Tension test elastic behavior

Eight compact tension It test specimens and four l/2t compact tension test specimens each of base metal (transverse) and weld metal material are provided to augment the fracture toughness data determined from the precracked Charpy tests. This guantity of specimens is sufficient to determine fracture toughness properties over the range extending from linear elastic to elastic-plastic fracture behavior. 

In Sect. 1.2 above, the stress-strain relation in uniaxial tension tests was given in Eq. (1.5), indicating a Hookean behavior. This section now considers linear elastic solids, as described by Hooke, according to which (Ty is linearly proportional to the strain, y. Each stress component is expected to depend linearly on each strain component. For example, the Cn may be expressed as follows ... 

FIG. 15 Characteristic stress-strain behavior of an elastic compressible agglomerate (solid lines) in common testing configurations uniaxial tension, uniaxial compression, and hydrostatic compression (from Bika et al., 2001). Yield point ay and tensile strength a, are indicated. 

Mechanical testing is the determination of the behavior of a material caused by some applied loading. The material is loaded in its bulk form via a mechanical testing machine (i.e., MTS, Instron, etc.) and its properties are evaluated. Typically these include the elastic modulus or stiffness, the yield strength, the fracture stress or ultimate strength, the elongation, and Poisson s ratio. These properties depend on the mode of loading, such as tension, compression, shear, or flexure. 

The evolution of the Kg factor has been based on simple analyses and limited test data. Krempl studied the low cycle fatigue behavior of notched cylinders and plates of three pipe materials.Tagart formulated design rules for the Nuclear Piping Code B31.7 based partly on these tests, which led to Eq. (11.3b). Langer performed elastic-plastic analyses of a beam in bending and a tapered bar in tension which led to Eq. (11.3c). 

For polymers, the torsion test is often the test of choice because, as discussed in Chapter 2, the time dependent (viscoelastic) behavior of polymers is principally due to the deviatoric (shear or shape change) stress components rather than the dilatoric (volume change) stress components. Typically, constant strain rate tests are often used for either tension, compression or torsion as discussed in Chapter 3. If the material is linear elastic, the stress rate is proportional to the strain rate as the modulus is time independent. That is. 

Material Parameter Characterization Elastic Modulus The first step in the process is to characterize the material model that describes the behavior of axes, flexible gear and rigid gear and also to quantify the variability in the material. Through physical measurements, tension/com-pression and torsional experiments, the material density, elastic and shear moduli were obtained calibrating to represent the dynamic behavior of them at room temperature. Using the data obtained from these samples and from these tests, a probabilistic description of the randomness of them was obtained and subsequently used in more complex system. More specifically, for these components, the elastic modulus is treated as random variable. 

The viscoelastic behavior of polymeric materials is dependent on both time and temperature several experimental techniques may be used to measure and quantify this behavior. Stress relaxation measurements represent one possibility. With these tests, a specimen is initially strained rapidly in tension to a predetermined and relatively low strain level. The stress necessary to maintain this strain is measured as a function of time while temperature is held constant. Stress is found to decrease with time because of molecular relaxation processes that take place within the polymer. We may define a relaxation modulus E t), a time-dependent elastic modulus for viscoelastic polymers, as... 

Muny [43]. One common feature of these estabhshed test methods is that they are all destructive measurements. In the first phase of the test, a bond is formed on contact of pressure sensitive adhesive with the substrate. Initially, depending on the applied pressure, only individual, small points of adhesion form, whose number and size increase during the contact phase due to elastic deformation, viscous flow and wetting of the substrate with the adhesive. Contact formation is, therefore, determined by mechanical behavior and surface properties, such as surface tension, roughness, and adsorbate layers. Other important influencing factors are contact time, contact pressure and temperature. During the second phase, the bond is separated under the action of a tensile force, with the bond being deformed. Both processes, i.e. contact formation and separation, are influenced by the test conditions, which are different in each measurement method [27, 30, 44]. 

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