What Does Compressive Stress Mean?
Compressive stress is a force that causes a material to deform to occupy a smaller volume. When a material is experiencing a compressive stress, it is said to be under compression. A high amount of compressive stress, such as tensile stress, leads to failure due to tension.
When compressive stress is applied to brittle materials, these materials can fracture from the sudden release of energy that was stored in the materials. On the other hand, when compressive stress is applied to ductile materials, they can often compress without sustaining damage. This is due to a calculated amount of compressive stress that structures and machines are built to withhold.
Assessing compressive stress is an essential feature in structural design, as materials tend to become shorter under different amounts of weight that may be applied to them. Calculating compressive stress ensures correct and safe building designs.
Coated substrates are known to corrode less rapidly as compressive stress is applied, although this also depends on what substance is used to coat the component.
Corrosionpedia Explains Compressive Stress
Compressive stress compresses a material by either crushing it or deforming it and ultimately causing it to fail during operation.
There are two types of materials that exist: ductile and brittle. Once solidified, concrete is a brittle material, and when such materials are subjected to compressive stress, they fracture because the stored energy in the material is suddenly released. Conversely, ductile materials will be squeezed into a smaller volume or will experience a slow distortion, but there will be no single point of failure.
Compressive stress has stress units - usually with negative values - to indicate the compaction that is being exerted. In geotechnical engineering, however, compressive stress has its units in positive values.
Compressive force is taken into consideration as well as how a material is used, and is an important function to consider in making structures that use stress for design and purpose. An arch, for instance, takes advantage of the compressive stress that is being exerted on the material between the columns in order to hold it and keep it stable. Thus, compressive stress is what makes these designs possible as well as ensuring stability in structures like bridges and cathedrals.
Compressive stress can lead to stress corrosion cracking (SCC), which is the growth of crack formation in a corrosive environment and can be observed in industrial settings. This occurrence can lead to sudden failure of metal alloys that are usually considered to be ductile but that are subjected to a tensile stress, with more drastic effects seen when this is done at elevated temperatures. It is highly specific chemically, considering that certain alloys are likely to undergo SCC only if exposed to certain chemical environments. Chemical environments that cause SCC in a given alloy are often the ones that are just mildly corrosive to the metal under normal conditions.
Compressive stresses are at times desirable within structural joints in an attempt to reduce the risk of structural failure from tensile stresses within the adhesive.
Residual stresses are important because they affect material performance. Fatigue cracking is one of the primary failure modes for many structures and components, particularly in the automotive industry. Compressive residual stress can have a very positive impact on fatigue performance because it acts to resist the applied tensile stress and tends to close the crack , thus increasing fatigue life.
To take advantage of this concept, many compressive residual stress surface treatments have been developed. For example, shot peening, laser shock peening, and cold expansion are used to apply compressive residual stress, which can significantly improve the fatigue life of components. Shot peening of automotive springs is a common example to improve the fatigue life of this highly stressed component.