An Experimental Modelling and Numerical FE Analysis of Steel-Strip Ironing Process
This paper deals with analysis of steel strip ironing using experimental modelling and numerical FE simulation. Since both approaches are complementary to each other, numerous results were obtained that enable complete analysis of the processes with in deformation zone. Device for modelling of strip ironing has been developed for experimental testing. Die cone angle, holding force, contact friction conditions on the die and the punch side were varied, due to easily replace able working elements of the device. Friction coefficient values used in numerical FE simulations were determined based on measured values of forces on die and punch, as well as forming load on machine. Experimentally obtained results were confirmed by FE analysis that provided additional information about physics of the process itself within deformation zone. Presented research results point to coherent influences of process factors on tensile wall stress values, which represents key indicator for efficiency of forming, resulting in recommendations for efficient process management.
EXPERIMENTAL AND NUMERICAL INVESTIGATION OF A NEW CONSTRAINED IRONING PROCESS WITH CAPABILITY OF EXTRA HIGH THICKNESS REDUCTION
Original Research Paper Received 13 November 2015 Accepted 29 December 2015 Available Online 14 February 2016 Ironing is a conventional metal forming process for producing thin walled cans with uniform thickness components manufactured from deep drawn cups. The most important drawback of the conventional ironing is that the lower thickness reduction ratio (TRR) requires annealing process and multi stage ironing. Recently a new ironing process named constrained ironing was presented by the current authors to achieve an extra TRR to solve the conventional ironing problems. This process which is based on the compressive stresses makes it possible to achieve high TRR without interruption for additional processing such as multi-stage ironing and annealing. In this paper FEM simulation was performed to investigate the effective parameters. The simulation results showed the process load increases with increasing the friction coefficient. Also the state of the stresses is fully compressive in constrained ironing process while it is tensile in the conventional ironing method. Thus compressive stress components minimize formability problems and higher thickness reduction ratio is achievable in the new ironing method. Moreover experimental results showed that the tensile strength and hardness increased after constrained ironed of the deep drawn cup.
Testosterone levels, handedness and sex ratio at birth.
Geschwind has hypothesized that levels of androgens in utero affect postnatal laterality preferences, high levels being associated with left-handedness of offspring. I have hypothesized that high parental androgen levels at the time of conception are associated with subsequent male births. However, left-handed parents seem to produce an excess of female, not male, offspring. This finding could be reconciled with the two hypotheses if individuals who were exposed to high levels of androgens in utero had low circulating levels in adulthood. Some evidence for this loophole is reviewed here. Lyster & Lloyd (1987, J. theor. Biol. 126, 125) have reported that (consistent with the hypotheses) index left-handed men have an excess of brothers; but, contrary to the hypotheses, index left-handed women have an excess of sisters. Accordingly these authors proposed that left-handedness in females is associated not with high levels of androgen in utero, but with a "sensitivity" to it. If such sensitivity were associated with low androgen levels, it might explain an excess of sisters among the sibs of left-handed women. It is shown here that evidence in agreement with this hypothesis (though not discriminating between it and Geschwind's) suggests that the sex ratios of offspring of LH male x RH female and of RH male x LH female matings, are both low.