TENSILE PROPERTIES Subject

NOTE Good design practice should be followed in the selection of fabrication methods, welding procedures, and materials for vendor-furnished steel pressureretalning parts that may be subject to temperatures below the ductile-brittle transition temperature. The published design-allowable stresses for metallic materials in internationally recognised standards such as the ASME Code and ANSI standards are based on minimum tensile properties. Some standards do not differentiate between rimmed, semi-killed, fully killed hot-rolled and normalised material, nor do they take into account whether materials were produced under fine- or course-grain practices. The vendor should exercise caution in the selection of materials intended for services between 0 °C (-20 °F) and 40 °C (100 °F). 

Scientists (Ref 12) welded HSLA-65 using tungsten-base tools. Subjected to bend tests, a 10 mm (0.4 in.) thick weld passed, and a 6 mm (0.24 in.) thick weld failed when bent with the root in tension, due to the formation of surface cracks. Tensile properties of the 10 mm thick welds exceeded the specifications for the base metal. Some 6 mm thick welds exceeded the plate specifications, while others were approximately 10% below the plate specifications. Charpy V-notch (CVN) toughness at both -29 and 0 °C (-20 and 0 °F) were below the base material toughness but exceeded the minimum specification of the plate. The surface of the welded material was found to have small defects due to the roughness caused by the interaction between the shoulder and the surface of the plate. Salt spray corrosion tests indicated no preference for corrosion in the weld zone. 

As noted in sections 6.1 and 7.1.6, the results derived from the DMTA measurements were rather less satisfactory than for hardness and tensile properties. In consequence, the predictions made are subject to even more uncertainty. Predictions were obtained in only 32% of cases and a number of these would appear highly suspect. The problem is a combination of the degree of change being relatively small in the majority of cases and the degree of scatter in the results. 

As reviewed, the mechanical properties of centrifugally molded pipe and 55° filament wound pipe are much more resin dependent than typical custom engineered pipe. With centrifugally cast pipe, the tensile properties are very resin dependent because the fibers are chopped into relatively short lengths. It is subjected to creep and time-loss of mechanical properties. In addition, resin properties drop radically with temperature especially near the glass transition temperature. 

The resistance to stretch is of particular interest with respect to the tensile properties. From previous sections, it will be appreciated that although the filter fabrics are rarely subjected to forces that will result in tensile failure, they may suffer a degree of stretch that could have serious consequences. The resistance to stretch at relatively low loads (e.g. less than lOON per 5 cm width) is therefore of particular importance from a control point of view. Furthermore, since this phenomenon is temperature related, the ability to carry out such measurements at elevated temperatures is also a useful asset. 

Evaluation of chemical resistance may establish the potential for extraction of plasticizer incorporated in the material as well as an effect of plasticizer on durability of tested material. The standard contains information on testing chemical resistance with 50 test liquids using two methods immersion test and test under mechanical stress. The list of test liquids includes white oil which may be regarded as the only example of plasticizer among test liquids. Samples of known dimensions and weights are immersed in selected liquids for 168 h at room temperature. Containers are stirred every 24 h. Changes in appearance are recorded and samples can be subjected to mechanical property testing. Tensile properties of immersed samples are most frequently compared with control samples but other mechanical tests may also be used. 

Polyurethane elastomers are known for their high elongation, tensile strength and modulus properties. The combination of these properties provides toughness and durability in fabricated parts. Cast elastomers extended with butanediol can maintain these tensile properties when the use temperature is about 80 C. When these elastomers are subjected to higher temperatures, reduction in the tensile properties are observed due to the weakening of physical bonds in the elastomer. 

Yam Tensile properties Specimens with gauge length of 100 mm were tested after being conditioned in a standard atmosphere for 48 hours. Breaking load [N] and strain [%] in single strand knotted and laced form were determined on yams subjected to tensile testing at 60%/min acconlii to the ASTM D 2101 Standard [3]. 

This method allows the sol-gel siliea NR latex eompound to be moulded into the desired shape. TESPT was eo-mixed with TEOS and eoneentrated NR latex. Ammonia which functioned as base catalyst was added into the concentrated NR latex. The silica-TESPT-NR latex compound was then subjected to heat to complete the sol-gel silica conversion process. The dried sol-gel silica-NR mixture was compounded as per normal mixing procedure. A good dispersion of silica particles of the size between 100 and 500 nm was achieved. Using the two-level factorial design, it was concluded that the mechanical properties, i.e. tensile properties and tear strength, were significantly affected by the TEOS loading. It was also found that the amount of ammonia present in the concentrated latex, i.e. 0.7% (w/w) was sufficient to convert TEOS into silica. 

Another common experience is leakage from flat-bottomed tanks. Prevention requires special attention to the design and fabrication of the bottom knuckle. Gates [76] points out that while the tensile properties of FRP approach those of alloys, the modulus of elasticity is only about 3% of that of steel. Therefore, flat-bottomed vessels should not be subjected to pressure or vacuum. 

Conditioning n. Subjecting a test specimen to standard environmental and/or stress history prior to testing. Several ambient conditioning atmospheres, approved by ISO, are hsted in ASTM specification E 171, and ASTM D 618 provides detailed information on conditioning. Plastics test specimens are usually conditioned at 23°C and 50% RH for several days or more. Test D 638 for tensile properties of plastics specifies not less than 40h.... at these... 

The changes in tensile properties were evaluated using two commercially available sutures Ethicon surgical silk and Mersilene , both in sizes 1/0, 2/0,3/0, and 4/0. Controlled knots were constructed on the device shown in Fig. 12.1, which also illustrates the principle involved. The suture is looped around two posts, set 2" (5 cm) apart. The first two throws are tied in the middle of the front post one end of the suture is clamped securely while the other is subjected to the required tension. The latter was maintained constant for 5 sec, it was then released, the ends undamped, the next throw tied. 

Glass fibre/resin reinforced bars used for the reinforcement of concrete are subject to alkali corrosion by the alkali present in concrete and this is a major cause of deterioration of the tensile properties of reinforced concrete. 

---