Torsional load

Tool Joint dimensions for drill pipe grades E, X, G and S (recommended by API) are given in Table 4-84. Selection of tool Joints should be discussed with the manufacturer. This is due to the fact that, up to the present time, there are no fully reliable formulas for calculating load capacity of tool Joints. It is recommended that a tool Joint be selected in such a manner that the torsional load capacity of the tool Joint and the drill pipe would be comparable. The decision can be based on data specified in Tables 4-85 through 4-88. 

Determine tool Joint outside diameter. Tool Joint box should have sufficient OD and tool Joint pin sufficient ID to withstand the same torsional loading as the pipe body. When tool Joints are eccentrically worn, determine the minimum shoulder width acceptable for tool Joint class in Table 4-101. Check the inside and outside surfaces for presence of cracks, notches and severe pitting. 

Both the jackshaft and spindle are designed to absorb transient increases or decreases in torsional power caused by twisting. In effect, the shaft or tube used in these designs winds, much like a spring, as the torsional power increases. Normally, this torque and the resultant twist of the spindle are maintained until the torsional load is... 

Figure 59.15 is an example of a keyed shaft that shows the key size versus the shaft diameter. Because of standardization and interchangeability, keys are generally proportioned with relation to shaft diameter instead of torsional load. 

Fig. 8.54 Susceptibility of Ti-8Al-lMo-lV to stress-corrosion cracking in 3.5% NaCl under both tensile and torsional loading, corresponding to mode I and mode 111, respectively. The ordinate consists of the ratio of failure value in solution to failure value in air °...

The shear mode involves the application of a load to a material specimen in such a way that cubic volume elements of the material comprising the specimen become distorted, their volume remaining constant, but with opposite faces sliding sideways with respect to each other. Shear deformation occurs in structural elements subjected to torsional loads and in short beams subjected to transverse loads. 

A shaft subject to torque is generally considered to have failed when the strength of the material in shear is exceeded. For a torsional load the shear strength used in design should be the published value or one half the tensile strength, whichever is less. The maximum shear stress on a shaft in torsion is given by the following equation ... 

The double cross-slip mechanism can then be considered as the most probable deformation process, complementary to the basal slip. Indeed, dislocation climb can hardly be invoked in this torsion loading conditions since most of the dislocations are of screw type. 

Figure 3.18 Total deformation vs time under torsional load at 23°C.i °>...

A material that is twisted is subjected to a torsional load (Figure 10.Id). Torsional strength is important for shafts that transmit rotation. 

Whenever there is lateral or oblique bending, there is the possibility of twisting the neck. The associated torsional loads may be responsible for unilateral facet dislocations or unilateral locked facets [Moffat et al., 1978]. However, the authors postulated that pure torsional loads on the neck are rarely encountered in automotive accidents. 

Parallel markings, shaped like a quarter ellipse, occur on some fracture surfaces (Fig. 9.3a). A surface crack has initiated when a blunt object pressed on the product surface (Fig. 9.3b). As this crack spreads sideways, the object penetrates the product and twists the two sides in opposite directions. This double torsion loading causes the crack to advance more rapidly on the lower surface in tension. The characteristic markings are due to momentary hesitations of the crack front. 

Cracks tend to initiate on the surface of products for a munber of reasons— bending or torsion loading causing high surface stresses, surface scratches causing stress concentrations or surface degradation. However, in some circumstances (yield stress concentrations at a notch or weak interfaces)... 

Figure 7.3 Influence of off-axis angle on the fatigue strength of glass/epoxy tubes under pulsating tension—torsion loading [50].

Figure 7.8 Influence of biaxiality ratio X2 on the fatigue strength of glass/polyester [0/90] tubes under combined tension and torsion loading [21],...

Figures 7.8 and 7.9 illustrate fatigue data for pulsating tension—torsion loading however, from the design point of view, the combination of compressive and shear loading could be even more interesting. Due to the difficulty of applying compression to thin tubes without causing buckling, very few papers have been published for this specific condition.

Anderson et al. [20] studied the effects of combined cyclic tension or compression loading and torsional loading on [ 30/90]s aramid/epoxy tubes. They reported that in the case of predominandy axial loading the combinafion with a small torsion... 

Figure 7.11 Influence of phase lag on the fatigue strength of [0/90] glass/polyester tubes under combined bending and torsion loading [37].

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