Torsion shear test

In Germany, standards have been published describing the Compression Shear Test (DIN 54452), Dynamic Viscosity Determination of Anaerobic Adhesives by Rotational Viscometer (DIN 54453), Initial Breakaway Test at Bonded Threads (DIN 54454), and Torsion Shear Test (DIN 54455). DIN 54455 is particularly interesting since it is one of a very few tests in which a nut and bolt (MIO) are seated to a measured torque before the anaerobic sealant is allowed to cure. 

DIN 54455 Testing of adhesives for metals and adhesively bonded metal joints torsional shear test. 

Verification of the effectiveness of improvement technique through laboratory tests, such as triax-ial tests, simple shear tests, and torsional shear tests, offers several advantages and disadvantages. One of the merits of these element tests is that by obtaining soil samples before and after improvement, a more direct inspection can be made. In addition, more accurate measurement of stress, strain, and other parameters can be performed, and therefore, a more accurate characterization of the improved soil is possible. 

Damping can be determined using the half-power bandwidth method or from the logarithmic decrement by placing the sample in free vibration (ASTM 2007). This technique has been modified to allow cyclic torsional shear testing to strain levels above those typically achieved during a... 

Deutsche Norm 54 454, Initial breakaway test on bonded threads. Deutsche Norm 54 455, Torsion shear test. 

The torsion-tube test described by Whitney, Pagano, and Pipes [2-14] involves a thin circular tube subjected to a torque, T, at the ends as in Figure 2-29. The tube is made of multiple laminae with their fiber directions aligned either all parallel to the tube axis or all circumferentially. Reasonable assurance of a constant stress state through the tube thickness exists if the tube is only a few laminae thick. However, then serious end-grip difficulties can arise because of the flimsy nature of the tube. Usually, the thickness of the tube ends must be built up by bonding on additional layers to introduce the load so that failure occurs in the central uniformly stressed portion of the tube (recall the test specimen criteria). Torsion tubes are expensive to fabricate and require relatively sophisticated instrumentation. If the shearing strain y 2 is measured under shear stress t.,2, then... 

The shear modulus of a material can be determined by a static torsion test or by a dynamic test employing a torsional pendulum or an oscillatory rheometer. The maximum short-term shear stress (strength) of a material can also be determined from a punch shear test. 

Torsion property As noted, the shear modulus is usually obtained by using pendulum and oscillatory rheometer techniques. The torsional pendulum (ASTM D 2236 Dynamic Mechanical Properties of Plastics by Means of a Torsional Pendulum Test Procedure) is a popular test, since it is applicable to virtually all plastics and uses a simple specimen readily fabricated by all commercial processes or easily cut from fabricated products. 

Apart from the short beam shear test, which measures the interlaminar shear properties, many different specimen geometry and loading configurations are available in the literature for the translaminar or in-plane strength measurements. These include the losipescu shear test, the 45°]5 tensile test, the [10°] off-axis tensile test, the rail-shear tests, the cross-beam sandwich test and the thin-walled tube torsion test. Since the state of shear stress in the test areas of the specimens is seldom pure or uniform in most of these techniques, the results obtained are likely to be inconsistent. In addition to the above shear tests, the transverse tension test is another simple popular method to assess the bond quality of bulk composites. Some of these methods are more widely used than others due to their simplicity in specimen preparation and data reduction methodology. 

In-Plane Shear Properties. The basic lamina in-plane shear stiffness and strength is characterized using a unidirectional hoop-wound (90°) 0.1 -m nominal internal diameter tube that is loaded in torsion. The test method has been standardized under the ASTM D5448 test method for in-plane shear properties of unidirectional fiber-resin composite cylinders. D5448 provides the specimen and hardware geometry necessary to conduct the test. The lamina in-plane shear curve is typically very nonlinear [51]. The test yields the lamina s in-plane shear strength, t12, in-plane shear strain at failure, y12, and in-plane chord shear modulus, G12. 

Dynamic-Mechanical Measurement. This is a very sensitive tool and has been used intensively by Nielsen (17) and by Takayanagi (18). When the damping curves from a torsion pendulum test are obtained for the parent components and for the polyblend and die results are compared, a compatible polyblend will show a damping maximum between those of the parent polymers whereas the incompatible polyblend gives two damping maxima at temperatures corresponding to those of the parent components. Dynamic mechanical measurement can also give information on the moduli of the parent polymer and the polyblend. It can be shear modulus or tensile modulus. If the modulus-temperature curve of a polyblend locates between those of the two parent polymers, the polyblend is compatible. If the modulus-temperature curve shows multiple transitions, the polyblend is incompatible. 

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). 

Elastomers are cross-linked macromolecules above the glass transition temperature. The cross-link density is the fundamental engineering quantity which, for instance, determines the modulus of elasticity. Usually, it is measured during vulcanization of well-defined rubber samples in a vulcameter by the moment necessary to perform a given torsional shear of the test sample. Swelling experiments can be performed alternatively, but are problematic for filled elastomers. Such measurements are based on the assumption that the measured quantity does not vary over the sample volume. Inhomogeneous cross-link densities can be determined from the surface hardness, but volumetric resolution is achieved by conventional methods only after cutting the sample. 

Dynamic torsional shear experiments were conducted on a Rheometric Scientific ARES rheometer. The samples were cut 6.35 cm in length strips, 0.30 cm thick. The single frequency temperature ramp test was taken at 1 Hz from -100°C to 150°C at 2°C/min in the linear strain regime (0.01 to 2.00%). 

A range of shear tests exists to satisfy all the requirements for in-plane and some throughthickness shear properties. Although torsion of tubes or rods is often recommended, it is rarely used in practice and has not been standardized. Equally, the rail shear test only appears as an ASTM guide [ASTM D 4255], It is not favored, since a large specimen is required and the test suffers from premature failure initiated at the bolt holes. Several other methods that have been standardized are discus.sed below. 

Davidson BD, Sediles FO. Mixed-mode I-B-IIl delamination toughness determination via a shear-torsion bending test. Compos Part A Appl Sci Manuf 2011 42 589-603. http //dx.doi.Org/10.1016/j.compositesa.2011.01.018. 

A torsional impact test, developed by the GMC Technical Center, Warren, Mich., was used to compare the relative toughness and impact resistance of structural adhesives. In this test, a 3.6-lb. weight falls in a 20-inch, 90 -arc to impact a one-half inch overlap bonded lap shear positioned at a right angle to the bond. The impact scale reads directly in inch-pounds of force needed to break the bond. Sixty inch-pounds is the limit of the test. Steel and aluminum lap shears severely deform near this limit. Table 4 illustrates the typical values obtained. 

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