Planes of tests

The curve of distribution of grain striking at the surface of the material under test follows a normal distribution, hence the depth of the resultant indentation varies with position of test, being roughly constant at points equidistant from the centre of the indentation. The bottom of the indentation thus formed has the shape of a spherical cup. The radius of the sphere has been determined experimentally, and in measurements with the Mackensen blower it is 3 mm, equal to the radius of the circle on the plane of tested material, within which abrasion proceeds. From examination of the forma-... 

The deformation between voids was examined using an optical microscope. Thin sections taken from mid-plane of test specimens were prepared for transmission optical mic-... 

Additional assistance is provided by secondary modification options that allow among others for a depiction of the original signal, the reconstruction of the depiction of the impedance plane of the eddy-current signals or for modifications of phase, amplification or zero point virtually in real time. That way, once C-scan images have been recorded, they can now be evaluated as needed without having to repeat the test. 

Any molecule with a plane of symmetry or a center of symmetry is achiral but their absence is not sufficient for a molecule to be chiral A molecule lacking a center of symmetry or a plane of symmetry is likely to be chiral but the supenmposability test should be applied to be certain... 

When using Fischer projections for this purpose however be sure to remember what three dimensional objects they stand for One should not for example test for superim position of the two chiral stereoisomers by a procedure that involves moving any part of a Fischer projection out of the plane of the paper in any step... 

Mech nic lF tig ue. Some mechanical fatigue tests have been conducted on explosion-clad composites where the plane of maximum tensile stress is placed near the bond 2one (30). 

In this test, a rectangular strip sample is formed around a die with a precisely machined edge of a known radius. The sample is formed by 90° or 180° about an axis in the plane of the sheet. The outer surface of the bend is inspected for cracking or unacceptably deep surface mmpling for the particular appHcation. The minimum bending radius (MBR) about which strip can be successfully formed depends on the strip thickness, t, and is reported with the test thickness specified or normali2ed with regard to thickness as MBR/1. Better formabiHty is indicated by smaller MBR/1 values. 

Fig. 8. The dependence on contact angle of the magnitude and location of maximum stress concentration in a lap shear test. As the contact angle decreases, the stress concentration decreases, and its locus moves toward the center-plane of the adhesive phase. Redrawn from ref. [51].

Table 1 contains the metal-to-metal engineering property requirements for Boeing Material Specification (BMS) 5-101, a structural film adhesive for metal to metal and honeycomb sandwich use in areas with normal temperature exposure. The requirements are dominated by shear strength tests. Shear strength is the most critical engineering property for structural adhesives, at least for the simplistic joint analysis that is commonly used for metal-to-metal secondary structure on commercial aircraft. Adhesive Joints are purposefully loaded primarily in shear as opposed to tension or peel modes as adhesives are typically stronger in shear than in Mode I (load normal to the plane of the bond) loading. 

Isotropic construction Identifies RPs having uniform properties in all directions. The measured properties of an isotropic material are independent on the axis of testing. The material will react consistently even if stress is applied in different directions stress-strain ratio is uniform throughout the flat plane of the material. 

The inherent plane of chirality in the metal carbene-modified cyclophane 45 was also tested in the benzannulation reaction as a source for stereoselectivity [48]. The racemic pentacarbonyl(4-[2.2]metacyclophanyl(methoxy)carbene)-chromium 45 reacts with 3,3-dimethyl-1-butyne to give a single diastereomer of naphthalenophane complex 46 in 50% yield the sterically less demanding 3-hexyne affords a 2 1 mixture of two diastereomers (Scheme 30). These moderate diastereomeric ratios indicate that [2.2]metacyclophanes do not serve as efficient chiral tools in the benzannulation reaction. 

Although the ultimate criterion is, of course, nonsuperimposability on the mirror image (chirality), other tests may be used that are simpler to apply but not always accurate. One such test is the presence of a plane of symmetry A plane of symmetry (also called a mirror plane) is a plane passing through an object such that the part on one side of the plane is the exact reflection of the part on the other side (the plane acting as a mirror). Compounds possessing such a plane are always optically inactive, but there are a few cases known in which compounds lack a plane of symmetry and are nevertheless inactive. Such compounds possess a center of symmetry, such as in a-truxillic acid, or an alternating axis of symmetry as in 1. A... 

In order to obtain proper results with these formulas, it should be remembered that they are projections and must be treated differently from the models in testing for superimposability. Every plane is superimposable on its mirror image hence, with these formulas there must be added the restriction that they may not be taken out of the plane of the blackboard or paper. Also, they may not be rotated 90°, though 180° rotation is permissible ... 

With these restrictions Fischer projections may be used instead of models to test whether a molecule containing asymmetric carbons is superimposable on its mirror image. However, there are no such conventions for molecules whose chirality arises from anything other than chiral atoms when such molecules are examined on paper, three-dimensional pictures must be used. With models or three-dimensional pictures there are no restrictions about the plane of the paper. 

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