Publications

Abstract not provided.

Abstract not provided.

Abstract not provided.

This work extends recent methods to calculate dynamic substructuring predictions of a weakly nonlinear structure using nonlinear pseudo-modal models. In previous works, constitutive joint models (such as the modal Iwan element) were used to capture the nonlinearity of each subcomponent on a mode-by-mode basis. This work uses simpler polynomial stiffness and damping elements to capture nonlinear dynamics from more diverse jointed connections including large continuous interfaces. The proposed method requires that the modes of the system remain distinct and uncoupled in the amplitude range of interest. A windowed sinusoidal loading is used to excite each experimental subcomponent mode in order to identify the nonlinear pseudo-modal models. This allows for a higher modal amplitude to be achieved when fitting these models and extends the applicable amplitude range of this method. Once subcomponent modal models have been experimentally extracted for each mode, the Transmission Simulator method is implemented to assemble the subcomponent models into a nonlinear assembled prediction. Numerical integration methods are used to evaluate this prediction compared to a truth test of the nonlinear assembly.

Abstract not provided.

Abstract not provided.

Abstract not provided.

In the aerospace industry, hail strikes on a structure are an environment that must be considered when qualifying a product. Performing a physical test on a product would require a test setup that would launch a fabricated hail stone at an expensive prototype. This test may be difficult or impossible to execute and destructive to the product. Instead of testing, a finite element model (FEM) may be used to simulate the damage and consequences of a hail strike. In order to use a FEM in this way, an accurate representation of the input force from a hail stone must be known. The purpose of this paper is to calculate the force that a hail stone imparts on an object using the inverse method SWAT-TEEM. This paper discusses the advantages of using SWAT-TEEM over other force identification methods and exercises the algorithm for a test series of hail strikes that include multiple angles of attack and multiple velocities which include speeds that are supersonic.

During an environment, it is desirable to know the forces or inputs on the system of interest. With the inputs, one can directly use a finite element or experimental model to predict responses not measured in a field test. One can attempt to measure point forces using force gauges, however, these gauges are insufficient due to the inability to place a gauge at a forcing interface or to measure a force applied over an area. SWAT (Sum of weighted acceleration technique) is a method that uses mode shapes as a modal filter with measured accelerations and to solve the inverse problem and calculate the forces and moments on the system. This paper will examine an application where the use of a force gauge is impossible due to the external forces being applied over an area. The paper will calculate the sum of the forces and moments imparted on the system and will use a finite element model to check the plausibility of the calculated forces.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.