Yr Fiorini

A CONSTANT TENSILE STRESS CREEP TESTING MACHINE

A new constant tensile stress creep testing machine is described. The machine makes it possible to keep the stress constant within 0.1% up to a strain 0.45, assuming the volume of the specimen does not change during the test. The cam profile has been solved for specimen gage lengths of 50.0, 35.0, and 25.0 mm. The static counterbalance of the loading system ensures its high sensitivity, which, together with the minimizing of frictional forces, offers the possibility for the tensile stress to be accurately defined. Erratum to this paper appears in 4(4)

Finite Element Modeling of Magnetic Field/Defect Interactions

Defect modeling and the prediction of magnetic field/defect interactions is of importance to the further refinement of electromagnetic methods of defect detection and categorization. Finite element methods are particularly suited to the analysis of field distributions within magnetic structures having complex boundary geometries and nonlinear B-H characteristics. This paper describes operational aspects of the finite element technique and shows how such methods can be applied to the analysis of electromagnetic methods of nondestructive testing, by predicting the magnetic field distribution around a rectangular slot in the surface of a circular ferromagnetic bar carrying an axial magnetisation current.

A Screening Bioassay Using Daphnia pulex for Refinery Wastes Discharged into Freshwater

A simple method using unsophisticated equipment is suggested for on-site toxicity testing of refinery effluents. This method will provide an inexpensive means of identifying problem materials and establishing priorities for coping with these materials. An arbitrary reference mixture, containing six common constituents of refinery wastewaters, was used for static toxicity tests on 15 species of freshwater invertebrates and 3 species of fish. Daphnia pulex was selected for further testing because it was the most sensitive of the animals tested, relatively inexpensive and easy to maintain, and a potential fish-food organism. If the reference mixture were representative of a refinery effluent, the Daphnia bioassay would be sufficiently sensitive to give reliable results within 48 h, whereas a fish bioassay would show no toxicity even after 96 h. To assess the suitability of the Daphnia bioassay, tests were conducted by personnel at six petroleum refineries. Duplicate tests were in agreement. Results of tests using actual refinery effluents ranged from no toxicity after 96 h to a mean lethal concentration of 1.2% effluent after 48 h. The data presented show that the method was reproducible and that refinery personnel were able to perform the bioassay. Potential problems and advantages of the method are discussed.

Asphalt Cements: Pen-Vis Number and Its Application to Moduli of Stiffness

Because of the false softening points of many Canadian asphalts due to the waxy crude oils from which they are derived, highly erroneous values for Pfeiffers and van Doormaals penetration index as a quantitative measure of the temperature susceptibility of asphalt cements occur. Consequently, it has been necessary to develop a different quantitative measure for temperature susceptibility, pen-vis number, which is based on an asphalt cements penetration at 77°F (25°C) and viscosity in centistokes at 275°F (135°C). The development of the pen-vis number of an asphalt cement and its application to the determination of moduli of stiffness of asphalt cements and asphalt paving mixtures are described.

Evaluation of Some Factors Affecting Measurements of Slip Resistance of Shoe Sole Materials on Floor Surfaces

Research done at Liberty Mutual Research Center consisted of 7090 slip tests in an attempt to show it is possible to determine differences in the slip-resistant qualities of various shoe soles. The tests included seven floor materials, eleven shoe sole materials, three sole pressures on wet and dry floors, and four widely different relative humidities. Thirteen operators took the measurements, using the Horizontal Pull Slipmeter. The measurements proved to be sensitive to relative humidity, sole pressure, repetitive measurements, and wet and dry conditions. Each operator demonstrated that consistent measurements can be taken with the Horizontal Pull Slipmeter. The conclusion is that it is possible to identify shoe sole materials that have desirable slip-resistant qualities for various floor surfaces under wet and dry conditions.

Strength and Ductility of Cr-Mo-V Steels in Creep at Elevated Temperatures

A state-of-the-art survey of literature pertaining to low alloy Cr-Mo-V steels has been completed with a view to elucidate the effects of composition, heat treatment, and microstructure on the creep strength and ductility of the steels. It appears that minor amounts of alloy additions such as boron, titanium, and cerium and impurity elements phosphorus, sulfur, tin, antimony, aluminum, and copper may affect the creep strength or ductility or both of the steels. Higher austenitizing and lower tempering temperatures lead to improved strength at the expense of rupture ductility. An upper bainite microstructure is associated with the highest creep strength and the lowest ductility, for temperatures up to 1050°F (565°C) and for times of at least up to 10,000 h. In bainite-ferrite aggregates, creep and rupture strengths increase in proportion to the amount of bainite, and the difference in strength between the various structures is maintained at least up to 10,000 h at 1070°F (575°C). Stress rupture strengths in general increase linearly with room temperature tensile strength for temperatures up to 1000°F (538°C) and times up to 10,000 h. Variation of rupture strength and minimum creep rate with temperature and time can be adequately described by the Orr-Sherby-Dorn parameter. Activation energies for both creep and for rupture are determined to be about 90 kcal/mole (375 kJ/mole). Further, it is observed that ˙e × tr ⋍ 3.3 and that tt ⋍ 0.3 tr, where ˙ϵ tt, and tr are the minimum creep rate, time for transition from second- to third-stage creep, and time to rupture, respectively.

Mechanical Properties of Cast Tin-Lead Solder

The tensile behavior of a near eutectic tin-lead solder has been determined as a function of various solidification parameters. The results indicate that at solidification rates observed in solder joints the solder alloy possesses superplastic properties similar to those previously observed in deformed and aged alloys.

Heat Transmission in Cellulosic Fiber Insulation Materials

Measurements of heat transmission in a number of different loose fill cellulosic insulations have been made by heat flow meter and guarded hot plate methods. Effect of temperature and density have been studied together with a limited investigation on moisture effects. Variations of up to 18 percent occur in the same nominal materials from different sources. This fact indicates that the raw materials and their processing can have a significant influence on the heat transmission properties. For the optimum density range of 35 to 40 kg/m3 and above, the different materials have a very similar temperature coefficient of thermal conductivity. Lower density materials have a significant radiation contribution to their total heat transmission characteristics.

A Modified Fourier Method of Shape and Surface Texture Analysis of Planar Sections of Particles

A mathematical model based on a Fourier series expansion has been used to represent the roughness of planar sections of particles, that is, the combined effect of shape and surface texture. A new coefficient T is introduced which more precisely expresses the total roughness of the projected two-dimensional profile. It also gives a measure of shape and texture contribution factors separately. The value of the total roughness coefficient depends on the Fourier amplitude coefficients Cn, the length of the perimeter of the profile, and the difference between the maximum and minimum radii. Therefore the value of the total roughness coefficient T is a better representation of grain morphology than is a coefficient derived only from Fourier terms to which shape makes a dominant contribution. This value is the sum of the shape contribution factor Pc and the texture contribution factor Tc.

Signal Processing in Nondestructive Testing

Signal averaging has been used to improve the clarity of flaw indications in an electron beam weld. The delay of an electronic gate has been synchronized to the transducer motion to improve the detectability of a tight interface crack in a tensile specimen. Cross-correlation techniques and multiple transducer arrays have been used to improve the signal-to-noise ratio of artificial flaws in welded panels. Signal averaging has been used to reduce random noise in the through-transmission ultrasonic inspection of a honeycomb composite. Megacycle range ultrasonic flaw information has been recorded on a low frequency FM tape recorder by rapidly sweeping an electronic gate through the time interval of interest. A lock-in amplifier has been used to produce quantitative data in both single-coil and double-coil eddy current systems. Cross-correlation techniques and a multiple-coil eddy current probe have been used to reduce surface roughness noise in an eddy current crack detection system.