Tensile elements

Although long-term experience is not yet available, these non-metallic tensile elements may be considered a promising alternative to steel. Probably the single most important aspect of the use of FRP as reinforcement is the durability. Work has concentrated on the development of alkali resistant glass or the use of carbons or aramids, but little attention has been paid to the resin. Considerable work is needed to establish methods and criteria by which the durability may be assessed (Clark, 1998). 

Fig. 9. Picture of simplified model of adhesive defonning as individual tensile elements.

When plastic deformation occurs at the notch root, Oy drops from its high elastic value to Oy M- Once the first imaginary tensile element at the notch root starts yielding, it deforms plastically at a constant volume that requires Poisson s value to be v = 0.5 instead of about 0.3 during elastic deformation. Therefore, a higher transverse stress, o = Ee = -E(v y) = -E[v(Oy/E)], will be developed to maintain the material continuity. The stress will also increase with the distance from the notch root more quickly than in the... 

The paper discusses the application of dynamic indentation method and apparatus for the evaluation of viscoelastic properties of polymeric materials. The three-element model of viscoelastic material has been used to calculate the rigidity and the viscosity. Using a measurements of the indentation as a function of a current velocity change on impact with the material under test, the contact force and the displacement diagrams as a function of time are plotted. Experimental results of the testing of polyvinyl chloride cable coating by dynamic indentation method and data of the static tensile test are presented. 

Returning to the Maxwell element, suppose we rapidly deform the system to some state of strain and secure it in such a way that it retains the initial deformation. Because the material possesses the capability to flow, some internal relaxation will occur such that less force will be required with the passage of time to sustain the deformation. Our goal with the Maxwell model is to calculate how the stress varies with time, or, expressing the stress relative to the constant strain, to describe the time-dependent modulus. Such an experiment can readily be performed on a polymer sample, the results yielding a time-dependent stress relaxation modulus. In principle, the experiment could be conducted in either a tensile or shear mode measuring E(t) or G(t), respectively. We shall discuss the Maxwell model in terms of shear. 

In conventional tenter orientation, the sequence of steps is as described above (MD—TD). In some cases it is advantageous to reverse the draw order (TD—MD) or to use multiple draw steps, eg, MD—TD—MD. These other techniques are used to produce "tensilized" films, where the MD tensile properties are enhanced by further stretching. The films are generally unbalanced in properties and in extreme cases may be fibrillated to give fiber-like elements for special textile appHcations. Tensilized poly(ethylene terephthalate) is a common substrate for audio and video magnetic tape and thermal transfer tape. 

Cold-roUed alloys of lead with 0.06 wt % teUurium often attain ultimate tensile strengths of 25—30 MPa (3625—5350 psi). High mechanical strength, excellent creep resistance, and low levels of alloying elements have made lead—teUurium aUoys the primary material for nuclear shielding for smaU reactors such as those aboard submarines. The aUoy is self-supporting and does not generate secondary radiation. 

Additions of selected alloying elements raise the recrystaUization temperature, extending to higher temperature regimes the tensile properties of the cold-worked molybdenum metal. The simultaneous additions of 0.5% titanium and 0.1% zirconium produce the TZM aUoy, which has a corresponding... 

Tensile Properties. Tensile properties of nylon-6 and nylon-6,6 yams shown in Table 1 are a function of polymer molecular weight, fiber spinning speed, quenching rate, and draw ratio. The degree of crystallinity and crystal and amorphous orientation obtained by modifying elements of the melt-spinning process have been related to the tenacity of nylon fiber (23,27). 

Commercially available clear sihcas typically have tensile strengths of 50—70 MPa (7,250—10,150 psi) and compressive strengths of 500—1900 MPa (72,500—275,500 psi). The opaque sihcas have tensile strengths of 5—50 MPa (725—7250 psi) and compressive strengths of 190—300 MPa (27,550—43,500 psi) (162). Safety factors of 10—20-fold are usually employed when developing stmctural elements made of vitreous sihca. 

The basis for reinforcement of a pneumatic tire requires placing the strength or tensile member in a preferred direction, depending on the location and cord function in the tire. An overview of the tire production process, including essential elements of transforming a continuous yam into a usehil embodiment for tire reinforcement, is shown in Figure 2. 

Copper increases tensile strength and hardness and offers some protection against elements that promote intergranular corrosion. However, copper reduces impact strength and dimensional stabiUty owing to aging and is therefore kept at 1.25% max. 

Elements that can dissolve in copper, such as zinc, tin, and nickel for example, increase annealed strength by varying amounts depending on the element and the quantity in solution. The effect of selected solution hardening elements on tensile properties of annealed copper aUoys is iUustrated by the data in Table 4, where the yield strength is the stress at 0.2% offset strain in a tensile test. 

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