Offset yield strength Arbitrary approximation of elastic limit. It is the stress that corresponds to the point of intersection of a stress-strain diagram and a line parallel to the straight line portion of the diagram. Offset refers to the distance between the origin of the stress-strain diagram, and the point of intersection of the parallel line and the 0 stress axis. Offset is expressed in terms of strain (often 0.2%).
Open cell Cellular construction with cells that are generally interconnected. Among RMT architectures, an open cell void array is one in which each void is connected to other voids. These cells cannot hold a gas. Gas moves freely within and throughout the entire cellular structure.
Operating stress Stress imposed on a part in service.
Organic Designation of any chemical compound containing carbon with the exception of some of the simple compounds of carbon, such as carbon dioxide, which are frequently classified as inorganic compounds.
Orthogonal Angular, as in cubic angles; pertaining to or involving right angles or perpendiculars.
Overstressing Application of high fluctuating loads at the beginning of a fatigue test and lower loads toward the end. It is a means for speeding up a fatigue test.
Oxidation The addition of oxygen to a compound or the reduction of hydrogen.