JPH0660866B2 - Three-point bending elastic modulus measuring machine using moving load - Google Patents

Description

TECHNICAL FIELD The present invention relates to a material testing machine used for measuring the longitudinal elastic modulus of metals, plastics, ceramics, composite materials and the like.

(B) Conventional technology In the measurement of elastic modulus by three-point bending test of various materials, conventionally, a general-purpose material testing machine was used and a gradually increasing load was applied to the center between the supports on the test specimen beam. The displacement of the test piece beam at the load point was measured and obtained (magnitude of load −
The elastic modulus of the material was calculated by analyzing the curve of the displacement of the test piece beam.

(C) Problems to be Solved by the Invention However, such a test method requires an expensive load increasing device with a load cell for measuring a changing load. In addition, it is difficult to analyze the displacement of the test piece beam due to the shear stress inevitably generated in the test piece beam, the structural rattling of the tester, and the dent of the test piece beam at the contact part with the support. It is difficult to obtain an accurate longitudinal elastic modulus because the displacement due to various causes is mixed in the measured value.

The present invention is a simple three-point bending elasticity that can accurately measure the longitudinal elastic modulus without using load devices and load cells of various capacities according to the size of the test piece of the type of material, which has been conventionally required. The purpose is to obtain a coefficient measuring machine.

(D) Means for Solving the Problems In order to solve the above problems, an example of the measuring device invented will be described with reference to FIGS. 1 and 2. In order to freely support a beam-shaped test piece 1 made of a material whose elastic coefficient is to be measured, two supports 2 are mounted on a saddle 3, and the saddle 3 is fixed on a carriage 5 of a linear motion mechanism 4. I am doing it. This carriage is driven by the motor 7 driven by the motor driver 6 to rotate the screw 8
Move in the direction of the arrow. The linear movement mechanism 4 and the motor 7 are fixed on the bed 9.

Four guides 11 are provided to add the weight of the weight 10 vertically.
Is attached to the frame 12 of the load device fixed to the bed 9, and the weight stand 13 with a rod on which the weight 10 is placed can be freely moved up and down by being guided by the guide 11. A load roller 14 is attached below the weight table 13 with a rod in order to conveniently apply a weight load to the moving test piece beam 1. Further, in order to measure the displacement of the test piece beam 1, the sensor 16 of the displacement measuring machine 15 is fixed to the saddle 3 so as to move simultaneously with the test piece beam 1.

The displacement amount is read from the sensor 16 and stored synchronously when the movement of the saddle 3 is controlled, or the relationship between the load position and the displacement amount is different due to various causes of displacement, and this stored amount is stored. Based on the relationship between the position of the load point (X is the distance from the support) and the displacement of the test piece beam (V), the displacement part (V _b ) caused by only the bending moment is separately analyzed and the correct longitudinal elasticity is obtained. A small calculator 17 is provided to calculate the coefficient.

The method of separating and analyzing V _b by a computer is as follows. Assuming that the displacement caused by the shear stress is V _S and the small displacement V _K caused by other causes is proportional to V, V = V _b + V
The relational expression of _S + Kx (K is a proportional constant) is
By analyzing by the least squares method so as to be established as accurately as possible, it becomes possible to separate V _b , and more accurate longitudinal elastic modulus can be obtained.

(E) Action Create a test piece with a circular or rectangular cross section using the material to be measured and measure its dimensions. Fix the two supports 2 to the saddle 3 by spacing them to suit the test piece,
A test piece is placed on it to form a test piece beam 1. The linear drive mechanism 4 is operated by operating the motor triber 6 manually or by a computer, and the position of the saddle 3 is adjusted so that the load point is just on one of the supports 2. At this position, a weight 10 having an appropriate weight is placed on the weight stand 13 with a rod to increase the load and load the beam. The displacement of the beam at this time is set to zero.

When the computer 17 loaded with the program for machine control and data analysis is started, the computer automatically operates the measuring machine after inputting necessary data such as the test piece size, load weight and support interval according to the computer's request. Then, the saddle 3 is continuously moved from the top of the support 2 on which the load point was initially placed to the top of the other support. in the meantime,
The computer also reads the displacement of the fixed point on the test piece beam 1 corresponding to each position of the load point by the sensor 16, calculates the longitudinal elastic coefficient from the obtained relationship between both, and outputs it.

(F) Example From a hard vinyl chloride plate having a thickness of 10 mm, a width of 10 mm and a thickness of 1
An example in which a 0 mm (original thickness) test piece was cut out to obtain a test piece, and the elastic modulus thereof was obtained by the test machine of the present patent application is as follows. In this case, the shape of the support is hemispherical, span L
= 100 mm, moving load W = 26.6 N, and the distance X from the support on the load starting side to the sensor for measuring the deflection of the test piece beam X = 80 mm. The relationship V between the position x of the load point and the displacement amount V of the position X of the sensor obtained as a result of the test
An example of the (x) -x curve is shown in FIG.

From this V (x) -x curve, the longitudinal elastic modulus could be easily calculated with a simple computer by an analysis method as shown in the next section. For V (x), in addition to _Vb (x) caused by the bending moment of the beam, displacement V due to shearing force, etc.
_s (x) and dents at the contact between the support and the test beam x
The displacement V _k is proportional to Therefore, it is considered that V (x) = V _b (x) + V _s (x) + V _k (x). _{Here, A, B, K V b} (x) in the constant = Ax (L-X) ( 2XL-x 2 -X 2) 0 <x < When _{X V b (x) = A} (L-x ^{) X (2xL-x 2 -X} 2) X <x < when _{L V s (x) = B} (L-X) x 0 <x < when _{X V s (x) = BX} (L-x) X <x <V _b as when the _{V k (x) = Kx 0} <x <L when L, V _s, V _k is represented by a different functional form of x.

Therefore, the constants A, B, and K are set to at least two so that the sum of V _b (x), V _s (x), and V _b (x) matches V (x) obtained in the experiment for all x as much as possible. It was decided by multiplication. Since the constant A is a constant given by A = W / (6ELL) (E: longitudinal elastic modulus, W: load, I: second moment of area of beam), the longitudinal elastic modulus E was calculated from the value of A. .

Steel, copper, aluminum, polyvinyl chloride, as a result of measuring the longitudinal elastic modulus of the carbon using the measuring device of the present invention, the tensile load and tensile force than the elastic modulus obtained by the conventional three-point bending measurement method. It was possible to obtain a value closer to the longitudinal elastic modulus obtained from the relationship with the elongation of the test piece.

As the support 2, a portion having a cylindrical surface in contact with the test piece beam 1 as shown in FIG. 1 could be used, but in the case of a test piece beam whose lower surface is inaccurate, the load position and the test piece are used. The precise relationship with the displacement of the beam was not obtained, and the measured elastic modulus became slightly inaccurate. This means that while the load point is close to one support 2, the nearer support makes almost line contact with the test beam and the other support makes almost point contact with the test beam, but the load point moves. This is because the contact condition between the support and the test beam is reversed when the other support is approached. Therefore, in the above experimental example, a hemispherical support is used so that the lower plane of the test piece beam and the support are almost in point contact, and the sensor of the displacement measuring machine is located at a fixed point on the straight line connecting the two contact points on both sides of the beam. Was installed so that the relationship between the load position and the displacement of the test piece beam could be precisely obtained, and the longitudinal elastic modulus could be obtained more accurately.

(G) Effect of the Invention As described above, according to the present invention, it is possible to detect the amount of displacement of the beam caused only by the bending moment, which is impossible with the conventional method, and the longitudinal elasticity is more accurate than the conventional method. The coefficient can be measured. Conventionally, a load increasing device, a load meter, and a displacement measuring device were required, but it is inexpensive because it is composed of a linear motion mechanism, a weight, and a displacement measuring device. It is particularly convenient for the construction of the elastic modulus measuring system under the special environment. As a computer required for the present invention, a simple general-purpose small computer normally possessed by a company or a university that needs to measure the elastic coefficient is also sufficient.

[Brief description of drawings]

The figure shows an embodiment of the elastic modulus measuring machine of the present invention,
FIG. 1 is a front view of the measuring machine, FIG. 2 is a cross-sectional view as seen from the front view AA, and FIG. 3 is a displacement V of the test piece beam obtained in the example.
-It is an example of a weight position x curve. 1 ... Test beam, 2 ... Support, 3 ... Saddle, 4 ...
… Linear motion mechanism, 5… Carriage, 6… Motor driver, 7… Motor, 8… Screw, 9… Bed,
10 ... Weight, 11 ... Guide, 12 ... Frame, 13 ...
Weight stand with rod, 14 …… Load roller, 15 …… Displacement measuring machine, 16 …… Sensor, 17 …… Calculator

Claims (2)

[Claims] 1. A bending load applying section (9, 10, 11, 12, 13, 14) using a constant weight of a weight and a load roller.
And a load point moving part (2, 3, 4, 5, 6, 7, 8) for continuously moving the position of the load point with respect to the support (2) in one direction along the test piece beam (1), Displacement measuring section (15, 16) for measuring the vertical displacement of the fixed point of the test piece beam placed on the support, and obtained by measurement (load position with respect to the support-vertical displacement of fixed point on the test piece beam). ) From the curve, a curve resulting from only one component, the bending moment, is analyzed and separated, and a calculator (17) for calculating the longitudinal elastic modulus of the material of the test piece beam is provided. Point bending elastic modulus measuring machine. 2. A three-point bending elastic modulus measurement according to claim 1, wherein a support having a spherical shape near a contact portion with the test piece beam is used as the two supports for supporting the test piece beam. Machine