Final answer:
Stress concentrations can be created by thermal expansion or contraction and stiffness irregularities.
Step-by-step explanation:
Stress concentrations can be created by thermal expansion or contraction and stiffness irregularities.
In the case of thermal stress, it is created by the expansion or contraction of a material due to changes in temperature. This can lead to concentrations of stress in certain areas.
Stiffness irregularities can also create stress concentrations. When a structure has variations in stiffness, such as areas that are stiffer or more rigid than others, it can result in localized stress concentrations.