Cyclic Loading Research Articles

High-Performance Triple-Network Hydrogels Derived from Chrome Leather Scraps: Ultrahigh Compressive Strength, Adhesion, and Self-Recovery.

The development of engineered hydrogels with high strength, self-recovery, and adhesion is essential for applications requiring resistance to large deformations and cyclic loading. Herein, a triple-network (TN) hydrogel with ultrahigh compressive strength, strong adhesion, and good self-recovery was constructed by using tannic acid-modified chrome leather scrap hydrolysate as the first network, polyacrylamide as the second network, and poly-2-propenamide-2-methylpropanesulfonic acid as the third network. The ultrahigh (70 MPa compressive strength and 95% compression deformation) TN hydrogels were effectively created, which is attributed to the synergy of the three networks. The TN hydrogels display adhesion (adhesion strength > 20 kPa) ascribed to the introduction of phenolic hydroxyl groups in tannic acid. Intriguingly, the TN hydrogels exhibit excellent self-recovery performance (93.6% dissipated energy recovery at 70 °C) and shape memory performance (restored to the original shape in 20 s). These properties are essential for the development of high-performance hydrogels and promote the resource utilization of leather waste.

Straight and helical plating with locking plates for proximal humeral shaft fractures- a biomechanical comparison under physiological load conditions.

Helical plating is an established method for treating proximal humeral shaft fractures, mitigating the risk of iatrogenic radial nerve damage. However, biomechanical test data on helical plates under physiological load condition is limited. Hence, the aim of this study was to compare the biomechanical performance of helical and straight PHILOS® Long plates in AO12C2 fractures using static and cyclic implant system testing. Helical and straight PHILOS® Long plates on artificial bone substitutes were tested under physiological axial static (n=6) and cyclic loading (n=12). The axial construct stiffness was the main parameter for comparing the biomechanical performance of the two groups. Mimicking a clinical scenario, the helical deformation was performed consecutively by an experienced surgeon using iron bending tools. The torsional angle was determined computationally from 3D-scanning models afterwards. Helical plating resulted in a significantly reduced axial construct stiffness in all test scenarios compared to conventional straight plating (static testing: p=0.012; cyclic testing: p≤0.010). No failure occurred within the range of physiological loading in both groups. Helical plating favors multidimensional deformation of the test sample in lateral-ventral direction under axial loading, resulting in a reduced axial construct stiffness and in an increased interfragmentary movement. No biomechanical failure is to be expected within physiological load boundaries.

On the prediction of fatigue life of WAAM-processed Ti-6Al-4V under consideration of manufacturing defects

PurposeThere is still a need for a comprehensive investigation into how wire and arc manufactured (WAAM) parts fail under cyclic loading. This study investigates the effect of process-induced defects on the high-cycle fatigue performance of WAAM-processed Ti-6Al-4V with dedicated thermal treatment. Furthermore, the study assesses the applicability of the fatigue life prediction model, which was originally developed and validated for laser beam-welded Ti-6Al-4V joints, to WAAM-fabricated structures.Design/methodology/approachThe fatigue life assessment model was adapted to WAAM-fabricated Ti-6Al-4V. This model is based on the NASGRO equation, which considers short crack growth from internal and surface defects, such as lack of fusion defects and pores. The model was used to create artificial Wöhler curves, and the results from stress intensity factor range-decreasing fatigue crack propagation rate tests are compared to the experimental data in the form of a Kitagawa–Takahashi (KT) diagram.FindingsThe results demonstrate that the model can accurately predict the minimum fatigue life of specimens extracted from WAAM structures. When considering that the crack from internal defects grows in a vacuum-like environment, accurate Wöhler curves are predicted. The experimental data does not follow the expected trends of the KT diagram. Nonetheless, the measured long crack threshold stress intensity factor range produces a suitable estimate of defect severity.Originality/valueThe study results in a model with which a probabilistic computation of the fatigue life of additively manufactured samples based on the defect size distribution is possible. Furthermore, the KT diagram as a criterion for the assessment of defect severity is evaluated.

A study on microscopic damage characteristics of freeze-thaw sandstone cyclic loading and unloading based on DEM

A study on microscopic damage characteristics of freeze-thaw sandstone cyclic loading and unloading based on DEM

Constitutive Model of TRIP-Type Duplex Stainless Steel Under Symmetrical Strain Cyclic Loading Considering the Effect of Martensitic Transformation

Constitutive Model of TRIP-Type Duplex Stainless Steel Under Symmetrical Strain Cyclic Loading Considering the Effect of Martensitic Transformation

Fatigue of SFRC in compression: Size effect & autogenous self-healing

This review synthesizes prior research on size effect and autogenous self-healing in steel fiber-reinforced concrete (SFRC) under compressive fatigue. It explores the fatigue behavior of SFRC, focusing on fiber reinforcement’s role in post-cracking toughness, crack propagation, and fatigue endurance. The review demonstrates that larger SFRC specimens have reduced fatigue lives, attributed to increased elastic energy driving microcrack growth, aligning with classical size effect theory. Additionally, it highlights autogenous self-healing, where fatigue-induced microcracks release occluded water, promoting rehydration and calcium carbonate precipitation, which enhances residual strength. The interaction between size effect, fiber content, and self-healing is examined, offering insights into improving SFRC’s durability under cyclic loading. These findings have practical implications for designing SFRC structures subjected to compressive fatigue, such as wind turbine towers and railway slabs.

CYCLIC LOW-THERMAL AGING OF DISSIMILAR AUSTENITIC STEEL WELDS USED IN NUCLEAR POWER PLANTS

The nuclear power plants in Eastern Europe face problems with supplies of spare parts manufactured according to the same Russian standards as the originals. Therefore, the dissimilar welds of original Russian steel 08Ch18N10T and substitutive 1.4541 were made and analyzed to consider the possibility of original steel replacement during the repairs. Two different filler wires were applied. The welds were subjected to cyclic thermal loading corresponding to the actual operating conditions of a nuclear unit, and their microstructure and mechanical properties were compared to the as-welded joints. An increase in weld metal microhardness induced by aging was found when the filler with higher C and Cr content was used. Although this could indicate possible ferrite decomposition, the detected changes in mechanical properties corresponded to the changes in homogeneous welds of the original steel. The strength requirements for the steel used in nuclear power plant devices were still matched.

Application of precast reinforced concrete fuse units as energy dissipation units in various self-centering precast bridge pier systems

This study proposes the implementation of scaled modular reinforced concrete (RC) units as replaceable energy dissipation (ED) elements in various RC self-centering (SC) precast bridge pier (PBP) systems. Regarding the resistance mechanism of RC ED units, two types can be integrated with the main SC system: modular RC units that dissipate energy through the well-known plastic hinge mechanism, and hybrid modular precast SC units that dissipate energy through the yielding of mild steel reinforcement. Using commercial finite element (FE) software, three-dimensional (3D) FE models for different PBP systems (single-column, double-column, and wall PBP systems) were developed and examined under lateral cyclic loading. Various potentially influential design parameters were carefully studied. The studied cases successfully demonstrated that the proposed system introduces a novel, cost-effective damage-control system, which provides customizable ED capabilities, offers additional designable lateral resistance, and ensures rapid repair without compromising the functionality of the main SC structural system. Furthermore, in accordance with the design codes/guidelines for concrete structures exposed to earthquakes, the components defined as ED units can achieve the predefined seismic response without compromising the seismic performance or SC capacity of the main system.

Numerical investigation of existing RC exterior beam-column joints under cyclic loading: case study of 1971 algerian building

Many reinforced concrete (RC) buildings constructed in Algeria before the 1980s may have serious structural deficiencies and are considered substandard according to the Algerian seismic code. Specifically, the failure of the beam-column joints has been the cause of building collapse in many earthquakes in the past: Alasnam October 10, 1980 and Boumerdes May 21, 2003. In this work, the behavior of RC exterior beam-column joints under quasi-static cyclic loading is studied by 3D nonlinear finite element analysis using ANSYS software. To perform the non-linear analysis, the load was applied step by step and the modified Newton-Raphson method was used for the solution. In order to prove that the program successfully captures the necessary response parameters without any modifications to the structure details, some available experimental works were modeled and non-linearly analyzed using ANSYS. Moment-rotation and load-displacement relationships were compared with the experimental data. It was observed that the results are quite similar to each other. Thereafter, a typical RC exterior beam-column joint belonging to a building constructed for residential use in Algeria in 1971 was modeled using ANSYS. The joint was subjected to quasi-static cyclic loading, and its performance was examined in terms of load resistance and failure. The moment-rotation hysteresis curve has been established. The hysteretic loops of the joint, representing the existing structure, showed stiffness degradation and strength deterioration.

Genomic Effects of Biomechanical Loading in Adolescent Human Growth Plate Cartilage: A Pilot Study.

The genomic effects of biomechanical loading on human growth plate cartilage are unknown so far. To address this, we used rare human growth plate biopsies obtained from children undergoing epiphysiodesis and exposed them to precisely controlled mechanical loading using a microloading device. The biopsies were cultured 24 hours after mechanical loading, followed by RNA-sequencing analyses to decipher the genomic regulation. We conducted RNA-seq analysis of human growth plate cartilage obtained from three patients cultured ex vivo and subjected to cyclical mechanical loading with peak 0.4 N with frequency 0.77 Hz during a 30-second duration, using a specialized microloading device. Gene ontology analysis revealed novel data showing three significantly upregulated signaling pathways, including notch, oxytocin, and tight junction, and three significantly downregulated signaling pathways, including lysosome, sphingolipid metabolism, and peroxisome proliferator-activated receptor (PPAR) in human growth plate cartilage. Moreover, we found 15 significantly regulated genes within these signaling pathways from all three patients. These genes included PSEN2, HEY1, and NCOR2 from the notch signaling; CACNB1 and PPP3R2 from the oxytocin signaling; ACTR3C, WHAMM, and ARHGEF18 from the tight junction signaling; ARSA, SMPD1, and CD68 from the lysosome signaling; ARSA and SMPD1 from the sphingolipid metabolism signaling; and SLC27A4 and AQP7 from the PPAR signaling pathway. In addition, 20 significantly upregulated genes and six significantly downregulated genes shared between two patient samples were identified. Our study provides the first-ever transcriptomic data of mechanical loading of human growth plate cartilage. These findings can potentially provide genetic targets for future investigations in physiological and pathological bone growth conditions.

Effective Stress-Based Numerical Method for Predicting Large-Diameter Monopile Response to Various Lateral Cyclic Loadings

Extreme marine environmental cyclic loading significantly affects the serviceability of monopiles applied for the foundation of offshore wind turbines (OWTs). Existing research has primarily used p-y methods or total stress-based models to investigate the behavior of monopile–marine clay systems, overlooking the pore pressure development in subsea clay. Studies on the effective stress-based behavior of clay under various lateral cyclic loading conditions are limited. This paper presents an effective stress-based 3D finite element numerical method developed to predict key behaviors of pile–clay systems, including permanent pile rotation under cyclic loading, pile bending moment, and the evolution of pore pressure in subsea clay. The model is verified by contrasting the simulations results to centrifuge experimental results. Cyclic lateral loading is divided into average cyclic load and amplitude of cyclic load to investigate their impacts on the pile–clay system response. The research findings offer insights for the design of large-diameter monopiles under complex cyclic loading conditions.

Strain analysis by neutron diffraction on Nb3Sn strands in ITER central solenoid conductors of short and long twist pitch

Abstract The ITER central solenoid (CS) conductors are composed of Nb3Sn superconducting cables and stainless steel jackets. Approximately 60 000 electromagnetic loading cycles will be applied to the Nb3Sn strands in the CS conductor over the course of ITER tokamak operation, and the CS conductor is required to maintain the current sharing temperature (T cs) for these electromagnetic loading cycles. However, in CS conductor prototypes, degradation of T cs was observed after electromagnetic loading cycles. Visual inspections of the tested CS conductors revealed large bending and buckling of the Nb3Sn strands. These strand deformations were considered to be the cause of T cs degradation because even a small amount of strain markedly affects the critical current of Nb3Sn strands. To prevent the strands from bending and buckling, the twist pitch of the cable was shortened to improve stiffness. The stiffer cables did prevent T cs from degrading after electromagnetic loading cycles owing to the shortened twist pitch of the conductors, but a slight increase of T cs was observed. Visual inspections revealed no significant bent or buckled strands, but small deformations cannot be investigated visually. Thus, internal strain was measured by neutron diffraction and the internal strain states of the prototype CS conductors having long twist pitches and the improved short-twist-pitch (STP) CS conductors were evaluated. The results indicated that, after electromagnetic loading cycles, bending of the strands in the STP CS conductor was limited and compressive strain was reduced. Therefore, we determined that this STP is not only effective to prevent degradation caused by bent strands but it also increases T cs by reducing compressive strain.

Experimental Investigation on the Critical Dynamic Stress of Frozen Silty Clay Under Different Temperature and Moisture Conditions

In this paper, a comprehensive series of dynamic triaxial tests were conducted to delve into the influence of temperature and moisture content on the behavior of frozen silty clay. Upon scrutinizing the experimental outcomes under prolonged reciprocal cyclic loading, insights were gained into how varying temperatures and moisture contents impact the cumulative permanent strain (CPS) and critical dynamic stress (CDS) of frozen clay. The results show that the variation curves of CPS with the number of cyclic loadings show significant changes at different temperatures and moisture contents. Additionally, based on the assessment of vertical CPS recorded at the 100th and 1000th loading iterations, criteria for assessing the plastic stability and plastic creep threshold of frozen silty clay were devised. Consequently, an analysis was conducted to delineate the correlation between the variation in vertical cumulative strains and the dynamic stresses applied within the frozen clay, resulting in the formulation of a series of correlation curves. The relationship between the changes in CDS affected by different temperatures and water contents were analyzed. The CDS under the plastic stability and plastic creep limits showed a slowly increasing trend with decreasing temperatures and a slowly decreasing trend with increasing water contents.

Fatigue-Induced Failure of Polysilicon MEMS: Nonlinear Reduced-Order Modeling and Geometry Optimization of On-Chip Testing Device

In the case of repeated loadings, the reliability of inertial microelectromechanical systems (MEMS) can be linked to failure processes occurring within the movable structure or at the anchors. In this work, possible debonding mechanisms taking place at the interface between the polycrystalline silicon film constituting the movable part of the device and the silicon dioxide at the anchor points are considered. In dealing with cyclic loadings possibly inducing fatigue failure, a strategy is proposed to optimize the geometry of an on-chip testing device designed to characterize the strength of the aforementioned interface. Dynamic analyses are carried out to assess the deformation mode of the device and maximize the stress field leading to interface debonding. To cope with the computational costs of numerical simulations within the structural optimization framework, a reduced-order modeling procedure for nonlinear systems is discussed, based on the direct parametrization of invariant manifolds (DPIM). The results are reported in terms of maximum stress intensification for varying geometry of the testing device and actuation frequency to demonstrate the accuracy and computational efficiency of the proposed methodology.

In vitro bonding strength of denture teeth to denture base in CAD/CAM-milled, 3D-printed and conventional manufacturing processes

ObjectivesTo investigate the survival rates and fracture resistance of dentures made from different teeth (milled, 3D-printed, fabricated), bases (milled, 3D-printed, pressed) and bonding combinations.Materials and methodsSpecimens (11 groups, n = 8 per group) were fabricated from combinations with a denture tooth (anterior tooth 21) and a denture base material. The groups consisted of combinations of teeth (6x), denture base materials (5x) and adhesive bonding options (4x). The teeth were printed, milled or prefabricated. The denture base was produced conventionally or was milled or 3D-printed. Two dentures were milled from one industrially produced block. The dentures were subjected to thermal and mechanical loading (TCML) and subsequent fracture test. Statistics: ANOVA, Bonferroni-test, Kaplan-Meier survival, Pearson correlation; α = 0.05.ResultsMean loading cycles varied between 221,869 (8), 367,610 (11), 513,616 (6) 875,371 (3) and 9,000,030 (4). ANOVA revealed significant (p ≤ 0.001) different surviving cycles. Log Rank test showed significantly (p < 0.001) different loading cycles. Fracture force after TCML varied between 129.8 +/- 97.1 N (3) and 780.8 +/- 62.5 N (9). ANOVA comparison revealed significant (p < 0.001) different fracture loadings between the individual systems. Correlation was found between fracture force and loading cycles (0.587, p < 0.001).ConclusionsDifferent survival rates and fracture forces were found for dentures made of different teeth (milled, 3D-printed, prefabricated), bases (milled, 3D-printed, pressed) and bonding combinations. Milled, pressed and prefabricated systems provided longer survival and fracture force than the other tested systems.Clinical relevance Optimal tooth-base combinations can help to produce a denture that is stable and resistant during clinical application.

Review on the Fatigue Strength of Additively Manufactured Metal Materials Under the Very High Cycle Fatigue

ABSTRACTThe primary goal of this systematic literature review is to identify, characterize, and make a comprehensive analysis of the available research on the fatigue strength of additively manufactured (AMed) metal materials when subjected to loading cycles that exceed the preconceptualized fatigue limit ( cycles) and the very high cycle fatigue (VHCF) regime. Considering the inherent complexity and magnitude of influential variables present in AM metal processes, this paper explores in‐depth the relevant conclusions taken by theoretical/experimental studies and their respective results of several AMed materials in the VHCF regime. The present review focuses on key research topics of metal AM fatigue strength, such as crack initiation and failure mechanisms, examining the influence of microstructure and defects, the effect of the input process parameters, postprocessing methods, and the influence of testing conditions on fatigue strength.

Evaluation of Dynamic Properties of Sand Mixed with Expanded Glass Granules by Energy Concept Under Cyclic Torsional Loadings

In recent years, lightweight materials have gained attention for their numerous benefits, including cost reduction, insulation, and bearing capacity. Expanded glass granules (EGG) stand out among these materials, showing significant potential in geotechnical engineering applications. This study examines the potential use and feasibility of a SAND-EGG mixture in geotechnical applications through cyclic torsional shear test for measuring shear strength, modulus reduction, and energy dissipation. This is conducted on the unmixed dry specimens (Reference Sand, EGG) and the mixed dry specimens by mass (1, 2%) and volume (5, 10, 15%) under 100 kPa effective pressure. The test also conducted along 0.02%–0.5% shear strain amplitudes for both samples group. An energy-based approach is used to analyze mixed material's capacity for energy dissipation, a crucial factor in determining seismic resistance during cyclic loading. The impact of employing EGG on modulus reduction behavior was also explored concerning energy dissipation. Considering the results, it is show that the use of EGG increases the resilience with high friction capacity and by taking up a significant portion of the available void ratio and provides lightness in geotechnical applications in examined shear strain amplitude range (0.02%–0.5%).

Cyclic and monotonic undrained response of unsaturated filtered copper tailings

This article studies the undrained behavior of filtered copper tailings in unsaturated conditions under monotonic and cyclic loading at controlled matric suction. Two dry densities with the same water content were used. The material behavior was studied in terms of the increase of saturation, the evolution of suction, and volumetric strain during the transition from unsaturated to saturated conditions. The results show that, during the shearing, suction decreases and the degree of saturation increases, regardless of the type of load applied (cyclic or monotonic). This effect is related to the volume reduction of the air phase during the transition to a fully saturated condition. In terms of undrained shear strength, the evolution of the material is studied in terms of the phase transformation line (PTL), comparing its location in saturated and unsaturated cases. Regarding the cyclic strength ratio (CSR), the unsaturated condition shows a higher value than the saturated case by about 26% and 58% for the high and low densities, respectively. However, when the volumetric strain is higher than 3% or the double amplitude axial strain exceeds 2%, a cyclic strain localization takes place, leading to an extension failure over the sample.

Materials and Structures Used in Aeronautics: Present and Future Perspectives

In recent years, significant advancements have been made in the development of novel materials for aeronautic applications. This effort aims to reduce costs by extending the operational life of structural and engine components, improving fuel economy, load capacity, and flight range. This paper investigates metallic materials such as aluminum alloys, titanium alloys, magnesium alloys, steels, nickel superalloys, and metal matrix composites (MMCs), providing an overview of recent advancements and highlighting current challenges and future perspectives in aeronautic metals. Several crucial factors are considered when selecting materials for aviation applications. These materials must withstand various environmental conditions, including humidity and temperature, as well as mechanical stresses such as tension, compression, bending, cyclic loads, creep, and torsion. The selection process is complicated by the wide range of available materials and the numerous variables involved, with cost being a critical factor in making an informed decision. In aviation, the most significant material characteristics are strength combined with lightness and stability in the operating environment. Trial and error can be costly in this context, necessitating well-planned design and engineering to ensure resistance to aerodynamic forces during flight. This approach has drawn the interest of aircraft designers since the inception of the Boeing 747, which utilized 1.3% composite materials. Modern aircraft, such as the Airbus A380 and Boeing 787, now incorporate 25% and 50% composite structures, respectively. Research has increasingly focused on enhancing the efficiency of structural engineering and material development through the use of sandwich structures. These structures are valued for their excellent stiffness-to-weight ratios and impact energy absorption properties. A typical sandwich structure consists of two thin, rigid face layers bonded to a core material. While various core materials like balsa and foam have been used in aviation, the honeycomb structure is the most prevalent. Honeycomb core configurations, including hexagon, reinforced hexagon, rectangle, flex-core, and square cell, primarily serve to support normal loads in the longitudinal direction and shear loads along the transverse axis.

Prediction of multistage fatigue curve based on the relaxation model of irreversible cyclic deformation

The paper studies the multi-stage fatigue dependence (Wöhler diagram) of the material and proposes a new model for its prediction based on considering the mechanisms of plastic deformation and fracture under cyclic loads and a combination of relaxation processes with the evolutionary development of damage, for which the initial condition is formed using the calculation calculated during the cycling process energy of irreversible deformation. The performance of the model is verified using the results of cyclic deformation tests on DP500 steel as an example. It is shown that within the framework of a unified approach it is possible to simultaneously evaluate the short-term, fatigue and long-term strength of the material.