Axial Load Research Articles

Energy-Preserving Perturbation Method for Thermally Induced Dynamics in Aerospace Tensegrity Structures

Tensegrity structures are emerging as pivotal components in the assembly of ultralarge modular spacecraft in orbit, primarily due to their exceptional volume-to-mass ratio and robust controllability. During on-orbit operations, given the low damping and high flexibility of tensegrity, its vibration-induced deformations affect the magnitude of the heat flux, presenting a typical force–shape coupling problem. This paper introduces an energy-preserving matrix perturbation solution designed to efficiently and accurately address the thermally induced vibration challenges in tensegrity. This method effectively mitigates the energy dissipation and numerical instability issues. Furthermore, the analysis incorporates the impact of the axial component of heat flux on structural vibration, uncovering the influence mechanism of this often-overlooked slow variable on the dynamic behavior of tensegrity. The proposed method demonstrates a deviation of less than 1% between the thermal response and the results obtained from finite element analysis, while achieving a 70% reduction in computation time. The varying axial thermal load leads to a rapid decrease in system frequency, resulting in divergent thermal vibrations. Additionally, the significant dynamic stress can potentially surpass the structural stress limits. These findings underscore the critical importance of considering such effects in the design and calculation of tensegrity structures for aerospace applications.

Finite element analysis of the Fibula's contribution to lower extremity torsional stiffness

AimsThe purpose of this article is to investigate the effects of the fibula on the torsional stiffness of the lower limb. A comprehensive model of the lower limb was constructed, including the resected femur, patella, tibia, fibula, and foot, with tendons and ligaments. Two configurations were developed, with and without the presence of the fibula, to evaluate the resulting stress state and consequently determine the contribution of the fibula to the torsional stiffness of the lower limb. MethodsThe finite element method was used to analyse how the fibula affects the stress distribution in the lower extremity under body weight loading and torsional forces. A detailed three-dimensional solid model of the lower extremity with and without the fibula was constructed. Loading conditions were imposed simulating an axial compressive load of 700 N applied to the upper extremity of the resected femur and a torsional load of 6000 Nmm applied to the proximal femur, and a fixed constraint was imposed on the foot. ResultsRemoving the fibula results in an increase in stress on all the tendons and ligaments tested. The increases ranged from 4 % (patellar tendon) to 21 % (lateral retinaculum). This suggests that the fibula plays a significant role in the distribution of mechanical stress in the lower extremity. The most affected structures are the lateral retinaculum and the posterior cruciate ligament, both with a 21 % increase in stress, suggesting that these structures may compensate more for the absence of the fibula. ConclusionThe fibula plays a critical role in maintaining the structural integrity and biomechanical function of the lower extremity. It acts as a lateral strut, contributing to the stability of the ankle and knee by providing an attachment point for several muscles and ligaments that are essential for coordinating complex movements and providing stability during dynamic activities.

IMPLEMENTATION OF THE MAIN COLUMN STRUCTURE USING THE FREESTANDING METHOD & STUDY OF LAP SPLICE CONNECTIONS ON THE GGM MAJALENGKA BUILDING PROJECT IN MAJALENGKA DISTRICT

The GGM Building is a circular sports building, has 2 floors with circular columns. Columns are the most important structural part for a building to stand. In accordance with SK SNI T-15-1991-03 what is meant is a building structural component column whose main task is to support axial, compressive and vertical loads. In this report study, the method used for the main column reinforcement work is Free Standing which can be interpreted as a structure that is strong and stands upright. The GGM Building is a high-rise building which of course has a structure that can stand perfectly upright at any height. The type of connection used in column cuttings is a contact lap splice which is a passing connection between two reinforcing bars that touch each other and are tied with concrete wire. SAP2000 software is used to analyze the values ​​of the forces acting on the main structural columns. Based on the results of analysis of the main structural columns using SAP 2000, the load distribution value was obtained, namely 22.81 KN/m with an axial force value of -229.220 KN for column type K1-1. 27.14 KN/m with an axial force value of -272.97 KN for column K1-2 and 31.86 KN/m with an axial force value of -320,150 KN for column K2. Then with manual calculations related to the self-load value of the main structural columns, namely 1,189.56 KN in column K1-1, 1,614.14 KN in column K1-2 and 1,981.11 KN in column K2. Keywords: column, lap splice, selfweight calculation, SAP 2000.

On Microplasticity-induced Fatigue Fracture and its Relation to Entropy

Abstract The study delves into the intricate effects of microplasticity on fracture formation in testing specimens under axial cyclic loading. The primary aim is to pinpoint the juncture at which microplasticity becomes discernible across the stress cycle. Fatigue tests are conducted on varied specimens until failure using a fatigue testing machine, while recording parameters such as frequency, stress amplitude, applied power, and tensile strain. The investigation seeks to ascertain whether cracks must attain a specific size before manifesting these subtle alterations. A conjectured relationship is proposed between the number of cycles and entropy throughout the process. Additionally, a hypothesis is posited suggesting that microplasticity emerges only once the crack surpasses a certain threshold, such as grain size. This research provides insights into material fracture mechanisms and their implications for product durability and safety. Such discernments into the product life cycle under analogous conditions hold promise for delineating operational limits.

A guidance of solid element application in predicting the ultimate strength of flat plates in compression

With the increasing demand in ocean engineering field for the ultimate limit state (ULS) analysis of thick plates, the solid (3D) element has been more frequently used in the ULS analysis. Compared to 2D element, 3D element can better consider the transverse shearing effect during the analysis which usually occurs on thick plates, due to its reliable reflection of geometrical characteristics and kinematic equations of the structures. Besides, 3D element can also facilitate the introduction of influencing factors into the ULS analysis, such as the erosions, cracks and residual stress. This may improve the simulation precision of ULS analysis of thick plate models. Until now, there is a lack of 3D element modelling technique in the ULS analysis of flat/stiffened plates. The present study aims to provide helpful information on 3D elements in the ULS analysis of flat plates under axial compression load. A total of 350 plate scenarios were adopted in the parametric study to consider the effects of 3D element shape (αyz). It is found that the element shape significantly influences the ULS analysis of flat plates, where planar-like 3D element is not recommended. An empirical formula for determining the optimal 3D element shape of the finite element (FE) model is proposed based on the parametric results. A guidance for implementing the 3D elements is then documented, which may help engineers further understand the ultimate strength characteristic of very thick flat plates.

Biomechanical comparison of Gofried positive support reduction of Pauwels type III femoral neck fractures: A finite elements analysis

ObjectiveThis study aims to investigate the biomechanical characteristics of non-anatomical reduction and different screw positions on the stability of Pauwels type III femoral neck fractures. MethodsThree-dimensional finite element models of femoral neck fractures were constructed using CT images. Four types of internal fixation methods were simulated, including biplane double-supported screw fixation (BDSF), three inverted triangular parallel cannulated screws (3CS), new parallel cannulated screws with posterior screws moving down (New 3CS), and two parallel cannulated screws (2CS). von Mises stress and total displacement were compared between the fracture models after the femoral head was subjected to an axial load of 2100 N. Stress and displacement data for the implants and the femur were recorded for each fixation method and compared. ResultsThe results demonstrated that positive reduction of a Pauwels type III femoral neck fracture provided greater stability than neutral or negative reduction. Specifically, the BDSF group showed the lowest maximum von Mises stress in the femur (17.66 MPa) in positive reduction, compared to 3CS (21.08 MPa), New 3CS (22.14 MPa), and 2CS (36.57 MPa). The total displacement of positive reduction in the BDSF group was 0.3143 mm, which was lower than in the 3CS (0.3498 mm), New 3CS (0.3343 mm), and 2CS (0.4533 mm) groups. The stress distribution in the positive support reduction group was lower than that of the other groups, indicating better load distribution. Among the three-screw fixation methods, the New 3CS system exhibited the highest stress in the screws (with a peak of 28.62 MPa), while the 2CS group displayed the highest stresses overall, both in the femur and the screws. ConclusionFor Pauwels type III femoral neck fractures, a positive support reduction with BDSF fixation exhibited superior biomechanical performance than negative reduction. Based on the finite element analysis conducted in this study, the positive support reduction with BDSF fixation can enhance fixation stability, suggesting that non-anatomical reduction is recommended.

Cyclic Behavior of Steel Tube-Confined Circular RC Columns under High Axial Load

Cyclic Behavior of Steel Tube-Confined Circular RC Columns under High Axial Load

Mechanical model analysis of column-footing joints with combined socket-corrugated pipe connection

The socket connection method is widely used in precast column, particularly in seismic regions. However, reducing the socket-depth to lower costs may lead to shear failure in the socketed part of the columns. To address this issue and achieve cost objectives, a new approach combines shallow sockets with corrugated pipes for column-footing joints. Comparative tests were conducted to investigate failure in columns with socket-corrugated pipe connections (SCPC), shallow sockets (SSC), and cast-in-place (CIP). Furthermore, finite element models were employed to validate the experimental and simplified model results. The findings suggest potential shear failure in shallow socket connections, which can be mitigated by using the combined socket-corrugated pipe method that alters force transmission paths. As the axial load ratio increases, both the ultimate lateral load capacity of the specimen and the local stresses at the column base increase. In addition, the ultimate lateral load capacity of the column and the stress of the connection reinforcement are increased by increasing the strength of the longitudinal reinforcement, consequently amplifying the extent of joint area damage. Finally, a simplified strut-and-tie model of the SCPC, validated against numerical and experimental data, accurately represents force paths, ultimate lateral load capacity and failure modes in socket joints.

Investigation of the dynamic mechanical response of corroded ultra-high performance fiber reinforced concrete (UHPFRC) with initial defects

This study addresses the dynamic mechanical response of the corroded ultra-high-performance fiber-reinforced concrete (UHPFRC) with initial defects, considering the possibility of corrosion deterioration induced by various pre-existing cracks during the long-term service life. For this purpose, an integrated accelerated corrosion method and Split Hopkinson Pressure Bar (SHPB)/high-speed camera etc. techniques are employed. Results show that increasing pre-impacting damage promotes the crack density and maximum width by 32.4%–62.3 % and 1.11–1.8 times, respectively. In terms of mechanical properties, coupling damages of initial defects and corrosion have adverse effects on the dynamic mechanical response. Typical fib Model Code 2010 applies to predict the DIF evolution of the corroded UHPFRC with initial defects. Numerous shear cracks are created at an angle along the weak interface as the corroded specimens with initial defects are again subjected to axial loading, revealing the associated failure mechanism. These results shed light on the dynamic response of corroded UHPFRC containing various initial defects and the failure mechanism gives some reference to service status evaluation.

EXPERIMENTAL AND OPTIMIZATION-BASED ANALYSIS TO MAXIMIZE MECHANICAL-RELATED ATTRIBUTES OF FRICTION STIR WELDED CDA101 CU ALLOY JOINTS

This paper deals with the identification of optimized process parameters for FSW of 6[Formula: see text]mm thick CDA 101 Cu alloy plates. Three distinctive parameters, the tool’s traverse speed, rotational speed, axial load, have been considered as self-reliant variables for formulating a numerical model based on nonlinear regression-type approach, with the objective of anticipating mechanical attributes of joints. From the surface- and contour-type plots, it was revealed that the axial load in combination with rotational speed has played a dominant role in influencing the tensile and yield strength of the CDA101 Cu alloy joints. At the same time, the traverse speed of the tool has played a dominant role in enhancing the ductility of the CDA101 joints through the generation of ample volumes of frictional heat, which in turn have facilitated both coarsening of grain structures and softening of materials in an ideal manner. Employing tool rotational speed, traverse speed and axial load in the ranges of 1750–1900[Formula: see text]rpm, 23–27[Formula: see text]mm/min and 5.75–6.5[Formula: see text]kN, respectively, was found to enhance the tensile strength of the CDA101 Cu alloy joints. FSW process parameters attained through the numerical meta-model of RSM have led to the attainment of the highest value of tensile strength of 209.5[Formula: see text]MPa together with a 141.4[Formula: see text]MPa yield strength with very minimal fitting errors of 0.28% and 0.52%, respectively. A collection of additional experimental data has been employed to verify the formulated empirical-based formula and additionally, an entirely different optimization technique namely PSO (i.e. particle swarm optimization) was implemented for comparison and validation purposes. The formulated meta-model of RSM generated the largest value of % of elongation of 14.23%, though the relative percent error was around 1.988%, which was slightly larger than that of the value (i.e. 14.11%) generated by PSO, with a relative error of 0.58%.

Effect of Sample‐Build Orientation on the Tensile Deformation and Properties of Ti6Al4V Processed by Laser Powder Bed Fusion

The effect of sample‐build orientation on the tensile properties and deformation behavior of Ti6Al4V fabricated by laser powder bed fusion (LPBF) has been investigated by examining the changes in X‐ray diffraction spectra, microstructure, and dimension on the longitudinal cross‐sections after fracture. The anisotropy in strength is dominated by the difference in martensite (α′) lattice distortion, and the highest strength is achieved in the diagonally built sample (Z45) due to its largest α′ lattice distortion. The plastic deformation is mainly accommodated by sliding and micro‐void formation between α′ laths due to the insufficient number of slip systems in hexagonal close‐packed α′ phase. Therefore, the spatial orientation of α′ laths with respect to the loading direction is critical to the ductility. Different deformation mechanisms have been observed in different prior‐β grains due to their different α′ crystallographic orientations. The highest elongation is achieved in the vertically built sample (Z) because α′ laths in the vertically built sample are spatially at ±45° with the loading axis.

Experimental Study on the Time-Dependent Resistance of Open-Ended Steel Piles in Sand

Open-ended steel piles are commonly used as the foundation for offshore structures. Numerous model and field tests have demonstrated a time-dependent increase in the resistance of these piles, a phenomenon referred to as pile ageing or pile setup. Additionally, for open-ended steel piles with comparably small diameters, soil plugging enhances the resistance against axial compressive loads. Realistically predicting these effects is necessary for their reliable incorporation into design practice. This contribution presents static compression and tension pile load testing conducted in an experimental pit filled with wet, uniformly graded silica sand. In total, twelve piles (L= 5.5 m, Do= 325 mm) were driven into homogeneously compacted sand using a pneumatic impact hammer. Firstly, static compression pile load testing was executed at various times after installation. Subsequently, static tension pile load tests were carried out. The results of the static compression pile load tests indicate that the compressive resistance doubles over an ageing period of 64 weeks. The experimental investigations of the effect of soil plugging showed marginal soil plugging during pile installation, but a significant influence of the soil plug on the compressive resistance.

THE IMPACT OF TUNNEL LINING ON THE REACTION OF THE GROUND SURFACE UNDER THE INFLUENCE OF TRANSPORT LOADS

When a tunnel is subjected to transport loads (loads from the moving transportation within it), vibrations occur in the tunnel lining and the surrounding massif. Traditional quasi-static methods do not account for the dynamic behavior of tunnel structures. Therefore, this paper aims to develop a dynamic calculation method using modern mechanics. The purpose of this paper is to develop such a method. The relevance of the research in this article is due to the trend of increasing the speed of vehicles in recent years. This paper considers an unsupported and lined circular cylindrical shallow tunnel. The tunnel is modeled as an extended circular cylindrical cavity or reinforcing shell located in an elastic half-space. The surface of the cavity or the inner surface of the shell is subjected to a normal load (the effect of the pressure of a moving object on the tunnel) and a tangential load parallel to this axis (the effect of the friction forces of a moving object on the tunnel) moving uniformly along its axis. The motion of the half-space and the shell are described by the dynamic equations of elasticity theory and the equations of classical shell theory, respectively, in moving coordinate systems. The integral Fourier transform method is used to solve the problem. In the case of moving axisymmetric normal and axial tangential loads acting on the tunnel, a numerical study of the influence of the tunnel lining on the stress-strain state of the ground surface is carried out.

Lateral capacity of group helical piles in sand: an experimental and numerical study for sustainable infrastructures

ABSTRACT Helical piles are integral to support resilient infrastructures subjected to axial and lateral loads. This study explored model-scale testing of group helical piles in cohesionless soil in a rigid box. Initially, a total load of 5000 N is applied to the pile raft model, followed by a lateral load of 1600 N. Nine model tests are performed with a configuration of four, six, and nine, having conventional, single helical, and double helical piles. The data logger facilitated data collection using MATLAB software, and the load was increased at rate of approximately 4.9N/sec. The computed average reduction in the displacement of Single and Double Helical Pile Rafts is observed as 36.43% and 55.71%, respectively, compared to Conventional Pile Rafts. The addition of a second helix further reduced lateral displacement by 19.27%. Numerical analysis on Plaxis-3d showed that the experimental and numerical results are in good agreement.

Study on energy absorption of paper honeycomb sandwich tube filled by polyethylene foam under axial loading

This work proposed an approach to multi-component non-metallic materials, namely regular polygonal paper honeycomb sandwich tubes filled with polyethylene (PE) foam, and focused on the influence of drop impact parameters and structural parameters on the deformation characteristics and energy absorption of the filled tubes. Axial drop impact tests were employed to exert drop impact loading on cross-sections of the specimens with a square drop weight. The results showed that the X-direction filled tube (X-DFT) had a higher crushing strength and yield strength than that of the Y-direction filled tube (Y-DFT). As the tubular cross-section edge number of the filled tube increased, the specific energy absorption (SEA) and specific total efficiency (STE) decreased. Under the same axial drop impact loading conditions, the SEA and STE of the X-DFT were superior to those of the Y-DFT. As the edge number of the tubular cross-section or the tubular length ratio increased, the SEA and STE of the filled honeycomb tube decreased significantly. While the impact energy increased, the SEA and STE of the filled tubes increased approximately linearly. This work investigated the influence of drop-impact and structural parameters on deformation characteristics and energy absorption. It is expected to provide supplementary documentation for the advancement of cushion protection technology and the optimization of product structure.

Study on hysteresis behavior of two kinds of reinforced CHS X-joints

Ultra-low cycle fatigue loading tests were conducted on two reinforced CHS X-joints (external stiffening rings and plates) and an unreinforced joint to analyze their post-yield failure modes, fracture mechanisms, and hysteretic properties. The findings indicate that these three joints exhibit varying failure modes post-yield: the unreinforced joints fail primarily due to chord fracture at the weld; the ring-reinforced joints initially see ring fracture, followed by chord crack at the weld; while the plate-reinforced joints initially fail from chord fracture and subsequently develop cracks at the plate-chord interface. The reinforced joints display plumper hysteretic loops and higher ultimate bearing capacities than the unreinforced joint. Compared to X-1, the tensile and compressive ultimate bearing capacities of RX-1 have increased significantly by 56.9 % and 74.1 %, respectively. In comparison, those of TX-1 have increased moderately by 2.2 % and 67.6 %, respectively, albeit with a slight compromise in ductility. The cumulative energy dissipation of RX-1 and TX-1 has risen by 22.62 % and 131.99 %, respectively, compared to the unreinforced joint. Notably, the dissipated energy before cracking accounts for 16.50 %, 18.16 %, and 22.29 % of the cumulative energy dissipationfor the three joints, respectively, highlighting the substantial contribution of crack propagation to energy dissipation under large deformations. The VUSDFLD subroutine based on Cyclic Void Growth Model (CVGM) is embedded into ABAQUS, this subroutine considers the initiation and propagation of joint cracks. Three finite element models with the same dimensions of the specimens were built to simulate the damage process of the joint. The results show that this method can accurately simulate such joints’ cracking and crack growth behavior under cyclic axial load. The simulated hysteresis curve is in good agreement with the test curve.

Understanding creep in vitrimers: Insights from molecular dynamics simulations

Vitrimers offer malleability and recyclability due to covalent adaptable networks, however, they are prone to low-temperature creep. In this work, we investigate the molecular mechanisms of vitrimer creep using molecular dynamics simulations. We model the interplay between dynamic bonding with mechanical loading using a topology-based reaction scheme. The creep behavior is compared against cross-linked epoxies with dynamic reactions to understand the unique aspects related to dynamic bonding. It is found that the free volume that arises from tensile loads is reduced in vitrimers through dynamic bond rearrangement. An important feature that distinguishes the secondary creep behavior between epoxies and vitrimers is the orientation of the dynamic bonds during loading. In vitrimers, the dynamic bonds preferentially align orthogonal to the loading axis, decreasing the axial stiffness during secondary creep, resulting in larger creep strain compared to epoxies. Over longer timescales, such increased strain leads to void growth, resulting in tertiary creep.

Selection of railway track superstructure design: Modern outlooks

The paper analyses the reasons for the current opinion that a higher mass of superstructure elements is necessary for railway track sections with higher traffi c density, speed and axial loads. With the help of known theories and the new one developed by the author that takes into account the time factor, it is proved that in terms of all the most signifi cant technical indicators the best solution within the realistic limits is to use lower-mass rails and reinforced concrete sleepers. The most essential argument in favour of the smaller mass of rails per unit length is the increased track stability produced by longitudinal compressive forces in rails. A reinforced concrete sleeper of a smaller mass has been proposed and tested that increases the resistance to shear in ballast across the track axis at least two times. For stable pressing of rails to sleepers by intermediate fasteners, elastic clips should be made of plate steel instead of bar steel. It is proposed to make a plate clip shaped as a ‘fish-bellied beam’. Specific examples of the proposed solutions for rails, reinforced concrete sleepers, and intermediate fastenings are given.

Experimental and numerical investigations of the octagonal concrete-filled thin-walled tube columns with binding bars (O-CFT-WBB) under compressive pressure and thermal loads

An experimental and theoretical investigation is conducted to evaluate the behavior of CFT columns with a unique geometric cross-section under axial loading and in a thermal environment. In this study, based on previous research on octagonal CFT columns, this geometry was chosen as a favorable option compared to other possible configurations. Additionally, binding bars were employed to enhance these columns' mechanical and thermal behavior. A thermal gradient (temperature changes ranging from 0 to 600 degrees) was applied in the laboratory to replicate extreme environmental conditions. By experimental results, a theoretical investigation was conducted to derive suggested formulas for considering confinement effects in O-CFT-WBB columns, and the results were then compared with experimental results and the closest existing formulas. After examining the experimental results, it was shown that the presented formulas had more accuracy than the existing ones. Additionally, based on the experimental results, the presence of binding bars at different temperatures led to different behaviors in the axial capacity of the columns. According to the results, the binding bars in the O-CFT-WB columns can lead to different behaviors in the axial capacity of the columns. Based on a constitutive model of confined concrete, a method for calculating the maximum strength of L-shaped CFT columns with and without binding bars is proposed. The method is verified with experimental results from this test program and data from other experiments.

Effect of different preparation designs and material types on fracture resistance of minimally invasive posterior indirect adhesive restorations.

To evaluate the impact of various preparation designs and the material type on fracture resistance of minimally invasive posterior indirect adhesive restorations after aging using a digital standardization method. One-hundred sixty human maxillary premolars free from caries were assigned into 16groups (n=10): bevel design on enamel substrate with mesial box only (VEM), butt joint design on enamel substrate with mesial box only (BEM), bevel design on enamel substrate with mesial and distal box (VED), butt joint design on enamel substrate with mesial and distal box (BED), bevel design on dentin substrate with mesial box only (VDM), butt joint design on dentin substrate with mesial box only (BDM), bevel design on dentin substrate with mesial and distal box (VDD), and butt joint design on dentin substrate with mesial and distal box (BDD). Each group was restored with pressable lithium disilicate (LS2) or disperse-filled polymer composite (DPC) materials. Adhesive resin cement was used to bond the restorations. The specimens were aged for 10,000 thermal cycles (5°C and 55°C), then 240,000 chewing cycles. Each specimen was subjected to compressive axial load until failure. A two-way analysis of variance (ANOVA) test followed by a post hoc Tukey test was used to analyze the data (α=0.05). The two-way ANOVA test revealed a significant difference among designs (p<0.001) and materials (p<0.001) with no interaction effect (p=0.07) between the variables. The Post hoc Tukey test revealed that the VEM group exhibited the highest mean fracture resistance value, while the BDM group had the lowest. The LS2 groups showed the highest mean fracture resistance values. The DPC groups showed a restorable fracture pattern compared to the LS2 groups. Bevel and butt joint designs with mesial or distal boxes are recommended for conservative posterior indirect adhesive restorations in premolar areas. Enamel substrate improved load distribution and fracture resistance. DPCs have restorable failure patterns, while pressed LS2 may harm underlying structures.