Tension Strength Research Articles

Unified characterizing fatigue performance of high modulus asphalt concretes under diverse stress state

As a new material, high modulus asphalt concrete (HMAC) with good durability is widely used in the pavement engineering. One of the most critical performance indexes of HMAC is the fatigue cracking. However, in the experiment of evaluating the fatigue properties, different anti-fatigue effects are obtained only by adding different modifiers. In addition, using only one loading mode to determine the fatigue properties of HMAC neglects the fact that there is a difference among the fatigue test results in various loading modes, which artificially leads to the non-uniqueness and unscientific design of high modulus asphalt pavements for the fatigue resistance. Therefore, four internationally accepted mainstream strength tests at different loading rates, including direct tension, indirect tension, unconfined compression and four-point bending tests, were carried out to enhance the veracity of structural resistance design of high modulus asphalt pavements. It is revealed that the fitted curve for the variation of strength with loading rate is a power function with velocity dependence, and the models for direct tension, indirect tension, unconfined compression, and four-point bending strengths established as a function of loading rate are SD = 3.218v0.1425, ST = 3.833v0.1768, SC = 14.391v0.1130 and SF = 7.839v0.1489 respectively. Besides, it is shown that the conventional S-N fatigue equation does not take into account the velocity dependence of the strength of HMAC in the stress ratios determined by the tests, and the velocity-dependent stress ratios defined in this paper are determined by the strength model and therefore take into account the viscoelasticity of HMAC. In addition, it is found that extending the fatigue curve backwards, when the fatigue life of HMAC is also close to 1, the velocity-dependent stress ratio is 1. Meanwhile, the fatigue model Nf = tv-5.318 was developed by unifying the characterization of HMAC and considering the effect of loading rate in various loading modes. It eliminated the difference of fatigue test results caused by the specimen sizes and loading modes, and effectively improved the completeness of structural design of high modulus asphalt pavements, which provided a theoretical basis for designing the high modulus asphalt pavements.

3D stability analysis method for toppling failure on rock slopes

In this paper, an optimized solution method is proposed for the 3D stability analysis of rock slopes subject to toppling failure, based on their geometric and mechanical properties. It was verified by a 3D block system that focused on the geometric properties of toppling slopes, considering the force and its action point on the interface of the block system as unknown variables, as well as introducing the definition of a safety factor considering both tension and shear strength reduction. The proposed method implied setting constraints, such as the balance equation corresponding to block force and moment, as well as non-violation of the yield criterion, considering the minimum value of the safety factor as the objective function. It was applied to the analysis of two typical 3D models simulating toppling failure on slopes. The example of a 3D spherical toppling slope was reconstructed and corroborated by calculation. The experimental results demonstrated that the proposed method could appropriately reflect the mechanical properties and stability behaviour of a 3D toppling slope, thereby facilitating the 3D stability analysis of toppling rock slopes.

The relationship between bending and tension strength of Irish and UK spruce and pine

The correct characterisation of wood properties is fundamental for the best utilisation of resources. In Europe, grading is defined by strength classes that are determined based on either bending or tension tests. The European standards give equations to estimate characteristic strength in tension from characteristic strength in bending, and vice versa depending on which was tested. These equations are applied to all softwoods. The aim of this paper is to empirically determine the relationship between bending and tension strength properties using two conifer species grown in Ireland and the UK. The results show that the relationships change with species. The standard conversion underestimates, importantly, the performance of spruce for tension loads calculated for the most common bending strength class for Ireland and the UK, C16. The opposite occurs on the reverse conversion. Additionally, the study includes published data from continental Europe, to establish a new conversion that uses timber from a broader range of grades, and that adjusts the tension performance of Irish and UK spruce obtained from bending strength classes, ensuring safe values for design.

Shear strength of ultra high-performance concrete

Tests were conducted to determine the shear strength of a non-proprietary Ultra High-Performance Concrete (UHPC) mix, designed by the University of Oklahoma. Results for both material properties and shear strength are reported here. The shear strength was determined using a special-purpose panel testing machine, which can subject a 2-D panel to any desired combination of in-plane stresses. Only pure shear was used here. It was found that the local sourcing had no perceptible effect on the material properties, that the fiber content had only a small effect on the compression strength, and that considerable scatter exists in the tension strength results, although those obtained from the flexural beam tests showed less scatter than those from the direct tension test. The shear strength lay in the range 7.5– 10 MPa, and correlates more closely with tension strength than with traditional measures, such as fc'.

Variation of mechanical properties of P. edulis (Moso) bamboo with moisture content

This study investigates the variation of bamboo mechanical properties under the effects of varying moisture content (MC). Because of some inconsistencies in international standards, this study places emphasis on the effect of MC on bamboo tension parallel to the fibres. A large experimental study is conducted to address tension and other mechanical properties with the aim of confirming, revising and/or refuting the standard-prescribed relationships for normalising mechanical properties of bamboo at MC = 12%. Mechanical property correction factors are reported for a sample of P. edulis bamboo having MC ranging from 5% < MC < 30%. Strength properties, other than tension, exhibit a trend of increasing strength as MC falls below the fibre saturation point (FSP). Tension strength decreases as MC falls and tension modulus is relatively unaffected by MC. The correction factors identified in this study correlate well with the trends implied by similar factors proposed in international standards although two potential revisions are identified and discussed. The large dataset developed in this study also permitted evaluation of test methods and assumptions used in determining characteristic mechanical properties.Taking the approach of correcting mechanical properties to a standard MC supports efforts for grading large populations of bamboo and can be used to promote partial safety factor design of bamboo.

Simulations of liquid metal flows over plasma-facing component edges and application to beryllium melt events in JET

Navier–Stokes simulations of liquid beryllium (Be) flows over the straight edge of plasma-facing components are carried out in conditions emulating upper dump plate (UDP) melting observed experimentally in JET. The results demonstrate the existence of three main hydrodynamic regimes featuring various degrees of downstream flow attachment to the underlying solid surface. Transitions between these regimes are characterized by critical values of the Weber number, which quantifies the relative strength of fluid inertia and surface tension, thereby providing a general stability criterion that can be applied to any instance of transient melt events in fusion devices. The predictive capabilities of the model are tested by comparing numerical output with JET data regarding the morphology of the frozen melt layers and the location of Be droplets splashed onto nearby vacuum vessel surfaces as a result of disruption current quench plasmas interacting with the solid Be tiles protecting the upper main chamber regions. Simulations accounting for the coupling between fluid flow and heat transfer confirm the key role played by re-solidification as a stabilizing process, as previously found through macroscopic melt dynamics calculations performed with the MEMOS-U code. The favourable agreement found between the simulations and the general characteristics of the JET Be UDP melt splashing give confidence that the same approach can be applied to estimate the possibility of such mechanisms occurring during disruptions on ITER.

Improving the mechanical performance of poroelastic road surface with low polyurethane content through surface activation

The poroelastic road surface (PERS) mixture with low polyurethane content (PERS-LPC) can reduce the construction cost of PERS pavement, which exhibits promising noise reduction capacity, whereas its mechanical performance needs to be further enhanced for real practice. This study aims to investigate the effectiveness of surface activations of crumb rubber and aggregate to improve the mechanical performance of PERS-LPC. Molecular dynamics (MD) simulations and indoor experiments have been conducted, including the indirect tension (IDT) test implemented on the dry-cured and freeze–thaw PERS-LPC specimens and Cantabro test performed on water-bathed specimens. The results showed that, the oxygen-containing groups, introduced by UV irradiation and KMnO4 soaking, enhanced surface polarity of crumb rubber and rubber-polyurethane bonding strength. The surface activity of basalt aggregate was increased by the inclusion of Portland cement but not by hydrated lime. The IDT strength of the dry-cured PERS-LPC mixture was improved by 10.3–17.5% with activated rubbers and by 35.6% with activated aggregates. The tension strength ratio (TSR) of the freeze–thaw mixture was increased only by 2% with activated rubber but up to 20.8% by the inclusion of 0.5 wt% cement. The Cantabro abrasion loss (CAL) of PERS-LPC specimens was reduced significantly from 20.1% to 11.6% with the soaked rubber and dropped dramatically to 7.9% after inclusion of 0.5 wt% cement. It was recommended to activate crumb rubber with UV irradiation for 24 h and mineral aggregate with 0.5 wt% cement in PERS-LPC mixture in terms of performance enhancement and operation convenience. The findings of this research were expected to support the mix design of an inexpensive and durable PERS-LPC mixture for noise reduction.

Генезис структурно-функціональних порушень та гідростатична модель кісти Бейкера

Вступ. Колінний суглоб оточують різноманітні кістоподібні утворення (КПУ) — бурси, які у нормі клінічно не проявляються. Усі синовіальні порожнини, до яких, зокрема, належать колінний суглоб та бурси, які оточують колінний суглоб, містять синовіальну рідину. Синовіальна рідина є ультрафільтратом плазми крові і складається із білків та інтерстиціальної рідини. У літературі описані бурси, що оточують колінний суглоб, висвітлена ультразвукова класифікація кіст Бейкера залежно від стадії перебігу, яка запропонована І.М. Даниловою [10], та класифікація кістозного переродження меніска, але відсутня інформація щодо патофізіологічних та гістохімічних змін, які відбуваються у КПУ ділянки колінного суглоба, а також відсутня патофізіологічна модель КПУ ділянки колінного суглоба, яка б відображала природу даного захворювання з точки зору фізико-біохімічних процесів. Матеріали та методи. У травматологічному відділенні клініки ­ушкоджень Військово-медичного клінічного центру Північного регіону з початку 2016 року під спостереженням знаходилось 15 пацієнтів із клінічної картиною кістоподібного утворення ділянки колінного суглоба, що підтверджено інструментальними методами обстеженнями: ультразвуковим дослідженням (УЗД), магнітно-резонансною томографією (МРТ) та спіральною комп’ютерною артрографією (СКТА) колінного суглоба. Із них литково-напівперетинчастий бурсит спостерігався у 9 пацієнтів, кісти менісків — у 5 пацієнтів, бурсит переднього відділу колінного суглоба — в 1 пацієнта. Серед пацієнтів 11 чоловіків та 4 жінки. Середній вік пацієнтів становив 43,5 року. Об’єктом дослідження були кістоподібні утворення ділянки колінного суглоба. Усім хворим із КПУ проводили комплексне інструментальне обстеження, яке включало УЗД, СКТА, МРТ, вимірювання внутрішньосуглобового та внутрішньокістозного тисків за допомогою контактного манометра фірми Stryker та надалі — діагностично-лікувальної артроскопії. На основі отриманих даних УЗД проводився розподіл хворих на 4 групи, що базується на процентному відношенню внутрішньопросвітних нашарувань (включень) до загального просвіту КПУ, що дало можливість сформувати нову класифікацію КПУ ділянки колінного суглоба для вибору того чи іншого методу лікування. Результати та обговорення. Для формування та прогресування КПУ має значення підвищений тиск, який становить у середньому 29 мм рт.ст. у положенні згинання та до 58,4 мм рт.ст. у положенні розгинання. Виходячи із попередніх даних, на нашу думку, критичним показником тиску, при якому може настати розрив кісти Бейкера, є тиск більше 60 мм рт.ст. Зазвичай таке ускладнення виникає при тривалому існуванні кісти, коли тривала адсорбція білкових молекул на стінці кісти призводить до адсорбційного зниження міцності та зниження поверхневого натягу — ефект Ребіндера. Висновки. Враховуючи дані біохімічних процесів, УЗД та ендоскопії кіст Бейкера на різних стадіях, ми дослідили, що сама стінка кісти не потовщується, а відбувається пристінкове нашарування білкових молекул із формуванням глобул, які і формують так звану псевдостінку. У подальшому ці нашарування починають формувати перетинки між протилежними стінки, ущільнюватись, що призводить до камерності КПУ. На пізніх стадіях дані нашарування переважають над просвітом КПУ. Запропонована нами класифікація заснована на визначенні процентного відношення внутрішньопросвітних нашарувань до загального просвіту КПУ у двох зрізах та відображає основні морфологічні зміни, що дає можливість визначити оптимальний метод лікування даного кістоподібного утворення та широкого практичного використання у травматології та ортопедії.

The quality control assessment of cyanate ester blend (EX-1515) resin based composites concerning hydrolysis

Cyanate ester resins are essential matrix materials for advanced composites demanding excellent mechanical properties and dimensional stability under varying hygrothermal and radiative environments. However, a critical processing complication arises due to moisture sensitivity during cure which compromizes mechanical and thermal properties. Therefore, a reliable evaluation technique is necessary to ensure the successful use of cyanate ester-based composites. In this report, quality control (QC) signatures of a cyanate ester blend (EX-1515) are evaluated in comparison to those of an unmodified single-component cyanate ester resin (RS3C). Varying degrees of EX-1515 hydrolysis, i.e., carbamate formation, were investigated via FTIR and correlated to decreases in glass transition temperature by DSC and changes in the thermal decomposition profile by TGA. Also flatwise tension (FWT) strengths were observed to decrease with increasing hydrolysis. These results on as-cured EX-1515 were analogous to what was previously reported on RS3C. However, with elevated thermal post-treatments, their thermomechanical properties displayed an opposite trend; While hydrolyzed RS3C exhibited even further progressive reductions in Tg with a post-cure, EX-1515 showed significant increases, likely due to a new polymerization reaction involving carbamates and additional chemical moieties in the blend formulation. Interestingly, the post-cure Tg increase did not translate to any improvement in mechanical properties. On the contrary, the strength showed a dramatic reduction due to thermal degradation of the hydrolysis by-products resulting in increased porosity. The QC signatures of EX-1515 proved to be more complex than RS3C. Therefore, it is necessary to consider multiple QC signatures with carefully chosen thermal treatments rather than relying on a single point Tg measurement without the full thermal history information of the cyanate ester material.

Experimental investigation on the fiber reinforced ash-based geopolymer concrete with Musa basjoo fibers

The research proposes a novel way of manufacturing the one-part geopolymer fiber reinforced concrete with Musa basjoo fibers (an agricultural waste). For the preparation of a one-part alkali medium, only sodium hydroxide (NaOH) is utilized. To test the performance of the concrete, specimens are tested for their workability, strength, and absorption properties. The molarity of the NaOH solution above 10 M is not recommended with Musa basjoo fibers. The sample strength in tension and flexure increased by 61% and 63%, respectively with the addition of fiber. Fiber works effectively in resisting the first crack and its propagation by taking additional stress and this is the reason for the incremental trend till 1.25% fiber dosage. Beyond 1.25% dosage, the specimen strength is reduced. As too much fiber content is detrimental to the bond between fibers and concrete matrix. Even without the secondary alkali medium (Na2SiO3), the strength results are matching with the two-part alkali medium specimens. This implies that Musa basjoo fibers are greatly contributing to the strength attributes. Though the strength of the specimen is increased to 1.25% fiber dosage, considering the workability aspects, Musa basjoo fiber addition beyond 1% of the raw feed is not recommended for the geopolymers.

Optimisation of Graphene Nanofiller Addition on the Mechanical and Adsorption Properties of Woven Banana/Polyester Hybrid Nanocomposites by Grey-Taguchi Method

Throughout history, techniques have shifted from mainstream metals and minerals to nanocomposites to generate smaller, more practical elements for particular purposes. Natural fibres have greater advantages than glass fibres, such as being cheaper, recyclable, and nonflammable. The main objective of the current experiment is to determine how the accumulation of graphene to hybrid polyester composites reinforced with woven banana fibre affects their mechanical properties. Composites were constructed utilising the hand lay-up process with the following limitations: (i) graphene filler weightiness, (ii) woven banana fibre thickness in gsm, and (iii) number of woven banana layers, all at three different levels. Using the L9 (33) orthogonal design, nine composite samples are generated and tested according to the ASTM standard. According to the grey research, hybrid composites having 5% graphene powder and 350 grammes per square metre of woven banana fibre in three layers have high mechanical strength. Adding fibre content to immaculate polyester increased its mechanical properties in general. As the fibre and filler concentrations grew, more energy was required to break the fibre bundles between the matrix and its resin. The confirmation test by the optimal process value utilising the grey relation analysis is considerably better than the actual test data. Tension strength has improved by 17.14%, bending strength has improved by 96.75%, and impact energy has increased by 16.17%.

Development of standard and high strength concretes using sustainable & recycled materials

One of the most complex challenges in the concrete technology is the utilization of additives and optimizing their proportions to enhance their performance. Construction activities cause damage to the environment in terms of pollution & waste generation. Hence, additives used in the concrete must not only be efficient but must also be sustainable to minimize such negative effects. The current research work thus provides an experimental investigation of the workability and mechanical strengths of the Self Compacting Concrete (SCC) for standard and higher grades with inclusion of sustainable materials like Fly ash, GGBS & fine recycled materials, and the results were compared to Nominal mix containing M-sand as the fine material. The different percentage replacements adopted for study were 50% and 100%. The results showed better flow and consistency but lesser strengths in compression, tension & flexure. The declining trend with increase in replacement of the recycled aggregates can be attributed to poor quality, moisture state and properties of the source. However, by replacing appropriate amounts of recycled fine materials, this method can be adopted for structural applications, thereby minimizing the environmental consequences of the recycled materials.

Strength characteristics of concrete by utilization of metakaolin and steel fibres as partial substitute to binding material

Cement has an unresolved problem of increased utilization of raw materials and energy consumption and also carbon dioxide emission during its production. Metakaolin is utilized as partial substitute to cement. It utilizes lime on hydration and causes an increase in the production of cementitious compounds leading to improved strength. The principal intention of this research activity is to find out the fresh (workability) and hardened properties (compressive, split tensile and flexure) of concrete by using metakaolin at varying percentages from 0%, 5%, 10%, 15% and 20% by weight of cement and again by incorporating various types of steel fibers in the limit of 2%, 2.5%, 3% and 3.5%. Concrete specimens were cast for a M40 grade of concrete. Cube specimens (150 × 150 × 150 mm), cylindrical specimens (300 × 150 mm) and prism specimens (100 × 100 × 500 mm) were tested and evaluated for strengths in direct compression, tension and bending for 7 and 28 days of curing span. The outcomes were compared with normal mix. The results have shown that the increase in compressive, tensile and flexure were 20.29%, 16.13% and 14.4% respectively.

Экспериментальные исследования прочностных характеристик высокопрочной сталефибробетонной смеси

The article discusses experimental studies of the strength characteristics of high-strength concrete and steel fiber reinforced concrete from highly mobile concrete and steel fiber reinforced concrete mixtures. There have been obtained experimental dependences of prism and cube strength before and after alternate cyclic freezing and thawing. Calculation formulas are proposed that demonstrate the relationship between cube and prism strength in compression and tension. Calculation diagrams of steel fiber reinforced concrete under compression and tension of experimental prism samples are formed.

Restoration of existing historic concrete structures with PE fiber strain hardening cementitious composites

Important historic buildings of the 20th century located in the seismogenic zones of the Mediterranean have been designed without the provisions of Eurocode 8; thus, they require strengthening to account for seismic excitations and to be rendered safe for use by future generations. A common disadvantage in historic concrete buildings is the insufficient or even null reinforcement in shear, which usually results in brittle shear failures. This research focuses on the use of a self-compacting, fiber reinforced cementitious composite, which can be applied as cover replacement, or in a thin layer around the perimeter of an existing column, thus providing confinement to the original core and increasing the shear strength of the structural member. Different mix designs prepared in various countries have been examined, all incorporating the use of industrial by-products, such as silica fume or fly ash. The aforementioned mixtures were replicated with the use of locally available raw materials at the laboratories of the University of Cyprus. Polyethylene (PE) fibers, with or without coating, measuring 12 and 18 mm in length were also included in the various mix designs. The mechanical properties of the hardened specimens were compared through compression, tension and flexure tests at 28 and 90 days of curing. Based on the results, a self-compacting mixture, presenting particularly high strengths in direct tension and bending, was eventually chosen to investigate the strengthening of existing historic concrete members.

An Experimental Investigation on Self Compacting Concrete by using Recycled Aggregate by using M40 Grade of Concrete

Concrete is the second-most-used substance after water, and more than six billion tons of cement are produced each year. As part of the current investigation for new innovations in concrete as well as to decrease aggregate waste, an experimental assessment on self-compacting concrete with varied percentages of coarse recycled concrete aggregate was conducted. The major objective was to investigate the use and effects of coarse recycled aggregate in next generation concretes. The environment is under a great deal of stress as a result of the considerable increase in trash produced during construction and demolition over the past few years, together with the rise in demand for building materials. As a result, the use of recycled aggregate in concrete has been encouraged, which not only enables a more efficient use of natural resources throughout their life cycles but also contributes to environmental protection. This study employs coarse recycled aggregate (RCA) in varying percentage replacements of natural coarse aggregate (NCA) from 0% to 100% with increments of 20% for the production of self-compacting concrete (SCC) of grade 40. Super-plasticizer is applied in order to achieve SCC flow properties at a dose dependent on cement weight. At 28, 56, and 90 days old, testing for split tension and compressive strength were performed on the animals. It has been shown that up to 40% recycled aggregate may be used to create SCC without noticeably decreasing strength and durability.

Comparative Study on Various Strength Parameters of Structural Elements Made from Cross-Laminated Timber

Cross laminated timber (CLT) is an innovative and environment friendly engineered timber product with superior structural performance. CLT offers strong resistance against both in-plane and out-of-plane loading. Hence, it is widely used as floors, roofs or wall elements. Considerable experimental research on CLT under various loading conditions has been done in the recent past. This article presents a comprehensive review of various design methods to determine basic mechanical properties such as tension, compression and rolling shear strength of CLT with primary focus on Norway spruce. All relevant experimental data available from existing literature were collated and consequently been used to evaluate the performance of various methods to design CLT structures. The comparison revealed that different methods show considerable variance in predicting the capacity of CLT panels due to the variation in timber species, which affects the corresponding mechanical properties of the lamella. In addition to species, rolling shear properties can also vary considerably depending on the type of experimental technique used for testing. A predictive model has also been proposed to correlate rolling shear strength obtained from shear analogy method to that obtained using planar shear.

Influence of reinforcing waste steel scraps on the strength of concrete

It is hard to underestimate the significance of incorporating waste materials into concrete materials for ecological rehabilitation. This study summarizes the results of investigations on the use of waste steel scraps from the machine shops, primarily from the CNC lathe, as supplementary cementitious materials. The waste steel scraps were used with the cementitious material without any further cleaning. In the different samples, waste steel scrap was substituted for fine aggregative materials in proportions of 4%, 8%, and 12% by mass of cement. Experiments were accompanied on the compression strength, tensile splitting characteristics, and flexural characteristics. With the introduction of waste scrap materials, the mechanical characteristics had been improved, significantly. The maximum mechanical strength was attributed to the 8% inclusion of metal scraps with the conventional concrete and it was noticed that the compression, split tension and flexural strength of the concrete was improved by 11.68%, 20.82% and 24.65%, respectively with addition of 8% steel scraps in concrete. The increase in metal scrap proportion after 8% in mortar resulted in the diminished properties of the concrete mixtures.

バッチベイズ最適化による複合材料積層板強度試験の複数の積層構成候補の提案

The strength prediction of a fiber-reinforced laminated composite is a big issue to achieve an efficient research and development. This study aims to develop a prediction method of the strength variation of composite laminates as one of the material integration (MI) method by adopting the Bayesian optimization (BO) method. As the BO method, this study adopts a batch Bayesian optimization (BBO) to obtain multiple laminate configuration candidates that maximize the strength based on the results of the strength test with considering empirical constraints such as the contiguous number limit of the same orientation angles. In order to obtain the multiple laminate configurations, an improved genetic algorithm based on the distributed genetic algorithm with adaptive mutation and gene repair strategies is adopted. Through numerical examples based on the open hole tension (OHT) strength test data, efficiency of the proposed method is demonstrated.

Relationship between cross tension strength and carbon content of lower sheet in friction element welded steel joint

Relationship between cross tension strength and carbon content of lower sheet in friction element welded steel joint