JP3487049B2 - Optical extensometer - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring elongation of a test piece by optically detecting a displacement of a light image of a mark attached to the test piece. And a related optical extensometer. 2. Description of the Related Art In a material test, it is essential to measure the elongation of a test piece (change in the distance between gauge points between upper and lower gauge lines). There is a contact-type extensometer for measuring by directly contacting and attaching a measuring device, and a non-contact-type extensometer for measuring without contacting a test piece by optical means. The former has the advantage that the elongation of the test piece can be measured accurately, but has the disadvantage that an improper load acts on the test piece because the measuring instrument is in direct contact with the test piece. On the other hand, the latter extensometer is often used because an improper load does not act on a test piece and it can measure a large displacement. As the latter extensometer, there has recently been proposed one that uses a laser beam or the like to directly irradiate a test piece with a laser beam and measure its reflected light. For the specimen, an optical extensometer that measures the elongation of the specimen by attaching a marked line to the test piece and optically capturing the displacement of the light image of the marked line with an attached optical device is used. . [0003] In an optical extensometer for attaching this mark to a test piece, even if the test piece is elongated, the mark attached to the test piece is always attached to an attached optical measuring instrument. It is assumed that they are facing in the direction of. However, as shown in FIG.
In such a case, when a tensile load is applied, the rope (test piece) rotates around its axis. Therefore, FIG.
0, in the case where a planar mark plate P having directivity as shown in FIG. 11 is attached by a band B or the like, the mark line S does not face the direction of the optical measuring instrument, and measurement cannot be continued. Therefore, it is necessary to attach a marked line around the specimen to the specimen, but even in this case, if the diameter shrinks as the specimen elongates, the attached state becomes unstable and accurate measurement cannot be performed. Have a problem. An object of the present invention is to provide an optical extensometer which solves such a problem, in particular, a mark which is supported by a test piece. SUMMARY OF THE INVENTION An optical extensometer provided by the present invention is a test piece having a needle inserted into a test piece and fixed to the test piece in a plane perpendicular to the axis of the test piece. A test piece marking device consisting of a support tool which is supported by being bent and a mark frame which is fitted around the support tool and has a mark on the outer peripheral surface thereof. It measures the elongation of the test piece by optically detecting the displacement of the light image of the marking line of the marking device. FIG. 1 to FIG. 6 show an optical extensometer provided by the present invention, and in particular, the construction of a specific marking device supported on a test piece. FIG. 1 is a view showing the overall configuration in a state in which the marking device SG is attached to the rope-shaped test piece TR. FIG. 2 is a view from the right side of FIG. 1, and FIG. 3 is a view of FIG. It is the figure seen from the side in the state attached to test piece TR in the figure seen from the lower part. FIG. 4 is a diagram showing the support frame 2 removed from FIG. 1 and viewed from above. 5 and 6 are views showing the configuration of the marking frame 1. FIG. The present invention comprises a mark frame 1 on which a mark 1S matching the mark of the test piece TR is formed, and a support for supporting the mark frame 1 on the test piece TR. . As shown in FIGS. 5 and 6, the marking frame 1 is formed not in a perfect circle but in a partially circular frame, and the angle of the circular arc is about 300 degrees. An outer peripheral surface of the arc portion is a black background, and a mark line 1S is provided at the center of the arc portion over a whole angle of the arc portion. The thickness of the mark line 1S differs depending on the optical measuring device and the measuring method. FIGS. 3 and 6 show different thicknesses, but the thickness is not limited to these thicknesses. 1H is a handle piece bent at both ends of the arc portion. The mark frame 1 is made of a synthetic resin material such as an elastic metal material or plastic. Therefore, when it is fitted to the support, it expands to increase the radius and is elastically contacted with the outer periphery of the support. When removing from the support, both handle pieces 1H are gripped and expanded, and the elastic contact from the outer periphery of the support is released. The structure of the support to which the mark frame 1 is fitted is as shown in FIGS. 1 to 4, and is of a sandwiching type utilizing a mechanism of so-called "selective scissors". The base of the support is composed of two support frames 2 and 3 having an arc shape, a support shaft 4 for swingably engaging the two support frames 2 and 3 with each other, and a support shaft 2 and three support frames 2 and 3. It is composed of a helical spring 7 which is biased in a direction in which the springs come close to each other. Reference numerals 2H and 3H denote extended ends of the support frames 2 and 3, respectively. The ends of the bent portions 2K, 3K of the two support frames 2, 3 are connected via a support shaft 4, and each of them is swingably engaged. At the same time, both ends of the helical spring 7 installed on the support shaft 4 are locked to the extended ends 2H, 3H of the respective support frames 2, 3, and the extended ends 2H, 3H are separated from each other. Biased in the direction. Therefore, as shown in the drawing, the ends (left) of the support frames 2 and 3 are in contact with each other. When the thumb and forefinger of one hand are hung on the extended ends 2H, 3H of the respective support frames 2, 3 by the mechanism of the "selective scissors" and pulled toward each other against the elasticity of the helical spring 7, the two support frames 2 , 3
Are separated from each other so that the test piece TR can be held therebetween. [0010] Further, the support is provided with locking means for determining the fixation to the test piece in the above base. The locking means includes needles (pins) P1 and P2 for determining a fixing position on the test piece, and knife edges N1 and N2 for stabilizing the fixation on the test piece. The needles (pins) P1 and P2 are held by a holding table 5 fixed to the support frame 2 via a holding plate 8, and the knife edges N1 and N2 are held by a holding table 6 fixed to the support frame 3 via a holding plate 9. Is held in. The holding plates 8 and 9 extend in the upper surface direction of the holding tables 5 and 6 and inward of the two support frames 2 and 3, and their base ends are fixed to the holding tables 5 and 6 with fixing screws 10 and 11. However, it is a so-called leaf spring made of elastic material,
When the diameter of the test piece TR is large, it is bent as shown in the figure according to the diameter, and the needles P1, P2 and the knife edges N1, N
2 hits. Even if the diameter of the test piece TR is reduced and thinned by this elastic contact method, it can be held in a certain range. The two needles P1 and P2 have sharp tips and pierce the test piece TR to determine the fixing position of the support to the test piece TR. On the other hand, the knife edges N1 and N2, although their tips are sharp, abut across the twisted ridges of the test piece TR and function to stabilize the fixation to the test piece TR. Numeral 12 designates the knife edges N1, N2 as holding plates 9
Is a fixing screw for fixing the holding tables 5 and 6 to the supporting frames 2 and 3, respectively. Also,
Reference numeral 14 denotes a concave guide member for fitting the marking frame 1 to the support frames 2 and 3. It is not necessary to install this member,
Even if it is installed, it can be formed integrally with the support frames 2 and 3. In that case, there is an advantage that the number of parts is reduced. As described above, in the support of the present invention, the tips of the needles P1 and P2 are inserted (entered) into the gap of the fiber in the rope with respect to the test piece (rope) TR.
The test piece T is fixed at a plane perpendicular to the axis TS of the test piece.
R is bent and supported. Moreover, it is characterized in that the fixed support is performed by a simple operation. Now, in the above configuration, when attaching the marking device SG of the present invention to the test piece TR as shown in FIG. 8, first remove the marking frame 1 from the support. Next, both support frames 2 and 3 of the support tool are made openable and closable, and the thumb and forefinger of one hand are respectively extended to the extension ends 2 of the support frame 2 and the support frame 3.
H and 3H, the springs 7 are pulled toward each other against the elasticity of the helical spring 7, and the ends of the support frames 2 and 3 are opened and separated from each other to position the test piece TR inward. Next, when the force of both fingers is released, the two supporting frames 2 and 3 are closed by the elasticity of the helical spring 7, and the state shown in FIG. Then, as shown in FIG. 1, the locking means P1, P2, N1, N2 which determine the fixing to the test piece TR are fixedly supported on the test piece TR by the elastic action of the holding plates 8, 9. In this fixing, the tips of the needles P1 and P2 pierce the positions P1 and P2 of the test piece TR in FIG. During the test, the needles P1, P2 are prevented from piercing over the different strands of the rope, as a shift occurs between the strands. After the support is surrounded and supported by the test piece TR on a plane perpendicular to the axis TS of the test piece and the fixing to the test piece TR is completed, the marking frame 1 is fixed to the support. Fit it. This fitted state is the state shown in FIG. The marking frame 1 is expanded and fitted, and the arc portion becomes approximately 260 degrees. Therefore, the reference line 1S exists over about 260 degrees around the test axis TS, and even if the test piece TR rotates during the test, the reference line 1S exists for the optical measurement device,
Ensures measurement of elongation displacement of the specimen. When the test piece is thin, it is necessary to prepare a support or a mark frame corresponding to the size of the test piece. However,
The support is of a type in which the needles P1, P2 and the knife edges N1, N2 are elastically contacted with the test piece by the holding plates 8, 9, and a single mark can be used for a certain size range. is there. The needles P1 and P2 have a function of fixing the position, whereas the knife edges N1 and N2 on the opposite side function to stabilize the support of the marking device SG. The knife edges N1 and N2 correspond to the positions of the marking lines 1S corresponding to the positions of the needles P1 and P2. The features of the optical extensometer, that is, the marker, provided by the present invention are as described above. However, in addition to the above or illustrated examples, the present invention includes various modified embodiments utilizing this feature. FIG. 7 shows an example in which one needle P3 is fixed to the holding plate 81, and this needle P3 pierces the twisted top of the test piece TR. However, in this case, two knife edges are preferable. The shape of the needle is not limited to the pin shown in the illustrated example, but may be a thin needle. The knife edges need to be joined around the test piece TR over a certain angle,
It is not limited to an individual. If the size (thickness) of the test piece is fixed, it is possible to install an arc-shaped knife edge corresponding to the size. In this case, only one knife edge is required and the configuration is simpler. It becomes. The knife edge is sharp because its tip is sharp.
This is because the contact with the position of the marking line 1S by line contact is effective in stabilizing the support of the marking line SG. A thin wire rod or the like can be used instead, but a knife edge is preferable. However,
The installation of a member (knife edge or the like) for stabilizing the support is not indispensable, and all members may be needles. The holding plate may be formed in an arc shape instead of in a bent shape as in the illustrated example. Further, the spring for urging the two support frames may be a leaf spring type, instead of a spiral shape, and the elastic means is not limited. Further, as for the material of the support, it is possible to select a metal material other than the above or a highly durable material such as a synthetic resin such as a stainless steel material or a vinyl chloride material. The configuration and functions of the optical measuring device (not shown) are various, such as those using a normal light source and those using a laser light source. However, the present invention is not limited to these points. The marking line may be formed by attaching a thin white line (vinyl wire) to the surface of the marking line frame 1 instead of applying the paint. In this case, a situation in which the measurement function is hindered by discoloration of the paint or the like is eliminated.
The present invention is not limited to a twisted one such as a rope, but can be applied to various round bar-shaped test pieces (fiber, resin material, etc.), and a needle is pierced (enterable).
If it is a material, it can be used for a test piece of a metal material. The present invention covers all these modifications. The present invention is summarized as follows. Supplementary Note 1 A support having the tip of a needle inserted into and fixed to a test piece and supported by surrounding the test piece in a plane perpendicular to the axis of the test piece, and a support around the support. It has a test piece marking device consisting of a marking frame fitted with marking lines on the outer peripheral surface,
An optical extensometer characterized in that the displacement of the optical image of the marking line of the test piece marking device is optically detected to measure the elongation of the test piece. (Supplementary note 2) A support having the tip of a needle inserted into and fixed to the test piece and supported by bending and surrounding the test piece on a plane perpendicular to the axis of the test piece. It has a test piece marking device consisting of a marking frame fitted with marking lines on the outer peripheral surface,
The supporter is capable of swinging about a support shaft and urged so as to be attracted to each other, a needle held by one of the support frames and having a tip inserted into a test piece, and the other support frame. And a knife edge whose tip abuts and joins the test piece to determine the fixation to the test piece. The mark frame is fitted around the outer periphery of both support frames. An optical extensometer wherein the displacement of a light image of a mark of the test piece mark is optically measured to measure the elongation of the test piece. (Supplementary Note 3) A support having the tip of a needle inserted and fixed to the test piece and supported so as to bend and support the test piece on a plane perpendicular to the axis of the test piece. It has a test piece marking device consisting of a marking frame fitted with marking lines on the outer peripheral surface,
The support tool is capable of swinging about a support shaft and two support frames urged so as to be attracted to each other. One end of the support frame is held via an elastic holding plate and the tip is inserted into a test piece. The needle and the other support frame are held by an elastic holding plate via an elastic holding plate, and are constituted by locking means for determining fixation to the test piece by a knife edge whose tip abuts on the test piece. An optical system, wherein the mark frame is configured to be fitted, and the displacement of the light image of the mark of the test piece mark is optically captured to measure the elongation of the test piece. Extensometer. As described above, the optical extensometer provided by the present invention, particularly the test piece marking device, is as described above. Therefore, the test piece is a rope made of a fiber material or the like, and the test piece is axially loaded. Even when the sample rotates around, the reference line always exists at the direction of the attached optical measuring device, and the displacement of the test piece can be measured. Therefore, the elongation can be measured up to the time of the test piece breaking. Further, even when the diameter of the test piece is reduced during the tensile test, the marking device has an advantage that it is always fixed and supported by the test piece.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a configuration of a test piece marking device according to the present invention. FIG. 2 is a diagram showing a configuration of a test piece marking device according to the present invention. FIG. 3 is a diagram showing a configuration of a test piece marking device according to the present invention. FIG. 4 is a diagram showing a configuration of a test piece marking device according to the present invention. FIG. 5 is a diagram showing a configuration of a test strip marking device according to the present invention. FIG. 6 is a diagram showing a configuration of a test piece marking device according to the present invention. FIG. 7 is a diagram showing a configuration of a test piece marking device according to the present invention. FIG. 8 is a view showing a test piece according to the present invention. FIG. 9 is a view showing a test piece according to the present invention. FIG. 10 is a diagram showing a conventional configuration according to the present invention. FIG. 11 is a diagram showing a conventional configuration according to the present invention. DESCRIPTION OF SYMBOLS 1 ... Mark line frame 1S ... Mark line 1H ... Handle pieces 2 and 3 at both ends of mark line frame ... Support frames 2H and 3H ... Extension ends 2K and 3K of support frames 2 and 3 ... Support frame 2 3 bent part 4 ... support shafts 5, 6 ... holding table 7 ... helical springs 8, 9 ... holding plates 10, 11, 12, 13 ... fixing screws 14 ... guide member TR ... test piece TS ... test piece axis SG ... Markers P1, P2, P3 ... Needles N1, N2 ... Knife edge

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G01B 11/00-11/30 G01N 3/00-3/62

Claims (1)

(57) [Claim 1] A support in which the tip of a needle is inserted into and fixed to a test piece, and the test piece is supported by being bent around a plane perpendicular to the axis of the test piece. And a mark frame fitted with a mark on the outer surface and fitted around the support, and an optical image of the mark of the mark An optical extensometer characterized in that the displacement of the specimen is measured optically to measure the elongation of the test piece.