Characteristic material response

The characteristic material response times for molecular reorientation are 10-12 s. Then, in the microwave band, electromagnetic fields lead to rotation of polar molecules or charge redistribution. The corresponding polarization processes are denoted orientation polarization. 

Conventional and highly crosslinked UHMWPE materials exhibit similar qualitative behavior as a result of the underlying similarities of the material microstructures. In this section we examine the behavior of four different UHMWPE materials to illustrate the characteristic material response of UHMWPE. This data will also be used as the basis for the development of material models in the rest of the review. Two of the four materials were conventional UHMWPE and two were highly crosslinked UHMWPE. All materials were created from the same lot of ram-extruded GUR 1050 (Eigure 14.1). 

All described sensor probes scan an edge of the same material to get the characteristic step response of each system. The derivation of this curve (see eq.(4) ) causes the impulse responses. The measurement frequency is 100 kHz, the distance between sensor and structure 0. Chapter 4.2.1. and 4.2.2. compare several sensors and measurement methods and show the importance of the impulse response for the comparison. 

Generally the material response stress versus particle velocity curves in Fig. 8.6 are nonlinear and either a graphical or more complicated analytic method is needed to extract a spall strength, Oj, from the velocity or stress profile. When behavior is nominally linear in the region of interest a characteristic impedance (Z for the window and for the sample) specify material... 

Fig. 2.2. The characteristic stress pulses produced by shock loading differ considerably depending upon the stress range of the loading. The first-order features of the stress pulses can be anticipated from critical features of the stress-volume relation. In the figure, P is the applied pressure and HEL is the Hugoniot elastic limit. Characteristic regimes of materials response can be categorized as elastic, elastic-plastic, or strong shock.

When subjected to a step function loading, solid samples respond in one of the characteristic response modes described in Chap. 2. Often it is desired to investigate materials response to structured loading or even to shear-pulse loading. Both of these loadings can be achieved with the use of an intervening disk of a solid material placed between the loading and the sample. 

Material response is typically studied using either direct (constant) applied voltage (DC) or alternating applied voltage (AC). The AC response as a function of frequency is characteristic of a material. In the future, such electric spectra may be used as a product identification tool, much like IR spectroscopy. Factors such as current strength, duration of measurement, specimen shape, temperature, and applied pressure affect the electric responses of materials. The response may be delayed because of a number of factors including the interaction between polymer chains, the presence within the chain of specific molecular groupings, and effects related to interactions in the specific atoms themselves. A number of properties, such as relaxation time, power loss, dissipation factor, and power factor are measures of this lag. The movement of dipoles (related to the dipole polarization (P) within a polymer can be divided into two types an orientation polarization (P ) and a dislocation or induced polarization. 

An interesting but relatively unexplored aspect is the existence of site-characteristic electrochemical responses in porous materials containing electroactive centers. As far as the electrochemical processes involve an interfacial electron transfer between the electroactive species and the electrode surface, it is reasonable to expect that the kinetics of that electron transfer should be conditioned by the... 

Interfaces. Interfaces play an Important role In determining the characteristics and responses of semiconductors. Typically, a layer or layers of a material Is laid down on the substrate as a metal film, as an Intermetallic or as a compound In an attempt to Impart particular electrical properties to the device. In doing so, close attention must be paid to the Interface, because the surface of a material is not like the bulk. Fortunately, films on semiconductor surfaces produce strong atomic and charge rearrangements at the microscopic Interface that changes can be characterized by XPS. As Brlllson (69) notes, XPS reveals that the "magnitude and... 

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