Flange height and lip accuracy are generally restricted by the formability of sheet metals in the conventional hole-flanging operation. A new hole-flanging process, named upsetting-flanging process, was proposed to ob...Flange height and lip accuracy are generally restricted by the formability of sheet metals in the conventional hole-flanging operation. A new hole-flanging process, named upsetting-flanging process, was proposed to obtain a more substantial flange from thick plate. The finite element method （FEM） with DEFORM was utilized to simulate the novel upsetting-flanging process and the influence of geometric parameters on the flange height was studied in details. A series of flanging experiments with A1050P-O were carried out to validate the FEM results, and the variations of Vicker hardness in the plate section were discussed. The results showed that the newly upsetting-flanging process revealed higher flange height and better lip accuracy than the conventional hole-flanging process, and the results between FEM simulations and experiments showed good agreement. Besides, the hardness of the plate around the flange part increases due to the work hardening after the upsetting-flanging process, which reveals better superiority in strength for the subsequent machining or assembling processes.展开更多
Curling results from the temperature differential across the concrete slab thickness and may induce undue stresses in newly placed slab. This study deals with the finite element （FE） analysis of curling, curling str...Curling results from the temperature differential across the concrete slab thickness and may induce undue stresses in newly placed slab. This study deals with the finite element （FE） analysis of curling, curling stresses, field measurement of curling on a newly built jointed plain concrete pavement, and comparison of its long-term performance using both Mechanistic-Empirical Pavement Design Guide （MEPDG） and HIPERPAVII software. The FE analysis was performed with a software program, ANSYS. The test section was modeled as a three-layer system with 300 mm concrete slab, 100 mm treated drainable base, and 150 mm lime-treated subgrade. All layers were assumed to be linear elastic. Temperature data was collected at five different depth locations across the concrete slab with digital data loggers. Curling was measured on five different days with a simple setup. The effect of temperature nonlinearities across the slab thickness was also examined. The results show that both upward and downward curling increase as the temperature differential increases. The maximum stress resulting from the combined effect of curling and traffic loading due to positive temperature differential is higher than that due to the negative temperature differential of the same magnitude. Since temperature differential has a significant influence on curling, both curling and curling stresses can be mitigated at an early age with temperature control, namely via enhanced curing. Both MEPDG and HIPERPAVII showed approximately the same performance for the PCC thickness ranging from 215 mm to 300 mm for this project. Performance prediction from HIPERPAVII is very sensitive to the change in PCC thickness less than 230 mm whereas MEPDG prediction is not as sensitive to the thickness change as with HIPERPAV 1I.展开更多
基金Project(51175445)supported by the National Natural Science Foundation of ChinaProject(2010DFA52130)supported by the International Cooperation Project of the Ministry of Science and Technology,ChinaProject(CX2013B277)supported by Hunan Provincial Innovation Foundation for Postgraduate,China
文摘Flange height and lip accuracy are generally restricted by the formability of sheet metals in the conventional hole-flanging operation. A new hole-flanging process, named upsetting-flanging process, was proposed to obtain a more substantial flange from thick plate. The finite element method （FEM） with DEFORM was utilized to simulate the novel upsetting-flanging process and the influence of geometric parameters on the flange height was studied in details. A series of flanging experiments with A1050P-O were carried out to validate the FEM results, and the variations of Vicker hardness in the plate section were discussed. The results showed that the newly upsetting-flanging process revealed higher flange height and better lip accuracy than the conventional hole-flanging process, and the results between FEM simulations and experiments showed good agreement. Besides, the hardness of the plate around the flange part increases due to the work hardening after the upsetting-flanging process, which reveals better superiority in strength for the subsequent machining or assembling processes.
文摘Curling results from the temperature differential across the concrete slab thickness and may induce undue stresses in newly placed slab. This study deals with the finite element （FE） analysis of curling, curling stresses, field measurement of curling on a newly built jointed plain concrete pavement, and comparison of its long-term performance using both Mechanistic-Empirical Pavement Design Guide （MEPDG） and HIPERPAVII software. The FE analysis was performed with a software program, ANSYS. The test section was modeled as a three-layer system with 300 mm concrete slab, 100 mm treated drainable base, and 150 mm lime-treated subgrade. All layers were assumed to be linear elastic. Temperature data was collected at five different depth locations across the concrete slab with digital data loggers. Curling was measured on five different days with a simple setup. The effect of temperature nonlinearities across the slab thickness was also examined. The results show that both upward and downward curling increase as the temperature differential increases. The maximum stress resulting from the combined effect of curling and traffic loading due to positive temperature differential is higher than that due to the negative temperature differential of the same magnitude. Since temperature differential has a significant influence on curling, both curling and curling stresses can be mitigated at an early age with temperature control, namely via enhanced curing. Both MEPDG and HIPERPAVII showed approximately the same performance for the PCC thickness ranging from 215 mm to 300 mm for this project. Performance prediction from HIPERPAVII is very sensitive to the change in PCC thickness less than 230 mm whereas MEPDG prediction is not as sensitive to the thickness change as with HIPERPAV 1I.
