DICTIONARY

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Salt Spray Test -
Exposure of a fastener, or a fastener installed in a workpiece to a spray of salt solution to simulate an accelerated exposure to a marine environment. The test is imposed to determine susceptibility of the specimen to forms of corrosion.
Sandwich -
A laminate composed of face sheets bonded to a core. Characterized by a high strength-to-weight ratio.
Satec Stress Rupture Machine -
A testing machine that maintains a constant tensile load on a specimen in conjunction with elevated temperature.
Scale -
The product of oxidation produced on the surface of metals exposed to air or certain gases at high temperatures.
Screw -
A term applied to small bolts which are fully threaded to the head, usually with internal wrenching recesses.
Seal -
A pre-fabricated device used to prevent leakage of fluids or gases in a fastener joint, such as "0" rings, metallic seals, and malleable washers.
Sealant -
An elastomeric substance used to prevent leakage. Usually applied as a viscuous liquid.
Seam -
An unwelded fold or lap in the surface of material.
Set Screw -
An externally threaded fastener that is threaded into an element perpendicular to a shaft or movable segment; when tightened, the point engages the movable member to fix it in relative position.
Shank -
That part of a fastener to which the head is attached.
Shear -
In a structural sense, that type of force which causes or tends to cause adjoining parts to slide relative to each other in a direction parallel to their plane of contact. In a fastened joint, the shear forces are applied at right angles to the sha...
Shear Jig -
A device for applying shear load to a fastener.
Shear Joint -
See Joint
Shear Strength (double) -
The maximum stress that a fastener can withstand when the load is applied in two planes perpendicular to the fastener shank (as in a clevis joint).
Shear Strength (single) -
The maximum stress that a fastener can withstand when the load is applied in a single plane perpendicular to the fastener shank (as in a lap joint).
Sheet Clamping (clampup) -
The capability of a fastener to pull sheets of a workpiece together, closing gaps prior to completion of the fastener installation.
Sheet Separation -
A gap between faying/contacting surfaces of joint members.
Sheet Takeup -
The capability of a fastener to engage separated joint members and bring them together, usually expressed in terms of the separation dimension.
Silver Plate -
An electrolytic method of applying a thin silver coating to fasteners. Will provide some corrosion-resistant properties and high temperature anti-galling characteristics.
Single Element Gage -
A thread gage used in the inspection of threaded fasteners. Checks the individual features of a thread.
Sintering -
Heating compacted metal powders to induce bonding of adjacent surfaces of the particles.
Size Effect -
In bolts, the primary effect in the apparent or real reduction of strength per unit area with the increase in bolt diameter. Caused by the variations in response to cold working, heat treatment, etc.
Skin -
Sheet material, such as aluminum or titanium, which constitutes the outer surface of aircraft. Often preformed to the contour defined by the sub-structure.
Sleeve -
A fastener component of a hollow cylindrical shape which normally deforms during installation.
Sleeve Bolt -
An internally threaded component of panel fastener assemblies which bears shear loads.
Slip -
A process of plastic deformation by the irreversible shear displacement of one part of a metal crystal relative to another.
Slug -
A prepared length of round bar which will be forged into a fastener. Also a rivet which is formed during installation at both ends.
SN Curve -
S-N is an abbreviation for "Stress-number of cycles". An S-N curve is a graphic illustration of the results of fatigue tests conducted at various stress levels.
Solution Heat Treat -
Sonntag Vibration and Fatigue Testing Machines -
Machines which utilize an eccentric rotating mass to apply variable cyclic loading.
Squareness -
In fastener geometry, the relationship of a surface to the truly perpendicular. For example, the bearing surfaces of bolt heads to the bolt axis, nut washer faces to the nut axis, etc. Usually applied to bearing surface squareness.
Squeezer -
A yoke type tool which operates as a press to apply compressive loads. Usually used to upset rivets.
Stainless Steel (CRES) Corrosion Resistant Steel -
A general term used to describe steels alloyed with non-ferrous metals to attain a high degree of corrosion resistance when compared with carbon steels and other alloy steels.
Stamping -
A general term for press operations, such as blanking, shearing, hot and cold forming, drawing, bending, and coining. In fasteners, the term is also applied to identification marking.
Stanley -
A test used to evaluate the vibration resistance of fasteners. The procedure is described in MS26531.
Strain (linear) -
A measure of the extension or deflection of a body, under stress, with reference to its original size. Expressed as change in length per unit length.
Strain Hardening -
An increase in hardness caused by plastic deformation of a material.
Strength, Ultimate -
The maximum conventional stress, tensile, compressive or shear, that a material can withstand.
Stress -
Force per unit area, usually express as Ibs/sq.in.
Stress Concentration -
Local increases in stress caused by changes in contour or structural discontinuities.
Stress Ratio -
In fatigue testing, the ratio of the minimum stress to the maximum stress in one cycle, considering tensile stresses as positive and compressive stresses as negative. Normally designated by "R".
Stress Relieving -
Stress Rupture -
A tension test performed at a constant load and constant elevated temperature to determine ultimate strength limits in a controlled environment.
Strike -
A thin electrodeposit of metal, normally to be followed by other plated coatings. Sometimes used to provide lubrication for in-process forming.
Structural Panel Fastener -
A multi-piece fastener assembly used to provide convenient removal and replacement of access panels in airframe structures. The device is capable of transmitting and sustaining loads comparable to permanently installed fasteners.
Stud -
When installed, the fastener provides a pin protruding from a workpiece for location or attachment; it may be threaded at one or both ends to aid in initial installation or subsequent joining.
Superalloys -
Alloys developed for extreme temperature service where relatively high stresses (tensile, thermal, vibratory, and shock) are encountered and where exceptional oxidation resistance is required.
Sustained Load (test) -
Fastener assembly (bolt and nut) exposed to a predetermined, relatively high preload for a given time. At the conclusion of test, the fastener is examined for cracks.
Swage -
Reforming of metal, normally in a hollow or cylindrical member, by squeezing, hammering, or forging into features of a mating part to provide locking or clamping.


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