JP2014081309A - Tensile test apparatus and tensile test method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tensile test apparatus and tensile test method capable of accurately performing a metal tensile strength test.SOLUTION: A tensile test apparatus according to the present invention comprises: a heat medium bath that holds a liquid heat medium bath at a predetermined temperature and in which a region to be measured of a test material is immersed in the heat medium so that a long side direction of the test material is almost in parallel with a vertical direction; an external force applying part for applying external force to one end of the long side direction of the test material while fixing the other end of the long side direction; a first holding member that holds the end fixed by the external force applying part, of the long side direction of the test material, with a holding part extended in a short side direction and that follows the stretch of the test material; a second holding member that holds the end applied with external force by the external force applying part, of the long side direction of the test material, with a holding part extended in the short side direction and that follows the stretch of the test material; a displacement sensor placed in each of the first holding member and the second holding member; and an arithmetic processing part for calculating a stretch amount of the test material on the basis of output from each of the displacement sensors.

Description

  The present invention relates to a tensile test apparatus and a tensile test method.

  One of the characteristics that characterize metal materials typified by steel is mechanical properties. As an example of a test for measuring such mechanical properties, a tensile strength test of a metal material (for example, see Patent Documents 1 to 3 below) and a thermal shock test (for example, see Patent Document 4 below). ), A heating load test (see, for example, Patent Document 5 below) and the like.

  Further, regarding the tensile strength test of the metal material, in addition to the method of measuring the metal material at a temperature of about room temperature as in the techniques disclosed in the following Patent Document 1 and Patent Document 2, it is disclosed in the following Patent Document 3. There is a method of performing measurement while heating a metal material as in the art.

JP-A-4-250336 Japanese Patent Laid-Open No. 5-249011 JP 2009-236757 A JP-A-10-170421 Japanese Patent Laid-Open No. 10-212231

  Here, when measuring the strain generated in the metal material by conducting a tensile strength test of the metal material, the amount of elongation of the metal material fluctuates due to the processing heat generated by the test material itself, and the accurate measurement result is In some cases, it could not be obtained.

  For example, the warm tensile strength test as disclosed in Patent Document 3 is performed in a heating furnace or in the air, and measuring the displacement of the test piece directly with a laser displacement meter is a very small displacement. It is important for accurate measurement. However, when the strain of a metal material is measured in heated air, there is a problem that the amount of elongation varies due to the influence of heat generated by processing the metal material itself.

  Further, when the tensile strength test of the metal material is performed, when the atmosphere is a gas such as air, the heat capacity of the gas is small, so that there is a problem that the metal material is easily affected by the heat generated in the metal material.

  Therefore, it is conceivable to suppress the influence of heat generated on the metal material by using a liquid such as silicon oil as a heat medium. However, when performing a tensile strength test of a metal material in a liquid heat medium such as silicon oil, The measurement system may be affected by a heat medium such as oil, and a stress-strain curve has not been obtained in a liquid heat medium.

  Thus, when performing the tensile strength test of a metal material, there existed a problem that acquisition of an exact test result may become difficult by the heat_generation | fever derived from metal material itself.

  Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide a tensile test apparatus and a tensile test method capable of performing a tensile strength test of a metal more accurately. There is.

  In order to solve the above problems, according to one aspect of the present invention, a tensile test is performed in which the elongation of the test material is detected by a displacement sensor, the strain generated in the test material is measured, and the tensile strength of the test material is measured. A heat medium bath for holding a liquid heat medium at a predetermined temperature and in which a part to be measured of the test material is immersed so that the longitudinal direction of the test material is substantially parallel to the vertical direction. And fixing one end in the longitudinal direction of the test material, and applying an external force to the other end in the longitudinal direction, and the external force applying unit in the longitudinal direction in the test material A first clamping member that clamps the end of the test piece in a short direction perpendicular to the longitudinal direction and follows the elongation of the test material, and the longitudinal direction of the test material The external force is applied by the external force application unit A second holding member that holds the end portion to be added by a holding portion that extends in the short-side direction and follows the elongation of the test material, the first holding member, and the second holding member There is provided a tensile test apparatus comprising: the displacement sensor installed in each of the first and second processing units; and an arithmetic processing unit that calculates an elongation amount of the test material based on an output from each of the displacement sensors.

  Each of the first clamping member and the second clamping member includes a clamping part that clamps the test material, and a connection part that is connected to one end of the clamping part and extends in the longitudinal direction. When the length of the connecting portion of the first holding member is A and the length of the connecting portion of the second holding member is B, the ratio value represented by B / A is 0. It is preferable that it is 0.5 or more and 2.0 or less.

  Each of the sandwiching portions of the first sandwiching member and the second sandwiching member is provided with a groove in which the test material is disposed, and the first member capable of elastic deformation and the test material are sandwiched between A second member disposed on the opposite side of the first member, and the test material is preferably sandwiched between the first member and the second member.

  The ratio value represented by B / A is preferably 1.0.

  The test material is a JIS No. 5 test piece, and a distance between the position of the test material held by the first holding member and the position of the test material held by the second holding member The distance is preferably 45 to 55 mm.

  The tensile test apparatus further includes a temperature control unit that controls the temperature of the heat medium, and a stirring member that stirs the heat medium in the heat medium bath, and the temperature control unit includes a temperature of the heat medium. May be maintained at a predetermined temperature in the range of -70 to 250 ° C.

  In order to solve the above problem, according to another aspect of the present invention, the elongation of the test material is detected by a displacement sensor, the strain generated in the test material is measured, and the tensile strength of the test material is measured. A tensile test method for fixing the test material in the longitudinal direction and fixing the test material to be tested to the external force application unit that applies an external force to the other end of the longitudinal direction. A clamping part that is fixed so as to be in the vertical direction, and that the end part of the test material that is fixed by the external force application part in the longitudinal direction is extended in a short direction perpendicular to the longitudinal direction And a first clamping member that follows the elongation of the test material is disposed on the test material to be tested, and the end of the test material on the side to which an external force is applied by the external force application unit in the longitudinal direction Part extending in the short direction For the heat medium bath that holds the liquid heat medium at a predetermined temperature by installing the second holding member that follows the elongation of the test material in the holding portion and installs the second holding member on the test material to be tested. The measured portion of the test material to be tested is immersed, and the elongation amount of the test material is calculated based on the output from the displacement sensor installed on each of the first clamping member and the second clamping member. A tensile test method is provided.

  As described above, according to the present invention, in addition to fixing the test material with the external force application unit, the first clamping member and the second clamping device that clamp the test material with the clamping part extending in the short direction of the test material. By sandwiching a test material to be tested using a member, it becomes possible to perform a metal tensile strength test more accurately.

It is the schematic which showed typically the case where the tension test apparatus which concerns on the 1st Embodiment of this invention is seen from the side. It is the schematic which showed typically the case where the tension test apparatus which concerns on the same embodiment is seen from upper direction. It is the schematic which showed the 1st clamping member and 2nd clamping member which concern on the same embodiment. It is the schematic which showed the 1st clamping member and 2nd clamping member which concern on the same embodiment. It is the schematic which showed the 1st clamping member and 2nd clamping member which concern on the same embodiment. It is the elements on larger scale of the 1st clamping member which concerns on the same embodiment. It is the elements on larger scale of the 2nd clamping member which concerns on the same embodiment. It is the elements on larger scale of the 1st clamping member which concerns on the same embodiment. It is the elements on larger scale of the 1st clamping member which concerns on the same embodiment. FIG. 4 is a graph showing the measurement results of Example 1.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

(First embodiment)
<Overall configuration of tensile testing device>
First, the overall configuration of a tensile test apparatus 10 according to the first embodiment of the present invention will be described with reference to FIGS. 1A and 1B. FIG. 1A is a schematic view schematically showing a case where the tensile test apparatus according to this embodiment is viewed from the side, and FIG. 1B is a schematic view when the tensile test apparatus according to this embodiment is viewed from above. FIG. Here, in the description regarding FIG. 1A and FIG. 1B, directions are described using the orthogonal coordinate system shown in each figure. FIG. 1A omits some of the members in order to more clearly illustrate the internal structure of the tensile test apparatus.

  The tensile test apparatus 10 according to the present embodiment is a tensile test apparatus that measures the tensile strength of a test material by measuring the strain generated in the test material by detecting the elongation of the metal test material with a displacement sensor. The tensile test apparatus 10 includes a heat medium bath 101 that functions as a thermostatic bath, and a liquid heat medium 103 such as silicon oil is held inside the heat medium bath 101. In this heat medium bath 101, the part to be measured of the test material S is immersed so that the longitudinal direction of the test material S is substantially parallel to the vertical direction (z-axis direction). By using a liquid medium such as silicon oil as the heat medium 103, the heat capacity of the heat medium can be increased, and the influence of heat generated on the test material can be reduced.

  The type of the heat medium 103 may be determined according to the temperature at which the tensile test is performed. When, for example, silicon oil is used as the heat medium 103, the allowable temperature range of silicon oil is −70 ° C. to 250 ° C. The tensile test can be performed.

  Here, the shape of the test material S is not particularly limited. For example, various test pieces such as a JIS No. 5 test piece as defined in JIS Z2201 (metal material tensile test piece) may be used. Is possible.

  The test material S includes a test material lower chuck jig (hereinafter also referred to as a lower chuck jig) 105 that fixes a lower end in the longitudinal direction (end on the negative side of the z axis) and an upper end in the longitudinal direction (z axis positive). It is fixed by the test material upper chuck jigs 107a and 107b for fixing the direction side end). The test material lower chuck jig 105 is fixed inside the heat medium bath 101 as shown in FIG. 1A. Moreover, the test material upper chuck jigs 107a and 107b are arranged outside the heat medium bath 101, and as shown in FIG. 1B, a jig for fixing the test material S from the x-axis positive direction side. 107a and a jig 107b for fixing the test material S from the x-axis negative direction side (hereinafter, these jigs 107a and 107b are collectively referred to as an upper chuck jig 107).

  The test material lower chuck jig 105 and the test material upper chuck jigs 107 a and 107 b are connected to a load-loaded jig 111 through a shaft 109. The test material lower chuck jig 105, the test material upper chuck jigs 107a and 107b, the shaft 109, and the load-loaded jig 111 function as an external force application unit for the test material S.

  That is, the load-loaded jig 111 is connected to a known drive device (not shown) such as an actuator, and is pulled to the z-axis positive direction side or moved to the z-axis negative direction side with the operation of the drive device. It is compressed. The load applied to the load-loaded jig 111 is transmitted to the test material upper chuck jigs 107a and 109b via the shaft 109, and as a result, an external force is applied to the test material S.

  Further, the test material S includes a first clamping member 113 that clamps an end of the test material S on the lower chuck jig 105 side (end on the z-axis negative direction side), and an upper chuck jig 107 of the test material S. And a second clamping member 115 that clamps the side end (the end on the z-axis positive direction side). One ends of the first clamping member 113 and the second clamping member 115 are located outside the heat medium bath 1. The first clamping member 113 and the second clamping member 115 will be described in detail below.

  A differential transformer type displacement meter 117 functioning as a displacement sensor is installed at each end of the first holding member 113 and the second holding member 115 located outside the heat medium bath 101. The differential transformer displacement meter 117 is a displacement sensor that outputs the displacement of the core 119 in the vertical direction (z-axis direction) as a voltage difference, and outputs the displacement generated in the core 119 as a highly accurate electrical signal called a voltage. be able to. Output data from each differential transformer displacement meter 117 (that is, an electrical signal related to voltage) is output to the arithmetic processing unit 123 described later. In the tensile test apparatus 10 according to the present embodiment, since the measuring device for measuring the displacement generated in the test material S is provided outside the heat medium bath 101, the measurement system is not affected by the heat medium 103. .

  As described above, in the tensile test apparatus 10 according to the present embodiment, the first clamping member 113, the second clamping member 115, and each differential transformer type displacement meter 117 work together to function as a strain gauge. .

  A heater 121 that functions as a temperature control unit that controls the temperature of the heat medium is provided below the heat medium bath 101, and the temperature of the heat medium 103 can be maintained at a predetermined temperature at which the tensile test is performed. it can.

  Further, the tensile test apparatus 10 includes an arithmetic processing unit 123 that calculates the amount of elongation (or the amount of contraction) generated in the test material S based on the electrical signal relating to the voltage output from each differential transformer displacement meter 117. Is provided.

  The differential transformer type displacement meter 117 is a measuring device in which the output voltage difference is proportional to the displacement generated in the measurement target. Accordingly, the difference between the displacement detected by the differential transformer displacement meter 117 installed on the first clamping member 113 and the displacement detected by the differential transformer displacement meter 117 installed on the second clamping member 115 is calculated as a difference. By taking this, the arithmetic processing unit 123 can calculate the amount of displacement (that is, the amount of expansion or contraction) generated in the test material S.

  Further, the arithmetic processing unit 123 uses the calculated amount of elongation of the test material S and the magnitude of the external force applied to the test material S to apply the strain generated in the test material S or the test material S. It is possible to calculate the magnitude of the stress. Further, the arithmetic processing unit 123 creates a stress-strain curve based on the obtained calculation result, and outputs the result to a display device such as a display or another computer, or prints out the result in a predetermined form format. It is also possible to do.

  The arithmetic processing unit 123 may be an electronic circuit including a CPU, ROM, RAM, and the like mounted on the tensile test apparatus 10, or various types of CPUs, ROMs, RAMs, and the like connected to the tensile test apparatus 10. It may be a computer.

  Further, as shown in FIG. 1B, it is preferable that a known stirring device 125 for stirring the heat medium 103 is installed in the heat medium bath 101. By stirring the heat medium 103 with the stirring device 125, the temperature distribution of the heat medium 103 in the heat medium bath 101 can be made more uniform, and the tensile test can be performed more accurately.

  Furthermore, as shown in FIG. 1B, in addition to the heater 121, a throwing heater 127 may be further installed in the heat medium bath 101.

  The overall configuration of the tensile test apparatus 10 according to the present embodiment has been described above with reference to FIGS. 1A and 1B.

<About the first clamping member and the second clamping member>
Next, the first clamping member 113 and the second clamping member 115 will be described in detail with reference to FIGS. 2 to 3B are schematic views showing a first clamping member and a second clamping member according to the present embodiment. 4A, 5 and 6 are partially enlarged views of the first holding member 113 according to this embodiment, and FIG. 4B is a partially enlarged view of the second holding member 115 according to this embodiment.

  FIG. 2 shows the test material S, the first clamping member 113 and the second clamping member 115 taken out from the overall configuration of the tensile test apparatus 10 shown in FIGS. 1A and 1B. As shown in FIG. 2, the first clamping member 113 is a substantially S-shaped member, and the second clamping member 115 is a substantially Z-shaped member. The first clamping member 113 and the second clamping member 115 clamp the test material S along the short direction (y-axis direction). In other words, the first sandwiching member 113 and the second sandwiching member 115 sandwich the test material S on the surface in a direction orthogonal to the tensile direction (z-axis direction) of the test material S. Further, the first clamping member 113 and the second clamping member 115 follow the expansion (or contraction) of the test material S without the first clamping member 113 and the second clamping member 115 themselves being deformed. Thereby, even if the test material S is immersed in a liquid heat medium 103 such as silicon oil, it is possible to reliably hold the test material S without slipping between the test material S and the liquid material. It is possible to accurately perform a tensile test in the heat medium.

  As shown in FIG. 2, the first clamping member 113 is connected to one end of the clamping part 113a that extends in the y-axis direction and clamps the test material S, and is connected to one end of the clamping part 113a. A connecting portion 113b extending in the direction) and a displacement sensor mounting portion 113c extending from one end of the connecting portion 113b. It is preferable that the clamping part 113a, the connecting part 113b, and the displacement sensor attaching part 113c are integrally formed.

  Similarly, the second clamping member 115 is connected to one end of the clamping part 115a that extends in the y-axis direction and clamps the test material S, and extends in the longitudinal direction (z-axis direction) of the test material S. The connection part 115b provided, and the displacement sensor attaching part 115c extended from the end of the connection part 115b are provided. It is preferable that these clamping part 115a, the connection part 115b, and the displacement sensor attaching part 115c are integrally formed.

  Further, when the first holding member 113 and the second holding member 115 are attached to the test material S, it is preferable to adjust the separation distance L1 between the holding portion 113a and the holding portion 115a to be a value within a predetermined range. . For example, when a JIS No. 5 test piece is used as the test material S, the separation distance L1 is preferably 45 mm to 55 mm. Regarding this numerical range, JIS Z2201 stipulates that the gauge distance is 50 mm when a JIS No. 5 test piece is used. Therefore, the separation distance L1 corresponding to the gauge distance is preferably 45 mm to 55 mm in view of a margin of 5 mm for the gauge distance defined by JIS. When the separation distance L1 is less than 45 mm, it is not preferable because the influence of local elongation becomes large and accurate evaluation may not be possible. In addition, when the separation distance L1 exceeds 55 mm, the influence of R of the JIS No. 5 test piece is increased, and an accurate evaluation may not be possible.

Subsequently, a more detailed structure of the first clamping member 113 and the second clamping member 115 will be described with reference to FIGS. 3A to 6.
As shown in FIG. 3A, when the length of the connecting portion 113b of the first holding member 113 is A [mm] and the length of the connecting portion 115b of the second holding member 115 is B [mm], The ratio of the lengths of the connecting parts represented by B / A) is preferably 0.5 or more and 2.0 or less. Hereinafter, the reason why the length ratio (B / A) is preferably in the above range will be described.

  When the test material S is attached to the lower chuck member 105 and the upper chuck member 107, it is desirable that the test material S be installed so that the longitudinal direction of the test material S is parallel to the vertical direction (z-axis direction). There may be a case where S is installed with a slight inclination from the vertical direction. When a tensile test is performed by applying an external force to the test material S installed in this way, the test material S is stretched (or contracted) while rotating in the yz plane in FIG. It becomes. As a result, the obtained test result includes an effect associated with the rotational motion, and an error is generated from the accurate test result that should be originally obtained. Therefore, by setting the length ratio (B / A) to 0.5 ≦ (B / A) ≦ 2.0, it is possible to reduce the influence of the rotational motion associated with the mounting error of the test material S. This makes it possible to obtain more accurate test results.

  When the length ratio (B / A) is less than 0.5 or exceeds 2.0, the influence of the rotational motion accompanying the mounting error of the test material S cannot be sufficiently mitigated. Is not preferable. Further, the length ratio (B / A) is preferably closer to 1.0, and the length ratio (B / A) is most preferably 1.0 as shown in FIG. 3B. When the ratio of the lengths of the connecting portions (B / A) is 1.0, the magnitude of the moment acting on the first connecting member 113 and the magnitude of the moment acting on the second connecting member 115 in accordance with the rotational motion. Therefore, the influence of the rotational motion accompanying the mounting error of the test material S can be more reliably mitigated.

  FIG. 4A is an exploded perspective view schematically showing the vicinity of the sandwiching portion 113a of the first sandwiching member 113 in an enlarged manner. As shown in FIG. 4A, the sandwiching portion 113a includes a first member 131 and a second member 133. The 2nd member 133 is a member extended from the connection part 113b, and the 1st member 131 is a member provided so that attachment or detachment to the 2nd member 133 is possible. The first member 131 is provided with a groove 135 in which the test material S is disposed, and is formed using a member that can be elastically deformed. Further, the first member 131 and the second member 133 are formed with screw holes 137 for fastening bolts, and the test material S is used as the first member 131 and the second member using bolts (not shown). It fixes between 133.

  FIG. 4B is an exploded perspective view schematically showing the vicinity of the sandwiching portion 115b of the second sandwiching member 115 in an enlarged manner. As illustrated in FIG. 4B, the clamping unit 115 a includes a first member 141 and a second member 143. The 2nd member 143 is a member extended from the connection part 115b, and the 1st member 141 is a member provided so that attachment or detachment to the 2nd member 143 is possible. The first member 141 is provided with a groove 145 in which the test material S is disposed, and is formed using a member that can be elastically deformed. The first member 141 and the second member 143 are formed with screw holes 147 for fastening bolts, and the test material S is used as the first member 141 and the second member using bolts (not shown). It fixes between 143.

  In addition, the depth of the groove part provided in the 1st member of the 1st clamping member 113 and the 2nd clamping member 115 is not specifically limited, If it determines suitably according to the thickness of the test material S which implements a tension test. Good.

  FIG. 5 is a diagram for explaining the clamping state of the test material S by taking the first clamping member 113 as an example, and the clamping part 113a of the first clamping member 113 is moved upward (on the z-axis positive direction side in FIG. 1A). ). Here, in the following, the first clamping member 113 will be described as an example, but the test material S is also clamped by the same mechanism for the second clamping member 115.

  While the test material S is disposed in the groove portion 135 of the first member 131, the test material S is sandwiched between the first member 131 and the second member 133, and bolts 147 are provided in the first member 131 and the second member 133, respectively. 149 and 151 are fastened (the upper part of FIG. 5). In this state, by further tightening the bolt 151 in contact with the test material S, the first member 131 is elastically deformed, and the test material S can be clamped more strongly (lower stage in FIG. 5). As a result, even in a liquid heat medium that easily slips between the test material S, the test material S can be clamped more strongly, and a more accurate test result can be obtained. .

  FIG. 6 is a schematic cross-sectional view showing a case where the sandwiching portion 113a of the first sandwiching member 113 is cut at a portion where the groove portion 135 is formed and viewed from the side (y-axis positive direction side in FIG. 1A). is there. In the tensile test apparatus 10 according to the present embodiment, for example, as illustrated in FIG. 6, the cross-sectional shape of the second member 133 may be a substantially triangular shape. As shown in FIG. 6, the cross-sectional shape of the second member 133 is a substantially triangular shape, and the area of the second member 133 that contacts the test material S is reduced, so that the test material S can be clamped more strongly. It becomes possible. In addition, the size of the apex angle of the portion in contact with the test material S may be appropriately determined according to the size of the test material holding force required for the clamping portion.

  The first clamping member 113 and the second clamping member 115 have been described in detail above with reference to FIGS.

  As described above, in the tensile test apparatus 10 according to this embodiment, by using a liquid heat medium such as silicon oil as the heat medium, not only the room temperature near 20 ° C. but also the allowable temperature of use of the heat medium. Within a range, it becomes possible to carry out a tensile test of a metal material such as a steel material or a nonferrous metal material. In addition, by using a liquid heat medium as the heat medium, it is possible to suppress the influence of heat generated in the metal material, and to change the temperature change occurring in the metal material to at least 30 ° C. or even within 15 ° C. It becomes. As a result, the strain generated in the metal material can be measured under the test conditions where the temperature is more stable, and the minute elongation of the test material can be accurately measured at a uniform temperature.

  Therefore, by using the tensile test apparatus 10 according to the present embodiment, not only various non-ferrous metal materials but also a steel plate including an austenitic structure such as stainless steel or TRIP steel (hereinafter referred to as an austenitic steel plate). Even with steel plates that are susceptible to the effects of processing heat generation and processing transformation heat, a more accurate tensile test can be performed.

  Hereinafter, the tensile test apparatus 10 according to the embodiment of the present invention will be specifically described with reference to examples. The tensile test apparatus 10 according to the embodiment of the present invention can be applied to a tensile test for various metal materials, but will be specifically described below by taking an austenitic steel sheet as an example. In addition, the Example shown below is only an example for demonstrating the tensile test apparatus 10 which concerns on embodiment of this invention, Comprising: The tensile test apparatus 10 which concerns on this invention is not necessarily limited to the example shown below. Absent.

Example 1
In Example 1, a tensile test was performed on an austenitic steel sheet using the tensile test apparatus 10 shown in FIGS. 1A and 1B. The austenitic steel plate used is SUS304. In the tensile test apparatus 10 used, the ratio (B / A) of the lengths of the connecting portions in the first holding member 113 and the second holding member 115 is 1.0, and the holding portion of each holding member 113, 115 is The cross-sectional shape of the first member is a substantially triangular shape as shown in FIG. Further, as the heat medium 103, silicon oil that can be used in a range of −70 ° C. to 250 ° C. was used.

  Here, the austenitic steel sheet was processed into a JIS No. 5 test piece, and the tensile test was performed after controlling the temperature of silicon oil as a heat medium at 20 ° C., thereby obtaining a stress-strain curve.

  Moreover, when performing a tensile test, the temperature of the test piece in the center part of the mark of a JIS5 test piece was also measured using the K thermocouple.

  Moreover, as a comparative example, a conventional tensile strength tester was used to conduct a tensile test on the JIS No. 5 test piece similar to the above in the air.

  The obtained results are also shown in FIG. In FIG. 7, the horizontal axis represents strain (nominal strain) [%] generated in the JIS No. 5 test piece. Moreover, the stress [MPa] given to the JIS5 test piece and the gage part temperature [° C.] are shown on the vertical axis. In FIG. 7, the curve shown as oil is a measurement result using the tensile strength test apparatus used in the examples, and the curve shown as air is a measurement result using a conventional tensile strength tester.

  As can be seen from FIG. 7, when a JIS No. 5 test piece using an austenitic steel sheet is measured in the atmosphere, it can be seen that the temperature of the gauge point rapidly increases as the amount of strain increases. This temperature rise is considered to be a temperature rise due to work transformation heat and work heat generation of the austenitic steel sheet, and it is thought that errors resulting from work transformation heat and work heat generation are superimposed on the obtained stress measurement results. .

  On the other hand, when a JIS No. 5 test piece using an austenitic steel sheet is measured in oil using a tensile test apparatus according to an embodiment of the present invention, even if the strain amount is large, the degree of increase in the gauge part temperature It can be seen that (temperature change) can be suppressed to about 1/3 of the conventional one. Therefore, it can be said that the measurement result of the stress by the tensile test apparatus according to the embodiment of the present invention represents the strain of the austenitic steel sheet more accurately because errors due to the work transformation heat and the work heat generation are reduced.

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 10 Tensile test apparatus 101 Heat medium bath 103 Heat medium 105 Test material lower chuck jig 107 (107a, 107b) Test material upper chuck jig 109 Shaft 111 Load loaded jig 113 First clamping member 113a Holding part 113b Connecting part 113c Displacement sensor attaching part 115 2nd clamping member 115a Holding part 115b Connection part 115c Displacement sensor attaching part 117 Differential transformer type displacement meter 119 Core 121 Heater 123 Arithmetic processing unit 125 Stirring device 127 Throw heater 131,141 First member 133,143 Second member 135, 145 Groove 137, 147 Screw hole 149, 151 Bolt

Claims (7)

A tensile test device that detects the elongation of the test material with a displacement sensor, measures the strain generated in the test material, and measures the tensile strength of the test material,
A heat medium bath that holds a liquid heat medium at a predetermined temperature, and in which the measurement site of the test material is immersed so that the longitudinal direction of the test material is substantially parallel to the vertical direction;
While fixing one end in the longitudinal direction of the test material, an external force application unit that applies an external force to the other end in the longitudinal direction;
The end of the test material that is fixed by the external force application unit in the longitudinal direction is sandwiched by a sandwiching portion that extends in a short direction perpendicular to the longitudinal direction, and the test material A first clamping member that follows the elongation;
A second end of the test material to which an external force is applied by the external force application portion in the longitudinal direction is sandwiched by a sandwiching portion extending in the short-side direction, and the second end following the elongation of the test material. A clamping member;
The displacement sensor installed in each of the first clamping member and the second clamping member;
Based on the output from each displacement sensor, an arithmetic processing unit that calculates the amount of elongation of the test material,
A tensile testing apparatus comprising: Each of the first clamping member and the second clamping member is
A clamping part for clamping the test material;
Connected to one end of the clamping part, and a connecting part extending in the longitudinal direction;
Have
When the length of the connecting portion of the first holding member is A and the length of the connecting portion of the second holding member is B, the ratio value represented by B / A is 0.5. The tensile test apparatus according to claim 1, wherein the tensile test apparatus is 2.0 or more and 2.0 or less. The clamping part of each of the first clamping member and the second clamping member is
A groove in which the test material is disposed, a first member capable of elastic deformation;
A second member disposed on the opposite side of the first member across the test material;
Have
The tensile test apparatus according to claim 1 or 2, wherein the test material is sandwiched between the first member and the second member. The tensile testing device according to claim 2, wherein the value of the ratio represented by B / A is 1.0. The test material is a JIS No. 5 test piece,
A separation distance between the position of the test material sandwiched by the first sandwiching member and the position of the test material sandwiched by the second sandwiching member is 45 to 55 mm, The tensile test apparatus according to any one of claims 1 to 4. A temperature control unit for controlling the temperature of the heat medium;
A stirring member for stirring the heat medium in the heat medium bath;
Further comprising
The tensile test apparatus according to any one of claims 1 to 5, wherein the temperature control unit maintains the temperature of the heat medium at a predetermined temperature in a range of -70 to 250 ° C. A tensile test method for detecting the elongation of the test material with a displacement sensor and measuring the strain generated in the test material, and measuring the tensile strength of the test material,
While fixing one end in the longitudinal direction of the test material, the test material to be tested is fixed so that the longitudinal direction is in the vertical direction with respect to the external force application unit that applies external force to the other end in the longitudinal direction. ,
The end of the test material that is fixed by the external force application unit in the longitudinal direction is sandwiched by a sandwiching portion that extends in a short direction perpendicular to the longitudinal direction, and the test material A first clamping member that follows the elongation is installed on the test material to be tested,
A second end of the test material to which an external force is applied by the external force application portion in the longitudinal direction is sandwiched by a sandwiching portion extending in the short-side direction, and the second end following the elongation of the test material. A clamping member is installed on the test material to be tested,
What holds a liquid heat medium at a predetermined temperature In a heat medium bath, immerse the measured part of the test material to be tested,
A tensile test method characterized in that an elongation amount of the test material is calculated on the basis of an output from the displacement sensor installed in each of the first clamping member and the second clamping member.

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