Dependence of deformation indices on initial yield strength and hardening intensity of wire material in the passage of drawing route

The model of hardening is considered, which provides for dependence of the current yield strength σт on the product of the initial yield strength σт0 and drawing coeffi cient μ to the degree of hardening coeffi cient k (σт = σт0μk). Difference of axial stress increase from action of anti-tension in absence and action of hardening depending on hardening coeffi cient is determined. Dependencies of drawing stress, safety factor I.L. Perlin and stress state index V.L. Kolmogorov on hardening coeffi cient at different values of initial yield strength are built. Limit hardening factor k is defi ned, at which safety factor is equal to 1. Dependencies of deformation indices on initial yield strength of σт0 at different deformation parameters are constructed.

Analytical Study of the Effect of NaCl Solution on Fatigue Resistance of Rotating Shafts

Dynamic shafts subjecting to salty rain water, especially in places with no rain water drainage networks, is undesirable because this media causes corrosion of the parts of shaft that increases as increasing of shaft immersion in a salty media (NaCl) also, increasing of concentration which in turns reducing number of operation runs. Increasing salt concentration from 3% to 6% NaCl results in decreasing of operation runs from 25600 to 17100 runs. Also, increasing salt concentration leads to raise the effect of alternating stress that makes strain hardening factor drop to 0.45 and ratio of dynamic shear stress to static one raise to 2.44 that affects shaft metal performance to resist fatigue. Samples were also, treated by oxy acetylene surface hardening and were cooled by immersion in oil then immersion in 6% NaCl salty solution, the results showed that number of operation runs before failure had increased up to 71022, the effect of alternating stress had decreased down to 6100 N/m2, surface strain hardening factor had increased up to , also ratio of dynamic shear stress to static one had decreased down to 0.839. This is a good indicator of the effectiveness of surface hardening process of shaft parts that subject to salty rain water during maintenance operations.

Research on the Reverse Loading Hardening Model of the X80 Pipeline Steel

Based on the reverse uniaxial loading test, the influences of the plastic deformation on the strength properties are studied. The softening of the X80 pipeline steel is observed which reveals the hardening type is mixed hardening. The expression of mixed hardening factor M and the material parameters of the nonlinear mixed hardening model under different M can be obtained. The results show that, if the pre-strain increases and ranges from 0.55% to 2.5%, the mixed hardening characteristics of the X80 pipeline steel will be more obvious and its M will also increase.

Comparison Between Membrane Theory and Finite Elements Analyses for Domed Shells Edged by Support Ring Beam

The present work devote the effect of shot peening time on the mechanical properties for two aluminum alloys AA2017-T4 and AA6063-T5. The test carried out using standard tensile specimens under various shot peening times. The results showed that the increase in yield and tensile strength values. The maximum increasing at 15 minute for AA 2017-T4, and at 9 minute for AA 6063-T5. The maximum values of strain hardening factor (n) and strength factor (k) are recorded at 15 minute for AA 2017-T4 while recorded the maximum values of (n) at 24 minute and (k) at 9 minute for AA 6063-T5. The results showed that the percent elongation are increased to maximum value at 9 minute for AA 2017-T4 while the minimum value was at the same time for AA 6063-T5.

BEHAVIOUR OF ALUMINIUM ALLOY STRUCTURES UNDER FIRE

In the paper the attention is focused on the influence of high temperatures on the mechanical properties of the aluminium alloys selected by Eurocode 9 for structural uses. Therefore, based on the analysis of existing data taken from technical literature, the variation of the Young's modulus, the conventional yielding strength, the ultimate strength, the hardening factor and the material ultimate strain are represented as a function of the temperature. A mechanical model, based on the well‐known Ramberg‐Osgood formulation, which appropriately takes into account the peculiarities of such materials at high temperatures, is provided. In particular, the combined influence of the hardening factor and temperature on the material stress‐strain relationship is considered and analysed. Then, the proposed model has been introduced in a finite element program, devoted to the global analysis of structures under fire. Finally, the results obtained for a simple portal frame structure, designed with different aluminium alloys, are presented, showing the valuable effect of the material modelling on the structural behaviour of aluminium structures under fire.