Tensile mode

Stress Intensity Factor K,5cc a fracture toughness parameter used for evaluating susceptibility to stress-corrosion cracking (the subscript I signifies a tensile mode of stressing). 

The fatigue behavior of a material is normally measured in a flexural but also in a tensile mode. Specimens may be deliberately cracked or notched prior to testing, to localize fatigue damage and permit measuring the crack-propagation rate. In constant-deflection amplitude testing a specimen is... 

Autovibron (imass) testing was conducted according to recommended procedures (Autovibron manual). Thin film were tested at a frequency of 11 Hz in a tensile mode. Specimens were scanned from -120°C to +320 C at 2.5 C/min. 

A powder compact s TS is the stress required to separate its constituent particles in tensile mode. This is measured for the tableting indices by transverse compression of the square compacts, using narrow platens. Stresses build within the sample until it fails in a tensile mode that is perpendicular to the direction of platen movement. Tablets that are manufactured on a traditional tablet press and that have high TS are considered hard and generally robust, and so this is a highly desired attribute for immediate release and other tablet types. 

The barrier dressings were tested in tensile mode, adhered at ends, as discussed in Sect. 2.3. These tests provided good relative adhesive values (kPa) for comparing the barrier dressings for their ability to adhere to tissue. 

The fracture properties of thermosets are often very difficult to measure the brittleness of these materials. If a thermoset is tested in uniaxial tensile mode, the stress and strain at break, strain rate, e = df/dt, and also on the sample dimensions (length and cross section). Thus, the parameters intrinsic values of the materials because they depend on the... 

Polyurethanes are occasionally used in the tensile mode. In these applications, the strength and toughness of ester-based materials are superior to those made from ethers. The ultimate elongation of all polyurethanes far exceeds any application, so the choice is not of any major consideration. 

Polyurethanes are more often used in compression or in the shear than in the tensile mode. There are a number of standard tests that may be used. 

Mechanical testing was conducted on samples 25 mm in length, 10 mm in width and 0.1 mm in thickness, Because of the high compliance of the films, it was difficult to mount an extensometer on the samples to measure E. A DMA was therefore used to assess the elastic properties of the composite samples in the tensile mode of loading. A 5 N static tensile load and displacement amplitude of 16 /tm at a frequency of 1 Hz were applied. Nine measurements for each sample were made and the average values are reported here. 

Figure 10.12. Temperature dependence of the storage modulus E and loss modulus E" of different PEEK/SWCNT nanocomposites with 1 wt% CNT content, obtained from DMA measurements performed in the tensile mode at frequency 1 Hz and heating rate of 2°C/min. The inset is a magnification showing the increment in Tg for the nanocomposites. From ref 11.

The temperature dependences of the storage modulus G are given in Figure 12.13 for unfilled and filled EPDM. The dynamic mechanical experiments were conducted from -100 to 150°C at a frequency of 1 Hz in tensile mode using a DMA (TA 2980). Heating rate was 5°C/min. 

The micromechanical deformation behavior of SAN copolymers and rubber-reinforced SAN copolymers have been examined in both compression [102] and in tension [103,104]. Both modes are important, as the geometry of the part in a given application and the nature of the deformation can create either stress state. However, the tensile mode is often viewed as more critical since these materials are more brittle in tension. The tensile properties also depend on temperature as illustrated in Figure 13.6 for a typical SAN copolymer [27]. This resin transforms from a brittle to ductile material under a tensile load between 40 and 60 C. 

In Figure 21.8, a softening temperature for the polystyrene endblock is shown as a function of endblock molecular weight (ranging from about 6000 to 30000). The softening temperature is characterized as the onset of test specimen creep (in a small-strain dynamic mechanical test in tensile mode), the creep point occurring when strain extension becomes considerable in order to maintain the appropriate stress level to continue the test. This softening temperature lies below the measured Tg, and it is an indication of the... 

Under some circumstances, as when unnotched samples of PS are stressed from a maximum to a minimum value in the tensile mode or when notched samples are tested in a similar mode the smooth region near the fracture source show... 

When smooth specimens of PS are cycled at 26.7 Hz in a tensile mode at a maximum stress of 17.2 MPa discontinuous crack growth bands similar to those shown in Fig. 8 are seen in the mirror region near the fracture source. These bands are also similar in morphology to those observed in testing notched PS specimens at a minimum stress that is maintained at one-tenth the maximum stress However, DCG bands were not seen when tests are carried out under a fully reversed stress of 17.2 MPa at... 

Fig. 14a and b. Fatigue fracture surfaces of HIPS tested at 21 Hz in a tensile mode. The maximum stress was 17.2 MPa and the minimum stress was 3.4 MPa a Low magnification scan b High magnification scan... 

Fig. 44a ami b. Fatigue fracture surface of an ABS sample tested at 21 Hz in an alternating tensile mode at a maximum stress of 27,5 MPa and a minimum stress of zero a Low magnification scan b Higher magnification of region near source... 

Cycles to craze breakdown and to fatigue fracture increase significantly upon changing from complete stress reversal to cycling in a tensile mode at the same maximum stress. Buckling of the craze fibrils under compressive stress is conducive to early crack formation within the craze. 

Dynamic mechanical properties were determined with a Polymer Laboratories Dynamic Mechanical Thermal Analyzer (DMTA) using the tensile mode. The fiber length was in all cases 20 mm at an initial 0.5% elongation. The heating rate was set to 5°C/min. Break tenacities were measured on an Instron tensile tester model 1130 using a sample length of 25.4 mm and a strain rate of 0.508 mm/min (0.02 in./min). All reported break-tenacities and moduli are the mean values of four measurements. 

Dynamic Mechanical Spectroscopy. Samples were run in the tensile mode using a Rheometrics Model 605 Mechanical Spectrometer. Temperature scans were run from -160 to 240 C using a strain of 0.15% and a frequency of 1 Hertz. Samples were maintained in a nitrogen atmosphere during testing. 

Characterization. Opacity of a sample was determined from its absorption at 700 nm. Dynamic mechanical characterization was carried out with an automated Rheovibron DDV-IIC (IMASS) in the tensile mode with a heating rate cf 1.5°/min data taken at 11 Hz are reported here. The same sample was used for the entire temperature range of -100° to 150°C. Because of the magnitude of the load cell compliance, properties of our samples in the glassy region below about -40°C were not viewed in any quantitative sense. 

A, 40/60, The lower temi erature maxima t orrespond to the Tg s (obtained in tensile mode), the upper to the Ti s (obtained in shear mode). 

These clamps are employed for the mechanical characterization of both films and fibers in tensile mode. Typically, the top of the film and fiber sample is mounted within the upper (static) portion of the clamp and the bottom section held by the... 

Figure 4. Variation of Tg with rubber content, as determined from dynamic mechanical analysis. The temperature at which tan 8 reached a maximum value was taken as Tg. The experiment was conducted in the tensile mode at a heating rate of 2 °C/min at 5 Hz.

Figure 5. Variation of the maximum value of tan 8 with rubber content Values of tan 8 were obtained using a Seiko DMS 200 dynamic mechanical analyzer in the tensile mode. The heating rate was 2 °C/min at 5 Hz.

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