The intention and importance of environmental experiment: With the rapid development of industrial production in China and the improvement of military equipment, the requirements for the quality and reliability of goods are getting higher and higher, so there is no shortage of equipment for the study of reliability-environmental experimental equipment. The type and quality of the request are also higher. In particular, the Gulf Campaign showed the important effects of weapons in the battle, and also promoted the research, experimentation and development of China's military technology and weapons.

Some calculations at home and abroad indicate that more than half of the elements of the weapon equipped with the problem of damage or damage are caused by the environmental factors in the use of the product. It can be seen that environmental factors are important for military equipment, and there is no negligible influence, in order to make military goods It has excellent environmental adaptability, and then its reliability is improved. It is necessary to conduct environmental experiments not only during development and development, but also during use.

For ordinary electricians and electronic goods, the calculation of the failure share caused by various environmental factors: It can be seen that the failure of ordinary electricians and electronic goods caused by environmental factors is similar to the calculation of the above table. An environmental experiment is an experiment that exposes a product in a natural or artificially mimicked environment and then evaluates the functions under storage, transportation, and use conditions that it may actually encounter. It is simply an experiment of environmental adaptability of the product.

The purpose of the environmental experiment: to explore and determine the impact of single or multiple environmental factors on the commodity, check the environmental adaptability of the commodity; as one of the type of experimental projects of the commodity, or the inspection experiment of the commodity, to see if it meets the specified environmental requirements Whether the goods are qualified or not, as the basis for decision-making for acceptance or rejection of goods. As a commodity environmental stress selection (ESS) experiment, select unqualified or potentially defective goods, and then improve the reliability of the goods.

Environmental experiments can be divided into field experiments and laboratory experiments:

(1) Laboratory experiments: usually carried out in the laboratory, also known as artificial imitation experiments, artificially create a certain climatic environment or mechanical environment, and test the samples in this environment. The artificial imitation experiment has similar imitation with the atmospheric exposure experiment, and has acceleration, which can greatly shorten the experimental time, and the application of environmental stress and load conditions can be strictly controlled within the tolerance range, ensuring that all experiments are under controlled conditions. The following is carried out, so the reproducibility is good and comparable. The disadvantage is that it is constrained by the equipment. Usually, some small-volume, light-weight goods are tested, and sometimes the imitation of the very real induction environment is poor.

(2) Field experiments can be divided into natural exposure experiments and field experiments:

Natural exposure experiment: expose the goods or materials under natural climatic conditions, check their environmental adaptability, the experimental samples usually do not work, the experiment time is very long, usually the demand is evaluated after many years, the experiment is accurate, severe, and practical. The conclusion is comparatively prestige, and such experiments are mostly used by the state or large industrial groups.

On-site experiment: Due to various constraints on laboratory equipment, many military equipment can not carry out various environmental experiments in the laboratory. Even if it can be experimented, the laboratory experiment can not completely imitate the application environment of the scene, so it can not be carried out. The actual check, so not only large equipment, that is, small equipment that can carry out environmental experiments in the laboratory also requires on-site environmental experiments to make up for the lack of laboratories, and fully verify whether the military equipment is damaged or able to be damaged in the field application environment. No normal work.

Before the start of the Gulf Campaign, the US military was equipped with a field experiment in Saudi Arabian combat outposts. It found that many of the questions were not suitable for the on-site environment. After the discussion and treatment, the equipment was greatly improved and the regulations were clearly defined. To organize the work environment verification experiment, combine the laboratory with the field, and replace the use of laboratory experiments and field experiments to help accelerate research and development and reduce the cost of research and development, and minimize the impact of environmental factors on the equipment, so that the equipment is reliable. Great progress.

The strengths of the field experiment are real and reliable, and can not achieve the effect that the laboratory can't. The disadvantage is that the experimental environmental conditions cannot be ensured under controlled conditions, so the experimental conditions and experimental results are less reproducible.

Environmental test equipment for environmental stress selection (ESS) Environmental experiments are mainly to check the environmental adaptability of goods, used to recognize planning, ESS is a selection process for checking the parts, materials and production technology of goods, demanding exposed goods The potential shortcomings and the failure of other properties that may occur on site, ESS requests 100% of the products for exposure experiments, but not for random sampling. Since the potential shortcomings of the goods are random, only 100% of the experiments are needed to ensure the usefulness of the selection. .

The key to the selection of environmental stress for commodities: (1) The optimal level of environmental stress, it is necessary to adapt to the shortcomings of forcible goods to become invalid. (2) It is necessary for stress to not exceed the limits of electrical and mechanical functions of the commodity, and should not invalidate the defective goods or reduce the useful life of the goods. As an environmental experimental device for ESS, the environmental stress should be satisfactory to the above request, which is significantly higher than the conventional environmental experimental equipment request.

Temperature cycling, random oscillation, high temperature, thermal shock, low temperature, damp heat, low air pressure, induction environment, etc. According to the research materials of the American Academy of Environmental Sciences (IES), the temperature cycle is the most useful way to select, followed by random oscillation. Therefore, the ESS experiment of Chinese electronic goods is recommended according to GJB 1032 "Electronic Commodity Environmental Stress Selection". And random oscillations two experimental methods.

The temperature cycle is not only the most useful, but also has a uniform stress on the test sample. It has greater flexibility in fulfilling procedures and correcting procedures: the selection time is larger and the other methods are shorter.

The ESS temperature cycle experiment has three requests: (1) The temperature difference of the temperature limit may be as large as possible: the temperature difference between high and low temperature is ≥100 °C, regardless of the application limit of the commodity reservation, only the commodity does not cause unnecessary risk, and does not make Imperfect goods are damaged. (2) The temperature rate between temperature limits is necessary to be as fast as possible, usually ≥ 5 ° C / min, in order to achieve optimal stress levels, and repeated cycles without damaging imperfect goods. (3) The wind speed on the sample is ≥3m/s, so that the surface temperature of the sample is as close as possible to the temperature of the box. The experimental equipment that can satisfy the above requirements can be used as the ESS temperature cycle experimental equipment. Obviously, the high and low temperature experimental chambers usually used for environmental experiments are not satisfactory.

The use of random oscillations for ESS experiments takes a short time, and is particularly useful for revealing mechanical defects such as desoldering and soldering. The random oscillation cost is too expensive. However, it is still considered to be better than other oscillation types, and is often used. If the cost allows, it can be selected with the temperature cycle to constitute an induction experiment.