The slitting process for manufacturing REBa2Cu3O7δ(REBCO,RE=Rare earth)tapes of required width significantly improves the production efficiency and reduces production costs.However,edge cracks induced by the slittin...The slitting process for manufacturing REBa2Cu3O7δ(REBCO,RE=Rare earth)tapes of required width significantly improves the production efficiency and reduces production costs.However,edge cracks induced by the slitting process of wide REBCO tapes may cause premature degradation under high tensile stress in highfield magnets.Therefore,it is necessary to evaluate the effect of edge cracks of REBCO tapes on the critical current(Ic)degradation.Firstly,Ic degradation under artificial cracks was measured to validate the applicability of linear elastic fracture mechanics for the REBCO layer.The maximum circumferential stress criterion was used to derive the mixed-mode stress intensity factor of multiple oblique edge cracks.A semi-analytical model considering edge crack properties such as angleβ,spacing d,and length a,was built to evaluate the critical load and critical crack.We found that when the stress intensity factor at the crack tip is below KIC?2:3 MPa ffiffiffiffim p,edge cracks did not propagate.We examined commercial REBCO tapes manufactured by two different processes,concluding that edge cracks in these tapes will not cause premature degradation.展开更多
On the basis of a potential theory and Euler-Bernoulli beam theory, an analytical solution for oblique wave scattering by a semi-infinite elastic plate with finite draft floating on a step topography is developed usin...On the basis of a potential theory and Euler-Bernoulli beam theory, an analytical solution for oblique wave scattering by a semi-infinite elastic plate with finite draft floating on a step topography is developed using matched eigenfunction expansions. Different from previous studies, the effects of a wave incident angle, a plate draft, three different plate edge conditions （free, simply supported and built-in） and a sea-bottom topography are all taken into account. Moreover, the plate edge conditions are directly incorporated into linear algebraic equations for determining unknown expansion coefficients in velocity potentials, which leads to a simple and efficient solving procedure. Numerical results show that the convergence of the present solution is good, and an energy conservation relation is well satisfied. Also, the present predictions are in good agreement with known results for special cases. The effects of the wave incident angle, the plate draft, the plate edge conditions and the sea-bottom topography on various hydrodynamic quantities are analyzed. Some useful results are presented for engineering designs.展开更多
By adopting an equivalent geometry model of machining process and considering thermo-plastic properties of the work material, a finite element method(FEM) to study oblique milling process of aluminum alloy with a doub...By adopting an equivalent geometry model of machining process and considering thermo-plastic properties of the work material, a finite element method(FEM) to study oblique milling process of aluminum alloy with a double-edge tool was presented. In the FEM, shear flow stress was determined by material test. Re-meshing technology was used to represent chip separation process. Comparing the predicted cutting forces with the measured forces shows the 3D FEM is reasonable. Using this FEM, chip forming process and temperature distribution were predicted. Chips obtained by the 3D FEM are in spiral shape and are similar to the experimental ones. Distribution and change trend of temperature in the tool and chip indicate that contact length between tool rake face and chip is extending as tool moving forward. These results confirm the capability of FEM simulation in predicting chip flow and selecting optimal tool.展开更多
基金the Strategic Priority Research Program of Chinese Academy of Sciences under Grant No.XDB25000000the National Natural Science Foundation of China under Grant No.52007089.
文摘The slitting process for manufacturing REBa2Cu3O7δ(REBCO,RE=Rare earth)tapes of required width significantly improves the production efficiency and reduces production costs.However,edge cracks induced by the slitting process of wide REBCO tapes may cause premature degradation under high tensile stress in highfield magnets.Therefore,it is necessary to evaluate the effect of edge cracks of REBCO tapes on the critical current(Ic)degradation.Firstly,Ic degradation under artificial cracks was measured to validate the applicability of linear elastic fracture mechanics for the REBCO layer.The maximum circumferential stress criterion was used to derive the mixed-mode stress intensity factor of multiple oblique edge cracks.A semi-analytical model considering edge crack properties such as angleβ,spacing d,and length a,was built to evaluate the critical load and critical crack.We found that when the stress intensity factor at the crack tip is below KIC?2:3 MPa ffiffiffiffim p,edge cracks did not propagate.We examined commercial REBCO tapes manufactured by two different processes,concluding that edge cracks in these tapes will not cause premature degradation.
基金The National Natural Science Foundation of China under contract Nos 51490675,51322903 and 51279224
文摘On the basis of a potential theory and Euler-Bernoulli beam theory, an analytical solution for oblique wave scattering by a semi-infinite elastic plate with finite draft floating on a step topography is developed using matched eigenfunction expansions. Different from previous studies, the effects of a wave incident angle, a plate draft, three different plate edge conditions （free, simply supported and built-in） and a sea-bottom topography are all taken into account. Moreover, the plate edge conditions are directly incorporated into linear algebraic equations for determining unknown expansion coefficients in velocity potentials, which leads to a simple and efficient solving procedure. Numerical results show that the convergence of the present solution is good, and an energy conservation relation is well satisfied. Also, the present predictions are in good agreement with known results for special cases. The effects of the wave incident angle, the plate draft, the plate edge conditions and the sea-bottom topography on various hydrodynamic quantities are analyzed. Some useful results are presented for engineering designs.
文摘By adopting an equivalent geometry model of machining process and considering thermo-plastic properties of the work material, a finite element method(FEM) to study oblique milling process of aluminum alloy with a double-edge tool was presented. In the FEM, shear flow stress was determined by material test. Re-meshing technology was used to represent chip separation process. Comparing the predicted cutting forces with the measured forces shows the 3D FEM is reasonable. Using this FEM, chip forming process and temperature distribution were predicted. Chips obtained by the 3D FEM are in spiral shape and are similar to the experimental ones. Distribution and change trend of temperature in the tool and chip indicate that contact length between tool rake face and chip is extending as tool moving forward. These results confirm the capability of FEM simulation in predicting chip flow and selecting optimal tool.
