Here are some of the books name for GATE 2018 Mechanical you can prefer.

Design of Machine Elements - Machine design - V.B. Bhandari

Engineering Mechanics -   Engineering Mechanics by Bhavikatti, Engineering Mechanics by Beer and Johnston, Engineering Mechanics by R K Rajput

Fluid Mechanics- Fluid Mechanics by R K Bansal, Fluid & Hydraulics- Modi and seth

Heat Transfer- Heat and Mass Transfer by J P Hollman and R C Sachdeva

Heat Transfer by Cengel and Holman

Industrial Engineering- Industrial Engineering by O P Khanna, Buffa and Sarin

Manufacturing Engineering- Production Technology: Manufacturing Processes, Technology and Automation by R.K. Jain

Strength of Materials- Strength of Materials - Gere & Timoshenko

Thermal Science- Engineering Thermodynamics by P.K. Nag

Thermo Dynamics- Theory of machines by Ratan

Vibrations- Mechanical Vibration by Grover

For further detail about  you can go through with given below link.

GATE Mechanical Books