Applied Mechanics and Materials Vol. 925

Abstract: The instrumented nanoindentation technique is widely used to investigate the local mechanical properties of cementitious composites. Due to its high-resolution load control and displacement sensing capabilities, this technique is increasingly being used to measure hardness, elastic modulus, creep parameters, and residual stresses that have been explored at micro and nanolevel. During the indentation of brittle materials, cracks may be generated around the impression, which depend on load conditions, material and indenter geometry. This work presents a simulation of the three-dimensional nanoindentation model established with finite element method and modified constitutive relation. The model is created to simulate on single phase (homogeneous) materials such as cement clinker (C3S and C2S separately) and the hydrated phase – Low Density CSH and High Density CSH separately that constitute the primary phases of cementitious matrix. Then numerical modelling (FEA) of indentation is conducted using the concrete damage plasticity (CDP) material model, with the constants calibrated for hardened cement paste. At the end, there was a good agreement when comparing the differences between the simulated and literature experimental results.

Abstract: The Yeoh constitutive model is widely utilized in finite element analysis for the compression packer rubber cylinder with special-shaped structures, owing to the model's ability to accurately predict the single tensile stress over broad ranges. Nevertheless, the Yeoh constitutive model demonstrates significant limitations in predicting the equal-biaxial tensile loading. Consequently, to achieve more precise forecasting of the compression packer rubber cylinder sealing performance, the novel Yeoh-Revised constitutive model is introduced in this paper. Initially, under the assumption of initial isotropy and totally incompressible of the hydrogenated nitrile butadiene rubber, the deformable sealing properties are analyzed using Yeoh-Revised and Yeoh models. The findings indicate that the Yeoh-Revised model is more effective in predicting the seal stability and reliability, thereby offering a suitable approach to determining the appropriate structure dimensions. Subsequently, the high pressure and high temperature test verifies that the material strength properties are the prerequisites to achieve a stable and reliable seal. The Yeoh-Revised constitutive model would offer reliable results for further slowing down the aging and optimizing the structural size.

Abstract: The vibration response of laminated sandwich beams, with a core layer filled with various foam materials, referred to as Foam-based Sandwich Laminated Composite (FSLC) beams, has been studied. First, to precisely capture the varying material properties across the thickness of the sandwich beams, a modified layerwise displacement theory was employed. This approach addresses the inhomogeneity of the foam material in the core, yielding more accurate results than conventional classical laminated plate theories typically used for analyzing laminated composite structures. Secondly, to assess the impact of foam properties on dynamic behavior, FSLC beams incorporating three distinct types of foam have been analyzed. Thirdly, a proof-of-concept experimental test was conducted to demonstrate the functionality of the proposed model under dynamic loading conditions. The natural frequencies and damping coefficients of the FSLC beams have been determined using the modified layerwise theory. The dynamic response of the FSLC beams under impulse loading has also been analyzed. It was observed that the addition of foam in the core layer enhances the damping properties of the sandwich beam by approximately ten percent while reducing the natural frequencies by approximately five percent under all types of loading considered.

Abstract: The primary focus of this research is to investigate the eigen values and strain energy release rate (SERR) of delaminated adhesively bonded single lap joint (SLJ). To achieve this, the study utilizes finite element analysis (FEA) to calculate eigenvalues for the adhesively bonded joints. These predictions are then compared with published data to validate the accuracy of the FEA model. Experimental work is also conducted on intact and delaminated bonded joints to further verify the FEA model reliability. Furthermore, the virtual crack closure technique (VCCT) in ABAQUS software was used to determine SERR values around the delamination edge. Simulation solutions are obtained for various overlapping lengths (e.g., 25, 30, 35, and 40 mm) to predict the natural frequency under different boundary conditions, bond thickness ratios (a/h), and delamination shapes. Similarly, changes in the lamination scheme are considered to predict SERR values. It has been noted that the natural frequency response decreases with increase in bond thickness ratio. Furthermore, a higher number of end restrictions contribute to improved outcomes. There is no significant impact of delamination shape on the natural frequency response. Notably, the cross-ply lamination sequence exhibits higher SERR values around the delamination edge than other sequences.

Abstract: The suspension system is crucial for durability testing, vibration analysis, and evaluating the smoothness and stability of vehicles. Leaf springs are commonly used in suspension systems of heavy-duty trucks. This study analyzed the durability using finite element analysis (FEA) and modeled a dual-leaf spring system on the HOWO truck, a popular vehicle in Vietnam. The research team compared the stress, displacement, and vibration of dual leaf springs made from two materials: steel and E-glass. Durability testing was conducted using HyperWorks software, and the team successfully built a vibration simulation model of the leaf spring suspension system using Matlab-Simulink software. The results showed that the stress in the E-glass material was lower, but its displacement was larger compared to steel, indicating that E-glass provides better smoothness than steel. The auxiliary springs only engage when the load on the main springs exceeds their capacity. Leaf springs made of E-glass showed slower damping of vibrations than steel but provided better smoothness.

Abstract: Triply periodic minimal surface (TPMS) represents a class of porous architectures characterized with continuous curved surface and periodic repetition, demonstrating significant potential for industrial applications requiring high specific surface area. In this work, a Gyroid-type TPMS sheet has been designed and manufactured with acrylonitrile butadiene styrene (ABS) resin via stereolithography 3D printing. The printed surface microstructure was characterized by scanning electron microscopy to evaluate the printing accuracy. Both the quasi-static compression test as well as the numeric finite element analysis were performed to study the mechanical response. Compared with the strut-based Re-entrant lattice, the Gyroid TPMS demonstrated a superior combination of high load-bearing and energy-absorption properties. Comparative analysis of compressive load-displacement curves and cracking behaviors elucidated the distinct deformation mechanisms between TPMS and Re-entrant structures. To validate the practical applicability, a prototype helmet liner with Gyroid TPMS structure was successfully manufactured with ABS resin using the studied printing procedures. These findings substantiate the promising implementation potential of TPMS structures in lightweight engineering and impact protection systems requiring synergistic mechanical performance.