Predictions of tool wear by estimating weight loss during polymer

composites processing

GENNADII KHAVIN, HOU ZHIWEN

Department of mechanical engineering and metal-cutting machines

National Technical University “KhPI”,

2, Kyrpychova str, 61002

UKRAINE

Abstract: - The main criterion for wear of the tooltip when processing polymer composites is a technological

criterion, namely the conventional amount of wear on the tool flank face. The cutting edge wear is

asymmetrical, and it was assumed that during the wear process, the initial tip of the sharpened tool moves along

the rank surface. Then, in the plane of the tool top, you can calculate the change in area and find the weight loss

over a certain period. A geometric model was developed that allows you to relate the amount of tool weight

loss and the classical determination of the wear value on the flank face. Using experimental data on fiberglass

processing, the relationship between the conditional amount of wear on the back surface and the loss of weight

and the change in the shape of the cutter for various technological parameters of processing - feed, speed, and

depth of cutting - was established. Generalized dependencies were obtained, which connect the amount of

weight loss by the tool with technological parameters and processing duration.

Key-Words: - polymer composites, cutting edge wear, weight loss, geometric model.

Received: July 22, 2022. Revised: November 2, 2023. Accepted: December 2, 2023. Published: December 31, 2023.

1 Introduction

Mechanical processing of composites, despite the

low values of cutting forces and temperature in the

tool-workpiece contact, is accompanied by high

wear of the cutting part of the tool. This is explained

by the intense abrasive effect of the reinforcing

elements in combination with the low thermal

conductivity of the polymer matrix of the

composite. In turn, this leads to the appearance of

specific processing defects such as chipping,

fluffing and pulling out of fibers, cracking, etc.

As the tool wears out, the likelihood of defects

increases. Wear leads to a change in the nature of

the interaction between the tool and the workpiece,

the appearance of high elastic recovery stresses of

the processed layer of material, and, as a

consequence, intensification of wear. Experimental

studies have shown [1,2] that the nature of wear has

significant differences from the classical case of

metal cutting, where wear can be divided into many

different independent phenomena that arise in

addition to direct abrasive wear.

The wear of the tooltip when cutting (turning)

composite materials has a pronounced asymmetrical

character [1,2]. The main features are the

dominance of wear on the flank surface of the tool

and the virtual absence of wear on the front surface,

Fig. 1 [3]. This leads to the initial conclusion that

the tooltip is worn due to an increase in the radius of

curvature of the cutting edge, which is not obvious

with asymmetrical wear.

Fig.1. Wear of the cutter tip on the flank surface

depending on the number of drilled holes [3].

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The easiest way to determine the distortion of the

cutting edge shape during wear is to display the

geometry in any way after some time of operation.

This is a direct characteristic, based on which one

can unambiguously conclude the further

performance of the tool and the nature of its wear

during operation.

Another indirect characteristic for assessing tool

wear may be weight loss due to removed material

during operation. This is an integral characteristic

that does not give an idea of the distortion of the

shape of the cutting part, but it can serve as a

reliable indicator of the possibility of its further

operation. The main advantage of this characteristic

when predicting the performance of a tool is the

ease of its determination by weighing it before

starting and after finishing work. Weight loss

reflects all the phenomena that took place during the

operation of the tool, that is, it reflects everything

that happened to it: changes in force, heating and

cooling, oxidation, etc.

Numerous studies have been done to predict the

wear rate and tool life [4]. Various prognostic

theories have been proposed, confirmed, or refuted

experimentally. Creating accurate models requires

an expensive and time-consuming study of the

problem in practice. Therefore, an important part of

research is numerical modeling, primarily the finite

element method (FEM) [5]. The application of

homogeneous material cutting models to multiphase

composites also did not give satisfactory results. To

satisfactorily model the cutting process, it is

necessary to take into account the properties of

fibers, matrix, and fiber-matrix joints, as well as

tool-fiber, tool-matrix, and fiber-matrix interactions

[6, 7].

Experimental studies on orthogonal cutting of

carbon fiber plastic have shown that the wear of the

cutting edge (rounding) is asymmetrical [3, 8], the

magnitude and intensity of which depends, first of

all, on the initial geometry of the tool (initial

sharpening) and the degree of sharpening, the

orientation of the reinforcing elements [3, 8].

The mechanism of brittle fracture when cutting

PCM assumes the absence of a stagnation zone

characteristic of metal cutting in the row of the

cutting edge, which is an accumulation of workpiece

material and protects the cutting edge. The absence

of such a zone leads to preferential abrasive wear

[9]. According to [10], tool wear primarily increases

in a small area near the cutting edge, where the

transition between the rake and flank cutting edges

occurs.

To quantitatively describe the wear process as a

phenomenon of corresponding rounding of the

cutting edge, several models of the contact area

between the cutting part of the tool and the

processed material have been proposed. Thus, in

[10], a model with five parameters was considered,

where the working part of the cutting edge is

described by simple geometric objects of the

“straight-ellipse-straight” type.

The geometry of the various tool types is fairly

clearly defined by the flank and rake angles, as well

as the actual cutting edge as the transition between

the flank and rake edges. As indicated in [11], rapid

initial wear determines the further condition of the

tool and its suitability for processing polymer

composite materials (PCMs). Therefore, a detailed

determination of tools microgeometry is of great

practical importance, and solving this problem is an

urgent task of PCM processing technology.

As a technological wear criterion, a conditional

value was proposed - a change in the linear size

along the flank surface, Fig. 2, [12]. A symmetrical

wear scheme is proposed, from which a relationship

is obtained that connects flank surface wear with the

current and initial rounding radius of the cutting

edge, or a relationship that connects the current

rounding radius with flank surface wear

Fig.2. Scheme of symmetrical wear and the

conditional value wear

calculation on the flank

surface [12].

However, experimental studies [3, 8] have shown

that the wear of the cutting edge has a pronounced

asymmetric shape. Intensive tool wear during PCM

processing dramatically changes the initial geometry

of the tool being sharpened, which significantly

affects machinability and increases the appearance

of various defects in the material being processed.

Analysis of experimental data showed that the

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intensity of wear along the flank surface of the tool

most significantly depends on the orientation angle

of the reinforcement θ relative to the processing

direction.

2 The relationship between the

change in the tool tip geometry and

the loss of weight

The general formulation of the problem comes

down to determining the shape of a worn tool and

establishing a relationship with weight loss. In other

words, it can be formulated as follows. It is

necessary to establish a connection between the total

weight loss of the tip of the cutter and wear on the

flank surface, which is accompanied by a change in

the value of the clearance angle, or to relate the

weight loss of the tool during its operation with its

wear on the flank surface.

As a working hypothesis, it was assumed that

during the wear of an initially sharpened tool, its tip

conditionally moves along the rake surface, i.e.

there is a constant displacement of the initial

rounding of the tip of the sharpened tool along its

rake surface, Fig. 3. In this case, it is assumed that

there is no change in the value of the rake angle.

This assumption became possible from the analysis

of the profile of the worn tip of the cutter, presented

in [3], [8], [13].

Fig.3. Offset of the sharpened tool top initial

rounding along the conventional rake surface

In the presented formulation, there is also an

inverse problem, when, based on the existing value

of the amount of wear on the flank surface (weight

loss) of the tool, it is necessary to determine the

overall change in the geometric shape of the tool

and the weight loss (amount of wear on the flank

surface). In addition, it is assumed that by using an

apparatus for geometrically changing the surface

area of the tooltip (actually losing weight), it is

possible to calculate the size of wear along the flank

surface and determine the tool life under given

processing conditions.

When machining composite materials, the

standards of different countries provide a limit value

for the size of wear on the flank surface, which on

average usually does not exceed 0.3 mm. Upon

reaching this value, unacceptable processing defects

appear during the cutting process, and the tool itself

must be replaced and, if possible, re-sharpened.

Two practical tasks follow from the formulated

formulation: given a given weight loss of a tool,

calculate its shape and, above all, the change in size

on the flank surface. The second task is to determine

the expected weight loss for a given value of flank

wear, and hence the tool life.

Considering that the wear rate changes with time,

and also with the appearance of wear, the stress state

in the contact changes, the tooltip heats, and the

friction conditions (friction coefficient) change, both

settings have a clearly expressed nonlinearity. To

solve such problems, it is necessary to use step-by-

step algorithms that take into account the hereditary

change in the shape of the tooltip.

Thus, the actual wear of a tool during its

operation can be represented as the difference in the

surface areas of the cutter tip, calculated for two

successive moments in time, multiplied by the width

of the cutting edge and the density of the tool

material.

3 Geometric wear model

Analyzing the change in the shape of the tool tip

during the wear process, presented, for example, in

works [1,8], one can notice that the tip of the

initially sharpened tool seems to move along the line

of the front surface, Fig. 3. With some error, we will

assume that the configuration of the rake surface

does not change its original position during the

operation of the tool. Physically this means there is

no wear on the rake face, which is not the case. The

amount of wear is much less than on the flank

surface and, therefore, can be neglected. Taking this

assumption into account, we will assume that the

conditional initial rounding of the sharpened tool

seems to move along the rake surface. In this case,

in the plane of the tooltip, Fig. 4., during the wear

process, the area of the tooltip adjacent to the rake

surface changes. The change in the position of the

contour of the flank surface is wear itself, i.e. tool

weight loss. Thus, the weight loss during operation

is proportional to the change (removal) of the area,

assuming a constant value of the width of the

cutting edge of the cutter.

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Fig.4. Geometric model of the incisor tip worn

profile.

Thus, the weight loss is proportional to the

difference between the nominal surface area of the

tool cutting edge after working for some time and

the initial nominal area of the unworn edge, the

width of the cutting edge, and the density of the

tooltip material.

The main parameter that determines the change

in area in the geometric model is the displacement

of the center O0 of the initial circle, which

determines the rounding of the cutting edge, along a

straight line parallel to the rake cutting edge – ∆,

Fig. 4.

Knowing or setting this value, you can describe a

new circle that approximately follows the profile

worn part of the tooltip along the flank surface. To

numerically determine the value of the lost area, it is

necessary to have an analytical expression that

describes the contour of the worn surface of the

cutting part along the flank surface. This is

practically impossible, even with experimental data.

Therefore, it is proposed to replace this curve with a

circular arc with a center at O1, and a point of

tangency with the original line of the flank surface

configuration – A1. The difference between the areas

for two geometric positions is the loss of area

(weight). Next, the process is repeated for a new ∆

and a new position of the O2 center. This procedure

is presented in more detail in [14].

4 The relationship between

technological processing parameters

and the wear criterion in the

mathematical model of weight loss

The relationship between technological

processing parameters and the wear criterion

formulated as weight loss is the most important

factor that ensures the tool´s stability. This

relationship consists, first of all, of the fact that the

technological parameters – cutting speed, feed, and

cutting depth – affect the nature and intensity of the

force load in the cutting process and thermal heating

in the contact.

It should be noted that the variety of composite

materials and tools for their processing in many

ways makes the task of researching the influence of

technological parameters on the force magnitude

factors so difficult that its solution requires private

research in each specific case. Despite this, there are

currently laws that describe the influence of

processing parameters on the change in power

factors of the process and, as a result, on the wear

intensity of the cutting edge.

In the work, it is assumed that the general

dependence between the tool wear, its working time,

and technological parameters has

( ) ( , , ) n

h K s v t   

, (1)

where

()

h

– wear on the flank surface, mm; τ –

time, min.; s – feed, mm/rev; v – cutting speed,

m/min.; t – cutting depth, mm; n is a constant.

The coefficient is most often taken in the form

( , , ) ( ) h h h

s v t

K s v t K s v t



    

, (2)

where

s v t

h h h

are constants, the coefficient is

()





, i.e. in most cases, it is taken as

constant.

This is a well-known artificial ratio in which the

requirements of a direct physical sense are not

fulfilled, that is, the dimension in the left and right

parts is not observed. However, the use of this ratio

is very common due to the ease of finding and

because in logarithmic coordinates the dependence

(1) has a linear form. By analogy with dependence

(1), let's construct a dependence to determine weight

loss

()w

( ) ( , , ) m

w K s v t   

, (3)

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where m is a constant.

We will accept the coefficient in the form

( , , ) ( ) w w w

s v t

K s v t K s v t



    

where

s v t

w w w

are constants,

()

K

is a

coefficient, which in general is a function of time.

The introduction of relation (3) is a statement that

the qualitative nature of the weight loss during wear

and the linear size of the conventional amount of

wear on the flank surface

is the same and differs

only quantitatively.

5 Tool stability and blunting criterion

in the mathematical model of wear

assessment due to weight loss

The tool stability and the criteria for its blunting

are inextricably linked factors, which are

collectively determined by the level of the tool

wear. The tool stability, which is understood as the

time of work (cutting), after which the degree of

wear is reached, is determined by the criterion of its

stability. On the other hand, the tool stability

criterion is determined or assigned by machining

objectives, such as designated acceptable levels of

cutting forces, surface quality, dimensional stability

of the final part, or machining process performance.

Based on this, the main requirement that

determines the amount of wear is the quality of the

treated surface. The wear criterion is the

technological factor. Therefore, the wear on the

flank surface is taken as the criterion for blunting

when mechanically cutting PCM products. At the

same time, there are recommendations to take the

average or maximum value of this value along the

cutting edge as a wear criterion. The values of wear

on the flank surface set by the norms differ in the

standards of different countries and, as a rule,

acquire values from 0.1 to 0.4 mm for the average

value, and 0.4 to 0.6 mm when using the maximum

value of the blunting criterion.

Values are assigned in each specific case and

depend, first of all, on the type of processed material

(reinforcement and binder), the type of

reinforcement (weaving) and the content of the

filler, the method of obtaining the processed

material, the requirements for the quality of the

workpiece final surface, the brand and type

processing tool, initial tool geometric parameters

and technological factors of processing (speed, feed,

cutting depth).

The generalized equation of tool stability, which

takes into account the influence of speed, feed and

cutting depth on tool stability, in the vast majority of

cases, engineers accept in the form

kk k

K v s t T   

, (4)

where Т – tool life, min;

, , ,

tl s t

K k k k

– constants.

Ratio (1) is a modification of the well-known

empirical Taylor ratio, which is widely used in

metal processing.

If we compare relations (1) and (4), we can see

that (4) is a limiting case of relation (1), where a

linear dependence of the wear on the flank surface

on the processing speed is assumed. In this case, the

relation (1) can be rewritten in the general form (1)

taking into account (2)

[ ] ( ) h h h n

s v t

h K s v t T



     

where

[]

– given value of the wear limit value on

the flank surface, which corresponds to the value of

stability T.

Then, by analogy with (2) and (3), for the weight

loss blunting criterion, we obtain

[ ] ( ) w w w n

s v t

w K s v t T



     

, (5)

where [w] – the given value of the weight loss limit

value, which corresponds to the stability value T.

6 Case Studies

To construct the generalized dependencies of the

tool weight loss in the wear process and the

relationship with wear on the flank surface, we will

use the results of experimental studies presented in

the paper [15].

This monograph presents the results of

experimental studies of various glass plastics during

turning in a wide range of processing parameters: v

= 60 – 140 m/min; s = 0.075 – 0.51 mm/rev; t = 1 –

5 mm. In the course of the experiments, it was

assumed that the amount of wear on the tool flank

surface does not exceed 0.3 mm, which for most

fiberglass provides a processing roughness of at

least the 4th class.

Fiberglass turning was carried out with cutters

made of VK3M alloy, the geometric parameters

were taken as follows: rake angle  = 10; flank

angle  = 25; the main angle in plan  = 45; the

additional angle in the plan 1 = 12; the initial

radius of the cutting edge rounding  = 0.75 mm.

The lengths of the additional cutting edge l are equal

to 0.5; 1; 3 and 5 mm.

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Based on these results, a general relationship

between tool wear on the flank surface, tool

operating time, cutting speed, cutting depth and feed

was established in the form of a power-law

relationship (5). As a result of processing

experimental data by the method of least squares, a

regression equation of the form was obtained

6 2,036 0,411 0,556 0,523

3,57695 10

h V s t



     



. (6)

The regression equation was obtained using

HomeSoftWear, significance

2 0,995R

, Fisher's

test

7645F

A comparison calculating results of the wear

amount on the flank rear surface and that calculated

from the ratio (6) for the values of the processing

technological parameters s = 0.21 mm/rev, v = 80

m/min, t = 1.5 mm, is presented in Fig. 5.

Fig.5. Comparison calculating results of the wear

amount on the cutter flank surface: calculated from

(6) – 1; experimental data – 2.

Let us construct for the data presented in Fig. 5

the dependence of the change in eccentricity ∆, the

displacement of the conditional initial circle center

on time, Fig. 4. To do this, we use the geometric

model discussed in Section 3, Fig. 6.

Fig.6. Dependence of change in eccentricity ∆

center displacement conditional initial circle.

It is clear from the graph that the change ∆

practically repeats the change in the experimental

values shown in Fig. 5. Next, the dependence of the

change in the cutter tip area S as a function of

eccentricity ∆ is presented in Fig. 7.

The latter circumstance allows us to assume that

the loss of cutting edge area S and the conditional

value of wear on the flank surface is linearly related,

Fig. 8.

Thus, to represent the dependence of the material

removal area S, you can use expression (6), which

will be written in the form

6 2,036 0,411 0,556 0,523

S S V s t



     



Fig.7. Dependence of the change in the cutter tip

area S as a function of eccentricity ∆.

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Fig.8. The relationship between the decrease in the

surface area of the cutter tip and the amount of

conditional wear on the flank surface.

This representation makes it possible to use all

previously accumulated experimental data and

empirical dependencies obtained for conditional

wear on the flank surface and determine the amount

of the removed area, and, consequently, the weight

lost by the tool. On the other hand, experiments

carried out to measure the weight of a worn tool

after processing can make it possible to determine

the value of conditional wear on the flank surface.

7 Conclusion

An approach to solving the problem of wear of

tool cutting edges when processing polymer

composites is proposed and formulated. As a

criterion for dullness, a criterion for the loss of tool

weight due to abrasive wear is proposed. Assuming

that the rake angle of the tool tip does not change

during operation, a geometric model has been

constructed that makes it possible to relate the

traditionally used conditional value of flank surface

wear to changes in the area of the cutter tip. The

geometric model is based on several simplifying

assumptions that are physically observable during

the wear process but do not have a strictly

mathematical proof or experimental confirmation.

The ability to relate the change in cutter tip area

(weight loss) to the traditional definition of flank

wear allows us to adapt existing experimental data

on measuring flank wear to the weight loss criterion

and vice versa.

An assessment of the available experimental data

on turning fiberglass plastics was carried out and a

power-law dependence of the amount of wear on the

flank surface on the processing parameters and

operating time was constructed. It is concluded that

there is a linear relationship between weight loss

and the conditional value of flank surface wear

when processing polymer composites.

The main and further direction of the research is

the implementation of experimental work

confirming or refuting the proposed methodology,

which was interrupted due to objective

circumstances. Further analysis of errors in

predicting weight loss and calculating the amount of

wear on the flank surface.

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Contribution of Individual Authors to the

Creation of a Scientific Article (Ghostwriting

Policy)

Gennadii KHAVIN: general idea, formal analysis,

methodology and investigation.

Hou ZHIWEN: organized and executed the

calculations, article administration and

methodology.

Alternatively, in case of no funding the following

text will be published:

No funding was received for conducting this study.

Conflict of Interest

The authors have no conflicts of interest to declare

that are relevant to the content of this article.

Creative Commons Attribution License 4.0

(Attribution 4.0 International, CC BY 4.0)

This article is published under the terms of the

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