Mechanical engineering

Mechanical engineering is a field of engineering that focuses on designing, analyzing, building, and running mechanical systems. It combines engineering physics and mathematics with materials science to create and improve machines, structures, manufacturing processes, and fluid, thermal, and energy systems. It is one of the oldest and broadest of the engineering branches.

Mechanical engineers learn key areas such as mechanics, dynamics, thermodynamics, materials science, design, structural analysis, electronics, and electricity. They also use tools like computer-aided design (CAD), computer-aided manufacturing (CAM), computer-aided engineering (CAE), and product lifecycle management. With these tools, they design and analyze manufacturing plants, industrial equipment and machinery, heating and cooling systems, transport systems, motor vehicles, aircraft, watercraft, robotics, medical devices, weapons, and many other things.

Mechanical engineering began as a field during the Industrial Revolution in Europe in the 1700s. Its roots, however, go back several thousand years around the world. In the 1800s, advances in physics helped the science of mechanical engineering grow. The field keeps changing as new discoveries are made. Today, mechanical engineers work on areas such as composites, mechatronics, and nanotechnology. The field also overlaps with aerospace engineering, metallurgical engineering, civil engineering, structural engineering, electrical engineering, manufacturing engineering, chemical engineering, industrial engineering, and other engineering fields to different degrees.

Mechanical engineers may also work in biomedical engineering, especially on topics such as biomechanics, transport phenomena, biomechatronics, bionanotechnology, and modelling of biological systems.

Main article: History of mechanical engineering

Ideas from mechanical engineering appear in the records of many ancient and medieval societies. The six classic simple machines were known in the ancient Near East, and the wedge and the inclined plane (ramp) were known since prehistoric times. Mesopotamian civilization is credited by several, mainly older, sources with inventing the wheel. However, some recent sources suggest it was invented separately in both Mesopotamia and Eastern Europe, or credit prehistoric Eastern Europeans with the invention. The lever first appeared around 5,000 years ago in the Near East. It was used in a simple balance scale and to move large objects in ancient Egyptian technology. The lever was also used in the shadoof water-lifting device, the first crane machine, which appeared in Mesopotamia around 3000 BC. The earliest evidence of pulleys dates back to Mesopotamia in the early 2nd millennium BC. The Saqiyah was developed in the Kingdom of Kush during the 4th century BC. It used animal power, which reduced the need for human energy. Kush also built Reservoirs in the form of Hafirs to store water and improve irrigation. Bloomeries and blast furnaces were developed during the seventh century BC in Meroe, and Kushite sundials used advanced trigonometry. The earliest practical water-powered machines, the water wheel and watermill, first appeared in the Persian Empire, in what are now Iraq and Iran, by the early 4th century BC. In ancient Greece, the works of Archimedes (287–212 BC) influenced the study of mechanics in the Western world. The geared Antikythera mechanisms was an Analog computer invented around the 2nd century BC.

In Roman Egypt, Heron of Alexandria (c. 10–70 AD) created the first steam-powered device, the Aeolipile. In China, Zhang Heng (78–139 AD) improved a water clock and invented a seismometer, and Ma Jun (200–265 AD) invented a chariot with differential gears. The medieval Chinese clockmaker and engineer Su Song (1020–1101 AD) added an escapement mechanism to his astronomical clock tower two centuries before escapement devices appeared in medieval European clocks. He also invented the world's first known endless power-transmitting chain drive. The cotton gin was invented in India by the 6th century AD, and the spinning wheel was invented in the Islamic world by the early 11th century. Dual-roller gins appeared in India and China between the 12th and 14th centuries. The worm gear roller gin appeared in the Indian subcontinent during the early Delhi Sultanate era, from the 13th to 14th centuries. During the Islamic Golden Age (7th to 15th century), Muslim inventors made remarkable contributions to mechanical technology. Al-Jazari wrote his famous Book of Knowledge of Ingenious Mechanical Devices in 1206 and presented many mechanical designs. In the 17th century, important discoveries that built the foundations of mechanical engineering were made in England and the Continent. The Dutch mathematician and physicist Christiaan Huygens invented the pendulum clock in 1657. It was the first reliable timekeeper for almost 300 years. He published a work about clock designs and the ideas behind them. In England, Isaac Newton developed his laws of motion and calculus, which became the mathematical basis of physics. Newton was reluctant to publish his work for years, but his colleagues, such as Edmond Halley, finally persuaded him to do so. Gottfried Wilhelm Leibniz, who had earlier designed a mechanical calculator, is also credited with developing calculus at the same time. During the early 1800s, machine tools were developed in England, Germany, and Scotland. This helped mechanical engineering grow into a separate field within engineering. The machine tools made manufacturing machines and the engines to power them. The first British professional society of mechanical engineers, the Institution of Mechanical Engineers, was formed in 1847, thirty years after civil engineers formed the first such society, the Institution of Civil Engineers. On the European continent, Johann von Zimmermann (1820–1901) founded the first factory for grinding machines in Chemnitz, Germany, in 1848. In the United States, the American Society of Mechanical Engineers (ASME) was formed in 1880. It became the third such professional engineering society, after the American Society of Civil Engineers (1852) and the American Institute of Mining Engineers (1871). The first US schools to offer an engineering education were the United States Military Academy in 1817, an institution now known as Norwich University in 1819, and Rensselaer Polytechnic Institute in 1825. Education in mechanical engineering has long been built on a strong foundation in mathematics and science.

Education

Many universities around the world offer degrees in mechanical engineering. These programs usually take four to five years. Students finish with a Bachelor of Engineering (B.Eng. or B.E.), Bachelor of Science (B.Sc. or B.S.), Bachelor of Technology (B.Tech.), or Bachelor of Applied Science (B.A.Sc.) degree. In Spain, Portugal, and most of South America, the degree is called "Mechanical Engineer" and takes five or six years. In Italy, students study for five years and must pass a state exam to become engineers. In the United States, most undergraduate programs are accredited by the Accreditation Board for Engineering and Technology (ABET). This helps keep the courses similar from one university to another. In Australia, Engineers Australia accredits degrees in line with the Washington Accord. Students must also complete at least 3 months of work experience in an engineering firm before they get their degree. In India, people can become engineers in several ways. They can earn an engineering degree or an engineering diploma, or they can take a trade course, such as fitter, from the Industrial Training Institute.

Some students go on to earn a postgraduate degree. These include a Master of Technology, Master of Science, Master of Engineering Management, Doctor of Philosophy, or engineer's degree. Many of these include research. The Doctor of Philosophy is often the path to working in universities. Accreditation standards help graduates learn a shared base of knowledge, though the exact courses can be different. Institutes of technology often combine or split subjects. Common subjects include Mathematics, calculus, linear algebra, physics, chemistry, Statics, Strength of materials, Thermodynamics, Fluid mechanics, Mechatronics, robotics, and computer-aided design (CAD). Many programs also include projects. Students in the US often complete internships, and Cooperative education is another option.

Job duties

Mechanical engineers plan, design, build, and test machines, tools, and engines that use heat and movement. They look at problems and think about how a machine could help. They design or redesign devices, build and test early versions, and change the designs based on what they learn. They also check how things are made and lead teams of specialists. Mechanical engineers design many products, from medical devices to new batteries. They also design power machines such as electric generators and engines. They use computers to help create designs, run simulations, and test how machines will work.

Engineers may apply for a license from a state, provincial, or national government. A license shows they have the knowledge, experience, and understanding of local laws needed to work as engineers. Once certified, they may use the title Professional Engineer or Chartered Engineer, depending on the country. In the U.S., the National Council of Examiners for Engineering and Surveying sets the steps for becoming a licensed Professional Engineer. In the UK, a Chartered Mechanical Engineer needs a BEng with a master's degree, or an integrated MEng degree. They also need several years of work experience and a project report. They are certified through the Institution of Mechanical Engineers. In most developed countries, some engineering work, such as designing bridges and power plants, must be approved by a professional engineer or a chartered engineer. In the UK, there is no such law. However, certifying groups have a code of ethics that members are expected to follow. In 2015, about 278,340 mechanical engineers worked in the U.S. This was the largest group of engineers there. In 2012, their median yearly income was $80,580.

Further information: FE Exam, Professional Engineer, Incorporated Engineer, Washington Accord (credentials), and Regulation and licensure in engineering

Subdisciplines

The field of mechanical engineering is made up of many smaller subdisciplines. Some belong only to mechanical engineering, while others mix it with other fields. Most of the work a mechanical engineer does uses skills from several of these, along with more specialized areas that are usually studied later.

Main article: Mechanics

Mechanics studies forces and how they affect matter. Engineers use it to predict how objects move, change shape, or bend when they are pushed or pulled by known loads or stresses. Its parts include statics, which studies objects that do not move; dynamics, which studies how forces affect moving objects; mechanics of materials, which studies how materials change under stress; fluid mechanics, which studies how fluids react to forces; kinematics, which studies motion without looking at the forces that cause it; and continuum mechanics, which treats objects as continuous rather than made of separate pieces. When designing a vehicle, statics can help shape the frame, dynamics can study the forces on the pistons and cams in the engine, and fluid mechanics can help design the HVAC system or the engine's intake.

Main articles: Mechatronics and Robotics

Mechatronics combines mechanics and electronics. It joins mechanical, electrical engineering, and software engineering to make machines work on their own, using electric motors, servo-mechanisms, and software. A CD-ROM drive is one example: mechanical parts spin the disc and move the laser, while an optical system reads the data and turns it into bits. Robotics applies these ideas to build robots. Robots are often used in factories for jobs that are dangerous, unpleasant, or repetitive. They work on assembly lines, and some factories can even run by themselves. Robots also help with space exploration and bomb disposal.

Main articles: Structural analysis and Failure analysis

Structural analysis looks at why and how objects break, and how to make them better. Objects can break when a force is too strong for them or when they are bent out of shape permanently. Fatigue failure happens after many cycles of loading and unloading, when tiny cracks grow until they cause ultimate failure.

Main articles: Thermodynamics, Heat Transfer, and Combustion

Thermodynamics is the study of heat, work, energy, and the properties of matter. Thermal engineering combines it with transport phenomena to study heat transfer, combustion, and compressible fluid flow. Engineers use these ideas to design engines, power plants, heat exchangers, heat sinks, radiators, refrigerators, insulation, and HVAC systems. A car engine turns the chemical energy of fuel (enthalpy) into heat and then into motion. Engineers try to waste as little energy as possible. An ideal design would get close to Carnot efficiency, named after Sadi Carnot, a French military engineer.

Main articles: Technical drawing and CNC

Drafting, or technical drawing, is how mechanical engineers design products and create instructions for making parts. A drawing shows the sizes, materials, and notes needed to put parts together. Drafting was once done in two dimensions, but computer-aided design (CAD) programs now let designers work in three dimensions. Instructions can be sent to machines through computer-aided manufacturing (CAM) or computer numerically controlled (CNC) manufacturing, so parts can be made with little help from workers. Some parts still need hand-applied spray coatings or surface finishes. Drafting is used across mechanical engineering and in other fields, such as architecture. 3D models support finite element analysis (FEA) and computational fluid dynamics (CFD).

Modern tools

Computer aided software suites

Many mechanical engineering companies, especially in wealthy industrial countries, use computer-aided engineering (CAE) programs. These include computer-aided design (CAD) tools that build 2D and 3D pictures of solid modeling objects. These programs make it easier to see products, put virtual parts together, and plan how parts fit and connect.

Other CAE programs include product lifecycle management (PLM) tools and analysis tools that run complex simulations. These tools can predict how a product will handle expected forces, how long it will last before wearing out, and whether it can be made. Examples include finite element analysis (FEA), computational fluid dynamics (CFD), and computer-aided manufacturing (CAM).

With CAE programs, a design team can quickly and cheaply improve a design so it better meets cost, performance, and other needs. A physical prototype does not need to be built until the design is nearly finished, so many more designs can be tested. CAE programs can also model hard effects, such as viscoelasticity, complex contact between parts, or non-Newtonian flows.

As mechanical engineering joins with other fields, as in mechatronics, multidisciplinary design optimization (MDO) tools are used with other CAE programs to automate and improve the design process. These tools keep checking products even after the analyst goes home. They also use smart methods to explore possible designs, often finding better, new solutions to hard problems.

On‑demand platforms for external FEA expertise

Engineering teams can get outside finite‑element analysis (FEA) help through on‑demand platforms. Users send in project details, such as CAD or FEA files, and the expected results. They then get quick price quotes and connect with approved simulation engineers. Providers do the whole job remotely, often using cloud and GPU‑based computers that can be much faster than in‑house systems. This approach can grow as needed and avoids the delays and costs of traditional buying. It is especially helpful for smaller teams with tight deadlines or few in‑house staff.

Artificial intelligence

Artificial intelligence is becoming a bigger part of mechanical engineering work. It helps with simulation, design improvement, condition monitoring, and predicting when maintenance is needed. Some approaches try to combine data-based predictions with physical laws. Even so, results still need testing, checks of uncertainty, and engineering judgment.

Areas of research

Main article: Friction stir welding

Main article: Composite material

Main article: Nanotechnology

Related fields

Some other fields are sometimes grouped with mechanical engineering. These include manufacturing engineering, aerospace engineering, automotive engineering and marine engineering. A bachelor's degree in these areas often differs only in a few special courses.