sisäjännitykset

Sisäjännitykset refer to stresses that exist within a material or structure without any external forces being applied. These stresses can arise from various sources during the manufacturing process, such as rapid cooling, welding, or plastic deformation. They can also develop over time due to environmental factors like temperature fluctuations or humidity changes.

In metals, internal stresses can be a consequence of processes like quenching, where rapid cooling creates differential cooling rates and thus localized stresses. For plastics, internal stresses can be locked in during molding due to uneven cooling or pressure. In construction, concrete can develop internal stresses from shrinkage as it cures.

These internal stresses can have significant implications. They can reduce a material's strength, making it more susceptible to cracking or failure under load. In some cases, internal stresses can lead to spontaneous fracture, especially in brittle materials. Conversely, carefully controlled internal stresses can sometimes be beneficial, for example, in creating compressive stresses on the surface of tempered glass to improve its resistance to impact.

Understanding and managing internal stresses is crucial in many engineering applications to ensure the safety and durability of products and structures. Techniques like stress relieving heat treatments or controlled annealing are often employed to reduce or redistribute these internal forces.