Materials

Low-temperature plasma (LTP) activation is increasingly used as a surface modification technique to enhance the wettability and biological performance of metallic implants. However, the stability of plasma-induced surface changes and their interaction with standard sterilisation procedures remain insufficiently understood. This study aimed to evaluate the effects of LTP activation, steam sterilisation, and their combination with the wettability of metallic implant materials, as well as the temporal stability of these effects. Samples manufactured from Ti6Al4V sheet, additively manufactured Ti6Al4V, and additively manufactured cobalt–chromium alloy were subjected to low-temperature plasma activation, steam sterilisation, or both procedures. Surface wettability was assessed by measuring the contact angle of canine blood droplets immediately after treatment and over a five-day observation period. Low-temperature plasma activation resulted in a substantial reduction in the contact angle for all tested materials, indicating a pronounced increase in surface wettability. However, this effect gradually diminished over time. Steam sterilisation alone moderately improved wettability and showed relatively stable effects. When steam sterilisation was applied after plasma activation, the plasma-induced enhancement was significantly attenuated and rapidly lost during storage. These findings demonstrate that while LTP activation effectively improves surface wettability, its benefits are highly time-dependent and strongly influenced by subsequent sterilisation. Plasma activation should therefore be performed immediately before implantation or combined with sterilisation and storage strategies that preserve surface modifications.

To mitigate the potential adverse effects of magnetic flux leakage from permanent-magnet sliding bearings on human health and the environment, this study proposes a leakage-suppressed design based on a multi-layer yoke configuration. The magnetic performance of the bearing was systematically investigated using finite element method (FEM) simulations. The results demonstrate a pronounced reduction in magnetic leakage when replacing a conventional single-layer yoke with an optimized multi-layer yoke structure. Targeted design refinements, including optimization of both the number and angular span of magnetic rings, as well as tuning of the yoke thickness, further enhance the effectiveness of the leakage-suppression strategy. The proposed multi-layer yoke configuration preserves both the magnetic force and the load-carrying capacity of the magnetic bearing, while concurrently providing a viable theoretical and engineering basis for the design and structural optimization of leakage-controlled permanent-magnet bearings.

Fiber-reinforced polymer (FRP) pipes are increasingly used in pressure piping systems due to their corrosion resistance and favorable mechanical performance; however, the direct experimental validation of design assumptions adopted in international standards remains limited. The objective of this study is to experimentally validate the mechanical response and stress distribution of filament-wound GFRP pipes under representative loading conditions and to assess the consistency of the measured behavior with the allowable-stress design framework of ISO 14692 and complementary ASME and BS codes. In this study, the mechanical behavior of filament-wound glass fiber-reinforced polymer (GFRP) pipes is investigated through a combined experimental program including tensile, bending, and full-scale internal pressure tests. Electrical resistance strain gauges were applied in axial and circumferential directions to directly measure deformation under internal pressure up to 31 bar, allowing experimental stresses to be derived using orthotropic laminate relationships. The results demonstrate a predominantly linear elastic response within the service range, followed by progressive damage initiation at higher load levels, with circumferential stresses consistently exceeding axial stresses, confirming a hoop-dominated response. At the maximum applied pressure of 31 bar, axial and circumferential strains reached approximately ε_a ≈ 1.30 × 10⁻³ and ε_h ≈ 1.60 × 10⁻³, corresponding to experimentally derived stresses of σ_a^exp ≈ 15.3 MPa and σ_h^exp ≈ 18.8 MPa, without catastrophic failure. The novelty of this work lies in the direct integration of full-scale strain gauge measurements with standardized allowable-stress design assumptions, enabling an experimental validation of ISO 14692 that is rarely addressed in existing studies. The experimentally derived stress–strain data show good agreement with theoretical models and provide a direct link between measured behavior and the allowable stress philosophy and design equations defined in ISO 14692 and complementary ASME and BS design codes. The findings validate the applicability of standardized design approaches and provide experimentally grounded support for engineering design decisions in FRP piping systems.