Internal stress detection method for complex plastic shell structure and application of internal stress detection method

Abstract

The invention discloses an internal stress detection method for a complex plastic shell structure and application thereof, and relates to the technical field of lead-acid storage batteries, a plastic sample to be detected is placed in a high-low temperature box, and a high-low temperature simulation change experiment is carried out; the high and low temperature simulation change experiment comprises a plurality of experiment units, and each experiment unit comprises constant temperature control of an intermediate temperature, a highest temperature and a lowest temperature, temperature change control between the intermediate temperature and the highest temperature, and temperature change control between the intermediate temperature and the lowest temperature; placing the to-be-detected plastic sample subjected to the high and low temperature simulation change experiment in an organic solvent for wetting or soaking, taking out the to-be-detected plastic sample, and checking whether the to-be-detected plastic sample has cracks or cracks. The internal stress detection method of a complex plastic shell structure is applied to the detection of the plastic shell of the lead-acid storage battery for communication, the temperature change at the use most extreme end of the storage battery is simulated, and whether the shell has stress or not is detected by utilizing the principle that stress cracking easily occurs at the part with relatively large stress concentration when the ABS plastic is wetted or soaked in an organic solvent.

Description

Technical Field

[0001] The invention relates to the technical field of lead-acid batteries, and more particularly to an internal stress detection method of a complex plastic shell structure and an application thereof in the detection of plastic shells of lead-acid batteries for communications. Background Art

[0002] The plastic shell material of lead-acid batteries for communication is flame-retardant ABS plastic. ABS is a terpolymer of acrylonitrile, butadiene and styrene, where A represents acrylonitrile, B represents butadiene and S represents styrene. Acrylonitrile gives ABS resin chemical stability, oil resistance, certain rigidity and hardness; butadiene improves its toughness, impact resistance and cold resistance; styrene gives it good dielectric properties and good processability. However, the shell will have internal stress to varying degrees during the design and processing process. The existence of internal stress not only causes stress cracking, warping and deformation of plastic products during storage and use, but also affects the mechanical properties, optical properties, electrical properties and appearance quality of plastic products.

[0003] Plastic internal stress includes orientation internal stress, cooling internal stress and environmental stress:

[0004] Oriented internal stress is the internal stress generated by the freezing of the oriented conformation of the macromolecular chains along the flow direction during the flow filling and pressure-holding filling process of the plastic melt. The freezing of oriented macromolecular chains in plastic products also means that there is unrelaxed reversible high elasticity in them. Therefore, the oriented internal stress is the macromolecular chain trying to transition from the oriented conformation to the non-oriented conformation. The oriented internal stress of plastic products is getting smaller from the surface layer to the inner layer of the product, and changes in a parabolic curve.

[0005] Cooling internal stress is the internal stress generated by the uneven shrinkage of plastic products during the melting process. Especially for thick-walled plastic products, the outer layer of the plastic product first cools and solidifies and shrinks, while the inner layer may still be hot melt. In this way, the core layer will limit the surface shrinkage, causing the core layer to be in a compressive stress state. The cooling internal stress of plastic products increases from the surface to the inner layer and changes in a parabolic curve. In addition, plastic products with metal inserts are prone to uneven shrinkage internal stress due to the large difference in thermal expansion coefficients between metal and plastic.

[0006] Environmental stress cracking is a phenomenon unique to polyolefin plastics. It means that when a product is under stress and comes into contact with certain active media, brittle cracks will appear, which may eventually cause the product to break. These active media can be detergents, soaps, water, acids, alkalis, salts, and organic solvents that do not significantly swell the material. When the raw materials are mixed with other impurities or doped with inappropriate or excessive organic solvents or other additives, cracks will occur at certain stress concentration locations.

[0007] When ABS plastic is heated in a damp state, it will react with water vapor to produce a catalytic cracking reaction, causing large strain cracking of the parts. In the field of communications, major operators have increased the battery warranty period year by year, and some products have been extended to 8 years. This long warranty has put forward higher requirements for battery housings.

[0008] In recent years, there have been many returns due to shell cracks. All plastic products have internal stress. Therefore, how to provide a detection method to find the shell stress concentration point so as to reduce the shell stress through optimized design and process adjustment, slow down the battery cracking time, and reduce the battery returns caused by shell cracks is an urgent problem to be solved by those skilled in the art. Summary of the invention

[0009] In view of this, the present invention provides an internal stress detection method for a complex plastic shell structure and its application, aiming to solve the above technical problems.

[0010] In order to achieve the above object, the present invention adopts the following technical solution:

[0011] A method for detecting internal stress of a complex plastic shell structure comprises the following steps:

[0012] S1. Place the plastic sample to be tested into a high and low temperature box to conduct a high and low temperature simulation change experiment; the high and low temperature simulation change experiment includes multiple experimental units, each of which includes constant temperature control of an intermediate temperature, a maximum temperature and a minimum temperature, as well as a temperature change control between the intermediate temperature and the maximum temperature, and a temperature change control between the intermediate temperature and the minimum temperature;

[0013] S2. After the high and low temperature simulation change experiment in step S1, the plastic sample to be tested is placed in an organic solvent for wetting or soaking, and then taken out to check whether there are cracks or cracks.

[0014] Through the above technical scheme, the present invention simulates the most extreme temperature changes of the plastic sample to be tested, and utilizes the principle that stress cracking is prone to occur in the parts with greater stress concentration when the plastic is wetted or immersed in an organic solvent. It can detect whether there is stress in a complex plastic shell structure, optimize the product design and improve the manufacturing process according to the cracks and cracking points, so as to reduce the shell stress and make the product design and manufacturing process more reasonable.

[0015] Preferably, in the above-mentioned internal stress detection method of a complex plastic shell structure, each of the experimental units comprises the following steps:

[0016] a. Constant temperature control of the intermediate temperature T1 time;

[0017] b. Within T2 time, raising the intermediate temperature to the maximum temperature;

[0018] c. Constant temperature control of the maximum temperature T1 time;

[0019] d. Within T2 time, lower the maximum temperature to the intermediate temperature;

[0020] e. Constant temperature control of the intermediate temperature T1 time;

[0021] f. Within T2 time, lower the intermediate temperature to the minimum temperature;

[0022] g. Constant temperature control of the minimum temperature T1 time;

[0023] h. Within time T2, raise the lowest temperature to the intermediate temperature.

[0024] Preferably, in the above-mentioned internal stress detection method for a complex plastic shell structure, time T1 is twice time T2.

[0025] Preferably, in the above-mentioned internal stress detection method of a complex plastic shell structure, in step S1, the high and low temperature simulation change experiment runs 5 experimental units.

[0026] Preferably, in the above-mentioned method for detecting internal stress of a complex plastic shell structure, in step S2, the organic solvent is glacial acetic acid.

[0027] The invention also provides an application of an internal stress detection method of a complex plastic shell structure in the detection of a plastic shell of a lead-acid battery for communication.

[0028] The plastic sample to be tested is a battery tank and cover structure made of ABS plastic.

[0029] It should be noted that communication bureaus (stations) are divided into four categories according to their importance and size, including:

[0030] Class I offices and stations: including national hubs, disaster recovery centers, provincial hubs, long-distance communication buildings, core network offices, Internet security centers, provincial IDC data centers, network management and billing centers, and international gateway offices;

[0031] Category II stations: including prefecture-level hubs, national-level transmission trunk stations, prefecture-level IDC data rooms, satellite earth stations, and customer service buildings;

[0032] Category III bureaus and stations: including county-level complexes and provincial-level transmission trunk stations;

[0033] Four types of stations: including terminal access sites, mobile communication base stations, indoor distribution stations, etc.

[0034] Among them: the application scenarios of Class I and Class II stations are relatively good, and the temperature of the battery does not change much during use; the application scenarios of Class III stations are slightly worse than those of Class I and Class II stations, but the temperature of the battery does not change much during use; the application environment of Class IV stations is relatively harsh, and the temperature range is relatively large, with environments below -20°C in the north in winter and high temperature and high humidity environments above 40°C in the south in summer. In order to adapt to the above environment and meet the warranty period requirements of operators, higher requirements are put forward for battery slots and covers, and batteries are not allowed to crack during the entire service life. The national standard GB / T23754-2019 stress detection method is: the battery slot and cover are baked at 60°C for 5-6 hours, and then wetted or soaked with non-polar solvent carbon tetrachloride to see if cracks occur in the parts of the slot and cover where stress concentration is greater. This method only detects the temperature of 60°C, but the actual operating temperature of the battery is relatively wide and the environmental changes are relatively large.

[0035] Therefore, the present invention applies the internal stress detection method of complex plastic shell structure to the detection of plastic shell of lead-acid battery for communication, simulates the most extreme temperature changes in the use of the battery, and uses the principle that stress cracking is prone to occur in areas with large stress concentration when ABS plastic is wetted or immersed in organic solvents to detect whether there is stress in the shell.

[0036] Preferably, in one of the above applications, the middle temperature of the high and low temperature box is set to 25°C, the maximum temperature is 65°C, and the minimum temperature is -40°C.

[0037] Preferably, in one of the above applications, the constant temperature control time is 4 hours, and the temperature change control time is 2 hours.

[0038] Preferably, in one of the above applications, the organic solvent is glacial acetic acid, and the soaking time is 5 minutes.

[0039] It can be known from the above technical solutions that, compared with the prior art, the present invention discloses a method for detecting internal stress of a complex plastic shell structure and its application. The battery slot and cover structure are relatively complex. When the design and manufacturing process design are unreasonable, cracks and splitting will occur in the parts with greater stress concentration. The present invention simulates the most extreme temperature changes of the plastic sample to be tested, and utilizes the principle that stress cracking is prone to occur in the parts with greater stress concentration when the plastic is wetted or soaked in an organic solvent. It can detect whether there is stress in the complex plastic shell structure, optimize the product design and improve the manufacturing process according to the cracks and cracking points, reduce the shell stress, make the product design and manufacturing process more reasonable, slow down the battery cracking time, and reduce the battery return problem caused by shell cracks. DETAILED DESCRIPTION

[0040] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] The embodiment of the present invention discloses a method for detecting internal stress of a complex plastic shell structure, comprising the following steps:

[0042] S1. Place the plastic sample to be tested into a high and low temperature box to conduct a high and low temperature simulation change experiment; the high and low temperature simulation change experiment includes multiple experimental units, each of which includes constant temperature control of the middle temperature, the highest temperature and the lowest temperature, as well as temperature change control between the middle temperature and the highest temperature, and temperature change control between the middle temperature and the lowest temperature;

[0043] S2. After the high and low temperature simulation change experiment in step S1, the plastic sample to be tested is placed in an organic solvent for wetting or soaking, and then taken out to check whether there are cracks or cracks.

[0044] In order to further optimize the above technical solution, each experimental unit includes the following steps:

[0045] a. Constant temperature control of intermediate temperature T1 time;

[0046] b. Within T2 time, raise the middle temperature to the highest temperature;

[0047] c. Constant temperature control of the highest temperature T1 time;

[0048] d. During time T2, reduce the highest temperature to the middle temperature;

[0049] e. Constant temperature control of intermediate temperature T1 time;

[0050] f. Within T2 time, reduce the intermediate temperature to the lowest temperature;

[0051] g. Constant temperature control of the lowest temperature T1 time;

[0052] h. Within T2 time, raise the lowest temperature to the middle temperature.

[0053] In order to further optimize the above technical solution, time T1 is twice time T2.

[0054] In order to further optimize the above technical solution, in step S1, the high and low temperature simulation variation experiment is run on 5 experimental units.

[0055] In order to further optimize the above technical solution, in step S2, the organic solvent is glacial acetic acid.

[0056] Embodiment 1:

[0057] This embodiment applies a method for detecting internal stress of a complex plastic shell structure to the detection of plastic shells of lead-acid batteries for communications. The plastic sample to be tested is a battery slot and cover structure made of ABS plastic.

[0058] Step 1: Preparation of standard samples:

[0059] The ABS raw material was added with masterbatch and stirred thoroughly to make the experimental raw material. The experimental raw material was used to make a standard sample of 100×35×5mm using an injection molding machine.

[0060] Step 2: High and low temperature simulation change experiment:

[0061] Two standard samples and three sets of battery slots and cover structures are placed in a high and low temperature box to conduct a high and low temperature simulation change experiment. The high and low temperature simulation change experiment includes 5 experimental units, and each experimental unit specifically includes the following steps:

[0062] (1) Maintain a constant temperature of 25°C for 4 hours;

[0063] (2) After 2 h, the temperature was raised from 25 °C to 65 °C;

[0064] (3) Maintain a constant temperature of 65°C for 4 hours;

[0065] (4) After 2 h, reduce the temperature from 65 °C to 25 °C;

[0066] (5) Maintain a constant temperature of 25°C for 4 hours;

[0067] (6) After 2 hours, lower the temperature from 25°C to -40°C;

[0068] (7) Maintain a constant temperature of -40°C for 4 hours;

[0069] (8) After 2 h, raise the temperature from -40 °C to 25 °C.

[0070] Step 3: Soak in organic solvent:

[0071] After completing the five experimental units in step 2, take out two standard samples and three sets of battery slots and cover structures, soak them in glacial acetic acid, pour out the glacial acetic acid after 5 minutes and wipe the samples dry, observe the slots and cover structures after 5 minutes, and compare them with the standard samples to see if there are cracks or cracks. If there are, the inspected battery slots and cover structures are unqualified.

[0072] The standard sample is a simple flat plate structure with no stress concentration points, cracks or splits. The battery slot and cover structure are relatively complex. When the design and manufacturing process are unreasonable, cracks and splits will appear in the parts with greater stress concentration. According to the cracks and splits, the product design is optimized and the manufacturing process is improved to reduce the shell stress, make the product design and manufacturing process more reasonable, slow down the battery cracking time, and reduce the battery return problem caused by shell cracks.

[0073] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0074] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for detecting internal stress of a complex plastic shell structure, characterized in that: The following steps are involved: S1. Place the plastic sample to be tested into a high and low temperature box to conduct a high and low temperature simulation change experiment; the high and low temperature simulation change experiment includes multiple experimental units, each of which includes constant temperature control of an intermediate temperature, a maximum temperature and a minimum temperature, as well as a temperature change control between the intermediate temperature and the maximum temperature, and a temperature change control between the intermediate temperature and the minimum temperature; S2. After the high and low temperature simulation change experiment in step S1, the plastic sample to be tested is placed in an organic solvent for wetting or soaking, and then taken out to check whether there are cracks or cracks.

2. The internal stress detection method of a complex plastic shell structure according to claim 1, characterized in that: Each of the experimental units comprises the following steps: a. Constant temperature control of the intermediate temperature T1 time; b. Within T2 time, raising the intermediate temperature to the maximum temperature; c. Constant temperature control of the maximum temperature T1 time; d. Within T2 time, lower the maximum temperature to the intermediate temperature; e. Constant temperature control of the intermediate temperature T1 time; f. Within T2 time, lower the intermediate temperature to the minimum temperature; g. Constant temperature control of the minimum temperature T1 time; h. Within time T2, raise the lowest temperature to the intermediate temperature.

3. The internal stress detection method of a complex plastic shell structure according to claim 2, characterized in that: Time T1 is twice time T2.

4. The internal stress detection method of a complex plastic shell structure according to claim 1, characterized in that: In step S1, the high and low temperature simulation variation experiment is run in 5 experimental units.

5. The internal stress detection method of a complex plastic shell structure according to claim 1, characterized in that: In step S2, the organic solvent is glacial acetic acid.

6. Application of the internal stress detection method of a complex plastic shell structure according to any one of claims 1 to 5 in the detection of plastic shells of lead-acid batteries for communications.

7. A use according to claim 6, characterized in that: The plastic sample to be tested is a battery tank and cover structure made of ABS plastic.

8. A use according to claim 6, characterized in that: The middle temperature of the high and low temperature box is set to 25°C, the maximum temperature is 65°C, and the minimum temperature is -40°C.

9. The use according to claim 6, characterized in that: The constant temperature control time is 4 hours, and the temperature change control time is 2 hours.

10. A use according to claim 6, characterized in that: The organic solvent is glacial acetic acid, and the soaking time is 5 minutes.