Conventional Material Case Study

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Zulaika & Campa (2009) and Rahman et al (1989) had summarized the main advantages of conventional materials as follows.
• Low cost
• Very good machinability
• Possibility to machine very accurate dimensions and geometric
• tolerances
• High value of elasticity modulus
• Excellent mass-to-stiffness ratio
• High material-damping ratio.

The limitations of conventional material are:
• Relatively high thermal expansion coefficients causing thermal deformation between the components
• Cast iron structures are subjected to self-excited vibrations called ‘chattering’ while operating at high speeds (Ema and Marui, 2000).

The following material properties are to be considered while considering any material for machine tool- According to N.Mahendrakumar,
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Brittle and expensive, low conductivity.
Polymer Concrete- Low Young’s Modulus, low thermal conductivity, high damping properties. Tensile and impact strengths lower, creep more under sustained load
Polymer-Impregnated Concrete (PIC)- Bond strength is low and mechanical properties are only slightly better than those of conventional concrete.
The advantages of Polymer concrete available from literature are-
• The extremely low thermal diffusivity of polymer castings makes them stable and robust from thermal point of view.
• Its structural damping is comparable to that of cast iron,
• Mineral-cast elements are resistant against oils, coolants and other aggressive liquids.
• They are light weight materials, their densities are less than those of the metals.
The limitations of polymers are,
• Its high cost,
• Their properties vary with temperature.
Polymer-Cement Concrete (PCC)- Mixing water soluble resin with cement
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have designed and fabricated a bed for ultra precision mirror surface grinding machine with optimum composition of resin concrete. The damping ratio of this bed was found to be 9 times that of cast iron bed but it is a little heavier than cast iron bed for the same stiffness. Coefficient of expansion is similar to cast iron, thermal conductivity smaller than cast iron. Expensive, therefore not an economical substitute for cast iron.
Polymer Impregnated Concrete (PIC)- Improved damping capacity (High damping at lower frequency range
Hollow Composites Sphere- It consists of hollow spheres as filler and epoxy resin as matrix material. Reduced weight. Higher thermal coefficient of expansion than steel. Hollow sphere consists of a mixture of metal oxides or plastic and size ranges from 10µm to 2mm.
Cementitious Composite Materials- Cement as binders.
Ferrocement- Better mechanical properties, durability. Ferrocement bed has high damping ratios and natural frequencies, is more stable. Fabrication is labor intensive and time consuming due to difficulty faced in bending, cutting etc.
Fiber Reinforced Cement Composites- Reinforced fiber to avoid brittle failure. Damping ratio increased.
Microfibre-reinforced cementitious composites-Improved toughness, impact resistance, damping properties and

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