Torsional bars

The polar moment of inertia of a surface about an axis through its center of gravity and perpendicular to the surface is the sum of the 

It has been found by tests as well as by mathematical analysis that the torsional resistance of a section, made up of a number of rectangular parts, is approximately equal to the sum of the resistances of the separate parts. It is on this basis that nearly all the formulas for noncircular sections have been developed. For example, the torsional resistance of an I-beam is approximately equal to the sum of the torsional resistances of the web and the outstanding flanges. In an I-beam in torsion the maximum shearing stress will occur at the middle of the side of the web, except where the flanges are thicker than the web, and then the maximum stress will be at the midpoint of the width of the flange. Reentrant angles, as those in I-beams and channels, are always a source of weakness in members subjected to torsion. 

The ultimate/failure strength in torsion, the outer fibers of a section are the first to shear, and the rupture extends toward the axis as the twisting is continued. The torsion formula for round shafts has no theoretical basis after the shearing stresses on the outer fibers exceed the proportional limit, as the stresses along the section then are no longer proportional to their distances from the axis. It is convenient, however, to compare the torsional strength of various materials by using the formula to compute values of t at which rupture takes place. 

Filament winding (FW) shapes are principally circular (cylinders, pipes, tubing, etc.) or enclosed vessel (storage tanks, oxygen tanks, etc.). They 

Two different techniques of applying the reinforcements in helical windings are used by industry. One technique is the application of only one complete revolution around the mandrel from end to end. The other technique involves a multi-circuit winding procedure that permits a greater degree of flexibility of wrapping and length of cylinder. 

---

Torsion bars and leaf springs are less efficient than axial springs because some of the material is not fully loaded the material at the neutral axis, for instance, is not loaded at all. Consider - since we will need the equations in a moment - the case of a leaf spring. 

To illustrate how traditional materials such as metals limit the design process, consider a spring. The manufacturing process in metals limits the options available in producing a variety of shapes in this material. As a result, steel springs are produced in basically only three shapes the torsion bar, the helical coil, and the flat-shaped leaf spring. By comparison, TPs and TSs can be easily fabricated into... 

An appropriate cure cycle was established based on the results obtained from the thermal analysis and cure rheology studies of the resin and cured BCB bar and dogbone shaped samples were fabricated for testing. Bar shaped specimens had the dimensions of 3.5 x 0.5 X 0.125 and were used to stake compact tension specimens for fracture toughness studies and for dynamic mechanical analysis of a torsion bar. Dogbone shaped specimens for tensile tests had a gauge area of 1 x 0.15 and were approximately 0.040 thick. 

Thermal analysis, moisture uptake and dynamic mechanical analysis was also accomplished on cured specimens. Thermal analysis parameters used to study cured specimens are the same as those described earlier to test resins. The moisture uptake in cured specimens was monitored by immersing dogbone shaped specimens in 71 C distilled water until no further weight gain is observed. A dynamic mechanical scan of a torsion bar of cured resin was obtained using the Rheometrics spectrometer with a temperature scan rate of 2°C/minute in nitrogen at a frequency of 1.6Hz. The following sections describe the results obtained from tests run on the two different BCB resin systems. Unless otherwise noted all tests have been run as specified above. 

Cured Olixomer Properties. The T, of the cured specimen ms not obvious by DSC, however the T was observed at 383°C (Q maac) by dynamic mechanical testing of a torsion bar. The T obtained by this method has been driven up in temperature by the slow heating rate of 2°C/minute used in the test, the actual T is somewhat lower... 

Note 3 A damping curve is usually obtained using a torsion pendulum, involving the measurement of decrease in the axial, torsional displacement of a specimen of uniform cross-section of known shape, with the torsional displacement initiated using a torsion bar of known moment of inertia. 

Transducers that use torsion bars or springs of known compliance may also oscillate at the beginning of the test as the step is imposed. This ringing is symptomatic of the detector and not the sample response, and thus needs to be removed by signal filtering. In a creep test this kind of behavior only occurs if the sample is... 

One of most popular techniques for dynamic mechanical analysis is the torsion pendulum method. In a modification of this method designed to follow curing processes, a torsion bar is manufactured from a braid of fibers impregnated with the composition to be studied this is the so-called torsional braid analysis (TBA) method.61 62,148 The forced harmonic oscillation method has been also used and has proven to be valuable. This method employs various types of rheogoniometers and vibroreometers,1 9,150 which measure the absolute values of the viscoelastic properties of the system under study these properties can be measured at any stage of the process. The use of computers further contributes to improvements in dynamic mechanical analysis methods for rheokinetic measurements. As will be seen below, new possibilities are opened up by applying computer methods to results of dynamic measurements. 

Pure shear tests are often performed with torsional bars or flexural tests with very close spans, or using grooved tensile specimens (Fig. 12.2a). They provide the shear yielding stress, ry, which can be related to ay using yielding criteria (see below). 

The viscoelastic parameters are generally measured by dynamic oscillatory measurements. Apparatus of three different configurations can be used cone and plate, parallel plates, or concentric cylinders. In the case of cone and plate geometry, the test material is contained between a cone and a plate with the angle between cone and plate being small (<4°). The bottom member undergoes forced harmonic oscillations about its axis and this motion is transmitted through the test material to the top member, the motion of which is constrained by a torsion bar. The relevant measurements are the amplitude ratio of the motions of the two members and the associated phase lag. From this information it is relatively simple to determine G and G". 

One of the latest developments in the area of steering torque sensors is an optical concept created by Bishop Innovation with Bosch. As in conventional hydraulic steering systems, a torsion bar is a part of the steering column. A disc with a barcode on its surface is attached to each end of the torsion bar. A light source within the sensor module illuminates the surface of the coded discs, partially reflecting the light through a lens onto an optoelectronic ASIC. 

The front suspension is the torsion bar spring, double-cylinder inflatable hydraulic damper, transverse stabilizer rod, double cross-arm independent suspension. The distance between the center of front shaft of lower arm fixing nut and level grormd is 295mm+lmm. 

Make the assembly mark on the torsion bar spring, bar base and adjusting arm. 

Loose the adjusting bolt until the torsion bar has not tension. 

Caution There are the L and R indication marks, which must not be exchanged on the read end of the torsion bar spring. Mark L means the left andRforright. 

---