Study of Correlation Criteria for Base Excitation of Spacecraft Structures

Use of Base Force Assurance Criterion for Spacecraft Structure Model Correlation

“…It is considered that, if the mathematical model meets the threshold values specified by the different agencies for these correlation checks, the model is fit for the purpose [8,9]; otherwise, the model needs to be updated. However, it is demonstrated using synthetic experimental results that the MAC and NCO check are not adequate for ensuring the quality of the FEMs to predict the forced response characteristics [10,11]. The frequency response correlation methods, such as the frequency response assurance criterion (FRAC) [12] and the frequency domain assurance criterion (FDAC) [13], have limited application in complex structures where hundreds of frequency responses need to be monitored; hence, their correlation will be a tedious task.…”

“…Generally, sine excitation tests are used to qualify the aerospace structures, and the transmitted force and moments are analytically computed using the Craig-Bampton method [14]. To analyze the accuracy of the FEM to predict the response characteristics under the base excitation, the base force assurance criterion (BFAC) is introduced by comparing the nominal and predicted transmitted force to the base [11]. The main advantage of the BFAC is that, using a single correlation index for each direction of excitation, the forced response characteristics of the base excited structure can be evaluated.…”

Correlation of finite element models of multi-physics systems

“…[27] that BFAC can correlate the forced dynamic characteristics of lightly damped (less than 2 percent critical damping) spacecraft under base excitation. To calculate the BFAC, the base force under a harmonic excitation of 1g (where g is the acceleration due to gravity, 9.81 m s À 2 ) in the Z direction at the base node for all the models has been determined using a MATLAB [36] program.…”

“…To calculate the BFAC, the base force under a harmonic excitation of 1g (where g is the acceleration due to gravity, 9.81 m s À 2 ) in the Z direction at the base node for all the models has been determined using a MATLAB [36] program. Then BFAC is calculated using the equation [27] where P is the absolute value of the transmitted forces to the base obtained using the nominal FEM and F is the corresponding absolute value obtained from the erroneous FEMs and the subscripts j and k vary from 1 to 6 for a statically determinate structure. Here, it should be noted that both P and F are functions of frequency and each of these parameters contains six columns; the first three are the forces in each of the axes and the last three columns correspond to the moments.…”

“…The effect of damping on the MAC is analyzed using the complex modes of the system. The recently introduced base force assurance criterion (BFAC) [27] is applied to correlate the viscoelastic systems. Also the effect of temperature on the MAC and NCO is studied using the viscoelastic systems.…”