Measurement method and measuring device

Abstract

To provide a measurement method and measurement device for internal compression stresses which is simple in measurement and can perform measurement even when a sample is small.SOLUTION: A measurement method for measuring an internal compression stresses of a sample includes a load application step of applying a compressive load in a direction to a stage to the sample, while rasing the temperature of a sample placed on a stage from a prescribed temperature that is lower than the glass transition temperature of the sample, and executing a control so that the probe position is fixed. In the load application step, the internal compression stress of the sample is calculated from a difference between maximum and minimum values when the compressive load exhibits a change shifting from an increasing trend to a decreasing trend through a maximum value and then indicating a minimum value.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a measurement method, and in particular to a measurement method and a measurement device for measuring the internal compressive stress of a sample. [Background technology]

[0002] As a measurement method capable of measuring the internal compressive stress of a material such as a resin, for example, a hole-drilling method is known. In the hole-drilling method, the internal compressive stress (residual stress) of a material sample is measured by attaching a strain gauge to the sample and forming a hole with a drill or the like, and then using the measurement results of the strain gauge. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Takao Mikami et al.: Verification test of residual stress measurement technique using hole drilling method IHI Technical Report Vol.58 No.3(2018) PP.27-37 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the hole-drilling method requires drilling holes in the sample and attaching a strain gauge to a position on the sample near the hole. As a result, there is a problem that the internal compressive stress of the sample cannot be easily measured. In addition, there is a problem that it is difficult to measure the internal compressive stress of a sample that is smaller than the strain gauge.

[0005] The present disclosure has been made in consideration of the above problems, and aims to provide a method and device for measuring internal compressive stress that is easy to measure and capable of measuring even when the sample is small. [Means for solving the problem]

[0006] In order to solve the above problems, a measurement method according to one aspect of the present disclosure is a method for measuring an internal compressive stress of a sample, the method comprising: a load application step in which a compressive load is applied to the sample in the direction of the stage with a probe while raising the temperature of the sample placed on a stage from a predetermined temperature lower than the glass transition temperature of the sample, and controlling the position of the probe to be constant; when, in the load application step, the compressive load changes from an increasing trend to a maximum value, then to a decreasing trend, and then to a minimum value, the internal compressive stress of the sample is calculated from the difference between the maximum value and the minimum value.

[0007] Moreover, a measuring apparatus according to one aspect of the present disclosure includes a stage on which a sample is placed, a heater for heating the sample on the stage, a temperature sensor for detecting a temperature of the sample on the stage, a probe for contacting the sample on the stage and applying a compressive load to the sample in a direction toward the stage, a load generating unit for driving the probe to generate the compressive load, a displacement detecting unit for detecting a position of the probe, and a control unit, wherein the control unit performs a load applying step of applying the compressive load to the sample with the probe while raising the temperature of the sample placed on the stage from a predetermined temperature lower than the glass transition temperature of the sample, and controlling the position of the probe to be constant, and when the compressive load changes from an increasing trend to a maximum value to a decreasing trend and then to a minimum value in the load applying step, the control unit calculates an internal compressive stress of the sample from the difference between the maximum value and the minimum value. Effect of the Invention

[0008] According to one aspect of the present disclosure, it is possible to provide a method and device for measuring internal compressive stress, which is simple and capable of measuring even when the sample is small. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic diagram illustrating an example of the configuration of a measurement device for implementing a measurement method according to an embodiment of the present disclosure. [Diagram 2]1 is a graph illustrating an example of measurement of glass transition temperature by a measurement method. [Diagram 3] 1 is a graph illustrating an example of measurement of internal compressive stress by a measurement method. [Figure 4] 1 is a flowchart showing a preliminary measurement step of a measurement method according to an embodiment of the present disclosure. [Diagram 5] 1 is a flowchart showing a procedure for evaluating residual stress using a measurement method according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] [Embodiment] Hereinafter, an embodiment of the present disclosure will be described in detail with reference to Fig. 1. Fig. 1 is a schematic diagram showing a configuration example of a measurement device that realizes a measurement method according to an embodiment of the present disclosure. In the following description, the measurement device that realizes the measurement method of the present disclosure will first be specifically described.

[0011] <Measurement device 1> As shown in Fig. 1, a measurement device 1 of this embodiment includes a thermomechanical analyzer (TMA) 10 and a control device 8 that controls each part of the thermomechanical analyzer 10. The measurement device 1 measures the internal compressive stress of a sample S using the measurement method of this embodiment. The sample S is made of a synthetic resin material such as epoxy resin. The measurement device 1 also calculates the glass transition temperature at which the sample S transitions from a glassy state to a rubbery state.

[0012] <Thermomechanical analyzer 10> The thermomechanical analysis device 10 includes a sample tube 2 in which a sample S is placed, a heater 3 that is disposed around the sample tube 2 and heats the sample S to increase the temperature of the sample S, and a temperature sensor 4 that detects the temperature of the sample S. The thermomechanical analysis device 10 includes a displacement detection unit 5 for detecting the length of the sample S, a probe 6 that comes into contact with the sample S to apply a compressive load, and a load generation unit 7 that generates the compressive load to be applied to the sample S.

[0013] The sample tube 2 is a bottomed cylinder having a bottom surface on which the sample S is placed. The sample tube 2 is placed on a stage St, and a load (compressive load) is applied to the sample S in the downward direction in Fig. 1 from a probe 6 arranged facing the stage St with the sample S interposed therebetween. In this embodiment, the internal compressive stress of the sample S can be measured with high accuracy.

[0014] A temperature sensor 4 is disposed inside the sample tube 2. A heater 3 is disposed outside the sample tube 2 so as to surround the sample S. A displacement detection unit 5 and a load generation unit 7 that generates a load and applies a compressive load to the sample S via a probe 6 are provided on the upper opening side of the sample tube 2.

[0015] In the above description, the sample S is placed inside the sample tube 2 on the stage St, but the present embodiment is not limited to this configuration, and is not limited in any way as long as the sample S placed on the stage St is used. In other words, instead of the above description, the sample S may be placed directly on the stage St without using the sample tube 2. However, as described above, using the sample tube 2 is preferable in that it makes it easier to appropriately heat the sample S by the heater 3.

[0016] The sample S is, for example, a rectangular parallelepiped having sides of 1 mm or more. In addition to the above-mentioned synthetic resin material, the sample S may be made of an amorphous material (which may contain a crystalline material in part), a transparent or non-transparent material, or a magnetic or non-magnetic material.

[0017] The heater 3 is configured, for example, using a so-called electric heater that generates heat in response to the amount of electricity controlled by the control device 8. The temperature sensor 4 is configured, for example, using a thermocouple or a thermistor, and outputs the detected temperature of the sample S to the control device 8.

[0018] The displacement detection unit 5 is configured using, for example, a differential transformer (LVDT: Linear Variable Differential Transformer). The displacement detection unit 5 detects the position of the probe 6 and outputs it to the control device 8. In this way, the control device 8 can determine the position of the probe 6 and detect the length of the sample S in the direction in which the compressive load is applied by the probe 6 (the direction toward the stage St).

[0019] The load generating unit 7 includes a driving mechanism such as a motor (not shown), and the driving mechanism can control and drive the probe 6 according to an instruction signal from the control device 8. Specifically, in the load generating unit 7, the driving mechanism can move the probe 6 in a direction perpendicular to the sample placement surface of the stage St. Furthermore, the driving mechanism of the load generating unit 7 can adjust the compressive load applied to the sample by the probe 6 to a required value. The load generating unit 7 may include a load sensor such as a torque sensor, which detects the compressive load applied to the sample S and outputs it to the control device 8.

[0020] In addition to the above description, a configuration may be adopted in which, without providing a load sensor, for example, the compressive load applied to the sample S via the probe 6 is calculated using the value of the current supplied to the driving mechanism of the load generating unit 7 and output to the control device 8.

[0021] <Control device 8> The control device 8 includes a communication unit 8a, a storage unit 8b, and a control unit 8c. The communication unit 8a is a functional block that communicates with each unit of the thermomechanical analysis device 10. The communication unit 8a is also a functional block of two-way communication that transmits and receives information to and from the outside of the measurement device 1. The storage unit 8b is, for example, an auxiliary storage device such as a hard disk drive or a solid state drive, and stores various processing programs executed by the control unit 8c. The storage unit 8b also stores data necessary for the measurement method, such as a predetermined temperature and an upper measurement limit temperature, which will be described later.

[0022] The control unit 8c is a functional block that includes, for example, a central processing unit (CPU), a random access memory (RAM), a read only memory (ROM), and the like, and controls each of the components in accordance with information processing.

[0023] The control unit 8c controls the thermomechanical analyzer 10 to switch the mode from the constant load mode to the constant length load variation measurement mode using the detection result of the temperature sensor 4 and the predetermined temperature stored in the storage unit 8b. The constant load mode and the constant length load variation measurement mode will be described in detail later.

[0024] <Overview of measurement method> Next, the operation of the measurement device 1 using the measurement method of the present embodiment will be specifically described with reference to Figs. 2 to 5. Fig. 2 is a graph illustrating an example of measurement of glass transition temperature by the measurement method. Fig. 3 is a graph illustrating an example of measurement of internal compressive stress by the measurement method. Fig. 4 is a flowchart showing a preliminary measurement step of the measurement method according to an embodiment of the present disclosure. Fig. 5 is a flowchart showing the procedure for evaluating residual stress by the measurement method according to an embodiment of the present disclosure.

[0025] <Preliminary measurement step for evaluating glass transition temperature> In the following description, the measurement method and the measurement device of this embodiment are used to measure the glass transition temperature of a spare sample S made of the same material as the sample S whose internal compressive stress is to be measured.

[0026] In the measuring device 1, a preliminary measurement step is performed in which the above-mentioned preliminary sample is used to determine the glass transition temperature of the preliminary sample by applying a constant compressive load to the preliminary sample in the direction of the stage St with the probe 6 while raising the temperature of the preliminary sample at a constant heating rate and measuring the change in the position of the probe 6.

[0027] Specifically, in this preliminary measurement step, in step S1 of Fig. 4, the load generating unit 7 applies a constant compressive load P (shown by line 50 in Fig. 2, e.g., 5.00 (g)) to a spare sample (not shown) placed in a sample tube 2 via a probe 6. In addition, the heater 3 heats the spare sample so that the temperature of the spare sample detected by the temperature sensor 4 (shown by the horizontal axis in Fig. 2) increases continuously at a constant heating rate.

[0028] More specifically, an epoxy resin having a size of, for example, 20 mm×5 mm×5 mm was used as a preliminary sample, and a preliminary measurement step was carried out on this preliminary sample using the thermomechanical analyzer 10 .

[0029] Next, in step S2 of Fig. 4, the displacement detection unit 5 detects a change in the position of the probe 6 and outputs it to the control unit 8c. The control unit 8c calculates the length of the spare sample based on the change in the position of the probe 6. Specifically, the control unit 8c detects the length of the spare sample by adding the value of the change in the position of the probe 6 detected in step S2 to the reference value, which is the length of the spare sample measured in advance before executing step S1 and stored in the memory unit 8b. As a result, the control unit 8c detects the length of the spare sample, which changes as exemplified by the curve 60 in Fig. 2.

[0030] Next, in step S3 of FIG. 4, the control unit 8c obtains the intersection point between the tangent to the graph of the position of the probe 6 when the spare sample is in a glassy state (i.e., the length of the spare sample) on the curve 60 and the tangent to the graph of the position of the probe 6 when the spare sample is in a rubbery state, and determines the glass transition temperature PT1 (e.g., 121.9°C) of the spare sample from the intersection point.

[0031] Specifically, when the control unit 8c detects a state in which the length of the preliminary sample increases almost uniformly in response to an increase in the temperature of the preliminary sample, as shown by the curve 60, it determines that the preliminary sample is in a solid, glassy state. Then, the control unit 8c obtains a tangent (shown by the left dotted arrow in FIG. 2) to the length shown by the curve 60 at an arbitrary temperature when it is determined to be in a glassy state, for example, the temperature shown at the left end of the left dotted arrow in FIG. 2 (for example, 80.00° C.).

[0032] Furthermore, when the control unit 8c detects a state shown by the curve 60 in which the length of the preliminary sample increases significantly as compared with the temperature rise and glassy state of the preliminary sample, the control unit 8c determines that the preliminary sample has transitioned from a glassy state to a rubbery state having rubber elasticity. The control unit 8c then obtains a tangent (shown by the dotted arrow on the right side in FIG. 2) to the length shown by the curve 60 at an arbitrary temperature when the preliminary sample is determined to be in the rubbery state, for example, the temperature shown at the right end of the dotted arrow on the right side in FIG. 2 (for example, 128.00° C.). The control unit 8c then calculates the intersection of the two tangents as shown in FIG. 2, and sets the temperature of the intersection as the glass transition temperature PT1 of the preliminary sample.

[0033] Furthermore, the control unit 8c calculates the linear expansion coefficient of the spare sample as shown by a curve 70 in Fig. 2, based on the detected temperature from the temperature sensor 4 and the detected length of the spare sample obtained by the displacement detection unit 5. Specifically, the control unit 8c obtains the linear expansion coefficient of the spare sample by differentiating the detected length with respect to the detected temperature.

[0034] In this manner, in the measurement method and measurement apparatus 1 of this embodiment, a preliminary measurement step is performed on a spare sample made of the same material as the sample S to determine the glass transition temperature PT1 of the same sample, so that a predetermined temperature PT, which will be described later, can be determined using a more accurate glass transition temperature PT1. As a result, the measurement method of this embodiment can accurately measure the internal compressive stress of the sample S.

[0035] As a result of the above-mentioned preliminary measurement process, in this preliminary sample, as shown by curve 70 in FIG. 2, in a glass state at a temperature lower than the glass transition temperature PT1, the linear expansion coefficient is about 30×10 -6 On the other hand, in the rubber state at temperatures 130°C or higher than the glass transition temperature PT1, the linear expansion coefficient was approximately 110×10 -6 / K and it grew bigger.

[0036] In addition, as shown by curve 70 in FIG. 2, the linear expansion coefficient is 200×10 -6 / K. This is thought to be because the internal compressive stress that had accumulated when the preliminary sample was in a glassy state was released by the transition to a rubbery state, resulting in the linear expansion coefficient reaching its peak. When the preliminary sample in a glassy state with accumulated internal compressive stress changes to a rubbery state, the accumulated internal compressive stress is released to the outside, so it is expected that it will be possible to measure the change in internal compressive stress.

[0037] <Outline of internal compressive stress measurement> In the measurement method and measurement device 1 of this embodiment, the thermomechanical analyzer 10 is used to measure the internal compressive stress of the sample S as follows. Specifically, the control unit 8c selects a constant load mode (indicated by an arrow M1 in FIG. 3). In this constant load mode, prior to a load application step described below, a temperature increase step is executed in which a constant compressive load is applied to the sample S in the direction of the stage St by the probe 6 while the temperature of the sample S is increased until it reaches a predetermined temperature PT.

[0038] The control unit 8c determines the predetermined temperature PT in advance based on the glass transition temperature PT1 of the preliminary sample obtained in the above-mentioned preliminary measurement step or the glass transition temperature PT1 of the sample S stored in advance in the memory unit 8b. Specifically, the control unit 8c determines the predetermined temperature PT as a value obtained by subtracting a predetermined temperature value from the glass transition temperature PT1. The predetermined temperature value is determined in advance and stored in the memory unit 8b in accordance with the material of the sample S, etc., so that the heating step is performed for an appropriate execution time.

[0039] 5, in this heating process, the load generating unit 7 applies a constant load (constant compressive load) to the sample S placed in the sample tube 2 via the probe 6. The heater 3 heats the sample S so that the temperature of the sample S detected by the temperature sensor 4 (shown on the horizontal axis in FIG. 3) increases continuously at a constant heating rate.

[0040] 5, the control unit 8c determines whether or not the temperature of the sample S has reached a predetermined temperature PT based on the detected temperature from the temperature sensor 4. If the control unit 8c determines that the temperature has not reached the predetermined temperature PT (NO in step S12), the control unit 8c returns to step S11.

[0041] On the other hand, if the control unit 8c determines that the temperature has reached the predetermined temperature PT (YES in step S12), the control unit 8c proceeds to step S13. That is, the control unit 8c switches the operation mode of the thermomechanical analysis device 10 from the constant load mode to the constant-length load variation measurement mode (indicated by the arrow M2 in FIG. 3).

[0042] In the fixed-length load variation measurement mode, the control unit 8c performs a load application process in which a compressive load is applied to the sample S in the direction of the stage St by the probe 6 while raising the temperature of the sample S placed on the stage St from a predetermined temperature PT lower than the glass transition temperature PT1 of the sample S, and controls the position of the probe 6 to be constant. Furthermore, in the load application process, when the compressive load changes from an increasing trend to a maximum value to a decreasing trend and then to a minimum value, the control unit 8c calculates the internal compressive stress of the sample S from the difference between the maximum value and the minimum value.

[0043] 5, the control unit 8c performs feedback control of the heater 3 based on the temperature detected by the temperature sensor 4 to raise the temperature of the sample S from the predetermined temperature PT at a constant heating rate. Furthermore, the control unit 8c operates the load generating unit 7 using the detection result of the displacement detecting unit 5 to control the position of the probe 6 to be constant while applying a compressive load to the sample with the probe 6.

[0044] 5, the control unit 8c determines whether or not the temperature of the sample S has reached the upper measurement limit temperature stored in the memory unit 8b, based on the detected temperature from the temperature sensor 4. If the control unit 8c detects that the temperature of the sample S has reached the upper measurement limit temperature (YES in step S14), the control unit 8c determines that it is difficult to measure the internal compressive stress of the sample S, and ends the measurement operation for the sample S.

[0045] When the control unit 8c ends the measurement operation for the sample S, the control unit 8c may be configured to perform a measurement operation for another sample, or to perform a measurement operation for the sample S under changed measurement conditions.

[0046] On the other hand, if the control unit 8c determines that the temperature of the sample S has not reached the upper measurement limit temperature (NO in step S14), the control unit 8c uses the load detection result from the load generating unit 7 to determine whether the compressive load applied to the sample S has changed from an increasing trend to a maximum value, then changed to a decreasing trend, and then detected a minimum value (step S15). If the control unit 8c determines that the minimum value has not been detected (NO in step S15), the process returns to step S13.

[0047] On the other hand, if the control unit 8c determines that the above-mentioned minimum value has been detected (YES in step S15), the control unit 8c uses the load detection result from the load generating unit 7 to calculate the internal compressive stress of the sample S from the difference between the maximum and minimum values ​​of the compressive load (step S16).

[0048] <Specific example of internal compressive stress measurement> More specifically, for example, an epoxy resin having a size of 3 mm×3 mm×5 mm was used as the sample S, and a temperature increasing step and a load applying step were sequentially performed on the sample S using the thermomechanical analyzer 10. Moreover, the control unit 8c selected a value of, for example, 90° C. as the predetermined temperature PT.

[0049] Then, in the temperature increase process in the constant load mode, the control unit 8c applies a constant (compressive) load of, for example, 5 g to the sample S with the probe 6 while controlling the heater 3 to increase the temperature of the sample S at a constant temperature increase rate of, for example, 5° C. / min, from the point when the temperature detected by the temperature sensor 4 is room temperature. As a result, in this temperature increase process, the length of the sample S obtained from the detection result of the displacement detection unit 5 increases up to the predetermined temperature PT, as shown by the curve 80 in FIG. 3. Also, the detection result of the load from the load generation unit 7 (i.e., the compressive load on the sample S) was almost constant up to the predetermined temperature PT, as shown by the curve 90 in FIG. 3.

[0050] Thereafter, when the temperature detected by the temperature sensor 4 exceeds the predetermined temperature PT, the control unit 8c switches to the fixed length load variation measurement mode and executes the load application process. Specifically, from the point in time when the temperature detected by the temperature sensor 4 becomes the predetermined temperature PT, the control unit 8c controls the heater 3 to raise the temperature of the sample S to 150°C at a constant heating rate of, for example, 5°C / min. In addition, the control unit 8c acquires the detection result of the compressive load from the load generating unit 7 while controlling the load generating unit 7 so that the length of the sample S is kept constant at the length of the sample S when the temperature detected by the temperature sensor 4 is the predetermined temperature PT of 90°C and the compressive load applied to the sample S by the probe 6 is 0 g.

[0051] As a result, the length of the sample S, which is obtained from the detection result of the displacement detection unit 5, showed a substantially constant value when the temperature exceeded the predetermined temperature PT, as shown by a curve 80 in FIG.

[0052] In addition, as shown by curve 90 in FIG. 3, the detection result of the compressive load from the load generation part 7 gradually increases when it exceeds a predetermined temperature PT, reaches a maximum value at a temperature before the glass transition temperature PT1, and reaches a minimum value at a temperature near the glass transition temperature PT1.

[0053] Then, the control unit 8c obtained the difference IPP between the maximum value and the minimum value as shown in FIG.

[0054] <Effects> As described above, in the measurement method and measurement device 1 of this embodiment, the load application step is performed, and in the load application step, when the compressive load applied to the sample S changes from an increasing trend to a maximum value, then to a decreasing trend, and then to a minimum value, the internal compressive stress of the sample S is calculated from the difference between the maximum value and the minimum value. As a result, in this embodiment, it is possible to provide a method for measuring internal compressive stress, which is easy to measure and can be used even when the sample S is small.

[0055] In other words, the measurement method and measurement device 1 of this embodiment make it possible to measure the internal compressive stress of the sample S without precision cutting of the sample S or using expensive dedicated equipment such as a laser displacement meter or analysis software.

[0056] Furthermore, the measurement method and measurement device 1 of this embodiment, unlike the above-mentioned conventional example, can measure the internal compressive stress of a small sample S made of a rectangular parallelepiped having sides of 1 mm or more.

[0057] Furthermore, in the measurement method and measurement device 1 of this embodiment, a temperature increase process is performed before the load application process, so that the state transition from the glassy state to the rubbery state in the sample S can be properly performed, and the measurement accuracy of the internal compressive stress can be easily improved.

[0058] Furthermore, in the measurement method and measurement apparatus 1 of this embodiment, during the load application process, the temperature of the sample S is continuously increased at a constant heating rate, so that the load application process can be easily simplified and the internal compressive stress can be measured with simple control.

[0059] In the above description, the measuring device 1 executes a preliminary measurement step for determining the glass transition temperature of a preliminary sample (sample S). However, the present embodiment is not limited to this. For example, when the glass transition temperature of sample S is a known existing value and is stored in advance in the memory unit 8b, the preliminary measurement step for determining the glass transition temperature may be omitted.

[0060] In the above description, the load application step is described as a case where the temperature of the sample S is continuously increased at a constant heating rate. The constant heating rate may be a substantially equal heating rate, and is not limited to a heating rate having an identical value. The load application step of this embodiment is not limited to this, and may be a step in which the temperature of the sample S is increased while a compressive load is applied to the sample S. Furthermore, for example, the temperature of the sample S may be increased while changing the heating rate value to have an amplitude, like a sine wave, so that the temperature of the sample S is a constant heating rate on average, or the temperature of the sample S may be increased while slightly changing the heating rate value.

[0061] [Software implementation example] The functional blocks of the measurement device 1 (particularly, the control unit 8c) may be realized by a logic circuit (hardware) formed in an integrated circuit (IC chip) or the like, or may be realized by software.

[0062] In the latter case, the control unit 8c includes a computer that executes instructions of a program, which is software that realizes each function. The computer includes, for example, one or more processors and a computer-readable recording medium that stores the program. In the computer, the processor reads the program from the recording medium and executes it, thereby achieving the object of the present disclosure.

[0063] The processor may be, for example, a CPU (Central Processing Unit). The recording medium may be a "non-transitory tangible medium" such as a ROM (Read Only Memory), a magnetic disk, a card, a semiconductor memory, a programmable logic circuit, or the like. The device may further include a RAM (Random Access Memory) for expanding the program.

[0064] The program may be supplied to the computer via any transmission medium capable of transmitting the program (such as a communication network or a broadcast wave). Note that one aspect of the present invention may also be realized in the form of a data signal embedded in a carrier wave, in which the program is embodied by electronic transmission.

[0065] 〔summary〕 In order to solve the above problems, a measurement method according to one aspect of the present disclosure is a method for measuring an internal compressive stress of a sample, the method comprising: a load application step in which a compressive load is applied to the sample in the direction of the stage with a probe while raising the temperature of the sample placed on a stage from a predetermined temperature lower than the glass transition temperature of the sample, and controlling the position of the probe to be constant; when, in the load application step, the compressive load changes from an increasing trend to a maximum value, then to a decreasing trend, and then to a minimum value, the internal compressive stress of the sample is calculated from the difference between the maximum value and the minimum value.

[0066] According to the above configuration, it is possible to provide a method for measuring internal compressive stress, which is simple and allows measurement even when the sample is small.

[0067] In the measurement method according to the above aspect, the method may further include a heating step of, prior to the load application step, applying a constant compressive load to the sample in a direction toward the stage with the probe while raising the temperature of the sample until it reaches the predetermined temperature.

[0068] According to the above-mentioned configuration, it is possible to appropriately perform the state transition from the glassy state to the rubbery state in the sample, and it is possible to easily improve the measurement accuracy of the internal compressive stress.

[0069] In the measurement method according to the above aspect, a preliminary measurement step may be performed in which a preliminary sample made of the same material as the sample is used, and a constant compressive load is applied to the preliminary sample in the direction of the stage by the probe while the temperature of the preliminary sample is increased at a constant heating rate and a change in the position of the probe is measured to determine the glass transition temperature of the preliminary sample.

[0070] According to the above-mentioned configuration, the predetermined temperature can be determined using a more accurate glass transition temperature, and the internal compressive stress can be measured with high precision.

[0071] In the measuring method according to the aforementioned aspect, in the load applying step, the temperature of the sample may be continuously increased at a constant heating rate.

[0072] According to the above-mentioned configuration, the load application process can be easily simplified, and the internal compressive stress can be measured with simple control.

[0073] A measuring device according to one aspect of the present disclosure includes a stage on which a sample is placed, a heater for heating the sample on the stage, a temperature sensor for detecting a temperature of the sample on the stage, a probe for contacting the sample on the stage and applying a compressive load to the sample in a direction toward the stage, and a load generating unit for driving the probe to generate the compressive load. The measuring device is provided with a displacement detection unit that detects the position of the probe, and a control unit that controls each unit of the measuring device, and the control unit carries out a load application process in which the temperature of the sample placed on the stage is raised from a predetermined temperature lower than the glass transition temperature of the sample, while the compressive load is applied to the sample by the probe and the position of the probe is controlled to be constant, and when, during the load application process, the compressive load changes from an increasing trend to a maximum value, then to a decreasing trend, and then to a minimum value, the internal compressive stress of the sample is calculated from the difference between the maximum value and the minimum value.

[0074] According to the above configuration, it is possible to provide an internal compressive stress measuring device which is easy to measure and capable of measuring even when the sample is small.

[0075] The present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in the embodiments are also included in the technical scope of the present disclosure. [Explanation of symbols]

[0076] 1. Measuring equipment 2 Sample tubes 3. Heater 4 Temperature Sensor 5 Displacement detection section 6 Probe 7 Load generating section 8 Control device 8c Control section 10 Thermomechanical analyzer S sample St Stage

Claims

1. A method for measuring an internal compressive stress of a sample, comprising the steps of: a load application step of applying a compressive load to the sample in the direction of the stage with a probe while increasing the temperature of the sample placed on the stage from a predetermined temperature lower than the glass transition temperature of the sample, and controlling the position of the probe to be constant; a measuring method characterized in that, in the load application step, when the compressive load changes from an increasing trend to a maximum value, then to a decreasing trend and then to a minimum value, the internal compressive stress of the sample is calculated from the difference between the maximum value and the minimum value.

2. 2. The measurement method according to claim 1, further comprising a heating step of, prior to the load application step, applying a constant compressive load to the sample in a direction toward the stage with the probe while raising the temperature of the sample until it reaches the predetermined temperature.

3. 3. The measurement method according to claim 1, further comprising a preliminary measurement step of determining the glass transition temperature of a preliminary sample made of the same material as the sample by applying a constant compressive load to the preliminary sample in the direction of the stage with the probe while increasing the temperature of the preliminary sample at a constant heating rate and measuring a change in the position of the probe.

4. 4. The measurement method according to claim 1, wherein in the load application step, the temperature of the sample is continuously increased at a constant heating rate.

5. A stage on which a sample is placed; a heater for heating the sample on the stage; a temperature sensor for detecting a temperature of the sample on the stage; a probe that contacts the sample on the stage and applies a compressive load to the sample in a direction toward the stage; a load generating unit that drives the probe to generate the compressive load; a displacement detection unit that detects a position of the probe; A control unit, The control unit is a load application step of applying the compressive load to the sample by the probe while increasing the temperature of the sample placed on the stage from a predetermined temperature lower than the glass transition temperature of the sample, and controlling the position of the probe to be constant; a measuring device for measuring an internal compressive stress of the sample, the measuring device being characterized in that, in the load application step, when the compressive load changes from an increasing trend to a maximum value, then to a decreasing trend, and then to a minimum value, the measuring device calculates an internal compressive stress of the sample from the difference between the maximum value and the minimum value.

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