Flexural cracks

Cold temperature brittleness (flexural) Visual appearance of flex edge No cracks Flexural testing in accordance with DIN EN 1876-1, flex edge in extrasion and transverse directions... 

Masonry Box Behavior, Fig. 10 Predicted damage sequence corresponding to the (a) +X and (b) +Y analysis (X diagonal shear, = tension cracks, flexural plastic hinge)... 

A similar procedure can be followed in the case of the shear sub-element (Fig. 8d), which represents the hysteretic shear behavior of the R/C member prior and subsequent to shear cracking, flexural yielding, and yielding of the shear reinforcement. In this case, the current shear... 

Crazed or cracked Flexural stress Filler 40% Glass fiber Specimen ASTM D638 tensile bars... 

Flexural modulus increases by a factor of five as crystallinity increases from 50 to 90% with a void content of 0.2% however, recovery decreases with increasing crystallinity. Therefore, the balance between stiffness and recovery depends on the appHcation requirements. Crystallinity is reduced by rapid cooling but increased by slow cooling. The stress—crack resistance of various PTFE insulations is correlated with the crystallinity and change in density due to thermal mechanical stress (118). 

The tensile and flexural properties as well as resistance to cracking in chemical environments can be substantially enhanced by the addition of fibrous reinforcements such as chopped glass fiber. Mechanical properties at room temperature for glass fiber-reinforced polysulfone and polyethersulfone are shown in Table 5. 

Due to the polyether blocks, these polymers retain their flexibility down to about -40°C and only Grade 6333 breaks in an Izod test at this temperature (using specimens of thickness 3.2 mm). The materials generally show excellent resistance to crack growth from a notch during flexure some grades are reported... 

Such degradation of the surface causes little effect on either flexural strength or flexural modulus of elasticity but the influence on the impact properties is more profound. In such instances the minute cracks form centres for crack initiation and samples struck on the face of samples opposite to the exposed surface show brittle behaviour. For example, a moulded disc which will withstand an impact of 12 ftlbf without fracture before weathering will still withstand this impact if struck on the exposed side but may resist impacts of only 0.75 ftlbf when struck on the unexposed face. 

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... 

Strength can be measured in compression, in tension, in shear and transversely (flexural strength). However, if we exclude plastic flow as a means of failure, then materials can only fracture in one of two ways (1) by the pulling apart of planes of atoms, i.e. tensile failure, or (2) by the slippage of planes of atoms, i.e. shear failure. Strength is essentially a measure of fracture stress, which is the point of catastrophic and imcontrolled failure because the initiation of a crack takes place at excessive stress values. 

Direct Shear. For type I cross-sections (0 < 2°) the concrete between the flexural reinforcement Is capable of resisting direct shear. However, because cracking at the support yield line reduces the shear capacity, diagonal bars must be provided to at least resist the shear capacity of the concrete, v. For type II and III cross-sections (0 > 2 ), with little or no concrete shear resistance, The diagonal reinforcing bars must be designed to resist the entire shear load at the support. 

Reinforced concrete is a complex material to model due to the brittle nature of concrete and non-homogenous properties. Although sophisticated methods are available to model crack propagation and other responses, simplified methods are normally used in blast design of facilities. These methods are based on a flexural response and rely on elimination of brittle modes of failure. To achieve a ductile response for concrete, proper proportioning and detailing of the reinforcing is necessary. 

For unreinforced masonry, flexure is based on the cracking strength of the masonry. 

For example, the required lower bulk electrical resistance and surface contact resistance are directly related to reducing internal power consumption in fuel cells to achieve maximum power output. The requirements of high flexural strength and flexibility (ultimate strain) are important to assure no distortion of fluid fields and no crack in a plate sustained in the large compressive loading when each unit cell is assembled together as a stack. This is particularly important when the thickness of the plate becomes thinner and thinner (can be close to or less than 1 mm [9]) and the dimension of the fluid field becomes smaller and smaller. Whether it is elastic or plastic, the large... 

Eqs. (3.20) and (3.21) are called the load method and displacement method (Hashemi et al., 1989), respectively, since only load and displacement records corresponding to crack lengths are required to evaluate the Gic values, once the flexural modulus E of the beam is known. These equations also apply to the WTDCB specimens where the ratio of the crack length to width, a/b, is constant. 

The permeability is affected not only by temperature, but also by relative humidity. For example, cellophane is an excellent oxygen blocker when dry, but becomes poor when moist. The values for permeability in Table 4.17 are strictly for flat materials. Real permeabilities can vary greatly due to flexural cracks, overlapping, and delamination that are common in real materials. There have been attempts, however, to model the diffusion in strained materials [16]. 

The flexural strength will depend on sample size, since with increasing size there is an increase in the probability of the existence of a crack-producing flaw, along with a corresponding decrease in the flexural strength. This test, and others like it such as the four-point bend, are common for brittle materials such as ceramics, which we... 

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

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