Bolted joints are widely used in the aerospace and automotive industries due to their ease of assembly, disassembly and design flexibility. Optimizing threaded fasteners is essential to achieve uniform load distribution and minimize the number of bolts required, thereby reducing system cost and weight. This review paper aims at summarizing the five optimization techniques available in the literature, including bolt layout, tightening strategies, tightening sequences, bolt size, and stresses. The purpose is to emphasize the importance of optimizing bolted joints via the proper selection of materials, geometry, patterns, and bolt sizes, to obtain efficient joints with low assembly time while maintaining strength.

Threaded fasteners are vastly used in the industry due to ease of mounting and dismounting and flexibility of design. Nonetheless, several researchers indicate that most failures recorded on nearly any kind of machinery and vehicles are initiated at fasteners. This review paper aims at summarising the failures involving threaded fasteners available in the literature. The analysis involves categorization of the failures according to the root cause, e.g., incorrect assembly, overload, fatigue, preload loss during operation, among others. The purpose of this review paper is to give a systematic glance of the topic to the scientific and technical community, to correctly orient future investigations on the broad topic of threaded fasteners.

Although extensive research has been carried out on the effects of temperature on the properties of parts by fused filament fabrication, no study considered the opportunity to use different temperatures and cooling strategies for the contour and the infill region. The purpose of this investigation is to explore such an opportunity through an experimental campaign on polylactic acid. Specifically, the variations in tensile properties and warping occurring with different infill temperatures and cooling methods are documented. The results demonstrate that diversifying process parameters used for the contour and infill of the part allow for significant improvements in mechanical properties without affecting the distortion of the manufactured samples. This result can be achieved by either increasing the nozzle temperature or switching off the cooling fan during infilling.