Gauge length, standard

Corrosion effect of forming Elongation X gauge length Standard hydropress specimen test True stress-strain curve Uniformity of characteristics... 

Fig. 2. Cellulose acetate stress—strain properties at standard and wet conditions, tested at 60% min extension rate, 3.9 cm gauge length. Sample conditions standard, 21°C, 65% rh wet, 21°C, water wet. To convert N/tex to gf/den, multiply by 11.33.

Tensile moduli were measured from standard dog-bone samples (2.0 mm thickness, 4.7 mm width, and 22.0 mm gauge length) in a Model 1122 Instron. Flexural modulus was determined using a testing apparatus which consists of two aluminium/steel pieces attached to the Instron which is fitted with a tensile load cell. This device effectively performs an inverted three-point bend the two side bars remain stationary above the sample as the central bar below the sample moves upward. Flexural samples measured ca. 52.0 x 1.7 x 13.1 mm and were tested using a 25.4 mm span (distance between the two side bars). Crosshead speed (CHS) for both flexural and tensile testing was 1.0 mm/min. 

Considerable effort has been expended on selecting the best dumb-bell shape and size, particularly by ISO Committee TC45. The type 1 dumb-bell of ISO 37 with a 6 mm wide centre portion and preferably cut from 2 mm thick sheet is very widely used (Figure 8.9) but the type 2 has gained in popularity simply because it is smaller and, hence, uses less material. The relative width of the centre and ends, and the radii where the two join, affect the ease of gripping and the incidence of shoulder breaks, and these standard dumb-bells were selected as the best compromise. However, the type 1A dumb-bell used in Japanese standards has now been introduced because it has been shown to exhibit less frequent breaks outside of the gauge length... 

Mechanical tests were carried out in a laboratory where the temperature was maintained at 25°C using a Universal Testing Machine, LR-50 K (LLOYD Instrument, England) at a crosshead speed of 50 mm/min and 98 mm as gauge length. Stress at break, strain at break, work of rupture, and initial modulus were determined as per ASTM standards. Izod notched impact test specimens were... 

The tensile force per unit area of the original cross-section within the gauge length carried by the test piece at any given moment. The standard unit is mega-Pascal (MPa = MN/m)... 

A great deal can be learned about the mechanical properties of materials by stressing them until they fracture or break. The most common mechanical test involving metals or polymers is the tensile test, in which a sample of the solid is stretched. The test uses a standard test piece with a shape dependent on the material to be tested. Metals usually have a central cylindrical section, of known gauge length. 

The sample is preferably prepared using a lathe and the conically shaped ends fit into specially shaped holders that make the fracture within the gauge marks more probable. The standard speed of test machine jaw separation should be between 3 to 6 minutes to rupture with a suggested rate of cross-head movement set at 1.3 mm minute for each 25.4 mm of test section gauge length. This test method also can be used to determine the tensile adhesion properties. 

The standard requires specimens whose elongation at break is less than 8% to be extended at a rate of 50% per minute. The normal nominal gauge length is 20 mm. Consequently if the fiber extension at break is, say, 3.5% to 4%, the cross-head traverse speed will be lOmm. min. This would result in a time to break of 4.5s, The standard alternatively specifies that if the extension at break is equal to or greater than 8% the elongation rate shall be 100%/minute. Therefore in this case if the extension at break were, say, 10%, the cross-head traverse speed would be 20 mm,/min and the time to break would be 6 s. 

The popular adhesively bonded resistance strain gauges provide an accurate, sensitive means of measuring strain at a point. They can be as small as 0.2 by 0. 1 7 cm with a gauge length of 0.02 cm, and in rosette configuration can measure strain in two perpendicular directions. With proper attention to technique, one can obtain resolutions of 1 or 2 cm/cm, and record strain from static to 20 kHz transient conditions. Accuracy is typically 4% of the measured strain but can be better than 1% with special procedures. Standard gauges may be used at temperatures... 

Specified minimum tensile properties from Aluminum Standards and Data, Aluminum Association, 1976. Tensile Strength = 276MPa (40k i) Yield Strength = 124 MPa (18 ksi) Elongation in 4D = 18% ( ]. t Offset = 0.2% gauge length 50.8 mm (2 in.). 

The tensile properties of the yams listed in Table 7.6 were determined using a Statimat M instrument with a gauge length of 500mm and at a speed of 300mm/min. The average values of 10 specimens (10 tests per cone specimen) tested for each yam are summarised in Table 7.6. The standard deviation is rounded off to the nearest whole number for breaking force, tenacity, and work of mpture. 

Standard sets are available with differing numbers of pieces. A typical set is shown in Fig. 5.2. These sets are identified by a number indicating the number of pieces prefixed by the letter M, to indicate metric sizes, and followed by the number 1 or 2. This latter number refers to a 1 mm-or 2mm-based series, this being the base gauge length of the smaller blocks. For example, an 88 piece set to a 1 mm base is designated M88/1 and contains the sizes shown in Table 5.1. 

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]. 

---