not yet completed or is undergoing vulcanization crosslinking reaction.

[0069] The magnetic adsorption force generated by the outer adsorption shell of the acoustic window array unit is represented by N and is determined by the material of the outer adsorption shell. The effective contact area between the prestressed viscoelastic coupling layer and the rubber under test is represented by m².

[0070] The preset constant positive pressure is transmitted through a double-layer suspended magnetic adsorption and damping structure within the acoustic window array unit. Specifically, the external magnetic force on the outer adsorption shell compresses the built-in high-damping elastomer, uniformly applying the force to the inner probe bearing shell. Ultimately, the constant positive pressure acts on the pre-stressed viscoelastic coupling layer, which is in direct contact with the rubber under test. This pre-stressed viscoelastic coupling layer maintains its viscosity and elasticity even at vulcanization temperatures, such as 150°C to 200°C, and can flow and deform under external force to fill microscopic gaps. During the entire vulcanization process, the rubber vulcanization mold and the rubber undergo thermal expansion and contraction due to drastic temperature changes. The phase change of the rubber from a soft rubber material to an elastomer also causes minute changes in surface morphology, resulting in micron-level gaps at the contact interface, which severely affects the transmission of acoustic signals.

[0071] Due to the continuous action of constant positive pressure, the prestressed viscoelastic coupling layer utilizes its properties at high temperatures—able to fill gaps like a fluid and transmit pressure like a solid—to continuously fill and compact these dynamically generated interfacial micro-gaps. A stable acoustic coupling interface is formed on the surface of the rubber under test. This stable acoustic coupling interface refers to the gapless contact surface with continuous acoustic impedance formed between the prestressed viscoelastic coupling layer and the surface of the rubber under test, ensuring that sound wave energy is transmitted into the interior of the rubber under test without attenuation or distortion.

[0072] For example, an actively voltage-stabilized coupling acoustic window array unit is deployed on the inner wall of a steel rubber vulcanizing mold used for producing large tires. The operating temperature of the steel rubber vulcanizing mold is 170°C. The high-temperature resistant magnet assembly of the acoustic window array unit is made of multiple samarium cobalt magnets and is calibrated to generate a magnetic attraction force of 50N. The magnetic attraction force is applied to a prestressed viscoelastic coupling layer with an area of ​​0.002m² through a double-layer suspended magnetic attraction and damping structure inside the acoustic window array unit. According to the formula, it is calculated to be 25000Pa. Under this constant positive pressure, the prestressed viscoelastic coupling layer adheres to the surface of the rubber under test inside the mold, actively compensating for the dynamic changes in the interface caused by the pre-expansion of the rubber due to temperature rise and the subsequent vulcanization shrinkage. A stable acoustic coupling interface is generated on the surface of the rubber under test to eliminate the fluctuations in the interfacial acoustic energy transmission.

[0073] In one embodiment of the present invention, step S2 includes the following steps:

[0074] Based on a stable acoustic coupling interface, an ultrasonic probe with a "sparse-dense-interlaced" composite layout is distributed inside the time-division triggered acoustic window array unit. A multi-path composite sound field composed of short-range high-density paths and long-range interlaced paths is constructed inside the rubber under test.

[0075] The "dense" part represents a pair of closely spaced parallel probes used to generate short-range parallel acoustic beams to detect differences in the microstructure of the local medium; the "sparse" part represents pairs of large-spaced diagonally staggered transmitting and receiving probes used to generate long-range cross acoustic beams that reflect the overall macroscopic properties; by controlling the host to activate different transmitting probes in sequence, the acoustic energy distribution formed inside the rubber under test is obtained, i.e., a multi-path composite sound field.

[0076] Specifically, based on the stable acoustic coupling interface already established on the surface of the rubber under test, the ultrasonic probes inside the actively voltage-coupled acoustic window array unit are sequentially excited by an external control host. A time-division triggering mechanism is adopted, meaning that at any given time, only one or a small group of specific probes are activated to emit ultrasonic pulses, avoiding complex interference caused by multiple acoustic signals propagating simultaneously in the medium. The control host sequentially selects and drives the ultrasonic probes distributed in a "sparse-dense-interlaced" composite layout according to a preset program. Time-division triggering divides time into multiple non-overlapping segments, with only one or a group of specific ultrasonic probes activated in each segment, ensuring that acoustic signals from different paths are separated in time, facilitating independent reception and analysis.

[0077] The "dense-sparse-interlaced" composite layout of the ultrasonic probe refers to a specific physical arrangement of probe elements within the sensor unit. Some probes are closely arranged for fine local detection, while others are distributed at greater distances around the perimeter for overall macroscopic detection. For example, in a 12-probe array, the "dense" section contains 8 probes with a spacing of 2mm; the "sparse" section consists of 4 probes located at the four corners, with a diagonal spacing of 30mm. This arrangement is based on a comprehensive consideration of the spatial scale of microscopic inhomogeneities during vulcanization and the volumetric effect of macroscopic modulus changes. The host activates one probe in the "dense" section, whose emitted sound wave energy is mainly concentrated in a local area directly in front of the probe, forming a short-range, parallel sound beam—a short-density path. The short-range, high-density path is the sound wave propagation path generated by the probes in the "dense" section, characterized by a small coverage area but dense paths, making it extremely sensitive to minute defects or local phase differences within the tested rubber.

[0078] After one or more short-path excitations, the host switches and activates one of the transmitting probes in the "sparse" section. The emitted sound waves propagate obliquely, reaching the receiving probe at the diagonal position to form a long-range cross path. The long-range cross path is the sound wave propagation path generated by the "sparse" probe. Its characteristics are that the path length is much greater than that of the short-path, traversing a large volume of the rubber under test, and there is spatial intersection between different paths, reflecting the overall macroscopic mechanical properties of the rubber under test.

[0079] By cyclically and alternately executing these two excitation modes throughout the probe array, a series of acoustic wave paths with different start points, end points, directions, and lengths are successively established within the rubber under test. The collection of all excited acoustic paths in space and time collectively constructs a non-uniform but structured energy field within the rubber under test—a multi-path composite sound field composed of short-range high-density paths and long-range intersecting paths. This multi-path composite sound field refers to the sum of all sound wave propagation paths formed within the rubber under test through time-division triggering, enabling comprehensive detection of the rubber's internal state at both microscopic and macroscopic scales.

[0080] For example, an acoustic window array unit, having established a stable acoustic coupling interface with the surface of the rubber under test within a tire mold, is controlled by a host computer that executes a time-division triggering program. The ultrasonic probes of the acoustic window array unit adopt a "dense-sparse-interlaced" composite layout. In the 12-probe array, 8 probes are linearly arranged at 2mm intervals to form the "dense" section, while the other 4 probes are located at the four corners of the array to form the "sparse" section. The host computer triggers probe number 1 in the "dense" section, and the sound wave passes through the rubber, forming a short-range high-density path pointing to adjacent probes such as probes 2 and 3. After a 50μs delay, the host computer triggers probe number 9 in the upper left corner of the "sparse" section, and the sound wave passes obliquely through the large piece of rubber, forming a long-range interlaced path pointing to probe number 12 in the lower right corner. Combining the above process, all preset transmitting probes are activated sequentially in a loop, and the successively generated sound wave paths construct a multi-path composite sound field inside the rubber under test, composed of short-range high-density paths and long-range interlaced paths.

[0081] In one embodiment of the present invention, step S3 includes the following steps:

[0082] When any transmitting probe emits an ultrasonic pulse, all receiving probes in the composite layout synchronously start their data acquisition windows and synchronously acquire the signals received by all receiving probes after the multi-path composite sound field passes through the rubber under test, forming a multi-channel synchronous acoustic response dataset containing short-range and long-range path response information.

[0083] Specifically, the process of constructing a multipath composite acoustic field within the rubber under test involves the control unit simultaneously sending trigger commands to all receiving probes for each ultrasonic pulse emission in the time-division trigger sequence. This simultaneous acquisition of the signals received by all receiving probes after the multipath composite acoustic field passes through the rubber under test ensures a unified starting time reference for multiple parallel measurement channels, guaranteeing that the data recorded by all channels are time-aligned and comparable. The receiving probes, set to receive mode during specific emission events, convert acoustic vibrations into electrical signals. These electrical signals represent the amplitude, phase, and frequency changes of the acoustic waves after they pass through the rubber under test. The waveform is a continuous function graph of analog voltage versus time, directly output by the receiving probes.

[0084] Upon receiving the trigger command, all receiving probes synchronously activate an electronic gate of a preset duration, i.e., a data acquisition window. The data acquisition window refers to a specific time period during which the receiving probe's electronic system is activated and records signals. Based on the size of the rubber under test and the approximate speed of sound, the longest estimated sound wave flight time is used to ensure the reception of all useful echo signals; for example, this is set to 100 μs. The ultrasonic pulse propagates inside the rubber under test, and after passing through different paths, its energy successively reaches each receiving probe. Each receiving probe converts the received sound pressure signal into a weak electrical signal waveform, which is completely recorded within its respective data acquisition window duration.

[0085] The system samples and quantizes the continuous electrical signal waveform recorded by each receiving probe using a high-speed analog-to-digital converter, converting it into a series of discrete digital data—this is digitization. Digitization is the process of converting continuous analog electrical signal waveforms into discrete digital sequences, a prerequisite for computer signal processing. After digitization, the system adds metadata to each digital waveform data, including a timestamp that triggered the transmission event, a unique identifier for the receiving probe that generated the digital waveform data, and its probe position information in the array. The timestamp is a time stamp accurate to the microsecond or nanosecond level, recording the absolute moment of each ultrasonic transmission. The probe position information is the three-dimensional coordinates of each probe in the sensor coordinate system, which are calibrated during sensor manufacturing, such as (x1, y1, z1). This process is repeated for each transmission event in the time-division trigger sequence.

[0086] The digitized waveforms and additional metadata from all receiving channels generated by all transmission events are integrated to form a structured dataset, namely the multi-channel synchronous acoustic response dataset containing short-range and long-range path response information. Each row of the multi-channel synchronous acoustic response dataset represents a complete record of the receiving channel in a single transmission event, including the transmitting probe ID, receiving probe ID, timestamp, and a time-series array representing the digitized waveform.

[0087] For example, when the control host triggers probe number 1 of the "secret" section to emit an ultrasonic pulse, a synchronization signal is sent to all other 15 receiving probes in the array. These 15 receiving probes simultaneously activate a 100μs data acquisition window, and each receiving probe records the received electrical signal waveform within its respective 100μs data acquisition window. These 15 electrical signal waveforms are simultaneously digitized and associated with the timestamp of the current transmission event (e.g., 10.052145s) and their respective probe position information.

[0088] When the host triggers the emission pulse from probe 9 of the "sparse" section, the same process occurs again, and another 15 signals containing long-range cross-path information are acquired and processed. This process repeats until all preset emission sequences are completed. The acquired, digitized, and labeled data are integrated to form a multi-channel synchronous acoustic response dataset containing hundreds of waveform records, including response information from short-range high-density paths and response information from long-range cross-paths.

[0089] In one embodiment of the present invention, step S4 includes the following steps:

[0090] Calculate the signal waveform similarity of adjacent pairs of densely arranged parallel probes in the multi-channel synchronous acoustic response dataset, and select the signal waveforms acquired by a pair of receiving probes that were triggered by the same transmission event and are physically adjacent from the multi-channel synchronous acoustic response dataset. and , and Normalized cross-correlation is performed within a preset time window, and the peak value is taken as a measure of the similarity between the two signal waveforms.

[0091] The acoustic homogeneity index, which characterizes the uniformity of the microstructure, is obtained. The value of the acoustic homogeneity index evolves from close to 0 (in the early stage of vulcanization, the inhomogeneity of the medium leads to large waveform differences) to close to 1 (after vulcanization is completed, the uniformity of the medium leads to highly consistent waveforms).

[0092] Specifically, the automated data processing program is initiated, systematically scanning the entire multi-channel synchronous acoustic response dataset. The goal of this program is to filter out specific signal pairs. For each ultrasonic emission event in the multi-channel synchronous acoustic response dataset, the automated program examines all received signals and, based on pre-stored probe position information, identifies signals recorded by probe pairs that are physically adjacent and belong to a densely parallel arrangement. A densely parallel pair of adjacent probes refers to any two adjacent probes randomly selected from those arranged side-by-side with very small spacing in a "sparse-staggered" composite layout. A pair of signals is found, for example named the signal waveform. and , signal waveform and These are two specific time series data selected from the multi-channel synchronous acoustic wave response dataset, representing the response of the acoustic wave after passing through two extremely similar but independent paths.

[0093] Extract each pair of signal waveforms and The normalized cross-correlation operation is performed within a preset time window. The preset time window is a specific time period selected for signal analysis, used to focus on the direct wave portion of the initial sound wave arrival, eliminating interference from subsequent reflected clutter. The normalized cross-correlation operation measures the similarity between two signal waveforms while eliminating the influence of the signal's own energy magnitude. Signal waveform similarity describes the degree of similarity in shape between two signal waveforms, and is a floating-point number between 0 and 1.

[0094] Normalized cross-correlation (NCC) involves time-shifting one waveform relative to another and calculating their similarity at each shift point. The system finds the shift point where the two waveforms best match and outputs the maximum similarity value at that point, which is the peak value of the result. This peak value is defined as the acoustic homogeneity index, characterizing the uniformity of the microstructure. The peak value refers to the highest point on the normalized cross-correlation curve, representing the maximum similarity between the two signals under optimal alignment.

[0095] In the initial stage of vulcanization, the interior of the rubber is acoustically heterogeneous, resulting in signal waveform... and Even with similar paths, the shapes can differ significantly, resulting in calculated peak values ​​close to 0. Acoustic heterogeneity refers to the uneven distribution of acoustic properties within a material, such as sound velocity and attenuation, at a microscopic scale. As the vulcanization reaction proceeds, the internal structure of the rubber tends to become uniform, transforming into an acoustically homogeneous state. Acoustic homogeneity represents the opposite of acoustic heterogeneity, indicating that the acoustic properties within the material are macroscopically consistent throughout. and The waveforms become highly similar, and the calculated peak value approaches 1. By continuously calculating this acoustic homogeneity index, a curve quantifying the transition process from acoustic heterogeneity to acoustic homogeneity within the rubber is obtained.

[0096] The signal waveform similarity is calculated using normalized cross-correlation, satisfying the following formula:

[0097]

[0098] AHI stands for Acoustic Homogeneity Index, which ranges from 0 to 1. and These represent the signal waveforms received by two probes in a densely arranged pair of adjacent probes. The voltage value, expressed in volts (V), varies with time t. t represents time, and τ represents the time delay, a variable used to shift the waveform to find the best match, expressed in seconds (s). W represents a preset time window, the time interval for integration calculations, for example, from 5 μs to 25 μs after triggering the transmission. This is the estimated arrival time range of the direct sound wave based on the probe spacing and the approximate sound velocity in the rubber. This represents time integration within a preset time window W. `max(...)` indicates taking the maximum value that the expression within the parentheses can reach as τ changes.

[0099] For example, in the multi-channel synchronous acoustic response dataset generated in step S3, which contains hundreds of waveform records, 2 minutes after the start of vulcanization, the automated data processing program filters the signal waveforms received in the same transmission event from the multi-channel synchronous acoustic response dataset by the densely arranged pair of adjacent probes, probes 2 and 3, in the "dense" region. and signal waveform Because the rubber under test is acoustically heterogeneous, the two waveforms show significant differences in shape. A preset time window of 5μs to 25μs was used, and normalized cross-correlation was performed on the two waveforms. The resulting peak value was 0.18, which is the acoustic homogeneity index characterizing the microstructure uniformity at that moment. At the 15-minute mark of vulcanization, the automated data processing program extracted the signal waveforms of the same probe pair from the new multi-channel synchronous acoustic response dataset. and .

[0100] The rubber under test is nearly acoustically homogeneous, and the two waveforms are visually similar. Performing the same normalized cross-correlation operation again, the peak value rises to 0.92, which is the updated acoustic homogeneity index characterizing the uniformity of the microstructure, quantifying the process of the rubber's internal transformation from acoustic heterogeneity to acoustic homogeneity.

[0101] In one embodiment of the present invention, step S5 includes the following steps:

[0102] The flight time of signals from a pair of diagonally staggered probes with large spacing is extracted from the multi-channel synchronous acoustic response data. The propagation speed of the sound wave inside the rubber under test is calculated to obtain the average propagation speed of sound that reflects the overall change in the elastic modulus and density of the rubber.

[0103] Specifically, the multi-channel synchronous acoustic response dataset is filtered to extract signals originating from diagonally staggered probe pairs with large spacing. A diagonally staggered probe pair refers to two probes selected for transmitting and receiving in the sensor array that are physically far apart and typically not on the same straight line, maximizing the acoustic path's coverage of the internal volume of the rubber under test. The program ignores short-range signals generated by densely packed probe pairs, focusing only on long-range signals emitted by the "sparse" probes and received by another probe diagonally or at a more distant end. For each extracted long-range signal waveform, the program executes a time measurement algorithm: by identifying the precise moment when the energy first arrives in the signal waveform—for example, the moment when the waveform amplitude first stably exceeds the background noise threshold—the arrival time of the ultrasonic pulse is determined; since the emission time of the ultrasonic pulse is timestamped in the multi-channel synchronous acoustic response dataset, the arrival time of the ultrasonic pulse is subtracted from its emission time to obtain the time difference, i.e., the signal flight time, of the ultrasonic pulse propagating through the rubber under test.

[0104] The signal time of flight (TFL) refers to the time interval between the emission of an ultrasonic pulse from the transmitting probe and its first detection by the designated receiving probe. It is defined based on precise extraction from the actual waveform using a time measurement algorithm. After acquiring the TFL, the automated data processing program reads the known geometric distances between probe pairs corresponding to the current transmitter-receiver pair from a preset configuration file. These known geometric distances between probe pairs are pre-calibrated constants representing the straight-line spatial distance between the center points of a specific transmitter-receiver probe, based on three-dimensional coordinate measurements taken during sensor manufacturing.

[0105] The propagation speed of sound waves within the tested rubber is calculated. This propagation speed reflects the average speed of sound, which in turn reflects the combined changes in the rubber's overall elastic modulus and density. Reflecting these combined changes explains the physical meaning of the average speed of sound, as the speed of sound in a material is directly proportional to the square root of the elastic modulus and inversely proportional to the square root of the density. The vulcanization process alters both of these parameters. The speed of sound wave propagation within the tested rubber satisfies the following formula: , It is the average speed of sound, which characterizes the speed at which sound waves propagate inside the rubber being tested, and is measured in m / s. This represents the known geometric distance between probe pairs, in meters (m). This represents the signal flight time, which is measured in real time by analyzing the received signal waveform, and is measured in seconds.

[0106] As the vulcanization reaction proceeds, the crosslinking density of the rubber under test increases, resulting in a significant increase in its elastic modulus and a corresponding increase in sound velocity. By continuously monitoring this average propagation sound velocity, the evolution of the macroscopic mechanical properties of the rubber can be understood.

[0107] For example, at the 5th minute of vulcanization, signals emitted by probe 9 and received by probe 16 in the "sparse" section are selected from the multi-channel synchronous acoustic response dataset. The two probes form a diagonally staggered pair with a large gap. The system queries the configuration information and finds that the known geometric distance between the probe pairs is 35mm. The signal waveform received by probe 16 is processed, and the signal flight time is measured to be 21.875μs. The average propagation speed at this moment is calculated using the formula to be 1600m / s, which reflects the combined change in the overall elastic modulus and density of the rubber. At the 15th minute of vulcanization, this process is repeated, and the signal flight time along the same path is shortened to 20μs. The calculated average propagation speed correspondingly increases to 1750m / s, indicating that the macroscopic stiffness of the tested rubber is increasing with the progress of the vulcanization reaction.

[0108] In one embodiment of the present invention, step S6 includes the following steps:

[0109] The acoustic homogeneity index AHI, calculated in real time, is used as the first dimension component, and the average propagation speed Vs, calculated in real time, is used as the second dimension component. The two-dimensional vector composed of [AHI, Vs] is the sulfurization state feature vector.

[0110] Specifically, the system receives the acoustic homogeneity index from step S4 and the average propagation speed from step S5, acquiring these two latest values ​​at any monitoring time point. The system performs simple assignment and construction operations, creating a one-dimensional array or ordered pair containing two elements. The real-time calculated acoustic homogeneity index is assigned to the first position of this array as the first dimension component; the real-time calculated average propagation speed is assigned to the second position of this array as the second dimension component. The characteristic vector of the vulcanization state, defined as representing the coupling state between microscopic homogeneity and macroscopic rigidity in the current vulcanization process, satisfies the formula: , The characteristic vector representing the sulfurization state contains an ordered array of two floating-point numbers, coupled through the evolution of the microstructure (represented by the acoustic homogeneity index) and the establishment of macroscopic mechanical properties (represented by the average propagation speed of sound).

[0111] The acoustic homogeneity index is calculated in step S4. The average propagation speed of sound is calculated in step S5. Characterizing the coupling state between microscopic homogeneity and macroscopic rigidity in the current vulcanization process is a description of the functional attributes of the vulcanization state feature vector, emphasizing its multidimensionality and ability to deeply characterize the physical essence of the vulcanization process.

[0112] For example, at the 15th minute of vulcanization, the acoustic homogeneity index, which characterizes the uniformity of the microstructure, is calculated to be 0.92, and the average sound velocity, reflecting the combined change in the overall elastic modulus and density of the rubber, is calculated to be 1750 m / s. The system uses the acoustic homogeneity index value of 0.92 as the first dimension component and the average sound velocity value of 1750 as the second dimension component, combining them to generate a two-dimensional vector composed of [0.92, 1750].

[0113] In one embodiment of the present invention, step S7 includes the following steps:

[0114] The vulcanization state feature vector is calculated in real time. The measured vulcanization state feature vector is projected onto a pre-calibrated standard vulcanization trajectory curve. The normalized position of the vulcanization state feature vector on the path of the standard vulcanization trajectory curve determines the absolute degree of vulcanization inside the current rubber material.

[0115] Specifically, the real-time vulcanization state feature vector, projected onto a pre-calibrated standard vulcanization trajectory curve, is equivalent to plotting this real-time data point in a two-dimensional coordinate system, where the standard vulcanization trajectory curve has already been pre-plotted. The standard vulcanization trajectory curve is an ordered two-dimensional point set {[AH... V ],[AH V ],...,[AH V The standard vulcanization trajectory curve is based on a complete vulcanization experiment conducted on the same rubber formulation under standard laboratory conditions, recording the evolution path of the vulcanization state characteristic vector throughout the process. The standard vulcanization trajectory curve is a continuous path depicted in a two-dimensional coordinate system, representing the vulcanization state characteristic vector of a specific rubber compound from the start to the end of vulcanization under standard process conditions. The geometric distances from real-time data points to all points on the standard vulcanization trajectory curve are calculated, and the point with the shortest distance is found; this closest point is the mapping position of the real-time data point on the curve.

[0116] Calculate the arc length from the starting point of the standard vulcanization trajectory curve (representing 0% vulcanization) to this mapped point along the curve path. Divide this arc length by the total arc length of the standard vulcanization trajectory curve (representing the complete path length from 0% to 100% vulcanization). The ratio between 0 and 1 is the normalized position. The normalized position is the relative representation of the position of a point on the standard vulcanization trajectory curve with respect to the total length of the curve, and the data structure is a floating-point number between 0 and 1. Define the absolute degree of vulcanization within the rubber material to be tested, satisfying the following formula:

[0117]

[0118] in, Represents the absolute degree of vulcanization at time t, indicating the percentage of chemical cross-linking reaction completed within the rubber. It is usually expressed as a percentage from 0% to 100%, such as 90% absolute vulcanization, which means that 90% of the cross-linking reaction has been completed. This represents the eigenvector of the sulfurization state measured in real time at time t. . This represents a pre-calibrated standard vulcanization trajectory curve; Representative standard vulcanization trajectory curve Total arc length; Representation finds vector In the curve The nearest point on the [planet]. Characterization calculation of standard sulfidation trajectory curve From the starting point to The path length.

[0119] For example, at the 15-minute mark of vulcanization, the system first obtains the vulcanization state feature vector [0.92, 1750]. The system has already loaded a pre-calibrated standard vulcanization trajectory curve for this type of tire rubber. The starting point of the standard vulcanization trajectory curve is [0.10, 1550], and the ending point is [0.98, 1780], with a total arc length calculated to be 250 units. The real-time point [0.92, 1750] is mapped in two-dimensional space to find its closest point on the standard vulcanization trajectory curve. The system calculates that the arc length from the curve starting point [0.10, 1550] along the curve path to this mapped point is 225 units. According to the formula, the normalized position is calculated to be 0.9, which is determined as the absolute degree of vulcanization within the current rubber material, meaning that the vulcanization process has been completed by 90%.

[0120] See appendix Fig. 2 The present invention also proposes an online monitoring system for the degree of rubber vulcanization based on an ultrasonic array, comprising the following modules:

[0121] The coupling interface generation module deploys an active voltage-stabilized coupling acoustic window array unit on the inner wall of the rubber vulcanizing mold to generate a stable acoustic coupling interface on the surface of the rubber to be tested.

[0122] The composite sound field construction module, based on a stable acoustic coupling interface, uses an ultrasonic probe in an active voltage-stabilized coupling acoustic window array unit to be triggered in a time-division manner to construct a multi-path composite sound field inside the rubber under test, consisting of short-range high-density paths and long-range cross paths.

[0123] The response data acquisition module synchronously acquires the signals received by the ultrasonic probe after the multi-path composite sound field passes through the rubber under test, forming a multi-channel synchronous acoustic wave response dataset.

[0124] The micro-homogeneity quantization module calculates the signal waveform similarity originating from densely parallel adjacent probe pairs in the multi-channel synchronous acoustic response dataset, and obtains the acoustic homogeneity index.

[0125] The macroscopic rigidity characterization module is used to extract the signal flight time from the large-spacing diagonally staggered probe pairs in the multi-channel synchronous acoustic response dataset, calculate the sound wave propagation speed, and obtain the average propagation speed of sound.

[0126] The multi-dimensional state feature fusion module integrates the acoustic homogeneity index and the average propagation speed of sound to generate a sulfurization state feature vector.

[0127] The absolute vulcanization degree calculation module maps the position of the vulcanization state feature vector on the pre-calibrated standard vulcanization trajectory curve to determine the absolute vulcanization degree inside the current rubber material.

[0128] It should be noted that the formulas described above, through the principle of dimensional consistency and mathematical standardization methods (such as normalization, dimensionless parameter conversion, or unit system unification), can translate physical quantities with different properties into unitless standard values ​​or superimposed parameters of the same dimension. This eliminates the interference of different dimensions on the computational logic, allowing the formulas to retain the original data distribution characteristics while possessing mathematical rationality and adaptability to objective laws. The descriptions are merely exemplary embodiments of the present invention and should not be construed as limiting the scope of the invention.

[0129] Each of the modules can be implemented in whole or in part through software, hardware, or a combination thereof. It supports hardware embedded in or independent of the processor in the computer device, and also supports software stored in the memory of the computer device, so that the processor can call and execute the operations corresponding to each of the above modules.

[0130] It should be noted that the human information (including but not limited to human device information and personal information) and data (including but not limited to data used for analysis, data stored and data displayed) involved in this invention are all information and data authorized by the human body or fully authorized by all parties. The collection, use and processing of related data require relevant legal standards.

[0131] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A method for online monitoring of rubber vulcanization degree based on ultrasonic array, characterized in that, Includes the following steps: S1. Deploy an active voltage-stabilized coupling acoustic window array unit on the inner wall of the rubber vulcanizing mold to generate a stable acoustic coupling interface on the surface of the rubber to be tested. S2. Based on a stable acoustic coupling interface, the ultrasonic probe in the active voltage-stabilized coupling acoustic window array unit is triggered in a time-division manner to construct a multi-path composite acoustic field inside the rubber under test, which is composed of short-range high-density paths and long-range cross paths. S3. Synchronously acquire the signal received by the ultrasonic probe after the multi-path composite sound field passes through the rubber under test, forming a multi-channel synchronous acoustic response dataset. S4. Calculate the signal waveform similarity of the multi-channel synchronous acoustic response data sourced from densely parallel adjacent probe pairs to obtain the acoustic homogeneity index. Two signal waveforms triggered by the same transmission event and acquired by a pair of physically adjacent receiving ultrasonic probes are centrally selected from the multi-channel synchronous acoustic response dataset. The two signal waveforms are then subjected to normalized cross-correlation within a preset time window, and the peak value of the result is extracted as the acoustic homogeneity index. S5. Extract the flight time of signals from the large-spacing diagonally staggered probe pairs in the multi-channel synchronous acoustic response data, calculate the acoustic propagation speed, and obtain the average propagation speed of sound. The signals recorded by the transmitting probe and the receiving probes arranged diagonally with a large spacing are centrally filtered from the multi-channel synchronous acoustic response data; the time difference between the ultrasonic pulse emitted from the transmitting probe and received by the receiving probe is measured to obtain the signal flight time; the average propagation speed is calculated based on the known geometric distance between the probe pairs and the measured signal flight time. S6. By integrating the acoustic homogeneity index and the average propagation speed, a sulfurization state feature vector is generated that characterizes the coupling state between microscopic homogeneity and macroscopic rigidity in the current sulfurization process. The acoustic homogeneity index, calculated in real time, is used as the first dimension component. The average propagation speed of sound calculated in real time is used as the second dimension component; a two-dimensional vector composed of the first dimension component and the second dimension component is constructed as the sulfurization state feature vector. S7. Map the position of the vulcanization state feature vector on the pre-calibrated standard vulcanization trajectory curve to determine the absolute degree of vulcanization inside the current rubber material. The currently measured vulcanization state feature vector is projected onto a pre-calibrated standard vulcanization trajectory curve to obtain a mapping point. The standard vulcanization trajectory curve is a continuous path depicted in a two-dimensional coordinate system by the vulcanization state feature vector of a specific rubber compound under standard process conditions. The arc length from the starting point of the pre-calibrated standard vulcanization trajectory curve along the curve path to the mapping point is calculated. The arc length is compared with the total arc length of the pre-calibrated standard vulcanization trajectory curve to obtain the normalized position, and this normalized position is determined as the absolute degree of vulcanization.

2. The online monitoring method for rubber vulcanization degree based on ultrasonic array according to claim 1, characterized in that, To generate a stable acoustic coupling interface on the surface of the rubber to be tested, the following steps are included: The active voltage-stabilized coupling acoustic window array unit is attached to the inner wall of the rubber vulcanizing mold with a preset constant positive pressure through the double-layer suspended magnetic adsorption and damping structure at the bottom of the active voltage-stabilized coupling acoustic window array unit. By applying a preset constant positive pressure to the prestressed viscoelastic coupling layer within the actively stabilized coupled acoustic window array unit, the prestressed viscoelastic coupling layer actively compensates for the minute interfacial gaps generated during vulcanization, thus forming a stable acoustic coupling interface.

3. The online monitoring method for rubber vulcanization degree based on ultrasonic array according to claim 1, characterized in that, A multi-path composite sound field, consisting of short-range high-density paths and long-range intersecting paths, is constructed inside the rubber to be tested, including the following steps: Time-division triggering of densely parallel ultrasonic probes generates short-range, high-density paths for detecting differences in the microstructure of local media. Time-division triggering of large-spacing diagonally staggered transmitting-receiving ultrasound probe pairs generates long-range cross paths to reflect overall macroscopic properties; Short-range high-density paths and long-range intersecting paths together constitute a multi-path composite sound field.

4. The online monitoring method for rubber vulcanization degree based on ultrasonic array according to claim 1, characterized in that, To create a multi-channel synchronous acoustic response dataset, the following steps are included: Each time the ultrasonic probe is triggered to transmit, the data acquisition windows of all receiving ultrasonic probes are simultaneously activated. The electrical signal waveforms recorded by each receiving probe within its respective data acquisition window are digitized; The digitized electrical signal waveform is correlated and integrated with the corresponding timestamp and probe position information to form a multi-channel synchronous acoustic response dataset.

5. The online monitoring method for the degree of rubber vulcanization based on an ultrasonic array according to claim 2, characterized in that, The double-layer suspended magnetic adsorption and damping structure includes the following steps: The outer shell is equipped with a high-temperature resistant magnet assembly, which is used to adhere to the inner wall of the rubber vulcanizing mold and generate a preset constant positive pressure. The inner housing that supports the ultrasonic probe; A high-damping elastomer connecting the outer shell and the inner shell is used to stably transmit a preset constant positive pressure from the outer shell to the inner shell and isolate the mechanical vibration of the rubber vulcanizing mold.

6. The online monitoring method for the degree of rubber vulcanization based on an ultrasonic array according to claim 1, characterized in that, The generation of a pre-calibrated standard vulcanization trajectory curve includes the following steps: For the same rubber compound as the rubber to be tested, perform a complete vulcanization process under standard process conditions; Throughout the complete vulcanization process, steps S1 to S6 are continuously executed to obtain a series of vulcanization state feature vectors that evolve over time. A series of vulcanization state feature vectors are connected in a two-dimensional coordinate system to form a pre-calibrated standard vulcanization trajectory curve.

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