The Application of a Digital Computer to Mechanical Testing

A digital computer is being used to record raw data and to provide automatic data calculations for mechanical tests. The computer which is connected through an analog-digital converter to a universal testing machine and to a torsion tester, stores the raw loadstrain data, converts it to stress-strain data, and calculates any of the mechanical properties desired from the test. The computer can also provice a printout and a paper tape, both of which contain the stress-strain data points and the calculated data. In addition, the loadstrain data that are normally obtained from the test machine are still available. An oscilloscope display is obtained as the data are being recorded. Tests which are presently being performed using the computer are: tensile, compression, pin bearing, double shear and torsion. Data which are being recorded include: ultimate strength, offset yield strength, elastic and shear moduli, energy under the stress-strain curve, and a mathematical expression for the stress-strain curve. In addition to the mechanical load-strain curve provided by the test machine, the computer can provide a stressstrain curve and a listing of stress-strain data points.     

Polymer reactions. II. Thermal decomposition of polyethylene hydroperoxide

Polyethylene hydroperoxide (PEH) was prepared by low-temperature autoxidation initiated by AIBN. Over 85% of the total hydroperoxyl groups decompose by a rapid process, the remainder dissociate at about one-tenth of that rate. The results are the same whether PEH is decomposed in solution or in the solid state. Large amounts of scavenger have no effect on these decompositions; there is no radical-induced processes. The results suggest mechanisms of decomposition involving neighboring group assistance.     

Über die Proliferationsfähigkeit hochvernetzter glasiger Polymerer

Zusammenfassung Die Modifizierung hochvernetzter Styrol—Divinylbenzolcopolymerisate durch Zusatz von Verdünnungsmitteln bei der Polymerisation führt zur Bildung proliferationsfähiger Polymerer. Es besteht ein enger optimaler Zusammensetzungsbereich. Der Zusammenhang der Proliferationsfähigkeit mit Gleichgewichtsquellung, permanenter Porosität und Gehalt an anhängenden Doppelbindungen wird untersucht; die Morphologie des Proliferationsprozesses wird in mikrokinematographischen Zeitrafferaufnahmen festgehalten.

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The modification of highly crosslinked styrene—divinylbenzene copolymers by adding diluents to the polymerizing system yields polymers showing proliferous polymerization. There exists an optimum concentration range of diluent. The correlation of proliferous polymerization to equilibrium swelling, permanent porosity, and content of pendent double bonds is investigated. The morphology of the proliferation process is observed in micro time lapse motion pictures.

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Mit 10 Abbildungen     

On a matroid identity

The purpose of this note is to prove an identity for generalized Tutte-Grothendieck invariants, at least two special cases of which have already proved to be of considerable use. In addition, one of these special cases is used to strengthen results of Lindström on the critical exponent of a representable matroid and the chromatic number of a regular matroid.     

The structure of (dibenzylideneacetone)(pentamethylcyclopentadienyl)rhodium(I)

The structure of (dibenzylideneacetone)(pentamethylcyclopentadienyl)rhodium(I), Rh(C₅Me₅)(dba), (dba = PhCHCHCOCHCHPh, Ph = C₆H₅, Me = CH₃), has been determined from three-dimensional X-ray data collected by counter methods. The structure has been refined by least-squares techniques to a final R index on F of 0.035 based on 2100 observations above background. The material crystallizes in the monoclinic space group C⁵_2hP2₁/a, with four molecules in a cell of dimensions a=14.348(12), b=14.063(13), c=11.393(10) », β=104.42(3)°. The observed and calculated densities are 1.35(3) and 1.41 g/cm³. The compound is monomeric. The Rh atom is bonded to the C₅Me₅ ring on one side and to the dba molecule through the two olefinic double bonds on the other. The C₅ and Me₅ portions of the C₅Me₅ ring are planar, but not coplanar as the Me group are bent away from the Rh atom by 0.10 » relative to the C₅ plane. The dba molecule is in the s-cis,s-cis conformation with the two double bonds in a plane which is parallel to the planes of the C₅Me₅ ring. The rest of the dba molecule is nonplanar with the CO group pointing away from Rh. The olefinic double bonds have lengthened on coordination to 1.411(9) ». The H atoms on the terminal C atoms of the dba molecule are in very close contact, the refined H?H distance being 1.83(9) ». It is suggested that the strain imposed on the coordinated dba molecule by this interaction might contribute to its ease of dissociation from the complex in solution and hence account for the catalytic properties of the complex.     

A new concept in friction testing

Methods of measuring friction are reviewed and their shortcomings discussed. The advantages of using the wide range of test speeds, environmental conditions and recording facilities available on a tensile test machine are indicated and a new apparatus designed to fit a tensile tester is described. The design concepts are outlined in some detail and the factors limiting stick-slip motion are indicated. The apparatus can be used either for studies of materials or as an aid to product selection. Test results on a polyurethane rubber, covering a range of velocities and temperatures, illustrate the former, and tests on windscreen wiper blades under both wet and dry conditions illustrate the latter. Although primarily designed for testing the friction of polymers the apparatus is of universal application and can be used for measuring, against a chosen substrate, the coefficients of friction of metals, fabrics, paper, glass, leather, or any other material capable of being mounted in a vertical plane. It is not suitable for particulate matter such as sand, but could be used, for example, for studying the effect of floor finishes on a range of flooring materials.