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Mechanical Engineering

Tapan Kumar Dey

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  1. Manufacturing method for Composites - Pultrusion The process of Pultrusion is utilised for the manufacture of the components which have a constant cross-sectional shape ( beams, rods, tubes etc.),and continuous lengths. In Pultrusion process, thermosetting resins are first used to impregnate continuous fiberrovings or tows; then they are pulled through a steel die which then provides the required shape to the stock and also sets the ratio resin/fibre. After this, the stock is then passed through a curing die which is precision machined so that it can give the final shape to it. This die is also heated to start curing of the resin matrix. Then the stock is drawn through the dies with the help of a pulling device. This step also determines the production speed as well. Glass, Aramid fibres and carbon are primary reinforcements materials, usually added in concentrations of approximately ranging from 40 and 70 vol%. The matrix materials commonly used in this process are polyesters, vinyl esters, and epoxy resins. Diagram of the pultrusion process. Continuous roll of reinforced fibers/woven fiber mat Tension roller Resin impregnator Resin soaked fiber Die and heat source Pull mechanism Finished hardened fiber reinforced polymer
  2. the key difference in the approach according to the buk is that, for the first problem the elongation in rod and compression in tube is taken to be same.however for the second problem, total movement of the nut is expressed as sum of compresson of tube and elongation of bolt and the degree of elongation and compression is not taken to be equal. is approach correct for the second qtn ?
  3. would appreciate an urgent response! Regards!
  4. Hi , i found below two qtns in a buk; the solution has really confused me. plss help wid correct approach to the qtns: 1.a steel rod 20 mm dia is passed through a brass tube of 25mm internal dia and 30 mm external dia. the tube is 80 cm long and is closed by thin rigid washers and fastened by nuts, screwed to the rod. the nuts are tightened until the compressive force in the tube is 5kN. cal the stresses in the rod and tube. Es = 200 GPa; Eb= 80 GPa 2. a steel bolt of 16 mm dia passes centrally through a copper tube of internal dia 20 mm and external dia 30 mm. the length of the whole assembly is 500 mm. after tight fitting of the assembly, the nut is overtightened by quarter of a turn. what are the stresses induced in the nut and the bolt if pitch of nut is 2mm. Es = 200 GPa ; Ec = 120 GPa thanks and regards!
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