Patent Number: 
Section: claims

1. An apparatus for forming stress corrosion cracks in a tube specimen having two ends, comprising:a heating unit, provided on an outer surface of the tube specimen for generating a steam pressure in the tube specimen;an end holding unit for closing and sealing both open ends of the tube specimen so that the steam pressure is generated and maintained in the tube specimen, wherein the end holding unit comprises an upper plate and a lower plate for closing both ends of the tube specimen, and a plurality of tension bars disposed around the tube specimen, each of which including a hydraulic or pneumatic cylinder using hydraulic or pneumatic pressure as an operation pressure or an actuator rod using power to adjust a distance between the upper plate and the lower plate;a control unit for controlling the heating unit and the end holding unit; anda cooling unit connected to the lower plate so that the steam in the tube specimen is passed through the cooling unit having at least a predetermined length for phase transition of steam into water to lower temperature and pressure of the steam. 2. The apparatus as set forth in claim 1, wherein the heating unit comprises a direct heating coil having a heating wire which is heated using power. 3. The apparatus as set forth in claim 1, wherein the control unit comprises a steam temperature measuring sensor for measuring a temperature of the steam in the tube specimen, an etchant temperature measuring sensor for measuring a temperature of an etchant in the tube specimen, a pressure measuring sensor for measuring an inner pressure of the tube specimen, and a controller electrically connected to the pressure measuring sensor to receive detection signals and to selectively output control signals to the heating unit based on the received detection signals. 4. An apparatus for forming stress corrosion cracks in a tube specimen having two ends, comprising:a heating unit provided on an outer surface of the tube specimen for generating a steam pressure in the tube specimen;an end holding unit for closing and sealing both open ends of the tube specimen so that the steam pressure is generated and maintained in the tube specimen, wherein the end holding unit comprises an upper plate and a lower plate for closing both ends of the tube specimen, and a plurality of tension bars disposed around the tube specimen, each of which including a hydraulic or pneumatic cylinder using hydraulic or pneumatic pressure as an operation pressure;a control unit for controlling the heating unit and the end holding unit; anda cooling unit connected to the lower plate so that the steam in the tube specimen is passed through the cooling unit having at least a predetermined length for phase transition of steam into water to lower temperature and pressure of the steam. 5. The apparatus as set forth in claim 4, wherein the control unit comprises a steam temperature measuring sensor for measuring a temperature of the steam in the tube specimen, an etchant temperature measuring sensor for measuring a temperature of an etchant in the tube specimen, a pressure measuring sensor for measuring an inner pressure of the tube specimen, and a controller electrically connected to the pressure measuring sensor to receive detection signals and to selectively output control signals to the heating unit based on the received detection signals.