Composites Open Road To Innovation In India
Railway and automotive applications point the way to composite mass production.
By S. Sundaram, Contributing Writer | October 2003
The composites industry in Asia currently accounts for 30 percent of the global market, growing annually at at rate of 7 percent, while worldwide growth averages 4 percent. Asia's two growth leaders, China and India, maintain double-digit expansion (15 percent and 12 percent, respectively). China, however, has surged ahead in composites usage with a 25 percent share of the Asian market compared to a paltry 4 percent for India. If India is to take a place next to China at the forefront of the Asian composites sector, composites must find applications in volume production markets. India time may have finally come, as growing financial and environmental pressures spur development of composite solutions to meet challenges faced in this populous nation's public and personal transportation arenas.
Source: TVSM
The prototype TVSM-HEV hybrid electric, three-wheeled taxi, designed by TVS Motor Company Ltd. and Owens Corning, India, features significant parts integration (note the one-piece cowl and "A" pillar construction), reducing part count by half compared to traditional steel three-wheelers.
SMC AXLE BOX COVERS FOR INDIAN RAILWAY COACHES
The Indian Railways (IR) is a vast network with laid track in excess of 100,000 kilometers/62,000 miles. To date, however, the application of composites in rolling stock construction in India is abysmally low even in comparison to Japan. But the high incidence of pilferage of stainless steel, aluminum and cast-iron components used in railway coaches continues to plague the IR, and is a factor driving increased interest in composites. Since thermosetting composites have no resale value, they are a viable anti-theft alternative.
It was against this backdrop that the IR considered development and commercialization of axle box covers in sheet molding compound (SMC). The disk-shaped axle box covers house the wheel bearings on railway coaches. There are four wheels per coach and each wheel has a front and rear axle box cover. Theft of the easily accessible, 4.5 kg/9.9 lb die-cast aluminum front covers resulted in heavy revenue losses.
When the SMC concept was first put forward, the RDSO (Research, Design and Standards Organization), Ministry of Railways (the approving authority for any new construction material used in railway applications) voiced a concern about the resistance of SMC to the grease used to lubricate the bearings, which is alkaline in nature. If an SMC cover could be attacked by grease while in service, glass fibers might invade the grease, inhibiting its lubricating performance and resulting, eventually, in a "hotbox" effect (overheating of the bearings). If not remedied, the condition could result in train derailment.
To convince Railway authorities that SMC posed no hazard, a prototype was developed at one of the Railway's coach repair workshops, in Hyderabad, South India. The design and fabrication of the chrome-plated steel dies was done in the workshop's own tool room. An existing hydraulic press (used for cold stamping of metal products) was modified to suit compression molding requirements of SMC with respect to pressure and temperature controls, closing speeds, provision of ejection pins, etc. To comply with fire safety regulations for railway coaches, fire retardant-grade SMC with a glass content of 25 percent was supplied by Devi Polymers (Chennai, India) a leading Indian manufacturer of SMC and BMC (bulk molding compound). The product combined glass fiber in the form of chopped strand mat, manufactured by FGP Ltd., (Bombay, India; now a Saint-Gobain company), with unsaturated isophthalic polyester resin supplied by Naptha Resins and Chemicals (Bangalore, India) a leading polyester resin manufacturer in South India. The cover was compression molded at a temperature of 120°C at a pressure of 120 kg/cm2 (1,765 psi). Total cycle time (including charge placement and demolding) was 15 minutes, which included an 11-minute cure. The average weight of the SMC cover was 4.0 kg (8.8 lb), 0.5 kg/11.1 lb less than the aluminum cover, with a maximum thickness of 10 mm (0.39 inch) along its periphery.
In Indian Railway composites development, the common practice is to subject the product to field trials and observe its performance over a period of time. Sixteen SMC front axle box covers were installed on four coaches and, after 18 months of service, were subjected to tests at the RDSO Central Testing Laboratory. Since the primary concern was the ability of SMC to resist attack by grease (i.e., the possibility of migration of glass fibers into grease); the penetration test was carried out at 25°C/77°F using new (fresh) grease and grease removed from the SMC axle box cover. While fresh grease gave penetration index values in the 220 to 250 range, grease removed from the SMC cover gave values in the 240 to 265 range. Another test determined the drop point for grease used in bearing applications. While the minimum value should be 180°C/64.4°F with fresh grease; the grease removed from the SMC cover registered a temperature of 190°C/66.2°F. The tests demonstrated that SMC covers were unaffected by grease.
The axle box cover is bolted in position on the wheel with four lugs, through holes drilled for the purpose. There should be no eccentricity during drilling of holes on the four lugs of the SMC cover, because this will cause the steel bolts to shear off in service, and dislodge the cover. A critical mechanical trial tests the bolt pullout load, which determines the ability of the lugs to hold individual bolts securely in position. When the lugs were tested, the pullout load for SMC covers was found to be 1,000 kg/2,200 lb per lug, double the load for conventional aluminum covers (500 kg/1,100 lb).
Source: S. Sundaram
Theft of easily accessible (and easily resold on the black market) die-cast aluminum front axle box covers from Indian Railway wheel assemblies accounted for heavy revenue losses. Replacement covers of composite sheet molding compound are now manufactured in quantities of 16,000 or more each year.
At high train speeds, trackbed ballast tends to hit the cover and could lead to cracking or breakage. A final test simulated the effect of ballast impact, using a steel indenter with a 6 mm/0.25-inch radius. The indenter was dropped onto the cover from a height of 0.85m/33.5 inches, with successively greater applied loads. The SMC cover matched die-cast aluminum, withstanding the same load of 10 kg/22 lb.
Though the tests proved conclusively SMC front axle box covers were a viable alternative, the IR's customary "play-it-safe" approach delayed formal approval for use on refurbished coaches for eight years following the initial field trials! RDSO has since framed technical specifications for the SMC covers that are now used by most of the zonal railways in India. The product is supplied by RDSO-approved molders who make the SMC in-house and subsequently carry out compression molding, using their own hydraulic presses. The number of new coaches produced by the Indian Railways annually is 2,400 to 2,500, with an equal number of old coaches being refurbished.
This successful application has provided the impetus for a multitude of new and potential load-bearing applications in composites, including insulated track rail joints, sleeper berths and main doors of coaches.
