Some standard content:
National Standard of the People's Republic of China
Equipment reliability testing
General requirements
UDC 621.3 - 192
.001.4 : 001.5
GB 5080.186bzxz.net
1EC 605-1—1978
The whole set of standards for equipment reliability testing specifies the procedures for equipment reliability verification tests and measurement tests. The entire set of standards consists of the following parts:
GB5080.1-86 Equipment reliability test
General requirements
GB 5080.2—86 i
Equipment reliability test
Guidelines for test cycle design
GB7288-87 Recommended test conditions for equipment reliability test GB5080.4-85 Equipment reliability test Point estimation and interval estimation methods for reliability determination tests (exponential distribution) GB5080.5---85 Equipment reliability test
Test plan for success rate
Validity test of the constant failure rate assumption
GB5080.6—85 Equipment reliability test
GB5080.7-86 Equipment reliability test
Verification test method for failure rate and mean time between failures under the constant failure rate assumption Users of the entire set of standards can choose the most suitable procedure. 1 Introduction
This standard is equivalent to IEC605-1 (1978) "Equipment Reliability Test Part 1: General Requirements". This standard provides the general principles for equipment reliability verification tests and measurement tests, and recommends specific procedures. The principles stated in this standard apply to all electronic, electromechanical and mechanical equipment. The term "equipment" used in this standard may refer to both equipment and systems.
The tests specified in this standard cannot generally be used to replace normal tests, such as identification tests, functional tests and environmental tests. It should be pointed out that equipment reliability tests are only a component of the reliability plan, and their purpose is to strengthen the reliability assurance of new equipment during the design, development and production stages.
The concepts of verification tests and measurement tests are defined as follows: Reliability verification test*A test to verify whether the reliability characteristic value of the equipment meets its specified reliability requirements. Reliability measurement test*A test to measure the reliability characteristic value of the equipment. Note: The reliability characteristic value of the equipment can also be determined by analyzing the valid data. Reliability verification test is usually one of the conditions for the ordering party to accept the equipment. When there is no special reliability requirement, measurement test is usually used to provide data.
Equipment reliability test can be a laboratory test or a field test. Their concepts are defined as follows: Laboratory reliability test**: It is a reliability verification test or measurement test conducted under specified controlled working and environmental conditions. Its working and environmental conditions can simulate or not simulate field conditions. *See GB3187-82 "Basic Terms and Definitions of Reliability". : *See GB3187-82 "Basic Terms and Definitions of Reliability". Issued by the National Bureau of Standards on November 19, 1986
Implementation on October 1, 1987
GB 5080.1---86
Field reliability test* is a reliability verification test or measurement test conducted on site. The working environment, maintenance and measurement conditions on site need to be recorded.
For equipment reliability test, the conditions of laboratory reliability test should be equivalent to the known use conditions, and the maintenance conditions should be specified and controlled.
Whether to stipulate in the equipment contract or the product standard of the equipment whether to conduct reliability testing of the equipment depends on many factors, the most important of which are:
The relevant history of the equipment;
The consequences of poor reliability of the equipment in terms of safety and economy;
The cost of reliability testing;
D. The time required for reliability testing;
The possibility of obtaining reliability assurance through measures other than reliability testing;
The availability of representative samples.
The final conclusion of reliability verification testing cannot be made based solely on the formal acceptance or rejection decision. The cause and consequences of each failure observed during the reliability test should be analyzed in detail, and the possibility of taking effective corrective measures should be studied. The purpose of reliability testing carried out in the reliability growth (or improvement) plan is mainly to improve the reliability of the equipment. To achieve this goal, failures must be continuously analyzed and improvement measures must be taken for the tested equipment. Therefore, whenever there is reason to believe that the reliability of the equipment does not meet the requirements, the equipment must be subjected to reliability growth testing, followed by reliability verification testing or measurement testing.
When the reliability verification test or determination test results are extended to the following occasions, special caution should be taken: a. Other equipment mother bodies,
b. Environmental conditions different from the test conditions, c. When the working time is longer than the working time during the test. However, due to the complexity and variability of the use environment of most equipment, it is impossible to establish an accurate relationship between laboratory reliability test data and actual convenient experience data for each situation. The flowchart provided in Appendix A of this standard provides a comprehensive introduction to the preparation and implementation of reliability verification tests. 2 Purpose
The purpose of this standard is to provide recommended methods and procedures for conducting equipment reliability tests, including: a. How to determine the reliability requirements of equipment (for verification tests) How to select test conditions for reliability tests b.
How to develop a detailed reliability test plan, e.
How to conduct laboratory and field reliability tests How to evaluate reliability test data,
f. How to fill in reliability test reports.
3 Applicability of recommended methods
The methods recommended in this standard are applicable to:
a. b. The case where the quantitative reliability requirements specified in the equipment contract must be verified by reliability verification tests, b. The case where there are reliability requirements in the product standards of the equipment and they must be verified by reliability verification tests. C. When the equipment manufacturer, test unit or user intends to confirm the reliability data of the reliability determination test for the special type or application of the equipment.
Although these methods are mainly used for electronic equipment, they are also applicable to other equipment and systems including electrical, electromechanical, mechanical, pneumatic and hydraulic *See GB3187-82 "Basic Terms and Definitions of Reliability". 354
GB5080.1-86
pressure devices, regardless of whether these devices are repaired during use and testing. These methods are also applicable to devices with limited life. These methods are applicable to any one or several stages of equipment: development (prototype), trial production, mass production and field use. These tests can be included in the initial qualification procedure (design finalization), re-qualification procedure (production finalization) and acceptance procedure of the normal production process (mass production)*. These test methods are applicable to laboratory tests and field tests. These methods are applicable when the reliability of the equipment is expressed by the following reliability characteristics: a. Failure rate, mean time between failures, mean time before first failure, other parameters of the time distribution before or between failures; b. Success rate within a specified time interval or number of operations (tests). This applicability is not limited by the time distribution before failure of any entity. Wherever the variable "time" is used in this standard, it can be converted into distance, number of cycles or other applicable quantities or units. When there is a conflict between this standard and the relevant contract or product standard of the equipment, the latter shall prevail. 4 Definitions and referenced documents
The meaning of terms not clearly defined in this standard shall be based on GB3187-82 "Basic Terms and Definitions of Reliability". Other referenced standards are as follows:
GB2421~2424-81 "Basic Environmental Test Procedures for Electrical and Electronic Products" (including relevant ones); GB6992-86 "Reliability and Maintainability Management", GB5081-85 "Guidelines for Collecting Reliability, Effectiveness and Maintainability Data of Electronic Products on-site". 5. Requirements and methods for reliability verification test
5.1 Reliability requirements
The reliability requirements of a certain equipment should be determined from the perspective of the entire system and expressed in indicators** that are easy to apply. These requirements should cover all ranges of operating conditions (including working, environmental and maintenance conditions) and the entire time range for maintaining good performance of the equipment. For verification tests, the reliability requirements of the equipment should be specified in the relevant test clauses and strive to achieve consistency between the reliability characteristic values obtained from the test and the reliability characteristic values under actual use conditions. However, it must be understood that it is difficult to achieve complete consistency between test and use reliability. When reliability requirements need to be confirmed by tests, the reliability requirements under actual use conditions are always converted into requirements applicable to reliability verification tests.
5.2 Requirements for reliability verification tests
Any requirements for equipment reliability verification tests should be included or rigidly specified in the equipment contract or the product standard of the equipment. These requirements should fully specify all special details of the reliability verification test. When formulating equipment reliability verification test plans according to this standard, the following should be considered: 5.2.1 Equipment under test and test types
a. b. The brand and model of the equipment under test,
b. The type of test to be performed: laboratory test or field test, see 5.3, c. The parent equipment from which the test samples are drawn. If necessary, a special procedure for drawing the equipment under test should also be specified, see 7.1. 5.2.2 Reliability characteristics and statistical test plans a. Provision of applicable reliability characteristics and acceptance values When the reliability characteristics refer to the reliability characteristics of a system and are derived from the reliability characteristics of each unit*** that are verified separately, the derivation procedure adopted should be specified and an appropriate reliability block diagram should be included. b. Verification test plan adopted
* "Design finalization", "production finalization" and "mass production" are added in combination with my country's situation. * * The original text is terms.
*** The original text is sub units, which should be units here, including sub-units. 355
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The scheme used is preferably selected from GB5080.5-85, GB5080.7-86 or other relevant standards, see Chapter 7. c. Verification of the validity of the distribution assumptions (if necessary) The validity test to be adopted and the possible risk considerations are shown in 7.2.2 and GB5080.685, GB5080.7-86 or relevant standards 5.2.3 Test conditions and test cycle*
a. Working and environmental test conditions include load, power supply conditions and actual operation, see 8.2 and Chapter 11. b.
Preventive maintenance adopted during the test, see 8.3 and Chapter 11. c.
The combination and sequence of items a and b above is the test cycle, see 8.1. 5.2.4 Performance and failure of the equipment under test
Monitoring of functional parameters during the test and identification of failures of the equipment under test, see 9.1 and 9.2. a.
Failure categories that require immediate rejection, see 9.4.1. b.
Failure categories that should be accounted for as non-related failures of the equipment under test, see 9.3. Determination of relevant test time, see 9.5. d.
e. Minimum and (or) maximum relevant test time or number of operations for each equipment under test, see 9.5. 5.2.5 Preparation and troubleshooting before testing
a. Testing, adjustment, calibration and aging of the equipment under test before reliability testing, see 7.1 and 10.1. b. The troubleshooting procedures adopted, including any allowable replacement of failed parts, components (components), etc., see 10.2. 5.3 Methods of reliability verification test
Before the equipment reliability test begins, a detailed reliability test plan should be formulated, which includes: a. Requirements for reliability verification test (see 5.2 above), which should be specified in detail for special test equipment; b. Corresponding requirements or project lists for test facilities such as environmental test equipment, monitoring equipment, maintenance facilities and test procedure control;
c. Test procedures and measures to be taken when the test equipment and test facilities fail; d. Requirements for test reports and measures to be taken based on test judgments. The contents (list) that should be included in the detailed reliability test plan or product standard of the equipment are shown in Chapter 13. Equipment reliability tests can be laboratory tests or field tests. The advantages of laboratory tests are that the test conditions can be limited and controlled, and the test results are reproducible and comparable. In addition, the monitoring of the performance of the test equipment and the display of failures can be better controlled. In many cases, laboratory test conditions can be designed more accurately according to the extreme conditions of use. Laboratory tests can also make judgments and discover problems in the test early, so corrective measures can be taken more promptly.
In some cases, field tests can provide more realistic test results with less test facilities. The direct cost of field tests is often lower than that of corresponding laboratory tests. The equipment under test can be operated under normal conditions. However, the biggest disadvantage of field tests is that they cannot be carried out under strictly controlled conditions. The reproducibility of field tests is generally not as good as that of laboratory tests. In terms of the requirements and implementation of reliability tests, laboratory tests and field test methods are very similar. Chapter 11 points out issues that should be considered specifically for field reliability tests.
6 Requirements and methods for reliability determination tests
In reliability determination tests, the estimated value of the reliability characteristic of interest is obtained from the analysis of the test observations. Applicable reliability characteristics should be specified.
The concepts of test conditions, equipment performance, test observations and test procedures for reliability determination tests are the same as those for reliability verification tests, so the requirements in 5.2.1, 5.2.3, 5.2.4 and 5.2.5 are all applicable. Since the determination test has no predetermined quantitative reproducible *The original text is test cycle.
**Original text XA checklist of items. 356
Reliability requirements, so 5.2, 2 are not applicable. GB 5080.1-86
As with the verification test, a detailed reliability test plan should be developed. Both laboratory tests and field tests can be used, see 5.3.
The estimation method of the reliability determination test results is described in 7.4. If the data from early tests or field observations are complete, accurate and applicable, the reliability characteristic value of the equipment can also be determined by analyzing them. 7 Sampling and statistical test plan for the test equipment Because the reliability characteristics have statistical properties, the test plan for reliability tests must be based on statistical principles. When the reliability indicator is the mean time between failures, (average) failure rate or other distribution parameters, the test is completed as a time test and the relevant time before failure is observed during the test. An assumption about the distribution of time before failure should be made (see GB5080.6-85, GB5080.7-86 and related standards). When the reliability index is the success rate, the reliability test only counts and statistically processes the number of tests and failures or the total number of tested equipment and the number of failed equipment.
7.1 Sampling of parent and test equipment
Equipment reliability testing is applicable to any of the following products: a. Developed models or prototypes: b. Trial production batches
c. Mass production.
The parent must be essentially the same, that is, the equipment is produced in the same way and under the same conditions to make the reliability test representative. In some cases, the number of parent equipment can be 1. The test equipment must be randomly selected from the representative parent. The detailed reliability test plan should specify the relevant parent and certain special procedures for selecting the test equipment. If considered appropriate, samples can be drawn by the ordering party or an independent testing unit. Any aging or other pre-treatment stress (such as loading and unloading transportation) of the test equipment should be equal to the stress to which the representative parent equipment that can be delivered for use is subjected.
7.2 Basic distribution
The random variables related to reliability testing in this standard are: a. Continuous random variables: the time before failure or the time between failures with a basic continuous distribution of the exponential, Weibull or normal type. b. Discrete random variables: the number of failures or the number of failed products with a discontinuous distribution of the binomial type. Other distributions may also be used if their validity is confirmed. 7.2.1 Guidelines for the selection of distribution assumptions
This paragraph describes the technical content of the distributions used in this standard. 7.2.1.1Continuous distribution
If the random variable is the time before failure or the time between failures, the following distributions should be considered:Exponential distribution: used when the failure rate is constant. For many devices, after the early failure period (failure rate decreases) and before the wear-out failure period (failure rate increases), the device is in a constant failure rate period. After reaching stability through a series of component replacements for preventive maintenance or troubleshooting, the device may have an approximately constant failure rate even if the failure rate of some components is increasing. Weibull distribution: used when the failure rate is increasing or decreasing. The failure rate of complex equipment may decrease, but the failure rate of equipment with wear mechanisms and equipment with a large number of non-repairable reserve units is increasing. Therefore, the Weibull model is successfully used in many cases. However, in terms of statistical methods, this model is not as widely used as the exponential distribution and the trochanteric distribution. Normal (Gaussian) distribution: used when the time before failure is approximately Gaussian and the failure rate is increasing. Although this distribution can be approximately replaced by a Weibull distribution with appropriate parameters, it is still much better to use a normal distribution. This is because many available statistical methods are based on the assumption of a normal distribution. 357
7.2.1.2 Discontinuous distribution of success rate GB5080.1-86
When the equipment under test or the test is classified as failure or success, the success rate is used as a reliability characteristic. The test plan specified in GB5080.5-85 uses a binomial distribution to determine the sample size and operating characteristic curve. 7.2.2 Initial assumptions for the distribution of time before failure or time between failures For equipment, unless there is a well-founded analysis or engineering appraisal to prove that any other distribution can be selected, the initial assumption should be an exponential distribution (constant failure rate), see 7.2.1. Any other distribution assumptions must be based on reliability studies or analyses conducted before the reliability test. Assumption estimates can be made during the design and development of the equipment or based on empirical data for a certain equipment. If it is not an exponential distribution, the detailed reliability test plan should specify the assumed distribution. When the detailed reliability test plan requires the validity of the initial assumptions of the distribution to be tested, the method described in GB5080.6-85 or relevant standards should be used. The validity test can be based on the same data as the reliability test. 7.3 Reliability verification test plan
The contents of 7.3.1 to 7.3.4 describe the statistical test plan used to determine the acceptance or rejection of the equipment based on the specified reliability characteristic values. All acceptance and rejection rules should be determined before the test begins and the test plan to be used should be specified in the detailed reliability test plan.
7.3.1 Test plan for failure rate and mean time between failures for constant failure rate assumptions For constant failure rates described by exponential distribution, the test plan should be based on GB 5080.7--86 Select a test plan. These tests are divided into the following two basic types with or without replacement of failed equipment during the test: a. Truncation Sequential Test: During the test, the equipment under test is monitored continuously or at short intervals and the accumulated relevant test time and the number of relevant failures are compared with the criteria for determining whether to accept, reject or continue testing. b. Timed or fixed number truncation test: During the test, the equipment under test is monitored continuously or at short intervals and the relevant test time is accumulated until or exceeds the predetermined relevant test time (acceptance) or a predetermined number of relevant failures occurs (rejection). Select the type of test plan Guide:
Figure 1 is a comparison between a truncated sequential test and a timed or fixed number truncated test with the same risk rate. This figure can be used to identify certain advantages and disadvantages of the two schemes. In addition, Figure 2 shows that for these two basic schemes, the total cumulative relevant test time required to make a decision is basically a function of the actual mean failure-free working time of the equipment, and the reason is obvious. Timed or fixed number truncated test
Truncation sequential test
Cumulative test time
Receiving line
Receiving line
Note: See GB5080.7-86 for time scale. GB 5080.1--86
Timed Truncation
Timed or Constant Truncation Test
Truncation Sequential Test
Zero Failure Truncation
True Mean Time Between Failures
The economic and management advantages and disadvantages of the two basic types of test schemes are as follows: Truncated Sequential Test
Advantages:
The average number of failures required to make a decision is the smallest, a.
b. The average cumulative test time required to make a decision is the smallest; c. The cumulative test time and number of failures of this test have a fixed maximum value. Disadvantages:
a. The number of failures and the related test equipment costs are The fluctuation range is larger than similar timed or fixed number truncation tests, which brings many management problems in arranging the tested equipment, test facilities and manpower; b. The maximum cumulative test time and the number of failures may exceed those of comparable timed or fixed number truncation tests. Timed or fixed number truncation tests
Advantages:
When the maximum cumulative test time is fixed, the maximum required test facilities and manpower can be determined before the test. a.
The maximum number of failures is determined before the test, so the maximum number of tested equipment can be determined without repair or replacement.
Disadvantages:
Its maximum cumulative test time is shorter than that of similar truncation sequential tests. The average number of failures and the average cumulative test time will exceed those of similar truncation sequential tests. a.
b. Whether the equipment is good or bad, it must reach the maximum cumulative test time or the number of failures before a judgment can be made, while similar truncation sequential tests can make such a judgment faster.
7.3.2 Test schemes for non-constant failure rates The test schemes for equipment with increasing or decreasing failure rates are selected from the relevant standards. If the failure rate of the equipment is increasing and the distribution of the time before failure is close to the normal distribution, the test plan is selected from the corresponding standard. 7.3.3 Test plan for success rate
When the reliability characteristic is the success rate, the test can be any of the following: a. [Test with a fixed number of tests or equipment, truncated sequential test.
The reliability verification test plan for success rate is shown in GB5080.5-85. 359
7.3.4 Risks associated with the test
GB 5080.1-86
There may be many reasons for judgment errors, the main reasons include: the way of extracting the test equipment, the choice of distribution assumptions and the statistical judgment risks of the user and the manufacturer. 7.3.4.1 Risks associated with the extraction of test equipment The selection of the parent body of the test equipment is usually based on the predetermined plan, the product standards of the equipment and the economy. It is generally impossible to quantitatively estimate the risks caused by improper selection of the parent body. In order to make a decision early in mass production, it is often practiced to use development or pre-production prototypes for reliability verification tests. However, since development and pre-production prototypes are not yet mature and their reliability needs to be improved, inappropriate rejection decisions may be made, and therefore they are often not representative of mass production products.
The tested equipment (sub-samples) should represent their parent population as much as possible so that information or judgments about the parent population can be provided. To ensure this representativeness, the tested equipment must be randomly selected. The risk caused by internal inconsistencies in the parent population and the failure of a part of the parent population to be represented by the sample cannot be quantitatively estimated.
7.3.4.2 Risks caused by incorrect use of the continuous distribution assumption Clause 7.2.2 introduces an initial assumption of a constant failure rate. Since this assumption may not be suitable for all equipment, it is necessary to examine the consequences when the equipment is assumed to have a constant failure rate but actually has a decreasing or increasing failure rate. In general, if the actual test time of each equipment is less than the actual mean failure-free working time of the equipment, the probability of a equipment with a decreasing failure rate passing the reliability verification test will be lower than the probability when it is assumed to have a constant failure rate. Likewise, the probability that a device with an increasing failure rate will pass the reliability verification test will be higher than if it were assumed to have a constant failure rate. The latter situation will result in the acceptance of devices that would have been unacceptable for a long period of time due to lower reliability levels. 7.3.4.3 Decision Risk
If the equipment has an acceptable specified reliability characteristic value, the manufacturer's risk is the probability of rejection. If the equipment has an unacceptable specified reliability characteristic value, the user's risk is the probability of acceptance. In order to minimize the probability of rejection of the equipment, the manufacturer must ensure that the equipment's reliability characteristic value is better than the specified acceptable value. The operating characteristic curve in the test plan clearly shows the decision risk. After weighing these risks against the cost of additional testing to reduce the risk and other factors such as the equipment under test, test facilities and available time, the manufacturer and user can jointly select the decision risk of the test. The relevant substandards of the entire set of standards give the working characteristic curve for each reliability verification test plan. If each unit of a piece of equipment is verified separately, the risk of making an erroneous acceptance or rejection decision for the entire equipment is higher than if the entire equipment is tested once.
7.4 Reliability Determination Test Plan
When the reliability requirements are not quantitatively specified, the reliability level achieved by a piece of equipment can be assessed by reliability determination tests. The reliability characteristic value of the equipment can be estimated by statistically analyzing the data obtained from the test. If necessary, a confidence interval around the point estimate can also be determined. This confidence interval includes the unknown true reliability characteristic value with a certain probability (i.e., confidence level). 7.4.1 Methods for estimating reliability characteristic values
Assuming that the equipment has a constant failure rate described by an exponential distribution, the reliability test with time as a variable can be terminated after a specified relevant test time or a specified number of relevant failures. Whether or not the failed equipment is repaired or replaced, point estimates and confidence intervals for the failure rate, mean time before failure, and mean time between failures can be obtained through testing. If a Weibull or normal distribution is assumed, graphical methods can be used, and in some cases, the observed values can be processed by calculation to determine point estimates and confidence intervals for the distribution parameters.
Point estimates and confidence intervals for the success rate can be obtained by testing with a fixed number of tests or equipment. The result of each test is either success or failure. In this case, the treatment of the observed values is based on the binomial distribution, but for a large number of failures, it is based on the normal distribution.
*Yuwen is sutunits, which should be units here, including subunits. 360
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The recommended method for determining the point estimate and confidence interval mentioned above is shown in GB5080.4-85.7.4.2 Cumulative test
If the reliability determination test is to put some equipment into the test without a predetermined truncation procedure, the reliability can be estimated at any time based on the cumulative test time and the number of failures. For a constant failure rate that follows an exponential distribution, it is not necessary to put all equipment into the test at the same time or to test it in the same period. The test results in each period can be collected and the point estimate and confidence interval can be calculated using these cumulative results. The confidence interval can be obtained using a procedure similar to the timed truncation test in 7.4.1. As for the success rate, it is always possible to calculate the point estimate and confidence interval using the cumulative test results. 7.4.3 Risks associated with the test
The causes of errors associated with point estimates and confidence intervals are similar to the causes of risks in verification tests discussed in 7.3.4.1 and 7.3.4.2.
8 Test conditions
The test conditions used in this standard involve any factors or effects other than the inherent characteristics of the equipment under test that may affect whether a failure of the equipment under test occurs or not. Test conditions include operating conditions, environmental conditions, and preventive maintenance. Troubleshooting during the test is described in Chapter 10, and test conditions for field tests are detailed in Chapter 11. 8.1 General considerations for selecting test conditions
When selecting equipment reliability test conditions, the following major factors should be considered: a. The basic reason for requiring or conducting reliability testing;
Expected changes in equipment operating conditions;
The possibility of failure caused by different stress factors in the operating conditions; c.
d. g. The corresponding test costs under different test conditions; the test facilities available; the test time available, g. The expected reliability characteristic values that vary with the test conditions. If the purpose of the test is to prove that the reliability of the equipment is not lower than a certain level, which may be critical from a safety point of view, for example, the test conditions must not exclude any important most severe use conditions. If the purpose is to prove or determine the reliability level of the equipment under normal use conditions, for example, to formulate the best maintenance plan, the test conditions should be highly realistic and representative of typical use conditions. If the purpose of the test is to compare different types of a certain equipment with reasonable and different test results, then reproducible test conditions close to the limit use stress level are the most fundamental. In any case, the severity of various stress factors shall not exceed the limit stress value that the equipment is specified to withstand. In the test process, if multiple operating conditions, environmental conditions and maintenance conditions must be considered, the test conditions are generally a periodic repetition of an appropriate test cycle. The detailed reliability test plan should include a test cycle diagram to indicate the existence, duration, time intervals and interrelationships of the working, environmental and preventive maintenance conditions during the test cycle. The duration of the test cycle should be short enough not to have a substantial effect on the test results, but long enough to allow the specified test conditions to reach stability. Under constant failure rate conditions, the test cycle should be less than 0.2 mo based on the cumulative relevant test time. mo is the specified acceptable mean time between failures, or the acceptable value of the reliability characteristic equivalent to the mean time between failures (see also 9.1.3).
Whenever possible, the test conditions (and typical test cycles) should be selected from the categories recommended in GB7288-87. For applications not covered in GB7288-87, a suitable test cycle should be designed based on the principles of GB5080.2-86. 8.2 Working and environmental test conditions
Whenever possible, 1. The working and environmental test conditions should include the main working and environmental conditions in actual field use. Normally, accelerated tests shall not be conducted at stress levels higher than those used on site. For equipment whose reliability characteristics depend on the number of operating cycles, accelerated working test conditions may be considered to compress calendar time. 361
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The following operating conditions shall be described in the detailed reliability test plan: Functional mode
Complex equipment can have various specified and different functional modes. The actual working conditions of the equipment in field use determine the percentage of time occupied by each mode and the way to switch from one mode to another. The switching can be directly controlled by the operator or automatically controlled by program signals. Examples of equipment with multiple operating modes: "A civil radio device can be used as a VHF receiver or as an audio amplifier; a measuring device can be used as a digital voltmeter or as a counter; a radar system can be manually controlled or automatically tracked.
b. Input signal
When determining the requirements for the input signal characteristics, the acceptable tolerances for all measurable signal parameters that may affect the operation of the test equipment should be specified. This requirement is particularly important for complex test equipment interfaces, as it can distinguish between failure of the test equipment and failure of the test equipment. c. Load Conditions
Electrical and mechanical loads are generally important components of the stress applied to the EUT and must be carefully specified. Electrical loads can be represented by input impedance and a transient characteristic. Mechanical loads can be static or dynamic. The actual power output of the EUT must be specified and applied in the test as one of the load conditions. d. Actual operation of the equipment
Operators are often required to simulate actual operation in field use. Conversely, excessive uncontrolled operation will impose additional stress on the EUT. These requirements and limitations should be specified in the detailed reliability test plan. e.Energy*
The required external power characteristics, such as voltage, frequency, waveform, transient, etc. and their tolerances should be specified. When necessary, requirements for other energy sources such as water and compressed air should also be specified. For equipment that obtains strong cooling from external energy sources, the actual temperature stress is determined in whole or in part by the characteristics of the cooling system. The detailed reliability test plan should specify the requirements for cooling system parameters such as flow rate, inlet temperature, humidity, purity, etc. The environmental conditions used on site are usually composed of a combination and sequence of many environmental factors of different severity. However, it is generally economically impossible to accurately simulate the use environment during the test, and it is also unimportant from the test point of view. For laboratory tests, environmental factors can be applied individually, in groups or sequentially. Whenever possible, the environmental test procedures specified in the corresponding test sub-standards of GB2423~2424-81i should be adopted. The detailed reliability test plan should specify the environmental test conditions used. It is best to follow the standardized test sequence and the conversion between them specified in GB2423-2424-81 and provide the "data required in the reliability test plan or the product standard of the equipment" according to the sub-standards of the corresponding tests**. All data on relevant tests that are not included in GB2423-2424-81 or inconsistent with the standard must be provided. GB5080.2-86 provides detailed guidelines for selecting working conditions and environmental conditions. 8.3 Preventive maintenance during the test
When the product standard of the equipment requires routine maintenance of the equipment during actual use, a preventive maintenance procedure should be considered for the reliability test of such equipment. In any case, the preventive maintenance performed during the test should be consistent with the maintenance performed in actual field use in principle, and the total amount of preventive maintenance during the test (number, time, degree, etc.) should not exceed the preventive maintenance amount in actual field use.
Typical types of preventive maintenance are replacement, adjustment, calibration, lubrication, cleaning, reset, recovery, etc. The maintenance program shall at least specify: a. The preventive maintenance measures to be taken; b. The interval or frequency of preventive maintenance or other criteria for determining the need for preventive maintenance. The maintenance program may include functional checks and replacement of necessary reserve units to the extent specified in the field use procedures. * Original text X supporting supplies . * * J Original text X \lnlormation required in the relevant Before the test begins, the interval or frequency of preventive maintenance or other criteria should be specified in the detailed reliability test plan. The maintenance interval or frequency can be specified in units of operating time or calendar time or related test time (number of cycles). These regulations should have an appropriate relationship with other cyclic items or measures of the reliability test. 8.4 Recommended laboratory test conditions
The working, environmental and maintenance conditions used in the field indicate that the combination, sequence and severity of various factors are varied in most applications. However, some application groups are similar to and often sufficient to be laboratory reliability tests. The preferred, standardized test cycle used for verification tests and determination tests. The recommended test conditions (cycles) are specified in detail in GB7288-187 and should be adopted whenever possible.
Observation of performance and test of equipment under test
The relevant test time of the corresponding equipment under test must be observed during the entire test, or the relevant number of failures must be observed at the end of the test, depending on the type of reliability test performed. Therefore, the monitoring of the performance of the equipment under test and the definition of failures and related test times must be clearly defined in the detailed reliability test plan. The following clauses provide rules and guidance in this regard. 9.1 Monitoring of performance of the equipment under test
The detailed reliability test plan should clearly specify the monitoring of the performance of the equipment under test. The following contents and methods should be used to measure the performance of the equipment under test*. 9.1.1 Parameters
The functional parameters of the equipment under test that need to be monitored during the test should be specified. It may be required to monitor all parameters or some parameters specified in the product standard of the equipment under test, mainly to monitor the output parameters. In the case where the equipment under test has a backup unit, the monitoring of the backup unit parameters should also be considered. 9.1.2 Measurement
For each monitored parameter, the measurement method and measurement accuracy requirements should be specified. An applicable procedure for calculating the total measurement error should also be given.
Monitoring interval
If monitoring cannot be performed continuously, the time interval between monitoring and the measurement points that should be monitored during the test cycle must be specified. Monitoring interval The time interval must be so short that it does not substantially affect the test results. Monitoring should be carried out continuously or intermittently. Under constant failure rate conditions. The monitoring interval should be less than 0.2m based on the cumulative relevant test time, where m is the specified acceptable mean time between failures, or the acceptable value of the specified reliability characteristic equivalent to the mean time between failures. Note: 0.2mo was determined after research, and its function is to limit the impact of the small monitoring interval on the risk of the producer and the user. 9.2 Failure of the equipment under test
For each parameter to be monitored, an acceptable limit range should be specified. When any of the measured parameters exceeds this limit range permanently or intermittently, a failure should be considered to have occurred. All failures shall be analyzed in accordance with the requirements of 10.3. Failures caused by measurement errors or failure of external test equipment shall not be considered as failures of the equipment under test. All other failures shall be considered as failures of the equipment under test. If more than ten parameters deviate from the specified limit range and it cannot be proved that they are caused by the same reason, then each deviation of the parameter shall be considered as a failure of the equipment under test. If the failures are caused by the same cause, the EUT is considered to have produced only one failure.
If two or more independent failure causes are present**, each failure cause shall be considered as a failure of the EUT. Each failure of the EUT shall be classified as either a dependent failure or an unrelated failure. All failures that cannot be clearly identified as unrelated failures in accordance with 9.3 or the supplementary provisions of the detailed reliability test plan shall be considered as dependent failures of the EUT. When making decisions on reliability verification tests and determining point estimates and confidence intervals in reliability determination tests, all dependent failures of the EUT observed during the test *original text as causes.
GB5080.1--86
or at the end of the test shall be counted. 9.3 Categories of unrelated failures
A failure of the EUT shall be considered as an unrelated failure only if there is a clear basis for the failure to fall into one of the categories specified in 9.3.1 to 9.3.3. These bases shall be documented and included in the test report. The detailed reliability test plan may specify other categories of unrelated failures that are applicable to special circumstances. 9.3.1 Dependent failures
The failure of a product* is directly or indirectly caused by the failure of another product. This failure is defined as a dependent failure. Dependent failures shall be considered as unrelated failures. The independent failure of the test equipment corresponding to the dependent failure is always a dependent failure. It should be noted that the dependent failure may occur after the independent failure occurs. The delay time must be approved by the ordering party or the test unit.
9.3.2 Misuse failures
refer to failures caused by stress applied to the equipment exceeding its specified capacity. Misuse failures may be caused by unintentional test conditions during the test, such as the severity of the test exceeding the stress specified for the test equipment, careless operation of the test or repair personnel, etc. Misuse failures are unrelated failures. 9.3.3 Failures that can be eliminated by modifying the design
refer to failures discovered early in the test that will lead to design changes or other corrective measures for all equipment in the parent body. If the corrective measures are proven to be effective, such failures can be classified as non-related failures according to the agreement. 9.4 Special categories of failures
The following only specifies two types of failures that require immediate rejection and repeated failures. The detailed reliability test plan can be based on the failure concept in GB3187-82, and specify other special failure categories of the test equipment according to the impact of the failure on system performance, whether the failure is located in a reserve unit or a non-essential unit, and the repair cost and time. 9.4.1 Failures requiring immediate rejection In individual cases of reliability verification testing, it is necessary to define such failures of the equipment under test: when such failures occur repeatedly, no matter how many failures occur, normal acceptance or rejection criteria will no longer be considered and an immediate rejection decision will be made. The detailed reliability test plan should have a definition of this type of failure.
For example, failures of the equipment under test that cause danger or unsafe conditions to the use of the equipment, maintenance personnel or related personnel, or failures that may cause significant material losses are such failures. 9.4.2 Recurrent failures
For the purpose of this standard, repeated failures are defined as two or more failures of the same part (component) or parts (components) of the same type and of the same manufacture that occur in the same or different locations for the same purpose, or at the same point in the test cycle but not at the same time.
The occurrence of repeated failures will indicate a defect in the design of the equipment or indicate that poor quality components are used in the equipment. Repeated failures are an important indication that the equipment may be damaged or otherwise degraded, resulting in an increased failure rate. In the event of repeated failures, a special analysis must be carried out to find out the causes of the repeated failures and their possible impact on the distribution assumptions, see GB5080.6-85.
9.5 Relevant test time
Relevant test time refers to the time related to the number of relevant failures of the test equipment used to verify the reliability requirements or to calculate the reliability characteristic values.
The relevant test time required during the test can be the relevant time of each test equipment as specified in the detailed reliability test plan, or the sum of the cumulative relevant time of all test equipment. This time does not include the warm-up time, maintenance time and downtime of the test equipment. When the test equipment is monitored intermittently, the failure is considered to have occurred at the moment before it was observed. Note: This convention of calculating the cumulative relevant time corresponding to the failure directly to the observation point is used to limit the production and use when the number of test equipment is small. * The original meaning is iem, which refers to the components (assemblies) or parts (core parts) of the test equipment. 364
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