RU2079831C1 - Method of determination of mechanical characteristics and device for its implementation - Google Patents

Abstract

FIELD: material testing, determination of physico-mechanical characteristics of materials. SUBSTANCE: indenter penetrates tested material by impact. With this transducer registers kinematic characteristics of impact indentation: maximum depth of penetration, maximum speed of penetration, maximum positive acceleration, maximum negative acceleration. Mechanical properties of materials: strength, yield point, relative elongation, impact viscosity, fatigue limit and hardness are found by dependence presented in the form of polynomial of n-th power:

, where a_o, a_ik, k=1,...n, j-1,. . . 7 are coefficients of polynominal determined for each j-th mechanical property at stage of preliminary investigations; X2 is maximum length of penetration; X3 is maximum positive acceleration; X4 is maximum negative acceleration. Essence of invention lies in that portable electron device incorporating loading unit, indenter, electron counting system is additionally inserted with transducer composed of permanent magnets and coil to register kinematic characteristics of impact penetration. It has spring realizing impact penetration of indenter. EFFECT: simplified design of device, improved reliability of method. 2 cl, 2 dwg

Description

 The invention relates to testing equipment, to strength tests.

A known method of determining mechanical characteristics, in which a spherical indenter introduces into the test material with increasing load. Measure the load and imprint depth, which determine the tensile strength [1]
A device for determining hardness is known, containing a loading mechanism, an indenter, a subject table and a mechanism for measuring the depth of penetration [2]
A device is known comprising a cylindrical body with a spring and an emphasis, a striker, a stopper.

 The disadvantages of the known technical solutions are low accuracy and low productivity.

Closest to the proposed is a method in which the indenter is pressed into the test material, the diagram "load imprint depth" is continuously recorded. The measured values determine the tensile strength. Then produce an increase in load, fix the depth of the print, fix the residual depth of the print and calculate the deformation [3]
The disadvantages of the known solutions are low accuracy and high complexity.

In terms of the device, a hardness measuring device is known, which is a design with a lever system for reproducing the load and applying an imprint on the sample [4]
The disadvantages of the device are the large weight, dimensions and the inability to test large products.

 The essence of the invention lies in the fact that an indenter is introduced into the test material by an impact method. In this case, the sensor registers the kinematic characteristics of impact indentation: maximum penetration depth, maximum penetration rate, maximum positive acceleration, maximum negative acceleration.

где a $\genfrac{}{}{0ex}{}{\text{(j)}}{\text{o}}$ , a $\genfrac{}{}{0ex}{}{\text{(j)}}{\text{ik}}$ , K 1, n, j 1,6 коэффициенты полинома,
определяемые экспериментально для каждого j-го механического свойства на стадии предварительных исследований,
x₁ максимальная глубина проникновения,
x₂ максимальная скорость проникновения,
x₃ максимальное положительное ускорение,
x₄ максимальное отрицательное ускорение.The mechanical properties of the material: tensile strength, yield strength, elongation, impact strength, endurance, hardness is determined by the dependence presented in the form of an nth degree polynomial

where a $\genfrac{}{}{0ex}{}{\text{(j)}}{\text{o}}$ , a $\genfrac{}{}{0ex}{}{\text{(j)}}{\text{ik}}$ , K 1, n, j 1,6 polynomial coefficients,
determined experimentally for each j-th mechanical property at the stage of preliminary studies,
x ₁ maximum penetration depth,
x ₂ maximum penetration rate,
x ₃ maximum positive acceleration,
x ₄ maximum negative acceleration.

 The invention also lies in the fact that the portable element, an electronic device containing a loading device, an indenter, an electronic-counting system, further comprises a sensor consisting of permanent magnets and a coil for recording the kinematic characteristics of impact indentation, and as a loading device contains a spring that implements shock indentation of the indenter, and the indenter is made in the form of a cone.

 In FIG. 1 shows a general view of the device, in FIG. 2 shows a diagram of the mechanical part and a block diagram of the electronic unit.

 The device comprises a housing 1, a holder 2 with an indenter 3 fixed thereon, a working spring 4, a button 5 connected to the striker 6 by a rod 7, a nut 8 screwed into the housing 1, which serves as the upper spore of the working spring 4, the preload spring 9, a sensor 10 for recording the kinematic characteristics of the indenter 3 during its introduction into the material, consisting of permanent magnets and a coil, a stopper 11, an interchangeable nozzle 12, which allows to determine the strength characteristics of the material of parts of various shapes. The electronic unit contains: a signal processing and normalization unit I, a reset device II, peak detectors III, functional converters IV, switch V, converter VI, digital indicator VII.

 The method is as follows.

When a conical indenter is pressed in, a material that can be characterized by a set of mechanical properties / yield and strength limits, elongation, impact strength, hardness, endurance limit, crack resistance, etc. /, undergoes elastic-elastic deformation and fracture, which is ultimately determined by the aforementioned properties. Thus, the kinematic characteristics of the indenter during indentation of X _i , i 1,4 depend on the mechanical properties of the material, and, therefore, from the known values of X _i , i 1,4, it is possible to determine the mechanical properties of the material: H, j 1, 7 In the general case the relationship between H _j and X _i can be represented by the function
H _j f _{j (X 1, ..., X 4} )
where f _{j is a} function depending on the indentation conditions.

Устройство работает следующим образом.This dependence can be represented as an nth degree polynomial

The device operates as follows.

 They connect the electric circuit: the mechanical part is connected by electric wires to the electronic unit, the electronic unit is connected to the electric network. Depending on the surface of the tested part, the corresponding nozzle 12 is installed and the percussion mechanism is cocked using the button 5, which is fixed by the stopper 11, after which the mechanical part is mounted on the tested part and pressed against it, while under the action of the spring 9, gaps are selected and the indenter fits snugly test surface, then press the "reset" button. The device is ready for measurement. Press the button 5, while the stopper 11 releases the stem 7, and the spring 4, unclenching, drives the hammer 6, which strikes the holder 2, giving off the energy of the spring 4. Under the influence of the impact, the indenter 3 is introduced into the surface of the test part, the sensor 10 registers parameters of the indenter injection process and transmits signals to the electronic unit where they are processed, and the value of the mechanical property corresponding to the pressed key is displayed on the digital board. If you need to know the other or all mechanical properties of this part, you do not need to make a new measurement, just press the key of the required mechanical property or press the keys sequentially / in any order, and the values of the mechanical properties corresponding to the pressed key will be displayed on the light indenter.

Claims (2)

1. A method for determining the mechanical characteristics of materials, including the introduction of an indenter in the test material, characterized in that the kinematic characteristics of impact indentation are recorded by the sensor: maximum penetration depth, maximum penetration rate, maximum positive acceleration, maximum negative acceleration, and mechanical properties are determined: tensile strength, limit yield strength, elongation, impact strength, endurance limit, hardness according to polynomial of the nth degree

polynomial coefficients determined experimentally for each j-th mechanical property at the stage of preliminary studies;
X ₁ maximum penetration depth;
X ₂ maximum penetration rate;
X ₃ maximum positive acceleration;
X ₄ maximum negative acceleration.  2. A device for determining the mechanical characteristics of materials containing a loading device, an indenter, an electronic-counting system, characterized in that it further comprises a sensor consisting of permanent magnets, and a coil for recording the kinematic characteristics of impact indentation, and as a loading device, a spring that implements shock indentation of the indenter, and the indenter is made in the form of a cone.

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