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51-488: [REDACTED] Look up soft in Wiktionary, the free dictionary. Soft may refer to: Softness , or hardness, a property of physical materials Arts and entertainment [ edit ] Soft! , a 1988 novel by Rupert Thomson Soft (band) , an American music group Soft (album) , by Dan Bodan, 2014 Softs (album) , by Soft Machine, 1976 "Soft",

102-422: A "load" or "test load") of 1 to 1000 gf . Microindentation tests typically have forces of 2  N (roughly 200 gf) 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. Unfortunately, it is difficult to standardize microhardness measurements; it has been found that the microhardness of almost any material

153-484: A decrease in the material's hardness. The way to inhibit the movement of planes of atoms, and thus make them harder, involves the interaction of dislocations with each other and interstitial atoms. When a dislocation intersects with a second dislocation, it can no longer traverse through the crystal lattice. The intersection of dislocations creates an anchor point and does not allow the planes of atoms to continue to slip over one another A dislocation can also be anchored by

204-424: A different type of atom at the lattice site that should normally be occupied by a metal atom, a substitutional defect is formed. If there exists an atom in a site where there should normally not be, an interstitial defect is formed. This is possible because space exists between atoms in a crystal lattice. While point defects are irregularities at a single site in the crystal lattice, line defects are irregularities on

255-416: A fundamental material property. Classical hardness testing usually 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 equation based definition of hardness is the pressure applied over the contact area between

306-428: A larger test load, such as 1  kgf or more. There are various macroindentation tests, including: 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

357-413: A plane of atoms. Dislocations are a type of line defect involving the misalignment of these planes. In the case of an edge dislocation, a half plane of atoms is wedged between two planes of atoms. In the case of a screw dislocation two planes of atoms are offset with a helical array running between them. In glasses, hardness seems to depend linearly on the number of topological constraints acting between

408-563: A result, techniques testing material "hardness" by indenting a material with a very small impression have been developed to attempt 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, and can be divided into three classes: macro, micro and nanoindentation tests. Microindentation tests typically have forces less than 2 N (0.45 lb f ). Hardness, however, cannot be considered to be

459-552: A song by Kings of Leon on the 2004 album Aha Shake Heartbreak "Soft"/"Rock" , a 2001 single by Lemon Jelly Other uses [ edit ] Sorgenti di Firenze Trekking (SOFT), a system of walking trails in Italy Soft matter , a subfield of condensed matter Magnetically soft, material with low coercivity soft water , which has low mineral content Soft skills , a person's people, social, and other skills Soft commodities , or softs A flaccid penis ,

510-462: A square-based pyramidal indenter made from diamond. They chose the pyramidal shape with an angle of 136° between opposite faces in order to obtain hardness numbers that would be as close as possible to Brinell hardness numbers for the specimen. The Vickers test has a great advantage of using one hardness scale to test all materials. The first reference to the Vickers indenter with low loads was made in

561-473: A tensile test. This relationship can be used to describe how the material will respond to almost any loading situation, often by using the Finite Element Method (FEM). This applies to the outcome of an indentation test (with a given size and shape of indenter, and a given applied load). However, while a hardness number thus depends on the stress-strain relationship, inferring the latter from

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612-436: A wide range, however, with Brinell only producing overestimated values at high loads. Indentation procedures can, however, be used to extract genuine stress-strain relationships. Certain criteria need to be met if reliable results are to be obtained. These include the need to deform a relatively large volume, and hence to use large loads. The methodologies involved are often grouped under the term Indentation plastometry , which

663-456: Is based on the applied force divided by the surface area of the indent itself, giving hardness units in kgf/mm . Microindentation hardness testing can be done using Vickers as well as Knoop indenters. For the Vickers test, both the diagonals are measured and the average value is used to compute the Vickers pyramid number. In the Knoop test, only the longer diagonal is measured, and the Knoop hardness

714-418: Is calculated based on the projected area of the indent divided by the applied force, also giving test units in kgf/mm . The Vickers microindentation test is carried out in a similar manner welling to the Vickers macroindentation tests, using the same pyramid. The Knoop test uses an elongated pyramid to indent material samples. This elongated pyramid creates a shallow impression, which is beneficial for measuring

765-424: Is calculated with an equation, wherein load ( L ) is in grams force and the mean of two diagonals ( d ) is in millimeters: For any given load, the hardness increases rapidly at low diagonal lengths, with the effect becoming more pronounced as the load decreases. Thus at low loads, small measurement errors will produce large hardness deviations. Thus one should always use the highest possible load in any test. Also, in

816-411: Is described in a separate article. The term " microhardness " has been widely 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 (commonly called

867-713: Is formed; these tests can be performed on a macroscopic or microscopic scale. When testing metals, indentation hardness correlates roughly linearly with tensile strength , but it is an imperfect correlation often 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, even 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 , cannot be done using conventional uniaxial tensile testing. As

918-412: Is higher than its macrohardness. Additionally, microhardness values vary with load and work-hardening effects of materials. The two most commonly used microhardness tests are tests that also can be applied with heavier loads as macroindentation tests: In microindentation testing, the hardness number is based on measurements made of the indent formed in the surface of the test specimen. The hardness number

969-669: Is known as a scleroscope . Two scales that measures rebound hardness are the Leeb rebound hardness test and Bennett hardness scale. Ultrasonic Contact Impedance (UCI) method determines hardness by measuring the frequency of an oscillating rod. The rod consists of a metal shaft with vibrating element and a pyramid-shaped diamond mounted on one end. There are five hardening processes: Hall-Petch strengthening , work hardening , solid solution strengthening , precipitation hardening , and martensitic transformation . In solid mechanics , solids generally have three responses to force , depending on

1020-465: Is known as the Hall-Petch relationship . However, below a critical grain-size, hardness decreases with decreasing grain size. This is known as the inverse Hall-Petch effect. Hardness of a material to deformation is dependent on its microdurability or small-scale shear modulus in any direction, not to any rigidity or stiffness properties such as its bulk modulus or Young's modulus . Stiffness

1071-426: Is 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 very 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

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1122-407: Is often confused for hardness. Some materials are stiffer than diamond (e.g. osmium) but are not harder, and are prone to spalling and flaking in squamose or acicular habits. The key to understanding the mechanism behind hardness is understanding the metallic microstructure , or the structure and arrangement of the atoms at the atomic level. In fact, most important metallic properties critical to

1173-413: Is the sclerometer . Another tool used to make these tests is the pocket hardness tester . This tool consists of a scale arm with graduated markings attached to a four-wheeled carriage. A scratch tool with a sharp rim is mounted at a predetermined angle to the testing surface. In order to use it a weight of known mass is added to the scale arm at one of the graduated markings, the tool is then drawn across

1224-453: Is the measure of how resistant a sample is to fracture or permanent plastic deformation due to friction from a sharp object. The principle is that an object made of a harder material will scratch an object made of a softer material. When testing coatings, scratch hardness refers to the force necessary to cut through the film to the substrate. The most common test is Mohs scale , which is used in mineralogy . One tool to make this measurement

1275-436: Is the tendency of a material to fracture with very little or no detectable plastic deformation beforehand. Thus in technical terms, a material can be both brittle and strong. In everyday usage "brittleness" usually refers to the tendency to fracture under a small amount of force, which exhibits both brittleness and a lack of strength (in the technical sense). For perfectly brittle materials, yield strength and ultimate strength are

1326-535: The hardness of brittle materials or thin components. Both the Knoop and Vickers indenters require polishing of the surface to achieve accurate results. Scratch tests at low loads, such as the Bierbaum microcharacter test , performed with either 3 gf or 9 gf loads, preceded the development of microhardness testers using traditional indenters. In 1925, Smith and Sandland of the UK developed an indentation test that employed

1377-451: The amount of force and the type of material: Strength is a measure of the extent of a material's elastic range, or elastic and plastic ranges together. This is quantified as compressive strength , shear strength , tensile strength depending on the direction of the forces involved. Ultimate strength is an engineering measure of the maximum load a part of a specific material and geometry can withstand. Brittleness , in technical usage,

1428-494: The annual report of the National Physical Laboratory in 1932. Lips and Sack describes the first Vickers tester using low loads in 1936. There is some disagreement in the literature regarding the load range applicable to microhardness testing. ASTM Specification E384, for example, states that the load range for microhardness testing is 1 to 1000 gf. For loads of 1 kgf and below, the Vickers hardness (HV)

1479-475: The atoms of the network. Hence, the rigidity theory has allowed predicting hardness values with respect to composition. Dislocations provide a mechanism for planes of atoms to slip and thus a method for plastic or permanent deformation. Planes of atoms can flip from one side of the dislocation to the other effectively allowing the dislocation to traverse through the material and the material to deform permanently. The movement allowed by these dislocations causes

1530-458: The critical dimensions of an indentation left by a specifically dimensioned and loaded indenter. Common indentation hardness scales are Rockwell , Vickers , Shore , and Brinell , amongst others. Rebound hardness , also known as dynamic hardness , measures the height of the "bounce" of a diamond-tipped hammer dropped from a fixed height onto a material. This type of hardness is related to elasticity . The device used to take this measurement

1581-433: The density of dislocations increases, there are more intersections created and consequently more anchor points. Similarly, as more interstitial atoms are added, more pinning points that impede the movements of dislocations are formed. As a result, the more anchor points added, the harder the material will become. Careful note should be taken of the relationship between a hardness number and the stress-strain curve exhibited by

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1632-419: 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

1683-488: The former is far from simple and is not attempted in any rigorous way during conventional hardness testing. (In fact, the Indentation Plastometry technique, which involves iterative FEM modelling of an indentation test, does allow a stress-strain curve to be obtained via indentation, but this is outside the scope of conventional hardness testing.) A hardness number is just a semi-quantitative indicator of

1734-400: The grain level of the microstructure that are responsible for the hardness of the material. These irregularities are point defects and line defects. A point defect is an irregularity located at a single lattice site inside of the overall three-dimensional lattice of the grain. There are three main point defects. If there is an atom missing from the array, a vacancy defect is formed. If there is

1785-454: The indentation. Both of these effects add to the error of the hardness measurement. When hardness, H {\displaystyle H} , is defined as the mean contact pressure (load/ projected contact area), the yield stress, σ y {\displaystyle \sigma _{y}} , of many materials is proportional to the hardness by a constant known as the constrain factor, C. where: The hardness differs from

1836-414: The indenter and the material being tested. As a result hardness values are typically reported in units of pressure, although this is only a "true" pressure if the indenter and surface interface is perfectly flat. Instrumented indentation basically indents a sharp tip into the surface of a material to obtain a force-displacement curve. The results provide a lot of information about the mechanical behavior of

1887-423: The indenter. Since typically, E i >> E s {\displaystyle E_{i}>>E_{s}} , the second term can typically be ignored. The most critical information, hardness, can be calculated by: Commonly used indentation techniques, as well as detailed calculation of each different method, are discussed as follows. The term "macroindentation" is applied to tests with

1938-610: The intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=Soft&oldid=1212781861 " Category : Disambiguation pages Hidden categories: Short description is different from Wikidata All article disambiguation pages All disambiguation pages Softness There are three main types of hardness measurements: scratch, indentation, and rebound. Within each of these classes of measurement there are individual measurement scales. For practical reasons conversion tables are used to convert between one scale and another. Scratch hardness

1989-443: The interaction with interstitial atoms. If a dislocation comes in contact with two or more interstitial atoms, the slip of the planes will again be disrupted. The interstitial atoms create anchor points, or pinning points, in the same manner as intersecting dislocations. By varying the presence of interstitial atoms and the density of dislocations, a particular metal's hardness can be controlled. Although seemingly counter-intuitive, as

2040-529: The manufacturing of today’s goods are determined by the microstructure of a material. At the atomic level, the atoms in a metal are arranged in an orderly three-dimensional array called a crystal lattice . In reality, however, a given specimen of a metal likely never contains a consistent single crystal lattice. A given sample of metal will contain many grains, with each grain having a fairly consistent array pattern. At an even smaller scale, each grain contains irregularities. There are two types of irregularities at

2091-499: The material, including hardness , e.g., elastic moduli and plastic deformation . One key factor of instrumented indentation test is that the tip needs to be controlled by force or displacement that can be measured simultaneously throughout the indentation cycle. Current technology can realize accurate force control in a wide range. Therefore hardness can be characterized at many different length scales, from hard materials like ceramics to soft materials like polymers. The earliest work

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2142-412: The material. The latter, which is conventionally obtained via tensile testing , captures the full plasticity response of the material (which is in most cases a metal). It is in fact a dependence of the (true) von Mises plastic strain on the (true) von Mises stress , but this is readily obtained from a nominal stress – nominal strain curve (in the pre- necking regime), which is the immediate outcome of

2193-408: The opposite of "hard" See also [ edit ] All pages with titles beginning with Soft All pages with titles containing Soft Softener (disambiguation) Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with the title Soft . If an internal link led you here, you may wish to change the link to point directly to

2244-400: 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 when measuring the hardness of practical surfaces. It also 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 that

2295-406: The resistance to plastic deformation. Although hardness is defined in a similar way for most types of test – usually as the load divided by the contact area – the numbers obtained for a particular material are different for different types of test, and even for the same test with different applied loads. Attempts are sometimes made to identify simple analytical expressions that allow features of

2346-400: The same hardness number. The use of hardness numbers for any quantitative purpose should, at best, be approached with considerable caution. Indentation hardness Indentation hardness tests are used in mechanical engineering to determine the hardness of a material to deformation . Several such tests exist, wherein the examined material is indented until an impression

2397-484: The same, because they do not experience detectable plastic deformation. The opposite of brittleness is ductility . The toughness of a material is the maximum amount of energy it can absorb before fracturing, which is different from the amount of force that can be applied. Toughness tends to be small for brittle materials, because elastic and plastic deformations allow materials to absorb large amounts of energy. Hardness increases with decreasing particle size . This

2448-464: The stress-strain curve, particularly the yield stress and Ultimate Tensile Stress (UTS), to be obtained from a particular type of hardness number. However, these are all based on empirical correlations, often specific to particular types of alloy: even with such a limitation, the values obtained are often quite unreliable. The underlying problem is that metals with a range of combinations of yield stress and work hardening characteristics can exhibit

2499-412: The test surface. The use of the weight and markings allows a known pressure to be applied without the need for complicated machinery. Indentation hardness measures the resistance of a sample to material deformation due to a constant compression load from a sharp object. Tests for indentation hardness are primarily used in engineering and metallurgy . The tests work on the basic premise of measuring

2550-414: The vertical portion of the curves, small measurement errors will produce large hardness deviations. The main sources of error with indentation tests are poor technique, poor calibration of the equipment, and 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

2601-613: Was finished by Bulychev, Alekhin, Shorshorov in the 1970s, who determined that Young's modulus of a material can be determined from the slope of a force vs. displacement indentation curve as: Where E s {\displaystyle E_{s}} and ν s {\displaystyle \nu _{s}} are the Young's modulus and Poisson's ratio of the sample, an E i {\displaystyle E_{i}} and ν i {\displaystyle \nu _{i}} are that of

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