초록 ▼

Disclosed herein is an apparatus for measuring residual stress, methods of measuring residual stress data and residual stress using the apparatus, and a recording medium for storing software of the residual stress measuring method. The present invention is advantageous for evaluation of a mechanical

Disclosed herein is an apparatus for measuring residual stress, methods of measuring residual stress data and residual stress using the apparatus, and a recording medium for storing software of the residual stress measuring method. The present invention is advantageous for evaluation of a mechanical material property and is non-destructive. Further, the present invention is widely applied to fields ranging from a microscopic area, such as a thin film or micro device, to a large-sized structure, and is not influenced by a microstructure by controlling the range of an applied load. Further, the measuring apparatus of the present invention is minimized in its volume to be easily attached to an actual structure. Further, in the present invention, various attaching devices are employed, thus enabling the apparatus to be attached to various materials regardless of the size and type of object materials to measure residual stress. Further, the measuring apparatus of the present invention is horizontally movable, so there is no need to move an apparatus body itself so as to take measurements at several positions of several materials. Further, the present invention does not require separate measurements for correcting experimental constants at the time of analyzing measured data.

대표청구항 ▼

1. An apparatus for measuring residual stress, comprising:a main body; a load applying device installed within the main body to generate a load applied to a material to be measured; a load sensor for continuously measuring variation of the load applied to the material by the load applying device; an

1. An apparatus for measuring residual stress, comprising:a main body; a load applying device installed within the main body to generate a load applied to a material to be measured; a load sensor for continuously measuring variation of the load applied to the material by the load applying device; an indenter holder connected to the load applying device and coaxially driven together with the load sensor; an indenter provided with a first end coupled with the indenter holder and a second end coming into contact with the material to apply the load generated by the load applying device to the material; a displacement sensor for continuously measuring variation of an indentation depth according to indentation of the indenter; an interface computer provided with a measurement program for measuring residual stress on the basis of values measured by the load sensor and the displacement sensor; an attaching device used to fix the material to be measured to the residual stress measuring apparatus, the attaching device being at least on of a magnet, a chain and a U-block; and a horizontal moving device for horizontally moving the main body with the indenter attached thereto in at least one direction after the attaching device is fixed to the residual stress measuring apparatus. 2. The residual stress measuring apparatus according to claim 1, wherein the horizontal moving device comprises:a slider base connected to a base supporting the main body on an upper surface of the base and provided with a dovetail groove formed in an upper portion of the slider base; a slider disposed between the slider base and the main body to be slidably interlocked with the slider base in a dovetail shape; and a moving handle for horizontally moving the slider on the slider base in at least one direction. 3. A method of measuring residual stress data of a material using a residual stress measuring apparatus, the apparatus comprising:a main body; a load applying device installed within the main body to generate a load applied to a material to be measured; a load sensor for continuously measuring variation of the load applied to the material by the load applying device; an indenter holder connected to the load applying device and coaxially driven together with the load sensor; an indenter provided with a first end coupled with the indenter holder and a second end coming into contact with the material to apply the load generated by the load applying device to the material; a displacement sensor for continuously measuring variation of an indentation depth according to indentation of the indenter; and an interface computer provided with a measurement program for measuring residual stress on the basis of values measured by the load sensor and the displacement sensor, the method of measuring comprising the steps of: a) moving the indenter to a position where a residual stress experiment can be started to allow the indenter to approach the material; b) setting a movement speed and a movement distance of the indenter and applying the load to the material; c) vertically moving the indenter by the set movement depth of the indenter and then moving the indenter upward by a certain load removal ratio of the movement distance of the indenter; d) measuring an indentation depth and an indentation load of the indenter according to the vertical movement of the indenter, simultaneously with performance of steps b) and c); e) repeatedly performing the steps b), c) and d) a plurality of times; f) removing the indenter from the material; and g) calculating residual stress of the material. 4. The residual stress data measuring method according to claim 3, wherein the step b) comprises the steps of:b1) moving the indenter downward; and b2) stopping the downward movement of the indenter and moving the indenter upward by a distance set value if the indentation load is greater than or equal to a load set value, and continuously performing the step b1) if the indentation load is less than the load set value. 5. The residual stress data measuring method according to claim 4, wherein the load set value is 0.01 to 2 kgf, and the distance set value is 0.1 to 30 μm.6. The residual stress data measuring method according to claim 3, wherein the step g) is performed before or after the step f) is executed.7. The residual stress data measuring method according to claim 3, wherein the step e) is performed in such a way that at least one of the movement speed of the indenter, the movement distance of the indenter and the load removal ratio can be varied in each experiment step.8. A method of measuring residual stress of a material using a residual stress measuring apparatus, the apparatus comprising:a main body; a load applying device installed within the main body to generate a load applied to a material to be measured; a load sensor for continuously measuring variation of the load applied to the material by the load applying device; an indenter holder connected to the load applying device and coaxially driven together with the load sensor; an indenter provided with a first end coupled with the indenter holder and a second end coming into contact with the material to apply the load generated by the load applying device to the material; a displacement sensor for continuously measuring variation of an indentation depth according to indentation of the indenter; and an interface computer provided with a measurement program for measuring residual stress on the basis of values measured by the load sensor and the displacement sensor, the method comprising the steps of: a) moving the indenter downward to a position where an indentation experiment can be started, stopping the downward movement of the indenter and moving the indenter upward by a distance set value if an indentation load is greater than or equal to a load set value, and continuously moving the indenter downward, if the indentation load is less than the load set value; b) setting a movement speed and a movement distance of the indenter and applying the load to the material; c) vertically moving the indenter downward by the set movement distance of the indenter and then moving the indenter upward by a certain load removal ratio of the movement distance of the indenter; d) measuring an indentation depth and an indentation load of the indenter according to the vertical movement of the indenter through the steps b) and c); e) repeatedly performing the steps b), c) and d) a plurality of times; f) measuring residual stress of the material by comparing measurement equations of a reference sample and the measured material with each other; and g) removing the indenter from the material. 9. A recording medium for storing software of a method of measuring residual stress of a material using a residual stress measuring apparatus, the apparatus comprising:a main body; a load applying device installed within the main body to generate a load applied to a material to be measured; a load sensor for continuously measuring variation of the load applied to the material by the load applying device; an indenter holder connected to the load applying device and coaxially driven together with the load sensor; an indenter provided with a first end coupled with the indenter holder and a second end coming into contact with the material to apply the load generated by the load applying device to the material; a displacement sensor for continuously measuring variation of an indentation depth according to indentation of the indenter; and an interface computer provided with a measurement program for measuring residual stress on the basis of values measured by the load sensor and the displacement sensor, the recording medium comprising: indenter approaching means for moving the indenter downward to a position where an indentation experiment can be started, stopping the downward movement of the indenter and moving the indenter upward by a distance set value if an indentation load is greater than or equal to a load set value, and continuously moving the indenter downward if the indentation load is less than the load set value; load applying means for setting a movement speed and a movement distance of the indenter and applying the load to the material; load removing means for vertically moving the indenter down by the set movement distance of the indenter and then moving the indenter upward by a certain load removal ratio of the movement distance of the indenter; measuring means for measuring an indentation depth and an indentation load of the indenter according to the vertical movement of the indenter through the load applying means and the load removing means; continuous measuring means for repeatedly performing operations of the load applying means, the load removing means and the measuring means a plurality of times; indenter removing means for removing the indenter from the material; and means for measuring residual stress of the material by comparing measurement equations of a reference sample and the measured material with each other. 10. An apparatus for measuring residual stress with a main body and a load applying device installed within the main body to generate a load applied to a material to be measured, comprising:a load sensor for continuously measuring variation of the load applied to the material by the load applying device; an indenter holder connected to the load applying device and coaxially driven together with the load sensor; an indenter provided with a first end coupled with the indenter holder and a second end coming into contact with the material to apply the load generated by the load applying device to the material; a displacement sensor for continuously measuring variation of an indentation depth according to indentation of the indenter; an interface computer provided with a measurement program for measuring residual stress on the basis of values measured by the load sensor and the displacement sensor and with one or more control buttons for controlling the load applying device; an attaching device used to fix the material to be measured to the residual stress measuring apparatus, the attaching device being at least one of a magnet, a chain and a U-block; and a horizontal moving device for horizontally moving the main body with the indenter attached thereto in at least one direction after the attaching device is fixed to the residual stress measuring apparatus; and wherein the measurement program measures the variations of the load and the indentation depth by allowing the indenter to approach the material to apply the load to the material by an operation of any one of the control buttons and removing the applied load, and further calculates residual stress by continuously measuring the variations of the load and the indentation depth. 11. The residual stress measuring apparatus according to claim 10, wherein the horizontal moving device comprises:a slider base connected to a base supporting the main body on an upper surface of the base and provided with a dovetail groove formed in an upper portion of the slider base; a slider disposed between the slider base and the main body to be slidably interlocked with the slider base in a dovetail shape; and a moving handle for horizontally moving the slider on the slider base in at least one direction. 12. The residual stress measuring apparatus according to claim 10, wherein the indenter is formed in at least one shape of a sphere, a cone and a square pyramid, and is integrated with the indenter holder.13. The residual stress measuring apparatus according to claim 11, wherein the indenter is formed in at least one shape of a sphere, a cone and a square pyramid, and is integrated with the indenter holder.14. A method of measuring residual stress data of a material using the residual stress measuring apparatus of claim 10, comprising the steps of:a) moving the indenter to a position where a residual stress experiment can be started to allow the indenter to approach the material; b) setting a movement speed and a movement distance of the indenter and applying the load to the material; c) vertically moving the indenter by the set movement depth of the indenter and then moving the indenter upward by a certain load removal ratio of the movement distance of the indenter; d) measuring an indentation depth and an indentation load of the indenter according to the vertical movement of the indenter, simultaneously with performance of steps b) and C); e) repeatedly performing the steps b), c) and d) a plurality of times; f) removing the indenter from the material; and g) calculating residual stress of the material. 15. The residual stress data measuring method according to claim 14, wherein the step b) comprises the steps of:b1) moving the indenter downward; and b2) stopping the downward movement of the indenter and moving the indenter upward by a distance set value if the indentation load is greater than or equal to a load set value, and continuously performing the step b1) if the indentation load is less than the load set value. 16. The residual stress data measuring method according to claim 15, wherein the load set value is 0.01 to 2 kgf, and the distance set value is 0.1 to 30 μm.17. The residual stress data measuring method according to claim 14, wherein the step g) is performed before or after the step f) is executed.18. The residual stress data measuring method according to claim 14, wherein the step e) is performed in such a way that at least one of the movement speed of the indenter, the movement distance of the indenter and the load removal ratio can be varied in each experiment step.