JIG FOR ULTRASONIC FATIGUE TESTING MACHINE

Abstract

A pair of jigs has the same mass and a weight is adjusted in consideration of a test piece shape so that stress of a center portion of a test piece becomes a desired value. That is, the jig serves as a weight adjustment tool for adjusting a resonance frequency and stress of the test piece. The upper and lower jigs are attached to both ends of the test piece S so that the center of gravity of the upper jig and the center of gravity of the lower jig are located on a perpendicular line passing through the center portion of the test piece.

Claims

1. A jig for an ultrasonic fatigue testing machine used in a fatigue test in which a vibration generated from an ultrasonic transducer is amplified by a horn and a test piece connected to a front end of the horn is resonated, comprising: a main body portion; and a grip portion holding an end of the test piece, wherein the jig is attached to both ends of the test piece to adjust the mass of both ends of the test piece.

2. The jig for the ultrasonic fatigue testing machine according to claim 1, wherein an end of the main body portion opposite to the grip portion is provided with a screw portion to be connected to the horn.

3. The jig for the ultrasonic fatigue testing machine according to claim 1, wherein when an end of the main body portion is connected to the horn, an adjustment plate is inserted between the main body portion and the horn, and when the end of the main body portion serves as a free end, the adjustment plate is attached to the free end to adjust the mass of both ends of the test piece.

4. The jig for the ultrasonic fatigue testing machine according to claim 1, wherein the grip portion includes a pressing force generation member that sandwiches the end of the test piece by a pressing force using a screw when holding the end of the test piece.

5. The jig for the ultrasonic fatigue testing machine according to claim 4, wherein the mass of both ends of the test piece is adjusted by changing the weight of the pressing force generation member.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] FIG. 1 is an outline diagram of an ultrasonic fatigue testing machine which performs a fatigue test by attaching a jig 10 for the ultrasonic fatigue testing machine according to the invention thereto;

[0022] FIG. 2 is an outline diagram of the jig 10 for the ultrasonic fatigue testing machine according to the invention;

[0023] FIG. 3 is an outline diagram illustrating a weight adjustment of the jig 10 for the ultrasonic fatigue testing machine;

[0024] FIG. 4 is an outline diagram of a jig 20 for an ultrasonic fatigue testing machine according to a second embodiment of the invention;

[0025] FIG. 5 is a front outline diagram of the jig 20 for the ultrasonic fatigue testing machine according to the second embodiment of the invention;

[0026] FIG. 6 is a front outline diagram of a jig 30 for an ultrasonic fatigue testing machine according to a third embodiment of the invention;

[0027] FIG. 7 is an outline diagram of a jig 40 for an ultrasonic fatigue testing machine according to a fourth embodiment of the invention;

[0028] FIG. 8 is a cross-sectional outline diagram of the jig 40 for the ultrasonic fatigue testing machine according to the fourth embodiment of the invention;

[0029] FIG. 9 is an explanatory diagram illustrating a relationship of a shape of a conventional annular test piece with respect to a stress curve and an amplitude curve; and

[0030] FIG. 10 is a diagram illustrating a resonance simulation of a plate-shaped test piece model.

DETAILED DESCRIPTION

[0031] Hereinafter, embodiments of the invention will be described with reference to the drawings. FIG. 1 is an outline diagram of an ultrasonic fatigue testing machine which performs a fatigue test by attaching a jig 10 for the ultrasonic fatigue testing machine according to the invention thereto.

[0032] The ultrasonic fatigue testing machine is used to perform a fatigue test by resonating a test piece S using ultrasonic waves and includes a vibration portion 7 which includes an ultrasonic transducer 5 vibrated by a signal generated from an oscillator 3 and a horn 6 amplifying a vibration and transmitting the vibration to the test piece S and a frame 1 which is attached to the vibration portion 7. The oscillator 3 generates the signal based on a test frequency set by a control unit 2. The arrangement of the vibration portion 13 and the test piece S illustrated in FIG. 1 is set to perform a fatigue test in which a longitudinal vibration is applied to the test piece S.

[0033] The test piece S is a plate-shaped test piece and both ends thereof are sandwiched by a pair of jigs 10 for the ultrasonic fatigue testing machine (hereinafter, the jig 10 for the ultrasonic fatigue testing machine will be referred to as the jig 10 if necessary in the specification). The pair of jigs 10 has the same mass and the mass is adjusted in consideration of the test piece shape so that the stress at the center portion of the test piece S becomes a desired value (target stress) within the ability range of the device. That is, the jig 10 serves as a weight adjustment tool for adjusting the resonance frequency and the stress of the test piece S. In order to adjust the weight, the length or width of the jig 10 may be adjusted. The upper and lower jigs 10 are attached to both ends of the test piece S so that the center of gravity of the upper jig 10 and the center of gravity of the lower jig 10 are located on a vertical line passing through the center portion of the test piece S. When the upper and lower jigs 10 and the test piece S are aligned to one another at the center of gravity thereof, it is possible to prevent the unnecessary lateral resonance. The upper jig 10 is connected to the horn 6 by the screw-connection. The lower jig 10 is connected to the horn 6 fixed to the frame 1 by the screw-connection. In the example of FIG. 1, the lower jig 10 is also connected to the horn 6 resonated at the same cycle in order to apply average stress to the test piece S. Additionally, the lower jig 10 may be a free end according to the purpose of the test. Further, in the example of FIG. 1, a longitudinal vibration is applied to the test piece S from the upper side of the test piece S, but when a vibration is applied to the test piece S from the upper and lower sides of the frame 1, the horn 6 connected to the lower jig 10 is also connected to the ultrasonic transducer 5 and the oscillator 3.

[0034] FIG. 2 is an outline diagram of the jig 10 for the ultrasonic fatigue testing machine according to the invention.

[0035] The jig 10 includes a main body portion 11 and a pair of grip portions 12 which sandwiches the end of the test piece S. An end (an end surface) of the main body portion 11 of the jig 10 at a connection side to the horn 6 and a side opposite to the grip portion 12 is provided with a screw portion 16 which is connected to the front end of the horn 6 by the screw-connection. The end of the test piece S is inserted between the pair of grip portions 12 and the test piece S and the jig 10 are integrally held by shrink fitting, crimping, or fixing such as welding, brazing, or adhering. Additionally, the pair of jigs 10 is attached to the test piece S so that the centers of gravity of the pair of jigs 10 are aligned to the line passing through the center portion of the test piece S.

[0036] FIG. 3 is an outline diagram illustrating a weight adjustment of the jig 10 for the ultrasonic fatigue testing machine. FIG. 3(a) illustrates the weight adjustment of the jig 10 connected to the horn 6 by the screw-connection and FIG. 3(b) illustrates the weight adjustment when the lower jig 10 is a free end.

[0037] The pair of jigs 10 is prepared to have the same mass according to the size of the test piece S. Meanwhile, in the prepared jig 10, there is a case where the weight is insufficient for the stress at the center portion of the test piece S to become a desired value (target stress). In such a case, as illustrated in FIG. 3, the weight of the pair of jigs 10 is adjusted.

[0038] Even when the accuracy of the desired resonance frequency is not obtained at the test piece S prepared to have a length obtained by a calculation, the weight of the jig 10 is adjusted. In this way, when the jig 10 is attached to the test piece S, the substantial mass of both ends of the test piece S can be set to be sufficiently larger than that of the center portion so that stress at the center portion of the test piece S becomes a target value. In this embodiment, a plurality of adjustment plates 13a and 13b each having a different thickness are provided. The adjustment plates 13a and 13b are provided with holes through which the screw portion 16 passes. Then, the adjustment plates 13a and 13b each having a different thickness are selected to have a target weight and are inserted between the front end of the horn 6 and the jig 10 so that the weight of both ends of the test piece S is adjusted. Additionally, when the lower jig 10 is not connected to the horn 6 and is used as a free end, an end surface of the jig 10 is provided with a male screw and the adjustment plates 14a and 14b each having a different thickness are fixed by a bolt 15 as illustrated in FIG. 3 (b).

[0039] When a test starts by connecting the jig 10 to the front end of the horn 6 while the pair of jigs 10 is attached to both ends of the test piece S, the jig 10 is resonated along with the test piece S. As in the related art, it is not necessary to process the test piece S to be directly connected to the horn 6. Then, the length of the test piece S is determined in consideration of the weight of the jig 10 so that the connection portion between the horn 6 and the jig 10 becomes the antinode of the displacement vibration and the center portion of the test piece S becomes the node of the displacement vibration.

[0040] FIG. 4 is an outline diagram of a jig 20 for an ultrasonic fatigue testing machine according to the invention. FIG. 5 is a front outline diagram of the jig 20 for the ultrasonic fatigue testing machine according to the invention.

[0041] The jig 20 includes a main body portion 21 and a pair of grip portions 22 which sandwiches the end of the test piece S by a pressing force. The main body portion 21 of the jig 20 at the connection side to the horn 6 is provided with a screw portion 26 which is connected to the front end of the horn 6 by the screw-connection. The pair of grip portions 22 is provided with a hole through which a screw 24 penetrating the test piece S and the grip portion 22 passes. Additionally, it is necessary to forma hole, through which the screw 24 passes, in the test piece S to be attached to the jig 20. Further, it is ideal that no gap is formed while the end of the test piece S is inserted between the pair of grip portions 22. In this embodiment, as illustrated in FIG. 5, since a split 27 is provided at a position of the main body portion 21 near the end of the test piece S, the inner surface of the grip portion 22 can be sufficiently brought into close contact with the side surface of the end of the test piece S by pressing the left and right two nuts 25 in a balanced manner and generating a pressing force to act on the test piece S. Additionally, a spacer may be inserted between the inner surface of the grip portion 22 and the end of the test piece S. As the spacer, for example, soft metal such as aluminum used as a tab can be adopted.

[0042] A user reliably clamps and holds the test piece S by the pair of grip portions 22 by fastening a nut 25 to both ends of the screw 24 and operating the screw 24 and the nut 25 so that the centers of gravity of the pair of jigs 20 are aligned to the line passing through the center portion of the test piece S. In this way, when the center of gravity of the jig 20 is aligned to the center of gravity of the test piece S, unnecessary lateral resonance can be prevented. Additionally, since the jig 20 of the second embodiment is fixed to the test piece S by a screw differently from the jig 10 of the first embodiment, the test piece S can be repeatedly used while being replaced.

[0043] When a test starts by connecting the jig 20 to the front end of the horn 6 while the pair of jigs 20 is attached to both ends of the test piece S, the jig 20 is resonated along with the test piece S. That is, the test piece S and the jig 20 are entirely resonated at the test frequency. When the weight of the jig 20 is adjusted as described above, the substantial mass of both ends of the test piece S can be set to be sufficiently larger than that of the center portion so that stress at the center portion of the test piece S becomes a target value. For this reason, in the existing ultrasonic fatigue testing machine, it is possible to perform a test for a material which cannot be easily subjected to a fatigue test of repeatedly applying high stress to the center portion of the test piece S without spending time and effort for manufacturing the test piece S and designing the test piece shape.

[0044] As in the related art, there is no need to process the test piece S so that the test piece is directly connected to the horn 6. Then, the length of the test piece S is determined in consideration of the weight of the jig 20 so that the connection portion between the horn 6 and the jig 20 becomes an antinode of the displacement vibration and the center portion of the test piece S becomes a node of the displacement vibration. In this embodiment, it is possible to easily change the height dimension of the nut 25, the length of the screw 24, the thickness of the nut 25 fastened to the screw 24, or the mass of both ends of the test piece S including the jig 20 connected to the front end of the horn 6 as the number increases or decreases. Thus, it is possible to adjust the weight of the jig 20 by changing the weight of the separable member such as the screw 24 or the nut 25 even when the accuracy of the desired resonance frequency is not obtained with the length of the test piece S obtained by a calculation.

[0045] In this way, in the jig 20 of FIG. 5, the screw 24 and the nut 25 are used as a pressing force generation member for pressing the pair of grip portions 22 against the test piece S and the weight of the jig 20 is changed by the nut 25. Additionally, the jig 20 may be provided as a pair of jigs such that the weight of the main body portion 21 of the jig 20 is different and may be replaced for the test piece S in response to a desired resonance frequency or target stress applied to the center portion of the test piece S. Further, the adjustment plate 13a, 13b, 14a, or 14b may be inserted into the pair of jigs 20 to adjust the weight as in the case of the first embodiment illustrated in FIG. 3.

[0046] FIG. 6 is a front outline diagram of a jig 30 for an ultrasonic fatigue testing machine according to a third embodiment of the invention. The same members as those in the second embodiment are denoted by the same reference numerals and a detailed description thereof will be omitted.

[0047] The jig 30 of the embodiment includes a pair of screws 34 instead of the screw 24. The screw 34 is, for example, a hexagon socket stop screw, a slit stop screw, or the like and can be tightened using a tool. Each of the left and right grip portions 22 is provided with a screw hole into which the screw 34 is threaded. A spacer 33 contacting the side surface of the end of the test piece S is disposed at the front end of the screw 34. At in the case of attaching the jig 20 of the second embodiment, the jig 30 is used when it is difficult to process a hole through which the screw 24 passes at both ends of the test piece S. The user clamps and holds the test piece S to the pair of grip portions 22 by operating each of the screws 34 threaded into the screw holes formed in the pair of grip portions 22 in a balanced manner and bringing the spacer 33 into close contact with the side surfaces of both ends of the test piece S so that a pressing force acts thereon. Then, the nut 25 is used to adjust the weight of the jig 30. Here, the test piece S is clamped by the screw 34 and the nut is threaded into the screw 34 so that the test piece is fixed against the outer surface of the grip portion 22. Accordingly, it is possible to adjust the weight of the jig 30 by using the nuts 25 each having a different thickness.

[0048] Additionally, in the jig 30 of FIG. 6, the screw 34 is used as a pressing force generation member that presses the pair of grip portions 22 against the test piece S and the weight of the jig 20 is changed by the nut 25. However, a bolt may be employed instead of the screw 34 and the nut 25. Even when the size of the bolt head is changed, the weight of the jig 30 can be changed.

[0049] FIG. 7 is an outline diagram of a jig 40 for an ultrasonic fatigue testing machine according to a fourth embodiment of the invention and FIG. 8 is a cross-sectional outline diagram thereof. In addition, FIG. 8(a) illustrates the jig 40 which holds the test piece S by shrink fitting, crimping, or fixing such as welding, brazing, or adhering and FIG. 8 (b) illustrates a modified example of the jig 40 which holds the test piece S by the screw 44.

[0050] The jig 40 of the embodiment is used to hold the test piece S called a steel wire. Here, it is not practical to prepare the test piece S having a bent shape at the center portion as described with reference to FIG. 9 when performing a test on the steel wire. However, even in the steel wire of which the center portion is difficult to be bent thinner, it is possible to apply high stress to the center portion of the test piece S by additionally attaching the jig 40 to both ends as illustrated in FIG. 7.

[0051] One end of the jig 40 is provided with a screw portion 46 to be connected to the horn 6 and the other end thereof is provided with a hole into which the front end of the test piece S is insertable as illustrated in FIG. 8(a). Additionally, since the inner wall of the hole is in close contact with the side surface of the test piece S, this hole serves as the grip portion of the invention. That is, the end of the test piece S is inserted into the hole and the jig 40 is attached to the test piece S by shrink fitting, crimping, or fixing such as welding, brazing, or adhering. Further, as illustrated in FIG. 8(b), the test piece S may be held by the jig 40 in such a manner that a screw hole is provided at the side portion of the jig 40 so as to perpetrate the inner wall of the hole and the screw 44 is inserted so that the front end of the screw 44 is in close contact with the side surface of the test piece S. Further, as in the case of the first embodiment illustrated in FIG. 3, the weight can be adjusted by inserting the adjustment plate 13a, 13b, 14a, or 14b into the pair of jigs 40.

[0052] When the jigs 10, 20, 30, and 40 of the invention are used, since there is no need to perform a method of preparing the test pieces S each having a different length, measuring a resonance frequency thereof, and determining an optimal length of the test piece S in order to finely adjust the optimal resonance frequency, the test piece S can be easily manufactured. For example, a plate-shaped test piece processed into a shape for a general static tensile test can be used for an ultrasonic fatigue test depending on the material.

REFERENCE SIGNS LIST

[0053] 1 frame

[0054] 2 control unit

[0055] 3 oscillator

[0056] 5 ultrasonic transducer

[0057] 6 horn

[0058] 7 vibration portion

[0059] 10 jig

[0060] 11 main body portion

[0061] 12 grip portion

[0062] 16 screw portion

[0063] 20 jig

[0064] 21 main body portion

[0065] 22 grip portion

[0066] 24 screw

[0067] 25 nut

[0068] 26 screw portion

[0069] 27 split

[0070] 30 jig

[0071] 33 spacer

[0072] 34 screw

[0073] 40 jig

[0074] 44 screw

[0075] 46 screw portion

[0076] S test piece