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This intermediate decomposes by the evolution of nitrogen gas forming the tertiary carbocation intermediate (3). Initial steps in the Buchner–Curtius–Schlotterbeck reaction mechanism The reaction is then completed either by the reformation of the carbonyl through an 1,2-rearrangement or by the formation of the epoxide.
Cyclic acetals are very much more stable against acid hydrolysis than acyclic acetals. Consequently acyclic acetals are used practically only when a very mild cleavage is required or when two different protected carbonyl groups must be differentiated in their liberation.
A yield criterion often expressed as yield surface, or yield locus, is a hypothesis concerning the limit of elasticity under any combination of stresses. There are two interpretations of yield criterion: one is purely mathematical in taking a statistical approach while other models attempt to provide a justification based on established ...
Metal forming operations result in situations exposing the metal workpiece to stresses of reversed sign. The Bauschinger effect contributes to work softening of the workpiece, for example in straightening of drawn bars or rolled sheets, where rollers subject the workpiece to alternate bending stresses, thereby reducing the yield strength and enabling greater cold drawability of the workpiece.
The relation can be plotted to determine the safe cyclic loading of a part; if the coordinate given by the mean stress and the alternating stress lies under the curve given by the relation, then the part will survive. If the coordinate is above the curve, then the part will fail for the given stress parameters. [7]
The yield strength or yield stress is a material property and is the stress corresponding to the yield point at which the material begins to deform plastically. The yield strength is often used to determine the maximum allowable load in a mechanical component, since it represents the upper limit to forces that can be applied without producing ...
In fluid dynamics, an isentropic flow is a fluid flow that is both adiabatic and reversible. That is, no heat is added to the flow, and no energy transformations occur due to friction or dissipative effects. For an isentropic flow of a perfect gas, several relations can be derived to define the pressure, density and temperature along a streamline.
S-N curve for a brittle aluminium with an ultimate tensile strength of 320 MPa. Materials fatigue performance is commonly characterized by an S-N curve, also known as a Wöhler curve. This is often plotted with the cyclic stress (S) against the cycles to failure (N) on a logarithmic scale. [31]