Effect Of Cyclic Loading Research Articles

Mechanical properties and constitutive models of shape memory alloy for structural engineering: A review

Shape Memory Alloys (SMAs) are an innovative material with the unique features of superelasticity and energy dissipation capabilities under extreme loads. Due to their unique features, they have a great potential to be employed in structural engineering applications under different conditions. However, in order to effectively use SMAs in civil engineering structures and model their behaviors accurately in Finite Element (FE) packages, it is crucial for structural engineers to comprehend the mechanical properties and cyclic behavior of different SMA compositions under varying loading conditions. While previous studies have focused mainly on the cyclic behavior of SMAs under tensile loading, it is important to evaluate their fatigue behavior under cyclic tension-compression loading for seismic applications. This literature review aims to discuss the current gaps in the existing literature on the behavior of SMA rebars under low-cycle fatigue (LCF). The review provides a comprehensive overview of the primary characteristics of SMAs, summarizes the mechanical properties of SMAs presented in the literature and the parameters that affect them, and critically evaluates the effects of cyclic loading and LCF on SMAs. The review also provides a summary of the different constitutive models of SMAs and compares their advantages and limitations, which helps structural engineers to employ an appropriate constitutive model for predicting the accurate behavior of SMAs in FE software.

Development of design typhoon profile for offshore wind turbine foundation design in Southern China

For offshore wind development in Southern China, typhoon represents the extreme environmental loading condition to be considered in the design of the turbine structures. For the geotechnical design of the foundations, it is specified by the design code that the effect of cyclic loading on the soil strength and stiffness must be considered. This necessitates the complete time history of loads on the foundation experienced during a design typhoon. Idealised storm profiles with staged mean wind speeds and significant wave heights are commonly used as input to time-domain simulations to generate the foundation load history. However, no such design typhoon profile is provided in the Chinese design standard which creates considerable difficulty and uncertainty in the design process. In this paper, the methodology and the rationale that were applied to derive the design typhoon profiles for an offshore wind project in Guangdong province are presented. The wind and wave characteristics generated by typhoon are described in detail and the implications for the foundation design are discussed. To demonstrate application of the proposed typhoon profile, a case study for the ULS design of a suction bucket jacket is presented.

Experimental study on cyclic lateral response of piles in sandy sloping ground

This study aims to experimentally investigate the cyclic lateral responses of piles in sloping ground. The effects of slope angle θ, number of cycles n, and loading pattern (static or dynamic) on the pile responses (inc. unloading stiffness and residual displacement) were revealed by a series of laboratory (1-g) model tests considering the combined effects of slope and cyclic lateral loading. The measured responses indicated that all the pile head displacement, bending moment, lateral earth pressure, and unloading stiffness increase non-linearly with n. Thereinto, the pile head displacement x can be fitted by the function x = A(θ)n0.1 where the coefficient A(θ) is linearly related to tanθ; the residual displacement decays exponentially with the number of cycles. In addition, the slope effect would exacerbate the pile responses under cyclic loading, for instance, the maximum bending moment is linearly related to tanθ, and the depth of contraflexure point increases by 0.14 times the pile diameter when the slope angle increases by 1°.

Evaluation of two implant-supported fixed partial denture abutment designs: Influence on screw surface characteristics.

To compare screw surface characteristics between hemi-engaging and non-engaging implant-supported fixed partial denture (FPD) designs after cyclic loading. Twenty-four implants measuring 4.3 × 10mm were mounted on acrylic resin blocks. Specimens were divided into two groups. An experimental group included twelve 3-unit FPD with a hemi-engaging design; a control group included twelve 3-unit FPDs with the conventional design of two non-engaging abutments. Both groups were subjected to two types of cycling loading (CL), first axial loading, and then lateral loading at 30°. Load was applied to the units one million times (1.0 × 106 cycles) for each loading axis. Data on screw surface roughness in three locations and screw thread depth were collected before (BL) and after (AL) each loading type. Screw surface roughness was measured in μm using a mechanical digital surface profilometer and optical profiler. To evaluate screw thread depth in μm, an upright optical microscope Axio-imager 2 was used. To confirm readings made from the optical microscope, four random samples were selected from each group for scanning electron microscopy (SEM) analysis. The effect of cyclic loading was evaluated by averaging values across the two screws within each specimen, then calculating difference scores (DL) between BL and AL (DL = AL - BL). Additional difference scores were computed between the non-engaging screws in each experimental group specimen, and one randomly selected non-engaging screw in each control specimen. This difference was referred to as the non-engaging DL. Statistical significance was assessed using Mann-Whitney U tests (α = 0.05). Comparisons of DL and non-engaging DL by loading type revealed one significant difference regarding surface roughness at the screw thread. Significantly greater mean changes were observed after axial loading compared to lateral loading regarding both DL (axial M = -0.36 ± 0.08; lateral M = -0.21 ± 0.09; U = 20; p = 0.003) and non-engaging DL (axial M = -0.40 ± 0.22; lateral M = -0.21 ± 0.11; U = 29; p = 0.013). No significant differences in screw surface roughness in other sites or thread depth were found between the experimental and control abutment designs in DL or in non-engaging DL. No significant differences were found for DL (axial U = 13, p = 0.423; lateral U = 9, p = 0.150;) or non-engaging DL (axial U = 13, p = 0.423; lateral U = 18, p = 1.00). Results suggest that overall, changes in screw surface physical characteristics did not differ between hemi-engaging and non-engaging designs after evaluating screw surface roughness and thread depth before and after axial and lateral cyclic loading.

The Practice and Development of T-Bar Penetrometer Tests in Offshore Engineering Investigation: A Comprehensive Review

In recent years, the development of marine hydrocarbon resources has led to an increased demand for research on the marine soil bearing capacity and cyclic loading effect in marine engineering design. Because of the difficulties and high costs involved in obtaining high-quality soil samples from offshore sites, in situ testing techniques have become the preferred method of determining design parameters in offshore geotechnical engineering projects. This paper provides a review of the current state of marine penetrometer deployment technology used in offshore engineering investigations and presents a summary of the T-bar penetrometer test for measuring marine soft clay. The existing literature research on penetration mechanisms, numerical simulations, laboratory experiments, and field tests of the T-bar penetrometer in the field of marine geotechnical engineering are analyzed. Finally, the potential difficulties, challenges, and prospects of the T-bar penetrometer tests are discussed.

Understanding the inelastic response of collagen fibrils: A viscoelastic-plastic constitutive model.

Collagen fibrils, which are the lowest level fibrillar unit of organization of collagen, are thus of primary interest towards understanding the mechanical behavior of load-bearing soft tissues. The deformation of collagen fibrils shows unique mechanical features; namely, their high energy dissipation is even superior compared to most engineering materials. Additionally, there are indications that cyclic loading can further improve the toughness of collagen fibrils. Recent experiments from Liu at al. (2018) focused on the response of type I collagen fibrils to uniaxial cyclic loading, revealing some interesting results regarding their rate-dependent and inelastic response. In this work, we aim to develop a model that allows interpreting the complex nonlinear and inelastic response of collagen fibrils under cyclic loading. We propose a constitutive model that accounts for viscoelastic deformations through a decoupled strain-energy density function (into an elastic and a viscous parts), and for plastic deformations through plastic evolution laws. The stress-stretch response results obtained using this constitutive law showed good agreement with experimental data over complex loading paths. Ultimately we use the model to gain more insights on how cyclic loading and rate effects control the interplay between viscoelastic and plastic deformation in collagen fibrils, and to extrapolate the results from experimental data, analyzing how complex cyclic load influences energy dissipation and deformation mechanisms. STATEMENT OF SIGNIFICANCE: In this work, we develop a viscoelastic-plastic constitutive model for collagen fibrils with the aim of analyzing the effects of inelasticity and energy dissipation in this material, and more specifically the competition between viscoelasticity and plasticity in the context of cyclic loading and overload. Experimental and theoretical approaches so far have not fully clarified the interplay between viscous and plastic deformations during cyclic loading of collagen fibrils. Here, we aim to interpret the complex nonlinear response of collagen fibrils and, ultimately, suggest predictive capabilities that can inform tissue-level response and injury. To validate our model, we compare our results against the stress-stretch data obtained from experiments of cyclic loaded single fibrils performed by Liu etal. (2018).

Craniocaudal toggling increases the risk of screw loosening in osteoporotic vertebrae

Background and ObjectiveScrew loosening remains a prominent problem for osteoporotic patients undergoing pedicle screw fixation surgeries but its underlying mechanisms are not fully understood. This study sought to examine the interactive effect of craniocaudal or axial cyclic loading (toggling) and osteoporosis on screw fixation. MethodsQCT-based finite element models of normal (n = 7; vBMD = 156 ± 13 mg/cm3) and osteoporotic vertebrae (n = 7; vBMD = 72 ± 6 mg/cm3) were inserted with pedicle screws and loaded with or without craniocaudal toggling. Among them, a representative normal vertebra (age: 55; BMD: 140 mg/cm3) and an osteoporotic vertebra (age: 64; BMD: 79 mg/cm3) were also loaded with or without axial toggling. The individual and interactive effects of craniocaudal toggling and osteoporosis on screw fixation strength (the force when the pull-up displacement of the screw head reached 1 mm) and bone tissue failure (characterized by equivalent plastic strain) were examined by repeated measure ANOVA. ResultsA significant interactive effect between craniocaudal toggling and osteoporosis on screw fixation strength was detected (p = 0.008). Specifically, craniocaudal toggling led to a marked decrease in the fixation strength (68%, p < 0.05) and stiffness (83%, p < 0.05) only in the osteoporotic vertebrae but had no effect on screw fixation strength and stiffness of the normal vertebrae (p > 0.05). Likewise, most of the bone tissues around the screw in the osteoporotic vertebrae yielded following craniocaudal toggling whereas this result was not seen in the normal vertebrae. The axial toggling had no significant effect on bone tissue failure as well as pedicle screw fixation in normal or osteoporotic vertebrae. ConclusionsCraniocaudal toggling substantially reduces the screw fixation strength of the osteoporotic vertebrae by progressively increasing tissue failure around the screw, and therefore may contribute to the higher rates of screw loosening in osteoporotic compared to normal patients, whereas axial toggling is not a risk factor for pedicle screw loosening in normal or osteoporotic patients.

The analysis of debonding damage between steel tension wire and epoxy resin in flexible end fitting under cyclic loading

Flexible pipe end fitting is a structure connecting flexible pipe and mental flange, which is a transition between flexible structure and rigid structure. Epoxy resin is used to fix tension steel wire in the end fitting. The bonding interface between epoxy resin and tension steel wire is prone to debonding when flexible pipe end fitting is used under cyclic loading. The damage of bonding interface is mainly due to the cumulative effect of cyclic loading. The damage of epoxy resin can cause temperature changes, which can affect the material properties of the resin and then affect the bonding strength. In this paper, the relationships between cycle numbers of epoxy resin and temperature, temperature and elastic modulus are obtained through fatigue analysis and dynamic mechanical analysis (DMA). The fatigue model is established based on the relationship between the modulus of epoxy resin and temperature. Based on the fatigue model, the bonding damage between steel tension wire and epoxy resin is obtained by finite element analysis (FEA). The results show that it is feasible to characterize the fatigue damage between steel tension wire and epoxy resin by temperature. This work provides a new method for predicting the fatigue of tensile steel wire and epoxy resin in end fitting.

Effect of cyclic load on mechanical properties and failure mechanisms of different rank coals

Underground coal is often subjected to periodic loads caused by mining stress. To determine the effect of cyclic load on mechanical properties of coal of different ranks and failure mechanisms, nanoindentation experiments and molecular dynamics (MD) simulations were used to study different rank coals. The results indicated that cyclic hardening occurred in all the coal matrices under cyclic loading. With the increase in coal rank, the change of the elastic modulus and the hardness, the energy dissipation rate, and the damage layer decreased, the cyclic hardening weakened, and the resistance of the six-membered ring structure increased. The plastic failure of the coal matrix was mainly connected with the bending and stretching of the bond, the dihedral angle twisting, and the out-of-plane bending vibration. The elastic deformation was correlated with the variation of the Coulomb force and the van der Waals force, the twisting and recuperation of the dihedral angle, and the out-of-plane bending vibration. With increasing coal rank, the effect of the elastic deformation of the Coulomb force weakened. When the coal rank exceeded a certain range, the influence of the plastic failure of the out-of-plane bending vibration was transformed into the elastic deformation, and the effect of the elastic deformation of the van der Waals force was transformed into the plastic failure.

EXPERIMENTAL COMPARISON OF THE DEGREE OF FIXING SCREW TIGHTENING FOR FULL ZIRCONIA CROWNS SUPPORTED BY STRAIGHT IMPLANTS, STRAIGHT IMPLANTS WITH ANGLED ABUTMENTS, AND ANGLED IMPLANTS WITH DIFFERENT PLATFORM INCLINATIONS. IN VITRO STUDY

ABSTRACT&#x0D; Background: Success of immediate implant placement in the area of maxillary central incisor greatly depends on the degree of tightening of the fixing screw of the fully zirconia crowns. For treatment of this kind, clinicians use implants of various designs and implants with angled abutments to bypass anatomical limitations, achieve primary implant stability, and fabricate a screw-retained crown. However, the crown fabricated for the implant placed can experience non-axial loads during occlusion, which can lead to screw loosening and adversely affect treatment success, especially in the early post-operative period.&#x0D; &#x0D; Objective: to perform a comparative analysis of the effect of cyclic loading on the reliability of the fixing screw in full zirconia crowns supported by angled implants with platform inclination of 12, 24, 36, by straight implants and straight implants with angled abutments.&#x0D; &#x0D; Materials and methods: the degree of the prosthetic screw tightening was studied in 30 samples, 6 groups of 5 implants (straight implants, straight implants with standard 17 angled abutments and 12 custom abutments, angled implants with platform inclination of 12, 24, and 36. A full zirconia crown of maxillary central incisor was fabricated and fixed on every implant and subsequently exposed to cyclic loading up to 1*106 cycles. Afterwards, the maximum unscrewing torque was determined for each group. Statistical analysis was carried out.&#x0D; &#x0D; Results: the minimum values of the maximum torque were 20.8040.01 N/cm for the group of straight implants with 17 angled abutments, and the maximum values for the group of straight implants were 22.820.04 N/cm. There was no significant difference in values between the straight and angled implant groups. However, the values in these groups were higher compared to the groups of implants with angled abutments.&#x0D; Conclusion: the study showed that fixing screws are more reliable in crowns supported by straight implants and angled implants with different platform inclinations. Therefore, these implants are the most preferred option for immediate implant placement in the anterior region.

Effect of Cyclic Temperature and Fatigue Load on the Performance of Bond Strength at High-Strength Concrete–UHPC Interface

One of the most important components of box beam bridges is the shear key that connects the box beams together. The shear keys in box beam bridges often fail at the interface. In recent years, ultrahigh-performance concrete (UHPC) has been successfully used to cast these shear keys. The current study investigates the effect of temperature cycles on bond performance between a high-strength concrete (HSC) box beam and UHPC shear key. The interfacial bond performance was evaluated by subjecting specimens to 60, 120, and 180 freeze-thaw (FT) cycles representing 1, 2, and 3 years of environmental exposure. Some direct tension specimens that were subjected to 180 FT cycles were additionally subjected to 1-Hz frequency fatigue cycles with stress reversals. Using the direct tension, pull-off, slant shear, and bishear assessment methods, the test results have demonstrated that the number of FT cycles did not affect bond performance in terms of strength and failure modes. The test results also showed that standard specifications underestimate the cohesion and friction coefficients evaluated using Mohr-Coulomb’s and Carol’s approaches for concrete placed against intentionally roughened surfaces. Furthermore, it was found that fatigue loading with stress reversals did not diminish the direct tensile bond strength of the specimens.

Accumulation of the Crushing Products in Ballast Layer under Cyclic Load

Increasing of ballast layer bearing capacity is a widespread problem during the operation and maintenance of a railway track nowadays. It is known that with an increase of the passed tonnage, the ballast layer tends to become contaminated both by the products of its own crushing and by the external weeds which rapidly leads to the strength and operational characteristics degradation of the crushed stone ballast. In this study, an attempt was made to simulate the effect of cyclic load from rolling stock on the ballast layer and to determine the extent of wear of crushed stone ballast of category II in accordance with GOST 7392.

Study of Mechanical Behavior and Deformation Field Characteristics of Sandstone under Cyclic Loading

The sandstone yield strength and tensile strength were increased under cyclic loading paths by using the Brazilian splitting method. The experiment shows that (1) the sandstone specimens exhibit multiple penetrating crack damage by cyclic loading, while the tensile strength slightly increases; (2) the sandstone horizontal strain (Exx) concentration area decreases, and the shear strain (Exy) concentration area increases under cyclic loading, and the damage form changes from completely brittle tensile damage to ductile mixed tensile-shear damage; (3) the mechanism of the increase in tensile strength of the specimen under cyclic loading was explained by digital image correlation (DIC) technique. The results indicate that a time lag occurs in the horizontal strain concentration zone, and the area of the penetration zone decreases from the cyclic loading effect, while the reduced stress concentration leads to increased tensile strength of the specimens.

Fatigue behavior of reinforced UHPC-NC composite beams

Ultra-high-performance concrete (UHPC) can be strategically applied in the lower part of a beam and combined with normal-strength concrete (NC) to achieve a more cost-effective design. The purpose of this research was to assess the effects of the UHPC layer thickness, reinforcement ratio, reinforcing bar type, and load level on the enhancement of the fatigue performance, as well as their interaction effects on the contribution of the UHPC layer. Four-point bending tests were conducted on eleven 500-mm-deep and 4400-mm-long T-beams under cyclic and monotonic loading. The test results indicated that the fatigue performance of the beam is strengthened by increasing the UHPC layer thickness, whereas the efficiency of the strengthening decreased as the thickness increased from 200 to 360 mm. The benefits of the UHPC layer on the fatigue resistance was magnified as the load levels decreased, which was also influenced by reinforcement ratio and reinforcing bar type. A method of deflection prediction was suggested, considering the contribution of the UHPC layer and effect of cyclic loading. Meanwhile, a fatigue relationship was established for reinforced UHPC-NC beams.

Experimental behavior of circular concrete-filled steel tabular columns under near-fault cyclic loadings

This study investigated the behavior of concrete-filled steel tabular (CFST) columns under near-fault cyclic loading experimentally. Ten CFST columns were tested: one under monotonic loading, one under conventional cyclic loading, and other eight under near-fault cyclic loadings. The results indicated that slow local buckling occurred at plastic hinges after 4%-drift cycles, resulted in slow strength degradation and pinching. These became more pronounced as the cycle amplitude increased. Load-carrying and deformation capacities marginally decreased by the effect of cyclic loading. Secant stiffness sharply dropped by the pulses of 4%-drift amplitude. The earlier arrival of the pulses caused higher drops of secant stiffness. Near-fault pulses imposed a considerable large amount of energy to columns, which resulted in slow local buckling, slow strength degradation, but significant stiffness degradation. Shifting the pulse cycles to the cycle five of a conventional cyclic loading history was proposed for testing structural components under near-fault earthquakes.

Effects of Loading Magnitude and Fatigue Crack Growth on Crack Opening-Closing Behavior on Silicon Nitride Ball under Cyclic Compression

To research effects of cyclic loadings and the loading magnitude on the crack opening-closing behavior, crack opening displacement evaluations for fatigue cracks on a silicon nitride ball were carried out. The compressive loading magnitude, which was less than 2.7 kN, did not affect crack opening-closing behavior. The crack opened at the early cycles of fatigue during 0 to 103 cycles.

Corrosion-Fatigue Analysis of Wires in Bridge Cables Considering Time-Dependent Electrochemical Corrosion Process

Environmental corrosion and cyclic dynamic loadings are the main causes of cable failures. In the degradation process of cables, the effects of corrosion and cyclic loading are coupled and the corrosion rate is time dependent. To consider the time-variant properties of the electrochemical corrosion process, the evolution curve of corrosion current density was proposed and introduced into a corrosion-fatigue model. Based on the model, we extracted in situ wires from a tied-arch bridge for the corrosion-fatigue analysis. The surface profiles of the wires from midregion and the anchored region were measured. We found that the corrosions in the anchored region of the wires distribute more uniformly than those in the midregion due to the different contact patterns among wires. And the corrosion characteristics of salt spray–corroded wires are close to those of wires from the anchored region. The corrosion-fatigue simulations considering the effect of environments, loadings, and contact patterns of wires show that the failure modes of wires are greatly affected by loadings; the lifetimes of wires and cables are particularly sensitive to environmental corrosivity; and due to different contact patterns, the lifetimes of cables from the midregion are shorter than those from the anchored region by 30%. The research on corrosion fatigue of cables provides a rational basis for the operation and maintenance of cable-supported bridges.

Stress Path Behaviour and Friction Angle Transition Due to the Cyclic Loading Effects

In various aspects, peat soil is different from mineral soil. Peat is a biogenic deposit that emerged within the last 10,000 years, during the post-glacial (Holocene) era. Peat is a soft soil that is unable to support external loads without experiencing significant deformations. Tyre pressure from automobiles and/or aeroplane wheels on paved surfaces creates traffic load, which can manifest as static or dynamic types of loading. To resolve the problem with peat soils, a thorough understanding of the static and dynamic behaviour of peat is still required. Many people who live near regularly used highways feel traffic vibration, and it is important to comprehend the nature of this issue to make predictions about potential solutions to this problem. As such, this study aims to investigate the cohesion (c) and friction angle (φ) properties of peat soil after it has been subjected to cyclic stress. Monotonic triaxial tests are conducted to ascertain the initial shear strength characteristics of the soil. Cyclic triaxial tests are performed with half of their maximum deviator stress to simulate the behaviour of peat soil under various effective stresses and frequencies of loading that are applied with 100 number of cycles. After applying various numbers of cycles of dynamic loading, the post-cyclic monotonic shear strengths were subsequently evaluated. It has been noted that irregular behaviour tends to occur more frequently at higher frequencies, particularly between 2 and 3 Hz. With higher frequencies being applied, the reduction in cohesion and friction angle becomes more evident. Doi: 10.28991/CEJ-2023-09-04-010 Full Text: PDF

Influence of Thermal and Mechanical Load Cycling on Fracture Resistance of Premolars Filled with Calcium Silicate Sealer

The aim of this study was to evaluate the aging effect of thermomechanical cyclic load on fracture resistance of lower premolars obturated with AH Plus and BioRoot RCS root canal sealers. Forty-eight single-rooted premolars teeth were instrumented with REVO-S files up to SU/0.06 taper. The teeth were randomly assigned into 2 main groups (n = 24) according to the selected two root canal sealers (AH Plus or BioRoot RCS). All teeth were obturated using matching gutta-percha. Each main group were further divided into 3 subgroups (A, B and C) (n = 8). Group A acted as the negative control group (non-Thermomechanical aging). Whereas Group B and C were subjected first to thermal variations in a thermal cycling machine (7500 and 15,000 thermal cycles), then two different dynamic loading periods namely 3 × 105 and 6 × 105 in a masticatory simulator with a nominal load of 5 kg at 1.2 Hz which simulate approximately 1 ½ and 3 years of clinical function respectively. The roots were decoronated and fracture resistance were measured using a universal testing machine. After thermal-mechanical aging, BioRoot RCS showed significantly higher fracture resistance (p &lt; 0.05) than AH Plus. As the thermal-mechanical cycles increased both AH Plus and BioRoot RCS exhibited a significant decrease in fracture resistance (p &lt; 0.05). It could be concluded that thermomechanical aging had a significant impact on the outcome of the fracture resistance of AH Plus and BioRoot RCS.

Cyclic loading effect on batter anchored pile group in dry sand

Cyclic loading effect on batter anchored pile group in dry sand