Lightweight vehicles are one of the most efficient solutions to reduce the fuel consumption and the emission of polluting gases, which leads the automotive industry to the constant need to manufacture ever lighter vehicles. Due to these current requirements, there is a general move toward compact and lightweight powertrain system designs. Although more compact, these systems must be able to transmit the same or even higher forces and torques. Dealing with these contradictory requirements adding to the constant request to minimize production and assembly costs is a huge challenge to engineers. One approach is to enhance the coefficient of static friction in friction joints. When friction joints are designed, physical parameters such as overall size and surface pressure usually can only be varied in a tight window. Load transmission capability in friction joints is thus limited by the friction coefficient of the mating materials. An efficient solution for these limitations is to apply a nickel diamond coating either to the actual parts of the joints or to friction shims for installation in the joint. In…

Fatigue performance can be a critical attribute for the production of structural parts or components via additive manufacturing (AM). In comparison to the static tensile behavior of AM components, there is a lack of knowledge regarding the fatigue performance. The growing market demand for AM implies the need for more accurate fatigue investigations to account for dynamically loaded applications. A357.0 parts are processed by laser-based powder bed fusion (L-PBF) in order to evaluate the effect of surface finishing on fatigue behavior. The specimens are surface finished by shot peening using ϕ = 0.2 and ϕ = 0.4 mm steel particles and ϕ = 0.21-0.3 mm zirconia-based ceramic particles. The investigation proves that all the considered post-processing surface treatments increase the fatigue resistance of as-built parts, but the effect of peening with ϕ = 0.4 mm steel particles or with ceramic particles is more pronounced than that of peening with ϕ = 0.2 mm steel particles, although this treatment has the same Almen A value as the ceramic one. The surface morphology and the crack surface…

Additive manufacturing (AM) is currently being used to produce many certified aerospace components. However, significant advantages of AM are not exploited due to unresolved issues associated with process control, feedstock materials, surface finish, inspection, and cost. Components subject to fatigue must undergo surface finish improvements to enable inspection. This adds cost and limits the use of topology optimization. Continued development of process models is also required to enable optimization and understand the potential for defects in thin-walled and slender sections. Costs are high for powder-fed processes due to material costs, machine costs, and low deposition rates. Costs for wire-fed processes are high due to the extensive postprocess machining required. In addition, these processes are limited to low-complexity features. Incremental improvements in all of these areas are being made, but a step change could potentially be achieved by hybrid processes, which use wire feedstock to deposit the bulk of the part and powder for fine detail.NOTE: SAE EDGE™ Research Reports are intended to identify and illuminate key issues in emerging, but still unsettled, technologies of interest…

This study reports on the effect of cutting fluids on friction behavior of the threaded fasteners. Underhead and thread friction are measured during tightening process of the hex-head threaded fasteners coated with different zinc-based coatings: electroplated zinc, zinc flake, and electroplated zinc nickel, commonly used in the automotive industry. The tests and data analysis are conducted considering ISO 16047 as a baseline. Test conditions are set close to the actual production conditions found in the motor vehicle industry. Water-based and ester-based cutting fluids are selected to unveil their impact on the reliability of the threaded fastener joints. It is shown that a change in the underhead interface conditions from dry to lubricated drastically reduces friction for the electroplated zinc and zinc nickel coatings.