Mechanical properties of samples

Scanning acoustic microscopy (SAM) is a relatively new technique which broke through in the mid-seventies and was commercialized recently. The SAM uses sound to create visual images of variations in the mechanical properties of samples. The ability of acoustic waves to penetrate optically opaque materials makes it possible to provide surface or subsurface stmctural images nondestmctively, which might... 

Figure 5. Dynamic-mechanical properties of samples of CPVC C8 ana its blends (E13) with 15% pure PVC. C8 = 67.8% chlorine, E13 = 65.7% chlorine.

It is clear that the anomalies in the mechanical properties of samples from low T compared with samples obtained at high Tcure are not due to their chemical differences (concentration of unreacted groups). 

Throughout a puncture test, mechanical properties of samples with different moisture content were analyzed. Parameters obtained from these curves were the maximum force required to break the sample (Fmax)/ distance at this point (d) and the ratio force-distance at the break point. The ratio force-distance at the break point (Fmax/rf) is related to the product resistance to fracture or sample firmness (Prothon et al., 2001). The ratio Fmax/d has been represented vs. the moisture content in Figure 63.3, showing a sigmoid relationship, also typical in crispy products (Peleg, 1994). This behavior indicates a decrease from the resistance to deformation with the increment in moisture product content, as a consequence of the plasticizing effect of water. The ratio was adjusted to the Fermi s model... 

Table 1. Mechanical properties of samples cut out from the Ti-64 SMC billet...

Fig.l2. Effects of crystallization temperature on mechanical properties of sample Z15... 

Figure 2. The mechanical properties of samples with different carbon fiber content...

The impact experiments of anthracite and limestone samples were conducted by using 4>50 mm split Hopkinson pressure bar (SHPB) experiment system, the dynamic mechanical properties of samples are analyzed under impact loading. Finally, the relationship between the dissipation energy and impact velocity is studied. The main conclusions are as follows. 

It is further noted that a low-melting polymer could be generated from the reaction of Af-lrimethylsilyl 5-trichloroborazine with excess of hexamethyldisilazane (Eq. 14.12) when the sample is exposed to liquid ammonia. A foamy white solid is obtained and could be hand drawn to form green fibers, but no information is provided on the mechanical properties of samples [47]. 

The performed experiments have shown the quality of constructed holograms to be strongly affected by physical and mechanical properties of samples, which are determined by their hardness, and the most important holographic characteristic, determined by synthesis conditions for medium samples, to be the dependence of diffraction efficiency, of recorded holograms on post-exposure warm-up time. The data given on Fig. 8a, curve 1, show a typical dependence, which is specific for optimal synthesis conditions and can be approximated with two straight lines, as shown on the figure (dashed line). 

The mechanical properties of samples produced by pressure filtration were examined using the MTS in axial compression and the RMS in torsion. In the MTS, the samples were found to flow slightly to relieve the applied pressure, and the elastic modulus was found to increase with increasing strain. In the RMS, the platens slipped on the pellet surface preventing good measuiements, although a lower bound on the torsion modulus can be estimated from the small displacement data. Work is underway to increase the friction between the platen and the samples. 

The behaviour of the mechanical properties of sample 82 is quite unique (Fig. 5.30). The decline in OIT of this sample is accompanied by a continuous decline of its mechanical strength and of the melt mass-flow rate over several years. However, the elongation at break is still far above the yield point (see Fig. 5.24 for the stress-strain curves). The MFR (190/5) and MFR (190/21.6) decreased from 1.4g/10min and 27 g/lOmin (initial values) to 0.9g/10min and 25g/10min (at 982 d) and then increased to 1.5 g/lOmin and 37 g/lOmin (at 2147 d) (Table 5.6). After about 6 years test time the OIT value has dropped below the detection limit both at... 

Knappe and Kress investigated the influence of repeated injection molding on the mechanical properties of samples for many different thermoplastics (Table 2.6) [32]. Similar experiments have also been performed by Shishova [33] and by Akutin and their co-workers [34] on polypropylene and polycarbonate, respectively, where decreases in tensile properties were found with repeated processing. Similar effects have also been reported during mixing of polyolefin melts in different equipment [30]. 

The solid mechanical properties of samples in simply supported 3-point bending mode were determined using a TA Instruments RSA 3. Temperature sweeps were performed by subjecting the samples to a pretension of 10 g and a strain of 0.01% was apphed. The strains were selected such that they were within the LVE r ime throughout the temperature sweq). 

The radiation and temperature dependent mechanical properties of viscoelastic materials (modulus and loss) are of great interest throughout the plastics, polymer, and rubber from initial design to routine production. There are a number of laboratory research instruments are available to determine these properties. All these hardness tests conducted on polymeric materials involve the penetration of the sample under consideration by loaded spheres or other geometric shapes [1]. Most of these tests are to some extent arbitrary because the penetration of an indenter into viscoelastic material increases with time. For example, standard durometer test (the "Shore A") is widely used to measure the static "hardness" or resistance to indentation. However, it does not measure basic material properties, and its results depend on the specimen geometry (it is difficult to make available the identity of the initial position of the devices on cylinder or spherical surfaces while measuring) and test conditions, and some arbitrary time must be selected to compare different materials. 

The kinetic nature of the glass transition should be clear from the last chapter, where we first identified this transition by a change in the mechanical properties of a sample in very rapid deformations. In that chapter we concluded that molecular motion could simply not keep up with these high-frequency deformations. The complementarity between time and temperature enters the picture in this way. At lower temperatures the motion of molecules becomes more sluggish and equivalent effects on mechanical properties are produced by cooling as by frequency variations. We shall return to an examination of this time-temperature equivalency in Sec. 4.10. First, however, it will be profitable to consider the possibility of a thermodynamic description of the transition which occurs at Tg. 

Dynamic mechanical analysis provides a useful technique to study the cure kinetics and high temperature mechanical properties of phenoHc resins. The volatile components of the resin do not affect the scan or limit the temperature range of the experiment. However, uncured samples must be... 

The mechanical properties of polystyrene depend to some extent on the nature of the polymer (e.g. its molecular weight), on the method of preparing the sample for testing and on the method of test, as is the case with all plastics materials. 

Table 4 Processing Condition and Mechanical Properties of PC-TLCP Composite Samples Injection Molded...

Table 4 also reports dependence of the mechanical tensile properties of the samples on the processing conditions. The highest tensile properties of sample 1, injection molded with a lower melt temperature and a lower volume flux, are attributed to the highest degree of fibrillation of the TLCP fibers, as shown in Fig. 12, by so-called in situ reinforcement. 

Edwards e/a/. carried out controlled potential, slow strain-rate tests on Zimaloy (a cobalt-chromium-molybdenum implant alloy) in Ringer s solution at 37°C and showed that hydrogen absorption may degrade the mechanical properties of the alloy. Potentials were controlled so that the tensile sample was either cathodic or anodic with respect to the metal s free corrosion potential. Hydrogen was generated on the sample surface when the specimen was cathodic, and dissolution of the sample was encouraged when the sample was anodic. The results of these controlled potential tests showed no susceptibility of this alloy to SCC at anodic potentials. 

Usually, crystallization of flexible-chain polymers from undeformed solutions and melts involves chain folding. Spherulite structures without a preferred orientation are generally formed. The structure of the sample as a whole is isotropic it is a system with a large number of folded-chain crystals distributed in an amorphous matrix and connected by a small number of tie chains (and an even smaller number of strained chains called loaded chains). In this case, the mechanical properties of polymer materials are determined by the small number of these ties and, hence, the tensile strength and elastic moduli of these polymers are not high. 

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