Flexural deflection

Note 1 For a Voigt-Kelvin solid of negligible mass, the absolute modulus can be evaluated from the ratio of the flexural force (/o) and the amplitude of the flexural deflection (y) with... 

Flexural deflection The distance over which the top or the bottom surface of the test piece at mid-span has deviated during flexure fi om its original position... 

We have pointed out that the extension at break for a glassy sample often is so small that it becomes hard to measure. In a flexural test, elongation occurs on one side of the sample and compression on the other. A small elongation at break corresponds to a large flexural deflection, which is easily measured. The simple beam with sliding supports is used most often. 

The relevant results of the tests are shown in Table 2. In our experience four parameters provide a very useful representation of the radiation tolerance of PP formulations. These are the color, tensile elongation at break, Gardner impact strength at 23°C, flexural deflection at peak load. 

The first three of these are well known. Flexural deflection at peak load is a test developed at ExxonMobil Chemical Company and described previously. In this test tolerance of high energy radiation by a polymer is exhibited by the retention of original level of deflection at peak load. [8]... 

Hysteretic whirl. This type of whirl occurs in flexible rotors and results from shrink fits. When a radial deflection is imposed on a shaft, a neutralstrain axis is induced normal to the direction of flexure. From first-order considerations, the neutral-stress axis is coincident with the neutral-strain axis, and a restoring force is developed perpendicular to the neutral-stress axis. The restoring force is then parallel to and opposing the induced force. In actuality, internal friction exists in the shaft, which causes a phase shift in the stress. The result is that the neutral-strain axis and neutral-stress axis are displaced so that the resultant force is not parallel to the deflection. The... 

There are a number of features that all couplings have in common. One is the need for a spacer. API 671 calls for an 18-inch spacer minimum, This is reasonable for smaller units, say to 5,000 hp however, as the size of train increases to 15,000 to 20,000 hp, a 24-inch spacer should be considered. Above that size, longer spacers, 30 to 36 inches, are in order. The spacer first of all provides for unit separation and maintenance space. Secondly, the longer the spacer, the less the angular deflection of the coupling at its flexure point for a given offset. This makes absolute equipment alignment less critical. 

Polycarbonates with superior notched impact strength, made by reacting bisphenol A, bis-phenol S and phosgene, were introduced in 1980 (Merlon T). These copolymers have a better impact strength at low temperatures than conventional polycarbonate, with little or no sacrifice in transparency. These co-carbonate polymers are also less notch sensitive and, unlike for the standard bis-phenol A polymer, the notched impact strength is almost independent of specimen thickness. Impact resistance increases with increase in the bis-phenol S component in the polymer feed. Whilst tensile and flexural properties are similar to those of the bis-phenol A polycarbonate, the polyco-carbonates have a slightly lower deflection temperature under load of about 126°C at 1.81 MPa loading. 

Beuge, /. bend, bow bending, flexure, beugen, v.t. bend, flex deflect diffract (light) ... 

Even plastics with fairly linear stress-strain curves to failure, for example short-fiber reinforced TSs (RPs), usually display moduli of rupture values that are higher than the tensile strength obtained in uniaxial tests wood behaves much the same. Qualitatively, this can be explained from statistically considering flaws and fractures and the fracture energy available in flexural samples under a constant rate of deflection as compared to tensile samples under the same load conditions. These differences become less as the... 

Creep-test specimens may be loaded in tension or flexure (to a lesser degree in compression) in a constant temperature environment. With the load kept constant, deflection or strain is recorded at regular intervals of hours, days, weeks, months, or years. Generally, results are obtained at three or more stress levels. 

The fatigue behavior of a material is normally measured in a flexural but also in a tensile mode. Specimens may be deliberately cracked or notched prior to testing, to localize fatigue damage and permit measuring the crack-propagation rate. In constant-deflection amplitude testing a specimen is... 

The flexural yield strength is determined from the calculated data of load-deflection curves that show a point where the load does not increase with an increase in deflection. 

The flexural modulus is the ratio, within the elastic limit, of stress to corresponding strain. It is calculated by drawing a tangent to the steepest initial straight-line portion of the load-deflection curve and using an appropriate formula. 

Although one can design flexures with quite extreme ratios of stiffness, often the design is also hmited by various space constraints, limits to allowed deflections, required load carrying capacity, and the need to avoid buckling. 

HDT heat deflection temperature under flexural load (1820 kPa) Heat distortion test (HDT) ASTM D-648-72 CEAST 6005... 

We use a variant of flexural testing to measure a sample s heat distortion temperature. In this test, we place the sample in a three point bending fixture, as shown in Fig. 8.6 b), and apply a load sufficient to generate a standard stress within it. We then ramp the temperature of the sample at a fixed rate and note the temperature at which the beam deflects by a specified amount. This test is very useful when selecting polymers for engineering applications that are used under severe conditions, such as under the hoods of automobiles or as gears in many small appliances or inside power tools where heat tends to accumulate. 

Young s modulus is often measured by a flexural test. In one such test a beam of rectangullar cross section supported at two points separated by ia distance Lq is loaded at the midpoint by a force F, as illustrated in Figure 1.2. The resulting central deflection V is measured and the Young s modulus E is calculated as follows ... 

Typical resistance-deflection curve for flexural response of concrete elements. 

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