Browse Topic: Fasteners

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Internal recirculating ball screws are widely used as linear motion components in automotive active safety systems, owing to their simple structure and compact size. The recirculation (or deflection) channel is a key feature that distinguishes this type from other ball screw designs. The objective of this article is to investigate this key feature that has been rarely addressed in existing research on internal ball screw. The conventional design method for the recirculation channel involves sweeping the cross-section along the center curve. The center curve is typically defined by various classical equations. These equations are applied in different application scenarios. In automotive braking systems, high loads and strict size constraints place critical demands on both the recirculation channel and its center curve. As a representative best-practice example, the machined channel in the screw is typically employed in this application. This article compares several classical center
Xia, XinanXia, YanzheZhao, Tina
E-25 General Standards for Aerospace and Propulsion Systems
SCOPE IS UNAVAILABLE.
E-25 General Standards for Aerospace and Propulsion Systems
E-25 General Standards for Aerospace and Propulsion Systems
Polymeric optical materials such as Cyclo Olefin Polymer (COP) are adopted in aerospace lighting systems due to their excellent optical clarity, dimensional stability, moldability and weight saving advantages over glass. However, their relatively low toughness and the presence of residual molding stress make them prone to crack initiation during mechanical fastening. During its installation, crack formation was consistently observed around self-tapping screw interfaces, raising concerns over reliability, maintainability, and compliance with durability requirements. A structured Design of Experiments (DOE) was performed to identify root causes and evaluate potential mitigation methods. The investigation revealed that residual stresses in the COP material, combined with localized stress concentrations during screw tightening, were the primary drivers of crack initiation. Two complementary process improvements were identified and validated as part of mitigation plan: (i) annealing of the
S, NikhilSingh, Abhimanyu KumarKatageri, PraveenSP, PradeepChandra, Praveen
Predicting the fatigue life of threaded bolts is crucial in aerospace and mechanical assemblies where cyclic loading can cause early joint failure. Existing studies, like [1], have created S-N curves for high-strength bolts under different pretension and temperature conditions through experimentation. However, there are few numerical methods that can replicate these results, especially for bolts without pretension. This study develops and validates a finite element analysis (FEA) methodology to predict the fatigue performance of pretensioned threaded bolts under axial loading, using the experimentally derived Series-2 S-N data for M20 high-strength bolts with pretension. The approach employs a detailed 3D solid model with explicit thread geometry and a two-step transient structural analysis. This first simulates the bolt tightening process to establish a realistic preload, followed by the application of a service tensile load. Local stress distributions are analyzed to extract peak
K R, LesanthS, Suhail AhmedC, ArunvetrivelP, KrishnakumarP S, PremkumarVasantharaj, C
Aircraft lighting systems play a vital role in ensuring operational safety, visibility, and regulatory compliance. Exterior lighting systems are essential for aircraft identification, navigation, collision avoidance, and ground operations under varying environmental conditions. These systems typically include navigation lights, anti-collision lights, landing and taxi lights. An aircraft lighting system comprises light sources, optical elements, electronic control units, power interfaces, wiring harnesses, and mechanical mounting structures. Among these components, optics are critical as they control light distribution, intensity, color accuracy, and efficiency while withstanding harsh aerospace environments such as vibration, thermal cycling, and aerodynamic loads. Aircraft exterior lights are subjected to severe thermo-mechanical stresses due to aerodynamic loading, vibration, and thermal cycling. The use of high-performance optical polymers such as Cyclo Olefin Polymers (COP
Vialta, FredericoS, NikhilKatageri, PraveenSP, PradeepSingh, Abhimanyu Kumar
E-25 General Standards for Aerospace and Propulsion Systems
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