Abstract
Blind fasteners are of special interest for aircraft construction since they allow working on joints where only one side is accessible, as is the case in many common aerospace box-type structures, such as stabilizers and flaps. This paper aims to deliver an online monitoring method for the detection of incorrect installed blind fasteners. In this type of fastener, the back side of the assembly is not accessible, so monitoring the process installation is suitable as a system to assess the formed head at the back side with no access. The solution proposed consists of an on-line monitoring system that is based on sensor signals acquired during the installation. The signals are conveniently analyzed in order to provide an evaluation outcome on how the fastener was installed. This new method will help production to decrease/eliminate time and cost-intensive inspections and fasteners over installation in structures. The decrease of the number of installed fasteners will also contribute to weight savings and will reduce the use of resources.
Highlights
Among the large variety of fasteners used in aircraft components, assembly-blind fasteners are a specific type, which, for installation, just require access the front side of the assembly
The scientific community has been involved in great efforts toward the understanding and modelling of the fastening process over the years [1,2] and in developing methods for assessing the state of fastened joints [3,4]
When blind fasteners are used in closed structures their evaluation after installation is not feasible without using time and cost-intensive equipment
Summary
Among the large variety of fasteners used in aircraft components, assembly-blind fasteners are a specific type, which, for installation, just require access the front side of the assembly. This offers the chance of cheaper and easier automation solutions. The fastening process is a challenging operation involving multiple knowledge fields (metallic materials, composite materials, classic mechanics, plastic deformation, machining and manufacturing, contact mechanics, tribology, and others). Quite often, these issues are solved by overcalculating the number of fasteners in order to meet safety requirements, though this leads to the increase of weight and production costs. A reduction of 15% fuselage weight could be Materials 2019, 12, 1157; doi:10.3390/ma12071157 www.mdpi.com/journal/materials potential benefits of blind fasteners are not currently being fully exploited
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