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Part One: Basic Introduction To Environmental Test

I. The origin, purpose, and introduction of environmental test

Origin: It first started in the military, and the first documented in the literature was a coupon test of a metal sample on the edge of a river entering the sea. This was the earliest natural environmental test.

During the First World War, a large proportion of weapons failed to work after being transported to the battlefield, and many weapons failed to work after being stored for a period of time. The proportion was high. Therefore, a series of environmental adaptability tests were developed.

During World War II, in order to further promote the environmental adaptation of weapons, the United States established the "Deterioration Protection Center" to formulate environmental test standards for military products.

Purpose: Quality is the basis of the product value. When quality problems occur after a product is put on the market, the degree of performance damage does not directly affect the cost of the product. For manufacturers, the biggest loss is the loss of brand reputation. In order to avoid these losses, it is necessary to appraise the quality of the product before it is put on the market. The environmental test is not only able to appraise product quality through simulation tests and product life aging tests but is also an indispensable part of the quality assurance system.

Introduction: Environmental test is a simulation test based on the (limitation) environment that may occur during product transportation and use, and try to find most of the problems in the product development stage so that there will be no major problems after the product is introduced to the market. The criterion for everything is to refer to the actual product user profile.

The environmental test is more to verify the design goals of the product, which are mainly transportation environment, storage environment, working environment, etc. However, through the environmental tests, it can only be said that the product can work in a specific environment, and it cannot explain the ability of the product to work continuously for a long time under specific conditions. That is to say, the environmental test cannot tell us the reliability level of the product.

Ⅱ. Classification of environmental test

1. The environmental test is divided by its means:

1.1 Natural exposure test:

The natural environment exposure test refers to the long-term exposure test in the natural environment, usually long-term exposure under natural outdoor conditions. The environmental exposure test is usually used for the environmental adaptability of outdoor product materials and production processes (plating and coating) research, focuses on corrosion and deterioration of materials.

1.1.1 The effect of natural exposure test:

l  Through the natural exposure test, the change rule, failure situation, failure level, and failure reason of the product under natural environmental conditions can be obtained.Also can understand the stability and protective ability of materials, craft, coatings, and other properties in the product manufacturing process.

l  Natural exposure tests can provide data for the study of artificial simulation test methods and their conversion relationships, and can also be used to verify and compare the effectiveness of accelerated tests.

1.1.2 The limitations of natural exposure test:

l  The test conditions cannot be controlled, which affects the reproducibility of the test to a certain extent.

l  In addition, the natural exposure test has a long test period, sometimes failing to keep up with the development of the product

1.2 Manual simulation test:

Through the test equipment (temperature and humidity chamber, vibration tester, salt spray chamber, light aging test chamber, etc.) to simulate the product in the storage, transportation, and use process of the climate and mechanical environment test.

1.2.1 Classification of artificial simulation test:

According to the environmental conditions encountered during storage, transportation, and use of the product, it can be divided into:

l  Climate environment-temperature and humidity: high temperature, low temperature, constant damp heat, alternating damp heat, the combined cycle of temperature and humidity, rapid temperature change, cold and heat shock, low air pressure (high simulation).

l  Weather environment-illumination: UV ultraviolet light test, xenon lamp test, metal halide lamp, carbon arc lamp.

l  Mechanical environment: random vibration test, sinusoidal vibration test, resonance search and dwell, sinusoidal + random vibration test, random + random vibration test, mechanical shock test, collision test, steady-state acceleration, drop test.

l  Comprehensive environment: temperature + humidity + vibration, temperature + humidity + shock, temperature + humidity + collision, HALT/HASS/HASA, temperature + humidity + stacking, high pressure cooking.

l  Protection level: IP protection (waterproof, dustproof), IK protection (protection against external mechanical collisions).

l  Biological and chemically active material environment: salt spray test, mold test, gas corrosion, chemical resistance, artificial sweat.

1.2.2 Advantages and disadvantages of manual stimulation test:

l  Compared with the natural exposure test, the artificial stimulation test can accelerate and strengthen the test, save time, and can be carried out at any time, the test parameters are easy to control, and the reproducibility is good.

l  Its disadvantage is that when the conditions and test procedures are not selected properly, the test will be distorted and even wrong conclusions can be drawn.

1.3 Field Test:

The product will be inspected and tested under actual use conditions

1.3.1 The effect of field test:

l  For large-scale products, especially mobile and large-scale complete sets of equipment (such as the environmental adaptability test when a car is tested at high speeds), only field tests can be carried out.

l  In addition, it is also necessary to conduct field tests in actual environments that need to collect actual field data, such as high-speed rail EMU operation, and actual packaging road running tests of large equipment.

1.3.2 Advantages and disadvantages of field test:

l  During the on-site use of the product, it is subject to the combined effects of various environmental factors, so it can expose the problems of the product more than a single or combined test. It can be seen that the results of the field use test are the truest and convincing.

l  Its shortcomings are long cycles and high costs.

2. Environmental tests are divided according to environmental conditions:

2.1 GB/T 4796-2017/IEC 60721-1:2002 《 Classification of environmental conditions—Environmental parameters and their severity》The environmental conditions of the products are divided into 7 categories: climatic conditions, biological conditions, chemically active substances, mechanically active substances, polluting liquids, mechanical conditions, electrical and electromagnetic interference.

2.2 ETSI 300 019 《European Communication Products Environmental Test Series》 divides the environmental conditions of products into air temperature, humidity, air (pressure and speed), water, radiation, chemically active substances, mechanically active substances, biology, vibration, shock, earthquake and so on.

Ⅲ. The effect of environmental test

In the product design and development stage, the environmental test is used to assess whether the selected components, designed structure, and adopted technology can meet the requirements of the actual environment and existing defects. In order to save time and fully expose the weak links of the product, an accelerated life aging test is used, that is, according to different environmental stress factors, different acceleration factors are used to strengthen and accelerate the process.

In the finalization stage of the product, the environmental test is used to determine whether the technical indicators of the product can meet the design requirements under the predetermined environment, whether the design life can be guaranteed under normal working conditions, and whether it can meet the safety requirements. The environmental test at this stage is an environmental adaptability test that is carried out under actual environmental conditions during product storage, transportation, and use.

In the normal production stage of the product, there is a major change in the production process, or after a period of time in production, the environmental test is used to check the quality of the product's workmanship or to check the stability of its quality. The environmental test at this stage is also an environmental adaptability test.

In the final product inspection stage, the environmental test checks all products by applying non-destructive stress to eliminate early failures, reduce the number of unqualified products, and try to stabilize product performance for a period of time before qualified products are put into use. The environmental test at this stage is an environmental screening test.

The environmental test can also be used for a safety inspection to check whether the product has problems that endanger health, life, and property. For example: use a vibration test to check the firmness of installation and connection. When environmental tests are used to assess safety, test conditions that are higher than normal tests are usually used.

Ⅳ. The importance of environmental test

The environmental test is an important means to evaluate the environmental adaptability of product devices, systems, and their packaging under actual storage, transportation, and use environmental conditions, as well as an important means to inspect and ensure product quality.

Ⅴ. When to do environmental test

Environmental test runs through the entire process of design, trial production, production, sales, and use of electronic and electrical products, and its role and manifestation are different at different stages.

The environmental test can play an important role in the certification of raw materials in the design stage of the product, the reliability growth in the development stage, the reliability statistics in the finalization stage, the environmental adaptability of the production process, and the environmental screening before leaving the factory.