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What is Environmental Testing?

What is Environmental Testing?

Yoshinori Kin*/Yasuko Sasaki*
To improve quality, the currently separate steps of "failure analysis", "environmental test planning", "environmental testing", and "test results analysis" should be unified into one common activity. However, at present due to such reasons as the large number of types of specimen and the complexity of evaluation technology, engineers engaged in individual research in each field carry out these steps separately. Because of this, the persons doing the testing rarely are aware of the purpose of the test or its effectiveness.
This series on environmental testing is for such persons as well as for those who have heard of "environmental testing" but aren't sure what it's all about.
Our greatest hope for this series is that each and every issue be enjoyed by such readers and that it lead to the ability to better carry out their duties. We are presenting "What is Environmental Testing?" and "Temperature Testing" as the first articles in the series, to be followed by "Humidity Testing" and "Temperature Cycle Testing". We hope you enjoy the articles.

1. Introduction

We are presenting this series to give an overview of "environmental testing". In this article we shall deal with "What is Environmental Testing?" and "Temperature Testing".
In the section on "What is Environmental Testing?", we would like to answer those who say, "I do environmental testing, but why are we doing it?" by giving a clear summary of the purposes, effectiveness, and standards of environmental testing.
In the section on "Temperature Testing", we would like to explain the effects and testing of temperature, which is known as the most important climatic-related environmental stress factor involved in the failure of parts and equipment.

2. An overview of environmental testing

  2.1 The purpose of environmental testing
  Evaluating the worth of manufactured goods is not limited to evaluating their function and performance.
•At what level can performance be maintained, and for how long? In other words, what is the product failure rate?
•How does performance change in response to the severity of the environment actually encountered?
That is to say, a crucial part of the worth of manufactured goods is in their quality.
  However, when quality defects occur after products have been put on the market, the cost is not limited to the significant amount that can be lost in the damages. The greatest loss is in the loss of reputation.
  To avoid such damages, quality must be confirmed before a product is put on the market. Environmental testing not only confirms quality through such tests as simulation testing and product life testing, it also can truly be called the indispensable prerequisite to quality assurance.
  Environmental testing can be broadly categorized, as shown in Fig. 1, into "Climatic (natural) environmental testing" and "Mechanical (causal) environmental testing" as well as a combination of the two, "Combined environmental testing". Climatic-related environmental testing deals with environmental factors such as pressure, humidity, and temperature, while mechanical environmental testing treats such factors as shock and vibration.

Fig 1 Types of environmental testing

Table 1 Environmental factors of climatic environmental testing and their major effects

Environment	Effects
Wind: Gusting and turbulence	Causes structural degradation and destruction, obstructs aircraft control functions, cools parts and surfaces at low wind speed, generates heat from friction at high wind speed, and causes functional failure due to invasion and adhesion of foreign matter.
Precipitation: Dew, frost, hail, rain, sleet, snow	Causes structural degradation and destruction, leaches heat from parts and structures, promotes corrosion, causes electrical failure, and damages protective film.
Sand and dust	Causes marring and abrasion of finished surfaces, increases surface friction, contaminates lubricants, clogs pipes, and promotes fatigue, cracking, and chipping of materials.
Atmospheric salt and brine spray	Conductivity of salt solution degrades insulation resistivity and promotes electrolytic etching and chemical corrosion of metals.
Humidity	Moisture invades porous substances, causes oxidation from conductance and corrosion between conductive materials, causes materials such as gaskets to swell, and extremely low humidity causes brittleness and granulation.
Solar radiation	Generates ozone, causes colors to fade, rubber to lose elasticity, and heat to rise inside containers, and results in heat-related aging.
High temperature	Causes changes in factors such as resistance, inductance, capacitance, power factors, and dielectric constants, destroys moving parts through softening and swelling of thermal insulation, causes finished surfaces to swell, causes parts to age through heat aging, promotes oxidation and chemical reactions, changes viscosity of and evaporates lubricants, and causes structural overloading due to physical expansion.
Low temperature	Embrittles and lowers flexibility of resin and rubber, changes electrical constants, causes moisture to freeze, increases viscosity of lubricants and causes gelling, increases heat loss, causes finished surfaces to crack, and causes structural overloading due to physical expansion.
Thermal shock	Causes permanent change in electrical performance, and sudden overloading of materials causes cracking and mechanical failure.
High or low pressure	Causes effects such as rupturing, exploding, and destruction of structures such as buildings, containers, and storage tanks, causes leakage of air-tight seals, causes damage due to internal bubbles forming, distorts flight characteristics of aircraft, missiles, and artillery shells, causes display errors in instruments such as altimeters, and changes electrical characteristics.
Gas	Promotes metal corrosion, degrades dielectric strength, creates explosive atmosphere, changes thermoelectric transfer characteristics, and promotes oxidation.

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