Occurrence of two-stage hardening in C-Mn steel wire rods containing pearlitic microstructure
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The 8 and 10 mm diameter wire rods intended for use as concrete reinforcement were produced/ hot rolled from C-Mn steel chemistry containing various elements within the range of C:0.55-0.65, Mn:0.85-1.50, Si:0.05-0.09, S:0.04 max, P:0.04 max and N:0.006 max wt%. Depending upon the C and Mn contents the product attained pearlitic microstructure in the range of 85-93% with balance amount of polygonal ferrite transformed at prior austenite grain boundaries. The pearlitic microstructure in the wire rods helped in achieving yield strength, tensile strength, total elongation and reduction in area values within the range of 422-515 MPa, 790-950 MPa, 22-15% and 45-35%, respectively. On analyzing the tensile results it was revealed that the material experienced hardening in two stages separable by a knee strain value of about 0.05. The occurrence of two stage hardening thus in the steel with hardening coefficients of 0.26 and 0.09 could be demonstrated with the help of derived relationships existed between flow stress and the strain.Keywords:
Elongation
Hardening (computing)
Rod
Strain hardening exponent
Flow stress
The stress recovery of the crimped yarn after the constant elongation for hours was investigated.Parameters taken into consideration are t1 (time required to arrive at constant elongation), ts (during which time elongation is kept at initial length), and tt (during which time elongation is kept at constant elongation).The resluts are as follows.It is apparent that recovery coefficient is lowered with increase of rate of elongation. The rate of elongation in this experiment is lower as compared with that of the ordinary. But recovery coefficient is also lowered with high increase in the rate of elongation in the case of felse-twist method yarn. Then it may be deduced that the recovery coefficient decreases with the rate of elongation.As a quantity of constant elongation is increased. ts the time required to recover initial state is increased. But in conventional-twist method yarn, recovery coefficient is small at lower elongation, because force of crimp friction is larger at lower elongaton in the yarn.Conventional-twist method yarn has a special property in water, because of due to the characteristic condition of heat treatment and shape of crimps.
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Constant (computer programming)
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The precise characterisation of hot flow behavior of titanium alloys is of vital importance for practical hot forming processes. To precisely determine the hot flow behavior of titanium alloys under the forming conditions, Gleeble hot tensile tests are usually performed to simulate the forming processes by accurately controlling the deformation temperatures and strain rates under designed conditions. However, there exists a non-uniform temperature distribution during the Gleeble tests, which leads to inaccuracies in the determined hot flow behavior. To overcome such an issue, this paper proposed a new strain-based correction method for Gleeble hot tensile tests, enabling the mitigation of the non-uniform temperature-induced stress-strain curve inaccuracies. The non-uniform temperature zones have been successfully excluded in the calculation of the true strain levels. A series of hot uniaxial tensile tests of TA32 at temperatures, ranging from 750 °C to 900 °C, and strain rates, 0.01/s~1/s, were carried out. The obtained stress-strain correlations for a large gauge zone were characterized using the new correction method, which was further used to evaluate the hardening behavior of titanium alloys. The results have shown that the ductility, strain hardening component (i.e., n), strain rate hardening component (i.e., m) and uniform strain value (i.e., εu) are over-estimated, compared to conventional method. Higher strain rates and lower temperature leads to enhanced hardening behavior. This research provides an alternative correction method and may achieve more accurate stress-strain curves for better guidance of the hot forming process for titanium alloys.
Flow stress
Strain hardening exponent
Hardening (computing)
Titanium alloy
Tensile testing
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Indole-3-acetic acid
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Aluminum (Al) is a phytotoxic element that inhibits root elongation. We used a root auxanometer to examine the kinetics of Al action on primary roots of maize (cv Merit) growing in oxygenated 0.4 mM CaCl{sub 2} adjusted to pH 4.5. One mM Al promoted elongation almost immediately (< 2 min). Within 30-45 min the rate of elongation began to decline and decreased to zero within 36-45 h. Exposure to 10 {mu}M Al also promoted elongation almost immediately; however, the new steady rate was achieved only after about 25 min. When roots were decapped prior to exposure to 10 {mu}M Al, elongation was still promoted but the new steady rate of elongation was not attained until 1.5 h after addition of Al. The results indicate that Al initially promotes root elongation and that the root cap is important for rapid responses to Al.
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The detectability of stored growth at various elongation rates (IAA- and acid- induced) was investigated in 5-mm wheat coleoptile segments. After 20 min turgor reduction by 0.15 M or 0.20 M mannitol, the detectability of stored growth depended on the elongation rate before turgor reduction. A hypothesis was proposed that the amount of stored growth is limited. Depending on the elongation rate, this then appears as complete or partial compensation of the growth lost during turgor reduction. The limit for full compensation was about 300 μm/hr·segment. At elongation rates of > 600 μm/hr·segment, no stored growth could be detected. The elongation of the wheat coleoptile sections at low and high elongation rates is assumed to be limited by different rate-determining steps.
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Turgor pressure
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1. The period of time roots were exposed to low temperatures influenced their elongation rate when returned to 20⚬ C. After two or three 24 hour periods the elongation rate tended to return to the elongation rate of the controls. 2. The hour of the day at which root tips were exposed to low temperatures determined the elongation rate of the roots when transferred to 25⚬C. The roots chilled when more cells were in prophase were retarded in elongation rate. Cells formed by mitotic activity of the embryonic cells started to elongate within the first 24 hours after their formation. Other factors may influence the results obtained. 3. Exposing roots grown at 15⚬ C. to high temperatures produced results similar to those produced in roots exposed to low temperatures. 4. The age of roots and their initial length did not affect the elongation rate of the roots which had been exposed to low temperatures.
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The elongation ratio of 18Ni(250) steel is low in actual test.When the steel is as thin as 1.4mm, the elongation ratio of it is only at 4%around,as if its plasticity is very bad and it approaches brittle materials. Series tensile test were carried out to find the reason for lower elongation ratio of the steel with different thickness 18Ni(250) steel plate as samples.The results show that 18Ni(250) steel has a size effect phenomena,that is its elongation ratio decreased with the decrease of the sectional dimension of the tensile samples.The plasticity of this steel is very fine in fact,and the plasticity of it reflected by its elongation ratio is a feint.
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Brittleness
Tensile testing
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Spatial and temporal analyses of elongation and cell length of monocotyledon leaves have most often been performed during the period when leaves are visible and elongate at a constant rate (steady-state). In the present study, the focus was on the earlier stages, during the establishment of the elongation zone. Regardless of leaf development stage, the segment located between 0 and 35 mm from the leaf insertion point had a relative elongation rate that increased with distance from insertion point ('accelerating zone') while the segment located further than 35 mm had a relative elongation rate that decreased ('decelerating zone'). This stable pattern held for both young, non-emerged leaves, where it was restricted to the portion corresponding to the length of the blade, and for leaves during steady-state elongation. In the same way, the profile of cell length was essentially the same during early development and during steady-state elongation. The results of a temporal analysis of whole-leaf elongation rate, carried out in the field and in the greenhouse at different light intensities were consistent with a time-invariant pattern of elongation. Whole-leaf relative elongation rate increased with time until the leaf reached 30-40 mm length (although at different leaf ages depending on conditions), and declined afterwards. These results suggest that the patterns governing the elongation rate of a sector of a maize leaf are independent of the leaf developmental stage but depend on sector position only.
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It is easy for Coiled Tubing(CT) to deform a plastic elongation because of many factors,such as the residual stress etc,in the process of coiled tubing service.The paper analyses the cause of coiled tubing plastic elongation and explains the principle of the same elongation.Coiled tubing plastic elongation has four mainly reasons: axial load causes plastic elongation,thermal causes plastic elongation,pressure difference causes plastic elongation,helical buckling causes elongation.The theoretical calculation formula and calculation method for CT plastic elongation are summarized.Calculation examples about CT plastic elongation give some basic CT plastic elongation conclusions by comparative analysis of relation curve on calculated value.The CT plastic elongation is more complicated and more obvious than conventional tube.The elongation caused by axial load and the shortening caused by helical buckling are larger than others and should be focused on the need to consider in the progress of coiled tubing service.The thermal expansion and the elongation caused by pressure difference are smaller than above all and should be given due consideration in the progress of coiled tubing service.Total elongation deformation is made up of four parts: the plastic elongation caused by axial load,thermal expansion,plastic elongation caused by pressure difference and the shortening caused by helical buckling.The four elongations may cancel partially each other,so the total elongation deformation generally is smaller than every single elongation.
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The difference between the percentage elongation after the break of aluminum plate and the total percentage elongation at the break of that is demonstrated from theoretical basis and test basis respectively,it is the assistant for better understanding of the percentage elongation after break and the total percentage elongation at break.
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