Thermal analysis of the chip formation in austenitic stainless steel

The most important property of austenitic stainless steels is corrosion resistance. In these steels, the transition between paramagnetic and ferromagnetic conditions occurs at low temperatures. Therefore, the use of austenitic stainless steels in conditions in which ferromagnetism absence is important can be considered. On the other hand, the formation of strain-induced martensite is detected when austenitic stainless steels are deformed as well as machined. The strain-induced martensite formed especially in the machining process is not uniform through the chip and its formation can also be related to the Md temperature. Therefore, both the temperature distribution and the gradient during the cutting and chip formation are important to identify regions in which martensite formation is propitiated. The main objective here is evaluate the strain-induced martensite formation throughout machining by observing microstructural features and comparing these to thermal results obtained through finite element method analysis. Results show that thermal analysis can give support to the martensite identified in the microstructural analysis.

Influence of HSM cutting parameters on the surface integrity characteristics of hardened AISI H13 steel

The purpose of this study is to evaluate the influence of the cutting parameters of high-speed machining milling on the characteristics of the surface integrity of hardened AISI H13 steel. High-speed machining has been used intensively in the mold and dies industry. The cutting parameters used as input variables were cutting speed (v c), depth of cut (a p), working engagement (a e) and feed per tooth (f z ), while the output variables were three-dimensional (3D) workpiece roughness parameters, surface and cross section microhardness, residual stress and white layer thickness. The subsurface layers were examined by scanning electron and optical microscopy. Cross section hardness was measured with an instrumented microhardness tester. Residual stress was measured by the X-ray diffraction method. From a statistical standpoint (the main effects of the input parameters were evaluated by analysis of variance), working engagement (a e) was the cutting parameter that exerted the strongest effect on most of the 3D roughness parameters. Feed per tooth (f z ) was the most important cutting parameter in cavity formation. Cutting speed (v c) and depth of cut (a p) did not significantly affect the 3D roughness parameters. Cutting speed showed the strongest influence on residual stress, while depth of cut exerted the strongest effect on the formation of white layer and on the increase in surface hardness.

Impact of thermal bridging on the performance of buildings using Light Steel Framing in Brazil

The Light Steel Framing building technology was introduced in Brazil in the late 1990s for the construction of residential houses. Because the design system was imported from the United States and is optimised to work well in that temperate climate, some modi fi cations must be made to adapt it for the Brazilian climate. The objective of this paper was to assess the impact of thermal bridging across enclosure elements on the thermal performance of buildings designed with Light Steel Framing in Brazil. The numerical simulation program EnergyPlus and a speci fi c method that considered the effects of metallic structures in the hourly simulations were used for the analysis. Two air-conditioned commercial buildings were used as case studies. The peak thermal load increased approximately 10% when an interior metal frame was included in the numerical simulations compared to non-metallic structures. Even when a metal frame panel was used only for vertical elements in the facade of a building with a conventional concrete structure, the simulations showed a 5% increase in annual energy use.

Friction and wear of performance of MoDTC and ester-containing lubrificants over steel surfaces under reciprocating conditions

Since the earliest developments of human history, friction has been a major issue. From the invention of the wheel and the use of the first lubricants to the studiesof coated and microtexturized surfaces, significant effort has been put on improvements that couldovercome the resistance to motion. Areview by Holmberg, Andersson and Erdemir[1] shows that, in an average passenger car, about one third of the total energy consumptionis due to friction losses. Of these, another one third is consumed in the engine system. The optimization of the lubricating oil formulation used ininternal combustion enginesis an important way to reduce friction, therefore improving energeticefficiencyand controllingemissions.Lubrication is also a way to assure the required protection to the system by maintaining wear rates in an adequate level, which helps to minimize maintenance costs.