JP2006343216A - Screw characteristic testing device and experience learning method, and practical skill educational method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a screw characteristic testing device for deepening one's understanding, concerning a screw, by making it easy to use, and it compact and portable and simply confirming characteristics and logic of the screw anywhere in front of one's eyes, and to provide an experience learning method and a practical skill educational method that uses it. <P>SOLUTION: The screw characteristic testing device is made portable by providing a hydraulic generation means (hydraulic pump 3), a load-generating means (a cylinder 21 and a piston 22) given to amplify oil pressure from the hydraulic generation means 3 on a test screw (bolt 4), and a load display means (oil pressure gage 4) for displaying load given to the screw 9 on the same substrate 10. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a test apparatus for examining a tightening characteristic of a screw such as a bolt, an experiential learning method for a tightening characteristic of a screw using the test apparatus, and a practical skill education method.

  Screws and screw parts have a variety of functions despite their simple structure, and play an important role in all industrial products such as familiar products, state-of-the-art rockets and precision machines.

  Screws and screw parts perform their functions only after obtaining the target tightening force, and if they are used incorrectly, they cannot perform their original functions. However, with general screws and screw parts, it cannot be confirmed from the appearance whether the tightening force is acting as intended.

  Also, the tightening method and tightening conditions may differ each time, such as during trial production, production, or after-market service, and it is necessary to carefully check the tightening condition in each case. There is.

  However, many of today's engineers often do not assemble the components themselves, and because they are less interested in screws, there is a lack of understanding about the characteristics of the screws. For this reason, it is required that mechanical engineers and designers fully understand the importance and contents of screw characteristics, and then design and manufacture products.

  Traditionally, engineers and designers have learned the characteristics of screws in textbooks and specialized books, but the principle of plastic zone tightening, which is particularly difficult to understand with only the figures and texts written in textbooks, etc. Is difficult to understand.

  Various devices for testing the characteristics related to screw tightening are commercially available, but such devices are large and cannot be used except at the installation site. Therefore, it is difficult for anyone to visually understand and understand the characteristics of the screw in front of the eyes.

  The present invention has been made in consideration of the above-described prior art, is easy to use, small and portable, and is a screw for deepening the understanding of screws by confirming the characteristics and theory of screws easily in front of the eyes. It is an object of the present invention to provide a characteristic test apparatus, an experience learning method and a practical skill education method using the apparatus.

  According to the first aspect of the present invention, the same circuit board includes the hydraulic pressure generating means, the load generating means for amplifying and applying the hydraulic pressure from the hydraulic pressure generating means to the test screw, and the load display means for displaying the load applied to the screw. Provided is a screw characteristic testing apparatus which is provided on the top and is portable.

  The invention of claim 2 is characterized in that, in the invention of claim 1, an upper catcher and a lower catcher for collecting fragments when the screw breaks above and below the screw mounting position during testing are provided.

  The invention of claim 3 is characterized in that, in the invention of claim 1, temperature adjusting means is provided to make the screw temperature variable.

  According to a fourth aspect of the present invention, in the first aspect of the invention, the load generating means comprises a piston (22) that moves up and down in the cylinder (21), and an upper end portion of the screw is provided on the piston (22). A nut holding portion (21a) supported by the support portion (22a) and facing the screw support portion (22a) is provided to hold the nut in the cylinder (21), and a lower end portion of the screw is screwed into the nut. The lower end surface of the screw support portion (22a) is in contact with the upper end surface of the nut holding portion (21a) at the lowest position of the piston (22).

  The invention of claim 5 is characterized in that, in the invention of any one of claims 1 to 4, it is used as a teaching material for learning or teaching the theory of tightening characteristics of a screw while performing a test using a screw characteristic test apparatus. And

  The invention of claim 6 is an experiential learning method using the invention of claim 1, characterized in that a screw characteristic is learned by reproducing a theoretical screw tightening characteristic diagram by a test.

  The invention according to claim 7 is a practical skill education method using the invention according to claim 1, characterized in that a screw characteristic is educated by reproducing a theoretical screw tightening characteristic diagram by a test.

  According to the first aspect of the present invention, the hydraulic pressure generating means, the load generating means and the load display means constituting the test apparatus are arranged on the same substrate so that they can be carried, so that the place of use is not restricted and can be easily carried anywhere. The test can be done at Therefore, many people can experience screw characteristic tests in front of their eyes in classrooms and demonstration venues. Then, by attaching a simple instrument such as a torque wrench or dial gauge to such a basic test apparatus, various characteristics relating to the screw can be examined.

  According to invention of Claim 2, when investigating the characteristic of the screw which is easy to fracture | rupture, such as an aluminum alloy and cast iron, it can collect | recover reliably, without scattering a fragment to the circumference | surroundings.

  According to the invention of claim 3, for example, by attaching a heater or the like for heating the screw and the seating surface, it becomes possible to measure the change in the surface pressure resistance due to heat and the hot creep amount of the bolt, and the application range is expanded.

  According to the invention of claim 4, when the hydraulic pressure is zero and the piston (22) is at the lowest position with respect to the cylinder (21), an upward tensile force acts on the head of the screw by, for example, rotation of the screw, When the nut holding portion (21a) screwed to the lower end portion is raised, the upper end surface of the nut holding portion (21a) is in contact with the lower end surface of the screw supporting portion (22a), so that the tensile force is screw supported. It is received by the part (22a). Therefore, the nut holding portion (21a) and the screw support portion (22a) are not deformed or damaged, and the device is protected.

  According to the invention of claim 5, by using the screw characteristic testing device of the present invention that is portable and portable as a teaching material, it can be actually used in front of a large number of trainees in a classroom, a lecture hall or a conference room of a company, etc. While conducting a screw test, the trainer is instructed and trained in the theory of tightening the screw, and the trainee can visually confirm and fully understand it.

  According to the invention of claim 6, the learner who wants to understand the theory of the tightening characteristics of the screw should actually test the screw in front of the difficult screw theory described in the textbooks and technical books. Allows you to fully understand the screw theory while experiencing it.

  According to the invention of claim 7, when a practical trainee or a learner who handles screws is taught and understood about the theory of the characteristics of the screw, the trainee is actually using the screw characteristic test device of the present invention. By reproducing and teaching the tightening characteristic diagrams of screws that are difficult to understand, it is possible to educate the trainees with a deep understanding of screw theory.

  1A and 1B show a test apparatus of the present invention. The test apparatus 1 attaches a test bolt 9 from the center on the upper surface side and collects fragments when the test machine main body 2, the hydraulic pump 3, the hydraulic gauge 4, and the bolt 9 break the bolt 9. It consists of an upper catcher 5 and a lower catcher 6, which are placed on a common integral substrate 10.

  The testing machine main body 2 has a cylindrical shape, and a through-hole 20 penetrating vertically is formed at the center. A cylinder 21 having a substantially U-shaped cross section is formed on the outer periphery of the through hole 20 over the entire periphery. A nut 12 for screwing the bolt 9 is fitted into the through hole 20, and the nut 12 is fixed inside the cylinder 21. The piston 22 is inserted into the cylinder 21 so as to be slidable in the vertical direction, and an oil chamber 23 is formed between the bottom of the piston 22 and the cylinder 21. An O-ring 27 is attached to the lower side surface of the piston 22 to keep the oil chamber 23 oil-tight. The lower part of the oil chamber 23 is connected to the hydraulic pump 3 and the hydraulic gauge 4, and oil is appropriately supplied from the hydraulic pump 3, and the hydraulic pressure is displayed by the hydraulic gauge 4.

  A cover 25 is attached to the upper part of the cylinder 21, and a spring 24 that biases the piston 22 downward is attached between the cover 25 and the lower part of the piston 22. An anti-rotation member 26 is fitted at one place on the piston 22.

  A seat plate 11 serving as a seat surface of the bolt 9 is attached above the nut 12, and the seat plate 11 is fixed to an upper portion of the piston 22. The bolt 9 is inserted from above the seat plate 11 and screwed into the nut 12 for various characteristic tests.

  The test bolt (screw) 9 has an upper head supported on a bolt (screw) support 22 a at the center upper end of the piston 22 via the seat plate 11. The lower end portion of the bolt 9 is fixed to the nut holding portion 21 a at the center upper end portion of the cylinder 21 via the nut 12. The nut holding part 21a and the bolt support part 22a are each formed in a flange shape, protrude toward the through hole 20, and oppose each other.

  When the piston 22 is lowered with respect to the cylinder 21, the nut holding portion where the lower surface of the bolt support portion 22 a of the piston 22 faces the lower side before the lower surface of the piston 22 of the oil chamber 23 contacts the bottom surface of the cylinder 21. The top surface of 21a is brought into contact with and closely contacts. That is, at the lowest position of the piston 21 with zero hydraulic pressure, the lower surface of the piston-side bolt support portion 22a is in close contact with the upper surface of the cylinder-side nut holding portion 21a. Therefore, when the test is performed with the hydraulic pressure set to zero (for example, a rotation angle test shown in FIG. 17 described later), the bolt 9 is turned with a torque wrench to apply an upward tensile force to the head of the bolt 9 and When the upward pulling force is applied together with the nut holding part 21a, the pulling force is received by the lower surface of the bolt support part 22a on the piston side, so that an excessive force is not applied to the nut holding part 21a and the bolt support part 22a, and deformation is caused. And damage is prevented.

  With the above structure, when the hydraulic pump 3 is operated to supply oil to the oil chamber 23 and apply hydraulic pressure, the piston 22 rises, and a force for pulling up the upper part of the bolt 9 via the seat plate 11 is generated. A load acts. A weight 31 is placed on the front end of the handle of the hydraulic pump 3 in order to keep the oil pressure higher than a predetermined oil pressure in the oil chamber 23 at all times.

  Since such a test apparatus 1 is compactly arranged on one substrate 10, it is easy to carry. In addition, since no electrical wiring is required, it can be easily carried and used anywhere.

  The oil pressure gauge 4 may display the value of the oil pressure as it is, or may be a load gauge that displays a value converted into a load acting on the bolt 9 by the oil pressure.

  Using the above-described test apparatus 1 as a basic form, as described below, it is possible to examine various characteristics related to bolts by attaching a commercially available simple instrument, attachment, or the like. During testing, data such as loads and strains applied to bolts, etc., as needed, can be recorded and graphed to understand the state at that time and deepen understanding. In addition, this test apparatus understands the phenomenon regarding the characteristic of a volt | bolt, and the precision of a test result is not requested | required. In other words, the main purpose of this test device is to use it as a teaching material and to allow screw trainers to understand the theory of screw characteristics. For that purpose, it is sufficient that the test shows a tendency of the screw characteristics, and it is not always necessary to exactly match the theoretical value.

  FIG. 2 shows the shapes of the catchers 5 and 6. FIG. 2A shows an upper catcher, which is used with a lid 51 on the upper side of the bolt 9. A shock absorbing material 52 made of resin or the like is provided on the inner top surface of the lid 51. A chain 53 is attached to the outside of the lid 51, and the other end of the chain 53 is fixed to the tester body 2 (FIG. 1), for example. FIG. 2B shows a lower catcher, which is used by locking the flange 62 to the notch 10 a of the substrate 10 below the bolt 9. An impact absorbing material 63 is provided on the inner bottom surface of the dish 61. Such upper and lower catchers 5 and 6 are used to collect fragments when examining characteristics of bolts that are easily broken, such as aluminum alloys and cast iron.

  FIG. 3 shows a test apparatus and results for knowing the relationship between axial force and strain when the bolt 9 is pulled in the axial direction.

  FIG. 3A shows an outline of the apparatus, in which a dial gauge 13 for measuring the strain amount of the bolt 9 is attached in addition to the test apparatus 1 of FIG. During the test, the testing machine main body 2 is pressurized by the hydraulic pump 3 and an axial tensile force is applied to the bolt 9. The tip of the dial gauge 13 is brought into contact with the head of the bolt 9, and the displacement of the head of the bolt 9 with the lower part fixed to the nut 12 (FIG. 1), that is, the axial distortion of the bolt 9 is measured.

  FIG. 3B illustrates the relationship between the axial force in the tensile direction acting on the bolt 9 by hydraulic pressure and the distortion of the bolt 9. In FIG. 3 (B), the axial force applied to the bolt 9 is applied immediately before the yield point, that is, up to point A within the elastic limit to obtain a loaded state, and then the axial force is released to unload. Since point A is within the elastic limit, the bolt strain returns to zero when unloaded. Further, even if loading and unloading are repeated, the relationship between the axial force and strain is the same as in the first loading as long as it is within the elastic limit, and reciprocates in the direction of the arrow on the solid line of the graph. The slope of this graph is the spring constant of the bolt 9.

  FIG. 3C shows the result of the stage following (B), and illustrates the relationship between axial force and strain when a tensile force is applied to the bolt 9 up to the plastic region.

Up to point A in the figure, loading is performed in the same manner as in (B), and loading is stopped at point B where the axial force of the bolt exceeds the point A of the elastic limit and reaches the plastic region, and the axial force hardly increases. If you then unloaded, when the axial force is zero, rather than the value 0 of the dial gauge 13 indicates the value of epsilon _1, it can be seen that the permanent strain epsilon ₁ remained. Then, when loading again, it turns out that the graph is linear and elastically deformed until point B, which is the maximum axial force at the first loading. That is, the new elastic limit is point B, and the axial force is higher than the first elastic limit A point. When actual bolts are used, there is a case where a tensile load is once applied to the plastic region in order to increase the elastic limit.

  FIG. 4 shows an apparatus and results for knowing the relationship between the axial force and strain when the bolt 9 is twisted and tightened.

  FIG. 4A is an outline of the apparatus, and a dial gauge 13 is installed to measure the axial displacement of the head of the bolt 9, that is, the distortion of the bolt 9, using a wrench 14 that turns the head of the bolt 9.

  FIG. 4B illustrates the relationship between axial force and strain when the bolt 9 is twisted with a wrench 14 without being pressurized by the hydraulic pump 3. When the wrench 14 is twisted and tightened, friction is generated on the thread surface of the bolt 9 and a shear stress acts. Therefore, it yields with an axial force lower than that during simple tension as shown in FIG. 3, and becomes an elastic limit at point A of an axial force smaller than the limit of the capacity of the bolt itself. In addition, since the shear stress varies depending on the friction coefficient of the thread surface, the yield point differs, and as shown by the broken line in the figure, the axial force varies particularly in the plastic region after the yield point.

Further, when the bolt is twisted in the reverse direction at the point B that has entered the plastic region beyond the yield point with twisting, the permanent strain ε ₁ remains.

  FIG. 4C illustrates the relationship between the axial force and strain when an axial tensile load is applied to the bolt 9 by the hydraulic pump 3 after twisting with the wrench 14 to point B in FIG. 4B. is there.

By applying a simple tensile load to the bolt once yielded by twisting without adding twist, the axial force further increases. When the loading is stopped and unloaded at the point C that exceeds the yield point due to the tensile load and enters the plastic region, the remaining permanent strain becomes ε ₁ + ε ₂ . After that, when a tensile force is applied to the bolt again, it is elastically deformed to the point C, and the point C becomes the new elastic limit.

  As described above, when the loading in the tensile direction is performed after being twisted and tightened, the permanent distortion increases, but the original nature of the bolt appears with respect to the axial force. That is, even if the yield point appears low due to twisting, the axial strength of the bolt does not become weak. This phenomenon cannot be explained by mathematical formulas or the like, but can be understood only by such a demonstration.

  FIG. 5 shows an apparatus and results for knowing the relationship between the axial force and the torque when the bolt 9 is twisted and tightened.

  FIG. 5A shows an outline of the apparatus, in which a torque wrench 15 is attached to the head of the bolt 9 of the basic test apparatus 1 shown in FIG. The bolt 9 is tightened by the torque wrench 15 and the torque value is read, and the axial force acting on the bolt 9 is read by the hydraulic gauge 4. In this test, no force is applied by the hydraulic pump 3.

  FIG. 5B illustrates the measurement results. If the frictional force of the bolt head or screw part is different, the axial force will be different even if tightened with the same torque. In other words, this measurement shows that the axial force decreases even when the same torque is applied, when the bolt 9 is tightened with lubricating oil and when the frictional resistance is high without using the lubricating oil. it can.

The torque coefficient k is
k = T / (F × d)
However, T: Tightening torque F: Axial force d: Obtained by the nominal diameter of the screw, and by obtaining the torque coefficient, the tightening torque for obtaining the necessary axial force can be known.

Moreover, the friction coefficient of the volt | bolt 9, the seat surface board 11, and the nut 12 (refer FIG. 1) can be measured using the apparatus of FIG. 5 (A). The relationship between torque T and axial force F during bolt tightening is
T = (dp / 2) × F × (μs / cos α) + (dp / 2) × F × tan β
+ (Dw / 2) × F × μw
However, dp: Effective diameter of screw α: Half angle of screw thread μs: Friction coefficient of screw surface dw: Equivalent diameter of seat surface β: Screw lead angle μw: Friction coefficient of seat surface The friction coefficient μw of the surface is obtained.

  First, a bolt is attached using a bearing washer whose equivalent diameter dw and friction coefficient μw are known as a seat plate, the bolt is tightened with a torque wrench, and the relationship between torque T and axial force F is measured. Since the effective diameter dp of the screw, the half angle α of the thread, and the lead angle β of the screw are known values at the time of bolt selection, the friction coefficient μs of the thread surface can be obtained by the above formula.

  Next, instead of the bearing washer, a properly used washer is used to similarly tighten the bolt and measure the relationship between the torque T and the axial force F. Since the friction coefficient μs of the screw surface has become a known numerical value by the measurement with the bearing washer, the friction coefficient μw of the seating surface can be obtained from the above equation.

  Accordingly, a relational expression between the torque T and the axial force F when the bolt is tightened using the washer used in the actual product is obtained, and the torque T for obtaining the necessary axial force F in the product using the bolt is known. .

  FIG. 6 shows an apparatus and result for measuring the spring constant of the bolt 9, and FIG. 7 shows an apparatus and result for measuring the spring constant of the collar 8 that is the object to be tightened. In both cases, the load is within the elastic limit.

  FIG. 6A is the same as FIG. 3A, in which a dial gauge 13 for measuring the strain of the bolt 9 is attached to the tester main body 2. By applying pressure with the hydraulic pump 3, an axial tensile force is applied to the bolt 9, and the axial force is read from the hydraulic gauge 4. The dial gauge 13 reads the axial displacement of the bolt 9 head, that is, the distortion of the bolt 9.

FIG. 6B illustrates the relationship between the axial force F of the bolt and the strain in the extension direction. The strain at point A when the axial force is Ff is λb, and the spring constant Kb of this bolt 9 is
Kb = Ff / λb
Is calculated by

  FIG. 7A shows a dial gauge 13 in which a cylindrical collar 8 is arranged around a bolt 9 and plates 16a and 16b are attached to both ends of the collar 8 in the vertical direction to measure the distance between the upper and lower plates 16a and 16b. Is installed. The tension in the axial direction is applied to the bolt 9 by applying pressure by the hydraulic pump 3, and the strain in the compression direction of the collar 8 is read from the value of the dial gauge 13 at that time.

FIG. 7B illustrates the relationship between the compression force and strain of the collar 8. Since a compressive force opposite to that of the bolt 9 acts, it is shown in the left-right opposite direction to FIG. 6B with respect to the reference vertical axis. The distortion of the collar 8 when the compression force Ff is the same as the axial force Ff in FIG. 6B is λc. Therefore, the spring constant Kc of the collar 8 (the object to be fastened) is Kc = Ff / λc
Is calculated by

  FIG. 8 shows an apparatus for performing a test for understanding a characteristic diagram called a tightening triangle indicating a tightening state of a screw. FIG. 8A is an outline of the entire apparatus, and FIG. 8B is used in the apparatus. The structure of the hydraulic nut 7 is shown.

  As shown in FIG. 8A, the tip end portion of the bolt 9 is attached to the testing machine main body 2, and the cylindrical collar 8 is disposed around the bolt 9. Plates 16 having a diameter larger than that of the collar 8 are attached to the upper and lower ends of the collar 8 in the horizontal direction. A hydraulic nut 7 is disposed at the lower end of the collar 8, and a spacer 17 is placed above the hydraulic nut 7. In the initial state before loading, a slight gap g is provided between the upper end surface of the spacer 17 and the plate 16 so that no force is applied to the plate 16.

  As shown in FIG. 8 (B), the hydraulic nut 7 is inserted into a cylinder 71 which is continuous in an annular shape and has a U-shaped cross section so that the piston 72 is slidable in the vertical direction. An oil chamber 73 is formed between the oil chamber 73 and the oil chamber 73. A sealing material 74 is attached to the upper end surface of the piston 72 to keep the oil chamber 73 oil-tight. The oil chamber 73 is connected to the second hydraulic pump 3b and the second hydraulic meter 4b, and oil is appropriately supplied from the second hydraulic pump 3b to pressurize the oil chamber 73, and the hydraulic pressure value is displayed by the second hydraulic meter 4b. The As shown in (A), since the position of the piston 72 of the hydraulic nut 7 is fixed, when the oil chamber 73 is pressurized, the cylinder 71 rises and pushes the plate 16 upward via the spacer 17. It takes power.

  FIG. 9 shows test conditions and results using the apparatus of FIG.

  FIGS. 9A and 9I show the state of force acting when a tensile load is loaded on the bolt 9 within the elastic range by the hydraulic pump 3 of FIG. 8, and the arrows act on the bolt 9 and the collar 8 respectively. Indicates the direction of force. FIGS. 9 (A) and (ii) show a state in which a strain ε is generated from the state of (i) by further pushing up the plate 16 by the hydraulic nut 7 of FIG.

  FIG. 9B illustrates the relationship between the axial force and strain at (A) and (i). The bolt 9 is illustrated with the left line, and the collar 8 is illustrated with the right line. That is, the spring constant Kb of the bolt 9 is represented by the slope of the left line, and the spring constant Kc of the collar 8 is represented by the slope of the right line. A tensile load is loaded on the bolt up to the point A at which the axial force reaches Ff, and at the time of the axial force Ff, the bolt 9 and the collar 8 generate strain λb and strain λc, respectively.

  FIG. 9C illustrates the relationship between the axial force and strain in the state of (A) and (ii). The external force W increases the axial force of the bolt 9 in which the internal force in the tensile direction is generated in (A) (i) and reduces the axial force of the collar 8 in which the internal force in the compression direction is generated. A strain ε in the tensile direction is generated. Accordingly, when the collar 8 is tightened with the bolt 9, if the bolt 9 on which the axial force Ff is applied is further pulled with the external force W, the axial force of the bolt 9 does not become (Ff + W). The axial force that is reduced by the amount of the force to be deleted increases, and the balance is maintained.

Expressing this in terms of an equation, the axial force Ft acting on the bolt 9 by the external force W and the axial force Fc acting on the collar 8 are:
Ft = Kb × ε
Fc = Kc × ε
Where Kb: spring constant of the bolt Kc: spring constant of the collar ε: represented by the strain due to the external force W, and from the balance of forces in FIG. 9 (A) (ii),
(Ff−Fc) + W = (Ff + Ft)
So,
W = Ft + Fc = (Kb × ε) + (Kc × ε)
Therefore,
ε = W / (Kb + Kc)
Accordingly, the axial force Ft indicating the increase in the axial force in the tensile direction acting on the bolt is
Ft = Kb × ε = W × Kb / (Kb + Kc)
It becomes.

FIG. 10 is an explanatory diagram for comparing the external forces of FIGS. 9A and ii. Comparing the external forces applied to the plate 16, the external force on the bolt 9 side is (Ff + Ft), and the external force on the collar 8 side is (Ff-Fc). Therefore, from the balance of power,
W + (Ff−Fc) = (Ff + Ft)
Therefore,
Ft + Fc = W
It becomes.

  FIG. 11 and FIG. 12 show examples of tightening triangles with various patterns such as bolts 9 and collars 8 and the like, and the same test as in FIG. In any case, the initial loading is within the elastic range of the bolt 9.

  FIG. 11 shows patterns with different spring constants depending on the material and dimensions of the collar 8 that is the object to be fastened. Each (i) of (A) to (C) shows the pattern of the specimen, and (ii) shows the result of (i). 11A shows a case where the collar 8 is made of iron, FIG. 11B shows a case where the collar 8 has the same dimensions as that of FIG. 11A and is made of aluminum, and FIG. This is when the cross-sectional dimension is large. Based on (A), (B) has a small spring constant of the collar 8, so the slope of the line shown on the right side is small, and (C) has a large spring constant of the collar 8, so the slope of the right line is small. growing.

  FIG. 12A shows the case where the object to be tightened is a stacked plate material 8a, and the spring constants of the bolt 9 and the plate material 8a are extremely high. In FIG. 12B, the external force is doubled to 2W. As a result, a gap is generated between the upper end of the collar 8 and the seating surface of the bolt 9. FIG. 12C shows a case where an external force of 1.5 W is loaded on the bolt 9 having a thin shaft portion and a low yield point. Since the yield point of the bolt 9 is low, the bolt 9 is pulled to the plastic region and unloaded. Remains.

  FIG. 13 shows a test in which a tensile force is applied after the bolt 9 is twisted to the plastic region and tightened. FIG. 13A shows the outline of the apparatus, and FIG. 13B shows the result. This test is performed by adding a wrench 14 to the apparatus of FIG. No force is applied by the hydraulic pump 3.

  First, the bolt 9 is twisted by using the wrench 14 and is tightened to a point B where the elastic limit is reached and the needle of the hydraulic gauge 4 stops rising. The axial force at this time is Ff.

  Thereafter, the hydraulic nut 7 is pressurized using the second hydraulic pump 3b, and the second hydraulic pressure gauge 4b pressurizes to the point C indicating the external force W. The axial force of the bolt at this time is (Ff + Ft). When the pressure of the second hydraulic pump 3b is released, the axial force displayed by the hydraulic gauge 4 becomes (Ff−ΔF), and balance is reached when the point D is reached. Further, when all the tightening force due to the twisting of the bolt 9 is released, permanent distortion remains.

  FIG. 14 is an apparatus for changing the loading position of the external force W in the axial direction of the bolt 9. The height of the plate 16c is appropriately adjusted by screwing the plate 16c screwed into the male screw into the collar 8 using the collar 8 having a male screw formed on the outer periphery. A hydraulic nut 7 similar to that shown in FIG. 8B is disposed at the lower end of the collar 8 to apply an external force W at a predetermined position. In the initial state before loading, a slight gap g is provided between the upper end surface of the hydraulic nut 7 and the plate 16c so that no force is applied to the plate 16c.

  FIG. 15 shows the results of the test pieces with different applied positions of the external force W and the results.

  In the test method, first, pressure is applied using the hydraulic pump 3 (FIG. 14) until the oil pressure gauge 4 shows the axial force Ff. This axial force Ff is within the range of elastic deformation. Next, the second hydraulic pump 3b is used to pressurize the hydraulic nut 7, push up the movable plate 16c installed at each predetermined position, and apply force until the second hydraulic gauge 4b indicates the external force W. At this time, the axial force indicated by the oil pressure gauge 4 is (Ff + Ft).

  By this test, the correction coefficient of the internal force coefficient, which is the ratio between the increase in the bolt axial force and the external force, according to the external force applied position can be obtained. FIG. 15A shows the case where the upper and lower ends of the collar 8 which is the object to be tightened is applied, FIG. 15B shows the case where the lower end and the center of the collar 8 are applied, and FIG. This is the case when force is applied.

The internal force coefficient φ is
φ = Ft / W
Is required. Further, the ratio n of the Ft value Ft ₁ when the distance between the bolt seat plate 11 and the plate 16 c is 0 and the Ft ₂ when the distance h is
n = Ft ₂ / Ft ₁
This is the correction coefficient for the internal force coefficient.

  FIG. 16 shows a test for understanding the meaning of the rotation angle method of tightening a bolt at a constant rotation angle. FIG. 16A shows the state of the test body when a bolt is twisted and tightened, and FIG. 16B shows the result.

The bolt 9 is tightened to the axial force Ff as shown on the left side of (B), and the spring constant is Kb. At this time, a distortion λb is generated in the bolt 9 in the extending direction. The collar 8 is tightened with an axial force Ff in the compression direction, the spring constant is Kc, and the strain λc is generated in the compression direction. At this time, the rotation angle θ of the bolt is
θ = 360 ° × (λb + λc) / P
Where P is the pitch of the screw. The strains λb and λc of the bolt 9 and the collar 8 are
λb = Ff / Kb
λc = Ff / Kc
Therefore, the rotation angle for obtaining the axial force Ff can be calculated.

  FIG. 17 shows test conditions and results for knowing the relationship between torque and rotation angle when bolts are tightened with a torque wrench 15 for iron and aluminum bolts 9f and 9a, for example.

FIG. 17A shows the fit around the mounting position of the bolt 9. In the basic test apparatus 1 shown in FIG. 1, the oil is removed from the oil chamber 23 and the cylinder 21 is seated on the piston 22 for testing. Thereby, even if the bolt 9 is tightened, the upper end portion of the piston 22 is not deformed. For example, the bolt 9 and the collar 8 are both made of iron, the bolt 9 is aluminum, and the collar 8 is iron. The torque wrench 15 is used to tighten the bolt 9 with torque T. FIG. 17B shows that the rotation angles of the bolts 9f and 9a when the torque T is applied are θ _A and θ _B , respectively. Thus, the rotation angle theta _B of the rotation angle theta _A and aluminum bolt 9a of iron bolts. 9f,
θ _B > 2θ _A
It becomes. This is because the spring coefficient K of each material is K = E × (A / L)
However, E: Young's modulus A: Cross-sectional area L: By expressing with length. By this test, it can be experienced that the rotation angle for obtaining a predetermined tightening force differs for each material of the bolt 9.

  18 and 19 are apparatuses for examining the hot surface pressure resistance. There are few published values of the hot surface pressure resistance of the bearing surface and screw surface of aluminum alloy and magnesium alloy, and when using them in products, the performance must be determined by measurement. Such a test can be performed by attaching a simple device to the basic test apparatus 1 of FIG.

  A heater 34 is attached around the round head bolt above the tester main body 2, and the controller 34 controls the heater 34 to a predetermined temperature to heat the seat plate 11. Further, a pressure regulator 32 (FIG. 18) is provided branching from the middle of the connecting pipe between the tester main body 2 and the hydraulic pump 3. Further, a weight 31 is attached to the arm of the hydraulic pump 3 so that the oil chamber 23 is always filled with oil. The axial force applied to the round head bolt 9b is read by the hydraulic gauge 4.

  FIG. 19 is an enlarged view around the round head bolt 9b of FIG. For example, the bolt 9b is tightened from above the seat plate 11 made of aluminum. A heat storage body 36 made of, for example, iron is provided inside the heater 34 and covers the periphery of the bolt 9b and the seat plate 11. The temperature inside the heater 34 is measured by inserting the tip of a thermocouple 37. A heat insulator 18 made of, for example, bakelite is inserted between the heater 34 and the tester main body 2 so that heat is not transmitted to the tester main body 2 side.

  When the seating plate 11 is inserted in a large amount, the pressure is adjusted using the pressure regulator 32 so that the axial force does not fluctuate so that the same pressure is always applied and the axial force of the bolt 9 becomes constant. . Similarly to the pressure pump 3, a weight 33 is attached to the pressure regulator 32.

As shown in FIG. 19B, the diameter D of the head of the bolt 9b is made larger than the diameter d of the hole 91 of the seating surface plate 11. If necessary, a washer or the like may be attached or a flanged bolt may be used. The pressure receiving area S of the seat plate 11 is
S = (π / 4) × (D ² −d ² )
It is.

  Thus, for example, at normal temperature and at 200 ° C., the surface pressure resistance at each temperature can be measured.

  20 and 21 show an apparatus for measuring bolt creep during hot. Even a bolt that is tightened within the elastic limit is known to creep at a relatively low temperature of 100 ° C. to 150 ° C., and this phenomenon can be confirmed.

  A collar 8 is disposed around the bolt 9. A heater 34 is provided around the collar 8, and the controller 35 controls the temperature of the heater 34. A weight 31 is attached to the arm of the hydraulic pump 3. A pressure regulator 32 is provided branching from the middle of the connecting pipe between the tester main body 2 and the hydraulic pump 3 and is controlled so that the same pressure is always applied to the oil chamber 23. Further, an auxiliary hydraulic pump 3a is provided branching from the connecting pipe. When the amount of creep of the bolt 9 is large and the amount of oil is insufficient in one stroke of the hydraulic pump 3, oil is fed using the auxiliary hydraulic pump 3a.

  FIG. 21 is an enlarged view around the bolt 9 of FIG. The bolt 9 is attached via a washer 19 made of a material that easily conducts heat, such as copper. Thermocouples 37a and 37b are inserted into the upper end and lower end of the bolt 9, respectively, and the temperature is measured. The upper part of the bolt 9 is provided with a groove 81 in a part of the collar 8 as shown in (B), and the tip of the thermocouple 37 a is inserted into the shaft part of the bolt 9. At the bottom of the bolt 9, a hole is made at the tip of the bolt 9, and the tip of the thermocouple 37b is inserted. Insulating materials 18a and 18b are attached between the heater 34 and the tester main body 2 and between the front end of the bolt 9 and the piston 21 to prevent heat from being transmitted to the tester main body 2 and the bolts. Do not let the heat of 9 escape. The heat insulating materials 18a and 18b are attached around the shaft portion of the bolt 9, and the front end side of the heat insulating material 18b is fixed with the nut 12a.

  FIG. 22 shows the result of measurement for each bolt 9 of SC material and SCM material by the above apparatus. Among general steel materials, the SC material and the SCM material have significantly different creep amounts at the time of high stress, and the SCM material has excellent heat resistance due to the influence of molybdenum. In any case, it can be understood from the test using this apparatus that the permanent strain due to temperature increases as it approaches the plastic region, and the yield point and yield strength decrease at high temperatures.

  The various characteristic tests described above need to be understood in order to learn the characteristics of the screw, and are usually understood step by step, but they can be performed in any order, or only one of the tests can be performed. May be.

  The present invention can be applied as a teaching material and an experiential learning method for understanding the characteristics of screws such as bolts.

The figure which shows the basic test apparatus of this invention. The longitudinal cross-sectional view which shows the upper catcher and lower catcher of FIG. The figure which shows the apparatus and the result which investigate the characteristic of a screw. The figure which shows the apparatus which investigates the different characteristic of a screw, and a result. The figure which shows the apparatus which investigates the further different characteristic of a screw, and a result. The figure which shows the apparatus which investigates the characteristic of a volt | bolt, and a result. The figure which shows the apparatus which investigates the characteristic of a color, and a result. Schematic showing an apparatus for examining further different characteristics of a screw. The figure which shows the state and result of a test body by the apparatus of FIG. The figure which shows the state and result of the external force of the characteristic of FIG. The figure which shows the result for every different test body by the apparatus of FIG. The figure which shows the result for every different test body by the apparatus of FIG. The figure which shows the apparatus which investigates the further different characteristic of a screw, and a result. Schematic showing an apparatus for examining further different characteristics of a screw. The figure which shows the result for every different applied force position by the apparatus of FIG. The figure which shows the further different characteristic of a screw. The figure which shows the part and result of an apparatus which investigates the further different characteristic of a screw. Schematic which shows the apparatus of the application example using the test apparatus of FIG. The longitudinal cross-sectional view which expanded a part of FIG. Schematic which shows the apparatus of the different application example of the test apparatus of FIG. The figure which expanded a part of FIG. The figure which shows the measurement result by the apparatus of FIG.

Explanation of symbols

1: Test apparatus, 2: Test machine body, 3, 3b: Hydraulic pump, 3a: Auxiliary hydraulic pump, 4, 4b: Hydraulic gauge, 5: Upper catcher, 6: Lower catcher, 7: Hydraulic nut, 8, 8b: Collar, 8a: Plate material, 9, 9f, 9a, 9b: Bolt, 10: Board, 10a: Notch, 11: Seat plate, 12, 12a: Nut, 13: Dial gauge, 14: Wrench, 15: Torque wrench, 16, 16a, 16b, 16c: plate, 17: spacer, 18, 18a, 18b: heat insulating material, 19: washer, 20: through hole, 21: cylinder, 21a: nut holder, 22: piston, 22a: bolt support Part, 23: oil chamber, 24: spring, 25: cover, 26: detent member, 27: O-ring, 31, 33: weight, 32: pressure regulator, 34: heater, 35: controller 36: heat storage body, 37, 37a, 37b: thermocouple, 51: lid, 52, 63: shock absorber, 53: chain, 61: dish, 62: flange, 71: cylinder, 72: piston, 73: oil chamber 74 sealing material, 81: groove, 91: hole.

Claims (7)

  The hydraulic pressure generating means, the load generating means for amplifying and applying the hydraulic pressure from the hydraulic pressure generating means to the test screw, and the load display means for displaying the load applied to the screw are provided on the same substrate for carrying. A screw characteristic testing device characterized by being made possible.   The screw characteristic testing device according to claim 1, further comprising an upper catcher and a lower catcher for collecting fragments when the screw is broken above and below the screw mounting position during the test.   2. The screw characteristic testing apparatus according to claim 1, further comprising a temperature adjusting means, wherein the temperature of the screw is variable.   The load generating means includes a piston (22) that moves up and down in the cylinder (21), and an upper end portion of the screw is supported by a screw support portion (22a) provided on the piston (22), and the screw support portion ( 22a) is provided with a nut holding portion (21a) for holding a nut in the cylinder (21), and a lower end portion of the screw is screwed into the nut, and at the lowest position of the piston (22), The screw characteristic test apparatus according to claim 1, wherein a lower end surface of the screw support portion (22a) is in contact with an upper end surface of the nut holding portion (21a).   5. The screw characteristic test apparatus according to claim 1, wherein the screw characteristic test apparatus is used as a teaching material for learning or teaching a screw tightening characteristic theory while performing a test using the screw characteristic test apparatus. .   An experiential learning method comprising: learning a screw characteristic by reproducing a theoretical screw tightening characteristic diagram by a test using the screw characteristic test apparatus according to claim 1. A practical skill education method characterized by educating screw characteristics by reproducing a theoretical screw tightening characteristic diagram by a test using the screw characteristic test apparatus according to claim 1.

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