Resistance to cold
Under cold resistance refers to the resistance of materials, components and technical products to low temperatures. Many material properties change depending on the temperature. If the temperature falls below the so-called lower usage temperature, there is a risk that a material or the object consisting of it no longer has the properties required for the application.
Typical effects that can occur at low temperatures are:
- Embrittlement : Some materials such as B. some steels have a temperature-dependent toughness . Below a transition temperature they become brittle (so-called cold embrittlement ), which can lead to fractures if the design does not take this into account. Plastics also have a glass transition temperature below which the material changes from a soft to a brittle, glass-like state. The cause of the Challenger disaster was, for example, an elastomer seal that lost its elasticity and thus its sealing effect as a result of too low ambient temperatures.
- Heat shrinkage : If an object contracts too much when it cools down, it may no longer be able to fulfill its function. Components made of materials with different coefficients of expansion are particularly critical. Here, due to the varying degrees of contraction, thermal stresses and thus cracks can occur.
- Changes in liquids: liquids can freeze at low temperatures, the viscosity usually increases with decreasing temperature and flocculation can occur. All of these problems occur, for example, when motor vehicles are used in winter. If there is insufficient antifreeze, the cooling water freezes; thick engine oils (summer oils) have an insufficient lubricating effect at low temperatures due to their high viscosity (see viscosity or SAE classes ) and if winter diesel is not used , the fuel filter may clog due to flocculation.
- Influence on electrical and electrochemical components: A typical example is the starter battery of a vehicle which no longer has sufficient capacity in winter because the electrochemical processes are impaired by the low temperature. The electrical resistance of materials also changes with temperature, which is why electrical components and circuits can malfunction at extreme temperatures.
The resistance to cold or the lower operating temperature is usually specified in the relevant technical documentation, data sheets, standards, etc. It must be observed when selecting and using a material, component or product.