Investigation of the joinability of the high-strength aluminum alloy AA7075 in shear-clinching processes

Shear-clinching has proven to be a suitable technology for joining of high-strength materials. However, the mechanical properties of the upper joining partner are limited due to the high strains, which occur during the process. Therefore, shear-clinching of the high-strength aluminum alloy AA7075 in the T6 temper is not possible. Yet, the mechanical properties of hardenable alloys of the 7000 series can be influenced by a heat treatment. Thus, within the scope of this work, the joinability of the high-strength alloy AA7075 in shear-clinching processes in dependance of its temper is investigated. The as fabricated state F, the artificially aged T6 temper, a paint baked state and the naturally aged T4 temper are compared to the fully solution annealed W temper as well as to a retrogression heat-treated state. For retrogression heat treatment, a laser is used as heat source, heating up the alloy for a short term in order to only partially dissolve precipitations. The resulting mechanical properties are determined with uniaxial tensile tests. Moreover, the influence of the mechanical properties of AA7075 on the shear-clinching process, the joint formation and the resulting joint strength is analyzed.

Technological features of autoclave molding of parts of complex configuration from В95оч alloy sheets

The development is shown with the use of modeling the technological process of autoclave molding, combined with the aging process, for the manufacture of upper wing skins from sheets of "В95оч" high-strength alloy taking into account the spring back of the workpiece. The results of studies of indicators of mechanical and corrosion properties of the resulting product are presented. Keywords: autoclave molding, heat treatment, springback, upper wing skin, sheet material, "В95оч". [email protected]

Thermal modelling of cutting tool temperatures and heat partition in orthogonal machining of high-strength alloy steel

Cutting temperatures and heat partition into the cutting tool are critical factors that significantly affect tool life and part accuracy during metal removal operations, especially in dry machining. Among many thermal modelling studies, uniform heat partition ratio, and/or uniform heat intensity along the tool-chip interface are frequently assumed. This assumption is not valid in actual machining and can lead to erroneous estimated results in the presence of sticking and sliding friction zones. Therefore, it is necessary to accurately predict the cutting tool temperature and heat partition during machining. This paper presents an analytical thermal modelling approach which considers the combined effect of the primary and the secondary heat sources and determines the temperature rise and non-uniform heat partition ratio along the tool-chip interface. Cutting tests were conducted on AISI/SAE 4140 high-strength alloy steel using carbide cutting tools over a wide range of cutting speeds. Cutting temperatures were measured experimentally using an infrared thermal imaging camera. Experimentally established sticking and sliding friction regions were used to evaluate non-uniform frictional heat intensity along the tool-chip interface. The temperature matching condition along the tool-chip interface leads to the solution of distributed non-uniform heat partition ratio by solving a set of linear equations through programming in MATLAB®. Experimental results show to be consistent well with those obtained from the thermal model, yielding a relative difference of predicted average tool-chip interface temperature from −0.8% to 6.3%. It is found that average heat partition into the cutting tool ( RT) varies from 35% down to 15% for the entire range of cutting speeds. These results suggest that, to address the thermal problem in metal cutting, the research and development of tooling should also focus on reducing friction on the tool rake face in addition to the contribution of the combined effect of primary and secondary heat sources on temperature rise at the tool-chip interface.