Browsing by Author "Kulkarni, S. M."

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Investigation on Mechanical and Wear Properties of Composites from Recycled Polymer for Gears with Optimized Compression Moulding
(National Institute of Technology Karnataka, Surathkal, 2014) Prabhu, B Krishna.; Kulkarni, S. M.
Cost of a product can be visualized as sum of the cost of materials and process cost. In a competitive world, producing quality products at low cost is need of the day. In reducing the process cost, the use of off line techniques like Design for manufacturing (DFM), design of experiments (DOE), Six Sigma optimization and process modeling could be adopted. Further, judicious development of low cost materials, will help in bringing down the total cost of the product. In view that polymer consumption is growing at a fast pace, reusing post consumer polymers could help reducing the material cost component of the product. Recycling engineering plastic such as post consumed Polyethylene Terephthalate (PET) provides not only a cheap and abundantly available source of material but also expands the sphere of application for recycled PET (r-PET). However, owing to reduction in the properties due to recycling procedures, the plastic need to be developed suitably, to meet the requirements of an application. Reinforcing r-PET with suitable material could address this issue. Fly ash cenospheres are low cost material that could be useful in improving the properties of recycled polymers. The cost of the product developed from low cost recycled materials could be further reduced by developing suitable low cost process. Compression moulding could be a low cost process. The process however needs to be optimized for moulding product with appreciable quality. Thus the present study is focused on developing r-PET based composites with FA cenospheres as reinforcement and compression moulding as a manufacturing process in order to cater the requirements of an industry to produce low cost engineering components such as gears. In the process of optimization, Six Sigma based DMAIC/DMADV methodology along with Taguchi’s method and RSM are utilized where as development of r-PET/FAC composite is carried out using design of experiments (DOE). Entire work is envisaged in five stages. The first stage of the experimentation is carried out with an intention to establish a thermo-mechanical moulding process for r-PET. Six Sigma DMADV methodology is utilized along with Failure Modes and Effects Analysis (FMEA) for successive improvement in the moulding procedure. A reduction in risk priority number (RPN) from 900 to 315 and finally to 8 is achieved on successive improvement in the process using FMEA. At the end of its successful application, a good, repeatable sample quality is achieved. In the second stage, R-PET, reinforced with FAC is studied for a set of compression moulding process variables and material variables using DOE as statistical tool. Five factors, critical to quality (CTQs) viz. moulding pressure (5, 10, 15 MPa); moulding time (5, 10, 15 min.); mould cooling (water, air, water and air); moulding temperature (50, 100, 150 ˚C) and weight fraction of cenospheres (5, 10, 15%), are considered at three levels. The DOE methodology adapted for such investigations showed a down ward trend for FAC content. The cause investigated using fractographic analysis, concludes debonding of FAC from the matrix due to improper interfacial characteristics. Further, the composite underwent brittle fracture making it not much useful for gear applications. The remedy considered for developing r-PET composite that makes it suitable for the gear application is to blend the matrix with an appropriate recycled polymer and to improve interfacial interactions of FAC with matrix by suitably treating FAC with (3-Aminopropyl) trimethoxy silane (3APTMS). The wear property of the composite however, proves promising as FAC reduced Specific wear rate (SWR). The preliminary work in developing the matrix, in the third stage, involves blending rPET with five softer polymers from recycled regime. R-LLDPE, r-LDPE, r-HDPE, r-PP and r-Nylon are these five polymers. Experimentation of r-PET blends suitably selects rLDPE as better suited polymer owing to its flexural and wear properties. . Blending rPET with 10% r-LDPE improves the toughness by 100% and by 112% at 30%. This is followed by r-HDPE that shows 25% and 100% increase at respective composition. Flexural strength and SWR of r-PET/r-LDPE blends affected marginally whencompared to the plastics considered in this study. The next part of third stage involves developing the composite with matrix blended with r-LDPE (30% by wt.), reinforced with FAC (5, 10, 15% by wt). An improvement in the fracture strain, over 87 % is noted at 30% of r-LDPE and 15% FAC. An improvement in toughness by about 66 MPa at 5% FAC and 13 MPa at 30% of FAC is observed. Thus studies on matrix blending conclude that blending r-PET with r-LDPE helps in reducing the brittleness of r-PET. Further, 3APTMS (6, 8, 10% by wt.) is used for treating FAC and to improve the interface. Reinforcing r-PET with 3APTMS (10% by wt.) treated FAC (T-FAC) improved flexural strength of r-PET/T-FAC composite. An increase of 34% strength at 5% T-FAC, 57% increase at 10% and 120% improvement in strength at 15 % of T-FAC is observed owing to surface treatments given to FAC. Such an increase in the properties leads to improvement in the toughness of the composite. Toughness improves by 95% at 5% of T-FAC, 200% at 10% and an increase of 271% in toughness when r-PET is reinforced with 15% T-FAC is observed. Owing to blending and treating of reinforcement, flexural and wears properties improved significantly. Further M-r-PET/T-FAC composite is also tested for their properties. The results of M-r-PET/T-FAC composite conclude favorably for developing low cost material from recycled means. In the next stage, the process and material thus developed are optimised for flexural and wear properties. In the fourth stage the process and material parameters are optimized for improved properties of the composite. Six Sigma DMAIC optimisation tool, Analysis of variance (ANOVA), Response surface methodology (RSM) are used to determine the optimum values. The final optimum parameters for moulding r-PET reinforced with FAC are Moulding pressure – 11.2 MPa, 3APTMS -7.9 % by wt., r-LDPE - 29 % by wt., moulding Temperature - 52.6 ºC and FAC – 12.5%. Confirmation experiments for these optimum values are done to verify the validity of the process adopted. In the fifth and final stage the material developed in the previous stages is moulded into gears with optimized compression moulding and their performance is evaluated on an indigenously designed and fabricated gear test rig. The increase in the gear life by about275% w. r .t the starting composite (r-PET/FAC) seems good for the applications sought for them. The gear can handle a load of about 30.5 N and can take about 50,000 revolutions. With such an improvement shown by the composite material developed in this work, it could be considered as an alternative to the existing gears made from neat polymers for lower loading applications. Thus the objectives set for this research work that to develop a low cost composite material from environment hazardous waste materials with optimized compression moulding for gear applications are met with the systematic application of Six Sigma methodologies as explained in this work.
Performance Evaluation of Power Transmission Line Tower Made of Polymer Matrix Composite
(National Institute of Technology Karnataka, Surathkal, 2013) M., Selvaraj; Kulkarni, S. M.; Ramesh Babu, R.
The design of power transmission lines is done to meet multiple constraints – electrical, mechanical and environmental. Thus designers are generous in deciding the margin to meet the above. But presently, with limited space for transmission lines, need for reduction in transmission line space in both horizontal i.e., Right of Way (ROW) and vertical i.e., height of tower has arisen. Several attempts are made to achieve this reduction at the same time reducing the cost. Use of composites for tower and its components is an attempt directed to decrease the space and the cost. Polymer composite materials have emerged as promising engineering materials due to their light weight and non – corrosiveness. The available literature provide few details of polymer matrix composites as alternative materials for tower but a systematic and holistic study on developing and testing of a tower with composites is yet to see the light. Thus, the present work is focused on development of a tower with composite members and test it for meeting mechanical and electrical performances and also achieve reduction in ROW and cost. The work considers two approaches, first is FE analysis and the next is physical building of tower components at different levels and the full tower to test for the performance. As a preliminary step, properties of glassepoxy material processed with pultrusion are determined to assess its suitability in tower applications. Subsequently, various tower members are fabricated with pultrusion process the details of which are provided in Table.1 The tower considered for present work is a 66 kV vertical double circuit lattice type in a line of 200m span operating at a wind speed of 47 m/s. Initially tower and its components are designed as suggested in standard IS: 802 providing all mandatory clearances from the point of electrical insulation. Cross arm which is one of the major components in tower, is modelled in FEM using dimensions determined earlier. The design of cross arm is verified with FE analysis. Subsequently, FE analysis of a portion of the tower body, tower sub assembly, followed by analysis with cross arm mounted is taken up. FE analysis of a full length tower made of composite member is envisaged as an ultimate part of the study.Analysis indicated that stress levels in members far below the permissible ones of a material. Thus design of tower and its components is verified. Table 1. Details of GE pultruded cross arm and tower members Sl. No Member Dimensions of member cross section Reinforcement Matrix 1 Solid rectangle section 20 mm x 70 mm E- Glass continuous fibres ( 70 - 75 % ) Epoxy (20-25%) Lapox L-12 Hardener K-6 2 Solid angle section 50x50x6mm 76.2 x 76.2x6.35 - do- - do- 3 Solid circular section Ø30 mm, Ø33 mm - do- - do- 4 Hollow sections 101.6x101.6x9.525 101.6x101.6x6.35 - do- - doIn order to reinforce the feasibility of tower with composite material, physical construction and testing of its components and in the end full tower is taken up. All tests are carried out at station in Central Power Research Institute (CPRI), Bangalore. Initially cross arm is constructed and loads as suggested in standard IS: 802 are applied on the cross arm. The deflection measured at the tip of cross arm is only about 44 mm also strains in members of the cross arm are found to be not vey excessive. Prototype testing is extended to a tower sub assembly without cross arm and with cross arm mounted successfully. Later a full length tower with all cross arms mounted in place is constructed and tested. The tower with composite member performed satisfactorily without any visible damage at 100 % full load suggested in standard. The maximum deflection of tower is found to be only 1.4 % of tower height and is within permissible limit of 5 %. The tower with composite member successfully withstood even 300 % full load without any visible signs of failure suggesting a Factor of safety 3.0.Tests for electrical performance of cross arm and tower with composite members are carried out. Table.2 provides the results of electrical test wherein it can be observed that the test parameters determined are higher than the suggested minimum values. Thus the cross arm and tower satisfactorily meet the electrical requirements. Table 2. Results of electrical testing Electrical Performance test Suggested minimum values in IS:2165 Experimentally determined values Cross arm with tower sub-assembly Full tower Power frequency ( kV ) 140 150 143 Impulse voltage ( kV ) 325 328 328 From the study it could be inferred that the tower with composite members satisfied both mechanical and electrical requirements. Since the tower is without insulator strings and the associated problems of their swing, the ROW for the line is less and a saving of about 17 % is achieved in ROW. The height of the proposed tower is only 15 m as against 18 m for metallic tower suggested by Indian standard IS: 5613. Thus a saving of about 18 % is achieved. Consequently on account of this lesser height and lower weight of composite members, the saving in total weight of the tower against a metallic tower is about 33 %. Thus with savings and benefits mentioned above, the proposed tower could be most suitable for earthquake prone zones and for Emergency Restoration Systems (ERS).