Vi self study exam preparatory note-part 2

Charlie Chong/ Fion Zhang

ASNT Level III VT- Reading 2Pre-Exam Preparatory NotesMy Self Study Notes 2014 August

Reading 2



Pump:

A pump is a device that moves fluids (liquids or gases), or sometimes slurries, by mechanical action. Pumps can be classified into three major groups according to the method they use to move the fluid: direct lift, displacement, and gravity pumps. Pumps operate by some mechanism (typically reciprocating or rotary), and consume energy to perform mechanical work by moving the fluid. Pumps operate via many energy sources, including manual operation, electricity, engines, or wind power, come in many sizes, from microscopic for use in medical applications to large industrial pumps.

Mechanical pumps serve in a wide range of applications such as pumping water from wells, aquarium filtering, pond filtering and aeration, in the car industry for water-cooling and fuel injection, in the energy industry for pumping oil and natural gas or for operating cooling towers. In the medical industry, pumps are used for biochemical processes in developing and manufacturing medicine, and as artificial replacements for body parts, in particular the artificial heart and penile prosthesis.


Dynamic & Displacement Pumpshttp://wiki.answers.com/Q/Differences_between_dynamic_pump_and_positive_displacement_pump

The main difference between them is the way that energy is added to the fluid to be converted to pressure increase. In dynamic pumps, energy is added to the fluid continuously through the rotary motion of the blades. These rotating blades raise the momentum of fluid and the momentum then is converted to pressure energy through diffuser in pump outlet. In positive displacement pumps, the energy is added periodically to the fluid. the pump has reciprocating motion by pistons for example. When the fluid enters the pump through valves, the reciprocating piston begins to press the fluid resulting in going out of the pump with pressure rise.

Type of positive displacement pumps: gear pump, crescent gear pump, axial-piston pump, radial-piston pump, linear-piston pump, & vane pumpAlso, fuel injection pumps such as linear piston pumps and rotary piston pumps.


Centrifugal Pumps

The pump impeller rotates within the pump housing (sometimes called the volute), thus causing a reduced pressure at the inlet (suction) side of the pump. The rotary motion of the impeller drives the fluid to the outside of the pump volute, increasing its pressure, and sending it out of the pump discharge, as shown in the diagram.

Both of these diagrams show a radial flow centrifugal pump, which has the flow pattern just described above. This is the most common centrifugal pump flow pattern. Another alternative is the axial flow centrifugal pump, which has an impeller shaped somewhat like a propeller, that draws fluid in along the pump axis and sends it out along the axis at the other side of the pump.

http://upload.wikimedia.org/wikipedia/commons/6/69/Flexible_impeller_pump.gif


Centrifugal Pump – Displacement pumphttp://en.wikipedia.org/wiki/Pump


Seismic snubbers


Seismic snubbers


Forging: Rolling Defects Hear what the Expert sayhttp://pmpaspeakingofprecision.com/tag/tears/

Miles Free


Forging: Rolled-in-Scales

Pre-rolled scale

Rolled-in-Scale


Scabs


Scabs

Scabs are irregularly shaped, flattened protrusions caused by splash, boiling or other problems from teeming, casting, or conditioning.-AISI Technical Committee on Rod and Bar Mills, Detection, Classification, and Elimination of Rod and Bar Surface Defect

(Teeming refers to the process of filling an ingot mold with molten steel from the ladle. We’ll point out some continuous casting analogs later in this post.)Scabs have scale and irregular surfaces beneath them; they tend to be round or oval shaped and concentrated to only certain blooms or billets. Scabs are always the same chemistry as the steel bloom or billet.(If the gross irregular surface protrusion characteristic is appearing on all product, it is not likely to be a scab. If the protrusion is a different analysis, it is likely to be mill shearing.)To differentiate between scabs and rolled in scale, scabs are ductile when bent while scale is brittle and crumbles.If the protrusion is brittle, it may be rolled in scale.


Scabs


Slivers


Slivers On Rolled Steel Products “Slivers are elongated pieces of metal attached to the base metal at one end only. They normally have been hot worked into the surface and are common to low strength grades which are easily torn, especially grades with high sulfur, lead and copper.”- AISI Technical Committee on Rod and Bar Mills, Detection, Classification, and Elimination of Rod and Bar Surface Defects

Slivers are loose or torn segments of steel that have been rolled into the surface of the bar.

Slivers are often mistaken for shearing, scabs, and laps.






Slivers often originate from short rolled out point defects or defects which were not removed by conditioning.Billet conditioning that results in fins or deep ridges have also been found to cause slivers and should be avoided. Feathering of deep conditioning edges can help to alleviate their occurrence.

Slivers often appeared on mills operating at higher rolling speeds.When the frequency and severity of sliver occurrence varies between heats, grades, or orders, that is a clue that the slivers probably did not originate in the mill. Slivers are often mistaken for shearing, scabs and lap.


Seams On Rolled Steel Products



“Seams are longitudinal crevices that are tight or even closed at the surface, but are not welded shut. They are close to radial in orientation and can originate in steelmaking, primary rolling, or on the bar or rod mill.”- AISI Technical Committee on Rod and Bar Mills, Detection, Classification, and Elimination of Rod and Bar Surface Defects

Seams may be present in the billet due to non-metallic inclusions, cracking, tears, subsurface cracking or porosity. During continuous casting loss of mold level control can promote a host of out of control conditions which can reseal while in the mold but leave a weakened surface. Seam frequency is higher in resulfurized steels compared to non-resulfurized grades. Seams are generally less frequent in fully deoxidized steels.






Seams can be detected visually by eye, and magnaglo methods; electronic means involving eddy current (mag testing or rotobar) can find seams both visible and not visible to the naked eye. Magnaflux methods are generally reserved for billet and bloom inspection.Seams are straight and can vary in length- often the length of several bars-due to elongation of the product (and the initiating imperfection!) during rolling. Bending a bar can reveal the presence of surface defects like seams.An upset test (compressing a short piece of the steel to expand its diameter) will split longitudinally where a seam is present.


“These long, straight, tight, linear defects are the result of gasses or bubbles formed when the steel solidified. Rolling causes these to lengthen as the steel is lengthened. Seams are dark, closed, but not welded”- my 1986 Junior Metallurgist definition taken from my lab notebook. We’ve a bit more sophisticated view of the causes now.

The frequency of seams appearing can help to define the cause. Randomly within a rolling, seams are likely due to incoming billets. A definite pattern to the seams indicates that the seams were likely mill induced- as a result of wrinkling associated with the section geometry. However a pattern related to repetitious conditioning could also testify to billet and conditioning causation-failure to remove the original defect, or associated with a repetitive grinding injury or artifact during conditioning.


My rule of thumb was that if it was straight, longitudinal, and when filed showed up dark against the brighter base metal it was a seam.

Rejection criteria are subject to negotiation with your supplier, as are detection limits for various inspection methods, but remember that since seams can occur anywhere on a rolled product, stock removal allowance is applied on a per side basis.

If you absolutely must be seam free, you should order turned and polished or cold drawn, turned and polished material. The stock removal assures that the seamy outer material has been removed.

Metallurgical note: seams can be a result of propogation of cracks formed when the metal soidifies, changes phase or is hot worked. Billet caused seams generally exhibit more pronounced decarburization.


Laps On Rolled Steel Products

“Laps are longitudinal crevices at least 30 degrees off radial, created by folding over, but not welding material during hot working (rolling). A longitudinal discontinuity in the bar may exist prior to folding over but the defect generally is developed at the mill.”- AISI Technical Committee on Rod and Bar Mills, Detection, Classification, and Elimination of Rod and Bar Surface Defectshttp://pmpaspeakingofprecision.com/2012/05/15/laps-on-rolled-steel-products/


Laps On Rolled Steel Products


Laps: In plain language, a lap is a ‘rolled over condition in a bar where a sharp over fill or fin has been formed and subsequently rolled back into the bar’s surface.’


Laps: An etch of the full section shows what is going on in the mill. Laps were often related to poor section quality on incoming billets, although overfill scratches, conditioning gouges from “chipping” have also been shown to cause laps.


Laps: Laps are often confused with slivers, and mill shearing which we shall describe and post soon. The term ‘lap seam’ is sometimes used, but it is careless usage; it implies the lap is caused by a seam – it is not; a seam is a longitudinally oriented imperfection, and so is used in this mongrel term as a shorthand way of saying ‘longitudinal.’

Modern speakers sometimes try to use the word ‘lamination’ to describe laps but as we will see, not all lamination type imperfections are laps…


Cross section of steel bar exhibiting laps (white angular linear indications). When two laps are present 180 degrees apart, the depth to which they are folded over can indicate where in the rolling the initial over fill ocurred. White indicates decarburization, which confirms my interpretation that this lapping occurred early in the rolling.


Central Bursts, Chevroning in Cold Drawn and Extruded SteelsIn cold worked steels, failures can be broadly categorized in two categories. The first, are those nucleated by localized defects- such as seams, pipe, and exogenous inclusions. The second, are those which result from exceeding the strength of the material itself.

The compressive stresses of cold working results in failures by shear along planes 45 degrees to the applied stress. These are known as shear failures. The presence of shear failures in an otherwise metallurgically normal material indicates excessive mechanical deformation. While often the result of tooling issues, conditions which lower material ductility including chemistry, macrostructure, nonmetallics, microstructure, aging, and hydrogen embrittlement have also been implicated in investigations of premature shear failure.

http://pmpaspeakingofprecision.com/tag/steel-defects/


This post will focus on the central Bursts in the product of cold drawn steel, especially from the point of view of a shop making parts on automated equipment.Ignoring the steel factors that may play a role in triggering the central bursts or chevrons, the role of tooling is usually considered to be the root cause, as replacement of dies typically eliminates the central bursting.A bar which exhibited central bursting was saw cut lengthwise to show the internal ruptures.


Burst- Chevron


Chevron


About Glaring:


Polarization: (also polarisation) is a property of waves that can oscillate with more than one orientation. Electromagnetic waves such as light exhibit polarization, as do some other types of wave, such as gravitational waves. Sound waves in a gas or liquid do not exhibit polarization, since the oscillation is always in the direction the wave travels.

In an electromagnetic wave, both the electric field and magnetic field are oscillating but in different directions; by convention the "polarization" of light refers to the polarization of the electric field. Light which can be approximated as a plane wave in free space or in an isotropic medium propagates as a transverse wave—both the electric and magnetic fields are perpendicular to the wave's direction of travel.

http://upload.wikimedia.org/wikipedia/commons/thumb/4/41/Rising_circular.gif/200px-Rising_circular.gif


About Bolt


Bolt Naming


Bolt Naming


About Photogrammetry


Photogrammetry


Photogrammetry


Photogrammetry


Photogrammetry


Borescope

Objective lens Relay lens Eye pieces


Borescope

Objective lens Relay lens Eye pieces


Borescope


Diffraction

refers to various phenomena which occur when a wave encounters an obstacle or a slit. In classical physics, the diffraction phenomenon is described as the interference of waves according the Huygens Fresnel principle. These characteristic behaviors are exhibited when a wave encounters an obstacle or a slit that is comparable in size to its wavelength. Similar effects occur when a light wave travels through a medium with a varying refractive index, or when a sound wave travels through a medium with varying acoustic impedance. Diffraction occurs with all waves, including sound waves, water waves, and electromagnetic waves such as visible light, X-rays and radio waves.Since physical objects have wave-like properties (at the atomic level), diffraction also occurs with matter and can be studied according to the principles of quantum mechanics. Italian scientist Francesco Maria Grimaldicoined the word "diffraction" and was the first to record accurate observations of the phenomenon in 1660.


Diffraction


Diffraction http://physicshelp.co.uk/images/waves/single-slit.gif


Diffraction


Diffraction


Diffraction


Diffraction


Diffraction


Diffraction


Diffraction


Optical filters

are devices that selectively transmit light of different wavelengths, usually implemented as plane glass or plastic devices in the optical path which are either dyed in the bulk or have interference coatings.

Filters mostly belong to one of two categories. The simplest, physically, is the absorptive filter; interference or dichroic filters can be quite complex.

Optical filters selectively transmit light in a particular range of wavelengths, that is, colours, while blocking the remainder. They can usually pass long wavelengths only (longpass), short wavelengths only (shortpass), or a band of wavelengths, blocking both longer and shorter wavelengths (bandpass). The passband may be narrower or wider; the transition or cutoff between maximal and minimal transmission can be sharp or gradual. There are filters with more complex transmission characteristic, for example with two peaks rather than a single band;[1] these are more usually older designs traditionally used for photography; filters with more regular characteristics are used for scientific and technical work


Optical Filters


Borescope


Item#: E-TS083250-OZ2X Type: Ocular zoom with 1 to 2x adjustable magnification Diameter: 8mm (.236") Working Length: 32cm (12.59") Field of View: 50°Direction of View: Variable Viewing from 45°-115°32 mm diameter standard eyepiece (1.259") Full metal handle Focus adjustment Multilayer coated optical components Removable connectors for compatibility with other brands of light cables Optical systems optimized for each instrument diameter

FEATURES INCLUDEFocusing Ring Scanning Ring: 45° fore-oblique to 115° retrograde direction of view. Viewing arc: 20° fore-oblique to 140° retrograde.Viewing orientation touch indictatorViewing orientation index in the image PVC Case


Level II- NotesMy self Study Notes


About Steel Ingots


Steel Ingots


Steel Ingots


Steel Ingots


Stainless Steel Ingots


Level II Question on Ingot (my mistake)

Q49: An inherent discontinuity associated with the original solidification of metal in the ingot is called:

a) A seamb) Thermal fatiguesc) Hot tear (wrong! )d) Porosity


Ingot Discontinuities

http://products.asminternational.org/fach/data/fullDisplay.do?database=faco&record=2081&trim=false


Ingot Discontinuities

http://www.substech.com/dokuwiki/doku.php?id=structure_of_killed_steel_ingot&DokuWiki=00c51b3aea35614ea05a35fd92dee0c3


Metal – More Reading

http://www.substech.com/dokuwiki/doku.php?id=metals

Metal – More ReadingNondestructive Examination (NDE) Technology and CodesStudent Manual

Chapter 3.0Classification and Interpretation of Indicationshttp://pbadupws.nrc.gov/docs/ML1214/ML12146A174.pdfhttp://pbadupws.nrc.gov/docs/



Bimetallic Thermometer:

A temperature-measuring instrument in which the differential thermal expansion of thin, dissimilar metals, bonded together into a narrow strip and coiled into the shape of a helix or spiral, is used to actuate a pointer. Also known as differential thermometer.

Read more: http://www.answers.com/topic/bimetallic-thermometer#ixzz3BJ3QtCnY


Bimetallic Thermometer:


Hyperthermia is elevated body temperature due to failed thermoregulation that occurs when a body produces or absorbs more heat than it dissipates. Extreme temperature elevation then becomes a medical emergency requiring immediate treatment to prevent disability or death.

The most common causes include heat stroke and adverse reactions to drugs. The former is an acute temperature elevation caused by exposure to excessive heat, or combination of heat and humidity, that overwhelms the heat-regulating mechanisms. The latter is a relatively rare side effect of many drugs, particularly those that affect the central nervous system. Malignant hyperthermia is a rare complication of some types of general anesthesia.

Hyperthermia can also be deliberately induced using drugs or medical devices and may be used in the treatment of some kinds of cancer and other conditions, most commonly in conjunction with radiotherapy.[1]

Hyperthermia differs from fever in that the body's temperature set point remains unchanged. The opposite is hypothermia, which occurs when the temperature drops below that required to maintain normal metabolism.


Hyperthermia Treatment

Sitting in a bathtub of tepid or cool water (immersion method) can remove a significant amount of heat in a relatively short period of time. A recent study using normal volunteers has shown that cooling rates were fastest when the coldest water was used".

In exertional heat stroke, studies have shown that although there are practical limitations, cool water immersion is the most effective cooling technique and the biggest predictor of outcome is degree and duration of hyperthermia. No superior cooling method has been found for non-exertional heat stroke. When the body temperature reaches about 40 °C, or if the affected person is unconscious or showing signs of confusion, hyperthermia is considered a medical emergency that requires treatment in a proper medical facility. In a hospital, more aggressive cooling measures are available, including intravenous hydration, gastric lavage with iced saline, and even hemodialysisto cool the blood.


Photometry & Radioscopy


Photometry is the science of the measurement of light, in terms of its perceived brightness to the human eye.[1] It is distinct from radiometry, which is the science of measurement of radiant energy (including light) in terms of absolute power. In modern photometry, the radiant power at each wavelength is weighted by a luminosity function that models human brightness sensitivity. Typically, this weighting function is the photopic sensitivity function, although the scotopic function or other functions may also be applied in the same way.


In optics, radiometry is a set of techniques for measuring electromagnetic radiation, including visible light. Radiometric techniques characterize the distribution of the radiation's power in space, as opposed to photometric techniques, which characterize the light's interaction with the human eye. Radiometry is distinct from quantum techniques such as photon counting.

Radiometry is important in astronomy, especially radio astronomy, and plays a significant role in Earth remote sensing. The measurement techniques categorized as radiometry in optics are called photometry in some astronomical applications, contrary to the optics usage of the term.

Spectroradiometry is the measurement of absolute radiometric quantities in narrow bands of wavelength


Stroboscope


A stroboscope, also known as a strobe, is an instrument used to make a cyclically moving object appear to be slow-moving, or stationary. The principle is used for the study of rotating, reciprocating, oscillating or vibrating objects. Machine parts and vibrating strings are common examples.

Intense flashing/pulsing light of various frequencies can trigger epileptic seizures in people who suffer from photosensitive epilepsy.


A stroboscope


Photometry & Radiometry: Photometry is the science of the measurement of light, in terms of its perceived brightness to the human eye.It is distinct from radiometry, which is the science of measurement of radiant energy (including light) in terms of absolute power.

In modern photometry, the radiant power at each wavelength is weighted by a luminosity function that models human brightness sensitivity. Typically, this weighting function is the photopic sensitivity function, although the scotopicfunction or other functions may also be applied in the same way.


Photopic (daytime-adapted, black curve) and scotopic (darkness-adapted, green curve) luminosity functions. The photopic includes the CIE 1931 standard (solid), the Judd-Vos 1978 modified data (dashed), and the Sharpe, Stockman, Jagla & Jägle 2005 data (dotted). The horizontal axis is wavelength in nm.

Photopicscotopic


Color

Color or colour (see spelling differences) is the visual perceptual property corresponding in humans to the categories called red, blue, yellow, green and others. Color derives from the spectrum of light (distribution of light power versus wavelength) interacting in the eye with the spectral sensitivities of the light receptors. Because perception of color stems from the varying spectral sensitivity of different types of cone cells in the retina to different parts of the spectrum, colors may be defined and quantified by the degree to which they stimulate these cells. These physical or physiological quantifications of color, however, do not fully explain the psychophysical perception of color appearance.

The science of color is sometimes called chromatics, colorimetry, or simply color science. It includes the perception of color by the human eye and brain, the origin of color in materials, color theory in art, and the physics of electromagnetic radiation in the visible range (that is, what we commonly refer to simply as light).


Color

Additive color is light created by mixing together light of two or more different colors. Red, green, and blue are the additive primary colors normally used in additive color systems such as projectors and computer terminals.


Subtractive coloring uses dyes, inks, and pigments to absorb some wavelengths of light and not others. The color that a surface displays comes from the parts of the visible spectrum that are not absorbed and therefore remain visible. Without pigments or dye, fabric fibers, paint base and paper are usually made of particles that scatter white light (all colors) well in all directions. When a pigment or ink is added, wavelengths are absorbed or "subtracted" from white light, so light of another color reaches the eye.

If the light is not a pure white source (the case of nearly all forms of artificial lighting), the resulting spectrum will appear a slightly different color. Red paint, viewed under blue light, may appear black. Red paint is red because it scatters only the red components of the spectrum. If red paint is illuminated by blue light, it will be absorbed by the red paint, creating the appearance of a black object.


Metallurgical Microscope

An optical microscope that is commonly use on the studies and observation of metals, ceramic and polymeric materials, plastics, minerals, precious stones, alloys and many other substances are known as Metallurgical Microscope. It differs from other microscope because it provides you a closer view on flat and highly polished surfaces like metals.

This type of microscope is often use on Metallography, Archaeometallurgy, Crystallography and Gemology. Metallography is an ocular observation using metallurgical microscope on metal surfaces that can discovers relevant information about crystals, chemicals, minerals and the mechanical composition of the matter.


Metallurgical Microscope


Ocular


Level III- NotesMy self Study Notes


Single Len Magnification

Magnifying glass: The maximum angular magnification (compared to the naked eye) of a magnifying glass depends on how the glass and the object are held, relative to the eye. If the lens is held at a distance from the object such that its front focal point is on the object being viewed, the relaxed eye (focused to infinity) can view the image with angular magnification:

Magnification = 25cm / f = 10 inches/ f

Here, is the focal length of the lens in centimeters. The constant 25 cm is an estimate of the "near point" distance of the eye—the closest distance at which the healthy naked eye can focus. In this case the angular magnification is independent from the distance kept between the eye and the magnifying glass. If instead the lens is held very close to the eye and the object is placed closer to the lens than its focal point so that the observer focuses on the near point, a larger angular magnification can be obtained, approaching:

Magnification = (25cm / f) + 1http://en.wikipedia.org/wiki/Magnification


Single Lens magnification


Astigmatism is an optical defect in which vision is blurred due to the inability of the optics of the eye to focus a point object into a sharp focused image on the retina. This may be due to an irregular or toric curvature of the cornea or lens. The two types of astigmatism are regular and irregular. Irregular astigmatism is often caused by a corneal scar or scattering in the crystalline lens, and cannot be corrected by standard spectacle lenses, but can be corrected by contact lenses. The more common regular astigmatism arising from either the cornea or crystalline lens can be corrected by eyeglasses or toric lenses. A 'toric' surface resembles a section of the surface of a Rugby ball or a doughnut where there are two regular radii, one smaller than the other one. This optical shape gives rise to astigmatism in the eye


Astigmatism- Hyperobia & Myopia

http://optical-casper-wyoming.com/vision/wp-admin/install.php


Farsightedness/ Hyperobia

http://www.lasik.md/learnaboutlasik/refractiveerrors.php#.U_piqZCS3IU


Short Sightedness/ Myopia


About Sampling Terms & Definitions


Acceptance Sampling

Sampling inspection in which decisions are made to accept or reject product.; also the science that deals with procedures by which decisions, dicisions to accept or reject are based on the results of the inspection of samples.

Comment: Typical uses of acceptance sampling in manufacturing include making acceptance decisions about incoming raw materials lots, in-process sub-lots, and finished product lots

Terms & Definitions from:Glossary and Tables for Statistical Quality Control - ASQC

More on Terms & Reference Curveshttp://www.samplingplans.com/glossary.htm


Acceptance Sampling Plan

A specific plan that states the sample size or sizes to be used and the associated acceptance and rejection criteria.

Comment: Most acceptance sampling plans in use are either attributes plans and variables plans.


AOQ curve

Acronym for Average Outgoing Quality. Useful to evaluate sampling plan applications where rejected lots are rectified by replacing or reworking defective items. The AOQ curve is the average quality of outgoing product as a function of the incoming quality.

Comment: AOQ is the quality of an average outgoing lot. Therefore, you should expect half of the lots to be worse than AOQ. The AOQ calculation does not consider that the incoming quality usually varies.


AOQL

Acronym for Average Outgoing Quality Limit. The maximum AOQ over all possible values of incoming product quality, for a given acceptance sampling plan.

Comment: Maximum of the AOQ curve. See AOQ


AQL

Acronym for Acceptable Quality Level. As used in the development of two-point acceptance sampling plans, the values of AQL and alpha jointly define the producers point of the operating characteristic curve.

If the value of a quality characteristic of a particular lot is exactly equal to the AQL of it's acceptance sampling plan, the probability that the plan will accept the lot is (Pa=1-alpha).Example of specifying AQLFor a discussion of common confusions about AQL, see AQL Primer."Glossary and Tables for Statistical Quality Control" - ASQC.


AQL ..continues

Comment: This definition of AQL is statistically exact and appropriate for use with two-point sampling plans, as supported by the software of H & H Servicco Corp.

On the other hand, a more vague definition of AQL is typically used by documents that support one-point sampling plans. The most common of such documents are:

Mil-Std-105,Mil-Std-414,ANSI/ASQC Z1.4,ANSI/ASQC Z1.9

These one-point sampling plans do not make use of the consumer's point -they do not address the issue of accepting low-quality lots. They are particularly vulnerable to this for small sample sizes.


ARL curve

Acronym for Average Run Length. ARL is the average number of accepted lots between rejections. The ARL curve is a plot of ARL as a function of lot quality level.

Comment: Use the ARL curve to assess the impact of an acceptancesampling plan on smoothness operations.


ASN curve

Acronym for Average Sample Number. ASN is the average number of sample units inspected per lot in reaching decisions to accept or reject. The ASN curve is a plot of ASN versus lot quality.

Comment: Use ASN curves to evaluate sequential sampling plans toanticipate the amount of inspection that each plan will require.


Audit sampling

Sampling in which the goal is to estimate the value a quality characteristic but not provide a firm decision rule. The sample size n is chosen to provide a desired margin of error of the estimate.

Comment: Many audit sampling situations involve more than one category, each having a different sample size. The categories having the smaller sample sizes will have estimates with larger margins of error. Conversely, the categories having the larger sample sizes will have estimates with smaller margins of error.


Margin of Error

The sampling error of the estimated statistic. The margin of error is usually expressed as half the the width of a confidence interval.


OC curve

Acronym for Operating Characteristic Curve. A curve showing, for a given sampling plan, the probability of accepting a lot, as a function of the lot quality level. It is knowledge (by the person who designs or selects the plan) of the oc curve that makes an acceptance sampling plan statistically valid.


RQL

Acronym for Rejectable Quality Level. As used in the development of two-point acceptance sampling plans, the values of RQL and beta jointly define the consumers point of the operating characteristic curve.

If the value of a quality characteristic of a particular lot is exactly equal to the RQL of it's acceptance sampling plan, the probability that the plan will accept the lot is (Pa=beta).


Sequential Analysis, Sequential Sampling

The technique by which we build up our sample one item at a time, and after inspecting each item, ask ourselves: "Can we be sure enough to accept or reject this batch on the information so far collected?"

Its value is in enabling reliable conclusions to be wrung from a minimum of data. This was deemed sufficient to require that it be classified "Restricted " within the meaning of the Espionage Act during the war of 1939-45.


Statistically Valid

An acceptance sampling plan is statistically valid when the person who designs or selects it knows the probabilities that the plan will accept lots that were manufactured to various quality levels. These probabilities are shown by the operating characteristic curve

http://www.samplingplans.com/glossary.htm


Birefringence is the optical property of a material having a refractive indexthat depends on the polarization and propagation direction of light.[1] These optically anisotropic materials are said to be birefringent (or birefractive). The birefringence is often quantified as the maximum difference between refractive indices exhibited by the material. Crystals with asymmetric crystal structures are often birefringent, as well as plastics under mechanical stress.

Birefringence is responsible for the phenomenon of double refraction whereby a ray of light, when incident upon a birefringent material, is split by polarization into two rays taking slightly different paths. This effect was first described by the Danish scientist Rasmus Bartholin in 1669, who observed it[2] in calcite, a crystal having one of the strongest birefringences. However it was not until the 19th century that Augustin-Jean Fresnel described the phenomenon in terms of polarization, understanding light as a wave with field components in transverse polarizations (perpendicular to the direction of the wave vector).


About Light & Vision


Birefringence


Blue-light hazard is defined as the potential for a photochemical induced retinal injury resulting from electromagnetic radiation exposure at wavelengths primarily between 400 ~ 500 nm. This has not been shown to occur in humans, only inconclusively in some rodent and primate studies. The mechanisms for photochemical induced retinal injury are caused by the absorption of light by photoreceptors in the eye. Under normal conditions when light hits a photoreceptor, the cell bleaches and becomes useless until it has recovered through a metabolic process called the visual cycle.


Absorption of blue light, however, has been shown in rats and a susceptible strain of mice to cause a reversal of the process where cells become unbleached and responsive again to light before they are ready. At wavelengths of blue light below 430 nm this greatly increases the potential for oxidative damage. For blue-light circadian therapy, harm is minimized by employing blue light at the near-green end of the blue spectrum. 1 ~ 2 min of 408 nm and 25 minutes of 430 nm are sufficient to cause irreversible death of photoreceptors and lesions of the retinal pigment epithelium. The action spectrum of light-sensitive retinal ganglion cells was found to peak at 470 ~ 480 nm, a range with lower damage potential, yet not completely outside the damaging range


Classical interference microscopy (also referred to as quantitative interference microscopy) uses two separate light beams with much greater lateral separation than that used in phase contrast microscopy or in differential interference microscopy (DIC).

In variants of the interference microscope where object and reference beam pass through the same objective, two images are produced of every object (one being the "ghost image"). The two images are separated either laterally within the visual field or at different focal planes, as determined by the optical principles employed. These two images can be a nuisance when they overlap, since they can severely affect the accuracy of mass thickness measurements. Rotation of the preparation may thus be necessary, as in the case of DIC.


About Fillet Weld


Fillet Weld


Convex Fillet Weld= Weld Size – Weld Length


Concave Fillet Weld= Weld Size < Weld Length

Fillet weld measurements: L: Leg length, S: Fillet weld Size, T: Theoretical throat, V: Convexity, C: Concavity, W: Effective weld length


Fillet Weld Legs Determine Size and Throat of Fillet Welds

In heavy machinery, ships, and buildings, extensive frameworks and intricate angles may be composed of many kilometers of welded joints. Among them, fillet welds are used to join corners, Ts. and lap joints because they are more economical than groove welds. That is, fillet welded joints are simple to prepare from the standpoint of edge preparation and fit-up.

The strength of a fillet weld is based, in the design, on the product (effective area of the weld: T x W) of the theoretical throat (design throat thickness) and effective weld length as shown in Fig. 1. Fillet weld legs determine fillet weld sizes. Fillet weld sizes are measured by the length of the legs of the largest right triangle that may be inscribed within the fillet weld cross section.

http://www.kobelco-welding.jp/education-center/abc/ABC_2000-01.html


Fig. 1 - Fillet weld measurements: L: Leg length, S: Fillet weld Size, T: Theoretical throat, V: Convexity, C: Concavity, W: Effective weld length


Fillet weld sizes determine theoretical throat. The product of the size and cos45° in case where an isosceles right triangle may inscribe within the fillet weld cross section: S x cos45° = 0.7S, as shown in Fig. 2.

Fig. 2 — How to calculate theoretical throat


Fillet weld sizes must be large enough to carry the applied load, but the specified fillet weld size should not be excessive to minimize welding distortion and costs. AWS D1.1 (Structural Welding Code- Steel) specifies the minimum fillet weld size for each base metal thickness: e.g. 6-mm size for thickness over 12.7 up to 19.0 mm. AWS D1.1 also specifies the maximum convexity, because excessive convexity may cause stress concentration at the toes of the fillet weld, which may result in premature failure of the joint. In quality control of fillet welds on actual work, leg or size, throat, convexity, and concavity are inspected by using several types of welding gages. Fig. 3 shows a multipurpose gage measuring a fillet weld leg.


Fig. 3 - Measuring a fillet weld leg by means of a multipurpose welding gage



Fastener Failures

http://ipgparts.com/blog/common-failures-for-fasteners-head-studs-main-studs-rod-bolts-etc/#channel=f25869488a334be&origin=http%3A%2F%2Fipgparts.comhttp://ipgparts.com/blog/common-failures-for-fasteners-head-studs-main-studs-rod-bolts-etc/


Photoemissive, Photovoltaic, Photoconductive


Photoemissive

Phototube or photoelectric cell is a type of gas-filled or vacuum tube that is sensitive to light. Such a tube is more correctly called a 'photoemissive cell' to distinguish it from photovoltaic or photoconductive cells. Phototubes were previously more widely used but are now replaced in many applications by solid state photodetectors. The photomultiplier tube is one of the most sensitive light detectors, and is still widely used in physics research.

Operating principles

Phototubes operate according to the photoelectric effect: Incoming photons strike a photocathode, knocking electrons out of its surface, which are attracted to an anode. Thus current flow is dependent on the frequency and intensity of incoming photons. Unlike photomultiplier tubes, no amplification takes place, so the current that flows through the device is typically of the order of a few microamperes.


The light wavelength range over which the device is sensitive depends on the material used for the photoemissive cathode. A caesium-antimony cathode gives a device that is very sensitive in the violet to ultra-violet region with sensitivity falling off to blindness to red light. Caesium on oxidised silver gives a cathode that is most sensitive to infra-red to red light, falling off towards blue, where the sensitivity is low but not zero.

Vacuum devices have a near constant anode current for a given level of illumination relative to anode voltage. Gas filled devices are more sensitive but the frequency response to modulated illumination falls off at lower frequencies compared to the vacuum devices. The frequency response of vacuum devices is generally limited by the transit time of the electrons from cathode to anode.


Photovoltaic

Photovoltaics (PV) is a method of generating electrical power by converting solar radiation into direct current electricity using semiconductors that exhibit the photovoltaic effect. Photovoltaic power generation employs solar panels composed of a number of solar cells containing a photovoltaic material. Solar photovoltaics power generation has long been seen as a clean sustainable energy technology which draws upon the planet’s most plentiful and widely distributed renewable energy source – the sun. The direct conversion of sunlight to electricity occurs without any moving parts or environmental emissions during operation. It is well proven, as photovoltaic systems have now been used for fifty years in specialized applications, and grid-connected systems have been in use for over twenty years


Photoconductivity is an optical and electrical phenomenon in which a material becomes more electrically conductive due to the absorption of electromagnetic radiation such as visible light, ultraviolet light, infrared light, or gamma radiation.

When light is absorbed by a material such as a semiconductor, the number of free electrons and electron holes increases and raises its electrical conductivity. To cause excitation, the light that strikes the semiconductor must have enough energy to raise electrons across the band gap, or to excite the impurities within the band gap. When a bias voltage and a load resistor are used in series with the semiconductor, a voltage drop across the load resistors can be measured when the change in electrical conductivity of the material varies the current flowing through the circuit.

Classic examples of photoconductive materials include the conductive polymer polyvinylcarbazole, used extensively in photocopying (xerography); lead sulfide, used in infrared detection applications, such as the U.S. Sidewinder and Russian Atoll heat-seeking missiles; and selenium, employed in early television and xerography.


The End

Engineering

Vi self study exam preparatory note-part 2