Tensile Conditions Research Articles

노후 함정 강재의 기계적 특성 평가

Ships operated at sea for a long time are subjected to various kinds of loads, which may cause various types of damage. Such damages will eventually reduce the strength of hull structures. Therefore, it is necessary to estimate and evaluate the residual strength and remaining fatigue life of aging ships in order to secure structural safety, establish a reasonable maintenance plan, and make a judgment of life extension. For this purpose, the corrosion damage and local denting damage should be measured, fatigue damage estimation should be performed, and material properties of aged steel should be identified. For this study, in order to investigate the mechanical properties of aged steel, steel plates were obtained from a naval ship that reached the end of her life span. The specimens were manufactured from the obtained steel plates, and static and dynamic tensile tests, fatigue tests, and metallographic tests were performed. The mechanical properties obtained from the aged steel plates were compared with those of new steel plates to quantify the aging effect on the mechanical properties of marine steel materials.

Effect of Seawater with Average Salinity on the Moisture Content, Ash Content and Tensile Strength of Some Coniferous Wood.

In this paper, the differences in mechanical strength tested during the static tensile and compression test of Scots pine (Pinus sylvestris L.), European larch (Larix decidua) and Norway spruce (Picea abies) wood exposed to continuous soaking in water with a salinity of 7‱ were determined. The value of salinity corresponded to the average salinity on the Polish Baltic coast. This paper also aimed to examine the content of mineral compounds absorbed during four cycles of two weeks each. The essence of the statistical research was to identify the effect of the mineral range compounds and salts depending on the mechanical strength of the wood. Based on the results of the experiments, it can be concluded that the medium used has a specific effect on the wood species' structure. The effects of soaking on the wood parameters depend obviously on the type of wood. A tensile strength test of pine, as well as the tensile strength other species, was enhanced by incubating it in seawater. A native sample's initial mean tensile strength was 82.5 MPa, which increased to 94.8 MPa in the last cycle. It was found that the larch wood had the lowest tensile strength difference (9 MPa) of the woods studied in the current study. Four to six weeks of soaking was necessary to notice an increase in tensile strength.

Static and Fatigue Tensile Properties of Cross-Ply Carbon-Fiber-Reinforced Epoxy-Matrix-Composite Laminates with Thin Plies

Carbon-fiber-reinforced epoxy-matrix composite (CFRP) laminates with thin plies have strong damage-resistance properties compared with standard prepregs. The static and fatigue tensile fracture behavior of cross-ply CFRP laminates with thin plies should be further studied to establish the applicability of thin-ply prepregs for industrial structures. In this study, the static and fatigue tensile properties of cross-ply, high-strength polyacrylonitrile (PAN)-based carbon-fiber (T800SC)-reinforced epoxy-matrix composites with thin plies were investigated. The fiber orientations of the CFRP specimens were set to cross-ply with [0/90]10S (subscript S means symmetry), [(0)5/(90)5]2S, and [(0)10/(90)10]S. The static and fatigue tensile characteristics of the cross-ply CFRPs with thick plies with [0/90]2S and [(0)2/(90)2]S were also investigated for comparison. Under static loading, the tensile strength and failure strain of the thinnest 90°-ply-CFRP specimens were more than 5% higher than those of the other 90°-ply-thickness specimens. However, the tensile moduli and Poisson’s ratios were comparable between the cross-ply CFRPs with thin and thick plies. Under fatigue loading, the fatigue responses of the thinnest 90°-ply-CFRP specimens were 3% higher than those of the other 90°-ply-thickness specimens during lower-fatigue-cycle testing (<105 cycles). However, during higher-fatigue-cycle testing (>105 cycles), the fatigue responses decreased, with a decrease in the 90°-ply thickness, and the fatigue characteristics of the thinnest 90°-ply-CFRP specimen were 7% lower than those of the other cross-ply thin- and thick-ply-CFRP specimens.

PLC Effect at Different Types of Loading During Static Tensile Testing of Aluminium Alloys

PLC Effect at Different Types of Loading During Static Tensile Testing of Aluminium Alloys

To the scrutiny of the experiential and computational elicitation of factors of the Williams multi-parameter expansion

The article defines stress fields near the tips of mathematical cracks in an isotropic linearly elastic plate with two horizontal collinear cracks lying on a straight line of different lengths under the uniaxial tensile condition, using two approaches - experimental, based on the method of digital photomechanics, and numerical, based on finite element calculations. To represent the stress field at the tip of the section, the Williams polynomial series is used - the canonical representation of the field at the top of the mathematical section of a two-dimensional problem of elasticity theory for isotropic media. The main idea of the current study is to take into consideration the regular (non-singular) terms of the series and analyze their impact on the holistic description of the stress field in the immediate vicinity of the top of the section. The first fifteen coefficients of the Max Williams series were preserved and determined in accordance with experimental patterns of isochromatic bands and finite element modeling. To extract the coefficients of the Williams series used a redefined method designed to solve systems of algebraic equations, the number of which is significantly greater than the unknown - amplitude multipliers. The influence of the non-singular terms of the Williams series on the processing of the experimental pattern of interference fringes is demonstrated. It is validated that the preservation of the terms of a high order of smallness makes it possible to expand the area adjacent to the tip of the crack, from which experimental points can be selected. The finite element study was carried out in the SIMULIA Abaqus engineering analysis system, in which experimental samples tested in a full-scale experiment were reproduced. It is revealed that the results obtained by the two methods are in good agreement with each other.

A Molecular Dynamics Simulation for Thermal Activation Process in Covalent Bond Dissociation of a Crosslinked Thermosetting Polymer

A novel algorithm for covalent bond dissociation is developed to accurately predict fracture behavior of thermosetting polymers via molecular dynamics simulation. This algorithm is based on the Monte Carlo method that considers the difference in local strain and bond-dissociation energies to reproduce a thermally activated process in a covalent bond dissociation. This study demonstrates the effectiveness of this algorithm in predicting the stress-strain relationship of fully crosslinked thermosetting polymers under uniaxial tensile conditions. Our results indicate that the bond-dissociation energy plays an important role in reproducing the brittle fracture behavior of a thermosetting polymer by affecting the number of covalent bonds that are dissociated simultaneously.

Static Experimental Study on New Arc Multi-Tendon CFRP Cable Anchorage System

CFRP has the potential to replace steel cables in large-span cable-stayed bridges due to its high strength and lightweight material properties. However, the weak lateral force performance of CFRP material creates the challenge of anchoring. This study introduces a new inner cone + arc + straight cylinder bond-type anchorage system to optimize CFRP tendons’ force state. Experimental and finite element analyses verified the new anchoring system’s performance. In static load tensile tests, six groups of seven CFRP tendon anchorage systems with different sleeve grooves were used to study the failure mode and load–strain variation law. The difference in mechanical properties between the new and traditional anchorage is evaluated in the finite element analysis. The results indicate that the new anchorage system can lower the stress concentration in the anchorage zone and enhance anchorage performance. The groove design of the sleeve can effectively increase the anchoring efficiency, where the groove depth is proportional to the anchoring efficiency and the groove spacing is inversely proportional to the anchoring efficiency. The magnitude of the stress inhomogeneity in the multi-tendon anchoring system during tensioning is proportional to the beginning conditions and the load size. When the inner wall of the sleeve becomes more abrasive, the force heterogeneity of the anchorage system reduces. The tests and finite element analysis show that the new anchoring may improve stress distribution and anchorage efficiency. In engineering practice, it can be utilized as a dependable anchorage system.

Patient-specific femoral implant design using metamaterials for improving load transfer at proximal-lateral region of the femur

Loading configuration of hip joint creates resultant bending effect on femoral implants. So, the lateral side of femoral implant which is under tension retracts from peri‑implant bone due to positive Poisson's ratio. This retraction of implant leads to load shielding and gap opening in proximal-lateral region, thereby allowing entry of wear particle to implant-bone interface. Retraction of femoral implant can be avoided by introducing auxetic metamaterial to the retracting side. This allows the implant to push peri‑implant bone under tensile condition by virtue of their auxetic (negative Poisson's ratio) nature. To develop such implants, a patient-specific conventional solid implant was first designed based on computed-tomography scan of a patient's femur. Two types of metamaterials (2D: type-1) and (3D: type-2) were employed to design femoral meta-implants. Type-1 and type-2 meta-implants were fabricated using metallic 3D printing method and mechanical compression testing was conducted. Three finite element (FE) models of the femur implanted with solid implant, type-1 meta-implant and type-2 meta-implant were developed and analysed under compression loading. Significant correlation (R2=0.9821 and R2=0.9977) was found between the experimental and FE predicted strains of the two meta-implants. In proximal-lateral region of the femur, an increase of 7.1% and 44.1% von-Mises strain was observed when implanted with type-1 and type-2 meta-implant over the solid implant. In this region, bone remodelling analysis revealed 2.5% bone resorption in case of solid implant. While bone apposition of 0.5% and 7.7% was observed in case of type-1 and type-2 meta-implants, respectively. The results of this study indicates that concept of introduction of metamaterial to the lateral side of femoral implant can prove to provide higher osseointegration-friendly environment in the proximal-lateral region of femur.

Effect of annealing temperature on microstructure and tensile properties of copper/aluminum composite thin strip

AbstractThe effect of annealing temperature on the microstructure and tensile properties of copper/aluminum (Cu/Al) composite thin strips was studied to improve the mechanical properties of materials. The change of interface layer, the diffusion of interface elements, and the microstructural evolution of each matrix of Cu and Al were observed and analyzed using scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and electron back-scatter diffraction (EBSD) techniques. The tensile properties of the Cu/Al composite thin strip were studied by static uniaxial tensile tests. The results show that recrystallization occurs in the Cu/Al matrix during annealing process, and the grains of the Al matrix grow into coarse grains after annealing at 400 °C. The thickness of diffusion layer increases with the increase of annealing temperature, and the thickness of the diffusion layer reaches 12 μm after annealing at 500 °C. The original typical rolling texture is transformed into the typical annealing texture components {001}〈100〉 and {001}〈110〉 after annealing treatment. In general, the annealing treatment reduces the tensile strength and improves the overall plasticity of the material, and the diffusion layer plays a significant role in transmitting tensile stress.

Evaluation of mechanical properties of glass fiber-reinforced composites depending on length and structural anisotropy

Recently, as the size of liquid natural gas (LNG) carriers has dramatically increased, applied force in the LNG Cargo Containment System (CCS) has also increased. However, the existing E-glass fiber-reinforced composite, which plays an important role to prevent accident as secondary barrier induced LNG leakage, has remained unchanged. In case of in-situ length of the composite in membrane type of MARK-III LNG CCS, it is continuously installed as a prolonged structure by using automatic bonding machine (ABM). From this point of view, it should be considered that the length effect of the mechanical properties to represent an infinitely long distance for structural reliability. Fracture strength of a brittle material, such as glass fiber components, is generally not constant because of the variable quantity and distribution of imperfections throughout the composites. In this study, 2-parameters of Weibull distribution were derived to standardize the widely dispersed fracture strengths under the quasi-static tensile test condition. As a result of the experiments by length, the standardized failure strength associated with scale parameter (63.2% probability of failure over all the repeated tests) in the Weibull distribution increases until it reaches a specific length at 250 mm, at which point it stops rising and converges to a constant value. This tendency indicates that material properties at the specific length will be reliable for mechanical evaluation of the composites under the infinitely prolonged condition.

Assessment of the influence of electric arc furnace slag as a non-conventional filler for Nitrile Butadiene Rubber

Reinforcement of polymers by the addition of particles filler is a complex phenomenon that depends mainly on the hydrodynamic effect and a complex interplay between polymer, filler, and interfacial region. Mineral fillers are usually adopted as low-cost extenders due to their lower cost.In this study, the influence of a waste material such as electric arc furnace steel slag is assessed as filler for Nitrile-Butadiene Rubber following experimental procedures and analytical calculations adopted for traditional fillers. It was found that the slag content affects the static and the dynamic properties by increasing the material's capability to storage and dissipate energy. In addition to an important contribution of the hydrodynamic effect, the presence of an increasing immobilized rubber fraction around the slag particles (quantified by a differential scanning calorimetry analysis) plays a central role. The slag stiffens the NBR composite; the increase of static tensile and dynamic shear storage moduli was found to be consistent with the Halpin-Tsai and Guth-Gold prevision models respectively. Moreover, the non-linear dynamic behavior was found to be well-fitted by the Kraus equation models. The reinforcing ability of the slag particles as filler was confirmed by the negative slope of the Kraus plot on swelling data.

Modelling of strain-induced martensite formation in advanced medium-Mn automotive sheet steel

The modelling of strain-induced martensite formation is simulated in advanced medium-Mn steel. The fraction of retained austenite (8%) embedded in the bainitic matrix is transforming into the strain-induced martensite during progressive static tensile tests. The originally elaborated technique and algorithms (using C++ language) are presented. The finite element method and LS-DYNA (LSTC Company, USA) have been deployed. The calculations of the stress-induced martensite start temperature were performed to characterize the austenite stability. The structural investigations using the SEM and EBSD have been conducted. The comparison of the experimental and numerical results has been made in terms of mechanical austenite stability.

Evaluation of Mechanical Properties of Different Casing Drilling Steels

An investigation into the mechanical properties of K55, N80, and P110 steels commonly used for casing drilling was carried out together with microstructural and fractographic analysis. The results show that P110 steel consisted of almost fully tempered martensite and exhibited a synergy combination of static tensile, dynamic impact, and fatigue crack propagation properties among the three steels, possessing a higher fatigue limit and deeper crack tolerance before failure occurred. The K55 steel consisted of the pearlite and network structure of ferrite and possessed a high strain hardening exponent and low impact property, which led to the more suitable application under incidental large overload and temperature change, but it was unsuitable under the condition of higher impact force. The properties of N80 steel were moderate, and its fatigue property was higher than that of K55 and lower than that of P110; its incidental overload resistance was also higher than that of P110. The casing drilling steel can be selected according to the environment.

Flexible Organic Photodetectors with Mechanically Robust Zinc Oxide Nanoparticle Thin Films.

Zinc oxide nanoparticle (ZnO-NP) thin films have been intensively used as electron transport layers (ETLs) in organic optoelectronic devices, but their moderate mechanical flexibility hinders their application to flexible electronic devices. This study reveals that the multivalent interaction between ZnO-NPs and multicharged conjugated electrolytes, such as diphenylfluorene pyridinium bromide derivative (DFPBr-6), can significantly improve the mechanical flexibility of ZnO-NP thin films. Intermixing ZnO-NPs and DFPBr-6 facilitates the coordination between bromide anions (from the DFPBr-6) and zinc cations on ZnO-NP surfaces, forming Zn2+-Br- bonds. Different from a conventional electrolyte (e.g., KBr), DFPBr-6 with six pyridinium ionic side chains holds the Br--chelated ZnO-NPs adjacent to DFP+ through Zn2+-Br--N+ bonds. Consequently, ZnO-NP:DFPBr-6 thin films exhibit improved mechanical flexibility with a critical bending radius as low as 1.5 mm under tensile bending conditions. Flexible organic photodetectors with ZnO-NP:DFPBr-6 thin films as ETLs demonstrate reliable device performances with high R (0.34 A/W) and D* (3.03 × 1012 Jones) even after 1000 times repetitive bending at a bending radius of 4.0 mm, whereas devices with ZnO-NP and ZnO-NP:KBr ETLs yield >85% reduction in R and D* under the same bending condition.

Effects of Specimen Thickness and Non-Isothermal Process on Creep Behavior of AA2024 Aluminum Alloy

Fiber metal laminate (FML) is a kind of lightweight material that has garnered much attention in recent years due to its excellent properties under tensile, flexure, and impact conditions. However, little attention has been paid to the evolution of aluminum alloy during the FML forming process. In this paper, the effects of specimen thickness and the non-isothermal process on creep behavior of AA2024 aluminum alloy, which is generally used in FMLs, were systematically studied in terms of creep strain, mechanical properties, and microstructure. The results show that the microstructure and mechanical properties of the aluminum alloy layer are greatly affected by the creep age during the FML forming process, but the specimen thickness has little effect on the creep behavior under experimental conditions. During the non-isothermal process, the creep strain generated during the heating stage is about 40% of total strain. Compared with the isothermal process, the creep strain of the non-isothermal process increases by 20–40%, and the apparent activation energy Qc is larger. According to the creep behavior of AA2024 aluminum alloy during the non-isothermal process, a creep constitutive model was established to accurately simulate the deformation of FMLs.

Time-Temperature Superposition Principle in Shearing Tests Compared to Tension Conditions for Polymers Close to Glass Transition.

The well-known principle of time-temperature superposition (TTS) is of prime interest for polymers close to their glass transition. First demonstrated in the range of linear viscoelasticity, it has been more recently extended to large deformations in tension. However, shear tests were not yet addressed. The present study depicted TTS in shearing conditions and compared it to results in tensile conditions both for low and high strains for a polymethylmethacrylate (PMMA) of different molar masses. The main objectives were to enlighten the relevance of the principle of time-temperature superposition for shearing at high strain and to discuss the way shift factors should be determined. It was suggested that shift factors could be dependent on compressibility, which should be taken into account when addressing various types of complex mechanical loadings.

Thermal analysis under static and fatigue conditions on HDPE

High Density Polyethylene (HDPE) represents one of the best choices for water and gas distribution pipeline thanks to its light weight and good mechanical performance. One of the strengths of this plastic material is the possibility to join it via welding adopting a procedure according to the standard. However, the welding procedure can severally alter the mechanical performance of the material under service loads. In the present work comparison between virgin and welded HDPE specimens is carried out adopting rapid approaches, such as the Risitano’s Thermographic Method and the Static Thermographic Method, monitoring the evolution of the specimen’s superficial temperature under static tensile and fatigue tests. Mechanical performance has been compared, as well as the fatigue limit obtained with traditional fatigue tests, showing good agreement. Reliable fatigue data have been obtained in a very short amount of time and with few specimens by adopting Energy Methods.

In-situ health monitoring of thermoplastic bio-composites using acoustic emission

This article aims to accomplish research’s that has been achieved recently in the scientific community on the manufacturing monitoring and structural health monitoring (SHM) of composite materials using in-situ piezoelectric sensors. A series of specimens of flax/Elium composite laminates with and without integrated piezoelectric sensors were subject to static and fatigue tensile tests. The effects of introducing the sensor into the composite materials were studied. Moreover, the Acoustic Emission (AE) method was used during experimental tests to follow the gradual degradation and damage evolution in the bio-composites. The AE data were analyzed by the k-means unsupervised pattern recognition algorithm. Moreover, the characteristics of the acoustic signals detected from specimens with and without integrated sensors were compared. The experimental results show that the integration of piezoelectric sensors within the flax/Elium composite without degrading its mechanical properties is possible. In addition, the integrated sensor shows good results regarding class detection and separation. The in-situ health monitoring methods performed on bio-composites presents an excellent alternative to the conventional technique in which sensors are generally bonded to the material surface.

Effect of the Combination of Torsional and Tensile Stress on Corrosion Behaviors of Biodegradable WE43 Alloy in Simulated Body Fluid.

The real physiological environment of the human body is complicated, with different degrees and forms of loads applied to biomedical implants caused by the daily life of the patients, which will definitely influence the degradation behaviors of Mg-based biodegradable implants. In the present study, the degradation behaviors of modified WE43 alloys under the combination of torsional and tensile stress were systematically investigated. Slow strain rate tensile tests revealed that the simulated body fluid (SBF) solution could deteriorate the ultimate tensile stress of WE43 alloy from 210.1 MPa to 169.2 MPa. In the meantime, the fracture surface of the specimens tested in the SBF showed an intergranular corrosion morphology in the marginal region, while the central area appeared not to have been affected by the corrosive media. The bio-degradation performances under the combination of torsional and tensile stressed conditions were much more severe than those under unstressed conditions or single tensile stressed situations. The combination of 40 MPa tensile and 40 MPa torsional stress resulted in a degradation rate over 20 mm/y, which was much higher than those under 80 MPa single tensile stress (4.5 mm/y) or 80 MPa single torsional stress (13.1 mm/y). The dynamic formation and destruction mechanism of the protective corrosion products film on the modified WE43 alloy could attribute to the exacerbated degradation performance and the unique corrosion morphology. The dynamic environment and multi-directional loading could severely accelerate the degradation process of modified WE43 alloy. Therefore, the SCC susceptibility derived from a single directional test may be not suitable for practical purposes. Complex external stress was necessary to simulate the in vivo environment for the development of biodegradable Mg-based implants for clinical applications.

Tensile and compressive mechanical properties of nanocrystalline calcite with grain size effect

Abstract Calcite is one of the most main components of microbially induced calcium carbonate precipitation (MICP). With the in-depth research of MICP, the mechanical properties of nanocrystalline calcite attract much attention. In this paper, the deformation and failure behaviors of nanocrystalline calcite under a uniaxial tensile or compressive condition are studied by molecular dynamics simulation, and then the dominant deformation and failure mechanisms, as well as their grain size effect, are analyzed. The results show that the grain boundary densification dominates the elastic deformation, while the intragranular phase transition dominates the plastic deformation. Compared with single-crystal calcite, the elastic modulus of nanocrystalline calcite is significantly reduced and its ultimate strength is decreased by more than 50%. Nanocrystalline calcite has stronger plastic deformation ability in compression than in tension. Its tensile and compressive elastic moduli and peak stresses all increase with the average grain size. The effects of grain size on the limit stresses can be described by the inverse Hall–Petch equation. This study is helpful for tailoring the mechanical properties of MICP by the morphology of nanocrystalline calcite.