JPH03225255A - Method for measuring elastic modulus - Google Patents

Abstract

PURPOSE:To make it possible to use comparatively small-sized mechanical parts as samples without working/destructing them and to improve the efficiency of measuring work by press-contacting a probe with the surface of a sample by a prescribed load to elastically deform the sample and finding out the elastic mudulus of the sample from the elastic deformation value. CONSTITUTION:A guide member 7 is positioned on a proper height in accordance with the size of a sample to be measured. A mechanical parts such as a sliding ring is fixed on a table 8 as a sample 19. When load is applied to the surface of the sample 19 by a load applying means 17 after allowing a fall 16 to come into contact with the surface of the sample 19, a rod 13 is moved down in a guide hole 9 and the surface of the sample 19 is elastically deformed. In this case, the tare weight of the rod 13 is initial load and load applied by the means 17 becomes secondary load. The moving variable of the ball 16, i.e. an elastic deformation value h1(h2) obtained at the time of the elastic deformation of the sample 19 is detected by a differential transformer 11. The elastic modulus of the sample 19 can be found out based upon the elastic deformation value, and when the press contact of the ball 16 with the sample 19 is released, the surface of the sample 19 is restored to the original plane.

Description

Detailed Description of the Invention (Industrial Application Field) This invention measures the elastic modulus of relatively small-sized mechanical parts, such as carbon sliding rings of mechanical seals, without processing or destroying them. This invention relates to a method for measuring elastic modulus that can be used to measure elastic modulus.

(Prior Art) Carbon sliding rings are commonly used as components of mechanical seals used in stirrers, mixers, and the like. At this time, the amount of elastic deformation of the sliding ring due to changes in sealing pressure has a great effect on sealing performance, so the operator needs to know the elastic modulus of the sliding ring in advance.

Conventionally, the elastic modulus of mechanical parts as described above is measured as follows. First, a sample is prepared by processing a material for a mechanical part into a predetermined size, and the sample is subjected to a tensile test, a bending test, etc. using various measuring devices, and the elastic modulus of the mechanical part is measured.

(Problems to be Solved by the Invention) However, in the conventional example, it is very troublesome because the material must be processed into a sample having a shape and size that can be applied to various measuring devices. Furthermore, the mechanical properties of a material may change before it is completed as a mechanical part, and the elastic modulus measured from a sample may not match the elastic modulus of the completed mechanical part. Therefore, it is possible to accurately measure the elastic modulus by taking a sample from a completed mechanical part and applying it to a measuring device. In many cases, it is impossible to collect a sample with a shape and size that can be applied to a measuring device.Furthermore, destroying completed mechanical parts to collect samples wastes the manufacturing process and mechanical parts. (becomes unusable).

This invention is intended to solve the above-mentioned problems. For example, it is possible to measure the elastic modulus of relatively small-sized mechanical parts, such as the sliding ring of a mechanical seal, by applying them as samples without destroying or processing them. The purpose is to provide a method for measuring elastic modulus.

(Means for Solving the Problems) In order to achieve the above object, the present invention brings a probe having an arcuate curved surface into pressure contact with the surface of a sample under a predetermined load to elastically deform the sample, and calculates the amount of elastic deformation from the Hertzian It is configured to determine the elastic modulus of a sample based on the theory of

Further, a sphere and a cylinder are used as the measuring element.

(Function) In the present invention based on the above configuration, the probe is pressed against the surface of the sample under a predetermined load to elastically deform the sample. Based on this amount of elastic deformation, the elastic modulus of the sample is determined using Hertz's theory of material mechanics.

Furthermore, when the load on the probe is released, the sample returns to its original shape.

(Example) Next, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a partially cutaway front view showing a schematic configuration of a measuring device 1 used in the present invention. A support 3 is erected on the base 2, and an arm 6 having a pulley 4.5 is provided on the top of the support 3.

7 is a guide member attached to the support column 3, and this guide member 7
is raised along the support column 3 in the direction of arrow A by a mechanism (for example, a worm and rack) not shown.

It can be lowered and stopped at a predetermined height. The guide member 7 is provided with a guide hole 9 that vertically passes through a position corresponding to the table 8 on the base 2, and a differential transformer 11 having a hollow portion 10 is placed therein. This differential transformer 11 is for detecting the amount of movement of a measuring head, which will be described later, and has a well-known configuration including an insulating bobbin, a secondary coil, etc. (none of which are shown), and a power source (not shown). Section 9 oscillator, amplifier.

Connected to rectifier, indicator, etc.

An end-shaped wire 12 is stretched over the pulley 4.5, and a rod 13 inserted into the hollow portion 10 of the differential transformer 11 and the guide hole 9 of the guide member 7 is attached to one end of the wire 12. A removable balance weight 14 is provided at the other end. A ball (measuring head) 16 is fixed to the lower end of the rod 13. This sphere 16 has a known elastic modulus and Poisson's ratio, and is preset to a predetermined radius. Note that the rod 13 serves as a core for the differential transformer 11.

17 is a disc-shaped plate 1 provided on the upper end side of the rod 13
8, this load applying means 17
puts ball 16 on table 8! By pressing the sample 19 at right angles to the flat surface of the sample 19,
This is for elastically deforming the surface of. There are many types of load applying means 17 with different loads.
You can increase or decrease them.

Next, a method of measuring the elastic modulus of the sample 19 using the measuring device 1 will be explained.

First, the guide member 7 is moved up and down in advance according to the size of the sample to be measured, and positioned at an appropriate height. Next, a mechanical component such as a carbon sliding ring of a mechanical seal is placed as it is on the table 8 as a sample 19, and the sample 19 is fixed by a fixing means (not shown).

Then, the sphere 16 is brought into contact with the surface of the sample 19 (see Fig. 2 (
a)) After that, when a load is applied by the load applying means 17, the rod 13 moves (descends) within the guide hole 9, and as shown in Fig. 2 Φ)
Or, as shown in (C), the surface of the sample 19 is elastically deformed (indented).During the above action, the weight of the rod 13 becomes the initial load, and the load applied by the load applying means 17 becomes the secondary load. . Since even the load of the rod 13 is too heavy when using a material with a small elastic modulus such as rubber as a sample, the load is adjusted using a balance weight 14.

The amount of movement of the ball 16 during elastic deformation of the sample 19, that is, the elastic deformation amount (ht), is detected by the differential transformer 11. That is, when the rod 13 moves within the hollow part 10 of the differential transformer 11, a voltage is generated depending on the position of the rod 13 in accordance with a change in mutual inductance between the coils (not shown), and the output difference is displayed on an indicator (not shown). Become. Then, when the load application by the load application means 17 is released, the sample 19 returns to its original shape.

Here, the principle of determining the elastic coefficient of the sample 19 from the elastic deformation 1h+(ht) of the sample 19 detected by the differential transformer 11 will be described. That is, the amount of elastic deformation of the sample 19 is:
It is given by the Hertzian equation of elastic mechanics. Now, R: Radius of the sphere EA: Elastic modulus of the sample ν^: Poisson's ratio of the sample E, elastic modulus of the two spheres C, Poisson's ratio of the two spheres P: Assuming the load to be applied to the sphere, the sphere 16 is the surface of the sample 19. The elastic deformation 1h that bites into is given by the following equation.

Here, if E, >> EA, the second term in equation (1) can be ignored, so the equation becomes simple, and ``= I:R(Hibiki)'P8...(2
) is now the elastic deformation due to the initial load P.

When the secondary load is increased to P2 from the state of = 9 (Te) X(1-Shinai η...(3)

Here, there are two unknowns, E and ν, and although it cannot be determined as is, assuming ν, the elastic coefficient E can be determined from equation (3). The Poisson's ratio of commonly used materials is approximately 0.2-0.3. Assuming Poisson's ratio, the influence on accuracy is (1-v”)”(D
Value = 0.2 and 0.3, respectively 0.92
．． 0.83, and even if it is treated as C 0.25, the error is within ±5%. When measuring rubber materials:
It may be calculated as 0.5.

Now, we prepared a carbon sliding ring of a mechanical seal as sample 19, elastically deformed it with measuring device 1, and calculated the elastic modulus of the sliding ring from the measured value.The results shown in the table below were obtained. In the table, initial load Og, secondary load 5
An example is shown in which the radius of the hard ball 16 is φ0.5.

(Margin below) table (Load: 5g.

(When ν=0.25) As a result of the above, it can be seen that the elastic modulus B of measurement point "3" is locally decreased for some reason.

As described above, in the present invention, the sample 19 is elastically deformed by applying a predetermined load to the ball 16, and the elastic modulus EA of the sample 19 can be determined using the elastic deformation scale. If this is released, the surface of the sample 19 will return to its original flat state.

Therefore, relatively small-sized mechanical parts can be used as samples without being processed or destroyed, and their elastic modulus can be measured, so there is no waste of the mechanical parts themselves in the manufacturing process of mechanical parts, and measurement work efficiency is greatly improved. It has the effect of

Further, the case where the measuring element is a cylinder 20 as shown in FIG. 3 will be explained.

First, when the cylinders 20.21 with half pI: r l + radius ", are in line contact, their Young's moduli are El, El, Poisson's ratio is 6.ν2, and the load per unit length is q. The convergence of the contact surface is given by the following equation.

(Excerpted from Yokendo, "Mechanics of Materials" by the middle layer) Here, considering the contact between the cylinder 20 and the plane of the sample 19, r2-ω
Therefore, by resetting r+=r, equation (1) becomes as follows.

Now, Et >> E Assuming that, E + = E ν1; ν Then, It is expressed by the simple formula:

In FIG. 4, the elastic deformation of sample 19 is b''+(r
-h)"-r" The relationship (7) holds true, but even though h << r, h=b"/
2r (8) Therefore, by substituting equation (8) into (method), the following relational expression is obtained.Assuming ν in equation (9) and measuring the elastic deformation against load q, the sample The elastic modulus E of 19 is (9
) can be obtained from the relationship of formula.

In the above embodiment, the guide member 7 is configured to be able to move up and down with respect to the support column 3, but the differential transformer II is configured to be able to move up and down on the guide member 7 (for example, by using a feed screw, etc.). ), and the position (height) may be adjusted according to the size of the sample 19.

(Effects of the Invention) As described above, in the present invention, a predetermined load is applied to the probe to elastically deform the sample, and the elastic modulus of the sample can be determined from Hertz's theory using the amount of elastic deformation.
When the load of the probe on the sample is released, the surface of the sample returns to its original flat state.

Therefore, relatively small mechanical parts can be used as samples without being processed or destroyed, and their elastic modulus can be measured, so there is no waste of the mechanical parts themselves in the manufacturing process of mechanical parts, and the efficiency of measurement work is greatly improved. It has the effect of

[Brief explanation of drawings]

FIG. 1 is a partially cutaway front view of a measuring device used in the present invention, and FIGS. 2(a) to (C), 3, and 4 are front sectional views showing elastic deformation of a sample. Explanation of symbols l...Sphere (measuring point) 20...Cylinder (measuring point)
19...Sample, h,,h! ...Amount of elastic deformation Figure Section <a> Cb) (C)

Claims (3)

[Claims] (1) A measuring element having an arc-shaped curved surface is pressed against the surface of the sample under a predetermined load to elastically deform the sample, and the elastic modulus of the sample is determined from the amount of elastic deformation based on Hertz's theory. Elastic modulus measurement method. (2) The elastic modulus measuring method according to claim 1, wherein the measuring element is a sphere. (3) The elastic modulus measuring method according to claim 1, wherein the measuring element is a cylinder.