Device, method, and computer program for determining screw fastening state

Abstract

The present invention provides technology for determining a screw fastening state, with which the screw fastening state can be determined easily and with a high degree of accuracy. A screw fastening state determination device (1) comprises: a vibration applying means (10) for applying vibration to a test object (100) having a screw fixing portion (101A); and an infrared camera (20) serving as a temperature measuring means for measuring the surface temperature of the test object (100). The vibration means (10) applies vibration to the test object (100), and the infrared camera (20) employs thermography to measure a change in the surface temperature of the test object (100) that has generated heat as a result of the vibration, to thereby determine the fastening state of the screw fixing portion (101A).

Description

Apparatus, method and computer program for determining screw tightening state

[0001] The present invention relates to an apparatus or method for determining the fastening state of a screw used, for example, to fasten a circuit board in an electrical product, or a computer program for automatically determining the fastening state of a screw using such an apparatus or system as a hardware resource.

[0002] Screws are still the mainstream and widely used method for fastening circuit boards in electrical products. Generally, the fastening state of a screw is controlled by the tightening torque, but the determination of screw looseness (failure in tightening) has basically had to be done visually. In relation to this issue, for example, Patent Document 1 discloses a technology for measuring the amount of looseness of a screw in a screw fastening machine equipped with a bit for tightening the screw and a suction pipe for suction-holding the screw, in which the relative linear displacement of the bit and the suction pipe is converted into rotational displacement by a pinion-rack mechanism, and the rotational displacement is electrically detected. Prior Art Documents

[0003] Japanese Patent Application Publication No. 8-257849

[0004] For example, for an M4 screw, a change in looseness from a tightening torque of 1.5 N m to 1.3 N m corresponds to a looseness of approximately 0.1 mm. In other words, if the looseness of the screw is to be managed to ensure a fastening guarantee of 0.2 N m or less from the specified value by the looseness of the screw, a high measurement accuracy of at least 0.1 mm or less is required. In particular, in the mass production department of electrical products with multiple screw fastening parts, measuring the looseness of each individual screw one by one for 100% product inspection is extremely cumbersome and inefficient, and a simpler and more efficient method of determination has been sought. Therefore, an object of the present invention is to provide a technology for determining the tightening condition of a screw that can easily determine the tightening condition of a screw with high accuracy.

[0005] In order to solve the above-mentioned problems, the present invention provides a screw fastening state determination device for determining the fastening state of a test object having a screw fastening portion, the device comprising: a vibration unit that applies vibrations to the test object; and a temperature measurement unit that measures the surface temperature of the test object, and the device is configured to determine the fastening state of the screw fastening portion by having the vibration unit apply vibrations to the test object and the temperature measurement unit measure changes in the surface temperature of the test object that has generated heat as a result. This screw fastening state determination device can determine the fastening state of the screw fastening portion with high accuracy and easily based on changes in the surface temperature of the test object that have generated heat as a result of the vibrations applied to the test object by the vibration unit. Furthermore, in the screw fastening state determination device, it is preferable that the temperature measurement unit includes an infrared camera, and changes in the surface temperature of the test object are measured based on thermography captured by the infrared camera. This screw fastening state determination device can easily determine the location of loosened screw fastening portions and the degree of looseness of the screw by visualizing the surface temperature distribution of the test object using thermography captured by the infrared camera. Preferably, the screw tightening state determination device further includes a means for sweeping the vibration frequency applied to the test object and determining an optimal value of the vibration frequency based on the response characteristics to the vibration frequency obtained thereby. According to this screw tightening state determination device, the accuracy of determining the tightening state of a screw fastening portion can be further improved by using a vibration frequency optimized based on the vibration response characteristics. The present invention also provides a screw tightening state determination method for determining the tightening state of a test object having a screw fastening portion, the method including the steps of applying vibration to the test object, measuring a change in the surface temperature of the test object heated by the application of the vibration, and determining the tightening state of the screw fastening portion based on the change in surface temperature. According to this screw tightening state determination method, the tightening state of the screw fastening portion can be determined easily and with high accuracy by applying vibration to the test object and measuring the change in the surface temperature of the test object heated by the application of vibration. Furthermore, in the screw tightening state determination method, it is preferable that the change in the surface temperature of the test object is measured based on thermography captured by an infrared camera.According to this method for determining the fastening state of a screw, the surface temperature distribution of the test object is visualized using thermography captured by an infrared camera, making it possible to easily determine the location of a loosened screw fastening portion and the degree of looseness of the screw. Preferably, the method for determining the fastening state of a screw further includes a step of sweeping a vibration frequency to be applied to the test object and determining an optimal value of the vibration frequency based on the response characteristics to the vibration frequency obtained thereby. According to this method for determining the fastening state of a screw fastening portion, the accuracy of determining the fastening state of the screw fastening portion can be further improved by using a vibration frequency optimized based on the response characteristics of the vibration. The present invention also provides a computer program using a system including a vibration excitation unit that applies vibration to a test object having a screw fastening portion, a temperature measurement unit that measures the surface temperature of the test object, and a measurement control device, the computer program causing the measurement control device to execute the following processes: controlling the vibration excitation unit to apply vibration to the test object; measuring, with the temperature measurement unit, changes in the surface temperature of the test object heated by the application of the vibration; and determining the fastening state of the screw fastening portion based on the change in surface temperature. This computer program controls the measurement and control device of the system to apply vibrations to the test object using a vibration applying unit, thereby enabling the fastening state of a screw fastening portion to be determined easily and with high accuracy based on changes in the surface temperature of the test object caused by the vibrations. Furthermore, the computer program preferably includes an infrared camera in which the temperature measuring unit measures changes in the surface temperature of the test object based on thermography captured by the infrared camera. This computer program visualizes the surface temperature distribution of the test object using thermography captured by the infrared camera, making it possible to easily determine the location of loosened screw fastening portions and the degree of screw loosening. Furthermore, the computer program preferably further causes the computer of the measurement and control device to execute a process of sweeping the vibration frequency to be applied to the test object and determining an optimal value for the vibration frequency based on the response characteristics to the vibration frequency obtained thereby. This computer program further improves the accuracy of determining the fastening state of a screw fastening portion by using a vibration frequency optimized based on the vibration response characteristics.The present invention also provides a computer-readable storage medium that stores the above program.

[0006] According to the present invention, vibrations are applied to an object to be inspected, and the fastening state of a screw fixing portion can be determined easily and with high accuracy based on the change in the surface temperature of the object to be inspected that has generated heat as a result of the vibrations.

[0007] FIG. 1 is a diagram showing a schematic configuration of a screw tightening state determination device according to an embodiment of the present invention. FIG. 2 is a functional block diagram for explaining the schematic configuration of a system including the screw tightening state determination device of FIG. 1 and a measurement control device. FIG. 3 is an example of thermography results showing a comparison of differences in heat generation reactions due to differences in screw tightening torque when a metal plate is used as the fastened object. FIG. 4 is an example of thermography results showing a comparison of differences in heat generation reactions due to differences in screw loosening angle when a metal plate is used as the fastened object. FIG. 5 is an example of thermography results showing a comparison of differences in heat generation reactions due to differences in screw tightening torque when a plastic plate is used as the fastened object. FIG. 6 is an example of thermography results showing a comparison of differences in heat generation reactions due to differences in screw loosening angle when a plastic plate is used as the fastened object. FIG. 7 is an example of thermography results measured on an actual product. FIG. 8 is an example of thermography results measured on another actual product. FIG. 9 is a flowchart for explaining the vibration condition optimization process. Fig. 10 is an example of an infrared image of a target area of ​​a subject. Fig. 11 is an example of response characteristics to a sweep frequency. Fig. 12 is an example of a measurement signal waveform used when optimizing vibration parameters. Fig. 13 is a block diagram showing the configuration of a computer of a measurement control device.

[0008] Hereinafter, as an example of determining the fastening state between members in a test object, a device for determining the fastening state of a test object having a screw fastening portion (fastening state determination device) and a specific determination method thereof (fastening state determination method) will be described. Here, Fig. 1 is a perspective view showing the schematic configuration of a screw fastening state determination device 1 according to one embodiment of the present invention. Fig. 2 is a functional block diagram for explaining the schematic configuration of a system including the screw fastening state determination device 1 and a measurement control device 30 electrically connected to the screw fastening state determination device 1. 1 and 2 includes a female-threaded block 120 having a plurality of female threads 121, 122, 123, and 124 machined by a tap or milling cutter, plate-like fastened objects 111, 112, 113, and 114, which are assumed to be electronic circuit boards, and male screws 101, 102, 103, and 104 for fastening and fixing the fastened objects 111, 112, 113, and 114 to the female threads 121, 122, 123, and 124 of the female-threaded block 120, respectively. The test object 100 has screw fixing portions 101A, 102A, 103A, and 104A, which are the targets of fixation state determination in this embodiment. The screw fixing portion 101A corresponds to the portion where the fastened object 111 is fixed to the female-threaded block 120 by the male screw 101. Similarly, screw fixing portion 102A corresponds to the portion where fastened object 112 is fixed to female-threaded block 120 by male screw 102, screw fixing portion 103A corresponds to the portion where fastened object 113 is fixed to female-threaded block 120 by male screw 103, and screw fixing portion 104A corresponds to the portion where fastened object 114 is fixed to female-threaded block 120 by male screw 104. Note that the specimen 100 illustrated in Figures 1 and 2 is one of the test pieces used to verify the effectiveness of the present invention, and it goes without saying that the implementation of the invention is not limited to the structure of specimen 100 shown in these figures. For example, the specimen may have a structure in which one fastened object is fixed at multiple points, or the specimen may be a member of any shape and size other than a plate, and made of any material. Also, FIG. 2 shows a support base 130 that supports the female thread block 120, but this support base 130 is provided to investigate how differences in the vibration transmission structure system including the test object 100 affect the vibration response characteristics, and is not an essential element of the invention.As illustrated in FIGS. 1 and 2 , a screw fastening state determination device 1 according to this embodiment includes a vibration generator 10 that applies vibrations to a test object 100 and a temperature measurement unit 20 that measures the surface temperature of the test object 100. This device can determine the fastening state of the test object 100, which has screw fastening portions 101A, 102A, 103A, and 104A. The screw fastening state determination device 1 may also be systemized by connecting a measurement control device 30 to the vibration generator 10 and the temperature measurement unit 20, as shown in FIG. 2 . The vibration generator 10 has a piezoelectric element 10A built into its truncated cylindrical vibration head. A vibration control unit 320 of the measurement control device 30 outputs a drive signal (also referred to as a measurement signal) to the piezoelectric element 10A, causing the piezoelectric element 10A to expand and contract, thereby generating vibrations with a vibration frequency and power corresponding to the drive signal. The vibration frequency range used in the fastening state determination according to this embodiment is preferably an ultrasonic band of, for example, 15 kHz to 25 kHz. The position (excitation point) at which the excitation unit 10 applies vibration to the test piece 100 is selected based on the maximum vibration response in the actual vibration transmission system including the test piece 100, as described below. Such an excitation point may be located at the end of the female-threaded block 120 shown in Figures 1 and 2 , or at a location distant from the fastening part. In some cases, vibration may be applied indirectly to the test piece 100 via a support 130 that supports the test piece 100, rather than directly. The temperature measurement unit 20 is equipped with an infrared camera. By generating a thermographic image based on infrared images captured by the infrared camera, the surface temperature distribution and temperature changes of the test piece 100 can be observed in real time. For example, in a fastening part using an M4 screw, the specified tightening torque is 1.5 N·m, while the lower limit of the tightening torque allowed due to loosening is 1.3 N·m. This torque difference (difference in screw axial force) corresponds to approximately 0.1 mm of loosening in terms of screw float. That is, to reliably control the quality of the fastening state of an M4 screw, it is necessary to determine the tightening torque to be at least 0.2 N·m or less and the amount of screw float to be 0.1 mm or less with accuracy.The inventors focused on the relationship between loosening of a screw and heat generated when vibration is applied, and came to the realization that a thermographic non-destructive inspection method is useful as a means for determining the fastening state of a screw with high accuracy and ease. Therefore, using the above-described fastening state determination device 1, verification was conducted to determine whether the loosening state of a screw can be determined from a thermographic image obtained by measuring the surface temperature of the test object 100. The attributes of the fastened object, female-threaded block, and screw used in the verification are shown in Tables 1, 2, and 3, respectively. In Table 1: Substrate No. 1 is a 0.8 mm thick copper plate made of tough pitch copper (C1100-1 / 2H). It is tin-plated as a surface treatment. Substrate No. 2 is a 1.0 mm thick copper plate made of tough pitch copper (C1100-1 / 2H). It is tin-plated as a surface treatment. Substrate No. 3 is a 1.2 mm thick copper plate made of tough pitch copper (C1100-1 / 2H). It is tin-plated as a surface treatment. Substrate No. 4 is a 1.0 mm thick copper plate made of tough pitch copper (C1100-1 / 2H). Substrate No. 5 is an electrogalvanized cold-rolled steel sheet (SECC) with a thickness of 1.0 mm. Substrate No. 6 is a glass epoxy resin substrate with a thickness of 1.6 mm. Surface treatment involves applying a resist and plating the through holes (TH) through which the screws pass. In Table 2: Block No. 1 is a block made of low carbon steel (S10C). Block No. 2 is a block made of copper (C3406). Block No. 3 is a block made of aluminum alloy (ADC12). In Table 3: Screw No. 1 is a 4 mm (M4) captive washer (Sems) screw with a trivalent chromate surface treatment. The under-head length is 10 mm. Screw No. 2 is a 4 mm (M4) captive washer (Sems) screw with a trivalent chromate surface treatment. The under-head length is 16 mm. Figure 3 shows an example of a thermography result according to this embodiment. In the example of Figure 3, metal substrate No. 1 shown in Table 1 was used as the object to be fastened to test piece 100. Furthermore, aluminum alloy block No. 3 shown in Table 2 was used as the female-threaded block, and screw No. 1 shown in Table 3 was used as the male thread. In Figure 3, the left image shows the case where the tightening torque was set to the design standard value of 1.5 N·m, and the right image shows the case where the tightening torque was set to 1.3 N·m. At a tightening torque of 1.5 N·m, sufficient axial force is applied, and the female screw block and the workpiece are integrated, so almost no vibration-induced reaction is observed. On the other hand, when the tightening torque is changed to 1.3 N·m, loosening is not detectable visually, but an exothermic reaction is observed around the outer periphery of the washer at the screw-fastening point. Figure 4 shows an example of thermography results using the same test specimen 100 as in Figure 3 . In Figure 4 , the left image shows the screw loosened 45° from the torque-up state, and the right image shows the screw further loosened to 90°. The amount of thread float at 45° loosening corresponds to 0.08 mm, and the amount of thread float at 90° loosening corresponds to 0.18 mm, resulting in a difference of 0.1 mm. At 45° loosening, an exothermic reaction was observed at the screw-fastening point. At 90° loosening, an even stronger reaction at the screw-fastening point and a significant reaction were also observed at the end of the workpiece 111. The vibration of the fastened object seen in the image on the right is thought to be due to the loss of the screw's fixing function. Next, Figures 5 and 6 show an example of the thermography results when the fastened object of the test subject 100 was changed to glass epoxy resin board No. 6 shown in Table 1. In this embodiment, aluminum alloy block No. 3 shown in Table 2 was used as the female threaded block, and screw No. 1 shown in Table 3 was used as the male thread. In Figure 5, the image on the left is when the fastening was performed at a standard value of 1.5 N m, and the image on the right is when the fastening was performed at 1.3 N m.In Figure 6, the left image shows the screw loosened by 45°, and the right image shows the screw loosened by 90°. As can be seen from Figures 5 and 6, the thermographic images show similar reaction trends between the washer and the fastened object, even when the fastened object is made of plastic. A difference of 0.2 N·m in tightening torque and a difference of 0.1 mm in screw float can be detected. Furthermore, at tightening torques of 1.3 N·m or greater, a significant vibration response was observed in the relatively soft plastic substrate. Even considering the fragile structure of the fastened object in this test, where the fastened object was fastened at a single point via a single through-hole, these results suggest that the proposed thermographic nondestructive testing method can also be a useful tool for identifying stress concentration points during the product development stage. Next, Figure 7 shows an example of thermographic results measured on an actual product. The test object in Figure 7 is an electronic circuit unit consisting of an electronic circuit board mounted in an aluminum die-cast case. 8 shows an example of thermography results measured on a test object in which a resin case is fixed to a metal stay with tapping screws. As described above, since the structural transmission system of vibration varies depending on the size, structure, material, etc. of the test object, it is desirable to apply vibration at multiple locations on a single product. It is also desirable to optimize the vibration parameter conditions for each vibration point to obtain an optimal thermographic display. The above-described method of determining the fastening state using the screw fastening state determination device 1 is preferably automated by the control and analysis processing of the measurement control device 30 in order to perform more objective and quantitative determination. 2 outputs a measurement signal that forms a vibration waveform to the vibrator 10 to apply vibration to the test object 100, the temperature measurement unit 20 generates a thermographic image based on an infrared image of the test object 100, and the thermographic analysis unit 301 measures the distribution and changes in the surface temperature of the test object 100 based on the generated thermographic image, thereby determining the fastening state of the screw fixing portions 101A, 102A, 103A, 104A. The present invention may also be provided to a user in the form of a coded program that causes a computer in the measurement control device 30 to execute all or part of the above-mentioned fastening state determination process.As described above, differences in the vibration transmission system of the test object, i.e., differences in the test object structure (including the shape and material of the components), the type of fixation means (e.g., screw fixation or crimping), and the position of the vibration point, result in differences in the heat generation reaction. Therefore, the present invention preferably includes a vibration condition optimization means 310 that optimizes the vibration parameter conditions to provide a thermographic display optimal for identifying the fixation state of the screws, etc. More specifically, as shown in FIG. 2 , the vibration condition optimization means 310 includes a vibration response detection unit 311, a measurement frequency determination unit 312, a vibration power determination unit 313, a measurement cycle determination unit 314, and a measurement count determination unit 315. These processing units realize their respective functions by the computer of the measurement control device 30 executing arithmetic processing. The vibration condition optimization process will be specifically described with reference to the flowchart in FIG. 9 . First, the vibration condition optimization means 310 instructs the vibration control unit 320 to sweep the vibration frequency while maintaining a constant vibration power. The vibration generator 10 generates vibrations in response to a measurement signal from the vibration controller 320, thereby applying vibration to the subject while sweeping the vibration frequency (step S11). Next, the vibration response detector 311 detects a vibration response in a target area on the subject from an image captured by the infrared camera 20 (step S12). FIG. 10 shows an example of an infrared image of the target area on the subject. FIG. 11 shows an example of a response characteristic, in which the power in response to the swept vibration frequency is shown as a broken line. Based on the response characteristic obtained by sweeping the vibration frequency, the measurement frequency determiner 312 determines the frequency at which the response is maximized as the optimal frequency for measurement (step S13). Next, the vibration condition optimizer 310 generates a measurement waveform having the determined optimal frequency and sends it to the vibration controller 320. FIG. 12 shows an example of a measurement signal waveform used for vibration. As shown in FIG. 12, in the measurement according to this embodiment, a vibration step in which the power changes in a sinusoidal, step-like manner is repeated multiple times. The vibration power determination unit 313 adjusts the power (amplitude) of the measurement signal so that the reaction on the thermograph is most efficient (step S14).The optimized power may be, for example, either the amplitude of the low-frequency component, which changes in a sinusoidal or step-like manner as shown in FIG. 12 , or the amplitude of the high-frequency (ultrasonic) component, which is shown within a circle in FIG. 12 . The measurement cycle determination unit 314 determines a measurement cycle that will produce a thermographic display suitable for identification, using a measurement signal having the optimal frequency and vibration power set in steps S13 and S14 (step S15). The measurement cycle here corresponds, for example, to the time required for one vibration step as shown in FIG. 12 . Furthermore, the measurement count determination unit 315 repeats the vibration step multiple times and determines the optimal number of measurements (number of vibration steps) that will most efficiently obtain reaction information (step S16). The processing performed by the vibration condition optimization unit 310 described above may be provided to the user in the form of a coded program 400 that is executed by the computer of the measurement control device 30. 13, the measurement control device 30 includes a central processing unit (CPU, GPU, DSP) 30B, a storage device (ROM, RAM, hard disk, cache memory) 30C, an input device (keyboard, touch panel, mouse) 30D, a display device (liquid crystal display) 30E, and the like, all of which are connected to one another via a bus 30A. The storage device 30C functions as a computer-readable storage medium. The storage device 30 stores a program 400 for causing the above-mentioned functional units to function. In other words, the program 400 stored in the storage devices 3C, 5C, and 8C is a program 400 that causes the computer of the measurement control device 30 to execute predetermined processing, and is a computer program 400 that uses a system including a vibration unit 10 that applies vibration to the test subject 100 having screw fixing portions 101A, 102A, 103A, and 104A, a temperature measurement unit 20 that measures the surface temperature of the test subject 100, and the measurement control device 30 to cause the computer of the measurement control device 30 to execute the following processes: controlling the vibration unit 10 to apply vibration to the test subject 100; measuring, with the temperature measurement unit 20, changes in the surface temperature of the test subject 100 that has generated heat due to the application of vibration; and determining the fastening state of the screw fixing portions 101A, 102A, 103A, and 104A based on the changes in the surface temperature.The program 400 is a computer program in which the temperature measurement unit 20 includes an infrared camera, and changes in the surface temperature of the test object 100 are measured based on thermography captured by the infrared camera. Furthermore, the program 400 further causes the computer of the measurement control device 30 to execute a process of sweeping the vibration frequency to be applied to the test object 100 and determining an optimal value for the vibration frequency based on the response characteristics to the vibration frequency obtained thereby. According to the present embodiment described above, a screw fastening state determination device and a screw fastening state determination method can be provided that can accurately and easily determine the fastening state of a screw fastening portion by applying vibration to the test object and measuring changes in the surface temperature of the test object that has generated heat using the temperature measurement unit. Furthermore, by including an infrared camera and measuring changes in the surface temperature of the test object based on thermography captured by the infrared camera, i.e., by visualizing the surface temperature distribution of the test object using thermography captured by the infrared camera, the location of loosened screw fastening portions and the degree of loosening of the screw can be easily determined. Furthermore, by further including a means and step of sweeping the vibration frequency to be applied to the test object and determining the optimal value of the vibration frequency based on the response characteristics to the vibration frequency obtained thereby, i.e., by using the vibration parameters optimized by the vibration condition optimization means based on the response characteristics of the vibration, the accuracy of determining the fastening state of the screw fastening portion can be further improved. Note that the targets for fastening state determination according to the present invention include, in addition to fastening with a "screw" as described here, fastening with a "leaf spring," fastening with an "adhesive," fastening by "welding," and fastening with "caulking," such as a flying rivet, press caulking, or spin caulking.

[0009] 1 Screw fastening state determination device 10 Vibration unit 20 Temperature measurement unit, infrared camera 30 Measurement control device 30A Bus 30B Central processing unit 30C Storage device 30D Input device 30E Storage device 100 Test object 101, 102, 103, 104 Male screw 101A, 102A, 103A, 104A Screw fixing unit 111, 112, 113, 114 Fastened object 120 Female screw block 121, 122, 123, 124 Male screw 130 Support base 301 Thermography analysis unit 302 Screw float amount determination unit 303 Tightening torque determination unit 310 Vibration condition optimization means 311 Vibration response detection unit 312 Measurement frequency determination unit 313 Vibration power determination unit 314 Measurement period determination unit 315 Measurement count determination unit 320 Vibration control unit 400 Program

Claims

1. A screw fastening state determination device for determining the fastening state of a specimen having a screw fastening portion, comprising: a vibration applying portion that applies vibration to the specimen; and a temperature measurement portion that measures the surface temperature of the specimen, wherein the vibration applying portion applies vibration to the specimen, and the temperature measurement portion measures a change in the surface temperature of the specimen that has generated heat thereby, so as to determine the fastening state of the screw fastening portion.

2. The screw fastening state determination device according to claim 1, wherein the temperature measurement portion includes an infrared camera, and a change in the surface temperature of the specimen is measured based on a thermograph photographed by the infrared camera.

3. The screw fastening state determination device according to claim 1 or 2, further comprising means for sweeping the vibration frequency applied to the specimen and determining an optimum value of the vibration frequency based on a reaction characteristic with respect to the vibration frequency obtained thereby.

4. A screw fastening state determination method for determining the fastening state of a specimen having a screw fastening portion, comprising: applying vibration to the specimen; measuring a change in the surface temperature of the specimen that has generated heat by applying the vibration; and determining the fastening state of the screw fastening portion based on the change in the surface temperature.

5. The screw fastening state determination method according to claim 4, wherein a change in the surface temperature of the specimen is measured based on a thermograph photographed by an infrared camera.

6. The screw fastening state determination method according to claim 4 or 5, further comprising sweeping the vibration frequency applied to the specimen and determining an optimum value of the vibration frequency based on a reaction characteristic with respect to the vibration frequency obtained thereby.

7. A computer program for causing a computer of a measurement control device to execute, using a system including a vibration applying portion that applies vibration to a specimen having a screw fastening portion, a temperature measurement portion that measures the surface temperature of the specimen, and the measurement control device: a process of controlling the vibration applying portion to apply vibration to the specimen; a process of measuring, by the temperature measurement portion, a change in the surface temperature of the specimen that has generated heat by applying the vibration; and a process of determining the fastening state of the screw fastening portion based on the change in the surface temperature.

8. The computer program according to claim 7, wherein the temperature measurement portion includes an infrared camera, and a change in the surface temperature of the specimen is measured based on a thermograph photographed by the infrared camera.

9. The computer program according to claim 7 or 8, further causing the computer of the measurement control device to execute a process of sweeping the vibration frequency applied to the subject and determining an optimum value of the vibration frequency based on the reaction characteristics with respect to the vibration frequency obtained thereby.

10. A computer-readable storage medium storing the program according to any one of claims 7 to 9.

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