Hello.

Mechanical engineering is ver wide field

These are the sub groups or SPECIALIZATIONS

• Aerospace Engineering
• Astronautical Engineering - deals with the R&D and manufacturing work of space shuttles, rockets and space station.
• Aeronautical Engineering - deals with the design and manufacturing of air-crafts, missiles and helicopters.
• Acoustical Engineering - deals with the measurement and analysis of sound and vibration. Acoustical engineers apply the science of sound and vibration to real world technologies.
• Opto-mechanical engineering - Field specific to the mechanical aspects of optical systems. Includes design, packaging, mounting, and alignment mechanisms specific to optical systems.
• Manufacturing Engineering - deals with the designing, analyzing and applying of manufacturing techniques and methods for the production of quality products at cost-effective prices.
• Nanotechnology - apply your knowledge of the principles of mechanical engineering to problem solving at this smallest of scales, where materials, because of their size, may behave differently.
• Thermal Engineering - focuses on thermodynamics, design of heating and cooling equipment and power management.
• Sports engineering - a field of engineering that involves the design, development and testing of sport equipment. The equipment used by athletes has always gone through technological design and development based on current knowledge and understanding.
• Production Engineering - a unique branch of engineering which deals with techniques and tools used in manufacturing industries.
• Power plant engineering - Field of engineering that designs, construct and maintains different types of power plants. Serves as the prime mover to produce electricity.
• Mechatronics - requires knowledge of mechanical engineering principles, electronics and computer science. The knowledge of various skill sets makes one very employable, especially with the growth of internet of things.
• Vehicle Engineering -
• Automotive Engineering – deals with the design, construction and maintenance of automobile and its spare parts.
• Naval Architecture Engineering–deals with the design, development and maintenance of marine vessels and the related structures.
• Energy engineering - a broad field of engineering dealing with energy efficiency, energy services, facility management, plant engineering, environmental compliance and alternative energy technologies.
• Robotics - involves automation of mechanical systems by programming hardware devices.

Hope this is helpful.

Good luck.