KR-20260062441-A - SYSTEM AND METHOD FOR CALCULATING STRESS AND STRAIN OF A MATERIAL

KR20260062441AKR 20260062441 AKR20260062441 AKR 20260062441AKR-20260062441-A

Abstract

The present invention relates to a system and method for calculating stress and strain of a specimen. Such a system and method for calculating stress and strain of a specimen is configured to form a protrusion on a predetermined part of a specimen and to calculate the stress and strain of the specimen using the strain of the protrusion measured while applying a load to the protrusion.

Inventors

이강헌

Assignees

알엑스 주식회사

Dates

Publication Date: 20260507
Application Date: 20241029

Claims (15)

A polishing module that polishes a predetermined portion of the surface of a specimen so that the predetermined portion becomes flat; A cutting module that cuts at least a portion of a predetermined part so that a cylindrical projection, having a circular cross-section in a direction parallel to the predetermined part, is formed on the predetermined part; A compression module that applies pressure to the above-mentioned protrusion in a direction perpendicular to the above-mentioned predetermined part; A measuring module for measuring a load, which is pressure applied to the projection by the compression module, a first height, which is the height before the load is applied, and a second height, which is the height after the load is applied, among the height, which is the vertical length of the projection; and A system for calculating stress and strain of a specimen, comprising a control module that controls the operation of the grinding module, the cutting module, the compression module, and the measuring module, and calculates the stress of the specimen and the strain of the specimen according to the stress based on information regarding the load, the first height, and the second height.
In paragraph 1, A stress and strain calculation system for a specimen, wherein the control unit calculates the nominal stress acting on the specimen using the following mathematical formula 1, calculates the nominal strain of the specimen using the following mathematical formula 2, calculates the true stress acting on the specimen using the following mathematical formula 3, and calculates the true strain of the specimen using the following mathematical formula 4. [Mathematical Formula 1] σ e = f/A (Here, σ e is the nominal stress, f is the load, and A is the cross-sectional area of the projection before the load is applied) [Mathematical Formula 2] ε e = d/L (Here, ε e is the nominal strain, d is the length obtained by subtracting the second height from the first height, and L is the vertical length of the projection before the load is applied) [Mathematical Formula 3] σ t = σ e *(1+ε e ) (Here, σt is true stress, σe is nominal stress, and εe is nominal strain) [Mathematical Formula 4] ε t = ln(1+ε e ) (Here, εt is the true strain and εe is the nominal strain)
In paragraph 2, The above cutting module is, A system for calculating stress and strain of a specimen, comprising a cutting member that is rotatable about a rotation axis parallel to the above-mentioned vertical direction and cuts the above-mentioned predetermined portion.
In paragraph 3, The above cutting member is, A recess formed by the recessing of at least a portion of one end that cuts the above-mentioned predetermined portion; and A system for calculating stress and strain of a specimen, comprising a cutting part installed on the outer periphery of the above-mentioned depression and capable of cutting the above-mentioned predetermined part by rotating and contacting the said predetermined part.
In paragraph 4, The above-mentioned depression is, A stress and strain calculation system for a specimen, formed in the same shape as the protrusion so as to accommodate the protrusion.
In paragraph 5, The above compression module includes a contact portion that contacts the above protrusion, and A system for calculating stress and strain of a specimen, wherein the above contact portion contacts the above protrusion to press the above protrusion and forms a contact surface that is formed flatly so as to be parallel to the above parallel direction.
In paragraph 6, The above contact surface is, The area of the contact surface is formed to be larger than the area of the cross-section of the projection and smaller than the area of the predetermined portion, A stress and strain calculation system for a specimen, formed such that when the above-mentioned protrusion is pressed, it contacts the entire cross-section of the above-mentioned protrusion, but prevents contact with the above-mentioned predetermined portion.
In Paragraph 7, The above measurement module is, A pressure measuring sensor for measuring the above load; and A system for calculating stress and strain of a specimen, comprising a height measuring sensor for measuring the height.
In Paragraph 7, A system for calculating stress and strain of a specimen, further comprising a power module that supplies power to the grinding module, the cutting module, the compression module, the measuring module, and the control module.
A polishing step for polishing a predetermined portion of the surface of a specimen so that a predetermined portion becomes flat; A cutting step of cutting at least a portion of the predetermined portion so that a cylindrical projection having a circular cross-section in a direction parallel to the predetermined portion is formed in the predetermined portion; A compression step of applying pressure to the above-mentioned projection in a direction perpendicular to the above-mentioned predetermined part; A measurement step for measuring a load, which is the pressure applied to the projection by the compression step, a first height, which is the height before the load is applied, and a second height, which is the height after the load is applied, among the height, which is the vertical length of the projection; and A method for calculating stress and strain of a specimen, comprising a calculation step of calculating the stress of the specimen and the strain of the specimen according to the stress based on information regarding the load, the first height, and the second height.
In Paragraph 10, A method for calculating stress and strain of a specimen, wherein the above calculation step calculates the nominal stress acting on the specimen using the following mathematical formula 1, calculates the nominal strain of the specimen using the following mathematical formula 2, calculates the true stress acting on the specimen using the following mathematical formula 3, and calculates the true strain of the specimen using the following mathematical formula 4. [Mathematical Formula 1] σ e = f/A (Here, σ e is the nominal stress, f is the load, and A is the cross-sectional area of the projection before the load is applied) [Mathematical Formula 2] ε e = d/L (Here, ε e is the nominal strain, d is the length obtained by subtracting the second height from the first height, and L is the vertical length of the projection before the load is applied) [Mathematical Formula 3] σ t = σ e *(1+ε e ) (Here, σt is true stress, σe is nominal stress, and εe is nominal strain) [Mathematical Formula 4] ε t = ln(1+ε e ) (Here, εt is the true strain and εe is the nominal strain)
In Paragraph 11, The above cutting step is, A method for calculating stress and strain of a specimen by using a cutting member rotatable about an axis of rotation parallel to the above vertical direction to cut at least a portion of the above-mentioned predetermined part.
In Paragraph 12, The above cutting member is, A recess formed by the recessing of at least a portion of one end that cuts the above-mentioned predetermined portion; and A method for calculating stress and strain of a specimen, comprising a cutting portion installed on the outer periphery of the above-mentioned depression and capable of cutting the above-mentioned predetermined portion by rotating and contacting the said predetermined portion.
In Paragraph 13, The above-mentioned depression is, A method for calculating stress and strain of a specimen formed with the same shape as the protrusion so as to accommodate the protrusion.
In Paragraph 14, The above compression step applies pressure to the projection using a contact portion that contacts the projection, and A method for calculating stress and strain of a specimen, wherein the above contact portion contacts the above protrusion and presses the above protrusion, and a contact surface is formed that is flat and parallel to the above parallel direction.

Description

System and Method for Calculating Stress and Strain of a Material The present invention relates to a system and method for calculating stress and strain of a specimen, and more specifically, to a system and method capable of accurately calculating the stress and strain of a specimen while enabling a quick and simple indentation test on the specimen. The non-destructive testing method for the plastic properties of specimens using the indentation test is one of the common methods for testing specimen properties. These indentation testing methods include instrumented indentation techniques and surface shape-based indentation testing methods. The instrumented indentation technique predicts the contact area between the specimen and the indenter based on the indentation load-displacement relationship when indenting the specimen, and calculates the strain of the specimen using conventionally established mathematical formulas and correction functions to predict the representative stress and representative strain of the specimen. However, since the instrumented indentation technique is configured to predict the deformation shape of the specimen using mathematical formulas and correction functions after indentation, there is a problem in that it is difficult to apply to specimens of various materials. In addition, since the instrumented indentation technique requires extracting a specimen from a structure such as a pipe and then performing an indentation test on the extracted specimen, there is a problem of cost and time required to extract the specimen. Meanwhile, the surface shape-based indentation test method is a method in which the deformation shape of a specimen is directly scanned via physical methods or measured via optical methods after the specimen is indented. Since the surface shape of the specimen can be directly measured, the strain of the specimen can be predicted based on more accurate information regarding the surface shape. However, surface shape-based indentation testing methods require the use of equipment to accurately measure the surface shape of a specimen, but there is a problem in that it is difficult to utilize portable equipment to measure the surface shape when a specimen with a relatively large volume is compressed. In addition, the surface shape-based indentation test method has the problem that relatively high-precision and expensive equipment must be used because the surface shape must be measured precisely. Furthermore, the surface shape-based indentation test method requires performing finite element inverse analysis to obtain information regarding the strain of the specimen from information regarding the surface shape of the specimen; however, there is a problem in that the time required for the finite element inverse analysis increases in order to improve the accuracy of the finite element inverse analysis, which prevents the indentation test from being performed quickly. Therefore, there is a need to develop a system and method for calculating the stress and strain of a specimen that can perform indentation tests on the specimen simply and quickly, while also accurately calculating the stress and strain of the specimen. FIG. 1 is a block diagram illustrating a system for calculating stress and strain of a specimen according to one embodiment of the present invention. FIG. 2 is a drawing illustrating a polishing module that polishes a specific part of a specimen. Figure 3 is a drawing illustrating a cutting member. Figure 4 is an enlarged view of A in Figure 3. FIG. 5 is a drawing showing a cutting module that cuts a predetermined part of a specimen while rotating around a rotation axis. Figure 6 is a drawing showing a protrusion formed on a specific part of a specimen by a cutting module. Figure 7 is a diagram illustrating a compression module. Figure 8 is a drawing showing a protrusion before a load is applied by a compression module. Figure 9 is a drawing showing the protrusion after a load is applied by a compression module. FIG. 10 is a graph showing a comparison between the stress of a specimen and the corresponding strain of the specimen calculated through a stress and strain calculation system of a specimen according to one embodiment of the present invention, and the actual strain of the specimen corresponding to the stress of the specimen. FIG. 11 is a drawing illustrating a polishing module that polishes a predetermined part of a specimen having a protrusion formed thereon. FIG. 12 is a flowchart illustrating a method for calculating stress and strain of a specimen according to one embodiment of the present invention. Embodiments of the present invention are described below with reference to the attached drawings to enable those skilled in the art to easily implement the invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein. Furthermore, in order to clearly explain the present invention