Purpose The purpose of this study is to investigate the effect of geometric imperfections on the transient thermal stress response of functionally graded material (FGM) folded plates subjected to thermal shock loading, which is motivated by the need to enhance the structural reliability and safety of FGM components having complex shapes, such as folded plates, when exposed to sudden high temperatures, where manufacturing defects like imperfections can significantly affect their performance. Design/methodology/approach An eight-noded isoparametric finite element, based on the first-order shear deformation theory (FSDT) and incorporating von Kármán-type geometric nonlinearity, is employed to develop the finite element formulation. The upper surface of the imperfect FGM folded plate is subjected to thermal shock loading, while the lower surface is maintained at room temperature. A nonlinear temperature variation is assumed across the thickness of the plate, and the material properties are considered to be temperature-dependent. The governing equations are formulated using a total Lagrangian approach and solved through the Newmark average acceleration method in conjunction with a modified Newton–Raphson iterative scheme. Findings The findings presented in the present work highlight that the magnitude of transient thermal stresses in a double-fold imperfect FGM plate is lower than that in configurations with a single fold. Furthermore, the sine-type imperfection results in the highest transient thermal stresses, followed by the global type, while the local type exhibits the lowest stress levels across imperfect FGM plate configurations with single and double folds. As the crank angle of the folded plate increases, the magnitude of transient thermal stresses also increases for configurations with single and double folds. Originality/value In this study, the transient thermal stress response of imperfect FGM folded plates subjected to thermal shock loading is analyzed, and to the best of the author’s knowledge, such studies are limited in the literature. A few formulations are reported in the literature where the combined effect of geometric imperfections and material gradation of FGM under thermal shock loading is investigated in a simple and generalized manner that is applicable to single and double folds, as presented in this study. The uniqueness of the present formulation also lies in its applicability to perform a wide range of parametric studies that include investigating the effect of crank angle, geometrical imperfection, volume fraction index and intensity of thermal shock on transient thermal stress analysis of FGM folded plate.
Purpose This study aims to optimize the friction stir welding (FSW) process parameters for AA1100 aluminum alloy pipe joints and evaluate their effects on tensile strength, microhardness, and microstructural characteristics. The objective is to identify the optimal combination of tool rotational speed, welding speed, and axial load for achieving superior joint performance suitable for industrial piping applications. Design/methodology/approach AA1100 aluminum alloy pipe joints were fabricated using friction stir welding. Response Surface Methodology (RSM) based on a Box-Behnken Design (BBD) was employed to investigate the influence of tool rotational speed, welding speed, and axial load on the mechanical properties of the welded joints. Analysis of Variance (ANOVA) was used to evaluate the significance of process parameters and their interactions. Multi-response optimization was performed using the desirability function approach to simultaneously maximize tensile strength and microhardness. Microstructural characterization was conducted to examine grain refinement and weld quality in the stir zone. Findings The ANOVA results indicated that tool rotational speed was the most influential process parameter for both tensile strength and microhardness. The quadratic models exhibited high coefficients of determination (Rˆ2 = 0.99 for tensile strength and Rˆ2 = 0.98 for microhardness), although significant lack of fit was observed for both responses. Multi-response desirability optimization predicted an optimum at 1100.24 rpm, 42.21 mm/min and 4.39 kN, with predicted tensile strength and microhardness of 116.001 MPa and 47.8767 HV, respectively, and an overall desirability of 0.979. Confirmation experiments at the nearest practically achievable settings of 1100 rpm, 42 mm/min and 4.5 kN produced responses within ±10% of the corresponding model predictions. Practical implications The optimized welding parameters obtained in this study can be utilized for the production of high-quality AA1100 aluminum pipe joints in lightweight structural, chemical processing, and industrial piping applications. The proposed optimization methodology can also be extended to other aluminum alloy welding applications to improve joint performance and process efficiency. Originality/value This study presents a comprehensive investigation of friction stir welding of AA1100 aluminum alloy pipe joints using an integrated RSM-based multi-objective optimization approach. The combined assessment of tensile strength, microhardness, and microstructural characteristics provides valuable insights into process optimization and contributes to the development of reliable high-performance welded aluminum pipe structures.
Purpose Nine multi-output regression models were compared for simultaneous HL and CL prediction, supplemented by domain-informed feature engineering, SHapley Additive exPlanations (SHAP explainability), robustness testing and a calibrated physics baseline comparison. The best-performing model, Gradient Boosting (Root Mean Square Error (RMSE) = 0.95 kWh, R2 = 0.990), was used as a surrogate within a Non-dominated Sorting Genetic Algorithm II (NSGA-II) multi-objective optimization framework to identify Pareto-optimal building designs minimizing total energy and peak load. Design/methodology/approach This study presents an integrated machine learning framework for predicting, interpreting and optimizing the heating load (HL) and cooling load (CL) of residential buildings. Findings SHAP analysis revealed that overall height and relative compactness dominate both loads, while orientation has negligible influence. Partial dependence analysis uncovered nonlinear response patterns, and counterfactual scenario testing confirmed that the energy gap between single-story and two-story buildings remains constant regardless of glazing level, establishing height as the primary design lever. The NSGA-II optimization identified designs achieving total energy as low as 17.06 kWh. Research limitations/implications The framework bridges prediction and actionable design guidance for energy-efficient buildings. Originality/value This work is a novel optimization of energy in a building using nine models.
Purpose This paper addresses the critical environmental challenge of decommissioned wind turbine blades by exploring their direct structural reuse in the built environment. It investigates the mechanical feasibility of repurposing these complex composite shells as self-supporting, load-bearing elements in architectural applications. Design/methodology/approach The study utilizes finite element method (FEM) simulations to evaluate the structural behavior of blades ranging from 30 to 105 meters under static loads. Structural viability is assessed under different boundary conditions (fixed and doubly pinned supports) and applied to four architectural case studies (stadium roofs, pedestrian bridges, slabs and pergolas) following Spanish regulatory frameworks (CTE and IAP-11). Findings The results suggest the structural feasibility of the blades, which exhibit significant bending stiffness and load-bearing capacity for architectural spans, provided that their primary high-stiffness axis is respected. In fixed support configurations, serviceability limit states (deflection) govern the design, whereas ultimate limit states (material strength) constrain doubly pinned configurations. Research limitations/implications This study adopts a deliberate macro-structural abstraction, evaluating the complex blade geometry as a continuous load-bearing beam. By employing static models with conservative, idealized properties, this methodology provides a reliable, code-compliant baseline for preliminary architectural design. Consequently, it consciously defers the evaluation of aeroelastic resonance, micromechanical failure criteria and residual fatigue degradation. This work functions as a necessary conceptual precursor; any practical implementation strictly requires individualized non-destructive testing (NDT) and site-specific dynamic validation to certify the element for its second structural life. Practical implications This research explores the possibility of giving these elements a second life by approaching them through the logic and intuition of architectural design. Through the study of various practical cases, it offers spatial solutions that illustrate the initial feasibility of this system, opening an inspiring path to transform what is currently industrial waste into a valuable structural resource. Originality/value The originality of this research lies in overcoming the aesthetic approach to the recycling of wind turbine components by proposing their direct structural integration. By interpreting the blade's behavior through a macrostructural beam model and strictly applying current regulatory limit states (CTE, IAP-11), the study evaluates its performance through architectural case studies. In this way, it provides an objective and well-founded methodological framework for the reuse of complex infrastructures in the built environment.
Purpose To overcome the limitation of deterministic topology optimization (DTO) which ignores uncertainties, this paper proposes a multi-probability-constrained reliability-based topology optimization (MRBTO) model for structures under multiple displacement constraints. Design/methodology/approach The MRBTO model treats loads and material properties as random variables and uses a series system to represent multiple failure modes. System failure probability is calculated using the first-order reliability method (FORM). An outer loop adaptively adjusts the structural volume to meet a target failure probability, while an inner loop employs a modified SIMP method to optimize the material layout. A two-stage dynamic Gaussian sensitivity filtering (DGSF) method eliminates checkerboards and gray elements. The framework is validated on a 2D MBB beam and a cantilever beam using Monte Carlo simulation. Findings Compared with DTO, MRBTO reduces the failure probability from approximately 50% to target levels (e.g. 5% or 1%) with high precision. The volume increase is modest - 5% for the cantilever beam even at the strictest target (1%), and about 7% for the MBB beam, which is a slight increase that is acceptable given the large reliability gain. Combined with DGSF, the discreteness rate (grayness ratio) drops from over 30% to nearly 0%, producing crisp boundaries and well-controlled displacements. MRBTO successfully handles multiple independent displacement constraints and different target failure probabilities simultaneously. Originality/value A novel volume-controlled MRBTO model that handles system-level multi-failure probabilities is introduced, integrating DGSF to eliminate gray elements and boundary blurring. The dual-loop solution strategy efficiently couples reliability analysis with topology optimization, offering a practical and robust design tool under uncertainties.
