Subultimate Prestrain and Aging in Mild Steel

1965 ◽  
Vol 87 (2) ◽  
pp. 319-324 ◽  
Author(s):  
D. K. Felbeck ◽  
W. G. Gibbons ◽  
W. G. Ovens
Keyword(s):  
Mild Steel ◽  
High Speed ◽  
Strain Curve ◽  
Local Stress ◽  
Tensile Tests ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Limited Region ◽  
Small Increments ◽  
Necessary And Sufficient

Room-temperature tensile straining of mild steel followed by aging at 350 F causes return of the upper yield and a raising of the stress-strain curve. Tensile tests on a special rimmed steel of low Mn/C ratio show not only the expected raising of the stress-strain curve, but raising by an additional amount when several small increments of strain are each followed by aging at moderate temperatures. Longitudinal tensile prestrain by rolling gives substantially the same results. Tests of specimens prestrained in a limited region by impact or in slow tension and aged indicate that embrittlement of the whole specimen may result. The combined theories of Griffith and Orowan, plus an extension of the Ludwik triaxiality concept, can provide a consistent description of the local stress and average stress (energy) criteria that are necessary and sufficient for high-speed low-energy fracture to occur.

The Development of a Machine for High-Speed Testing of Materials

1937 ◽  
Vol 135 (1) ◽  
pp. 467-483
Author(s):  
R. J. Lean ◽  
H. Quinney
Keyword(s):  
Mild Steel ◽  
Yield Point ◽  
High Speed ◽  
Testing Machine ◽  
Strain Curve ◽  
Maximum Point ◽  
Variable Speed ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
High Speed Machine

The paper contains an account of a research into the effect on metals of different speeds of fracture, using a specially designed high-speed testing machine which is described in detail. The experiments were conducted both in this machine and in a 5-ton variable-speed autographic tensile machine, on five steels, the rate of loading being varied for each. With the high-speed machine toughness, ductility, time to produce fracture, and the stress-strain curve were obtained. The results of these combined tests, given in tables and graphs, show that there is a marked increase in stress due to higher speed of testing; and also that the work required to cause fracture increases with the speed. For mild steel the stress at the initial yield point was found to be in excess of that at the maximum point, when the speed of testing was increased the ductility did not appear to suffer.

scholarly journals A stress-strain curve for the atomic lattice of mild steel in compression

1942 ◽  
Vol 181 (984) ◽  
pp. 72-83 ◽  
Keyword(s):  
Mild Steel ◽  
Yield Point ◽  
Applied Stress ◽  
Pure Iron ◽  
Lattice Strain ◽  
Strain Curve ◽  
Partial Recovery ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Atomic Lattice

A stress-strain curve has been obtained for the atomic lattice of mild steel subjected to compression. A set of atomic planes is selected of which the spacing is practically perpendicular to the direction of the stress, and the change in spacing is measured as the magnitude of the applied stress is systematically varied. The behaviour of the lattice is compared with the corresponding stress-strain relation for the external dimensions in the compression test, and also with the lattice stress-strain curve previously obtained for the same material when subjected to tensile stress. Other experiments are described on the behaviour of the lattice of pure iron in compression. It had been previously shown that at the external yield in tension, the atomic spacing exhibited an abrupt change which remained indefinitely on removal of the stress; the effect was interpreted as a lattice yield point. The present work establishes that the lattice possesses a yield point also in compression, again marking the onset of a permanent lattice strain. The direction of this strain, however, is opposite to that found in tension, and the magnitude increases systematically with the applied stress. The experiments on the pure iron show that under extreme deformation the permanent lattice strain tends to a limit and that with continued deformation partial recovery from the strain may occur. The results suggest that the mechanics of the metallic lattice involve the principle that, after the lattice yield point, in a given direction the lattice systematically assumes a permanent strain in such a sense as to oppose the elastic strain induced by the applied stress.

scholarly journals A stress-strain curve for the atomic lattice of mild steel, and the physical significance of the yield point of a metal

1942 ◽  
Vol 179 (979) ◽  
pp. 450-460 ◽  
Keyword(s):  
Mild Steel ◽  
Yield Point ◽  
Lattice Spacing ◽  
Strain Curve ◽  
Sudden Expansion ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Atomic Lattice ◽  
Tensile Test Specimen ◽  
Technical Interest

A stress-strain curve is obtained for the atomic lattice of mild steel subjected to tensile stress. A set of atomic planes is selected of which the spacing is practically perpendicular to the direction of the stress applied to the tensile test specimen, and which should contract with the cross-section as the specimen extends along its length. It is shown that up to the external yield point the lattice spacing contracts in proportion to the applied stress in conformity with Hooke’s Law; but at the external yield point, instead of a continued contraction, the spacing undergoes an abrupt expansion. As the stress is still further increased, the lattice dimension remains approximately constant in the expanded condition. It is further shown that the sudden expansion which sets in at the yield point while the specimen is under load is fully retained as the load is removed. Also that with the application of increasing stress, the permanent expansion imposed on the lattice spacing systematically increases up to the ultimate stress preceding fracture. It is found in addition that the sharp changes in the lattice spacing at the yield are accompanied by a striking drop in the intensity of the X-ray diffraction ring on which the spacing measurements are based. The experiments have established that the atomic lattice of a metal itself possesses a yield point which marks the onset of permanent lattice strains of an unexpected character and of direct technical interest in connexion with the mechanical properties of metals.

scholarly journals Constitutive Model of 30CrMoA Steel with Strain Correction

Metals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1214
Author(s):  
Song Zhang ◽  
Xuedao Shu ◽  
Jitai Wang ◽  
Yingxiang Xia
Keyword(s):  
Flow Stress ◽  
Constitutive Model ◽  
High Speed ◽  
Strain Curve ◽  
Material Constant ◽  
Test Machine ◽  
Experimental Stress ◽  
High Speed Train ◽  
Stress Strain Curve ◽  
Stress Strain

It is necessary to establish a constitutive model of 30CrMoA steel to optimize the forming shape and mechanical properties of high-speed train axles. The experimental stress–strain curve of 30CrMoA steel was obtained by an isothermal compression test on a Gleeble-3500 thermal simulation test machine under temperature of 1273~1423 K and strain rate of 0.01~10 s−1. Considering the effect of strain on the material constant, an empirical constitutive model was proposed with strain correction for 30CrMoA steel. In addition, the material constant in the constitutive model is determined by linear regression analysis of the experimental stress–strain curve. Comparing the theoretical value and experimental value of flow stress, the correlation R is 0.9828 and the average relative error (ARRE) is 4.652%. The constitutive model of 30CrMoA steel with strain correction can reasonably predict the flow stress under various conditions. The results provide an effective numerical tool for further study on accurate near-net forming of high-speed train axles.

Strain-Rate Effects on Constitutive Behavior of Sn3.8-Ag0.7-Cu Lead-Free Solder

2009 ◽  
Author(s):  
Kok Ee Tan ◽  
John H. L. Pang
Keyword(s):  
Strain Rate ◽  
Yield Stress ◽  
Strain Curve ◽  
Tensile Tests ◽  
Lead Free ◽  
Indentation Hardness ◽  
Strain Rates ◽  
Test Results ◽  
Stress Strain Curve ◽  
Stress Strain

In this paper, the strain-rate dependent mechanical properties and stress-strain curve behavior of Sn3.8Ag0.7Cu (SAC387) solder is presented for a range of strain-rates at room temperature. The apparent elastic modulus, yield stress properties and stress-strain curve equation of the solder material is needed to facilitate finite element modeling work. Tensile tests on dog-bone shaped bulk solder specimens were conducted using a non-contact video extensometer system. Constant strain-rate uni-axial tensile tests were conducted over the strain-rates of 0.001, 0.01, 0.1 and 1 (s−1) at 25°C. The effects of strain-rate on the stress-strain behavior for lead-free Sn3.8Ag0.7Cu solder are presented. The tensile yield stress results were compared to equivalent yield stress values derived from nano-indentation hardness test results. Constitutive models based on the Ramberg-Osgood model and the Cowper-Symond model were fitted for the tensile test results to describe the elastic-plastic behavior of solder deformation behavior.

scholarly journals A study of the Cu0.95Al0.05 alloy: stress-strain curve and microstructure

2018 ◽  
Vol 20 (2) ◽  
Author(s):  
Emilio Medrano ◽  
Mauro Quiroga ◽  
Felipe A. Reyes
Keyword(s):  
Room Temperature ◽  
Single Phase ◽  
Strain Curve ◽  
Tensile Tests ◽  
Optical Microscope ◽  
Metal Alloys ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Electrolytic Copper ◽  
Mechanical Traction

After fabricating five metallographic specimens of the Cu0.95Al0.05 alloy from electrolytic copper and aluminum, these ones were both microstructurally characterized by using a metallographic optical microscope at room temperature and subjected to mechanical traction in order to chart the stress-strain curve. From the characterization, it has been found out that the Cu0.95Al0.05 microstructure is composed of a single phase, and from the tensile tests, it has been obtained its rupture point, 249.361 MPa. The obtained results were explained in the framework of the theory of metals and metal alloys.

scholarly journals Stress-Strain Curve of Mild Steel in the Initial Stage

1972 ◽  
Vol 38 (316) ◽  
pp. 3029-3037
Author(s):  
Yoshio OHASHI ◽  
Koichiro KAWASHIMA ◽  
Sadao MlZUNO
Keyword(s):  
Mild Steel ◽  
Strain Curve ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Initial Stage

scholarly journals Torsional hysteresis of mild steel

1917 ◽  
Vol 93 (651) ◽  
pp. 313-332 ◽  
Keyword(s):  
Mild Steel ◽  
Yield Point ◽  
Elastic Limit ◽  
Strain Curve ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Straight Line ◽  
Straight Portion ◽  
Strain Axis ◽  
Inferior Limit

The stress-strain curve from no load to fracture for mild steel as usually obtained consists of three parts: (1) A straight line, followed by a part deviating only slightly from this straight portion; (2) a sharp bend, followed by a part approximately parallel to the strain axis; and (3) a curved rising part, leading ultimately to the breaking point. It is generally assumed that Hooke’s Law holds throughout the part (1), and is immediately followed by the sharply defined bend which constitutes the yield point. For mild steel first stressed in tension and then in compression, or subjected to positive and then negative torsional stresses, the stress-strain curve within a considerable range of stress is also supposed to be a straight line. It is further well known that if mild steel is stressed in tension beyond the yield point the elastic limit is raised, but only at the expense of lowering it in compression; or, if it is twisted beyond the yield point in one direction, its elastic limit is raised for stresses in that direction, but lowered for those in the opposite direction. Attempts have been made to relate the range of stress through which the stress-strain curve is a straight line with that through which a material, such as mild steel, can be stressed an infinite number of times without fracture. This is expressed by the well known Bauschinger’s Law, which, as stated by Mr. Leonard Bairstow, is as follows:—“The superior limit of elasticity can be raised or lowered by cyclical variations of stress, and at the inferior limit of elasticity will be raised or lowered by a definite, but not necessarily the same, amount. The range of stress between the two elastic limits has therefore a value which depends only on the material and the stress at the inferior limit of elasticity. This elastic range of stress is the same in magnitude as the maximum range of stress, which can be repeatedly applied to a bar without causing fracture, no matter how great the number of repetitions.”

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