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Formation of Physical and Mechanical Properties of
Surface Layer of Machine Parts
V Zablotskyi, O Dahnyuk, S Prystupa, A Tkachuk
To cite this version:
Formation of Physical and Mechanical Properties of Surface Layer of Machine
Parts
V. Zablotskyi1,a, O. Dahnyuk1, S. Prystupa1,b, A. Tkachuk1,c
1 – Lutsk National Technical University, Lutsk, Ukraine a – v.zablotsky@lntu.edu.ua
b – s.prystupa@lntu.edu.ua
c – a.tkachuk@lntu.edu.ua
DOI 10.2412/mmse.99.57.43 provided by Seo4U.link
Keywor ds: dynamometer, the cut power, detail, machining, lathe, sensitivity, precision, measuring installation, tool holder.
ABSTRACT. The aim of the paper is to solve scientific and practical problem that is to explore the impact of operations of machining surfaces of parts of the "body rotation" type on the formation of the physical and mechanical properties of the surface layer. The method of research and analysis planned is by mea suring the cutting force. It is suggested that components of cutting force affect the formation of physical and mechanical properties in varying degrees. For the analysis and separation of components of the cutting force specialized measuring equipment suc h as multi dynamometer was developed. The complex of theoretical studies, calculations and simulations revealed major sensitive zones of mechanical dynamometer.
Introduction. In connection with the development of technology higher demands on the quality of the surface layers of parts are put forward. In engineering machining operations in general cause major influence on the physical and mechanical, geometric characteristics of the surface layer and on the quality of machined parts in particular. Thus, new demands require the use of modern high-precision equipment and improved methods of treatment. Is not possible to get details accurately regulated in the size and quality of the surface layer without the introduction of new methods of research and machining accuracy process control and improvement of existing ones. Thus, ensuring the quality characteristics of parts using active control at every stage of their production and especially in the treatment of operational control quality parameters of the surface layer is important and urgent scientific and practical issue.
One of the important parameters of machining which directly affects the quality of received surface is a cutting force [1]. This option can be divided into three components:
– Constant component of cutting force;
use standard cutting tool.
The process of lather turning is a powerful dynamic process with complex relationships and many disturbing factors. It is therefore necessary to monitor its progress with high precision and speed. To measure the components of the cutting forces that arise during the turning processing we have designed and produced a design tool (Fig. 1), which is designed as a set of four elastic elements that allow you to record the deformation resulting from the impact component of treatment in node points of elastic elements.
The device is designed as a mechanism that is installed on a seat tool holder of a screw-cutting lathe, a cutter is attached with screws to a boarding hole [2]. A part of the device with a fixed cutter is joined to a massive body with four elastic elements in the form of semirings with facets outside. Tenzogive rs are placed on the faces and the inner cylindrical surface of the nodal points of each elastic element.
Fig. 1. Multicomponent dynamometer for measuring cutting forces components: a) dynamometer model; b) installation piece for measuring components of cutting forces.
Measurement procedure: when performing machining operations cutting force is perceived through the instrument power link where the registration of the processing components is made (Fig. 2). The radial component of Py cutting force is perceived by elastic elements which are weakened by
longitudinal sections in order to improve the sensitivity of the system. Clutching four elastic links it provides tensile deformation to sensors which are placed outside the elastic elements (1у, 2у, 5у, 6у), and provides compression deformation to sensors which are placed inside – (3у, 4у, 7у, 8у).
The vertical Pz component creates a bending moment, which results in stretching the top of elastic
elements and shrinking the bottom elements. Sensors, which receive Pz power, are pasted on the same
sides as the Py power sensors while sensors of the lower zone (2z, 4z, 6z, 8z) get the same sign
deformation as the neighboring sensors (2у, 4у, 6у, 8у), while sensors of the upper zone (1z, 3z, 5z, 7z)
perceive deformation with the opposite sign.
To increase the sensitivity Pz power sensors are placed as far away as possible from the point of
application of the measured force. Power sensors, Py on the contrary are placed as close as possible
Fig. 2. Block diagram of the measurement setup.
The third component of the Рх in relation to other parts of the dynamometer is a tangential force. For its registration shift in the maximums nodal points diagrams of stresses in the annular elastic element under the action of tangential forces is used. Appropriate sensors are placed on the sloping sides of sensing elements symmetrically to maximum points. The strength of Рх causes tension of sensors (3х, 4х, 5х, 6х) and compression of sensors (1х, 2х, 7х, 8х). Connection of strain gauges in bridge circuits
was carried according to two general rules: to try to achieve the greatest sensitivity of the measuring system and to provide automatic compensation of mutual influence of components of cutting forces. To confirm the hypothesis of the location of key areas of placing strain gauge sensors for register ing components of Рх, Ру, Рz cutting forces software Autodesk Inventor Pro 2010 was used. The model
of the dynamometer taking into account its design features was developed. The dynamometer was made of the material with such characteristics – Steel 45 GOST 1050-88, the mass of 6.04424 kg, volume – 769,967 mm3, the center of gravity of the body is located at the following coordinates: x =
80.496 mm; y = 40 mm; z = 37,3697 mm.
Fig. 3. Basic verge fixation а) the line to which the component machining forces Pz b) is exerted upon.
The second stage is the creation of loads acting on the object in the course of its work, namely a choice of facets of operating forces and determining their specific vectors (Fig. 3b). Since this load cell is designed to measure three components of cutting force, the main objective was to determine the location of nodal points where maximum deformations of each component of forces are observed. A series of studies in which a total cutting force was laid on its components Px, Py, Pz was conducted.
The values of the applied load were determined experimentally according to technological modes of the machine and taking into account the material of the workpiece and the tool. So in the first case there was modeled an impact of Рz component resulting from the rotation of the workpiece, according
to the calculations it equals to 465 Н (Table. 1).
Table 1. Strength and depending reaction time caused by Pz component.
Name of the dependence
Reaction strength Jet point
Size Component (X, Y, Z) Size Component (X, Y, Z) Fixing dependence: 1 465 N 0 N 48,2435 N·m 0 N·m 0 N -48,2435 N·m 465 N 0 N·m
Table 2. The result of simulation of the Pz force component.
Name Value (min) Value (max)
Von Mises stress 0,0000365918 MPa 10,433 MPa 1-st main stress -1,31019 MPa 11,7692 MPa 3-d main stress -11,8199 MPa 1,35378 MPa
Shift 0 mm 0,00743231 mm
Ultimate factor of safety 15 br 15 br
Stress XX -7,34826 MPa 7,67991 MPa
Stress XY -4,83475 MPa 4,64143 MPa
Stress XZ -2,72776 MPa 1,16707 MPa
Stress YY -6,53714 MPa 6,7057 MPa
Stress YZ -5,1942 MPa 5,23698 MPa
Stress ZZ -8,39489 MPa 8,85921 MPa
Offset by X shaft -0,0017662 mm 0,00181829 mm Offset by Y shaft -0,000401373 mm 0,000396639 mm Offset by Z shaft -0,00741761 mm 0,0000110142 mm
Modeling and creating graphical visualization occurs by finite element analysis that form the grid. To increase the accuracy its parameters had the following values (Table. 3).
Table 3. The main parameters of finite element net.
Average element size (fractional value from the diameter model) 0,05 The minimum element size (fractional value from the average size) 0,1
Diversity factor 1,5
Fig. 4. Equivalent dynamometer deformation because of Pz component influence.
Based on the analysis of simulation results and graphical visualization (Fig. 4) the location of nodal points, which accumulate the greatest stress and therefore having equivale nt deformation because of component force Pz was defined.
In the second case, there was built a model to investigate the impact of Py component, resulting from
longitudinal tool input that is equal to 219 N (Table. 4) according to the calculations but its vector is aimed at the side facet (Fig. 5).
Fig. 5. The facet to which machining force Py component is attached.
Table 4. Strength and reaction time in dependences induced by component Py
Name of the dependence
Reaction strength Jet point
Because of the simulation a number of calculation of parameters (tab. 5) was received and the creation of graphical visualization was made (Fig. 4).
The third component of the Рх in relation to other parts of the dynamometer is a tangential force. For its registration shift in the maximums nodal points diagrams of stresses in the annular elastic element under the action of tangential forces is used. Appropriate sensors are placed on the sloping sides of sensing elements symmetrically to maximum points. The strength of Рх causes tension of sensors (3х, 4х, 5х, 6х) and compression of sensors (1х, 2х, 7х, 8х). Connection of strain gauges in bridge circuits was carried according to two general rules: to try to achieve the greatest sensitivity of the measuring system and to provide automatic compensation of mutual influence of components of cutting forces.
Table 5. Results of simulation of the Py force component.
Name Value (min) Value (max)
Von Mises stress 0,0000769117 MPa 6,77654 MPa 1-st main stress -0,697035 MPa 6,8717 MPa 3-rd main stress -6,97715 MPa 0,771266 MPa
Shift 0 mm 0,00456053 mm
Ultimate factor of safety 15 br 15 br
Stress XX -2,35183 MPa 2,31139 MPa
Stress XY -2,41393 MPa 1,97715 MPa
Stress XZ -0,558817 MPa 0,617342 MPa
Stress YY -6,72168 MPa 6,59781 MPa
Stress YZ -1,43862 MPa 1,57453 MPa
Stress ZZ -1,74296 MPa 1,84711 MPa
Fig. 6. The equivalent dynamometer deformation as a result of Py force component.
Based on the analysis of simulation results and graphical visualization (Fig. 6) the location of nodal points, which accumulate the greatest stress and therefore have equivalent deformations as a result of
Py force component was determined.
In the third case a model has been built to investigate the impact of the resulting Px component, which
occurs as a resultant of Pz and Py forces. However, in order to properly direct its vector, vector
application efforts were used, which according to the calculations equals to 184 Н (Table. 6), its vector is directed to the bottom and side edges of the dynamometer (Fig. 7).
Fig. 7. Facets to which the resultant Px force component is attached to.
Table 6. Strength and reaction time in dependences induced by Px component.
Name of the dependence
Reaction strength Jet point
As a result of the simulation a number of calculation of parameters (tab. 7) was received and the creation of graphical visualization was made (Fig. 8).
Table 7. Results of simulation of the of Px force component.
Name Value (min) Value (max)
Von Mises stress 0,000122972 MPa 11,7738 MPa 1-st main stress -1,4375 MPa 12,1039 MPa 3-rd main stress -8,56584 MPa 1,173 MPa
Shift 0 mm 0,00649382 mm
Ultimate factor of safety 15 br 15 br
Stress XX -6,01391 MPa 5,41856 MPa
Stress XY -3,89862 MPa 3,94826 MPa
Stress XZ -2,65661 MPa 0,799517 MPa
Stress YY -7,03252 MPa 11,3099 MPa
Stress YZ -3,29472 MPa 3,50969 MPa
Stress ZZ -4,48025 MPa 5,47884 MPa
To confirm the hypothesis of stresses locations analyzed the diagram of stress of the ring dynamometer part of the designed tool of carrier (Fig. 9). Nodal point of the stress diagram under the influence of axial component will coincide with the midpoints of sensors of unmeasured components. Therefore, one-half of each of them will be stretched and the other part will equally be compressed. As a result, the sensor resistance will change. Sensors of Pz, and Py components on the Px power will
not respond no meter what its values is. The impact on performance of main and radial component of
Px force sensors are eliminated automatically in a similar way.
Under the influence of the force, the ring resiliently deforms and takes the form of an ellipse Fig. 9, and the ring deflection is calculated by the formula [3-4].
Ebh h D P Ebh h D P D 0,223 ( 2 ) 1,775 ( ) 3 , (1)
where D – is the diameter of the outer ring;
E is a modulus of elasticity;
b and h – are the width and thickness of the ring.
Fig. 9 presents diagrams of the distribution of relative strain caused by P force on the outer and inner surfaces of the ring. The greatest deformation occur in the plane I-I of the force performance and in diametrical section II-II that must be considered when placing sensors. To get the highest sensitivit y sensors should be placed symmetrically relatively to section II-II. Since the deformation of outer and inner rings are opposite in sign, the sensors can be placed on both sides.
Fig. 9. Diagrams of dynamometer ring stress.
To determine the strain ε-section at II-II the following formulae can be used:
Ebh P D Ebh h D h D P 2 ) 5 , 1 ( ) ( 362 , 0 2 . (2)
d h D D 8 2 8 , (3)
where d – is the inner diameter of the ring.
If you use circular elastic elements with sensors with strain the ratio ε / ΔD should be maximized, as it is tantamount to increasing sensitivity without changing the working movement of elastic link. According to equation (3) internal diameter should be made as small as possible. Its minimum value depends on sensor size, which will be glued to the inner surface of the ring. It should also be noted that in-section III-III and IV-IV, inclined to the plane II-II at an angle of about 50 °, there is no deformation. These are diagram nodes. Their placement depends on the direction of the active force. Before measurement each bridge circuit is connected to the amplifier with a differential input and output and built-in voltage source for tenzomosta LP-04. In turn, each amplifier is connected to the ADC / DAC E-154 module. Module E-154 through the input USB 1.1 (2.0) is connected to the computer. Visualization and registration of data was performed with the software – UM ADC1. Example of flow process of measurement of components of the cutting force is presented in Fig. 10.
Fig. 10. Sample variability flow of components of cutting forces.
Thus, the obtained profilogram are used to analyze the components of the cutting force to identify the peculiarities of a particular component on forming the surface layer of the parts.
References
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