Single creep

Flaw detection by contact method of manual-manipulating 5MHz single creeping wave probe. 

The simplest model that can be used for describing a single creep experiment is the Burgers element, consisting of a Maxwell model and a Voigt-Kelvin model in series. This element is able to describe qualitatively the creep behaviour of viscoelastic materials... 

A blind test was conducted with a cotton sample 814 days old. A single creep test was performed and the age was estimated. The result achieved was an estimated age of 214 days. This result seems to indicate a rather large error. However, when the datum is plotted, the point is not very far from the curve. In fact, it is quite consistent with the trend set by the data for 47- and 400-year-old samples and suggests that the curve rather than the 814-day datum is incorrect. In view of the limited number of calibration points used to fit the curves, this explanation seems plausible. Consequently, the curve in Figure 8 represents a curve fitted to all cotton specimens measured, including the 814-day specimen. The fitted equations presented here should be used only to evaluate the... 

The models discussed here, which are phenomenological and have no direct relation with chemical composition or molecular structure, in principle enable the response to a complicated loading pattern to be deduced from a single creep (or stress-relaxation) plot extending over a long time interval. Interpretation depends on the assumption in linear viscoelasticity that the total deformation can be considered as the sum of independent elastic (Hookean) and viscous (Newtonian) components. In essence, the simple behaviour is modelled by a set of either integral or differential equations, which are then applicable in other situations. 

Zhang conducted extensive creep and creep to failure tests of polycarbonate and polysulfone for both single creep loads and multiple step-up or step-down creep loads as illustrated in Fig. 11.21 and developed an equation of the form. 

The models discussed here, which are phenomenological and have no direct relation with chemical composition or molecular structure, in principle enable the response to a complicated loading pattern to be deduced from a single creep (or stress-relaxation) plot extending... 

A single creep test in tension or flexure gives information on long-term dimensional stability of a load-bearing element. When combined with a variable temperature, the test provides a simple means of measuring the heat deflection temperature. 

A Technique of Ultrasonic Testing without Dead Zone for Coarse-Grained TC4 Extrusion Pipe. - The Development of Single Crystal Creeping Wave Prohe. 

KEYWORDS ultrasonic testing coares grain pipe single crystal creeping wave probe... 

The properties of a single crystal creeping wave probe The a single crystal creeping wave probe is suitable for testing various artificial defects such as surface cracks, FBH, columned hole and SDH etc. and its distance amplitude cruve is shown in Fig.6... 

Mechanical properties of plastics can be determined by short, single-point quaUty control tests and longer, generally multipoint or multiple condition procedures that relate to fundamental polymer properties. Single-point tests iaclude tensile, compressive, flexural, shear, and impact properties of plastics creep, heat aging, creep mpture, and environmental stress-crackiag tests usually result ia multipoint curves or tables for comparison of the original response to post-exposure response. 

For isotropic homogeneous porous media (uniform permeability and porosity), the pressure for creeping incompressible single phase-flow may be shown to satisfy the LaPlace equation ... 

While for many years, metal single crystals were used only as tools for fundamental research, at the beginning of the 1970s single-crystal gas-turbine blades began to be made in the hope of improving creep performance, and today all such blades are routinely manufactured in this form (Duhl 1989). 

On top of this alloy development, turbine blades for the past two decades have been routinely made from single crystals of predetermined orientation the absence of grain boundaries greatly enhances creep resistance. Metallic monocrystals have come a long way since the early research-centred uses described in Section 4.2.1. 

The viscoelastic creep modulus may be determined at a given temperature by dividing the constant applied stress by the total strain prevailing at a particular time. Since the creep strain increases with time, the viscoelastic creep modulus must decrease with time (Fig. 2-23). Below its critical stress for linear viscoelasticity, the viscoelastic creep modulus versus time curve for a material is independent of the applied stress. In other words, the family of strain versus time curves for a material at a given temperature and several levels of applied stress may be collapsed to a single viscoelastic creep-modulus-time-curve if the highest applied stress is less than the critical value. 

The first of these assumptions drops the momentum terms from the equations of motion, giving a situation known as creeping flow. This leaves Vr and coupled through a pair of simultaneous, partial differential equations. The pair can be solved when circumstances warrant, but the second assumption allows much greater simplification. It allows to be given by a single, ordinary differential equation ... 

In conclusion, it may be mentioned that the characterization of the mechanical behaviour of materials has many facets. Different methods of testing pertain to different aspects and conditions. The tensile properties, as determined by the tensile test, correspond to slowly applied single load applications. Rapidly applied and cyclic load applications respectively provide the impact and the fatigue properties. Hardness is an analog of the tensile strength which a tensile test measures. The creep test pertains to mechanical behaviour under long term loading at elevated temperatures. 

The creeping flow of a single fluid phase through a rigid permeable medium is modeled with the continuity equation and Darcy s Law ... 

To get accurate distributions of relaxation or retardation times, the expetimcntal data should cover about 10 or 15 decades of time. It is impossible to get experimental data covering such a great range of times at one temperature from a single type of experiment, such as creep or stress relaxation-t Therefore, master curves (discussed later) have been developed that cover the required time scales by combining data at different temperatures through the use of time-temperature superposition principles. 

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