MenuISSN (0970-2083)
ISSN (0970-2083)
Palanivendhan M*, Rishidev Chowdary K, Raj Kumar K and Narendra Varma N
Department of Automobile Engineering, SRM University, Kattankullathur, Tamil Nadu, India
Received Date: 25 May, 2017 Accepted Date: 22 December, 2017
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In developing world, the usage of fossil fuel and electricity charges are being increased day by day and they produce more environmental pollution. In intention of the above factor, there is need to develop alternative energy with low cost. Solar power is one of the best ways to produce energy. Solar flat plate type air collector (SFPTAC) is widely used for many solar applications. Drying of agricultural food products is attractive and cost –effective application of solar power as it becomes a potentially viable substitute for fuel-wood in major development of the world. A SFPTAC is 2 × 1 m2 area and 5 mm thick aluminium sheet is coated with a black paint. An insulated collector of about 10cm thickness and inside is covered by the glass wool of thickness 25 mm are used on the surface of the enclosure. These tests were conducted to gather data from different atmospheric conditions. The results were examined by both the free and forced convection.
Taguchi analysis, Electric discharge machining, High carbon high chromium steel, Machining time
EDM is a non-conventional machining process. The material is expelled from the workpiece through limited liquefying and vaporization of material. Electric flashes are created between two cathodes when the anodes are held at a little separation from each other in a dielectric medium and a high potential distinction is connected crosswise over them. Flashes happening between the two anode surfaces is the explanation behind high temperatures of restricted districts. Workpiece material in this limited zone dissolves and vaporizes. From the between cathode hole by the dielectric stream a large portion of the liquid and vaporized material is diverted as trash particles. To avoid over the top warming, electric power is provided as short heartbeats. The start happens wherever the hole between the device and the workpiece surface is littlest. After the material is expelled because of a start, this whole increments and the area of the following sparkle movements to an alternate point on the workpiece surface. Along these lines, a few flashes happen at a few areas on the whole surface of the workpiece in view of the work piece-apparatus hole. Due to the material expulsion because of sparkles, after some time all through the crevice between the apparatus and the workpiece a uniform hole separation is framed. In the electric circuit apparatus and the workpiece shape the two conductive cathodes. To the anodes, beat power is provided from a different power supply unit. It keeps up a steady whole remove between the instrument and the workpiece by required sustain movement of hardware towards the workpiece. This is performed by either a servo engine control or stepper engine control of the apparatus holder. The instrument is moved descending towards the workpiece to keep up a consistent between anode services as the material gets expelled from the workpiece. The apparatus and the workpiece are dived in a dielectric tank and flushing game plans are made for the best possible stream of dielectric in the between terminal crevice. Beat DC control supply is utilized as a part of oil bite the dust sinking EDM where the instrument is associated with the negative terminal and the workpiece is associated with the positive terminal. From a couple kHz to a few MHz the beat recurrence may fluctuate. The between anode crevice is in the scope of a couple of several micrometers to a couple of hundred micrometers. Material evacuation rates of up to 300 mm3/min can be accomplished amid EDM. The surface complete (Ra esteem) can be as high as 50 μm amid unpleasant machining and even under 1 μm amid get done with machining. (Figure. 1) explains the setup of the EDM machining process.
Figure 1: Schematic of an E lectric Discharge Machining (EDM) machine tool.
(Shailesh, et al., 2015) In electric release machine surface respectability is one of the significant regions of worry in which metals are investigated. In late reviews, the half and half streamlining system which depends on dim fluffy rationale are utilized to know and to remedy the ideal settings of EDM process parameters which expect to enhance surface respectability viewpoints after EDM of AISI P20 device steel. The investigation is directed utilizing reaction surface philosophy (RSM) considering release current (Ip), beat on-time (Ton), instrument work time (Tw) and device lift time (Tup) as parameters. A portion of the other surface trustworthiness parameters like white layer thickness (WLT), surface break thickness (SCD) and surface harshness (SR) are considered amid the momentum look into work. Dark fluffy rationale joined with Gray social investigation (GRA) of difference is utilized to decide dim fluffy thinking grade (GFRG). The greatest arrangement in light of this investigation was observed to be Ip ¼ 1 A, Ton ¼ 10 ms, Tw ¼ 0.2 s, and Tup ¼ 0.0 s. Ton is thought to be the most utilized parameter took after by Ip, for numerous execution attributes of surface uprightness.
(Milan, et al., 2014) In electric release machine(EDM), the union of parameters for ideal surface unpleasantness and material evacuation rate of EN31 instrument steel utilizing fake honey bee province (ABC) calculation was explored. For the exploratory process, in view of the focal composite outline (CCD), machining parameters, for example, beat on time, beat off time, release current and voltage are changed. Utilizing Response Surface Methodology (RSM), second request reaction conditions for MRR and Surface Roughness are computed. Both single and multi-target reactions (MRR and surface unpleasantness: Ra) are utilized for improvement. From ABC investigation, the ideal mixes of process parameters are determined and required estimations of greatest MRR and least Ra are found. Affirmation tests are done to check the examinations and it is watched that the anticipated values around match with the trial values. This review how machining exhibitions get influenced with an adjustment in machine parameters. It is demonstrated that with an expansion in current and heartbeat on time, there is an increment in MRR and surface harshness in the trial procedure. At last, utilizing Scanning Electron Microscope (SEM) pictures, the surface morphology of machined surfaces is contemplated.
(Dastagiri and Hemantha, 2014) These were tentatively broke down the impact of four plan variables current (I), voltage (V), beat on(Ton), and obligation. consider 
which are the most utilized parameters that are controlled by the EDM procedure over machining details, for example, material expulsion rate (MRR) and apparatus wear rate(TWR) and qualities of surface honesty, for example, normal surface unpleasantness (Ra) and the hardness (HR) and furthermore to gauge them. In this paper, a scientific model to foresee material expulsion rate, normal surface harshness and hardness utilizing input parameters, for example, current, voltage, beat on, and obligation variable is created by utilizing full factorial plan 23 with three essential issues in the DOE strategies. The anticipated outcomes were practically equivalent to test values. Henceforth this numerical model is utilized to know the progressions, for example, material evacuation rate, and normal surface unpleasantness effectively inside the info parameters is considered.
(Vikas, et al., 2014; Durairaja, et al., 2013) were introduced a thought regarding the impact of the different info handle parameters such as Pulse-on time, Pulse-off time, Discharge Current, and Voltage over the Surface Roughness for an EN41 material. Here, 5 diverse yield parameters worried with surface harshnesses like Ra, Rq, Rsk, Rku and Rsm are taken and advanced in like manner, utilizing the Gray- Taguchi technique. The Gray-Taguchi technique utilized as a part of the article considers an L27 orthogonal exhibit, which utilizes an alternate blend of the 4-input parameters to acquire an advanced estimation of the surface unpleasantness for EN41 material. The 5 diverse yield estimations of the surface harshness are adjusted into a solitary esteem (i.e., Review) by figuring their standardized, Δ and ξ values. On the premise of their Grade, the S/N proportion is acquired and likewise, the ANOVA table is created. It was found that the Current largely affected the Surface Roughness esteem, trailed by the Voltage. The trial comes about accordingly, got were contrasted and the hypothetical outcomes and they were discovered near each other.
(Guu, 2005) works were broke down surface morphology, surface unpleasantness and miniaturized scale split of AISI D2 device steel machined by the electrical release machining (EDM) process were dissected by methods for the nuclear compel microscopy (AFM) strategy. The Trial comes about demonstrate that the surface after EDM is dictated by the release vitality amid preparing. A fabulous machine complete can be acquired by setting the machine parameters at a low heartbeat vitality. The surface harshness and the profundity of the smaller scale breaks were relative to the power input. Besides, the AFM application yielded data about the profundity of the miniaturized scale splits is especially essential in the post treatment of AISI D2 apparatus steel machined by EDM.
(Azadi and Kolahan, 2014) were investigated, response surface method (RSM) is used to investigate the effect of four controllable information components to be particular: discharge current, beat traverse, beat off time and hole voltage on surface obnoxiousness (Ra). A face-centered central composite arrangement matrix is used to coordinate the trials on EN31 with the copper terminal. The response is shown using RSM on exploratory data. The tremendous coefficients are obtained by performing examination of contrast (ANOVA) at 95% assurance level. It is found that discharge current and pulse term are basic components. RSM is an exactness system that needs only 31 tests to assess the conditions and is to a great degree strong.
Experimental Setup
Terminals were machined to a round and hollow state of 20 mm distance across and 25mm length. A Cylindrical bit of 32 mm breadth and thickness 15 mm of HDS must be arranged.
Electrode Materials
Cathode material impacts essential yield parameters, for example, material expulsion rate, surface harshness, and dimensional exactness. Copper and metal are two ordinarily utilized EDM cathode materials in the business in light of the fact that these materials have high dissolving temperature and astounding electrical and warm conductivity. Copper can be effortlessly machined to any shape, endure less wear, has great warm conductivity, and is prudent.
Metal is reasonable and simple to the machine, however, it has high terminal wear. It is frequently utilized for tubular cathodes in specific little opening EDM penetrating machines where high wear is satisfactory. Terminals produced using exceptional powders by utilizing powder metallurgy innovation have been utilized to change EDM surfaces lately and incredible wear and consumption resistance have been accomplished under particular machining conditions. In any case, this system is yet to increase wide acknowledgment (Table 1).
| Property | Units | Material Copper |
|---|---|---|
| Thermal conductivity | W/m-K | 391 |
| Electrical resistivity | Ohm-cm | 1.67 |
| Specific heat capacity | J/g-̢̮̉ | 0.325 |
| Melting point | ̢̮̉ | 1083 |
Table 1. Properties of inconel work material and cooper electrode.
Work Material Details
Work material –HCHCR steel.
Work material size–32 mm dia 10 mm thickness.
Chemical properties (Table 2).
| Elements | Composition in Weight % I |
|---|---|
| Carbon, C | 1.55 |
| Manganese Mn | 0.35 |
| Silicon, Si | 0.25 |
| Molybdenum Mo | 0.80 |
| Chromium Cr | 12.0 |
| Vanadium V | 0.90 |
Table 2. Chemical properties.
Physical properties (Table 3).
| Property | Values |
|---|---|
| Density | 7.7 g/cm3 |
| Melting Point | 1421°C |
| Thermal expansion (@20-100ºC/68-212ºF) |
12 x 10 -6 /ºC |
Table 3. Physical properties.
Machining parameters (general) (Table 4).
| Sparking Voltage (V) | V80 ± 5% |
| Discharge Current (A) | 15.11.10.8.7.6.5.4 |
| Servo Control | Electro Mechanical |
| Polarity | Normal (Electrode-Positive) |
| Dielectric Fluid | Commercial Grade Kerosene |
| Flushing Side | Flushing with Pressure |
| Work Piece Material | OHNS Die Steel (Hardness and Tampered) |
| Electrode Material | Copper and Brass |
Table 4. Machining parameters.
Design of Orthogonal Array
To start with Taguchi Orthogonal cluster is composed in minitab-16 to figure S/N proportion and means which steps is given underneath. Make Taguchi Design is chosen as appeared in the figure. At that point a window of Taguchi configuration is opened. To begin Minitab, tap the alternate route of Minitab on Desktop of the PC.
Design of Experiment
Process parameters and their levels (Table 5).
| S. No | Pulse-On | Pulse-Off | Gap Current |
|---|---|---|---|
| 1 | 4 | 5 | 8 |
| 2 | 5 | 6 | 10 |
| 3 | 6 | 7 | 12 |
Table 5. Process parameters and their levels.
An orthogonal array L9 formation (Table 6).
| Trial No. | Designation | Pulse- On | Pulse-Off | Amps |
|---|---|---|---|---|
| 1 | A1B1C1 | 4 | 5 | 8 |
| 2 | A1B2C2 | 4 | 6 | 10 |
| 3 | A1B3C3 | 4 | 7 | 12 |
| 4 | A2B1C2 | 5 | 5 | 10 |
| 5 | A2B2C3 | 5 | 6 | 12 |
| 6 | A2B3C1 | 5 | 7 | 8 |
| 7 | A3B1C3 | 6 | 5 | 12 |
| 8 | A3B2C1 | 6 | 6 | 8 |
| 9 | A3B3C2 | 6 | 7 | 10 |
Table 6. Orthogonal array L9 formation.
Rockwell Hardness Test
1. Rockwell Hardness systems use a prompt readout machine choosing the hardness number in perspective of the significance of invasion of either a gem point or a steel ball. Significant penetration demonstrated a material having a low Rockwell Hardness number.
2. In any case, a low penetration demonstrates a material having a bigger Rockwell Hardness number. The Rockwell Hardness number relies on upon the refinement in the significance to which a penetrator is driven by a reasonable light or "minor" load and an unmistakable overpowering or "Noteworthy" load.
3. The ball penetrators are tosses that are made to hold 1/16" or 1/8" remove crosswise over hardened steel balls. Moreover open are ¼" and ½" ball penetrators for the testing of gentler materials.
4. There are two sorts of iron obstructs that are used on the Rockwell hardness analyzers. The level faceplate models are used for level illustrations. The "V" sort press pieces hold round illustrations determinedly.
5. Test pieces or alteration squares are level steel or metal squares, which have been attempted and separate with the measurement and Rockwell number. They should be used to check the precision and arrangement of the analyzer a significant part of the time.
Topography Analysis
The examination on machining of HCHCR steel uncovered that surface geography continues changing as the machining conditions are shifted. It was likewise watched that the way of breaks additionally shifts with the variety of machining conditions are changed.
Surface Morphology
It is the exploration of the shape and structure of material. The surface morphology of the sparker stacked surface can be concentrated through the accompanying:
1. Surface wrap up
2. Auxiliary change in the surface
Surface Characteristics
EDM machined surfaces by and large have a matt appearance secured by shallow holes globules of trash and blemishes shaped by captured gasses getting away from the re-kept material, at low release vitality, the pits are shallow and the thickness of worldwide members and scars is low. The regular component on EDM surface is the wealth of splits, particularly at high release energies. These splits are shaped thus of the exceedingly high warm burdens winning at the example surface as it was cooled at a quicker rate after charge.
Surface Microstructures
The EDMed surface microstructure is mind boggling and for the most part, varies surprisingly when contrasted with that of the parent metals. Under the extraordinary state of the release, both the apparatus material and the workpiece have privately dissolved and the impact of dielectric splitting amid the procedure. Between the anode materials as well as with the pyrolysis result of the dielectric alloying happens. This exceedingly alloyed metal is then cooled at a greatly quick rate to room temperature. Notwithstanding the liquid surface, the fundamental metal has been subjected to a sharp temperature inclination. The correct profile of the temperature slope relies on upon the cathode materials, the dielectric and the real release condition. The aftereffect of stage change of the metal and the high-temperature angle set up amid the procedure are the leftover worries inside the EDM surface. In the miniaturized scale structures of the surface, three unmistakable layers are distinguished. The external most layer, a middle of the road layer, and the unaffected parent metal. It has been likewise found that with increment of warm conductivity microhardness additionally increments
Metallurgical Changes during EDM Process
The surface respectability of a part depicts the topological, mechanical, metallurgical and concoction states of the surface district which additionally incorporate the surface and subsurface structure after start machining, If the material is inspected, it indicates three distinctive zones(a) a white surface layer (b) a warmth influenced zone and (c) the unaffected parent metal. The top surface is made of advanced dielectric and anode material. This begins with the cementing procedure from the liquid state. Beneath this layer, there is a layer which thickness is fairly 20 times that of the white layer is a metallurgical and synthetically influenced locale which is mostly because of warm discharge and dissemination of material from the liquid layer. The re-set layer every now and again experiences strange stage changes determined because of the breaking of the dielectric, and because of alloying of the work material layer with the exchanged instrument material. When all is said in done, unadulterated non-ferrous materials show few stage changes, while, ferrous immaculate iron, carbon steels, and composite steels display changes of expanding many-sided quality. A few creators have concentrated the surface testimony and dissemination of hardware material on the machined surfaces. They watched that basically the adjustments in compound arrangement stay restricted to the re-cemented layer and furthermore up to thin zone beneath it. While machining instrument steel with copper terminals, it was found that up to 10% copper is gathered in a zone of the 5 μm profundity of the work material and this focus diminishes pointedly past 20 μm profundity. It has additionally been accounted for [68] that materials with poor warm conductivity demonstrate the lower profundity of dissemination, which, in any case, increments as higher vitality heartbeats are utilized. These adjustments in substance creation of the work surface layer, for the most part, brought on by the ingestion of carbon from a decayed dielectric.
In (Figure. 2) the loss of material is a direct result of liquefying took after by its vanishing that can be seen from the elements existing at the interface of the split. The nearness of grain limit (upper left side corner) demonstrates that the start of a break has not happened from the grain limit; rather, it has begun from the zone where the re-set layer exists. The compositional investigation was done from the dull stage (profound hole), the dark stage.
Figure 2: (Pulse on time-2μs, Pulse off time-6 μs, Amps-10).
In (Figure. 3) the dark area represents the existence of deep craters; the grey area represents the hallow craters with heat affected zone and the white phase represents a re-solidified layer.
Figure 3: (Pulse on time-3 μs, Pulse off time-6 μs, Amps-6).
In (Figure. 4) the system of the dark layer watched compares to the re-hardened layer. The nearness of breaks up and down these systems demonstrates that the instrument of split arrangement is because of mechanical anxieties which are apparent all the more obviously in higher amplification micrograph. The nearness of anticipated smooth, liquid layer up and down the cavity, in which little size volcanic emissions are, demonstrates that material underneath this white layer was still in the fluid state.
Figure 4: (Pulse on time-4 μs, Pulse off time-6 μs, Amps-8).
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