Properties Of Tested Materials Research Articles

Characterization and Assessment of Physical Properties of 3 Single Syringe Hydraulic Cement–based Sealers

IntroductionA number of sealers with different chemistries are badged as Bioceramic, implying biological activity, but have dissimilar properties, which has implications on the sealer properties and will affect the quality and outcome of root canal treatment. This study aimed to assess the physical and chemical properties of 3 hydraulic cement–based sealers, namely BC Universal sealer compared with Totalfill BC sealer and AH Plus Bioceramic. MethodsThe microstructure and composition of the sealers were assessed using scanning electron microscopy and energy dispersive spectroscopy after setting. The crystalline phases were assessed by X-ray diffraction analysis and the leachates were tested using inductively coupled plasma. All testing was performed at 0, 7, and 28 days. The physical properties of film thickness, flow, radiopacity, and solubility were evaluated using ISO 6876:2012 standards. ResultsAll 3 sealers contained calcium, zirconium, and silicon. Totalfill BC had the highest calcium release at 7 and 28 days followed by AH Plus Bioceramic and BC Universal sealer. All 3 sealers adhered to the ISO standard in terms of flow and radiopacity. BC Universal sealer was slightly over the range (>50 μm) for film thickness. All sealers exceeded the solubility range set by ISO 6876:2012. ConclusionAlthough these hydraulic cement sealers had similar components and delivery, the properties varied significantly. The testing of material properties to confirm the suitability for clinical use is necessary.

Experimental and numerical study on the load-bearing capacity of cold-formed stiffened high-strength steel box columns

This paper reports a comprehensive experimental and numerical study on the load-bearing capacity of cold-formed stiffened high-strength steel box columns. A novel cold-formed stiffened section for box columns with width-to-thickness ratios exceeding design limits was presented. Column buckling tests were conducted, including precise measurements of initial geometric imperfections, material property tests, and axial compression tests. The results revealed that the stability factors of the stiffened specimens consistently surpassed those of the corresponding box section specimens within the same experimental group, with an average increase ratio of 19.9%. Finite element models were developed, validated, and used for parametric studies, considering variations in width-to-thickness ratios, slenderness ratios, and steel strengths. A total of 144 finite element models were analyzed to comprehensively investigate the effects of the selected parameters. The obtained parameter analysis results were compared with calculation methods and design codes, such as GB 50017–2017, EN 1993-1-1, ANSI/AISC 360–16, and AISI S100-16, to investigate their applicability. The Direct Strength Method (DSM) was found to overestimate the bearing capacity of these columns. Therefore, a modified DSM was proposed specifically for predicting the ultimate strength of cold-formed stiffened high-strength steel box columns. Extensive verification confirmed that the design strengths obtained using the modified DSM provide accurate and reliable predictions for the behavior of these columns.

Axial compression stability of corroded circular steel tubes in simulated seawater environments

To investigate the influence of seawater corrosion damage on the axial compression stability of circular steel tubes, this study proposes a novel method (hereinafter referred to as the ‘thickness equivalent method’) for calculating the equivalent wall thickness based on the yield load determined through material property tests. To this end, a formula for calculating the equivalent regularised slenderness ratio of corroded circular steel tubes is derived. Subsequently, corrosion, material property and axial compression tests are conducted using circular steel tubes with different sectional dimensions, and numerical models are developed. The numerically obtained load–lateral displacement and load–strain curves are in good agreement with the test curves, validating the accuracy of the numerical models. Finally, a parameter study is conducted using the validated numerical models. To facilitate the examination of corroded circular steel tubes, a novel formula, representing a continuous function of the regularised slenderness ratio as opposed to the previous piecewise function, for computing the stability coefficient is derived. The test results demonstrate that the proposed method accurately predicts the ultimate axial compression bearing capacity of corroded circular steel tubes. Furthermore, based on the theoretical derivation, the relationship between the axial compression ultimate bearing capacity and the corrosion ratio for ϕ48 × 3 and ϕ57 × 3.5 steel tubes, considering various equivalent regularised slenderness ratios, is established.

Numerical simulation and mechanism analysis of thermal fatigue crack for low-alloy steel brake disc of high-speed train

ABSTRACT High-speed train brake discs face severe service conditions and subsequently risk of material failure during emergency braking. Thermal fatigue cracking is a major concern leading to catastrophic disc failure and is regarded as a primary service bottleneck in rapid rail transportation. Our proposed work establishes a numerical prediction model to estimate thermal fatigue crack initiation and propagation in low-alloy steel. We used a modified Cockcroft-Latham criterion and material property tests to determine the critical crack initiation value. Through numerical simulations and in-situ experiments, we observed plastic deformation at the median temperature of the thermal fatigue cycle and found that tailored material composition improves brake disc fatigue performance. This research aims to enhance understanding of the cracking mechanism and improve the reliability of brake systems for high-speed trains.

Study on material and mechanical characteristics of silicone rubber shed of field-aged 110 kV composite insulators

Composite insulators have excellent performance and are more and more widely used in power grid. The performance of composite insulators with different service duration will decline in varying degrees, which could pose a threat to the safe operation of power grid. In order to investigate the influence of service duration and electric field strength on insulator shed performance, the sheds at different positions of insulators with different service duration are sampled. The hydrophobicity, material and mechanical properties of the samples are tested, and then the micro material properties tests are performed in terms of SEM, FTIR and XPS tests. Based on the above test results, the aging law and its mechanism of silicone rubber sheds are analyzed. The results reveal that the performance of insulator shed gradually decline with the increase of service life. The hydrophobicity and hardness of high-voltage end insulator are similar to that of middle section insulator, while other parameters are obviously different, indicating that the electric field can aggravate the aging. FTIR results show that the main chain and hydrophobic side chain of silicone rubber are destroyed, and the oxygen-containing groups increased, indicating that thermal oxygen aging occurred during operation. XPS and SEM results show that the crosslinking degree of silicone rubber increases and the porosity increases. The above changes in the microstructure of silicone rubber lead to the decline of insulator performance.

A multiscale optimization methodology for cyclic elastoplastic performance of beam-pile joint member in pile-supported wharf

A material-member-structure multiscale optimization methodology, which can be utilized for improving the elastoplastic behaviour of the beam-pile joint member in pile-supported wharf under cyclic loading, was developed on the base of the application of high-specific stiffness material. Based on the representative volume element (RVE) method, the parameterized relations between the mesoscale phases (e.g., steel fibers, interfacial transition zone, and matrix) and macroscale homogenized elastoplasticity of ultrahigh-performance concrete (UHPC) reinforced with steel fibers were obtained under periodic boundary conditions. The physical equivalence relation between material scale and member scale was established by utilizing the refined constitutive model with the macroscopic mechanical parameters and exponential decay damage evolution factors. UHPC material property tests and cyclic loading tests of small-scale beam-pile joint specimens were performed respectively, and the results were analyzed and utilized to validate the numerical model and multiscale optimization method. Using the computational platform ABAQUS, the cyclic elastoplastic performances of the novel beam-pile joint members were evaluated numerically by pseudo-static hysteretic loading. As an illustration, a multiscale modelling approach for the pile-supported wharf frame system was presented and employed to assess the seismic performance improvement through the optimization of the beam-pile joint members. The coupled solution of refined member damage and large-scale structural bearing capacity was realized by utilizing the deformation coordination condition and force balance equation, which bridges the member scale and structure scale. This study aims to provide a reference for future design and optimization of the joint members in marine frame structures, to enhance cyclic bearing capacities and reduce reinforcement consumptions.

Biochemical and Physiological Dynamics in Ligament Injury & Healing

Ligaments play a crucial role in the musculoskeletal system. When maximal and sub-maximal ligamentous injury occur, a cascading response is initiated, starting with platelet plug formation and ending with remodeling. A rodent model was used to examine the role of modulating the initial recruitment of platelets and their impact on biochemical, histological, functional, and mechanical material properties. Functional gait testing, Enzyme Linked Immunosorbent Assay (ELISA), histological evaluations, and material property testing were performed. Animals (n=150) were randomized to a no-treatment group, a platelet rich fibrin treatment group and, a Nonsteroidal Anti-inflammatory Drug (NSIAD) treatment group. Initial results show that antiinflammatory drugs slow gait functional recovery; whereas, PRF shows faster functional recovery. PRF shows a faster increase in VEGF, and NSAIDs slows down VEGF and reduced its intensity. Evaluating injury recovery and impact of treatment methods, in both occupational and sports settings, provides insights about the healing response.

Influence of material properties on the high-speed wheel-rail rolling contact behaviour

Here a comprehensive 3-D wheel-rail rolling contact finite element model was developed to investigate the influence of wheel-rail material properties on the dynamic wheel-rail interaction. The wheel-rail contact responses induced by two typical wheel tread defects (i.e. wheel flat and tread spalling) were discussed and compared to the responses of perfect wheel in this work. The dynamic wheel-rail responses of three typical material models involved (i.e. rigid, elastic, and elastic-plastic models) were investigated in terms of contact force, contact pressure/stress, and wheel/rail degradation. Furthermore, the strain rate levels during wheel-rail rolling contact at various train speeds were estimated with emphasis on the elastic-plastic model, which was helpful for determining strain rate range of wheel/rail material property tests. Finally, the influences of strain rate effect and initial fatigue damage of wheel/rail materials on dynamic wheel-rail responses were discussed. These results illustrated that the rigid model grossly overestimated wheel-rail impact force caused by wheel tread defects, while the elastic model overestimated wheel-rail contact pressure/stress, damage index, and frictional work. The strain rate effect could significantly increase Mises stress and inhibit plastic deformation of wheel-rail system, while the initial fatigue damage would reduce Mises stress and aggravate plastic deformation.

Welding Joint Made of Two Different Austenitic Materials

Using austenitic steel in welding structures requires both destructive and non-destructive testing (NDT) to approve the use of intended welding specification, but also testing of material properties, even if they are guaranteed by manufacturer. In this particular case, X2CrNiMo17-12-2 (commercial trademark AISI 316L) is the material that has to be partly replaced by NiCr21Mo (commercial trademark Incoloy 825) in a piece of process equipment exposed to elevated temperature and highly corrosive environment. This research presents an investigation of overmatching V groove welded joint made of these two austenitic steels. Due to materials properties and specific application conditions, low heat input TIG welding was utilized. Mechanical properties of welded joint have been examined to check criteria which guarantees safe work and integrity of welded components. Chemical composition of used filler material was close to the one of NiCr21Mo alloy, providing weld overmatching, which needs to be checked as well. Mechanical testing (tensile, bending, impact, hardness), macro-and microstructure analysis provided detailed insight into welded joint characteristics and a ground for further investigation concerning heterogeneous austenitic welded joint, taking into account overmatching effect.

Simulation Study on Static Characteristics of Qing-style ‘One Bucket Three Liters’ Column-cap Dou-Gong Bracket

The Dou-Gong bracket is a key transition component between the roof and the column in ancient Chinese wooden structures. In this paper, the static structural behavior of Qing-style ‘one bucket three liters’ Column-cap Dou-Gong Bracket (third-class material) full-scale test model was studied by simulation. The simulation of monotonic static loading was carried out in the vertical (Z-axis) direction, and the simulation of quasi-static loading under horizontal low-cycle reciprocating load was carried out in the horizontal direction (Y-axis, X-axis). The material of the simulation was P. sylvestris, and the setting of its material parameters referred to the results obtained from the material property tests. An anisotropic constitutive model suitable for the properties of wood materials was selected, and the elastoplasticity of wood in the simulation was defined by the Hill yield rule. The static structural behavior of the component in the Z-axis could be described by the variable stiffness linear elastic mechanical model. The static structural behavior of the component in the Y-axis and X-axis could be described by a multi-linear restoring force model. According to the simulation results, the key mechanical indexes of Dou-Gong bracket component in the Z, Y, and X axes were calculated from three aspects of strength, deformation, and energy.

Experimental investigation on the seismic performance of prefabricated fiber‐reinforced concrete beam‐column joints using grouted sleeve connections

AbstractTo improve the seismic performance of prefabricated reinforced conventional concrete (PRC) beam‐column joints, fiber‐reinforced concrete (FRC) was used instead of concrete in the core zone of the joint in this article. The optimum volume contents of polyvinyl alcohol (PVA) fibers and steel fibers were first determined to be 0.3% and 1%, respectively, through the material properties tests. Then, four PRC beam‐column joint specimens using grouted sleeve connections and one cast‐in‐place reinforced concrete beam‐column joint specimen were designed considering the factors of PVA fibers, steel fibers, with or without stirrups. The test phenomena and failure mode of the five specimens under low‐cycle cyclic loads were obtained. Finally, the effects of PVA fibers, steel fibers, with or without stirrups on the seismic performance of specimens were analyzed and discussed. The test phenomena indicated that the failure mode of specimens was anchorage damage of steel bars. The prefabricated FRC specimens showed relatively little damage in the core zone of the joint. FRC had a significant improvement on the seismic performance of prefabricated beam‐column joints. The use of FRC in the core zone of the joint can reduce or even eliminate the use of stirrups.

Improvement of Low Plasticity Clay with Crushed Glass: A Mechanical and Microstructural Study

AbstractLow plasticity clays are found in abundance worldwide, exerting undue stresses on civil structures, road pavements and railway infrastructure, owing to the periodic settlement caused by their low bearing capacity and slight swelling potential. They are often encountered as natural soil when constructing road subgrade and have the potential to compromise the integrity of the entire pavement system unless improved appropriately. Furthermore, the accumulation of vast quantities of non-biodegradable glass waste is identified as a challenge in many countries. Considering the above, this paper aims to provide a sustainable solution by studying the effect of crushed glass (CG) at varied inclusions of 0, 5, 10, 15 and 20% in a clay subgrade. The testing procedure implemented includes three distinct testing phases, namely, material properties, microstructural properties and mechanical strength tests. The material property tests involved particle size distribution, X-ray fluorescence (XRF) and X-ray diffraction (XRD) testing. Microstructural tests considered include scanning electron microscope (SEM) and micro-CT (CT) testing, which enabled a vital understanding of how the introduction of glass affects the internal structure of the clay matrix, where an increase in the porosity was evident upon adding CG. The mechanical testing phase involved standard compaction, unconfined comprehensive strength (UCS), California bearing ratio (CBR), resilient modulus and swelling–shrinkage tests. It can be concluded that introducing CG improved the clay’s mechanical strength with respect to UCS, CBR and resilient modulus whilst also reducing its swelling potential, where the optimum inclusion of CG at 15% best enhanced the mechanical strength properties of the low plasticity clay.

Investigation of modelling approaches to study the structural performance of 3D printed plain wall under uniform axial compression

This study reports an experimental and numerical examination performed on a 3D printed (3DP) wall subjected to vertical axial compression. A detailed investigation of material property and full-scale testing of the 3DP plain wall was performed to explore the structural performance of the 3D printed wall. To obtain the mechanical properties of mortar, test prisms obtained by printing mortar as layers resulted in undesirable failure modes. Hence, this study proposes a unique methodology to obtain the mechanical property of mortar with an assumption of mortar material as isotropic. However, to consider the effect of the interface within the printed layers, interface strength tests in terms of normal and shear strength were performed. Likewise, the behavior of 3DP wall being anisotropic, a unique analysis concept was adopted in a current study comprising of modelling the printed layers as in actual thickness and cross-section and providing material property obtained from an assumption of mortar material as isotropic. Moreover, orthotropic material properties of the printed material were provided to FE models via testing of the 3D printed specimens parallel and normal to the interface. The full-scale test specimen was modeled as layers in a numerical tool and results from the test and simulation were compared in terms of load-displacement behavior, distribution of strain on the wall surface, and damage pattern of the wall. Moreover, recommendation on the selection of the suitable material model and contact algorithm is provided in the current study for simulating the behavior of 3DP structures.

Endurance tests for a fabric_reinforced inflatable soft actuator

This paper describes a series of endurance and material property tests conducted on a pneumatic, fabric-reinforced inflatable soft actuator made of Dragon Skin 30 silicone, which exhibited performance variations during operation. It is important to understand the level of variation over time and how it affects the motions of the soft actuators. The tests were designed to investigate the repeatability and durability of the actuator by measuring changes in its trajectories after long working periods, determining its failure pressure, and examining its elasticity through tensile tests. The experiments were performed on multiple soft actuators, and the results show pertinent information about the variation in their motion and how it relates to the material behavior of the silicone. This information enhances our understanding of the real-world behavior of silicone soft actuators and enables us to better control their performance in our applications.

Hygrothermal Properties Analysis of Bamboo Building Envelope with Different Insulation Systems in Five Climate Zones

Laminated bamboo lumber (BLL) and bamboo scrimber (BS) are potential environmentally friendly building materials, considering that they are hygroscopic materials and that their hygrothermal performance is closely related to the occupants’ comfort, their building durability, and building energy consumption. This study carried out material property tests on bamboo-based materials (BLL and BS) and analyzed hygrothermal performance simulations on bamboo exterior wall constructions in five major climatic zones using WUFI. Results show that BS had a greater heat storage capacity than BLL. However, BLL showed a relatively higher moisture sorption capacity, and BLL was more easily permeated by vapor than BS. The water content (WC) of 12 walls of BLL and BS was below 20%. BLL and BS met the requirements of the envelope, and the WC of BS was lower than that of BLL. Based on the results, the walls designed in this study are suitable for the corresponding climate zones. In the cold and severe climate zones especially, the external insulation system walls performed better than the internal insulation system. The external insulation system was recommended for these two climate zones. The design and simulation results of walls made of two types of bamboo-based materials provide a scientific basis for the application of the material.

Behavior of concrete-filled cold-formed steel built-up section stub columns

This paper presents a test campaign concerning the behavior of concrete-filled cold-formed steel built-up section stub columns. The test program consisted of five types of cold-formed steel built-up sections infilled with concrete of three different grades (C40, C80 and C120). A pair of identical open sections were built-up to form a closed section by discrete self-tapping screws and connected using steel strips where necessary. A total of 42 stub columns, including 32 concrete-filled specimens and 10 hollow counterparts, was axially compressed between fixed-ends. Details of material properties tests and stub column tests are described in this paper. The stub column compressive strengths, full range axial load-shortening histories as well as load–strain responses and failure modes are presented and discussed. The test strengths were compared with the design predictions by the current American Specification ACI318, despite that this design rule was originally developed for concrete-filled steel columns with conventional tubular sections rather than built-up sections. The comparison demonstrated that the American Specification ACI318 provides generally unconservative and unreliable compressive strength predictions for the concrete-filled cold-formed steel built-up section stub columns. Necessary improvements shall be made in order to yield accurate compressive strength predictions.

Numerical Investigation of the Axial Stress Distribution of Self-Tapping Screws in Mass Timber Products during Wetting or Drying

Self-tapping screws (STS) are used in wood-to-wood and wood-to-steel connections in timber structures. Premature failure of STS during the construction phase has been reported by structural engineers and contractors in relation to a few North American mass-timber projects. This STS failure type is suspected of having been precipitated by additional axial stress exerted on STS from swelling of the wood resulting from prolonged wetting. This study investigates the axial stress distribution of STS installed in two mass timber products, cross-laminated timber (CLT) and glulam, under axial loading and changing moisture conditions in the linear elastic regime. The focus is on modelling the stress distribution of STS during wood-wetting. Properties of self-tapping screws under axial loads, such as tensile and withdrawal properties, along with swelling properties of CLT and glulam, have been investigated. A numerical method to predict the axial stress distribution of the screw from these material property tests has been developed. The numerical model has been calibrated with test results. The method developed in this research helps in understanding the premature failure of self-tapping screw connections under the moisture content variation of wood. The next step will be developing an analytical model to predict the axial stress distribution of STS.

Research on the local-distortional interaction buckling capacity of stainless steel lipped C-section columns

The plates of the specimens subjected to a large section width to thickness ratio are prone to multiple instances of mode interaction buckling failure under compression. Hence, to investigate the local-distortional interaction buckling capacity of stainless steel lipped C-section columns, the material properties test of 4 stainless steel plate specimens and the capacity tests of 19 stainless steel lipped C-section column specimens under axial compression were carried out. The development process and failure mode of the local-distortional interaction buckling of stainless steel columns were revealed, and the local-distortional interaction buckling capacities, load-axial shortening curves, load-lateral displacement curves and load–strain curves of the stainless steel columns were obtained. The numerical analysis model of the stainless steel lipped C-section column under compression was established based on ABAQUS finite element software. The finite element results were in agreement with the test results, which verified the accuracy of the finite element model. A parametric analysis was carried out on two key factors, the initial geometric imperfection amplitude and boundary conditions, which affect the local-distortional interaction buckling capacity of stainless steel lipped C-section columns. The results show that the initial geometric imperfection amplitude of specimen has a significant influence on the local-distortional interaction buckling capacity of stainless steel lipped C-section column, while the influence of boundary conditions is small.

Primary Corrosion Cause of P110S Steel Tubing Corrosion Thinning in CO2–H2S Well and Its Remaining Life Prediction

To investigate the tube thinning of gas wells in the northwestern oilfield, the failed tubing was analyzed by using material property testing, SEM, EDS, and XRD. A novel model that was specific to the service life of tubing in terms of the wall thickness of tubing was established. The model is based on the circumferential stress of tubing. The safety factor against internal pressure and corrosion rate are considered in the model. Our results make clear that the chemical composition, non-metallic inclusion, hardness, and tensile strength of the pipe meet the requirements of relevant standards. The corrosion products on the inner and outer wall of the tubing are mainly FeCO3 and BaSO4, while CaCO3 exists in the outer wall. Additionally, we prove that the corrosion process of the failed tubing is CO2 corrosion. The tubing under the packer suffers from water-accumulation corrosion, and the tubing above the packer suffers from water-carrying corrosion. It is observed that the failed tubing arises under-deposit corrosion in local areas. According to the model calculation, the safe service life of tubing above the packer is 20.6 years. However, the safe service life of tubing below the packer is only 4.9 years.

Ternary diagrams of phase, stability, and optical properties of cesium lead mixed-halide perovskites

Cesium lead halides have been intensively studied as promising light absorption and emission materials. However, the complexity and instability of their phases has prevented a comprehensive investigation of the structural and optical properties of Cs-based mixed halides over a broad range of mixing ratios. Herein, we derive the ternary diagrams of phase, optical bandgap, and photoluminescence intensity of cesium lead halide perovskites (CsPbX3), with three vertices of CsPbI3, CsPbBr3 and CsPbCl3. For material property tests, mixed halide perovskite powders are synthesized using a facile solid-state reaction method. The orthorhombic perovskite (γ) phase, which is desired for photovoltaic and optoelectronic applications, is successfully obtained by quenching the powders from 350 °C to room temperature. By comparing the phase diagrams of as-ball-milled and heat-treated powders, we report a single-phase region (γ-phase) and a multi-phase region (I-rich and Cl-rich γ-phases). In aged powders having single-phase compositions, Cl-rich compositions presented considerably higher phase stability than I-rich ones. In the single-phase region, the lattice constant increases and optical bandgap decreases almost linearly with increase in average size of X-site ions, as per Vegard's law with extremely small bowing parameters (< 0.1 Å). Therefore, one can easily design an infinite number of composition combinations in the single-phase boundary to achieve a desired bandgap in the range of 1.73–2.96 eV. Ternary maps of photoluminescence intensity demonstrate potential compositions for high-performance optoelectronics. Our results provide a valuable database for developing desirable perovskite compositions for various optoelectronic applications.