CN113092349A - Method for detecting stress cracking problem of polycarbonate automobile parts - Google Patents
Method for detecting stress cracking problem of polycarbonate automobile parts Download PDFInfo
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- 229920000515 polycarbonate Polymers 0.000 title claims abstract description 201
- 239000004417 polycarbonate Substances 0.000 title claims abstract description 201
- 238000005336 cracking Methods 0.000 title claims abstract description 139
- 238000000034 method Methods 0.000 title claims abstract description 101
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- 150000002148 esters Chemical class 0.000 claims abstract description 27
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims abstract description 23
- 238000002791 soaking Methods 0.000 claims abstract description 18
- XEKOWRVHYACXOJ-UHFFFAOYSA-N Ethyl acetate Chemical compound CCOC(C)=O XEKOWRVHYACXOJ-UHFFFAOYSA-N 0.000 claims description 57
- BDERNNFJNOPAEC-UHFFFAOYSA-N propan-1-ol Chemical compound CCCO BDERNNFJNOPAEC-UHFFFAOYSA-N 0.000 claims description 38
- 238000000137 annealing Methods 0.000 claims description 27
- 238000002156 mixing Methods 0.000 claims description 13
- 238000007789 sealing Methods 0.000 claims description 11
- LRHPLDYGYMQRHN-UHFFFAOYSA-N N-Butanol Chemical compound CCCCO LRHPLDYGYMQRHN-UHFFFAOYSA-N 0.000 claims description 8
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 8
- DKPFZGUDAPQIHT-UHFFFAOYSA-N Butyl acetate Natural products CCCCOC(C)=O DKPFZGUDAPQIHT-UHFFFAOYSA-N 0.000 claims description 4
- FUZZWVXGSFPDMH-UHFFFAOYSA-N hexanoic acid Chemical compound CCCCCC(O)=O FUZZWVXGSFPDMH-UHFFFAOYSA-N 0.000 claims description 4
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- 230000035882 stress Effects 0.000 description 106
- VZGDMQKNWNREIO-UHFFFAOYSA-N tetrachloromethane Chemical compound ClC(Cl)(Cl)Cl VZGDMQKNWNREIO-UHFFFAOYSA-N 0.000 description 24
- 238000001746 injection moulding Methods 0.000 description 16
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- 231100000252 nontoxic Toxicity 0.000 description 2
- 230000003000 nontoxic effect Effects 0.000 description 2
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- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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Abstract
The invention relates to a method for detecting stress cracking problem of an automobile part made of polycarbonate. The detection method comprises the following steps: preparing polycarbonate automobile parts and surrounding environment parts thereof to obtain automobile part samples and part assembly samples; preparing an ester substance and an alcohol substance according to a set volume fraction ratio to form an inducer, and respectively soaking an automobile part sample and a part assembly sample into the inducer for a preset time and then taking out the automobile part sample and the part assembly sample; and observing the soaked part assembly sample and the automobile part sample, and judging that the polycarbonate automobile part of the part assembly sample generates stress cracking in the assembling process when the cracking or the cracking of the surface of the polycarbonate automobile part of the part assembly sample is detected and the cracking or the cracking of the surface of the automobile part sample is not detected. The invention can solve the problems that the detection time period in the related technology is long, the shape and the size of the part are limited, the applicability is limited, and the traditional solvent is toxic and difficult to purchase.
Description
Technical Field
The invention relates to the technical field of stress detection of automobile parts, in particular to a method for detecting stress cracking of an automobile part made of polycarbonate.
Background
Polycarbonate (PC) is a polyester amorphous engineering plastic, has the advantages of excellent mechanical properties, high light transmittance and the like, and is generally used for manufacturing parts such as switch keys, light-transmitting panels, lamp masks and the like on automobiles. However, the part made of PC material has a great defect that the part is sensitive to continuous internal stress. Under the action of continuous internal stress, the PC parts have the quality faults that the stress is far lower than the allowable strength of the materials, even under the condition of no external stress, the parts crack, and the faults are usually in batches and are not easy to be noticed in the development stage, thereby causing great loss to manufacturers. Therefore, how to identify the cracking problem of the PC parts, locate the cracking reason, find the improvement measure, and make the anti-flowing measure is the pain point to be solved.
In the conventional art, there are four methods for identifying the stress cracking of a part made of a PC material: the first method is to carry out cold and hot alternating impact on a sample to realize induced cracking, the method has a long period, at least needs 20 days, and the cracking can be identified only when the internal stress is large, so the effect is not good; the second method is an external load measurement method, which applies constant strain to a sample and calculates the time for generating the silver lines/cracks, and is suitable for quantitatively evaluating the anti-cracking performance of the material, and the special sample shape and size are required, and the special-shaped small-size part can not meet the sample preparation requirement; the third method is a polarizing microscope observation method, the refractive index distribution and the size are detected through birefringence to directly reflect the internal stress distribution in a sample, the method is only suitable for measuring transparent and weak-color materials, and the actual PC material is often subjected to color matching to form semi-transparent or opaque, so the method has limited applicability; the fourth method is a solvent induction method, and the PC part is soaked by carbon tetrachloride (CCl4) or a mixed reagent thereof for inducing cracking, the method is simple to operate, but the CCl4 has a strong effect on the PC material, the evaluation scale is difficult to control, and the carbon tetrachloride (CCl4) or the mixed reagent thereof is toxic and volatile, has large harm to the body of a tester and is extremely difficult to purchase.
Disclosure of Invention
The invention provides a method for detecting stress cracking of an automobile part made of polycarbonate, which can solve the problems that the detection time period in the related technology is long, the shape and the size of the part are limited, the applicability is limited, and the traditional solvent is toxic and difficult to purchase.
In a first aspect, the invention provides a method for detecting stress cracking problems of polycarbonate automobile parts, which comprises the following steps:
preparing polycarbonate automobile parts and surrounding environment parts thereof, taking part of the polycarbonate automobile parts as an automobile part sample, and assembling the other part of the polycarbonate automobile parts and the surrounding environment parts to form a part assembly sample;
preparing an ester substance and an alcohol substance according to a set volume fraction ratio to form an inducer, and respectively soaking an automobile part sample and a part assembly sample into the inducer for a preset time and then taking out the automobile part sample and the part assembly sample;
and observing the soaked part assembly sample and the automobile part sample, and judging that the polycarbonate automobile part of the part assembly sample generates stress cracking in the assembling process when the cracking or the cracking of the surface of the polycarbonate automobile part of the part assembly sample is detected and the cracking or the cracking of the surface of the automobile part sample is not detected.
In some embodiments, in the step of formulating an inducer according to the set volume fraction ratio, the ester substance is one of ethyl acetate and butyl acetate, and the alcohol substance is one of n-propanol and n-butanol.
In some embodiments, the step of "formulating the ester and alcohol to form the inducer according to the set volume fraction ratio" specifically includes the following steps:
according to the set volume fraction ratio, 50-70 parts of ethyl acetate and 30-50 parts of n-propanol are mixed to prepare the inducer, and the inducer is sealed and kept stand for 0.8-1.2 hours for later use.
In some embodiments, the step of "formulating the ester and alcohol to form the inducer according to the set volume fraction ratio" specifically includes the following steps:
mixing ethyl acetate and n-propanol according to the volume fraction ratio of 70:30 to prepare a first inducer, and sealing and standing the first inducer for 0.8-1.2 hours for later use;
mixing ethyl acetate and n-propanol according to the volume fraction ratio of 65:35 to prepare a second inducer, and sealing and standing the second inducer for 0.8-1.2 hours for later use;
mixing ethyl acetate and n-propanol according to the volume fraction ratio of 60:40 to prepare a third inducer, and sealing and standing the third inducer for 0.8-1.2 hours for later use;
according to the volume fraction ratio of 50:50, ethyl acetate and n-propanol are mixed to prepare a fourth inducer, and the fourth inducer is sealed and stands for 0.8-1.2 hours for standby.
In some embodiments, the step of "respectively soaking the automobile part sample and the part assembly sample in the inducer for a preset time and then taking out" includes the following steps:
after soaking the automobile part sample in the prepared inducer for 2.5-3 minutes, taking the automobile part sample out of the inducer, and removing the residual inducer on the surface of the automobile part sample by using clear water;
and (3) soaking the part assembly sample in the prepared inducer for 2.5-3 minutes, taking the part assembly sample out of the inducer, and removing the residual inducer on the surface of the part assembly sample by using clear water.
In some embodiments, the step of determining that the polycarbonate automobile part of the part assembly sample is stress cracked in the assembling process when the cracking or the cracking of the surface of the polycarbonate automobile part of the part assembly sample is detected and the cracking or the cracking of the surface of the automobile part sample is not detected includes the following steps:
when the cracking or the cracking of the surface of the polycarbonate automobile part of the part assembly sample is detected, the section of the polycarbonate automobile part of the part assembly sample is further observed in an amplification way through a microscope;
when the cross section of the polycarbonate automobile part of the part assembly sample is observed to have a smooth and flat brittle morphology, judging that the polycarbonate automobile part of the part assembly sample generates stress cracking;
when the surface of the automobile part sample is not cracked or cracked, the automobile part sample is judged not to generate stress cracking, and then the polycarbonate automobile part of the part assembly sample is further judged to generate stress cracking in the assembling process.
In some embodiments, after the step of determining that the polycarbonate automobile part of the part assembly sample generates stress cracking in the assembling process, the method specifically includes the following steps:
annealing the part assembly sample generating the stress cracking at the preset temperature of 85-95 ℃ for 0.9-1.1 hour in preset time.
In some embodiments, after the step of annealing the part assembly sample generating the stress cracking, the method specifically comprises the following steps:
soaking the part assembly sample subjected to annealing treatment into the inducer again for a preset time, and taking out the part assembly sample;
and observing the soaked part assembly sample again, and judging that the stress cracking generated by the polycarbonate automobile part of the part assembly sample is eliminated when the surface of the polycarbonate automobile part of the part assembly sample is not cracked or cracked.
In some embodiments, the step of "preparing the polycarbonate automobile part and the surrounding environment part thereof, using a part of the polycarbonate automobile part as an automobile part sample, and assembling another part of the polycarbonate automobile part and the surrounding environment part to form a part assembly sample" includes the following steps:
cooling the plurality of injection-molded polycarbonate automobile parts at room temperature for at least 24 hours for later use, and preparing a plurality of peripheral environment parts for assembling with the polycarbonate automobile parts;
taking a part of the cooled polycarbonate automobile parts as automobile part samples for later use;
and assembling the other part of the cooled polycarbonate automobile parts with the surrounding environment parts according to the normal assembling process of the parts to form part assembly samples for later use.
In some embodiments, the step of "using a part of the cooled polycarbonate automobile part as an automobile part sample for standby" includes the following steps:
dividing a part of the cooled polycarbonate automobile parts into a plurality of groups of polycarbonate automobile parts, and taking the plurality of groups of polycarbonate automobile parts as a plurality of groups of automobile part samples for later use;
the step of assembling the other part of cooled polycarbonate automobile parts with surrounding environment parts according to the normal assembling process of the parts to form a part assembly sample for standby application specifically comprises the following steps:
and assembling the other part of the cooled polycarbonate automobile parts with surrounding environment parts according to the normal assembly process of the parts to form a plurality of groups of part assembly structures, and taking the plurality of groups of part assembly structures as part assembly samples for later use.
The technical scheme provided by the invention has the beneficial effects that: the detection method for releasing cracks by using solvent to induce stress is adopted to detect the polycarbonate automobile parts and the assembly thereof, the adopted inducer is a mixed solution of ester substances and alcohol substances, the detection time is short, the application range is wide, and the inducer is nontoxic and has wide and easily-obtained sources; in addition, the inducer is directly used to act on the final product in the detection process, and the limitation on the shape and the size of the part is avoided; moreover, the assembly of the polycarbonate automobile part and the polycarbonate automobile part can be detected, so that the internal stress of the polycarbonate automobile part in the injection molding processing link is detected, the internal stress caused in the assembling link is also detected, the accuracy of crack problem identification is favorably improved, and the essential reason of stress crack generation is favorably and quickly found out.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a schematic flow chart illustrating steps of a method for detecting stress cracking problems of polycarbonate automobile parts according to an embodiment of the present invention;
FIG. 2 is a flowchart illustrating a detailed step S100 of the method for detecting the stress cracking problem of the polycarbonate automobile part according to the embodiment of the present invention;
FIG. 3 is a flowchart illustrating a detailed step of step S200 of the method for detecting the stress cracking problem of the polycarbonate automobile part according to the embodiment of the present invention;
FIG. 4 is a flowchart illustrating a detailed step S300 of the method for detecting a stress cracking problem of a polycarbonate automobile part according to an embodiment of the present invention;
FIG. 5 is a flowchart illustrating steps of a method for detecting a stress cracking problem of a polycarbonate automotive part according to another embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.
In the conventional art, there are four methods for identifying the stress cracking of a part made of a PC material: the first method is to carry out cold and hot alternating impact on a sample to realize induced cracking, the method has a long period, at least needs 20 days, and the cracking can be identified only when the internal stress is large, so the effect is not good; the second method is an external load measurement method, which applies constant strain to a sample and calculates the time for generating the silver lines/cracks, and is suitable for quantitatively evaluating the anti-cracking performance of the material, and the special sample shape and size are required, and the special-shaped small-size part can not meet the sample preparation requirement; the third method is a polarizing microscope observation method, the refractive index distribution and the size are detected through birefringence to directly reflect the internal stress distribution in a sample, the method is only suitable for measuring transparent and weak-color materials, and the actual PC material is often subjected to color matching to form semi-transparent or opaque, so the method has limited applicability; the fourth method is a solvent induction method, and the PC part is soaked by carbon tetrachloride (CCl4) or a mixed reagent thereof for inducing cracking, the method is simple to operate, but the CCl4 has a strong effect on the PC material, the evaluation scale is difficult to control, and the carbon tetrachloride (CCl4) or the mixed reagent thereof is toxic and volatile, has large harm to the body of a tester and is extremely difficult to purchase. In order to solve the technical problem, the invention provides a method for detecting the stress cracking problem of an automobile part made of polycarbonate.
As shown in FIG. 1, the method for detecting the stress cracking problem of the polycarbonate automobile part provided by the invention comprises the following steps:
s100, preparing polycarbonate automobile parts and surrounding environment parts thereof, taking part of the polycarbonate automobile parts as an automobile part sample, and assembling the other part of the polycarbonate automobile parts and the surrounding environment parts to form a part assembly sample;
s200, preparing an inducer from an ester substance and an alcohol substance according to a set volume fraction ratio, and respectively soaking an automobile part sample and a part assembly sample into the inducer for a preset time and then taking out the automobile part sample and the part assembly sample;
s300, observing the soaked part assembly sample and the automobile part sample, and judging that the polycarbonate automobile part of the part assembly sample generates stress cracking in the assembling process when cracking or cracks are detected on the surface of the polycarbonate automobile part of the part assembly sample and no cracking or cracks are detected on the surface of the automobile part sample.
The invention adopts a detection method of solvent induced stress release cracking to detect the polycarbonate automobile parts and the assembly thereof, adopts the type of the inducer which is a mixed solution of ester substances and alcohol substances, has short detection time and wide application range, and has no toxicity and wide and easily obtained sources; in addition, the inducer is directly used to act on the final product in the detection process, and the limitation on the shape and the size of the part is avoided; moreover, the assembly of the polycarbonate automobile part and the polycarbonate automobile part can be detected, so that the internal stress of the polycarbonate automobile part in the injection molding processing link is detected, the internal stress caused in the assembling link is also detected, the accuracy of crack problem identification is favorably improved, and the essential reason of stress crack generation is favorably and quickly found out.
As shown in fig. 2, the step S100 of preparing the polycarbonate automobile part and the surrounding environment member, using a part of the polycarbonate automobile part as an automobile part sample, and assembling another part of the polycarbonate automobile part and the surrounding environment member to form a part assembly sample includes the following steps:
s110, cooling the plurality of injection-molded polycarbonate automobile parts at room temperature for at least 24 hours for later use, and preparing a plurality of surrounding environment parts for assembling with the polycarbonate automobile parts;
s120, taking a part of the cooled polycarbonate automobile parts as automobile part samples for later use;
and S130, assembling the other part of the cooled polycarbonate automobile parts with surrounding environment parts according to the normal assembling process of the parts to form part assembly samples for standby.
The method can be used for preparing an independent polycarbonate automobile part as an automobile part sample, can also be used for preparing a part assembly sample formed by assembling the polycarbonate automobile part and the surrounding environment parts at the same time, and can be used for subsequently and respectively carrying out stress detection on the automobile part sample and the part assembly sample, so that the subsequent detection of whether internal stress is generated in the injection molding stage of the polycarbonate automobile part or the assembling stage of the polycarbonate automobile part is facilitated. In this embodiment, the surrounding environment member refers to a member having a direct connection relationship with a polycarbonate automobile member, such as snap-fit connection, riveting connection, welding connection, etc., and the assembling operation is performed according to a normal assembling process of the member.
Further, the step S120 of "using a part of the cooled polycarbonate automobile parts as an automobile part sample for standby" includes the following steps:
and dividing a part of the cooled polycarbonate automobile parts into a plurality of groups of polycarbonate automobile parts, and taking the plurality of groups of polycarbonate automobile parts as a plurality of groups of automobile part samples for later use.
The multiple polycarbonate automobile parts are divided into multiple groups to form multiple groups of automobile part samples, multiple groups of detection can be carried out subsequently, and the detection result is more accurate and reliable.
In step S130, namely, the step of assembling the other part of the cooled polycarbonate automotive parts with the surrounding environment parts according to the normal assembling process of the parts to form the part assembly sample for standby use, the method specifically comprises the following steps:
and assembling the other part of the cooled polycarbonate automobile parts with surrounding environment parts according to the normal assembly process of the parts to form a plurality of groups of part assembly structures, and taking the plurality of groups of part assembly structures as part assembly samples for later use.
Similarly, the part assembly structure assembled by a plurality of polycarbonate automobile parts is divided into a plurality of groups to form a plurality of groups of part assembly samples, and then a plurality of groups of detection can be carried out, so that the detection result is more accurate and reliable.
In the step S200, the step of "preparing an inducer by mixing an ester substance and an alcohol substance at a predetermined volume fraction ratio" may be performed, wherein the ester substance is one of ethyl acetate and butyl acetate, and the alcohol substance is one of n-propanol and n-butanol. The esters and alcohols are easily obtained and have no toxicity; moreover, the inducer formed by mixing the ester substances and the alcohol substances has good induction effect on the polycarbonate automobile parts, and can enable the internal stress of the polycarbonate automobile parts to be displayed in a short time, thereby greatly shortening the internal stress detection period of the polycarbonate automobile parts. In addition, the esters and alcohols are selected from analytical grade.
Further, as shown in fig. 3, in the step S200, the step of "preparing the ester substance and the alcohol substance according to the set volume fraction ratio to form the inducer" specifically includes the following steps:
s210, mixing 50-70 parts of ethyl acetate and 30-50 parts of n-propanol according to a set volume fraction ratio to prepare an inducer, and sealing and standing the inducer for 0.8-1.2 hours for later use.
The two organic solvents of ester substances and alcohol substances are weighed according to a set volume ratio, are uniformly stirred in a beaker, are sealed and stand for 0.8 to 1.2 hours, and are prepared into an inducer solution. In addition, in the prepared inducer solution, the proportion of the ester substances and the alcohol substances can be set according to the solubility parameter range of the inducer, namely 20.3 +/-0.5 (J.cm)-3)1/2The process is carried out. Furthermore, the inducer solubility parameter can be calculated according to the following formula:
wherein deltam、δ1、δ2Can respectively represent solubility parameters of an inducer, an ester substance and an alcohol substance;
can respectively represent the volume fractions of esters and alcohols.
Moreover, in some embodiments, the step of "formulating the ester substance and the alcohol substance according to a set volume fraction ratio to form the inducer" specifically includes the following steps:
mixing ethyl acetate and n-propanol according to the volume fraction ratio of 70:30 to prepare a first inducer, and sealing and standing the first inducer for 0.8-1.2 hours for later use;
mixing ethyl acetate and n-propanol according to the volume fraction ratio of 65:35 to prepare a second inducer, and sealing and standing the second inducer for 0.8-1.2 hours for later use;
mixing ethyl acetate and n-propanol according to the volume fraction ratio of 60:40 to prepare a third inducer, and sealing and standing the third inducer for 0.8-1.2 hours for later use;
according to the volume fraction ratio of 50:50, ethyl acetate and n-propanol are mixed to prepare a fourth inducer, and the fourth inducer is sealed and stands for 0.8-1.2 hours for standby.
The method can be used for preparing the revulsants with different proportions in a set range to revulse the polycarbonate automobile parts and the assembly thereof, so as to prove the good effect of the revulsants prepared from the esters and the alcohols.
As shown in fig. 3, in the step S200, the step of "respectively soaking the automobile part sample and the part assembly sample in the inducing agent for a predetermined time and then taking out" includes the following steps:
s220, soaking the automobile part sample in the prepared inducer for 2.5-3 minutes, taking the automobile part sample out of the inducer, and removing the residual inducer on the surface of the automobile part sample by using clear water;
and S230, soaking the part assembly sample in the prepared inducer for 2.5-3 minutes, taking the part assembly sample out of the inducer, and removing the residual inducer on the surface of the part assembly sample by using clear water.
The method comprises the steps of respectively putting an automobile part sample formed by polycarbonate automobile parts and a part assembly sample formed by assembling the polycarbonate automobile parts into a prepared inducer to be soaked for a preset time so as to respectively induce the automobile part sample and the part assembly sample.
As shown in fig. 4, the step S300 of determining that stress cracking occurs in the polycarbonate automobile part of the part assembly sample during the assembling process when cracking or cracking is detected on the surface of the polycarbonate automobile part of the part assembly sample and no cracking or cracking is detected on the surface of the automobile part sample includes the following steps:
s310, when cracking or cracking of the surface of the polycarbonate automobile part of the part assembly sample is detected, carrying out amplification observation on the section of the polycarbonate automobile part of the part assembly sample through a microscope;
when the surface of the polycarbonate automobile part of the part assembly sample is detected to be not cracked or cracked, judging that the polycarbonate automobile part of the part assembly sample is detected not to be subjected to internal stress in the injection molding process and the assembling process to cause stress cracking;
s320, when the cross section of the polycarbonate automobile part of the part assembly sample is observed to have a smooth and flat brittle appearance, judging that the polycarbonate automobile part of the part assembly sample generates stress cracking;
the polycarbonate automobile part of the part assembly sample is judged to be likely to generate internal stress in the injection molding process to cause stress cracking, or generate the internal stress in the assembling process to cause stress cracking, or generate the internal stress in the injection molding process and the assembling process.
S330, when the surface of the automobile part sample is not cracked or cracked, judging that the automobile part sample does not generate stress cracking, and further judging that the polycarbonate automobile part of the part assembly sample generates stress cracking in the assembling process. When the surface of the automobile part sample is detected to be not cracked or cracked, the polycarbonate automobile part does not generate internal stress in the injection molding process to cause stress cracking, namely the polycarbonate automobile part of the part assembly sample is proved not to generate internal stress in the injection molding process to cause stress cracking, and the polycarbonate automobile part of the part assembly sample is proved to be stress cracked due to the internal stress generated in the assembling process.
When the surface of the automobile part sample is detected to crack or crack, the automobile part sample is judged to generate stress cracking, and then the polycarbonate automobile part of the part assembly sample is further judged to generate stress cracking in the injection molding process or the assembly process.
In addition, as shown in fig. 5, after the step of "determining that the polycarbonate automobile part of the part assembly sample has stress cracking during the assembling process" in the step S300, the method specifically includes the following steps:
s400, annealing the part assembly sample generating the stress cracking by adopting the preset temperature of 85-95 ℃ and the preset time of 0.9-1.1 h.
The part assembly sample formed by assembling the polycarbonate automobile parts with stress cracking is annealed, and the stress cracking of the polycarbonate automobile parts of the part assembly sample can be eliminated by setting proper annealing temperature and annealing time.
Similarly, the annealing treatment can also be carried out on the automobile part sample generating the stress cracking at the preset temperature of 115-125 ℃ for 1.8-2.2 hours. The method is characterized in that the stress cracking of the polycarbonate automobile parts of the automobile part sample can be eliminated by annealing the polycarbonate automobile parts with the stress cracking, and setting proper annealing temperature and annealing time.
As shown in fig. 5, after the step of "annealing the sample of the part assembly in which the stress cracking occurs" in the step S400, the method specifically includes the following steps:
s500, soaking the part assembly sample subjected to annealing treatment into the inducer again for a preset time, and taking out the part assembly sample;
s600, observing the soaked part assembly sample again, and judging that the stress cracking generated by the polycarbonate automobile part of the part assembly sample is eliminated when the situation that the surface of the polycarbonate automobile part of the part assembly sample is not cracked or cracked is detected.
The method is characterized in that after a part assembly sample formed by assembling polycarbonate automobile parts with stress cracking is annealed, whether the part assembly sample has internal stress or not can be detected, and the stress cracking phenomenon is caused. When the part assembly sample treated by the inducer again is detected, and no crack or crack is found on the surface of the polycarbonate automobile part of the part assembly sample, the stress cracking phenomenon generated when the polycarbonate automobile part is assembled to form the part assembly sample can be eliminated by judging the annealing treatment.
In addition, the automobile part sample subjected to annealing treatment and having stress cracking can be taken out after being soaked in the inducer again for a preset time;
and observing the soaked automobile part sample again, and judging that the stress cracking generated by the polycarbonate automobile part of the automobile part sample is eliminated when the surface of the polycarbonate automobile part of the automobile part sample is not cracked or cracked.
Moreover, the polycarbonate automobile parts of the automobile part sample with the stress crack eliminated can be assembled with surrounding environment parts again to form a part assembly sample, and the part assembly sample is induced and observed; when the surface of the polycarbonate automobile part of the part assembly sample is detected to be cracked or cracked, judging that the polycarbonate automobile part is subjected to stress cracking in the injection molding process and the assembling process; when the surface of the polycarbonate automobile part of the part assembly sample is detected not to crack or crack, the polycarbonate automobile part is judged to have stress crack in the injection molding process, but has no stress crack in the assembling process.
Example 1
In this embodiment, the method for detecting the stress cracking problem of the polycarbonate automobile part provided by the invention specifically comprises the following steps:
firstly, selecting a polycarbonate automobile part exposed in an actual use process and having a cracking fault as an analysis object, wherein in the embodiment, a PC key is used as the analysis object; specifically, the PC key 200 piece can be produced by injection molding, and is cooled and placed for 24 hours (or more than 24 hours) for standby;
then, taking 50 PC keys out of 200 PC keys as automobile part samples for standby; and 50 pieces of PC keys are divided into 5 groups of 10 pieces of PC keys;
and, take 50 pieces of PC buttons from 200 pieces of PC buttons in addition, assemble with the peripheral environment pieces (including switch casing, base) that have assembling relation according to the normal production technology, get 50 pieces of button assembly, namely can get 50 pieces of part assembly samples; dividing 50 key assembly assemblies into 5 groups, and placing 10 key assembly assemblies in each group at room temperature for 24 hours (or more than 24 hours) for standby;
then, the formulation of the inducer is carried out: preparing four different types of inducer solvents according to a set volume fraction ratio. The four inducer solvents respectively comprise 70:30 parts of ethyl acetate and 65:35 parts of n-propanol, 60:40 parts of butyl acetate and 50:50 parts of n-butanol; mixing and stirring the solvent uniformly in a beaker, sealing and standing for 1 hour (or 0.8 hour or 1.2 hours) for later use;
then, sample testing was performed: and (3) sequentially and completely soaking the 4 groups of PC keys and the 4 groups of key assemblies into the four inducers for 3 minutes (or 2.5 minutes or 3.5 minutes), taking out, and removing the surface residual inducers by using clean water. For comparison, 1 group of PC keys and 1 group of key assembly assemblies are synchronously taken and respectively soaked in carbon tetrachloride (CCl4) solvent for 10-15 seconds, and then taken out and cleaned with clear water to remove the surface residual inducer.
Then, evaluation of the detection results was performed: each test sample (including the PC key and the key assembly) was visually inspected, and if cracking or cracks occurred on the PC key surface of the sample, the cross-sectional morphology was further observed under a microscope at 30 times magnification, and if a smooth and flat brittle morphology was observed, stress cracking was judged, and the number of these stress cracking samples was recorded, and the results are shown in table 1 below.
TABLE 1 comparative table for sample testing
Moreover, the stress cracking risk is judged according to the following principle that if the number of cracked samples in each group of samples (PC keys or key assembly assemblies) exceeds 50 percent and the crack sections meet the brittle fracture morphology, the stress cracking risk of the parts is high; if the number of cracks in each group of samples is less than 50%, and the fracture section meets the brittle fracture morphology, the stress cracking risk of the part is low; if the number of cracks appearing in each group of samples is 0, the part is free from stress cracking risk.
Moreover, for a plurality of PC keys and a plurality of key assembly assemblies, if the PC keys and the key assembly assemblies thereof crack simultaneously, and the number of cracks is equivalent, the reason of stress cracking is explained to be in the injection molding process of the PC keys; if the PC key is not cracked, the assembly of the PC key is cracked, which indicates that the stress cracking is caused by the assembly process of the PC key and the surrounding environment parts.
Then, part stress cracking improvement is carried out: when the risk of cracking of the PC key is mainly determined to be caused by the assembly stress in the assembly link, the key assembly after the PC key assembly is processed by adopting an annealing process of 90 ℃/1 hour (or 95 ℃/0.9 hour, or 85 ℃/1.1 hour) as an improvement countermeasure. As a comparison group, after the individual PC keys are respectively subjected to 90 ℃/1 hour (or 95 ℃/0.9 hour, or 85 degrees centigrade/1.1 hour) annealing treatment and 120 ℃/2 hour (or 115 ℃/2.2 hours, or 125 degrees centigrade/1.8 hour) annealing treatment, the individual PC keys are assembled with the surrounding environment components to form the key assembly, and then synchronous verification is performed, and the results can be shown in table 2 below.
TABLE 2 comparison table for annealing treatment of PC keys and key assembly
As can be seen from Table 2, the stress cracking of the PC key during the assembly process can be effectively eliminated by applying an annealing process of 90 deg.C/1 hour to the key assembly.
It should be noted that the annealing method adopted in the present invention and the above embodiments improves the problem of stress cracking of PC parts (such as PC keys), and should have applicability in most cases. However, some special cases exist, the internal stress of the PC part is too large, the cracking risk cannot be completely eliminated by simple annealing improvement, and deep sub-optimization needs to be carried out on the part structure, the material and the die.
The tests of the above embodiments show that the detection method, the tracing means and the improvement scheme in the invention are simple and effective to operate.
The invention provides a method for detecting, tracing and improving the stress cracking problem of a polycarbonate automobile part, which comprises the steps of taking the polycarbonate automobile part and a part assembly formed by assembling the polycarbonate automobile part and surrounding environment parts as samples to be detected (an automobile part sample and a part assembly sample), soaking the samples to be detected in an ester/alcohol mixed solvent to induce the stress cracking of the samples to be detected, and judging the essential reason of the stress cracking by observing the stress cracking condition of the polycarbonate automobile part and the surrounding environment parts, namely judging whether the cracking reason is generated in an injection molding link or an assembly link, and further improving the cracking problem by corresponding annealing treatment.
The method adopts an inducer induction method to identify the stress cracking of the PC part, and the inducer directly acts on a final product without being limited by the shape and the size of the part, so that the method is simple to operate, short in period and direct and effective; the invention adopts the mixed solution of ester substances and alcohol substances as the stress inducer, and the solvents are nontoxic and harmless, have no influence on the health of testers, have wide reagent sources and are easy to purchase; according to the invention, the PC part and the environment part are assembled and then tested, so that the internal stress of the PC part in the injection molding processing link and the internal stress caused in the assembling link are tested, the evaluation accuracy of stress cracking risk in the using process is improved, the essential reason of stress cracking can be found out, and an effective improvement scheme can be provided; in addition, the invention adopts the annealing at 85-95 ℃/1 hour after assembly as an improvement scheme for the cracking problem of parts caused by assembly stress, and can be compared with the annealing scheme at 115-125 ℃/2 hour after injection molding, thereby improving the effectiveness, improving the detection efficiency, reducing the energy consumption and reducing the production cost of parts.
The foregoing are merely exemplary embodiments of the present invention, which enable those skilled in the art to understand or practice the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (10)
1. A method for detecting the stress cracking problem of an automobile part made of polycarbonate is characterized by comprising the following steps:
preparing polycarbonate automobile parts and surrounding environment parts thereof, taking part of the polycarbonate automobile parts as an automobile part sample, and assembling the other part of the polycarbonate automobile parts and the surrounding environment parts to form a part assembly sample;
preparing an ester substance and an alcohol substance according to a set volume fraction ratio to form an inducer, and respectively soaking an automobile part sample and a part assembly sample into the inducer for a preset time and then taking out the automobile part sample and the part assembly sample;
and observing the soaked part assembly sample and the automobile part sample, and judging that the polycarbonate automobile part of the part assembly sample generates stress cracking in the assembling process when the cracking or the cracking of the surface of the polycarbonate automobile part of the part assembly sample is detected and the cracking or the cracking of the surface of the automobile part sample is not detected.
2. The method for detecting the stress cracking problem of the polycarbonate automobile part as claimed in claim 1, wherein in the step of preparing the inducer by using an ester substance and an alcohol substance according to a set volume fraction ratio, the ester substance is one of ethyl acetate and butyl acetate, and the alcohol substance is one of n-propanol and n-butanol.
3. The method for detecting the stress cracking problem of the polycarbonate automobile part as claimed in claim 2, wherein the step of preparing the ester substance and the alcohol substance to form the inducer according to the set volume fraction ratio specifically comprises the following steps:
according to the set volume fraction ratio, 50-70 parts of ethyl acetate and 30-50 parts of n-propanol are mixed to prepare the inducer, and the inducer is sealed and kept stand for 0.8-1.2 hours for later use.
4. The method for detecting the stress cracking problem of the polycarbonate automobile part as claimed in claim 3, wherein the step of preparing the ester substance and the alcohol substance to form the inducer according to the set volume fraction ratio comprises the following steps:
mixing ethyl acetate and n-propanol according to the volume fraction ratio of 70:30 to prepare a first inducer, and sealing and standing the first inducer for 0.8-1.2 hours for later use;
mixing ethyl acetate and n-propanol according to the volume fraction ratio of 65:35 to prepare a second inducer, and sealing and standing the second inducer for 0.8-1.2 hours for later use;
mixing ethyl acetate and n-propanol according to the volume fraction ratio of 60:40 to prepare a third inducer, and sealing and standing the third inducer for 0.8-1.2 hours for later use;
according to the volume fraction ratio of 50:50, ethyl acetate and n-propanol are mixed to prepare a fourth inducer, and the fourth inducer is sealed and stands for 0.8-1.2 hours for standby.
5. The method for detecting the stress cracking problem of the polycarbonate automobile part, as claimed in claim 1, wherein the step of taking out the automobile part sample and the part assembly sample after soaking the automobile part sample and the part assembly sample respectively in the inducer for a preset time, comprises the steps of:
after soaking the automobile part sample in the prepared inducer for 2.5-3 minutes, taking the automobile part sample out of the inducer, and removing the residual inducer on the surface of the automobile part sample by using clear water;
and (3) soaking the part assembly sample in the prepared inducer for 2.5-3 minutes, taking the part assembly sample out of the inducer, and removing the residual inducer on the surface of the part assembly sample by using clear water.
6. The method for detecting the stress cracking problem of the polycarbonate automobile part as claimed in claim 1, wherein the step of determining that the polycarbonate automobile part of the part assembly sample is subjected to stress cracking in the assembling process when the cracking or the cracking of the surface of the polycarbonate automobile part of the part assembly sample is detected and the cracking or the cracking of the surface of the automobile part sample is not detected comprises the following steps:
when the cracking or the cracking of the surface of the polycarbonate automobile part of the part assembly sample is detected, the section of the polycarbonate automobile part of the part assembly sample is further observed in an amplification way through a microscope;
when the cross section of the polycarbonate automobile part of the part assembly sample is observed to have a smooth and flat brittle morphology, judging that the polycarbonate automobile part of the part assembly sample generates stress cracking;
when the surface of the automobile part sample is not cracked or cracked, the automobile part sample is judged not to generate stress cracking, and then the polycarbonate automobile part of the part assembly sample is further judged to generate stress cracking in the assembling process.
7. The method for detecting the stress cracking problem of the polycarbonate automobile part as claimed in claim 1, wherein after the step of determining that the polycarbonate automobile part of the part assembly sample is subjected to stress cracking in the assembling process, the method specifically comprises the following steps:
annealing the part assembly sample generating the stress cracking at the preset temperature of 85-95 ℃ for 0.9-1.1 hour in preset time.
8. The method for detecting the stress cracking problem of the polycarbonate automobile part, as claimed in claim 7, wherein the step of annealing the part assembly sample which generates the stress cracking comprises the following steps:
soaking the part assembly sample subjected to annealing treatment into the inducer again for a preset time, and taking out the part assembly sample;
and observing the soaked part assembly sample again, and judging that the stress cracking generated by the polycarbonate automobile part of the part assembly sample is eliminated when the surface of the polycarbonate automobile part of the part assembly sample is not cracked or cracked.
9. The method for detecting the stress cracking problem of the polycarbonate automobile part as claimed in claim 1, wherein the step of preparing the polycarbonate automobile part and the surrounding environment part thereof, using a part of the polycarbonate automobile part as an automobile part sample, and assembling the other part of the polycarbonate automobile part and the surrounding environment part to form a part assembly sample comprises the following steps:
cooling the plurality of injection-molded polycarbonate automobile parts at room temperature for at least 24 hours for later use, and preparing a plurality of peripheral environment parts for assembling with the polycarbonate automobile parts;
taking a part of the cooled polycarbonate automobile parts as automobile part samples for later use;
and assembling the other part of the cooled polycarbonate automobile parts with the surrounding environment parts according to the normal assembling process of the parts to form part assembly samples for later use.
10. The method for detecting the stress cracking problem of the polycarbonate automobile part as claimed in claim 9, wherein the step of using a part of the cooled polycarbonate automobile part as an automobile part sample for standby comprises the following steps:
dividing a part of the cooled polycarbonate automobile parts into a plurality of groups of polycarbonate automobile parts, and taking the plurality of groups of polycarbonate automobile parts as a plurality of groups of automobile part samples for later use;
the step of assembling the other part of cooled polycarbonate automobile parts with surrounding environment parts according to the normal assembling process of the parts to form a part assembly sample for standby application specifically comprises the following steps:
and assembling the other part of the cooled polycarbonate automobile parts with surrounding environment parts according to the normal assembly process of the parts to form a plurality of groups of part assembly structures, and taking the plurality of groups of part assembly structures as part assembly samples for later use.
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