Compact tension test specimen

Fig. 1. Compact tension test specimen. All dimensions are in millimeters.

Eight compact tension It test specimens and four l/2t compact tension test specimens each of base metal (transverse) and weld metal material are provided to augment the fracture toughness data determined from the precracked Charpy tests. This guantity of specimens is sufficient to determine fracture toughness properties over the range extending from linear elastic to elastic-plastic fracture behavior. 

Tensile test, standard and precracked Charpy impact and l/2t compact tension test specimens are used for determining changes in the strength and static and dynamic toughness properties of the materials due to neutron irradiation. A total of 333 standard Charpy impact, 81 precracked Charpy impact, 60 l/2t compact tension and 36 tensile test specimens are provided. The type and quantity of tests specimens provided for establishing the properties of irradiated materials over the lifetime of the vessel are presented in Table 5.3-3. Compact tension specimens provided for capsule irradiation are precracked prior to insertion to reduce the time required for post irradiation testing. The types and quantity of specimens provided exceed the minimum requirements of ASTM E-185-82. 

A rectangular bar of polymer of thickness B = S mm and width = 20 mm has a central notch of length a = 10 mm. The bar is loaded in a three-point bending test with an 80 mm span, S, at room temperature. The bar fractures when the force applied is 300 N. Calculate (a) Kjc for the polymer and (b) the force needed to fracture in a compact tension test a specimen of dimensions IT = 50 mm, J = 10 mm, having a single-edge sharp crack of = 25 mm. 

The fracture behavior of an acetylene-terminated polyimide has been experimentally investigated. Engineering fracture methods were adapted and applied to small quantities of this material. Miniature compact-tension (CT) specimens were fabricated and subjected to a programmed series of post-cure cycles. Fracture tests were then conducted at room temperature and at several elevated temperatures in a nitrogen purged environment. The fracture toughness was found to vary with temperature and to depend upon post-cure. These Fracture tests clearly discriminate between the specimens resulting from the different cure cycles with only a small investment of material. 

Using a diamond wafering saw, each bar was cut into four equilength rectangles. Holes were then carefully drilled and a central slot with a chevron tip was cut in each rectangle as shown in Figure 2. The chevron tip was then precracked by carefully tapping a razor blade in the slot. It is noted that the specimen is patterned after the ASTM compact tension (CT) specimen used to test metals. 

In mode I compact tension tests, there is a considerable increase in fracture toughness of (3-PP over that of a-PP in certain ranges of temperature and test speed. Figure 11.26(a)-(d) show the variations of Kiq with the crack-tip loading rate, dKIdt, for the a-PP and (3-PP CT specimens tested at various temperatures. The dK/dt is defined as... 

Compact tension tests on PMMA specimens give a value of 325 J m" for Gic at 23°C, for a crosshead speed of 5 mm min". The critical crack tip opening displacement 8, determined using an optical interferometry technique, is 4.2 m. Calculate the surface stress acting on the craze formed ahead of the crack tip. 

In treating adhesives as polymeric materials, it is possible to use Fracture-mechanics test specimens to determine material properties independent of geometry. A typical sample would be the compact tension test-piece, where a sheet of material, typically 6-mm thick and 100-mm square, has a sharp crack inserted in one edge. The sample is then loaded perpendicular to the plane of the crack and the load at which crack propagation... 

Prompted by the success, TOFD measurements were conducted on a fatigue crack in a stainless steel compact tension specimen. Test and system parameters were optimised following the same procedure used for carbon steel specimens. A clear diffracted signal was observed with relatively good SNR and its depth as measured from the time-of-flight measurements matched exactly with the actual depth. 

Fig. 6. Fracture toughness test specimens (a) single-edge notch (b) center notch (c) compact tension and (d) three-point bend. Terms are defined in text.

For comparison, the following relationship has been found for an X70 pipeline steel (slow strain rate test using compact tension specimens with the precrack located in the heat-affected zone of a weld) ... 

An appropriate cure cycle was established based on the results obtained from the thermal analysis and cure rheology studies of the resin and cured BCB bar and dogbone shaped samples were fabricated for testing. Bar shaped specimens had the dimensions of 3.5 x 0.5 X 0.125 and were used to stake compact tension specimens for fracture toughness studies and for dynamic mechanical analysis of a torsion bar. Dogbone shaped specimens for tensile tests had a gauge area of 1 x 0.15 and were approximately 0.040 thick. 

Pig. 1 a and b. Fracture toughness test specimens a three-point bend and b compact tension. Pre-crack length denoted by a. Movement of crosshead is vertical for both... 

Specimen geometry for the compact-tension (CT) test is shown in Fig. 9a. 

Fig. 18 Evolution of the a stress intensity factor, Kc, and the b energy release rate, Gc, for a low flowable and a medium flowable non-nucleated and /S-modified PP. The legend is the same for both parts of the figure. Injection molded specimens tested at 1 ms-1 in three-point bending [78] and compact tension [77] configuration...

Fig. 20 Deformation maps of a a non-nucleated iPP and b its -nucleated homologue (MFR 12dgmin ) for different temperatures and crack tip loading rates as deduced from the fracture surfaces of compact tension specimens. A rough indication of the test speed is provided by the upper scale. Same grades as in Fig. 19...

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