Tensile stress tests

The weld factor, which is generally defined as the relation between the strength of the weld and the strength outside the welded zones, determined by tensile stress tests, will give values between 0.7 and... 

The tests used in cereal labs to measure dough properties are similar to those used in industry to test polymers. For example, the extensograph essentially carries out a tensile stress test. An extensograph measurement differs in fhaf if measures force rather than stress and a constant stretching rate is used instead of a constant strain rate. A tensile stress-strain curve is shown in Figure 6.6. In this test, a sample is strained at a constant rate and the stress needed to maintain this strain rate is measured until the point at which it breaks. The peak stress is the ultimate tensile strength. 

Exposure stress is stress at which fracture occurs given time and temperature Tensile stress testing stress to failure Makrolon 6455 Miles Specimen Injection molded tensile bars... 

Fig. 2. Etependence of Wirotest (a) indications as a function of tensile stress, when applying different lengths between the probe and the tested surface.

Mech nic lF tig ue. Some mechanical fatigue tests have been conducted on explosion-clad composites where the plane of maximum tensile stress is placed near the bond 2one (30). 

Definitions of the commonly measured tensile properties are as follows Unear density (tex) is the weight in grams of 1000 m of yam. Tenacity is the tensile stress at break and is expressed in force-per-unit linear density of unstrained specimen, N /tex. Knot tenacity is the tensile stress required to mpture a single strand of yam with an overhand knot tied in the segment of sample between the testing clamps. It is expressed as force-per-unit linear density and is an approximate measure of the britdeness of the yam. Toop tenacity is the tensile stress required to mpture yam when one strand of yam is looped through... 

Test Method for Tensile Stress—Strain of Carbon and Graphite... 

Impact of a thin plate on a sample of interest which is, in turn, backed by a lower impedance window material leads to an interaction of waves which will carry an interior planar region into tension. Spall will ensue if tension exceeds the transient strength of the test sample. A velocity or stress history monitored at the interface indicated in Fig. 8.4 may look as indicated in Fig. 8.5. The velocity (stress) pull-back or undershoot carries information concerning the ability of the test material to support transient tensile stress and, with appropriate interpretation, can provide a reasonable measure of the spall strength of the material. 

The common tests are shown in Fig. 17.2. The obvious one is the simple tensile test (Fig. 17.2a). It measures the stress required to make the longest crack in the sample propagate unstably in the way shown in Fig. 17.3(a). But it is hard to do tensile tests on ceramics - they tend to break in the grips. It is much easier to measure the force required to break a beam in bending (Fig. 17.2b). The maximum tensile stress in the surface of the beam when it breaks is called the modulus of rupture, o for an elastic beam it is related to the maximum moment in the beam, M by... 

In order to test the strength of a ceramic, cylindrical specimens of length 25 mm and diameter 5 mm are put into axial tension. The tensile stress a which causes 50% of the specimens to break is 120 MPa. Cylindrical ceramic components of length 50 mm and diameter 11 mm are required to withstand an axial tensile stress with a survival probability of 99%. Given that m = 5, use eqn. (18.9) to determine oh... 

Answer In the tensile test, the whole volume of the sample is subjected to a tensile stress of 230 MPa. In the bend test, only the lower half of the sample is subjected to a tensile stress. Furthermore, the average value of this tensile stress is considerably less than the peak value of 400 MPa (which is only reached at the underside of the sample beneath the central loading point). The probability of finding a fracture-initiating defect in the small volume subjected to the highest stresses is small. 

Ps = survival probability of component V = volume of component o= tensile stress on component 1/q = volume of test sample (Tq = stress that, when applied to test sample, gives Ps = 1/e (= 0.37) m = Weibull modulus. 

Type of stress. A uniaxial tensile creep test would not be expected to give the required data if the designer was concerned with torsional or compressive creep. 

ASTM C 749-92, "Standard Test Method for Tensile Stress-Strain of Carbon and Graphite". ASTM Standards Vol. 15.01, pp. 196 207, Pub. American Society for Testing of Materials, Philadelphia, USA (1994). 

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