The safe tensile strength of Portland cement concrete would be something like one-tenth of its compressive strength, and might be far less.
Some experiments were next undertaken with the view of ascertaining how far magnetic changes of length in iron were dependent upon the hardness of the metal, and the unexpected result was arrived at that softening produces the same effect as tensile stress; it depresses the elongation curve, diminishing the maximum extension, and reducing the " critical value " of the magnetizing force.
Its tensile strength is higher than that of steel.
58) has two vertical asymptotes x = ~ 3/4irx; this shows that however the thickness of a cable be adjusted there is a limit irA to the horizontal span, where A depends on the tensile strength of the material.
Assuming the materials to be of equal tensile strength per unit of area - hard-drawn copper is stronger, but has a lower conductivity - the adoption of aluminium thus leads to a reduction of 52% in the weight, a gain of 60% in the strength, and an increase of 26% in the diameter of the conductor.
Ewing has shown that it is diminished and may even be reversed by tensile stress.
Further, it was shown that the thermo-electric curves were modified both by tensile stress and by annealing in the same manner as were the change-of-length curves, the modification being sometimes of a complex nature.
By the addition of a small quantity of silicon the tensile strength of copper is much increased; a sample of such silicon bronze, used for telegraph wires, on analysis was found to consist of 99.94% of copper, 0.03% of tin, and traces of iron and silicon.
Most metals when molten are capable of dissolving at least small proportions of carbon, which, in general, leads to a deterioration in metallicity, except in the case of iron, which by the addition of small percentages of carbon gains in elasticity and tensile strength with little loss of plasticity.
They have shown that columns of water of very small diameter can so resist tensile strain that they can be lifted bodily instead of flowing along the channel, They suggest that the forces causing the movement are complex, and draw particular attention to the pull upwards in consequence of disturbances in the leaves.
It would appear, however, that the finest " wild " Para rubber as a rule possesses greater tensile strength than the " plantation " rubber.
Cobalt, curiously enough, was found to be quite unaffected by tensile stress.
4 Some writers have indeed contended that the stress in magnetized iron is not compressive, but tensile, even when, as in the case of a ring-magnet, there are no free ends.
Such an alloy can be cast like ordinary bronze, but excels the latter in hardness, elasticity, toughness and tensile strength.
Schleissen, to split), in geology, a fissile, fine-grained argillaceous rock which cleaves or splits readily into thin slabs having great tensile strength and durability.
On this account it is usual to neglect the tensile strength of concrete in designing structures, and to arrange the material in such a way that tensile stresses are avoided.
It has considerable compressive or crushing strength, but is somewhat deficient in shearing strength, and distinctly weak in tensile or pulling strength.
But it is difficult and expensive to work up into various forms. Concrete has been avoided for making beams, slabs and thin walls, just because its deficiency in tensile strength doomed it to failure in such structures.
To meet tensile stresses the steel is nearly always inserted in the form of bars running along the beam.
In each case the object is to place the bars as nearly as possible where the tensile stresses occur.
The average strength of 98% metal is approximately shown by the following table: - Weight for weight, therefore, aluminium is only exceeded in tensile strength by the best cast steel, and its own alloy, aluminium bronze.
The tenacity or tensile strength increases till the carbon-content reaches about 1.25%, and the cementite about 19%, and then in turn falls, a result by no means surprising.
Nickel steel, which usually contains from 3 to 3.50% of nickel and about 0.25% of carbon, combines very great tensile strength and hardness, and a very high limit of elasticity, with great ductility.
Hence, as with the progressive transfer of the carbon from the graphitic to the cementite state in our imaginary series of cast irons, the combined carbon present in the matrix increases, so does the tensile strength of the mass as a whole for two reasons; first, because the strength of the matrix itself is increasing (DE), and second, because the discontinuity is decreasing with the decreasing proportion of graphite.
As regards both tensile strength and ductility not only the quantity but the distribution of the graphite is of great importance.
To sum this up, as graphite is replaced by carbon combined as cementite, the hardness, brittleness and density increase, and the expansion in solidification decreases, in both cases continuously, while the tensile strength increases till the combined carbon-content rises a little above I %, and then in turn decreases.
It is, however, principally a cordage fibre, and in tensile strength it is second only to manila hemp; but it does not bear well the alternations of wet and dry to which ship-ropes are subject.
Such composite structures take advantage at once of the high tensile strength of iron and of the high compressive strength of cement mortar.
There is considerable distortion of the clay, resulting from combined shearing and tensile stress, above each of the steps of rock, and reaching its maximum at and above the highest rise ab, where it has proved sufficient to produce a dangerous line of weakness ac, the tension at a either causing actual rupture, or such increased porosity as to permit of percolation capable of keeping open the wound.
Tensile stresses (indicated by broken lines on the diagram) are shown at the upstream toe notwithstanding that the line of resistance is well within the middle third of the section.
Similar experiments upon models with rounded toes but otherwise of the same form showed a considerable reduction in the magnitude of the tensile stresses.
Concrete by itself, though strong in compression, can offer but little resistance to tensile and shearing stresses, and as these stresses always occur in beams the problem arises how best to arrange the steel so as to assist the concrete in bearing them.
But in a thin slab, with its comparatively small span and light load, the concrete is generally strong enough to bear the shearing stresses unaided, and the reinforcement is devoted to assisting it where the tensile stresses occur.