No abstract

No abstract

The ideal pinhole imaging model commonly assumed for an ordinary two-dimensional digital image correlation (2D-DIC) system is neither perfect nor stable because of the existence of small out-of-plane motion of the test sample surface that occurred after loading, small out-of-plane motion of the sensor target due to temperature variation of a camera and unavoidable geometric distortion of an imaging lens. In certain cases, these disadvantages can lead to significant errors in the measured displacements and strains. Although a high-quality bilateral telecentric lens has been strongly recommended to be used in the 2D-DIC system as an essential optical component to achieve high-accuracy measurement, it is not generally applicable due to its fixed field of view, limited depth of focus and high cost. To minimize the errors associated with the imperfectness and instability of a common 2D-DIC system using a low-cost imaging lens, a generalized compensation method using a non-deformable reference sample is proposed in this work. With the proposed method, the displacement of the reference sample rigidly attached behind the test sample is first measured using 2D-DIC, and then it is fitted using a parametric model. The fitted parametric model is then used to correct the displacements of the deformed sample to remove the influences of these unfavorable factors. The validity of the proposed compensation method is first verified using out-of-plane translation, out-of-plane rotation, in-plane translation tests and their combinations. Uniaxial tensile tests of an aluminum specimen were also performed to quantitatively examine the strain accuracy of the proposed compensation method. Experiments show that the proposed compensation method is an easy-to-implement yet effective technique for achieving high-accuracy deformation measurement using an ordinary 2D-DIC system.

Measurements of complete and incomplete fusion cross sections for 6 Li+ 154 Sm have been performed at energies above the Coulomb barrier by the online γ -ray method, to investigate the effect of breakup and inelastic couplings on the complete fusion (CF) of this weakly bound system. We show that inelastic excitation couplings have non-negligible effects, when compared with the breakup effect, for deformed nuclei at energies very close to the Coulomb barrier. The average CF suppression corresponding to dynamic breakup effects was found to be around 35%. The total fusion cross section is not affected by the breakup coupling. A comparison between the 6 Li-induced CF suppression for three different samarium isotopes shows that the breakup effect is larger for the more spherical isotope.

No abstract