Hi,ENGINEERZ

ABSTRACT

Some recent developments in research, equipment and practical applications are reviewed together with on-going activities. The last NDT-CE conference to be held in the UK was in 1997, and attention is focused on the period since that event. Techniques include subsurface radar, dynamic response, acoustic emission, electrochemical reinforcement corrosion assessment, ultrasonics, chloride detection, magnetic imaging and soils performance, together with pull-out and maturity insitu concrete early age strength estimation. Dissemination of research to industry is considered, including the role of the British Institute of NDT and other organisations such as the Concrete Society and Highways Agency. Potential future trends are noted both in the UK and broader international context.

Commercially available equipment now includes:-

'PUNDIT PLUS' - which is a new generation, microprocessor-based, development of the long-established PUNDIT ultrasonic tester widely used on concrete, now offering data storage facilities [2].
New sub-surface radar equipment for testing concrete structures offering improved portability, and higher frequency antennas with improved performance characteristics.
New hand-held 4-probe resistivity test equipment for concrete structures, with automatic data storage.
Acoustic-Emission (AE) equipment suitable for routine field use, including one system developed in the UK.
Improved covermeters, including a 'borehole probe' device.
Improved radiography systems including reductions in size and increased energy levels, together with better image capture and processing as well as safety features (eg 'MEGASCAN [TM]').
Laser-based surface strain and pavement deformation measuring devices.
Several specialist test companies have also successfully developed equipment configurations and software for use in specific situations for example, multiple radar antenna arrays for highway surveys. Another interesting example is the 'TERRIG' system for determining the bearing capacity of material below existing concrete ground-slabs based on load/deflection measurements as illustrated in figure 1. This is particularly useful when an assessment of floor capacity is needed relating to change of use.These improvements in availability and performance of equipment have all led to enhanced field usage of the techniques and helped to improve awareness of the potential benefits to be gained from non-destructive testing within the civil engineering community.

SUPPORT FOR RESEARCH AND DISSEMINATION

In considering research and development activity, it is perhaps useful to examine the principal mechanisms for funding, undertaking the work, and dissemination of results. These have been outlined in Figure 2 which shows the key interactions between Government, Industry, Professional organisations, Research organisations and Universities.

Direct government funding, channelled in some cases through bodies such as the Highways Agency (responsible for Motorway Bridges), tends to focus on short to medium term projects relating to a clear industrial need - often with a strong review and developmental content. An example of this is the wide ranging work on NDT methods applied to masonry structures, as well as post-tensioned concrete, undertaken at the University of Edinburgh over recent years.

Much of this work is undertaken by industrial research organisations, possibly with some specialised university input, and perhaps also with industrial financial contributions. The Cardington European Concrete Building project is a good example, with work undertaken by the University of Liverpool and Queens University, Belfast on early-age insitu concrete strength assessment using maturity and pull-out methods as part of a wider range of overall activity managed by the Building Research Establishment (BRE). This has led to a Technical Report [4] published through the BRE as well as Best Practice Guides for industry.

Research Council (eg Engineering and Physical Science Research Council - EPSRC) and EU funding tends to focus on more basic research activity, usually with strong industrial collaboration and input. In this case, development into commercially usable systems is undertaken by industry - sometimes in the form of spin-off exploitation companies. Examples here include work at Imperial College on ultrasonic testing of rock bolts, and at Queens University, Belfast on insitu concrete strength and permeability testing methods.

An important new development is the recent establishment of the EPSRC supported Research Centre for NDE (see Figure 2). This is led by Imperial College and Strathclyde University and involves several other Universities, with major industrial input to support activity ranging from longer-term strategic core research to short-term industrial technology solutions. This will seek to provide improved coordination of NDE research and increased University/Industry collaboration. The total funding over the next few years will be substantial, but the scale of Civil Engineering activity to be included is unclear at present, and may be relatively small.
In-house industrial research tends to focus on development of particular systems or procedures (including software) for direct commercial use, with dissemination limited to a marketing role. In all other areas however, industrial-level dissemination and technology transfer is promoted by bodies such as the British Institute of NDT and the Concrete Society through technical journals, conferences, seminars, guidance notes and technical reports. In some cases, these include research-level dissemination, although specialist international conferences and scientific journals are the primary route for this activity, often supplementing industrial dissemination.

RECENT AND CURRENT RESEARCH AND INDUSTRIAL USAGE

It is convenient to consider this in terms of technique rather than application. International trends over the preceding four-year period were reviewed in 1997 [5], and it is interesting to note that subsequent activity in the UK has continued to reflect many of these. In particular, new interests focus on assessment of sub-surface integrity and monitoring, rather than insitu strength (apart from early age development), although prediction of future performance is an important issue. There has also been increased activity relating to masonry structures and railway track-beds in response to national concerns.

Acoustic emission

This is an area in which there has been substantial increase in industrial usage within Civil Engineering. Reported applications, to bridges in particular, cover a wide range of monitoring situations including:-

Orthotropic steel deck weld cracking;
Steel box deck weld crack propagation [6];
Fatigue of shear-studs in steel/concrete composite construction;
Reinforced concrete half-joint cracking;
Reinforced concrete hinge joint corrosion;
Post-tensioned concrete tendon wire fracture;
Roller bearing cracking;
Spherical bearing friction and plinth cracking;
Load testing of masonry arches.
This has been possible as a result of improved instrumentation and the ability to isolate traffic and other environmental noise from genuine acoustic emission sources. Much of this has been stimulated by research on steel structures at Cardiff University, but it is known that there is current research activity on reinforced concrete and masonry at Loughborough and Edinburgh Universities including use for corrosion monitoring.

Sub-surface Radar

There has been continued growth in industrial usage, coupled with wide-ranging research activity including:-

Antenna performance characterisation including coupling effects, antenna development for measurement of insitu concrete dielectric properties taking account of moisture gradients, and development of neural networks for reinforcing bar identification (University of Liverpool).

The work on insitu dielectric property assessment is described in more detail elsewhere in this Conference and utilises a horn antenna operating in the frequency domain with an inversion/optimisation routine to reconstruct the dielectric profile of the material tested [8]. This has been validated on simple layered materials in the laboratory, and is shown in Figure 3 during site trials on a car-park structure using a portable network-analyser system.

Inspection of masonry structures, including use of tomography, and non-metallic ducts in post-tensioned concrete; signal velocity assessment in materials (University of Edinburgh).
Assessment of depth of surface cracking in flexible highway pavement using high frequency systems (Transport Research Laboratory).
Characterisation of railway track-bed ballast (Transport Research Laboratory [TRL] and University of Edinburgh, Aperio).
Other ongoing research activity includes participation in the EU SMARTRAD programme within which the Building Research Establishment is developing processing software to improve interpretation capabilities. It should be noted that many examples of practical use recognise the advantages of combination with other techniques such as thermography or in some cases, such as tunnel inspections, with ground conductivity.

Ultrasonics

High frequency 'Guided wave' techniques have been very successfully applied to testing steel rock bolts as illustrated in and has been developed commercially as noted above. In coal mines bolts are typically about 20mm diameter and up to 3m length, with testing aimed at detecting fractures and major defects. Minimising leakage of the energy into the surrounding rock is crucial to success, with curvature effects causing particular problems.

Efforts are being made by the same group at Imperial College to apply the guided wave technique to inspection of rails and, using arrays, to large steel plate structures such as storage tanks. Work with guided acoustic waves has also shown promise in detecting leakage of metallic water pipes from the effects on signal propagation of the surrounding soil properties.

Other developments continue at an experimental stage to produce improved one-sided pulse-echo transducers and signal processing for use on concrete (in collaboration with German partners) with penetration depths up to 1m [10]. Air-coupled through transmission transducers are also under development at Warwick University. In both cases, use is made of multi-frequency 'chirp' technology.

Magnetic Imaging/Electrochemical Methods
Laboratory studies at University of Manchester Institute of Science & Technology (UMIST) using inductive magnetic imaging systems to locate embedded reinforcing bars have been underway for some years. Recent work, which has a strong signal processing emphasis including use of Synthetic Aperture Focussing Techniques, includes detection of bar surface corrosion and procedures to speed-up the process prior to commercialisation for field use. Work at Liverpool and Heriot-Watt Universities using electrochemical techniques such as Linear Polarisation Resistance coupled with weight-loss measurements continues to try to predict future lifetime performance where corrosion is present, whilst TRL are concerned with risk assessment for bridges. Work on moisture and chloride movement in cover zones using embedded sensors is also underway at Belfast and Heriot-Watt Universities.

Dynamic and Related Techniques
Seismic cross-hole methods using tomography to detect disturbed ground beneath foundations have been reported by the British Geological Survey, whilst other similar work using ultrasonics is reported at this conference.

Efforts have also been made to characterise physical characteristics of rail-track ballast from impact tests and continuous surface wave measurements (Napier University) whilst modal wave detection of bridge damage is known to be underway at Bristol University.

Alongside these, and other, projects has been an increasing interest in the use of uncertainty methods in the analysis of test results, with one test company providing a confidence rating according to circumstances. The need for 'whole systems planning' to avoid fragmentation of inspection and testing responsibilities and the consequent dangers of poor performance and communication, is increasingly recognised and is an important worldwide issue.

In general, civil engineering is concerned with the overall interface of human created fixed projects with the greater world. General civil engineers work closely with surveyors and specialized civil engineers to fit and serve fixed projects within their given site, community and terrain by designing grading, drainage, pavement, water supply, sewer service, electric and communications supply, and land divisions. General engineers spend much of their time visiting project sites, developing community consensus, and preparing construction plans. General civil engineering is also referred to as site engineering, a branch of civil engineering that primarily focuses on converting a tract of land from one usage to another. Civil engineers typically apply the principles of geotechnical engineering, structural engineering, environmental engineering, transportation engineering and construction engineering to residential, commercial, industrial and public works projects of all sizes and levels of construction.

Coastal engineering

Coastal engineering is concerned with managing coastal areas. In some jurisdictions the terms sea defense and coastal protection are used to mean, respectively, defence against flooding and erosion. The term coastal defence is the more traditional term, but coastal management has become more popular as the field has expanded to include techniques that allow erosion to claim land Building construction for several apartment blocks

Construction engineering

Construction engineering involves planning and execution of the designs from transportation, site development, hydraulic, environmental, structural and geotechnical engineers. As construction firms tend to have higher business risk than other types of civil engineering firms, many construction engineers tend to take on a role that is more business-like in nature: drafting and reviewing contracts, evaluating logistical operations, and closely-monitoring prices of necessary supplies.

Earthquake engineering

Earthquake engineering covers ability of various structures to withstand hazardous earthquake exposures at the sites of their particular location.

Earthquake-proof and massive pyramid El Castillo, Chichen ItzaEarthquake engineering is a sub discipline of the broader category of Structural engineering. The main objectives of earthquake engineering are:[citation needed]

Snapshot from shake-table video of testing base-isolated (right) and regular (left) building modelUnderstand interaction of structures with the shaky ground.
Foresee the consequences of possible earthquakes.
Design, construct and maintain structures to perform at earthquake exposure up to the expectations and in compliance with building codes.
Earthquake engineering structure does not necessarily mean "extremely strong" or "expensive", e.g., El Castillo pyramid at Chichen Itza shown above.[original research?]

Now, the most powerful and budgetary tool in earthquake engineering is base isolation which pertains to the passive structural vibration control technologies.[citation needed]

Environmental engineering

A filter bed, a part of sewage treatment Environmental engineering deals with the treatment of chemical, biological, and/or thermal waste, the purification of water and air, and the remediation of contaminated sites, due to prior waste disposal or accidental contamination. Among the topics covered by environmental engineering are pollutant transport, water purification, waste water treatment, air pollution, solid waste treatment and hazardous waste management. Environmental engineers can be involved with pollution reduction, green engineering, and industrial ecology. Environmental engineering also deals with the gathering of information on the environmental consequences of proposed actions and the assessment of effects of proposed actions for the purpose of assisting society and policy makers in the decision making process.

Environmental engineering is the contemporary term for sanitary engineering, though sanitary engineering traditionally had not included much of the hazardous waste management and environmental remediation work covered by the term environmental engineering. Some other terms in use are public health engineering and environmental health engineering.

Geotechnical engineering

Geotechnical engineering is an area of civil engineering concerned with the rock and soil that civil engineering systems are supported by. Knowledge from the fields of geology, material science and testing, mechanics, and hydraulics are applied by geotechnical engineers to safely and economically design foundations, retaining walls, and similar structures. Environmental concerns in relation to groundwater and waste disposal have spawned a new area of study called geoenvironmental engineering where biology and chemistry are important.

Some of the unique difficulties of geotechnical engineering are the result of the variability and properties of soil. Boundary conditions are often well defined in other branches of civil engineering, but with soil, clearly defining these conditions can be impossible. The material properties and behavior of soil are also difficult to predict due to the variability of soil and limited investigation. This contrasts with the relatively well defined material properties of steel and concrete used in other areas of civil engineering. Soil mechanics, which define the behavior of soil, is complex due to stress-dependent material properties such as volume change, stress–strain relationship, and strength.[18]

Water resources engineering

Water resources engineering is concerned with the collection and management of water (as a natural resource). As a discipline it therefore combines hydrology, environmental science, meteorology, geology, conservation, and resource management. This area of civil engineering relates to the prediction and management of both the quality and the quantity of water in both underground (aquifers) and above ground (lakes, rivers, and streams) resources. Water resource engineers analyze and model very small to very large areas of the earth to predict the amount and content of water as it flows into, through, or out of a facility. Although the actual design of the facility may be left to other engineers. Hydraulic engineering is concerned with the flow and conveyance of fluids, principally water. This area of civil engineering is intimately related to the design of pipelines, water distribution systems, drainage facilities (including bridges, dams, channels, culverts, levees, storm sewers), and canals. Hydraulic engineers design these facilities using the concepts of fluid pressure, fluid statics, fluid dynamics, and hydraulics, among others.

Materials engineering

Another aspect of Civil engineering is materials science. Material engineering deals with ceramics such as concrete, mix asphalt concrete, metals Focus around increased strength, metals such as aluminum and steel, and polymers such as polymethylmethacrylate (PMMA) and carbon fibers.

Materials engineering also consists of protection and prevention like paints and finishes. Alloying is another aspect of material engineering, combining two different types of metals to produce a stronger metal.

Structural engineering

Burj Khalifa, the world's tallest building, in Dubai
Clifton Suspension Bridge, designed by Isambard Kingdom Brunel, in Bristol, UK Structural engineering is concerned with the structural design and structural analysis of buildings, bridges, towers, flyovers, tunnels, off shore structures like oil and gas fields in the sea, and other structures. This involves identifying the loads which act upon a structure and the forces and stresses which arise within that structure due to those loads, and then designing the structure to successfully support and resist those loads. The loads can be self weight of the structures, other dead load, live loads, moving (wheel) load, wind load, earthquake load, load from temperature change etc. The structural engineer must design structures to be safe for their users and to successfully fulfill the function they are designed for (to be serviceable). Due to the nature of some loading conditions, sub-disciplines within structural engineering have emerged, including wind engineering and earthquake engineering.

Design considerations will include strength, stiffness, and stability of the structure when subjected to loads which may be static, such as furniture or self-weight, or dynamic, such as wind, seismic, crowd or vehicle loads, or transitory, such as temporary construction loads or impact. Other considerations include cost, constructability, safety, aesthetics and sustainability.

Surveying

An all-female surveying crew in Idaho, 1918Surveying is the process by which a surveyor measures certain dimensions that generally occur on the surface of the Earth. Surveying equipment, such as levels and theodolites, are used for accurate measurement of angular deviation, horizontal, vertical and slope distances. With computerisation, electronic distance measurement (EDM), total stations, GPS surveying and laser scanning have supplemented (and to a large extent supplanted) the traditional optical instruments. This information is crucial to convert the data into a graphical representation of the Earth's surface, in the form of a map. This information is then used by civil engineers, contractors and even realtors to design from, build on, and trade, respectively. Elements of a building or structure must be correctly sized and positioned in relation to each other and to site boundaries and adjacent structures. Although surveying is a distinct profession with separate qualifications and licensing arrangements, civil engineers are trained in the basics of surveying and mapping, as well as geographic information systems. Surveyors may also lay out the routes of railways, tramway tracks, highways, roads, pipelines and streets as well as position other infrastructures, such as harbors, before construction.

Land Surveying

In the United States, Canada, the United Kingdom and most Commonwealth countries land surveying is considered to be a distinct profession. Land surveyors are not considered to be engineers, and have their own professional associations and licencing requirements. The services of a licenced land surveyor are generally required for boundary surveys (to establish the boundaries of a parcel using its legal description) and subdivision plans (a plot or map based on a survey of a parcel of land, with boundary lines drawn inside the larger parcel to indicated the creation of new boundary lines and roads).

Construction Surveying

Construction surveying is generally performed by specialised technicians. Unlike land surveyors, the resulting plan does not have legal status. Construction surveyors perform the following tasks:

Survey existing conditions of the future work site, including topography, existing buildings and infrastructure, and even including underground infrastructure whenever possible;

Construction surveying (otherwise "lay-out" or "setting-out"): to stake out reference points and markers that will guide the construction of new structures such as roads or buildings for subsequent construction;
Verify the location of structures during construction;
As-Built surveying: a survey conducted at the end of the construction project to verify that the work authorized was completed to the specifications set on plans.

Transportation engineering

Transportation engineering is concerned with moving people and goods efficiently, safely, and in a manner conducive to a vibrant community. This involves specifying, designing, constructing, and maintaining transportation infrastructure which includes streets, canals, highways, rail systems, airports, ports, and mass transit. It includes areas such as transportation design, transportation planning, traffic engineering, some aspects of urban engineering, queueing theory, pavement engineering, Intelligent Transportation System (ITS), and infrastructure management.

Municipal or urban engineering

Municipal engineering is concerned with municipal infrastructure. This involves specifying, designing, constructing, and maintaining streets, sidewalks, water supply networks, sewers, street lighting, municipal solid waste management and disposal, storage depots for various bulk materials used for maintenance and public works (salt, sand, etc), public parks and bicycle paths. In the case of underground utility networks, it may also include the civil portion (conduits and access chambers) of the local distribution networks of electrical and telecommunications services. It can also include the optimizing of garbage collection and bus service networks. Some of these disciplines overlap with other civil engineering specialties, however municipal engineering focuses on the coordination of these infrastructure networks and services, as they are often built simultaneously, and managed by the same municipal authority.

Civil engineering is a professional engineering discipline that deals with the design, construction and maintenance of the physical and naturally built environment, including works such as bridges, roads, canals, dams and buildings. Civil engineering is the oldest engineering discipline after military engineering, and it was defined to distinguish non-military engineering from military engineering.It is traditionally broken into several sub-disciplines including environmental engineering, geotechnical engineering, structural engineering, transportation engineering, municipal or urban engineering, water resources engineering, materials engineering, coastal engineering,surveying, and construction engineering.Civil engineering takes place on all levels: in the public sector from municipal through to federal levels, and in the private sector from individual homeowners through to international companies.

Applications of mechanical engineering are found in the records of many ancient and medieval societies throughout the globe. In ancient Greece, the works of Archimedes (287 BC–212 BC) and Heron of Alexandria (c. 10–70 AD) deeply influenced mechanics in the Western tradition. 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 horologist and engineer Su Song (1020–1101 AD) incorporated an escapement mechanism into his astronomical clock tower two centuries before any escapement could be found in clocks of medieval Europe, as well as the world's first known endless power-transmitting chain drive.[1]

During the years from 7th to 15th century, the era called the Islamic golden age, there have been remarkable contributions from Muslims in the field of mechanical technology, Al-Jazari, who was one of them wrote his famous "Book of Knowledge of Ingenious Mechanical Devices" in 1206 presented many mechanical designs. He is also considered to be the inventor of such mechanical devices which now form the very basic of mechanisms, such as crank and cam shafts.[2]

During the early 19th century in England, Germany and Scotland, the development of machine tools led mechanical engineering to develop as a separate field within engineering, providing manufacturing machines and the engines to power them.[3] The first British professional society of mechanical engineers was formed in 1847, thirty years after civil engineers formed the first such professional society.[4] 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, becoming the third such professional engineering society, after the American Society of Civil Engineers (1852) and the American Institute of Mining Engineers (1871).[5] The first schools in the United States 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 historically been based on a strong foundation in mathematics and science.[6]

The field of mechanical engineering is considered among the broadest of engineering disciplines. The work of mechanical engineering ranges from the depths of the ocean to outer space.

The field of mechanical engineering can be thought of as a collection of many mechanical disciplines. Several of these subdisciplines which are typically taught at the undergraduate level are listed below, with a brief explanation and the most common application of each. Some of these subdisciplines are unique to mechanical engineering, while others are a combination of mechanical engineering and one or more other disciplines. Most work that a mechanical engineer does uses skills and techniques from several of these subdisciplines, as well as specialized subdisciplines. Specialized subdisciplines, as used in this article, are more likely to be the subject of graduate studies or on-the-job training than undergraduate research. Several specialized subdisciplines are discussed at the end of this section.

Mechanics

Mohr's circle, a common tool to study stresses in a mechanical elementMechanics is, in the most general sense, the study of forces and their effect upon matter. Typically, engineering mechanics is used to analyze and predict the acceleration and deformation (both elastic and plastic) of objects under known forces (also called loads) or stresses. Subdisciplines of mechanics include

Statics, the study of non-moving bodies under known loads
Dynamics (or kinetics), the study of how forces affect moving bodies
Mechanics of materials, the study of how different materials deform under various types of stress
Fluid mechanics, the study of how fluids react to forces[20]
Continuum mechanics, a method of applying mechanics that assumes that objects are continuous (rather than discrete)
Mechanical engineers typically use mechanics in the design or analysis phases of engineering. If the engineering project were the design of a vehicle, statics might be employed to design the frame of the vehicle, in order to evaluate where the stresses will be most intense. Dynamics might be used when designing the car's engine, to evaluate the forces in the pistons and cams as the engine cycles. Mechanics of materials might be used to choose appropriate materials for the frame and engine. Fluid mechanics might be used to design a ventilation system for the vehicle (see HVAC), or to design the intake system for the engine.

Kinematics

Kinematics is the study of the motion of bodies (objects) and systems (groups of objects), while ignoring the forces that cause the motion. The movement of a crane and the oscillations of a piston in an engine are both simple kinematic systems. The crane is a type of open kinematic chain, while the piston is part of a closed four-bar linkage.

Mechanical engineers typically use kinematics in the design and analysis of mechanisms. Kinematics can be used to find the possible range of motion for a given mechanism, or, working in reverse, can be used to design a mechanism that has a desired range of motion.

Mechatronics and robotics

Training FMS with learning robot SCORBOT-ER 4u, workbench CNC Mill and CNC LatheMechatronics is an interdisciplinary branch of mechanical engineering, electrical engineering and software engineering that is concerned with integrating electrical and mechanical engineering to create hybrid systems. In this way, machines can be automated through the use of electric motors, servo-mechanisms, and other electrical systems in conjunction with special software. A common example of a mechatronics system is a CD-ROM drive. Mechanical systems open and close the drive, spin the CD and move the laser, while an optical system reads the data on the CD and converts it to bits. Integrated software controls the process and communicates the contents of the CD to the computer.

Robotics is the application of mechatronics to create robots, which are often used in industry to perform tasks that are dangerous, unpleasant, or repetitive. These robots may be of any shape and size, but all are preprogrammed and interact physically with the world. To create a robot, an engineer typically employs kinematics (to determine the robot's range of motion) and mechanics (to determine the stresses within the robot).

Robots are used extensively in industrial engineering. They allow businesses to save money on labor, perform tasks that are either too dangerous or too precise for humans to perform them economically, and to insure better quality. Many companies employ assembly lines of robots, and some factories are so robotized that they can run by themselves. Outside the factory, robots have been employed in bomb disposal, space exploration, and many other fields. Robots are also sold for various residential applications.

Structural analysis

Structural analysis is the branch of mechanical engineering (and also civil engineering) devoted to examining why and how objects fail and to fix the objects and their performance. Structural failures occur in two general modes: static failure, and fatigue failure. Static structural failure occurs when, upon being loaded (having a force applied) the object being analyzed either breaks or is deformed plastically, depending on the criterion for failure. Fatigue failure occurs when an object fails after a number of repeated loading and unloading cycles. Fatigue failure occurs because of imperfections in the object: a microscopic crack on the surface of the object, for instance, will grow slightly with each cycle (propagation) until the crack is large enough to cause ultimate failure.

Failure is not simply defined as when a part breaks, however; it is defined as when a part does not operate as intended. Some systems, such as the perforated top sections of some plastic bags, are designed to break. If these systems do not break, failure analysis might be employed to determine the cause.

Structural analysis is often used by mechanical engineers after a failure has occurred, or when designing to prevent failure. Engineers often use online documents and books such as those published by ASM[21] to aid them in determining the type of failure and possible causes.

Structural analysis may be used in the office when designing parts, in the field to analyze failed parts, or in laboratories where parts might undergo controlled failure tests.

Thermodynamics

Thermodynamics is an applied science used in several branches of engineering, including mechanical and chemical engineering. At its simplest, thermodynamics is the study of energy, its use and transformation through a system. Typically, engineering thermodynamics is concerned with changing energy from one form to another. As an example, automotive engines convert chemical energy (enthalpy) from the fuel into heat, and then into mechanical work that eventually turns the wheels.

Thermodynamics principles are used by mechanical engineers in the fields of heat transfer, thermofluids, and energy conversion. Mechanical engineers use thermo-science to design engines and power plants, heating, ventilation, and air-conditioning (HVAC) systems, heat exchangers, heat sinks, radiators, refrigeration, insulation, and others.

Drafting

A CAD model of a mechanical double sealDrafting or technical drawing is the means by which mechanical engineers create instructions for manufacturing parts. A technical drawing can be a computer model or hand-drawn schematic showing all the dimensions necessary to manufacture a part, as well as assembly notes, a list of required materials, and other pertinent information. A U.S. mechanical engineer or skilled worker who creates technical drawings may be referred to as a drafter or draftsman. Drafting has historically been a two-dimensional process, but computer-aided design (CAD) programs now allow the designer to create in three dimensions.

Instructions for manufacturing a part must be fed to the necessary machinery, either manually, through programmed instructions, or through the use of a computer-aided manufacturing (CAM) or combined CAD/CAM program. Optionally, an engineer may also manually manufacture a part using the technical drawings, but this is becoming an increasing rarity, with the advent of computer numerically controlled (CNC) manufacturing. Engineers primarily manually manufacture parts in the areas of applied spray coatings, finishes, and other processes that cannot economically or practically be done by a machine.

Drafting is used in nearly every subdiscipline of mechanical engineering, and by many other branches of engineering and architecture. Three-dimensional models created using CAD software are also commonly used in finite element analysis (FEA) and computational fluid dynamics (CFD).

The field of mechanical engineering can be thought of as a collection of many mechanical disciplines. Several of these subdisciplines which are typically taught at the undergraduate level are listed below, with a brief explanation and the most common application of each. Some of these subdisciplines are unique to mechanical engineering, while others are a combination of mechanical engineering and one or more other disciplines. Most work that a mechanical engineer does uses skills and techniques from several of these subdisciplines, as well as specialized subdisciplines. Specialized subdisciplines, as used in this article, are more likely to be the subject of graduate studies or on-the-job training than undergraduate research. Several specialized subdisciplines are discussed at the end of this section.

Mechanics

Mechanics is, in the most general sense, the study of forces and their effect upon matter. Typically, engineering mechanics is used to analyze and predict the acceleration and deformation (both elastic and plastic) of objects under known forces (also called loads) or stresses. Subdisciplines of mechanics include

Statics, the study of non-moving bodies under known loads
Dynamics (or kinetics), the study of how forces affect moving bodies
Mechanics of materials, the study of how different materials deform under various types of stress
Fluid mechanics, the study of how fluids react to forces[20]
Continuum mechanics, a method of applying mechanics that assumes that objects are continuous (rather than discrete)
Mechanical engineers typically use mechanics in the design or analysis phases of engineering. If the engineering project were the design of a vehicle, statics might be employed to design the frame of the vehicle, in order to evaluate where the stresses will be most intense. Dynamics might be used when designing the car's engine, to evaluate the forces in the pistons and cams as the engine cycles. Mechanics of materials might be used to choose appropriate materials for the frame and engine. Fluid mechanics might be used to design a ventilation system for the vehicle (see HVAC), or to design the intake system for the engine.

Kinematics

Kinematics is the study of the motion of bodies (objects) and systems (groups of objects), while ignoring the forces that cause the motion. The movement of a crane and the oscillations of a piston in an engine are both simple kinematic systems. The crane is a type of open kinematic chain, while the piston is part of a closed four-bar linkage.

Mechanical engineers typically use kinematics in the design and analysis of mechanisms. Kinematics can be used to find the possible range of motion for a given mechanism, or, working in reverse, can be used to design a mechanism that has a desired range of motion.

Mechatronics and Robotics

Mechatronics is an interdisciplinary branch of mechanical engineering, electrical engineering and software engineering that is concerned with integrating electrical and mechanical engineering to create hybrid systems. In this way, machines can be automated through the use of electric motors, servo-mechanisms, and other electrical systems in conjunction with special software. A common example of a mechatronics system is a CD-ROM drive. Mechanical systems open and close the drive, spin the CD and move the laser, while an optical system reads the data on the CD and converts it to bits. Integrated software controls the process and communicates the contents of the CD to the computer.

Robotics is the application of mechatronics to create robots, which are often used in industry to perform tasks that are dangerous, unpleasant, or repetitive. These robots may be of any shape and size, but all are preprogrammed and interact physically with the world. To create a robot, an engineer typically employs kinematics (to determine the robot's range of motion) and mechanics (to determine the stresses within the robot).

Robots are used extensively in industrial engineering. They allow businesses to save money on labor, perform tasks that are either too dangerous or too precise for humans to perform them economically, and to insure better quality. Many companies employ assembly lines of robots, and some factories are so robotized that they can run by themselves. Outside the factory, robots have been employed in bomb disposal, space exploration, and many other fields. Robots are also sold for various residential applications.

Structural Analysis

Structural analysis is the branch of mechanical engineering (and also civil engineering) devoted to examining why and how objects fail and to fix the objects and their performance. Structural failures occur in two general modes: static failure, and fatigue failure. Static structural failure occurs when, upon being loaded (having a force applied) the object being analyzed either breaks or is deformed plastically, depending on the criterion for failure. Fatigue failure occurs when an object fails after a number of repeated loading and unloading cycles. Fatigue failure occurs because of imperfections in the object: a microscopic crack on the surface of the object, for instance, will grow slightly with each cycle (propagation) until the crack is large enough to cause ultimate failure.

Failure is not simply defined as when a part breaks, however; it is defined as when a part does not operate as intended. Some systems, such as the perforated top sections of some plastic bags, are designed to break. If these systems do not break, failure analysis might be employed to determine the cause.

Structural analysis is often used by mechanical engineers after a failure has occurred, or when designing to prevent failure. Engineers often use online documents and books such as those published by ASM[21] to aid them in determining the type of failure and possible causes.

Structural analysis may be used in the office when designing parts, in the field to analyze failed parts, or in laboratories where parts might undergo controlled failure tests.

Thermodynamics and thermo-science

Thermodynamics is an applied science used in several branches of engineering, including mechanical and chemical engineering. At its simplest, thermodynamics is the study of energy, its use and transformation through a system. Typically, engineering thermodynamics is concerned with changing energy from one form to another. As an example, automotive engines convert chemical energy (enthalpy) from the fuel into heat, and then into mechanical work that eventually turns the wheels.

Thermodynamics principles are used by mechanical engineers in the fields of heat transfer, thermofluids, and energy conversion. Mechanical engineers use thermo-science to design engines and power plants, heating, ventilation, and air-conditioning (HVAC) systems, heat exchangers, heat sinks, radiators, refrigeration, insulation, and others.

Drafting

Drafting or technical drawing is the means by which mechanical engineers create instructions for manufacturing parts. A technical drawing can be a computer model or hand-drawn schematic showing all the dimensions necessary to manufacture a part, as well as assembly notes, a list of required materials, and other pertinent information. A U.S. mechanical engineer or skilled worker who creates technical drawings may be referred to as a drafter or draftsman. Drafting has historically been a two-dimensional process, but computer-aided design (CAD) programs now allow the designer to create in three dimensions.

Instructions for manufacturing a part must be fed to the necessary machinery, either manually, through programmed instructions, or through the use of a computer-aided manufacturing (CAM) or combined CAD/CAM program. Optionally, an engineer may also manually manufacture a part using the technical drawings, but this is becoming an increasing rarity, with the advent of computer numerically controlled (CNC) manufacturing. Engineers primarily manually manufacture parts in the areas of applied spray coatings, finishes, and other processes that cannot economically or practically be done by a machine.

Drafting is used in nearly every subdiscipline of mechanical engineering, and by many other branches of engineering and architecture. Three-dimensional models created using CAD software are also commonly used in finite element analysis (FEA) and computational fluid dynamics (CFD).

Mechanical engineering is an engineering discipline that was developed from the application of principles from physics and materials science. According to the American Heritage Dictionary, it is the branch of engineering that encompasses the generation and application of heat and mechanical power and the design, production, and use of machines and tools. It is one of the oldest and broadest engineering disciplines.

The field requires a solid understanding of core concepts including mechanics, kinematics, thermodynamics, fluid mechanics, heat transfer, materials science, and energy. Mechanical engineers use the core principles as well as other knowledge in the field to design and analyze manufacturing plants, industrial equipment and machinery, heating and cooling systems, motor vehicles, aircraft, watercraft, robotics, medical devices and more.

During the development of radio, many scientists and inventors contributed to radio technology and electronics. In his classic UHF experiments of 1888, Heinrich Hertz transmitted (via a spark-gap transmitter) and detected radio waves using electrical equipment. In 1895, Nikola Tesla was able to detect signals from the transmissions of his New York lab at West Point (a distance of 80.4 km / 49.95 miles).[9] In 1897, Karl Ferdinand Braun introduced the cathode ray tube as part of an oscilloscope, a crucial enabling technology for electronic television.[10] John Fleming invented the first radio tube, the diode, in 1904. Two years later, Robert von Lieben and Lee De Forest independently developed the amplifier tube, called the triode.[11] In 1895, Guglielmo Marconi furthered the art of hertzian wireless methods. Early on, he sent wireless signals over a distance of one and a half miles. In December 1901, he sent wireless waves that were not affected by the curvature of the Earth. Marconi later transmitted the wireless signals across the Atlantic between Poldhu, Cornwall, and St. John's, Newfoundland, a distance of 2,100 miles (3,400 km).[12] In 1920 Albert Hull developed the magnetron which would eventually lead to the development of the microwave oven in 1946 by Percy Spencer.[13][14] In 1934 the British military began to make strides toward radar (which also uses the magnetron) under the direction of Dr Wimperis, culminating in the operation of the first radar station at Bawdsey in August 1936.[15]
In 1941 Konrad Zuse presented the Z3, the world's first fully functional and programmable computer.[16] In 1946 the ENIAC (Electronic Numerical Integrator and Computer) of John Presper Eckert and John Mauchly followed, beginning the computing era. The arithmetic performance of these machines allowed engineers to develop completely new technologies and achieve new objectives, including the Apollo missions and the NASA moon landing.[17]
The invention of the transistor in 1947 by William B. Shockley, John Bardeen and Walter Brattain opened the door for more compact devices and led to the development of the integrated circuit in 1958 by Jack Kilby and independently in 1959 by Robert Noyce.[18] Starting in 1968, Ted Hoff and a team at Intel invented the first commercial microprocessor, which presaged the personal computer. The Intel 4004 was a 4-bit processor released in 1971, but in 1973 the Intel 8080, an 8-bit processor, made the first personal computer, the Altair 8800, possible.

Power

Power engineering deals with the generation, transmission and distribution of electricity as well as the design of a range of related devices. These include transformers, electric generators, electric motors, high voltage engineering and power electronics. In many regions of the world, governments maintain an electrical network called a power grid that connects a variety of generators together with users of their energy. Users purchase electrical energy from the grid, avoiding the costly exercise of having to generate their own. Power engineers may work on the design and maintenance of the power grid as well as the power systems that connect to it. Such systems are called on-grid power systems and may supply the grid with additional power, draw power from the grid or do both. Power engineers may also work on systems that do not connect to the grid, called off-grid power systems, which in some cases are preferable to on-grid systems. The future includes Satellite controlled power systems, with feedback in real time to prevent power surges and prevent blackouts.

Control

Control systems play a critical role in space flight
Control engineering focuses on the modeling of a diverse range of dynamic systems and the design of controllers that will cause these systems to behave in the desired manner. To implement such controllers electrical engineers may use electrical circuits, digital signal processors, microcontrollers and PLCs (Programmable Logic Controllers). Control engineering has a wide range of applications from the flight and propulsion systems of commercial airliners to the cruise control present in many modern automobiles. It also plays an important role in industrial automation.
Control engineers often utilize feedback when designing control systems. For example, in an automobile with cruise control the vehicle's speed is continuously monitored and fed back to the system which adjusts the motor's power output accordingly. Where there is regular feedback, control theory can be used to determine how the system responds to such feedback.

Electronics

Electronic engineering involves the design and testing of electronic circuits that use the properties of components such as resistors, capacitors, inductors, diodes and transistors to achieve a particular functionality. The tuned circuit, which allows the user of a radio to filter out all but a single station, is just one example of such a circuit. Another example (of a pneumatic signal conditioner) is shown in the adjacent photograph.
Prior to the second world war, the subject was commonly known as radio engineering and basically was restricted to aspects of communications and radar, commercial radio and early television. Later, in post war years, as consumer devices began to be developed, the field grew to include modern television, audio systems, computers and microprocessors. In the mid to late 1950s, the term radio engineering gradually gave way to the name electronic engineering.
Before the invention of the integrated circuit in 1959, electronic circuits were constructed from discrete components that could be manipulated by humans. These discrete circuits consumed much space and power and were limited in speed, although they are still common in some applications. By contrast, integrated circuits packed a large number—often millions—of tiny electrical components, mainly transistors, into a small chip around the size of a coin. This allowed for the powerful computers and other electronic devices we see today.

Microelectronics

Microelectronics engineering deals with the design and microfabrication of very small electronic circuit components for use in an integrated circuit or sometimes for use on their own as a general electronic component. The most common microelectronic components are semiconductor transistors, although all main electronic components (resistors, capacitors, inductors) can be created at a microscopic level. Nanoelectronics is the further scaling of devices down to nanometer levels.
Microelectronic components are created by chemically fabricating wafers of semiconductors such as silicon (at higher frequencies, compound semiconductors like gallium arsenide and indium phosphide) to obtain the desired transport of electronic charge and control of current. The field of microelectronics involves a significant amount of chemistry and material science and requires the electronic engineer working in the field to have a very good working knowledge of the effects of quantum mechanics.

Signal Processing

Signal processing deals with the analysis and manipulation of signals. Signals can be either analog, in which case the signal varies continuously according to the information, or digital, in which case the signal varies according to a series of discrete values representing the information. For analog signals, signal processing may involve the amplification and filtering of audio signals for audio equipment or the modulation and demodulation of signals for telecommunications. For digital signals, signal processing may involve the compression, error detection and error correction of digitally sampled signals.
Signal Processing is a very mathematically oriented and intensive area forming the core of digital signal processing and it is rapidly expanding with new applications in every field of electrical engineering such as communications, control, radar, TV/Audio/Video engineering, power electronics and bio-medical engineering as many already existing analog systems are replaced with their digital counterparts.
Although in the classical era, analog signal processing only provided a mathematical description of a system to be designed, which is actually implemented by the analog hardware engineers, Digital Signal Processing both provides a mathematical description of the systems to be designed and also actually implements them (either by software programming or by hardware embedding) without much dependency on hardware issues, which exponentiates the importance and success of DSP engineering.
The deep and strong relations between signals and the information they carry makes signal processing equivalent of information processing. Which is the reason why the field finds so many diversified applications. DSP processor ICs are found in every type of modern electronic systems and products including, SDTV | HDTV sets, radios and mobile communication devices, Hi-Fi audio equipments, Dolby noise reduction algorithms, GSM mobile phones, mp3 multimedia players, camcorders and digital cameras, automobile control systems, noise cancelling headphones, digital spectrum analyzers, intelligent missile guidance, radar, GPS based cruise control systems and all kinds of image processing, video processing, audio processing and speech processing systems.

Telecommunications

Telecommunications engineering focuses on the transmission of information across a channel such as a coax cable, optical fiber or free space. Transmissions across free space require information to be encoded in a carrier wave in order to shift the information to a carrier frequency suitable for transmission, this is known as modulation. Popular analog modulation techniques include amplitude modulation and frequency modulation. The choice of modulation affects the cost and performance of a system and these two factors must be balanced carefully by the engineer.
Once the transmission characteristics of a system are determined, telecommunication engineers design the transmitters and receivers needed for such systems. These two are sometimes combined to form a two-way communication device known as a transceiver. A key consideration in the design of transmitters is their power consumption as this is closely related to their signal strength. If the signal strength of a transmitter is insufficient the signal's information will be corrupted by noise.

Computers

Computer engineering deals with the design of computers and computer systems. This may involve the design of new hardware, the design of PDAs or the use of computers to control an industrial plant. Computer engineers may also work on a system's software. However, the design of complex software systems is often the domain of software engineering, which is usually considered a separate discipline. Desktop computers represent a tiny fraction of the devices a computer engineer might work on, as computer-like architectures are now found in a range of devices including video game consoles and DVD players.

Electrical engineering, sometimes referred to as electrical and electronic engineering, is a field of engineering that deals with the study and application of electricity, electronics and electromagnetism. The field first became an identifiable occupation in the late nineteenth century after commercialization of the electric telegraph and electrical power supply. It now covers a range of subtopics including power, electronics, control systems, signal processing and telecommunications.
Electrical engineering may or may not include electronic engineering. Where a distinction is made, usually outside of the United States, electrical engineering is considered to deal with the problems associated with large-scale electrical systems such as power transmission and motor control, whereas electronic engineering deals with the study of small-scale electronic systems including computers and integrated circuits.[1] Alternatively, electrical engineers are usually concerned with using electricity to transmit energy, while electronic engineers are concerned with using electricity to transmit information.