CN-121994680-A - Test method for evaluating chemical solvent permeation resistance of reinforced plastic

CN121994680ACN 121994680 ACN121994680 ACN 121994680ACN-121994680-A

Abstract

The invention relates to the technical field of material performance test, and discloses a test method for evaluating the chemical solvent permeation resistance of reinforced plastics, which comprises the following steps: constructing an inverse transfer function to compensate platform hysteresis, predicting the starting moment of opening of microcracks in the next period by using historical strain data, calculating the instruction sending moment by combining the inherent delay of the platform, adaptively adjusting the optimal disturbance frequency based on the stiffness attenuation rate calculated in real time, generating a corrected disturbance instruction by using the inverse transfer function, superposing and injecting, subtracting the fluid viscosity damping power calibrated in advance from single period data to obtain effective dissipation density, and judging a failure end point based on the second derivative change of the effective dissipation density sequence. According to the invention, the time synchronization of pressure waves and crack opening is realized through a predictive feedforward strategy, the deep penetration driving force is maintained by utilizing self-adaptive disturbance, the fluid damping interference is eliminated through an energy decoupling mechanism, and the authenticity and the result accuracy of the stress auxiliary solvent penetration test are improved.

Inventors

DONG LICHUN
WANG BO
YAN HUANHUAN
RUAN ZHENXIANG

Assignees

宁波瑞隆新材料科技有限公司

Dates

Publication Date: 20260508
Application Date: 20260408

Claims (10)

1. A test method for evaluating the resistance of a reinforced plastic to penetration by a chemical solvent, comprising the steps of: inputting a random pressure command and collecting the actual measured internal pressure under the condition of keeping the basic static pressure, and constructing an inverse transfer function based on the relation between the random pressure command and the actual measured internal pressure; collecting historical strain data of a tubular sample by using a laser scanning micrometer, calculating the starting moment of opening of microcracks in the next period, and calculating the instruction sending moment by combining the inherent delay of a platform; Calculating the stiffness attenuation rate of the current period based on real-time data acquired by a laser scanning micrometer and a pressure sensor, calculating the optimal disturbance frequency matched with the current damage state according to a disturbance frequency self-adaptive formula, generating a correction disturbance command by using the inverse transfer function, and superposing and transmitting the correction disturbance command to an electrohydraulic servo valve at the command transmitting moment; Extracting measured internal pressure and radial strain data from the acquired monocycle data, deducting the pre-calibrated fluid viscosity damping work, and calculating effective dissipation density by utilizing a corrected dissipation energy formula; and calculating a second derivative value of the time sequence of the effective dissipation density, judging a failure end point based on the change of the second derivative value, and taking the cycle number when judging the failure end point as the medium-resistant life of the reinforced plastic.
2. The method of claim 1, wherein the step of constructing an inverse transfer function based on the relationship between the random pressure command and the measured internal pressure comprises: inputting the random pressure command to an electrohydraulic servo valve in a state of maintaining a basic static pressure, and synchronously collecting command voltage generated by the random pressure command and the actually measured internal pressure fed back by a pressure sensor; processing the command voltage and the actually measured internal pressure by using a Fourier transform algorithm, and calculating to obtain a forward transfer function reflecting the frequency response characteristic of the platform; and performing inversion operation on the forward transfer function, generating and storing the inverse transfer function, wherein the inverse transfer function is used as a pre-filter of a subsequent high-frequency disturbance instruction.
3. The method of claim 2, wherein in the step of performing an inversion operation on the forward transfer function, further comprising the step of introducing a lower threshold of magnitude to determine: when the modulus value of the forward transfer function is larger than the amplitude lower limit threshold value, directly calculating the reciprocal to obtain the inverse transfer function; when the modulus value of the forward transfer function is smaller than or equal to the amplitude lower limit threshold value, limiting the inverse function gain of the corresponding frequency point to a preset saturation value to obtain the inverse transfer function; the amplitude lower limit threshold is preset according to the background noise level of the system, and the preset saturation value is preset according to the numerical stability requirement of the test platform.
4. A test method for evaluating the resistance of a reinforced plastic to penetration by chemical solvents as in claim 3 wherein the step of calculating the onset of the opening of the microcracks of the next cycle comprises: Driving an electrohydraulic servo valve to apply a basic load to a tubular sample, and collecting the historical strain data of the tubular sample for a set number of periods by using a laser scanning micrometer; Constructing a time sequence prediction model by utilizing the historical strain data, projecting waveform characteristics of a complete period in the historical strain data to the future on a time axis, and reconstructing a predicted strain curve of a next period; searching in the predicted strain curve, searching a time point of a first-time threading opening threshold value of a numerical value, and marking the time point as the starting moment; wherein the opening threshold is a critical strain value determined from the stress-strain constitutive relation of the reinforced plastic material.
5. The method of claim 4, wherein the calculation logic in combination with the platform inherent delay calculation command transmission time comprises: The instruction sending moment is equal to the initial moment of the opening of the micro-crack of the next period obtained by prediction minus the inherent delay of the platform; wherein the platform-inherent delay is scaled by a phase lag of the forward transfer function at a base load frequency.
6. The method of claim 4, wherein the step of calculating the optimal disturbance frequency for matching the current damage condition according to a disturbance frequency adaptive formula comprises: based on the real-time data acquired by the laser scanning micrometer and the pressure sensor, extracting stress and strain data of the current period in the linear section of the rising of the basic load, calculating the current dynamic stiffness modulus, and calculating the stiffness attenuation rate by combining the initial dynamic stiffness modulus; Substituting the stiffness attenuation rate into a disturbance frequency adaptive formula, wherein the disturbance frequency adaptive formula defines that the optimal disturbance frequency is in direct proportion to a preset initial frequency and in inverse proportion to a logarithmic function term containing the stiffness attenuation rate; The disturbance frequency self-adaptive formula comprises a frequency attenuation coefficient, wherein the frequency attenuation coefficient is preset according to the kinematic viscosity of a chemical solvent to be tested and the fiber content of reinforced plastic, and the initial dynamic stiffness modulus is calculated according to average data in an initial stage of testing.
7. The method for evaluating the chemical solvent permeation resistance of reinforced plastics according to claim 1, wherein the step of generating a modified disturbance command by using the inverse transfer function and superimposing and transmitting the modified disturbance command to the electrohydraulic servo valve at the command transmission timing specifically comprises: Generating an original disturbance command in a sine wave form according to the optimal disturbance frequency; Invoking the stored inverse transfer function to perform preprocessing correction of amplitude and phase of the original disturbance instruction, and generating the corrected disturbance instruction; and when the clock of the test platform controller reaches the command sending time, the modified disturbance command is overlapped into a basic load command sequence of the low-frequency trapezoidal wave and is sent to the electrohydraulic servo valve.
8. A test method for evaluating the resistance of a reinforced plastic to penetration by chemical solvents according to claim 1, characterized in that the step of calculating the effective dissipation density using a modified dissipation energy formula comprises: Extracting the actually measured internal pressure and the radial strain data which are synchronously acquired by a pressure sensor and a laser scanning micrometer in a single period, and performing differential processing on the radial strain data to obtain a radial strain rate; Performing closed loop integral calculation on a data sequence extracted from the acquired monocycle data to obtain total dissipation energy, and subtracting a pre-calibrated fluid viscosity damping work to obtain effective dissipation density; wherein the pre-calibrated fluid viscous damping work is determined from the hysteresis loop area measured under the same test conditions for a rigid standard tube.
9. The method for evaluating the chemical solvent permeation resistance of reinforced plastics according to claim 1, wherein the step of determining the failure end point based on the change in the second derivative value and regarding the number of cycles at the time of determining the failure end point as the dielectric life of the reinforced plastics specifically comprises: The second derivative value is monitored in real time, and the absolute difference value between the second derivative value of the current sampling period and the second derivative value of the last sampling period is calculated; When the absolute difference value is larger than a preset failure threshold value, judging that the front edge of the solvent breaks through the surface layer resin-rich region and enters the fiber interface layer, sending a stop instruction to the electrohydraulic servo fatigue testing machine, and recording the current cycle number as the medium-resistant life of the reinforced plastic; The failure threshold is preset according to a statistical dynamic setting method, the dynamic setting method comprises the steps of intercepting second derivative data of a section of stable section in a test initial stage as a background noise sample, calculating standard deviation of data in the background noise sample, and setting the failure threshold to be a multiple of the standard deviation.
10. A test method for evaluating the resistance of a reinforced plastic to penetration by chemical solvents as recited in claim 9, wherein the step of calculating a time series of second derivative values of said effective dissipation density further comprises: before second order derivative operation is carried out, smoothing is carried out on the time sequence by adopting a moving average filtering method; the second order derivative operation is specifically carried out by adopting a three-point center difference formula to carry out numerical calculation.

Description

Test method for evaluating chemical solvent permeation resistance of reinforced plastic Technical Field The invention relates to the technical field of material performance test, in particular to a test method for evaluating the chemical solvent permeation resistance of reinforced plastics. Background In the field of robots, particularly heavy-duty hydraulic robots for executing complex environmental operations, a hydraulic power transmission system of the heavy-duty hydraulic robots often adopts glass fiber or carbon fiber reinforced engineering plastic pipelines so as to meet the requirements of light weight and corrosion resistance. In the service process of the power pipelines, the inner walls of the power pipelines are required to be in long-term contact with chemical solvents (such as glycol-based hydraulic oil) with permeability as well as bear high-frequency and high-pressure pulse mechanical stress. The environment of the stress and the solvent coupling can lead the solvent to be accelerated to infiltrate into the material matrix under the action of alternating stress, so that the resin swelling and interface debonding are initiated, and the operation reliability of the robot is further affected. To evaluate the service life of such materials, conventional pressure pulse tests or static soaking fatigue tests are used in most of the existing test techniques. However, in the simulation test for the high dynamic response condition, the physical response lag existing between the instruction from the controller to the actual establishment of the target pressure field inside the tubular sample is limited by the bulk modulus of the hydraulic oil in the electrohydraulic servo loading system and the inertial mass of the mechanical actuator. The hysteresis causes that the fluid pressure wave crest cannot be accurately aligned with the opening moment of the microcracks of the material, so that the stress auxiliary penetration test condition deviates from the real working condition, and the physical process of promoting the solvent penetration into the microcracks by high-frequency alternating stress cannot be effectively simulated. Meanwhile, the existing test method generally adopts constant loading frequency and waveform parameters in the whole life cycle. With the deep penetration of chemical solvents into the reinforced plastic, the resin matrix has plasticizing effect, so that the dynamic rigidity and damping characteristics of the material are changed. If the fixed disturbance frequency is maintained all the time, the fluid dynamic excitation is difficult to adapt to the change of the pore structure of the material, so that the osmotic driving force in the later test period is insufficient, and the deep damage evolution rule of the material in the stiffness attenuation state cannot be truly reflected. Furthermore, in fluid-to-structure coupling tests involving high viscosity chemical solvents, viscous frictional heat generated by the fluid reciprocating within the tube can create energy dissipation. The traditional damage evaluation method usually calculates dissipation energy directly according to the total hysteresis loop area, and the treatment mode can not separate fluid dissipation generated by fluid viscous damping from irreversible work generated by material microscopic interface damage, so that hydrodynamic factors interfere with the identification of fiber and matrix interface debonding signals, and accurate judgment of failure end points is difficult to realize. Disclosure of Invention Aiming at the defects of the prior art, the invention provides a test method for evaluating the chemical solvent permeation resistance of reinforced plastics, which solves the problems that pressure waves and crack opening time sequence misplacement are caused by system physical response lag, permeation driving efficiency is reduced due to the fact that fixed frequency loading cannot be suitable for material stiffness attenuation, and the failure end point of material interface damage cannot be accurately identified due to fluid viscosity damping interference. In order to achieve the above purpose, the invention is realized by the following technical scheme: The invention provides a test method for evaluating the chemical solvent permeation resistance of reinforced plastics, which is executed based on a fluid and mechanical coupling test platform and comprises the following steps: Inputting a random pressure command and collecting the actual measured internal pressure under the condition of keeping the basic static pressure, and constructing an inverse transfer function based on the relation between the random pressure command and the actual measured internal pressure; collecting historical strain data of a tubular sample by using a laser scanning micrometer, calculating the starting moment of opening of microcracks in the next period, and calculating the instruction sending moment by combining the inherent dela