=Paper=
{{Paper
|id=Vol-1623/paperapp11
|storemode=property
|title=Optimizing the Properties of Tool Materials by Means of the Mathematical Modeling of their Fracture Processes
|pdfUrl=https://ceur-ws.org/Vol-1623/paperapp11.pdf
|volume=Vol-1623
|authors=Elena Mokritskaya
|dblpUrl=https://dblp.org/rec/conf/door/Mokritskaya16
}}
==Optimizing the Properties of Tool Materials by Means of the Mathematical Modeling of their Fracture Processes==
https://ceur-ws.org/Vol-1623/paperapp11.pdf
Optimizing the Properties of Tool Materials by Means
of the Mathematical Modeling of their Fracture Processes
Elena Mokritskaya
Far Eastern Federal University, Sukhanova st. 8, Vladivostok 690950, Russia
mokritskayae@mail.ru
Abstract. The article deals with the modern approaches to the study of physical
and mechanical properties of materials. A brief description is given on the ex-
press method for metal-cutting tool health assessment that has been developed
within the framework of this approach. The paper suggests ways to improve the
performance of by modeling the properties of materials. It presents the method-
ology for assessing the tool material performance of coated surfaces by acoustic
emission.
Keywords: mathematical modeling, optimizing the properties, tool material
performance, modeling of properties, computer program
1 Introduction
The modern development in mechanic engineering involves creating new tools and
construction materials with predetermined properties, expanding the range of these
materials and improving their technical and economic characteristics.
The widespread use of metals and their alloys requires a thorough and comprehen-
sive study of their physical and mechanical properties in a wide range of tempera-
tures. There is a number of abnormal physical phenomena, at high temperatures espe-
cially in the area of structural and phase transitions. At that, changes in physical pa-
rameters of the material may occur, which cause the reduction in operating span of
expensive engineering products [1].
Performance and efficiency of metal processing depend on the strength and endur-
ance of metal-cutting tools. More than 50 % of failures in technological cutting sys-
tems are due to the loss of functional of a metal-cutting tool. The modern models of
tool fracture mechanisms are based on the structure-and-energy approach to the anal-
ysis of the strength of material. This approach describes the tool material fracture in
terms of the thermodynamics and dislocation notions. In this paper the author sug-
gests new ways to increase the productivity of metal processing by improving the
properties of tool materials [2] and [3].
The article attempts to develop the approach which considers a tool as a compo-
nent of a technological cutting system and, thus, its productivity can be determined by
the properties of tool material and the processes in the others parts of the cutting sys-
Copyright © by the paper's authors. Copying permitted for private and academic purposes.
In: A. Kononov et al. (eds.): DOOR 2016, Vladivostok, Russia, published at http://ceur-ws.org
Optimizing the Properties of Tool Materials 765
tem. Let us now look at the of process fracture formation and changes in the condition
of the elastic system in a metal-working machine. The choice of these processes is
explained by cyclic loading on the tools, which influences their working capacity [4].
At present, there is no full and adequate information about the dependence of the
physical properties for a number of construction and instrumental steels and other
metals in a wide range of temperatures depending on their deformation extent and
heat treatment conditions. Comprehensive studies into the properties of materials are
very important for the fundamental knowledge and search for solutions to a number of
issues in materials science, solid state physics, and physics of metals [5].
The author approached this problem by creating new methods, systems and devic-
es that use the latest achievements of fundamental sciences, such as materials science,
thermal physics, acoustics, and mathematical modeling.
The practical relevance of the studies consists in the unique software and expresses
assessment methods that have been developed. These methods assess the working
capacity of a coated tool to ensure the non-destructive quality control for mechanical
engineering products.
2 The mathematical modeling of the process of compound
material fracture
Since the tool loading in metal cutting has a cyclic nature, we suggest a mathematical
model of stabilizing the changes in loading conditions by optimizing the properties.
To perform the express-assessment of coated tool materials, we suggest methods that
provide an authentic modeling of real operating conditions for compound tools.
The model of optimal control of the tool’s productivity consists of four tasks:
1– optimization of properties tool material;
2– development of materials with predetermined properties;
3– modeling the unstable pattern of fracture;
4– increase in the dynamic quality of metal-cutting machine.
The structure-and-energy approach was applied to take the optimal decision
[2]. As a part of if studies with the use of transmission and raster electronic microsco-
py, X-ray structural analysis were performed. Within the structure-and-energy ap-
proach, a model of grain interaction has been developed for compound tool materials.
This model describes the dynamics-and-energy interaction of grains when impulse
application of a load is performed on the surface layers of the cutting tool. Based on
the model, a mathematical formula (correlation) has been obtained that makes it pos-
sible to examine the accumulation and distribution of energy in microvolumes of a
tool material. Also, the formula determines the critical number of grain interactions
before the critical energy is accumulated in a gain that collapses once the
energy is exceeded.
In article number of interactions can be considered as an objective to be maximized
(1)
766 Elena Mokritskaya
where, is the initial impulse energy, J; Е is the current value of residual impulse
energy at the investigated distance from initial impulse application point;
j is the parameter which describes the correlation between the size of the grains and
the distance between them (of the layer thickness between them); α is the grain
interactionangle.
The analysis of dynamics-and-energy model and the dependence (1) allows to de-
velop models of tool material fracture mechanisms in terms of optimizing the energy
condition of micro volumes once the critical value of energy is reached in cutting.
This allowed to formulate (1) as a number of requirements for the shape, size and
location of the grains, as well as to clarify various mechanisms of tool material frac-
ture. Since the productivity of a tool is primarily determined by the condition, wear
rate, micro-chipping, etc. of its upper layers, it is important to assess the strength of
the structural components in the material coating when optimizing the properties of
the tool material. This assessment will make it possible to detect the weakest point in
the structure, which will help to forecast the fracture of the tool on every stage.
The results of assessing the strength of hard-alloy tools showed that their edges are
their weakest point. The edges are inter-granular in some hard alloys and inter-phasic
in others. Let us consider the role of the material structure in the process of hard-
allow tool fracture using, as an example, the explanation of externality of a well-
known classic correlation between the tool durability T and the cutting speed v (cut-
ting temperature θ). Based on the example of this correlation, a model has been de-
veloped that demonstrates the influence of the cutting speed (temperature) on the
changes in the structure of a hard-alloy material and the impact of the emerged struc-
tures on the mechanism of material fracture.
3 Methods for modeling materials with predetermined
properties
In this section we describe the methods for increasing the tool working capacity by
improving and optimizing the properties of coated tool materials.
Modeling the properties of tool materials is based on the express methods of assessing
the tool working capacity. In addition to the common methods for assessing the phys-
ical, mechanical, and operational characteristics of tool materials [1], there have been
developed several express methods to assess the additional parameters (such as crack
resistance). These methods using acoustic emission (AE) to exercise control, assess
the quality, diagnose and forecast the working capacity of a metal-cutting tool with a
wear-resistant coating.
The similarity of kinetics and fracture mechanisms under the loading conditions has
been proved by fractographic studies. The relation to the tool fracture kinetics is
proved by the comparison of kinetograms. Test for the compliance with the real
mechanisms has been performed by comparison with the results of fractographic stud-
ies in well-known works such as [4].
The basic results of the performed studies can be summarized as follows:
Optimizing the Properties of Tool Materials 767
- the temperature dependence of the sound velocity, ultrasonic vibrations, the elastic
modulus and internal friction for a number of ferromagnetic materials, and titanium
alloys under various degrees of deformation and heat treatment conditions was deter-
mined;
- the behavior of the acoustic and mechanical parameters in phase and magnetic tran-
sitions in metals and alloys was studied;
- the dependence of elastic of thermal coefficient for the modulus of a number of pure
metals, structural and tool steels and alloys on the degree of deformation and heat
treatment was found out ;
- the activation energy for defect modulus for cobalt, nickel, steel that were heat-
treated was determined.
The practical significance of the work consists in:
- the development of the technique for investigation of the temperature dependences
of the acoustic parameters for pure metals and their alloys [3];
- creation of the original equipment for high-precision measurements of sound veloci-
ty and ultrasonic vibration at various frequencies in a wide temperature range for the
wire samples [5];
- construction of the experimental system that allows to study the mechanical proper-
ties and performance of materials and record AE signals;
- development of software that allows the acoustic path and fixing the details of PC,
keeping all thread data of modeling nondestructive control method on the basis of
these settings;
- collection of a unique experimental data on the elastic modulus and internal friction
in the high-temperature aviation materials [6].
References
1. Bekker, M.S., Kulikov, M.Yu., Egorychev, E. V.: Physical model of tool wear of high speed,
pp.41-44. Engineering newspaper #8, (2000)
2. Mokritsky, B.Ya.: Structural and dynamic aspects in estimating the performance of cutting
tools, pp. 122. Mechanical Engineering #10, (2001)
3. Semashko, N.A., Mokritskaya, E.B., Mokritskii, B.Ya., Vahrushev, O.M.: The method of
acoustic control for fracture toughness of products, Russian Federation patent #2140076, Bull.
#29, (2002)
4. Kabaldin, Yu. G., Mokritskii, B. Ya., Semashko, N.A., Taraev, S.P.: Modern design
methods, quality control and forecasting performance of the cutting tool, pp. 122. Publishing
House of the State University, Vladivostok, (2005)
5. Mokritskii, B. Ya., Mokritskaya, E.B.: The issue of management of working capacity of
cutting tools, pp. 40-47. Engineering newspaper #12, (2008)
6. Semashko, N.A., Mokritskaya, E.B., Mokritskii, B.Ya., Filonenko, S.F., Vahrushev, O.M.:
The method of controlling the physical and mechanical properties of products, Russian
Federation patent #2138038, Bull. #26, (2009)