The stress-strain curve unravels the behavior of steel bars when subjected to varying loads. This insightful representation is crafted through testing steel specimens. The process involves gradually pulling a steel specimen through a testing machine until it reaches its breaking point, recording stress and corresponding strains throughout the journey.
Upon plotting stresses on the vertical axis and corresponding strains on the horizontal axis, the stress-strain curve takes shape. This curve encapsulates the distinct phases a steel specimen undergoes before reaching fracture, offering key insights into the response of steel bars under different loads.
The stress-strain curve is marked by critical points that signify different stages in the behavior of steel specimens. Understanding these stages is vital for comprehending how steel bars respond to external forces.
In this initial phase, depicted from the starting point to “A” on the curve, low stress is applied, generating no permanent strain. The stress and strain exhibit proportionality, allowing the steel bar to regain its original shape upon stress removal.
Positioned between points “A” and “B,” this stage introduces elastic strain as the stress on the steel specimen increases. Stress and strain cease to be proportional, marking a departure from the elastic behavior.
Represented by point “B,” the yield point is pivotal in the design context. It is considered the failure point in the design of reinforced concrete structures. Beyond this point, the steel bar experiences plastic deformation, where stress and strain are no longer proportional. Points “B” and “C” signify the upper and lower yield points, respectively.
Progressing beyond the yield point, strain hardening occurs from point “C” to “D.” This phase brings about changes in the atomic and crystalline structure of the material, enhancing its resistance to further deformation. Point “D” represents the ultimate strength or tensile strength.
The rupture strength, also known as breaking strength, is observed at point “E” on the stress-strain diagram. This marks the point of material rupture.
Understanding the stress-strain curve is essential for gauging how steel bars behave under different loads. Each phase on the curve offers valuable insights into the material’s response, aiding in the design and assessment of structures.