High Rupture Strength Research Articles

WALL STABILIZATION IN MINES BY SPRAY-ON LINERS

AbstractThin spray-on liners (TSLs) have been found to be effective for structurally supporting the walls of mining tunnels and thus reducing the occurrence of rock bursts, an effect primarily due to the penetration of cracks by the liner. Surface tension effects are thus important. However, TSLs are also used to simply stabilize rock surfaces, for example, to prevent rock fall, and in this context crack penetration is desirable but not necessary, and the tensile and shearing strength and adhesive properties of the liner determine its effectiveness. We examine the effectiveness of nonpenetrating TSLs in a global lined tunnel and in a local rock support context. In the tunnel context, we examine the effect of the liner on the stress distribution in a tunnel subjected to a geological or mining event. We show that the liner has little effect on stresses in the surrounding rock and that tensile stresses in the rock surface are transmitted across the liner, so that failure is likely to be due to liner rupture or detachment from the surface. In the local rock support context, loose rock movements are shown to be better achieved using a liner with small Young’s modulus, but high rupture strength.

Structural and elastic properties of binary FCC Pt-Rh alloys – a first-principles study

Alloying Pt with Rh significantly enhances the high temperature stress rupture strength and maintains both oxidation and corrosion resistance at elevated temperatures. Such unique property combination renders Pt-Rh alloys mainstay in space technology, glass and chemical industries. However, the exponential increase in the price of Rh in the past few years stirs an industrial concern. As a result, some industries are beginning to search for alternative alloys that can offer similar properties. This study conducted first-principles calculations to generate structural and elasticity data on binary Pt-Rh alloys using both supercell and virtual crystal approximation (VCA) approaches, to serve as a benchmark for new alternative Pt-based alloys.

Three interacting regions of the Ndc80 and Dam1 complexes support microtubule tip-coupling under load.

Accurate mitosis requires kinetochores to make persistent, load-bearing attachments to dynamic microtubule tips, thereby coupling chromosome movements to tip growth and shortening. This tip-coupling behavior depends on the conserved Ndc80 complex and, in budding yeast, on the Dam1 complex, which bind each other directly via three distinct interacting regions. The functional relevance of these multiple interactions was mysterious. Here we show that interactions between two of these regions support the high rupture strengths that occur when applied force is rapidly increased and also support the stability of tip-coupling when force is held constant over longer durations. The contribution of either of these two regions to tip-coupling is reduced by phosphorylation by Aurora B kinase. The third interaction region makes no apparent contribution to rupture strength, but its phosphorylation by Aurora B kinase specifically decreases the long-term stability of tip-coupling. The specific reduction of long-term stability relative to short-term strength might have important implications for mitotic error correction.

Effect of temperature on the mechanical properties of two polymeric geogrid materials

Understanding the tensile behavior of geosynthetic reinforcement materials at different temperatures is essential for the design of reinforced soil structures in seasonally cold regions. This study describes a series of tensile tests performed on two polypropylene geogrid materials, namely a biaxial geogrid and a geogrid composite. A total of 84 tests were performed in an environmental chamber with temperatures as low as −30°C and as high as +40°C. The response of each material is examined over the range of investigated temperatures to evaluate the effect of temperature changes on the tensile strength of the two geogrid materials. The response of the biaxial geogrid is found to be sensitive to temperature variations, with samples tested at low temperatures exhibiting brittle behavior characterized by high rupture strength and small ultimate strain while samples tested at elevated temperatures displayed ductile behavior with large elongation at failure and comparatively small rupture strength. A similar response was found for the geogrid composite, however, the rupture strength seemed to be less sensitive to temperature changes. The modes of failure observed at each temperature are examined based on photographic evidence taken during the experiments.

Optimization of Ultimate Tensile Strength with DOE Approach for Application FSW Process in the Aluminum alloys AA6061-T651 & AA7075 -T651

As it is imperative to control the materials development processes well, in parallel, it will be necessary to constantly adapt very efficient assembly methods. Friction stir welding makes it much easier for us to fusion the aluminum alloys like AA6061-T651 and AA7075 -T651. But we noted the difficulty of containing its many parameters such as the welding speed, the rotation speed and the type of pin used during the operation to optimize mechanical properties and in particular to obtain high rupture strength with the tensile test. This why in this paper we treat carefully this process in order to define it drastically, by using the design of experiment method which is an original approach that resides in the possibility of interpretation of experimental results with a minimal effort on the experimental level whichever generates the minimization of the necessary number of experiments and allows a saving in time and in financial cost.

Study of boriding surface treatment in the tribological behavior of an AISI 316L stainless steel

AISI 316L stainless steel possesses high tensile and rupture strength at low and high temperatures; therefore, it is employed in several industry fields like manufacturing gas turbine parts, automotive pieces, and prosthetic devices like joints prosthesis. However, the debris and oxide products resulting from wear lead to detrimental performance, particularly in medical applications like partial hip prosthesis, orthopedic screws, or bone plates. This liberation of metallic ions may cause aseptic implant loosening, granuloma formation, and demineralization of bone tissue. On the other hand, research in the last few years has focused on improving the tribological performance of the steel surface, including ceramic coatings and different engineering surface treatments. In this work, the tribological performance of boride layers synthesized on an AISI 316L was studied. As it was mentioned before, the AISI 316L steel is widely used for biomedical applications, so the improvement of their tribological properties is the particular interest in this field. Also, boriding treatment increases the corrosion resistance of the steel due to the boride layers acting as a barrier that reduces the pitting corrosion properly of the stainless steel. For this purpose, diffusional boriding treatments were performed at the following parameters: 850, 950, and 1050 °C over 2, 4, and 6 h for each temperature. Surfaces were characterized using scanning electron microscopy, X-ray diffraction, micro and nano-hardness testing, and roughness measurements. The tribological response was studied through a ball on disc tribometer under dry-sliding conditions with a distance of 10 km, tracking the coefficient of friction, mass loss, wear rate, and surface damage. All borided conditions decreased the wear rate in comparison with the untreated samples. The differences in wear performance among the borided surfaces were detailed discussed in this paper.

Dissimilar Welding of Austenitic and Martensitic Stainless Steel Joints for Nuclear Applications: a review

Dissimilar Welding of Austenitic and Martensitic Stainless Steel Joints are commonly preferred in Nuclear Reactors where high temperature applications are needed. There has been a huge demand for materials which sustain corrosive environment with high rupture strength along with high temperature and pressure. These materials can be directly replaced with the traditional nickel based alloys to compensate for cost cutting and satisfy strength requirements. Dissimilar welding of these materials has been challenging due to the difference in its composition, properties and also heterogeneity in microstructure of these materials. A Study was done to identify what are the commonly used joining techniques, the mechanical properties of the joints and also the microstructure evolution of the dissimilar weld joints. This paper will emphasize on the work that was previously published in the area of dissimilar welding of these combinations of materials and also their challenges.

An Investigation on Surfactant Added PMWEDM of Inconel 718

This paper shows the impact of different process parameters and powder characteristics on the material removal rate and surface roughness obtained in surfactant added Powder Mixed Wire Electric Discharge Machining (PMWEDM). Inconel-718 is selected as the workpiece material, which has ample application in the industries handling environment of extreme stress, pressure and temperature. It has high work hardening properties along with high rupture strength, fatigue, and creep, making it extremely difficult to machine. So, additives having different thermo-physical properties are studied to improve the machining efficiency. The additives experimented includes aluminium, silicon carbide, graphite, and aluminium oxide. It is found that the electrostatic force present creates an agglomeration effect with dielectric additive powders, causing inhomogeneity in the mixture. So, a surfactant SPAN20 is used here to maintain the homogeneity of the mixture. The obtained MRR and SR are then modelled and optimised through Particle Swarm Optimization technique (PSO). It is observed that the addition of SPAN20 has improved the MRR by 13.56% and, SR by 45.05%. Also, it has been found that due to the combined abrasive action, abrasive powders increase MRR significantly than others. Furthermore, it is found that low grit size powders with lower density produces better machined surfaces.

Fatigue behavior of GFRP-reinforced ECC link slabs under variable stress levels and number of cycles

Glass Fibre Reinforced Polymer (GFRP) bars have been used in the Province of Ontario as top layer of bridge deck reinforcement near surfaces exposed to de-icing chemicals. The intent of replacing deck reinforcements with GFRP is to mitigate negative effects of conventional steel rebar corrosion. Furthermore, the development of Engineered Cementitious Composite (ECC) with inherent crack width control and strain-hardening tensile behaviour for link slab application provides design engineers with a new effective way to construct joint-free bridge decks with improved durability. This paper presents experimental investigation of ECC-link slabs reinforced with sand-coated GFRP bars. The link slab specimens were subjected to variable mean fatigue stress levels of up to 55% load capacity and fatigue cycles of up to 1 million, followed by post-fatigue monotonic loading to failure. Link slab load–deflection, stiffness degradation, end rotation, GFRP and ECC strains, crack development, failure modes, energy absorbing capacity, and ductility were determined. Results were then compared with companion steel-reinforced ECC link slabs in the literature to quantify benefits of using GFRP bars. Experimental results showed that GFRP-reinforced link slabs failure by concrete crushing due to high rupture strength of GFRP, whereas steel-reinforced link slabs failed by rebar yielding. Besides exhibiting improved overall strength, the GFRP reinforced ECC link slabs showed greater post-fatigue residual rotational capacity, lower rate of stiffness degradation, enhanced post-fatigue retention of energy absorbing capacity.

Effects of Thermal Treatment on the Physical Properties of Edible Calcium Alginate Gel Beads: Response Surface Methodological Approach.

Calcium alginate gel (CAG) has been widely investigated for the development of artificial foods; however, there are few studies on its thermal stability. This study aimed to monitor changes in the physical properties of CAG beads during heat treatment using response surface methodology. Heating temperature (X1, 40–100 °C) and heating time (X2, 5–60 min) were chosen as independent variables. The dependent variables were rupture strength (Y1, kPa), size (Y2, μm), and sphericity (Y3, %). The heating temperature (X1) was the independent variable that had a significant effect on the rupture strength (Y1) and size (Y2). Rupture strength (Y1) increased as the heating temperature (X1) increased; at the same time, the CAG beads size (Y2) decreased. With all conditions, the values of sphericity (Y3) were over 94%. SEM images revealed that increase in the rupture strength of the CAG beads by heat treatment resulted from their porous structures. Loss of moisture by syneresis, occurring with heat treatment, was judged to create a dense porous structure of CAG beads. Our findings offer useful information for cooking or sterilizing food products utilizing CAG beads. In addition, thermal treatment could be applied to produce hard CAG beads with a high rupture strength.

Physicochemical Processes of Fabricating Ceramic Materials Based on Nanopowders of Zirconium, Yttrium, Cerium, and Aluminum Oxides

When studying nanoceramics, it is necessary to constantly keep in mind the closest interrelation of their fabrication method, structure, and properties. Nanoceramic materials are used in various branches of technology as structural and functional materials. Nanoceramics are also widely used in medicine. They are harmless, stable, and have great affinity to living organisms. ZrO2-based nanoceramics have a lower elastic modulus than other oxide materials. The specificity of their application lies in their high rupture strength, thermal shock resistance, and chemical stability at high temperatures. However, it is necessary to solve the problem of increasing the fracture toughness of ZrO2-based ceramic materials. The complex alloying of ZrO2 with yttrium and cerium oxides and the use of the Al2O3 additive leads to an increase in the fracture toughness and lowering of the negative effect of materials in the biological medium. In this work, the physicochemical properties of ceramic powders and materials of the ZrO2–2Y2O3–4CeO2–Al2O3 system synthesized by the chemical deposition of inorganic precursors when applying the sol-gel technology are considered based on scientific data and experimental studies. Alloying pure zirconium oxide by stabilizing Y2O3 and CeO2 oxides and thermal hardening of Al2O3 ensure the conservation of the tetragonal structure at room temperature, which makes it possible to retard and control the crack resistance of the material under the load. Investigations into the influence of the sintering temperature and aluminum oxide content on the microstructure and grain size, as well as physicomechanical properties of ceramic materials of compositions ZrO2–2Y2O3–4CeO2 + 1 wt % Al2O3 and ZrO2–2Y2O3–4CeO2 + 3 wt % Al2O3, are carried out.

GA-based optimisation using RSM in WEDM of Nimonic-90: a nickel-based super alloy

The present research work is focused on optimisation of WEDM process parameters for machining of Nimonic-90. It is a nickel-based alloy possessing creep resistance and high rupture strength at high temperature (up to 950°C). Genetic algorithm (GA) and response surface methodology (RSM) incorporated with each other to optimise the process parameters. Four input process parameters viz. discharge current (Ip), pulse-off time (Toff), pulse-on time (Ton), and servo voltage (SV) have been investigated and modelled for surface roughness (SR) utilising RSM. In present experimentation, quadratic model has been suggested for surface roughness. Pulse-on time is most significant effect on surface roughness as compared to other parameters. Finally, genetic algorithm, a popular evolutionary approach is used to optimise the process parameters. Using SEM micrographs and micro-hardness profile, effect of discharge energy on surface morphology has been examined.

GA-based optimisation using RSM in WEDM of Nimonic-90: a nickel-based super alloy

The present research work is focused on optimisation of WEDM process parameters for machining of Nimonic-90. It is a nickel-based alloy possessing creep resistance and high rupture strength at high temperature (up to 950°C). Genetic algorithm (GA) and response surface methodology (RSM) incorporated with each other to optimise the process parameters. Four input process parameters viz. discharge current (Ip), pulse-off time (Toff), pulse-on time (Ton), and servo voltage (SV) have been investigated and modelled for surface roughness (SR) utilising RSM. In present experimentation, quadratic model has been suggested for surface roughness. Pulse-on time is most significant effect on surface roughness as compared to other parameters. Finally, genetic algorithm, a popular evolutionary approach is used to optimise the process parameters. Using SEM micrographs and micro-hardness profile, effect of discharge energy on surface morphology has been examined.

Mechanical Properties of Composite Hydrogels of Alginate and Cellulose Nanofibrils.

Alginate and cellulose nanofibrils (CNF) are attractive materials for tissue engineering and regenerative medicine. CNF gels are generally weaker and more brittle than alginate gels, while alginate gels are elastic and have high rupture strength. Alginate properties depend on their guluronan and mannuronan content and their sequence pattern and molecular weight. Likewise, CNF exists in various qualities with properties depending on, e.g., morphology and charge density. In this study combinations of three types of alginate with different composition and two types of CNF with different charge and degree of fibrillation have been studied. Assessments of the composite gels revealed that attractive properties like high rupture strength, high compressibility, high gel rigidity at small deformations (Young’s modulus), and low syneresis was obtained compared to the pure gels. The effects varied with relative amounts of CNF and alginate, alginate type, and CNF quality. The largest effects were obtained by combining oxidized CNF with the alginates. Hence, by combining the two biopolymers in composite gels, it is possible to tune the rupture strength, Young’s modulus, syneresis, as well as stability in physiological saline solution, which are all important properties for the use as scaffolds in tissue engineering.

Organic Filling Mitigates Flaw-Sensitivity of Nanoscale Aragonite

Engineering at nanoscale holds the promise of tuning materials with extraordinary properties. However, macroscopic approaches commonly used to predict mechanical properties do not fully apply at nanoscale level. A controversial feature is the presence of nanoflaws in aragonite nacre, as it is expected that flaws would weaken the material, whereas nacre still shows high toughness and rupture strength. Here, we performed molecular dynamics and finite element simulations emulating flaws found in aragonite nacre. Our simulations reveal two regimes for fracture: nacre remains flaw-insensitive only for flaws smaller than 1.2 nm depth, or flaws of a few atoms, whereas larger flaws follow a Griffith-like trend resembling macroscopic fracture. We tested an alternative mechanism for flaw-insensitivity in nacre, and investigated the mechanical effect of organic filling to mitigate fracture. We found that a single nacre protein, perlucin, decreases the stress concentration at the fracture point, producing enhancements of up to 15% in rupture strength. Our study reveals a more comprehensive understanding of mechanical stability at the nanoscale and offers new routes toward hybrid nanomaterials.

Rupture Strength of some Mould Flux Slag Films relevant to Swedish Continuous Casting Practice

In this paper, the high temperature rupture strengths of some solid mould flux slag films in Swedish continuous casting processes are presented. The apparatus, designed and constructed in the prese ...

A Study on the Microstructural Characterization of René 142 Deposited Atop René 125 Processed through Scanning Laser Epitaxy

Advancements in the design, optimization and manufacture of turbine engine hot-section components during the past few decades have contributed enormously to the improvement in power-ratings and efficiency levels of gas turbine engines. Nickel-base superalloys are extensively used to produce the hot-section components as this class of alloys offer improved creep strength and higher fatigue resistance compared to other alloys due to the presence of precipitate-strengthening γ' phases i.e. Ni3[Ti, Al, Ta etc.] in the normally face centered cubic (FCC) structure of the solidified nickel. Although this second phase is the main reason for the improvement in properties, it also results in increased processing difficulty as these alloys are prone to crack formation. In this work, we demonstrate powder-bed additive manufacturing of René 142 onto René 125 substrates through scanning laser epitaxy (SLE). René 142 is a high strength, nickel-base directionally solidified (DS) alloy that has high rupture strength, excellent resistance to grain boundary cracking, and superior high-velocity oxidation resistance. Successful deposition of René 142 on René 125 provides an avenue to repair legacy hot-section components by depositing superior quality alloys at the damage locations. The microstructure of the deposited René 142 is observed to follow the polycrystalline or EQ morphology of the underlying René 125 substrate. The SLE processed René 142 exhibits dense and crack-free deposits, and microstructure refinement compared to the underlying cast René 125 substrate. This work is sponsored by the Office of Naval Research through grants N00014-11-1-0670 and N00014-14-1-0658.

Effect of wire diameter on surface integrity of wire electrical discharge machined Inconel 706 for gas turbine application

Inconel 706 superalloy has established itself in the field of gas turbine industry because of its easy fabricability combined with high mechanical strength. Due to its high stress rupture and tensile yield strength, conventional machining of this superalloy exhibits poor surface and low dimensional accuracy of the machined components. It is well known that most of the gas turbine components include complex shaped profile with high precision and hence, wire electrical discharge machining (WEDM) of Inconel 706 has been performed to achieve the feasibility in manufacturing of complex shaped components for gas turbine application. In the current investigation, the effect of wire diameter on WEDM performance characteristics such as cutting speed, surface roughness, surface topography, recast layer formation, microhardness, microstructural and metallurgical changes have been evaluated. It was investigated that smaller diameter wire is advantageous over the larger diameter wire since it improves productivity as well as surface quality of the machined components under the same settings of control parameters. In addition, smaller diameter wire has shown comparatively lower recast layer thickness, minimum hardness alteration and shorter manufacturing time. The XRD result has confirmed the presence of residual stress within WED machined component.

Shear Strength of Steel Fiber-Reinforced Concrete Dry Joints in Precast Segmental Bridges

AbstractDry joints represent locations of discontinuity in precast concrete segmental bridges (PCSBs) through which compressive and shear stresses must be transmitted. Cracks in dry joints occur more easily than those in epoxy joints during the construction period or in service. Steel fiber-reinforced concrete (SFRC) with high rupture strength might be beneficial to the shear resistance of dry joints. In this study, shear behavior of various types of dry joints in PCSBs was investigated by experiments, especially focusing on shear strength of keyed dry joints of SFRC. The experimental parameters were joint types, concrete types, key numbers, contacting portions in the sliding plane, and horizontal confining stress levels. Cracking loads, cracking patterns, failure modes, and ultimate loads were recorded. Normalized shear stress-vertical slip curves and load-horizontal dilation relationships have been investigated. It can be concluded that the use of SFRC can improve shear strength and ductility of dry joi...

Weldability assessment and high-temperature properties of advanced creep resisting austenitic steel X6CrNiNbN25-20 (DMV310N/HR3C)

The modern Ultra Super Critical Power Plants (USC PP) applying the 600 °C technology require advanced stainless steels in superheater/reheater systems in order to cope with the increased steam parameters. Different grades of stainless steels have been developed by increasing Cr-contents, alloying with stabilizing and precipitating elements as well as thermomechanical heat treatments resulting in high creep rupture strengths and improved oxidation/corrosion resistance. In the context of a collaborative research project, X6CrNiNbN25-20 (DMV310N/HR3C) has been investigated. The main focus of the research project was on characterization and weldability assessment. As a result, the base metal under investigation was compared with governing code cases and specifications. Base metal chemical composition, microstructures, mechanical properties, reheat cracking sensitivity, and hot ductility as well as creep rupture strengths have been investigated. A weldability assessment, including thermal simulation and welding procedure qualifications, has been performed to establish parameter windows for similar and dissimilar welding. Dissimilar welding between grade 92 and austenitic steel tubes has been performed. The project also took the opportunity to investigate the behavior of a recently developed gas tungsten arc welding (GTAW) P87 consumable for dissimilar welding. Cross-weld creep rupture tests have been conducted for both similar and dissimilar welding, while aging tests addressed microstructural stability.