RU2373515C1 - Facility for evaluating hardness of material by method of scratching - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: invention refers to test engineering. The facility is installed directly on a structure. The facility consists of a working element including a resilient part and a rod with an indenter; a square diamond pyramid with angles between facets at top of 136 degrees is used as an indenter; also the facility consists of a load measuring device and of an instrument for autonomous measuring of scratch width. Further the facility consists of a hollow cylinder, a resilient element in form of a screw cylinder spring the degree of compression of which is the measure of load, pair screw-nut for spring loading, a plate on a lower part of the facility with screws for fixing the facility on curvilinear surface of an item, and stop rod with a tempered pointed end to be immovably fixed on the item by means of punching and connected with the cylinder by pivots and by the screw-nut mechanism for transfer of the cylinder with the indenter over surface of the item; also the facility consists of the load measuring device in form of a graduated scale.

EFFECT: expanded functionality.

4 dwg

Description

The invention relates to testing equipment and can be used to determine the hardness of materials directly in machines and mechanisms.

Microhardness testers which [Friedman Ya.B. The mechanical properties of metals. In 2 hours. Part 2. Mechanical tests. Structural Strength / Ya.B. Fridman. - M .: Mashinostroenie, 1974. 368 p., P. 84] do not fundamentally differ from devices designed to determine macrohardness.

It is known [Tenenbaum M.M. Sclerometers for resistance studies. // Sclerometry, p.118 - p.134] device - CT sclerometer of various modifications to determine the resistance of materials to scratching.

The main elements of this device are: a supporting table with a microscope, a pivotally mounted lever with an indenter in the form of a diamond trihedral pyramid at the end, a set of discrete weights installed directly on the lever, a drive device with an RD-09 type electric motor with an integrated gearbox.

The main disadvantage of this device is the functional limitation, consisting in measuring the hardness of materials only on samples of limited sizes, as well as the discreteness of the loading force, a small scratch length (2 mm), along the length of which the number of measurements of the scratch width is extremely small (1 ÷ 2), the need for processing sample surface (образцов11), which is used to measure the hardness of materials.

As a prototype, a device was selected (patent RU 2308018 G01N 3/46) for determining the hardness of materials by scratching, containing two rigid levers, an elastic element, a support table, an indenter in the form of a square diamond pyramid with an angle between the faces at the top of 136 °, clamps, loading a device in the form of a screw, a load meter in the form of a dial indicator, the device is mounted directly on the structure, the material hardness of which is determined. The device for measuring the width of the scratch is autonomous.

The disadvantages of this device are: the limited functional application, which consists in the fact that it cannot be used to determine the hardness of the material of structures that do not have constant thickness and flat surfaces, for example round shafts, teeth with an involute surface, as well as the inability to use when accessing one of two surfaces, for example a closed tank, a ball of the bearing.

The aim of the invention is to expand the functionality of the device for determining the hardness of materials by scratching directly in the structural elements and in the details of machines with curved, broken and other geometric surfaces with difficult access to them, for closed, spherical and other objects.

This goal is achieved by the fact that the device for determining the hardness of materials by scratching is mounted directly on the structure, contains a working body consisting of a rod with an indenter, a square diamond pyramid with angles between the faces at the top of 136 degrees is used as an indenter, a device for offline measurement of scratch width , also a hollow cylinder, an elastic element in the form of a coil spring, the compression ratio of which will be a measure of loading, a screw-nut pair for spring loading, p um, on the bottom of the device with screws to fix the devices on the curved surface of the workpiece, the thrust rod is pivotally connected to the cylinder via a screw-nut mechanism for moving the cylinder with the indenter on the workpiece surface, a load meter calibrated scale.

Figure 1 shows the proposed device, where 1 is a screw pair, 2 is a hollow cylinder, 3 is a rod with an indenter, 4 is a spring, 5 is a thrust bearing to avoid twisting of the spring, 6 is an arrow, 7 is a ruler with a calibrated scale, 8 - plate, 9 - supporting screws securing the position of the device on the surface of the part, 10 - thrust rod with a hardened pointed end connected to the cylinder by a hinge 11 and a screw pair 12 for translational movement of the cylinder with the indenter.

Figure 2 is a top view.

Figure 3 shows the calibration scheme of the device, where 13 is the overlay of the dynamometer, 14 is an elastic element, 15 is an indicator.

Figure 4 is a calibration graph.

с цилиндром 2, перемещают индентор по поверхности детали с образованием царапины длиной 4-6 мм. Если поверхность детали легкодоступна, то устройство перемещают вручную без использования упорного стержня 10. Таким образом делают 3-4 царапины. Ширину царапины в 2-х разных местах измеряют автономным прибором - микроскопом МПБ с ценой деления 0.02 мм для стальной детали с подсветкой.The device operates as follows. The device is mounted on the surface of the test machine part or structural member. If the part is located inside the housing and access to it is difficult, then a tapered recess (1-2 mm) is made in it with a punch and a hardened pointed end of the thrust rod 10 is installed in the recess. Then the device is fixed on the surface of the part using the support screws 9, located in the plate 8. Screw pair 1 install the rod 3 at a certain load, determined by the amount of movement of the arrow 6 using a calibrated scale 7. Hand pressure on the upper part of the device’s body compresses the spring 4. The compression ratio is the weight will determine the load on the rod with the indenter (for steel, the force is 80 N [Friedman Y.B. Mechanical properties of metals. In 2 hours. Part 2. Mechanical tests. Structural strength / Ya. B. Friedman. - M .: Mechanical engineering, 1974. 368 p., P. 84]). Rotate the nut of the screw pair 12 connecting the thrust rod 10

with cylinder 2, the indenter is moved along the surface of the part with the formation of a scratch of 4-6 mm in length. If the surface of the part is easily accessible, the device is moved manually without using the thrust rod 10. In this way, 3-4 scratches are made. The width of the scratch in 2 different places is measured by an autonomous instrument - an MPB microscope with a division value of 0.02 mm for a backlighted steel part.

The hardness of the material is determined by the formula:

Where

- среднее значение ширины царапины,F is the pressure from the indenter on the material,

- the average value of the width of the scratch,

n is the number of measured values b _i,

c is the coefficient determined by the test loading of the material at which the scratch width b should be such that the relative measurement error is not more than 10%. So, when measured with a microscope with a scale division of 0.02 mm, the scratch width should be at least 0.2 mm.

Depending on the hardness of the material, the thickness of the structural element and, accordingly, the indenter pressure force, a different amount of compression of the spring 4 is used.

The device is calibrated using a DOSM-100 dynamometer as follows (Fig. 3): it is mounted on the dynamometer on the plate 13 by the indenter, the spring 4 is loaded with a screw pair 1, the load is transmitted through the rod 3 to the elastic element 14 of the dynamometer, flag 6 is moved relative to scale 7 according to the values on the dynamometer indicator 15. Based on the measurement results, a Δ-F graph is constructed (Fig. 4) of the dependence of the movement of the flag (rod) 6 on the force value F on the dynamometer indicator 15.

The developed device allows you to determine the hardness of machine parts and structures in inaccessible and cramped places, parts having complex geometric shapes of various sizes.

Claims (1)

A device for determining the hardness of materials by scratching installed directly on the structure, containing a working body consisting of an elastic element, a rod with an indenter, a square diamond pyramid with angles between the faces at a vertex of 136 °, a load meter, an instrument for autonomous width measurement is used as an indenter scratches, characterized in that it further comprises a hollow cylinder, an elastic element in the form of a helical coil spring, the compression ratio of which is a measure of loading, pa screw nut for spring loading, a plate on the bottom of the device with screws for fixing the device on the curved surface of the part, a thrust rod with a hardened sharp end for fixed fastening to the part by punching, connected to the cylinder by a screw-nut mechanism for moving the cylinder with an indenter on the surface of the part and equipped with hinges, a load meter in the form of a calibrated scale.

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