Description: Abaqus/Standard issues an error message by default if the global mass matrix is singular for dynamics models with an application-type setting of “transient fidelity.” The global mass matrix is affected by material densities, concentrated masses and rotary inertias, and nonstructural mass. A singular global mass matrix is most commonly due to omitting specification of inertia properties. A warning message is also issued if a density definition is omitted for any materials in a dynamic analysis. Other more subtle causes of a singular global mass matrix include the density being zero for certain values of temperature or field variables and unconstrained degrees of freedom at massless nodes that are connected to other nodes by constraints.