Temperature-Dependence of Mechanical Properties

The torsional vibration test according to DIN 53445 is used to investigate temperature-dependent viscoelastic material behavior. This is a short-term test. The time-to-mpture test according to DIN 53444 registers the influence of stress duration, stress type, and temperature. The torsional vibration test provides additional information on the damping behavior of the plastics tested (mechanical loss or damping factor d). Fig. 13 [9]. 

Knowledge of the processes that take place in the transitional phase between the defined states  

Impact strength can be increased by mixing plastics with higher glass transitimi temperatures and plastics with lower glass transiticm temperatures. The same thing applies to polymerization with suitable comonomers, see Sect 1.1. 

The energy elastic range and glass transition point are succeeded, as the temper-atiue rises, by the entropy elastic (soft or viscoelastic) range, i.e., the application range for polyolefins. 

For comparisOTi with the shear modulus curves in Fig. 13 for plastics. Fig. 14 shows the temperature-dependence of the modulus of elasticity of some metallic materials [91]. The properties also show pronounced temperature-dependent changes, but only within the 1,000-1,500 °C range. The data for iron (Fe) reflect 

---

Softening as a result of micro-Brownian motion occurs in amorphous and crystalline polymers, even if they are crosslinked. However, there are characteristic differences in the temperature-dependence of mechanical properties like hardness, elastic modulus, or mechanic strength when different classes of polymers change into the molten state. In amorphous, non-crosslinked polymers, raise of temperature to values above results in a decrease of viscosity until the material starts to flow. Parallel to this softening the elastic modulus and the strength decrease (see Fig. 1.9). 

It was noted above, that the as-cast eutectic alloys of binary Ti-Si system have no appreciable plasticity at room temperature. Alloying with aluminum, zirconium and use of various modifiers has also not allowed appreciable RT plasticity to be obtained. Data on temperature dependence of mechanical properties of deformed alloys of system Ti-3A1 6Zr-(2-6) Si show that, in contrast to as-cast alloys, deformed state with about 2 % Si demonstrate high plasticity ( 4%) reducing to 1.8 % in alloy with 6-wt.% Si. At the same time high-temperature strength of these alloys are practically the same, at 540-560 MPa level (600 °C). In such a way there is no reason to increase silicon content higher 2-wt.% in deformed state. 

Fig. 10. Temperature dependences of mechanical properties of superconducting Cu-plated Ti-40Nb and Ti-50Nb cables.

M. Oshima, R. Sato, F. Hayashi and W. Koyanagi Thermal properties and temperature dependency of mechanical properties of resin concretes for structural use. in Proceedings of the 10th International Congress on Polymers in Concrete (CD-ROM), Department of Civil Engineering, The University of Texas at Austin, Austin, Texas (2001). 

Only two sources of data for the temperature dependence of mechanical properties of samarium were found. The data are shown in figs. 8.28 and 8.29. 

Environmental conditions such as ambient humidity [48], temperature [49], and UV radiation [50] aU affect the mechanical properties of native siUc. In particular, the two unusual properties of spider draghne silk, supercontraction and temperature dependence of mechanical properties, are briefly reviewed in this section. 

In addition to the temperature dependence of the properties such as strength and modulus, which we will discuss individually for each material class, there are two fundamental topics that are often described in the context of heat transfer properties or thermodynamics of materials—for example, thermal conductivity or specific heat—but are related more to mechanical properties because they involve dimensional changes. These two properties, thermoelasticity and thermal expansion, are closely related, but will be described separately. 

The temperature dependences of optical properties of organic conductors beyond the phase-transition region have not been investigated sufficiently so far. The quantitative temperature studies of the e-mv coupling are very difficult and possible only for some selected low-dimensional salts. It was shown [94,95] that an analysis of T dependence of the IR spectra of the salts composed of isolated dimers (TCNQ)2- makes it possible to pinpoint the main mechanisms responsible for thermal evolution of the IR spectra and changes in the absorption coefficients. Among other things it was... 

The typical dependence of mechanical properties of Ti-Si binary alloys in as-cast and as-deformed states is shown in Fig. 3. It is seen that in as-cast state room temperature plasticity decreases with increase of silicon content, reducing practically to zero at silicon content of 2-3 wt. % then it raises a little at eutectic formation. Unfortunately, our attempts to increase room temperature plasticity in as-cast condition more or less substantially via employing various kinds of heat treatment procedures were not successful. At the same time, using thermo-mechanical treatment (forging at temperature 1050 °C), it was possible to increase plasticity of deformed alloys essentially. 

There are fundamental interrelationships, as well as significant differences, between the physical factors which determine the magnitudes of the elastic and viscous components of the three types of mechanical moduli, and of the corresponding electrical quantities. The definitive identification of these interrelationships and differences, and their embodiment in simple and reliable predictive equations, are areas of ongoing research in fundamental polymer physics. We will, therefore, only deal with the real-valued properties E, G, B and v, which are equivalent to the elastic (real) components E, G, B and v of the corresponding complex quantities. Furthermore, only the temperature dependences of these properties will be discussed in detail. The calculated values of these properties will therefore correspond to measurements made under "typical" testing conditions, with commonly used strain rates for each type of test. 

Fig. 3.1-67 Dependence of mechanical properties of naturally aged G-AlCu4TiMg casting alloy on the maximum solution treatment temperature (1) Step annealing (2) Single step annealing...

Although the frequency can be varied somewhat by changing the moment of inertia of the oscillating portion of the mechanism, torsion pendulums are usually intended to study only the temperature dependence of dynamic properties at a constant, relatively low frequency ( 1 cycle/s). On the other hand, they are inexpensive and rather simple to constmct. 

---