Torsional stress

Fig. 6. The envelope of the writhing number of closed circular DNA subject to torsional stress as a function of 7, as computed from Langevin trajectories. Data are from [31].

Stress and Distortion. The forces acting on a stmcture are transmitted through the welded joints that is, the joint is subjected to simple tension (or compression), bending, shear, or torsional stresses, or to combinations of these stresses owing to combined loading situations. Weldments must be of a proper size, length, and location to withstand the loads imposed during service. 

Textile fibers must be flexible to be useful. The flexural rigidity or stiffness of a fiber is defined as the couple required to bend the fiber to unit curvature (3). The stiffness of an ideal cylindrical rod is proportional to the square of the linear density. Because the linear density is proportional to the square of the diameter, stiffness increases in proportion to the fourth power of the filament diameter. In addition, the shape of the filament cross-section must be considered also. For textile purposes and when flexibiUty is requisite, shear and torsional stresses are relatively minor factors compared to tensile stresses. Techniques for measuring flexural rigidity of fibers have been given in the Hterature (67—73). 

Flexibility Stresses Bending and torsional stresses shall be computed using the as-instaUed modulus of elasticity E and then combined in accordance with Eq. (10-100) to determine the computed displacement stress range Sg, which shah not exceed the allowable stress range [Eqs. (10-93) and (10-94).]... 

Note The shaft deflection should not be more lhan 11% of the air gap between the stator and the rotor. For loads that exert more force and torsional stress on the motor shaft and bearings than is permissible, due to the larger width of pulleys which may shift the... 

Figure 4.41 shows the Stress-Strength Interference (SSI) diagrams for the two assembly operation failure modes. The instantaneous stress on the relief section on first assembly is composed of two parts first the applied tensile stress,. v, due to the pre-load, F, and secondly, the torsional stress, t, due to the torque on assembly, M, and this is shown in Figure 4.41(a) (Edwards and McKee, 1991). This stress is at a maximum during the assembly operation. If the component survives this stress, it will not fail by stress rupture later in life. 

It is required to find the torque without slippage that can be transmitted by a hub that is assembled by an interference fit to a powered shaft. The hub outside diameter D = 070 mm, and the shaft diameter d = 050 mm, as shown in Figure 4.55. The length of the hub is 100 mm. Both hub and shaft are machined from hot rolled steel SAE 1035 with a yield strength Sy A(342,26) MPa (see Table 4.6). Given that the hub is stopped suddenly in service due to a malfunction, and considering only the torsional stresses, what is the probability that the shaft will yield ... 

It is a generally accepted assumption that the axial stress will not exceed 20% of the torsional stress, can therefore be obtained by = 0.20 tt-These two stresses will be the same for either type of coupling however, the bending stress will vary depending on which type of coupling is used. 

The stress eoneentration faetor kf results from the keyway and must be used in torsional stress ealeulations. Faetor /c takes into aeeount the shaft step it must be used in the bending stress ealeulation. 

Hafner, K. E., Torsional Stresses of Shafts Caused by Reciprocating Engines Running through Resonance Speeds, ASME 74-DGPl, New York American Society of Mechanical Engineers, 1974. 

Torsions-faden, m. torsion filament or wire, -festigkeit, /, torsional strength, -kraft, /, torsional force, -spaonung, /, torsional stress, twisting stress, -wa(a)ge,/. torsion balance, winkeh m. angle of torsion. 

Minimum drive-end peak torques, reducing drive train torsional stresses. 

Consider a uniform cylindrical bar or tube to which some balanced torque T is applied (Figure 2-28). The bar will be subject to a torsional stress, or shear stress which increases with the radial position within the bar. 

A uniform steel bar 3 ft long and 2.5 in. in diameter is subjected to a torque of 800 ft-lb. What will be the maximum torsional stress and the angular deflection between the two ends ... 

However, makeup torque applied to the tool Joint produces as axial preloading in the pin and the box as well as a torsional stress. 

The conjoint action of a tensile stress and a specific corrodent on a material results in stress corrosion cracking (SCC) if the conditions are sufficiently severe. The tensile stress can be the residual stress in a fabricated structure, the hoop stress in a pipe containing fluid at pressures above ambient or in a vessel by virtue of the internal hydraulic pressure created by the weight of its contents. Stresses result from thermal expansion effects, the torsional stresses on a pump or agitator shaft and many more causes. 

Torsional stresses are developed when power is transmitted through shafts. In addition, the tooth loads of gears mounted on shafts create bending stresses. Shaft design, therefore, is based on safe limits of torsion and bending. 

Concepts characteristic of piping flexibility analysis are covered in the following paragraphs. Special consideration is given to displacements (strains) in the piping system, and to resultant bending and torsional stresses. 

Mt = torsional moment Si, = resultant bending stress S, = torsional stress = M,/2Z... 

Fig. 26a,b. High resolution height SFM-micrographs of a 14-ABG-PS on mica [86] b Twisted ribbon structure of polypeptide /i-sheets [ 167]. The plectoneme conformation is caused by the backward folding of the torsionally stressed molecules [86]. Insert in (a) depicts a plectoneme supercoil... 

In the absence of conclusive data on the role of a positive supercoiling wave, static positive supercoiling elicited by nucleosome reconstitution on relaxed or slightly positively-supercoiled plasmids [51] or by ethidium bromide intercalation in the loop of mononucleosomes on DNA minicircles [52] did not succeed either in releasing dimers. Moreover, circular dichroism, histone chemical modi-flcation and H3-thiol accessibility failed to detect an even slight alteration in the structure of such torsionally-stressed nucleosomes [51]. The reason was later found to lie in the ability of nucleosome entry/exit DNAs to form a positive crossing [52]. 

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