Rigid materials such as metals, concrete, or rocks sustain large forces while undergoing little deformation, but if sufficiently large forces are applied, the materials can no longer sustain them by elastic deformation alone.
What happens then depends upon the internal structure of the material.
Some might experience flow while engaging in a sport such as skiing, tennis, soccer, dancing, or running.
Others might have such an experience while engaged in an activity such as painting, drawing, or writing.
"Flow also happens when a person's skills are fully involved in overcoming a challenge that is just about manageable, so it acts as a magnet for learning new skills and increasing challenges," Csíkszentmihályi explains.
In his book, Csíkszentmihályi explains that flow is likely to occur when an individual is faced with a task that has clear goals that require specific responses.As greater and greater force is applied to a brittle substance, such as a block of rock or concrete, a point will be reached at which the internal structure can no longer sustain the applied load by elastic deformation alone.Thereupon, the specimen will quite suddenly For a ductile material, such as mild steel or aluminum, after the initial period of elastic deformation, the same critical point—the specimen’s limit of elastic deformability—is reached.These internal shearing forces produce the characteristic behaviour of liquids such as treacle, heavy oils, or molten plastics.This characteristic motion, known as shearing flow, is an energy-dissipative process.