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17TITANIUM ALLOYS FINISHING PROCESSING WITH TOOLS BASED ON POLYMER-ABRASIVE FIBERS
PhD Kondratjuk E. V.
PhD Honchar N. V.
Stepanov D. N.
Ukraine, Zaporozhye, Zaporozhye National Technical University
Abstract. The article deals with the possibility of polishing complex profile parts of aviation and medical industries from hard titanium alloys with instruments based on polymer-abrasive fibers. Rational modes, processing conditions and parameters of disk polymer-abrasive tools for compliance with temperature condition, high tool durability, surface quality and productivity ofpolishing are set.
Key words: finishing processing, parts with complex geometry, titanium alloys, brush tool based on polymer-abrasive, temperature limitation.
Titanium alloys got a wide distribution in aerospace and medical industry because of their low specific gravity and high corrosion resistance. Critical titanium parts of aircraft engines such as blades, discs, shafts and also different kinds of medical prosthetic devices in most cases have complex profile geometry. Special attention is paid to high requirements to above-listed parts surface condition, tool select procedure and final polishing methods because of specific character of parts material, availability structural component of complex profile and nooks.
One of the perspective directions in this field is processing with tools of brush type (brush tool) based on polymer-abrasive (PA) fibers (fig.1). These tools are relatively new in the field of hard alloys finishing processing because of lack of information about them.
Today this type of tools can be widely adopted for:
- finishing processing of hardened parts, parts of ductile material or hard alloy;
- processing of intricate profile and thin-walled parts because low force used can cause damage or alternate basic form;
- polishing for providing certain surface roughness;
- removing of contamination, protective coating after operation with saving primary relief of surfaces integrity;
- deburring and rounding of sharp edge;
- removing of tarnish or etching layer.
a) 6) b)
Fig. 1. Tool based on polymer-abrasive fibers by "Osborn" company
PA tool is a tool of rotary effect. As a rule, it is a metal hub with fixed fibers in it (fig. 1a). Fiber of PA tool (fig. 1b) consists of two components:
- polyamide (nylon) - hard high-elasticity polymeric material as a binding element;
- abrasive grains directly used in cutting; their content in total fiber material is up to 40% and that gives resistance and elasticity to cutting behavior fibers;
PA tool can have different forms and designs (fig.2). Tool function application depends on shape and curvature of surface, and also on surface coating properties, which must be provided.
A wide range of choice of tool setups in combination with defined parameters and operating mode provides quality and high capability of finishing.
It is necessary to note that PA tool has characteristics for industrial application. Processing of thin-walled and complex contoured part surfaces from different materials, including heat-resistant and tough alloys is possible because of fibrous structure (which repeats surface profile), and low chip loading of delicate tool [1, 2, 3]. At the same time high quality of processed surface is provided as a result (Ra0,2...0,8 mkm). Processing with PA tools results in hardening of part surface layer and brings compressive residual stress at a depth 20.50 mkm. It is very important for production of critical parts with high service requirements.
e) f) g)
Fig. 2. Types of polymer-abrasive tools a) disk, b) circular, c) face, d) end, e) roll, f) leaf, g) brush
PA tool also demonstrates advantage of flexible tool such as lowering of requirements to accuracy of part and process tool spacing. Decreasing of tool movement complexity makes automation of these operations technically and economically acceptable because of automaton, programming and servicing cost lowering. Automation of complex contoured part finishing allows process efficiency raising and manual labour deleting.
One of the peculiarity of PA tools is that they have limitation of temperature mode, which must be taking into account in titanium alloys processing.
Titanium alloys cutting (such as processing in similar conditions alloys based on iron and aluminium) initiates high temperatures (on average two- threefold). High temperature is the result of titanium and its alloys thermal characteristic: low specific heat and minimal thermal conductance factor [4].
This thermal limiting determination intraprocess with PA tool is important, because PA tool have wide durability period by keeping specified temperature conditions.
Distinguishing feature of fiber polymeric base during heating is a period of glass transition, when polymer softens but doesn't melt [5, 6]. At glass transition temperature PA tool capability decreases but durability doesn't modify. At further heating above melting temperature (fluidity) decomposition is observed. PA tool leaves on machined surface a thin layer of fiber polymer base which can be easily removed off the surface, but tool durability decreases.
The object of this work was determination of thermal limiting to titanium alloys with PA tool finishing. Accurate fitting of PA tool parameters, operating conditions and modes permit to prevent thermal limiting elevation. BT3 and BT8-M alloys were chosen for analysis.
For ranges limitations of testing operating mode series of initial tests on titanium alloys models were carried. It was determined that rational coverage rate of titanium alloys with PA tool is much less (4...10 m/s) than in processing of steel, aluminium and nickel alloys (15...20 m/s). It is emphasized that high processing rates (about 15.18 m/s) are necessary for gas-saturated layer removal.
Also interference was predetermined. It is the size of conditional overlap of PA tool contours and machining surface, which defines fibers application force to the part. The interference was changed in range of 0.5....0.6 mm. Rational size is 1.5 mm. At further interference increasing work of end part is lowering, side part is increasing and process efficiency is reducing.
The following values were taken for operating modes determination: rate V=4, 6, 10 m/s, tightness /=1.5mm, line feed S =3.6 m/min. PA tool parameters were also modified. For purity of experiment identical diameters of three PA disk tools £=150 mm were taken. Fiber diameters are different: df = 0,6; 1,0; 1,2 mm. Abrasive material - is silicon carbide 63C. Fiber extension L=8 mm and L=32 mm was changed by using special double-sided covers (fig. 1 a,b). Passes quantity was determined as 6. It must be pointed that BT3 and BT8-M alloys had identical results.
Limitation range of operating temperature depends on polymer structure. For used in test tools with definite fiber base [7] this range is 80...120°C. Stable operation and high durability of PA tools are provided with temperature level in working area about 80.85 °C.
According to plan of experiments it is necessary to carry out 6 series (3 series in twos), each consists of 9 tests (table 1 and 2). Line feed, cutting speed, fibers diameter and extension values were modified.
Experiments were carried out on a surface grinder of 3T71 model. Wooden base and models in the gripe were fixed on magnetic holding plate [8]. A semi synthetic micro-thermocouple (Fe-Con), analog - digital transducer, PC (notebook) was used as a test bar. Micro-thermocouple calibration was made before testing.
The testing was carried out without lubricant-cooling agent. The highest temperatures in contact area in processing with PA tool, fiber extension L=32 mm and fiber diameter df = 0,6; 1,0; 1,2 mm (according to experiments 1A, 2A, 3A) will have the hardest tool with df=1,2 mm. So 3A series of experiments were carried out first (table 1, 2).
Table 1. Experimental testing plan of contact temperature
№ series of experiments Tool diameter D, mm Fiber extension L, mm Fiber diameter df, mm
1A 0,6
2A 32 1,0
3A 150 1,2
1E 0,6
2E 8 1,0
3E 1,2
All testing mode ranges had temperature lower limiting 80.85 °C (fig. 3a, table 2) and no polymer pickup on model surface was observed. Therefore, PA tools with more fine fiber df = 0,6 h 1,0 mm (series 2A and 3A) guarantee normal processing without lubricant-cooling agent and modes limitations.
For "hard" PA tools with fibers extension L=8mm, after 1B series experiments with the finest fiber df = 0,6 mm (fig.3b, table 2) it was determined that contact temperatures in processing area exceeded 80.85 °C (achieve sometimes 150 °C) even at the minimal rate. Processing without lubricant-cooling agent is possible at feed 6 m/min, but pilot experiments showed extremely low capability at such rate.
Table 2. Results of contact temperature experimental testing
Tested tool № experiment Tightness i, mm Feed S, m/min Rate V, m/s Max. temperature T in contact area, degree
1 4 32,8
2 6 8 39,6
Series 3A: D=150 mm; df = 1,2 mm; L=32 mm. 3 10 43
4 4 49,2
5 1,5 3 8 59,2
6 10 63,5
7 4 61,6
8 1 8 71,1
9 10 72,3
10 4 49,5
11 6 8 87,5
Series 1B: D=150 mm; df-0,6 mm; L=8 mm. 12 10 95,7
13 4 83,2
14 1,5 3 8 118,6
15 10 131,3
16 4 106,8
17 1 8 142,8
18 10 155
180
n 160
a^ 140
K 120
100
s
1 80
ft
<D 60
s 40
<D H 20
0
Series IB: Z)=150 mm; df= 0,6 mm; L=8 mm, /'=1,5 mm.
—«-v -4, m/C
—■—v = 0, m/c
v =10, m/c
3 4
Feed S, m/min
Series 3A: Z)=150 mm; df= 1,2 mm; L=32 mm, /'=1,5 mm.
80 T-
0 -I-i-t-,-,-,-,-
0 1 2 3 4 5 6 7
Feed S, m/min
Fig.3. Contact temperature in titanium alloys (BT8-M and BT3) processing dependence diagrams
In experiments 2B and 3B tool with more wiry fiber (df=1,0 h 1,2 mm) was used. As a result temperatures in processing area will further increase. That's why there is no necessity to carry out such experiments.
Results of the experiments: it is impossible to process titanium alloys with PA tools (as materials with low thermal conductivity) on "hard" modes with L=8 mm without lubricant-cooling
agent. The flow of lubricant-cooling agent must be generous, constant and be aimed at contact surface. There are two reasons for that: firstly, fibers are fixed with strips, therefore the tool is similar to grinding disk with polymer couplant or brush with pointed wire fibers, the contact spot is small and all heat concentrated local; secondly, fiber self-refrigeration is difficult because of their compact pressing to each other
The model hasn't time to warm up to limiting temperature at fiber extension L=32 mm because of their fluffing and self-refrigeration, so processing with testing range operation modes: S=1.6 m/min; /=1,5 mm; V=4.. .10 m/s is possible without lubricant-cooling agent.
REFERENCES
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2. Provolotsky A.E., Negrub S.L. Technological possibilities of polymer-abrasive tool // Naukovi pratsi of DNTU. - 2004. - Seriya: Machinebuilding, V. 71. - P.125-133.
3. Abrashkevich Y.D., Oglobinsky A.V. Rational use of polymer-abrasive brushes // Mounting and special works in building. - 2007. - №7. - P.23-26.
4. Krivoukhov V.A., Chubarov A.D. Machining titanium alloys. - Moscow: Mechanical Engineering, 1970. - 180 pages.
5. Adaskina A.M., Zuev V.M. Materialovededenie (processing of metals). - Moscow: Publishing Center "Academy", 2002. - 240 pages.
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7. OSBORN International: Product Catalog / Osborn PRO, 2008. - 101 pages.
8. Stepanov DN, Vnukov Y.N. Methods of measurement of contact temperature in the working area during the processing with the tool based on a polymer-abrasive fibers // Engineering -by the eyes young: International Scientific Conference, Kyiv, 30.10-01.11.2013: Proceedings "Tool provision of modern production," KNU - section 1, 2013. - P. 32-33.
ANALYSIS OF THE THE ENERGY BALANCE OF UKRAINE TO IMPROVE THE ENERGY EFFICIENCY OF FUEL AND
ENERGY COMPLEX
Doctor of technical sciences, prof., head of Department Rosen V. P.
Postgraduate Trachuk A. R.
Ukraine, Kiev city, Institute of Energy Saving and Energy management National Technical University of Ukraine "Kiev Polytechnic Institute" Department of Automation Management of Electrotechnical Complexes
Abstract. The main problems that arise in front of Ukraine's energy sector and the direct negative impact on the level of energy, as well as national security. A review of the empirical data on the production, supply and consumption of fuel and energy resources, as well as carried out analysis of the energy balance of the country. It describes the main causes of energy waste and low energy efficiency in Ukraine. The possible measures to resolve the existing problems in the sphere of energy saving and prospects for future research.
Keywords: energy balance state, energy saving, energy efficiency, fuel and energy sector, fuel and energy resources, the energy intensity of the economy, energy security.
Formulation of the problem. Today, the energy sector of Ukraine appeared a number of unprecedented challenges, a direct negative impact on the level of energy, and thus the national security of our country. The main problems in this context can be defined as follows:
• excessive level of dependence on the monopoly of the imports of energy resources;
