Temperature/time behavior

Figure 3.29 Axial stress-time and temperature time behavior of the SMP foam with a nylon liner at a programming temperature of 79 °C and pre-strain level of 60%. The three steps (step 1 pre-stressing, step 2 cooling and unloading, and step 3 stress recovery) are shown by the three regions and the peak stress, programming stress, and peak recovered stress are indicated using black dots. Source [42] Reproduced...

Pecharsky, Moorman, and Gschneidner (1997) used the temperature-time behavior during the initial drift and the final drift period to automatically... 

Harmonic analysis (normal modes) at given temperature and curvature gives complete time behavior of the system in the harmonic limit [1, 2, 3]. Although the harmonic model may be incomplete because of the contribution of anharmonic terms to the potential energy, it is nevertheless of considerable importance because it serves as a first approximation for which the theory is highly developed. This model is also useful in SISM which uses harmonic analysis. 

At high temperature, the behavior is different. A stmcture designed according to the principles employed for room temperature service continues to deform with time after load apphcation, even though the design data may have been based on tension tests at the temperature of interest. This deformation with time is called creep because the design stresses at which it was first recognized occurred at a relatively low rate. 

The evaluation of ehemieal reaetion hazards involves establishing exothermie aetivity and/or gas evolution that eould give rise to inei-dents. Flowever, sueh evaluation eannot be earried out in isolation or by some simple sequenee of testing. The teehniques employed and the results obtained need to simulate large-seale plant behavior. Adiabatie ealorimeters ean be used to measure the temperature time eurve of selfheating and the induetion time of thermal explosions. The pertinent experimental parameters, whieh allow the data to be determined under speeified eonditions, ean be used to simulate plant situations. 

This book provides a simplified and practical approach to designing with plastics that fundamentally relates to the load, temperature, time, and environment subjected to a product. It will provide the basic behaviors in what to consider when designing plastic products to meet performance and cost requirements. Important aspects are presented such as understanding the advantages of different shapes and how they influence designs. 

The allowable stress for occasional loads of short duration, such as surge, extreme wind, or earthquake, may be taken as the strength reduction factor times 90% of the yield strength at temperature times Mj for materials with ductile behavior. This yield strength shall be as listed in ASME BPV Code Section II, Part D, Table Y-l (ensure materials are suitable for hydrogen service see API 941), or determined in accordance with para. 

A quite different group of experiments is concerned with the investigation of dye lasers themselves, or of lasers based on the photodissociation of molecules. Studies of the time behavior, concentration, or pressure and temperature dependence of fluorescence and... 

Thermal analysis measurements allow the measure of polymer behavior as a function of temperature, time, and atmosphere. DSC or DTA measures change in energy as temperature is changed and allows the determination of many valuable parameters including Tg and T. TGA measures weight changes as a function of temperature. 

Figure 11. Series of LEEM images[31,35] showing a short sequence in the disappearance of islands at a maximum of a 2-D grating on Si(OOl) at 950C the relative annealing times are indicated. At this temperature the behavior of the holes at the minima is essentially the same. Note that the islands are elliptical when separated from the rest of the stack.

For the case of p = 8, the quantum effects of the dynamics become more evident. The CMD method gives the correct short time behavior, but there is a small frequency shift. However, the classical result is much worse at this temperature. 

Figure 3.4 Typical transient response characteristic for hole carrier transport in a-As2Sc3 at room temperature. The behavior is displayed with both linear (a) and logarithmic (b) axes of current and time.

Weakliem, P. C. and Carter, E. A. Constant temperature molecular dynamics simulations of Si(100) and Ge(100) equilibrium structure and short-time behavior. Journal of Chemical Physics 96, 3240 (1992). 

What would happen if the radii of the spheres were made smaller and smaller In general, changes in the magnitude of a parameter (size, temperature, time, velocity, field, etc.) ultimately lead to new phenomena Thus, the engineer knows well that scaling up or scaling down generally results in new modes of behavior. 

The creep of a viscoelastic body or the stress relaxation of an elasacoviscous one is employed in the evaluation of T] and G. In such studies, the long-time behavior of a material at low temperatures resembles the short-time response at high temperatures. A means of superimposing data over a wide range of temperatures has resulted which permits the mechanical behavior of viscoelastic materials to be expressed as a master curve over a reduced time scale covering as much as twenty decades (powers of ten). 

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