Applied Mechanics

29 pages, 30122 KB

Open AccessArticle

Micro-Structured Multifunctional Greener Coatings Obtained by Plasma Spray

by Spyridoula G. Farmaki, Dimitrios A. Exarchos, Panagiota T. Dalla, Elias A. Ananiadis, Vasileios Kechagias, Alexandros E. Karantzalis and Theodore E. Matikas

Appl. Mech. 2025, 6(4), 76; https://doi.org/10.3390/applmech6040076 - 13 Oct 2025

Abstract

The increasing reliance on conventional coatings such as WC-Co raises serious environmental and health concerns due to the toxicity of cobalt and the ecological footprint of these materials. To address this challenge, the present study explores the development of eco-friendly multifunctional coatings via the Plasma Spray (PS) process, using titanium (Ti), silicon carbide (SiC), and tungsten carbide-cobalt (WC-Co) mixtures as alternative feedstocks. Steel substrates were coated under different deposition strategies (powder mixing, layer-by-layer) and current settings (800-900 A). The coatings were characterized by scanning electron microscopy (SEM/EDX), 3D profilometry, sliding wear testing, and potentiodynamic corrosion measurements. Results showed that Ti-WC (mix, 900 A) and Ti-SiC (layer, 900 A) coatings achieved the most favorable performance, combining excellent adhesion, uniform coverage, reduced porosity, and improved resistance to wear and corrosion compared to conventional Cr₂O₃ coatings. Notably, Ti-WC coatings provided surface roughness values comparable to Cr₂O₃, while significantly lowering the environmental impact. These findings demonstrate that PS-based Ti-WC and Ti-SiC systems can serve as sustainable and high-performance alternatives for protective applications in harsh environments, particularly in marine industries, supporting the transition toward coatings with reduced ecological footprint. Full article

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15 pages, 543 KB

Open AccessArticle

Residual Stress in Surface-Grown Cylindrical Vessels via Out-of-Plane Material Configuration

by Eric Puntel

Appl. Mech. 2025, 6(4), 75; https://doi.org/10.3390/applmech6040075 - 10 Oct 2025

Viewed by 158

Abstract

We consider an axysimmetric cylindrical vessel grown by surface deposition at the inner boundary. The residual stress in the vessel can vary, e.g., depending on the loading history during growth. Can we represent and characterize a stress-free material (namely, reference) configuration for the vessel? Extending an idea initially proposed for surface growth occurring on a fixed boundary, the material configuration is introduced as a two-dimensional manifold immersed in a three-dimensional space. The problem is first formulated in fairly general terms for an incompressible neo-Hookean material in plane strain and then specialized to material configurations represented by ruled surfaces. An illustrative example using geometric and material parameters of carotid arteries shows the characterization of different material configurations based on their three-dimensional slope and computes the corresponding residual stress fields. Finally, such a slope is shown to be in a one to one relationship with the customary measure of residual stress in arteries, i.e., the opening angle in response to a cut. The present work introduces a novel framework for residual stress and shows its applicability in a special setting. Several generalizations and extensions are certainly necessary in the following sections to further test and assess the proposed method. Full article

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25 pages, 999 KB

Open AccessArticle

Modeling Kinematic and Dynamic Structures with Hypergraph-Based Formalism

by Csaba Hajdu and Norbert Hegyi

Appl. Mech. 2025, 6(4), 74; https://doi.org/10.3390/applmech6040074 - 9 Oct 2025

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Abstract

This paper introduces a hypergraph-based formalism for modeling kinematic and dynamic structures in robotics, addressing limitations of the existing formats such as Unified Robot Description Format (URDF), MuJoCo-XML, and Simulation Description Format (SDF). Our method represents mechanical constraints and connections as hyperedges, enabling the native description of multi-joint closures, tendon-driven actuation, and multi-physics coupling. We present a tensor-based representation derived via star-expansion, implemented in the Hypergraph Model Cognition Framework (HyMeKo) language. Comparative experiments show a substantial reduction in model verbosity compared to URDF while retaining expressiveness for large-language model integration. The approach is demonstrated on simple robotic arms and a quarter vehicle model, with derived state-space equations. This work suggests that hypergraph-based models can provide a modular, compact, and semantically rich alternative for the next-generation simulation and design workflows. The introduced formalism reaches 50% reduction compared to URDF descriptions and 20% reduction compared to MuJoCo-XML descriptions. Full article

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18 pages, 3975 KB

Open AccessArticle

Accelerated Carbonation for Improving Mechanical Performance of Sustainable Fiber-Cements Containing Lime Sludge

by Rudicler Pereira Ramos, Felipe Vahl Ribeiro, Cristian da Conceição Gomes, Thamires Alves da Silveira, Arthur Behenck Aramburu, Neftali Lenin Villarreal Carreno, Angela Azevedo de Azevedo and Rafael de Avila Delucis

Appl. Mech. 2025, 6(4), 73; https://doi.org/10.3390/applmech6040073 - 30 Sep 2025

Viewed by 320

Abstract

The combined effects of accelerated carbonation and lime sludge incorporation on the mechanical and durability performance of fiber-cement composites were assessed in this study. Lime sludge was used to replace 0%, 10%, and 20% of the cement in the composites, which were then autoclave-cured and carbonated more quickly for two or eight hours. With LS20-C8 (20% lime sludge, 8 h carbonation) achieving the highest carbonation efficiency (74.0%), X-ray diffraction (XRD) verified the gradual conversion of portlandite into well-crystallized calcium carbonate (CaCO₃). In terms of mechanical performance, LS20-C8 outperformed the control by increasing toughness by 16.7%, flexural strength by 14.2%, compressive strength by 14.6%, and compressive modulus by 20.3%. The properties of LS20-C8 were better preserved after aging under wetting-drying cycles, as evidenced by lower losses of toughness (10.0%) and compressive strength (10.1%) compared to the control (14.6% and 18.3%, respectively). The mechanical improvements were explained by optical microscopy, which showed decreased porosity and an enhanced fiber–matrix interface. Overall, the findings show that adding lime sludge to accelerated carbonation improves durability, toughness, strength, and stiffness while decreasing porosity. This method helps to value industrial byproducts and is a sustainable and efficient way to create long-lasting fiber-cement composites. Full article

(This article belongs to the Topic Advances in Fiber–Matrix Interface: Cohesion Enhancement, Characterization and Modeling of Interfacial Debonding)

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Appl. Mech., Volume 6, Issue 4 (December 2025) – 4 articles

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