Test specimen cross-section

Figure 5. All test pieces were cut from the billet in the same orientation. The test specimen cross section plane is parallel to the direction of hot pressing. The small arrows on the cross section planes show the direction of crack propagation. The fraeture toughness is certified only for crack planes parallel to the hot pressing direction.

It is beyond the scope of this paper to cover all details, but a remarkable interaction between the calculated stress intensity shape factor and the measured crack size was beneficial in mitigating errors or uncertainties in the crack size interpretation or measurements. The stress intensity shape factor for a semi-elliptical surface crack depends upon the precrack depth and width, and the test specimen cross-section size. The Newman-Raju stress intensity factors (Y) for surface cracks in beams in bending were used in accordance with C1421. For the SRM test specimen geometries, it was discovered that a slight measurement error of the precrack size (depth or width) was offset by a compensating error in the computed Y factor. That is to say, a+10 % error in a precrack depth measurement also led to a — 5 % error in the calculated stress intensity shape factor. The computed fracture toughness depends upon the square root of the crack size and linearly with the Y factor. 

Several additional, non-microstructural, inputs are required for the fracture model (i) Particle critical stress intensity factor, KIc. Here, the value determined in a previous study (Klc = 0.285 MPa in )[3] was adopted for all four graphites studied. This value is significantly less than the bulk Klc of graphites (typically -0.8-1.2 MPa rn). However, as discussed in the previous section, when considering fracture occurring in volumes commensurate in size with the process zone a reduced value of Klc is appropriate (ii) the specimen volume, taken to be the stressed volume of the ASTM tensile test specimens specimen used to determine the tensile strength distributions and (iii) the specimen breadth, b, of a square section specimen. For cylindrical specimens, such as those used here, an equivalent breadth is calculated such that the specimen cross sectional area is identical, i.e.,... 

For a tensile test or a compressive test, the cross-sectional area (width X thickness) of the specimen should be determined. Stress is the ratio of the load (P) to the cross-sectional area (A) ... 

Thus, tensile strength = maximum force in tensile test/original cross-sectional area of specimen. 

Textured geomembranes are tested in BAM under the following conditions. The test stress produced by the continuously acting, steady tensile force (range of variation 1 %) is 4 N/mm (4 MPa). The specimen cross-section area is calculated from the specimen width at the narrowest place and the core thickness of the textured geomembrane. The test temperature is adjusted to (80 1) °C. A mixture of deionised water and 2 % by mass of Marlophen 812 surfactant is used as a test liquid which is renewed be-... 

Figure 6.20 (a) Variation of the tninitnum specimen cross-section during an intermpted creep test (steel grade 91, 350 MPa, 500°C). Measnrement (b) schematic decomposition of the specimen during necking in three cylindrical segments, each with uniform radius [10]. 

The tests were carried out on prismatic specimens 150 mm long, 60 mm wide and 50 mm thick, with saw-cuts 5 mm deep and 5 mm wide on both sides. The geometry of the specimens was selected in order to guarantee a uniform distribution of the deformation within the specimen cross-sections. They were sawed out of 50 mm thick panels casted in a battery mould. Curying conditions were as follows after 2 days the mould was stripped and the panels were stored under water for 13 days, then cut to the proper dimensions and dried in the laboratory up to the... 

Calibration procedure bases on rope specimens and corresponds to the Standard Pratice ASTM 1574. It takes a piece of the rope under test having a nominal metallic cross-section area (LMA=0) to set zero point of the instrument. Rope section with the LMA value known is used to set the second point of LMA calibration charactiristics. It is possible to use the air point calibration when there is no rope in a magnetic head (LMA=100%). 

Tunnel Test. The tunnel test is widely used to test the flame spread potential of building products such as electrical cable (15) and wall coverings (16). The test apparatus consists of a tunnel 7.62 x 0.445 m x 0.305 m ia cross section, one end of which contains two gas burners. The total heat suppHed by the burners is 5.3 MJ/min. The test specimen (7.62 m x 50.8 cm), attached to the ceiling, is exposed to the gas flames for 10 minutes while the maximum flame spread, temperature, and smoke evolved are measured. The use of this and other flame spread test methods has been reviewed (17). 

Ra.m Tensile. A ram tensile test has been developed to evaluate the bond-2one tensile strength of explosion-bonded composites. The specimen is designed to subject the bonded interface to a pure tensile load. The cross-section area of the specimen is the area of the aimulus between the outer and inner diameters of the specimen. The specimen typically has a very short tensile gauge length and is constmcted so as to cause failure at the bonded interface. The ultimate tensile strength and relative ductihty of the explosion-bonded interface can be obtained by this technique. 

Sketch curves of the nominal stress against nominal strain obtained from tensile tests on (a) a typical ductile material, (b) a typical non-ductile material. The following data were obtained in a tensile test on a specimen with 50 mm gauge length and a cross-sectional area of 160 mm. ... 

Dead-weight loading (with or without the assistance of levers to reduce the load requirements) of tensile specimens has the advantage of avoiding some of the difficulties already discussed, not the least in allowing accurate determination of the stress if the specimen is uniaxially loaded. The relatively massive machinery usually required for such tests upon specimens of appreciable cross section is sometimes circumvented by the use of a... 

The equipment required for slow strain-rate testing is simply a device that permits a selection of deflection rates whilst being powerful enough to cope with the loads generated. Plain or precracked specimens in tension may be used but if the cross-section of these needs to be large or the loads high for any reason, cantilever bend specimens with the beam deflected at appropriate rates may be used. It is important to appreciate that the same deflection rate does not produce the same response in all systems and that the rate has to be chosen in relation to the particular system studied (see Section 8.1). 

In calculating the strength properties of the corroded specimens and comparing them with those of the uncorroded control specimens after appropriate mechanical tests, it will be necessary to take into account the actual area of the cross-section of the corroded metal and report results on this basis instead of, or as well as, on the basis of the original cross-section prior to exposure such as would be represented by the uncorroded control specimens. 

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