Tangent modulus of elasticity. Instantaneous rate of change of stress as a function of strain. It is the slope at any point on a stress-strain diagram.

Tear length. Measure of the drawability of sheet metal. Two small parallel slots are cut in the edge of the sheet to form a tab which is gripped and torn from the sheet. The variation in length of tabs torn in different directions is an indication of crystal orientation in the sheet. (Tabs torn in the direction of orientation are longer.) The degree of orientation is an indication of difficulty to be expected in drawing the sheet to uniform shapes.

Tear resistance. Measure of the ability of sheet or film materials to resist tearing. For paper it is the force required to tear a single ply of paper after the tear has been started. (ASTM D-689). Three standard methods are available for determining tear resistance of plastic films: ASTM D-1004 details a method for determining tear resistance at low rates of loading. A test in ASTM D-1922 measures the force required to propagate a pre-cut slit across the sheet specimen. ASTM D-1038 gives a method for determining tear propagation resistance that is recommended for specification acceptance testing only. Tear resistance of rubber is the force required to tear a 1 in. thick specimen under the conditions outlined in ASTM D-624. Tear resistance of textiles is the force required to propagate a single-rip tongue-type tear (starting from a cut) by means of a falling pendulum apparatus. (ASTM D-1424).

Tearing strength. Tensile force required to rupture a pre-slit woven fabric specimen under the conditions out-lined in ASTM D-2261 and ASTM D-2262. Edge tearing strength of paper is the force required to tear a specimen folded over a V-notch and loaded in a tensile test machine. (ASTM D-827).

Temper test. Method for measuring the ability of strip or sheet metal to recover its original shape after bending. Temper of strip and sheet metals for electronic devices is measured by clamping a rectangular specimen in a rotatable clamp, bending it and recording the angle of spring-back. (ASTM F-155). To determine temper of zinc strip, a rectangular specimen is clamped in a rotating mandrel, pressed against the mandrel and released. Spring back is reported in a scale based on the apparatus used. (ASTM B-69).

Tenacity. Force required to break a yarn or filament expressed in grams per denier. It is equal to breaking strength divided by denier.

Tensile impact energy. Energy required to break a plastic specimen in tension by a single swing of a calibrated pendulum. (ASTM D-1822). It is a measure of impact strength obtained in a tension impact test.

Tensile modulus of elasticity. Tangent or secant modulus of elasticity of a material subjected to tensile loading. Alternate terms are Young's modulus and modulus of elasticity in tension. It can be measured in a tension test or in a dynamic test where it is related to resonant frequency of a cylindrical rod by the equation: E = 412 12 p f2/k2 j4 where E is modulus of elasticity; 1, length of the rod; p, density; f, resonant frequency; k, radius of gyration of the rod about an axis normal to the rod axis and plane of motion (d/4 for cylindrical rods) and j, a constant dependent on the mode of vibration. Tensile modulus of elasticity is approximately equal to compressive modulus of elasticity within the proportional limit. An alternate term is Young's modulus.

Tensile strength. Ultimate strength of a material subjected to tensile loading. It is the maximum stress developed in a material in a tension test.

Tension impact test. Method for determining energy required to fracture a specimen under shock tensile loading. (ASTM D-1822).

Tension set. Extent to which vulcanized rubber is permanently deformed after being stretched a specified amount for a short time. It is expressed as % of original length or distance between gage marks (ASTM D-412).

Tension test. Method for determining behavior of materials under axial stretch loading. Data from test are used to determine elastic limit, elongation, modulus of elasticity, proportional limit, reduction in area, tensile strength, yield point, yield strength and other tensile properties. Tension tests at elevated temperatures provide creep data.

Procedures for tension tests of metals are given in ASTM E-8, ASTM E-150 (creep tension tests) and ASTM E-151 (elevated temperatures). Methods for tension tests of plastics are outlined in ASTM D 638, ASTM D-2289 (high strain rates), ASTM D-882 and ASTM D 1923 (thin sheets) and ASTM D 795 (high and low temperatures). ASTM D-2343 outlines a method for tension testing of glass fibers; ASTM D-897, adhesives; ASTM D-987, paper products; ASTM D 412, vulcanized rubber.

Thermal stress. Internal stress in part caused by uneven heating.

Time for rupture. Time required to rupture specimen under constant stress and temperature in a creep test.

Torque twist diagram. Graph of torque vs torsional deformation plotted from data obtained in a torsion test.

Torsion resistance. Measure of the resistance to cracking of porcelain enamel coatings on an iron or steel substrate when the base metal is twisted. (ASTM D-409).

Torsion test. Method for determining behavior of materials subjected to twisting loads. Data from torsion test is used to construct a stress strain diagram and to determine elastic limit, torsional modulus of elasticity, modulus of rupture in torsion and torsional strength. Shear properties are often determined in a torsion test. (ASTM E-143).

Torsional deformation. Angular displacement of specimen caused by a specified torque in torsion test. It is equal to the angular twist (radians) divided by gage length (in.).

Torsional modulus of elasticity. Modulus of elasticity of material subjected to twist loading. It is approximately equal to shear modulus and also is called modulus of rigidity.

Torsional strain. Strain corresponding to a specified torque in the torsion test. It is equal to torsional deformation multiplied by the radius of the specimen.

Torsional strength. Measure of the ability of a material to withstand a twisting load. It is the ultimate strength of a material subjected to torsional loading, and is the maximum torsional stress that a material sustains before rupture. Alternate terms are modulus of rupture and shear strength.

Torsional stress. Shear stress developed in a material subjected to a specified torque in torsion test. It is calculated by the equation: s = Tr/J where T is torque, r is the distance from the axis of twist to the outer most fiber of the specimen and J is the polar moment of inertia

Torsional Yield strength. Yield strength of material under twist loading.

Toughness. Extent to which a material absorbs energy without fracture. It is usually expressed as energy absorbed in an impact test. The area under a stress-strain diagram also is a measure of toughness of a material. (ASTM D-256, plastics and ASTM E-23, metals).

Transition temperature. Alternate term for ductile-to-brittle transition temperature.

Transverse bend test. Alternate term for flexure test, often used in connection with cast iron.

True strain. Instantaneous % change in length of specimen in mechanical test. It is equal to the natural logarithm of the ratio of length at any instant to original length.

True stress. Applied load divided by actual area of the cross section through which load operates. It takes into account the change in cross section that occurs with changing load.

Twisting test. Method for measuring shear properties of structural materials. (ASTM E-143).