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Numerical Assessment Of Shot Peening Contribution To The Fatigue Strength Of Gear Tooth Root
No full textGears are commonly treated with shot peening (SP) and/or case hardening to enhance fatigue resistance. However, their effects are often conservatively assessed using standardized methods, which can limit their optimal application in industrial components. Particularly, the effect of SP over case-hardened gears remains insufficiently explored. Therefore, the present study evaluates the contribution of SP on single tooth bending fatigue (STBF) strength of raw and case-hardened spur gears, commonly used in automotive and heavy machinery industries. In the study four conditions are addressed: (i) untreated, (ii) case-hardened, (iii) shot-peened, and (iv) case-hardened and shot-peened. First, the residual stress field of the corresponding treatment states are estimated by means of high-fidelity numerical models. Then, STBF strength under different loading conditions is assessed by means of a multi-axial fatigue criteria in combination with the theory of critical distances (TCD). The results confirm that SP significantly enhances fatigue strength by inducing compressive residual stresses that delay crack initiation and slow propagation. When combined with case-hardening, SP further improves fatigue resistance, revealing a strong synergistic effect. These findings highlight the need for an optimized surface treatment strategy beyond conventional design methodologies. In addition, they provide valuable insights into fatigue life improvement in shot-peened and case-hardened gears, contributing to the development of more durable and efficient industrial components
Investigations On The Fatigue Strength Of Threads Produced By Different Fabrication Techniques
No full textThe increasing importance of sustainability in engineering demands the development of long-lasting, high-performance components that reduce material and energy consumption over time. This study investigates how different thread manufacturing processes, i.e., cutting, rolling, and deep rolling, affect the fatigue strength of bolts made from 42CrMo4+QT steel. Cylindrical specimens with M12 threads were subjected to cyclic tensile loading with constant mean stress. Fatigue strength was evaluated using the staircase method, and supporting analyses included X-ray diffraction for residual stress, and full width half maximum examination and Vickers microhardness measurements. Results show that thread rolling significantly improves fatigue strength, achieving 113.8 MPa compared to 45.1 MPa for cut threads. Deep rolling also enhanced fatigue strength to 71.1 MPa, offering a practical alternative for low volume production. Residual stress and hardness distributions confirmed the mechanical benefits of both rolling methods
Improvement of Lithium-Metal Electrode All-Solid-State Batteries Performance by Shot Peening and Magnetron Sputtering
No full textTo enable fast charging in lithium-metal anode all-solid-state batteries, suppressing lithium dendrite formation at the solid electrolyte (SE) interface is critical. Increasing fracture toughness via shot peening (SP) and improving interfacial contact with Au sputtering can inhibit dendrite growth. However, conventional sputtering may reduce toughness due to localized thermal damage. This study investigated magnetron sputtering as a low-damage, plasma-based Au deposition method. SEs with and without SP were fabricated and coated via normal and magnetron sputtering. Critical current density (CCD) and fracture toughness were evaluated. Without SP, CCD improvement was limited regardless of sputtering method due to poor bonding. With SP, CCD was significantly enhanced, and magnetron sputtering yielded higher CCD than conventional sputtering. Fracture toughness tests confirmed that thermal damage from normal sputtering reduced strength, while magnetron sputtering preserved it. These findings demonstrate that combining SP with magnetron sputtering improves SE interfacial properties, enhancing fast-charging capability and cycling stability
Molecular Dynamics and Machine Learning Approaches for Cementitious Material Design
No full textThe brittleness and cracking issues in concrete significantly compromise its structural safety and durability. This study combines molecular simulations and machine learning to address these challenges and enhance cementitious material performance. First-principles calculations, reactive force field, and classical molecular dynamics were employed to decode hydration mechanisms, mechanical properties, and interfacial behaviors, with the aid of a novel machine learning force field achieving near-DFT accuracy at reactive force field speeds. Concurrently, generative adversarial networks (GANs) were used to augment data for predicting concrete strength, enabling the development of high-accuracy machine learning models. These integrated approaches reveal fundamental mechanisms and establish predictive frameworks, offering a transformative pathway for the rational design of next-generation high-performance cementitious materials, thereby contributing to improved structural safety and sustainability in construction
Advancing the Use of Supplementary Cementitious Materials: A Novel Framework for Quantitative Reactivity Estimation
No full textThe partial replacement of Portland cement (PC) with supplementary cementitious materials (SCMs) presents an effective strategy to reduce CO2 emissions associated with cement production while preserving essential mechanical properties and durability. SCMs, such as fly ash, blast furnace slag, calcined clays, and other aluminosilicate-rich materials, enhance sustainability through their pozzolanic and hydraulic reactivity. Despite their significant potential, the widespread adoption of SCMs has been limited by the absence of straightforward and quantitative methods to assess their reactivity‒a crucial property influenced by chemical composition, amorphous content, and particle fineness. To overcome these challenges, this study proposes a novel, simplified quantitative method for evaluating the time- and composition-dependent reactivity of SCMs in a PC-like environment. The approach combines isothermal calorimetry with detailed composition-based reaction enthalpy calculations, providing a robust framework for reactivity assessment. The method was applied to 17 chemically diverse SCMs, yielding reactivity values ranging from 9.3% to 63.2% at 7 days. Analytical models developed in the study reveal the relationships between the chemo-structural parameter (number of constraints, nc), heat release, and reactivity, enabling preliminary predictions based on chemical composition or calorimetric data. Validation across a broad spectrum of SCMs, including slags and calcined clays, confirms the reliability and versatility of this proposed methodology. This cost-effective and straightforward approach offers quantitative insights into SCM reactivity, enabling better control over binder properties and supporting the advancement of sustainable cementitious materials. The findings hold significant implications for optimizing SCM usage and advancing the design of environmentally sustainable construction materials
Exploring the use of cattle manure digestate ash for partial cement replacement in the production of concrete
No full textThe paper investigates, through preliminary tests on mortar mixes, the possibility of substi-tuting a relevant percentage of cement with cattle manure ash for production of sustainable concretes
The Water Absorption of Alternative Supplementary Cementitious Materials and its Impact on the Rheological Properties of Fresh Paste
No full textSupplementary cementitious materials (SCMs) are used to reduce the global warming potential (GWP) of concrete as cement replacements. ASTM 311 has historically been used to determine the water demand of SCMs; however, recent work has shown that the specific gravity, particle shape, and water absorption of the SCM can all impact the water demand. Alternative SCMS can have variable composition, specific gravity, reactivity, surface area, and water absorption. This study evaluates the rheology and setting time of alternative SCMs after accounting for their specific gravity and internal porosity. The yield stress development and water absorption of the natural pozzolans (NPs) are discussed with respect to water demand and structure development
Environmental and Economic Evaluation of Sustainable Concrete
No full textConcrete, as the most used material in construction industry, shows a great potential to reduce greenhouse gas emissions. Substituting cement, as the most expensive and environmentally detrimental concrete component, with innovative material would improve concrete environmental and economic performance. This study explores CO2-mineralized solid waste as a cost-effective supplementary cementitious material that matches conventional concrete’s strength in the same class, while lowering its environmental impact. Life cycle assessment and techno-economic analysis will be employed to quantify the environmental performance and economic feasibility of concrete, respectively
Reactivating recycled hydrated cement into a value-added cementitious material using CO2
No full textThe mineralization of CO₂ from industrial emissions using hydrated cement components, primarily sourced from abundant end-of-life concrete or other waste concrete materials, could provide a unique pathway for reducing GHG emissions associated with the construction industry. Calcium silicate hydrates, along with other hydrated and unhydrated clinker phases, undergo dissolution- precipitation reactions, forming stable calcium carbonates and amorphous decalcified silicate-rich phases, which can be utilized as supplementary cementitious materials. This work demonstrates the characteristics of CO₂ mineralization in hydrated cement paste materials and the resulting products
Experimental Study about Various Factors that Influence Quantitative Accuracy of CO2 Content in Carbonated Cementitious Material
No full textWe investigated a method to accurately quantify the amount of CO2 fixed in concrete. There are major measurement methods which have different sample decomposition process by acid (AC) and thermal decomposition (TC) method, and the type of CO2 which is able to be quantified is determined by the decomposition methods. Theoretically AC method can quantify only inorganic carbon in cementitious materials. On the other hand, CO2 content by TC method would be affected by organic and elemental carbon containing in the sample, because TC method cannot recognize those. In this study, we designed to compare the CO2 content of cement paste that does not contain organic carbon in the mix design by using AC and TC method. As the result, the TC measurement method showed higher CO2 content than AC method. It could be caused by the presence of carbon that cannot be decomposed by AC. In addition, analysis result of the residue after AC showed the CO2 which was not completely decomposed by AC seems to be remained on silica gel