Tensile Strength Limit Research Articles

Hetero-bonding strength investigation into opto-mechanical interface

Glass-metal hetero-bonding through optical epoxy adhesive is frequently used in opto-mechanics and requires high stability. However, the bonding stability is difficult to achieve and predict in massive use cases, where dozens to thousands of metal pads are bonded to mount large optics. Here a universal adhesive bonding technology was proposed and evaluated through reliability analyses based on a limited number of sample tests. Specimens were prepared and tested via standard procedures and equipment; afterward, the lower strength limits were calculated with high reliability. Nominal tensile (6.7 MPa) and shear (4.3 MPa) strength limits at 99.95% reliability were expected for ongoing 30 m aperture telescopes. This study may improve the quality of opto-mechanical interfaces and reduce the risk on constructing extremely large telescopes.

Stress ratio influence on Paris parameter and fatigue driving force pertinent to material properties

Paris model is widely used since it was proposed in 1963 due to simplicity and universality, but it cannot consider stress ratio (R) effect and curve fitting is always needed to obtain Paris parameters when R is changed. Based on Goodman curve and analysis of 22 groups of fatigue crack growth (FCG) data, an analytical FCG rate model is proposed by linking Paris parameters and fatigue driving force at R ≠ 0 (from 0 to 0.5) to those at R = 0 and material constants (tensile strength and fatigue limit at R = −1). Results show that proposed model can well predict FCG behavior at different R values based on Paris parameters at R = 0.

Geotechnical performance of isotropic and foliated quartzite waste as aggregate for road base and asphalt mixture

Quartzite mines produce a large amount of waste. Although the reuse of materials is essential for sustainable constructions, little is known about the geotechnical properties of isotropic (massive) and foliated (discontinuous) quartzite waste. In this paper, the potential use of these wastes as base layers and asphalt mixtures were examined by a series of laboratory tests and numerical simulations. This paper presents an analysis of the particle properties, durability, strength, and deformation response of quartzite waste in isotropic (IGM) and foliated granular (FGM) mixtures. Asphalt mixtures with isotropic (IAM) and foliated (FAM) quartzite waste as aggregates are evaluated using Brazilian tensile strength, moisture susceptibility, and repeated-load indirect tension tests, such as the resilient modulus and fatigue. To estimate the performance of these materials as pavement layers, numerical experiments are also carried out using the mechanistic-empirical design framework of the MeDiNa software package. As a base material, the mixtures showed plastic creep responses at the highest stress level (higher permanent strain of 1.2 % at σ3/σd = 360/120 kPa) and negligible expansion. The California bearing ratio (higher than 130 % for both IGM and FGM) and resilient modulus (average of 224 and 130 MPa for IGM and FGM, respectively) greatly exceeded the minimum requirement of Brazilian standards. As asphalt mixtures, both IAM and FAM met the minimum limit of tensile strength, but IAM showed greater stiffness. According to the stress–strain analysis of the MeDiNa software, granular and asphalt mixtures incorporating quartzite waste fulfilled the fatigue crack area and rut depth criteria, falling within the allowed thickness ranges for road pavements subjected to up to 5×106 repetitions (medium heavy traffic). This study provides support for the transformation of quartzite waste into a valuable byproduct.

Fabrication Methods of Aluminium Metal Matrix Composite: A State of Review

Aluminium's use in aerospace, marine and automobiles has grown significantly due to its lightweight nature, enhancing fuel efficiency and overall performance. Its corrosion resistance also contributes to longevity, reducing maintenance costs. However, its low hardness, low tensile strength and poor tribological behaviour limit its usage. These demerits can be overcomed by adding specific reinforcement to enrich its properties. As there are two types of fabrication methods for fabrication of MMCs such as Solid state processing and liquid state processing, the above fabrication techniques result in varying mechanical property, tribological property and production cost. So far from the available literature we’ve found that the liquid state processing is more popular than solid-state processing due to the better dispersion of the reinforcement particles in the matrix materials. The Addition of nanoparticles has been found to be essential to provide requisite strength and hardness to these composites. Overall, study concludes that the hybrid aluminium matrix composites will ensure to serve as an alternative for the unreinforced Al-alloys and ceramic reinforced composites in various automotive applications requiring high strength-to-weight ratio, low cost and superior wear resistance.

Accelerated design of Al−Zn−Mg−Cu alloys via machine learning

A machine learning-based alloy rapid design system (ARDS) was proposed to customize the preparation strategies for the desired properties or predict the alloy properties following the preparation strategies. For achieving this, three regression algorithms: linear regression (LR), support vector regression (SVR), and back propagation neural network (BPNN), were employed separately to train the multi-property prediction model, in which the machine learning (ML) model built using SVR was proved to be the best. Then, inspired by the generative adversarial network (GAN) algorithm, the ARDS was constructed. The predictive reliability of ARDS was examined, and for the accurate prediction of the preparation strategies, the upper limits of ultimate tensile strength (UTS), yield strength (YS), and elongation (EL) are about 790 MPa, 730 MPa, and 28%, respectively. Moreover, an ARDS-designed aluminum alloy with superior mechanical properties (764 MPa for UTS, 732 MPa for YS, and 10.1% for EL) was experimentally fabricated, further verifying the reliability of ARDS.

ASSESSMENT OF THE TECHNOLOGICAL CAPABILITIES OF MODERN CHEMICAL MATERIALS FOR LIQUID FINISHING OF LEATHER

Natural leather is a by-product of the meat industry, which turns into a valuable product that has high strength, stability, comfort, breathability and is considered one of the best products of the circular economy. In addition, less materials from non-renewable sources are used in leather production than in other industries, recycling of waste is practiced, which contributes to the protection of the environment and sustainable development of society. The choice of processing method, type of equipment and chemical materials is of great importance for the quality of leather and the ecological imperative of its manufacturing technology. At the same time, despite the progress of modern chemical technology, the leather industry constantly needs to find and introduce new, more effective means, which would not only be stable in their properties, available and compatible with the components of the «collagen-chemical material» system, but would also contribute the formation of this system in the direction of creating quality products while reducing the harmful load on the environment. The results of previous studies indicate the prospects of modified liquor materials and polymer compounds. Taking into account the above, the technological capabilities of modern commercial chemical materials - modified fats of various origins and acrylic polymer - were analyzed by using them in the liquid decoration of semi-finished Wet-blue half skin. Using the methods of organoleptic assessment, chemical analysis, physico-mechanical tests and microscopy, the advantages of these materials compared to those known during retanning-filling and liquoring have been established. The improvement of the indicators of the content of unbound fat in the leather, the limit of tensile strength and elongation at a stress of 10 MPa was revealed. Good elastic-plastic properties and no difference between the strength of the test skins as a whole and their front layer indicate a more even distribution of materials in the structure of the dermis. This correlates with the results of microscopic studies and allows predicting an increase in area yield, that is, a more rational use of scarce leather raw materials. The results of the work will be used in further studies devoted to the optimization of the parameters of the technology of liquid finishing of natural leather.

Dynamic Tensile Strength Limit of BL-Group Ceramic Matrix Composites Synthesized in the cBN–Carbide–Al System

Dynamic Tensile Strength Limit of BL-Group Ceramic Matrix Composites Synthesized in the cBN–Carbide–Al System

Impact of air jet impingement technology on the strength of tissue paper

Impinging air jets can be used to dewater, heat, and dry the web of tissue paper. High velocities of the air jets degrade the paper, and appropriate adjustments to the jet velocity and the distance of the nozzle from the surface of the wet web are crucial to obtain the highest quality product. This work investigated the correlation between the velocity of the air jet and the strength of paper subjected to the impingement method. Papers with an initial moisture content of 20% and various pulp mixes were tested, and the physical properties of papers were explored. After impinging an air jet, different tensile strength limits were obtained in the machine and cross directions. The paper had lower apparent density and higher roughness compared to classical pressing. The dependence of tensile strength and roughness on the fibers composition also was determined. Increasing the amount of eucalyptus fibers in impingement dewatered paper resulted in a decrease in its tensile strength and roughness. The value of elongation before breaking was the highest for softwood papers after the impingement method. The maximum velocity of an air jet that can be used to dewater or dry paper without the risk of damage to the papers was determined.

Mechanical properties and statistical analysis of polyester composite reinforced with miriti fibers braided using crochet technique

This work presents an experimental investigation of the mechanical properties of composites reinforced with crocheted fabrics of miriti fibers (Mauritia flexuosa) in a polyester matrix. The fabrics were manufactured under different grammages, with and without alkaline fiber treatment. The composites were produced using two different viscosity conditions of the polyester matrix and part of these underwent post-cure treatment at 60 °C. In order to evaluate the effects of the input variables, the samples were produced by manual lamination with curing under vacuum, following a complete factorial experimental matrix type 24, tested according to the ASTM D 3039. The results showed that the variables alkaline treatment of the fibers and viscosity of the matrix presented statistically significant effects on the responses limit of tensile strength and modulus of elasticity. The highest level of tensile strength (13.02 MPa) was obtained in composites with alkaline treatment of the fibers, fabric grammage 473.9 g/cm2, matrix with higher viscosity and post-cure application, while the modulus of elasticity obtained the best performance (1.59 GPa) in samples without alkaline treatment of the fibers, manufactured with the fabric of lower grammage, with a more viscous matrix and that underwent post-curing.

Analysis of the stress state at the contours of underground horizontal workings of elliptical cross-section shape subjected to all-round uniform pressure

The results of the research to determine the stress state on the contours of underground horizontal excavations, the cross-section of which has the form of an ellipse of any size and shape are presented. When changing the intensity of tensile uniform pressure applied to the points of elliptical shape cross-section excavation contours, the given values of excavation depths, ellipse parameters and rock side spreading coefficient values, the areas of the contours with tensile and compressive stresses are identified. If the depths of workings of the considered form of cross-section change, the areas where tensile and compressive stresses act at given values of the intensity of tensile uniform pressure applied to the points of working's contours, ellipse parameters and values of the coefficient of rock lateral spreading are highlighted. The graphical images of the normal tangential stresses, acting on the contours of the considered workings are given. The ranges of intensity of the tensile uniform pressure, at which, depending on the depth of excavation, values of ellipse parameters and the coefficient of rock lateral spread, tensile and (or) compressive stresses act in the points of excavation contours have been determined. The given relations and results can be applied to calculate the values of the permissible values of all-round uniform pressure in the points of the workings contours and to determine the permissible depths of their embedding. As a criterion for determining the values of these values, the condition of absente on the contours of excavations of points in which the normal tangential stresses exceed the limits of tensile and compression strength of the rock can be accepted.

Modification of the properties of coal electrode pitch

We considered the use of electrode pitch as a binding material and the ways of processing it in order to improve its operational properties as an electrode material. The existing methods of modifying electrode pitches do not sufficiently ensure the formation of the properties of electrode masses and, accordingly, the operational characteristics of self-igniting electrodes. Therefore, in this research, a technological method was developed aimed at improving these properties by modifying it with a surface-active substance. The modification with a surface-active substance made it possible to establish the structural and chemical modification of the electrode masses by evaluating, based on the structural changes, the main characteristics and physicochemical properties that determine their behavior in the process of carbonization of the working end of the self-igniting electrode. Phenol-formaldehyde resin was used as a surfactant. The results of the study showed that the use of phenol-formaldehyde resin as a modifier of electrode pitch allowed reducing the specific electrical resistance of carbon masses by 11% and increasing the tensile strength limits by 9% due to the change in diffusion properties in the "filler–binder" system. It was established that the modifier contributes to the intensification of the processes of association of supramolecular substances (graphitosomes); the relationship between the rheological parameters and the rational composition of the polydisperse system of organic pitch mass was revealed. It was proposed to add a modifier of up to 2% at the expense of medium-temperature pitch B1 in the composition of carbon masses. This made it possible to reduce the use of medium-temperature pitch, improve the operational properties of carbon graphite products and reduce the burden on the environment.

Effect of Heat Treatment on Interface Behavior and Fatigue Property of 316L/2Cr13 Multilayered Steel

In this study, multilayered stainless steel (MLS) composed of the austenitic stainless steel 316 L and the martensitic stainless steel 2Cr13 is prepared by the cumulative rolling method. Specifically, changes in interface and fatigue properties before and after the heat treatment are verified by scanning electron microscope, tensile test, and fatigue test. In the results, it is revealed that common grains appear at the interface after the heat treatment. Although the overall mechanical properties are improved, the interfacial bonding strength is increased and the plasticity is greatly improved after heat treatment, the fatigue properties are greatly decreased simultaneously. The main cause is that during the rolling process, large deformation leads to grain fragmentation as well as the generation of a large number of subgrains, resulting in higher dislocation density and increased deformation resistance. Therefore, the fatigue performance of MLS in as‐rolled state is better than that of MLS in the heat‐treatment state. In addition, fatigue fracture analysis indicates that cracks usually initiate at the 2Cr13 layer or at the interface between the 316 L layer and the 2Cr13 layer. Ultimately, in this study, the quadratic relationship between tensile strength and fatigue limit is analyzed through fatigue ratio to predict fatigue limit.

Influence of Pulsed Arc Parameters on the Tig Welding Process for the Stainless Steel Duplex UNS S31803.

The influence of parameters involved in the pulsed electric arc, used as an energy source in the tungsten inert gas (TIG)-mediated welding of Duplex UNS S31803 stainless steel, to attend the manufacture of flexible pipes for the extraction of oil and gas is presented. A fundamental part in the manufacturing process of flexible pipelines is the welding of these strips so that corresponding TIG welds will be subjected to the same process and work conditions. Therefore, it is necessary to maintain the same properties in the welded regions. Covering the effects of each parameter of the pulsed electric arc such as peak and base current as welds, cyclic ratio, and pulsation frequency is a desirable endeavor. The final objective is the mitigation of problems that have a great impact on production, such as weld breakage during the conformation of the strip in the process and test failures. With this, tensile, bending, and ferrite percentage tests were performed on 12 samples that qualified as satisfactory in the visual aspect. A minimum tensile strength of 734.57 MPa and a maximum of 775.77 MPa were obtained where all values found are above the tensile strength limit of the base material of 620 MPa. With the completion of the study, it is possible to understand not only the response of the process to each parameter but also the tendency when changing them. Moreover, it is possible to explore the possibility of guiding the changes to achieve results about the visual aspect and the mechanical properties of the welded material.

Probabilistic analysis for the reinforced fill over void problem

Analytical and numerical solutions for the problem of geosynthetic-reinforced fills over a void have been the subject of investigation for the last four decades. A common feature of this prior work is that all methods have treated the analytical solutions as deterministic. While the treatment of some input parameters must be taken as deterministic, there are other parameters that have uncertainty. Furthermore, the underlying mechanistic models for load and resistance terms in the limit state equations for the reinforced fill over a void problem can be expected to have different accuracy. This paper revisits the problem of geosynthetic-reinforced fills over voids from a probabilistic point of view for reinforcement tensile strain, tensile strength, and geosynthetic stiffness limit states. Particular attention is paid to the method used to select the isochronous stiffness of the reinforcement and the associated uncertainty in the magnitude of that value. The paper demonstrates how the factor of safety from deterministic past practice can be linked quantitatively to the reliability index used in contemporary probabilistic design. Finally, the paper demonstrates the advantage of using product-specific constant-load creep test results to maximise margins of safety for strength and stiffness limit states in both deterministic and probabilistic frameworks.

Evaluation of the mechanical properties of polyamide 12 regarding different percentages of reused material in the selective laser sintering process

PurposeAdditive manufacturing (AM) has been one of the most highlighted processes of the last few years. AM prints complex parts and items from 3D files regarding different materials, such as polymers. Moreover, there are different AM techniques available for polymers, such as selective laser sintering. In the SLS technology, polyamides 11 and 12 lead 88% of the market. These materials are high-cost and use an average of 50% of virgin material at each printing. It is possible to use lower rates of virgin material, but at least 30% is recommended. Low rates of virgin material decrease mechanical properties.Design/methodology/approachThis study aims to evaluate the influence on the mechanical properties of the percentage of reused PA12 in parts manufactured by the SLS process. The specimens of PA12 were manufactured with a percentage of virgin/reused polymer of 50/50, 40/60, 30/70, 20/80 and 10/90. We considered three distinct printing directions to compare the mechanical properties of the specimens: horizontal, perpendicular and vertical.FindingsThe results showed that when the percentage of reused material increases, the tensile strength limit (TSL), flexural strength limit and Shore D hardness decrease. Another aspect visualized was the fragile behavior presented in the vertical specimens. In addition, DSC analysis indicated a 2% reduction of crystallinity. Scanning electron microscopy images revealed spherical voids and unfused particles of PA12 at the fracture of tensile test specimens. The material thermal history and unfused particles could decrease the material properties.Originality/valueWe observed that the mechanical properties, such as the TSL, flexural strength limit and hardness, decrease as the percentage of reused material increases. In addition, the process presented a printing-direction dependence, where the vertical direction presented as the more brittle between the ones used.

On the numerical and mesh-dependent parameters in a computationally enhanced phase-field fracture model coupled with a novel mesh refinement strategy

The phase-field method has been proven as a robust and computationally efficient approach to model the propagation of fractures in brittle solids. However, the performance of this technique in the context of finite element method can be questioned due to restrictions in the mesh structure and the element size to capture the fracture as a diffusive damaged region. This study is dedicated to developing a methodology for finding an appropriate length-scale parameter to model the fracturing process in a way that matches the physical character of failure in materials. The fracture process zone is chosen as the key feature in this study to propose relationships for estimating the length-scale parameter based on the tensile strength and cracking properties, and the robustness of the method is verified using experimental data. To employ the phase-field method in modelling large-scale domains and complex geometries, a novel mesh refinement strategy is developed to increase the computational efficiency based on predicting a corrected tensile strength limit depending on the element size to capture the crack-tip effectively. The proposed mesh refinement strategy reduces the computational effort significantly. Reliability and robustness of the developed relationships are successfully examined by simulating benchmark cases and comparisons with physically measured data.

THE RELATIONSHIP BETWEEN THE MECHANICAL PROPERTIES OF ARMOR STEEL AND ITS BALLISTIC RESISTANCE (overview)

The relevance of the work. Today the industry is actively developing in the field of manufacturing means for protection of all types of armored vehicles against fire damage by small arms and artillery weapons. At present, ensuring high dynamic resistance of armor against modern weapons without increasing its thickness and, accordingly, the mass of the structure as a whole is achieved due to the use of various non-metallic materials (armor ceramics, high-strength fabrics, etc.) as part of compositions with traditional steel armor. The development and design of workable materials and structures of armor protection is a complex scientific and technical problem. To ensure high stability and survivability of armor, it is necessary to establish a relationship between the mechanical properties of armor steel and its ballistic characteristics. Purpose. Based on the analysis of literary sources, determine the relationship between the mechanical properties of steel armor and its ballistic characteristics. Methodology. The method of scientific and technical literature analysis regarding the requirements for armored obstacles is applied. The results. Analytical investigations of the relationship between the main mechanical properties of steel armor and its ballistic characteristics are conducted in the work, which will allow predicting the optimal combination of mechanical properties’ values that will ensure high ballistic resistance. Increasing the hardness of armor steel usually reduces the impact toughness of steels. It is noted that the ballistic characteristics of structural and armor steels are correlated with the tensile strength limit. The existence of a correlation between the strength properties of materials and their resistance to crack propagation under high-speed (explosive) loading is shown. For a number of materials, there is a close relationship between predicted and measured ballistic characteristics at high deformations associated with ballistic impact, when compressive flow stress is used as a measure of material strength. Increasing impact toughness, especially in high and ultra-high hardness classes, is an important task in the development of armor steel. Hardness limits are therefore set for specific grades of steel armor to control impact toughness during production and reduce the risk of fracture or other brittle damage for specific steel compositions and applications.

Technology and mechanical properties of reinforced continuous fiber 3D-printed thermoplastic composite

Background. Additive technologies based on Fused Deposition Modeling (FDM) modeling methods attract a lot of attention from both industry and research groups, which is explained by low investment costs, ease of production, etc. If the processing parameters are correctly selected, products with mechanical properties close to products obtained by traditional technologies can be obtained. Objective. Practical implementation of the modernized technology for 3D printing of Polylactid Acid (PLA) samples reinforced with continuous Kevlar fiber using the FDM method and determination of their mechanical properties. Methods is based on experimental and theoretical studies of the limit of tensile strength and modulus of elasticity of the composite and includes testing of samples on the SHIMADZU AGS-X testing machine and solving the inverse problem. Results. Experimental samples of thermoplastic composite (PLA+Kevlar fiber Æ0.3 mm) were tested for tension. It was found that the tensile strength of the reinforced composite compared to the unreinforced one with a Kevlar volume fraction of about 12% increases by 2.38 times, and the modulus of elasticity increases by 1.45 times. With a confidence interval of 0.68, the error of determining the ultimate tensile strength is 3.5%, and the modulus of elasticity is 4.5%. A theoretical dependence was obtained for predicting the modulus of elasticity of thermoplastic composites in the range of changes in the degree of reinforcement up to 15%. Conclusions. The application of additive technologies based on FDM for 3D printing of thermoplastic composites with increased mechanical properties is substantiated.

Influence of Retrogression Time on the Fatigue Crack Growth Behavior of a Modified AA7475 Aluminum Alloy

This paper investigates the effect of retrogression time on the fatigue crack growth of a modified AA7475 aluminum alloy. Tests including tensile strength, fracture toughness, and fatigue limits were performed to understand the changes in properties with different retrogression procedures at 180 °C. The microstructure was characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The findings indicated that as the retrogression time increased, the yield strength decreased from 508 MPa to 461 MPa, whereas the fracture toughness increased from 48 MPa√m to 63.5 MPa√m. The highest fracture toughness of 63.5 MPa√m was seen after 5 h of retrogression. The measured diameter of η' precipitates increased from 6.13 nm at the retrogression 1 h condition to 6.50 nm at the retrogression 5 h condition. Prolonged retrogression also increased the chance of crack initiation, with slower crack growth rate in the long transverse direction compared to the longitudinal direction. An empirical relationship was established between fracture toughness and the volume fraction of age-hardening precipitates, with increasing number density of precipitates seen with increasing retrogression time.

Physical background of significant increase in mechanical properties and fatigue strength of groove-rolled Cu-Ni-Si alloy with discontinuous precipitates

Prolonged aging of Cu-Ni-Si alloy induced the formation of discontinuous precipitates (DPs) of fiber-shaped Ni2Si intermetallic compounds, rendering good conductivity and relatively inferior strength. To improve the strength of Cu-Ni-Si alloy with DPs, groove-rolling technique was utilized to plastically deform the aged Cu-6Ni-1.5Si specimen. As the rate of area reduction increased from 20% to 50% and 80%, the diameter and interspacing of Ni2Si fibers decreased. Both tensile strength and fatigue limit stress, which are essential for the design of electrical and electronic mechanical components, of Cu-6Ni-1.5Si specimen increased significantly with groove-rolling. It was suggested that an extra strengthening was achieved by Ni2Si fiber reinforcement in addition to work hardening. The increase in yield strength by fiber reinforcement was estimated by Orowan strengthening principle, assuming ideal fiber arrangement. The estimated yield strength based on Orowan mechanism was found to be much greater than the experimentally measured value. This was because actual morphology and arrangement of fibers were largely different from the ideal state, necessitating an error factor, k, which varied with the true strain, εt, due to groove-rolling. The k showed initial steep increase and subsequent mild increase to εt, followed by decreasing trend after εt ≒ 0.7. The physical background of enhanced fatigue strength of rolled specimen was discussed based on the detailed microstructural observation on crack initiation and propagation behavior.