JPH0120370B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a hardness testing device using impact means configured to cause a probe to collide with a test material under the action of a movable mass. A movable mass having arbitrary geometrical conditions and made of arbitrary material and moved until it collides will be simply referred to as an impacting body in the following description. The impactor and the probe may be configured as one piece, or may be configured as separate parts that are movable relative to each other. The probe may be, for example, a sphere, a partially spherical pin or bolt, or a sphere connected to a bolt. In addition to the well-known static so-called penetration method of Brinell, Bitkers and Rockwell, dynamic testing methods are often used to measure the hardness of materials. These known methods bring the probe into contact with the material under test under impact or impact action and, depending on the method, the deformation remaining in the material, the impact force between the probe and the material, the impact duration, or the release of the material. The potential energy remaining in the impact body with a probe after repulsion forms the hardness measurement value. However, in dynamic testing methods, the energy of the collision or impact action is usually chosen to be large so that the contact between the probe and the material is accompanied by the residual deformation. An object of the present invention is to provide a method and apparatus for hardness testing using a dynamic testing method, which quickly performs hardness tests regardless of the direction of gravity using a small and extremely simple testing device with good measurement accuracy. The hardness testing method of the present invention measures the velocity of an impacting body with a probe moved by an arbitrary energy source immediately before and after the collision with the test material, and then forms a characteristic value as a guide to the material hardness from both velocities. It is characterized by In the present invention, the same applies to the following description, but the pre-collision velocity exhibited by the probe-equipped impactor moving relative to the stationary material at or in the immediate vicinity of the collision position is the velocity immediately before the collision. If this is expressed strictly theoretically, it is the velocity of the impactor at the moment when the probe and the material come into contact. Similarly, the velocity immediately after impact is the velocity after rebound of the impactor with a probe, which is moved in the opposite direction by the resistance of the material, at or in the immediate vicinity of the impact location. If this is expressed strictly theoretically, it is the velocity of the impactor at the moment the probe moves upward from the material again. Depending on the duration and magnitude of the energy acting on the impacting object, the impacting object will increase the velocity as a measurable quantity, i.e., the impact velocity, not only in the immediate vicinity of the impact location, but also at a distance from the impact location. and repulsion speed. For example, regarding the collision speed, assuming that the impacting body is accelerated not to the collision position but to a predetermined distance from this collision position, and then the effects of other forces can be ignored, the collision velocity is maintained at a constant speed, that is, the collision velocity. Exercise until. The method of the invention is based on the analysis of known energy equations; for example, in the case of a spring impact device, the residual energy after a collision is expressed by the following equation: m・v _R ² /2=c・s _R ² /2±mg・s _R +E _R 1) However, m=mass of the impacting body. v _R = repulsion velocity of impactor. c = spring constant. s _R = rebound stroke of the impactor against the spring action (part of the spring stroke). g = gravitational constant. The value m·v _R ² /2 is the potential energy of the impactor at the start of repulsion, and is converted into the following energy components at the end of repulsion. c・s _R ² /2 = potential energy remaining in the spring device. mg・s _R = residual potential gravitational energy. This energy component can be positive, negative, or zero depending on the impact direction. E _R = Energy produced by the effect of friction along the repulsion stroke s _R. In the repulsion device, the repulsion stroke s _R , that is, the stroke of the residual potential energy, is measured as a measurement quantity representing the hardness. This value is influenced by the action of the frictional forces along the impact direction and the rebound path, as seen in equation 1). On the other hand, if the characteristic value of kinetic energy, that is, the repulsion speed, is measured as the residual energy measurement quantity, the above two error factors will completely disappear. However, the above two error factors also appear during the generation of impact energy in all dynamic testing methods, as is evident from similar energy equations for the impact energy present prior to impact. That is, c・s ² /2±mgs+E=m・v _A ² /2 2) However, m, c and g=same as equation 1). s = total stroke. v _A = impact velocity of impactor. E = energy component caused by frictional action along the total stroke. The value m·v _A ² /2 is the kinetic energy of the impactor just before the impact, and is formed by converting the potential energy of the spring device c·s ² /2, where again the potential gravitational energy and the along the path Frictional force appears as an error element. In the case of spring-type impact devices used in dynamic hardness testing methods, the impact energy can only be maintained constant by providing a constant value in advance corresponding to the spring constant and spring stroke. The kinetic energy appearing in the equation is not constant under the influence of the two error factors mentioned above. Here again, if the collision velocity v _A is measured as a measurement quantity of kinetic energy, the above two error elements will necessarily be involved, contrary to the repulsion velocity. However, in connection with the velocity measurement, the invention relates the two velocities to one another, ie forms the quotient v _R /v _A of the two velocities, for example, as a characteristic value representing the hardness. By forming the quotient in this way, the error in collision speed is significantly reduced. This is because if the change in collision speed is not too large, the repulsion speed will change approximately in proportion to this change. From the measured speed e.g.

or (v _R /v _A ) and use this as a characteristic value, the latter being directly proportional to the change in kinetic energy due to the collision. The error factor associated with the impact velocity due to the impact direction is such that the kinetic energy present in the impactor before impact is greater than the positive or negative energy component when the impactor mass is under the action of gravity. Further reductions can be made by relatively quantifying the impactor mass and the speed at which this mass is driven by any energy source. The device of the present invention for carrying out the method described above is characterized in that the impactor is fixedly connected to a movable part of a transformer that converts the velocity exhibited by the impactor in the immediate vicinity of the collision position into an electrical signal proportional to the velocity. shall be. The transformer is a plunger magnet type signal generator in which a movable permanent magnet is connected to an impact body and a fixed coil part is fixed to an impact body guide, or a plunger magnet type signal generator in which a movable magnetic part is connected to the impact body and a fixed coil/permanent coil is connected to the impact body. Other electromagnetic signal generators having a magnet fixed to an impact guide may be used. The fixed transformer part mounted on the impact body guide may be conductively connected to a measuring device for measuring and storing the velocity proportional signal generated, and to this measuring device a device for ascertaining the hardness characteristic value formed from said signal. All you have to do is include. Utilizing the transformer described above to generate an electrical signal proportional to velocity, the instantaneous velocity of an impacting body virtually anywhere in the vicinity of the impact location can be measured without contact. Since the signals can be measured electronically and further processed, the measurement results have the advantage, in addition to high accuracy, of being digitized immediately after measurement. Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. The hardness testing apparatus shown in FIG. 1 comprises a tubular front housing 4 whose open front end rests perpendicularly to the surface 15 of the material to be tested during hardness testing. An impact body 2 and a coil compression spring 5 are installed in a case 4 whose inner surface constitutes a guide so as to be movable in the longitudinal direction. The front end of the cylindrical impact body 2 is fixedly connected to the probe 1, and a cylindrical permanent magnet 3 having poles 3a and 3b in the axial direction is fixed inside.
In the embodiment shown, probe 1 is a sphere made of hardened steel or other suitable hard material capable of penetrating the material under test. The impact body has an axial cylindrical hole 2a at its rear end for receiving a clamp jaw tip 8,
The clamp jaw tip can be inserted into this cylindrical hole 2a along the overrun conical surface 2b. The compression spring 5, shown in a relaxed state in FIG. 1, generates an impact energy large enough to leave the material under test deformed after the probe 1 has penetrated the material. The spring force is transmitted to the impact body at the rear end surface 2 of the impact body.
This is done via c. The rear end of the housing 4 is connected to a guide sleeve 6 in which a clamp jaw 7 is provided in the inner hole so as to be freely movable in the longitudinal direction. The rear end of the clamp jaw 7 is fixedly connected to a rear tubular housing 11 via a cap 10, and the housing 11 is mounted so as to be movable longitudinally on the housing 4. The front end of the clamping jaw, which is made radially resilient by means of a cross-shaped longitudinal slot, is equipped with a clamping jaw tip 8 and a release device 9 as special devices. The clamp jaw tip 8 consists of four overrun shoulders 8a which have a conical shape toward the front, and these shoulders act as joints for the impact body when the clamp jaw tip is inserted into the cylindrical hole 2a. act. The release device 9 consists of an overrun cone 9a and an end stop 9b. The purpose of the overrun cone is to sufficiently compress the elastic arm of the clamp jaw when the clamp jaw is withdrawn, thereby re-releasing the impact body with which the clamp jaw tip is engaged. The return process of the clamp jaw is guided by the guide sleeve 6.
by a terminal stop 9b which abuts the surface 6a. The rear housing 11 is provided with another coil compression spring 12 which is normally in a stored state, and its both ends abut against the guide sleeve 6 and the cap 10, respectively, so that the clamp jaw connected to the cap is normally held. It is urged rearward so that it is placed on the end stop portion 9b. The force reserve of the spring 12 is at least equivalent to the spring force of the front spring 5, including the resistance created in the overrun cone 9a. Furthermore, at the time when the impact body collides with the outside of the casing 4, the coil axis xx is aligned with the front end 3a of the permanent magnet.
The coil 14 housed in the holder 13 is arranged so as to substantially match the . To precisely adjust the coil axis with respect to the front end of the permanent magnet, the holder 13 consisting of two parts may be moved, for example, along a thread provided on the housing 4. The coil 14 is connected to a measuring and display device 17 via conductors 16a, 16b. FIG. 2 shows the typical behavior of the voltage U present at the transformers 3, 14 as the permanent magnets in and moving with the impactor enter the coil area and exit again. This voltage trend is shown schematically in relation to the time t, where the time interval t ₁ corresponds to the approach of the impacting body to the impact position, and the time interval t ₂ corresponds to the rebound process. Since the time from collision to repulsion is the true collision time and is extremely short compared to time segments t ₁ and t ₂ , they are indicated by A and R in FIG. 2 as occurring simultaneously. Maximum value +U _nax , −U _nax
appears when the coil axis xx and the magnet end 3a occupy a certain relative position, and is directly proportional to the speed at this position of the impact body fixedly connected to the magnet. Second
In the figure, this maximum value appears just before the collision and immediately after the rebound. That is, at the time when the velocity of the impactor is converted into an electrical signal proportional to the speed, the impactor is located in the immediate vicinity of the collision position. However, the coil movable on the enclosure 4 must be adjusted so that the maximum value coincides with the collisions A and R shown in Figure 2, that is, the velocity of the impacting body is measured at the time of collision and rebound. You can also do it. The circuit diagram of the measurement and display device shown in FIG. 3 includes an amplifier 17', two peak memories 18, 1
8', and the stored values in the memory are controlled by a double ramp type A/D transformer 19 under the control of a controller 19'.
In the transformer, a digital quotient is formed from the repulsion velocity and the impact velocity and is displayed by a counter 20 and a display 21. The operating mode of the hardness testing apparatus of the present invention will be explained below. When measuring the hardness of a sample, place the front end of the casing 4 perpendicularly on the surface 15 of the test material, and while fixing the holder 13 with one hand, use the other hand to hold the holder 13 between the rear casing 11 and the cap 10. The clamp jaw 7 fixedly connected is pressed against the material until the clamp jaw tip 8 is inserted into the bore 2a of the impact body (FIG. 5). When the clamp jaw 7 returns under the action of the energy storage spring 12 simply by releasing the pressure on the rear housing 11, the impact body 2 also returns together, thereby causing the spring 5 to store energy (FIG. 6). . As the return operation continues, the conical surface of the overrun cone 9a fits into the hole of the guide sleeve 6, and the clamp jaw tip 8
is compressed, and as a result, the impact body 2 is released (FIG. 7) and is caused to collide with the test material by the spring 5 in the charged state (FIG. 8). The velocity of the impactor immediately before and after impact is converted to a proportional voltage as described above, measured and processed by the measurement and display device shown in FIG. The quotient of the two velocities, which is formed as a measure of hardness, is always less than 1 and takes a value between 0.300 and 0.800 for a range of steels for a constant combination of probe type and impact energy. It goes without saying that the apparatus for carrying out the method of the present invention is not limited to the above embodiments. As an example of the impactor, it is preferable that the impactor and the probe are integrated, but it is also possible to configure the impactor and the probe as separate parts, move only the impactor, and move the probe onto the test material. Of course, it is also possible to configure the percussion device so that it rests. In this case, the velocimetric hardness testing method can be carried out in two different ways. The method of the first aspect is characterized in that the velocity of the impactor is measured immediately before impact and immediately after rebound from the probe on the material. The method of the second aspect includes measuring the maximum velocity appearing on the probe immediately after the impact of the impacting object, that is, at the beginning of penetration into the test material, and measuring the maximum velocity after repulsion from the test material. It is characterized by Unlike the impactor velocity measurements in the first embodiment, the maximum velocity measured in the second embodiment is due to the acceleration of the probe occurring over a very short stroke. In the embodiment shown in FIG. 4, the impact body 24 and the probe 22 are configured separately in order to measure the maximum velocity of the probe 22. In this embodiment, a test body 22a separate from the impact body is used. A probe 22 and a permanent magnet 23 are incorporated in the probe. In this embodiment, probe 22 consists of a hardened steel bolt with a spherically ground front end. The impact body 24 also has a cylindrical cross section, for example, and the probe 22
Similarly, it is provided within the tubular casing 25 so as to be freely movable in the longitudinal direction. The mass of the impacting body 24 may be equal to or larger than that of the probe 22. Although not shown in FIG. 4, the rear end of the impact body 24 may be constructed in the same manner as the impact energy generating device as shown in FIG. As in the case of FIG. 1, the coil 26 housed in the holder 27 in FIG.
It is connected to a measuring and display device 29 via a and 28b.

[Brief explanation of drawings]

Fig. 1 is a longitudinal cross-sectional view of a hardness testing device that is an embodiment of the present invention, Fig. 2 is a characteristic diagram depicting a typical output signal from a transformer, and Fig. 3 is an evaluation of the transformer signal. FIG. 4 is a longitudinal sectional view showing the front part of the hardness testing device in which the impact body and the probe are configured separately; FIGS. 5 to 8 FIG. 2 is a diagram showing the operating sequence of the hardness testing device of the present invention. DESCRIPTION OF SYMBOLS 1... Probe, 2... Impact body, 3... Permanent magnet, 4... Linear guide member, 5... Drive spring, 6a... Release device,
7, 8, 12... Return device, 8a... Capture chuck, 14... Electromagnetic coil, 17... Measurement/storage device,
18, 18'... Peak value memory, 19, 19'... Quotient forming circuit.

Claims (1)

[Scope of Claims] 1. A device for testing the hardness of a material using an impact device, which comprises: an impact device 2 having a probe 1 formed integrally with the impact device; In an apparatus comprising a linear guide member 4 for guiding an impactor and a compressible drive spring 5 for driving the impactor 2 toward the surface of the material to be tested, the impactor 2 is located inside the impactor. The first transformer part 3 fixed to
A second transformer portion 14 is provided at the front end of the guide member 4, and the second transformer portion 14 is stationary relative to the surface of the material to be tested, and the first and second transformer portions 3, 14 are located at the front end of the guide member 4. The electromagnetic transformers 3 and 14 cooperate to form an electromagnetic transformer that directly generates an electromagnetic signal proportional to the instantaneous velocity of the impacting body 2 immediately before and after colliding with the impact body 2. A measurement/memory circuit 17 is connected to the 1000 to measure and store the maximum value of the electromagnetic signal immediately before and after the impact body 2 collides with the surface of the material to be tested, and the quotient of the two maximum values is calculated as the hardness of the material. A hardness testing device for materials characterized by using it as a guideline. 2 A first transformer part is formed by a permanent magnet 3 fixed to the impact body 2, and a second transformer part is formed by an electromagnetic coil 1 attached to the front end of the linear guide member 4.
4. Device according to claim 1, characterized in that the electromagnetic coil (14) is connected to the measurement and storage circuit (17). 3. The transformer part 3, 14 is of the plunger solenoid type, and the solenoid part surrounds the front end of the linear guide member 4.
Apparatus described in section. 4. The permanent magnet 3 of the impact body 2 and the electromagnetic coil 14 of the linear guide member 4 are mutually adjusted so that the maximum value of the electromagnetic signal occurs immediately before and after the impact body collides with the surface of the test material. An apparatus according to claim 2 or 3, wherein the apparatus is adapted to perform the following steps. 5 includes return devices 7, 8, and 12 for the impact body 2, and the return device is configured to be movable within the guide member 4 against the biasing force of a return spring 12 acting toward the front end of the guide member 4; At the same time, it is equipped with a capture device that captures the impacting body 2, and after each measurement, the impacting body is captured and the impacting body is returned to its initial position by the force of the above-mentioned return spring 12, and when the above-mentioned impacting body returns, the above-mentioned 5. A device according to claim 1, wherein the drive spring 5 is compressed. 6. A capturing device for capturing the impacting body is equipped with a capturing chuck 8a and a releasing device 6a, and the capturing chuck 8a is operated by the releasing device 6a to release the impacting body 2 when the device returns to its initial position. The device according to claim 5. 7. The device according to any one of claims 1 to 6, wherein a probe 1 is provided at the front end of the impactor 2, the probe has a spherical surface and is fixed to the impactor 2. 8 The measurement/display circuit 17 includes peak value memories 18 and 18' that store the maximum value of the electromagnetic signal immediately before and after the impact body 2 collides with the surface of the test material, and a quotient of the maximum value of the electromagnetic signal. An apparatus according to any one of claims 1 to 7, comprising quotient forming circuits 19, 19' for calculating .