Elaine Carballo Siqueira Corrêa

Effect of reverse and cyclic shear on the work-hardening of AISI 430 stainless steel

Sheet metal forming commonly involves various processing steps leading to complex strain paths. The work hardening of the metal under these circumstances is different from that observed for monotonic straining. The effect of the strain path on the hardening of materials is usually studied through sequences of standard mechanical tests, and the shear test is especially well adapted to such studies in sheet forming. Shear straining covering Bauschinger and cyclic strain paths were used in the analysis of the hardening of AISI 430 stainless steel sheets. The tests were conducted at 0°RD, 45°RD, and 90°RD (Rolling Direction) and for three effective strain amplitudes. The results indicate that the material presents Bauschinger effects and strain hardening transients that are sensitive to the testing direction. In addition, the cyclic straining leads to an oscillating stress pattern for the forward and reverse shearing cycles, which depends on the deformation amplitude.

Behavior of surface integrity in cylindrical plunge grinding using different cooling systems

The superficial texture of the material can exert a decisive influence on the application and performance of the machined component. The conventional fluids used in grinding processes are environmental risk and can also be dangerous to the health. The disposal of these toxic fluids is expensive and the contamination in the proximities of the machines can present risks to the health for the personnel in the shop floor. This paper analyzes the performance of the minimum quantity lubricant (MQL) technique and compares it with the conventional cooling method, developing an optimized fluid application method using a specially designed nozzle, through which a minimum amount of oil is sprayed in a compressed air flow. This paper also explores and discusses the concept of the MQL in the grinding process of hardened AISI 4340 steel. The performance of the MQL technique in grinding was evaluated based on an analysis of the surface integrity (roughness, microstructure and microhardness). As a result, it was realized that the MQL technique provides very similar characteristics to conventional process and can be applied in industry, thus contributing to an environment friendly manufacturing.

The effect of cyclic bending on the mechanical properties and dislocation structures of drawn steel bars

Axisymmetric bar drawing increases the strength and decreases the ductility of metals. The recovery of these final mechanical properties often employs costly annealing processes. This paper discusses the possibility of controlling the mechanical properties of AISI 1010 steel bars through cyclic bending after one or two drawing passes and between these two successive passes. It is shown that cyclic bending softens the drawn material and increases its uniform elongation. The attending dislocation structures are presented and related to the associated mechanical properties. It is considered that cyclic bending is of interest in the industrial control of the final mechanical properties of drawn AISI 1010 steel bars.

Effect of the Thermo-Mechanical Processing Characteristics on the Recrystallization of CuZn34 Brass

The effect of the temperature and the annealing time on the recrystallization characteristics of metals has been widely researched. However, the influence of the deformation history (involving changes in the strain path) on the recrystallization of metals is seldom studied. The aim of this paper was to investigate the effect of the mechanical loading sequence (monotonic and Bauschinger shearing tests), the amount of forward (effective strain of 0.10, 0.20, and 0.30) and reverse strain (effective strain of −0.35, −0.45, and −0.55), and the initial state (as-received and annealed) on the recrystallization kinetics of CuZn34 brass sheets. The softening caused by recrystallization is reduced as the forward and reverse strains applied during the Bauschinger shear tests are increased. For all investigated conditions, the data also revealed that the initial state and the amount of the reverse strain were the main variables on the recrystallization kinetics of CuZn34 brass.

Study of the Influence of Chemical Composition on the Pozzolanicity of Soda-lime Glass Microparticles

The use of residues, in partial or total substitution of aggregates or binders in concrete, presents interesting possibilities for obtaining eco-efficient concretes. Research has investigated the use of glass residue in Portland cement composite, whether as an aggregate or a supplementary cementitious material. However, there is still no consensus on the influence of the chemical composition of glass on the behaviour of the composites in which it is used. This paper analyse the influence of this composition on the performance of cement composites produced with microparticles of colourless and amber glass. Pozzolanicity was assessed by direct (Modified Chapelle, electrical conductivity) and indirect test (chemical characterization, X-ray diffraction, thermogravimetric analysis, differential thermal analysis and Strength Activity Index testing. The results show that microparticles of both glass display pozzolanic activity, with no significant differences between them. This confirms the potential for the use of glass microparticles as a supplementary material in cement composites.