A torsion pendulum facility for a ground-based performance test of the inertial sensor for ASTROD-1 has been constructed. The twist motion of the test mass is monitored and servo-controlled. The sensitivity of the electrostatic servo-controlled actuator is calibrated based on the elastic torque of the torsion fibre, and the torque resolution of the servo-controlled torsion pendulum comes to 2 × 10−11 N m Hz−1/2 from 1 mHz to 0.1 Hz, which is likely limited by the seismic noise, electronic noise and the cross coupling between the translation and twist modes.

Hull structure has sharp corners with singularity which tends to produce fatigue cracks and cause structural damages. Its not straightforward to assess FE analysis results of stiffened plating structures because of the stress singularities that are inherent in the overall geometry. This paper concentrates on the analysis of a simple planar right angled cruciform corner and a 135-degree sheet corner through a series of FE analyses using ANSYS. The aim is to try and provide an understanding of the nature of the singularities. Through the understanding a simple method is proposed to estimate the singular stress at the corners using as named as singularity strength which is based on notch-stress intensity factor theory. Finally the estimation methods of as are given for the 2D corners.

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