| 主权项 |
1. Process for strengthening a sheet, the process comprising:
cooling a sheet comprising a material, the sheet having first and second sheet surfaces, the material having a transition temperature, the sheet being at a temperature greater than the transition temperature at the start of the cooling, wherein the cooling is performed:
a. positioning the first sheet surface adjacent to a first heat sink surface with a first gap between the first sheet surface and the first heat sink surface such that thermal conduction from the first sheet surface to the first heat sink surface occurs, the first gap having a length across the first gap of g1 and an area of the first gap of Ag1,b. positioning the second sheet surface adjacent to a second heat sink surface with a second gap between the second sheet surface and the second heat sink surface such that thermal conduction from the second sheet surface to the second heat sink surface occurs, the second gap having a length across the second gap of g2 and an area of the second gap of Ag2,c. providing a first flow of a first gas to the first gap and providing a second flow of a second gas to the second gap, the first gas having a heat capacity Cp1 and a thermal conductivity k1, the second gas having a heat capacity Cp2 and a thermal conductivity k2, the flow provided at a mass flow rate {dot over (m)}1 of the first gas, wherein {dot over (m)}1 is greater than zero and less than (2k1Ag1)/(g1Cp), to the first gap, and at a mass flow rate {dot over (m)}2 of the second gas, wherein {dot over (m)}2 is greater than zero and less than (2k2Ag2)/(g2Cp2), to the second gap, whereby the first and second flows contact the sheet, and the sheet is cooled, by conduction more than by convection,d. sufficiently to create a surface compressive stress and a central tension of the sheet. |
