Rupture modulus

Test Explosive, Density Temp, °F Stress at Rupture, psi Elongation at Rupture, % Modulus of Elasticity, psi x 10-3 Work to Produce Rupture, ft-lb/in3... 

Bamboo between three to five years old has higher compressive strength, modulus of rupture, modulus of elasticity, and specific gravity. 

Fiber stress at proportional limit Modulus of rupture Modulus of elasticity Work to proportional limit Work to maximum load Impact bending... 

Properties Rupture modulus up to 50,000 psi, d 2.5, thermal shock resistance 900C, highest continuous-use temperature 700C. Glass ceramics lie between borosilicate glasses and fused silica in high-temper-ature capability. 

Table IV. Rupture Modulus of Sulfur—Additive Combinations ...

Moisture content. AD is air-dry G is water saturated. Modulus of rupture. "Modulus of elasticity. 

Methods of Testing. ASTM tests for various concrete masonry units are available. These consist of compressive strength and sometimes per cent moisture and rupture modulus tests at a 28-day period. Compressive tests are often made by core-sampling actual construction work during early stages. To avoid waiting, 7-day tests are made and related to 28-day tests as follows ... 

Fiber Tenacity Extension Rupture Modulus Tenacity Extension Rupture Modulus... 

The shear strength, splitting tensile strength and rupture modulus (Fig.2,3 and 6 ) are improved by addition of 2% fibres by 35 percent, 44 percent and 55 percent, respectively. 

As we showed in Chapter 6 (on the modulus), the slope of the interatomic force-distance curve at the equilibrium separation is proportional to Young s modulus E. Interatomic forces typically drop off to negligible values at a distance of separaHon of the atom centres of 2rg. The maximum in the force-distance curve is typically reached at 1.25ro separation, and if the stress applied to the material is sufficient to exceed this maximum force per bond, fracture is bound to occur. We will denote the stress at which this bond rupture takes place by d, the ideal strength a material cannot be stronger than this. From Fig. 9.1... 

Because of this, the data listed in Table 15.7 for ceramic materials differ in emphasis from those listed for metals. In particular, the Table shows the modulus of rupture (the maximum surface stress when a beam breaks in bending) and the thermal shoek resist-anee (the ability of the solid to withstand sudden changes in temperature). These, rather than the yield strength, tend to be the critical properties in any design exercise. 

There are, of course, many more ceramics available than those listed here alumina is available in many densities, silicon carbide in many qualities. As before, the structure-insensitive properties (density, modulus and melting point) depend little on quality -they do not vary by more than 10%. But the structure-sensitive properties (fracture toughness, modulus of rupture and some thermal properties including expansion) are much more variable. For these, it is essential to consult manufacturers data sheets or conduct your own tests. 

Fig. 17.2. Tests which measure the fracture strengths of ceramics, (a) The tensile test measures the tensile strength, CTj. (b) The bend test measures the modulus of rupture, o , typically 1.7 x CTj. (<) The compression test measures the crushing strength, a, typically 15 x...

The common tests are shown in Fig. 17.2. The obvious one is the simple tensile test (Fig. 17.2a). It measures the stress required to make the longest crack in the sample propagate unstably in the way shown in Fig. 17.3(a). But it is hard to do tensile tests on ceramics - they tend to break in the grips. It is much easier to measure the force required to break a beam in bending (Fig. 17.2b). The maximum tensile stress in the surface of the beam when it breaks is called the modulus of rupture, o for an elastic beam it is related to the maximum moment in the beam, M by... 

Modulus-of-rupture tests are carried out using the arrangement shown in Fig. 17.2. The specimens break at a load F of about 330 N. Find the modulus of rupture, given that I = 50 mm, and that b = d = 5 mm. 

Estimate the thermal shock resistance AT for the ceramics listed in Table 15.7. Use the data for Young s modulus E, modulus of rupture c, and thermal expansion coefficient a given in Table 15.7. How well do your calculated estimates of AT agree with the values given for AT in Table 15.7 ... 

Ductility. A load-bearing device or component must not distort so much under the action of the service stresses that its function is impaired, nor must it fail by rupture, though local yielding may be tolerable. Therefore, high modulus and high strength, with ductility, is the desired combination of attributes. However, the inherent nature of plastics is such that high modulus tends to be associated with low ductility and steps that are taken to improve the one cause the other to deteriorate. The major effects are summarised in Table 1.6. Thus it may be seen that there is an almost inescapable rule by which increased modulus is accompanied by decreased ductility and vice versa. 

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