Instytut Podstawowych Problemów Techniki

Deshpande S., Rappel H., Hobbs M., Bordas S., Lengiewicz J.A., Gaussian process regression + deep neural network autoencoder for probabilistic surrogate modeling in nonlinear mechanics of solids, COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING, ISSN: 0045-7825, DOI: 10.1016/j.cma.2025.117790, Vol.437, No.117790, pp.1-17, 2025

Abstract:
Many real-world applications demand accurate and fast predictions, as well as reliable uncertainty estimates. However, quantifying uncertainty on high-dimensional predictions is still a severely under-investigated problem, especially when input–output relationships are non-linear. To handle this problem, the present work introduces an innovative approach that combines autoencoder deep neural networks with the probabilistic regression capabilities of Gaussian processes. The autoencoder provides a low-dimensional representation of the solution space, while the Gaussian process is a Bayesian method that provides a probabilistic mapping between the low-dimensional inputs and outputs. We validate the proposed framework for its application to surrogate modeling of non-linear finite element simulations. Our findings highlight that the proposed framework is computationally efficient as well as accurate in predicting non-linear deformations of solid bodies subjected to external forces, all the while providing insightful uncertainty assessments.

Keywords:
Surrogate modeling,Deep neural networks,Gaussian proces,Autoencoders,Uncertainty quantification,Finite element method

Liu S., Wu J., Teng F., He S., Yuan X., Stupkiewicz S., Wang Y., Effect of surface adhesion characteristics on stick-slip mechanism of flexible film/substrate bilayer structure: Multiscale insight, TRIBOLOGY INTERNATIONAL, ISSN: 0301-679X, DOI: 10.1016/j.triboint.2025.110520, Vol.204, pp.110520-1-16, 2025

Abstract:
The key to tactile sensors' sliding perception is the stick-slip modulation of the soft material through surface design. Herein, in-situ sliding tests were conducted on polydimethylsiloxane (PDMS) film/substrate bilayer structures (PF/SBS) with three surface adhesion characteristics tailored by crosslinking degrees of PDMS film. Microscopic damage mechanisms during Schallamach wave propagation were analyzed using mixed-mode cohesive contact models. Intermolecular interaction mechanisms at microscopic crack tips were also explored using PDMS-Silica (SiO2) molecular models with varying PDMS crosslinking degrees. The Schallamach waves and tangential force strongly depended on the crosslinking degree of PDMS film. The varying effects of crosslinking degree on normal and tangential separation mechanisms lead to a transition in Schallamach wave damage from mixed mode to Mode II during propagation.

Keywords:
Stick-slip,Film/substrate bilayer structures,Cohesive contact model,Intermolecular interaction

Brachaczek A., Tokpatayeva R., Olek J., Jarząbek D.M., Piotrowski P., Jenczyk P., Jóźwiak-Niedźwiedzka D., Impact of formate based deicing agents on ASR products: Microstructural, chemical and mechanical characteristics, CONSTRUCTION AND BUILDING MATERIALS, ISSN: 0950-0618, DOI: 10.1016/j.conbuildmat.2025.140729, Vol.471, No.140729, pp.1-12, 2025

Abstract:
This study investigates the effects of formate-based deicing agents, specifically potassium formate (HCOOK) and sodium formate (HCOONa), on alkali-silica reaction (ASR) in concrete. By adapting ASTM C1260 standards, mortar bars were subjected to deicing solutions of varying concentrations to evaluate their influence on mortar expansion and ASR product characteristics. Results revealed that high concentrations of formate solutions significantly accelerated ASR, inducing expansions comparable to or greater than those caused by sodium hydroxide, while sodium chloride showed minimal expansion effects. Microstructural and chemical analyses demonstrated that ASR gels formed in formate solutions were predominantly amorphous, with different chemical composition depending on the deicer type. Pore solution analysis indicated a strong correlation between alkali ion concentration and mortar expansion. Furthermore, mechanical testing of ASR products revealed that gels formed in potassium formate exhibited higher hardness and elastic modulus compared to those formed in sodium formate. These findings enhance understanding of the detrimental effects of formate-based deicing agents on ASR and provide a foundation for developing mitigation strategies to preserve concrete infrastructure.

Keywords:
Alkali-silica reaction,Concrete microstructure,Expansion,Nanoindentation,Deicing agents,Pore solution analysis

Fathalian M., Darban H., Postek E. W., Atomistic insights into tensile damage of functionally Graded Al-SiC composites, INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES, ISSN: 0020-7403, DOI: 10.1016/j.ijmecsci.2025.110012, Vol.288, pp.110012-1-110012-16, 2025

Abstract:
The tensile behavior and damage mechanisms of functionally graded (FG) Al-SiC composites are systematically investigated using molecular dynamics (MD) simulations. A comprehensive set of large-scale MD simulations is conducted on FG composites composed of three layers reinforced with different volume fractions of randomly distributed three-dimensional SiC particles. This work introduces a novel approach by modeling the reinforcement ceramic as three-dimensional particles, thereby more accurately representing the FG composite microstructure. Predictions of the model for Young's moduli of composites align with experimental data from the literature. The yield and ultimate tensile strength are overestimated due to the high applied strain rates and idealized crystal structures used in the simulations, which lack common defects such as vacancies and dislocations. The model is utilized to study the influence of reinforcement particle shape, size, orientation, and distribution on the tensile and damage behavior of composites. The FG composites reinforced with cubic particles demonstrate lower yield and tensile strength than those with spherical particles, primarily due to the high-stress concentrations around the corners of the cubic reinforcements. Reducing the size of SiC particles enhances the elastic modulus, yield, and tensile strength of the FG composites. It is shown that the stiffness of the FG composites reinforced with rectangular prisms can be effectively tailored by changing the orientation of the reinforcements. When SiC rectangular prisms are aligned along the tensile direction, the resulting FG composites exhibit higher yield and tensile strength. This work offers fundamental atomistic insights that help design FG composites with better mechanical performance.

Entezari E., Singh A., Mousavisogolitappeh H., Velazquez J., Szpunar J., A cost-effective model for synergistic effects of microstructure and crystallographic texture on hydrogen-induced crack growth and corrosion rates in pipeline steels, Materials Characterization, ISSN: 1044-5803, DOI: 10.1016/j.matchar.2025.114917, Vol.223, No.114917, pp.1-23, 2025

Abstract:
his study proposes a Cost-Effective model based on microstructure, crystallographic texture, and hydrogen (H) diffusion to evaluate H-damage in pipeline steels. H-crack growth and corrosion rates, measured using ultrasonic inspection and a Gamry electrochemical setup, were correlated with microstructure and texture. Results show that smaller ferrite grain size, lower density of co-incidence site lattice boundaries (CSLB), higher densities of geometrically necessary boundaries (GNB) and random high-angle grain boundaries (RHAGB), and higher overall stored energy (EAve) in texture fibers increase H-trap sites and reduce effective H-diffusivity, contributing to higher H-crack growth rates. Conversely, these same factors enhance corrosion resistance by improving passivation. Secondary phases have a detrimental effect on H-crack growth and corrosion resistance, varying with size, continuity, and volume fraction of phases. The proposed model, using hyperparameter tuning, quantifies the synergistic effects of microstructure, texture, and H-diffusion on H-damage and highlights the role of ferrite grain size in mitigating H-damage in pipeline steels. Finally, finite element (FE) analysis of grain structures provided supporting observations.

Keywords:
H-crack growth rate, Corrosion rate, Microstructure, Crystallographic texture, Cost- effective model, Finite element stress analysis

Nabavian Kalat M., Ziai Y., Dziedzic K., Gradys A. D., Urbański L., Zaszczyńska A., Andrés Díaz L., Kowalewski Z. L., Experimental evaluation of build orientation effects on the microstructure, thermal, mechanical, and shape memory properties of SLA 3D-printed epoxy resin, EUROPEAN POLYMER JOURNAL, ISSN: 0014-3057, DOI: 10.1016/j.eurpolymj.2025.113829, Vol.228, pp.113829-1-18, 2025

Abstract:
Additive manufacturing (AM) methods, popularly known as 3D printing technologies, particularly the pioneering laser stereolithography (SLA), have revolutionized the production of complex polymeric components. However, challenges such as anisotropy, resulting from the layer-by-layer construction method, can affect the thermomechanical properties and dimensional stability of 3D-printed objects. Although anisotropy in SLA 3D printing is often overlooked due to the high precision of this technique, its impact on the properties and structural performance of the 3D-printed prototype becomes more significant when printing small devices designed for precise micro-mechanisms. This experimental study investigates the impact of the chosen printing surface – a less explored factor – on the performance of SLA 4D-printed thermo-responsive shape memory epoxy (SMEp) specimens. Two identical dog-bone specimens were printed from two distinct surfaces: edge and flat surface, to examine how variations in surface area and quantity of layers influence the microstructure, thermal behavior, mechanical properties, and shape memory performance. The results of this experimental investigation reveal that specimens printed from the edge, with a higher number of layers and smaller surface area, exhibit superior interlayer bonding, tensile strength, dimensional stability, and shape recovery efficiency compared to those printed from the flat surface. Conversely, specimens with fewer, larger layers demonstrated greater elongation and thermal expansion but reduced structural integrity and shape recovery performance. These results highlight the importance of experimentally investigating how different build orientations affect the properties and performance of SLA 3D-printed materials, especially before designing and employing them in applications demanding high precision and reliability.

Keywords:
Additive manufacturing, Laser stereolithography, Shape memory polymers, Materials processing, Anisotropy, Printing orientation

Sitek R., Bochenek K., Maj P., Marczak M., Żaba K., Kopeć M., Kaczmarczyk G., Kamiński J., Hot-Pressing of Ti-Al-N Multiphase Composite: Microstructure and Properties, Applied Sciences, ISSN: 2076-3417, DOI: 10.3390/app15031341, Vol.15, No.1341, pp.1-15, 2025

Abstract:
This study focuses on the development and characterization of a bulk Ti-Al-N
multiphase composite enriched with BN addition and sintered through hot pressing. The
research aimed to create a material with optimized mechanical and corrosion-resistant
properties suitable for demanding industrial applications. The composite was synthesized using a powder metallurgy approach with a mixture of AlN, TiN, and BN powders, processed under a high temperature and pressure. Comprehensive analyses, including microstructural evaluation, hardness testing, X-ray tomography, and electrochemical corrosion assessments, were conducted. The results confirmed the formation of a multiphase microstructure consisting of TiN, Ti₂AlN and Ti₃AlN phases. The microstructure was uniform with minimal porosity, achieving a hardness within the range of 500–540 HV2. Electrochemical tests revealed the formation of a passive oxide layer that provided moderate corrosion resistance in chloride-rich environment. However, localized pitting corrosion was observed under extreme conditions. The study highlights the potential of a BN admixture to enhance mechanical and corrosion-resistant properties and suggests directions for further optimization in sintering processes and material formulations.

Keywords:
AlN-TiN(BN) composite,hot-pressing,μCT,corrosion resistance

Rosowska J., Kaszewski J., Krajewski M., Małolepszy A., Witkowski B. S., Wachnicki Ł., Lev-Ivan B., Sybilski P., Godlewski M., Godlewski M., Growth of ZnO Nanoparticles Using Microwave Hydrothermal Method — Search for Defect-Free Particles, Nanomaterials, ISSN: 2079-4991, DOI: 10.3390/nano15030230, Vol.15, No.230, pp.1-21, 2025

Keywords:
zinc oxide (ZnO) nanoparticles, microwave hydrothermal method , microwave-assisted synthesis, near-band-edge (NBE) emission, deep-level emission (DLE), luminescent properties of ZnO, photoluminescence (PL), cathodoluminescence (CL), defect-related luminescence

Nazir S., Singh P., Rawat N., Jain A., Michalska M., Yahya M., Yusuf S., Diantoro M., Polyether (polyethylene oxide) derived carbon electrode material and polymer electrolyte for supercapacitor and dye-sensitized solar cell, Ionics, ISSN: 0947-7047, DOI: 10.1007/s11581-024-06052-9, pp.1-11, 2025

Abstract:
This study investigates the development and performance analysis of a supercapacitor using activated carbon synthesized from polyethylene oxide (PEO) as the electrode material, and a poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP)-based polymer electrolyte, prepared using a solution-cast technique for dye-sensitized solar cell (DSSC) application. This paper deals with polyether-based electrochemical devices, where electrode material is developed by polyethylene oxide (PEO), while an electrolyte is prepared using PVdF-HFP. Detailed electrical and photoelectrochemical studies were carried out using various characterization tools, and the results are discussed in detail. Sandwich structure supercapacitors and DSSCs are developed using maximum conducting polymer electrolyte that has an ionic conductivity of (8.3 × 10−5) Scm−1, exhibiting a high specific capacitance of 395 Fg−1 and DSSC efficiency ranging from 1.6 to 3.5% under 1 sun condition. The findings underscore the capability of PEO-derived carbon and polymer electrolytes in improving the efficiency of energy storage and conversion systems.

Keywords:
Polyether, Activated carbon, Supercapacitor, Dye-sensitized solar cell