Cyclic Tensile Loading Research Articles

Differential response of inner and outer zone meniscal cells to tensile load under non-inflammatory and inflammatory conditions

Differential response of inner and outer zone meniscal cells to tensile load under non-inflammatory and inflammatory conditions

Shape memory alloy strands as cross-ties: Fatigue behavior and model-cable net tests

NiTi Shape Memory Alloy (SMA) has the potential for use as cross-ties to mitigate cable vibration due to its superelasticity and high damping capacity. However, recent studies revealed that the fatigue problem of the NiTi SMA should be addressed. This paper investigates the fatigue characteristic of SMA strands. The superelastic and structural fatigue characteristics of SMA strands were tested under uniaxial cyclic tensile loading at different strain amplitudes. The maximum stress, residual strain, and dissipated energy were derived from a superplastic fatigue test with 2000 cycles. The test results showed that the parameter values related to the superelastic behavior of the SMA strand decreased in the early stage and then stabilized. A structural fatigue test conducted at strain amplitudes of 0.3% to 2.5% indicated that the structural fatigue life of the SMA strand decreased with increasing strain amplitude; the fatigue life reached two million cycles at the strain amplitude of 0.3%. The free vibration test result indicated that the SMA cross-tie significantly increased the frequency and moderately increased the damping ratio of the cable net. An optimal cross-tie location existed in each vibration mode with the maximum damping ratio.

Evaluation of durability against wetting and drying cycles of cement-natural rubber latex stabilised unpaved road under cyclic tensile loading

ABSTRACT Cement stabilised unpaved roads have been implemented worldwide in both developed and developing countries. In this research project, natural rubber latex (NRL) was used to improve the durability against wetting and drying (w-d) cycles of cement stabilised soil, under cyclic tensile loads. The influences of NRL replacement ratio on the indirect tensile strength (ITS), indirect tensile resilient modulus (IT Mr), and indirect tensile fatigue life (ITFL) prior to and after w-d cycles were studied. Cement-NRL stabilised soil was found to have superior resilient properties to minimise the plastic deformation and prevent sudden damage against the repetitive tensile stresses. The NRL replacement could improve the durability against w-d cycles of cement stabilised soil whereby the highest ITS, IT Mr, and ITFL were found at the optimum NRL replacement ratio of 20% for all number of w-d cycles tested. NRL was found to enhance the service life of cement stabilized soil as an unpaved material against fatigue cracking failure. The outcome of this research will promote the usage of NRL, which is available in plentiful supply in Thailand and other Southeast Asian and South American countries, as a sustainable additive in pavement applications.

Can the body slope of interference screw affect initial stability of reconstructed anterior cruciate ligament?: An in-vitro investigation

BackgroundSuperior biomechanical performance of tapered interference screws, compared with non-tapered screws, with reference to the anterior cruciate ligament (ACL) reconstruction process, has been reported in the literature. However, the effect of tapered interference screw’s body slope on the initial stability of ACL is poorly understood. Thus, the main goal of this study was to investigate the effect of the interference screw’s body slope on the initial stability of the reconstructed ACL.MethodsBased on the best screw-bone tunnel diameter ratios in non-tapered screws, two different tapered interference screws were designed and fabricated. The diameters of both screws were equal to bone tunnel diameter in one-third of their length from screw tip, then they were gradually increased by 1mm, in the lower slope (LSTIS), and 2 mm, in the higher slope (HSTIS) screws. To simulate the ACL reconstruction, sixteen soft tissue grafts were fixed, using HSTIS and LSTIS, in synthetic bone blocks. Through applying sub-failure cyclic incremental tensile load, graft-bone-screw construct’s stiffness and graft laxity in each cycle, also through applying subsequent step of loading graft to the failure, maximum load to failure, and graft’s mode of failure were determined. Accordingly, the performance of the fabricated interference screws was compared with each other.ResultsHSTIS provides a greater graft-bone-screw construct stiffness, and a lower graft laxity, compared to LSTIS. Moreover, transverse rupture of graft fibers for LSTIS, and necking of graft in the HSTIS group were the major types of grafts’ failure.ConclusionsHSTIS better replicates the intact ACL’s behavior, compared to LSTIS, by causing less damage in graft’s fibers; reducing graft laxity; and increasing fixation stability. Nonetheless, finding the optimal slope remains as an unknown and can be the subject of future studies.

Synthesis, structure, and properties of carbon/carbon composites artificial rib for chest wall reconstruction

In this work, braided carbon fiber reinforced carbon matrix composites (3D-C/C composites) are prepared by chemical vapor infiltration process. Their composite structure, mechanical properties, biocompatibility, and in vivo experiments are investigated and compared with those of traditional 2.5D-C/C composites and titanium alloys TC4. The results show that 3D-C/C composites are composed of reinforced braided carbon fiber bundles and pyrolytic carbon matrix and provide 51% open pores with a size larger than 100 μm for tissue adhesion and growth. The Young’s modulus of 3D-C/C composites is about 5 GPa, much smaller than those of 2.5D-C/C composites and TC4, while close to the autogenous bone. 3D-C/C composites have a higher tensile strength (167 MPa) and larger elongation (5.0%) than 2.5D-C/C composites (81 MPa and 0.7%), and do not show obvious degradation after 1 × 106 cyclic tensile loading. The 3D-C/C composites display good biocompatibility and have almost no artifacts on CT imaging. The in vivo experiment reveals that 3D-C/C composites artificial ribs implanted in dogs do not show displacement or fracture in 1 year, and there are no obvious proliferation and inflammation in the soft tissues around 3D-C/C composites implant. Our findings demonstrate that 3D-C/C composites are suitable for chest wall reconstruction and present great potentials in artificial bones.

Effect of stochastic brittle fragmentations on cyclic loading/unloading hysteresis behavior of fiber-reinforced ceramic-matrix composites

Under monotonic tensile and cyclic tensile loading, the occurrence of stochastic brittle fragmentations will affect monotonic and cyclic loading/unloading mechanical behavior of fiber-reinforced ceramic-matrix composites (CMCs). In this work, synergistic effects of stochastic brittle matrix and fiber fragmentations on monotonic and cyclic loading/unloading hysteresis behavior of fiber-reinforced CMCs were investigated. Different matrix fragmentation lengths and distributions of stresses between intact and broken fibers were determined using stochastic fragmentation models, taking into account cyclic loading/unloading hysteresis constitutive relationships. Experimental monotonic tensile and hysteresis curves, matrix fragmentation density, and fiber fragmentation probability for two different SiC/SiC minicomposites were forecasted. Theoretical tensile curves and loading/unloading hysteresis loops for different peak stresses agreed well with the actual data collected. Interface slip is constrained by the debonding of the interface for long matrix brittle fragmentation (LMBF) length and the fragmentation length of the matrix for short matrix brittle fragmentation (SMBF) length. The impacts of fiber volume fraction and fiber's strength on monotonic and cyclic tensile loading/unloading hysteresis loops were analyzed. Fiber volume fraction increase resulted in increased proportional limit stress and tensile fractured strength and decreased tensile failure strain; in addition, the peak strain of hysteresis loops as well as valley strain and area decreased, with increased hysteresis loops modulus for different matrix fragmentations.

Suction Bucket Foundations under Cyclic Tensile Loading—Physical and Numerical Modeling

Abstract Although suction buckets are believed to be a promising alternative for multipod foundations of offshore wind turbines, the economic and ecological advantages are still limited because of a lack of knowledge regarding the tensile bearing behavior. Major uncertainties exist in terms of the response under cyclic loading and the assessment of the partially drained loading condition, where negative differential pressure beneath the suction bucket’s lid contributes to the total tensile resistance. This article presents findings from 1-g model tests of suction buckets in sand subjected to various cyclic tensile loads. The suction bucket was installed via negative differential pressure (suction). The results show a strong effect of the applied load magnitude on the evolution of displacement, plug heave, and suction induced. Greater displacement accumulation is observed for the smaller considered frequency. Monotonic tests with varying displacement rates supplement the cyclic tests and serve for the verification of a hydraulic-mechanic coupled finite element model, which is afterward utilized for the back-calculation of cyclic model tests. Although a rather simple elasto-plastic material law was used for the sand, good agreement was found, indicating that the bearing behavior is mainly governed by the hydraulic conditions and only subordinately by the soil mechanics.

Graphene as a piezo-resistive coating to enable strain monitoring in glass fiber composites

In this study, the electromechanical properties and strain monitoring behavior of graphene-coated glass fiber reinforced epoxy (GGFRE) composites were investigated. Glass fabrics were first coated with 2 wt% graphene dispersions using a blade coating method and composites of these graphene-coated glass fabrics were manufactured using vacuum resin infusion. As-prepared GGFRE showed an increase in normalized resistance (ΔR/R0) by 4.46%, 10.5%, 11.07% and 11.27% proportional to the applied cyclic tensile forces up to 2000N, 3000N, 4000N and 5000N, respectively. The corresponding gauge factors were calculated to be 14.56 ± 1, 13.32 ± 1, 11.23 ± 0.5 and 8.69 ± 2, respectively. It was also observed that under cyclic tensile loadings at 2000N, ΔR/R0 values were consistent within 11 cycles indicating a reliable sensing performance. The integration of graphene into the composite has shown to decrease the tensile strength as well as flexural strength and flexural modulus by 26%, 37% and 39%, respectively. This drop is believed to be caused by the lower fiber volume content in the GGFRE compared to that of the neat glass fiber composite and the ineffective interfacial interaction between the glass fiber and the graphene dispersion. The piezo-resistive behavior indicated by GGFRE along with their scalable manufacturing method suggest them as promising potential candidates for strain sensing applications.

Design of mooring system for a floating production storage and offloading (FPSO) terminal

The use of FPSO for deep sea exploration of hydrocarbon resources has been on trend. Thus, there is a need for ensuring safety with regards to station keeping. However, there are mainly two materials used for mooring line fabrication: Synthetic and Steel. Polyester rope is regarded as a good synthetic option for deep water mooring application. This is as a result of its durability in cyclic tensile fatigue loading. This work compares the end forces between the proposed polyester (with top and bottom chains) rope with that of steel-wire rope from existing systems. From the dynamic analysis of the mooring lines with joint criteria for extremes dominated sea states, the maximum value of the end tension for wire rope is 1668.5722 kN of S-1 (Starboard-1) and the total force is 1668.5799 kN. Conversely for polyester rope, the maximum value of the end tension is 1130.0381 kN of S-1 and the total force is 1130.0511 kN. This result shows that the force and tension in polyester rope are lower than those of steel wire rope: indicating the effects of reduced vertical (gravity) forces of mooring rope on the FPSO with an associated improvement in horizontal restoring force. The substantial decrease in rope weight reduces the complexity of installation, and increases the vessel’s payload. The latter enhances its capaciousness for crude oil cargo which consequently boosts its economic viability. Also, the fatigue life of the polyester rope is more than that of steel rope because of its low frequency load.

Effect of shear and tensile-dominant cyclic loading on failure in SnAgCu solder

In the first part of this paper the differences between simulated SN-Curves under shearing and tensile cyclic loads are presented and compared with measurements published by A. Deshpande and A. Dasgupta [1, 2]. The measurements under the two load modes are simulated until a significant force reduction.The material model used in this work is based on visco-plasticity extended with an implicit damage formulation, enabling damage-driven cyclic softening of the structure. Additionally, multiaxiality of governing stress state is intrinsically included, with aim to account for different damage evolutions under shear and tensile load cases. The calculated damage paths are investigated and compared with cross-sections. Finally, numerically determined times to failure under different shear and tensile load levels are represented by means of SN-Woehler curves, showing a good agreement with experimental findings.Second part of the paper extends the investigation scope to lifetime prediction of a chip resistor soldered to free expanding PCB subjected to temperature cycling with variation of temperature amplitude, mean temperature and dwell time duration. The component is simulated under different temperature profiles until a specific lifetime reduction is observed. Also in this case, simulated lifetime is compared with measured data, and a good agreement with experimental results is achieved.

Mechanical behaviours of heat-damaged grouted sleeve connections

An experimental study with 72 specimens was conducted to determine the effects of various factors on the mechanical behaviours of grouted sleeve connections, including an increase in temperature from 20 °C to 600 °C, the loading regime (uniaxial tensile loading or cyclic loading), and the grout compressive strength (83.1–91.1 MPa). After the specimens were exposed to elevated temperatures of up to 600 °C and then uniaxial tensile loading or cyclic loadings, the experimental results indicated that the sleeve was still elastic and the grout had a compressive strength of more than 83.1 MPa, which was beneficial for maintaining the mechanical behaviours of the specimens. In this study, the sleeve region was equal to the gauge length, which consisted of the length of the sleeve and three times the diameter of the rebar from each end of the sleeve. Moreover, a bilinear model was formulated to calculate the yield and ultimate loads of the heat-damaged grouted sleeve connections after different loading regimes. Finally, the constitutive relationship of the heat-damaged grouted sleeve connection was investigated. These findings will be helpful in the fire safety design of precast concrete structures.

Strain Sensing Coatings for Large Composite Structures Based on 2D MXene Nanoparticles.

Real-time strain monitoring of large composite structures such as wind turbine blades requires scalable, easily processable and lightweight sensors. In this study, a new type of strain-sensing coating based on 2D MXene nanoparticles was developed. A Ti3C2Tz MXene was prepared from Ti3AlC2 MAX phase using hydrochloric acid and lithium fluoride etching. Epoxy and glass fibre–reinforced composites were spray-coated using an MXene water solution. The morphology of the MXenes and the roughness of the substrate were characterised using optical microscopy and scanning electron microscopy. MXene coatings were first investigated under various ambient conditions. The coating experienced no significant change in electrical resistance due to temperature variation but was responsive to the 301–365 nm UV spectrum. In addition, the coating adhesion properties, electrical resistance stability over time and sensitivity to roughness were also analysed in this study. The electromechanical response of the MXene coating was investigated under tensile loading and cyclic loading conditions. The gauge factor at a strain of 4% was 10.88. After 21,650 loading cycles, the MXene coating experienced a 16.25% increase in permanent resistance, but the response to loading was more stable. This work provides novel findings on electrical resistance sensitivity to roughness and electromechanical behaviour under cyclic loading, necessary for further development of MXene-based nanocoatings. The advantages of MXene coatings for large composite structures are processability, scalability, lightweight and adhesion properties.

Mechanical Properties of GFRPs Exposed to Tensile, Compression and Tensile-Tensile Cyclic Tests.

Currently there are many applications for the use of composites reinforced with fiberglass mat and fabrics with polyester resin: automotive, aerospace, construction of wind turbines blades, sanitary ware, furniture, etc. The structures made of composites have a complex geometry, can be simultaneously subjected to tensile–compression, shear, bending and torsion. In this paper we analyzed the mechanical properties of a polyester composite material reinforced with glass fiber (denoted GFRP) of which were carried out two types of samples: The former contains four layers of plain fabric (GFRP-RT500) and the second type contains three layers of chopped strand mat (GFRP-MAT450). The samples were subjected to tensile, compression and tensile–tensile cyclic loading. The results highlight the differences between the two types of GFRP in terms of initial elastic modulus, post yield stiffness and viscoelastic behavior under cyclic loading. Thus, it was observed that the value of the modulus of elasticity and the value of ultimate tensile stress are approximately twice higher in the case of GFRP-RT500 than for the composite reinforced with short fibers type GFRP-MAT450. The tensile–tensile cyclic test highlights that the short glass fiber-reinforced composite broke after the first stress cycle, compared to the fabric-reinforced composite in which rupture occurred after 15 stress cycles. The elasticity modulus of GFRP-RT500 decreased by 13% for the applied loading with the speed of 1 mm/min and by 15% for a loading speed of 20 mm/min.

The use of the empirical crack orientation tensor to characterize the damage anisotropy

In practice, a dominant failure mode of brittle materials, such as fiber-reinforced thermosets is the initiation and propagation of cracks under cyclic loading. In general, the damage in composites with irregular microstructure do not occur in regular patterns. There are several state-of-the-art continuum mechanical models which take the anisotropic damage for predicting the material behavior into account. Since damage generally occurs in an anisotropic way, methods that experimentally characterize the damage anisotropy are needed.Micro-Computed Tomography systems (μCT) acquire volumetric images in a non-destructive way. By combining μCT scanning and mechanical in-situ testing, detailed microstructure data of specimens under load are generated. Based on image processing methods, the damage propagation from crack initiation to fracture is analyzed. In practice, cyclic load is a common load case for many components. Consequently, fatigue and cycle load tests are essential for a comprehensive material characterization.In this contribution interrupted in-situ μCT tests with cyclic tensile load are performed on Sheet Molding Compounds (SMC), a discontinuous glass fiber-reinforced thermset composite. Image processing methods are introduced for the experimental determination of the anisotropic damage characteristic based on volumetric images. The methods enable analyzing the spatial crack orientation distribution. In order to quantify the damage anisotropy, empirical formulations of the crack density distribution and second-order crack orientation tensor are applied. The presented work in this contribution extends the results of preliminary experimental damage investigations. In addition to previous studies, the damage anisotropy is quantified and analyzed.

Fabrication and electromechanical performance of carbon nanotube based conductive membrane and its application in real-time multimode strain detection in composites

In this study, a flexible conductive membrane (CM) consisting of a network of carbon nanotubes is produced and the electromechanical behavior of this CM was studied experimentally and the gauge factor (GF) of CM was in the 8–8.25 range. Then, a multi-mode strain detection is carried out in composites using this CM sensor. The CM is embedded gradually at directions i.e. 0°, +45°, 90°, −45° between the plies for real-time/in-situ strain monitoring. The composite specimens are then cut in star profile and then tested under tensile and bending cyclic loading. There is a good reproducibility in the results and the mechanical response of composite correlated perfectly with the electrical resistance of the CM sensor however, a sensor in each position showed distinct behavior. The results established that the CM sensor exhibited good potential as a flexible strain sensor for in-situ monitoring of composites and can provide detection over a large section and unapproachable locations.

Electromechanical properties of embedded multifunctional energy storage composite with activated carbon fiber/PVDF gel electrolyte

ABSTRACT This paper presents a standardized process for fabricating multifunctional energy storage composites that involves using activated carbon fiber (CF) electrodes and a poly(vinylene fluoride) (PVDF)-based gel polymer electrolyte (GPE) as building materials for embedded supercapacitors. A two-step packaging method was used to fabricate composites that can simultaneously bear mechanical loads and store energy. CF electrodes were subjected to three activation procedures, and the optimal composition of the PVDF-based GPE was determined by comparing the performance of PVDF-based GPEs of various compositions through electrochemical tests. The specific capacitance and energy density of a supercapacitor embedded with a glass-fiber-reinforced composite was 168 mF/g and 140 J/kg, respectively. The aforementioned values were 15.3% and 21.9% higher, respectively, than the corresponding values obtained for a bare cell. Mechanical tests indicated that the average tensile strength of the aforementioned composite was 350.1 MPa. With a gradual increase in the tensile load, the supercapacitor energy density increased by approximately 10% and then plateaued until fracture. Under cyclic tensile loads, the fabricated supercapacitors functioned normally until the composite failed.

Numerical life prediction of unidirectional fiber composites under block loading conditions using a progressive fatigue damage model

Practical applied components made of Fiber-Reinforced Plastics (FRPs) are usually subjected to cyclic loading with variable load amplitudes and arbitrary load orientation in the course of their service life. For a cost-effective design process of composite structures, it is essential to use computationally efficient and detailed fatigue damage design tools. This contribution focuses on the extension and application of a progressive Finite-Element-based Fatigue Damage Model (FDM) for unidirectional FRPs for lifetime prediction under different block loading conditions. The employed FDM relies on a layer- and energy-based approach, and it is capable of including basic fatigue phenomena such as load sequence effects and stress redistributions. First, the damage evolution laws on which the FDM is based are extended to block loading conditions with arbitrary load sequences. The effects of passive damage, which occur in this context under alternating cyclical tensile and compressive loading, are also taken into account. Secondly, appropriate block loading patterns are defined for the numerical prediction of the lifetime. Finally, the calculation results are presented and critically evaluated based on experimental findings from literature. The comparison of simulations with experiments demonstrates the high predictive capacity of the presented FDM.

Comparison Between Monotonic, Cyclic and Post-Cyclic Pullout Behavior of a PET Geogrid Embedded in Clean Sand and Clayey Sand

A series of monotonic and multistage pullout tests were performed using a large pullout apparatus to study the monotonic, cyclic and post-cyclic pullout behavior of a uniaxial woven geogrid under different conditions. The monotonic and multistage pullout tests were performed for clean sand and sand containing 10% and 20% clay. The effect of vertical effective stress on the pullout resistance and deformation along the geogrid was investigated using monotonic testing. In the multistage pullout test, the influence of vertical effective stress, cyclic load amplitude and the frequency and the number of tensile load cycles on the post-cyclic pullout resistance and deformation during the cyclic stage was studied. The monotonic test results indicated that an increase in clay content increased the pullout resistance at the lower effective vertical stress (20 kPa), while at higher vertical stresses (40 and 60 kPa), this effect was insignificant. Moreover, when a geogrid was embedded in clean sand and 20% clayey sand, the post-cyclic peak pullout resistance was slightly lower than the values attained in monotonic tests at a vertical effective stress of 20 kPa. The reductions varied from 3.5 to 8% for clean sand and 5.5 to 7% for 20% clayey sand. An increase in the cyclic load amplitude had no effect on the post-cyclic resistance of the geogrid-embedded in clean sand, but post-cyclic resistance of geogrid embedded in 20% clayey sand decreases with increasing cyclic load amplitude.

Seismic performance of steel columns corroded in general atmosphere

Steel structures exposed to general atmosphere for a long time are highly susceptible to corrosion damage, which would lead to the degradation of service performance of the components and even structures. This article focuses on the effect of corrosion on the seismic performance of steel column. The accelerated corrosion tests in general atmosphere were conducted on 7 H-shaped steel columns and 20 steel plates. Then the obtained plate specimens were subjected to monotonic tensile tests and cyclic loading tests, and the steel columns were subjected to pseudo-static tests, respectively, to study the effects of corrosion on their mechanical properties and seismic performance. Then, a simplified three-dimensional finite element model (FEM) capable of accurately simulating the hysteretic response of corroded steel columns under low-cycle loading was established. Experimental results indicated that the yield strength, tensile strength, elastic modulus and peak strain of corroded steel plate decreased linearly with the proposed corrosion damage parameter Dn, and the energy dissipations under low-cycle loading were significantly reduced. There is a correlation between the cyclic hardening parameters of corroded steel and the yield-tensile strength difference (SD), and then a simplified formula was proposed. Corrosion could result in the premature entrance of each loading stage of corroded columns and the deterioration of buckling deformation range, bearing capacity and energy dissipation, etc. In addition, a larger axial compression ratio (CR) would further accelerate the failure process of corroded columns. The parametric finite element analysis (FEA) indicated that greater damage was found for steel columns with non-uniform corrosion, and hysteretic performance degraded more significantly when corrosion distributed at flanges or foot zone.

Cyclic tensile behavior of high strain hardening UHPC analyzed by acoustic emission techniques

Understanding the cyclic tensile behavior of high strain hardening ultra high performance concrete (UHPC) is important in structural design and for predicting its damage state. In this study, acoustic emission (AE) analysis was applied to monitor the damage evolution process of high strain hardening UHPC under direct tensile cyclic loading at different objective tensile strain levels. The test results show that when the objective strain is in the elastic state, the tensile cyclic stress–strain curves show marginal change, whereas when it is in the strain hardening state, the residual strain and the stiffness of UHPC are reduced by increasing the number of cycles and finally tends toward stability, the maximum stress remains stable. The AE analysis results can help to explain the evolution of the mechanical properties of high strain hardening UHPC under cyclic tensile loading and proves the existence of the Kaiser effect, which can be used to quantify the deformation and the degree of damage of UHPC. The stiffness of UHPC under cyclic tension is controlled by the nominal debonding length of the steel fibers. Finally, the relationship between the total tensile strain and the loading stiffness degradation ratio under cyclic tension was proposed and could be employed in evaluate of stiffness of the high strain hardening UHPC under cyclic tension in some extent.