Torque/tension method

In some critical assemblies, such as the fitting of an internal combustion engine cylinder head, correct clamping load is vital. Either the traditional torque/tension method, or the more recently developed techniques of differential torque analysis must therefore be used. With torque/tension, the relationship must not be modified by the anaerobic materials used to lock the stud and nut. It has been shown that the relationship remains effectively unaltered if the fasteners are not degreased before assembly. For maximum precision, cleaned fasteners may be used in conjunction with special lubricating anaerobic versions. 

D5648-01 Standard test method for torque-tension relationship of adhesives used on threaded fasteners (lubricity)... 

The critical values are generally obtained from a standard tensile test. Once the critical values are obtained the application of any (or all) of these criteria in conjunction with a dependable stress analysis is straightforward. Here we demonstrate the method by a simple example. Let us assume that it is desired to determine the torque required to cause failure of a 25 mm in diameter shaft constructed of an homogeneous isotropic plastic with a failure stress in tension, o, of 7 x 10 N/m. Assume further tlmt the modulus of elasticity, E, for this plastic is given by 3 x 10° N/m, and that is has a Poisson ratio of 0.3. We will explore the prediction of the three criteria just discussed. 

Regardless of the method chosen to unwind the coil, the performance requirements of the application must be satisfied in terms of payoff speed and acceleration/deceleration time. The uncoiler drive will have to be sized to accommodate the power required to overcome friction, accelerate the inertia of the coil and any other rotating component to line speed prior to exhausting the stored material in the loop, straighten if required, overcome a drag tensioning brake if supplied, and run at the required production speed. The horsepower required is directly proportional to the torque and speed requirements. For a given application, if the payoff speed requirement is doubled, then the horsepower requirement will be doubled as well. Always use the worst case in terms of material thickness and width, coil size, and payoff speed to determine the drive size requirement for any application. 

An incremental calculation method that allows the torque factor and torsional stiffness to vary in response to changes in rope rotation and tension... 

PP-g-MA (0.1 mol% MA). Characterization methods included SEM, ESCA, and interfacial tension measurement. Tselios et al. (1998) have prepared compatibilized blends of LDPE and PP through inclusion of PP-g-MA (0.8 mol% MA) and EVAl (7.5 mol% vinyl alcohol). Blends were characterized using SEM, torque rheometry, mechanical properties, FTIR, and micro-Raman spectroscopy. 

Procedures for this test method are covered in ISO 4624 Paint and Varnish Pull-off Test for adhesion. In preparation for this test a stud, normally made of steel, is glued with the coating and is subjected to axial tension until detachment of the paint film takes place. The result is a maximum tensile stress that is possible at the interface (see Figure 15.6). The maximum shear stress is obtained when a torque is applied about the axis of the stud. 

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