Lead is a chemical element with symbol Pb and atomic number 82. It is a heavy metal, denser than most common materials. Lead is soft and malleable, has a low melting point; when freshly cut, lead is silvery with a hint of blue. Lead has the highest atomic number of any stable element and three of its isotopes each include a major decay chain of heavier elements. Lead is a unreactive post-transition metal, its weak metallic character is illustrated by its amphoteric nature. Compounds of lead are found in the +2 oxidation state rather than the +4 state common with lighter members of the carbon group. Exceptions are limited to organolead compounds. Like the lighter members of the group, lead tends to bond with itself. Lead is extracted from its ores. Galena, a principal ore of lead bears silver, interest in which helped initiate widespread extraction and use of lead in ancient Rome. Lead production declined after the fall of Rome and did not reach comparable levels until the Industrial Revolution. In 2014, the annual global production of lead was about ten million tonnes, over half of, from recycling.
Lead's high density, low melting point and relative inertness to oxidation make it useful. These properties, combined with its relative abundance and low cost, resulted in its extensive use in construction, batteries and shot, solders, fusible alloys, white paints, leaded gasoline, radiation shielding. In the late 19th century, lead's toxicity was recognized, its use has since been phased out of many applications. However, many countries still allow the sale of products that expose humans to lead, including some types of paints and bullets. Lead is a toxin that accumulates in soft tissues and bones, it acts as a neurotoxin damaging the nervous system and interfering with the function of biological enzymes, causing neurological disorders, such as brain damage and behavioral problems. A lead atom has 82 electrons, arranged in an electron configuration of 4f145d106s26p2; the sum of lead's first and second ionization energies—the total energy required to remove the two 6p electrons—is close to that of tin, lead's upper neighbor in the carbon group.
This is unusual. The similarity of ionization energies is caused by the lanthanide contraction—the decrease in element radii from lanthanum to lutetium, the small radii of the elements from hafnium onwards; this is due to poor shielding of the nucleus by the lanthanide 4f electrons. The sum of the first four ionization energies of lead exceeds that of tin, contrary to what periodic trends would predict. Relativistic effects, which become significant in heavier atoms, contribute to this behavior. One such effect is the inert pair effect: the 6s electrons of lead become reluctant to participate in bonding, making the distance between nearest atoms in crystalline lead unusually long. Lead's lighter carbon group congeners form stable or metastable allotropes with the tetrahedrally coordinated and covalently bonded diamond cubic structure; the energy levels of their outer s- and p-orbitals are close enough to allow mixing into four hybrid sp3 orbitals. In lead, the inert pair effect increases the separation between its s- and p-orbitals, the gap cannot be overcome by the energy that would be released by extra bonds following hybridization.
Rather than having a diamond cubic structure, lead forms metallic bonds in which only the p-electrons are delocalized and shared between the Pb2+ ions. Lead has a face-centered cubic structure like the sized divalent metals calcium and strontium. Pure lead has a silvery appearance with a hint of blue, it tarnishes on contact with moist air and takes on a dull appearance, the hue of which depends on the prevailing conditions. Characteristic properties of lead include high density, malleability and high resistance to corrosion due to passivation. Lead's close-packed face-centered cubic structure and high atomic weight result in a density of 11.34 g/cm3, greater than that of common metals such as iron and zinc. This density is the origin of the idiom to go over like a lead balloon; some rarer metals are denser: tungsten and gold are both at 19.3 g/cm3, osmium—the densest metal known—has a density of 22.59 g/cm3 twice that of lead. Lead is a soft metal with a Mohs hardness of 1.5. It is somewhat ductile.
The bulk modulus of lead—a measure of its ease of compressibility—is 45.8 GPa. In comparison, that of aluminium is 75.2 GPa. Lead's tensile strength, at 12–17 MPa, is low; the melting point of lead—at 327.5 °C —is low compared to most metals. Its boiling point of 1749 °C is the lowest among the carbon group elements; the electrical resistivity of lead at 20 °C is 192 nanoohm-meters an order of magnitude higher than those of other industrial metals. Lead is a superconductor at temperatures lower than 7.19 K.
Sweden the Kingdom of Sweden, is a Scandinavian Nordic country in Northern Europe. It borders Norway to the west and north and Finland to the east, is connected to Denmark in the southwest by a bridge-tunnel across the Öresund, a strait at the Swedish-Danish border. At 450,295 square kilometres, Sweden is the largest country in Northern Europe, the third-largest country in the European Union and the fifth largest country in Europe by area. Sweden has a total population of 10.2 million. It has a low population density of 22 inhabitants per square kilometre; the highest concentration is in the southern half of the country. Germanic peoples have inhabited Sweden since prehistoric times, emerging into history as the Geats and Swedes and constituting the sea peoples known as the Norsemen. Southern Sweden is predominantly agricultural, while the north is forested. Sweden is part of the geographical area of Fennoscandia; the climate is in general mild for its northerly latitude due to significant maritime influence, that in spite of this still retains warm continental summers.
Today, the sovereign state of Sweden is a constitutional monarchy and parliamentary democracy, with a monarch as head of state, like its neighbour Norway. The capital city is Stockholm, the most populous city in the country. Legislative power is vested in the 349-member unicameral Riksdag. Executive power is exercised by the government chaired by the prime minister. Sweden is a unitary state divided into 21 counties and 290 municipalities. An independent Swedish state emerged during the early 12th century. After the Black Death in the middle of the 14th century killed about a third of the Scandinavian population, the Hanseatic League threatened Scandinavia's culture and languages; this led to the forming of the Scandinavian Kalmar Union in 1397, which Sweden left in 1523. When Sweden became involved in the Thirty Years War on the Reformist side, an expansion of its territories began and the Swedish Empire was formed; this became one of the great powers of Europe until the early 18th century. Swedish territories outside the Scandinavian Peninsula were lost during the 18th and 19th centuries, ending with the annexation of present-day Finland by Russia in 1809.
The last war in which Sweden was directly involved was in 1814, when Norway was militarily forced into personal union. Since Sweden has been at peace, maintaining an official policy of neutrality in foreign affairs; the union with Norway was peacefully dissolved in 1905. Sweden was formally neutral through both world wars and the Cold War, albeit Sweden has since 2009 moved towards cooperation with NATO. After the end of the Cold War, Sweden joined the European Union on 1 January 1995, but declined NATO membership, as well as Eurozone membership following a referendum, it is a member of the United Nations, the Nordic Council, the Council of Europe, the World Trade Organization and the Organisation for Economic Co-operation and Development. Sweden maintains a Nordic social welfare system that provides universal health care and tertiary education for its citizens, it has the world's eleventh-highest per capita income and ranks in numerous metrics of national performance, including quality of life, education, protection of civil liberties, economic competitiveness, equality and human development.
The name Sweden was loaned from Dutch in the 17th century to refer to Sweden as an emerging great power. Before Sweden's imperial expansion, Early Modern English used Swedeland. Sweden is derived through back-formation from Old English Swēoþēod, which meant "people of the Swedes"; this word is derived from Sweon/Sweonas. The Swedish name Sverige means "realm of the Swedes", excluding the Geats in Götaland. Variations of the name Sweden are used in most languages, with the exception of Danish and Norwegian using Sverige, Faroese Svøríki, Icelandic Svíþjóð, the more notable exception of some Finnic languages where Ruotsi and Rootsi are used, names considered as referring to the people from the coastal areas of Roslagen, who were known as the Rus', through them etymologically related to the English name for Russia; the etymology of Swedes, thus Sweden, is not agreed upon but may derive from Proto-Germanic Swihoniz meaning "one's own", referring to one's own Germanic tribe. Sweden's prehistory begins in the Allerød oscillation, a warm period around 12,000 BC, with Late Palaeolithic reindeer-hunting camps of the Bromme culture at the edge of the ice in what is now the country's southernmost province, Scania.
This period was characterised by small bands of hunter-gatherer-fishers using flint technology. Sweden is first described in a written source in Germania by Tacitus in 98 AD. In Germania 44 and 45 he mentions the Swedes as a powerful tribe with ships that had a prow at each end. Which kings ruled these Suiones is unknown, but Norse mythology presents a long line of legendary and semi-legendary kings going back to the last centuries BC; as for literacy in Sweden itself, the runic script was in use among the south Scandinavian elite by at least the 2nd century AD, but all that has come down to the present from the Roman Period is curt inscriptions on artefacts of male names, demonstrating th
The newton is the International System of Units derived unit of force. It is named after Isaac Newton in recognition of his work on classical mechanics Newton's second law of motion. See below for the conversion factors. One newton is the force needed to accelerate one kilogram of mass at the rate of one metre per second squared in the direction of the applied force. In 1946, Conférence Générale des Poids et Mesures Resolution 2 standardized the unit of force in the MKS system of units to be the amount needed to accelerate 1 kilogram of mass at the rate of 1 metre per second squared. In 1948, the 9th CGPM Resolution 7 adopted the name newton for this force; the MKS system became the blueprint for today's SI system of units. The newton thus became the standard unit of force in the Système international d'unités, or International System of Units; this SI unit is named after Isaac Newton. As with every International System of Units unit named for a person, the first letter of its symbol is upper case.
However, when an SI unit is spelled out in English, it is treated as a common noun and should always begin with a lower case letter —except in a situation where any word in that position would be capitalized, such as at the beginning of a sentence or in material using title case. Newton's second law of motion states that F = ma, where F is the force applied, m is the mass of the object receiving the force, a is the acceleration of the object; the newton is therefore: where the following symbols are used for the units: N for newton, kg for kilogram, m for metre, s for second. In dimensional analysis: F = M L T 2 where F is force, M is mass, L is length and T is time. At average gravity on Earth, a kilogram mass exerts a force of about 9.8 newtons. An average-sized apple exerts about one newton of force. 1 N = 0.10197 kg × 9.80665 m/s2 The weight of an average adult exerts a force of about 608 N. 608 N = 62 kg × 9.80665 m/s2 It is common to see forces expressed in kilonewtons where 1 kN = 1000 N.
For example, the tractive effort of a Class Y steam train locomotive and the thrust of an F100 fighter jet engine are both around 130 kN. One kilonewton, 1 kN, is about 100 kg of load. 1 kN = 102 kg × 9.81 m/s2 So for example, a platform that shows it is rated at 321 kilonewtons, will safely support a 32,100 kilograms load. Specifications in kilonewtons are common in safety specifications for: the holding values of fasteners, Earth anchors, other items used in the building industry. Working loads in tension and in shear. Rock climbing equipment. Thrust of rocket engines and launch vehicles clamping forces of the various moulds in injection moulding machines used to manufacture plastic parts
In metallurgy, stainless steel known as inox steel or inox from French inoxydable, is a steel alloy, with highest percentage contents of iron and nickel, with a minimum of 10.5% chromium content by mass and a maximum of 1.2% carbon by mass. Stainless steels are most notable for their corrosion resistance, which increases with increasing chromium content. Additions of molybdenum increase corrosion resistance in reducing acids and against pitting attack in chloride solutions. Thus, there are numerous grades of stainless steel with varying chromium and molybdenum contents to suit the environment the alloy must endure. Stainless steel's resistance to corrosion and staining, low maintenance, familiar luster make it an ideal material for many applications where both the strength of steel and corrosion resistance are required. Stainless steels are rolled into sheets, bars and tubing to be used in: cookware, surgical instruments, major appliances. Stainless steel's corrosion resistance, the ease with which it can be steam cleaned and sterilized, no need for surface coatings has influenced its use in commercial kitchens and food processing plants.
Stainless steels do not suffer uniform corrosion, like carbon steel, when exposed to wet environments. Unprotected carbon steel rusts when exposed to the combination of air and moisture; the resulting iron oxide surface layer is fragile. Since iron oxide occupies a larger volume than the original steel this layer expands and tends to flake and fall away exposing the underlying steel to further attack. In comparison, stainless steels contain sufficient chromium to undergo passivation, spontaneously forming a microscopically thin inert surface film of chromium oxide by reaction with the oxygen in air and the small amount of dissolved oxygen in water; this passive film prevents further corrosion by blocking oxygen diffusion to the steel surface and thus prevents corrosion from spreading into the bulk of the metal. This film is self-repairing if it is scratched or temporarily disturbed by an upset condition in the environment that exceeds the inherent corrosion resistance of that grade; the resistance of this film to corrosion depends upon the chemical composition of the stainless steel, chiefly the chromium content.
Corrosion of stainless steels can occur. It is customary to distinguish between 4 forms of corrosion: uniform, galvanic and SCC. Uniform corrosion takes place in aggressive environments chemical production or use and paper industries, etc; the whole surface of the steel is attacked and the corrosion is expressed as corrosion rate in mm/year Corrosion tables provide guidelines This is the case when stainless steels are exposed to acidic or basic solutions. Whether a stainless steel corrodes depends on the kind and concentration of acid or base, the solution temperature. Uniform corrosion is easy to avoid because of extensive published corrosion data or easy to perform laboratory corrosion testing. However, stainless steels are susceptible to localized corrosion under certain conditions, which need to be recognized and avoided; such localized corrosion is problematic for stainless steels because it is unexpected and difficult to predict. Acidic solutions can be categorized into two general categories, reducing acids such as hydrochloric acid and dilute sulfuric acid, oxidizing acids such as nitric acid and concentrated sulfuric acid.
Increasing chromium and molybdenum contents provide increasing resistance to reducing acids, while increasing chromium and silicon contents provide increasing resistance to oxidizing acids. Sulfuric acid is one of the largest tonnage industrial chemical manufactured. At room temperature Type 304 is only resistant to 3% acid while Type 316 is resistant to 3% acid up to 50 °C and 20% acid at room temperature, thus Type 304 is used in contact with sulfuric acid. Type 904L and Alloy 20 are resistant to sulfuric acid at higher concentrations above room temperature. Concentrated sulfuric acid possesses oxidizing characteristics like nitric acid and thus silicon bearing stainless steels find application. Hydrochloric acid will damage any kind of stainless steel, should be avoided. All types of stainless steel resist attack from phosphoric acid and nitric acid at room temperature. At high concentration and elevated temperature attack will occur and higher alloy stainless steels are required. In general, organic acids are less corrosive than mineral acids such as hydrochloric and sulfuric acid.
As the molecular weight of organic acids increase their corrosivity decreases. Formic acid is a strong acid. Type 304 can be used with formic acid. Acetic acid is the most commercially important of the organic acids and Type 316 is used for storing and handling acetic acid. Stainless steels Type 304 and 316 are unaffected by any of the weak bases such as ammonium hydroxide in high concentrations and at high temperatures; the same grades of stainless exposed to stronger bases such as sodium hydroxide at high concentrations and high temperatures will experience some etching and cracking. Increasing chromium and nickel contents provide increasing resistance. All grades resist damage from aldehydes and amines, though in the latter
Indentation hardness tests are used in mechanical engineering to determine the hardness of a material to deformation. Several such tests exist; when testing metals, indentation hardness correlates linearly with tensile strength. But it is an imperfect correlation limited to small ranges of strength and hardness for each indentation geometry; this relation permits economically important nondestructive testing of bulk metal deliveries with lightweight portable equipment, such as hand-held Rockwell hardness testers. Different techniques are used to quantify material characteristics at smaller scales. Measuring mechanical properties for materials, for instance, of thin films, can not be done using conventional uniaxial tensile testing; as a result, techniques testing material "hardness" by indenting a material with a small impression have been developed to determine to estimate these properties. Hardness measurements quantify the resistance of a material to plastic deformation. Indentation hardness tests compose the majority of processes used to determine material hardness, can be divided into two classes: microindentation and macroindentation tests.
Microindentation tests have forces less than 2 N. Hardness, cannot be considered to be a fundamental material property. Classical hardness testing creates a number which can be used to provide a relative idea of material properties; as such, hardness can only offer a comparative idea of the material's resistance to plastic deformation since different hardness techniques have different scales. The main sources of error with indentation tests are poor technique, poor calibration of the equipment, the strain hardening effect of the process. However, it has been experimentally determined through "strainless hardness tests" that the effect is minimal with smaller indentations. Surface finish of the part and the indenter do not have an effect on the hardness measurement, as long as the indentation is large compared to the surface roughness; this proves to be useful. It is helpful when leaving a shallow indentation, because a finely etched indenter leaves a much easier to read indentation than a smooth indenter.
The indentation, left after the indenter and load are removed is known to "recover", or spring back slightly. This effect is properly known as shallowing. For spherical indenters the indentation is known to stay symmetrical and spherical, but with a larger radius. For hard materials the radius can be three times as large as the indenter's radius; this effect is attributed to the release of elastic stresses. Because of this effect the diameter and depth of the indentation do contain errors; the error from the change in diameter is known to be only a few percent, with the error for the depth being greater. Another effect the load has on the indentation is the piling-up or sinking-in of the surrounding material. If the metal is work hardened it has a tendency to pile up and form a "crater". If the metal is annealed it will sink in around the indentation. Both of these effects add to the error of the hardness measurement; the equation based definition of hardness is the pressure applied over the contact area between the indenter and the material being tested.
As a result hardness values are reported in units of pressure, although this is only a "true" pressure if the indenter and surface interface is flat. The term "macroindentation" is applied to tests with a larger test load, such as more. There are various macroindentation tests, including: Vickers hardness test, which has one of the widest scales. Used to test hardness of all kinds of metal materials. Brinell hardness test BHN and HBW are used Knoop hardness test, for measurement over small areas used to test glass or ceramic material. Janka hardness test, for wood Meyer hardness test Rockwell hardness test, principally used in the USA. HRA, HRB and HRC scales are most used. Shore hardness test, for polymers used in rubbler industrials. Barcol hardness test, for composite materials. There is, in general, no simple relationship between the results of different hardness tests. Though there are practical conversion tables for hard steels, for example, some materials show qualitatively different behaviors under the various measurement methods.
The Vickers and Brinell hardness scales correlate well over a wide range, with Brinell only producing overestimated values at high loads. The term "microhardness" has been employed in the literature to describe the hardness testing of materials with low applied loads. A more precise term is "microindentation hardness testing." In microindentation hardness testing, a diamond indenter of specific geometry is impressed into the surface of the test specimen using a known applied force of 1 to 1000 gf. Microindentation tests have forces of 2 N and produce indentations of about 50 μm. Due to their specificity, microhardness testing can be used to observe changes in hardness on the microscopic scale, it is difficult to standardize microhardness measurements. Additionally, microhardness values vary with work-hardening effects of materials; the two most used microhardness tests are tests that can be a
Ultimate tensile strength
Ultimate tensile strength shortened to tensile strength, ultimate strength, or Ftu within equations, is the capacity of a material or structure to withstand loads tending to elongate, as opposed to compressive strength, which withstands loads tending to reduce size. In other words, tensile strength resists tension. Ultimate tensile strength is measured by the maximum stress that a material can withstand while being stretched or pulled before breaking. In the study of strength of materials, tensile strength, compressive strength, shear strength can be analyzed independently; some materials break sharply, without plastic deformation, in what is called a brittle failure. Others, which are more ductile, including most metals, experience some plastic deformation and necking before fracture; the UTS is found by performing a tensile test and recording the engineering stress versus strain. The highest point of the stress–strain curve is the UTS, it is an intensive property. However, it is dependent on other factors, such as the preparation of the specimen, the presence or otherwise of surface defects, the temperature of the test environment and material.
Tensile strengths are used in the design of ductile members, but they are important in brittle members. They are tabulated for common materials such as alloys, composite materials, ceramics and wood. Tensile strength can be defined for liquids as well as solids under certain conditions. For example, when a tree draws water from its roots to its upper leaves by transpiration, the column of water is pulled upwards from the top by the cohesion of the water in the xylem, this force is transmitted down the column by its tensile strength. Air pressure, osmotic pressure, capillary tension plays a small part in a tree's ability to draw up water, but this alone would only be sufficient to push the column of water to a height of less than ten metres, trees can grow much higher than that. Tensile strength is defined as a stress, measured as force per unit area. For some non-homogeneous materials it can be reported just as a force per unit width. In the International System of Units, the unit is the pascal.
A United States customary unit is pounds per square inch, or kilo-pounds per square inch, equal to 1000 psi. Many materials can display linear elastic behavior, defined by a linear stress–strain relationship, as shown in figure 1 up to point 3; the elastic behavior of materials extends into a non-linear region, represented in figure 1 by point 2, up to which deformations are recoverable upon removal of the load. Beyond this elastic region, for ductile materials, such as steel, deformations are plastic. A plastically deformed specimen does not return to its original size and shape when unloaded. For many applications, plastic deformation is unacceptable, is used as the design limitation. After the yield point, ductile metals undergo a period of strain hardening, in which the stress increases again with increasing strain, they begin to neck, as the cross-sectional area of the specimen decreases due to plastic flow. In a sufficiently ductile material, when necking becomes substantial, it causes a reversal of the engineering stress–strain curve.
The reversal point is the maximum stress on the engineering stress–strain curve, the engineering stress coordinate of this point is the ultimate tensile strength, given by point 1. UTS is not used in the design of ductile static members because design practices dictate the use of the yield stress, it is, used for quality control, because of the ease of testing. It is used to determine material types for unknown samples; the UTS is a common engineering parameter to design members made of brittle material because such materials have no yield point. The testing involves taking a small sample with a fixed cross-sectional area, pulling it with a tensometer at a constant strain rate until the sample breaks; when testing some metals, indentation hardness correlates linearly with tensile strength. This important relation permits economically important nondestructive testing of bulk metal deliveries with lightweight portable equipment, such as hand-held Rockwell hardness testers; this practical correlation helps quality assurance in metalworking industries to extend well beyond the laboratory and universal testing machines.
^ a Many of the values depend on purity or composition. ^b Multiwalled carbon nanotubes have the highest tensile strength of any material yet measured, with labs producing them at a tensile strength of 63 GPa, still well below their theoretical limit of 300 GPa. The first nanotube ropes whose tensile strength was published had a strength of 3.6 GPa. The density depends on the manufacturing method, the lowest value is 0.037 or 0.55. ^c The strength of spider silk i
Engineers, as practitioners of engineering, are professionals who invent, analyze and test machines, systems and materials to fulfill objectives and requirements while considering the limitations imposed by practicality, regulation and cost. The word engineer is derived from the Latin words ingenium; the foundational qualifications of an engineer include a four-year bachelor's degree in an engineering discipline, or in some jurisdictions, a master's degree in an engineering discipline plus four to six years of peer-reviewed professional practice and passage of engineering board examinations. The work of engineers forms the link between scientific discoveries and their subsequent applications to human and business needs and quality of life. In 1961, the Conference of Engineering Societies of Western Europe and the United States of America defined "professional engineer" as follows: A professional engineer is competent by virtue of his/her fundamental education and training to apply the scientific method and outlook to the analysis and solution of engineering problems.
He/she is able to assume personal responsibility for the development and application of engineering science and knowledge, notably in research, construction, superintending, managing and in the education of the engineer. His/her work is predominantly intellectual and varied and not of a routine mental or physical character, it requires the exercise of original thought and judgement and the ability to supervise the technical and administrative work of others. His/her education will have been such as to make him/her capable of and continuously following progress in his/her branch of engineering science by consulting newly published works on a worldwide basis, assimilating such information and applying it independently. He/she is thus placed in a position to make contributions to the development of engineering science or its applications. His/her education and training will have been such that he/she will have acquired a broad and general appreciation of the engineering sciences as well as thorough insight into the special features of his/her own branch.
In due time he/she will be able to give authoritative technical advice and to assume responsibility for the direction of important tasks in his/her branch. Engineers develop new technological solutions. During the engineering design process, the responsibilities of the engineer may include defining problems and narrowing research, analyzing criteria and analyzing solutions, making decisions. Much of an engineer's time is spent on researching, locating and transferring information. Indeed, research suggests engineers spend 56% of their time engaged in various information behaviours, including 14% searching for information. Engineers must weigh different design choices on their merits and choose the solution that best matches the requirements and needs, their crucial and unique task is to identify and interpret the constraints on a design in order to produce a successful result. Engineers apply techniques of engineering analysis in production, or maintenance. Analytical engineers may supervise production in factories and elsewhere, determine the causes of a process failure, test output to maintain quality.
They estimate the time and cost required to complete projects. Supervisory engineers are responsible for entire projects. Engineering analysis involves the application of scientific analytic principles and processes to reveal the properties and state of the system, device or mechanism under study. Engineering analysis proceeds by separating the engineering design into the mechanisms of operation or failure, analyzing or estimating each component of the operation or failure mechanism in isolation, recombining the components, they may analyze risk. Many engineers use computers to produce and analyze designs, to simulate and test how a machine, structure, or system operates, to generate specifications for parts, to monitor the quality of products, to control the efficiency of processes. Most engineers specialize in one or more engineering disciplines. Numerous specialties are recognized by professional societies, each of the major branches of engineering has numerous subdivisions. Civil engineering, for example, includes structural and transportation engineering and materials engineering include ceramic and polymer engineering.
Mechanical engineering cuts across just about every discipline since its core essence is applied physics. Engineers may specialize in one industry, such as motor vehicles, or in one type of technology, such as turbines or semiconductor materials. Several recent studies have investigated. Research suggests that there are several key themes present in engineers' work: technical work, social work, computer-based work and information behaviours. Among other more detailed findings, a recent work sampling study found that engineers spend 62.92% of their time engaged in technical work, 40.37% in social work, 49.66% in computer-based work. Furthermore, there was considerable overlap between these different types of work, with engineers spending 24.96% of their time engaged in technical and social work, 37.97% in technical and non-social, 15.42% in non-technical and social, 21.66% in non-technical and non-social. Engineering is an information-intensive field, with research finding that engineers spend 55